Susan - The number of passes is very dependant on many factors. For instance, the severity of the reflow profile can degrade OSP's. Also, any flux or paste contact on the OSP finish will degrade the OSP. The OSP choice is also a major factor. There are many OSP choices, from simple mono-molecular types, like the Enthone CU-56 (typically good for one thermal excursion) to the more robust imidiazoles and modified imidiazoles. These latter types are designed to withstand multiple thermal cycles. The use of an inert atmosphere in the reflow oven will be expected to allow more thermal passes as well. Enthone is a leader in this technology. Hope this helps - regards Brian ############################################################## 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 Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################