Reliability Behavior of A Resin-Free Nanosilver Paste at Ultra-Low Temperature of 180°C

Abstract

In this paper, excellent thermo-mechanical reliability of resin-free silver sintering for large-area (20 × 20 mm²) bonding was successfully achieved by using a trimodal particle system composed of nano-, submicron-, and micron-sized Ag particles. After 1000 cycles of the thermal shock (TS) test, the transient thermal impedance (Z_th) increase of the proposed resin-free silver paste sintered at 180°C under 2 MPa and 5 MPa is only 5.8% and 6.1%, respectively. Due to the avoidance of resin degradation, the obtained resin-free silver paste as-sintered under 5 MPa exhibt outstanding shear strength (>12.5 MPa) even after 1000 cycles TS test. The obtained cross-sectional microstructure can confirms the excellent thermo-mechanical reliability of the sintered resin-free silver paste, which exhibits a denser and more homogeneous bonding layer with a porosity as low as 12.5%. Furthermore, distinct indications of plastic flow can be observed on the fracture surfaces of corresponding joints before and after aging, which further confirm the superiority of proposed resin-free sintering method. The development of novel resin-free silver paste successfully promotes the thermo-mechanical reliability of silicon carbide (SiC) power devices at a low processing temperature of 180°C, and greatly benefits the practical application of SiC power devices.