Deformation Fracture Characteristics of Microelectronic Sn-3.0Ag-0.5Cu-<I>x</I>Ni Solders

Abstract

The effect of Ni content on the microstructure, as well as the tensile and vibration fracture mechanisms of a potential lead-free solder, Sn-3.0Ag-0.5Cu-xNi (0.02, 0.07, 0.1, 0.2 and 0.3 mass%), are examined in this study. The results show that both Sn-Ni-Cu and Sn-Cu-Ni-Ag intermetallic compounds (IMC) increased with increasing the Ni content. The IMCs mostly formed in the eutectic zones and a few in proeutectic Sn-rich phases. Notably, the Ni content of the bar-like Sn-Ni-Cu compounds was higher than that of the particle-like Sn-Cu-Ni-Ag compounds. In addition, the tensile deformed resistance of Sn-3.0Ag-0.5Cu-xNi solders decreased when the Ni content was increased. Adding Ni obtained finer structures, however the hard massive Sn-Ni-Cu in the eutectic zone deteriorated the tensile deformation resistance. For the lower Ni content specimens, the 0.07Ni specimen not only possessed finer structures but a large number of compounds which congregated were able to increase the crack tortuosity, which in turn increased the crack propagation resistance and the vibration life.