The Use of Silver as an Alternative to Copper in the Fabrication of Reliable Thick‐film Hybrid Microcircuits Requiring High Conductivity Conductor Tracks

It is proposed that reliable multilevel thick‐film conductor interconnect, having high track conductivity, can be fabricated with conventional air‐firing thick‐film materials, by combining the high conductivity of a pure silver conductor with the solderability of a palladium‐silver conductor. Thick‐film conductor interconnect fabricated in this manner was shown to meet comfortably the stringent requirements of a 20 year service life. A development in the standard technology used to obtain high conductivity interconnect, nitrogen‐firing copper thick‐film materials was also evaluated. It was found that new lower porosity dielectrics may allow copper thick‐film conductor interconnect to be as reliable as the air‐firing alternatives. The activation energy for the process of silver migration through a thick‐film dielectric in a humid environment was found to be in the region of 0.6 eV. The accelerating influence of humidity was also measured.