I would be grateful if someone could give me information, or a document(s) to reference on the post mechanical drill cleaning of multi-layer PC boards. I am looking for references to: a) De-smearing, the chemicals commonly used, the cost and why this would be necessary. b) Etch-back with the above information. c) Pumice wash with the above information. d) Any other cleaning techniques in common use. Many thanks in advance. Alan Cable Electro Scientific Industries