Effects of Electromigration on Interfacial Reactions in the Ni/Sn-Zn/Cu Solder Interconnect

Electromigration in the Ni/Sn-Zn/Cu solder interconnect was studied with an average current density of 3.51 × 104 A/cm2 for 168.5 h at 150°C. When the electrons flowed from the Ni side to the Cu side, uniform layers of Ni5Zn21 and Cu5Zn8 were formed at the Ni/Sn-Zn and Cu/Sn-Zn interfaces. However, upon reversing the current direction, where electron flow was from the Cu side to the Ni side, a thicker Cu6Sn5 phase replaced the Ni5Zn21 phase at the Ni/Sn-Zn interface, whereas at the Cu/Sn-Zn interface, a thicker β-CuZn phase replaced the Cu5Zn8 phase.