Copper nanoparticles with a mean diameter of 20 nm were used to prepare electrical conductive films at low temperature. After dispersal in an organic solvent, the copper nanoparticle pastes were coated onto a glass substrate, which was then annealed under various conditions to investigate the effects of various atmospheric conditions, such as air, nitrogen gas or hydrogen gas, as well as different annealing temperatures. Two-step annealing, which first involves oxidation in air followed by reduction, is effective in the preparation of high electrical conductive copper nanoparticle films. The copper nanoparticle films that were calcined in air for 1 h and then hydrogen gas for 1 h at a low temperature of 200 C showed a low resistivity of 2 x 10(-5) Omega, cm. (C) 2010 Elsevier B.V. All rights reserved.