Wayne

Paste layer mods in decal

Discussion created by Wayne on Jan 14, 2013
Latest reply on Jan 17, 2013 by wolferm

Hi all,

I've been attempting this off and on for quite some time now.  I think I know the answer to the question but am interested if there are some insights out there....

 

In decal editor I create a part - say a QFN for this discussion - with a thermal pad in the center.  I add my vias through the different ways to do it.  Now I want to restrict the amount of solder that is placed during the stencil printing cycle so I want to add "X-outs" to the decal on the paste layer.

How do I do that.  I've tried every which way I can think of and still have not found it.  The closest I've gotten is by placing an unassociated piece of copper on layer 1 as the thermal pad, placed the vias, added copper on the soldermask layer to prevent mask from being applied and made my paste apertures on the paste layer, again using copper shapes.  The issue is, however, that because layer 1 copper shape is unassociated with a pin it will be not be tied to ground - and so will cause an issue with the vias that are tied to ground.  (Unless I add it to ground in the layout process which I'm trying to avoid having to do.)

Making the thermal pad connected to one of the ground vias seems to make that shape appear on all layers with no way to control/modify the aperture on the paste layer.

 

Anyone have any insights into doing this?  So far I've let me stencil manufacturer know which apertures I need X'ed out or thermaled...not an ideal situation.

 

I hope I've made the situation clear, if not, let me know.

 

Thanks in advance for any advice.

 

Wayne.

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