Capacitor specs seem a little confusing about expected lifetimes. It seems to depend on various factors of temperature, current, frequency, etc.
Just as a general rule, how many continuous hours of operation would you expect from a electrolytic or tantalum capacitor assuming the charge/discharge cycle is fairly long at maybe 1 cycle per second?
Which will live longer, Electrolytic or Tantalum, and does packaging make much difference (SMD verses axial leads)?
-Bill
MnO2 tantalums, the common kind, will last forever if they're not stressed. High dV/dT (ie, high peak currents) can make them fail shorted or even explosive.
Aluminum electrolytics slowly lose water through the seals and eventually lose capacitance, very roughly half in 20 years? Depends on the construction quality. High temperature accelerates the dryout.
John
"John Larkin"
** Aluminium electros are made with excess electrolyte inside - to allow for evaporation loss over lifetime. The first sign that loss has reached the limit is the ESR (or internal impedance) begins to rise. Not until the ESR has risen by a large factor, maybe 10 to 100 times, will the actual capacitance value drop.This is the reason service techs always use ESR meters to test electros, rather than capacitance bridges.
Also, I have seen many electros that have good ESR readings and full capacitance when they are 50 years old.
.... Phil
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