Effects of inorganic encapsulation on power cycling lifetime of aluminum bond wires

Abstract

Bond wire lift-offs and heel cracks are regarded as one of the main failure mechanisms of the bond wires in the power modules. In previous studies, the reliability of the bond wires can be improved by applying encapsulations to cover the bond wires. In this work, the investigation was mainly focused on the effect of inorganic encapsulation on the reliability of the aluminum bond wires under the power cycling test. Samples with different encapsulation positions were tested in order to evaluate the dependency of the encapsulation position on the reliability of the bond stitches. The results of power cycling tests and shear tests showed a reliability improvement of the tested samples when the aluminum bond wires was covered by the inorganic encapsulation. Besides, the reliability improvement of the samples was highly related to the covered position of the bond stitches. Thermal-mechanical simulation results indicated the heel cracks had stronger influence on the encapsulated bond wires at the certain position than the other position, which may be the reason of the position dependency of the encapsulation on the reliability improvement of the bond wires.