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60 DESIGN007 MAGAZINE I JANUARY 2021 Understanding where the drillings are and all of that is really, really important to make sure that you get what you think you're going to get. We certainly see that culture in some big OEMs where they say, "Just listen to us; we're this major OEM and you do it the way we say." The fabricator says, "But there's drilling on that layer, so we're going to plate it." And the OEM replies, "No, no, we specified the copper to be this level of foil," but they forget that it's plated. It gets worse when there is a supply chain involved where it might be prototyped in one place and put into volume somewhere else. Dan Feinberg: Martyn, what percentage of boards do you think are FR-4 now? It's cer- tainly not close to 100% like it was 20 or 30 years ago. Is it still mainly FR-4? Gaudion: We tend to see the high-end fabrica- tors, so we see a huge number using modified FR-4s or ceramic-filled materials and higher speed materials. But there's still an awful lot of boards that are four layers for general purpose use that stay with basic halogen-free FR-4s. What we start to see are people mixing mate- rials where they've got the low-speed layers on basic materials and then they'll mix them with a more expensive material to carry the high speed. You get stacks which are a mix of different materials, and there it's really impor- tant that the designer talks to the fabricator to make sure they can actually laminate them and they actually bond them together because that becomes an issue. Feinberg: That's always been a thing for me. Designers and suppliers should communicate better, and it seems like they are starting to communicate better. They didn't communicate at all years ago. Gaudion: Communication has improved because it had to, and we see that reflected in requests to put even more detail into our stackup tools. I guess where we see a challenge is in terms of where we carry the data in our stackup tool, which isn't necessarily carried along with the CAD data. So if ODB++, IPC-2581 or Gerber doesn't have the right data for the stackup, you still need to carry a stackup file separately from the CAD because there's a lot of Z-axis information in the stackup which isn't always in the CAD tools. We've also noticed that in the last 20 years, certainly in the U.S. and Europe, many of the skilled people from fabricators have ended up working for a brokerage. Now, there are some really good high-end brokers who have a num- ber of PCB fabricator people there who can talk to designers, and that's been a big difference. Historically, you might have thought, "Why would a broker want a stackup tool?" But now a lot of brokers use a stackup tool because they're actually assisting the designer because they're PCB people. Sometimes I find the designers don't really want to communicate too much because they might feel they're expos- ing their limited knowledge of PCB fabrication. They can be quite reticent about that some- times—certainly the European designers—and we encourage them to ask those sorts of ques- tions. The high-end brokers are very good at providing that interface between fabrication and design. Martyn Gaudion

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