Issue link: https://iconnect007.uberflip.com/i/1490123
12 PCB007 MAGAZINE I JANUARY 2023 Vardaman: An alternative that a set of custom- ers agree to. In other words, you must have customers that line up and agree to use what- ever you will put in place. Johnson: What are some of the technical con- siderations? Vardaman: Based on the demand, we talk about finer and finer bump pitch. If you look at a printed circuit board, it's large dimension with respect to line and space. Printed circuit boards oen are measured in mils (1/1,000 of an inch). A mil is 25.4 microns, so printed cir- cuit boards are a long way from the density that you need to put a bare die semiconductor on. Johnson: Yet some part of your product needs to be in dimensions that will fit a human finger. It seems that the sorts of dimensions we need in substrate interposers match with the semi- conductor fabs of, say, 20 years ago. ose fabs have been decommissioned. Vardaman: To your point, a substrate facility is not the same as a semiconductor fab. e semiconductor fab is ultra clean, it's process- ing on silicon, and we're using a wide variety of process equipment. ere are some similar- ities between printed circuit boards and sub- strates, but as we go forward, the feature sizes are getting increasingly smaller. If you talk to Intel about the future of the substrates they'll need, they will tell you they need finer features and equipment that is more like fab equip- ment—which is certainly not what is used in the printed circuit board business today. In a high-end build-up substrate today, they're made with the Ajinomoto film, which is likely very different from what the substrate of tomorrow will be with even finer feature sizes. I hear talk about going down to 2-micron line and space. ere's no way that a printed circuit board operation could build anything like that without a clean room and different equipment. We interviewed a lot of substrate companies, and a single production line could be in the range of $300 million. Intel says that in a facil- ity with multiple production lines doing high volume, you wouldn't be spending less than $1 billion. R&D Altanova, a test head company in New Jersey, has added some prototype substrate capability, and they certainly can prototype using the Ajinomoto film. It's not like you can't do this in the U.S., but you must recognize what's involved, the equipment that's needed, and the budget you need to do it. Johnson: What I'm hearing is that substrate man- ufacturing is neither a PCB nor a semiconductor opportunity. You're not pivoting into this with your existing equipment; you may be investing in a brand-new facility to do this kind of work. Vardaman: You couldn't do it in an existing printed circuit board facility unless it already has the necessary clean room because when you do fine feature sizes, you can't have par- ticles that would cause failures or yield loss. If you're doing a real production line you need to have it highly automated. Jan Vardaman