Hello,
I have a large two layer board that is driving high power LEDs. The bottom layer is a thermal ground layer with many stitching via’s to help dissipate heat. The bottom will be attached to a solid aluminum heatsink. I can have the fab house not apply any soldermask to the bottom layer, but since there are other traces and small pours on that layer, will short out unless we use a electrically insulative heatsink.
That is possible, but will add to the cost, and will make the thermals not as good. So Ideally, I will have mask removed from only the ground pour, and the mount holes, but nothing else. So is there any easy way to have a mask drawn on the entirety of my pour, to show where the mask is to be removed? Since there’s traces and small pours for LEDs, there’s no way to do it by hand.
Attached is an image of my bottom layer. The main pour is ground, the rest are misc traces.
There’s (of course) no direct way to do it, but you could try this kind of workaround.
After you have generated gerbers, copy the board file. You need only the B.Cu layer there. Use Edit->Global Deletions. Delete everything except zones. Now you should have the shape of the GND copper pour in the layer. You can draw manually if you need more mask removed but not get back removed copper. If you need more mask you have to draw keepout zones to the copper layer and refill before deleting items. Plot the gerber of that layer. Make sure you don’t hit B by accident and don’t run zone fill in plot dialog. Change the gerber name to B.Mask.
