On Wed, 20 Feb 2019 09:03:47 -0600, Dave Schaefer <[log in to unmask]> wrote:

>This might help .. define your via so that mask covers a portion of the pad but leaves the hole open.
>Example:
>Pad 0.020"
>Drill 0.010"
>Soldermask 0.014"
>
>Obviously makes sense to factor in the soldermask "minimum dam" from your fabricator when adjusting your design / libraries.
>
>Hth,
>Dave

Yes, we are already doing that on the top side, but leave vias fully exposed on the bottom for ICT.

Anyway, I have only heard of slivers being related to the space between rectangular pads. 
This new supplier is flagging round to round so I wanted a sanity check...
thanks everyone