Hello Dom,

Just put a fill on the solder mask layer.
You can do this in a footprint library part if you like as well.

regards,

Phil.

-----Original Message-----
From: Dom Bragge [mailto:[EMAIL PROTECTED]
Sent: Thursday, 29 January 2004 3:53 PM
To: protel
Subject: [PEDA] TO-220 4th pin?


I just would like to ask a question about how you handle TO-220 
footprints (& the like)...

I have the three (electrical) pin device, that's fine.
I'm placing the T)-220's flat on the board.

What if I want to (selectively) put copper on the top layer under the 
TO-220 & have a suitable soldermask antipad? This could aid in cooling 
without resorting to an actual heatsink.
How should I best do that?

Do I place on the board a free pad, rectangle, with a hole the same size

as the hole for the TO-220 tab? Seems a bit ugly, two holes etc etc but 
it should probably give me the SMask opening.

Do I make a 4pin lib part, have a 4th pin on the footprint being the 
large hole & add a polygon connected to that net? I suppose I'll have to

add an opening for the SMask on the TO-220 footprint as well.


What say you?

-- 
Regards,

Dom   99SESP6

Dom Bragge, CID MIEEE  | Silverbrook Research PL, PO Box 207
Snr PCB Layout Engr    | Balmain NSW 2041, AUSTRALIA
Ph +61-2-9818-6633xt163| [EMAIL PROTECTED]




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