Dear Lee: We are a rework and repair facility/training company. When we have done repairs of this type for our client per IPC7721 3.2 in the past and we used temperature and pressure (through fixturing) to "repair" these boards to where they can provide the form/fit/function intended for the PCB. In extreme cases you may need to also repair damaged laminate via IPC 7721 3.5.1. Regards Bob Wettermann BEST Inc --- On Mon, 2/1/10, Paul Edwards <[log in to unmask]> wrote: From: Paul Edwards <[log in to unmask]> Subject: Re: [TN] IPC-7721 LESSONS LEARNED To: [log in to unmask] Date: Monday, February 1, 2010, 1:46 PM Lee, What we do occasionally is to take the PCBs put them on the belt in a reflow oven and run them to just under reflow temperatures for in an extended profile... Need to set the oven for a balanced thermal exposure and partial moisture bake-out...Baking the PCBs ahead of time helps a lot... Pushing the PCB over Tg seem to relieve the stress in the PCB... DANGER... This may effect the number of thermal cycles you can put on the PCB. Also depending on the cooling rate and thermal balance you may have additional warping... I always talk to my customer first then try one PCB... Paul Paul Edwards Surface Art Engineering -----Original Message----- From: [log in to unmask] [mailto:[log in to unmask]] Sent: Monday, February 01, 2010 11:20 AM To: TechNet E-Mail Forum; Paul Edwards Subject: RE: [TN] IPC-7721 LESSONS LEARNED No - These are bare unpopulated boards. Lee Whiteman, PMP Senior Member Engineering Staff L-3 Communications East Telephone: (856) 338-3508 FAX: (856) 338-2906 E-Mail: [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Edwards Sent: Monday, February 01, 2010 2:19 PM To: [log in to unmask] Subject: Re: [TN] IPC-7721 LESSONS LEARNED Lee, Are these populated PCBs? Paul Paul Edwards Surface Art Engineering -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee Whiteman Sent: Monday, February 01, 2010 7:07 AM To: [log in to unmask] Subject: [TN] IPC-7721 LESSONS LEARNED We got some boards that are warped (bent & twisted that exceeded the flatness requirements per the J-STD-001). IPC-7721 has a repair procedure for warped boards. I'm getting a copy of IPC-7721 so I can familiarize myself with the process. In the meantime, does anyone have any "lessons learned" from using this procedure? THANKS. Lee Whiteman, PMP Senior Member Engineering Staff L-3 Communications East Telephone: (856) 338-3508 FAX: (856) 338-2906 E-Mail: [log in to unmask] --------------------------------------------------- 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 ----------------------------------------------------- ======================================================================== ====== This email and any attachments thereto may contain private, confidential, and privileged material for the sole use of the intended recipient. 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