Microstructures and properties of copper thick-films fired under nitrogen atmospheres doped with gaseous oxidizers

The authors studied the effects on copper thick-film systems of several gaseous oxidizers (O₂, CO₂, N₂O, H₂O) injected into nitrogen furnace atmospheres, either throughout the whole furnace or only into its burnout zone. SEM (scanning electron microscopy) examinations of the copper film microstructures correlated with properties such as adhesion, solderability, and resistivity allows the establishment of ideal firing atmosphere conditions for copper thick-film manufacturing: namely, it is necessary to restrict the atmosphere doping to the burnout zone; and oxygen and water vapor are the more effective gaseous dopants. Specific equipment has been developed to control injection of these dopants into the furnace atmosphere