About the failure rate for aluminum electrolytic capacitors
The failure rate of electronic components is generally calculated based on the following formula.
Compliant with JIS C 5003, this formula uses the total component time (the results of endurance testing calculated as No. of test pieces × endurance test time) and the number of failures.
Furthermore, the following description is used when the number of failures is zero.
- T
- : Total component-hours[hrs.]
- γ
- : Number of failures[pcs]
- n
- : Number of test pieces[pcs]
- t
- : Endurance test time[hrs.]
- a
- : Reliability standard coefficient (0.917 when the No. of failures is zero and the reliability standard is 60%)
Aluminum electrolytic capacitors are considered as components of wear-out failure mode, the electrical characteristics of which gradually deteriorate and their failure rate increases with time.
the failure rate in FIT is determined by total component-hours (product of the number of tested components and test hours).
Due to the definition of FIT, the same FIT rate can be calculated in both cases of testing on the large number of tested components and also testing for long test periods of time.
However, these
cases mean differently for aluminum electrolytic capacitors. Using the failure rate is not suited to express the reliability of aluminum electrolytic capacitors, but the electrical characteristics based lifetime in hour should be considered to express the reliability.
Please see the following for details on the reliability of aluminum electrolytic capacitors.
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