Three-dimensional visualization of multilayered assemblies using X-ray laminography

The imaging technique of X-ray laminography is useful for studying defects in ball grid array, gull-wing and J-lead solder joints. In this process, X-ray images are made to depict cross-sectional planes in multilayered assemblies. It is desirable to be able to create a three-dimensional (3-D) visualization of the assembly by stacking a succession of laminographic cross sections of neighboring planes. In the past this has not been possible for highly layered assemblies because the images contain inherent blurring, which causes the signal-to noise ratio for a 3-D reconstruction to be extremely poor. This paper explains a technique for reconstructing accurate 3-D visualizations of assemblies based upon a small number of laminographic images. Experimental results are described that show that this technique is sensitive to small defects in metallic objects such as ball grid array (BGA) joints