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12 The PCB Design Magazine • March 2017 by Craig Armenti MENTOR GRAPHICS As rigid-flex design becomes commonplace across many industry segments, education on terminology, requirements, processes and best practices are all critical in order to ensure a high probability for first-pass success. As the name indicates, rigid-flex circuits are comprised of a combination of rigid and flexible board tech- nologies. These types of designs consist of mul- tiple layers of flexible circuit substrates attached internally and/or externally to one or more rig- id boards. By combining the advantages of the two technologies, designers have more options when working with dense designs that must conform to a specific form factor. Rigid-flex is a truly enabling technology that lets product de- velopment teams cost-efficiently apply greater functionality to a smaller volume of space while at the same time providing the mechanical sta- bility required by most applications. Prior to the advent of rigid-flex design, when a product required a flex PCB (or mul- tiple flex PCBs), the flex and rigid PCBs were designed separately. Each PCB contained one or more physical connectors in order to as- semble the individual boards into a product- level design. In this design methodology , the flex designs were assigned to a specialist who was familiar with stackup and material options along with the best practices and requirements for flex-specific items such as bend regions and stiffeners. There is, after all, a certain science to flex design that, when properly applied, can help ensure first-pass success. While this traditional "design-separately-then-assemble" approach minimized potential issues with the flex portions of the product, it also had several inherent disadvantages. These include the cost associated with the physical connectors; the space required for the physical connectors; the need to properly manage interconnects that have to transition between the separate rigid and flex PCBs (through the connectors); and, of course, the time and cost associated with assembly. The move to the current generation of rigid-flex technology mitigates these issues; however, they are replaced with a different set of challenges and concerns. The good news is these challenges and concerns can be alleviat - ed simply by following some key best practices and guidelines. Rigid-flex Design Tips and Best Practices FEATURE