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Kovar alloy is a vacuum melted, iron-nickel-cobalt alloy that is widely used in the electronics industry. Kovar is a nickel-iron-cobalt, controlled-expansion alloy which contains 29% nickel. Its coefficient of expansion, which decreases with rising temperature to the inflection point, matches the expansion rate of borosilicate glasses and alumina ceramics.
Kovar alloy has been used for making hermetic seals with the harder Pyrex glasses and ceramic materials. This alloy has found wide application in power tubes, microwave tubes, transistors, and diodes. In integrated circuits, it has been used for the flat pack and the dual-in-line package.
Chemical Composition
| Grade | C% | P% | S% | Mn% | Si% | Cu% | Cr% | Mo% | Ni% | Co% | Fe% |
| Kovar | Max 0.03 | Max 0.020 | Max 0.020 | Max 0.50 | Max 0.30 | Max 0.20 | Max 0.20 | Max 0.20 | 28.5-29.5 | 16.8-17.8 | Bal. |
Specifications
| Grade | UNS | Werkstoff Nr. |
| Kovar | K94610 | 1.3981 |
Physical Properties
| Grade | Density | Melting Point |
| Kovar | 8.17 g/cm3 | 1449°C |
Mechanical Properties
| Grade | Tensile Strength N/mm² | ||||
| Soft | 1/4 Hard | 1/2 Hard | 3/4 Hard | Full Hard | |
| Kovar Strip | <570 | 520-630 | 590-700 | 600-770 | >700 |
| Kovar Wire | <585 | 585-725 | 655-795 | 725-860 | >860 |
Coefficient of Expansion
| Alloy | Linear Coefficient of Thermal Expansion a,10-6/°C | |||||||
| 20-200°C | 20-300°C | 20-400°C | 20-450°C | 20-500°C | 20-600°C | 20-700°C | 20-800°C | |
| Kovar | 5.9 | 5.3 | 5.1 | 5.3 | 6.2 | 7.8 | 9.2 | 10.2 |
