Issue link: https://iconnect007.uberflip.com/i/1073397
JANUARY 2019 I FLEX007 MAGAZINE 29 imide-based that is far different from normal FR-4 materials. The stack-up, mechanical and chemical processes used, signal integrity, overall product reliability, and even storage and assembly conditions are all impacted by this material change. However, the most dif- ficult part will still be the manufacturing pro- cess. Especially with rigid-flex, many of the processes are customized based on different design features and requirements. There is a lot of engineering and know-how involved; normally it requires the manufacturing process experts working together to get to the optimum solution with the least compromises from origi- nal design needs. Even for PCB companies like us, we still need training on our manufactur- ing considerations, not to mention the custom- ers. Luckily we have a strong engineering team from both the manufacturing end and cus- tomer end and they sync all the time and can work seamlessly to address the requirements and needs of our customers. Matties: With this area grow- ing and a lot of material issues, I would think that there are a lot of education needs. Now, in terms of the flex offerings, I see you do quite a bit, from single- sided all the way to rigid-flex HDI. Are you seeing more of a trend around the HDI? Zha: For HDI, it has started booming not only for rigid-flex but also for rigid. Part of the rea- son is that it is component-driven because most of the components are getting to a level where you have to route with microvias. There's no way you can route with PTH holes simply because the through- hole and off-pad design are too large for those kinds of pitches. Another reason is that we're seeing the needs coming from signal integrity considerations, especially for 5G. With HDI, you can use the microvia structure to form a very good termi- nation at the different layers with high den- sity routing so that you don't have too much loss on the stubs. You also don't want a signal going through the power and grounding in the middle where you're going to generate a lot of noises to your signal. In that sense, I see a lot of requirements on HDI for both rigid-flex and the rigid section. Matties: And you said you're doing assembly as well for the flex and rigid-flex products. One thing we hear is flex assembly is quite challenging if the board is not configured or layed out properly. What should a buyer know when it comes to the assembly process? Zha: Yes, and that's the reason why we have flex assembly in-house, which is normally required in the flex products. That's mainly because the flexibility of the material itself makes it hard to handle. Usually, the rigid assembly house can't or doesn't want to handle it because it doesn't fit their high volume, high-speed environment. Thus, only very specialized assemblers on the flex side can handle these kinds of materials. Matties: What advice do you give your customers when it comes to the assembly? Zha: What we see is that the flex assembly is really happening at the flex manufacturer side, like an in-house service. Usually there are not a lot of compo- nents on the flex portion; most likely, there are a few connectors here or there from the main components and most of the functional com- ponents are on the rigid portion. Matties: Clay, you mentioned that TTM has 29 facilities. Do you have flex-dedicated facilities, or is it just embedded in other manufacturing facilities? Zha: We do have an independent flex operation, but it's located in the same building as one of our rigid shops. We have our TTM Guangzhou (FPC) operation inside the TTM Guangzhou Winnie Ng