A Green Approach to Synthesis of Nanoparticles of Sn-3.0Ag-0.5Cu Lead-Free Solder Alloy

Sn-3.0Ag-0.5Cu nanoparticles can provide a potential solution to the high soldering temperature problem of lead-free solder alloy because the nanosize effect can depress the melting temperature. In this paper, a green approach to the synthesis of Sn-3.0Ag-0.5Cu nanoparticles by chemical reduction at room temperature is reported. A safe organic solvent, ethanol, was used to prevent the formation of tin oxide during synthesis without the help of capping agents and N-2 purging. Vigorous stirring instead of the use of capping agents was applied to the reaction mixture to reduce agglomeration of particles during the reaction time. Owing to not having capping agents on the nanoparticles and no detection of tin oxide, the subsequent steps for eliminating them are not necessary. Ag3Sn revealed by the XRD pattern and the electron diffraction pattern confirmed the successful alloying of Sn and Ag during synthesis. The TEM image showed that the nanoparticles were composed of a crystalline core embedded by an amorphous matrix. The average particle diameter was 53.3 nm with a standard deviation of 8.9 nm. An onset melting temperature of 187.3 degrees C and a peak melting temperature of 212.7 degrees C were achieved. This simple, safe and environmentally friendly method can reduce the production cost of nanosolder and may be applicable to the synthesis of other metal nanoparticles. [doi:10.2320/matertrans.M2012112]