The influence of phase inhomogeneity on the current density and temperature gradient in Cu/Sn58Bi/Cu solder joint

The failure of electronic products and devices is mainly caused by the failure of solder joints. For the size of solder joint has been reduced to tens of micrometers or even several micrometers, there are obvious phenomena of phase inhomogeneity in the solder matrix. In this study, compared to a homogeneous finite element (FE) model, an inhomogeneous FE model of the line-type Cu/Sn-Bi/Cu solder joint containing the microstructure of Sn58Bi solder matrix was established, and the electromigration (EM) and thermomigration (TM) under current stressing and temperature difference were analyzed. Results show that, different with the uniform or regular distribution in the homogeneous FE model, the distribution of current density and temperature gradient is complex and irregular in the inhomogeneous FE model, and the difference of phase property between the Sn-rich phase and Bi-rich phase increases the maximum current density and temperature gradient in the solder joint, proving that the influence of phase inhomogeneity on the reliability of EM and TM of solder joint should not be neglected.