Preparation of antioxidative nano copper pastes for printed electronics application

Copper nanoparticles are alternative for silver and gold nanoparticles which are currently used in inkjet printing of conductive patterns because of the low price and high electrical conductivity. However, the serious impediment to using copper nanoparticles for conductive inks is their spontaneous oxidation. In the paper, the well-dispersed antioxidative copper pastes were prepared by dispersing the nanoparticles in an ethanol solution of lactic acid, and then deposited on glass slides. The resistivity of conductive copper films was 1.4×10^-5 Ω·cm after annealing at 200 °C for 30 min. It was experimentally proved that lactic acid could react with the copper oxides surrounding Cu to form copper carboxylate, which was then reduced to Cu after annealing at 200 °C under nitrogen atmosphere. Furthermore, the copper film after annealing at 200 °C for 30 min under nitrogen atmosphere showed antioxidative characteristic.