# 4J29

> Kovar — Fe-Ni-Co expansion alloy for glass-to-metal and ceramic-to-metal seals in electronics packaging.

4J29 (Kovar) is an iron-nickel-cobalt controlled expansion alloy whose thermal expansion coefficient closely matches that of borosilicate glass and alumina ceramics. It is the universal standard for hermetic glass-to-metal seals in electronic packages, transistor headers, microwave tubes and optoelectronic housings.

## Key features

- Thermal expansion matches borosilicate glass
- Kovar / ASTM F15 standard
- Hermetic seal qualified
- Good plating and brazing
- Leak-tight to 10⁻⁹ cc He/s

## Applications

- Transistor and IC hermetic packages
- Microwave tube windows
- Optoelectronic device housings
- Reed switch glass seals
- Cryogenic electrical feedthroughs

## Standards

- ASTM F15
- GB/T 14986
- MIL-I-23011