RF PCB

Every laminate material discussed in this series so far — standard FR4, High-Tg FR4, polyimide — shares a common selection logic. You choose among them based on thermal performance, mechanical requirements, and environmental resistance. Electrical properties rarely drive the decision because at the frequencies where these materials are used, the differences are manageable. PTFE-based laminates exist in a different category entirely. They are selected primarily for their electrical properties — specifically their ability to transmit high-frequency signals with minimal loss and maximum dimensional consistency.

One of the most persistent misconceptions about PTFE-based PCB laminates comes from handling the material. Pick up a sheet of Rogers RO4350B or RT/duroid 5880 and compare it to a sheet of standard FR4. The PTFE laminate feels different — slightly softer, with a quality that engineers sometimes describe as rubbery or compliant. Bend it gently and it flexes slightly before springing back. This tactile impression leads directly to a dangerous assumption: that PTFE can be used in flexible PCB applications, or treated with more mechanical freedom than a rigid board.