Abstract
The electronics industry has become interested in a thick film materials system based on copper for both technical and economic reasons. Copper conductors offer excellent conductivity, solderability, and solder leach resistance as well as lower intrinsic metal cost and price stability.Significant adoption of copper in thick film applications requires a complete system of materials for the designer and manufacturer to choose from and sufficient processing information to assist the industry to get started. Industry has begun the adoption of copper in selected applications. Design of new applications and experience in processing will move this technology forward in the industry.Du Pont has developed a copper materials system which includes copper conductor compositions, low K dielectric and compatible resistor compositions. The compositions are screen printed, dried in an air atmosphere at 120℃ for ten minutes and fired in a nitrogen atmosphere to a peak temperature of 900℃. All materials in the copper system may be processed in commercially available atmosphere conveyor furnaces using commercial nitrogen.The copper compositions provide high adhesion conductors with resistivity values in the range of one to two milliohms per square. They can be used to make multilayer interconnect structures, microwave circuits, and as a replacement for Mo-Mn metallizing. In addition, copper may be used as the conductor on porcelain-enamelled steel substrates. The dielectric composition provides a dense film with a dielectric constant of about eight which can be used With copper to make multilayer interconnect structures. The resistor compositions produce resistors with temperature coefficient of resistance (TCR) less than 150 ppm per ℃ and are useful for resistor networks and hybrid microcircuits.