Electro - Caps is it true they last longer at lower temperatures

[John Biles]

Hello Everyone,
Is it true that a electro capacitor last about 2000 hours at 85 degrees "C" if it is rated at 85 degrees "C" on it case.
I heard that as the running temperature goes down the life expectancy goes up. Is this true? If so by how much?

[Tekko]

Yes, they dry out faster in higher temps.

[Mr Evil]

Virtually everything lasts longer at lower temperatures. At 0K everything lasts forever!

As for how much longer, here's a quote from Wikipedia:

Since the electrolytes evaporate, design life is most often rated in hours at a set temperature. For example, typically as 2000 hours at 105 degrees Celsius (which is the highest working temperature). Design life doubles for each 10 degrees lower, reaching 15 years at 45 degrees.

[TwoSpoons]

Yep, double life for every 10C drop. I spent a lot of time measuring cap temperatures and calculating lifetimes while designing motor drive electronics for a washing machine manufacturer. The ripple current heating calcs were truly hideous, once you started adding harmonics.

[sam9]

Speaking of electros, when they fail (catastrophically) do they tend to fail short or open?

Second, are they flamable?

I've had them go phisssst in my face (I always wear eye protection) but nothing too dramatic so far.

The answers will guide something I've got floating around in my brain.

[mzzj]

Originally posted by sam9
Speaking of electros, when they fail (catastrophically) do they tend to fail short or open?

Normal failure is increase in internal resistance, but this is not so catastrofic, usually leading to reduced performance and ultimately completely non-functionin circuit.

Tantals are more famous of their violent behaviour, overvoltage spikes or reverse polarity causes them to short-circuit and explode violently.

[Enzo]

Lytics when failing catastrophically tend to short. Over time they dry out, but that would not be considered a right now failure.

Opens in my experience are more likely mechanical failure, probably due to stress on the lead coming out. Vibration can break the lead off of the innards.

But they can dry out to the point that they do little or nothing.

[sam9]

Thank you. That helps.

[Stocker]

Originally posted by Enzo

But they can dry out to the point that they do little or nothing.

Have I ever told the story about the oscilloscope I took apart, that one of the power supply caps had dried out to the point that, if shaken, it would rattle?

[Enzo]

There is music everywhere. Start a rhythm bandwith it.