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32 The PCB Design Magazine • April 2016 derstand the manufacturing aspects as well (in- cluding test). The only challenge we experience with engineering honestly is playing the role of middleman between engineering and manufac- turing. Engineering may want parts located too close to another component or too close to a through-hole pin, not allowing a proper wave soldering operation to be performed. Those drive costs and can affect reliability. If the lay- out designer is effective, engineering is happy and manufacturing is also happy. That makes the boss happy! Shaughnessy: What do you think is the proper role for a PCB design engineer? Faucette: Outside of creating a correct sche- matic, the PCB design engineer needs to effec- tively communicate ALL of the requirements of the board and then review the board once designed to ensure all the requirements have been achieved. Some examples of requirements would be interface impedances, timing rules, and power requirements. It's also important to identify high-speed nets, clock lines, sensi- tive nets/circuits, high-current buses, thermally hot nodes, high switching loops. The stackup is critical in most designs today and this must be considered early. One thing that should be communicated early on is the environment of the product and the expected reliability. The temperature and humidity can drive what com- ponent packages to use (or more importantly what not to use). The reliability can drive board technology and spacings. The best way to com- municate all the rules is in a PCB requirements document. This is the scope of the layout. If it's in the document, it's important. It also removes the flurry of comments, instructions, and "Oh, BTWs" that tend to arrive in various emails and in cubicle conversations. It's a captive, living document to keep everyone straight. It's also it a perfect checklist at review time. Shaughnessy: What do you think is the proper role for a PCB designer? Faucette: The PCB designer's role is to take the requirements (hopefully as spelled out in the requirements document) and create a layout that performs as needed electrically, but that can also be manufactured with high yield, and that will be reliable. The PCB designer should pull in all the mechanical requirements (out- line, mounting holes, critical component loca- tions, keepouts and other restrictions) and en- sure form and fit are correct. The PCB designer should also ask all the questions to spark con- versations so that all requirements can be dis- cussed and documented early. At final review is not the time to find out that an ICT fixture is needed. Shaughnessy: Can you give us an example of how your designers and engineers function together? Faucette: Early collaboration is key. Hopefully, every design provides the opportunity to learn and that knowledge can be implemented going forward. Learning never stops. As we grow in our careers, we become more and more effec- tive and efficient in our roles. The result should Randy Faucette the partnership: Design engineers anD pcB Designers