Issue link: https://iconnect007.uberflip.com/i/1073397
36 FLEX007 MAGAZINE I JANUARY 2019 of products having unique form factors. The form factor is enabled because the substrate is no longer rigid but can be flexible, stretch- able, and conformal. The use of FHE building blocks also enables flexibility in the design lay- out itself—you can still have one component or a few components that are silicon-based that provide the necessary functionality (e.g., computation speed or TX/RX performance for communications) while integrating printed elements to build your product. Another critical set of design rules which were established for FHE was related to the copper traces on the substrate. These stringent design rules did not allow us to realize some of the products that we wanted in the past. Today, there are new materials (e.g., inks) that are being developed that may expand the product opportunities. These materials can conform to rough surfaces and planarize them to achieve the necessary flatness. For a long time, we were limited in the number of dif- ferent products that we could develop because we were constrained by the lack of a smooth base conductive trace surface. Andy Shaughnessy: What are some of the more interesting substrates and surfaces that you're working with or that you see coming online in the future? Futuristic types always talk about putting printed electronics on every cereal box, which would light up when you walked by on the grocery aisle. Gamota: All of that is doable. The packaging materials that are used, whether it's the mate- rials for candy wrappers or materials that are used for cereal boxes have surfaces that are pristine and perfect for electronics integration. But to me, for the most part, those are not the ones that are going to take us to the next realm. What I see moving us forward are stretchables. When you talk about silicone materials which can deform in millions of directions, that's where the excitement lies. Many of these stretchable substrates are being investigated for digital tattoos that we put on our arms for perhaps monitoring our body's core temperature. That's great, but just wait until you can build a suite of sensors that you can place inside a person's body to monitor their heart rate or the stresses on their organs or artery walls. That's the electronics journey that we are experiencing. There are some hurdles associated with it, but people are establishing guidelines to identify the substrates and their critical properties such as biocompatibility and stretchability. Now, we just need to appreciate the other criteria that are necessary to insert these products into our body to achieve the desired functionality and long-term performance. Shaughnessy: We always thought that copper was going to hit the wall before now, and we keep seeming to be able to make FR-4 do more and more. Do you think it will get to the point where we finally run out of a use for FR-4, or we have to start using some of these boutique materials or others? Gamota: I have history on my side, right? If I go back to my experience developing flip chip technologies at Motorola, everybody was pre- dicting that flip chip was the future because wire bonding technology was reaching its limit. I wouldn't say it happened overnight, but in two years, I went from thinking wire bonding was dead to the introduction of ball-grid arrays (BGAs), micro BGAs, and chip-scale packages. What I learned is that you never can say a tech- nology is going to go away with a high level of For a long time, we were limited in the number of different products that we could develop because we were constrained by the lack of a smooth base conductive trace surface.