Effect of Aging Conditions on Impact Strength of Sn-3.5 Based Solder Joint

In general, lead-free solders possess more brittle mechanical properties compared with Sn-Pb eutectic solder, and the thick intermetallic layer at the interface between the solder and substrate is sensitive to stress and provides sites of initiation and paths of propagation for cracks. Therefore, it is important to study the relationship between the interfacial reaction and the joint strength by using a solder bump. In this study, in order to evaluate the joint reliability for Sn-3.5Ag based solder with a Ni-P plating, a new ball impact test were applied. And the effect of aging conditions on impact strength of the solder joint was investigated. As a result, it was clear that the fracture at the interface, where intermetallic compounds was formed, was occurred. In the case of Sn-3.5Ag-Co solder, the impact strength gradually decreased with the increase of the aging time. The ball impact test was suitable for the characterization of the strength of intermetallic compound at the interface and the evaluation of the reliability for drop impact.