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DECEMBER 2019 I DESIGN007 MAGAZINE 47 Miller: A perfect example is that most compa- nies may develop one or two backplanes a year unless they're a specialist in backplane technology. We do probably 25–30 back- planes 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 frequent- ly 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 cus- tomers 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 changed the design approach? Are we designing the same way when you design a board for addi- tive? Miller: We worked with a company to do some of the additive process designs for their test- ing, and it is little difference in terms of the de- sign 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 trapezoi- dal effect on the traces. And they can add a much thinner layer of copper than a one-quar- ter ounce or even less. Matties: In your design work, do you see more people going to that additive process? Miller: Not yet, predominantly 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 ac- curately. 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. From a design stand- point, 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 do- ing this where it might be new for somebody else, and you have already mastered the learn- ing 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 un- til 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 fab- ricators to validate our stackups for DFM, and when we manage the prototyping for our cus- tomers, we work directly with them. The inti- macy between the design and fabricator con- tinues to get closer and closer because of the challenges around stackups; as mentioned in our book, picking the right stackup is the cor- nerstone of a successful design. 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.

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