Effect of Cu6Sn5 nanoparticle on thermal behavior, mechanical properties and interfacial reaction of Sn3.0Ag0.5Cu solder alloys

This work studied the additions of nano-Cu6Sn5 intermetallic particles into a lead-free Sn3.0Ag0.5Cu (SAC305) solder alloy with content ranging from 0.05 to 2 wt%. The thermal behavior, mechanical properties and interfacial reaction of Cu6Sn5 nanoparticle containing SAC305 solder alloys were evaluated. The Cu6Sn5 nanoparticles successfully synthesized by using chemical precipitation method were re-melted in SAC305 solder and the X-ray diffraction analysis exhibited more obvious Cu6Sn5 diffraction peak with nanoparticles addition. The thermal behavior was revealed that the Cu6Sn5 nanoparticles addition has not visibly changed the solidus temperature but significantly reduced the onset temperature of composite solder alloy during cooling, which resulted in a higher undercooling. In addition, a slight decline of melting point was found and it dropped to 222.7 °C with 0.1 wt% Cu6Sn5 nanoparticles addition. The nanoindentation results showed that nanoparticles addition could distinctly improve the mechanical performances of composite solder alloy, including hardness and elastic modulus, which were optimal for SAC305–0.1Cu6Sn5 solder alloy. Furthermore, nanoparticles addition could effectively suppressed the growth of interfacial IMCs layers and IMCs grains formed between Cu substrate and composite solders during aging. The inhibiting effect was the most obvious when the content of Cu6Sn5 nanoparticles was 0.1 wt% and the restraining mechanism was also explained.