Effect of precompression on the thermal cycling stability of glass-to-metal seals

Abstract

Hermeticity is a critical performance attribute of glass-to-metal (GTM) compressive seals, whose long-term reliability is often compromised by crack initiation and propagation. These failures primarily originate from the nonuniform stress distribution on the GTM seal surface and the inherent material properties, such as the weak mechanical strength, both of which exacerbate structural vulnerabilities over prolonged service periods. In this study, precompression was introduced during the heat treatment stage as a means to increase the thermal cycling stability of GTM seals. The results indicated a proportional relationship between the precompression stress and the thermal cycling stability of GTM seals. Porosity analysis was conducted on three different samples, which demonstrated that precompression improved the distribution of bubbles within the GTM seals, as evidenced by a reduction in the porosity and a decrease in the bubble size. In addition, the mechanical properties of the sealing glass were enhanced, thereby reducing the probability of leakage. Furthermore, nanoindentation measurements and finite element analysis of the surface stress distribution revealed that precompression led to an increase in residual compressive stress. The alleviation of stress concentration regions significantly lowered the probability of crack initiation during thermal cycling, thus establishing a more uniform stress distribution and enhancing the thermal stability of GTM seals.