Enhanced high-temperature service reliability of sinter-bonded joints with micro-nano hybrid Ag paste

There are inevitable cracking defects in pressureless bonded joints with single nanoparticle system silver (Ag) pastes, which could potentially compromise the long-term service reliability of the bonded joints. To address this issue, a novel hybrid Ag paste suitable for pressureless sintering was developed by introducing micron Ag flakes into the modified Ag nanoparticles. The effects of process parameters, such as the mass ratio of Ag nanoparticles to micron-sized Ag flakes in the paste and the sintering time, on the electrical performance of the sintered films and the bonding performance of the joints were investigated. The mechanism of sintering reliability enhancement of micro-nano hybrid Ag paste was also investigated. After a long time of high-temperature aging, micro-nano hybrid Ag paste joints with optimized micro/nano ratio exhibit reduced surface defects (with porosity of 22.19 % for hybrid Ag paste joints while 28.67 % for nano-Ag paste joints), which contributes to the enhanced mechanical stability compared to nano-Ag paste bonded joints (with shear strength of 45.78 MPa for hybrid Ag paste joints while 33.38 MPa for nano-Ag paste joints). The obtained hybrid Ag paste with high mechanical service reliability and superior repeatability would find a broad application prospect in the field of power device packaging.