Good old days, att lab got a paper outlined allowable rework that showed rework temp, time effect the reliability (set limit to allowable using accelerate life test to define it). IMC got higher resistance compare to the solderjoints. Thick IMC would eventually resulted high resistance joint, either by void formation or resistance change. You need to define it as your product requires. (For something that in the space, for example, you can not get customer repair and overhaul easily, caution should be taken. For a toy for your kid or 5 dollar watch, may not matter - provide you are not on road to airport. -------------------------- Sent using BlackBerry ----- Original Message ----- From: Stadem, Richard D. [mailto:[log in to unmask]] Sent: Thursday, June 02, 2011 09:19 AM To: [log in to unmask] <[log in to unmask]> Subject: Re: [TN] Re-balling BGAs I'm sorry, but I completely disagree with that logic. Rework is defined as bringing a component or CCA into full compliance with print requirements. If I have a BGA with SAC alloy balls, remove the SAC balls and re-attach Sn63 balls and use that re-balled BGA on a CCA whose print requires Sn63, then it is rework, not repair. One does not need to follow the original manufacturing method. That is completely irrelevant. You can rework a CCA (or a component) using hot gas, hot air, laser, solder iron, selective solder, selective vapor phase soldering, and any number of other methods. By your definition, any touchup done with a solder iron on a board that had been vapor-phase soldered would be considered a repair, and thus would require approval by the customer. Do you do that? -----Original Message----- From: [log in to unmask] [mailto:[log in to unmask]] Sent: Thursday, June 02, 2011 6:08 AM To: Stadem, Richard D. Subject: RE: Re-balling BGAs June 2, 2011 Because re-balling is not the original manufacturing method used by the part manufacturer and the difference between repair and rework is when you follow the original manufacturing method (like replacement of a part soldered on an assembly) it is considered a rework and not a repair. However, if you are not following the original manufacturing method it is considered a repair and therefore the process of re-balling is a repair not a rework. -----Original Message----- From: Stadem, Richard D. [mailto:[log in to unmask]] Sent: Wednesday, June 01, 2011 5:43 PM To: TechNet E-Mail Forum; Bogert, Gerald L (Contractor) Subject: RE: Re-balling BGAs Why would it be a repair? -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Gerald Bogert Sent: Wednesday, June 01, 2011 2:22 PM To: [log in to unmask] Subject: [TN] Re-balling BGAs June 1, 2011 Anyone have technical data to support (or not support) re-balling of BGAs to change from SAC balls to Pb balls??? My understanding is that because of the extra heat cycle involved, BGA manufacturers may not stand behind their part warranty if re-balling is done. I also seem to recall a technical poster or paper presented at IPC several years ago which I believe indicated a reduction in reliability of the part if it is re-balled. Also seems to me that if one were to re-ball a BGA, this would be a repair and not a reqork process and as such may require specific customer approval. ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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