Conductivity of silver and copper film printed by particle-free reactive inks

The particle-free silver and copper conductive ink were used as the reactive inks, respectively. For the Ag ink, during the printing process, a layer of ink drops would be printed. After that, the printed liquid drops were sintered in an oven to obtain a compact silver layer. Repeat the “printing and sintering” process to form a silver film by a layer-by-layer way. The film is consisted of irregular nanoparticles. Since the ink droplets were heated after each layer printing, the ink droplets near the substrate would be heated for the longest time in total. Small silver grains merged and grew into bigger ones, and the gaps between nanoparticles would be shrunk to make the grains connect well. For the Cu ink, the film was obtained by baking the ink drop on a glass substrate. The annealing temperature and time was higher and longer than that of silver ink. The resistivity of silver-film decreased significantly with the increased of printed layers. The three-dimensional conductive network increased significantly with contact area increased of the ink droplets. The film increased in the thickness direction with the increased of printed layers. On the basis of these data, we founded that the lowest resistivity of Ag film was ~4.8μO·cm, about three times to the bulk silver. For Cu film, the lowest resistivity was 6.5μO·cm, around four times of the bulk copper. The effects of annealing temperature and time was also studied on the change of resistivity for both silver and copper film.