We have experienced a random problem with three or four parts relative to rim
voids.

In some cases it was part of the lot and in others it was the whole lot. 

They have been partial, full, top and or bottom. (no consistency) 

They are typically one to two mils down from the surface copper and one to
three mils in height. 

They are not specific to any hole size. 

We use Dupont APG715 Dry Film, and develop on a Atotech/Chemcut horizontal
system using Potassium Carbonate.



I would appreciate any suggestions, as to the cause.