I posted this just over a week ago, but didn't receive any responses.
Thought I'd try again

> We have a few PCB's that we use a SM IC power amp with a heat slug that is
> reflow soldered to the board.  We have a via hole pattern under the
> device, and the opp side of the board is exposed HASL finish gnd plane
> that is mounted against a metal heatsink.  As has been discussed on this
> forum, a problem with this design idea is during reflow, solder will tend
> to drain away from the slug through the vias, but we have generally had
> acceptable via fill by overprinting solder paste, except for a recent
> batch of boards.
> The bare boards had less consistent HASL finish leaving more solder on the
> gnd plane side in places, and the QA person is wondering if that may be
> the cause for increased solder drain?  Or alternatively if it is just
> related to reflow temp profile?  Or some combination of both?
>
> Genny

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