Compression seals employ a different coefficient of thermal expansion between glass, housing and pins. The hermetic seal between glass and metal is established because of the material compression after cooling down. Housing materials with a high CTE such as stainless steel or titanium are therefore suited for compression seals. Depending on design, a compression seal can withstand a very high level of pressure (up to 3000 bars possible). This type of glass-to-metal seal is among other uses perfectly suited for high pressure sensors.
In a matched glass-to-metal seal the coefficient of thermal expansion of glass, housing and pins are matched as close as possible. Matched seals have the advantage that only small levels of residual stress are present and that the feedthrough can withstand very high temperatures. The seal between glass and metal is mainly established chemically by an oxide layer. Typically, Kovar is used as a housing material for matched seals. This type of glass-to-metal seal is often used for electronics packages.
|Compression Seal||Matched Seal|
|Sealing principle||Thermal compression||chemical|
|Typical housing material||Steel, stainless steel, titanium, …||Kovar, alloy 42, …|
|Special Properties||High bust pressure
Chemically very inert
| High-Temperature capability
High insulation resistance
Very high hermeticity
|Applications||Sensor-housings, hermetic connectors, sight glasses, power feedthrougs||Electronic-housings|
The Dietze Group provides custom interconnection solutions from concept to series production. All our products are designed in close collaboration with our customers and engineered to the application’s specific needs.