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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.

The increasing demand for high-power SiC semiconductors necessitate the development of a die attachment material that combines high-temperature resistance, reliability, and cost-effectiveness. In this study, a novel micro-sized composite, Ag-10Al paste, containing 10 wt% Al particles, was designed. A remarkable phenomenon, the ejection of ultrafine Ag nanoparticles from micron-sized Ag flakes, was observed for the first time. The phenomenon was utilized for the in-situ surface modification of Al. Subsequently, the microstructure and mechanical properties of the sintered Ag-10Al/direct bonded copper (DBC) joints were studied. Results indicated that the Ag-10Al composite exhibited superior microstructure stability compared to sintered Ag. The Ag/Al interface was systematically analyzed, revealing a unique Ag/nano Ag2O/Al2O3 amorphous/Al structure. This structure was formed through the Ag nanoparticle jetting effect of Ag flakes, achieving effective bonding between nano Ag2O and Al2O3 amorphous phases through mutual dissolution at the atomic level. Moreover, the sintered Ag-10Al joint demonstrated enhanced mechanical performance stability over the sintered Ag joint. After 1000 h aging at 300 ℃, the shear strength of the sintered Ag-10Al joint reached 34.1 MPa, meeting the requirements for power semiconductor packaging. In conclusion, the Ag-10Al composite paste was thoughtfully designed, excelling in both performance and cost-effectiveness.