Influence of nano-metric Al₂O₃ particles addition on thermal behavior, microstructural and tensile characteristics of hypoeutectic Sn-5.0Zn-0.3Cu Pb-free solder alloy

Sn-5.0Zn-0.3 wt% Cu (SZC-503) plain solder and Sn-5.0Zn-0.3Cu-0.5 wt% Al₂O₃ (SZC-Al₂O₃) composite solder have been investigated. The differential scanning calorimetery (DSC) measurements revealed that both alloys have two thermal peaks. The melting and liquids temperature of the first peak of both solders were less than 1.0 °C. However, the melting and liquids temperatures of second peak for composite solder increased by 3.02 and 3.37 °C, respectively than those of plain solder alloy. Moreover, the undercooling range (UCR) reduced after addition of nano-metric Al₂O₃ particles due to its high melting temperature and sacrifices them as additional nucleation seeds to initiate the solidification process. The microstructural characteristic was studied using X-ray diffraction (XRD), scanning electronic microscope (SEM), and energy dispersive X-ray spectroscopy (EDS). The refinement of β-Sn grains of SZC-Al₂O₃ composite alloy can be attributed to the pinning effect of Al₂O₃ nanoparticles on grain boundaries. In addition, a limited growth of IMC correlated to the adsorption theory of nano-metric Al₂O₃ particles of surface-active materials. The uniformed distribution of refined β-Sn grain and IMC in SZC-Al₂O₃ enhanced the yield stress (YS) by ~ 56% and ultimate tensile strength (UTS) by ~ 76.2% but reduced the ductility by ~ 32%. Moreover, the experimental value of the yield stress of composite solder is very close to that calculated by simple simulation program which included the different strengthens mechanism of composite alloys.