GLASS-CERAMIC INTERACTIONS AND THICK-FILM METALLIZATION OF ALUMINUM NITRIDE

A frit-bonded thick-film metallization for aluminum nitride (AIN) ceramic substrates has been developed. The glass system is thermodnamically stable with respect to AIN at the temperatures employed during thick-film processing. The model glass, a lithium borate, has comparable physical properties to that of the standard lead borosilicate glasses used in frit-bonded films designed for oxide ceramics. The wetting properties of the glass on AIN, in both air and nitrogen atmospheres, have been determined by use of a hot-stage microscope. The low-temperature oxidation of the AIN surface was found to be a significant factor in the glass spreading rate. The glass was formulated into a palladium-silver thick-film metallization and the performance of this material on three types of AIN substrate was determined. Examination of the film morphology and the fracture surfaces was carried out using scanning electron microscopy.