Revealing the Mechanical Properties and Fracture Mechanism of Ag Paste Sintered Solder by Two Different Preparation Methods

This paper studied the microstructure and mechanical properties of sintered Ag-Cu joints and semi-sintered Ag-Cu joints under tensile and shearing actions. By a comparative analysis of the differences in sintered Ag layer microstructure characteristics, crack propagation directions, and fracture surface characteristics, the differences in the fracture mechanisms of the two types of sintered joints under the influence of tensile and shearing forces were further explained. Research shows that the sintered Ag joints have higher tensile and shearing properties than the semi-sintered Ag joints, but the two show similar fracture modes under the action of tensile force. The same phenomenon also occurs in the fracture mechanism under the action of shearing force. The difference is that under the action of tensile stress, cracks in the joints initiate from the Ag-Cu interface and grow along the interface until fracture occurs, while under the action of shearing force, cracks in the joints still initiate from the Ag-Cu interface, but then turn, and the cracks grow along the silver layer towards another Ag-Cu interface, which is a composite fracture mode. Under the action of tensile stress, the adhesive force of the Ag-Cu interface is shown to be weaker than the cohesive force within the sintered Ag layer itself, and the sintered Ag layer shows better ductile deformation. Under the action of shearing force, the advantage of the cohesive force within the sintered Ag layer is weakened, and the sintered Ag layer begins to fracture. Since sintered Ag joints have a better Ag-Cu interface and lower porosity than semi-sintered Ag joints, the energy required for failure increases correspondingly, showing better mechanical properties.