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48 DESIGN007 MAGAZINE I DECEMBER 2023 plating up a trench—that little trench gets filled up—and that's exactly at the width the designer intended, so it's a lot easier to hit the impedance requirements. Also, this technology has a lot of potential in the medical industry. You can make biocom- patible circuit boards because A-SAP does not have any copper or nickel in the construction— which are toxic to the body. You can do traces that are all noble metals like palladium and gold, and that's a big improvement. Are you doing anything biocompatible? We are. We've built a couple of programs here with more to come. One of the foundations of the process is liquid metal ink (LMIä). Tell me about that. LMI is a patented Averatek chemistry for put- ting down a very, very thin coating of palla- dium on the surface. It's very dense—basically several levels deep of atoms touching atoms. It's just a few nanometers thick. at density really helps in getting plating down into all the small crevices and small vias that need to be plated. e liquid metal ink is a non-aqueous base, so that wets very well in all the little nooks and crannies that you'll see in drilled holes. You can metallize these holes much easier than stan- dard plating chemistry. Now, bear in mind we still do use electrolytes from a variety of manufactur- ers, so this doesn't replace electrolytes. It creates that catalyst level that you need to get the plating accom- plished, and it works with different metals. e prop- erties of liquid metal ink could be with gold or silver as well; it's not just for palladium in this case. That's pretty interesting. When you look at the comparison between the LMI and the standard process, it's striking. Figure 1 illustrates what happens in a standard process when you have palladium deposited out of an aqueous solution that is dis- persed. e copper tends to build slower and it's less dense during the early stages of plating. Over time it will build up a thickness dense enough that will support an electrolytic copper plating. Whereas with the LMI tech- nique, you have a very dense level of palladium, as you see illustrated. You can plate electro- less copper in a very thin deposition that will be able to conduct electricity for electroplate. at's the key differences. In the SEM image on the right of Figure 1, it shows the electroless deposition, not the palladium, which is so fine that you need a transmission electron micro- scope to see it. When you look, you'll see how fine the electroless deposition is, and how it has followed the topography of the copper foil that was there beforehand. at helps to give very good adhesion to that surface. John Johnson Figure 1: This is what happens in a standard process when you have palladium deposited out of an aqueous solution that is dispersed.