Effect of Silane Functional Group on Adhesion of Selected Epoxies for Microelectronic Packaging

This paper describes experiments designed to evaluate the effect of various silane surface treatments on the thin-film adhesion of epoxies filled with spherical silicon oxide. Fracture mechanics-based methods evaluated adhesion of both filled and unfilled epoxies to silicon oxide. SEM was used to examine fracture surfaces and evaluate fracture mechanisms. Two different epoxies were tested, including one with four components and multiple intermediate cure reactions. It was found that the only silanes that augmented adhesion of the epoxies to silicon oxide were those with functional groups identical to those of the epoxies which take part in the final curing reaction. However, when these silanes were used to coat filler, adhesion of filled epoxies to silicon oxide wafers remained the same or was slightly reduced. In all cases, fracture occurred at or near the epoxy-wafer interface, suggesting that deformation within the epoxy layer was limited. Only one set of specimens, in which the silane was improperly prepared, resulted in augmented epoxy-wafer adhesion facilitated by filler-matrix delamination. In other words, filled epoxy-wafer adhesion increases with decreasing efficacy of silane adhesion promoter treatment.