Characterization of DuPont 1900 series resistors applied to DuPont 5704 dielectric on alumina substrates

Existing thick film hybrid microcircuit (HMC) production utilizing integral thick film resistors requires that thick film resistors be deposited via screen printing directly on the base alumina substrate material. This requirement, when coupled with circuits of moderate to high density and associated layer buildup prior to resistor application, results in printing on surfaces with significant topography surrounding the resistor, compared to required as-printed resistor thicknesses. Due to the technological requirement to print resistors after most other thick film processing has been completed, resistor printing is seldom performed on a flat surface. The surface topography of the substrate surrounding the resistor area prohibits the printing process from maintaining a relatively uniform printed resistor thickness across the substrate. Although resistors are, in most cases, adjusted to final electrical values by physically modifying the length-to-width ratio through laser trimming, the resistors must be within certain resistance ranges. This variation in thickness translates into potential scrap product through extreme variation in as-fired resistor electrical values and/or product incapable of being laser trimmed due to excessive resistor thickness. The development of a thick film resistor application process compatible with existing conductor and dielectric materials and enabling more planarization of the print surface was needed to enhance production yields on products of moderate complexity