Capacitors fail due to overvoltage, overcurrent, temperature extremes, moisture ingress, aging, manufacturing defects, and incorrect use, impacting circuit stability and performance.
Mica and tantalum capacitors are more likely to fail in the early period of use (early failure), while aluminum electrolytic capacitors are more likely to experience wear-out failure due to aging use. In the case of film capacitors, when a local short circuit failure occurs, the shorted area may temporarily self-heal.
What happens if a capacitor fails?
Power Failure: Capacitors are crucial for smoothing out voltage fluctuations in power supplies. A failed capacitor can lead to power failures or, in severe cases, damage to the power supply. Audio Noise: Audio equipment capacitors are used for signal coupling and noise filtering. Failure can introduce noise or distortions in the audio output.
Paper and plastic film capacitors are subject to two classic failure modes: opens or shorts. Included in these categories are intermittent opens, shorts or high resistance shorts. In addition to these failures, capacitors may fail due to capacitance drift, instability with temperature, high dissipation factor or low insulation resistance.
Generally, a capacitor is considered to have failed when its capacitance drops by 3% or more compared to its initial value. The probability that a failure will occur is called 'failure rate'. There are two types of failure rates: average failure rate and hazard rate (instantaneous failure rate).
What is the failure mode of a capacitor?
Electromigration is one of failure mechanisms of semiconductor, but the failure mode can appear as a short, open, or characteristic degradation. Capacitors have several failure modes, the degree of which depends on the type of capacitor (Table 1).
There are two main reasons why dissipation factors can cause capacitor failure. First, if the dissipation factor is too high, the capacitor will overheat and eventually catch fire. Second, if the dissipation factor is too high, the capacitor will lose its ability to hold a charge.