Enhancing sustainability in soldering: effects of recycled welding slag and rice husk ash on microstructural, thermal, and mechanical properties of Sn–Cu composite solders

This study investigated the microstructural, thermal and mechanical properties of a series of plain and composite lead-free solder systems (Sn-0.7Cu - xWS; Sn-0.7Cu - xRHA; x = 0, 6, and 12 wt%), as well as sustainable reinforcing solutions. The microstructural characteristics of the present alloys were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), electron probe microanalysis (EPMA), and X-ray diffraction (XRD). Moreover, thermal properties of the present composites were investigated utilizing differential scanning calorimetry (DSC). Images obtained from the SEM demonstrate that welding slag (WS) and rice husk ash (RHA) nanoparticles are uniformly distributed within the composite material. The findings showed that the incorporation of WS and RHA nanoparticles markedly altered the microstructure of these alloys and improved their thermal and mechanical properties. It was observed that the mechanical properties of the Sn-0.7Cu-xRHA composites were superior to those of the Sn-0.7Cu-xWS composites. Additionally, compared to other composites, the Sn-0.7Cu-6RHA composites exhibited significantly higher levels of tensile strength and hardness, while the Sn-0.7Cu-12RHA composites revealed superior thermal characteristics. It also focused on the environmental benefits and potential challenges of using recycled agricultural waste and welding slag in Sn-0.7Cu solders from a life cycle assessment perspective.