Novel interface regulation of Sn1.0Ag0.5Cu composite solders reinforced with modified ZrO2: Microstructure and mechanical properties

• The concept of Sn/NiO/ZrO 2 interface system design is first proposed. • Surface modification of ZrO 2 is conducted with ball milling−pyrolysis methods. • The refinement mechanism of microstructure is systematically investigated. • A micro-mechanical lock and non-micropored clean interface is formed. • 5.The strength and ductility are simultaneously improved with NiO/ZrO 2 addition. With the trends of miniaturization and high density of electronic packaging, there has been an urgent demand to open up lead-free solders with high strength and ductility. In this study, a ZrO 2 -reinforced Sn1.0Ag0.5Cu composite solder was designed. First, surface modification on ZrO 2 was conducted with ball milling-pyrolysis method. Subsequently, NiO modified ZrO 2 (NiO/ZrO 2 ) was added to the solder matrix with ultrasonic stirring. The morphology and interface of NiO/ZrO 2 were discussed. Moreover, the microstructure, interface and mechanical properties of the composite solders were systematically studied. The results showed that NiO nanoparticles were evenly adhered to the ZrO 2 surface, and the interface relationship between them was semi-coherent and coherent. Further, an appropriate addition of NiO/ZrO 2 could refine the microstructure of composite solders. The refinement mechanism was systematically investigated. Besides, a micro-mechanical lock and non-micropored clean interface was formed between NiO/ZrO 2 and the solder matrix. The Sn/NiO/ZrO 2 interface system based on mutual solid solution was ingeniously designed. The ultimate tensile strength and elongation were increased synergistically, and the fracture mechanism transformed from a ductile−brittle mixed fracture mode to a ductile fracture mode. Therefore, a lead-free solder with high strength and ductility was obtained.