Hi Technetters: We are having an outside lab do thermally stressed cross-sections on 5 layer rigid-flex product and are finding that some fail due to delamination of the coverfilm from the rigid layer and partial seperation on the internal pad. However this conditions do not exist in the "as is" cross-sections prior to thermal stress. The rigid-flex is 5 layer 0.040" thick with 2 layers of flex in between the rigid section. Layer 2 is the rigid solid ground. The delamination is only noticed on this ground layer where the coverfilm that acts as a pouch seem to seperate from the copper surface. The boards are Hot air levelled prior to thermal stress. The thermal stress is performed per IPC procedure at 540F for 10 sec. The drilled looks very good, plating is between 1.4 to 1.8 mils in the holes. The smallest via is only 13.5 mil drilled and the etchback is 0.2 to 0.5 mil. The rigid-flex is made with modified acrylic adhesive system for coverfilm and bonding. Can the thermal stress procedure induce these defects? Athough the boards have good plating and hole quality and pass as is cross-sections, are they rejects or is there any other tests that can be performed to prove that the boards are reliable? Thanks in advance for your help. Chetan Shah ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com ############################################################## 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 ##############################################################