What happens if you over-voltage a ceramic capacitor

william chan

I have 22uF SMD 1210 ceramic capacitors rated at 16 volts.
Recently I applied about 25 volts continuously to about 20 of them, so far none has smoked or exploded. It has been 3 days.
I wonder how long they would last and what would be the failure modes.

kwinn

Like most components they probably have a safety margin in that voltage rating so they may be fine for a long time. Also, a steady voltage with little or no current in or out from the capacitor puts very little stress on it. Drawing pulsed currents such as you might have in a PWM circuit would stress them much more.

Peter Jakacki

Normally MLCCs are run at 50% of rated voltage to avoid wearout but since you are running at 150% you can expect wearout rather prematurely and at any time. Also if there are transient voltage spikes on top of the already 150% then expect more trouble. The trouble is that wearout is accumulative/iterative and before they fail completely you can have increased leakage and self-heating, and perhaps I would expect some capacitance change too. While you can play with this on the bench I wouldn't put any of those boards out in service anywhere until you have changed over the caps which are very easy to remove and replace manually anyway.

edit - found a pdf with a lot of info about failure mechanisms here