Ian, I would never dream of manually cracking a v-groove panel with SMT parts. Get a "pizza slicer" style depaneler. They can be had relatively cheap and work great. They put zero stress on the board. Even an inexpensive manual one is faster and more ergonomic than manually breaking them. -Mike -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea Sent: Friday, July 18, 2008 1:48 PM To: [log in to unmask] Subject: [TN] Mechanical damage to BGA Dear Technos, I have this BGA that gives me a headache. In many instances the boards do not pass test, we press on the BGA and they start working; a classic... The problem solder joints are always on the same side of the component and on the outer row; needless to say, we have a V-groove line that is manually cracked. So the cause is most likely mechanical stress that causes the pads to detach from the PCB. After prying off some BGAs we see the soldering is good, all the pads come off the board and stay solidly attached to the balls. The specifics of this board are a bit special and I would need your opinion on what to improve in the design in order to eliminate the propensity to damage. PCB is 18.55x28.65mm, FR4, 0.55mm [0.021"] thick The BGA is 17x17mm, 1mm pitch, 0.65mm balls assembled on 0.25mm circular pads. In the troubled zone the pads are connected to 0.050mm traces. My opinion is that the board flexes very easily and even if we fix the depanelization (I will modify the panel) all the subsequent handling, including the integration of this module, puts the joints at high risk. I think the pads are too small so they do not have sufficient adhesive force to stay put on the PCB. On top of it, the traces are so minute, so the slightest stress will be destructive. Would increasing the pad size help? Is this construction (thin PCB + superfine traces) viable? Could the CTE mismatch be strong enough to cause the damage, instead of the mechanical stress from bending the board? Thank you, Ioan --------------------------------------------------- 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 -----------------------------------------------------