Microwave related properties of fritless Ag thick film metallisation and effect of long-term air exposure

Abstract

Investigations on the laboratory- formulated fritless silver thick film metallisation for use at microwave frequencies is reported here. The reflectometer method has been used to measure the microwave (8-18 GHz) transmittance and reflectance of these films deposited by screen printing onto 96% alumina substrates. The effects of firing temperature, composition and long term air exposure on the microwave properties and d.c. resistivity are also reported. In the X-band frequency, composition and firing temperature-dependent transmittance and reflectance of metallisation are obtained whereas at Ku-band, the above properties are to a large extent independent of these factors. The microwave conductivity as well as the d.c. resistivity are found to increase on aging. The results indicate the utility of these fritless Ag thick film metallisation up to 18 GHz. Firing temperature-independent properties provide substantial energy saving and increased furnace life as the films fired at 800°C compare well with those fired at 900°C especially at higher frequencies.