Issue link: https://iconnect007.uberflip.com/i/1533085
58 DESIGN007 MAGAZINE I MARCH 2025 Another good rule is to not put fine features on the external layers. It's much easier for fabrica- tors to do fine work on internal layers. We'll see a design with a 1-to-3, 1-to-6, or 1-to-12, and the designer wants it hole-filled, and the copper on via 1-to-3 becomes an issue as it gets planarized three times, so we can't achieve wrap. en the customer asks, "Why not?" and we explain how we actually manufactured the board so they understand what they're asking for. One of my frequent customer requests is, "What's your capability?" I'd answer that with our standard capability. I would never tell them the bleeding edge, because then they would design everything to that. at leaves me explaining that this line and space will reduce yield by 3%, and each of these other factors can reduce it by 2%, and the customer will be lucky to get 85% yield. I may not care because I will charge 15% more, but their lead time has now been extended by two weeks, and they don't understand why. is is all about trying to get them to understand how boards are fabricated, so they can better understand the design rules and what we're trying to do with them. Marcy LaRont: What did you think about the questions you received in your presentation? is was the best class I've ever had for ques- tions. I always encourage questions, but some- times designers get a bit shy. But this time, they asked so many questions about things like microvias and the CTE of materials. I was telling them about a customer that asked me who could build a 26-layer, 7-stackup microvia board. I said, "Wait a minute, you guys weren't using any microvias a year ago, but now you're doing a 26-layer with a 7-stack? Who designed this, and what's the material selection?" at's when they asked, "Why is material important?" I said, "Because that subassembly sees seven laminations before it even goes to assembly." So, if you don't select the right material, it will be compromised by the time it gets above Tg 10 times. at's when they realized why they were having trouble finding a fabricator. Designers are starting to slowly learn all this, but they don't talk to fabricators enough. LaRont: Some designers don't even know who will fab the board, so they don't have the