As highlighted in the article titled “Types of glass-to-metal hermetic seals” on Wikiwand, presents various methods crucial to diverse industrial applications. These seals ensure airtight integrity, offering distinct advantages based on their design and composition.
A pivotal classification in hermetic sealing is the “matched seal,” where glass and metal with identical coefficients of thermal expansion are bonded, relying on the connection between glass and the metal’s oxide. This type, while relatively less robust, finds utility in low-intensity scenarios like light bulb bases.
In contrast, “compression seals” address the challenge of varying coefficients of thermal expansion. In these seals, the metal compresses around the cooled solidified glass, making them capable of withstanding high pressure. This attribute positions compression seals as key players across a spectrum of industrial applications.
Glass-to-metal seals outperform epoxy counterparts in elevated temperature environments, with compression seals operable up to 250 °C and matched seals enduring temperatures as high as 450 °C. Nevertheless, material selection remains limited due to thermal expansion considerations. The sealing process takes place at approximately 1000 °C in an inert or reducing atmosphere to preserve component appearance.
Diversifying the field, ceramic-to-metal hermetic seals introduce co-fired ceramic alternatives to glass. These ceramic seals excel in demanding, high-stress environments, showcasing superior hermetic performance. The choice between glass and ceramic hinges on factors such as application, weight, thermal requirements, and material specifications.
Beyond metal, glass taper joints also feature in hermetic sealing, secured by PTFE sealing rings, encapsulated o-rings, or PTFE sleeves. Additional options like PTFE tape, PTFE resin string, and wax are emerging, offering airtight solutions without the risk of contamination caused by dissolvable substances like grease.
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