T. Oyama, A. Demmons, Morgan Advanced Ceramic / WESGO Metals, Hayward, CA; H. Mizuhara, Mizuhara Consulting Services, Hayward, CA
Alumina material is routinely brazed to Kovar® for hermetic applications. In most applications, alumina is metallized with a Mo-Mn process and a conventional brazing filler metal, e.g. BAg8, is used to join alumina to Kovar®. In the present investigation, active brazing process was used to directly braze un-metallized alumina to Kovar®. Two active brazing filler metals, based on AgCu, were utilized in this investigation ;AgCu+1.8%Ti and AgCu+4.5%Ti. Effects of process parameters on achieving consistent hermetic joints were investigated, including preparation of alumina, heat-treatment of Kovar®, titanium content, brazing cycle, as well as fixture design. Hermeticity of the joints was measured by He leak detector, and microstructure at the joints were observed by both optical and scanning electron microscopy. It was demonstrated that the active brazing process can be used for forming consistent hermetic joint between alumina to Kovar® .
Summary: Alumina material is routinely brazed to KovarŪ for hermetic applications.