Using X-ray imaging for the study of crack development in solder reliability testing

Abstract

The possibility of monitoring the progressive damage and cracking in solder joints is investigated through a non-destructive method. As X-ray 3D Computed Tomography is known to require small sample dimensions in order to ensure a good resolution, Computed Laminography was used to get a high-resolution top view of various types of solder joints located on a large printed circuit board. In a first step, the assemblies were cross-sectioned after X-ray imaging in order to verify the findings and confirm the crack morphology. Then, by avoiding a destructive sample preparation step, it was possible to identify in a single sample the effects of solder fatigue during a standard reliability test. Firstly, multiple crack initiation sites could be highlighted in a single X-ray analysis. Moreover, the study gave an interesting insight of the time evolution of voids in solder joints. X-ray laminography produces 3D-like images that contain more information than a conventional cross section. By improving the recognition of horizontal cracks in this unusual point of view of solder joints, the refinement of this imaging and monitoring method can result in a real progress in failure analysis time and efficiency.