A study on test image production using frequency domain correlation with convex function for radiographic inspection equipments

X-ray inspection is frequently used to inspect the solder bonds of surface-mounted components. This is especially true for LSIs since visual examination is made impossible because the package covers the BGA. The inherent instability of X-ray inspection and the low SNR of the resulting images are commonly offset by averaging a number of images; unfortunately, this increases the time taken. Our solution is to use fewer inspection images but achieve acceptable image quality by correlating them to a reference image by an image processing technique in the frequency domain.