Rigid-flex Design Tips and Best Practices


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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 technologies. These types of designs consist of multiple layers of flexible circuit substrates attached internally and/or externally to one or more rigid 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 development teams cost-efficiently apply greater functionality to a smaller volume of space while at the same time providing the mechanical stability required by most applications.

Prior to the advent of rigid-flex design, when a product required a flex PCB (or multiple flex PCBs), the flex and rigid PCBs were designed separately. Each PCB contained one or more physical connectors in order to assemble 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 alleviated simply by following some key best practices and guidelines.

To read this entire article, which appeared in the March 2017 issue of The PCB Design Magazine, click here.

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