Effect of miniaturization on the microstructure and mechanical property of solder joints

In present paper, the effect of miniaturization on the microstructure and mechanical property of solder joints is investigated. With the miniaturization of solder joints, the thickness of IMC decreases, while, the IMC proportion to the solder joint increases; meanwhile, the concentrations of base materials in the bulk also increase with the reducing stand-off height (SOH). Due to the interaction of interfacial reactions in the Cu/Sn/Ni solder joints, the IMC layers with incompact connection are formed at Ni side, and tensile test results show that the incompact IMC are the weakest part in the solder joints. When the SOH reduces to 10 mum, the solder bulk contains only one grain in height in the Cu/Sn/Cu and Cu/Sn/Ni solder joints, leading to dramatic changes in fracture mode and the ultimate tensile strength (UTS). When the SOH is lowered to 10 mum, the UTS of Cu/Sn/Ni solder joints decreases dramatically to be lower than that of Cu/Sn/Cu solder joints.