Ed Anderson wrote:

Geeze, Jim.  Here I've been using tantalum capacitors in my circuit boards.  Are these failure modes spontaneous or are they triggered by something like over voltage, over temp, etc.  I guess I'm a bit surprised at the violence of their demise - I would think something like that would have curtailed their use in electronic circuits.

I've had the same experience, Ed.

In my case, I worked as a QA tester.  I stood at the end of an assembly line, and tested the circuit boards on a bed-of-nails test set.  One particular board used cheap tatalums, and when the vacuum sucked the board and power went to the nails, a random cap would pop, blow fire a foot high and stink to high heaven.  I was second shift, and management wouldn't believe what I was telling them until they started testing the same boards on first shift 8*)  THEN THEY BELIEVED, as they were shaking the poo out of their underwear.

The test engineer implemented a partial fix by ramping the voltage up much slower.  The initial charge inrush was responsible for finding many of the cheaper caps.  Or so he said.  It didn't cure the problem completely, but it did alleviate it some.

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