Issue link: https://iconnect007.uberflip.com/i/1307491
16 DESIGN007 MAGAZINE I NOVEMBER 2020 which is why I preach process control and automated analytics. Chavez: I agree. You must have that feedback loop constantly going because if you don't, you're potentially going to end up with issues. Holden: Making PCBs is one of the toughest manufacturing processes in the world because of the variability. You look at materials in our chemical processes, and nobody in their right mind would take hydroscopic materi- als, dunk them in water, try to make precise control of them, dunk them in water again, dry them out, and then dunk them in water again. The silicon companies don't have any aqueous processes. It's silicon and hydropho- bic on practically everything—but laminate sure isn't. Chavez: I feel it's important for every EE and every designer who's designing boards to get their butt over to a fab shop and walk through it to see what a board goes through to get fab- ricated and to see all the required intricate details that need to be addressed to success- fully produce a PCB. Shaughnessy: We see a lot of designers who haven't been in a board shop in 25 years, or they've never been in one. Chavez: Or even worse, a lot of companies don't allow their engineering teams to talk to the suppliers. Instead, it's the supply chain that's talking to them, which I have a hard time understanding, but there are companies out there that are so big and complex regarding their departmental structure that all the engi- neering teams know is that they release their design into their PLM system, and then the supply chain takes it from there. Holden: I never had so much fun as when I took a bunch of EDA software designers and coders on a tour of a PCB fab shop. These are the people who write all the design tools, and they'd never been through the process and seen how a PCB is actually made. Chavez: It is extremely important to go take these tours. It's a great way to continue one's education. Within most successful corpora- tions, they make sure to continually develop engineering teams. Collaborating with today's PCB suppliers, whether they come on-site to provide training or education sessions, or do tours of their facilities, continued professional development is crucial for success. Another great way to continue professional develop- ment is to get involved with industry asso- ciations. I highly recommend that everyone join the PCEA collective and get involved. It's an excellent industry source to tap into. The PCEA's core mission is to collaborate, inspire, and educate. I definitely encourage anyone that has anything to do with PCBs to get involved with their local PCEA chapter. Shaughnessy: I was at the IPC Reliability Con- ference last year, and it was all about military PCBs having microvia failures. They didn't real- ize the failures were happening during reflow, and they were undetectable at room tempera- ture or during assembly. Members of this IPC group have been investigating this. Right now, they advise against using stacked vias, espe- cially complex stacked microvias. Has this been an issue for you and your company? Chavez: We do both stacked and staggered microvias, but it depends on what product you're designing and where it's going to go on the aircraft. With stacked microvias, it's pre- ferred not to stack them more than two on top to each other. The main reason for limiting the number of stacked vias is due to DFM and reli- ability concerns. And because we're working Making PCBs is one of the toughest manufacturing processes in the world because of the variability.