Dittos to all what Dwight said. . Seal bagging will prevent oxidation only. If warpage occurs during assembly, it can be corrected. Many boards are mounted in such a way that will make them flat. As long as warpage is within limits, it's fine. On the other hand, boards that need to slide into a card cage have to be straight or very little warpage, much less than the limits. Regards, Ramon. > -----Original Message----- > From: Dwight Mattix [SMTP:[log in to unmask]] > Sent: Wednesday, May 05, 2004 1:54 PM > To: [log in to unmask] > Subject: Re: [TN] Raw Card warpage > > At 12:09 PM 5/5/2004 -0500, Victor G. Hernandez wrote: > >Fellow TechNetters, > > > > At a PWB factory setting is a final baking process permissible to > >correct any warpage prior to customer shipment. > > Some customers allow it or do not specify either way. Some customers > specify against it. If not specified either way then tacit approval for > "flat baking" is generally assumed to be given. > > >Once the sealed bag is > >open and product not used for an extended period of time will the > >warpage return. > > Not necessarily. It will only rewarp if the pwb design is unbalanced > (either in dielectric stackup or in metal pattern distribution). An > unbalanced design will (re)warp to some degree when heated during solder > assembly. > > Dwight Mattix > Sr Staff QE, Corp Eng > > >Victor G. Hernandez > > > >--------------------------------------------------- > >Technet Mail List provided as a service by IPC using LISTSERV 1.8e > >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 or (re-start) delivery of Technet send e-mail to > >[log in to unmask]: SET Technet NOMAIL or (MAIL) > >To receive ONE mailing per day of all the posts: send e-mail to > >[log in to unmask]: SET Technet Digest > >Search the archives of previous posts at: http://listserv.ipc.org/archives > >Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 > >for additional information, or contact Keach Sasamori at [log in to unmask] or > >847-509-9700 ext.5315 > >----------------------------------------------------- > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 1.8e > 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) > To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest > Search the archives of previous posts at: http://listserv.ipc.org/archives > Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 > ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------