Effect of electromigration on the tensile strength of Cu/Sn-9Zn/Cu solder interconnects

The effect of electromigration (EM) on the tensile strength of Cu/Sn-9Zn/Cu solder interconnects was investigated under a current density of 5×10³ A/cm² at 150 °C. After aging and EM, the thickness of interfacial IMCs increased. The IMC layer at the cathode side was thicker than that at the anode side for the samples after EM. Compared with the as-soldered interconnects, the tensile strength of those after both aging and EM significantly decreased. Solder joints undergoing EM deteriorated more severely and their strength decreased more than the aging cases. As for the as-soldered samples, fracture occurred at the IMC/solder interface, while with increasing aging time, the fracture position changed from at the interface to in the bulk solder. With increasing EM time, the tensile fracture tended to occur at the cathode interface, since voids formed at the cathode side after EM.