Effect of inorganic binders on the properties of silver thick films

The technology for realizing conductive thick films from metal powders is of considerable importance in the manufacture of various electronic devices, such as hybrid integrated circuits, multilayer ceramic capacitors, three-dimensional circuits for mobile communication, etc. Silver thick films have been extensively used to provide electrical contacts in silicon solar cells, hybrid circuits, and other devices, as they have the lowest resistivity as well as the lowest cost among the noble metals. Metal powders for thick-film pastes are normally obtained through chemical precipitation from an aqueous or organic solution of their corresponding salts. This method is able to provide the desired particle shape and size and also offers a low preparation cost. In this paper, we have reported the effect of inorganic binders on the properties of silver thick films. The thick-film pastes were formulated from specially treated silver powders and using the three different types of inorganic binders such as glass frit, metal oxides, and a mixture of both. The effect of these inorganic binders on the surface structure, adhesion with alumina, solderability, and electrical properties was determined by analyzing the physical and chemical behavior of the inorganic binders in the silver thick films during firing. The films with an addition of glass frit and mixtures of glass frit and metal oxide did not provide good adhesion and solderability simultaneously. However, the silver thick films containing 10 wt% bismuth oxides exhibited excellent characteristics, i.e. high adhesion strength, good solderability, and low sheet resistivity. As expected, the adhesion strength decreased with decrease in the binder content. (C) 2004 Kluwer Academic Publishers.