Earl, one test I've been performing is a somewhat suggestive ball shear
test, where I grab a ball with a pair of stiff tweezers and slowly rock it
back and forth until it shears off.  Looking at the fracture surface, you
want to see complete solder coverage on the component.  One other thing...
when looking at my balls under a microscope (no jokes, please) I can see
probe marks from the electrical tester.  These marks are not located on the
top of the ball but on the side, meaning that the test probes contact the
side of the ball.  (This was verified by the supplier.)  Could this be
overstressing marginal solder joints?  Who knows?

Jim Marsico
Senior Engineer
Production Engineering
EDO Electronics Systems Group
[log in to unmask] <mailto:[log in to unmask]>
631-595-5879


        -----Original Message-----
        From:   Earl Moon [SMTP:[log in to unmask]]
        Sent:   Thursday, March 14, 2002 3:08 AM
        To:     [log in to unmask]
        Subject:        Re: [TN] Earls pics are up, and a question...

        I hear you Dave. Over the years doing BGA stuff, I developed a very
        calibrated index finger and thumb. The whole thing about these
devices and
        their balls, has always facinated me.

        Earl on, I began using my talented digits attempting to dislodge the
little
        bastards. I know what it takes, and for all the other balls on these
crap
        devices, they pass my test. They adhere very well. It's after
they're
        soldered when most of the problems, besides as received, occur.

        Earl


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