The laminating is done before the holes are drilled and plated. The effect of the curing cycle on reliability depends on the board thickness, plating thickness, copper ductility and hole quality. The thicker the board, the more stress will be put on the plated hole barrels. My guess would be that your single curing cycle would not cause a problem unless the board is extremely thick and has thin plating and/or rough hole walls. And in that case it would probably have been destroyed by the soldering process. The FR4 will probably just cure some more. To be on the safe side, why not use 180 deg. Tg multifunctional FR4 or other higher temperature material to be decrease Z-axis expansion? Nick Wander Unisys, Roseville, MN ---------- From: [log in to unmask][SMTP:[log in to unmask]] Sent: Monday, February 03, 1997 11:03 PM To: [log in to unmask] Subject: PCBs at 150oC for more than 2 hours Hi TechNetters! We use a multilayer pcb made from basically FR4 with a Tg of 135oC. There are pths, blind microvias, buried vias and some fine line wiring (only on top and bottom). One of our processing steps in building up the assembly (after smd-soldering both sides and cleaning) is die attach with an adhesive. The recommended curing cycle of the adhesive is 1 h (actual it may be 2h ore more) at 150oC and is done in a convection oven under normal atmosphere. I am interested in the cons of above curing temperature and time. Are there any reliability issues concerning the pcb? To my knowledge, laminating the pcb's by the manufacturer is done at even higher temperatures (although under vacuum). Any comments are welcome. Ulrich Korndorfer *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************