Fracture Mechanism of Sintered Silver Film Revealed by in-situ SEM Uniaxial Tensile Loading

This paper investigates the mechanism of brittle-ductile deformation and fracture for sintered silver (s-Ag) film by means of in-situ scanning electron microscopy (SEM) uniaxial tensile loading at room temperature (RT) and 300 °C. The s-Ag film specimen originating from nano-Ag paste, including 18 nm diameter Ag particles, is sintered at 300 °C under 60 MPa pressure. A pre-crack and slope surface are fabricated in the s-Ag specimen with a focused ion beam (FIB) for conducting in-situ SEM observation during applied tensile loading. A local in-situ SEM observation area is set to 8 × 5 μm ² around the specimen’s pre-crack tip. At RT, the s-Ag specimen shows a brittle fracture, whereas at 300 °C, the s-Ag specimen shows a ductile fracture with microstructural changes involving pore growth and grain boundary degradation. However, fracture surface morphology provides opposite impression, where the fracture surface at 300 °C looks like an intergranular fracture. Finite element analyses (FEAs) and electron backscatter diffraction (EBSD) suggest that the stress in the plastic region can accelerate the microstructure changes. The Ag atomic gliding speed at the grain boundary determines brittle-ductile deformation and fracture characteristics in s-Ag film. The reason why fracture surface impression differs from actual deformation is discussed using detailed snapshots during the fracture of s-Ag film at 300 °C.