01Thermal Reliability & Failure Prevention
How do I know my design will survive its rated thermal cycling life, not just pass initial qualification?
Power cycling and structure-function monitoring to quantify degradation and predict remaining life.
02The problem
A component or module passes initial thermal qualification at time zero, but the question that actually determines field reliability is how its thermal path degrades over thousands of power cycles — bond-wire lift-off, solder fatigue, die-attach voiding, TIM pump-out — and a single-point qualification test doesn't answer that.
Design margin calculated against the as-built thermal resistance overstates real service life if the thermal path is expected to degrade meaningfully before end of life, and teams frequently discover this only after a field failure.
Why it's hard
- Thermal degradation mechanisms (bond-wire lift-off, solder fatigue, die-attach voiding, TIM pump-out) develop gradually and are invisible to a single time-zero measurement
- Non-destructive detection of internal degradation requires resolving the structure function, which most standard test equipment cannot do
- Simulating end-of-life thermal margin requires knowing how thermal resistance actually shifts with cycling — not an assumed derating factor
- Statistically meaningful reliability data (Weibull life curves) requires cycling a population of parts under controlled, repeatable conditions
- A design margin calculated only against as-built thermal resistance can be a poor predictor of field reliability if degradation is significant before end of life
03How we solve it
Predict — simulation
- Simulate the design at time-zero thermal resistance in Flotherm or STAR-CCM+ to establish the baseline design margin
- Re-run the simulation with degraded, measured end-of-life thermal properties to quantify how much margin actually remains in service
Measure — hardware
- Power cycle devices under controlled conditions with Simcenter Micred Power Tester while continuously monitoring the structure function
- Detect and quantify bond-wire, solder and die-attach degradation non-destructively as it develops, producing lifetime curves and Weibull data
Correlate — close the loop
- Feed measured degradation data back into the thermal simulation as an aged boundary condition to calculate true end-of-life design margin
- Use the correlated model to set realistic derating guidance instead of a generic industry rule of thumb
05Standards in scope
- AQG 324 power cycling qualification
- JEDEC JESD51 package characterization
07Questions engineers ask
Quantify degradation before it becomes a field failure.
Tell us the failure mode you're concerned about and where you are in qualification. We'll help you set up a power-cycling and structure-function program.