1. Introduce
– Material similar to the thermal expansion rate of ceramics and glass
→ Kovar : Low thermal expansion Fe-Ni-Co alloy
→ Material applied as a sealing and bonding material for semiconductor parts, electronic products
(For glass-to-metal, ceramic-to-metal bonding)
– UNS K94610
* Kovar bonding properties
– Most metals cannot be joined with glass and ceramics due to different thermal expansion rates, but Kovar can be joined due to the matching thermal expansion rates
– Bonds to glass and ceramics through an intermediate oxide layer of Ni oxide and Co oxide
[Thermal Expansion Coefficient Comparison]
| Kovar | Glass | Ceramic | Invar | |
|---|---|---|---|---|
| Coefficient of Thermal Expansion (CTE) | 4.9~6.2 | 6.7 | 6.5 | 1.2~2.7 |
* Key properties that must be met as a glass and ceramic sealing material
: Similar coefficient of thermal expansion to glass and ceramics, uniform surface oxidation, good toughness and machinability
* UNS
- Abbreviation for the Unified Numbering System for Metals and Alloys
- Unified unique numbering system for metals and alloys
- A representative number compatible with metals and alloys defined in several material-related codes, including ASTM, AISI, ASME, AWS, etc.
* K : Miscellaneous steels and Ferrous alloys
2. Property
– Uniform thermal expansion properties, excellent thermal shock resistance
[Kovar Chemical Composition (%)]
| C | Mn | Si | Ni | Co | Fe |
|---|---|---|---|---|---|
| Max. 0.020 | Max. 0.3 | Max. 0.2 | Max. 29.0 | Max. 17.0 | Bal. |
[Kovar Mechanical Properties]
| Tensile Strength (Mpa) | Yield Strength (Mpa) | Elongation (%) |
|---|---|---|
| 317 | 345 | 30 |
[Kovar Physical Properties]
| Density (g/㎤) | Melting Range (℃) | Specific Heat (0-100℃), J/kg*℃ | Curie Temperature (℃) | Electrical resistivity (µΩ-㎝) |
|---|---|---|---|---|
| 8.36 | 1450 | 439 | 435 | 49 |
3. Standard & Specification
– Specification : UNS K94610
| Product Form | ASTM | AMS |
|---|---|---|
| Wire | F-15 | 7726 |
| Sheet, Strip, Foil | F-15 | 7728 |
| Bar, Rod, Forgings | F-15 | 7727 |
| Pipe, Tube | F-15 | – |
4. Available Form
– Wire
– Sheet, Strip, Foil
– Bar, Rod, Forgings
– Pipe, Tube
5. Application & Product
– Electrical, Electronic
| Application | Product |
|---|---|
| Electrical | Shock tube, igniter, magnetron, transistor, relay, integrated circuit, cathode ray tube, vacuum tube |
| Electronic | Semiconductor components, sealing of electronic products, bonding materials, high-energy emission tubes, transistor leads, IC lead frames, photographic flash valves |
(1) Igniter / (2) Magnetron / (3) Transistor / (4) Semiconductor parts
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