On Sep 26, 2004, at 1:11 AM, Russell McMahon wrote:

> - When a tantalum capacitor is connected to a "high energy" source
> (power supply rail) and is subject to an over-voltage spike of
> relatively low magnitude, the capacitor can (and often does) fail
> short circuit and allow destructive dissipation in the capacitor.

Perhaps the problem is no so much tantalum itself, but the trend
to put as much capacitance as possible in a package by fine-tuning
the voltage rating (dielectric thickness, presumably.)  Those 4V
470uF tantalums are very impressive, I'm sure, but perhaps it was
a bad idea to expect them to work on your 3.3V power supply rail.

Likewise, I wonder if the older tantalums (16V and higher?) had
the same failure mode, or whether they were just inherently made
with more leeway in their voltage spec...

And then there's the fact that it's hard to tell whether those little
SMT packages sprinkled all over the power supply rails are tantalums,
or something newer (niobium, aluminum, etc) - WHEN I WAS A BOY...
you could tell whether a cap was tantalum just by looking at it.

If your (reasnoably overrated) tantalums are exploding on your
power supply rail because of over-voltage spikes, perhaps you
have more serious problems than the failure characteristics of
the caps themselves...

BillW

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