As a novel application of ECT (Eddy-Current Testing), an inspection method of printed circuit board using planar type ECT probe has been proposed [1], and verified to be useful for the detection of not only tiny disconnection but also chipping defect and imperfection of thickness which are hard-to-find by conventional image processing methods But, for the actual use of this method in in-site inspection, the image processing in addition to ECT data acquisition, which automatically detects the existence and position of the defect from the output signal of ECT probe, is indispensable. This paper describes one approach to this request based on the comparison of the ECT images. To make a correct judgement even when the defect signal is relatively smaller than others, the proposed method utilizes the correlation operation of the signals to emphasize the waveform similar to the defect signal.
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