Oxidation Behavior and Intermetallic Compound Growth Dynamics of SAC305/Cu Solder Joints under Rapid Thermal Shock

Oxidation behavior of SAC305/Cu solder joints and kinetics of intermetallic compound (IMC) growth were investigated using an electromagnetic induction heating device. The results show that the solder joint undergoes oxidation when subjected to rapid thermal shock. The oxidation behavior of the solder joint itself is the main factor, which is exacerbated by the presence of the internal Cu6Sn5 IMC. The growth of the Cu6Sn5 layer is controlled by grain boundary diffusion, while that of the Cu3Sn layer is controlled by bulk diffusion. The dissolved Cu of the substrate diffuses mainly into the interfacial IMC and the interior of the solder. Under rapid thermal shock, the shear strength of the solder joint decreases substantially, by 49.2% after 72 h. The fracture mechanism changes from ductile fracture to mixed tough−brittle fracture and finally, to brittle fracture.