Modern Printed Circuits: June, 2014 by EEWeb Magazines

JUNE â&#x20AC;&#x2DC;14

Interview with

Zulki Khan

President & Founder of Nexlogic

New iDesign Fuse Selector Price Quoting for Printed Circuits

PCB DESIGN & ASSEMBLY

for High Stakes

Medical Electronics

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CONTENTS

Modern Printed Circuits

packaging and ever-shrinking tate will also call for ly improved PCB cleaning These devices are so small iest of flux residue can den and undetected in a ce. That cannot happen in a ctronics PCB because even st contaminant will cause sues. Advanced packages and of ultra-clean PCBs are definite we will soon encounter.

How can those milestones best be met?

TOOLING AND TEST CHARGES

You have to meet these milestones head on with an even stronger mindset and a more disciplined design through assembly ever before. Key Costprocess Drivingthan Factors WhenLike Quoting they say, past experience the best Printed Circuit Boardsis(Part 2) platform to successfully move forward. In this case, the principles remain the same, although there can be some adjustments PCB is being reflowedThe or wave soldered, the is and improvements. point being [Part 2] By Peter Brissette, Bay Area Circuitsthe contamination can outgas and destroy the successful EMS Provider dealing with via and thus the board. When you tent a via, make certain you only do it on one side. medical electronics OEMs will have toby a Our last post covered many of the cost factors used PCB Reliability: An encroached via eliminates this issue by fabricator to calculate cost of a printed circuit board. continue to be at the top of its game, beFor keeping the hole itself open and also has the Via Design added benefit versus a tented via of being those with industry of these factorstomay creative,experience improvise,many and not fall victim possible no matter the via size. While tented be obvious complacency. but there are other factors that contribute vias need to In be small enough for the solder short, you’ve got to stayto cost that may be less obvious andthe we’ll cover several of these mask to bridge drill hole, the encroached ahead via ofonly thecovers curve. the annular ring and can be as

TECH COLUMN KEY

COST DRIVING FACTORS When Quoting Printed Circuit Boards

Solder Dam

ng an account, you will be he iDesign™ landing page. e layout allows users to not through a list of fuses, but ut other parts and actually he user on some alternate their application. For those ign™ and online design tools here are comprehensive d slideshows for newcomers for the selection and process. “Many believe that mplistic component or a ” Shenoy explains. “However, an get very complicated with ctures of fuses that give them nt characteristics. If a proper elected, it can even be a ern.” With iDesign™, Littelfuse prevent these potential for their customers, allowing sy starting point for designing heir boards.

Encroached Via

Tented Via

TECH ARTICLE

today. Having an understanding of these cost factors will big or small as needed. not only empower buyers to ask the right questions of their are also designers an option, whichto increase fabricator but will Filled alsovias enable design strength, electrical/thermal conductivity, with optimal performance and cost efficiency. and protect the via from solderwicking and

The tool is logically separated into tabbed sections—one for each step of the design process. The first tab asks for the initial circuit parameters for the application, whether it is the maximum operating voltage, nominal operating current, maximum operating temperature, and the location of the fuse on the circuit board. These values can be entered manually into each field so the general requirements for the user application can remain throughout the iDesign™ fuse selection process. “For those unfamiliar with designing in fuses, we offer a tutorial section for each search parameter,” Shenoy assures. “If the user is unsure of what the nominal operating current is for their application, we have a tutorial that will hopefully clarify that.”

Fuse Series Selection

COVER INTERVIEW

Being the global company that it is, Littelfuse was aware of the fact that the compliance standards for each customer will vary based on their location throughout the world. The safety standards in the “Compliance” section of the tool divides the standards into geographic region—North America, Europe/World, and Asia—to the “With iDesign™, customer that their safety certification Littelfuse is needs are met early on in the process. Once trying to prevent potential those certifications are selected, the user roadblocks for is brought to the next tab, which deals their customers, with the enclosure size of the application allowing them you are designing. This section also lets an easy starting you determine the mechanical structure point for for the specific type of fuse the user is designing implementing, whether it is SMD, an axial/ in fuses on cartridge, or radial. Again, the iDesign™ tool their boards.” provides supplemental material to educate the user on any essential requirements a fuse needs before implementation.

Zulkicontamination. Kahn The main drawback to filled vias is that they can add significant costs to President & Founder of Nexlogic the board. The other methods should have no impact on cost whatsoever.

To read the previous article, click on the image at the right.

Every design has different requirements and constraints. However, when possible, utilize these tips by using the largest vias, the appropriate aspect ratio, and by thoughtfully choosing the solder masking style that suits your needs. This will ™ help reduce the overall lifetime costs by increasing reliability of your products.

FEATURED ARTICLE

KEY

COST DRIVING FACTORS When Quoting Printed Circuit Boards [Part 1]

By Peter Brissette, Bay Area Circuits

Customers and buyers who are relatively new to the printed circuit board (PCB) industry may be confused as to how a particular project is priced by the fabricator. In this article series, we’ll begin to demystify the factors used by fabricators to calculate price, empowering you to better plan and price your next PCB project.

Introducing iDesign The World’s First, Comprehensive Fuse Selection Tool Content provided courtesy of Advanced Assembly, leader in quick-turn, PCB assembly.

Tooling costs may include cost for CAM time, fil costs, etc. There are a variety of tests that can b performed related to manufacturing a PCB. An Electrical Test would be the most common, whi will do a basic open and shorts test of the PCB t make sure it is electrically sound. Additional tes that typically add more costs would be TDR for Impedance Testing, Ionic Testing, etc. The spec costs related to these items vary greatly by manufacturer.

FINISH TYPE

The most common finish type is still a lead finish referred to as HASL (Hot Air Solder Leveled). Oth finishes can add 10% to 20% or more to the cost Those include a variety of gold finish options (ENIG, body gold, gold fingers etc.), silver finish options and more.

DRILL TYPE

We mentioned the mechanical drill cost alread this article. If you need much smaller holes, refe to often as microvias, then a laser drill process is required. Laser drill can add significant costs to overall process.

Another factor would be blind or buried vias. These are vias that do not go all the way throug the entire board. Each additional drill process can add as much as 20% or more to the cost.

LAMINATION PROCESS

Processing a multi-layer printed circuit board th requires something outside the standard proce can add costs. Some other processes could be sequential lamination or laminating FR4 with a different material type such as polyamide.

Get a F

http://www.bay

For more information on the company, visit www.aa-pcbassembly.com or call 1-800-838-5650.

"An encroached via eliminates this issue by keeping the hole itself open and also has the added benefit versus a tented via of being possible no matter the via size."

Modern Printed Circuits

KEY

COST DRIVING FACTORS When Quoting Printed Circuit Boards [Part 2]

By Peter Brissette, Bay Area Circuits

Our last post covered many of the cost factors used by a fabricator to calculate cost of a printed circuit board. For those with industry experience many of these factors may be obvious but there are other factors that contribute to cost that may be less obvious and weâ&#x20AC;&#x2122;ll cover several of these today. Having an understanding of these cost factors will not only empower buyers to ask the right questions of their fabricator but will also enable designers to design with optimal performance and cost efficiency. KEY

COST DRIVING FACTORS When Quoting Printed Circuit Boards [Part 1]

To read the previous article, click on the image at the right.

By Peter Brissette, Bay Area Circuits

Customers and buyers who are relatively new to the printed circuit board (PCB) industry may be confused as to how a particular project is priced by the fabricator. In this article series, weâ&#x20AC;&#x2122;ll begin to demystify the factors used by fabricators to calculate price, empowering you to better plan and price your next PCB project.

TECH COLUMN

TOOLING AND TEST CHARGES

SPECIFICATION STANDARDS

Tooling costs may include cost for CAM time, film costs, etc. There are a variety of tests that can be performed related to manufacturing a PCB. An Electrical Test would be the most common, which will do a basic open and shorts test of the PCB to make sure it is electrically sound. Additional tests that typically add more costs would be TDR for Impedance Testing, Ionic Testing, etc. The specific costs related to these items vary greatly by manufacturer.

IPC Class 2 is a common standard for final PCB inspection and quality processes. Class 3 is a step up from Class 2 that requires additional processes such as coupons and cross-sections to be added to the manufacturing process and can see a cost increase of 15% to 20%.

FINISH TYPE The most common finish type is still a lead finish referred to as HASL (Hot Air Solder Leveled). Other finishes can add 10% to 20% or more to the cost. Those include a variety of gold finish options (ENIG, body gold, gold fingers etc.), silver finish options and more.

DRILL TYPE We mentioned the mechanical drill cost already in this article. If you need much smaller holes, referred to often as microvias, then a laser drill process is required. Laser drill can add significant costs to the overall process. Another factor would be blind or buried vias. These are vias that do not go all the way through the entire board. Each additional drill process can add as much as 20% or more to the cost.

LAMINATION PROCESS Processing a multi-layer printed circuit board that requires something outside the standard process can add costs. Some other processes could be sequential lamination or laminating FR4 with a different material type such as polyamide.

VIA FILL Vias on a PCB are usually not filled completely. They will have copper plating and the finish in the holes but they will not be completely filled. You can fill vias with either non-conductive or conductive material. This process will add 10% or more to the cost of the PCB.

FABRICATION Additional costs will be incurred when there is additional fabrication that needs to be done to the finished board. These include things like counterbores, countersinks, complex routing, controlled depth drilling etc. These costs vary greatly. These are many of the primary and secondary variables a fabricator uses when preparing a price quotation for a customer. Of course, for a customer, the price of a printed circuit board is not always a measurement of the true costs in the manufacturing process. Delays in delivery by the fabricator or a board failure because of an inferior manufacturing process can cause the real price to be much higher. So, when quoting your next printed circuit board project, be sure to clearly identify your project requirements, ask the right questions of your fabricator and design for optimal performance and price efficiency.

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http://www.bayareacircuits.com/freepcb

Modern Printed Circuits

TECH ARTICLE

PCB RELIABILITY:

Via Design W hen considering the long term reliability of a PCB, you must take into account the vias that you have on your board. While an invaluable and essential part of board design, vias introduce weaknesses and affect solderability. This article will discuss vias, the potential concerns that are introduced into your board through their implementation, and how to minimize those concerns to acceptable levels.

Modern Printed Circuits

6:1 Aspect Ratio

The first rule for via design is simple: bigger is better. Larger vias have greater mechanical strength as well as greater electrical and thermal conductivity. While space is always a consideration when it comes to PCB design, vias should have a minimum 20 mil drill width with an annular ring of 7 mil and a minimum aspect ratio of 6:1. For many boards this may be an unacheivable goal, however, the basic premise of bigger is better stands true. When a PCB is exposed to thermal changes in its processing or in its end working environment, the varying coefficient of thermal expansion (CTE) between the laminate and the copper can cause issues. PCBs are constrained through structural latticework to limit horizontal expansion but can expand and contract significantly in the vertical direction. As copper expands and contracts at slightly less than one fourth of the rate of FR-4 laminate, vias are literally being pulled apart every time the board is heated. If the board is too thick and

â&#x20AC;&#x153;If the board is too thick and the copper in the via too thin, then the board will expand too much and the copper will break, literally tearing the via apart.â&#x20AC;? the copper in the via too thin, then the board will expand too much and the copper will break, literally tearing the via apart. In the example above, to get the appropriate aspect ratio with a drill width of 20 mil, this would result in a total pad diameter of 34 mil and allow a max board thickness of 120 mil. Size is important with vias, but location is tantamount. If a via is located close to a solder

TECH ARTICLE

Solder Wicking

pad, a myriad of problems may arise. Foremost is the problem with solder wicking. As the via heats up, it pulls the solder from the solder pad, through the via, and onto the other side of the board, leaving the pad either solder deficient or completely solder free. The larger the via, the more solder will likely wick away, making it less likely that you will have a solid mechanical and electrical joint. Fortunately, this concern can be fixed by any of three nocost methods. Providing a solder mask between the lead and the via creates a barrier to the movement of the solder. This is a simple yet effective method, though it does have its drawbacks. Due to the minimum width required for a solder mask, this may require the via to be moved even farther from the lead. The distances required may seem minimal, in the 2 - 5 mil range, however, when space is at a premium or the board is carrying high

frequency signals, this may have a profound effect on your design. However, when these arenâ&#x20AC;&#x2122;t issues, this is a great way to avoid the solder wicking concerns. If there is no space to move the via and you need to minimize the via size, it is possible to use an encroached or tented via. By masking the via pad, you save space and also make it possible to silkscreen over the via. However, this makes it impossible to use the via as a test point as the copper will no longer be accessible. At this point, you need to make a decision on whether an encroached or tented via is best. A tented via is completely sealed and will create a better surface for silkscreening as well as a better barrier against contamination. This barrier works both ways, though. If a via is tented on both sides of the board, contamination can fill the void during the board construction. At elevated temperatures, such as when the

Modern Printed Circuits

Solder Dam

Encroached Via

PCB is being reflowed or wave soldered, the contamination can outgas and destroy the via and thus the board. When you tent a via, make certain you only do it on one side. An encroached via eliminates this issue by keeping the hole itself open and also has the added benefit versus a tented via of being possible no matter the via size. While tented vias need to be small enough for the solder mask to bridge the drill hole, the encroached via only covers the annular ring and can be as big or small as needed. Filled vias are also an option, which increase strength, electrical/thermal conductivity, and protect the via from solderwicking and contamination. The main drawback to filled vias is that they can add significant costs to the board. The other methods should have no impact on cost whatsoever. Every design has different requirements and constraints. However, when possible, utilize these tips by using the largest vias, the appropriate aspect ratio, and by thoughtfully choosing the solder masking style that suits your needs. This will help reduce the overall lifetime costs by increasing reliability of your products.

Tented Via

Content provided courtesy of Advanced Assembly, leader in quick-turn, PCB assembly. For more information on the company, visit www.aa-pcbassembly.com or call 1-800-838-5650.

"An encroached via eliminates this issue by keeping the hole itself open and also has the added benefit versus a tented via of being possible no matter the via size."

TECH ARTICLE

Modern Printed Circuits

COVER INTERVIEW

PCB

Design and Assembly

For Medical Electronics OEMs Interview with Zulki Khanâ&#x20AC;&#x201D; President and Founder of NexLogic Technologies, Inc.

exLogic Technologies, Inc. is a one-stop PCB design, fabrication, and assembly electronic manufacturing services (EMS) Provider. As a leading EMS Provider, it offers total integrated circuit board solutions. The company was established in 1995 and successfully serves over 1,000 customers in North America. Nexlogicâ&#x20AC;&#x2122;s mission is to provide high quality PCB design and manufacturing processes to a wide swath of OEM markets, ranging from consumer to medical electronics. EEWeb spoke with Zulki Khan, President and Founder of NexLogic Technologies, Inc., about how his company is meeting the growing and demanding PCB design and assembly requirements of medical electronics OEMs, and the critical aspect of high quality and reliability these OEMs expect.

Modern Printed Circuits

What are the key PCB design and assembly challenges facing medical electronics OEMs?

PCB real estate, as well as making sure that all the layout-related DFM issues are taken care of.

Technology is rapidly advancing. Twenty years ago, hospitals used bulky desktop EKG machines. Today, a trained medical technician can travel anywhere with a portable EKG device that is less than 10 pounds and take your EKG data in less than five minutes. That portable EKG device is based on small PCBs packed with highly advanced electronics. However, the technology doesn’t stop here. The beauty of technology is it constantly advances and evolves. PCB design and assembly is on the front line of these advances. The challenges for PCB design and assembly stem from the fact that medical electronics OEMs continue to demand more features and functionality in an ever-shrinking board area. The design challenges deal with properly managing heat dissipation, placing all the components in smaller

Meanwhile, advanced medical electronics products rely on such state-of-the-art device packaging as package-on-package (PoP), flip chip, land grid arrays (LGAs), and tiny passive device packages such as 0201 and 01005 packages. If the EMS Provider or Contract Manufacturer lacks the necessary experience, this newer device packaging can pose significant reliability issues at PCB assembly. There are a number of so-called “quality gates” a PCB assembly house has to pass through to maintain ultra-reliability. That includes complying with the strict medical electronics ISO 13485-quality standard. These aren’t easy assemblies to begin with, but when you factor in ISO 13485’s high quality requirements, you’re adding on another level of challenges.

COVER INTERVIEW High reliability is of utmost importance to medical electronics OEMs. How should an EMS Provider or Contract Manufacturer (CM) think in terms of providing this high level of reliability to its customers? First and foremost, medical electronics products across the board cannot afford to have failures whether it’s in the lab or in the field. The burden is on the EMS Provider to assure that these products are designed extremely reliable, and they deliver quality time after time. In effect, the EMS Provider or CM must have quality and reliability imprinted in its DNA. This means quality steps are embedded in the overall design through the assembly and testing process. There must also be a number of welldisciplined quality control (QC) steps within the assembly process to include first article inspection (FAI), automated optical inspection, x-ray, and multiple sets of QC gates along the way. These are all embedded in the process. If you run manufacturing based on a set of disciplined processes, the end result is a medical electronics product that embodies the highest level of quality. On the other hand, when quality is left to inexperience and questionable decisions that assembly personnel make, quality and reliability are severely jeopardized.

What role does experience play in providing the ultra-reliability these OEMs expect? Vast experience and know-how are at the crux of providing medical electronics OEMs the high reliability they seek. Experience clearly reflects that both PCB design and assembly engineers have honed and continue to hone their skills and know-how over time and have learned great lessons based on inadvertent miscalculations— and they are much the better for it. Along with experience, you also have to blend in a continually growing knowledge about electronics engineering. For example, achieving Certified Interconnect Designer (CID) or CID+ certification plays a major part in successfully dealing with the different aspects of PCB layout, routing, high-speed terminations, impedance control issues, and other related design points. Another point to make is that when it comes to ultra-reliability and builtin quality, military/aerospace and medical electronics PCBs have similar requirements. When an EMS provider or CM serves both markets, the medical electronics OEM can rest assured that both reliability and quality reign high at that location. In cases like this, there is a healthy interchange and application of reliability and quality actions. As a matter of fact, the

“The challenges for PCB design and assembly stem from the fact that medical electronics OEMs continue to demand more features and functionality in an ever-shrinking board area.”

Modern Printed Circuits

ISO 13485 medical electronics standard is the equivalent of Mil/Aero J Standard for manufacturing. Both demand tight tolerance controls. EMS companies that serve these specialized markets have all the process details clearly defined and are followed on line after time to achieve optimal results.

What special design-for-manufacturing (DFM) steps need to be taken? DFM is often taken for granted. That is old thinking, and today you cannot afford to maintain that mentality any more, especially for medical electronics PCBs. PCB design layout, fabrication, and assembly and manufacturing engineers must clearly understand they must work closely together to avoid costly mistakes that arise at different manufacturing stages. That is the most critical step an EMS provider must institute within its core operations. The next critical step is to put in place welldocumented and stringent procedures. Itâ&#x20AC;&#x2122;s also vital to institute a strong culture that assures that design, fabrication, and assembly engineers collaborate on each and every PCB project to keep from sending poor designs to manufacturing, which can later create assembly or testing issues. A third step is for the PCB

designer to be in close communications with the fab house. A medical electronics PCB can have special requirements, and the designer must provide the leadership to assure that board is fabricated correctly. Another step is to give experienced QC personnel greater authority for them to take it upon themselves to monitor DFM. Here, the burden is on EMS management to nurture resourcefulness and encourage assembly personnel to learn and grow in their jobs. An EMSâ&#x20AC;&#x2122;s DNA and culture should be such that everyone from top to bottom in the organization is quality conscious and takes quality and reliability exceedingly serious. Today, we still see evidence that OEMs fail to fully acknowledge the value of DFM. A case in point is when an OEM designer reduced pad size to match trace width on a high-speed portable system design, similar to a medical electronics handheld device. That decision was made without consulting manufacturing engineering.

COVER INTERVIEW As a result, a number of issues cropped up at manufacturing. Together with other DFM issues, this design caused manufacturing yields below 60 percent when the goal was above 90 percent.

Why is it so important for medical electronics OEMs to deal with so-called “one-stop-shop” PCB design and assembly houses? What can go wrong when they select separate design and assembly operations? As I mentioned in my earlier answer, poor communications among design, fabrication, and assembly personnel can lead to disastrous results in manufacturing. Medical electronics OEMs simply cannot jeopardize product quality and reliability, which is their hallmark. Aside from this issue, other major ones deal with time-consuming problem searching, product liability, and traceability, all of which are relatively intertwined. When a problem occurs, the medical electronics OEM has to spend endless time going from one vendor to another trying to solve that problem. What usually happens in these instances is that each vendor points the finger at the other. That issue has a direct bearing on product liability, time to market, and time to revenue. It’s difficult for the

OEM to pinpoint liability when there are various vendors involved. But when there’s only one design, fab, and assembly house involved, the liability issue becomes a moot point and is quickly resolved. As far as the traceability aspect, again, multiple vendors can create havoc with trying to locate and define date codes, lot codes, and components associated with a given PCB project. With a one-stop shop vendor, the medical electronics OEM can efficiently trace a product problem by quickly pinpointing a failed device and finding out its vendor, lot code, and date code. This gives the medical electronics OEM enormous power. It allows it to quickly and efficiently learn about the problem, recall those projects, and expeditiously fix those issues, if and when they arise.

“PCB design layout, fabrication, and assembly and manufacturing engineers must clearly understand they must work closely together to avoid costly mistakes that arise at different manufacturing stages.”

Modern Printed Circuits

As far as PCB assembly and manufacturing, where should the emphasis be placed so that OEM medical electronics sub-assemblies achieve the highest reliability possible? As I alluded to earlier, maintaining high quality manufacturing translates directly into high reliability. Emphasis must be placed on the quality steps that are embedded in the assembly and manufacturing process. You are always checking, evaluating, tweaking, and streamlining that process to make it as strong as possible to achieve the reliability medical electronics OEMs demand. That stringent manufacturing process is followed day in and day out. Sometimes, it gets mundane and cumbersome. Quality and reliability come at a price. The price an EMS company pays is to diligently pursue each and every small step, one at a time, to assure attaining quality and the resulting reliability. Here, a top notch and highly experienced reliability manager on the assembly floor is a valuable asset to make sure there are no shortcuts, cutting corners, or short-changing each quality step.

Based on today’s PCB technology trends, what do you foresee for the design and assembly requirements medical electronics OEMs in the future? In the near term, the roadmap for medical electronics PCBs will be dominated by increasing numbers of small, yet highly complex products sporting the state-ofthe-art in technology. The milestones involved will deal with newer packaging and ways to maintain high quality and reliability. This means dealing with smaller, but innovative device packaging that chipmakers will soon develop to meet market demands. At the top of the list is third-level package-on-package or PoP, which means stacking three BGA packaged devices, one on top of another to make the most of valuable PCB real estate. Extremely tiny 0201 and 01005 passive devices are already being used in these products. These minute devices are so small they don’t have sufficient mass or body size to allow placing reference designators on them. As a result, automated optical inspection will have difficulty capturing an image to decipher the right component placement from the wrong one.

“The price an EMS company pays is to diligently pursue each and every small step, one at a time, to assure attaining quality and the resulting reliability. ”

COVER INTERVIEW Advanced packaging and ever-shrinking PCB real estate will also call for considerably improved PCB cleaning solutions. These devices are so small that the tiniest of flux residue can remain hidden and undetected in a small crevice. That cannot happen in a medical electronics PCB because even the minutest contaminant will cause reliability issues. Advanced packages and assurance of ultra-clean PCBs are definite milestones we will soon encounter.

How can those milestones best be met? You have to meet these milestones head on with an even stronger mindset and a more disciplined design through assembly process than ever before. Like they say, past experience is the best platform to successfully move forward. In this case, the principles remain the same, although there can be some adjustments and improvements. The point being is the successful EMS Provider dealing with medical electronics OEMs will have to continue to be at the top of its game, be creative, improvise, and not fall victim to complacency. In short, youâ&#x20AC;&#x2122;ve got to stay ahead of the curve.

Modern Printed Circuits

Introducing

iDesign

â&#x201E;˘

from

Littelfuse