Capacitors of the same make/series that consistently fail in one amplifier while they rarely fail in a different make amp

[Perry Babin]

This is for car audio amplifiers but I doubt that matters. There are amplifiers that use the same make/series capacitor as a different manufacturer and they consistently fail in one brand. In the other they are OK. The amplifiers are from the same era. Is it possible that the heating profile used when flow-soldering the boards could be the reason for the failure? If not, any ideas on what the difference could be?

[dmill89]

This is for car audio amplifiers but I doubt that matters. There are amplifiers that use the same make/series capacitor as a different manufacturer and they consistently fail in one brand. In the other they are OK. The amplifiers are from the same era. Is it possible that the heating profile used when flow-soldering the boards could be the reason for the failure? If not, any ideas on what the difference could be?

Exposure to heat during assembly could potentially affect lifespan, but circuit design and component placement would also have a significant affect. In general electrolytic capacitor failure (aside from defective manufacturing and seal failure) is caused by heat and ripple. So a capacitor in a "dirty" circuit with lots of ripple and/or next to a hot running component will generally have a much shorter life than that same cap that is well cooled in a comparatively "clean" circuit.

[Perry Babin]

The primary-side filter caps can take a beating and those are the only ones that fail in some amps. Other amps have caps of various makes and series that fail throughout the amp, even in linear voltage regulators for the ±15v op-amp supplies. I'm sure that this is one of the questions that could never be answered definitively with so few specifics. I always blamed heating during assembly and wanted to know if is was ridiculous or something that could cause problems.

[momaka]

It's not something ridiculous. Overheating during assembly can compromise the seal of the cap. And from that point forward, it's just a matter of time (and more abuse from the circuit) before complete failure.

Another thing to be considered is vibration. If the cap is installed in equipment that sees a lot of vibration and if the in question is not glued or held down to the board properly to minimize vibration, that too can cause early / premature failure of the bung seal.

So there are a lot of factors really.

In general, when it comes to non-Japanese caps, anything is possible in terms of failure.

You mention you see this failure in one amp brand but not in others. Just curious how many times this was so we could say the results have statistical significance. If it was just with one or two amplifiers, I'd say we need to see more cases to confirm the results.