Enhancing the tensile properties of Sn-Zn-Ag lead-free solder alloy by loading MgO nanoparticles and irradiation

Abstract

Lead-free composite solders has attracted more attention as they are required in the microelectronics industry to assure good electrical connections and the best mechanical response between integrated circuit devices and the substrate. The mechanical mixing technique was used to prepare the plain (Sn-5.3 wt% Zn-1 wt% Ag, SZA531) and composite solder (SZA531/0.5 wt% MgO), while MgO nanoparticles were synthesized by sol-gel technique. The aim to investigate the effects of loading 0.5 wt% MgO NPs and $\gamma$ -irradiation doses (0–2.0 MGy) on the tensile properties of plain solder at different strain rates (ε^•). The microstructural properties revealed that MgO was pure, crystalline, and had a nanoparticle-like morphology with an average crystallite size of 9.61 nm. Plain and composite solders contained β-Sn, Zn, and Ag, as well as some intermetallic compounds, Ag₃Sn and AgZn. Loading MgO refined $\beta$ -Sn and Ag₃Sn, while AgZn particles were partially dissolved. The thermal analysis reported that the melting point slightly increased from 206.1°C with SZA531 to 208.7°C when loaded which confirms the good solderability of composite solder. The tensile properties revealed that ultimate tensile strength and the tensile toughness increased with increasing ε^•, dose of γ-rays, and MgO loading, while ductility decreased. The strain rate sensitivity index (m) decrease with increasing the dose and MgO loading because of the decrease in the resistance to necking. These results were interpreted based on Orowan strengthening and dislocation strengthening.