Interfacial Versus Cohesive Failure on Polymer-Metal Interfaces in Electronic Packaging—Effects of Interface Roughness

Abstract

Debonding of polymer-metal interfaces often involves both interfacial and cohesive failure. Since the cohesive strength of polymers is usually much greater than the polymer-metal interfacial strength, cohesive failure near the interface is usually desired for enhancing the interfacial adhesion. Roughened surfaces generally produce more cohesive failure; therefore, they are used commonly in practice to obtain better adhesion. This paper develops a fracture mechanics model that can be used to quantitatively predict the amount of cohesive failure once the surface roughness data are given. An epoxy/Al interface was investigated using this fracture mechanics model. The predicted amount of cohesive failure as a function of surface roughness compares very well with the experimentally measured values. It is believed that this model can be extended to other polymer–metal interfaces. Contributed by the Electronic and Photonic Packaging Division for publication in the JOURNAL OF ELECTRONIC PACKAGING . Manuscript received by the EPPD.