Issue link: https://iconnect007.uberflip.com/i/1503357
60 DESIGN007 MAGAZINE I JULY 2023 Article by Mike Morando PFC FLEXIBLE CIRCUITS One of the most recent topics in the flex world has been the evaluation of materials required to build a rigid-flex or flex circuit. Discussions around flex and materials include variations of polyimide and copper. Here I will discuss another material that plays a very important role in the world of flex circuits: stiffeners. ese are critical components to a flex circuit because they broaden its scope and potential applications. A "stiffener" in the flex circuit world is a generic term used to identify a material that prevents a flex circuit from bending and flex- ing. In all these instances, we will not be talk- ing about rigid-flex—just flex circuits only. Stiffeners are, in most cases, a non-electrical component/addition to a flex circuit and func- tion as a mechanical support. Stiffeners are attached in a secondary opera- tion by either thermal bonding, pressure sen- sitive adhesives (PSAs), or epoxy. Stiffeners Stiffeners for Flex Circuits require a secondary operation in the manufac- turing process, so it is a cost adder. Materials we have used to add stiffeners include FR-4, polyimide, aluminum, alumina, steel, and ceramic. As technology progresses and flex is used in more and different applica- tions, a variety of materials are being used to support and create flex stiffeners. Reasons to include stiffeners into your flex circuit design include: • e SMT process and component support • rough-hole component mounting • Flatness requirements • Mechanical infrastructure and design support • Increased material thickness requirements • ZIF connector interface • Heat dissipation • Wire bond pads