Issue link: https://iconnect007.uberflip.com/i/811341
April 2017 • The PCB Design Magazine 25 TTM SHINES A LIGHT ON OPTICAL INTERCONNECT nect at reasonable costs and at these kinds of performance levels. TTM's goal is to ensure we have the technology if it's needed and in that time frame. Matties: Now, with regard to your technology, is this already being used in any practical, commer- cial application or is it all design and experiment at this point? Davidson: Well, we're past the experimental stage. We have a stable manufacturing process now. Of course, we continue development of new materials and the maturation of our man- ufacturing processes. We provide pilot-level quantities with good yield. The industry focus has been on proving out the overall technology with evaluations and demonstrators. We are en- gaged with many companies and consortia to do demonstrators assessing how optical inter- connect technology could be used in package substrates, line cards and backplanes and mea- sure the benefits. TTM has built many demonstrators for com- panies—mostly through joint development ac- tivities either one-on-one, bilateral types of de- velopment, or through the many consortia of which we are members or with which we coop- erate closely, for example PhoxTrot in Europe and AIM Photonics here in the U.S. They have designed demonstrators to determine how best to employ these tools and determine design parameters. We're building functional dem- onstrators for companies that include routers, switches, other types of networking devices, and storage applications. Cloud storage arrays have different requirements and configurations than a network line card, as an example. Matties: Now, with regard to manufacturing and your techniques, you mentioned that TTM has an optical line. Is this manufacturing equipment that you've partnered with suppliers to produce or is this internal development to create the manufac- turing process? Davidson: We're using existing PCB fabrication technologies including material deposition, im- aging, patterning, etc. I don't think at this point we have to design or develop any unique tools but rather utilize our innovative approaches to fabrication and incorporate light transmission materials—for example, polymer waveguides. These tend to be photoactive materials. We can deposit and define using typical phototools with high precision. But it's something that the industry understands and is recognized by our customers which reduces risk and raises confi- dence. We have already done up to two embed- ded optical layers on a 20-layer backplane as one of the demonstrators. This is a demonstra- tion of real product containing all regular cop- per layers and functions and it is quite a com- plex product to build. Matties: That's quite the undertaking. Davidson: Yes, it is. It's quite exciting and not a revolution from a technology point of view. We can deliver the tolerances required and continue to evaluate some of the newer opti- cal materials that are available to us now. We've been evaluating the polymer waveguide materi- als that are offered by different companies. And now the new glass waveguide materials are also being offered. We are already using these em- bedded glass waveguides for the higher-perfor- mance applications. Quite interesting. Matties: I bet. For other fabricators, I assume you are licensing this process; when they embrace the process, it doesn't sound like a lot of capital invest- ment, but more process knowledge and training. Davidson: Yes. I'd say that is mostly true. We know how to set up a manufacturing line to do this. Obviously, because of the geometries and materials, cleanliness is important. So, we're " We are already using these embedded glass waveguides for the higher-performance applications. "