Tensile strength and interfacial reaction of Cu-cored SAC305 solder joint

In this study, Cu-cored ball with the diameter of 350µm and 550µm were applied to connect the Cu wire with the diameter of 400µm and 600µm, and the gap was then filled with the SAC305 solder. As a comparison, the SAC305 solder joints were also prepared. In addition, a thermal aging experiment at 150°C was carried out, and then the tensile strength and solder/Cu interfaces before and after the experiment were studied. The result shows that the tensile strength of 400µm diameter joints soldered by Cu-cored and SAC305 solder is higher than that of the 600µm diameter joints, which are, in order, 66.16MPa, 62.12MPa, 59.47MPa, 52.90.16MPa. For the joints with the same geometry scaling factor d/t (d is the diameter of the joint and t is the thickness of the joint), the small-sized ones can provide a better strength. After a 24h thermal aging treatment, the strength of all the joints declined sharply, as the ageing time prolong to 48h or more, descending of tensile strength developed slowly. The interfacial IMC thickens markedly after high-temperature ageing and in turn makes a negative impact on the strength.