Issue link: https://iconnect007.uberflip.com/i/1419905
OCTOBER 2021 I PCB007 MAGAZINE 23 mature, there will be another new active component, one that's going to obsolete it. You need to have what I call a tran- sitional interposer. e old tradi- tional motherboard that used to be super advanced is more than just a glorified wiring board that connects everything. You will have optical fly- over, copper, flyover. You're going to have all kinds of things moving in and out. e PCB industry, at least what I see as our next great evolu- tion, means we can't think of that like a normal PCB. Happy started doing HDI microelectronics 30 years ago. Moore's law didn't always work at the PCB level because higher resolution didn't cause lower prices. But all of that is changing now because of 3D system-on-chip. Now you don't have an Intel or an AMD or somebody driving the whole industry. You have smaller drivers all over the place. Anyone with a design with ASIC can marry these together and create an IP that's unique. at's going to completely change the structure of the interconnects below it. at's where I see the big next jump. To that end, near-billion-dollar factories are not that outlandish anymore because if you're talking about near 50-micron lines and spaces, you're basically building a traditional inter- poser with attributes that were chip or die level 10 years ago. Johnson: Seems there are two opposing direc- tions here. Talking about interposer applica- tions, increased density is the driver and there needs to capital equipment investment. But at the same time, with a shi back to a more traditional function for the main printed cir- cuit board—a motherboard backplane sort of operation—you're saying that it's getting sim- pler. e 3D element is more advanced, but the large PCB will continue with similar attri- butes. e 3D is a system-on-chip or system- on-PCB, right? Dickson: Happy called it a silicon interposer; that's probably the best terminology I've heard. It's a sub 50-micron L/S interposer as opposed to an above 50-micron interposer. Some have three layers; some have four layers. I'm see- ing PCB-like structures that are on flip chips with a silicon interposer that's built in there. en there's another transitional interposer in the 0.5 to 0.9 mm pitch range that allows these systems to be mounted on the main PCB. e idea that you have just one die and then a sin- gle interposer just doesn't work, because the CPU is not the center of the universe anymore. ere are multiple levels of data processing. Holden: e signal integrity, like you said, is such a thing that you have a very fast CPU die, but when you put it on a relatively larger pack- age and bring it out to any kind of BGA or pin grid array, you induce so many parasitics that if you want to eliminate the package, you put the memory right next to it, you put the IO right next to it. Now you've got what we call system- on-package, not system-on-chip. Maybe what has happened is that when we had the daughterboard, the motherboard, and the back panel, that's going out the door through miniaturization. Now we have an organic printed circuit board, which is the cumulative back panel, and on it are all these system-on-packages that look like very fine pitch BGAs, but they're replacing the daugh-