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August 2014 • SMT Magazine 57 INtRODuCtION tO INLINE aXI tEChNOLOgy continues aRTIClE cover a different segment of manufacturing defects. While all three can detect gross faults such as opens, shorts and missing components. AXI specializes in solder joint integrity in- spection, revealing voids, non-wetting and poor wetting joints. Its unique capability to re- veal hidden solder joints, their deformities and faults makes AXI an indispensable component in maintaining a modern high yield electronics production. Image Quality and Enhancement Base X-ray imaging quality depends on key system components and their settings: namely the X-ray source tube, system resolution, power settings and magnification ratio. X-ray Magnification The wavelength of X-rays is about 100x shorter than of visible light. This enables the rays to penetrate through matter and explains why X-rays cannot be focused by lenses as visi- ble light and the image resolution depends sole- ly on the resolution of the system X-ray detec- Figure 13: The size of the focal spot directly impacts final image sharpness, but it also depends on the X-ray source power used for imaging. tor. In order to reveal more detail, X-ray systems employ geometric magnification by moving the source tube closer to the subject, which results in a larger shadow image that is projected onto the detector. As magnification of the radiographic "shad- ow" is increased geometrically (that is, by mov- ing the specimen toward the radiation source), the physical size of the source, or focal spot in- duces a penumbra, or blurry edge, in the X-ray shadow. Therefore, to increase magnification with- out increasing the image blur, manufacturers are compelled to reduce focal spot size, as seen in the figure below. Image Processing and Auto Focus Imaging Successful inspection of 3D X-ray data de- pends on accurate layer separation. Using laser height measurement to set up source and cam- era offset, laminography systems are therefore very sensitive to height measurement errors. Tomosynthesis allows automatic focusing of