Electromigration behavior in in-situ Cu6Sn5 reinforced eutectic SnAg composite solder joints

Due to the excellent resistance to thermal mechanical fatigue and creep resistance properties of in-situ Cu₆Sn₅ reinforced composite solder, it´s meaningful to further investigate the Electromigration (EM) behaviors of such novel composite solder. We used in-situ method to prepare Cu₆Sn₅ reinforced Sn-3.5Ag composite solders, the weight fraction of which was 1 vol.%, 5 vol.%, and 20 vol.%, respectively. A constant electric current was applied to a one-dimensional solder joint which ensures a uniform distribution of current density. For this study, a current density of 104 A/cm2 was applied to solder joints under 75°C. The evolution of interior microstructure due to current stressing effects was observed by using scanning electron microscopy (SEM). The results revealed that after current stressing for 96 and 192 h, no remarkable EM damages exhibited in solder matrix. Whereas, after current stressing for 384 h, 1 vol.% and 20 vol.% Cu₆Sn₅ reinforced composite solder joints have suffered different degrees of polarity effects.