Issue link: https://iconnect007.uberflip.com/i/1327102
62 DESIGN007 MAGAZINE I JANUARY 2021 Holden: Yes, and now with the VeCS, the 3D aspect of the stackup has added another layer of complexity. Have you started looking into how you're going to handle the vertical con- ductive structure? Gaudion: I met Joan Tourné last year and we talked about VeCS. We haven't looked at it yet, but we're usually driven by our custom- ers. When our customers start to approach us with questions on VeCS, then that's a technol- ogy that we would look into. We tend to be driven by customers. We get so many requests for enhancements on our stackup tools that just juggling them to find which one we need to focus on is tricky. VeCS is a very exciting technology, Joan is a very creative guy, and so we sit and wait for our customers to come out and say, "We're using this. How are you going to document it?" It opens the ability to increase the interconnect density without really increas- ing the complexity of the board, which is a very clever piece of engineering. Holden: I gave a keynote talk on VeCS at the Electronic Circuits World Convention in Hong Kong with some of the new diagrams. It's really quite interesting to go from layer one to layer 18, which we can't do with HDI or any- thing else. But in the same channel, we could go to layer six, or layer four, or layer 12, or layer 28. And, interestingly, we could do this with excellent reliability, and the signal integ- rity improves significantly. Gaudion: Certainly, what Joan was explaining is that the beauty of it is you can use conven- tional manufacturing technology to do it. The challenge is getting the CAD tools to support it, and that's really the interesting path forward on that technology. The ability to not need to up the technology in the fab shop, and actually get a lot more interconnectivity without need- ing more complexity, is very creative. Holden: I'm looking forward to fabricators exper- imenting with it. Since they don't need to drill microvias, if they have laser drilling, they can use their lasers to produce the channels a lot faster than we can with a drill router machine. I always talk to students about this—if you're choosing the electronics industry, the innova- tions and changes are constant. The only thing you've got to recognize is this is not the last time you're sitting in class. If you're going to go into electronics, you're going to be in a class- room and learning for the rest of your career. Feinberg: That's so true. Holden: Nothing is static in this industry. But with circuit boards, for some reason, we're still making single-sided phenolic print and etch (laughs). Gaudion: It's interesting that the old technol- ogy stays, doesn't it? Then you get all this new stuff laid on top of it. At one time, we thought as speeds go up people won't really need to be worrying about just reflections and impedance. Insertion will also become the primary thing, but with most PCBs, there are some parts that run next to DC, there are other parts that run at a few hundred hertz, and other parts that run a few hundred megahertz; then, some are two-, three-, 30-gigahertz and you've got a whole range of frequencies and everything needs to be designed to work for the right price for the kind of performance level that's needed. It's interesting that the need to check for opens and shorts doesn't go away just because there's a new high-speed technology. Shaughnessy: I don't know if it's tribal knowl- edge, but I've seen designers approach the stackup process in so many different ways. Maybe that's a big part of the problem? Gaudion: If you look at the money, the fabrica- tors jokingly say that the designers who think about stackup last will keep asking to add another couple of layers of HDI. If you're a pro- totype manufacturer, and the designer has to build a stackup first and they make a 12-layer board, and then they spin it to 14 and then 18, it's happy days for the fabricator, but it's not the most efficient way of doing things. If they can start on a stackup first, then actually that's