Pete,

I think you misread the OP's email. He's not sandwiching soldermask
between the copper and a heatsink, he's just adding copper to the pcb as
a "just in case" type of situation. Of course, if you're using a
heatsink then you'd remove the mask.

-Jason


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Pete Houwen
Sent: Friday, September 10, 2010 8:03 AM
To: [log in to unmask]
Subject: Re: [TN] PCB Heatsink Pads

I'm not sure it's a violation, but certainly not common, and likely not
very 
effective at dissipating heat.

With no physical connection, and the solder mask in between, you aren't
going 
to dissipate enough heat to bother with the pad.  In the days of dry
film, it 
was a violation, but now the biggest concern is the time it takes to
answer 
the question each time.

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