Just Ask Tara Dunn: DFM for Flex and Rigid-Flex


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First, we asked you to send in your questions for Happy Holden, Joe Fjelstad, John Mitchell, and others in our “Just Ask” series. Now, it’s Omni PCB President Tara Dunn’s turn! A regular Flex007 columnist, Tara discusses flexible circuits, rigid-flex, and rigid PCBs, as well as RF/microwave technology, microelectronics, and additive processes. Tara is the co-founder of Geek-a-Palooza and a show manager for the SMTA Additive Electronics TechXchange event. She has over 20 years of experience in the PCB industry. We hope you enjoy “Just Ask Tara.”

Q: Flex designers don’t seem to pay much attention to a fabricator’s limitations. What would you advise new flex designers as far as DFM?

A: Knowing your fabricator’s limitations is important, whether that be for rigid PCBs or flexible circuits. And this is especially important with flexible circuit designs. There is a wide range of capabilities across the supply base. Some focus on simple flex, single-sided, double-sided, or low layer counts. Others focus on high-complexity technology, including complex rigid-flex and bookbinder technology. It is critical to really understand your fabricator’s capabilities and design to those capabilities.

As important, in a general sense, is to understand that flexible circuit fabrication, while similar to rigid PCB fabrication, has subtle differences that impact things, such as minimum line width and space and hole size. Not only are the layers thinner, with considerations needed for handling and processing, but the materials themselves are less stable than traditional rigid materials, with subtle shifts in material size through processing and changing environmental conditions. These things impact registration during fabrication, and feature sizes that may be common in rigid PCB fabrication may not be the “standard” for flexible circuit designs. Communication is king.

To submit your questions for Tara, click here.

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