Issue link: https://iconnect007.uberflip.com/i/1527613
42 DESIGN007 MAGAZINE I OCTOBER 2024 Dack: From the standpoint of designers, this is a "design for" just like DFM or DFT. We can't just shrink the lines. We have to know all the other parameters: the performance param- eters, but also the manufacturing parameters. Chris, I think you mentioned that anybody with a current DI system can build it, correct? Yes. So many exposure units are capable and I would say that most shops by now have the exposure capability. e challenge then becomes plating and etching, with etching being—probably—the cutoff at some point, depending on the equipment set they have. Dack: We know we can call Chris and get the materials. Who do we call to get the process going? We have designs coming in, and all of a sudden, we hear that they can't be built. We get engineering queries back from our offshore suppliers, who say, "We can't build this." What do we do now? Let me ask you a question. For a particular copper thickness, what are you using as an etch factor? Dack: Well, from the standpoint of around 10 mils, we can get down to one ounce. I don't have the chart with the etch factor number values in front of me. We know that once we start getting smaller and smaller, we have to go down to a third-ounce copper, half- ounce copper, and such. From there, our cus- tomer already has designed it. We had one design with 3-mil lines, and they used a full one-ounce copper base. The customer specified the copper base. This is what we're up against. We have to get them talked into a third-ounce or quarter-ounce copper, but then that will affect the impedance or performance all over the place. What if you can get two ounce thickness in 3-mil lines? Dack: That's what the mSAP process is, right? Yes. Really, again, it's modified semi-additive vs. semi-additive. Keep in mind that pattern plating is a semi-additive process already. Every shop's doing it, so they have the inherent know-how. Where it gets more challenging is asking, "What's their capability? What are the numbers?" When you're etching down through copper, let's say I have a photoresist on copper to make a trace that's blocking the etch chem- These examples show how tin flash can optimize the imaging process.