Electromigration effect upon the Zn/Ni and Bi/Ni interfacial reactions

This study investigates the electromigration effect upon the Zn/Ni and Bi/Ni interfacial reactions by using reaction couple techniques. Three phases, β₁-NiZn, γ-Ni₅Zn₂₁, and δ-NiZn₈ formed in the Zn/Ni couples reacted at 150°C and 200°C for 4 h to 360 h, and the reaction layers grow thicker with longer reaction time. Passage of a 300 A/cm² current through the Zn/Ni couples has no significant effect upon the interfacial reaction. There is no noticeable difference in the phase formation and layer thickness of the two kinds of Zn/Ni couples with and without the passage of electric currents. Only NiBi₃ phase was found in the Bi/Ni couples reacted at 150, 170, 185 and 200°C. Passage of a 300 A/cm² electric current through the Bi/Ni couples did not change the phase formation, and growth rates of the NiBi₃ phase in the couples reacted at 185°C and 200°C were not affected by passage of electric currents either. However, growth rate of the NiBi₃ phase was enhanced in the Bi/Ni couples reacted at 150°C and 170°C with the passage of a 300 A/cm² electric current. A mathematical model was proposed to describe the electromigration effect upon the growth of the intermetallic compounds. Physical parameters in the models were determined by optimization based on experimental measurements, and the results indicate that the values of the apparent effective charge of Bi and Ni decreased sharply with increasing temperatures.