| Decision | Alumina | Aluminum nitride |
|---|---|---|
| Baseline role | Cost-conscious insulating circuit carrier | Candidate for low substrate thermal resistance |
| Named conductivity example | 24 W/m·K, curamik Power | 170 W/m·K, curamik Thermal |
| Bare ceramic CTE example | 6.8 ppm/K | 4.8 ppm/K |
| Main review | Is the available thermal path sufficient? | Does lower substrate resistance improve the system? |
Use an equal-geometry comparison first
For the same thickness and area, the ideal ceramic resistance scales inversely with conductivity. This gives a clean first estimate, but the finished temperature also depends on spreading, attachments and cooling. Use named grade data at relevant conditions.
Then compare manufacturable alternatives
An available thinner alumina or a different attachment may change the economics. Check insulation, handling and supplier limits before changing thickness. Copper and finish requirements must be compatible with the chosen ceramic.
Do not infer complete-assembly expansion
The table uses bare-ceramic CTE examples. Copper-clad stack expansion is different and depends on construction. Evaluate joints to dies, connectors and housings using the appropriate properties.
Engineering example
With 0.635 mm thickness and 100 mm² area, the ideal layer resistance is 0.265 K/W at k = 24 and 0.0374 K/W at k = 170. The remaining assembly resistance is unchanged by this calculation.
Before you release the design
- Use the same thermal boundary conditions.
- Compare qualified thickness and finish options.
- Evaluate system benefit per completed-part cost.
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.