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42 SMT Magazine • March 2017 by Stephen Las Marias I-CONNECT007 UK-based JJS Manufacturing is an EMS part- ner specializing in end-to-end procurement, manufacture (PCB assembly, box build, cabi- net, electro-mechanical) and supply chain so- lutions. The company supplies complex, highly configurable, low-to-medium-volume industri- al electronics products across a range of market sectors including industrial automation, pro- cess control, test and measurement, and labora- tory technology. Russell Poppe, director of technology, dis- cusses with SMT Magazine the challenges when dealing with flex circuit assemblies and pro- vides strategies to address them. Stephen Las Marias: From your experience, what are the major challenges in flex-circuit assembly? Russell Poppe: From an assembly perspective, baking the flex circuits prior to manufacturing assembly is crucial as they can be susceptible to delamination. That said, baking any PCB pri- or to manufacturing is best practice and some- thing we always do at JJS. One of the biggest challenges in flex circuit assembly is making sure the circuits remain flat, particularly during the printing and pick-and- place processes. The parts of the circuit requir- ing SMT placement should have an FR4 stiff- ener designed in underneath; but it is also im- portant to work with the PCB supplier up front. Getting the panelization right is important so that the boards don't bend when the parts are placed or when they pass through reflow. Panel design can be a challenge as flex circuits are of- ten strange shapes! It might also be necessary to have a bespoke carrier or pallet to hold the flex circuits in place throughout the process; how- ever, these carry additional costs—typically a few hundred pounds each. Las Marias: What are the specific steps in a flex- ible circuit assembly process that have the biggest effect on yields? Poppe: Failure to bake the flex circuits prior to assembly can lead to delamination issues. If JJS Stresses the Need for Baking Prior to Flex-Circuit Assembly FEATURE INTERVIEW