Method and apparatus for detecting through-hole voids in multi-l

Details Method and apparatus for detecting through-hole voids in multi-l Method and apparatus for detecting through-hole voids in multi-l

1988-06-22

1990-06-05

Willis, Davis L.

Optics: measuring and testing

Inspection of flaws or impurities

Bore inspection

356237, G01N 2188

Patent

active

049308904

ABSTRACT:
A method and apparatus for detecting through-hole voids in a multi-layer printed circuit board. The through-hole is formed with an electrical conductor for interconnecting wiring patterns of upper layers and wiring patterns of lower layers of the printed wiring board and is illuminated with a beam having a wavelength falling within a specified wavelength band capable of exciting an luminescent beam from a layer material. The layer material is exposed by a through-hole void in the through-hole of the printed wiring board. The luminescent beam excited by the illumination beam impinging upon the layer material by way of the through-hole void in the through-hole is focussed by means of a focussing optical system and a photoelectric converter. The photoelectric converter converts the luminescent beam into an electrical signal. The presence of a through-hole void is indicated by the electrical signal.

REFERENCES:
patent: 4145714 (1979-03-01), MacDonald et al.
patent: 4538909 (1985-09-01), Bible et al.
patent: 4679938 (1987-07-01), Flamholz
Ernst A. Gutbier, "A New Method of Inspecting Plated-Through-Hole Connections", Processing Technical Program Natl., Electron Packaging Production Conference, Vol. 1974, pp. 56-62, (1974).

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