Linear coefficient α — ΔL / L₀ = α · ΔT. Values in 10⁻⁶ / °C (ppm/°C). Approximate at room temperature.
Material table
| Material | α (ppm/°C) |
|---|---|
| Aluminum | 23.1 |
| Brass | 19 |
| Copper | 16.5 |
| Gold | 14.2 |
| Iron (pure) | 11.8 |
| Carbon steel | 11–13 |
| Stainless 304 | 17.3 |
| Stainless 316 | 16 |
| Invar (36% Ni) | 1.2 (very low) |
| Titanium | 8.6 |
| Tungsten | 4.5 |
| Nickel | 13 |
| Lead | 29 |
| Zinc | 30.2 |
| Silicon | 2.6 |
| Glass (soda-lime) | 9 |
| Borosilicate (Pyrex) | 3.3 |
| Quartz (fused) | 0.59 |
| Concrete | 12 |
| Brick | 5–7 |
| Wood (along grain) | 3–5 |
| Nylon | 80–95 |
| ABS | 72–108 |
| Polyethylene (HDPE) | 150 |
| PVC | 50–100 |
| Rubber | 77 |
| FR-4 PCB (in plane) | 14–17 |
| FR-4 PCB (out of plane) | 50–70 |
| Ceramic (alumina) | 7.2 |
Notes
- Volumetric expansion ≈ 3α for isotropic materials.
- Bimetallic strips exploit differential expansion — brass + Invar gives a large deflection per degree.
- BGA solder joints fail from CTE mismatch between silicon chip (~2.6 ppm/°C) and FR-4 (~17 ppm/°C) — underfill mitigates.
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