Effect of ZnO nanoparticles addition on thermal, microstructure and tensile properties of Sn–3.5 Ag–0.5 Cu (SAC355) solder alloy

Abstract

Regarding to the development of Sn–Ag–Cu (SAC) lead-free solders for advance electronic components, the effect of 0.5 wt% nano-sized ZnO particles on the thermal, microstructure and tensile properties of Sn–3.5 wt% Ag–0.5 wt% Cu (SAC355) lead-free solder alloy is investigated. The results showed that addition of 0.5 wt% nano-sized ZnO particles into the conventional lead-free SAC355 solder caused a slight increase of its liquidus temperature by about 1.1 K. Metallographic observations of SAC355–0.5 wt% ZnO (composite solder) revealed an obvious refinement in the microstructure compared with the SAC355 (non-composite) solder. Consequently, addition of nano sized-ZnO particles could improve the stress–strain characteristics proof stress (σy0.2) and ultimate strength (σUTS). This was rendered to suppressing effect of ZnO on the coarsening of the intemetallic compounds (IMCs) Ag3Sn and Cu6Sn5 during the solidification process in the composite solder and subsequently dispersion strengthening is considered to be the dominating mechanism. This will allow the use of SAC355 composite lead-free solder alloy, to be consistent with the conditions of usage for conventional SAC solder alloys and to overcome the serious problem of the excessive growth of IMCs and the formation of microvoids in the SAC lead-free solder alloys.