When I image a board using nickel/gold as an etch resist on part of the panel and solder as an etch resist on another area, when I etch in alkaline etch the copper near the solder area etches much slower than the copper near the nickel gold. The electropotentials of the metals are different enough to explain the differences in etch rate. My question is this; when we use tin as an etch resist we seem to get much more undercut than when we use solder as an etch resist. Can this difference in copper etch rate be explained the same way? ################################################################ 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 ################################################################