Tin/silver/copper alloy nanoparticle pastes for low temperature lead-free interconnect applications

Chemical reduction methods were used to synthesize tin/silver/copper (SnAgCu) alloy nanoparticles with various sizes. The thermal properties of the SnAgCu alloy nanoparticles were studied by differential scanning calorimetry. Both the particle size dependent melting temperature and latent heat of fusion have been observed. The as-synthesized SnAgCu alloy nanoparticles were dispersed into an acidic type flux to form the nano solder pastes. Their wetting properties on the cleaned copper surface were studied. It was found that the nanoparticle pastes completely melted and wetted on the copper surface and the tin and copper intermetallic compounds formed. These low melting point SnAgCu alloy nanoparticles could be used for low temperature lead-free interconnect applications.