Sealing of glass with titanium by glass pressing at the softening point

Hermetic and mechanically strong glass-to-metal seals are required for many applications in technological fields such as aerospace engineering or medical engineering. While traditional glass-to-metal bonding technologies require melting of the glass, modern technologies such as anodic bonding use glass in its solid state. In this publication, a novel glass-to-metal bonding method with process temperatures around the softening point of the glass material is investigated. A glass window (silica based crown glass B270) in a titanium (grade 5) housing is manufactured by applying compressive force to the glass in a controlled low pressure argon atmosphere. Adherence of the glass-to-metal interface is determined with a universal testing machine. Hermeticity is measured directly with either pressure gain test or helium leak test. Experiments were performed in a full factorial design with 3 different process temperatures, 3 different process forces and 3 different methods for preparing the titanium surface. The results indicate that the bonding method is capable of producing hermetic seals with leak rates below 10−8 mbar l/s. Roughening of the metal surface generally improves both hermeticity and interface strength. Bonding strength can be further improved by increasing either processes temperature or, especially for rough surfaces, process force. For improving hermeticity either processes temperature or, especially for smooth surfaces, process force must be increased. The results indicate that successful bonding of glass and titanium with the new bonding method is influenced by the effects of mechanical interlocking and chemical reactions at the material interface.