Issue link: https://iconnect007.uberflip.com/i/1276973
AUGUST 2020 I DESIGN007 MAGAZINE 31 people have been doing it for 35–40 years, but they're still going around in circles with data. Thompson: When they do a whiteboard pro- cess and go through an engineering review, and they say to themselves, "We're going to have to drive this down to six-mil vias." Now, sending it to us with a six-mil via, if they want it epoxy-filled, we're going to have to increase that between 0.008" and 0.20." That's the sweet spot for us for epoxy fill. How do we get there? All of what we've been talking about is only relative to signal integrity. What about the things that they are grossly neglect- ing, such as missing drill files, IPC netlists, and layers? We'll have a 10-layer board, and we'll just get outer layers. Where are the inner layers? Shaughnessy: Right. But if they're using an EDA tool, doesn't the EDA tool sort of say, "You're forgetting this extra layer?" It seems like there would be something. Thompson: You mean a DFM tool? Frequently, they get in such a hurry that they negate that process. It's sort of like saying, "We're going to send the space shuttle up, and we're going to forget about that particular process. We're not going to go through those 30 days of that particular thing for flight. We're just going to go ahead and push it and make it work," and that's when you end up having space shuttles blowing up. Matties: Oftentimes, you invest six or seven hours, in some cases, just preparing to give them a quote, and you may not get the job. Thompson: Sometimes, it's way more than that. At times, I'll have a series of 28 emails, and we won't get the job. Thompson: But do you really want a fabrica- tor to tweak your stuff? That's really the ques- tion you have to ask yourself. Do you really want the fabricator to tweak with your stuff to the point where they're making a two- or three- mil change of their sig- nal to be able to accom- modate the impedance? Matties: You could say no, but apparently they don't mind if what we're hearing is accurate. How do we get designers to do it right the first time? Thompson: More training, I'd say. Matties: Part of it is more training, but is the information available that they need to provide the fab notes that you need, or how do they go about getting that? Thompson: Most of them use templates that are boiler notes that they have straight from their CAD system. Altium, for instance, has a tem- plate that has boiler notes that they can go in and they can massage, if you will, to fit the needs of their particular board. Matties: Is it board-specific, or is it fabricator- specific too? Thompson: It's board-specific—not fabricator- specific. Fabricators are vastly different. Even between our two facilities, I just made the point about temperature and humidity driving a big change between our facilities. Shaughnessy: But designers must be aware of the difference in humidity in Seattle vs. Tuc- son, right? It seems like this goes back to our discussion about whether designers need to be experts at manufacturing. Nobody sets out to design a board that isn't manufacturable. These