PCB Talk: Pin-Out Challenge—Re-think the Solution

Semi-additive PCB fabrication is getting a lot of attention as fabricators install new processes that enable them to provide much finer features than traditional subtractive etch processes. This is opening new opportunities and tools for PCB designers to solve today’s complex electronics challenges. These packaging and interconnect solutions can reduce size and weight by 90% over traditional processing techniques in the U.S. and bring significant signal integrity benefits. As with any new technology, there are many questions: How to apply this new capability to the design, what are the signal integrity considerations, and who has the capability to supply these fine features?

This column kicks off a series of interviews with veteran PCB designer who share their thoughts, opinions, and questions as they navigate this new frontier. I recently sat down with Cherie Litson, MIT CID/CID+, president of Litson1 Consulting and an instructor at Everett Community College, to understand her perspective on this new fabrication capability.

Tara Dunn: Cherie, you are a well-known designer and instructor in the industry, but for those who have not had the opportunity to meet you, could you please start with a quick introduction? 


Cherie Litson: My background is broad and deep: it has been an amazing opportunity to work with so many companies, notably Microsoft—where I helped create their design database for the Surface and, earlier, the first wireless mouse. The first hand-held ultrasound from SonoSite was another passion project. Passing on what I have learned from others led me to become a Master Instructor for the IPC Designer Certification program. I learn more every time I teach. As a member of the Averatek Community of Interest, I encourage everyone in the industry to share their experiences with this new technology so we can all learn and optimize the benefits of new developments.

Figure 1: Cherie Litson is an instructor at Everett Community College.

Golf is my other passion: I have been involved in the LPGA Amateur Association (previously EWGA) since 2001. While learning how golf and the professional world mix, I have been able to take my golfing teams from local to national competitions for the past five years. I could go on about golf, but let’s tee up this discussion!

Dunn_Fig_2_cap.jpgDunn: Impressive! My golf skills stop with my highly developed golf cart driving expertise; actually hitting that ball in a straight line is something I am still working on. You mention Averatek’s Community of Interest; this is new. Can you tell me about that?

Litson: Averatek, a Silicon Valley innovation company, manufactures key chemistries and licenses the processes for their use. Two processes, in particular, are having an effect on the PCB design industry: LMITM, the catalytic ink used in the A-SAP™ process, and Mina™, a surface treatment that enables soldering to aluminum. These products are now commercially available through licensed fabricators, so it is important for designers to learn about them. The Community of Interest is starting to bring together a wide range of people from all sectors of the industry who are interested in learning more about semi-additive PCB processes. Nothing formal yet, but we're hoping to set up a website or blog to pool our knowledge on these types of products.

Dunn: What aspect of these new PCB fabrication capabilities is most valuable to you?

Litson: I am excited by the ability to route traces at 1 mil or even below, as that opens possibilities for designers to produce increased density at lower cost. The A-SAP process provides the designer an opportunity to significantly reduce layer count, simplifying complex designs. 

These geometries can potentially eliminate pin-out challenges while maintaining reliable signal integrity. I can see the advantages of using a taller yet narrower trace for signal integrity; this is the winning factor for me. This process results in traces with vertical rather than trapezoidal sidewalls, realizing benefits in both size and RF advantages, eliminating the etch compensation requirements.

Designers working on next-generation products will be excited about the ability to form a 15-µm trace and space with the semi-additive processes. Many designs are being driven to require line and spaces at 50 µm due to smaller pin spacing on components and smaller package products. The fabrication of these traces is something that has not been available in the U.S. until now.

Dunn: Cherie, I know you are an avid learner; when you are researching new technology, which reliability tests mean the most to you?

Litson: As I consider how to best apply this technology, material compatibility is an important aspect. It is important to know that a new process is going to be compatible with nearly all materials. Next, I’m looking into the electrical aspects of these new geometries.

I also look at proven reliability parameters: the A-SAP process passed peel strength, IST coupon testing, and signal integrity analysis across a variety of materials.


Dunn: Working with something new can be exciting and just a little intimidating. Navigating the learning curve, do you see any challenges for designing with this new technology in mind?

Litson: In my opinion, designers should remember their basic electronics—it influences everything we do. We must understand the physics to make certain we know what will be affected. With these new parameters, we will need to go back and take another look at our calculations, which are based on the resistance of copper which is based on the area. Then bring into the equations the resistance of the dielectric materials, layer structures, etc. I am curious to see how the geometry of the conductors shifts the electrical results.

Because each product is different, there are few set-in-stone design rules for semi-additive processed layer-only guidelines. The most important guideline: this process requires close collaboration between design and fabrication. For additional guidance, a collection of case studies would be great, maybe online as a dynamic design guide. Just brainstorming!

Dunn: An online dynamic design guide is a great idea. Taking a step back from design, why do you feel that this new technology is important to the industry?

Litson: I think this is important to the industry for several reasons. One is implementation of this process—it is designed to integrate with existing PCB fabrication equipment, so it does not require the costly capital investment usually associated with new technologies, allowing even the smaller and mid-size shops to offer this advanced technology to their customers.  

While this process certainly gives us the benefit of 25 µm line/space and below, the additive process also has RF benefits at larger feature sizes, such as improving impedance control. I think we are just scratching the surface of how to get the most benefit from this capability. I am already seeing the simplification of complex designs, improving yields, and reducing costs. I am excited to see where this technology takes us. 

Dunn: Cherie, as we wrap up, what advice would you give to PCB designers who are just hearing about the opportunity to work with fabricators that can now offer these fine feature sizes?

Litson: Start today! Do some research, share your concerns, share your experiences, try it out. I can see many benefits to utilizing this process at the 75 µm, 50 µm, and 25 µm trace sizes and smaller.

Dunn: Thank you so much for talking with me today. To learn more, what is the best way to reach you?

Litson: The best way to reach me is at Litson1@aol.com. Thank you.

This column originally appeared in the May 2021 issue of Design007 Magazine.




PCB Talk: Pin-Out Challenge—Re-think the Solution


This column is kicking off a series of interviews with veteran PCB designers: getting their thoughts, opinions and questions as they navigate this new frontier. Tara Dunn interviews Cherie Litson, MIT CID/CID+, president of Litson1 Consulting, and an instructor at Everett Community College, to understand her perspective on this new fabrication capability.

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PCB Talk: Additive Electronics—Next Generation PCB Capabilities


Exciting news! This column marks the launch of a series of columns diving into semi-additive PCB (SAP) manufacturing processes. We will explore topics ranging from SWaP benefits, signal integrity benefits, materials characterization, reliability testing and even the search to find a calculator that is compatible with straight conductor sidewalls and line width and space at 1 mil and below.

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Flex Talk: Simplified Assembly of Aluminum Flexible Circuits


Tara Dunn sits down to discuss Mina™ with Divyakant Kadiwala, vice president of manufacturing for Averatek. He has been instrumental in the development of this assembly process.

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Flex Talk: Demystify Flexible Stack-ups


The sheer number of flexible laminate materials and constructions can be a bit daunting for those new to flex and rigid flex design. Tara Dunn sits down with Jeff Martin from Omni PCB to hear his insight into flexible laminates and his advice when working on a flex stack up.

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Flex Talk: Communicating Outside the Box Is Key to Flex DFM


What do you do when you are designing a flexible circuit and need to go “way outside the box” to get the desired end-result? Tara Dunn looks at a few success stories, including gold conductors and complex rigid-flex, and emphasizes the power of communication.

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Flex Talk: Communication Goes Both Ways


Technology, whether new to you or new to the industry, both require communication between the end-user and the fabricators. Tara Dunn explains how a collaborative approach benefits not only the end-user seeking the information but also the fabricator that will be providing the technology.

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Flex Talk: The Black Magic in the Business


When you work with flex or rigid-flex, the communication between designer and fabricator needs to be impeccable, and the primary method of transferring information is through the fabrication notes. Tara Dunn gives a recommendation that, although not strictly required by the fabricator to build the product, will certainly benefit the end-user.

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Flex Talk: Additive and Subtractive—When Opposites Attract


Market dynamics in the electronics industry are quickly changing. Some solutions add considerable cost to the PCB and often introduce reliability and yield concerns. Tara Dunn explains an alternative that has been installed in three U.S.-based PCB fabrication facilities: the A-SAP™ process, which is Averatek’s semi-additive process.

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Flex Talk: It’s the Little Things


Let me share a personal moment. Shortly after we started staying home and socially distancing, I came down the stairs from my home office and noticed something colorful on the sidewalk. Keep in mind that I live in Minnesota, and anything colorful is extremely eye-catching while in stark contrast to the winter grass and leafless trees. Looking closer, someone had colored big, beautiful hearts all along my sidewalk and driveway, leaving a fun message at the end of all those colorful hearts. That simple act of kindness made me smile for days, anytime I looked outside and saw the chalk drawings and messages. It also reminded me that in the midst of uncertainty and life being unsettled, one small thing could make a significant impact.

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Flex Talk: Unintentionally Adding Cost?


When designing a PCB, rigid or flex, there is a continuing series of choices and trade-offs, some with greater cost impact than others. Tara Dunn discusses a few things that can easily be overlooked when putting together the puzzle pieces of a design and that may have an unintended impact on the overall cost.

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Flex Talk: Mina—Enabling Soldering to Aluminum


Averatek recently launched Mina™, a chemistry that offers exciting benefits over traditional methods of soldering to aluminum. Tara Dunn had the opportunity to speak with Divyakant Kadiwala, director of manufacturing at Averatek, to learn more.

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Flex Talk: Additive PCB Technology for Next-generation Electronics


Semi-additive PCB processes help to enable very fine features, with trace and space down to 25 microns and below, significantly reducing space and weight for next-generation electronics. Tara Dunn speaks with Todd Brassard and Meredith LaBeau from Calumet Electronics about how the company is the first domestic PCB manufacturer to license Averatek’s A-SAP™ process and will be presenting information on the industrialization of this process at this year’s IPC APEX EXPO.

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Flex Talk: The Challenge of Change


I recently kicked off a presentation on flex and rigid-flex by asking for a show of hands of those who had never worked with flex materials or considered themselves to be just learning how to design with flex. Over half of the room raised their hands, which excited me because I could help them learn something new. In my opinion, the best way to lessen the challenges and uncertainty of change is to arm yourself with as much knowledge as possible.

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Flex Talk: Additive Electronics Momentum


I have been involved with additive electronics for the past several years, and I have seen the discussion of and demand for sub-75-micron feature sizes slowly grow. Conversations, questions, and research about SAP and mSAP increased significantly when it was announced that the mSAP process was used to create the circuitry in the more recent versions of our smartphones. While this process is available in very high volume in some areas of the world, it is still in the early stages of development in other areas.

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Flex Talk: Don’t Build Flex That Doesn’t Flex


One of the primary advantages of moving to a flexible circuit design from a rigid board is the ability to package the flex in three dimensions, bending or folding into imaginative configurations and saving precious space in the final package.

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Flex Talk: When You Do Everything Right and Something Still Goes Wrong


This industry is full of tales describing the work and effort needed to overcome fabrication hurdles to produce a complex design. Tara Dunn shares a case study of one of those types of designs.

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Spark an Idea


One of the favorite parts of my job are the days when I meet with a group of engineers and designers to talk about flex and rigid-flex. We might do a "lunch and learn" with a general overview of the technology or address a specific challenge. It is always helpful to bring samples to pass around and show different features. Usually, looking at a sample will spark an idea and the comment, "I wonder if we could do something like this.” From there, the brainstorming begins.

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Flex Talk: New Materials or New to You?


There are so many new processes and materials in the PCB segment that it can be a challenge to keep up with all the new developments. It is fun to start chasing the next new thing, but it is important to keep in mind that even materials and processes that have been around for a while are still new to someone.

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Flex Talk: New Engineering Talent Joining the Electronics Industry


Last spring, Ross Olson, an undergraduate student at the University of Minnesota and member of the U of M Solar Vehicle Project team, attended the Geek-a-Palooza event in Minneapolis and displayed one of their race cars. Tara Dunn had the opportunity to get to know Ross, and recently sat down with him to talk about his interest in engineering and his thoughts on the future of the electronics industry.

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Flex Talk: Old-fashioned Networking


We live in a connected world. Information is collected at an astonishing rate, and people are working diligently to put this information to good use. It is new, fun, and exciting. But I sometimes wonder what is going to happen to the good, "old-fashioned" networking. Not networked devices, but the act of going out and meeting people in our industry, learning about their story and expertise, and sharing yours—mutually beneficial sharing of information and resources.

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Flex Talk: FlexFactor—Imagination and Innovation


The ultimate goal of FlexFactor is to create a generation of students who use their critical thinking, creativity, communication, and collaboration skills to create the materials and devices that will address and mitigate the biggest challenges of the future.

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Flex Talk: The Myth About Rigid-Flex Costs


Do you cringe when you think of the option of rigid-flex? It is not an uncommon reaction when talking with designers and engineering managers about using rigid-flex to solve a packaging problem. Why? The most frequent answer is, “They are so expensive.” While it is true that a rigid-flex PCB is typically more expensive on the surface when compared to rigid-board solutions with cables and connectors, a lot is being missed with that mindset.

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Flex Talk: Mina—RFID, LED and What Else?


“The science of today is the technology of tomorrow.” This Edward Teller quote is an apt description of the Mina product. This advanced surface treatment, recently developed to enable low-temperature soldering to aluminum in the RFID market, is not only finding success in that market, but quickly finding a home in other markets, including the LED market, where the incentive is both cost and improved LED performance.

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Raising the Capability Ceiling: SMTA Upper Midwest Chapter Expo


An energetic and engaged crowd filled the recent SMTA Upper Midwest Expo & Tech Forum. The event, held in June 14 in Minneapolis, Minnesota, hosted 57 exhibiting companies and had over 100 pre-registered attendees. The underlying theme for the technical presentations was "Raising the Capability Ceiling!" Here's a wrap-up of the event.

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Flex Talk: E-Textiles—the Wild Frontier


How many hours is your car sitting idle outside in your driveway or a parking lot? What if your car was used for solar harvesting—converting heat to energy? What about biometric sensors in automotives: skin sensors for preventing DUI, posture identification to monitor driver fatigue, monitoring exposure to hazardous materials in a load for truck drivers.

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Flex Talk: Something New for Everyone


Whether you are new to single- and double-sided flex, moving into rigid-flex construction, thinking of using bookbinder technology, or investigating an additive process, working with new technology can be both exciting and challenging.

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Flex Talk: Invited Guests to the Party


Hanging on the wall in my office is this quote from Jeff Bezos: “We see our customers as invited guests to a party, and we are the hosts. It’s our job every day to make every important aspect of the customer experience a little bit better.”

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FlexFactor: Faith in the Future


Take just a minute and read through this list of new product ideas. Can you identify the common thread? Yes, they are all enabled by advanced technology, but would you believe that these products were all pitched in the last year by high school students?

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Flex Talk: The Man Behind the Curtain


“Pay no attention to the man behind the curtain.” This famous quote from The Wizard of Oz conjures up the image of Dorothy, the Tin Man, the Cowardly Lion and the Scarecrow discovering that the great Wizard of Oz isn’t as grand or as magical as he seems.

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Flex Talk: Knowledge is Power


“What can I do to help drive cost from my design?” This is a question that I am asked routinely. That question is often followed by, “Can I get these faster?” Both questions are even more predominant when talking about flexible circuits or rigid-flex.

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Flex Talk: Mina—Trouble-Free Soldering to Aluminum


Thinking about the RFID market and the significant growth projected in this market, I decided to do a little research on RFID tag manufacturing. During this research, I learned of a relatively new offering, Mina, an advanced surface treatment technology that addresses the common constraints of large scale manufacturing of aluminum on polyester (Al-PET) circuits.

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Flex Talk: Squink—Integrating Fabrication and Assembly in one Package


When walking through trade show expos, I tend to be drawn into product demonstrations on the show floor. Recently, at the IPC APEX EXPO, I stopped in front of a piece of desktop printing equipment that was demonstrating with a flexible circuit.

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Flex Talk: Flex Material Handling—An Inside Peek


As increasingly more designs move to flexible materials to take advantage of space, weight or packaging benefits, it has been clear that flexible circuits require a different set of rules than their rigid counterparts. We spend substantial time working through the design to ensure that he flex is as robust as possible.

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Flex Talk: Final Surface Finish—How Do You Choose?


There are so many final surface finish options to choose from today. How do you decide which is best? HASL—both tin-lead and lead-free—immersion tin, immersion silver, ENIG, OSP, and ENIPIG are the primary finishes used in PCB fabrication.

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Flex Talk: A Glimpse into PCB Sales


Summarizing the feedback from both customers and manufacturers, the most successful PCB salespeople are organized, take a genuine interest in their customers’ needs and business challenges, have a better than average understanding of the PCB industry, fully understand the manufacturer’s strengths and capabilities and advocate for both to find the best solution.

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Flex Talk: Troubleshooting Flex Circuit Applications for Mil/Aero Projects


I imagine that everyone has been in this position at one time or another: Despite everyone’s best attempt at creating the perfect design, PCB fabrication and assembly, something goes wrong and the troubleshooting begins.

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Flex Talk: Inaugural West Coast Geek-A-Palooza a Fun-filled Success


Geek-A-Palooza kicked off the 2016 schedule May 12 in Irvine, California. Historically, Geek-A-Palooza has been held in Minneapolis but is expanding this year to include Orange County and Boston as well.

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Flex Talk: PCB Sourcing? One Size Does Not Fit All


When analyzing a set of PCBs to improve yields and maximize profits, the first place to start is with a critical review of each PCB design. Are there any attributes that are pushing your manufacturer’s standard design rules? If so, is this necessary to the design or is there another approach that could improve the manufacturer’s yields, reduce cost, and ultimately increase profit?

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Flex Talk: Thoughts on the IPC Flexible Circuits–HDI Forum


As an attendee at the IPC Flexible Circuits–HDI Conference held October 28–30, I found myself in a room of people, all eager for technical information, with the opportunity to reconnect with industry friends and to make new connections. The audience was diverse with young people, new to our industry, sitting alongside industry veterans willingly sharing their knowledge and passion for HDI design and flexible circuit technology.

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Designing Flex Circuits for Domestic Prototyping


Designing a flex circuit to be prototyped domestically? No problem. Designing a rigid-flex circuit for production offshore? Got it. Designing a part that will be prototyped domestically with a seamless transition to offshore production? That can be a little more challenging.

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Rigid Flex: Total Cost Comparison


The transition to a rigid-flex design from the traditional approach of using cable assemblies to join two or more PCBs has obvious benefits—space, weight, packaging, reliability and increased currently carrying capabilities. Yet many times the perception that rigid-flex is a high-cost solution causes designers and engineers to hesitate.

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Primary Cost Drivers for Flex Circuit Designs


Someone once told me that the potential applications for flexible circuits are really only limited by our imaginations. After pondering that a bit, I had to agree. In fact, one of the things I like best about what I do is that moment during a discussion when I can see the light bulb go off in a designer's head.

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The Flex-to-Fit Approach


The flex-to-fit concept reminds us that creativity and engineering go hand-in-hand. When there is not ample space for a conventional approach, this process, which is the convergence of the mechanical world and the electronics world, results in the ability to design a flexible circuit along the contour of an existing, irregularly shaped structure.

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