Polarity effect of electromigration on intermetallic compound formation in a Cu/Sn–9Zn/Cu sandwich

This study investigated the polarity effect of electromigration (EM) on the interfacial intermetallic compounds (IMCs) (γ-Cu₅Zn₈, Cu₆Sn₅) formation at the anode and the cathode in a Cu/Sn-9Zn/Cu sandwich with a constant direct current density of 1.0 × 10³ A/cm² at 100 °C. The EM had different polarity effects on the nucleation and growth rates of the interfacial Cu₅Zn₈ IMC from those of Cu₆Sn₅ IMC. Upon current stressing, the growth rate of the Cu-Zn intermetallic compound (γ-Cu₅Zn₈) at the cathode interface was much faster than that at the anode. However, the nucleation and growth of the Cu₆Sn₅ IMC at the anode interface were enhanced, though retarded at the cathode, under the influence of electric current. The mechanism of EM-induced Cu₆Sn₅ IMC formation towards the anodic Cu is also discussed.