Issue link: https://iconnect007.uberflip.com/i/1453746
12 PCB007 MAGAZINE I FEBRUARY 2022 know there are a lot of reliability concerns with that in our market. ose type of applications, I think, are where the semi-additive processes are going to take over and offer some relief to the designers. Fabricators serving that portion of the market will have to strongly consider moving in that direction. Barry Matties: What's the attitude toward addi- tive or semi-additive? Dunn: It depends on the market. Early adapt- ers are embracing the technology and mov- ing forward, and some of those are compa- nies looking for a smaller package size. at's very important, and this enables them to do it. ey're jumping in, taking the bull by the horns, and learning as they go. I think there's a whole group of other PCB designers and companies that are being cautiously optimis- tic. Let's see where the reliability data is. Let's prove it out with some testing. So, I see two different areas of adoption there. Matties: With input costs rising, the case could be made that additive can lower your total. Are you seeing that as part of the impetus for people? Dunn: I don't see the motivation being the cost savings, but it is a benefit. One customer we're working with has a design with 12 layers, three lamination cycles, and stacked microvias. eir drive was not for cost, but to simplify the design for lead-time purposes. It could be made on a shorter cycle time and be made more reliably. ey wanted to shrink that form factor at the same time, so they could accom- plish that by switching in some layers that had the semi-additive process. A combination of both technologies reduced their cost overall. But that wasn't what started the drive for the change in technology. Mike can give a short tutorial on the differ- ence between fully additive and semi-additive in terms of circuit board manufacturing. Vinson: When we look at additive technologies, there are typically those that strictly add metal to the substrate or to the application and don't remove any of it. With subtractive, the more conventional ones are the ones where you start with a full metal coverage, then you subtract away the areas you don't want. Semi-additive allows us to add metal where we really want it in thick layers, subtract the metal that we don't want off the thin layers, and still leave the thick layers undisturbed. ese processes are very attractive because, as Tara mentioned, they pretty much drop right into a conventional PCB facility. e additive process may require a bit more work and is going to limit how much metal you can build up without being able to remove anything around it, the shape of the trace that you'll get aer that, or the pattern that you're putting down. So, while some appli- cations are fully additive, most of the transition that you're going to see in the PCB industry will be toward semi-additive processes. Matties: Fully additive opens a wide range of new material opportunities, doesn't it? Tara Dunn