Steve We have seen this event before at CSL. This appears to be a soldermask that was was overcured at the fabricator and then more at wavesolder. The soldermask had poor adhesion to the copper ground areas and the temperature cycle conditions created the loss of the soldermask by lifting and peeling off. The rings appear to come from the thermal effects on the copper material from wave soldering. Look for soldermask flakes at the bottom of the chamber. Terry Munson --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------