Low temperature sintering-bonding through in-situ formation of Ag nanoparticles using micro-scaled Ag₂O composite paste

In order to reduce the cost of using Ag nanoparticle paste as bonding materials in electronic packaging, micro-scaled Ag₂O powders were mixed with triethylene glycol (TEG) to form a paste to replace the Ag particle paste. The reaction mechanism of in-situ formation of Ag nanoparticles, the sintering characteristics of micro-Ag₂O paste at low temperature, and the bonding of Ag-coated Cu bulks using this paste were investigated. The results reveal that the Ag₂O particles in the paste were more easily transformed into Ag nanoparticles than micro-Ag₂O itself, and with increasing the sintering temperature, more Ag nanoparticles formed and grew larger by sintering, accompanied with some gaseous products which could escape easily. The effect of sintering-bonding time on the strength of joints fabricated at 250°C under a pressure of 2 MPa was analyzed. The average shear strength of the joints increased with sintering-bonding time and reached about 24 MPa when the sintering-bonding time was 5 min. And the microstructure of the fractured surface and the cross-section of typical joints made at 250°C under 2 MPa were also examined.