Inspection of Bare Printed Circuit Board Using Planar Type ECT Probe

Abstract

The eddy‐current testing technique gives a new skill for inspection of bare printed circuit board (PCB). The combination of the high‐sensitive micro eddy‐current testing (ECT) probe and the image processing technique enables us to inspect defect (disconnection, and chipping crack) on the trace of bare PCB. This paper deals with the structure of the probe and characteristics to apply the ECT approach to the inspection of high‐density PCB. We proposed the ECT probes of the meander coil (transmitter) and Spin‐Valve Giant Magnetoresistance sensor(receiver). The high frequency excitation up to 5 MHz enables us to detect the disconnection on the trace of less than 100 μm width and 35 μm thickness.