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April 2001

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Subject:
From:
"Stephen R. Gregory" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 10 Apr 2001 15:12:05 EDT
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Hi all!

This is a weird one for me. We've got some boards that have 1210  .1uf
capacitors epoxied on the bottom and are waved. Test is now telling me that
there are capacitors shorted on the bottom...they can't tell me which one (or
ones) because they are all in parallel in the circuit, and they can't tell
which one it is. So what test does is give the boards back to the operators
and have them take all the caps off (over 100) and hand solder them back on
the boards...then the board will pass test.

I stencil the glue down (I use loctite 368), the glue apertures in the
stencil more or less creates a dam of glue bewteen each pad. See the picture
at:

http://www.xdrive.com/share/986929035134m7P20WC5Rnno6fT1pb7n

I don't see how in the world a cap would short given the way the glue is
printed. I have not been able to physically see a short, nor has one been
shown to me. Test is just telling me there is a short, and when all the caps
get removed and then resoldered back down the board works...

Has anybody else ever had this weird problem? This just started here
recently...

Thanks!

-Steve Gregory-

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