ALBERT

Description: This paper discusses the status of thick conductive films formed by firing in air. The metals under study include nickel, chromium, aluminum and copper. The properties of the films are presented for firing temperatures ranging from 580 to 850 degrees C. Compatibility with various dielectrics and glasses have been studied. Multilayer wiring seems promising. Potential uses on porcelain enamelled steel, window glass and alumina substrates seem feasible.Initial studies have been made of compatibility with thick film ruthenium-based resistors. Some preliminary information on termination resistance and other properties observed in such combinations is presented.Possible applications in gas discharge displays for cathodes and conductor runs are discussed. Potential uses may include economical ground planes, solar cell electrodes, varistor and thermistor terminations, and resistance thermometers.

Description: Porcelain enameled steels have had a long history of industrial, structural and related applications. Recent interest in such materials has centered on electrical uses as a substrate for hybrid circuits, additive printed wiring, and packaging. A study of some of the critical properties of available enameled steels was undertaken.Five types of enameled steel substrates from three manufacturers were tested. The electrical properties studied included dielectric constant, dissipation factor, voltage breakdown, surface and bulk insulation resistance. The effect of humidity on the insulation resistance of the enamel coatings themselves was compared. The influence of the thermal conductivity of the substrates was also examined.The properties of a thick film resistor system was determined on the various enamel steel substrates. The properties tested included resistivity and TCR firing sensitivity.The effect of the type of substrate on the properties of a selection of thick film conductors was determined. Conductivity and gold and aluminum wire bond strength were compared on the various substrates.The dielectric properties of a multilayer/crossover dielectric thick film material were compared among 96% alumina, soda-lime glass and the various enameled steel substrates.Many individual differences between the enameled steel substrates were found. However, all of the substrates could be utilized to produce satisfactory thick film circuits when the proper choice of thick film materials was made.Continuing changes, improvements and additional sources of supply are expected to overcome some of the present shortcomings. These should enhance the use of such substrates for large area uses and lower cost applications.