An item is said to be hermetic when it is perfectly sealed and airtight and cannot be penetrated by any element (gas, fluid).
Ceramic-to-metal brazing, subject to a certain level of control, is a method for providing a hermetic seal between a metal component and a ceramic component.
Hermeticity is achieved by adding material which prevents leaking between the two components. This material must be able to withstand the pressure differential between the two environments, fluid/gas circulating.
The most reliable control procedure is the helium leak test. The part, as well as the detector, is placed in a vacuum. Helium is then applied to the part. In the presence of a leak, the gas flow is measured using the detector.
Applications include the aeronautical and spatial industry with sensors, hermetic feedthroughs for fire detectors, and satellite battery covers. In the medical industry, they are used to treat heart failure or to apply neurostimulation. Another major application is the manufacture of industrial and medical X-Ray tubes. Lastly, in the energy sector, they are used to manufacture ceramic feedthroughs or electrical connectors but also for off-shore applications.