Effect of SiC Nanoparticle Additions on Microstructure and Microhardness of Sn-Ag-Cu Solder Alloy

Abstract

In this work, lead-free composite solders were produced by mechanically mixing nominal 20 nm moissanite SiC particles with Sn-3.8Ag-0.7Cu solder paste. The effects of the amount of SiC addition on the melting behavior, microstructure, and microhardness of as-solidified composite solders were systematically investigated. In comparison with solder without the addition of SiC nanoparticles, the subgrain of β-Sn, the intermetallic compounds (IMCs) average grain size and distance decreased significantly in the composite solder matrix. This was possibly ascribed to the strong adsorption effect and high surface free energy of the SiC nanoparticles. Our results showed that 0.05 wt.% addition of SiC nanoparticles could improve the microhardness by 44% compared with the noncomposite and that the average grain size and distance changed from 0.5 μm to 0.2 μm and from 0.6 μm to 0.32 μm, respectively. The refined IMCs, acting as a strengthening phase in the solder matrix, enhanced the microhardness of the composite solders, in good agreement with the prediction of the classic theory of dispersion strengthening.