Effective charge number of Cu in Cu-Sn compound

As current-stressing a Cu/Sn joint interface, the Cu atoms in the interfacial cathode Cu-Sn compound would experience the direct electromigration force and chemical potential force simultaneously, which have never been decoupled. In this work, a triple-junction Cu-Sn-Cu joint was designed and current-stressed to separate the above electromigration and chemical forces imposed on the Cu atoms in the Cu-Sn compound. In addition, by obtaining the individual value of the electromigration Cu flux in the cathode Cu ₆Sn₅ compound layer, the effective charge number (Z*) of Cu atoms in the Cu₆Sn₅ compound can be determined to be 35.6.