As the design stands now there is no stiffener under the bga. Design has placed approx 100 test pads on the opposite side of this bga and I raised the concern that 100 po-go pins at 6oz of force works out to 37.5 lb of force. I think this is significant enough to cause failure, however I have been unsuccessful in convincing design otherwise. To bolster my position I have started investigating if there is any research into this area. Such as given a certain BGA size, how close and with what max force can test pads be placed. It has been decided not to underfill the BGA prior to the in-circuit-test. This decision was made based on ease of rework. Regards G. Alfson -----Original Message----- From: Eric Christison [mailto:[log in to unmask]] Sent: Wednesday, April 10, 2002 7:37 AM To: [log in to unmask] Subject: Re: [TN] BGA flex circuit failure Hi Geordie, I presume there's a stiffener underneath the BGA device? Provided it's substantial enough eg, steel or FR4 rather than polyimide AND it extends a little way past the ball pattern the design should be reasonably robust. Do you also underfill the BGA? Regards, [log in to unmask] wrote: > I guess my first question is why are you mounting the BGA a flex circuit ?? > The potential for fractures due to lack of a strain relief is HUGH. Really > need a solid surface to mount the BGA to. > > Randy Bock Sr. > Quality Manage > Bryce Office Systems LLC > email [log in to unmask] > > ----- Original Message ----- > From: Alfson, Geordie (STP) <[log in to unmask]> > To: <[log in to unmask]> > Sent: Tuesday, April 09, 2002 3:50 PM > Subject: [TN] BGA flex circuit failure > > > Greetings, > > > > I work as a test engineer for a medical device maker. I found this forum > by > > way of the Circuits Assembly web site. > > > > My area of concern, as a test engineer, is the probing of test pads on > > flexible double sided PCA's, especially when test pads are located on the > > opposite side of a BGA. I am concerned that the probing force may result > in > > 1)solder joint fracture 2) de-lamination of the PCA 3) dislodgement of > > components, just to name a few. > > > > Do you know of any research (published papers) or colleagues with > knowledge > > in this area of flex circuits that can assist me. I want to establish test > > pin density and force limits and board layout criteria so I (hopefully) > can > > prevent PCA failure at the testing phase. > > > > Thank you > > > > Geordie Alfson > > [log in to unmask] > > Test Fixture Mechanical Engineer > > Guidant Corp > > Tel 651-582-7635 Fax 651-582-7599 > > > > -------------------------------------------------------------------------- > ------- > > Technet Mail List provided as a free service by IPC using LISTSERV 1.8d > > 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 delivery of Technet send e-mail to [log in to unmask]: > SET Technet NOMAIL > > 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/html/forum.htm for additional > > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 > ext.5315 > > -------------------------------------------------------------------------- > ------- > > > > ---------------------------------------------------------------------------- ----- > Technet Mail List provided as a free service by IPC using LISTSERV 1.8d > 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL > 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/html/forum.htm for additional > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 > ---------------------------------------------------------------------------- ----- -- Eric Christison Mechanical Engineer STMicroelectronics 33 Pinkhill Edinburgh EH12 7BF Tel: (0)131 336 6165 Fax: (0)131 336 6001 ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------