HOLE POSITION DETECTOR FOR MULTI-LAYER PRINTED CIRCUIT BOARD EMPLOYING METAL PLATE AS CORE

摘要

PURPOSE:To detect the center position of a through hole accurately in a non- destructive and non-contact manner, by scanning the detection surface of a proximity switch which generates the oscillation amplitude varying according to the eddy current loss as detection output on a multi-layer printed circuit board. CONSTITUTION:A proximity switch 7 is so arranged that the oscillation amplitude at an oscillator section 7a changes due to an overcurrent loss as a metal material approaches a leakage magnetic field generated in an oscillation coil 7b and the output level varies according to the changes in the amplitude. A decision section 8 discriminates the coordinate point of the position where the output level of the proximity switch 7 decreases depending on the presence of a through hole while determining the center position based on the results of the discrimination. Then, the surface of a printed circuit board 4 is scanned with the proximity switch 7 to detect the position of the through hole with the decision section 8.