Issue link: https://iconnect007.uberflip.com/i/1073397
JANUARY 2019 I FLEX007 MAGAZINE 35 Our team was called the "Dream Team." We combined a veteran group of experienced talent with a rookie group of individuals who did not know the technology barriers of the past. The team believed that we were going to launch a multi-billion-dollar business based on novel products realized by a portfolio of innovations—designs materials, processes, manufacturing equipment. Goldman: When you were designing some of those early flexible or rigid-flex boards, there must have been a lot of failures and having to do it over again until you caught on to it such as the direction of the copper grain at flex points and things like that. Am I right? Gamota: You're right. It was the days of Mac- Gyver because people were fabricating a bot- tom-gate transistor using any materials you had available. We had people using a Juicy Fruit gum wrapper, paperclip, and semicon- ductor ink to make a transistor. They looked at everything in an open transistor and IC design world where you simply required a conductive material for the gate, dielectric material for the gate insulator, another conductive material for the source and drain, and a material that had semiconductor-like properties. When we would visit printing services com- panies—because ultimately, we were going to use printing equipment such as a screen printer, gravure, or flexography—we would go to their shelf of inks that they were using for graphic arts printing, and we would look at the ink chemical compositions. We learned that in graphic arts printing (e.g., a magazine) sev- eral of the inks used have electrical properties. Some inks are great conductors while others are great insulators. Except for not having a semiconductor ink, the printers had all the nec- essary materials to print transistors as well as the process know-how to align and print very fine features necessary for electronics. They knew how to ensure that transistor structure layers were pinhole-free and how to achieve sub-50 micron registration from printed layer to printed layer. It seemed like everything was going to align perfectly, and the only thing that was a potential concern for us was the semiconductor material. The advancements in semiconductor material electrical mobility were a little bit tempered and the materials weren't as high performing once you took them out of a well-controlled environment—a chemistry lab. Once you moved the material into a manufacturing or NPI environment, you lost a couple orders of magnitude in mobility performance. You still have these issues today when transitioning technologies from lab to fab. Also, we lack the ability to consistently print 1,000 transistors and ensure that all 1,000 provide the same electrical performance. That's where the deficiency of printed tran- sistors lies—robust high mobility semiconduc- tor inks. Printed transistors would have a very difficult time replacing silicon based transis- tors. Once we realized that printing 1,000 tran- sistors that all worked within a certain opera- tion window would be very difficult and we observed the cost coming down quickly for sil- icon-based ICs, an all-printed transistor-based circuit was no longer an option. This was the start of flexible hybrid electronics (FHE). Today you see flexible hybrid electronics (printed electronic devices combined with sili- con-based devices assembled on a flexible sub- strate)—enabling the design and manufacture