Kovar, also known as 4J29, is a nickel–cobalt–iron controlled expansion alloy designed to provide an exact match between metal and glass expansion rates. This property makes it ideal for glass-to-metal seals, ensuring that assemblies remain leak-tight even when exposed to temperature variations. Typically, Kovar wire contains about 29% nickel, 17% cobalt, and the balance iron, with trace elements precisely controlled to guarantee consistent performance.
At DLX, our high-purity Kovar (4J29) wire is produced through advanced melting and drawing technologies that ensure uniform composition, fine surface finish, and consistent thermal expansion. These features make it the go-to choice for electronics, vacuum components, and aerospace instruments requiring high structural integrity and thermal compatibility.
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In modern industries, where precision and durability are key, Kovar (4J29) wire remains an indispensable material. The ability to bond securely with glass without cracking or leaking under thermal stress gives it a unique advantage across several sectors.
Main Application Areas:
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Glass-to-Metal Seals:
Used in hermetic seals for electronic components such as diodes, transistors, and vacuum tubes. Kovar’s expansion rate closely matches borosilicate glass, ensuring a reliable seal during heating and cooling cycles. -
Aerospace and Defense:
Found in sensor housings, hermetic connectors, and navigation control systems where vacuum integrity is essential. -
Electronics and Semiconductor:
Kovar wire serves as feedthrough pins, lead frames, and support components in microelectronic packaging. -
Optical Devices:
Used for sealing glass windows, lenses, and fiber optics into metal housings. -
Medical Equipment:
In sensors and hermetic encapsulations that must remain leak-free under sterilization or high-vacuum conditions. -
Vacuum Systems:
Applied in X-ray tubes, photomultiplier tubes, and cathode ray devices requiring reliable sealing under temperature fluctuations.
The ongoing shift toward high-performance electronics and miniaturized aerospace systems drives the need for precision sealing materials like Kovar. The growth of semiconductor fabrication and optical communication industries also adds to the rising global demand.
| Elements | 4J29 | 4J36 | |
| Carbon (C) | Not greater than | 0.03 | 0.05 |
| Sulfur (S) | 0.02 | 0.02 | |
| Phosphorus (P) | 0.02 | 0.02 | |
| Manganese (Mn) | ≤0.50 | 0.20-0.60 | |
| Silicon (Si) | ≤0.30 | ≤0.30 | |
| Nickel (Ni) | 28.5-29.5 | 35.0-37.0 | |
| Chromium (Cr) | - | - | |
| Cobalt (Co) | 16.8-17.8 | - | |
| Iron (Fe) | Rest | Rest | |
| Other Elements |
| Alloy Grade | 20°C-100°C | 20°C-300°C | 20°C-500°C |
| 4J36 Invar Alloy | 1.2×10⁻⁶ /°C | 2.5×10⁻⁶ /°C | - |
| 4J29 Kovar Alloy | 4.6×10⁻⁶ /°C | 5.5×10⁻⁶ /°C | 6.2×10⁻⁶ /°C |
| Alloy Grade | 4J36 Invar Alloy | 4J29 Kovar Alloy |
| Density (g/cm³) | 8.1 | 8.2 |
| Tensile Strength (MPa) | 500-600 | 600-700 |
| Yield Strength (MPa) | 250-350 | 300-400 |
| Hardness (HV) | 150-200 | 200-250 |
| Alloy Grade | 4J36 Invar Alloy | 4J29 Kovar Alloy |
| Electrical Resistivity (10⁻⁶ Ω·cm) | 80 | 50 |
| Thermal Conductivity (W/m·K) | 10-12 | 16-18 |
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DLX has positioned itself as a leading manufacturer of precision alloy wire by focusing on metallurgical control, quality consistency, and customer customization. Our Kovar (4J29) wire is engineered to meet the most stringent technical standards required by aerospace, vacuum, and electronics industries.
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Strict Alloy Composition Control:
DLX utilizes vacuum induction melting and vacuum arc remelting to achieve exceptional purity. This ensures uniform distribution of nickel, cobalt, and iron for stable expansion behavior. -
Advanced Wire Processing:
Our drawing, annealing, and straightening technologies produce wire with tight dimensional tolerance and smooth surface quality, ideal for fine sealing and winding. -
Thermal Expansion Precision:
Every batch of 4J29 wire undergoes expansion testing to ensure it matches borosilicate glass precisely, preventing micro-leakage during glass-to-metal joining. -
Customizable Solutions:
DLX offers tailored dimensions (0.05–5 mm), coil forms, and mechanical properties according to customer applications, including aerospace-grade and vacuum-grade options. -
Complete Quality Assurance:
In-house inspection ensures compliance with mechanical, electrical, and magnetic standards, providing full traceability from raw material to final spool. -
Global Support and Fast Delivery:
DLX’s streamlined logistics and engineering support help clients integrate 4J29 wire smoothly into production lines with minimal downtime.
| Property | Kovar (4J29) Wire | 4J36 (Invar) Wire | 4J32 Alloy |
|---|---|---|---|
| Main Composition | Ni 29%, Co 17%, Fe balance | Ni 36%, Fe balance | Ni 32%, Fe balance |
| Density (g/cm³) | 8.3 | 8.1 | 8.2 |
| Melting Point (°C) | 1450 | 1430 | 1440 |
| Coefficient of Thermal Expansion (20–400°C, ×10⁻⁶/°C) | 5.0 | 1.2 | 3.2 |
| Electrical Resistivity (μΩ·m) | 0.5 | 0.78 | 0.65 |
| Tensile Strength (MPa) | 500–600 | 450–500 | 460–520 |
| Magnetic Permeability | Moderate | High | Moderate |
| Typical Applications | Glass-to-metal seals, vacuum tubes | Precision instruments | Relays, sensors |
The global demand for Kovar (4J29) wire is growing rapidly due to the miniaturization of electronic components and increasing demand for reliable sealing materials. As semiconductor packaging, optical communication, and aerospace sensor industries expand, Kovar wire plays a vital role in ensuring long-term device reliability.
Moreover, the market trend is shifting toward ultra-thin and high-purity Kovar wires, driven by innovations in microelectronics and vacuum devices. DLX is meeting this demand by refining its drawing process to produce wires with consistent expansion and reduced inclusion levels.
We also focus on sustainability and material efficiency, optimizing production to minimize waste and energy usage while maintaining high performance and compliance with environmental standards.
About Us:
Our 12,000㎡ factory is equipped with complete capabilities for research, production, testing, and packaging. We strictly adhere to ISO 9001 standards in our production processes, with an annual output of 1,200 tons. This ensures that we meet both quantity and quality demands. Furthermore, all products undergo rigorous simulated environment testing including high temperature, high pressure, and corrosion tests before being dispatched, ensuring they meet customer specifications.
For all our clients, we offer timely and multilingual after-sales support and technical consulting, helping you resolve any issues swiftly and efficiently.
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We support all kinds of testing:
1. What is Kovar (4J29) wire?
Kovar is a nickel–cobalt–iron alloy designed to match the thermal expansion of glass and ceramics, ensuring strong glass-to-metal seals.
2. What makes Kovar unique for glass sealing?
Its expansion coefficient closely matches borosilicate glass, preventing stress or cracking during temperature changes.
3. What is the typical operating temperature range for Kovar?
Kovar performs reliably between -60°C and 400°C, maintaining mechanical and thermal stability.
4. Can DLX produce customized wire diameters?
Yes, DLX offers a full range of wire diameters from 0.05 mm to 5 mm, customized to client requirements.
5. How does Kovar compare to Invar (4J36)?
Invar has a lower expansion rate but lacks Kovar’s compatibility with glass sealing. Kovar is specifically designed for metal–glass interfaces.
6. What are the main applications of Kovar wire?
It’s used in hermetic seals for electronics, aerospace sensors, vacuum tubes, and optical devices.
7. Is Kovar magnetic?
Yes, it has moderate magnetic permeability, which can be useful in some electronic shielding applications.
8. Does DLX provide material certification?
All Kovar wire from DLX is supplied with detailed chemical analysis and mechanical property reports for traceability.
DLX Company Perspective
At DLX, precision and reliability define our approach to manufacturing. Our Kovar (4J29) wire supports industries that operate where even microscopic leaks or expansion mismatches can lead to failure. From aerospace instruments to semiconductor packaging, every wire we produce reflects our commitment to metallurgical excellence.
We continuously invest in material testing and quality optimization to ensure every spool of DLX Kovar wire meets or exceeds industry standards. Our technical team collaborates with global customers to solve engineering challenges—from complex glass-to-metal seals to next-generation electronic feedthroughs.
With our proven record in supplying high-quality controlled expansion alloys, DLX has become a trusted partner for companies aiming to achieve consistent performance in high-vacuum, thermal, and electronic systems.
