The most sensitive parts are the leadless ones, such as Vishay/Sprague 195D or 596D.  I had some of these fail about 12 years ago and tried to contact them to see what I'd done to them or if there were any documented problems with that lot.  At first, Sprague told me there was no such lot number, so I sent the Certificate of Compliance, which stated the lot number, and was signed by the Quality guy who told me there was no such lot number (the most ironic fact I have seen in this kind of situation) .  This guy was much more interested in telling me I must have abused the part than helping me determine how I might have damaged it!  I switched to Nichicon, which has better parts but longer lead times.
 
Wayne Thayer

________________________________

From: TechNet on behalf of Stadem, Richard D.
Sent: Wed 10/24/2007 1:37 PM
To: [log in to unmask]
Subject: Re: [TN] Surface Mount Tantalum Capacitor Repair and Rework--Risks Involved



This type of rework should only be performed using either a hand-held
hot air gun (Hakko) or use the hot gas rework station, and should only
be done by a skilled operator. If the hot gas rework station is used, it
is not usually necessary to include a board pre-heat stage, just a
ramp-up to preheat the area from the top only using a small nozzle to
direct the air flow in the immediate vicinity of the capacitor and then
quickly lift it off. This can easily be accomplished without allowing
the PWB temperature to go above 125C. MLCCC capacitors should use the
same processes.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Chafin, Ken G.
Sent: Wednesday, October 24, 2007 10:22 AM
To: [log in to unmask]
Subject: [TN] Surface Mount Tantalum Capacitor Repair and Rework--Risks
Involved

I would be interested in receiving any literature on the above subject.
Approx. 8--9 years ago we encountered many failures because  we
outsourced some surface mount boards and the supplier did a lot of
repair and replacement of SMT tantalum capacitors using soldering irons.

Both Kemet and Vishay Sprague were helpful by providing Engineering
Bulletins on the risks involved in the hand soldering of SMT tantalum
Caps.
We are again contemplating outsourcing this type of rework.  We really
need to know the risks involved in doing this and how best to do the
rework if it must be done.

Any documents (or personal experience) you think might help with this
decision would be appreciated--- [log in to unmask]

Thanks

Kenneth Chafin


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