I have noticed that the solder mask of my top layer to disappear over my big vias. I don’t want this so I ran a test. By increasing the drill size of my small vias, the solder mask disappears going from 0.5mm to 0.6mm. What is controlling this?
Ideally, I would like my vias covered but pads for devices not covered. I have two size vias: big 4.2mm and small 0.9mm. Those are the annular ring diameters. The drill sizes are 1.3mm and 0.4mm, respectively.
I am a beginner so I expect there is more to this issue. Can anyone advise me?