Microstructure evolution and microimpact performance of Sn–Ag–Cu solder joints under thermal cycle test

The microstructure and microimpact performance of Sn1Ag0.1Cu0.02Ni0.05In (SAC101NiIn)/AuNi/Cu solder ball joints were investigated after a thermal cycle test (TCT). The joints show complete bulk fracture behavior before TCT. Moreover, TCT facilitated interfacial fracture behavior with lower fracture energy. The intermetallic compounds (IMCs) formed in the solder joints before and after TCT were investigated. TCT induces a variety of structural variations in the solder joints, including slipping bands, whisker formation, the squeezing of the IMC layer, the formation of cavities, the rotation and pop-up of grain, and the deformation and rotation of the entire joint. The variations in fracture behavior induced by TCT are correlated with the structural variations in the solder joints.