Degradation of gold-aluminium ball bonds by aging and contamination

The degradation of gold aluminium ball bonds has been studied by shear tests, resistivity measurements, micrographs, EDX and AES as a function of aging time at elevated temperatures and after various contamination treatments before and after bonding. Samples were subjected to ion etching treatment immediately before bonding in order to guarantee a comparable initial state. Incorporation of large amounts of Cl, Br, and F into the surface layer of the pad and other contamination treatments before bonding did not show detectable effects in subsequent annealing treatments as long as the bonding process itself has not been impeded by thick surface layers. The degradation process during annealing can be described as a three stage mechanism. Each stage can be clearly distinguished by the fracture behavior in the shear test, the morphology of the bond shown by the micrographs and by the change of contact resistivity.