Microstructures and Fusing Electrical Current of Microelectronic Sn-9Zn-(0.25RE) Solders

Abstract

Both Sn-9Zn and Sn-9Zn-0.25RE solders were used to investigate the effect of RE (rare earth elements) addition on their solidification structures and electrical current properties. The results indicate that adding RE not only made the needle-like Zn-rich phases finer, but also caused the Sn-Zn eutectic phases to decrease. RE elements existed mostly in the β-Sn phases and could not form intermetallic compounds. After direct current (DC) testing and electrical conductivity (%IACS) testing, the fusing electrical direct current density of the 0.25RE solder was higher than the Sn-9Zn solder, however, the electrical conductivity had an inverse tendency. Also, the RE element addition restrained electromigration and enhanced diffusion to occur easily in the Sn-9Zn solder.