Material
Kovar (4J29)
Kovar (4J29) is a nickel-cobalt-iron alloy engineered to match the thermal expansion of hard borosilicate glass and alumina ceramics for reliable, crack-free hermetic seals.
Manufacturing processes
About
Kovar (4J29) is the classic hermetic-sealing alloy: Its thermal expansion closely matches borosilicate glass and 98% alumina ceramics from 20-450 °C, preventing the cracking that occurs when mismatched metals and glass cool after sealing.
It has a dense, glass-wettable oxide layer and doesn't react with mercury, making it suitable for mercury-containing vacuum devices. It isn't chosen for general structural strength – its value is dimensional and thermal matching.
This material is a good choice for IC and transistor packages, vacuum tube seals, and X-ray tube components.
Technical Details
- Accuracy
- ±0.2% (lower limit of ±0.13 mm)
- Density
- 8.36 g/cm³
- Min. wall thickness
- -
Technical Properties
- Tensile strength
- 485 MPa
- Tensile elongation
- 20%
- Embossing
- min. 0.3 mm
- Engraving
- min. 0.3 mm
- Warping risk
- N/A