It would not be at all unexpected to observe a higher relative concentration of tin in an area determined to have a "thin" HAL deposit. The XRF is responding to the ratio of tin to lead, and given you are approaching the copper/solder interface, and more specifically the tin/copper interface, it would be naturally preferential to tin concentration. Sounds like you are within expected conditions, other than the thin solder deposits. May I assume they are on larger ground areas? There is a direct correlation between deposit thickness and area size under given conditions Hope this helps! Joseph Webb TET/Halco ################################################################ 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 ################################################################