Melting and solidification properties of the nanoparticles of Sn3.0Ag0.5Cu lead-free solder alloy

The Sn3.0Ag0.5Cu (wt.%) lead-free solder alloy is considered to be one of the most promising candidates to replace the traditionally used Sn-Pb solder. However, this alloy composition has some weaknesses, mainly as a result of its higher melting temperature compared to the eutectic Sn-Pb solder. In this paper, lead-free solder alloy nanoparticles of Sn3.0Ag0.5Cu were synthesized by chemical reduction with NaBH4 as reducing agent. The experimental results indicated that the major particle size of Sn3.0Ag0.5Cu nanoparticles was smaller than 100 nm. The melting and solidification properties of the Sn3.0Ag0.5Cu nanoparticles were studied by differential scanning calorimetry at different scanning rates. It was evidenced by the differential scanning calorimetry curves that the melting temperature of Sn3.0Ag0.5Cu nanoparticles was lower than that of the bulk alloy. In addition, the undercooling of the Sn3.0Ag0.5Cu nanoparticles was in the range of 82.0-88.5 °C at different cooling rates, which was much larger than that of the Sn3.0Ag0.5Cu micro-sized particles, showing stronger cooling rate dependence.