Steve, I think there would be no problem with the storage in itself, however, what happens when the part is to be used after 20 years. It might depend, as a certain person use to say, parts are used differently. A part that is vibrating or is part of moving function will react to small changes more than a 'stiff' one. I have seen flexes with sharp bends delaminate after long use. On the other side, non movable and fixed flexes in e.g. cameras seem to live for ever. And finally an example from a copiator used in one of our vehicles for 'desert' use. The machines had been half filled by sand, had been frequently used and under awful conditions. There was absolutely no problem with the large flex that operates the head. So, PI is very tough. The answer to your question is probably dependant of the application. Interesting case, I recognise your situation. Missiles, grenades and a lot of other mil stuff is often stored for many years, and are supposed to work instantly despite the long storage time. In such cases, there will be little wear with operational time only seconds or minutes and hence no problems. I suppose you get the best information from the PI manufacturers themselves. Would be surprised if someone at TN can give a real safe answer to your q. Good Luck. Who seekest will find. /Inge ----- Original Message ----- From: "Steve Kelly" <[log in to unmask]> To: <[log in to unmask]> Sent: Tuesday, July 14, 2009 10:28 PM Subject: Re: [TN] Storage life for rigid flex Hi Dave and all, 1)The rigid flex would be assembled 2) I have read all of the multitude reports on kapton and airplanes and the problems. In my opinion the problems where associated with kapton wiring (wire wrapped with kapton) - never seen any major problems with a flexible printed circuit board anymore than a standard rigid board. Build it right like the people at Rockwell for example expect and it will last a long, long time. So I go back to my question is polyimide rigid better in long term storage conditions than a high end FR-4. The operative word is storage - a finished assembly never used sitting in some bunker in the desert or Arctic that 20 years from now has to turn on. Regards Steve Kelly From: [log in to unmask] [mailto:[log in to unmask]] Sent: July-14-09 3:30 PM To: TechNet E-Mail Forum; Steve Kelly Cc: [log in to unmask] Subject: Re: [TN] Storage life for rigid flex Hi Steve - Wow, if you really are going to sit around for 20 years, I would make the pwb surface finish bare copper and apply an OSP treatment right before assembly. A good tin/lead finish might make 20 years self life but you are really on the edge. Good Luck. Dave Hillman Rockwell Collins [log in to unmask] Steve Kelly <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 07/14/2009 02:11 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Steve Kelly <[log in to unmask]> To [log in to unmask] cc Subject [TN] Storage life for rigid flex Good Afternoon, We have a program for some reasonably simple rigid flex (4-8 layer) where the requirement is a 20 year life in storage conditions from -40C to +125C. Is there any evidence that polyimide rigid material and pre-pregs would be better than a good FR-4 (170C) for long term reliability. Thanks. Steve Kelly Steve Kelly (PLEASE NOTE NEW E-MAIL ADDRESS) (416) 750-8433 (work) (416) 750-0016 (fax) (416) 577-8433 (cell) --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 847-615-7100 ext.2815 -----------------------------------------------------