Kovar

Kovar was originally a trade name, and called alloys, which have a low coefficient of thermal expansion ( CTE engl. ), typically about 5 ppm / K, which is therefore less than the coefficient of typical metals.

A typical composition is 54 % iron, 29 % nickel and 17% cobalt (in mass percent).

Some technical ceramics (such as aluminum oxide Al2O3, aluminum nitride AlN) and semiconductor materials have thermal expansion coefficients of the same magnitude. In the field of microelectronics and microsystems technology Kovar is therefore used as a housing material or as a submount. Submounts lie between the actual carrier material and material with mostly a significantly larger expansion coefficient (sandwich principle). Thus, the submount Kovar is used as compensating element, which receives and decreases the problems caused by the different coefficients of thermal expansion of the other materials thermomechanical stresses.

In the same way serve Kovar materials for glass and metal bushings of electronic components, material transitions in vacuum chambers, etc.

The similar Invar alloys designated with a thermal expansion coefficient close to 0

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