Kovar

Kovar is a controlled-expansion alloy in the iron-nickel-cobalt family designed to have a coefficient of thermal expansion (CTE) closely matching that of borosilicate glass and other “hard” glass/ceramic materials.

Because of this matched expansion characteristic, it is widely used for hermetic glass-to-metal and ceramic-to-metal seals over a range of temperatures.

It also exhibits good mechanical strength, works well under thermal cycling, and can bond reliably to glass via controlled oxide layers (nickel/cobalt oxides) that promote wetting by molten glass.

Because of its matched thermal expansion and ability to form reliable seals with glass or ceramics, Kovar is widely used in electronics, optics and vacuum systems. Common applications include:

• X-ray windows, seals in lighting and display devices.

• Hermetic glass-to-metal or ceramic seals in vacuum tubes, x-ray tubes, microwave tubes, and other electron devices.

• Lead-in wires or feedthroughs through glass envelopes.

• Components in aerospace or satellite systems, sensors and optoelectronics, where matched expansion with optics or glass is critical.

Kovar plate is typically used in structural or substrate applications where polished, flat surfaces or machined shapes are needed. For example, the plate form may serve as mounting bases or flanges that interface with glass windows or ceramic parts, or as backing plates in hermetic packages where machining or finishing is required.

Round bar is often used for feedthrough pins, rods, or supports that pass through glass or ceramic seals. It can be machined into pins or leads, or used as structural supports within hermetically sealed devices.

Kovar sheet is used when thin, flat, sealed walls or covers are required, such as in lids, vacuum enclosures, or as thin membrane substrates. It can also be stamped or laser cut for packaging or sealing frames.

Coil (strip) form of Kovar is useful for continuous processing, stamping, coil-fed forming of leads, or as a base for leadframe-style geometries that will later be cut to shape. It allows economical manufacturing of repeated small features.

Kovar wire is used primarily for lead-in wires, springs, or extremely fine conductors that must traverse a glass or ceramic seal while maintaining matched expansion. It is also used in micro-electronic or optoelectronic lead frames.

Kovar tube can be used as sealed tubes through which electrical or optical fibres pass, or structural tubes that interface with glass windows. Tubing offers a hollow geometry that can support internal wiring or act as a sealed passage.