I have a question about footprints for QFN packages. Specifically the solder paste/mask for the center thermal pad
I am using my first QFN package and I thought I would read up on it a little since I didn't want any problems during production. I came across the following two documents on the web. http://www.wolfsonmicro.com/uploads/documents/WAN0118.pdf http://www.ssec.honeywell.com/microwave/appnotes/QFNsolder-AN310.pdf Both documents state that the center pad on the QFN should be only be %50 covered by solder paste and the Wolfson document stated that the solder paste should be in a star shape and that any via's should not be covered by the solder paste. Are they correct, only have %50 of the pad covered with solder paste or does it matter? Also if they are correct how do I change the solder mask in Protel 99 SE? For the solder mask I always just place a pad and let Protel do the work. In case you are curious I am using a Maxim footprint, 16-QFN thin 5x5x0.8mm. As far as QFN's go it is pretty forgiving with a pad width of 0.3mm (not the center pad) and a pad spacing of 0.8mm (http://www.maxim-ic.com/cgi-bin/packages?Type=Max) Trent ____________________________________________________________ You are subscribed to the PEDA discussion forum To Post messages: mailto:[email protected] Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/peda_techservinc.com Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected] Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected]
