Kovar has been in use for many decades. Despite its relatively long history, many people outside of engineering fields may never have heard of this valuable alloy. This is an overview of kovar.
The name Kovar is actually trademarked by a Delaware corporation, CRS Holdings, Inc. Kovar was first patented in the U.S. in 1936. The alloy itself is made from iron, nickel, and cobalt.
The uniqueness of Kovar, and thus its importance, is that it has a coefficient of thermal expansion that is remarkably similar to borosilicate glass (hard glass) or ceramic. This alloy’s coefficient of thermal expansion is not an accident. Kovar was, in fact, carefully formulated to meet a specific need.
The challenge with pairing metal to glass is that each has a different coefficient of thermal expansion. The problem is that as the glass and metal are heated or cooled they expand and contract at different rates and in varying amounts. Consequently, the hermetic seal between metal and glass components may be destroyed, or the glass may be broken, when the two are paired together and there is a change in temperature.
One common, everyday example of the need for an alloy that can be safely paired with glass is light bulbs. A light bulb made with a base that has a different coefficient of thermal expansion from glass would break quickly due to the heat that the bulb produces while in use. Kovar solves this problem because the alloy base and the glass bulb expand and contact at nearly the same rate.
Light bulbs are perhaps the most common example of the use of Kovar, but this alloy is used in many different products. Kovar is also used to manufacture x-ray tubes, microwave tubes, diodes, transistors, and more.
Kovar may not be a household name, but this incredible alloy is still used in products in every home.
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