Thanks for yours and Vladimir's comments. These are SAC balls. We don't have any SEM available. These are the best magnification we can come up with right now. We have better microscope images that we can see, but the camera is not on the best microscope. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: May 28, 2010 12:24 PM To: [log in to unmask] Subject: Re: [TN] Crystalline solder balls Hi Genny - yes, these structures have been reported in the industry before so you are in luck. If these were tin/lead solderballs, you most likely are looking at copper/tin intermetallic needles structures and if these are SAC305 solderballs, you are most likely looking at silver/nickel intermetallic needles. These structures are an indication that the original reflow solder profile or the rework profile was temperature/time excessive. Once the intermetallic phases form, they have melting points much higher than the surrounding solder so when you removed the BGA component, they become more visible as the solder joint volume is removed. A second root cause would be incorrect metallurgical composition issues. Nice photo - the first one is going into my photo gallery. Do you have any higher magnification shots? Dave Hillman Rockwell Collins [log in to unmask] Genny Gibbard <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 05/28/2010 12:52 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Genny Gibbard <[log in to unmask]> To [log in to unmask] cc Subject [TN] Crystalline solder balls http://ipc-technet.groupsite.com/gallery/13595 May not get many responses on a Friday before a long weekend, but your ideas on what I am seeing is appreciated. Sorry the camera on our microscope is not great. This is some of what remains on a board after a BGA is removed with a Summit hot air rework station. > Genny ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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