Even unabused conventional liquid electrolytic capacitors made by the most reputable manufacturers degrade by loss of electrolyte.
There is some gradual loss by evaporation past lead seal(s) even when idle at room temperature.
Loss is compounded if seals are thermally abused by soldering process and/or chemically compromised by cleaning solvents.
With respect to a given seal technology electrolyte loss is accelerated if the internal vapor pressure increases for any reason, such as:
- a higher vapor pressure electrolyte formulation is selected to achieve extended temperature operation (varies by mfg and exact capacitor model),
- breakdown of electrolyte either by electrolysis in operation with DC voltage applied or local corrosion electrolysis due to impurities in capacitor internal construction
- high temperature environment, storage and/or application
- elevated core temperature due to I^2*ESR internal heating where I is the ac ripple current in the particular application--Mfg specifies that operation lifetime spec'd will be met or exceeded in an endurance test using the associated AC ripple current specified combined with applied DC volts per the capacitor rating, and a mfg stated test temperature--The application should apply less than this spec'd datasheet current to achieve improved operation life hours beyond the life spec.
-sudden application of voltage to a capacitor that has sat idle for years, causing local overheating where oxide has not had time to reform, sometimes announcing itself with a chemical steam explosion.
In power supplies the highest ripple current rating cap choices should be preferred in the rail caps right after the rectifiers, both after the mains 50/60 Hz direct rectification, and after the high frequency inverter output rectification. But it would not hurt to pick high ripple current rated caps for the DC output rails after the chokes and the various linear regulators also that see ripple from the dynamic load currents.
Upsizing of capacitance value to achieve even lower ESR and higher ripple current specs should be avoided, this can increase turn on surge currents and if taken too far can let the magic smoke out of the rectifiers, which is often followed by steam explosions.
Absolutely avoid picking the caps in the catalog that have exceptionally low ripple ratings combined with the most compact packaging. Even the best mfgs have these in their catalogs for the small signal almost no power coupling applications where small size is required.
For motherboards Japanese solid electrolyte aluminum capacitors are the new thing, but I have no experience with these yet.
