Issue link: https://iconnect007.uberflip.com/i/1464168
APRIL 2022 I DESIGN007 MAGAZINE 15 house out of it. at's the way the subtractive process works. With the additive process, you're building from the bottom up, so it's a little bit different methodology as far as how you put the layers together. We work with the designers, and a lot of the military and aerospace guys are look- ing to get finer and finer features which, within the U.S. footprint, are increasingly difficult to come by. ere are very few circuit board shops that can get down to the lines and spaces that we're capable of achieving with the addi- tive process. Shaughnessy: Talk a little bit more about that, Dave. How else is the design process different? Torp: It's different in some respects. You'll find with the ultra-thin foils, if you're famil- iar with traditional laminate structure, is that it's required to have a tooth on one side, and then you laminate the foil onto the substrate, whether it be the FR-4 or some of the BT or the PTFE-based substrate. You required a little bit of a tooth that acts as a nail, so when you make your copper-clad laminate, you've got to bite into the laminate. With the technology that we're using, it's a chemistry that's applied to the substrate or the prepreg, at that time. It conforms to the contour of the surface, so you wind up with a better bite than you do with these ultra-thin foils, because they just don't have much of a tooth. If you think of the tooth as a nail that gets driven into the substrate, the adhesion there is minimal at best because you just don't have the length of nail being driven into the sub- strate. With the capabilities that additive cir- cuits bring, it can conform to every nook and cranny. You wind up with this very, very good adhesion on all layers of the substrates that you're applying it to, and specifically the out- side layers of the multilayer, where you need really good adhesion strength. e inner layers are laminated together. You can get away with some minimal adhesion, but on those outer layers, you must have good peel strength, sheer strength, and strength in connection with the substrate. en there's the trick of making the microvias between the layers because, typically, you're building the layers up. You're going through plating the vias and the same plating technolo- gies used, but the order of operations to get the via into contact with the capture pad below is a little bit tricky, a little bit different than what people are used to. But we've done the reliabil- ity testing. We've sent the assemblies to cap for thermal cycling resistance testing. We're doing very well with respect to the performance of that thermal cycling testing. As I'm sure you're familiar, that type of test- ing is meant to shred the microvia into pieces. We were able to survive their -55°C to +205°C thermal cycling without too many issues. We have a few defense electronics-related cus- tomers very interested in that technology, particularly on the stuff that's really hard to stick to, which is typically the PTFE-based laminate material. We can get pretty good adhesion onto some substrates that are very difficult to work with. In a nutshell, that's what differentiates us from some of the other processes out there. Shaughnessy: A lot of it sounds like different steps for a designer. Torp: e order of the steps is a little bit differ- ent. You're not trying to do it in a subtractive methodology. You're building from the inside out, rather than the outside in. Our website covers a little bit of it, but it's a very proprietary process. Many of our customers are keeping a tight lid on what they do, so it's tough to find information on exactly how to do this. Typi- cally, we work with the designers one-on-one. ey have their requirements with respect to impedance and signal-to-noise ratios. ey have some ideas of what the end functionality needs to have. en, we work with them on what's capable. What is stretching it? We invite