In situ study of electrochemical migration of Sn3Ag0.5Cu solder reinforced by Cu₆Sn₅ nanoparticles

The increasing packaging density and power density have led to a drastic increase in the electric field strength between solder joints, and the accelerated movement of ions significantly rises the potential for failure of solder joints caused by electrochemical migration (ECM). To improve the anti-electrochemical migration ability of Sn3Ag0.5Cu solder (SAC305), we doped Cu₆Sn₅ nanoparticles (NPs) into SAC305 solder paste and studied its mechanism for inhibiting ECM. In this experiment, Cu₆Sn₅ NPs were prepared by ultrasound-assisted chemical reduction, and composite solder pastes were prepared by mechanically mixing Cu₆Sn₅ NPs with SAC305. In situ observation of the ECM between electrodes was carried out under different operating conditions. The addition of Cu₆Sn₅ NPs within 0.6 wt% could effectively inhibit the ECM by prolonging the incubation period. However, when the amount of Cu₆Sn₅ NPs exceeded 0.6 wt%, the catalytic effect of Cu₆Sn₅ NPs on the hydrogen evolution reaction would create vigorous convection within the droplet, which accelerated the failure by ECM. Apart from that, it was found that the addition of Cu₆Sn₅ NPs could increase the threshold for instantaneous failure of solder joints under high voltage.