Comparison of mechanical properties of lead-free microscale solder joints under tensile and shear loading

In this study, adopting a dynamic mechanical analyzer (DMA Q800, TA-Instruments), the mechanical properties and fracture behaviors of “copper wire/Sn-3.0Ag-0.5Cu solder/copper wire” sandwich structured microscale solder joints with a constant diameter of 400 μm and a height of 125-325 μm were investigated under two different quasi-static loading modes (i.e., tensile loading and shear loading) at 100 °C. The experimental results show that the tensile and shear strength of all microscale Sn-3.0Ag-0.5Cu solder joints decreased with the increasing of joint height. Under same loading rate of 1N/min at 100°C, the shear strength and shear fracture strain of Sn-3.0Ag-0.5Cu solder joints are much lower than tensile strength and tensile fracture strain, this means the shear stress is more severe for solder joint interconnections in electronic packaging. In addition, the fracture position and fracture mechanism of microscale Sn-3.0Ag-0.5Cu solder joints are significantly different under different loading modes.