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22 The PCB Design Magazine • March 2017 whose software I still use, CAD Design Software, makes something called Electronics Packaging Designer, which sits atop AutoCAD and then makes AutoCAD do the circuit board designing. Whereas most board tools will only do 45° angles, this can make any shape or trace you want. Then just press the button and it burps it out into Gerber. So I've used that tool ever since. As the years have gone on, I've purchased other tools like Allegro and Altium too, because that's what customers have required. Shaughnessy: It used to be that flex was so expensive that people didn't use it. When I first started in the '90s covering this industry, flex was kind of like an afterthought. Woznicki: You only used flex if nothing else would work. To a large extent that is still the same because, I mean, a cable harness and a rigid board will always be cheaper than a flex circuit. You've got to have another reason to use flex. Either weight or reliability, it's got to bend or it's got to fold, or you need really fine traces, finer that you can make on a rigid board. There's got to be a reason for it, but it's much more a commodity than it used to be, that's for sure. Shaughnessy: And the prices of stiffeners and all these things, did they all come down too? Woznicki: Stiffeners add very little to the cost. The cost of the materials have gone down quite a bit, just from the sheer volume of flexes that are being made, and of course all the Asian manufacturing. Shaughnessy: I hear about some people starting with flex because it has signal integrity benefits compared to copper. Woznicki: It does. Your dielectric constant is a little bit lower; it's right around 3, and some people say 2.7, but it's definitely a lot lower than the 4.3 that you usually associate with FR- 4. You can make a lot finer traces with it because the material is so smooth. You don't have that orange peel look on FR-4 that you get from the weave of the glass and the epoxy filling in. The film is just smooth, so you can etch two-mil lines, one and a half-mil lines if you have to, and even tighter. Shaughnessy: It's funny we just, we see flex all the time now. I guess there's standards now? Woznicki: Yeah, there are standards. Shaughnessy: IPC has some flex standards. They're not everywhere but you see rigid-flex in every camera. Woznicki: Oh yeah. You take your smart phone apart and you've got a good eight or 10 flex cir- cuits, rigid-flexes in there. Shaughnessy: It seems like fabricators are getting better at building it too. Woznicki: Oh, my goodness, yes. I was thinking about this the other day because flex circuits, at least like you were saying back in the day, were very expensive so you had to be pretty careful. If you made a bad batch of flex circuits, that's a pretty expensive pile of scrap. But now, like you said, it's a little bit more of a commodity item, especially in the Asian market. You've got so many people anxious to build it for you and build it at a real low cost. There's a lot more trial and error, so they'll get somebody and it's not a very good design but it half works so they "FLEXDUDE" TOM WOZNICKI CELEBRATES COMPANY'S 25 TH ANNIVERSARY

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