Abnormal accumulation and rotation of Sn in Cu-cored Sn solder joints under current stressing

The electromigration behavior of Cu-cored Sn solder joints under a current density of 1.3 × 104 A cm−2 was investigated in this work. Finite element simulation was performed to obtain the distribution of the current density in the solder joint. The Cu core was chosen primarily as the path for current flux, as it has a lower resistivity than Sn. It is found that most morphology changes appeared at the regions where current crowding occurred, demonstrating the consistency of the experimental and simulation results. Taking the special structure into consideration, the Cu core contributed additional electrodes to the solder joint at the interfaces, resulting in abnormal accumulation and rotation of Sn at both the cathode and the anode. The IMC growth was quite slow in the Cu-cored solder joint.