Re: Use of Tantalums - DRSSTCs

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Esondrmn@xxxxxxx 

In a message dated 12/7/04 3:18:56 PM Pacific Standard Time, 
tesla@xxxxxxxxxx writes:

> Hi,
>
> Tantalum capacitors are known for not being terribly reliable.  They are
> very finely made and if there is any contamination they will fail in the
> future. Now a days, they are getting pretty good at making them
> however.  In high current applications, they can catch fire and burn up
> which is a real problem.
>
> In the case of Dan's controller board, the tantalums failing are the very
> least of "my" concerns though ;-)))  I will blow everything else up long
> before the tans decide to fail for whatever reason ;-)
>
> Cheers,
>
>      Terry


Back when I was in the Electrical Engineering business, we used to design 
tantalum caps into all our circuit boards as 5 v dc power filters.  I think 
they were 10 ufd 35 volt caps.  They had a small red dot on the + 
side.  Sometimes they were mis-marked by the supplier and sometimes our 
production facility would just install a few backwards.  It seems that they 
would work fine for 10, 20 or 30 minutes - just enough to test the product 
and ship it out the door.  Then after some time in use, they would self 
distruct, causing  a direct short across the + 5 volt supply.  Lots of 
smoke, burned up circuit boards, etc.  Even if they were installed properly 
it seems that a small percentage of them would eventually short.  We had a 
difficult time finding reliable suppliers of these tantalum caps.  Things 
have probably changed a lot - that was about 25 years ago.  They seemed 
like little time bombs just waiting to go off.  Some of our customers would 
not allow us to use them.

Ed Sonderman