Steve,

Do you have XRay capability? Perhaps you could determine if shorting is site
specific or random. Also, you might be able to identify the shorted
components prior to removal allowing for better evaluation of root cause.

Thanks,
Robert Furrow
Printed Wiring Board Engineer
Strategic Supply Global Account Manager
Supply Chain Networks
Lucent Technologies
978-960-3224    [log in to unmask]

> -----Original Message-----
> From: Stephen R. Gregory [SMTP:[log in to unmask]]
> Sent: Tuesday, April 10, 2001 3:12 PM
> To:   [log in to unmask]
> Subject:      [TN] Caps shorting on bottomside after wave...
>
> 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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