I've never had problems with playa dust (other than the usual corrosion - just wash everything when you get back) As far as soldering QFN parts is concerned -

I've never had problems with playa dust (other than the usual corrosion - just wash everything when you get back) As far as soldering QFN parts is concerned - hot plates suck because you can't control the reflow envelope - if you're doing it by hand I think better to use a hot air rework station, drop some paste on the pads, pop the die on top, fire up the air until you see it float on the liquid solder and let it cool - if it doesn't work rework is easy (heat it up again then lift it with tweezers. Alternately real reflow ovens are cheap from China