It is a measurement for the failure mode of units, especially of components.
It is important regarding examination of reliability.
The failure cause is the fraction of failures per time unit referred to the sum of an examined quantity.
If, e. g., an integrated circuit has a failure rate of 10-9 per hour, within one hour it will fail with a probability of 10-9. Or: In case of 109 circuits in average one failure per hour can be expected.
Within the elements-life time the failure rate is not always the same. Dependent on the time it follows the so-called bath-tub curve. This means, when an element is applied for the first time, it is high due to the so-called
Early failures, then it remains on the same level for a certain period of time, where the so-called
Random failures occur, and at the end of the life-time it rises due to the influence of the
Wear-out failures.
