I have gotten excessive solder/shorts where vias are located (in my opinion)
too close to the ends of the pads and end up with, certain PCB
manufacturers, solder mask lumps on top of the vias (probably because the
vias are tented and not encroached) which (of course) raises the stencil up
where upon you loose gasketing and you have a mass of excessive solder.

Aside from that did you adjust the apertures of the pads to be less than its
dimensions to allow for stencil/printing/PCB tolerances?

Dorothy Lush

> ----------
> From:         Michael Bell[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.
> Sent:         Tuesday, November 06, 2001 2:13 PM
> To:   [log in to unmask]
> Subject:      QFP Solder Pad  Shorts
>
> Hi all,
>
> I have just come across a problem with a reflowed PCB that has a footprint
> for a QFP on it, but no QFP placed.  It seems the footprint has paste
> stenciled onto it, various other components placed, and then reflowed.
> However, after reflow, it is notorious for having a number of solder
> shorts.
> We have tried masking off the apetures in the stencil to avoid depositing
> paste on the pads, but I am noticing wear on the stencil.  Has anyone got
> any ideas of what is causing the solder shorts between the pads, or how to
> solve this???
>
> Cheers
>
> Mike
>
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