Ag-Pd thick film conductor for AlN ceramics

An Ag-Pd thick-film conductor for aluminum nitride (AlN) ceramics was developed. The conductor showed adhesion strength and reliability almost comparable to those of commercial conductors for alumina ceramics. The influence of physical properties of the lead oxide glass frit on conductor performance was studied, and the most suitable glass was selected for the frit material. The softening point of frit glass has the largest effect on conductor performance; this temperature should be approximately 500°C. If the softening point was either too high or too low, compared to the sintering temperature of the conducting metals, poor adhesion strength resulted. Use of glass with too high a softening point caused poor wettability but resistance to erosion by Pb-Sn solder, while it resulted in good wettability but poor erosion resistance when the softening point was too low. Additionally, Cr-, Ti, and Zr-oxides were identified as wettability-promoting agents. The molten glass did not penetrate into the AlN ceramics; rather, it remained on the surface. This behavior differed from that in the case of alumina ceramics, for which the molten glass penetrated along the grain boundaries