What causes a capacitor to blow?

Answer 1

Capacitors can fail for a few reasons, and sometimes the do "blow".

Capacitors have voltage limitations which, if they are exceeded may cause internal arcing or flashover. Once initiated, arcing can cause sudden heating and if the circuit supports high enough energy the capacitor can be damaged and may actually come apart. For polarized capacitors, reversing the polarity may even result in catastrophic failure at normal voltage levels.

Another reason capacitors fail is as a result of high current. If a capacitor is subjected to high frequency currents of sufficient magnitude internal heating can result and once again damage will result. With enough energy it may come apart.

One last way capacitors may be damaged is through sudden discharge. Generally high voltage ceramic capacitors may be charged to high energy levels. With a sudden discharge ceramic capacitors can respond with a piezoelectric effect and the ceramic may actually shatter.

Answer 2

There are four main causes of capacitor failure.

First is defective capacitors. Now that almost all our parts come from China, this is becoming WAY too common.

Second is overvoltage - after bad parts, THE most common reason they fail.

Third is reverse voltage. Electrolytic capacitors (aluminum electrolytic and tantalum electrolytic alike) are polarized. Put positive voltage on the negative lead and...pop.

And fourth is overheating.

Age used to be a big problem with electrolytics; before they learned how to seal the cans, the electrolyte would dry out and the capacitor stopped working.

Answer 3

A problem with electrolytic capacitors is moisture getting into the electrolyte, this causes "clicks" in power amplifiers.

Answer 4

due to too much heat, just worn out, water, or just loose connections.

Answer 5

Overvoltage - usually the capacitor have it's voltage, Charging the capacitor over the limit can cause burned capacitor