Impact of reliability tests on the adhesion of the epoxy mold compound

The epoxy mold compound of power modules serves as protection and isolation of the electrical components. Adhesion of the mold compound to the components and especially to the substrate affects substantially the module reliability. Tight connection between both parts guarantees, that no harmful substances e.g. humidity can reach the electrical components, and by that avoid damage of the module. In this study, the reliability of two different materials was tested through thermal cycling and highly accelerated stress test by the button shear method. The proposed method enables comparing the adhesion properties of mold material directly on the final product and helps to select optimum mold compound. In addition, the effect of spiral flow was investigated by comparing adhesion properties of two different corner lots of the mold materials after reliability test.