Issue link: https://iconnect007.uberflip.com/i/1392944
42 PCB007 MAGAZINE I JULY 2021 needed there?" ere's really no reason for it when you talk to the customer and tell them, "If you look at this area, this four-mil pitch makes it feel really hard to do, so could you just space all these out?" But by that time, they've already done all their engineering to prove out that this is going to work like they want it, not like it's manufactured to be made, but like they want it to do. With that extra cost that they have to apply, they may say, "We've already done the modeling, and everything seems to be fine. If you can make it this way, please make it this way. If you can't, then we need to have other discussions." Johnson: at is part of the mismatch, right? In my opinion, the DFM tools should be called CFM, or "check for manufacturing," because you've already done the design. e design has to be complete to start the determination whether it's designed to be manufacturable. In your experiences working with DFM tools, can you draw a correlation between passing the DFM analysis using the rule deck, and having increased manufacturability yields? Link: Oh, absolutely. You can draw a correla- tion without a doubt. Johnson: It does help, but it involves a great deal of human heuristic knowledge to make it work. Link: Right. And sometimes at the expense of annoying the customers because you're asking them questions that they didn't really want to be asked. ey want you to simply analyze their board and see if there are any glaring problems; they don't want to be second-guessed on their design. It takes the PCB manufacturers out of that uncomfortable situation that says, "Hey, what if you did this and that?" We don't want to be designing boards, we want to be building them. Sometimes those conversations can be pretty tricky to have. Johnson: It seems in some cases, the engineers, and I'm probably being unfair, but they don't want to be bothered with those details on the manufacturing side. I've heard it said, "I've done my design, here you go, just make it hap- pen; make my vision work." And yet you have to talk about these messy little details like sit- uational areas of trace and space or the like. e CAM department at a fabricator brings up these details to increase their customers' yields, or to decrease the customer's manufac- turing costs. Link: Absolutely. Johnson: What are some of the most common DFM errors that your team sees? You know that these are going to show up, so you're look- ing for them immediately. Link: Let's talk about checks that we catch. e netlist doesn't match up, hole counts are off, the dimensions are wrong from a fab print to a Gerber file. ose are probably the major ones. From a design, checks we catch might be gaps in reference ground plane. It could be line Greg Link