Feasibility of inspecting defects in printed circuit boards by using eddy-current testing techniques

摘要

The inspection of etching defects in an as-madeprinted circuit boards (PCBs) is an attractive application of eddy-current testing (ECT) technology, since ECT inspection hasvarious advantages such as non-contact, low stress, conductivetesting, and fast scanning. When the technique is applied to high-density PCBs, the difference from conventional approachesbecomes more remarkable. This paper describes the relationshipbetween the shape of the inductive sensor and the width of printedwiring. The evaluation of signal-to-noise ratio results obtained byexperiment clarifies the limits of detection. To improve inspectionfor higher-density PCBs requires a finer ECT sensor, but it wasconfirmed the defects in the printed wiring with a width less thanone third of the sensor pitch can be detected.