A study of using nonnegative matrix factorization to detect solder-voids from radiographic images of solder

Accurate detection of voids in solder bumps on ball grid arrays (BGAs) is important for improving device quality. Radiographic imaging is commonly used to inspect BGA packages incorporate into LSI circuits. In the case of conventional method, imaging is normally done four times, and the images obtained are averaged to reduce noises. We have developed a nonnegative matrix factorization method for detecting solder-voids using only three radiographic images. Computer simulation demonstrated that it has the same level of accuracy as the conventional method.