Comparative studies on thermal and laser sintering for highly conductive Cu films printable on plastic substrate

Compound-based Cu paste was synthesized to prepare electrically conductive films on plastic substrate. The Cu pastes screen-printed onto polyimide were annealed inside a furnace and also by an ultraviolet laser beam and the effects of annealing conditions on the microstructures and electrical properties were investigated. Both of thermal and laser processes were carried out under N ₂ gas flow, which was very effective in preventing oxidation. The minimum resistivity available with thermal sintering was 1.30 × 10 ^{- 5} Ω cm and a slightly higher resistivity was obtained by laser sintering. This value is several orders of magnitude lower than that reported for the copper nanoparticle paste thermally sintered under N ₂ atmosphere. The variation of microstructure and electrical property with the laser power was very similar to the temperature dependence of these factors in thermal sintering.