Industrial & Specialty Printing - May / June 2011 by Steve Duccilli

Photonic Sintering For Flexible Circuits

MAY/JUNE 2011

Membrane Switches and Touchscreens Specialty Substrates Roll-to-Roll Printing

www.industrial-printing.net

P. 20

Get the free mobile app at

http:/ / gettag.mobi

The Right Partner

for your printed electronic needs

When you need fine line conductive traces, or the highest quality graphics to be printed with the utmost precision and consistency, MacDermid Autotype is in the forefront of developing screen printing stencil materials, substrates and scientifically proven software tools to achieve your ultimate goals. Improve consistency of your printed images with our unique capillary films, Capillex CP or CX and validate your prints using the "Acuity Index" from our QA software.

For more information on our capabilities to support your printed electronic needs , visit: www.macdermidautotype.com or call Toll free: 800-323-0632

Specialty substrates are manufactured and converted in clean room environments to the most exacting standards to meet your highest quality needs for precision printing. Gain control of your web process by using Autostat heat stabilized polyesters for critical flexible circuitry. Hard coated, specialty finish film coatings are provided on polycarbonate and polyester for film insert molding, membrane touch switches, displays and touch screens.

CONTENTS

INDUSTRIAL + SPECIALTY PRINTING May/June 2011 • Volume 02/Issue 03

FEATURES

14 Membrane Switch and Touchscreen Basics

Dawar Technologies This article discusses the processes involved in manufacturing membrane switches and touchscreens and provides a glossary of terms and a list of material suppliers.

20 Sintering Nanoparticle-Based Inks on Challenging Substrates Saad Ahmed, Xenon Corp.

Find out how photonic sintering can form a homogenous strip of metal to achieve better resistivity while protecting temperature-sensitive substrates.

24 Specialty Substrates: Growing Applications for 21st Century Industrial Printers

James R. Williams, Ph.D., Polyonics, Inc. The use of specialty materials is on the rise, which is why you need to bring yourself up to speed about applications and performance characteristics.

28 Roll-to-Roll Printing in Electronics Applications

Deokkyun Yoon and Dong-Soo Kim, Korea Institute of Machinery and Materials This article discusses the many types of roll-based printing processes used in the manufacture of modern electronics.

www.linkedin.com/ groups?gid=2658424

www.twitter.com/iSPmag

www.facebook.com/iSPmag

INDUSTRIAL + SPECIALTY PRINTING, (ISSN 2125-9469) is published bi-monthly by ST Media Group International Inc., 11262 Cornell Park Dr., Cincinnati, OH 45242-1812. Telephone: (513) 421-2050, Fax: (513) 362-0317. No charge for subscriptions to qualified individuals. Annual rate for subscriptions to non-qualified individuals in the U.S.A.: $42 USD. Annual rate for subscriptions in Canada: $70 USD (includes GST & postage); all other countries: $92 (Int’l mail) payable in U.S. funds. Printed in the U.S.A. Copyright 2011, by ST Media Group International Inc. All rights reserved. The contents of this publication may not be reproduced in whole or in part without the consent of the publisher. The publisher is not responsible for product claims and representations. POSTMASTER: Send address changes to: Industrial + Specialty Printing, P.O. Box 1060, Skokie, IL 60076. Change of address: Send old address label along with new address to Industrial + Specialty Printing, P.O. Box 1060, Skokie, IL 60076. For single copies or back issues: contact Debbie Reed at (513) 421-9356 or Debbie.Reed@STMediaGroup.com. Subscription Services: ISP@halldata.com, Fax: (847) 763-9030, Phone: (847) 763-4938, New Subscriptions: www.industrial-printing.net/subscribe.

COLUMNS 12 Business Management

Krista Crotty, Alberi EcoTech The author reviews RoHS and REACH and talks about how companies can assess their compliance with these enforced regulations.

32 Printing Methods

Marcus Maiwald, Christian Werner, and Volker Zöllmer; Fraunhofer Institute for Manufacturing Technology and Advanced Materials Research The authors go through the process chain for functional printing and include information about the technology for handling atomized suspensions of ink particles.

38 Industry Insider

Dave Torp, IPC Discover how standards for flexible electronics can provide immediate guidance for industrial printers.

40 Shop Tour

Printec Take a look inside Printec’s membrane-switch-manufacturing operation in Taipei City, Taiwan.

DEPARTMENTS 4 Editorial Response 6 Advisory Board 8 Product Focus 36 Industry News 39 Advertising Index ON THE COVER

Assembling printed electronics on thin, fragile, flexible substrates can be a challenge. Turn to page 20 to learn how photonic sintering can help stabilize the process. Cover photo courtesy of Xenon Corp. Cover design by Keri Harper.

DOUTHITT CONVENTIONAL OR CTS - DOUTHITT HAS THE OPTIMAL SOLUTION! 0RGHO &76 'LJLWDO 6FUHHQ ,PDJHU 3ULQW KHDG WHFKQRORJ\ ZLWK VPDOOHU GURS VL]H and solid ink technology enables imaging KDOIWRQH IUHTXHQFLHV XS WR OSL 2SWLPL]H image quality without compromising on throughput or consumable cost. Call us to see if CTS is right for you. The Worldâ&#x20AC;&#x2122;s Best Metal Halide Lamps

0RGHO 6DKDUD 6FUHHQ 'U\HU Â&#x2021;8QLIRUP $LU DQG +HDW WR ,QVXUH )DVW DQG Complete Drying of Screens Â&#x2021;6WDLQOHVV 6WHHO 5DFNV Â&#x2021;'LJLWDO 7HPSHUDWXUH &RQWURO Â&#x2021;$Q\ 6L]H $YDLODEOH

0RGHO '0$

0RGHO '0=

Douthittâ&#x20AC;&#x2122;s self contained screen exposure systems provide the best vacuum contact and the best registration. Combined with our IRFXVHG UHĂ&#x20AC;HFWRU PHWDO KDOLGH SULQWLQJ ODPSV RXU XQLWV RIIHU WKH sharpest resolution, guaranteed coverage, shorter exposures and completely hardened emulsion.

Olec Olite & Theimer Violux Lamps & Parts in Stock! Contact us for more information on Douthittâ&#x20AC;&#x2122;s complete line of Exposure Units, Vacuum Frames, CTS Imagers, Dryers, Inspection Tables, High Wattage UV Printing Lamps, Integrators and Blankets for any vacuum frame. Visit us at www.douthittcorp.com Contact us for a free catalog! 2QFH \RXÂśYH VHHQ LW \RXÂśOO QHYHU EH VDWLVÂżHG XQWLO \RX RZQ LW

THE DOUTHITT CORPORATION &DOO 7ROO )UHH '287+,7 7 Â&#x2021; ZZZ GRXWKLWWFRUS FRP 3KRQH )D[ ( 0DLO HP#GRXWKLWWFRUS FRP

EDITORIAL RESPONSE

Flex Those Artificial Muscles GAIL FLOWER Editor

They say that when you lose one sense, the others take over. Recently I came down with the flu, which ended up blocking my senses of smell, hearing, and taste. After a while, even my eyes didn’t see as clearly as they usually do. It wasn’t the best of times, but it taught me to isolate my activities to those that did work and make my brain ignore the other negative responses—like Spock in Star Trek, who was really great at turning off feelings. What does this have to with the current issue of iSP? Consider the article about membrane switches and touchscreens from Dawar. When it comes to making touchscreens, even on a flat glass, a button should look like a button, click like a button, and feel like a button to give the user a sensory awareness that everything works properly. Touchscreens and intermediate user interfaces with immediate tactile feedback should improve the usability and appeal of consumer electronic devices. By combining the sense of touch with sound and sight, the user of touchscreens gets a much more natural experience. Artificial Muscle Inc. (AMI) is one company that focuses on haptic (touch) applications through the manufacture of actuator and sensing components and application of a proprietary technology platform called Electroactive Polymer Artificial Muscle (EPAM). How does EPAM work? EPAM comprises a thin layer of dielectric polymer film between two conductive, compliant electrodes. When a voltage potential is applied across the electrodes, the Maxwellian pressure of the positive charge attracting the negative charge causes the electrodes to attract each other, and since the film is

elastomeric and incompressible, the film contracts in thickness and expands in area. The technology works like an elastomeric capacitor that is capable of changing capacitance by applying a voltage or by an external mechanical force. EPAM film turns into an actuator by attaching frames or materials that direct the motion to the desired axis. EPAM achieves motion (strain) from this electrostatic pressure as compared to other technologies. The displacement is a function of the area of EPAM, and the force exerted is a function of the number of layers of EPAM. The electrode layer of the EPAM can be patterned to achieve specific regions and directions of motions. The architecture along with configurations were developed and patented by SRI Int’l and are now licensed exclusively to Artificial Muscle, Inc. In March 2010, Bayer MaterialScience LLC acquired Artificial Muscle, Inc. Bayer recognized the need for tactile, or haptic, feedback in consumer electronic products that use touchscreens—products such as portable gaming controllers, industrial controls, and casino games. The rumble packs common to hand-held game controllers are only able to produce simple, one-dimensional effects from a single frequency. The time lag felt as the motor spins up or down disassociates the feel from the event. With Bayfol Reflex, a printed, customized actuator technology, it is said that the results are real-time effects with high-fidelity feel. Let’s take it out of the game venue. Could a blind person be able to use an adapted smart phone when given touch responses? Could people who had specific fears (flying, falling, etc.) be able to face simulated situations through haptic responses? What other applications can fit? It will be interesting to see how many areas this will affect in the developing world of technology.

4 | INDUSTRIAL + SPECIALTY PRINTING www.industrial-printing.net

Industrial + Specialty Printing www.industrial-printing.net

STEVE DUCCILLI Group Publisher steve.duccilli@stmediagroup.com GREGORY SHARPLESS Associate Publisher gregory.sharpless@stmediagroup.com GAIL FLOWER Editor gail.flower@stmediagroup.com BEN P. ROSENFIELD Managing Editor ben.rosenfield@stmediagroup.com KERI HARPER Art Director keri.harper@stmediagroup.com LINDA VOLZ Production Coordinator linda.volz@stmediagroup.com BUSINESS DEVELOPMENT MANAGERS Lou Arneberg – Midwest Lisa Zurick – East US, East Canada, Europe Ben Stauss – West US, West Canada, Asia EDITORIAL ADVISORY BOARD Joe Fjelstad, Dolf Kahle, Bruce Kahn, Ph.D., Rita Mohanty, Ph.D., Randall Sherman, Mike Young, Wim Zoomer

JERRY SWORMSTEDT Chairman of the Board TEDD SWORMSTEDT President JOHN TYMOSKI Associate Director/Online

CUSTOMER SERVICE Industral + Specialty Printing Magazine Customer Service P.O. Box 1060 Skokie, IL 60076 ISP@halldata.com F: 847-763-9040

I M AG E Q UA L I T Y o R S P E E D? E F I R A S T E k G I V ES Yo U B oT H .

Don’t compromise image quality for speeD The EFI Rastek H652 UV printer delivers best-in-class image quality, speed and white ink capability. The EFI™ Rastek™ H652 UV hybrid printer is the perfect choice for stunning four-color and grayscale image quality that meets stringent customer demands fast. Direct-to-rigid, roll-to-roll and white ink capability let you offer more applications to get more business and profits.

Get it all with the EFI Rastek H562. Call 800-875-7117 or visit efi.com/GetItAll6.

EFI 970 Rastek Ad I&SP.indd 1

4/13/11 8:37:34 AM

advisory board

Joe Fjelstad

Joseph Fjelstad (josephfjelstad@aol.com) is a 34-year veteran of the electronics-interconnection industry and is an international authority, author, columnist, lecturer, and innovator who holds more than 150 issued and pending US patents in the field. He is the founder and president of Verdant Electronics, a firm dedicated to environmentally friendly electronics assembly. He is co-founder and CEO of SiliconPipe, a specialist in highspeed interconnection-architecture design, much of which is based on flexible-circuit technology. Prior to founding SiliconPipe, he worked with IC-package-technology developer Tessera Technologies, where he was appointed the company’s first fellow. Fjelstad and his innovations have received many industry awards and accolades. Verdant Electronics

Dolf Kahle (rkahle@vmsinc.com) is the CEO of Twinsburg, OH-based Visual Marking Systems, Inc., (VMS), a company that specializes in the OEM durableproduct-identification market and manufactures overlays, decals, and decorative trim for Fortune 1000 companies. Beyond the OEM market, VMS also produces fleet graphics, P-O-P products, and durable signage for the public-transportation market. VMS is an ISO 9000- certified company that enjoys statewide recognition as a Lean Enterprise. Kahle is an active member of SGIA, SPIRE, and GPI. He served on the SGIA board for more than 10 years and was its chairman in 1999. He is currently the chairman of SPIRE. He holds a bachelor’s degree in mechanical engineering from the University of Michigan and an MBA from Arizona State University.

Dolf Kahle

Visual Marking Systems, Inc.

Bruce kahn, ph.d.

Bruce Kahn (bkahn@electronicsprinting.com) is a consultant who specializes in the multidisciplinary fields of printable electronics, nanotechnology, RFID, and smart packaging. Kahn holds a Ph.D. in chemistry from the University of Nebraska and is the author of more than 75 publications, including the recently published “Developments in Printable Organic Transistors,” “Printed and Thin Film Photovoltaics and Batteries,” and “Displays and Lighting: OLED, e-paper, electroluminescent and beyond.” He is a frequent lecturer and author, and he regularly teaches workshops in the U.S. and abroad. Printed Electronics Consulting

rita mohanty, ph.d.

Rita Mohanty (rmohanty@speedlinetech.com) is the director of advanced development at Speedline Technology and a certified Six Sigma Master Black Belt instructor. She has more than 15 years of experience in industries and academics relating to engineering and electronic polymers, electronic packaging, and board assembly. She is a patent holder and has authored and edited books on electronics and numerous technical papers. Mohanty is active in and holds various leadership positions with IMAPS, SMTA, IPC, iNEME, and SGIA. She received her Ph.D. in chemical engineering from the University of Rhode Island. Speedline Technology

Randall Sherman (rsherman@newventureresearch. com) is the president and CEO of New Venture Research, a technology market research firm. He holds a B.S. in astrophysics, an M.S. in electrical engineering from the University of Colorado, and an M.B.A. from Edinburgh School of Business. Visit www.newventureresearch.com for more information.

RANDALL SHERMAN New Venture Research

Mike Young (mikeyyoung@aol.com) has spent 40 years as a specialist in high-definition graphic and industrial screen printing. He is an SGIA Fellow, a member of the Academy of Screen Printing Technology, and a recipient of the prestigious Swormstedt Award for technical writing. He frequently writes for industry trade publications and speaks at international industry events. Young has published several technical books on advanced screen-printing techniques and frequently conducts seminars for high-profile screen-printing companies worldwide. Young is a consultant with Imagetek Consulting Int’l.

mike young

Imagetek Consulting Int’l.

Wim Zoomer (wimzoomer@planet.nl) is owner of Nijmegen, Netherlands-based Technical Language, a consulting and communication business that focuses on flatbed and reel-to-reel rotary screen printing and other printing processes. He has written numerous articles for international screen-printing, art, and glass-processing magazines and is frequently called on to translate technical documents, manuals, books, advertisements, and other materials in English, French, German, Spanish, and Dutch. He is also the author of the book, “Printing Flat Glass,” as well as several case studies that appear online. He holds a degree in chemical engineering. You can visit his Website at www.technicallanguage.eu.

wim zoomer

Technical Language

| Industrial + Specialty Printing www.industrial-printing.net

s S e m i c o n d u c to r s P h o t o v o lta i c s led s memS

SEMI

Expositions

s Printed/Flexible electronicS s emerging marketS

t h e P r e m i e r i n t e r n at i o n a l e v e n t S F o r m i c r o â&#x20AC;&#x201C; a n d n a n o â&#x20AC;&#x201C; S c a l e m a n u F a c t u r i n g

UPCOMING EVENTS Semicon WeSt 2011 JulY 12-14 Moscone Center San Francisco, California www.semiconwest.org

s north Americaâ&#x20AC;&#x2122;s largest microelectronics manufacturing event s More than 100 hours of technical conferences, sessions, an presentations covering the microelectronics supply chain from design/EDA to advanced packaging and test s newâ&#x20AC;&#x201D;techZonE exhibit pavilions covering high-brightness LEDs, MEMs, printed/flexible electronics, design, manufacturing services, materials, and secondary equipment and services

Semicon taiWan 2011 SePtember 7-9 taipei World trade center Taipei, Taiwan www.semicontaiwan.org

s 3PECIAL PAVILIONS $ )# !DVANCED 0ACKAGING 4ESTING !DVANCED -ATERIALS #OMPOUND 3EMICONDUCTOR 'REEN -ANAGEMENT ,%$ -%-3 /%- %QUIPMENT 0ARTS #ROSS 3TRAIT s -ORE THAN PROGRAMS INCLUDING &2%% TECHNICAL PRESENTATIONS at the innovation technolOGY #ENTER ON THE SHOW mOOR s 4HE 3%-)#/. 4AIWAN 'OLF 4OURNAMENT ATTRACTS PARTICIPANTS FROM THE SEMICONDUCTOR &0$ AND 06 INDUSTRIES

Semicon euroPa 2011 october 11-13 messe dresden Dresden, Germany www.semiconeuropa.org

s 3%-)#/. %UROPA IS IN THE HEART OF THE THE LARGEST semiconductor cluster in Europe s 3EGMENTS IN 3EMICONDUCTOR &RONT %ND 4EST !DVANCED 0ACKAGING -%-3 -34 436 3ECONDARY %QUIPMENT 3ERVICES and technology s )N CONJUNCTION WITH 0% #ONFERENCE AND %XHIBITIONÂ&#x2C6; where plastic, organic and printed technology meets manufacturing

For the complete schedule of 2011 SEMI Expositions, visit

www.semi.org/events

product focus

The latest equipment and materials for industrial printing

Stencil-Cutting System The StencilLaser G 6080 from LPKF Laser & Electronics AG (www. lpkf.com) now has a real-time qualityinspection system that uses a proprietary optical process to monitor stencil cutting. According to LPKF, the system uses carbon-fiber materials to reduce the weight of moving parts and increase acceleration and deceleration, cuts apertures at speeds up to 51,200 apertures/hr, cuts metal sheets up to 600 μm thick, and features software designed to ease customizing, global editing of aperture dimensions, and changing information. A 23.6 x 31.4-in. (600 x 800-mm) working area enables the system to cut two stencils in one production step.

Printing and Converting System The Flytec F2010 is a standalone printing and converting system from A B Graphic Int’l (www.abgint.com) that is designed to facilitate inkjet printing, slitting, and rewinding in one work step. It is available for rewind web widths of 13 or 16 in. (330 or 410 mm) and performs print-face inspection through a FleyeVision camera that also allows the production of pharmaceutical or safety labels. The machine is prepared for integration with an inkjet printer for production of serial numbers, sell-by dates, and barcodes on either side of a web. Slitting is through a scissor or razor-blade system. Options include fly-cut slitting and second rewind shaft. The system is capable of handling roll diameters up to 27.5 in. (700 mm) at winding speeds up to 656 ft/min (200 m/min).

Stencil Photo Stencil (www.photostencil.com) recently introduced NicAlloy-XT, a stencil that the company says bridges the gap between laser-cut and electroform stencils. According to Photo Stencil, NicAlloy-XT meets challenging aspect ratios down to 0.46. It incorporates Photo Stencil’s proprietary NiPlate process, designed to ensure ultra-smooth aperture walls, superior paste release, and improved under-screen clean performance. The company bills NicAlloy-XT as more cost-effective than electroform stencils and as a high-quality high-performance alternative to laser-cut stencils.

| Industrial + Specialty Printing www.industrial-printing.net

Metallization Paste

Upgraded Cylinder Screen Press Sakurai (www.sakurai.com) has updated its Maestro MS-80SD Cylinder Screen Press with an optical camera-registration system with monitor, laser-positioning assist for screen-frame changes, and a numerical-indication system designed to improve registration and performance. The Maestro MS-80SD supports media up to 31.625 x 21.75 (800 x 550 mm) and 0.001-0.031 in. (0.05-0.8 mm) thick, a maximum print size of 28.375 x 19.75 in. (720 x 500 mm), and print speeds of 100-2000 impressions/hr.

Flexo Press Solamet PV701 photovoltaic metallization paste from DuPont Microcircuit Materials (www.dupont.com) is the company’s newest generation of Metal Wrap Through (MWT) technology for back-side-interconnected silicon-solar-cell designs. According to DuPont, advanced product composition enables the manufacture of back-contact-cell designs that deliver up to 0.4% greater conversion efficiency for solar cells. DuPont explains that MWT is a specialized cell structure that transfers the bus bars on the front side to the backside, reducing shading on the front side of the cell. The connections are made through holes in the silicon with the same composition as the bus bars. Solamet PV701 is formulated for excellent electrical contact to front-side silver grid structures, high-mechanical strength, low shunting, high-line conductivity, and outstanding solderability as a p-contact metallization.

Overlaminate 3M Commercial Graphics (www.3m.com) introduces Scotchcal Gloss Overlaminate 8528. It is designed to withstand harsh environmental conditions, including extreme temperatures, UV rays, and acid dew. The company has a published warranty of two years for horizontal surfaces and up to seven years for vertical surfaces. The 2-mil cast vinyl is engineered for conformability and dimensional stability and is compatible with solvent, latex, and UV inks. Sample rolls are available.

K2 Int’l (www.k2flexo. com) offers its FA Fast Action flexo press in seven configurations. Models range from six to 12 colors, 10- to 25-in. (255- to 635-mm) maximum cutting-die widths, 10.25- to 32-in. (260- to 820-mm) maximum printing widths, one or two product rewinders, and maximum print speeds of 495 ft/min (150 m/min). Standard equipment includes PLC touchscreen controls, automatic web tension, print and die stations of equal height, ceramic anilox rolls, and more. Options include rotary cold-foil stamping, UV laminating, sheeting, fan folding, and video web inspection.

Stencil

Optical Registration System Systematic Automation Inc. (www. systauto.com) has introduced a modular optical registration system for screen printing on glass, plastic, or stainless-steel bottles. The first color is printed randomly or in relation to a bottle seam. Subsequent colors are printed in relation to the first color. The sensor uses servo technology to find the leading edge of the first image, and Systematic Automation reports sensor accuracy of ±0.002 in. (±0.05 mm). This device is designed for use on any semiautomatic screen press, including Systematic Automation’s Model F-1 DC.

FCT Assembly (www.fctassembly.com) recently debuted UltraSlic Stencil with Nano-Coating. The company says the addition of nano-coating to UltraSlic further increases the performance gap between it and any other stencil technology available today. According to FCT, the addition of a permanent, hydrophobic nano-coating to the UltraSlic stencil foil minimizes the ability of solder paste to stick to the stencil apertures and the bottom side of the foil. The nano-coating is engineered to facilitate up to a 10X increase in the number of prints before cleaning the stencil, as well as successful printing at surface-area ratios below 0.45. The company notes that UltraSlic FG stencils have lower standard deviations, higher repeatability, and cleaner release of solder paste compared to other stencil technologies.

may/june 2011 |

Screen-Cleaning System The Kleen-View Automatic from A.W.T. World Trade Inc. (www.awt-gpi.com) is billed as an environmentally friendly, fully air-operated system that cleans screens, recycles solvent, and simplifies disposal of ink residue. It features stainless-steel construction and is available in seven models to accommodate frame sizes from 36 x 54 in. (914 x 1372 mm) to 88 x 148 in. (2235 x 3759 mm). The Kleen-View Automatic comes standard with either a 20- or 50-gal chemistry reservoir. Larger units have a 100-gal chemistry reservoir. A four-chambered chemistry reservoir provides progressive chemical filtering. The screen-cleaning system is air-powered, and its closed-loop recycling system provides a double-sided chemistry sprayer with variable-speed controls for adjustable chemical flow.

Silicone Adhesive

Roll-Cleaning Agent

NuSil Technology LLC (www.nusil. com) introduces EPM-2890, a thermally conductive, non-corrosive silicone adhesive. It is formulated to provide moderate heat transfer between electrical components and their heat sinks. In addition, EPM-2890 is designed to exhibit less than or equal to 1% weight loss when heated for 30 min at 527°F (275ºC) to withstand lead-free solder reflow. EPM-2890 is a one-part, white, silicone adhesive that will vulcanize at room temperature, with moisture, in 72 hr. It can be used as an adhesive or sealing, caulking, or potting material in electronics applications that require minimal volatility to avoid condensation in sensitive devices. EPM-2890 is RoHS-compliant. According to NuSil, it has low sodium, potassium, and chloride content to help prevent corrosion of electronic components.

Bubbles & Beyond (www.bubbles-beyond.com) formulated its enpurex line of water-based cleaning agents for the printing industry. According to the company, the non-flammable cleansers are free from aggressive chemicals, are biodegradable, and offer significant process-cost savings, excellent material compatibility, optimum efficacy, and operating safety. Agents in the product line include Online, 95 Plus, and Pro. Online is designed for cleaning printing rolls—anilox rolls, in particular—during production and removing UV-curing, solvent-, and water-based printing inks, as well as ink glazing. The 95 Plus agent is designed to remove dispersion- and water-based printing ink, as well as print lacquer from printing rolls. Pro is intended for removing persistent and older staining. It uses what the company describes as micro-erasers to remove printing inks, lacquer, UV ink, and calcium glazing.

Wide-Format UV Inkjet Printer

UV Inks for Glass Applications Polytype’s (www. polytype.com) Virtu Vetro series consists of CMYK+White UV inks that are formulated for digital printing onto glass surfaces. The company says recent performance tests demonstrate excellent compatibility, durability, and behavior of Virtu Vetro inks on float, safety, and other glass types for a variety of industrial applications. Polytype also notes that the inks are highly resistant to abrasion, scratching, grinding and polishing and that they do not chip or flake when cut. 10 | Industrial + Specialty Printing www.industrial-printing.net

Inca Digital Printers (www.incadigital.com) recently launched the Inca Onset S40, the latest addition to its Onset line of wide-format UV flatbed inkjet printers. It prints at speeds up to 5,059 sq ft/hr (470 sq m/hr) and uses up to 168 user-replaceable printheads (28/color) on a full-width print bar, delivering a 27-pl drop size. The system supports 600-dpi imaging resolution with a four- or six-color Fujifilm UVijet OB inkset. The Onset S40 accepts fullbed-width substrates up to 123.6 x 62.9 in. (3.14 x 1.6 m) and 2 in. (50 mm) thick. Operators can select from uni- and bi-directional print modes.

Analysis Solution for Flexo Printing

Send us your product news!

Email ben.rosenfield@stmediagroup.com

The Betaflex Pro from Beta Industries (www.betascreen.com) is an analysis solution for flexo printing that includes software and hardware designed to assess small highlight dots and advanced surface treatments. According to the company, Betaflex Proâ&#x20AC;&#x2122;s 3D Dot Structure Imaging, operating at 22,000 pixels/in., delivers numerical analysis and visual confirmation of these small halftone dots in such a way that operators are no longer left guessing or making subjective judgments. Beta Industries explains that 2D imaging of the full tonal range occurs at 14,000 pixels/in., yielding precise and repeatable measurements from 50- to 200-line/in. conventional and FM screens. Production samples are imaged with a topographical visualization and comparison function, in addition to a numerical readout. The system generates pass, warning, or fail indicators to guide the operator in accepting or rejecting plates.

UV Coater TEC Lighting (www.teclighting.com) recently unveiled the XB18, a system the company bills as the industryâ&#x20AC;&#x2122;s first doublesided UV coater. The XB18 offers on-thefly shifting between single- and double sided coating, and the coatings can be varied. For example, a production manager can choose a satin coating on one side of the sheet and gloss on the other. The XB18 also can be arranged inline with a digital press. Standard configurations for the initial offering include 18-in.-wide (457-mm) handfed, auto-feeder, and inline presses. According to TEC Lighting, 40-in.-wide (1016-mm) models are scheduled for future release.

may/june 2011 | 11

business management

Making Product Eco-Compliance Easy Krista Crotty Alberi EcoTech

In today’s global market, equipment companies need not only know about safety, performance, and quality, but they also need to keep an eye on the amount of hazardous substances contained within the final product. Many industrialized countries and areas have restricted the use of certain hazardous substances in equipment. In 2006, product environmental compliance in the electronics industry began with the EU’s Restriction on the use of certain Hazardous Substances in electrical and electronic equipment Directive (commonly referred to as RoHS). RoHS is in a state of change, as documented in Table 1. Companies were busy gathering documents and data-information sheets on whether or not a part contained the restricted six substances: lead, mercury, hexavalent chromium, cadmium, poly-brominated biphenyls (PBBs), and poly-brominated biphenyl ethers (PBDEs). Companies did not focus on this task as a process, but as a once-and-done project. In 2007, when China released its version of RoHS for electronics, the requirements were different, as were the products covered; and companies scrambled to make changed to their projects to meet the new requirements. In addition to the RoHS–type requirements, companies also need to know about the reporting requirements for regulations such as EU REACH. In 2008, with the introduction of EU’s Registration, Evaluation, Authorization and registration of CHemicals regulation (REACH), the list of substances increased

to more than double the number of substances in the RoHS Directive; with the potential to exceed thousands of reportable substances. Nowadays, with every country looking at its own list, where do you start? Companies must look at the big picture now and treat product environmental compliance as a process, not a project. Companies should focus on how all the countries and various legislations paint a total picture, not just focus on each individual country and its legislation. An audit of the product-environmental-compliance program does just this. The company saves money by taking the insight and direction from an audit. Understanding, tracking, and meeting the multiple environmental requirements around the world, without driving yourself crazy, is a daunting task. Companies typically focus too much on the details and not the overall picture. Additionally, com-

panies focus on the individual countries as individual projects, when they should be looking at the matrix of countries and requirements—finding the lowest common denominator and creating a process for compliance. The audit process In today’s market, companies not only need to concern themselves with government enforcement, but also customer requirements. Customers are now looking for information on the products they are purchasing. A customer audit or inquiry can be more tasking than a government enforcement audit. Why? Because a customer looks at a matrix of parts and legislation, not one product or one legislative requirement. So where does one start with determining compliance? Perform an audit. Audit the entire product-environmental-compli-

Table 1 Estimated timetable for the RoHS recast. Dates are subject to change. Action / Event

Date / Timeline

Approval by EC of RoHS Recast Directive translated into all languages

March 2011

Publication into EC Official Journal

April/May 2011

Directive Entry into Force

+20 days

Member State deadline for transposition into National Law

+18 months

Estimated enforcement date by Member States

November 2012

* Dates may change, dates as of information March 2011

12 | Industrial + Specialty Printing www.industrial-printing.net

ance process. Focus on three things initially: awareness, preparation, and execution. Review how you are approaching compliance instead of taking stock and reviewing every data sheet for every component that makes up a product. When assessing a program, consider:

team members supporting this lead • Where the program information is stored and how program information is organized • Whether the program gives a sense of progressive understanding and adjustment or a sense of panic and fire fighting

• Listing of products, distribution regions, and type of distribution in each region • Listing of legislation in those areas, which eases the process of determining where a program falls short and in crossreferencing requirements so project tasks are not duplicated • How the company or a company representative keeps abreast of legislation and changes in the legislation (tracking news and happenings through industry groups or standards organizations allows for cross-pollination of best practices from others in the industry) • Whether there is a company lead responsible for answering questions about the program and whether there is a listing of

If you are facing a government audit or customer inquiry, be responsive, anticipate questions, and assume nothing. Productenvironmental-compliance legislation and customer requirements change continuously. Having an eco-compliance program for products that does the same is critical to continued success. Sharing your plan, execution of that plan, and a general knowledge of the requirements will lessen the corrective actions from an audit or inquiry. Are you sure you have implemented your eco-compliance program successfully? If not, consider a mock audit to get an outside opinion. A mock audit is simple. Someone unfamiliar with the program

looks under the hood to see whether they can understand the basic information about the program. The mock auditor reviews your program and attempts to answer the questions listed above and determine whether you’ve executed a describable, detailed plan that showing the program meets stated requirements.

krista crotty Alberi EcoTech

Krista Crotty holds a B.S. in mechanical engineering and an M.S. in production and operations management. She is the chief eco-geek and managing partner of Alberi EcoTech located in Las Vegas, NV, USA. Krista’s experience crosses aerospace, semiconductor-manufacturing equipment, electrical-component technology and reliability, and motorsports preparation and competition.

For the lab and beyond. The right systems.

The right price.

The right company.

Need to sinter copper or silver ink on flexible substrates? Choose from our family of Sinteron systems to match your research and development needs.

From the benchtop to our largest unit, Xenon Sinteron systems cost a fraction of competitive solutions, while offering the features you need.

Xenon has pioneered the use of photonic curing in numerous industries. Now we’re using our experience to revolutionize sintering for heat-sensitive flexible circuits.

See our video The Future of Flexible Printed Circuits

SINTERON 500

SINTERON 2000 Linear Stage Unit

Learn more about our lowtemperature sintering solutions at www.xenoncorp.com/sinter

Scan this QR code with your smart phone to see the video.

may/june 2011 | 13

FEATURE STORY

Membrane Switch and Touchscreen Basics

This technology overview examines the design, materials, production, and finishing of membrane switches and touchscreens. From “Membrane Switch Basics” Dawar Technologies

he design, prototype, and production processes for a user interface occur at several distinct stages of product development for original equipment manufacturers (OEMs). Typically, the in-house engineering and marketing team of the OEM coordinate the functional and aesthetic requirements for the user interface. These design requirements are then coordinated with the OEM’s contract manufacturer if that is how their assembly normally proceeds. It is very important to allow sufficient time for this process to include changes and prototype stages. Design consultations and a review of material choices and assembly options can reduce costs and assist in compliance with any special requirements, such as environmentally friendly materials. The first step in designing an effective user interface for a product is to determine the functionality desired and what you want the user experience to be with your equipment. Options for user interfaces vary significantly from membrane switches to silicone rubber keypads to touchscreens (Figure 1). These solutions can also be combined to create unique solutions that meet various requirements. This article provides an introduction into the factors that must be considered to develop an effective user interface solution. It all starts with a design. DESIGN ELEMENTS OEMs should require that the membrane-switch manufacturer provide a complete set of drawings (graphic and electrical) for customer review and approval and to retain for records prior to manufacturing. These drawings are the guidelines for production and should have the customer’s approval because these drawings also flow through the shop during production (Figure 2). This provides detailed direction at each manufacturing stage. Figure 1 The first step for designing a touch switch is to determine the desired functionality. Photo courtesy of MacDermid Autotype Inc. 14 | INDUSTRIAL + SPECIALTY PRINTING www.industrial-printing.net

4.724"

CORNER 0" RADIUSS(3X) WITH 0.06 EY 5" K 33 ED 0. S X 0.500" PILLOW EMBOS

Check with the user-interface manufacturer to confirm which file types are supported, and ask for computer-graphics specifications before you begin. Include or embed the fonts with your file, especially when there are specialty or uncommon fonts. It’s also helpful to send a hard copy of the artwork to the manufacturer and a sample of the equipment’s outer bezel to ensure proper fit and adhesion. OVERLAY MATERIALS The overlay is the top layer of a membrane switch that provides the interface between the user and the machine. The overlay creates the final product’s look and feel. It’s the first thing a customer sees and has to be aesthetically pleasing. Look for a contract manufacturer of membrane-switch or touchscreen products to offer a complete line of glass, polycarbonate, polyester, or acrylic materials in various gloss levels, textures, pencil hardness, and other characteristics to meet your needs. If you have special UL or CSA requirements, seek assistance from the manufacturer to meet the required compliance. Two of the most important issues are durability and environmental concerns. Choose a material that will out-live the application requirements. Polycarbonate offers more flexibility with regard to design, but polyester is more durable. For touchscreen applications, a technology with a glass front instead of a polyester front layer may offer advantages. If the application calls for less than 50,000 actuations, polycarbonate is a good choice; otherwise, polyester is the material of choice. Most agree that life-cycle tests show that polyester can be actuated more than 1,000,000 times in a tactile switch without showing signs of wear. For solid tactile feedback in a membrane switch, choose an overlay thickness between 0.0060.010 in. These thickness ranges offer the durability to meet most requirements. Choose between available color-matching systems. Some manufacturers use a computerized color-formulation system to achieve consistent results from one printing to another. The colors on the overlay generally are screen printed on the second surface. The thickness of the overlay protects the graphics from the environment and from operator wear. Selective textures and window-clearing agents are printed on

3.532"

0.531" OW 2.291" XED WIND R TU EX -T N CLEAR NO 2.8385"

1.738" 1.303" .868" .433" 0

1.781" 0.452" 1.617" 0.617" 1.117" 2.234"

Figure 2 A design drawing for a membrane switch as it flows through the shop during production. Graphic courtesy of Dawar. the first surface and UV-cured to produce a durable finish. THE RIGHT ADHESIVE Adhesives for mounting the membrane switch to the housing of the equipment vary in many ways, and selecting the proper one for a membrane-switch application requires consideration of environment, surface appearance, and other performance requirements. Surface contact is fundamental to adhesive performance. The strength of the bond is determined by the surface energy. Adhesives are manufactured for applications according to these three surface categories: metals, high surface energy, and low surface energy. Again, the contract manufacturer or the adhesive supplier offers the most reliable advice on which adhesive to use for each membrane-switch application. EMBOSSING Embossing dramatically enhances the look and functionality of the overlay. Three basic styles of embossing are pillow, rim, and dome. There are two ways to emboss an overlay. Male and female magnesium-

die-set embossing is one method that works for most applications. However, there are height limitations. Embossing height is usually two to two and a half times the material thickness; the minimum width of a rim thickness is 0.05 in.; the distance between embossed objects should be 0.100 in.; and the minimum inside radius should be 0.005 in. Hydroforming is the second method, and it has more design flexibility. Applying heat to the system is recommended for optimum embossing of polyester. CIRCUITS Membrane-switch manufacturers offer one or more of the following: screen-printed, conductive-silver-ink circuits; copper flex circuits; and PCBs (printed circuit boards). The conductive silver can be printed on 0.005-in. polyester, resistance range is <10100 Ω with a rating of 30 volts DC. Copper-flex-circuit base materials are 0.001-, 0.002-, 0.003-, and 0.005-in. polyimide or polyester. Minimum trace width is 0.004 in. with a pitch of 0.004 in. Copper can be 0.5-, 1.0-, or 2.0-oz RA or ED copper. PCBs can be single- or double-sided. Most use FR4, CEM-1, or CEM-4 base MAY/JUNE 2011 | 15

connector, which allows the shield to terminate into the pins of the membrane-switch tail; and wraparound, where the shield layer wraps around the membrane switch and grounds to the enclosure.

material. The minimum trace width for gold is 0.003 in. for hot-air leveling of 0.006 in. Plating thickness can be 1-25 µm. Plating options include copper, carbon, nickel, or gold. Embedded electronics, such as LEDs and resistors, are placed using surfacemount technology, either via in-house pickand-place machines or outside purchased. The surface-mounted device (SMD) adheres to the circuit layer with conductive epoxy and is typically encapsulated with a UV-cured polyurethane.

Tactile and non-tactile membrane switches Non-tactile membrane switches can be designed with a wide range of actuation forces. The actuation force is determined by circuit spacer thickness. If required, a nontactile membrane switch can be designed as thin as 0.21 in. Tactile membrane switches (Figure 3) incorporate a metal dome or a polydome to achieve the desired tactile response. Using different sizes of metal domes or polydomes varies actuation force. Metal domes come in a large variety of shapes and sizes with actuation forces between 180-700 g. Different polydome actuation forces can be achieved by changing the diameter and height of the polydome to meet requirements.

Shielding Seek the advice of the manufacturer on the proper shielding to meet the ESD, EMI, or RFI requirements. There are two common methods of shielding. The first is by using copper or aluminum foil with or without laminated polyester to the second surface. The second method uses screen-printed conductive silver ink in a grid or complete coating of the first surface. The shield can be terminated by three methods: tab, which can be attached to a stud or standoff on the metal backer or the metal enclosure;

Touchscreen basics Many products that may traditionally have been operated with membrane switches now have those capabilities provided with touchscreen products to provide a complete front-panel assembly. The touchscreen has several advantages over other computer devices. Unlike moving a mouse, swiveling a joystick, or pushing a key in a membrane switch to perform a desired function indirectly, users can simply touch an object on a screen. Touchscreens have no moving parts and, therefore, are durable and appropriate

Figure 3 (above) Examples of custom tactile membrane switches. Photo courtesy of MacDermid Autotype Inc. Figure 4 (right) Touchscreens come in many formats from desktop computer screens to handheld smart phones.

16 | Industrial + Specialty Printing www.industrial-printing.net

for frequent use in unlimited applications. A touchscreen can also be operated with a countless menu of screens for which each touch point on the screen can cause the equipment to respond in different ways, unlike the defined position and functionality of a membrane-switch key (Figure 4). The main components of a touchscreen that allow users to operate a device simply by touching an optically clear sensor directly in front of the display screen include the touchscreen sensor, controller, and software driver. The sensor typically is a glass panel with a touch-responsive surface. The controller is a PCB acting as an interface between the sensor and the display. The controller takes information from the touchscreen and translates it into information a computer can understand. The software driver is a computer program that allows the operating system and the controller to communicate and helps the computer recognize input. There are many types of touchscreens. One of the oldest and most common technologies is the four-wire resistive touchscreen. The four-wire resistive touchscreen comprises a conductive bottom layer of either glass or film and a conductive top film layer, separated by small, transparent spacer dots. Voltage is applied across the conductive surface. Any type of probe, finger, gloved finger, credit card, pen, or stylus can be used to apply pressure against the top film to activate the screen. When ample touch pressure is applied to the top layer, the film flexes inward and makes contact with the bottom layer, resulting in a voltage drop. This change in voltage is detected by the controller. By alternating the voltage signal between the top and bottom layer, the X and Y coordinates of the user’s touch are computed. In a film-on-glass (FG) construction, the bottom layer is an ITO-coated glass. In a polyester laminated (PL) or film-filmglass construction, the bottom conductive layer is also polyester. An additional layer of optically clear adhesive (OCA) bonds the bottom polyester layer to a backer typically made of glass or poly material. Editor’s note: This article was created from information excerpted from Dawar Technologies, “Membrane Switch Basics” and in “Touchscreen Basics.” For more information about the source, visit www.dawar.com.

MANUFACTURERS OF CONDUCTIVE INKS ATOTECH www.atotech.com BASF www.basf.com CABOT www.cabot-corp.com CIMA NANOTECH www.cimananotech.com CONDUCTIVE COMPOUNDS www.conductivecompounds.com CREATIVE MATERIALS www.creativematerials.com DECO-CHEM www.decochem.com DOW CORNING www.dowcorning.com DUPONT www.dupont.com ERCON www.erconinc.com IIMAK www.iimak.com METHODE ELECTRONICS www.methode.com NANOGAP www.nanogap-usa.com NANOMAS www.nanomastech.com NOVACENTRIX www.novacentrix.com PLEXTRONICS www.plextronics.com SIGMA-ALDRICH www.sigmaaldrich.com SUNRAY SCIENTIFIC www.sunrayscientific.com TEKRA www.tekra.com THINK & TINKER www.thinktink.com VORBECK MATERIALS www.vorbeck.com XEROX www.xerox.com

MANUFACTURERS OF PLASTICS FOR GRAPHIC OVERLAYS BAYER MATERIALSCIENCE www.bayerfilms.com DUPONT TEIJIN FILMS www.dupontteijinfilms.com MACDERMID AUTOTYPE www.macdermidautotype.com MITSUBISHI PLASTICS www.mpi.co.jp R TAPE www.rtape.com ROWLAND TECHNOLOGIES www.rowtec.com SABIC INNOVATIVE PLASTICS www.sabic-ip.com TEKRA www.tekra.com

HOW MEMBRANE-SWITCH FILMS ARE USED NEIL BOLDING

MacDermid Autotype Inc.

Figure 1 A membrane keypad for a mobile phone base station. Chippenham, UK-based, Fascia Graphics works closely with PowerOasis, a company known for remote base station power. Fascia supplies the company with membrane touch keypads for its PowerOasis Controller D—a new 19” rack-mounted diesel generator management unit. When deployed, this product typically will reduce diesel consumption by at least 50 % and generator maintenance costs by 70 %. PowerOasis has identified the potential future growth for Green Telecoms. There are presently more than 400,000 base stations globally powered by diesel generators, with this figure expected to increase by 50 % over the next four years, as reported by ABI Research. By 2013, Green Telecoms equipment will account for 46 % of the $277 billion telecom infrastructure market, according to Pike Research. Specifically, PowerOasis products and services reduce diesel consumption for remote mobile phone base stations by supplementing or replacing diesel generators with wind and/or solar renewable energy and by intelligently managing diesel generators when present. PowerOasis has already deployed systems for Digicel Vanuatu, Dialog Sri Lanka, T-Mobile Montenegro, Vodafone Qatar, Samsung South Korea, and it is also part of Alcatel-Lucent’s Alternative Energy Test Program.

POWEROASIS AND FASCIA GRAPHICS PowerOasis identified Fascia Graphics in May 2009 through an internet search for local manufacturers of graphic overlays and membrane keypads. “It was crucial that we also embodied our brand into the design; to stand out from the other 19” units on the market. The general design was undertaken by our graphic design company, and then converted into engineering drawings by Fascia Graphics,” said Ivan Harris, chief marketing officer of PowerOasis Fascia Graphics has established relationships with the leading suppliers in the market and was able to incorporate Autotex Steel from MacDermid Autotype as the graphic overlay material. This hardcoated polyester film produces stainless steel eff ects for membrane keyboards, keypads, and fascia panels. It can be embossed, making it applicable for use with domed tactile membrane keypads or in applications where keys or panel areas need to have raised edges (Figure 1). Its outer surface also off ers resistance to abrasion and a wide range of chemicals and solvents. Therefore, it suits the rigors of being mounted on a mobile phone base station.

MAY/JUNE 2011 | 17

Membrane switCh and touchscreen basics Glossary of Terms ABRASION RESISTANCE Ability to resist surface wear. ACCELERATED AGING A test method that simulates long-term environmental effects. ADHESION The molecular force of attraction between unlike materials. The strength of attraction is determined by the surface energy of the material. The higher the surface energy, the greater the molecular attraction. The lower the surface energy, the weaker the attractive force. AMPERE (AMP) A standard unit of current. Defined as the amount of current that flows when one volt of EMF is applied across one ohm of resistance. An ampere of current is produced by one coulomb of charge passing a point in one second. AQL Acceptable quality level. ASTM American Society for Testing and Materials International. AUTOTEX Trademark for textured polyester graphic overlay film from MacDermid Autotype Ltd. BOND STRENGTH Amount of adhesion between two surfaces. BREAKDOWN VOLTAGE The voltage at which the insulation between two conductors is destroyed. CAD/CAM Computer-aided design/computer-aided manufacturing. CAPACITANCE The property of conductors and dielectrics that allows the storage of an electrical charge when voltage is applied. See ASTM F1663-95. CARBON/GRAPHITE INKS Specially prepared suspensions of carbon black. These systems are used for lowering cost when the conductivity of a metal base system is not required. Often printed over silver circuitry to reduce the potential for silver migration. Also used for printed resistors. CERTIFICATE OF COMPLIANCE (C OF C) A certificate generated by a quality control department confirming that the product being shipped meets the manufacturing document. CONDUCTIVITY The ability of a material to allow electrons to flow measured by the current per unit of voltage applied. CONTACT BOUNCE Intermittent contact opening and closure that may occur after switch operation. See ASTM F161-95. CSA Canadian Standards Association. CURRENT, ALTERNATING (AC) An electric current that periodically reverses direction of the electron flow. The rate at which a full cycle occurs in a given unit of time (usually a second) is called the frequency of the current. CURRENT, DIRECT (DC) Electrical current whose electrons flow in one direction only. It may be constant or pulsating as long as its movement is in the same direction.

DEAD FRONT Cosmetic feature of a graphic overlay allowing for a display feature to be visible only when backlit. DIE CUTTING Process for blanking or cutting sheet or roll materials to predetermined shapes for membrane switch components, graphic overlays, and labels. DIELECTRIC An insulating (non-conducting) medium. DOME RETAINER An adhesive layer designed to hold metal domes in keys. EL LAMPS A thin (0.010- to 0.025-in.) illuminating devices used to light large areas, commonly used in LCD, control panel, and membrane switch backlighting. EMBEDDED LED The practice of encapsulating a surface-mount LED into a membrane switch construction. EMBOSS Mechanical and thermoforming of graphic features, providing a raised feature for accenting key surfaces, logos and to allow for embedding of surface-mount LEDs within the switch. EMBOSS, RAIL Creates a raised ridge around the perimeter of the key area. EMBOSS, PILLOW Creates a raised surface in the graphic overlay over the entire key area. EMI/RFI/ESD SHIELD Printed conductor pattern or separate aluminum or copper film employed in membrane switch designs to reduce the effects of electromagnetic and radio frequency interference. FIBEROPTIC BACKLIGHTING Illuminating device used to light large areas. Strands of clear fiber are woven and bundled, after polishing the fiber ends are illuminated by an LED or halogen lamp. FLAT FLEX CONNECTOR (FFC) Connector type commonly used to terminate membrane switch circuitry. FONT A set of characters having a unified design. GLOSS LEVEL The degree of shininess of a substrate, usual specified in percentages, for example, 75% gloss, 90% gloss. HB-94HB Underwriters Laboratories flame-retardant specification (horizontal burn). HSE High surface energy. INSERT LEGEND (INSERT GRAPHICS) A design feature allowing for changes to nomenclature and symbols by the client or end user. The feature is accomplished by creating a pocket in the membrane switch assembly to allow for an insert card. INTERNALLY VENTED Switch openings are connected to each other but not to the outside atmosphere. This design approach is used to seal the switch from moisture and contaminants.

18 | Industrial + Specialty Printing www.industrial-printing.net

ISO International Organization for Standardization. Known for the development of a series of standards called ISO 9000 for developing Total Quality Management, and creating a continuous Quality Improvement Process. ITO Indium tin oxide, a thin-film conductive material vacuum deposited on the surface of a film substrate. Material is often the base material for resistive touchscreens. KEY HEIGHT The measured distance from the bottom (base) of the keypad to the top surface of the key. KEY TRAVEL The distance a switch moves to close an electrical contact, expressed in inches or MM. LED Light-emitting diode. LEXAN Sabic, formerly General Electric registered trademark for polycarbonate film. LSE Low surface energy. MEMBRANE SWITCH A momentary switching device in which at least one contact is on or made of a flexible substrate. METAL DOME Stainless-steel disc or element. One of several approaches used to produce tactile response. MOISTURE RESISTANCE The ability of a material to resist absorbing moisture from the air or after immersion in water. MP Modified performance. An adhesive classification of 3M products. MUNSELL Color-matching system that defines color by three attributes: hue, value, chroma. Fifteen hundred color samples are available as opaque pigmented films. MYLAR DuPont trademark for polyethylene terephthalate (polyester) film. NEMA National Electrical Manufacturers Association. NON-TACTILE Membrane switch constructed without snap action. OHM The electrical unit of resistance. The value of resistance through which a potential difference of one volt will maintain a current of one ampere. OVERLAY Decorative front layer of a membrane switch or control panel. OVER-TRAVEL The additional travel of a rubber keypad or metal dome after making contact with the circuit. PANTONE MATCHING SYSTEM (PMS) Color-matching system originally developed for the offset printing industry, commonly used in the membrane switch industry for its broad acceptance, range of colors, and ease of use. PCB Printed circuit board.

Membrane switCh and touchscreen basics Glossary of Terms PINOUT The schematic describing the circuit-output requirements for a membrane switch or another electronic device. POLYCARBONATE Graphic-overlay film wide used for control panels. POLYESTER DOME A spherically formed element in polyester circuit material to provide tactile response in membrane switches. Usually the domes are formed in arrays or sets to match the key configuration of the keypad. POLYESTER Bi-axially oriented polyethylene terephthalate film (PET). PRESSURE SENSITIVE Adhesive materials that bond with the application of pressure alone and do not require activation by heat or solvents. RESISTANCE In DC circuits, the opposition a material offers to current flow, measured in Ohms. RFI Radio-frequency interference SCREEN PRINTING Print process using mesh stretched over a frame, allowing ink to selectively pass through by using a stencil. The process commonly used for producing graphic overlays and membrane-switch circuits.

SECOND-SURFACE PRINTED Inks are applied to the non-exposed side of the film to allow for the film to protect the inks from scratches or other damage. SELECTIVE TEXTURING The creation of surface effects on matte or gloss films normally applied using the screenprinting process. SILICONE RUBBER Rubber made from silicone elastomers and noted for its retention of flexibility, resilience, and tensile strength over a wide temperature range. SILVER INKS Specially prepared suspensions of finely milled silver particles in a variety of resin systems used to produce conductive patterns on flexible substrates. SPACER An adhesive layer of a membrane switch used to separate circuit layers and to provide key openings allowing for conductors to contact each other when depressed. STATIC SHIELD Printed conductor pattern or separate aluminum or copper film used in membraneswitch designs to reduce the effects of static discharges. STEEL RULE DIE Consists of a 0.750- to 0.875-in.-thick dieboard of plywood construction with 0.37-in.high knives inserted into laser-cut grooves.

TACTILE SWITCH A switch or switch assembly providing a positive snap-action response. The response can be achieved through the use of stainlesssteel domes embedded in the membrane switch or polyester domes formed in either the circuit or graphic-overlay layers. THIXOTROPHY The property of becoming fluid when disturbed, as by shaking. VISIBLE LIGHT TRANSMISSION The ratio of the amount of total visible solar energy (370-780 nm) that is allowed to pass through a filter, to the amount of total solar energy falling on that filter. WATT A unit of electrical power that is equivalent to the power represented by 1 amp of current with a pressure of 1 volt in a DC circuit. ZIF Zero insertion force.

Mimaki_UJF706_H_ISP10.qxd:Layout 1 4/14/10 3:52 PM Page 1

Gimorevinperformance, g you more opti o ns per square i n ch... more resolution, more vibrant color, more versatility, INDUSTRIAL FLATBED PRODUCTS APPLICATION

LOW VOC UV INKS

ULTRA-HIGH RESOLUTION

more choices, more speed,

The UJF-706 is a newly developed, higher speed UV curing flatbed printer for industrial applications.

APPLICATIONS: • POP & POS Displays • Promotional Products • Packaging Proofs & Prototypes • Industrial Applications & Signage • Membrane Switches • Nameplates & Plastic Cards

u Prints on substrates up to 5.9” thick including non-coated. u Vivid prints on transparent materials with white ink underprint function. u Uses hard or flexible inks. u Four point optical positioning recognition system; 1200x1200 dpi resolution. u Satellite drop-free printing with Spray Suppressor System. u Optional roll media printing.

Industrial UV Flatbed

...because more is what we do.

For inquiries outside the USA: Mimaki Engineering Co., Ltd. • 2182-3 Shigeno-otsu, Tomi-city, Nagano 389-0512 Japan • Ph: +81-268-64-2281 Fx:+81-268-64-2285 www.mimaki.co.jp

888-530-3988 888-530-3986 888-530-3985 888-530-3987 w w w. m i m a k i u s a . c o m ATLANTA: BOSTON: CHICAGO: LOS ANGELES:

may/june 2011 | 19

cover story

Sintering Nanoparticle-Based Inks on Challenging Substrates Exposure to extreme processing environments is a major roadblock that stands in the way of using thin, temperature-sensitive materials in the production of printed electronics. Discover the ways in which photonic sintering can clear a path to success. Saad Ahmed Xenon Corp.

20 | Industrial + Specialty Printing www.industrial-printing.net

Sintering nanoparticle-based inks Nanoparticles are defined as particles as small as 1-1000 nm. In general, particle sizes up to 100 nm most commonly fit the description. A particle’s physical characteristics change as it becomes smaller, including absorption characteristics and melting point (Figure 2). Melting-point depression is a phenomenon expressed by metal nanoparticles. In normal scales, the melting point of the material does not depend on size. As particles become smaller, their surface-area-to-volume ratio changes such that the atoms on the outer surface become more loosely attached, which causes the melting point to decrease. Lowering the melting point allows the use of a low-bake oven—a system that maintains a temperature below 200oC—for sintering nano-inks without damaging the substrate. The time required for this process is approximately 10 minutes and, therefore, makes high-speed roll-to-roll processing difficult. Nanoparticles absorb light (Figure 3) and react by heating up. Melting-point depression and light absorption allow nanoparticles to be sintered effectively with high-energy light sources such as lasers or flash lamps. Using flash lamps is simpler, particularly when

Substrate

Substrate Deposit Copper layer (Vacuum Sputter)

Print traces with Ink Sinter (High energy Pulsed light)

Deposit Etch Resist

Light Mask

Etch (Chemical)

Figure 1 A standard printing process (left) compared to photonic sintering (right)

Tm /TMB

Figure 2 The influence of particle size on the melting point of gold

100 150 Particle Diameter (nm)

22 nm

99 nm

48 nm

.2 350

200

Figure 3 Absorbance spectra of gold with particle size

9 nm

absorbance

e live in a world surrounded by electronics. Even though the technology for manufacturing devices and components has advanced in leaps and bounds, the basic printed circuit board (PCB) has not changed significantly. The process of applying photo resist to a sheet of copper that is fixed on a rigid board and using a photo-lithographic process with a chemical-etch process to create tracks and pads to form interconnects between components is still the most common way of building PCBs. Conventional PCB creation is a subtractive, multistep process that requires chemicals, is wasteful of copper, and does not lend itself to a high-speed, low-cost solution. In some special cases, flexible or rigid-flex PCBs are used, but they are based on the same principles of standard PCB manufacture but use flexible plastic substrates instead of rigid materials. An alternative approach to PCB manufacture is to print the copper traces on the substrate rather than etch away unused copper (Figure 1). This would be a totally additive process and would eliminate the need for lithography and etching. High-speed printing processes could then be used to mass produce circuit boards at a very low cost. Low-cost substrates such as paper or PET could be used to produce circuits that are cheap enough to be disposable; however, we must overcome some significant challenges to achieve that goal. The most important challenge is that of resistivity. Copper, silver, and gold, which are often used in PCBs, are very good conductors and have very low resistivity. This property allows circuits to run more efficiently. Conduction though metals is possible because electrons are free to move about the metal lattice. Resistance increases when metal clusters are deposited in ink form because the lattice is disjointed. Gaps and voids between metal particles do not allow for the free movement of electrons, which causes increased resistance. Ideally, the metal particles would be melted together or sintered to form a homogenous strip of metal to achieve better resistivity. However, melting points of metals are typically very high. Gold, as an example, melts at 1064°C, and this amount of heat means that lowtemperature substrates, such paper and PET, are not useable. But all of this has changed with the advent of nanoparticle-based inks.

400

450

500

550 600 650 wavelength λ/nm

700

750

800

large-area processing is required. In addition, the use of a broadband source, such as a xenon flash lamp, is more effective for inks that have a spread of particle size and a wide absorption region. Nanoparticles lose their properties once they are sintered, and they behave similar to bulk materials. The process is, therefore, self-limiting in that multiple flashing does not improve the resistivity significantly and limited sintering takes place. This behavior raises an important challenge in the use of pulsed light for sintering related to stitching. All light sources have a limited exposure area. The boundary between the exposed area and unexposed area creates partial sintered regions. The overlap region is defined as the stitch when two adjacent boundaries are flashed. These partially sintered regions, when flashed again, behave differently from the fully exposed areas. This change is observable as differences in resistivity across the stitch region. Careful control of the boundary profile, light energy, and overlap can reduce the effect of stitching significantly. However, the most significant factor is the nano-ink may/june 2011 | 21

Substrates Substrate selection is another important factor. Interestingly, paper and specially coated paper are very good substrates because they can absorb the ink and wick away the carrier agents in the ink. This allows the ink to dry effectively and improves ink adhesion. PET and Teflon are also good substrates to use because they are good insulators and, therefore, allow more photonic energy to be absorbed by the ink rather than the substrate. These substrates are often transparent, which means they absorb less light and, in doing so, allow for greater amounts of pulsed-light energy in the sintering process. Print-related anomalies are less tolerable when dealing with functional inks. Errors in printing can lead to short and open circuits and, if critically located, can render the printed electronic circuit unusable. Ink-layer thickness, which affects resistivity, also becomes more critical. Most PCBs are based on two or more layers of conductive traces with vias between them. As circuits become more complex, the trace width, gap between traces, and via sizes are made smaller. High-precision printing is required to overcome the challenge. However, multilayer printing on flexible substrates brings an additional problem to the forefront: substrate expansion. When PET is used in a roll-to-roll application and is drawn through the printing process, the material is under tension, which causes elastic deformation. Heating the material can increase this single-axis deformation. Failure to account for this deformation leads to mismatched layers and a loss of connectivity. Placement of ICs and other components is another consideration when working with low-temperature, flexible surfaces. Soldering, which is the traditional method of connecting devices to PCBs, is less suited to the application because it would damage the low-temperature substrate. Special conductive pastes are used to overcome this issue; however, the challenge of achieving solder’s low resistivity remains. Semi-conductive inks The use of conductive inks has allowed development of simple components such as switches, resistors, capacitors, inductors, and antennae. One challenge that still exists is the develop22 | Industrial + Specialty Printing www.industrial-printing.net

Relative Irradiance

.75

.50

.25

UVC

200

UVB UVA

300

400 500 600 wavelength (nm)

700

800

Figure 4 Spectra of a xenon-arc flash lamp Amplitude (Watts) 400,000

Single pulse, 1200 Watt-seconds, .003 seconds duration Multiple pulse train, 100 Watt-seconds/Pulse, .001 second duration 28,000 Watt-seconds continuous radiation

100,000 0 0

100 140 180 Time (seconds)

220

260

280

Figure 5 Pulsed vs. continuous light

100% Relative Transmission

formulation used. Inks designed for multiple flashing generally mitigate the effects of stitching. Resistivity of sintered inks is generally higher than that of bulk material because of the final material’s remaining porosity after sintering. Resistivity values of four to five times that of bulk is considered a good result. Some self-drying inks can achieve resistances of six times bulk. Photonic sintering to date has achieved results ranging between three and five times bulk for certain inks. Ink formulation plays a major role in photonic sintering. The ink-deposition method must be suited to the ink in terms of viscosity and surface tension. The formulation also determines the drying time for the inks and the adhesion of the ink to the substrate. Photonic sintering performs better with dry ink because pockets of solvent that are trapped in the ink are likely to expand and erupt when exposed to a high-energy light pulse. This causes inks to blow off of the surface, which leads to a reduction in resistivity.

UV Energy

Visible Spectrum

80% 60%

Lamp

Spectral Cut-off

40%

370nm

240nm

190nm

20%

150 200 250 300 350 400 450 500 550 600 650 Wavelength (nm) Figure 6 Envelope cut of spectra ment of semi-conductive inks for the fabrication of components such as transistors, LEDs, sensors and ICs. Bonding conventional, silicon-wafer-based devices to low-temperature substrates is a challenge because these devices typically are rigid. One way to overcome this is to make a silicon wafer sufficiently thin so it too becomes flexible. Wafer thinning can create silicon wafers that are around 50 μm thick, allowing them flexibility and enabling direct bonding to the substrate using conductive adhesives. Organic semi-conductive inks exist, but their use in development of ICs is limited not only by the issues of registration mentioned above, but also by the feature size achievable by the printing process. The simplest functional IC can have hundreds—if not thousands—of

transistors, and a silicon wafer can have a footprint a few nanometers. Conventionally printed transistors carry a footprint size in the range of tens of microns at best. Even the simplest IC can take up a few centimeters of real estate in circuits where even a single print defect can produce non-functional results. Therefore, it does not seem feasible to make fully functional circuits on flexible substrates at this time, but rather more practical to address the issues of bonding silicon wafers and other active components directly onto the substrate that has traces formed by regular printing. Flash-lamp technology Flash lamps have the ability to generate light with wide bandwidth spectra, from deep UV to infrared (Figure 4). High-energy xenonarc flash lamps can generate high-peak power pulses and are capable of delivering significantly greater peak energies compared to continuous sources like mercury, fluorescent, or halogen lamps by storing energy over time and delivering it as a short-duration, high-intensity pulse. This high-peak pulse energy is sufficient to cause sintering to take place. Xenon-arc lamps generate light by using high voltage to break down the inert gas within the lamp envelope, thereby creating a conductive discharge path where the flash exists. Very short on times enable flash lamps to deliver high peak photonic power effectively without a dramatic increase in substrate surface temperature (Figure 5). Typical on times can be in the order of a few microseconds to milliseconds with duty cycles ranging from tens of hertz to a few hertz. Peak powers of a few megawatts can be generated in these very short durations. Flash lamps can be tailored for specific applications and deliver repeatable and uniform intensities over a broad spectrum by adjusting voltage and current delivery through the lamp. These are ideal characteristics for sintering applications where adjustment of peak and total energy must be made for different samples. High peak power means greater penetration depth and sufficient energy for useful workâ&#x20AC;&#x201D;particularly in the case of sintering. Lamps are manufactured with a low-pressure xenon gas inside a transparent envelope. There are two electrodes, typically made of different materials. The cathode is typically barium doped and designed to have a low work function for the generation of electrons, whereas the anode is usually made of tungsten to sustain the bombardment of electrons during a flash. These lamps do have a polarity, and improper connection of the lamp can cause lamp damage and early lamp failure. Metal particles are deposited on the lampâ&#x20AC;&#x2122;s glass as electrodes age or are damaged during normal use. This, as well as other forms of lamp aging, results in a fall-off in intensity. Lamp life is usually reported in millions of pulses in typical use and is approximately the number of pulses for the lamp to remain within 20% of its initial intensity. This value changes based on the energy of the pulse and cooling. Lamp life can be extended significantly by driving the lamps with lower energy. The lamp envelope defines the physical lamp profile. The material used for the envelope can define the output spectra from the lamp (Figure 6). Clear fused quartz (CFQ) is used when deep UV is required, but high-energy flashes from this source can generate significant amounts of possibly undesirable ozone. Alternatives include doped quartz tubes that block UVC and, therefore, do not generate ozone. Envelope thickness, bore diameter, length, and gas pressure are important parameters in defining the optical power that can be generated safely by the lamp. A theoretical limit called the explosion

energy for the lamp is a function of some of these parameters and is the energy that can destroy a lamp catastrophically. Typical operation of the lamp is set at 10% of this explosion energy. Electronics used to drive flash lamps can be quite simple: a high-voltage supply, a storage capacitor, a pulse-forming inductor, and a trigger circuit. However, the systemâ&#x20AC;&#x2122;s high power requirements require special designs to account for safety, noise, and power management. As mentioned earlier, lamp cooling is a very significant component of the optical system and sets the operational limits of the lamp and affects lamp life. Forced air for cooling offers the simplest solution for most applications. Water-cooled flash lamps offer higher power solutions, but they tend to be more costly and complex. Maintenance of a water-cooled system is also more complicated and required operators to manage the risks associated with the close proximity of water and high voltage. Photonic sintering in roll-to-roll printing Simplicity is the key to successful deployment of photonic sintering in roll-to-roll printing. The solution offered by photonic sintering from this perspective looks very attractive. First, we have an inkdeposition phase that lends itself to standard printing processes, followed by a standard ink-drying phase. The only additional step is the photonic-sintering phase, which can be as easy as a retro fit of a flash-lamp system over the printing web. There are no additional process requirements like pressure, special gas, or chemicals. Dwell time in photonic sintering is not an issue because the reaction is instantaneous as opposed to thermal sintering, which can take minutes. Pulse rate, however, is critical to controlling the overlap of photo-sintered regions and avoiding overexposure or banding when a gap exists between the two adjacent regions. Scalability becomes an important factor from the standpoint of versatility, especially when considering different roll-to-roll speeds and ink formulations. Photonic sintering systems can be scaled easily by increasing the number of lamps required for a given process speed. A flexible solution for numerous applications Low-temperature photonic sintering is compatible with a variety of substrates and functional inks, including silver flakes, ITO, and copper, silver, and gold nanoparticle-based inks. The development of new, flexible tools that can help process developers, ink formulators, printing-equipment manufacturers, and end users evaluate the technology rapidly and find solutions for their specific needs is the ultimate key to successful deployment of photonic sintering in the production arena. It is clear that photonic sintering will play a major role in the production of flexible electronics and will have farreaching consequences in the production of electronics and in our everyday lives in the near future.

Saad Ahmed, Ph.D. Xenon Corp.

Saad Ahmed is engineering manager at Wilmington, MA-based Xenon Corp., a developer of pulsed-light solutions for a variety of industries. His expertise includes R&D, product conceptualization and design, and more. Ahmed earned a Ph.D. in electrical engineering from the University of Liverpool, UK. may/june 2011 | 23

FEATURE STORY

SPECIALTY SUBSTRATES

Growing Applications for 21st Century Industrial Printers

lobal projections from a cross section of major industrial segments (automotive, consumer, aerospace, government pharmaceutical, textile, etc.) indicate that the 21st century will present widespread opportunities for industrial printing with innovations in printable electronics—also known as organic electronics. This glowing future includes applications in solar energy, medical sensors, smart labels, new generations of miniaturized computers, media players, smart phones, and even virtual battlefield weaponry. The list seems endless. In addition to futuristic applications, these technologies are already in use in medical, military, outdoor displays, flatscreen televisions, and solar applications, among others—each with enormous potential for sustained growth. The majority of these futuristic applications will be manufactured by printing on plastic films, dramatically changing the manufacturing landscape for capital intensive and cumbersome silicon-chip foundries, and electronics contract manufacturing as we know it (three or four orders of magnitude less expensive). This promise of the future will use enhancements of today’s printing technologies, with different inks, printing-process controls, and printable substrates—enhancements that increase reproducibility and print-quality reliability, while lowering cost and ultimate size of the final products. Specifically, this widening use will require highly specialized substrates. There are

dozens of such substrates commercially available today, with tongue-twisting chemical names, such as polybenzimadazole, polyimide, polyetherimide, polyetheretherketone, polyethylene naphthenate, and so on. Not surprisingly, each of these materials has acquired acronyms, such as PBI, PI, PEI, PEEK, and PEN, respectively. So what are the differences between these exotic materials, and which characteristics create differences in performance, cost, and other factors? WHAT ARE SPECIALTY SUBSTRATES? In my opinion, a specialty substrate is one that a printer is unfamiliar with, based on its performance characteristics and associated costs in the field and on press. Moreover, many label producers try to avoid so-called specialty substrates, because they have stereotyped them as too expensive. When customers require specific performance characteristics that are not available with conventional, less expensive materials, the customer will pay for that value-based product because of performance, not a product at commoditized prices. The business model is as different as are the performance characteristics. SPECIALTY SUBSTRATES ARE NOT ALL THAT DIFFERENT Printing on specialty substrates for any industrial, or harsh environment is no different from printing on conventional, familiar substrates, such as PET and PVC,

24 | INDUSTRIAL + SPECIALTY PRINTING www.industrial-printing.net

This article describes the differences between specialty and conventional materials and discusses the roles these materials play in printed electronics.

James R. Williams, Ph.D. Polyonics, Inc.

among others. The print quality and image durability must meet either specific, customer-defined criteria, or other, well characterized criteria (UL 969, MILPRF-61002, and others). Typically, both of these must address the usual destructors of printed products: abrasion, extreme temperatures (both hot and cold, as well as maxima and minima) and duration of exposure to these conditions and exposure (and its duration) to chemicals, solvents, acids, caustic, oxidants, and any other process used in handling, manufacturing, or distributing the products and its printed surface(s). Given the nature of automated or conveyorized manufacturing operations, sequential exposures and other operations must be taken into account. Higher performance requirements for a substrate generally result in higher substrate cost, compared to substrates with lower performance. However, unused features, including excessive margins of safety, offer only higher prices—that is, the application is over-engineered. Perhaps the most critical step in material selection is to define the performance characteristics that cannot be compromised under any circumstance. Can some specification requirements be loosened or minimized to lower cost without affecting performance appreciably? Simultaneously, when higher performance is inherently available in the specialty substrate, and it delivers the value required to satisfy the performance requirements, the customer will pay more

for it. In my opinion, the burden is on the printer to educate himself, his company, and the customer about the tradeoffs and issues of the specialty material to show the value of that substrate for the application at hand. Some paradigm shifts are required We all know that excellent print quality requires proper matching of the ink(s) with the printing process used and the substrate surface. We use specific physical criteria, such as viscosity, solids content, pigmentparticle size, distribution and uniformity of dispersion, and pot life, for each ink to ensure its general suitability for the printing process we plan to use. Moreover, we know that print quality and image durability rely on the chemical compatibility between the ink and the surface of the substrate—the proper matching of the surface tension of the ink and polymer systems with the surface energy of the substrate, as well as compatibility of the binders with these same surfaces in the dried/cured printed image. We all agree that poor print quality means poor aesthetics and appeal. However, in the projected brave new world of printable electronics, the ultimate criteria for success will change from how good it looks aesthetically to how well it performs electronically. In the future, poor print quality will mean inconsistent product performance or short product lifetime or failure due to poor signal quality, rather than a cheap appearance due to poor aesthetics. The critical difference is that the printed images, circuits and components, are functional—that is, they perform work rather than project aesthetic appeal. Compromising that function for any reason unequivocally means marginal or intermittent circuit performance. This new era of printable electronics requires additive processes because electronic components such as resistors, capacitors, power sources, and the like will be printed directly on the substrates, along with the conductive elements for the connections between components. This direct printing eliminates multiple process steps used in etching of circuits, a subtractive process, followed by sequential component placement, soldering, etc., thereby reducing overall product costs. Smaller form factors result, which in turn create new market opportunities for electronic products.

Success requires that specific choices be made from a broad array of specialty inks, coatings, and substrates that are compatible with the printed patterns (circuits and components) to deliver the wide range of electrical responses required for electronic performance. This also requires understanding and control of the substrate’s surface uniformity and smoothness. For example, in printed-electronics applications, a highly planarized PET is a specialty substrate for printed electronic products, because of the performance requirements of the circuits in the final device, compared to PET—a commodity for most applications. The driving force for print quality is the fidelity (purity or clarity) of the electronics signal(s) in the circuitry. Because the circuits and components are now printed with functional inks, the results of each printed area depend on the specific properties and the amount of the material used. For example, a surface coating can be changed from a conductive one (surface resistivity between 1 x 102 - 1 x 105 Ω)3, to static dissipative (surface resistivity between 1 x 105 - 1 x 1011 Ω)3, to a dielectric/insulative one (surface resistivity > 1 x 1011 Ω)3 in one of three ways:

• Composition and concentration of the functional materials used • Coating thickness, ranging from Å (angstroms) to nm (nanometers), to µ (microns) • Surface uniformity, or planarity—surface roughness causing variations in coating thickness. Different materials in an ink or coating determine the resistivity of the printed image. Indium-tin oxide (ITO), carbon black, PEDOT, carbon nanotubes, nanoparticle silver, and many others are typical of conductive materials from which we can choose. Each has strengths and weaknesses, depending upon the requirements under consideration. Not surprisingly, each is used at different concentrations in a given ink formulation to support the required functional performance within the technical limitations for each material. Likewise, each specific printing process lays down a different amount of ink, which results in a different amount of conductive material being deposited from one process to another. Less conductive material available for circuit continuity generally means higher circuit resistance and/or lower signal fidelity. Variations in coating thickness

Figure 1 Visualizing the several layers of printed electronic devices may/june 2011 | 25

WVTR (g/m2/day)

Application(s)

<10-6

Organic bio-sensors

OLED displays

10-5 – 10-6

OLEDs

10 – 10

Organic solid state lighting

Solar cells organic photovoltaics

<10-3

Thin-film batteries

Inorganic photovoltaics (2nd generation)

<10-2

Sensors, electrophoretic

<10

Sensors & devices

RFID electrochromic displays

Medical packaging

Food packaging

-4

<10

-1

-5

-4

-1

Table 1 Market segments defined by barrier performance

from point to point along a circuit, due to surface-area roughness, also contributes to decline of signal purity. The ink will be thicker in rough areas as it tries to flow into peaks and valleys, compared to a smoother area. Finally, it is clear to all of us that the compatibility of the ink with the substrate determines the surface-contact area between the two layers, as well as the adhesion strength between them. As noted above, surface smoothness also influences coating thickness and uniformity. Specialty substrates play a critical role for the success of printable electronics. A typical electronic device is truly built in layers (Figure 1). The printer builds the components layer by layer on the board, which is now a plastic film. The subtleties of the printed circuitry and components each require specific ink and/or substrate characteristics, as layers of printed components are registered upon other layers of printed components and circuits. Alignment problems with membrane-switch assemblies promise to be child’s play compared to the alignment of coating patterns as resistors, capacitors, and diodes are printed one layer over another in very tight registration, along with precise connection—again, by printing—with the conductive paths of the circuits. Dimensional stability of the film provides the mechanical and thermal stability for the device. These characteristics influence not only print-to-print registration during printing processes, but they also determine processing and end-use temperatures for the products. Physical surface properties in terms of roughness and physical cleanliness influence the layer quality of the printed matter on the substrate

surface dramatically. Compatibility of the inks and coatings with the substrate—surface energy and solvent resistance—also influences layer quality. Chemical resistance is important because components are overprinted in discrete layers one upon the other. Finally, barrier properties of each substrate chosen determine the type of device that can be manufactured. Just as components today are encapsulated (resistors, chips, LEDs, diodes, etc.) to protect them, the new components and circuits must be protected as well. In addition to heat, dust, and UV radiation, the worst enemies of the new electronics are water vapor and oxygen, which can interfere with or destroy the performance of the new-era electronics. In general, it is widely accepted that for printed electronic devices to be viable, the barriers for oxygen exposure (known as the OTR, or oxygen transmission rate) should be on the order of 10 -3-10 -5 cc/m2/day, and for water vapor (known as the WVTR or water vapor transmission rate), on the order of 10 -3-10 -6 g/m2/day. To put this in perspective, many films forpharmaceutical and food packages that printers already use, such as metalized mylar or high-tensity-oriented polypropylene, require OTRs in the range of 10 0 -10 -2 cc/m/day and WVTRs between 10 -1-10 -3 g/m2/day. Different types of electronic devices require different levels of protection. For example, Table 1 shows market-segment definition based on the protection against water vapor. To summarize, there are a stack of engineering criteria that must be considered when selecting the optimum substrate for each printable-electronics requirement:

26 | Industrial + Specialty Printing www.industrial-printing.net

• Low coefficient of thermal expansion • Low shrinkage at appropriate temperatures • Upper temperature for processing • Surface smoothness • Barrier (OTR, WVTR) • Solvent/chemical resistance • Moisture resistance • Clarity • Transparency • Rigidity • Commercial availability The entire stack must be considered in the context of processing and use environments when selecting substrates for printed-electronics applications. From this perspective, each new electronic product may require its own unique specialty substrate. As applications progress from simple circuitry to those with organic active matrix (AM) backplanes, to inorganic AM backplanes, to OLED lighting, the substrate structure necessarily becomes more complex, requiring a more demanding property set from the stacks listed above. In closing, I will reiterate that even these specialty substrates are not all that different from the ones we are comfortable with today. Based on years of experience in working with plastic films, such as PET, we take for granted many of the properties highlighted above; or, they are not important for success in our traditional business. It is our technical and process-related understanding of the differences required for proper printed functionality—compared to printed appearance—that must change. We can accomplish this by educating ourselves, our colleagues, and our customers about these new materials and processes, using common sense, controlled process experimentation, and realistic expectations.

James Williams, Ph.D Polyonics, Inc.

James Williams, Ph.D, is founder and chairman of Westmoreland, NH-based Polyonics, Inc., a manufacturer of specialty film, tape, tag, and label materials for industrial printing applications. He holds a Ph.D. in chemistry from the University of Massachusetts, is actively involved in a wide range of industrial printing technologies and their commercial development, and is a featured speaker at many printing symposia and technical conferences. He can be contacted at jim.williams@polyonics.com.

ANNOUNCING... A new Website that speaks to the unique needs of industrial printing facilities

Late-breaking news Features Editorials New products Calendar Classiﬁeds Free posted user forums

Advertising Opportunities Contact Steve Duccilli 800.925.1110 x344 513.263.9344 steve.duccilli@stmediagroup.com

www.facebook.com/iSPmag www.linkedin.com/ groups?gid=2658424

password

username

Printing equipment used in manufacturing News & Trends

Products

INDUSTRY UPDATE

Message Boards

PROD

Top Stories • Printing Photovoltaics Screen printing photovoltaic cells is the most reliable method and fastest growing application in industrial printing.

Text

• Automating Your Pad-Printing Operation Automation is an important part of efﬁcient, consistent pad printing. Find out about some of the options designed to enhance speed and precision for industrial applications. • Membrane Switch: Screen Printing 101 The membrane-switch market has experienced dramatic growth and soared to an unprecedented level. • Industry Insider The Importance of Printed Electronics to P&G

Subscribe Today March/april 2010

www.industrial-printing.net

www.twitter.com/iSPmag printing photovoltaics P. 22

Co De Fin Ho InInk

TECHNIQUES, TIPS & APPLICATIONS

FEATURE STORY

Roll-to-Roll Printing in Electronics Applications

This article describes the current state of roll-fed electronics printing and discusses what we may expect to see in the near future.

Deokkyun Yoon and Dong-Soo Kim Korea Institute of Machinery and Materials

he printed-electronics field is garnering attention from entrepreneurs, investors, and researchers around the world. This field of industry is multidisciplinary; as such, combined knowledge in machinery, materials, manufacturing process, and business is necessary to deliver the right product to the right market. As the name suggests, printed electronics involves using a printing process in the manufacture of electronic devices and products. These processes include gravure, offset, flexography, inkjet, screen printing, and many more. Some technical challenges arise from the use of printing in producing electronics. We discuss them further on in this article. At this stage of technological development, printing on either rigid or flexible substrates is considered a supplement to or replacement for traditional electronicdevice-manufacturing processes. Table 1 summarizes the comparison between printed mediaâ&#x20AC;&#x201D;newspapers and magazines, for exampleâ&#x20AC;&#x201D;and printed electronics. The difference stems from the fact

that printed media are used to convey information for people to process using their eyes, while printed electronic devices require machines to process electronic information; the level of required resolution and functionality make the difference. Some of the widely used functional materials for printed electronics include nano/micro-size metal particles, semiconductive polymers, and dielectric materials. Due to the available and required readout resolution, feature sizes smaller than 20 Îźm need to be printed. Layer thickness and registration accuracy of printed products are closely related to quality control of electronic devices, and ink materials require a high level of quality. Overall, printing tolerance is much tighter in printed electronics. ROLL-TO-ROLL PRINTING Roll-to-roll printing is considered the holy grail of manufacturing processes for production of flexible and large-area electronics. Substrate materials used in roll-to-roll printing are typically paper and

28 | INDUSTRIAL + SPECIALTY PRINTING www.industrial-printing.net

plastic films. Metal foil is also widely used in solar-cell and energy-storage applications. Plastic films such as PET, PEN, and PC are commonly used for their low cost; however, the use of plastic film has involves some technical challenges that must be addressed. Electronic devices, such as TFTs, solar cells, supercapacitors, thin-film batteries, RFID circuits and OLEDs, are produced continuously by various additive processes, such as flexography, gravure, offset, inkjet, and slot-die coating, in the order of square meters per second. This type of manufacturing process increases productivity by orders of magnitude when compared to the processes used in semiconductor fabrication, such as lithography for silicon wafers. Gravure, offset, and flexography are most commonly used in roll-to-roll printed electronics. Figure 1 summarizes and compares some of the manufacturing processes used for printed electronics in throughput and feature-size areas. You will see that gravure, offset, and flexography have an advantage in high-speed processing

100

High (>1)

Offset Gravure

Rotary screen

Flexo

Flat screen Medium (0.01-1)

Ink-jet

R2R photolitho

10-2

Low (<0.01)

PRINTING PROCESSES Let’s discuss the aforementioned three printing processes in greater detail. Gravure, flexography, and offset printing were developed in the 19th century. Originally used in printed media, these processes are now used to print functional inks on flexible substrates. In gravure printing, patterns to be transferred to the substrate are engraved on a cylinder (Figure 2). Engraving methods include chemical etching, laser machining, and direct mechanical machining. The entire patterned cylinder—also called the plate cylinder—is covered with ink (viscosity 50-200 cP). Then, the excess ink is doctored off, leaving ink in the cup-shaped engraved pattern. The plate cylinder is brought in contact with the impression cylinder to transfer what is in the ink cup to the substrate. Controlling impression pressure changes the surface energy, giving room for ink transfer control. In flexography, only the raised area in the pattern cylinder is inked, and the pattern is transferred to the substrate (Figure 3). A soft, raised pattern is often used instead of a hard pattern, and due to this common usage, the achievable feature size tends to be bigger than gravure. Flexo ink is similar in viscosity to formulations used in gravure. Offset is slightly different from the two methods shown above. First, it requires an ink with a much higher viscosity (20,000100,000 cP). Second, it uses a blanket cylinder that bridges the plate cylinder and the substrate. The pattern is transferred to the blanket, typically made of rubber, and then the transferred pattern is re-transferred to the substrate. The former process is called off and the latter is called set. One of the advantages of the offset method is that it can use low impression pressure. Where layers of functional materials are deposited on top of each other, high impression pressure commonly seen in the gravure method may damage other functional layers underneath. On the other hand, the print quality depends on the nature of the blanket rubber. The

Figure 1 Throughput vs. feature size for typical production processes

Throroughput (m2 /s)

and throughput while achieving medium resolution. Researchers around the world are actively seeking ways to achieve smaller feature size while maintaining high productivity.

Laser ablation

10 -4

High Resolution (<10 µm) 1

Medium Resolution (10-50 µm) 10

Low Resolution (>50 µm) 100

500

Minimum feature size (µm) Table 1 Printed media vs. printed electronics

Printed Media

Printed Electronics

Ink requirement

Color (visuals)

Ink material Resolution Layer thickness Registration Ink homogeneity Ink formulation Ink chemistry purity Ink transfer

Color pigment > 20 μm ~ 1 μm ± 50 μm Somewhat important Cost driven Somewhat important Small issue

Electronic performance (conductivity, semiconductivity, dielectric, etc.) Functional material < 20 μm 0.1 - 0.3 μm ± 1 – 10 μm Very important Function driven Very important Big issue

Figure 2 Gravure printing Impression cylinder

Image elements are equally spaced but variable in depth and area Gravure cylinder

Blade

Ink

MAY/JUNE 2011 | 29

Elastic printing plate with inked image elements

Printing substrate Elastic printing plate

Hard impression cylinder

Anilox roller Ink supply

Figure 3 The flexographic printing process

Cells of the anilox roller ink-filled

Inking system

Dampening system

Plate cylinder

Figure 4 The offset printing process

Inking Printing plate

Blanket cylinder

Oleophilic ink-accepting area Residual ink layer

Hydrophilic ink-repellent area Dampening

Impression cylinder

blanket rubber absorbs solvent and gets swollen over time, which leads to a change in absorption rate. Solving this issue is one of the most important technical challenges in system reliability. The method of delivering a pattern to the blanket cylinder is up to the user. Pattern transfer in offset printing relies on the properties of two different inking solutions (Figure 4). Because the final product in printed electronics requires not only the visuals, but also the functionality, this traditional method used in printed media is not readily applicable. To addressing this issue, a gravure plate cylinder can be used to transfer a pattern to the blanket cylinder in lieu of direct transfer to the substrate.

This specific method is called gravure-offset. Recent research results suggest that it is possible to produce feature sizes smaller than 10 μm in a continuous roll-to-roll fashion using this gravure-offset method. WEB-TRANSPORT CONTROL Precise web-transport control is necessary to guarantee sound functionality of the finished product. Having uniform tension on the substrate web throughout the process is important. Abrupt changes compromise the stability of deposited materials. The material web expands in response to force loading, and change in strain may cause cracks, short circuiting, and delamination of layers. Tension disturbance, which is caused by either an outside source or equipment design itself, should be minimized and affected materials should be rejected upon detection.

30 | INDUSTRIAL + SPECIALTY PRINTING www.industrial-printing.net

Another important aspect of web-transport control is velocity control. Precise synchronization of various cylinders in printing equipment is needed to ensure the printing quality and reliability of functional materials. Under precise angular velocity control, axles on feeder, plate cylinders, blanket cylinders, and impression cylinders are all in perfect harmony to achieve fine printing lines and uniform print thickness. Take this simple calculation for example: 10 arc-sec (that is 1/360 of a degree, and this state of precision is expensive to achieve) difference on a shaft with 300-mm-radius roll equates to a difference of 15 µm, which in some printed-electronics applications crosses the line between overall success and failure. DRYING AND CURING TECHNOLOGY Printed ink is typically dried and cured using hot air and/or ultraviolet (UV) rays. Hot air blown toward the substrate is the most commonly used implementation of the drying system; the air temperature is set, and a blower sends the hot air toward the substrate where needed. These methods mainly have two shortcomings: long curing times and thermal strain on flexible substrates. These shortcomings are somewhat interrelated. Because most printed-electronics devices are made on plastic film, high temperature drying and curing are not easy to implement. The glass-transition temperature for plastics is as low as 80°C. Higher curing temperatures are possible when glass or metal substrates are used, but these materials are not common in rollto-roll applications; glass is rigid, and metal foil is expensive. Because drying and curing are done at relatively low temperatures, it takes several minutes or more—in some cases, hours—of drying and curing time for proper performance of functional materials. When everything is processed continuously inline, this means a very long dryer. Increasing the curing temperature is not a feasible option because the substrate’s stiffness decreases as temperature increases and the substrate itself starts melting when its melting point is exceeded. Another shortcoming discussed above is the thermal strain on flexible substrates. Substrate material length can be extended up to a couple of percentage points under thermal stress inside the hot-air dryer.

Registration accuracy Registration accuracy, the hottest research topic of late in rollto-roll printing, is the ability to print multiple layers on top of each other precisely as requested by the device designer. Registration technologies were developed in printed media to apply four-color inksets (CMYK) accurately to create a vast array of colors. Printed Figure 5 High-resolution cameras are central to the optical electronics involves the measurement systems used to ensure optimum print quality deposition of layers of and functionality in printed-electronics applications. different functional materials. For example, Thermal expansion complicates the tenseveral layers of functional materials need sion and velocity control algorithm. Thorto be printed to create an RFID tag, and ough knowledge of how they influence desired feature size approaches 20-30 μm. each other is needed to address this issue. Registration accuracy is more important Knowing how much the substrate’s length in printed electronics than it is in printed would increase is essential in maintaining media because human eyes can only detect the desired web tension and shaft synchro- defects that are approximately 50 µm or nization. Thermal strain coupled with larger. Printing equipment designed for a long hot-air dryer makes registration media product was developed to meet the control a difficult problem to solve. requirements of the human eye. This level Some novel methods are being proof accuracy cannot be applied to many posed and studied to address problems printed-electronics applications, such as associated with drying and curing. They printed TFTs for display backplanes, where include laser curing and pulsed, highelectric circuitry must be printed with intensity light curing. The commonality registration tighter than 10 μm. between the two is that they both use Many printing presses now implement high-energy discharge and selective curoptical measurement systems that use highing of ink material. In laser curing, the speed, high-resolution cameras (Figure 5). wavelength of the laser is chosen strateThe cameras are used to measure the regisgically to target solvent and functional tration accuracy in the printed product, and materials to deliver the right amount of this information is fed back to the control energy, which shortens processing time system. The control system modulates and reduces the possibility of substrate the angular velocity of successive printing damage. Similarly, the pulsed, high-intencylinders to compensate for errors. The sity light source can be discharged with key to controlling registration accuracy is a large amount of energy—in the order thorough knowledge of how web tension, of tens of MJ—during a short period of transport velocity, and registration accuracy time (microseconds or milliseconds) to are interconnected; these three measurable evaporate the solvents instantly and cure attributes are joined together. You must the functional materials. Because of the make strategic decisions about how to convery short process time, there is no time trol these attributes in advance and during for heat transfer to take place, leaving the design stage. the substrate undamaged from high heat energy. Some of these types of equipment Materials are available on the market today for selec- The printed electronics we know totive ink materials. day—and hope for tomorrow—wouldn’t be

possible without functional, roll-to-roll materials. Having the right material with right functional properties—mobility, dielectric constant, conductivity, and more—is essential to produce electronic devices that operate as product designers intend. Note that the printed-electronics business revolves around printed products that have functional performance and visual requirements to meet. Functional materials must be durable, repeatable, and—most importantly—printable. Materials suppliers are working hard to deliver mass-produced substrates for the printed-electronics industry. Last, but not the least, printable materials must dry or cure quickly. Considering all these requirements, many materials are still in the development stage, and more work must be done in functional-materials research and development. Future outlook It has been about a decade since the term printed electronics gained profound meaning in the business of electronics manufacturing. Researchers and companies around the world are dedicating their resources to investigate and develop solutions to achieve the key technical attributes in the web control, drying and curing technology, and printable materials. Starting from rudimentary product groups that require low-resolution printing and simple structures, printed electronics—especially roll-to-roll applications—will be in our daily lives soon.

Deokkyun Yoon

Korea Institute of Machinery and Materials

Deokkyun Yoon is a researcher at Korea Institute of Machinery and Materials. His research interest includes machine design and control in printing applications. He holds B.S. and M.S. degrees in mechanical engineering from the University of Michigan.

Dong-Soo Kim

Korea Institute of Machinery and Materials

Dong-Soo Kim is the vice president of Korea Institute of Machinery and Materials and the principal investigator of numerous governmentfunded research projects in printed electronics. He holds B.S., M.S., and Ph.D. degrees in mechanical engineering from Yeongnam University. may/june 2011 | 31

PRINTING METHODS

Functional Printing: Maskless Deposition of Sensors Marcus Maiwald, Christian Werner, and Volker Zöllmer

Fraunhofer Institute for Manufacturing Technology and Advanced Materials Research

There are many application areas for sensors, and market studies forecast future growth in the sensor market within the next few years. In addition to conventional sensors made by using microsystems technology, functional printing allows for the direct deposition of sensors and other functional structures—conductive paths on different planar and non-planar surfaces and components by means of maskless printing technologies, for example. Functional printing Functional printing (Figure 1) starts with a structural layout that usually comes in a CAD (computer-aided design) file adapted to the desired function, process, and used surface. It follows the material selection and development step. Typical materials for functional printing are nanoscale suspensions or so-called functional inks. These inks consist of nanoparticles dispersed in a fluid. Additionally, stabilizing agents are used to avoid agglomeration and particle sedimentation. Here, a wide range of different materials can be used, such as commercially available metal and ceramic inks. Polymer inks are also available, and different metal-alloy suspensions can be produced by using sputtering and other processes. The next steps include maskless printing and, finally, thermal activation of the printed structures for densification. Typical printing technologies include high-resolution processes such as inkjet and Aerosol Jet, the latter of which was developed by Optomec Inc. to handle suspensions with a viscosity range from 0.7-1000 mPa∙s and a particle size up to 1000 nm for metals. The so-called atomizer produces an aerosol from the suspension, which is car-

Layout

Material Development/Ink formulation

ried to the printhead. A sheath gas (nitrogen) is used inside the printhead to focus the aerosol beam and prevent nozzle clogging. The aerosol droplets have a diameter of 1-5 µm, which corresponds to volumes calculated in femtoliters. The use of sheath gas and the focused aerosol beam enable Aerosol Jet to print on non-planar surfaces. There are different solutions for the thermal activation that depend on the printed material and the surface or component. Polymer inks typically are cured using a furnace or UV curing. Metal inks are mostly sintered using a furnace or a laser. The final structure is characterized in terms of physical, electrical, and other properties. Functional printed sensors and strain gauges Non-destructive testing is very important—especially with aerospace and automotive products. Here, functional printing offers the possibility of depositing metal strain gauges directly on surfaces and components for continuous measurements. The piezoresistive effect enables strain gauges to measure stress and strain. A change in length of the strain gauge is proportional to a change in electrical resistance. Commercially available strain gauges are mostly fabricated on foil substrates and consist of a metal-alloy meander. Metal-alloy materials are used because of the small temperature coefficient of resistance, which means that temperature will not influence the strain signal. Foil strain gauges are glued onto substrates or components. Functional, printed strain gauges have the advantages that the strain gauge is placed automatically via the printing process, and

Printing process

Figure 1 The functional printing process steps 32 | Industrial + Specialty Printing www.industrial-printing.net

Thermal activation

Characterization

Figure 2 A printed strain gauge

Figure 3 The signal from a printed strain gauge Figure 4 A scanning electron microscope (SEM) photo of a printed metal oxide close up

the sensor can be placed on either planar or non-planar surfaces. It is also possible to deposit a sensor network, which allows precise measurements of the strain distribution. Printed strain gauges can be fabricated by using Aerosol Jet technology. First, an isolation layer is printed using a polymer ink. After curing the polymer isolation, the metal strain gauge is deposited using a commercially available silver ink. The particle size of the silver ink is around 20 nm with a metal loading of about 50 wt %. After deposition and sintering at 350°C, diffusion processes connect the silver particles and form a dense structure. At last, the polymer ink is used for encapsulation of the printed strain gauge to protect the sensor from external influences. The total thickness of all three printed layers is approximately 20 µm. Figure 2 shows an example of a printed silver strain gauge on a metal surface with isolation layer, silver meander, and encapsulation. For characterization, the metal substrate is fixed in a tensile tester and periodically stressed. Figure 3 shows the resistance change of the printed strain gauge for 7675 cycles with 1000-N tensile stress and 500-N compressive stresses. The sensor signal shows a reliable and reproducible behavior within the tested range.

Several metal oxides, like tin oxide (SnO2), zinc oxide (ZnO), and wolfram trioxide (WO3), are sensitive to different gases such as carbon oxide (CO), nitrogen dioxide (NO2), and ammonia (NH3). Metal-oxide gas sensors change their electrical resistance when exposed to gas. An operating temperature of about 400°C is required for these kind of sensors, as adsorption and desorption of gases occurs rapidly at this temperature. Further improvement of the sensing performance is achieved when the gas-sensitive metal oxide is doped with a noble metal. Metal-oxide powder is dispersed in ethylene glycol, and adding a dispersing agent to the ink prevents particle sedimentation. The deposition of this dispersion was done by Aersol Jet technology. Layer thickness varied from 1-20 µm by increasing the material-deposition rate and the number of printed layers. Subsequently, the thermal treatment of the printed metal-oxide structure was performed by conventional radiation-conduction-convection under ambient air at 700°C for 30 minutes. An image from scanning electron microscopy (SEM) shows the highly porous morphology of the printed and sintered metal oxide (Figure 4). Due to the highly porous morphology, an increased ratio of surface area to volume is achieved, which has a positive influence on the effectiveness of the sensor. The porous layer needs to be printed on a hotplate to ensure accurate operation. The ability to print areas with dimensions smaller than 1 mm and a thickness of only a few microns allows for the development of new energy-efficient hotplates. Gas exposure of the printed metal oxide results in a change of the electrical resistivity, which is measured by a multimeter and allows the determination of the gas concentration.

Functional printed gas sensor Gas sensors can be found in the food industry, workplaces, or as air-quality sensors in automobiles. Harmful concentrations of gas in the air can be detected and counteraction initialized. Typical specifications of gas sensors are high selectivity, high sensitivity, and low energy consumption. Gas-sensitive films typically are sputtered or deposited by thick-film techniques on a hotplate.

Conclusion Functional printing allows the direct application of sensor structures like strain gauges and gas sensors. Printed strain gauges show a reliable signal, and the gas-sensing films show a good performance because of their highly porous structure. Please consult the authors directly for a complete list of references.

Marcus Maiwald, Ph.D. Fraunhofer Institute

Marcus Maiwald, Ph.D., studied electrical engineering with main emphasis micro system technology at the University of Bremen, Germany. In 2006 he received his diploma and joined the Fraunhofer-Institute for Manufacturing Technology and Advanced Materials Research in Bremen as project manager. In 2010, he received his Ph.D. from the University of Bremen.

Christian Werner Fraunhofer Institute

Christian Werner studied industrial engineering and management at the University of Bremen, Germany. In 2007, he received his diploma and joined the Fraunhofer Institute for Manufacturing Technology and Advanced Materials Research as project manager. He is working in the functional structures department and with focus on surface functionalization by printing and rapid sintering techniques.

Volker Zöllmer, Ph.D. Fraunhofer Institute

Volker Zöllmer, Ph.D., obtained his degree from the University of Kiel, Germany, in 2002. Since then he has worked at the Fraunhofer Institute for Manufacturing Technology and Applied Materials Research in Bremen as project manager. Since 2003, he has been the head of the functional structures department. may/june 2011 | 33

Market movements and association updates

INDUSTRY NEWS

Reduced Solar Module Shipments Predicted for 2011 According to market forecaster Solarbuzz, following a strong growth of 139% in 2010, global solar photovoltaic demand is off to a weak start in 2011. Preliminary estimates of Q1 2011 end-market demand in Germany show it running at less than 50% of its Q1 2010 level. The gradual price reductions seen so far this year have been insufficient in energizing the market. However, in Q2 2011, global demand is still projected to reach 7.4 GW, representing 77% Y/Y growth, according to the latest Solarbuzz report. Any changes to government PV policies as a consequence of the nuclear disaster that has followed the earthquake and tsunami in Japan are not expected to impact demand until 2012. At the same time, the disaster’s impact on the nine major plants engaged in polysilicon wafer and cell production in Japan so far appear to be minimal. Craig Stevens, president of Solarbuzz, says, “2011 will be a challenging year for the industry as it manages a slowdown in the market. Europe will not be the growth engine it has been in recent years, and manufacturers will need to access new markets or be exposed to the risk of rising inventories or production cuts during a period of falling prices.”

Polysilicon in China in Tight Supply China imported 5,521 tons of polysilicon in January, representing a year-on-year rise of 74.8%, according to the latest stats released by the General Administration of Customs. The figure is 40% above the 2010 average monthly import, which was approximately 3,958 tons, providing evidence that the material is in tight supply across the country. The domestic supply shortages are attributable to a production halt as a result of routine year-end audits performed by major polysilicon makers in China before the Chinese Spring Festival break. Polysilicon imports in February were high as well. Tight supplies of polysilicon, which is used in the manufacture of solar PV modules, is experiencing rapid price hikes. The spot price for polysilicon has reached $114 per kilogram early in March—an increase of nearly 100% from the end of last year.

34 | Industrial + Specialty Printing www.industrial-printing.net

Europe Set to Dominate Solar Market in 2011 The latest research from IHS iSuppli indicates that Europe will continue to account for the lion’s share of the PV installations in the world in 2011, claiming 68.6% of the global total. Comprising nine of the world’s 15 major solar markets, European PV installations this year will amount to 14.3 gigawatts (GW), more than two-thirds of the global level of approximately 20.9 GW. HIS iSuppli says Europe will be home to the world’s two largest solar markets—Germany with an estimated 7.1 GW and Italy with 4.1 GW—as well as seven other important PV territories, including France, Belgium, the UK, the Czech Republic, Spain, Greece, and Bulgaria. Looking ahead, the highest growth PV markets in Europe will be Belgium, Bulgaria, Spain, and the UK. By 2015, however, the U.S. will become the world’s single largest solar market, overtaking Germany, which drops to second place after years of being on top, IHS iSuppli predicts.

FLEXcon Acquires Arlon Business Units

Avery Dennison Unveils New Business Unit

Spencer, MA-based FLEXcon, manufacturer of pressure-sensitive films and adhesives, has acquired the business assets of Arlon Engineered Coated Products and Arlon SignTech, Ltd. of San Antonio, TX, forming FLEXcon Industrial, LLC. This move expands FLEXcon’s manufacturing capabilities to the production of engineered products. For more than 50 years, Arlon Engineered Coated products has manufactured a range of industrial products for a variety of markets. The company coats and laminates films, synthetic materials, and foils. Arlon SignTech, Ltd. produces flexible PVC substrates used in outdoor signage and is a supplier to Arlon Graphics, LLC. The new FLEXcon Industrial, LLC will continue to manufacturer and sell its full line of adhesive tapes and laminates.

Avery Dennison has given its businesses units new names to communicate their focus on market-driven solutions. Roll Materials becomes Label and Packaging Materials to reflect the fact that its innovations in self-adhesive technology extend beyond labeling to packaging. Retain Information Services is now Retail Branding and Information Solutions to reflect its suite of products and services in retail and apparel brands. Office Products becomes Office and Consumer Products. Graphics and Reflective Products becomes Graphics and Reflective Solutions, and Specialty Tapes becomes Performance Tapes. Specialty Converting is now Designed and Engineered Solutions. Medical Products, the RFID Division, and Automotive are now Medical Solutions, RFID, and Automotive Solutions.

Clemson Institute Approved for GM Nameplate and Northern Color-Logic Certification Testing Engraving Form Joint Venture West Chester, OH-based Clemson University Sonoco Institute of Packaging Design & Graphics has been qualified for Color-Logic certification testing, says Color Logic. “The Sonoco Institute at Clemson University—one of the most capable flexographic printing facilities in North America—has been approved as a site qualified to test and certify materials used in Color-Logic Process Metallic Color System,” says Color-Logic CTO Richard Ainge. The qualification is based on tests recently conducted at the Sonoco Center involving a wide variety of inks and substrates. Manufacturers wishing to certify flexographic materials for use with the Color-Logic Process Metallic Color system may now have them tested and certified at the Clemson facility.

GM Nameplate and Northern Engraving have agreed to form a joint venture in China for manufacturing nameplates, overlays, dials, and decorative trim. The venture is designed to enhance the ability of both companies to serve customers that leverage the China-based supply chain for their products. This agreement combines the facilities and infrastructure GM Nameplate has in place in China with technical and manufacturing capabilities from Northern Engraving. Limited production is available now with full production capabilities expected in the fall of 2011. Both companies have manufacturing operations in the U.S.

IPC Holds Conference on Flexible Circuits The IPC—Association Connecting Electronics Industries will hold a technical conference on flexible circuits in Minneapolis, MN, June 22-23, 2011. The conference will cover military- and medical-sector issues, end-user requirements, manufacturing flexibility, and developments in materials, processing, and performance reliability. Presentations will range from basic to advanced levels. For more information, visit www.ipc.org. may/june 2011 | 35

Polyera Names Ramachandran CFO Prakash Ramachandran is now the chief financial officer of Polyera. Before leading Polyera’s financial direction, he was CFO of Nordic Windpower, prior to which he served as CFO of start-up Novariant, a company producing machine-control products for mining and farming industries. Skokie, IL-based Polyera Corp. is a supplier in semiconductor, dielectric, and interfacial materials for the printed- and flexible-electronics industry. Polyera’s focus has been on developing materials for its portfolio of ActivInk products. “We’re delighted that Prakash has decided to join us at Polyera,” says CEO Phil Inagaki. “He brings a wealth of experience in fundraising, international finance, and teambuilding in high-tech industries to our organization, and we know he’ll be a tremendous asset as we continue to build our business.”

UPCOMING EVENTS MAY 24-27 FESPA HAMBURG, GERMANY

www.fespa.com JUNE 14-16 SGIA Printed Electronics & Membrane Switch Symposium SAN JOSE, CA

www.sgia.org JULY 12-14 SEMICON West IPC

LPKF Expands Headquarters

SEPTEMBER 22-23 International Conference on Flexible and Printed Electronics TOKYO, JAPAN

www.icfpe2011.org SEPTEMBER 27-28 RFID Europe IdTechEx CAMBRIDGE, UK

www.idtechex.com

SAN FRANCISCO, CA

Hannover, Germany-based LPKF Laser & Electronics AG, a provider of technologies for PCB prototyping, SMT stencils, PCB processing, laser welding, and more, recently invested €5 million into purchasing a neighboring building, giving an additional 32,000 square feet for product development and production. The new building is currently under renovation and is expected to become a part of the company’s existing complex by June 2011. The company says the need for the additional space stems from the high demand for laser technology and notes that it brought on more than 100 new employees—increasing the total to 470—in 2011 to meet this rising demand.

www.ipc.org

SEND US YOUR NEWS!

Email gail.flower@stmediagroup.com

Here’s what to expect in the July/August issue of iSP.

PREVIEW

FEATURE HIGHLIGHTS:

BUSINESS MANAGEMENT:

• Organic Solar Cells • Printed Batteries/ Power Supplies • Finishing Processes • E-Book Technology • Automative Labels/Decals • Photovoltaic Update

Matching stencil needs for a changing technology INDUSTRY INSIDER:

Underwriters Lab testing for membrane switches and touchscreens. SHOP TOUR:

Photo tour of the Cubbinson Company. PLUS:

DO YOU CONSIDER YOURSELF AN ORIGINAL THINKER? Blue Spark Technologies, NorTech, and the editors of iSP present,

“Visionary Innovator: Find a Use for This Battery Contest.” IT’S COMING THIS SUMMER!

36 | INDUSTRIAL + SPECIALTY PRINTING www.industrial-printing.net

An article submitted by Blue Spark Technologies telling you all about their 1.5v printed battery, and the details for this contest will be in the July/August issue. What can you use the battery for?

WILL YOU BE DECLARED A VISIONARY INNOVATOR?

FUNCTIONALITY Blog Conversations within the industrial-printing community • Post your comment • Share information • Keep the conversation going • Look, learn, and maybe even laugh

industrial-printing.net

ADVERTISING INDEX

May/June 2011

Advertiser

page

Advertiser

page

Aixtron SE

Kammann Machines Inc.

American Ultraviolet

MacDermid Autotype

AWT World Trade Inc.

Mimaki USA

Douthitt Corp.

Nazdar

OBC

Dynamesh Inc.

Polyonics Inc.

EFI

Sakura

Franmar Chemical Inc.

IBC

SEMI

Graphic Parts International

Tekra Corp.

Industrial-Printing.net

Xenon Corp.

Inx Digital

IFC

industry insider

Beyond Flexible Circuits

Pushing the Boundary for Printable Electronics Dave Torp IPC

Printable electronics push the outer limits of flexible material standards. For the past two decades, printed electronics have grown and found commercial applications in markets for radio-frequency identification (RFID), smart labels and displays, sensors, and lighting (OLED). Advancements in conductive printable inks, with a little help from nanotechnology, have overcome some of the early consistency problems in conductive additive materials. Improvements in printing equipment and processes, including the application of flexo-gravure printing, have made highspeed processing of printable electronics a reality. However, variations in materials and processes for printable electronics create many opportunities for improvement. Several of the largest markets for printable electronics involve being able to process conductive inks on flexible substrates. Adding some further complications—the substrates are often moving at high speed during ink application. The electronics industry and the graphics-arts industry have met at the crossroads of printed electronics. IPC standards have provided definition and characterization for traditional flexible electronic circuits for many years. IPC-2223, Sectional Design Standard for Flexible Printed Boards, provides insight into the design requirements for flexible circuits. Drilling down further into the flexible-circuit standards is IPC-4202A, Flexible Base Dielectrics for Use in Flexible Printed Circuitry, which defines the flexible bare substrate (dielectric) materials. Some of the big issues with flexible substrates are addressed in IPC-4202A including: inspection criteria, dimensional stability, surface finish, strength, tear resistance, etc. IPC-6013B, Qualification and Performance Specification for Flexible Printed

Boards, provides insights into qualification and performance requirements for flexible printed circuit boards. Some of the requirements given within IPC-6013B can be directly applied to printable electronics as well. Scratches, surface voids, cover films, adhesion requirements, and accuracy requirements are all included in IPC-6013B. Each of the IPC standards for flexible circuits reflects the best practices for design and fabrication using a traditional subtractive process. There are some areas where these standards include additive plating process, as well as adhesive application; however, none of the standards addresses the use of a conductive-ink additive process on which the printable-electronics industry depends. The printable-electronics market is beginning to mature and experience some of the growing pains that are associated with rapid advancement. For many working in the printable electronic industry, there is a realization that standardization is not too far away. IPC has taken the first steps toward standardization by sponsoring conferences on printable electronics. Although no formal standards development has taken place yet, eventually the materials and processes that reflect best practices within certain segments of the printable-electronics industry will definitely be included in IPC’s future standards-development activities. Those who have participated on IPC standards-development committees understand the power of standards development. IPC connects thousands of subject-matter experts on a global basis. The amount of knowledge that is shared among users, suppliers, academia, and laboratories within the electronics community is phenomenal. Problems that seem to be insurmountable to one company are within the core competency of another participating company.

38 | Industrial + Specialty Printing www.industrial-printing.net

IPC standards committees are open to all who want to contribute. There is no fee required to participate on IPC standardsdevelopment committees. IPC policies require open and balanced participation on standards-development committees. The output of IPC standards-development committees results in some of the best standards in the world for electronics and the electronics-assembly industry. The standards-development opportunity that exists for printable electronics is in defining the materials and processes for high-performance applications. The uniformity of materials, combined with the process requirements, makes for some great opportunities to develop standards. Development of test methods required to define critical parameters in a reproducible and repeatable way is one of IPC’s core competencies. If you are interested in joining a standards-development group for printable electronics, please contact Dave Torp, vice president standards and technology, at dptorp@ipc.org. The next conference on flexible circuits sponsored by IPC will be in Minneapolis, MN, June 22-23, 2011. For more information, visit www.ipc.org.

DAve torp IPC

David Torp is the VP of standards and technology for IPC—Association Connecting Electronics Industries, Bannockburn, IL. He has held that position since 2007. Prior to joining IPC, he was a senior staff engineer at Plexus. He also served as VP of marketing and business development at Kester and held various engineering positions at Rockwell Collins as well as Underwriters Laboratories. He has a B.S. degree in Chemical Engineering from Iowa State University.

PRODUCT SPOTLGHT A Paid Advertising service to iSP magazine.

shop tour 6

2 3

Printec

location Waltham, MA (headquarters in New Taipei City, Taiwan) other info Printec is a global membrane-switch-manufacturing and technology firm that offers services

for high-volume, low-volume, and prototype projects. The company uses a variety of printing, curing, and post-production finishing equipment as part of the manufacturing process. The companyâ&#x20AC;&#x2122;s product line includes membrane switches, flex circuits, touchscreens, integrated touchscreens and LCDs, in-molddecorated components, overlays and labels, keypads and support panels, and enclosures. Printec is a suppler to a range of markets, including medical, military, aerospace, homeland security, alternative energy, electronics, automotive, and more. For more information, visit www.printec-usa.com.

1 Screen printing for overlays and circuits 2 Digital printing for overlays and circuits 3 Die cutting cutting for quick-turn samples 4 Laser and prototypes 40 | Industrial + Specialty Printing www.industrial-printing.net

ranges from simple keypads to 5 Assembly more complicated, full-body applications. assesses all products in the assem6 QC bly process.

7 Printec uses three Class 10,000 cleanrooms.