Back-lighted fiducial recognition system and method of use

• US 20020109775A1
• Filed: 02/09/2001
• Published: 08/15/2002
• Est. Priority Date: 02/09/2001
• Status: Abandoned Application

• Current Assignee: Excellon Automation Co.
• Original Assignee: Excellon Automation Co.
• Inventors: White, Paul David, Vu, Huong Duc
• Application Number:
  US09/779,635
• Publication Number:
  US 20020109775A1
• Time in Patent Office: Days
• US Class Current: 348/87
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 26/04 Automatically aligning, aiming or focusing the laser beam, e.g. using the back-scattered light
• CPC Class Codes: B23K 26/0853 Devices involving movement of the workpiece in at least in two axial directions, e.g. in a plane
• CPC Class Codes: B23K 26/382 by boring
• CPC Class Codes: H05K 1/0269 for visual or optical inspection
• CPC Class Codes: H05K 13/0015 Orientation; Alignment; Positioning
• CPC Class Codes: H05K 2201/0108 Transparent
• CPC Class Codes: H05K 2201/09918 Optically detected marks used for aligning tool relative to the PCB, e.g. for mounting of components
• CPC Class Codes: H05K 3/0008 for aligning or positioning of tools relative to the circuit board H05K3/4638, H05K3/4679 take precedence; for manufacturing assemblages of components H05K13/0015
• CPC Class Codes: H05K 3/0032 of organic insulating material

Abstract

A system is disclosed for exact positioning of a printed circuit board to be drilled utilizing a camera vision system. The fiducial is formed in a semi-opaque area of the circuit board panel that is free of copper or other metallic layer material on top and bottom surfaces thereof, enabling light to be directed upwardly through a transparent surface area of a vacuum chuck on which the panel is disposed. In this manner, the outline of the fiducial is silhouetted through this back lighted arrangement so that the camera vision system can easily ‘see’ the fiducial to communicate the precise location of the circuit board and enable movement of the vacuum chuck in X and Y directions to effect the desired precise drilling at predetermined locations on the panel.

Claims

1. A method of precisely locating a printed circuit board panel containing at least one fiducial on a vacuum chuck of a drilling machine, comprising the steps of:

a. positioning the panel on the vacuum chuck;

b. projecting an image of the fiducial towards an overhead camera vision system by shining a light upwards through the fiducial from a source located below the panel; and

c. recording the position of the fiducial with the overhead camera vision system.

2. The method of claim 1, comprising the further step of positioning a predetermined area of the panel containing the fiducial over a transparent surface portion of the vacuum chuck, and shining the light upwards through the transparent surface portion.

3. The method of claim 2, comprising the further step of applying vacuum directly to the predetermined area through the transparent portion.

4. The method of claim 1, wherein the step of shining the light silhouettes or back lights fiducial.

5. The method of claim 2, wherein the predetermined area is bare and thereby formed without any copper or metallic layer.

6. The method of claim 5, wherein said predetermined area is made from a semi-opaque material.

7. The method of claim 1, wherein each corner of the panel has a fiducial, and comprising the further step of shining a light upward through each fiducial from an associated light source, and moving the overhead camera vision system over each backlit fiducial to record the position thereof.

8. The method of claim 2, wherein light from a plurality of light sources is directed through said transparent portion.

9. The method of claim 8, wherein said plurality of light sources is a two dimensional array of said light sources.

10. The method of claim 2, wherein said transparent surface portion is clear.

11. The method of claim 2, wherein said transparent surface portion is colored.

12. The method of claim 5, wherein the bare predetermined areas are formed without skiving.

14. The apparatus of claim 13, wherein said vacuum chuck includes a transparent surface portion and said light source is positioned beneath the transparent surface portion to shine light upwards there through.

15. The apparatus of claim 14, further comprising vacuum openings formed in said transparent surface portion, said openings being adapted to apply vacuum to suck the portion of the panel containing the fiducial tightly against the transparent surface portion.

16. The apparatus of claim 15, wherein said transparent surface portion is a clear panel.

17. The apparatus of claim 16, wherein said light source includes a plurality of lights positioned beneath the clear panel.

18. The apparatus of claim 17, wherein said plurality of lights are light emitting diodes (LEDs) in an m×

n array.

19. The apparatus of claim 18, wherein m and n are integers having the same value.

20. The apparatus of claim 19, wherein m and n equal 7.

21. The apparatus of claim 19, wherein the surface area of the light source is smaller than the surface area of the transparent surface portion.

22. The apparatus of claim 17, wherein said lights are mounted to a mounting board that is releaseably attached into position beneath the clear panel through a mounting cavity communicating with a bottom surface of a vacuum chuck.

13. A laser drilling apparatus, comprising:

a. a laser radiation source positioned for generating a laser beam;

b. a motorized table beneath the laser beam;

c. a vacuum chuck positioned on the table to receive a circuit board panel to be drilled;

d. a light source positioned below a panel support upper surface of the vacuum chuck for transmitting light upwardly to back light a portion of the panel containing the fiducial;

e. an overhead camera vision system for detecting the image of the fiducial to determine the exact positioning of the panel on the table; and

f. a scanner operatively connected to the camera vision system to point the laser beam to drill holes in precise predetermined locations in the panel.