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.