Kovar

Kovar

An inert metal alloy that does not oxidize.

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kovar [′kō‚vär]

(metallurgy)

An alloy (54% iron-29% nickel-17% cobalt) that exhibits low thermal expansion; widely used for electronic devices with glass-to-metal seals because its expansion is low enough to match that of glass.

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Kovar 

an iron-based alloy containing 18 percent cobalt and 29 percent nickel. Kovar is characterized by a low coefficient of thermal expansion [(4.5–5.2) X 10^-6 1/°C between 20° and 400°C], approximating the coefficient of thermal expansion of glass. Melting point, 1450°C; specific electrical resistance, 0.5 microhm · m; Curie temperature, 420°C. The alloy corrodes in a moist medium and requires protective coatings. When sealed in glass, Kovar forms a strong vacuum-tight adhesion, which is used in electrical engineering for the manufacture of casings and current outlets in various tubes and devices.