Synthesis of metal nanoparticles with specific properties is a newly established research area attracting a great deal of attention. Several methods have been put forward for synthesis of these materials, namely chemical vapor condensation, arc discharge, hydrogen plasma-metal reaction, and laser pyrolysis in the vapor phase, microemulsion, hydrothermal, sol-gel, sonochemical. Nanoscale lead-free solders (i.e., Sn-xAg [x=0, 20, 40, 60, 80, 100(wt%)], Sn-3.0Ag-0.5Cu, Sn-3.5Ag-0.5Cu, Sn-3.5Ag-xZn (x=0.5 to 3.5wt%) and Sn-0.7Cu) have been investigated. For Sn-3.5Ag and Sn-3.5Ag-0.5Cu nanoparticles, the melting temperature with average size of 30nm was 210°C and 201°C, much lower than that of bulk alloy. Also, Sn-Ag-Cu nanopowders showed good wettability with contact angles less than 30°. The peak melting temperatures of the 21nm, 18nm and 14nm Sn-0.7Cu nanoparticles were 212.9°C,207.9°C and 205.2°C, respectively. In this paper, the fundamentals of synthesis of nanolead-free solder materials including their characterization and their use in microelectronic packaging are reviewed.

nanolead-free solders,alloy, melting temperature, wettability, mechanical properties, microstructure.