Use the appropriate coefficient
A bare ceramic’s CTE is different from the effective CTE of a copper-clad stack. Values also refer to temperature intervals and may vary with direction. Use the material or assembly property that corresponds to the part being modeled.
Estimate free movement first
For constant CTE, differential free expansion is ΔL = L × Δα × ΔT. This helps identify scale and sensitivity. It does not calculate stress, solder strain or fatigue life because it excludes constraints, temperature gradients and material constitutive behavior.
Reduce strain at sensitive interfaces
Attachment footprint, joint thickness, compliant interconnects and mounting strategy can affect how movement is accommodated. Review large components and connections to metal housings. Validate the resulting design under the relevant temperature and power cycles.
Engineering example
Across 20 mm, a 10 ppm/K mismatch and 100 K temperature change create 20 µm of differential free movement. Whether that damages a joint depends on the joint geometry and mechanical response.
Before you release the design
- Distinguish bare-ceramic and stack CTE.
- Record the temperature interval.
- Evaluate attachment compliance and constraints.
Sources and further technical reading
Manufacturer references support the material and process context. Worked examples and checklists are engineering guidance; they are not test results or supplier guarantees.