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14 The PCB Design Magazine • June 2017 A DEEP LOOK INTO EMBEDDED TECHNOLOGY use their name, but we're designing their next model. As these phones increase they use more and more microphones. The original micro- phone was designed to listen to your voice, but there are microphones to listen to noise, and there are microphones in the speakers and in earbuds. All of these sensors are MEMS modules that use resistors. They're simple boards, basically two to six- layer boards that have one or two layers of Oh- mega in our case. These are used as part of filters which means they have capacitors embedded as well and most of the time, I'd say the clear ma- jority of it you will have different layers. Let's say we have an OhmegaPly layer and a capacitive layer, and a capacitive layer might be 3M C-ply or it might be Oak Mitsui as a capacitive layer in a separate core. However, we do have a joint patent with Oak Mitsui for a combined prod- uct, which means the same core has both the embedded capacitor and the resistance. There are some advantages to that. The reason it's not more widely used is that it's a more expensive product and therefore the economics are rather working against us. Plus, there are some difficul- ties in the way you test capacitors; it's a lot dif- ferent than the way you test resistors. So for now, most of these applications, par- ticularly in cellphones, are at the capacitive embedded layers, and the resistive embedded layers are separate and can be handled and pro- cessed separately and then all laminated togeth- er. This totally blindsided us 10 years ago, by the way, and that has become the biggest part of our business. Originally our core technology was the high-end, very expensive military aero- space—all those things. That's what we thought was our main application. Telecom and ad- vanced high-end file servers would be the main part of our business. But what has happened is that suddenly these low-frequency applications came along, and then the audio. With 100 mil- lion cellphones, that became the largest part of our business, mostly being exported to China. Our materials are shipping to the Far East all the time because there are so many board shops and so much assembly work done in the Far East. We export primarily to China, but also Taiwan and Malaysia and various Pacific Rim countries. The technology is well established although the applications are new; it's standard print- and-etch technology. Board shops already have almost all the equipment, although there are a couple that might need a nickel strip tank, or their testers would have to be different. But basically, it's the same print-and-etch technol- ogy that they all use. The first etcher we don't care, they might use cupric chloride which they would have to use if they used Nichrome. Also, the big thing in miniaturization is using laser di- rect imaging. Almost none of our PCBs are laser trimmed. Close to 90+% is "as is," which means they have very precision printing and etching which is sufficient to hold the necessary toler- ances. We're not a big fan of laser trimming; on the other hand, we love direct imaging, either laser or LED technology. The imaging technology has improved and our product has improved to allow very min- iature resistors like 50-micron (2 mm) wide re- sistors, 2 mm by 4 mm or 8 mm and holding a reasonable tolerance. That's the new, biggest thing. We saw this coming, but seeing it didn't necessarily mean we had all the answers to it. There were two worlds: there was the world of high-speed digital and there was the world of RF microwave. In the world of microwave, the gigahertz technology needed very smooth con- ductors because of skin effects, and the smooth conductors lowered the resistance. Since we control sheet resistivity, that's why it's about resistance, not thickness. What happens is the conductors get smoother and smoother and " So for now, most of these ap- plications, particularly in cellphones, is at the capacitive embedded layers and the resistive embedded layers are separate and can be handled and processed separately and then all laminated together. "