Flexible Circuit Materials for High Temperature Applications

Sidney Cox
DuPont Circuit and Packaging Materials Research Triangle Park, NC USA

Many opportunities exist for flexible circuits in high temperature applications (Automotive, Military, Aerospace, Oil and Gas). Flex circuits in these applications have been hindered by a lack of materials that can survive higher temperatures. Some materials, especially some thermoset adhesives, break down over time at higher temperature, becoming brittle or losing adhesion to copper. Polyimides tend to perform much better under high temperature.

The other issue is the lack of good test methods to verify that flex materials can survive higher temperatures. Several methods for testing copper clad laminates exist but there are very few for coverlays and bondplies. We will discuss different test methods for measuring high temperature capability including the new IPC Service Temperature test. We will also report on test results for various flexible materials and our recommendations for the best flexible materials for high temperature applications. This will include development work on new flex materials for high temperature applications.

To meet the increasing needs for flexible circuit materials for high temperature applications, new test methods will need to be developed. These new methods will assign new ratings, and we believe ratings that are consistent with actual performance.

The present IPC Service Temperature test seems to work well for testing copper clad laminates. It does not work well for bondplies and especially coverlays. We have demonstrated a new coverlay test based on bend testing. The overall results clearly show that all polyimide clads, bondplies and coverlays will provide the highest Service Temperature performance.