I have a 0.167mm diameter via under a BGA component to provide ground connections to two adjacent pads (ENIG-finish PCB). Our PCB fab house recommended that we plug the via to prevent solder from flowing into the via which might leave the pads with insufficient solder.
I am using Altium Designer 20. I'm familiar with tenting vias with soldermask (I generally tent the top and leave the bottom open to avoid trapping heated gas). How do I specify that the via should be plugged? I haven't been able to find any appropriate property to set in Altium. Is this commonly done by callout on the drill guide layer or some other method?