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Invar® Foil/Sheet
Available Configurations
Properties common to all products in this list
| Thickness | Size | Temper ⓘ | Other Variant |
|---|---|---|---|
| 0.008 mm (foil) to 25 mm (plate) | 10 x 10 mm to 500 x 500 mm | As rolled Annealed Quarter hard Half hard Hard |
Light Tight (Pinhole Free) |
Need custom configurations? Please contact us.
Key Features
Invar® Foil (Fe64/Ni36, UNS K93600) is the industry-standard low-thermal-expansion alloy in flat sheet form, with a CTE of 1.7–2.0 × 10⁻⁶ K⁻¹ at 20–90 °C and below 1.2 × 10⁻⁶ /°C between −100 °C and +200 °C:
CTE 1.7–2.0 × 10⁻⁶ K⁻¹
The near-zero CTE is the product of a magnetovolume interaction between magnetic ordering and lattice expansion in the Fe-Ni system at this specific composition.
CTE Below 1.2 × 10⁻⁶ /°C from −100 °C to +200 °C
The low-expansion property extends across the cryogenic range, maintaining dimensional stability at temperatures encountered in liquid nitrogen and near-liquid helium service where other metallic foils would contract substantially.
Curie Temperature 279 °C
The upper service limit of the low-CTE behavior. Above 279 °C the magnetovolume effect responsible for the anomalous expansion dissipates and CTE returns toward normal ferrous alloy values. Service temperature must remain below this limit for the low-expansion property to apply.
Tensile Strength 450–590 MPa
Meaningful mechanical performance alongside the defining dimensional stability, supporting use in mechanically loaded foil applications such as composite tooling face sheets and shadow masks.
Elongation 45%
Good ductility in the foil form supports forming, cutting, and integration into complex assemblies without fracture.
Modulus of Elasticity 140–150 GPa
High stiffness relative to most metallic foils maintains flatness under the tension applied during fine metal mask and shadow mask processing, where foil deformation or wrinkling would compromise pattern registration.
Industrial Applications
Invar® Foil is used wherever dimensional stability through thermal cycling is required in a thin metallic sheet format:
- ✦ Fine Metal Masks for OLED Display Manufacture
- The primary high-volume application. Electroformed and rolled Invar foil is the established material for fine metal masks in RGB organic material vapour deposition, where the CTE — typically four times lower than conventional electroformed nickel or nickel-cobalt alloys at equivalent thickness — maintains aperture registration through the thermal cycles of the deposition process.
- ✦ Shadow Masks in Display Production
- Used as shadow masks in display manufacturing processes, where dimensional stability of the mask aperture pattern through repeated thermal cycles determines pixel registration accuracy.
- ✦ Precision Optical Mirror Substrates
- Applied as thin mirror substrates in precision optical systems, where near-zero CTE maintains surface figure through temperature changes that would defocus higher-CTE alternatives.
- ✦ Thermal Compensation Shims
- Used as thermal compensation shims in laser and interferometric systems, where the near-zero CTE provides a dimensional reference element whose thickness is stable through the temperature variations of instrument operation.
- ✦ Composite Tooling Face Sheets for Aerospace
- Applied as face sheets in composite lay-up moulds for aerospace manufacture, where CTE matching to carbon fiber reinforced polymer ensures dimensional fidelity of the moulded component through the elevated-temperature cure cycle.
Material Properties
| Element | Value |
|---|---|
| Hardness - Brinell | 160 |
| Elongation at break( % ) | 45 |
| Modulus of elasticity( GPa ) | 140-150 |
| Tensile strength( MPa ) | 450-590 |
| Element | Value |
|---|---|
| Electrical resistivity( µOhmcm ) | 75-85 |
| Element | Value |
|---|---|
| Curie temperature( C ) | 279 |
| Element | Value |
|---|---|
| Melting point( C ) | 1427 |
| Specific heat( J K⁻¹ kg⁻¹ ) | 515@23°C |
| Thermal conductivity( W m⁻¹ K⁻¹ ) | 13@23°C |
| Coefficient of thermal expansion( x10⁻⁶ K⁻¹ ) | 1.7-2@20-90°C |
| Element | Value |
|---|---|
| Density( gcm⁻³ ) | 8 |
Tolerances
| Thickness | <0.01mm | ±25% |
|---|---|---|
| Thickness | 0.01mm - 0.05mm | ±15% |
| Thickness | >0.05mm | ±10% |
| Linear dimension | <100mm | ±1mm |
| Linear dimension | >=100mm | +2 / -1% |