Tantalums give you the advantage of a high Capacitance per unit volume. Their
reliability is proportional to the applied voltage versus rated voltage,
operating temperature versus rated temperature and power dissipation
(Vripple*2*pi*f*C)
The do most often fail in a short circuit. They should be derated to a maximum
of 60% but no less than 40% in a hi-rel circuit. If there are a lot of spikes
on the bus they are attached to, then of course, their reliability will be
significantly lower, especially if the spikes are 50% OV or higher. If you
have a lot of spikes, then go for the aluminum electrolytics.
Hans
