Shape measurement of BGA for analysis of defects by X-ray imaging

This paper deals with the developmment of image analysis for the detection of defects at BGA solder joints in PC boards by using X-ray imaging. We can't detect visually defects at BGA solder joints, because they are hidden under the IC package. To improve a cost performance and the reliability of PC boards, an inspection of BGA is required in the surface mount process. Types of defects at BGA solder joints are solder bridge, missing connection, solder voids, open connection and miss-registration of parts. As we can find mostly solder bridge in these defects, we pick up this to detect solder bridge in a production line. The problems of image analysis for the detection of defects at BGA solder joints are the detection accuracy and image processing time according to a line speed of production. To get design data for the development of the inspection system, which can be used easily in the surface mount process, it is important to develop image analysis techniques based on X-ray image data. At the first step of our study, we attempt to measure the shape of BGA based on X-ray imaging.