Enhancing mechanical properties via adding Ni and Zn in Cu/Sn3.5Ag/Cu transient liquid phase bonding for advanced electronic packaging

Recently, the transient liquid phase (TLP) bonding process has become a promising method in advanced electronic packaging. Full intermetallic compounds joints provide good strength and reliable high-melting-point phase after bonding. However, Kirkendall voids and the preferred orientation of Cu 6 Sn 5 may deteriorate the reliability in conventional Cu/Sn/Cu bumps. To resolve these problems and further enhance the mechanical proprieties, Ni and Zn are used to modify the overall microstructures of the TLP bond. After the addition of Ni and Zn, the strength of Cu18Ni/Sn3.5Ag/Cu and Cu18Ni18Zn/Sn3.5Ag/Cu bump increased significantly, as compared to Cu/Sn3.5Ag/Cu. Both Cu18Ni/Sn3.5Ag/Cu and Cu18Ni18Zn/Sn3.5Ag/Cu bump demonstrated outstanding strength and toughness. Moreover, microstructure, grain, and mechanical analyses are employed to elucidate the mechanisms behind the strengthening effect of Ni and Zn in Cu18Ni/Sn3.5Ag/Cu and Cu18Ni18Zn/Sn3.5Ag/Cu bump.