Testing Todd: Design for Manufacturing? Don't Forget Test!

Over the last 35 years we have seen astonishing advances in printed circuits, flex circuits, and component technology. The introduction of surface mount technology back in the ‘80s and the continued progression of that technology has proven to be a challenge for PCB manufacturers and the electrical test arena as well.

From a development engineer standpoint, the task is to economically create the design using the best available technologies that provide the optimum result. This includes, but is not limited to, component packages, blind and buried via technology, and buried passives, while also considering the manufacturing abilities of the selected PCB fab vendor. Considerations are line width, spacing, component density, and deliverable characteristics such as TDR, HiPot, inductance, and of course, overall electrical compliance. In the early days this was never a problem as most PCBs were plated through-hole (PTH) and electrical test was straightforward. Not so much today.

Design for manufacturing (DFM) is a great discipline for creating designs that provide optimum performance while still maintaining affordability. However, what can be, and does get overlooked, is the design for test (DFT) variable. As greater manufacturing demands are put to the manufacturer, it also creates challenges to validate the electrical deliverables that may be required.

From an electrical test standpoint, the layer count of a given PCB is not an issue. The CAM systems of today can process many layers including blind/buried vias, buried passives and the like. The challenge becomes the actual test. Net intelligence is not the hurdle but how to effectively interrogate the PCB to provide validation of the electrical characteristics. Historically this has been easy.

Fixture technology and fixture testers were all the rave through the ‘80s, ‘90s, and into the new millennium. Using headed pin technology through featureless music wire allowed the successful test of most designs. Even with the higher density, the CAM systems were able to split fixtures to A and B tests to encapsulate the extremely dense PCBs. Unfortunately, this has some drawbacks. The extra fixtures and increased drilling and assembly time adds cost and time to the equation. Whether ET is captured in the quoting process by the manufacturer will be the decision of the individual manufacturer, but these costs are real in both time and materials/labor.

As today’s designs get more complex, economics come in to play as to whether fixtures are the answer. Extremely dense designs are now requiring quad-density or greater to still utilize fixture technology, or they are being converted to dedicated spring probe fixtures that are very costly. These variables are usually not considered during the quoting process (remember DFT) and can cause loss of margin by the time the electrical deliverables are met.

Now, today’s flying probe machines can test extremely dense designs without using fixtures. The cost is much less but there are trade-offs from the fixture test. Flying probes cannot provide the full parametric test that fixture testers can provide. This can be an issue when testing some military, aerospace, and high reliability medical products. These require the “simultaneous” test of the PCB for opens and more importantly, shorts. So, in some of these cases a fixture or multiple fixtures will be required. This increases cost and can cause delays in the manufacturing window due to manufacture of the fixture(s).

Where is this going? Design for test. Speaking for the ET arena, PCB designers are encouraged to take into consideration how their electrical deliverables can be met. Sure, flying probes can tackle most designs and requirements of today, including test of buried passives, HiPot, inductance, and even capacitance. However, in high-reliability products that require full parametric tests, fixtures will be required. Here is where consideration will be most beneficial. Consult with your manufacturer on electrical test density capabilities to make sure your design can be tested effectively. If your design is beyond the capability, consider adding a pad or feature to allow the effective probing of the network. Sometimes adding a small 0.010-0.015” pad, spaced appropriately for ET capability, may turn your untestable design into a routine build. This can be increasingly effective for wire-bond technology where direct probing of the wire-bond pristine area is prohibited. Doing so may stress you out a bit finding real estate to add these features for test, but usually this would not increase the price of the actual PCB build. However, it does make a significant difference in the testability of the PCB design.

While DFM is an absolute necessity in the market of today, DFT needs the attention more today than ever. An overall great design implementing DFM and DFT will make the manufacturing cycle less expensive and keep the time frame for deliverables in check. Don’t forget ET.

This column originally appeared in the August 2021 issue of PCB007 Magazine.

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2021

Testing Todd: Design for Manufacturing? Don't Forget Test!

09-07-2021

Design for manufacture (DFM) is a great discipline for creating designs that provide optimum performance while still maintaining affordability. However, what can be, and does get overlooked is the DFT (Design for Test) variable. As greater manufacturing demands are put to the manufacturer it also creates challenges to validate the electrical deliverables that may be required.

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Testing Todd: The PCB Limbo—How Low Can You Go?

07-26-2021

Columnist Todd Kolmodin takes a stinging look at the price of printed circuit boards over the past 30 years. What caused this "downward spiral" in the industry?

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Testing Todd: Meet Mr. Henry and Do Not Blow a Fuse

06-18-2021

Columnist Todd Kolmodin explains the connection between electrical test and Joseph Henry. Can you figure it out?

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Testing Todd: Keeping the Tools Sharp

05-18-2021

Quality is not just an action; it is a way of life. We can say we are quality conscious but as the days pass the discipline can fade. The tools become worn, dull and finally discarded. So, we must revisit the tool shed periodically to make sure our tools are razor sharp and at the ready.

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Testing Todd: A Point of Order—Do Not Just Rearrange the Pencils!

04-28-2021

In our concentration on continuous improvement, we should look in to the order of things. Efficiency comes from streamlining processes, effective training, and the ability to monitor success through KPIs and feedback on deliverables.

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Testing Todd: Homing in on the Target

03-30-2021

Although electrical testing provides a beneficial safeguard against an electrically inferior product reaching a customer, it does require adherence to critical processes.

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Testing Todd: Owning Your Processes

02-23-2021

It’s extremely common to write a process or work instruction and let it loose in the wild to thrive. The problem is, if there is a problem or a glitch it may never get noticed. Why you ask? It’s simple. Humans have an extraordinary ability to adapt.

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Testing Todd: Getting 'Lean' in 2021

01-26-2021

Many companies and individuals had to make life-altering adjustments in 2020 because of the pandemic, including reduced hours, telecommuting and examining how we do things in this “new normal.” Although the circumstances causing these changes are tragic, it forced us into becoming lean.

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2020

Testing Todd: Training the Force or the Few

12-31-2020

As with any business, the quality of goods and/or services is of the utmost importance. Company reputations are gauged by the success or failure in maintaining high-quality outputs. Todd Kolmodin explains how maintaining high-quality and on-time delivery depends on multiple factors: first, equipment and tools to produce the product or service, and second, the power of the workforce behind the product.

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Testing Todd: Don’t Get Pickled by the Barrel

11-25-2020

Whether you have two layers or 50 layers, it all comes down to how the layers communicate. Otherwise, you just have a bunch of two-dimensional layers, and that isn’t practical. Todd Kolmodin describes how the practical magic, of course, is plated drilled holes.

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Testing Todd: Roadmap? First, Find the Road!

10-22-2020

Todd Kolmodin originally thought of discussing roadmaps and how they pertain to our industry and analyzing trends. However, it’s difficult to work with the roadmap when you cannot find the road. Todd shares his thoughts and experiences regarding the wildfires in Oregon and the West Coast of the U.S.

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Testing Todd: Don’t Be a Boss—Be a Leader

08-26-2020

Leader, boss, follower, collaborator, teammate. These are terms we have heard many times during our travels through this thing called life. Todd Kolmodin explores the difference between a boss and a leader and shares his observations on leadership.

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Testing Todd: Too Much Automation?

08-03-2020

The last six months have brought monumental changes to commerce, manufacturing, recreation, and almost every aspect of our daily lives. Todd Kolmodin shares his thoughts on how much automation is enough?

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Testing Todd: Down-shifting to the New Normal

05-17-2020

Today, we find ourselves in a place none of us even thought could happen due to the global COVID-19 outbreak. Todd Kolmodin encourages readers to be heroes and shift down to the new normal for a bit.

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Testing Todd: It’s Not Easy Being Green (or Is It?)

04-24-2020

“It’s not easy being green,” are well-spoken words from our amphibian friend, Kermit the Frog. Now, more than ever, there is a focus on being green. Todd Kolmodin explains how one of the largest—if not the largest—contributor to waste is paper, but the difficulty is letting go of it in the consumer and manufacturing segments. For the workplace, this can be more difficult, or is it?

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Testing Todd: Waste Not, Want Not

03-15-2020

Any time we overestimate our projects, we lose costs. For individuals, it may not be as monumental, but for manufacturing, it can be painful.

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Testing Todd: Looking at Digital With 11111100100 Vision

02-12-2020

Todd Kolmodin explores how far technology has come, from the challenge to "plug in" in the '80s, to how difficult it can be to "unplug" in this digital age.

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2019

Testing Todd: Go To Bed Hungry

12-19-2019

Another decade is coming to an end, so, forward thinkers, let's take this time to review the past, evaluate past decisions, and hopefully make prudent decisions to move forward in the ever-changing marketplace in which we exist. There has never been a Magic 8 Ball to predict what is going to happen, so we all do our best to calculate, look over the fences, and aim to remain in this competitive meat grinder we call “the market.”

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Testing Todd: Staying in Your Lane

12-15-2019

As 2019 comes to a close, Todd Kolmodin addresses the importance of standardization, which comes down to an agreement that we are to perform a task or set of tasks the same way every time. Putting your engineering hat on, this provides predictability with a high degree of accuracy.

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Testing Todd: Understanding the Fine Print

10-08-2019

New technologies are emerging each day with more stringent requirements than the past. Also, reversals in obsolescence programs bring products back to the market for which the original documentation and/or requirements are ancient compared to today’s standards; in some cases, this documentation is even lost. Further, it is not uncommon to find that original artwork isn’t available or that the part must be recreated from a finished circuit board sample.

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Testing Todd: What Do You Mean 'Passed' Isn't Enough?

08-05-2019

From a reliability standpoint, we need to quickly assess what risk we may have uncovered when faults are detected during electrical test (ET). "Passed" is not always passed. We must be diligent to scrutinize the failures found during routine ET as a high yield may not indicate high reliability.

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Testing Todd: The Evolution of Probers and Fixture Testers: Blinded by Science

06-26-2019

The evolution of the PCB has come a long way in the last 30 years. The science of electrical test has had to travel that road as well. It's not just a question of screening for opens and shorts. Today, the library extends to interrogating passive components, efficiently and cost-effectively evaluating dielectrics with multiple planes and pairs involved, and adhering to strict requirements from the military, export regulations, and OEMs alike.

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Confidence in Inspection

04-12-2019

The job of third-party inspection is to provide an unbiased review of the customer requirements versus the final product manufactured. This inspection can include both physical and functional criteria. Read on to understand the growing acceptance and requirement of third-party inspection in many areas of the manufacturing industry, including military, aerospace, and medical.

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2018

Testing Todd: What’s in your ET?

07-13-2018

With all the buzz around automation, paperless operation, and integrated processes, it’s time to think about how the connected systems work within an electrical test department. We are all familiar with computer-aided design (CAD) and computer-aided manufacturing (CAM), but with electrical test we can also add computer-aided test (CAT) and computer-aided repair (CAR).

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Testing Todd: How are the Ratings?

05-24-2018

Hello, readers! Thank you for stopping by again. Let’s talk about ratings. No, I’m not talking about the latest Facebook likes or Twitter retweets, but a topic that confuses many final QA technicians the world over. I’m talking PCB voltage ratings.

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Testing Todd: AVI—Your Tireless Friend in Final Inspection

05-01-2018

The “automation vs. human” debate continues. There are experts with many years of experience -performing final inspection with precise detail. This is not debated. However, in the course of human events, circumstances change with unpredictable results. This presents challenges to manufacturers striving to deliver product on-time and within specification guidelines.

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2017

Testing Todd: No Missed Steps—5S Methodology

08-22-2017

In today’s work environment, a company should strive to produce quality product, maximize margins and reduce cost as much as possible. At times, this can be very difficult. Work ethics and methodologies of “how to do things” have developed over many years and can be deeply rooted in many manufacturing theatres. We find at times the “way we have always done it” may not be the most practical way today. This is apparent with the advances in automation, labor force reduction and shifting market demands.

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Flying Probe Testing vs IPC-9252B

05-30-2017

Flying probe testing is extremely popular in today’s manufacturing theatres. The main factor is cost reduction in contrast to dedicated fixtures and fixture testing. However, there are some limitations in flying probe testing when gauged against industry specifications—specifically, the use of indirect vs direct testing in Test Level C.

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Testing Todd: Go With the Flow

04-18-2017

In today’s testing theatre, the flow of information from the OEMs and manufacturers to the independent contractors is mission-critical. Missing information can cause delays, incorrect processing and ultimately scrap or end user rejection of the product. The buzz term being used a lot today is “flow-down.” It pretty much describes itself: It is the flow of information down the supply chain.

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Testing Todd: Plating and Surface Finish—The Challenges to Electrical Test

01-23-2017

Plating and surface finish applications are not without their own set of challenges but these manufacturing processes also affect the electrical test theatre. Microvias, high-aspect ratio plate quality, and surface finish all have their own challenges in ET.

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2016

Testing Todd: Are You a Leader or a Manager?

10-21-2016

The question can be asked, are you a manager or a leader? Can you be both? Is there even a difference? The answer to this latter question is, yes. In a successful organization there are many people performing different tasks all in harmony to make the business successful. Some individuals can be phenomenal leaders while others can be excellent managers. Some can actually be both. How do we define a leader from a manager?

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Test & Measurement—The Case for Validation

07-15-2016

Test and measurement (T&M) are terms that can strike fear into the most robust of minds. Many engineers create designs and products of the future with specific results predicted for performance.

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Testing Todd: Quality Management and the Hidden 'I' in Team

05-24-2016

Today, businesses of all types are jumping on the quality bandwagon. The more critical the product, the more the consumer/customer wishes the highest possible quality in the goods or services requested.

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Quality Management and the Hidden 'I' in Team

05-06-2016

Today, businesses of all types are jumping on the quality bandwagon. The more critical the product, the more the consumer/customer wishes the highest possible quality in the goods or services requested. Customers send surveys with buzzwords like ISO, QMS, and AVL for their suppliers to complete so they have confidence that what they receive is of the highest quality.

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Testing Todd: Process Management: Doing It Right

04-27-2016

Simply put, process management is the idea of figuring out how to do something, documenting it and then monitoring the effectiveness of the steps you created for the end result. Simple, right? Unfortunately, many who take on this endeavor fall short due to missing some key attributes to creating and maintaining a robust process. This article features eight steps in building and maintaining a robust process.

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2015

Flex and Rigid-Flex Circuit Testing: Challenges & Solutions

06-24-2015

Although flex circuits are nothing new in today’s technology roadmap, the testing of unpopulated flexible circuits can be challenging. In this article, columnist Todd Kolmodin writes about the different methods available to test these circuits.

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Electrical Test: Surface Finish vs. Water Marks

05-20-2015

New finishes have come to market; some allow better conductivity, while others reduce the overall cost of precious materials. Regardless of the finish, electrical test must be performed on these circuits. With that comes the caveat of how much of a witness mark can be left on any given landing pad and still be acceptable to the CM or the final OEM user. Todd Kolmodin explains.

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Challenges of Electrical Test

01-28-2015

In our arena today, we can solve pitch and density with flying probe machines, and volume with our grid testers, but the catalyst that is in the mix is that pesky soldermask! Here's why I bring up that necessary process as a problem for electrical test.

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2014

What is 4-Wire Kelvin?

12-05-2014

"I've been asked many times, 'What is 4-Wire Kelvin?' So, this month I will explain the 4-Wire Kelvin Test and how it can help uncover defects that normally would go undetected in standard electrical test methodology," writes Columnist Todd Kolmodin.

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Where Do We Go From Here?

12-01-2014

In this installment of "Testing Todd," Gardien's resident expert Todd Kolmodin answers questions from Dan Beaulieu concerning the future of electrical test. His focus is on the future of testing technologies, testing equipment, and E-test.

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Testing Todd: Where Do We Go From Here?

12-01-2014

In this installment of "Testing Todd," Gardien's resident expert Todd Kolmodin answers questions from Dan Beaulieu concerning the future of electrical test. His focus is on the future of testing technologies, testing equipment, and E-test.

View Story

Flying Probe - Indirect Testing vs. Military

08-19-2014

The use of flying probe testers has become increasingly popular in recent times, mainly due to the affordability of the equipment and also the reduced cost of testing, as no dedicated or "bed of nails" fixture is required. When using flying probes to test military product, one must be diligent to make sure the test method is allowable.

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Testing Todd: Flying Probe - Indirect Testing vs. Military

08-19-2014

The use of flying probe testers has become increasingly popular in recent times, mainly due to the affordability of the equipment and also the reduced cost of testing, as no dedicated or "bed of nails" fixture is required. When using flying probes to test military product, one must be diligent to make sure the test method is allowable.

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Everything You Wanted to Know, But Were Afraid to Ask

07-30-2014

This month, "Testing Todd" author Todd Kolmodin of Gardien Services USA presents readers' questions about the basics of electrical test, including the different types of testing available today.

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Testing Todd: Everything You Wanted to Know, But Were Afraid to Ask

07-30-2014

This month, "Testing Todd" author Todd Kolmodin of Gardien Services USA presents readers' questions about the basics of electrical test, including the different types of testing available today.

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Seven Tips for Choosing the Right Test Service

06-12-2014

Do you need to go outside your company for your testing service? Maybe you have capacity issues, maybe your equipment is down, or maybe you just want an established back-up plan? Whatever the reason, it is very important to choose the right outside testing service because, ultimately, you're not just choosing an objective service provider; you're choosing a partner.

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A Summary of Various Test Requirements

06-03-2014

The PCB industry has advanced significantly in the recent millennium. OEM specifications and requirements have also advanced due to the maturing of technologies, which has caused the requirements of electrical test of these higher technology products to advance and increase in intensity.

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Testing Todd: A Summary of Various Test Requirements

06-03-2014

The PCB industry has advanced significantly in the recent millennium. OEM specifications and requirements have also advanced due to the maturing of technologies, which has caused the requirements of electrical test of these higher technology products to advance and increase in intensity.

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