Design007 Magazine

Design007-Jan2021

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28 DESIGN007 MAGAZINE I JANUARY 2021 accustomed to relying on being able to use multiple layers for routing instead of planning a more efficient layout. "Can't get this bus routed in? No problem; we'll just throw in another couple of layers for you to work with." It probably wasn't quite that easy, as memo- ries like that tend to be a bit untrustworthy. It is true, though, that they were very gener- ous with the amount of board layers that you had to work with, and critical board configu- ration decisions like layer stackups were cre- ated for me by others. This proved to be quite an inconvenience later in my career when my next employers didn't give me the same flexi- bility in board layers that I was used to in order to work myself out of a jam. Instead, not only was I expected to work with what I had, but I was also supposed to reduce the layer count to improve on it whenever possible. This meant dealing with a whole new set of design rules and considerations related to board layer stack- ups that I had never had to work with before. As we all know, it takes a herculean balanc- ing act to create a circuit board that will deliver the maximum amount of performance for the least amount of manufacturing expense. Try- ing to sort out all the different pieces of the cir- cuit board puzzle to achieve this balancing act can end up being a real brain teaser for new designers. Just for starters, you need to con- sider the following as you configure the board layer stackup that you will be working with: • Signal integrity • Power integrity • Placability • Routability • Manufacturability • Profitability There are enough "itys" in that list to sink a ship, and we haven't gotten to testability or designer confusability yet. Thankfully, I worked with some great people who helped me to relearn some of the basics of PCB layout. They taught me how to work correctly with circuit board layer stackups, and why there was a whole lot more to multi- layer boards than just providing more room to route on. It took some time, but after a while I came to a better understanding of the relation- ship between the different board materials and thicknesses, and how they should all be con- figured to design the board correctly. I was very fortunate to have co-workers who helped me understand and refine the art of printed circuit board layout. I wonder, though, who will help today's new designers work through problems like these. Company cultures are changing, experienced designers are retiring, and more is being expected of PCB layout personnel with less time to make it hap- pen. How are today's puppies going to learn some of these more advanced skills, such as how to correctly configure their board layer stackup? Here are some of my ideas on how this can happen: • Circuit board manufacturers: I have talked to different manufacturers, and one of the more common themes I have heard is that they want to engage with their customers more before the board is designed. They typi- cally have years and years of experience build- ing circuit b oards under their belts, and they understand the challenges that designers face better than most. They also are very aware of the capabilities and limitations of their own manufacturing processes, and the PCB mate- rials being used. They want to help design- ers come up with the best layer stackup configurations possible because their custom- er's success will ultimately translate to their own success. New designers can gain a wealth of information simply by working with their manufacturers. • Professional resources: There is more technical training available out there than you probably realize. It not only covers PCB layer stackups, but many other aspects of PCB design. You can easily find a variety of seminars and classes from various organizations and groups within the design industry. There are design conferences that feature instructional sessions from some of the brightest minds in our indus- try, along with product demos and information on new design methods and technologies. In addition, you can also find a plethora of online

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