Creep of sintered porous micron-silver: nanoindentation experiment and theoretical analysis

Nano/micron-silver paste has been applied in high-temperature packaging of chips as a potential lead-free solder. At specific sintering temperature, the particle size in the silver paste affects the sintering quality, which plays an important role in the mechanical properties of the sintered nano/micron-silver materials. In the current study, the macro- and micromechanical properties of the sintered specimens by three micron-silver paste with different average particle sizes were studied. It was found that the tensile and shear strength of the micron-silver joint sintering at 300 °C for 50 min decreased gradually with the increase in average particle size, while the compressive strength and fracture strain increased with the increase in average particle size. Scanning electron microscope analysis showed that smaller silver particle size leads to better sintered effect. At the microlevel, the creep properties of specimens sintered with three kinds of micron-silver paste were studied by nanoindentation experiment. Based on the entropy theory and continuous damage mechanics, a micro-creep model incorporating damage was developed. The proposed model could accurately predict the micro-creep compared with the nanoindentation experimental results.