Joining of Kovar to Alumina and to Low-Temperature Co-Fired Ceramics (LTCC)

摘要

For integration of ceramic sensor elements based on low-temperature co-fired ceramics (LTCC) into standardized steel housings it is necessary to compensate the mismatching thermal expansion behavior. Therefore balancing elements made of Kovar (Fe-29Ni-17Co) and alumina ceramic (Al_2O_3) can be used. However, these elements have to be joined hermetically to each other and to the LTCC sensors. In this study, brazing experiments were performed for combinations of Kovar/Al_2O_3 and Kovar/LTCC with Ag-Cu-Ti and Ag-Cu-In-Ti based commercial braze filler metals, Cusil-ABA and Incusil-ABA, respectively. For both active braze filler metals optimized processing parameters were investigated to realize hermetic Kovar/Al_2O_3 and Kovar/LTCC joints.