Issue link: https://iconnect007.uberflip.com/i/1007258
JULY 2018 I FLEX007 MAGAZINE 17 lot of these changes that we were hoping to see. Like automatically calculating the bend radius based on your inputs and helping you create a curved line instead of having to do hand draw- ing. Some of our designers were actually doing this. It seemed like madness. Rigid-flex can be complicated with the transi- tion zones between the rigid and the flex areas. You want to make sure that your keep-outs are well defined, so you don't have too much adhe - sive squeezed out onto the flex portion so that it limits your bend radius. The updated design tools have really helped the engineers under - stand what those boundaries and limitations are. Shaughnessy: Is there anything you would like to add? Any advice? MacFadden: I think my number one piece of advice would be to interact early and often with the technical reps from your respective suppliers, because they have a lot of informa- tion that they could share with you before you make expensive mistakes. It's really just talk- ing about ideas. Then, I guess the other piece is be prepared to iterate. It's even becoming easier now with laser cutting and models using actual material sets that are representative of what you're going to get. Shaughnessy: I appreciate your insight, Todd. Thanks for your time. MacFadden: Thank you. I enjoyed it. FLEX007 not just designing for a robust circuit, but it's robust assembly as well. How is it going to actu- ally go into housing? You could have the most elegant and interesting design in the world, but if you can't make it fit in your housing reliably and repeatedly, you must review that. Shaughnessy: That is interesting. Twenty years ago, when I started covering this industry, only about 5% of designers had ever done any flex work because it was just so expensive and completely different. MacFadden: Yes, it's the 3D aspect that's chal- lenging for a lot of us older engineers who are so used to two-dimensional. New design tools have made it easy now to visualize three dimen- sions, but to visualize it is one thing; trying to incorporate these things into a housing can be a challenge. Recently we had LED components on a surface that were meant to be inserted into a product housing and behind a molded light pipe fixture, and there was always one of a series getting damaged. We just needed to move one support rib maybe one millime- ter, and it made the problem go away. No one could have anticipated that this was going to be a problem until assembly. Another one was one time we tried to cheat a little bit on the recommended bend radius. I won't recommend that, not without at least first trying it. We did have some issues with cracked fingers. I will say that on a ZIF connec- tor, that's become a problem for some people, but had we just given ourselves a little more bend radii step that probably wouldn't have existed. Eventually we did manage to fix it. Fortunately it was before product launch. Shaughnessy: You mentioned the design tools. Have EDA tools caught up with flex design? I know not very long ago they weren't set up for flex. MacFadden: No. There's been a lag in the tools in terms of what they can do. I mean, a lot of the first flex designs that we made were just by brute force, manual manipulation of the tool to make it do what you needed to do. But I know some of the latest versions have incorporated a Figure 4: The Bose SoundWear Companion speaker uses a multilayer flexible printed circuit for board interconnects, and for mounting components such as LEDs, tactile switches, and microphones.