Automatic circuit board tester

• US 4,240,750 A
• Filed: 10/02/1978
• Issued: 12/23/1980
• Est. Priority Date: 10/02/1978
• Status: Expired due to Term

• Current Assignee: Robert L. Kurtz, William A. Hurd
• Original Assignee: Robert L. Kurtz, William A. Hurd
• Inventors: Kurtz, Robert L., Hurd, William A.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Rosenberger, R. A.
• Application Number:
  US05/947,870
• Time in Patent Office: 813 Days
• Field of Search: 356/71, 356/237, 356/394, 356/398
• US Class Current: 356/394
• CPC Class Codes: G01B 11/00 Measuring arrangements characterised by the use of optical techniques
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01N 21/95607 using a comparative method
• CPC Class Codes: G01R 31/2806 Apparatus therefor, e.g. test stations, drivers, analysers, conveyors G01R31/2805, G01R31/281, G01R31/2818 take precedence
• CPC Class Codes: G01R 31/309 of printed or hybrid circuits or circuit substrates

Abstract

An automatic printed circuit board tester in which a laser beam is directed onto and scanned around solder pads and foil regions of a printed circuit board, and errors in structure are determined by detecting patterns of scattered light and comparing these patterns with similarly obtained ones from a properly constructed board.

Claims

1. An electrical circuit board testing system comprising:

a circuit board having a plurality of connective holes therethrough and electrically conductive leads of components extending along said board in discrete and varied directions to said holes;

positioning means for holding and positioning a said printed circuit board under test at a precise position, wherein a face of said board to be examined is unobscured;

a counter;

illumination means, including a laser and focusing optics, for focusing a beam of laser light onto the face of said printed circuit board held by said positioning means;

scanning means responsive to a discrete count from said counter for positioning said beam along selected paths which include paths substantially normal to and across radial lines from said holes and accordingly substantially normal to said leads on said board;

detection means spaced from said printed circuit board and spaced from and to the side of said beam for sensing the amplitude of scattered laser light from separate discrete regions of said board as said board is scanned and for providing discrete electrical outputs, each representative of the amplitude of scattered light from a discrete region of said board as it is scanned; and

reference means including an electrical memory having discrete electrical values, representative of discrete amplitude values of scattered light from a reference circuit board resulting from exposure of said reference circuit board along like said selected paths, said values being stored in said memory and located by discrete counter addresses, and said reference means including means for reading out said discrete electrical values responsive to said counter;

whereby selected paths, or a selected series of paths, of scanning may be effected in any direction and at any location on said board, and the existence and location of a conductor on the surface of said board detected and compared with the existence or location of a conductor on said reference board which lies substantially normal to a said path.

2. A printed circuit board tester as set forth in claim 1 further comprising digital display means responsive to said detection means and said counter for displaying a count occurring when signals from said detection means and said reference means are not substantially identical.