Dispersion and incorporation of TiO₂ and SiC nano-particles in SAC alloy: SIMS and DFT study

Ceramic nano-particles are frequently used as reinforcements in SAC alloys to improve their mechanical properties; however, the nano-particle dispersion and incorporation mechanisms are not well known. Composite SAC alloys were prepared from Sn99Ag0.3Cu0.7 alloy with TiO2 and SiC nano-particles in 0.5wt%. Solder joints were prepared by SMT technology between two Cu plates with 150 mu m thickness. SIMS was used to determine the nano-particle distribution along the solder joints' vertical cross-section. DFT calculations were done to investigate the possible interaction between the different nano-particles and the Sn atoms. SIMS results showed that the distribution of the nano-particles is inhomogeneous in the solder bulk; furthermore, the density characteristics highly depend on the size and shape of the nano-particles. DFT calculations proved that the non-soluble TiO2 and SiC could form chemical bonds with the Sn during the soldering, which might further explain their positive effect on the physical properties of composite SAC alloys.