An aqueous developable photoimageable silver conductor composition for high density electronic packaging

Abstract

In our preliminary work, we have formulated aqueous developable photoimageable thick film conductor pastes, consisting of ‘ inhouse processed’ submicron sized silver powders (functional material), micron sized lead borosilicate glass frits (permanent binder), epoxy acrylate resin with pendant –COOH group (base photoimageable polymer/temporary binder/organic vehicle) and 2,2′-dimethoxy-2-phenylacetophenone (photoinitiator). The conductor pastes thus formulated were manually screen printed on the alumina substrates, dried, exposed to the ultra-violet light through the desired test patterns, developed in a 1% aqueous sodium carbonate solution, and subjected to a standard one-hour thick film firing cycle. Solid content of the polymer appears to influence the paste performance. Prima facie observations indicate that the paste with the organic:inorganic ratio of 28:72 (corresponding to solid content of 89.9% of the polymer system) exhibits better electrical conductivity, relatively smooth surface finish and line/space resolution of 100 μm with ±5 μm accuracy. Investigations related to the effect of glass content on the properties of photoimageable conductor paste are also furnished in this communication.