Steve: Presume you mean stripping resist from Tin/Lead plated boards using Caustic Soda. Tin/Lead is about the only thing you can strip well using caustic, other than innerlayers, as the Tin is so readily attacked using Caustic. However, when the Caustic gets to the Lead it stops, so you get a buildup of Tin in the Caustic, which then can immersion plate on to the exposed Copper. Caustic is the slowest, worst stripper for photoresist that you can use, and if you overplate at all, it becomes a near miracle that you can strip the photoresist cleanly enough to etch properly. All around, there is a good reason why most shops in the US strip outers using proprietary strippers, and I suspect you are more familiar with these reasons than most people. There has been some movement in the direction of making additives for Caustic to assist in alleviating some of these issues, and with Tin/Lead, they turn it into a manageable situation. Are there any more specific questions that we can answer? Rudy Sedlak RD Chemical Company ################################################################ 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 ################################################################