More than 90% of the failures in tantalum solid-state
electrolytic capacitors are caused by shorts
or increased leakage current due to deterioration
of the dielectric thin film layer. A variety
of factors affect the reliability (failure rates)
of the tantalum solid-state electrolytic capacitors.
The factors having the largest impact on reliability
are the temperature, applied voltage, and series
resistance.

The failure rate for the tantalum solid
state electrolytic capacitors has been
set at <1% per 1000 hours (60% reliability
level) at 85°C, the rated voltage,
and a circuit resistance of 3 per volt.
(See the Elna catalog and technical notes.)
The mean time between failures (MTBF)
for this logarithmic reliability function
shows the same failure rate regardless
of the time. Also, the MTBF is the inverse
of the failure rate.

With the above settings, the MTBF = 1/(1x10-5)
= 1 x 105 Hours = more than 11.4 years