I could use some help. The last 3 boards I have ordered have had the same issue. Something I have done has caused the solder mask to very slightly separate between the pad and the plane. This is causing an issue for me if the solder makes a bit outside of the pad, it will cause the pad to short to the ground or power plane. I asked OshPark about it and they were very helpful explaining to me what I had done wrong. In trying to decipher the explanation I am googling for “Stop Mask Expansion” in KiCAD and I cannot figure out how the advice applies to KiCAD.
I would really appreciate it if someone could help me understand which KiCAD settings I need to change and then I will re-order the PCBs. I was able to get 1 of each board working so far, but it has been pretty time consuming.
Here is the feedback I received:
"The issue on this is that the board itself is fabricated without shorts, as expected. However, the stop mask aperture is so large that it can expose the nearby ground plane. Here’s a image of what the design calls for, with the green circle being the exposed area.
Because of this, it’s very easy to inadvertently short the ground plane to other signals, even if you’re careful with soldering.
There’s two relatively quick and easy ways to prevent this on future designs:
- Decrease the stop mask expansion. We recommend setting this to 2mils.
- Increase the ground plane isolation so it’s (mask expansion + 3mil). This is generally not the ideal solution, but is sometimes needed for smaller footprints.
With a 2 mil mask expansion, combined with our 3 mil mask shift, the exposed area around each pad will never be more than 5 mil from the pad edge. When factoring in a 6 mil ground pour isolation, you’ll always have at least 1 mil of purple solder resist protecting your ground plane from shorts."
Here’s my project: