Publications

Fatigue behavior of thin Cu foils and Cu/Kapton flexible circuits

Beck, David F.; Susan, D.F.; Sorensen, Neil R.; Thayer, Gayle E.

A series of thin electrodeposited Cu foils and Cu foil/Kapton flex circuits were tested in bending fatigue according to ASTM E796 and IPC-TM-650. The fatigue behavior was analyzed in terms of strain vs. number of cycles to failure, using a Coffin-Manson approach. The effects of Cu foil thickness and Cu trace width are discussed. The Cu foils performed as expected and the Cu foil/Kapton® (E.I. du Pont de Nemours and Company, Wilmington, DE) composites showed significant improvement in fatigue lifetime due to the composite strengthening effect of the Kapton layers. However, the flex circuits showed more scatter in fatigue life based on electrical continuity. The effect of the Kapton layers manifests itself by significantly more widespread microcracking in the Cu traces and the extent of microcracking depended on the strain level. *Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. © 2008 MS&T'08 ®.