Ioan, Any chance the parts are MSL parts that were not properly stored and handled and they have pop corned, resulting in broken bond wires that are really, really close and when a temp change happens things touch. The other suggestions have been good too. Bev -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Brinkman, Mark Sent: September 23, 2005 3:59 PM To: [log in to unmask] Subject: Re: [TN] Soldering or design problem? At this point I think I would try to isolate the problem by debugging the failing board. The designer should be able to find what is not working. He should know the sequence of events that should take place once power is applied to get the design up and running. He's going to have get dirty. Find the event that is not working. What would cause this event not to happen? Find it and see if it's the same on the other failed boards. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Tempea, Ioan Sent: Friday, September 23, 2005 2:40 PM To: [log in to unmask] Subject: [TN] Soldering or design problem? Hi Technos, we are faced here with a very delicate problem: the customer suspects a workmanship issue on our side, we are suspecting a design or component problem. Here it goes: 50% of the cards do not function due to the same problem, something wrong with the same PBGA. We tweaked the thermal recipe, we are at about 220C peak; no improvement. We played with lower temperatures for fear not to thermally stress the part; no improvement. Now I get into the weird zone: * if the BGA is heated, it instantly starts working, but also starts working if the BGA is frozen * it also works if we freeze the opposite side of the PCB * We use the flying probe to test for open joints, everything seems to be OK, but the card does not work * we did all kinds of re-reflow of the BGA on the bad boards, in the oven, but also on the rework station, even at extreme temperatures that send the top of the part at 280C. Same pattern, heat/freeze, it works, ambient temperature - fail. So we didn't even manage to kill the part for good. * we change the component, bingo, it works in 90% of the cases I am sure the soldering is OK and the joints are properly formed, but don't have a solid proof, for some people BGA soldering is still the cause of all problems. My question is: if it's not the soldering, what else can it be? Can an electronic design be borderline so that it does not work with the first time reflowed BGA, but works right after replacing the part with parts from the same tray? Can something be in the design of the PCB, in the manufacturing of the PCB? And a last one, what is the test that can confirm the absence of open joints under a BGA? Can the balls be cross-sectioned parallell with the PCB, like half-ball, so an eventual open be redily spotted? Thanks, Ioan --------------------------------------------------- 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 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- 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 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------------------------- This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. 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