I’m running into an issue with solder mask clearances in a custom footprint and could use some advice. Here’s the situation:
I’m trying to use a negative solder mask clearance (e.g., -0.3mm) on a pad in a footprint to protect the edges of the pad slightly. This works perfectly on the top layer—the mask adjusts as expected in the 3D viewer. However, when I apply the same negative clearance to the bottom layer of a mirrored pad, it doesn’t seem to take effect. The bottom layer mask remains unchanged, as if the negative value is being ignored.
Details:
KiCad Version: 9.0 (stable, macOS)
Steps to reproduce: Set a negative solder mask clearance on a pad’s bottom layer in the footprint editor, then inspect in PCB Editor 3D viewer/Gerbers.
Is this a known limitation, a bug, or am I missing a workflow step?
I will wait 1…2 days until the bugfix is transferred to the 9.0.x series testing versions and see if the issue remains (== bugreport necessary) or if the issue is fixed.
You can install a 9.0.x “testing” version and see for yourself. The testing versions (not “nightly”!) are bugfix only, so there’s no danger, and you can install the latest release version back if needed, all 9.0 versions, including the testing versions, are file format compatible within 9.0 series.
Your issue was fixed by the linked gitlab issue.
Either wait for 9.0.1 or follow eeliks advice and install the most recent “testing” version.
On Win10/Win11 this minimal update works flawlessly, but I can’t say anything about the update on Mac.
