Shear performance of BGA structure Cu/Sn-3.0Ag-0.5Cu/Cu solder joints after deep cryogenic treatment with different time

In this study, the ball grid array (BGA) structure microscale lead-free Cu/Sn-3.0Ag-0.5Cu/Cu (Cu/SAC305/Cu) joints with different heights (i.e., 100 and 200 μm) were used to investigate the shear deformation and fracture behavior after soaking treatment with liquid nitrogen for different time. The experimental results indicated that the ultimate strength of the joint under shear loading generally decreases slightly with the increase in time of liquid nitrogen soaking, while it increases obviously with the decrease in joint height. Moreover, the fracture locations of all tested solder joints are inside the solder matrix. At the same time, it can be deduced from the stress- strain curve and fracture morphology that the fracture behavior remains ductile.