I have used quite a few QFN parts (analog) that use the paddle as an ground connection so check the datasheet very  carefully.  It's not entirely obvious, esp. with Maxim parts.

Bob Landman

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Pete Houwen
Sent: Thursday, June 03, 2010 10:10 AM
To: [log in to unmask]
Subject: Re: [TN] Relying on soldermask as an insulator

routing should NEVER be placed on the top layer under a QFN.  That "big 
paddle" is a heatsink, and should be soldered to a pad on the board.   And 
even if you choose not to solder it, how can you inspect production quantity boards well enough to be sure the mask is providing adequate insulation?  It's just asking for trouble.

(but I have seen it done)



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