Electrically Conductive Thick Film Made from Silver Alkylcarbamates

A homogeneous electrically conductive silver paste without solid or particle phase was developed using silver alkylcarbamates [(CnH2n-1NHCOO)(2)Ag, n <= 4] as the precursor of the functional phase. The silver alkylcarbamates were light insensitive and had a low decomposition temperature (below 200 degrees C). The paste was a non-Newtonian fluid with viscosity significantly depending on the content of the thickening agent ethyl cellulose. Array patterns with a resolution of 20 mu m were obtained using this paste by a micropen direct-writing method. After the paste with about 48 wt.% silver methylcarbamate [(CH3NHCOO)(2)Ag] precursor was sintered at 180 degrees C for 15 min, an electrically conductive network consisting of more than 95 wt.% silver was formed, and was found to have a volume electrical resistivity on the order of 10(-5) Omega cm and a sheet electrical resistivity on the order of 10(-2)-10(-3) Omega/square. The cohesion strength within the sintered paste and the adhesion strength between the sintered paste layer and the alumina ceramic substrate were tested according to test method B of the American Society for Testing and Materials standard D3359-08. None of the sintered paste layer was detached under the test conditions, and the cohesion and adhesion strengths met the highest grade according to the standard.