material

Kovar alloy

Kovar alloy

Material type: Metal, Corrosion resistant, Thermal expansion controlled, High strength, Heat resistant

Kovar alloy is a nickel–cobalt ferrous alloy with a coefficient of thermal expansion similar to that of hard glass, ceramics, and certain crystals. It is designed to form a hermetic seal with glass and ceramic materials, making it widely used in electronic, optical, and aerospace applications.

Material advantages

  • Excellent thermal expansion match with borosilicate glass and alumina ceramics

  • Good machinability and weldability

  • High dimensional stability under thermal cycling

  • Maintains strength at elevated temperatures

Material shortcomings

  • Not suitable for applications requiring high corrosion resistance in harsh environments (e.g., salt water, strong acids)

  • Relatively expensive compared to common steels

  • Requires controlled atmosphere or plating (nickel/gold) to avoid oxidation

NameValue
Tensile strength450–620 MPa
Yield strength~275 MPa
Elongation20–30%
Hardness, Rockwell B70–85
Modulus of elasticity138 GPa
Poisson’s ratio0.317
Melting Point Range1450–1500 °C
Density8.36 g/cm³
Coefficient of thermal expansion (20–400 °C)~5.0 × 10⁻⁶ /°C
Kovar alloy machining

Common applications

  • Hermetic sealing in electronic and optical components

  • Lead frames and headers in semiconductor packaging

  • Glass-to-metal seals in vacuum tubes, transistors, diodes

  • Microwave and RF packages

  • Aerospace sensor housings

  • Sealed feedthroughs for instrumentation

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