Dear Ms Polmanteer, When we were building PWBs at GE Fanuc, we occasionally experienced the exact "pits" that you are describing. The primary cause invariably was supersaturation of the copper plating solution with air. The air was induced to the plating tank through the filtration system, and could be very difficult to trace. One thing that made troubleshooting difficult was that it took about 24 hours for the air to come "out of solution"-----just turning off your filters for "a little while" will not make this go away. Try leaving your filtration off overnight, and do not turn it back on until after you have plated a rack to look for pits the next morning (this assumes that you are not using liquid sparging). You may find your problem gone. I must credit the Tech guys at DuPont with this advice as they were the ones who pointed us in this direction initially. They used to have a tech paper on this. . . maybe it is still available. Greg Anderson Advanced Manufacturing Engineer GE Fanuc Automation, N.A. Charlottesville, VA e-mail: [log in to unmask] -----Original Message----- From: Sharon Polmanteer [SMTP:[log in to unmask]] Sent: Thursday, December 10, 1998 11:46 AM To: [log in to unmask] Subject: 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 ################################################################ ################################################################ 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 ################################################################