Design007 Magazine

Design007-May2019

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10 DESIGN007 MAGAZINE I MAY 2019 Feature Interview by The I-Connect007 Editorial Team One thing that we've noticed lately: Each de- signer seems to have his or her own way of us- ing PCB design rules. There doesn't seem to be much agreement about setting or using design rules. So, in this true experts panel, Mike Creeden of San Diego PCB joined Freedom CAD's Scott McCurdy, Jay Carbone, and Rich Kluever to share their views on PCB design rules. This wide-ranging discussion with Andy Shaugh- nessy, Nolan Johnson, Barry Matties and Hap- py Holden covers everything from identifying the required constraints to setting electrical and manufacturing design rules and managing these often disparate requirements. Andy Shaughnessy: Welcome, gentlemen. The topic of design rules keeps popping up, and there's not much agreement about best prac- tices. Or is there? Mike, can you talk about how you go about setting up design rules? Mike Creeden: Design rules help us utilize the strength of our CAD tool to make the circuit do what we want it to do, and that occurs in three areas. I always talk about what I call the "de- signer's triangle," which are three perspectives when we look at the layout. The first perspective would be the layout solvability. You have to solve the layout, and your design rules enable you to do that. I'm able to pin-escape from fine-pitch parts, and at the same time, I want to balance that with DFX or DFM. Second, physically speaking, I must address the concerns for the manufac - turing process and capabilities of my supply chain. I want to optimize them because the more robust I can make it, the higher produc- ibility and reliability I would have long term and in a production volume. Third, the oth- er perspective is performance. Performance is many things, including signal integrity, pow- er delivery, thermal, etc., and all those things have to be met. We don't want to over-constrain anything. And you cannot do one or two of those per- spectives I just mentioned and ignore the oth- er one. When we apply our design rules, there might be an EE as well as a layout person— sometimes, that is the same person—and then there's also design rules from the manufactur-

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