I recently generated Gerbers for a design with some rounded rectangle pads. I usually use 1:1 pad to mask and let the fab optimize the mask. They flagged a DFM error because there is a flashed round pad inside the rounded rectangle which I think is drawn as a copper polygon on top of it. Their tool picked up the inside pad and made a circular mask opening instead of just enlarging the existing mask. I think I can fix it by making the pads regular rectangles but I wanted to see if anyone else had this issue with a fab house and how they handled it.
I’ve pasted some images below to show what I am describing.
Thanks for the reply. This is the footprint from the supplied libraries. The foot print name is “Connector_JST:JST_SH_SM02B-SRSS-TB_1x02-1MP_P1.00mm_Horizontal”. The pad was made as a rounded rectangle, not a custom shape.
Hm it seems kicad does indeed add a circle inside a roundrect pad when exporting gerbers. This shoudl however not matter to be honest. Not sure why it does for your manufacturers software. Is it possibly that they do not support rounded rectangle pads? (Gerber itself has no rounded rectangle code so the pad is build up from a polygon. Maybe your manufacturers software is too old to support polygons as pads.)
You could also ask over on the bugtracker for help. Maybe some devs know more about this.
I think the only reason it was flagged was because the soldermask is the same size and when the fab house receives the Gerbers it sees that the soldermask violates its clearance rules and then oversizes it for their process. The software is looking for the pad (I assume) and so it finds the round circle and not the rounded rectangle. The interesting thing is if the flashed circle is inside a rounded rectangle pad of the of the same diameter (rectangle width / height = circle diameter), then the fab house software picks it up.
I suspect I could just fix it by specifying a soldermask oversize specifically on those pads and then the fab house would just leave them alone in the first place. I was really just more curious why this was happening.
Well set the clearance to the required level then. Not just for the rounded rectangle pads but for the full board. (Or do you really want the manufacturer to modify your files without you being in control?)
If the rounded rectangle features in copper layers are flashed then there should not be any issues. Globally increasing should increase both these features. Yes, there will be an issue with the rounded rectangle feature if they are not in flash mode in the copper layer.