The main performance symptoms of the low-voltage failure of the amperometric capacitor are
One: the voltage in actual application is much lower than the rated withstand voltage value of the capacitor, generally below 10% of the rated value.
Two: the capacitor will fail after damp heat test or humidity pretreatment.
Three: the capacitor will return to normal after high heat test or board baking from damp heat test and damp pre-treatment.
Four: Or remove the failed capacitor from the circuit board and add higher point voltage at both ends, about 60%-75% of the rated value, the performance of the capacitor will return to normal.
Then why there is a low voltage failure of the safety capacitor and what is the reason?
In fact, the encapsulated shell is not completely dense, which gives the possibility of moisture infiltration. For example, if the capacitor with 50V withstanding voltage is infiltrated, when 5V voltage is added at both ends of the capacitor, the moisture attached to the dielectric becomes a leakage current, but because of the low voltage, the leakage current is not very large, and the heat generated by the impedance of the path is not large enough to heat the water vapor and evaporate it, but it is enough to destroy the energy storage characteristics of the capacitor. Thus, the amperometric capacitor fails