Evaluate fracture behavior alongside conductivity
Material selection for a power module is not a contest to maximize W/m·K. Copper expansion, substrate thickness, edge condition and the thermal cycle can make cracking resistance decisive. Compare a qualified Si₃N₄ AMB structure against the actual AlN or alumina alternative, not against an isolated material number.
Use the right grade data
Silicon nitride formulations and manufacturing routes vary. Representative power-substrate grades have different conductivity, strength and toughness. The thermal tool uses an editable named product value of 90 W/m·K; it is not a minimum procurement specification or a lifetime prediction.
Validate the metallized part
The braze, copper profile and ceramic form a coupled structure. Ask for tests using relevant copper thickness, top/bottom coverage and edge geometry. A cycling claim without temperature range, dwell, ramp rate, failure criterion and sample count is not a useful qualification target.
Engineering example
At the same 100 mm² area, a 0.32 mm layer with k = 90 gives 0.0356 K/W, close to 0.635 mm AlN at k = 170. This is a thickness/conductivity comparison; it does not establish equivalent insulation or reliability.
Before you release the design
- Confirm the Si₃N₄ grade and AMB construction.
- Compare ceramic thicknesses that meet the insulation requirement.
- Define the service mission profile before selecting cycle tests.
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.