Effect of Ag Content on Mechanical Properties of Lead-Free Sn-Ag-Cu-Ni-Ge Alloy

Abstract

The tensile properties of Sn-x(x=1, 2, 3)Ag-0.5Cu-0.05Ni-0.005Ge (mass%) alloys were investigated. In addition, the ball shear force was investigated with solder balls and two types electrodes, Cu and electroless Ni/Au plated Cu, to examine joint reliability under heat exposure conditions. Tensile strength of the alloy decreases with decreasing the Ag content. On the contrary, elongation increases with decreasing the Ag content. When the Ag content reduces, primary β-Sn phases are coarsened and eutectic microstructures diminish. The decrease of the eutectic microstructures causes a reduction of the tensile strength. In as-soldered joints with Sn-Ag-Cu-Ni-Ge solder balls and Cu electrodes, the ball shear force increases with increasing the Ag content. However, the ball shear force decreases with increasing heat exposure time. After heat exposure treatment at 423 K for 500 h, the ball shear force is relatively stable at lower values regardless of the Ag content. In the joints with electroless Ni/Au plated Cu electrodes, the ball shear force slightly increases with increasing heat exposure time. Even after heat exposure treatment at 423 K for 500 h, hierarchy of the ball shear force is maintained. The ball shear force becomes high with increasing the Ag content.