Capacitor Terms
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Capacitor Failure Rate
Failure Rate: The rate that a capacitor will suffer a failure as a function of temperature, applied voltage, and circuit impedance. Capacitors will experience failure at a rate depending almost exclusively upon the manner in which the capacitors are used.
Capacitor Failure Rates
The graph shows Temperature vs Failure Rate x Rated Voltage for Mil Spec capacitors designed to MIL-PFR-19978.
Note that for any given rated voltage, as the temperature is increased the failure rate increases. Also note that as the temperature is decreased the rated voltage is allowed to increase.
A related topic concerns Capacitor Derating. Limiting the operating temperature or rated voltage by design to increase the capacitors reliability and decrease its failure rate.
The two obvious rules of thumb are never operate the component at or near its rated temperature [never exceed the rated temperature], and design in a capacitor that does not operate at its rated voltage. Use a capacitor with a rated voltage that exceeds the applied voltage in the circuit.
