Ken,

We have seen a similar thing happen with some thru-hole tantalums when they went through the wave solder machine.  I haven't heard of a recent problem with these. We never implemented a fix, it seemed the problem went away... or maybe we haven't made any of those boards in the recent past.

Phil 

-----Original Message-----
From: Ken Carlile [mailto:[log in to unmask]]
Sent: Thursday, March 07, 2002 1:58 PM
To: [log in to unmask]
Subject: [TN] Tantalum Capacitor Failure


I am wondering if anybody has had similiar issues or can help resolve
a failure we are experiencing.  On about 4% of our units at first time
power up 1 of two capacitors that are in parallel are burning up.  Upon
replacement the capacitor it to will work fine.
The cap we are using is Vishay Sprague 594D336X9035R2.  Since the other
capacitor in parallel is unaffected, I am assuming that it is a Vishay
issue.

Per Vishay:
The root cause of failure could not be identified. It is requested that the
failure circumstances be reviewed. Failures can occur due to thermal stress
during board mounting, strenuous application conditions, or because of
reduced capacitor capability. There was no specific evidence of reduced
capacitor capability identified. Please be aware, the thermal profile used
for board mounting, and the application conditions (even transient
conditions such as may occur with unregulated power supplies) can affect
product performance.

Has anyone else experienced a similiar failure or have an opinion?  I wish I
could pre-test the caps prior to them burning to supply an intact
capacitor to Vishay for their analysis.

Please note:  When allowed to play its course the cap turned red hot,
unsoldered itself from the PCB and burned a whole in the lab bench!

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