Effect of Particle Shapes on Thermal Shock Reliability of Sintered Ag Joints under Low-Temperature Pressureless Sintering

The long-term reliability of the die-attach module under low-temperature pressureless sintering with two different shapes of Ag particle, flake particles paste, and spherical particles paste was investigated by means of thermal shock tests. The utilized particle shape determines the microstructure of sintered Ag, which leads to an important effect on sintered Ag joints’ microstructural evolution and mechanical properties after the thermal reliability test. The Ag flake particles provide thinner necking, resulting in the delamination at the interface after 1000 thermal shock cycles, while the microstructure has no obvious change for spherical particles. The difference in mechanical properties is discussed based on the shear strength results, which revealed that the die-attach module sintered with spherical particles paste has a much greater bonding strength above 20 MPa than that of sintering with flake particles paste after thermal shock tests. For further study, the fracture surface of bonding joints sintered with different shapes of Ag particles was also observed. The SEM observation revealed that many sharp protrusions indicated ductile deformation was observed in the sintered Ag spherical structure, while the sharp protrusions translated smooth flat area represented brittle fracture after thermal shock 1000 cycles.