Effect of inorganic binders on the properties of thick film copper conductor

Adhesion strength and solderability of a copper thick film on alumina substrate were studied. Films were prepared with three kinds of inorganic binders, i.e., glass frits, mixture of glass frits and metal oxides, and metal oxides. The effects of inorganic binders on the adhesion and solderability were examined by analyzing physical and chemical behavior of the inorganic binders in the copper thick film during firing. The films with an addition of glass frit or mixtures of glass frit and metal oxide did not provide good adhesion and solderability simultaneously. However, the copper thick film containing 10 wt.% bismuth oxide had excellent characteristics, i.e. high adhesion strength, good solderability, and low sheet resistivity