Effects of Nd on microstructure and properties of Sn-Zn-Ga Lead-free solder

The effects of alloying element Ga and rare earth element Nd on the wettability,microstructure and mechanical properties of the Sn-Zn solder were investigated. The results indicated that the wetting properties of the solder were improved with appropriate addition of Nd. When the Nd content was 0.1wt%,the wetting properties reached the best. It was also found that the wettability was improved when the temperature rose properly. With the Nd content increasing,the amount of black needle-like Zn-rich phases gradually decreased and the matrix microstructure of the solder was refined. When the Nd content reached 0.1wt%,the grains in the solder was the most uniform and smallest. Meanwhile,the mechanical properties of the joints made with solders containing Nd were also improved, and the shear strength of the resultant joints with solder containing 0.1wt% Nd reached the maximum. Therefore,the optimal amount of Nd in the Sn9Zn0.5Ga solder was around 0.1wt%.