Why Kovar Is Used in Telecommunications and Electronic Packaging

Kovar is widely used in telecommunications and electronic packaging because its controlled thermal expansion closely matches materials such as borosilicate glass and certain ceramics. This makes it particularly valuable for creating reliable glass-to-metal and ceramic-to-metal seals in components that need to remain protected from moisture, gases and changing temperatures.

For engineers and procurement teams, this combination of thermal stability and sealing performance can make Kovar a practical choice for electronic packages, connectors, housings and other components where long-term reliability matters.

What Is Kovar?

Kovar is an iron, nickel and cobalt controlled expansion alloy. Its composition is designed to give it a predictable coefficient of thermal expansion across a defined temperature range.

This is the property that separates Kovar from many conventional engineering metals.

When a metal component is joined to glass or ceramic, the materials expand and contract at different rates as temperatures change. If that difference is too great, stresses can develop around the joint. Over repeated thermal cycles, these stresses may cause cracking or compromise a seal.

Kovar helps address this problem because its expansion characteristics can be closely matched to borosilicate glass and alumina ceramics.

Why Is Kovar Used in Electronic Packaging?

Electronic packaging has to do more than hold components in place. In many applications, it protects sensitive electronics from external conditions while maintaining electrical connections through the package.

Kovar is particularly useful when the package requires a hermetic seal.

Creating Reliable Hermetic Seals

A hermetic package is designed to prevent gases and moisture passing through its sealed enclosure.

This matters for electronic components that could be damaged by humidity, contaminants or changes in atmosphere. Semiconductor devices, sensors, microwave components and optoelectronic assemblies may all require this level of protection.

Kovar can form glass-to-metal seals without creating the large thermal stresses that could occur if the metal and glass had very different expansion rates.

That makes it useful for headers, feedthroughs and sealed electronic housings.

Managing Thermal Expansion

Electronic components can experience significant temperature changes during manufacturing and service.

Soldering, brazing and sealing processes may expose a package to elevated temperatures. Once in use, electrical components themselves generate heat. Equipment installed outside or in demanding industrial settings can also experience wider environmental temperature changes.

A controlled expansion alloy reduces movement between joined materials.

This can help maintain the integrity of the seal through repeated heating and cooling cycles, which is especially important when the component is expected to operate for many years without maintenance.

Maintaining Dimensional Stability

Small dimensional changes can matter in tightly engineered electronic assemblies.

Components may need to remain aligned with pins, optical elements, ceramic substrates or other parts inside the package. Kovar’s predictable thermal behaviour helps engineers control those changes.

It isn’t completely expansion-free. Instead, its advantage is that engineers can account for its behaviour and match it with compatible materials.

Why Is Kovar Important to the Telecommunications Industry?

Modern telecommunications infrastructure depends on electronics that must perform reliably for long periods, often in equipment where replacement or repair is difficult.

Within the telecommunications industry, Kovar can be used in specialist electronic packages, microwave components, connectors, feedthroughs and optoelectronic systems.

The material is particularly relevant where electronic or optical components need to be protected inside a sealed package.

Telecommunications Equipment Faces Temperature Changes

Telecommunications equipment isn’t always installed in a controlled indoor environment.

Infrastructure can be exposed to outdoor temperatures, heat generated by electronics and repeated operational thermal cycles. Components inside sealed assemblies must continue to perform despite those changes.

If the materials surrounding a glass or ceramic seal expand at very different rates, the resulting stress can shorten the life of the component.

Kovar provides a more closely matched expansion rate, helping engineers design packages that cope with these conditions.

Protection From Moisture and Contamination

Moisture can be a serious problem for sensitive electronics.

A hermetically sealed Kovar package can help isolate components from humidity and other environmental contaminants. This is useful in communications equipment where reliability and a long service life are important.

The same principle explains why Kovar is also found in electronic packages for aerospace, defence, scientific and medical applications.

How Does Kovar Work With Glass and Ceramics?

The relationship between the materials is central to Kovar’s usefulness.

Borosilicate glass and specialist ceramics are widely used as electrical insulators because they can separate conductive pins or components while still forming part of a sealed enclosure.

However, glass and ceramics are brittle. They cannot accommodate the same degree of thermal movement as many metals.

Kovar was developed with controlled expansion characteristics that are closer to those materials. When correctly designed and processed, this reduces the stresses placed on the seal as the assembly heats and cools.

The result can be a strong, stable joint suitable for hermetic electronic packaging.

Common Kovar Components in Electronic Packaging

Kovar can be supplied and manufactured into a range of component types.

Typical applications include:

• Electronic package lids
• Headers
• Lead frames
• Feedthrough components
• Connector bodies
• Semiconductor packages
• Microwave housings
• Optical and optoelectronic packages
• Glass-to-metal sealing components
• Ceramic-to-metal assemblies

The final material form will depend on the manufacturing process and component design.

City Special Metals supplies Kovar in forms including sheet, plate, bar, rod and wire, allowing engineers and manufacturers to source material suited to different production requirements.

Does Kovar Conduct Electricity?

Kovar is electrically conductive, but conductivity is not the main reason engineers specify it for electronic packages.

Copper and other high conductivity materials are usually more appropriate when electrical or thermal conductivity is the dominant requirement.

Kovar is chosen because it combines useful electrical properties with controlled thermal expansion and compatibility with glass and ceramics.

This distinction matters when specifying electronic packaging. The material surrounding an electrical feedthrough, for example, has a different job from the conductor passing through it.

Is Kovar Corrosion Resistant?

Kovar offers some resistance to corrosion, but it should not be treated as a direct substitute for corrosion resistant stainless steel or nickel alloys.

Surface treatment, plating and environmental protection may be required depending on the application.

Electronic packages are often plated to improve surface characteristics and support processes such as brazing, soldering or wire bonding. The correct treatment depends on the manufacturing method and operating environment.

Material and finishing requirements should therefore be considered together at the design stage.

What Should Engineers Consider When Specifying Kovar?

Controlled thermal expansion is a major advantage, but selecting Kovar still requires a clear understanding of the finished component.

Engineers should consider:

• The glass or ceramic being joined to the metal
• Expected operating temperature range
• Thermal cycling during manufacture and service
• Required level of hermeticity
• Component dimensions and tolerances
• Machining and forming requirements
• Brazing, welding or sealing processes
• Required surface treatments or plating
• Material certification and traceability

The condition of the supplied material can also affect subsequent manufacturing.

Working with a specialist metals supplier early in the process can help manufacturers confirm available forms, dimensions and material specifications before production begins.

Why Material Consistency Matters for Electronic Packaging

Controlled expansion alloys depend on precise chemistry and processing.

Small variations can affect thermal behaviour, which becomes important when the metal has to match another material across repeated temperature changes.

For procurement teams, this makes material consistency and traceability a key consideration rather than an administrative detail.

Reliable material certification can help confirm that supplied Kovar meets the required specification. It also gives manufacturers greater confidence when controlling production batches and investigating any quality issues.

Lead time matters too. Electronic manufacturing schedules can be disrupted when a specialist alloy isn’t available in the required form or dimensions.

Working with a supplier that understands controlled expansion alloys can help avoid material substitutions that compromise the original engineering specification.

Frequently Asked Questions

Why is Kovar good for electronic packaging?

Kovar has controlled thermal expansion characteristics that closely match borosilicate glass and certain ceramics. This reduces thermal stress at sealed joints and makes the alloy well suited to hermetic electronic packages.

What is Kovar made from?

Kovar is an iron, nickel and cobalt alloy. Its composition is tightly controlled to achieve predictable thermal expansion properties.

Is Kovar used in telecommunications equipment?

Yes. Kovar can be used in specialist telecommunications components including electronic packages, microwave assemblies, feedthroughs and optoelectronic housings where sealed protection and thermal stability are required.

Why is Kovar used for glass-to-metal seals?

Glass is brittle and can crack if the metal joined to it expands at a substantially different rate. Kovar’s thermal expansion can be closely matched to suitable glass, reducing stress as temperatures change.

Is Kovar the same as Invar?

No. Both are controlled expansion alloys, but they are designed for different purposes. Invar is primarily selected when very low dimensional change is required. Kovar is particularly useful when the expansion of a metal needs to match glass or ceramic for sealing applications.

Can Kovar be machined?

Yes. Kovar can be machined, formed and fabricated, although machining parameters need to account for the behaviour of the alloy. Tool selection, cutting conditions and component tolerances should be planned around the required finished part.

Final Thoughts

Kovar solves a specific engineering problem that is particularly important in electronic packaging. Its controlled thermal expansion allows metal, glass and ceramic components to work together through temperature changes without placing excessive stress on critical seals.

For telecommunications manufacturers, that can mean better protection for sensitive electronics and more reliable performance in components expected to remain in service for long periods.

If you need Kovar for telecommunications or electronic packaging, contact City Special Metals to discuss your specification, required material form and availability with the team.