Comments are: * A good looking solder ball does not necessarily mean that you have a good solder connection between the ball and the pad. We've all seen a bright and shiney solder ball on the floor, but that doesn't mean there's a good metalurgical bond between the floor and the ball. * You probably can see the poor solder connection that your customer sees with Scanning Acoustic Microscopy (SAM) and avoid distructive techniques. [Pity, we do enjoy those distructive techniques.] Your local university probaly has a SAM machine and a technician to assist in your analysis.
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