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PCB Talk: SAP Evaluating From Design Perspective

Semi-additive PCB fabrication processes add a new tool to the PCB designer’s toolbox. As with any new tool, there is a learning curve. To help shorten that curve and expand the growing body of knowledge, I spoke with Randy Chase, CID, senior manager of PCB and Module Design at pSemi, a Murata Company.    

Tara Dunn: Randy, you and I have known each other quite a while. I think your expertise in both design and fabrication makes you uniquely qualified to evaluate new technologies and PCB design approaches. Would you please tell us more about your background?

Randy Chase: My career started in middle school with basic drafting classes. In 1973, while I was in high school, I got a job in drafting and design for a small electronics company. After learning about schematics and design, I wound up in a service bureau. I learned so much that I am forever grateful to L&M Drafting Service for really getting me going. After that, I was a “road shopper” for many years, and continued to develop as a designer, keeping pace with the most senior guys. After paying my dues, I created my own successful service bureau. Then I partnered with a buddy who was going out on his own; we had developed a relationship from working together years earlier, so we decided to make a bigger service bureau. It became very successful. 

From there, I became an independent consultant to large and small companies. I’ve been involved in every aspect of configuration management, mechanical drafting, and PCB design, most recently in a director or manager position, coaching more junior designers and exploring developing technologies.

My experience is quite unique and diversified, but as for PCB designs, I’ve designed everything from satellites and aircraft, broadcast systems, cellphones, and super computers, to irrigation systems, semi-trucks, submarines, medical devices, and electronic wine stoppers. I even have a design on Mars. Everything had its challenges, but all were successful.

There may not always be a readily available solution to a given issue, but the joy comes from the creative process—to develop or create a solution. After nearly 50 years in the industry, I must say that the Averatek Semi-Additive Process (A-SAP™) is one of the needed breakthrough solutions for the roadblocks designers have been running into for years.

Dunn: How did you first hear about semi-additive processes, and what made you want to learn more?

Chase: In the semiconductor industry, everything keeps shrinking and precision is paramount, so a few years ago we hit the limits of physics for what could be fabricated on a PCB. Back then, we tried a semi-additive process that had just been developed. While it was eventually successful, the turn times and communication with the vendor were poor at best. So, we kept searching for other solutions, and found that using a laminate interposer on a generic PCB got us by for a while. But alas, we eventually needed to remove the interposer as part of the signal integrity equation, so it was back to searching for a PCB-only solution. To test, characterize, and evaluate our ICs, we must mount the bumped die directly on a PCB, so that means our ball pitch can be anywhere from 100 to 150 mm apart. Yes, it’s kind of humorous when you hear about designers dealing with 0.35–0.4mm pitch BGAs and our issues are tackling 100–150 mm pitch. We don’t even deal in millimeters; we deal in microns.

During the search, I came across Averatek and started communicating to learn more. We got in touch with a fabricator that was implementing the A-SAP process and did a trial run of the original board from many years ago. Low and behold, we came out with terrific results, had great communication with the fab vendor, and were extremely pleased with a quick turnaround on the fabrication cycle. We now have many boards using the process and continue to develop technology alongside the fab vendor.  

So, trace/space is just one part of the equation, but since our ICs are typically RF, the topology of creating a squared-off trace (instead of the typically etched trapezoidal results of an etching process) is very beneficial as we continue to increase frequencies. I got a bit carried away here, but there is a lot to be excited about.

Dunn: Why do you feel that this technology is important to the industry?

Chase: In the PCB industry, our current solutions can only take us so far due to the limitations of physics. I mean, PCB fabrication has remained basically unchanged over the past 50 years. Sure, there are lasers for smaller holes, and bigger and better presses for multi-lamination cycles, but in the end, you still need to etch copper and plate in order to create your conductors. The whole etch process can only take you so far (or so small, if you will) that the limitations of the etch process become evident with very small or very dense boards.

Another benefit is for RF performance. If you look at a cross-section, instead of having a trapezoidal trace (which will be more lossy), you’ll see a squared-off trace with a much tighter tolerance. This will be hugely beneficial as frequencies get higher and higher.

 Dunn: As you discuss this technology with other industry experts/customers that have a need for fine feature sizes, what stands out to you? Are they receptive? What constraints do they mention, and what benefits intrigue them the most?

 Chase: I find that most of my colleagues are very receptive to a semi-additive process, but it’s going to take time to gain traction. Fifty years of “this is the way we’ve always done it” is hard to change overnight. In my humble opinion, this technology could revolutionize the PCB fabrication industry. In chatting with some of the larger fabricators, they are seriously looking at the minimal investment to break the 25-mm trace/space barrier. 

Dunn: Collaboration between fabricator and designer is especially critical with semi-additive processes. How do you facilitate communication, and what is your advice for maximizing the advantages of these new capabilities?

Chase: The approach that we have used is cautious for sure; we didn’t announce to every design engineering group that “we’ve got it covered.” We targeted one group, did an evaluation skunk works layout, submitted it to the fabricator, and received feedback. Realistically, not all design parameters have been defined by the fabricator as they are learning just as we are, so collaboration is the key. Initially it will be a somewhat iterative process, and you absolutely must have a relationship with your vendor that includes great communication. Don’t expect to design something and just hand it off. We’re in the middle of a design right now that has had a great deal of communication with our fabricator, and we negotiated some of the critical parameters to make the circuit work. The good aspect of A-SAP is that the material is not an issue. We are using some higher end, RF-specific materials with great success.

Dunn: Can you tell us a little about high-level projects you are working on now?

Chase: Sorry, not specifically; but I can say that we have a current project consisting of 12 boards that are using this process because we have 25 mm trace/space with no other options available. And again, we have been communicating with the fabrication vendor throughout the design process. Our process is that whenever a change is made on the PCB, we resubmit for fabrication approval prior to finalizing for a design review. While it’s a very iterative and time-consuming process, we know there will not be any surprises in the end because the fabrication vendor knows exactly what to expect, as they’ve been involved throughout the entire process. Is this approach over-cautious? Maybe, but the proof will be on-time delivery within budget.

Dunn: You have a strong commitment to continuous improvement, growth, and customer service. What is your vision for the future?

Chase: Part of the mission statement in my departments and businesses has always been “2% better” and “customer first.” Those two statements encapsulate how and why we have been successful. Because if you are not improving, you are falling behind, and without customers, you don’t have a business.

My vision for the future of PCB design and fabrication? That brings me back to the autorouter days—just hit the “easy” button and the board is finished. No, there is still no “easy” button with PCB design or fabrication. PCB designers are becoming much more engineering-savvy and need to be respected much more in the industry; we are driving new technology.

Dunn: Thanks for sharing your perspective. 

This column originally appeared in the January 2022 issue of Design007 Magazine.