System for inspecting pin grid arrays

• US 5,648,853 A
• Filed: 05/18/1995
• Issued: 07/15/1997
• Est. Priority Date: 12/09/1993
• Status: Expired due to Term

• Current Assignee: Rudolph Technologies Incorporated (Onto Innovation Inc.)
• Original Assignee: Robotic Vision Systems, Inc. (Omron Corporation)
• Inventors: Stern, Howard, Yonescu, William E.
• Primary Examiner(s): Pham, Hoa Q.
• Application Number:
  US08/444,258
• Time in Patent Office: 789 Days
• Field of Search: 356/394, 356/398, 356/372, 356/375, 356/376, 356/380, 356/386, 356/387, 356/237, 250/561, 250/562, 250/563, 250/572, 348/125, 348/126, 29/720, 29/721, 29/759
• US Class Current: 356/394
• CPC Class Codes: H01L 22/12 for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions electrical measurement of diffusions H01L22/14

Abstract

An arrangement for inspecting straightness of an array of pins in which the array is illuminated by a thin beam of light. Images of surfaces of the array of pins that are illuminated are projected on a photo-sensitive device. The array of pins is movable relative to the beam of light and the imaging device. The imaging device and photo-sensitive device are also movable relative to the array of pins.

Claims

1. Apparatus for inspecting straightness of an array of pins comprising:

means for illuminating said array of pins with an encompassing thin beam of light;

photo sensitive surface means for reporting the locations of images incident thereon;

means for collecting diffuse illumination reflected from said pins at a plane of intersection of said thin beam of light with said pins without obscuration of any pin by any of the other pins;

means for imaging surfaces of said array of pins illuminated by said beam of light onto said photosensitive surface means;

means for moving said array of pins relative to said beam of light and means for imaging; and

means for moving said means for imaging and photo sensitive means relative to said array of pins for producing a full contour image of each entire pin;

images of said pins being obtained in three dimensions along the entire length of the pin;

optical elements for intercepting said thin beam of light and diverging said beam of light to provide an effect that said beam of light emanates from an array of contiguous light sources located adjacent said optical elements for reducing shadowing effects of adjacent pins, each of said pins having a tip, said diffuse illumination only being radiated at substantially 90 degrees to said beam of light and being directed at said photo sensitive means when said plane intersects a pin below the tip of the pin, said diffuse illumination having a substantially lower intensity than the light intensity reflected from the tip;

unobscured images of pins in inner rows of pins being obtainable from said diffuse reflected intensity.

2. Apparatus as defined in claim 1 wherein said beam of light is strobed.

3. Apparatus as defined in claim 1 wherein said means for imaging comprises a linear array of lenses spaced at intervals equal to a nominal spacing of one row of said array of pins.

4. Apparatus as defined in claim 3 wherein further field stops are positioned adjacent to each said lens to block light from adjacent pins of said array of pins that could enter the imaging area of each said lens.

5. Apparatus as defined in claim 1 wherein said photo sensitive surface means comprises a linear array of sites at defined linear locations capable of reporting individually in known sequence the amount of light incident upon each said site during a prescribed time period.

6. Apparatus as defined in claim 5 wherein said means for imaging comprises more than one linear array of lenses, with associated reflecting surfaces for imaging upon said linear array of sites, spaced at intervals equal to the nominal spacing of one row of said array of pins multiplied by the number of said arrays of lenses.

7. Apparatus as defined in claim 6 wherein only one of said reflecting surfaces is associated with each said lens and each said lens is oriented to provide an image plane in the plane of said photo-sensitive surface means.

8. Apparatus as defined in claim 1 wherein said means for moving said array of pins provides an accurate readout of position.

9. Apparatus as defined in claim 1 wherein said means for moving said means for imaging provides an accurate readout of position and a trigger signal signifying the time the imaging means reaches said position readout.

10. Apparatus as defined in claim 1 wherein said means for illuminating provides two parallel thin beams of light separated by a given distance and said means for imaging has a depth of field adequate to image both surface areas illuminated by said beams of light onto said photo sensitive means.

11. Apparatus as defined in claim 1 wherein said photo-sensitive surface means comprises a rectangular imaging array at defined locations in an area capable of reporting individually in known sequence the amount of light incident upon each said site during a prescribed time period.

12. Apparatus as defined in claim 11 wherein said means for imaging comprises a single lens capable of imaging the surface of more than one pin of said array of pins at a time onto said photo-sensitive surface.

13. Apparatus as defined in claim 11 wherein said means for moving said array of pins provides an accurate readout of position.

14. Apparatus as defined in claim 11 herein said means for moving said means for imaging provides an accurate readout of position.

15. Apparatus as defined in claim 1 including a plurality of diverging light sources located along a path for generating said beam of light.

16. Apparatus for inspecting straightness of an array of pins comprising:

means for illuminating said array of pins with encompassing two parallel thin beam of light;

photo sensitive surface means for reporting the locations of images incident thereon;

means for collecting diffuse illumination reflected from said pins at a plane of intersection of said thin beam of light with said pins without obscuration of any pin by any of the other pins;

means for imaging surfaces of said array of pins illuminated by said beams of light onto said photosensitive surface means;

means for moving said means for imaging and photo sensitive means relative to said array of pins for producing a full contour image of each entire pin;

images of said pins being obtained in three dimensions along the length of the pin;

optical elements for intercepting said thin beams of light and diverging said beam of light to provide an effect that said beam of light emanates from an array of contiguous light sources located adjacent said optical elements for reducing shadowing effects of adjacent pins, each of said pins having a tip, said diffuse illumination only being radiated at substantially 90 degrees to said beams of light and being directed at said photo sensitive means when said plane intersects a pin below the tip of the pin, said diffuse illumination having a substantially lower intensity than the light intensity reflected from the tip;

unobscured images of pins in inner rows of pins being obtainable from said diffuse reflected intensity;

said two parallel thin beams of light being separated by a given distance and said means for imaging having a depth of field adequate to image both surface areas illuminated by said beams of light onto said photosensitive means.

17. Apparatus as defined in claim 16 wherein said light beams can be separately strobed.

18. Apparatus as defined in claim 16 wherein said means for illuminating provides two parallel thin beams of light separated by a given distance, said photo sensitive means comprising two photo-sensitive surfaces capable of reporting the locations of images incident thereon, and said imaging means comprising means for imaging the surfaces of said array of pins illuminated by said beams of light and beam splitter means for directing said images to said photosensitive surfaces.

19. Apparatus as defined in claim 18 wherein said light beams can be separately strobed.

20. Apparatus as defined in claim 18 wherein said light beams are of two distinct wavelengths and said imaging means further comprises two filters for blocking light of one said light beam while passing the light of the other said light beam, one said filters being placed to pass the image of one said light beam to one said photo-sensitive surface, the other of said filters passing the image of the other said light beam to the other said photo-sensitive surface.

21. Apparatus as defined in claim 16, wherein said photosensitive surface means comprises at least one line of sites at defined lines of locations capable of reporting individually in known sequence the amount of light incident upon each said site during a prescribed time period, said means for imaging comprising at least one line of lenses spaced at intervals equal to the nominal spacing of one row of said array of pins multiplied by the number of said arrays of lenses.

22. Apparatus as defined in claim 16, wherein said two parallel thin beams of light are two separately strobed parallel thin beams of light.

23. Apparatus as defined in claim 22 including further means for moving said photo-sensitive means, for enabling said means for imaging to image the surfaces of said array of pins illuminated by said beams of light onto said photo-sensitive means.

24. Apparatus as defined in claim 22, including refracting means, said means for imaging having a focal length and comprising further means for inserting and retracting said refracting means for altering said focal length of said imaging means to image the surfaces of said array of pins illuminated by said beams of light onto said photo-sensitive means.

25. A system for measuring an array of regularly spaced articles comprising:

means for illuminating said array of articles with an encompassing thin beam of light;

a plurality of diverging light sources located along a path for generating said beam of light and effectively eliminating shadows within said array of articles, said illumination occurring in pulses initiated by a trigger signal;

means for collecting diffuse illumination reflected from said articles at a plane of intersection of said thin beam of light with said articles;

means for imaging one row of said array of articles, providing images of the portions of said array of articles illuminated by said means for illuminating;

means for reporting the location and amount of light incident at prescribed locations along a line through said images;

means for moving said means for imaging and means for reporting relative to said array of articles, said means for moving providing an indication of position and a trigger signal at the time said indication of position becomes valid;

means for controlling said means for moving said means for imaging and means for reporting relative to said array of articles;

means for processing said indication of position from said means for moving said means for imaging, said imaging means imaging illuminated surfaces;

said indication of position from said means for moving said array of articles and said location and amount of light from said means for reporting into three dimensional co-ordinate values representative of said illuminated surfaces being imaged by said means for imaging for producing a full contour image of each entire article;

images of said articles being obtained in three dimensions along the entire length of the article;

optical elements for intercepting said thin beam of light and diverging said beam of light to provide an effect that said beam of light emanates from an array of contiguous light sources located adjacent said optical elements for reducing shadowing effects of adjacent articles; and

computer means for directing said controlling means and means for processing, and accepting said three dimensional value from said means for processing to produce control signals and reports based on said three dimensional values, said articles being pins, each of said pins having a tip, said diffuse illumination only being radiated at substantially 90 degrees to said beam of light and being directed at said photo sensitive means when said plane intersects a pin below the tip of the pin, said diffuse illumination having a substantially lower intensity than the light intensity reflected from the tip;

unobscured images of pins in inner rows of pins being obtainable from said diffuse reflected intensity.