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April 2017 • The PCB Design Magazine 29 see companies engaged in networking, telecom, and storage systems. Steven Las Marias: Craig, with the proliferation of optical boards, do you think it will require a differ- ent set of manufacturing or assembly expertise or techniques? Davidson: Yes, I do. The early work in this space was subject to many issues, not the least of which was registration and making sure you know the precise location of the fiber. This has a major impact on assembly. You probably know that the connectors have to be lined up with the waveguides requiring a lot of precision and even active positioning perhaps. That is, putting an optical signal through the board to optimize component and connector positioning during the assembly operation. In some of the higher speed optical, we're talking about a few microns of registration accuracy required. That's quite a change for most of the assembly operations. Our embedded wave guides, as opposed to fi- bers, reduce this overall problem, but new ap- proaches to assembly are required. For the con- sortia work in which we have participated parts were sent to the connector companies because they have the tools to do this type of connector alignment and assembly. That's obviously not a very happy solution for volume manufacturing. So the industry needs appropriate volume assembly solutions. It's also very dependent on the type of connectors you're going to be using and the board technology. TTM is heavily in- volved with the connector companies. I didn't really point that out before, but in all of the demonstrators and prototypes, we're heavily in- volved with all the connector companies, and are aware of their new connector technologies and connector designs coming to meet this re- quirement. It is a challenge to put these connec- tors on and make sure that they're within a few microns of where they need to be. If you could do that without active alignment by using new assembly approaches that would be interesting. It's also an area that TTM is looking at as we also have assembly capabilities in-house. Matties: I think there's a whole list of new con- nectors that have to be developed to be compat- ible with this technology as well. It's not just items off the shelf. They have to design and develop new technology for this specifically, right? Davidson: Yes, there are connectors now like today's cable connection; you just plug it into the receptors on the board. But as we begin to integrate optics into the board, we clearly need new sets of connectors. The connector compa- nies are developing them and we are evaluating them. It's also true that in the evaluations the connectors are a significant part of the losses in the system. Connectors represent a discontinu- ity—electrical or optical—so I guess you'd be surprised if they weren't also a loss problem in optical systems as well. We're quite happy with the performance of the embedded optical wave- guides we have in our boards, but we know that there needs to be improvements in the connec- tors and at that interface to keep loss at a mini- mum. So, yes, a very important part. These technologies play together in a very systems-oriented solution, I think, includ- ing design which also plays a prominent role. Our ability to embed waveguides in the right configurations is a major part of the solution. When you start thinking about it all, all the components must be ready for a manufactur- ing production capability by 2020. There's not much time to put it all in place and prove it out and make sure it's integrated and with a supply chain that's ready to go. Matties: It's a large undertaking for sure, and I know when we first started talking about it with Marika in 2015, TTM was thinking three to four years. To me that seemed like a long time, but when you start looking at the entire infrastructure that needs to be developed and supported, it's not long at all. It goes by very fast. Davidson: Yeah, not long at all. In fact, it's quite exciting and very interesting for sure. Matties: I bet. Davidson: In the 1980s and '90s, companies were more vertically integrated. They had their own board shop, wafer fab, and did all the assembly on their own designs. We could put together a TTM SHINES A LIGHT ON OPTICAL INTERCONNECT