The influence of solder composition on the impact strength of lead-free solder BGA joints

Abstract

At the interface between Sn-based solders and substrates, intermetallic compounds (IMCs) form and grow during soldering operations and subsequent use. Such IMCs provide a metallurgical bond, and their interface microstructure has a critical effect on solder joint mechanical reliability. In the present study, the impact strength of BGA solder joints between (i) Cu substrates and Sn-Cu solders and (ii) Cu substrates and Sn-Cu-Ni solders has been evaluated using shear and tensile ball tests and Finite Element Modelling. In both tests, connections made using Sn-Cu-Ni solders show consistently better properties than those made using Sn-Cu solders, particularly at high displacement rates. Microstructural analysis and fractography are used to interpret the results and develop the FEM