Ken,
        There are some problems with aluminum electrolytic chip caps in that
the dielectric tends to leak out at 220?C reflow temps.  I realize that not
all electrolytic caps are made equal, so some are completely unsolderable,
and some are O.K..  And I realize the pending tantalum cap shortage make
eletrolytics a necessary evil.  That said, top side of the board is usually
the last to be build on SMT, so that would be the best side for aluminum
electrolytic chip caps because it would see fewer thermal excursions.

        And what Steve said about the 1812's is exactly right.

Thanks

Ryan Grant
Advanced Technology Engineer
MCMS
(208) 898-1145
[log in to unmask]


> -----Original Message-----
> From: Ken Bloomquist [SMTP:[log in to unmask]]
> Sent: Wednesday, May 31, 2000 10:50 AM
> To:   [log in to unmask]
> Subject:      [TN] SMT Components
>
> Good Morning TechNet,
>
> I have a couple of questions on a couple of SMT parts.
>
> The First part is an aluminum electrolytic chip cap(wet cap)(SMT D Case).
> Does anyone know of any problems with these if used on the top side of the
> board?
>
> The Second part is a ceramic chip cap in a 1812 package. Again this part
> is
> on the top side of the board. Is the size of the part and the thermal
> coefficient difference great enough to cause solder joint cracking?
>
> Thanks in advance to all you SMT component experts!
>
> Ken Bloomquist
>
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