To Richard Haynes Hi Richard, We have been having intermittent trouble with (what most people call) pits in electrolytic Cu plating. The location of these pits is always at the resist sidewall, they are always perfectly round, as are caused by bubbles. Popular opinion is that this has been caused by oxygen induction via filtration system. All four of the copper tanks we have are different in physical construction and to have all the tanks cavitating air at one time seems an outside possibility to me. However, we have asked for vendor guidance in new filtration system setup. Your comment on cathode-hydrogen evolution and oxygen evolution interested me and I have some questions: A vendor told me that there is no hydrogen evolution in acid copper as it is 100% efficient. I don't know. What physical characteristics do annodes exhibit when polizaration occurs? Is there extremely irregular surface? Can high chloride concentration also cause polizaration, i.e. 144 ppm? When I pull a sample in a glass flask and look at the amount of bubbles present, is turbidity the condition I'm looking for or the size/quantity of the bubbles present? I don't know what amount of bubbles should cause concern. Sorry if these are dumb questions. Thanks very much Sharon ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################