Effect of stand-off height on the microstructure and fracture mode of Cu/Sn-9Zn/Cu solder joint under tensile test

Abstract

This study investigates the effect of the stand-off height (SOH) on the microstructure and tensile fracture mode of Cu/Sn9Zn/Cu solder joints. Solder joints with SOH of 100 mum, 50 mum and 20 mum are studied. It is found that as the SOH is reduced, Zn content has a rapid decrease in the solder bulk, while, the intermetallic compound (IMC) layer proportion increases. SOH of the solder joint also has an important effect on the tensile strength and tensile fracture mode. Tensile strength of solder joints decreases with lower SOH, which correlates with the change of microstructure and composition in solder joint. When the SOH is reduced, the fracture path of solder joint transfers from the bulk of the solder joint into the IMC/solder interface, and the fracture mode tends to transform from ductile fracture into brittle fracture.