i have seen CSR13 Ta caps last for about 150 hours when reversed and then
short.
The failure rate is about 1000 to 10,000 times worse than correct polarity
configuration. Reversed life also depends on series resistance in circuit
(ohms/volt), See MIL-HDBK-217.
Best way to really find out is to run some on a life test with actual
reversed voltage and actual circit series resistance.
The Ta2O5 oxide film probably starts to thin out, (the reverse of the forming
process - DeForming) then it shorts out.
There is also a very accelerated failure rate if you exceed the voltage rating
with the correct polarity.
Paul Signorelli
Reliability Engineer
RW Systems
_______________________________________________________________________________
_
From: TechNet on Thu, Jun 25, 1998 18?41
Subject: Re: [TN] tantalum caps
To: [log in to unmask]@inetgw


I'd be very interested in hearing of anyone's
experience with polarized caps that survive
reverse polarity in circuit with power applied
over a long period of time.  We have done a
test with a SMT style cap that just sits there
for a while doing nothing.  I'm familiar with
reversed caps blowing up within a short period
of time.  These are different.  5 volt level
but tons of current if demanded.

Any ideas?  We are talking to the cap mfr,
but it's not getting anywhere ...

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