An acceleration factor converts stress-test results into use-condition predictions. For temperature-driven mechanisms the Arrhenius model gives AF = exp[(Ea/k)(1/T_use minus 1/T_stress)], with temperatures in kelvin and k = 8.617e-5 eV/K; with an activation energy of 0.7 eV, testing at 125 C instead of 55 C gives an AF near 78. Voltage, humidity and thermal cycling have their own models, and a wrong activation energy can move the answer by a factor of ten.
With an AF of 78, the 1,000-hour HTOL covers about nine years at 55 C. Customer wants ten, so extend it.
Also heard as
- AF
- Arrhenius acceleration
Related terms
Burn-in
Operating products under raised stress before shipment so weak units fail in the factory instead of in the field.
Censoring
Incomplete life data where a unit's exact failure time is unknown because the test ended or the unit was removed first.
FIT
Failures in time: one failure per billion device-hours, the standard unit for semiconductor failure rates.
MTTF
Mean time to failure: expected life of a non-repairable item, the average time until its first and only failure.