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40 PCB007 MAGAZINE I JULY 2021 Feature Interview by Nolan Johnson I-CONNECT007 Nolan Johnson speaks to Greg Link of WUS Printed Circuit Co. Ltd. to gain a better under- standing of where design for manufacturing (DFM) fits in from a fabricator's perspective. Nolan Johnson: Greg, what we call DFM in the PCB world, the semiconductor community calls layout verification. e PCB industry re- fers to the soware tools as DFM, and yet, I would posit that the soware tools don't actu- ally perform a DFM. Greg Link: I agree. Johnson: From a fabricator's point of view, where is the mismatch between what DFM should be and what the tools do in the market? Link: DFM should be, by definition, designing to improve manufacturability, but most of the time, we fix an error here or an error there. e tool is not guiding us by saying that this is what we want to do to improve how a board is made, this is how expensive it is to make, or how quick it is to make. Is this really what the cus- tomer needs? ose types of questions aren't really being asked. And I don't know how you do that in a functional world. I think this is the weakness. Johnson: You're right. Philosophically, the goal is to give guidance that increases yields, sim- plifies the manufacturing steps, and maximiz- es your mean time between failure. If your goal is using design rule checks to make sure your trace and space parameters are sufficient, then that's a piece of it, but that doesn't get you to your goal. Link: Right. It needs to be a separate tool that our end-customers need to run through. For example, I was just looking at a board that had four-mil line and spaces with PFE inside of a pitch; there were four lines together, and then suddenly there were two more lines that were spaced, six mils apart. You look at and say, "If six mils is okay here, and here, why is four mils DFM for Your PCBs

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