Preparation and Brazing of Nickel-plated ZrO₂ Reinforced Low Silver SnAgCu Composite Filler Metal by Pyrolysis Reduction Method

Ni-plated ZrO2 reinforced alloy was prepared by thermal decomposition and reduction method, and Ni-plated ZrO2 reinforced Sn1.0Ag0.5Cu composite filler metal was prepared by powder metallurgy method. The surface metallization of ZrO2 nanoparticles and its effect on the microstructure, properties and brazing joints of Sn1.0Ag0.5Cu composite filler metal were studied. The results show that the particle size and agglomeration of ZrO2 decrease after mechanical pretreatment. The Ni-plated ZrO2 enhanced phase is successfully prepared by thermal decomposition and reduction method. The Ni particles are uniformly attached to the surface of ZrO2 with a spacing of 8-11 nm, and the interface between ZrO2((1) over bar 02) and Ni(11 (1) over bar) shows a semi-coherent relationship. Resistivity of Ni/ZrO2-Sn1.0Ag0.5Cu composites is not significantly affected by adding a proper amount of nickel-plated ZrO2, but the wettability and tensile strength are improved. The tensile strength and shear strength of brazed joint of Ni/ZrO2-Sn1.0Ag0.5Cu composite filler metal reach the peak when the adding amount of ZrO2 reinforcing phase is 0.7wt%, which are increased by 43.3% and 45%, respectively, compared with those of the matrix material. With the addition of Ni/ZrO2 reinforcing phase, the fracture position of the brazing joint of the composite filler metal moves from the interfacial IMC layer to the side near the brazing seam in the transition zone, and the fracture mechanism gradually changes from the mixed tough-brittle fracture to the ductile fracture dominated by dimple.