Abstract: A thick film is formed initially as a paste and made up of such oxidizable conductor ingredients as copper which is then mixed with glass frit and next printed on a non-conductive inert substrate by silk screening. The silk screen printed thick film with vehicle is then dried, and a coating of boron in suitable paste or paint form having been mixed with a thixotropic organic vehicle is covered over the entirety of the substrate and silk screen printed thick film. The resulting product after a second air drying is then fired to bond the glass frit-copper as a thick film onto the substrate, with the copper particles being sintered throughout into a thick film. Superposed boron, where contiguous with the copper printing, is fused as a protective layer over the copper allowing the sintering of the copper and bonding with the substrate to occur without oxidation of the copper.

Abstract: A paste for forming a thick film conductor of a base metal on a non-conductive substrate comprises a base metal powder (particularly nickel) which ordinarily would oxidize when fired in air, boron powder and a vehicle. In one embodiment, the paste may also contain glass frit. By proper selection of the composition, in particular the amounts of boron and glass frit, a base metal conductor can be formed which strongly adheres to the substrate and has excellent conductive properties. Ranges of compositions are disclosed within which the pastes can be fired in air and produce conductive thick films and outside which conductive properties are inferior and/or the bond strength is unsatisfactory.