I do not know of an IPC criteria on this.  I have seen 25% (The BGA criteria) cited, but this is not, to my knowledge accurate.
The limits I have used in the past are 50% Coverage with no void exceeding 15% in the center and no more than 10% anywhere else.
I also used a 70% Coverage and 10% Void criteria for a very heat sensitive application.

Question 1: Is there now a citable IPC criteria? and if NO,
Question 2: What are some of this groups recommended criteria?

Thanks and Regards, Wayne Showers, NPI/Technical Manager, 4Front Solutions