Effects of temperature, time, atmosphere and sealing geometry on defects occurred in borosilicate glass-kovar alloy seal

Abstract

Glass-metal sealing has wide applications, especially in chemical, optical, electronic, and energy industries. Sealing of borosilicate glass to Kovar alloy using an oxide interlayer was investigated considering the effects of sealing process variables i.e. temperature, time, and atmosphere on macroscopic soundness of seal specimens. The bubble formation tendency was decreased significantly by limiting the sealing temperature and time. In tubular butt joints, the soundness of the specimens showed an inverse correlation with the thickness of the metal tube and a direct correlation with the thickness of the glass tube. Some fracture tests were performed using tubular seals cooled with common rates (25–60 °C/min). The failures occurred inside the glass, often taking the form of a circle situated parallel to the seal interface. Structural studies based on SEM as well as EDS analysis showed that compositional segregation happened in the glass beside the interface and second phases, essentially made up of fayalite, nucleated on the interface.