Kovar

Alloy K (Kovar®*) is an iron-nickel-cobalt alloy whose chemical composition is controlled within narrow limits to ensure precise and uniform thermal expansion and mechanical characteristics. These properties make it an ideal alloy for use in high integrity glass-to-metal and ceramic-to-metal seals, particularly where the application requires resistance to thermal shock.

Alloy K (Kovar®*) is often used for the manufacture of hermetic seals with both the harder Pyrex or borosilicate glasses and alumina-type ceramic materials. The alloy finds extensive application in the production of transistors and diodes for lids and closures in a variety of hybrid electronic circuit packages and also in the manufacture of microwave tubes. In order to achieve optimum conditions for subsequent sealing operations, it is recommended to first condition the material using a thermal degassing / decarburizing treatment carried out in a moist hydrogen atmosphere. This is then normally followed by a controlled oxidizing heat treatment in order to create a tightly adherent surface oxide film of optimum nature and thickness.