What is Estimated Failure Rate（FIT）?
Quality
FIT (Failure In Time) is a unit of measure of failure rate (109hours), which indicates how many failures occur per operating hour.
Estimated Failure Rate (FIT) by Life Test (High Temperature Operating Life Test) is calculated by the following formula.
- FIT＝（Total number of failures）/（（Total number of test samples × Test time）× Temperature acceleration rate）
If the number of failures is 0(zero), the total number of failures is 0.917 using a confidence level factor of 60％. Temperature acceleration rate is calculated from the following equation using the Arrhenius Model.
Temperature acceleration rate ＝exp（（Ea / k）×（1/（Use temperature ＋ K）－1/（Test temperature ＋ K）））
- *Ea ：Activation energy（eV）
- k ：Boltzmann constant of 8.6173×10-5（eV/K）
- Temperature：Absolute temperature（K）
MTTF (Mean Time to Failure) is the average operating time to failure for non-repairable products and is the reciprocal of the FIT.
For information on Estimated Failure Rate （FIT）, Mean Time To Failure (MTTF), and each parameter, please refer to
“Estimated Failure Rate : FIT/MTTF (Electronic device products)“
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