Richard, Our goal in baking the boards is to remove moisture which may lead to delamination during reflow or wave. If after baking the boards are stored in a drybox and then only taken out for processing (paste application, part installation) then you should be fine. The amount of moisture that has bee re-absorbed will be minimal. If, however, you keep the boards out in the air for awhile (some number of days, I am not sure how many), then you are correct, you will take in all of that moisture again. As far as moisture sensitive components are concerned, we bake those which are susceptible to "popcorning" when they go through the reflow oven. I agree that we should minimize the number of bakes and thus work to keep the moisture from getting into the boards in the first place. I hope this helps. -Steve Steven K. Lustig Process Engineer EMS Technologies, Inc. Norcross, GA (770) 263-9200 x4714 [log in to unmask] -----Original Message----- From: Richard Tilbrook [mailto:[log in to unmask]] Sent: Thursday, October 14, 1999 11:16 AM To: [log in to unmask] Subject: Re: [TN] Board Delamination . . . RT Steve, If you vacuum oven your boards (boiling off and evacuating any moisture), then open them into an environment, perhaps 22deg.C and 60%RH, won't the boards quickly absorb the moisture in that environment? If you then manufacture the boards, then ATE and inspect them, then conformal coat / dip them, you'll be sealing moisture in. I only ask because I am researching into moisture sensitive components, and one of the options is to put the components into a vacuum (oven / chamber). I am concerned that putting non-hermetically sealed electronics components (boards or devices) into a vacuum oven leads to little or no advantage, and only the acceleration of intermetallic formations between copper and tinned layer as a result. My question (finally) is would this be the case? Or would the rate of absorption be so slow that it wouldn't really matter? Regards, Richard Tilbrook ############################################################## 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 ############################################################## ############################################################## 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 ##############################################################