Design of Ni-rGO reinforced Sn2.5Ag0.7Cu0.1Ce composite solder based on micro-alloying and composite principles: Microstructure and properties

Based on the principles of micro-alloying and composite, the graphene reinforced Sn2.5Ag0.7Cu0.1Ce composite solder was designed. Ni nanoparticle-modified reduced graphene oxide (Ni-rGO) was prepared by thermal decomposition method, and the powder-melting method was proposed for the first time to prepare Ni-rGO reinforced Sn2.5Ag0.7Cu0.1Ce composite solder. The microstructure, wettability, electrical resistivity, and mechanical properties of the composite solder were systematically studied. Results indicated that the Ni nanoparticles uniformly adhered to the rGO with a size of 26.3 nm. The effective incorporation of Ni-rGO into the solder matrix was achieved. The result broke the technical difficulty that graphene cannot be effectively added to low melting point metals. With the addition of Ni-rGO, the grain size gradually decreased, and the eutectic structures increased. Deep etching results revealed that columnar β-Sn was stacked from layered β-Sn, the addition of 0.05 wt% Ni-rGO led to an increase in sheet-like Ag3Sn within the eutectics. Additionally, Ni-rGO was found at the grain boundaries of composite solder, serving as nucleation sites for Ag3Sn and Cu6Sn5. At an addition of 0.05 wt%, the tensile strength reaches a maximum of 58.1 MPa, with elongation of 33.8%, surpassing the strength of commercial Sn3.0Ag0.5Cu solder. Therefore, the high-strength and tough composite solder was obtained. This study offered a new approach for the development of low-melting-point composite materials.