Hello, 

We are currently using the Black Hole process in our double-sided shop and
have problems getting the surface clean enough to go directly into outer
layer imaging without scrubbing first. If we do not scrub we don't have
resist adhesion problems, but end up with electrical shorts due to
insufficient etching in spots. By scrubbing, we risk creating interfacial
voids on large PTH's (and have seen some). My question is for people using
Black Hole, Shadow or other similar technology. Do you have to scrub and
have you had similar experience? By the way, we use pumice scrub.