Influence of small Sb nanoparticles additions on the microstructure, hardness and tensile properties of Sn-9Zn binary eutectic solder alloy

In the present study, different weight percentages of Sb nanoparticles (100-120 nm) ranging from 0 to 1.5 wt% were added to Sn-9Zn eutectic solder alloy to investigate the effect of third element addition on the microstructure, mechanical properties as well as thermal behavior of the newly developed composite solder alloys. The results indicate that the Sb nano-particle based inter-metallic compounds (IMC) were found uniformly distributed, refined the microstructure and formed IMC particles in the eutectic solder alloy. After the addition of nano Sb particles in Sn-9Zn solder, fine α-Zn phase and ε-Sb3Zn4IMC particles were clearly observed in the β-Sn matrix. The ε-Sb3Zn4IMC particles were uniformly distributed in the b-Sn phase, which resulted in an increase in the tensile strength due to the second phase dispersion strengthening mechanism. However, in the doped Sn-9Zn/1.5Sb alloys, α-Zn phases were broken enormously, depleted and round shaped compared to the normal rod shaped α-Zn phase microstructure in plain Sn-9Zn solder. In comparison, the ε-Sb3Zn4IMC particle in the doped Sn-9Zn/1.0Sb alloy were star shaped. The average tensile strength and micro-hardness of the Sb doped Sn-9Zn solder alloys were consistently higher than the plain un-doped Sn-9Zn solder. The tensile strength and the microhardness increased with increasing Sb nano-particle content, up to 1.0 wt% of Sb content, and then decreased beyond that threshold value. Consequently the percentage (%) elongation of the Sb nanoparticle doped Sn-9Zn solder decreased with increasing Sb nano-particle content, up to 1.0 wt% of Sb content, and then increased beyond that threshold value.