Just Ask Tara Dunn: What Is the Thickest Flex Layer Available?


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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 Tara Dunn’s turn! Tara is the vice president of marketing and business development for Averatek. A regular Flex007 columnist, Tara discusses flexible circuits, rigid-flex, and rigid PCBs, as well as RF/microwave technology, microelectronics, and additive processes. She is also 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: What is the maximum thickness of a single flex layer, not just for a test vehicle but a flexible circuit layer manufactured commercially?

A: There are a lot of different ways to answer this question. There are examples of flexible circuits being manufactured with 10-ounce copper bonded to dielectric. In this case, the “body” of the flexible circuit is typically etched to a thinner copper for flexibility and leaves the contact fingers with the thicker copper.

Looking at what laminate thickness are commercially available for fabricators, Dupont provides a laminate with 0.005” dielectric, bonded on each side to four-ounce copper, with 0.003” adhesive. That is an extremely thick laminate, at 0.0222”. The most common flexible laminates are much thinner, with half-ounce or one-ounce copper bonded to 0.001” or 0.002” polyimide, resulting in thicknesses of 0.0024–0.0068”, depending on adhesive requirements, dielectric thicknesses, and copper weight.

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