Lou, I believe there are two mechanisms that tend to deplete tin with time. The first and I think predominant one is that tin oxides form faster than the lead oxides. Therefore as you dross the solder pot, a higher percentage of tin is removed. The second factor is that intermetalics are generally Cu/Sn compounds. Therefore the tin is preferentially removed from the solder pot during intermetallic growth. This is not as big an issue with HASL finished boards as the majority of intermetallic is already formed. However, with OSP boards all the tin that forms intermetalics is coming from the solder pot. I hope this helps. Thanks, Robert Furrow SMT Process Engineer Lucent Technologies 978-960-3224 [log in to unmask] > -----Original Message----- > From: Lou Hart [SMTP:[log in to unmask]] > Sent: Monday, August 21, 2000 12:36 PM > To: [log in to unmask] > Subject: [TN] tin depletion > > TechNetters, is tin preferentially depleted from the solder pot in wave > soldering? If so, what is the mechanism? My recollection is that I > learned some months back that, left unadjusted, tin content of a solder > pot will slowly drop. Thanks for any comments. > > Lou Hart > > ############################################################## > TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for > additional > information. > If you need assistance - contact Keach Sasamori at [log in to unmask] or > 847-509-9700 ext.5315 > ############################################################## ############################################################## TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################