Development of an automatic detection machine for cracks originating at side faces of ceramic chips

Both surfaces of fine ceramics used for electronic 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 chips, the surfaces of which are covered with the men- tioned materials, is developed and is reported. A laser beam is diffused into the specimen by illumination onto the side faces through an objec- tive lens. When the specimen has a crack near the laser spot, the dif- fused 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 en- larged by the objective lens and detected by four photomultiplier tubes. It is clarified experimentally that it is possible to recognize the region sur- rounded by a close-ended crack wider than 20 mm and longer than 35 mm, or an open-ended crack longer than 50 mm, by detecting signals higher than the average level. Experimental results revel that the cracks in the ceramic parts can be detected automatically in a production line. © 2003 Society of Photo-Optical Instrumentation Engineers. (DOI: 10.1117/1.1553451)