Electromigration behavior of Cu-core/Sn-shell solder joints

The electromigration behavior of a solder joint with Cu-core/Sn-shell structure under 1.3×104 A/cm2 was investigated in this work. As Cu has lower electrical resistivity than Sn, the Cu core was chosen primarily as the path for current flux. Compared with the traditional solder joint, this core/shell solder has two couples of cathode and anode due to the additional Cu core. It is found that most morphology changes appeared at the region where current crowding occurred according to finite element simulation. Under electron wind force, some Sn grain at the anodes rotated as a result of stress relaxation and the angle of the rotation increased with prolonging the stressing time. No obvious intermetallic compound growth was found.