The environmental concerns over the toxicity of lead- bearing electronics are forcing electronic industry to use leadfree solders. Among various lead-free candidate material, Sn-3.0Ag-0.5Cu (SAC305) appeared as a strong candidate. However, due to the coarse microstructure and formation of hard and brittle Inter-Metallic Compounds (IMCs), a number ofreliability problems are hindering its use in high-temperature microelectronics. To improve the properties, a number of researchers used the Rare-Earth (RE) materials to refine the microstructure of lead-free solders due to their suiface-active properties. The focus of this research is to investigate the effect of lanthanum-doping and thermal aging on the growth of the IMCs of SAC305 solder alloy in terms of size and dispersion. It was observed that addition of lanthanum refined the microstructure to a great extent by reducing the IMCs particle size.