Designing for Complex PCBs

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The I-Connect007 editorial team sat down with Freedom CAD’s Scott Miller to talk about the industry’s demand for more increasingly complex PCBs, and the challenges this presents. They also discuss Freedom CAD’s in-house training programs, the company’s recent book authored by Scott, and why communication is such an important tool in a PCB designer’s toolbox.

Barry Matties: First, tell us a little bit about Freedom CAD and what you do.

Scott Miller: Freedom CAD was founded in 2003 by a husband and wife, Lou and Lauren Primmer. In May of 2003, they acquired Plexus’ Nashua, New Hampshire, design center, and started Freedom CAD Services with 12 employees. They were fortunate to be able to bring some of the best designers from Plexus with them to start the business. Since then, we have fluctuated from 40–60 employees, depending on how the demand for our services has swung. Our focus is on PCB design, servicing all of the aspects of PCB design, electrical engineering, mechanical engineering, and signal, power, and thermal analysis. However, we’re best known in the market as a PCB layout specialist for complex, rule-driven designs. We also provide turnkey manufacturing solutions through strategic partners to provide customers with the ability to get from what I call the “CAD to the lab” with one-stop shopping.

Matties: In the years that you’ve been doing this, you’ve seen the complexity of the boards increase.

Miller: Dramatically. And the funny thing is that everybody’s perspective of complexity is big. Big boards can be very complex. However, the irony is that small boards can also drive a lot of the complexity because you have less space to work with. Everybody’s trying to make things smaller and power-efficient. We’re used to being challenged by large, complex boards. We still do those types of designs with multiple high pin count FPGAs and multiple banks of DDR, but now we see more of these smaller boards that are also complex and tight. They are similar to a system on a chip, but still a PCB. They can be challenging, with the HDI technology and high-component densities, and are similar technologies to what you find on a larger-scale board, but now you’re confined to a much smaller footprint to work within. The cellphone is a perfect example of advancing technology that has driven so much capability into a handheld device.

Matties: Have you seen a shift in the type of customers as well?

Miller: With the IoT or wearables industry, there’s a whole other realm of customers that you wouldn’t have thought of as a good candidate for PCB design and layout. But our core customers still come from the military/aerospace and telecom/datacom sectors. We see much more activity out of the automotive industry, too, and there’s a growing demand from the AI industry.

Matties: So, your customer list must be growing as well.

Miller: It’s a challenge, but it’s a good challenge because you want to make sure that you’re working with the right customers. As we are identified as a solution for customers, we try to work our way through to make sure they are a good fit for us, and we’re a good fit for them, more importantly.

Matties: What makes a customer a good fit?

Miller: Typically, for us, they’re a technology-driven customer looking for an expert solution, not just to connect the dots design house. If it’s a company that has a lower technology, then we’re probably not the best fit for them. Our usual customers are looking for a value-adding supplier—someone who is going to provide feedback and make recommendations and suggestions, such as working through optimized stackups or making placement recommendations, and all of the things that can make the design more efficient and help to get it right the first time.

Matties: You recently published The Printed Circuit Designer's Guide to… Executing Complex PCBs. That book has been wildly successful with a lot of downloads and positive reviews. What feedback have you received, and how is that affecting you?

Miller: It has been great by helping us get more exposure and opening the doors to new customers. Some of the downloads are from customers that already know us, but it has helped to raise our credibility with them. The feedback has been that it was very well-written and hit on the hot points. Readers felt that they got something out of it, and the book provided something that wasn’t in the marketplace before. That’s the feedback I’ve received. It’s not just in the design itself, but it’s how you communicate, share data, and do things efficiently and effectively.

Matties: It wasn’t a book about you, but about helping the industry because you are the experts and have been doing this for many years.

Miller: The origins of Freedom CAD go back to the earliest days of PCB design when laying out a PCB was done by putting tape on Mylar. So, we have been through all the evolution of PCB design. We wanted to share these years of experience in the book.

Matties: With that topic of complex PCBs, a lot of companies are now moving into that realm where maybe they didn’t have to do that before, and there are design challenges. Do you see any instances where people are coming to you with their designs just for analysis and review?

Miller: We are. I think the visibility from the book and some of the other marketing that we’ve been doing is opening customers’ eyes who may not have been thinking about going outside for a design review. This past week, we received a request from a customer that had an existing design to perform a review. They were going to take the design into volume production, and they came to us and asked us to do a review of it, to add test points, and to look for improvements for manufacturability.

Andy Shaughnessy: What are some of the biggest challenges that you see as a company and for your customers?

Miller: If you’re familiar with the PCB design industry, it’s no surprise that it’s a graying industry. The majority of the North American PCB designers are age 50 and above, with lots of experience, but also closing in on retirement. One of the biggest challenges is to identify and develop talent that can replace those who are going to exit the industry for retirement or whatever the reason.

Shaughnessy: And it seems to be changing a little. Do you see more young people in the design community?

Miller: As PCB design becomes more visible, younger people are becoming interested. As one of the largest and more visible design companies, we are approached by young people who are interested to know if we have trainee positions. Some of them are individuals with parents who were or are designers, but some become interested as they hear and learn about the PCB design career path. I do see things changing, but more older people are leaving the industry than younger people coming into it.

Shaughnessy: You mentioned training. Do you work with schools?

Miller: No, we have a homegrown training program. We’ve run four different training classes where we have hired interns to teach them the process of PCB design. We have a syllabus and a proven methodology for training them on all aspects of layout. We start with the basics of silkscreens and assemblies and then help them understand schematics, routing, and placement. We take them through the whole process. We have been successful to the point where most of our young designers are the ones we brought in and trained.

Shaughnessy: You can’t assume that everybody knows about that.

Miller: Right. The value to trainees is they are partnered and mentored by some of the best designers in the business. They are exposed to a lot of experience and knowledge. In addition, one of the tools we have within our company to help promote shared learning is an email alias called the “Designer” alias. This alias copies our entire design team and is like an intracompany helpdesk. If a designer is tackling something they haven’t dealt with before, they can ask questions of the team. As we learn a new tip or trick, the designers can share it via Designer alias to the 30 or so designers that we have. And if they find a way to do something or there’s a new technology or technique that’s either board-related or fabrication-related, we share it. To be part of that environment as a young designer can be more valuable than a classroom only experience.

Nolan Johnson: As you’re recruiting and talking to young engineers and designers, what are some of the attributes you look for? For example, do you look for specific job skills or a general attitude?

Miller: I’ll steal a phrase from a former employee who worked for us, Robert Jardon; it’s aptitude and attitude. We look for somebody who has an ambition and is seriously interested in learning the art of PCB design. Then, do they have the aptitude to pick it up and the attitude to dig in, learn, and keep learning? There’s a lot to learn. Our best designers, even with years of experience, continue to learn every day. It’s not, “I’m now a senior PCB designer. I know what I need to do.” The best designers recognize that to be the best and add the most value in their companies, they need to continue learning.

Shaughnessy: We certainly need more mentors in the design world.

Miller: We need to mentor younger people to replace those who are going to retire. We need to make the mentor-trainee connection so we can teach them not only the design skills of PCB layout but also professional communication and problem-solving skills. Mentoring helps to facilitate a broader level and faster pace of learning.

Matties: Is there anything that we haven’t talked about that you feel like we should be sharing with the industry?

Miller: What has become an interesting trend is that PCB layout is more than just physical design skills; it is influenced by signal and power integrity simulations and thermal analysis. There are lots of challenges that go into a successful design, and the upfront analysis and simulations enable the designer to be much more likely to be successful. The days of designing, measuring, figuring out what we did wrong, and fixing don’t cut it today; that’s not efficient, and you can miss your market window if the board design needs to be redone because of crosstalk or voltage drop. We perform more signal and power integrity simulations and thermal analysis as part of our design process now than ever before. Five years ago, it used to be mostly signal integrity for high-speed designs, but now it often requires power integrity and thermal analysis.

Matties: We were talking about design review, but maybe there’s a pre-design review meeting that people can also come to your organization before they embark on their journey.

Miller: Yes, particularly with complex PCB designs. They require some detailed planning before you even start the design to get the results you expect. Floorplanning the design is important; it’s a collaborative effort between the design engineer and the layout designer when we do these complex designs. It requires design rules and guidelines, crisp mechanical data, placement guidance, stackup selection, and the use of HDI. All of these factors need to be carefully reviewed before the layout begins.

Matties: And collaboration is something that people have been talking about for many years but seem not to follow through. Do you see more collaborative efforts out there?

Miller: Absolutely, even to the point where we work with a number of customers where their own layout team works on a design, passes it to us, and then we work on it, pass it back to them, and then they work on it. We have truly tried to become an extension of our customer’s team in a seamless way, and it works.

Matties: When I look at the reasons for coming to a design service like yours, it’s because you have a broader pool to draw from for that knowledge rather than relying on one designer. As you pointed out, there’s so much to know today, and no one designer can know at all.

Miller: A perfect example is that most companies may develop one or two backplanes a year unless they’re a specialist in backplane technology. We do probably 25–30 backplanes each year because of the number of customers with which we work. As a result, we are aware of the unique requirements and challenges of backplane design because we design backplanes much more frequently than most companies. Another example is that we’ve dealt with a lot of customers who have migrated from DDR3 to DDR4 and were not familiar with the different routing requirements. We’ve been doing DDR4 since early in its evolution due to some of our customers being early adopters. These are just a couple of examples of how we are exposed to leading-edge technologies early in their evolutions.

Matties: How has the additive process changing the design approach? Are we designing the same way when you design a board for additive?

Miller: We worked with a company to do some of the additive process designs for their testing, and it is little difference in terms of the design impact. The major difference is how fine they can control the line widths and spacings because it’s adding copper versus removing it. With the additive process, there’s no trapezoidal effect on the traces. And they can add a much thinner layer of copper than a one-quarter ounce or even less.

Matties: In your design work, do you see more people going to that additive process?

Miller: Not yet, predominately because it still has some certifications and qualifications to get through.

Matties: But there is certainly a trend to move in that direction.

Miller: Right, it fits the smaller packaging. You can go down to one-mil lines and control it accurately.

Matties: I would think that as everything gets tighter, more of the power integrity and other attributes you mentioned come into play.

Miller: To some degree. But from a design standpoint, the physical characteristics don’t change it. But from a technological standpoint, you can do things differently with thinner lines, smaller spaces, and better control.

Matties: And this is where the education of a design service comes in because you are doing this where it might be new for somebody else, and you have already mastered the learning curves.

Miller: Exactly. And fortunately, we’re involved up front with one of the additive companies to help them develop their process.

Matties: That’s a big advantage. Do you work closely with fabricators?

Miller: We do. The design isn’t complete until the board is built, and the OEM puts it on the bench and figures out whether it works or not. We work with most North American fabricators to validate our stackups for DFM, and when we manage the prototyping for our customers, we work directly with them. The intimacy between the design and fabricator continues to get closer and closer because of the challenges around stackups; as mentioned in our book, picking the right stackup is the cornerstone of a successful design.

Matties: We commonly hear that designers need to know the manufacturing process, and then a smaller group will say that they don’t need to be the manufacturing experts. What sort of feedback should a designer look for from a fabricator?

Miller: Describing the requirements in a clear manner is important. A lot of times, designers will say, “I need this. I need 100 ohms on these layers and 90 ohms on these layers. I need to use blind or buried vias. I need to carry this amount of power. I need a material that can deliver 40-gigabit data rates,” and so on. The fabricators will come back with their recommendations. This is critical because we start with something that falls within the capabilities of the fabricator. As the design progresses, we may need to refine the stackup to address unforeseen challenges in the layout that require changes. For instance, we may need to shuffle the stackup due to the results of the signal or power integrity analysis. When we do those kinds of things, we need to go back to the fabricators and make sure that we aren’t doing something that’s going to cause a DFM problem. Our connection and communication with the fabricator are vital.

Matties: Regarding post-production, is there any feedback that you look for after the fact from even the OEM or end-user?

Miller: There’s always feedback. Even though we go through a DFM process during the design process, we’ll specifically ask our customers to go back to their PCB fabricator and PCBA assembler for their feedback. We recognize that each shop has their unique capabilities, so we try to get that feedback and incorporate it before we ship the design. When there is a requirement to do a re-spin on a board design, we like to collect the feedback from the fabricator or assembler regarding yield issues and see if we can make any changes for yield improvements on future spins.

Matties: When you’re working that close up front, it’s almost more of a predictive engineering approach than a DFM approach.

Miller: To some degree, it’s predictive engineering. You’re trying to do what you can to make yourself successful up front, which is also a part of our book.

Matties: We highly recommend it, of course. It has had great reviews, and thank you for putting that out there for the industry. Scott, we certainly appreciate your time today.

Miller: Thank you, Barry. I appreciate it.

Scott Miller is the author of The Printed Circuit Designer's Guide to… Executing Complex PCBs. Visit to download this book and other free, educational titles.



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