When Capacitors Spring Leaks

Partially leaked capacitors next to an AGP connectors.

Interior ESR is basically defined by the electrolyte's conductibility. Hence, electrolytes used in low ESR capacitors have to be especially conductive. To increase the conductibility of the electrolyte (mostly consisting of dispersants), you simply need to add additives. One of these additives is water. And because of this water allotment, the number of free ions and therefore the electronic conductibility increases.

However, unclean water can attack the aluminium body of the capacitor, which causes corrosion. The corrosion process creates gases on the inside of the body, increasing the interior pressure - you can watch the capacitor turn baggy. On the top, the aluminium body comes with a predetermined breaking point, so the gas can escape in case pressure gets too high. Yet, from time to time this breaking point will not rip and the capacitor will explode with a bang. The same thing happens in case of extreme overvoltage. The electrolyte still present can pollute the motherboard and cause short circuits, which might even set your computer on fire. Motherboard durability caused some manufacturers quite some problems between 1999 and 2005. Capacitors with improper or low-grade electrolytes were used, causing numerous failures and a drastic decrease in motherboard durability.

But not only unclean electrolytes can damage capacitors. Like any other liquid, the electrolyte can simply change its physical condition and evaporate. This happens not only when you operate your system, but can also occur while the system is shut down or the motherboard is stored somewhere. Not only components such as RAM and processors benefit from proper cooling of the computer case. Cooling also increases life expectancy of capacitors, since the probability of evaporation correlates with ambient temperature. An unwritten law says that a 10°C drop in temperature doubles the life expectancy of a capacitor.