Distinguish test types
Chamber temperature cycling changes the surrounding temperature. Power cycling generates heat inside an operating device and can create different gradients and time scales. Neither test can be translated into field life using a generic cycle-count multiplier.
Define the mission profile
Record temperature range, dwell, ramp rate, power pulse, cooling conditions and mechanical constraints. Select tests based on likely failure mechanisms: ceramic cracking, copper adhesion, die attach or wire-bond degradation. Track which interface actually fails.
Make evidence comparable
Ask for sample size, geometry, copper pattern, material grade and criteria for failure. A high cycle count for a small symmetrical coupon does not establish the same lifetime for a large asymmetrical module. Combine testing with model correlation and process control.
Engineering example
If a module fails at the die attach while the ceramic remains sound, changing to a tougher ceramic may not address the limiting mechanism. Investigate the failed interface before selecting a new substrate.
Before you release the design
- Define actual service conditions.
- Keep chamber and power cycling results distinct.
- Record construction, sample count and failure mode.
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.