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

Abstract

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 ZrO2-reinforced Sn1.0Ag0.5Cu composite solder was designed. First, surface modification on ZrO2 was conducted with ball milling-pyrolysis method. Subsequently, NiO modified ZrO2 (NiO/ZrO2) was added to the solder matrix with ultrasonic stirring. The morphology and interface of NiO/ZrO2 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 ZrO2 surface, and the interface relationship between them was semi-coherent and coherent. Further, an appropriate addition of NiO/ZrO2 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/ZrO2 and the solder matrix. The Sn/NiO/ZrO2 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.