Reliability evaluation of Au-20Sn flip chip solder bump fabricated by sequential electroplating method with Sn and Au

The formation of Au-20 wt.%Sn flip chip solder bumps using sequential electroplating method with Sn and Au was investigated. We obtained eutectic Au-20Sn solder bumps with a diameter of 100 μm on the patterned Si wafer. After reflowing and aging at 150 °C for up to 1000 h, we investigated the interfacial reaction between the Au-20Sn solder and Ni under bump metallization (UBM). The Au-Ni-Sn, ternary, intermetallic compound (IMC) layer was formed, and the resettlement of δ-phase was confirmed during aging. The shear force was also measured to evaluate the effect of the interfacial reactions on the mechanical reliability as a function of aging time. The shear force was stable and the fracture occurred on the Ti/Cu metallization layer independent of the aging time. The results from this study confirm the mechanical robustness of the Au-20Sn/Ni flip chip solder joint.