Effect of extreme thermal shocking on the reliability of Sn50Pb49Sb1/Cu solder joint

The cosmic extreme temperature is deemed to be an enormous problem for the electronic devices and solder joints of on-orbit satellite. In this paper, an extreme thermal shocking test from 77 to 423 K was carried out to partly simulate the space temperature environment. The extreme thermal shocking effect on the microstructure, shear force and fracture behavior of Sn₅₀Pb₄₉Sb₁/Cu solder joint was investigated to try to clarify the reliability evolution of solder joint. It was found that after the thermal shocking, Cu₆Sn₅ layer thickened significantly with the formation of micro-cracks. The columnar shape of Cu₆Sn₅ layer in as-soldered joint was changed to plane shape due to its excessive growth. The Cu₃Sn layer formed and coarsened during the thermal shocking process, but no defects were observed. Owing to the growing interfacial layers and prolonging cracks, the shear force of solder joint was reduced with the increasing shock cycles. The fracture of solder joint was also transformed from solder-controlled mode to a mixed mode of solder and intermetallic compound, giving a different fracture location and lower ductility.