Abstract: Disclosed is a method of fabricating bi-level circuits which include metallization of via holes (14 and 15) in insulating subustrates (10). A thick film metal paste (13) is prepared which according to one embodiment comprises copper, glass frit and an organic vehicle including a low molecular weight ethyl cellulose binder and solvents of butyl carbitol acetate and alpha terpineol. The paste is deposited onto the substrate and through the holes. The structure is baked with the printed surface (12) down in order to establish a solvent concentration gradient in the paste which results in solid material accumulating away from the printed surface to form the contact pad (16). The material is then fired to establish the desired conductivity.

Abstract: Disclosed is a method and resulting product whereby thick film conductors which require a reducing firing atmosphere may be included in circuits with thick film resistors requiring an oxidizing firing atmosphere. In accordance with one embodiment, a fritless paste including copper is deposited onto a substrate in a desired conductor pattern and fired to establish adhesion. The copper oxide in the pattern is then reduced to copper metal at a high temperature. This is followed by oxidation of the copper to produce a copper oxide of lower density than the oxide formed after the initial firing. The resistor material is then deposited and fired in an oxidizing atmosphere. The low density copper oxide may then be reduced at a low temperature so that resistor properties are not adversely affected.