Hi Dave. eeh, FA? No, they wanted to solder to the bottom package after separating the two parts. The solder was SAC 305 to NiAu. I have never considered cutting as a method of separating parts. So, I've never seen the result. I recognized the non-solderable result but was surprised by the uniformity of the those few that fractured right along the package. I doubted that it had ever been properly soldered. It seems, from the reaction of the group, that some of the connections might well fracture along the intermetallic leaving an non-solderable surface. FA may be in order. But, I think we'll try desoldering before we cross-section. We have SEM, but we are separated by 1500 miles, and a level of fear. The project involves some pretty sensitive new product. If the reflowed solder connections look normal we'll assume the slicing procedure caused the condition. Thanks guys. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: Friday, November 20, 2009 4:13 PM To: [log in to unmask] Subject: Re: [TN] solder fracture solderable? Hi Guy! One of the first rules of failure analysis is to not contribute any additional damage to the article under assessment or to understand what type of damage contribution could be contributed if something is unavoidable. The cutting procedure you describe most certainly contributes additional damage to the BGA which you would not be able to differentiate from damage already in place. I do not believe the knife procedure you described is a good practice to use. Dave Hillman Rockwell Collins [log in to unmask] Guy Ramsey <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 11/20/2009 02:28 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Guy Ramsey <[log in to unmask]> To [log in to unmask] cc Subject [TN] solder fracture solderable? I was visiting a customer earlier this week. They were attempting to cut a the top part off of a package on package, BGA on top of BGA. They didn't want to reflow it off because they didn't want to damage the balls on the bottom of the bottom package. They had made a little fixture affair with two knives adjusted to slice between the two packages. They placed the PoP in the tool and pushed it through the knives, rotated 90 degrees and repeated the cycle. Most of the pads on top of the bottom package ended up with half a ball remaining on the pad. But some of the pads did not have any solder on them at all. The entire pad was mat finish silver in color. None of these features would accept solder. The number of pads without solder varied from one or two to 30% of the pads. I wondered if rather than cutting through, some of the connections has simply fractured along the intermetallic, leaving a non-solderable surface with this uniform appearance. Some of those observing conjectured that the package was bad, They conjectured that the silver was merely solder loaded with gold and that the nickel had never accepted solder. I asked where their SEM was and if they had EDAX equipment . . . nope. Would anyone care to guess along? How likely is it that prying off a BGA would fracture the connection right along the intermetallic and leave a completely non-solderable surface? --------------------------------------------------- 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 -----------------------------------------------------