Development of Glass-Free Metal Electrically Conductive Thick Films

Air-firable glass-free metal electrically conductive thick film pastes of different compositions were developed by using a titanium alloy component, and tin and zinc metal substitutes for glass frit used in traditional thick film pastes. The effect of different components on the electrical resistivity and bonding between the thick film and the alumina substrate was investigated. Thick films with low electrical resistivity and good bonding to the alumina substrate were obtained by using silver, zinc, tin, and TiCu alloy powders in the pastes. The addition of zinc at a small proportion (<0.5 wt.%) to a thick film paste enhanced the adhesion between the thick film and the alumina substrate with negligible increase in the electrical resistivity. The use of titanium alloy powder instead of pure titanium powder is preferred. Better composition distribution, and consequently, better wetting and bonding are expected by using active metal particles of a smaller size.