EFFECT OF NANO-PARTICLE ON THE PROPERTIES OF SN-3AG-0.5CU SOLDER

摘要

Sn-Ag-Cu (SAC) solder system is popular in lead-free solders for electronics industry. However, the mechanical properties are sometimes quite seriously affected by the formation of large intermetallic compounds (IMC) of Ag_3Sn and Cu_6Sn_5. In order to solve this problem many researches have been performed extensively. Among them, a new category of lead-free solders is nanocomposite solder which contains nanoparticles in the solder matrix. In this study effect of nano-particle such as graphene nanoplatelets (GNPs) on a Sn-3Ag-0.5Cu (SAC 305) solder was investigated. The nano particles can act as a seed of nuclei during solidification of solder, which can reduce grain size, Ag_3Sn and Cu_6Sn_5 size of solder. Microstructure, wettability, and tensile properties of Sn-3.0Ag-0.5Cu (SAC 305) were studied. Intermetallic compounds (IMCs) were identified by a scanning electron microscope (SEM) and EPMA (electron probe micro-analyzer), and the solderability in terms of the spreading and wetting properties were evaluated on Cu substrates. These properties were compared to the monolithic SAC305 solder alloy. The experimental results show that the composite solder showed significantly improved spreading ratio around 80% compared to 70% of monolithic SAC305 solder alloy up to an optimum amount of GNPs. Tensile test results of the composite solder show that the ultimate tensile (UTS) strength exhibits higher and the optimum elongation is increased up to more than 10% compared to monolithic SAC alloy. The increase in strength can be ascribed due to the finer Ag_3Sn IMCs and the grain size of the composite solder compared to the monolithic SAC305 solder alloy.