On Tue, Aug 21, 2012 at 11:09 PM, Forrest Christian wr= ote: > Not sure about specifics on each part, but I can tell you there is a lot = of > issues relating to correct assembly of those middle pads on QFN parts, > generally related to incorrect amounts of paste in the wrong spots > producing either voiding or issues where the rest of the qfn doesn't end = up > soldered up correctly. > > Personally, if it's truly optional, and not needed for heat dissipation, > I'm not sure I would even consider atttaching it. > > -forrest > A QFN center pad has to have less than 100% coverage of solder paste. I remember reading a technical note specifying around 50%. I think it creates a more reliable PCB to have the center pad soldered at least partially. --=20 Martin K. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .