The melting, microstructure, and hardness properties of the tin (Sn)-bismuth (Bi) solder alloy added with molybdenum (Mo) nanoparticles were investigated. The results showed that the Sn-Bi solder alloy with Mo nanoparticles fully melts at 148.00 °C, and the melting temperature was not drastically disordered by the Mo nanoparticles additions. The Mo has a high-melting point of 2623 °C, hence could not interfere with the solidification process of the molten Sn-Bi solder alloy. The microstructural morphology of the Sn-Bi added with Mo nanoparticles had much finer and compact lamellar structure compared to that of the unreinforced Sn-Bi solder alloy. Together with the dispersed Mo nanoparticles, there were Bi phases breaking out in the microstructure of the Mo-reinforced Sn-Bi solder alloy. Results from the hardness test showed a leap in the hardness value of 0.4 Hv, for the Mo containing Sn-Bi solder alloy. Presence of Mo nanoparticles and finer microstructure are believed to be the factors behind the increase. Reinforcing small quantity of Mo nanoparticles to the Sn-Bi solder alloy shows improvement to the microstructure and hardness as well as keeping the melting temperature below 150 °C.
