Francisco,

        It will be very difficult if not impossible to detect these
micro-cracks using X-ray. Two things --

        1.) Cracking usually occurs at the ball/component interface after
extended accelerated testing. Cracking at the ball/board interface
might suggest plating problems.
        2.) If your board is ceramic, monolithic, or very thin, you might be
able to detect the cracks using acoustic microscopy. Otherwise, your
best bet is to perform screens with in-situ electrical testing. As
Werner has mentioned a few times recently, a good screen for solder
joint defects is vibration at low temperatures.

If you have any additional questions, please feel free to contact me
directly.

Craig


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Dr. Craig Hillman
CALCE Electronic Products and Systems Consortium
University of Maryland
College Park, MD  20742
(301)-405-5316
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