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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
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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]>
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[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
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