Circuit board inspection apparatus and method
AssigneeAutomation Engineering, Inc.
InventorsRobert E. Bible, Robert E. Bible, Jr., Richard S. Mason
Life of this patent
Estimating the term…
Abstract
Apparatus and method for illuminating circuit boards to quickly and efficiently inspect them for various imperfections. An intense light beam is directed at an oblique angle at the surface of the board to be inspected. Some of the light enters the board and is partially scattered while some of it is reflected from the opposite surface. A detector array positioned above the inspected surface is scanned over that surface and distinguishes light and dark areas. Any light opaque area such as a conductive path or pad is a dark area while portions of the board free of circuitry is interpreted as a light area by the detector. Signals from the detector may be employed for many purposes relating to the circuit pattern on the board.
Claims25
Apparatus for illuminating a circuit board for inspection thereof, said circuit board having a translucent substrate and conductive circuitry on at least one side thereof, said apparatus comprising:
- a frame;
- a first carriage mounted to said frame for holding said circuit boards during inspection thereof;
- a second carriage mounted to said frame and spaced from said first carriage, at least one of said carriages being movable on said frame and with respect to the other carriage;
- first light source means mounted to said second carriage and directed at an oblique angle to the surface to be inspected of said circuit board;
- first detector means sensitive to light from said first light source means, said first detector means being mounted to said second carriage in fixed relationship with respect to said first light source means and arranged to detect light in a predefined field of view on the surface of said circuit board;
- and
- means cooperatively arranged with said first light source means to limit illumination of that portion of said circuit board to a predefined area having an edge closely adjacent but spaced from said field of view;
- whereby light directed onto said surface by said first light source means penetrates said circuit board, is scattered and reflected therewithin, and illuminates said field of view, said first detector means determining the presence or absence of an opaque conductive element in said field of view by the level of light sensed, said conductive element being opaque with respect to said substrate at the wavelength of said first light source means.
The apparatus recited in claim 14 and further comprising filter means positioned between said third light source and said second detector means, said filter having a transmissive bandwidth sufficient to pass light from said third light source and exclude substantially all other light.
A method of inspecting a circuit board having a translucent substrate and conductive circuitry on at least one surface thereof, said method comprising the steps of:
- directing at least one beam of light at an oblique angle onto the surface of said board to be inspected;
- viewing from above said surface by means of a first detector array a sharply defined field of view, said light beam having a defined edge on said surface closely adjacent but spaced from said field of view;
- illuminating said field of view on said surface from within said board by scattering and reflection of said light within said board;
- and
- detecting by means of sensors in said detector array light variations on said field of view from the scattered and reflected light within said circuit board indicative of the presence and absence in said field of view of conductive circuitry, said conductive circuitry being opaque with respect to said substrate at the wavelength of said light.
A method of inspecting a circuit board having a translucent substrate and conductive circuitry on at least one surface thereof, said method comprising the steps of:
- directing light at an oblique angle onto a predetermined portion of the surface of said board to be inspected;
- blanking an area of said light on said surface to leave said area dark;
- viewing from above said surface by means of a first detector array a sharply defined field of view within said dark area, said light having a defined edge on said surface closely adjacent but spaced from said field of view;
- illuminating said field of view on said surface from within said board by scattering and reflection of said light within said board;
- and
- detecting by means of sensors in said detector array light variations on said field of view form the scattered and reflected light within said circuit board indicative of the presence and absence in said field of view of conductive circuitry, said conductive circuitry being opaque with respect to said substrate at the wavelength of said light.
Dependencies are inferred from the claim text.