Ceramic substrates play an important role in thick film hybrid microelectronic circuits. Existing substrates such as alumina and beryllia do not meet satisfactorily the desired requirements. The newly developed aluminum nitride (AIN) substrate shows a great deal of promise and potentially embraces the best qualities of alumina and beryllia.

The objective of this dissertation is to study the electrical properties, thick film interaction, and environmental effects on AIN substrates, and also to examine the performance of this material for high power - high frequency hybrid thick film applications. In particular, wideband dielectric constant measurements of A1N and other ceramic substrates are performed, oxidization and humidity effects on surface properties of AIN are addressed, and short and long term aging effects on several circuit parameters are studied.

To evaluate the performance of AIN in high power and high frequency applications, two circuits; an impulse generator and a power converter, are realized, tested and compared with those on alumina substrates. The thick film circuits realized on AIN perform considerably better than those on alumina.