Abstract

Today's printed circuit assemblies comprise of several layers with components populated on both sides of the PCBs. This presents challenges to conventional 2D nondestructive X-ray techniques due to shadowing and absorption of the x-ray energy. Tilting of the samples while imaging helps to get around this problem, however, often it might not always be adequate. This article proposes a non-destructive method for detecting solder defects at the second level interconnect using 3D X-ray tomography. A total of 6084 solder joints of 0.8mm and 0.5mm pitch BGAs were analyzed. Correlation between dye stain and package pull analysis and 3D-uCT X-ray revealed a 100% correlation. Virtual cross sections obtained using 3D x-ray tomography methods showed that it is possible to evaluate non-destructively the solder joint failure mode "H" known as "head-pillow or snowman" at the second level interconnect.

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