Is this random with respect to location?  Is it particular to one part/supplier?

It seems very strange that a properly reflowed BGA solderball connection would "dewet" itself during a subsequent reflow operation.

A cross section after the first reflow will probably explain what happened.




-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Julie Silk
Sent: Thursday, June 30, 2011 3:29 PM
To: [log in to unmask]
Subject: Re: [TN] BGA ball dewet from substrate

The substrate pad shows an intermetallic layer, demonstrating that there had been a metallurgical bond.  Also, the surface of both pad and ball are smooth -- not a fracture, but as if reflowed.  I have a good picture from the FA report to share once I figure out how.  I believe that if you were to analyze the very first layer on the BGA substrate pad, it would have a layer of solder.

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