19. Symmetric and Asymmetric Double Cantilever Beam Methods for Interfacial Adhesion Strength Measurement in Electronic Packaging

This paper discusses Double Cantilever Beam (DCB) test methods that were developed for characterizing adhesion strength of several critical interfaces in advanced microelectronic packaging. Those interfaces include silicon-epoxy underfill and solder resist-epoxy underfill. A unique sample preparation technique was developed for DCB testing of each interface in order to avoid the testing challenges specific to that interface—for example, silicon cracking and voiding in silicon-underfill samples and cracking of solder resist films in solder resist-underfill samples. Additionally, asymmetric DCB samples (i.e., different cantilever beam thickness on top compared to the bottom) were found to be more effective in maintaining the crack at the interface of interest and in reducing the occurrence of cohesive cracking when compared to symmetric DCB samples. Several case studies using DCB for material selection and assembly process optimization are also discussed. Furthermore, fractography results from SEM examination of the fractured surfaces are also presented for better understanding of the failure mode.