Temperature Dependent Physical Properties of Sintered Silver Layers for Power Electronics

Low-temperature silver sintering is a lead-free alternative interconnection technology for power modules. In addition to high electrical and thermal conductivity, silver with its moderate homologous temperature in comparison to conventional solder alloys is a promising material for applications with elevated operation temperature (above 130°C). Therefore, investigations of the material behavior of the sintered Ag layer at various temperatures and stress conditions are essential for reliable model-based lifetime predictions. This work focuses on characterization of mechanical and electrical properties of sintered Ag coupons in relationship with their preparation and testing conditions. Simultaneous thermal analysis and residual carbon analysis are executed for the selected Ag-pastes. Dog-bone shaped specimens of Ag-paste were prepared using different sintering temperature (230°C or 300°C), pressure (pressureless or 70MPa), and time (10min, 30min, 60min) after drying at 130°C for an hour under nitrogen flow. For the defined sample series, the thickness of the sintered Ag-layer and the density are quantified using microscopic techniques. Electrical resistivity at room and elevated temperature is measured using the Van-der-Pauw Method. The tensile strength is obtained for 25°C,130°C, and 200°C. Fracture surfaces of fresh and thermal treated (at 250°C) samples are analyzed by scanning electron microscopy.