Abstract
The inspection of etching defects in an as-made printed circuit boards (PCBs) is an attractive application of eddy-current testing (ECT) technology, since ECT inspection has various advantages such as non-contact, low stress, conductive testing, and fast scanning. When the technique is applied to high-density PCBs, the difference from conventional approaches becomes more remarkable. This paper describes the relationship between the shape of the inductive sensor and the width of printed wiring. The evaluation of signal-to-noise ratio results obtained by experiment clarifies the limits of detection. To improve inspection for higher-density PCBs requires a finer ECT sensor, but it was confirmed the defects in the printed wiring with a width less than one third of the sensor pitch can be detected.
