Development of Automatic Detection Method for Cracks Originating at Side Face of Ceramic Parts. (1st Report). Detection of Diffused Light near Cracks and Development of Detection Method

Both surfaces of fine ceramics used for electric parts are covered with, for example, a resin, a ceramic alumina or a solder. An automatic optical method for detecting cracks originating at the side faces of ceramic parts, the surfaces of which are covered with the above-mentioned materials, has been developed and is reported in this work. A laser beam is diffused into the specimen by illumination onto the side faces through an objective lens. When the specimen has a crack near the laser spot, the diffused laser light is reflected by the crack and the amount of radiant exitance near the crack is increased. The image of the side face is enlarged by the objective lens and detected by a CCD camera. It is clarified experimentally that it is possible to recognize the region surrounded by a close-ended crack wider than 20μm and longer than 351im, or an open-ended crack longer than 50μm, by detecting signals higher than the average level with the CCD camera.