Hi Bill - Baking multilayer boards prior to soldering is a technique many of us adopted in the late 1970's to "maximize delamination resistance". This method of removing absorbed water moisture was adopted after a considerable amount of work with the old classic FR-4 with a ~110C Tg. Baking was proven to restore Tg on moisture laden boards - we used 125C for 4 to 6 hours. You may want to sample some of your polyimide boards with TMA or DSC testing to determine whether Tg is up to the manufacturers range for your specific laminates. If Tg is normal, then there would seem to be no reason to bake. (I am assuming this is not an acrylic bonded rigid-flex.) As an alternative to baking, you might consider having the board fabricator package your boards in sealed vapor barrier bags (bulk quantities) immediately after final cleaning & post-lam bake. Keep the boards stored in the sealed bags until just prior to assembly. Got to remember, the additional heat cycle of baking is not going to improve solderability, and it will, at a minimum, cost you the handling and process labor. Regards - Kelly ################################################################ 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 ################################################################