Issue link: https://iconnect007.uberflip.com/i/1467185
16 DESIGN007 MAGAZINE I MAY 2022 happens at the end or in the beginning—and it costs more at the end. Kolar: I think part of the barrier can be that, depending on your fab vendor, you're asking of their time to do pre-DFM. Depending on that vendor, they may or may not want to spend that time with you. Plan your questions well so that you can have your lightweight, upfront questions answered, such as, "What are some of the core requirements I must work around?" and, "Can you confirm the stackup is build- able?" en you can move forward with a fair amount of confidence without wasting a ton of their time. Shaughnessy: Jen, tell us about your pre-DFM pro- cess. Kolar: If we are building the boards, we will work with our fab vendors in advance to get a stackup pre-approved. We'll usu- ally do initial calculations with Polar on our own to get a starting point. en we'll work with the ven- dor based on what they have in stock and get a stackup as early as pos- sible in the process. If it's not a complex board, we're not typically sending a pre-DFM pack- age, unless it's a crazy fast turn time. But we are doing that upfront iteration to confirm capa- bilities and the stackup. Shaughnessy: In our past conversations, you described yourself as being a detective. at's really what working in a vacuum is like—you must be able to answer questions on your own. How do you approach that? Kolar: You must dig for the information because you're not getting all the requirements. Grunwald: at's right. From a customer's perspective, we need to have power require- ments, current draw requirements, impedance requirements, and length matching. ose are a lot of things that we oen must dig up from a customer. ey may put it in a schematic or not even mark it up. From a board shop per- spective, usually it's finding capability sheets from known shops that either I've worked with before or shops in the area, if you're lucky enough to have local shops. I'm basing my design decisions on their design specs, so I can expect that the end-shop will be able to meet those designs as well. It can add a lot of time—making assumptions f o r w h e r e c o n n e c to r s need to be placed when it's going into a hous- ing. I make sure I get that nailed down before I start working on anything else because that can drive so much of the rest of the design. Trying to get to the engineer to confirm placement is a big deal. Kolar: The other place that can sometimes feel like a vacuum is tr ying to get feedback from the end-customer that we're going along, doing placement, trying to make sure that's approved and locked before we go to route. Meanwhile, we're not getting feed- back, so we're having to make assumptions to keep moving forward. en suddenly, we get a lot of feedback at once at the very end. It's that feedback along the way, trying to figure out how much review the end customer is really doing. How much of this is on us? Shaughnessy: Some designers tell us they don't even know who to ask in their company to get the final answer about where the board is being built.