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 Adding areas of resist to smt pads
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jlawton

United Kingdom
108 Posts

Posted - 19 Nov 2010 :  14:38:42  Show Profile  Visit jlawton's Homepage  Reply with Quote
I have created a smt Led part which has large pads (larger than the part) for heat dissipation reasons.

To prevent the component swimming about on the large pads I would like to add resist to the pads to define areas for solder and solder paste.

Can this be done for the library part - I don't want to modify a board with 50 - 90 leds on!

John

Iain Wilkie

United Kingdom
1015 Posts

Posted - 19 Nov 2010 :  16:32:39  Show Profile  Visit Iain Wilkie's Homepage  Reply with Quote
Just tried it .... yes you can. Make sure you construct the area where you want no resist and paste as "pads" ..... anything else use copper shape (filled) .... if the shape needs to be connected to the "pad" (and is touching it) in the properties box simply give it the pad number.

Iain
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jlawton

United Kingdom
108 Posts

Posted - 19 Nov 2010 :  17:06:40  Show Profile  Visit jlawton's Homepage  Reply with Quote
Thanks, that's very helpful.

John

John Lawton Electronics
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Peter Johnson

United Kingdom
498 Posts

Posted - 23 Nov 2010 :  11:51:20  Show Profile  Visit Peter Johnson's Homepage  Reply with Quote
The alternative method is to define custom resist and paste layers. You can edit an existing technology file and save it under a different name as 'your' copy. Use pad exceptions to change the pad size on the resist and paste layers, then add filled shapes on the layers to define any off-centre areas.

If you're adding shapes to the copper, then use the shape properties to link it to a pad by number. That way it will link to the same net as the pad.
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jlawton

United Kingdom
108 Posts

Posted - 24 Nov 2010 :  15:33:15  Show Profile  Visit jlawton's Homepage  Reply with Quote
Thanks Peter.

John

John Lawton Electronics
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