Study on Performance Optimization of Nanometer Copper Paste

In this paper, in order to improve the sintering property of copper paste as interconnection material, the influence of solvent content and solvent type in copper paste on sintering strength was studied, so as to select the solvent type and solvent content with the best sintering effect. A certain amount of solvents such as ethylene glycol, diethylene glycol, glycerol and terpineol were added into the copper nanoparticles with an average particle size of 100nm-400nm. After mixing and vacuum homogenization, the nano-copper paste with solid content of 85% was obtained. Four kinds of copper pastes were sintered in 260°C sintering temperature, 2MPa sintering pressure, 5% hydrogen and 95% argon mixture for 30min to obtain interconnection joints. Furthermore, the shear strength of the sintered joints was tested. The shear strength of the copper paste prepared with ethylene glycol as solvent is 50.1 MPa, while the shear strength of the copper paste prepared with the other three solvents is less than 50 MPa. Then, ethylene glycol was added into copper nanoparticles as solvent to prepare copper paste with solid content of 55%, 70% and 85%, respectively. Pure copper nanoparticles were used as control group. The above four groups of samples were sintered in 260 $^{\circ} \mathrm{C}$ sintering temperature, 2MPa sintering pressure, 5% hydrogen and 95% argon mixture for 30min to obtain the interconnection joint. Finally, the shear strength of four kinds of interconnects was tested, and the shear strength of the interconnects sintered with 85% solid content copper paste was the highest, reaching 50.1MPa. In conclusion, the best sintering performance can be obtained by adding ethylene glycol as solvent into copper powder to form a paste with solid content of 85%, which can reach 50.1MPa. The surface morphology of the failure surfaces of the interconnection joints was observed by scanning electron microscopy.