Empty location identification of component parts

Abstract

An empty location identification of component parts is provided which detects the presence, absence, orientation or polarity of components located on a printed circuit board or other type of component assembly. The identification is accomplished by utilizing a pattern of marks which are located in such a manner so as to be either partially or totally obscured when a component is placed in its correct location.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of achieving improved productivity in the manufacture of printed circuit boards. The improved productivity occurs because of increasing the efficiency and data accuracy of an inspection cycle.

2. Description of the Prior Art

Most types of electronic equipment produced today incorporate one or more printed circuit boards which have various types of electronic components thereon. As electronic equipment becomes more and more complex, printed circuit boards are being designed which have a greater density of components. As component density increases, inspection of the printed circuit boards, throughout the manufacturing process, becomes much more difficult. Human operators have experienced greater difficulty in visually inspecting the printed circuit boards for defects. Occasionally, even an experienced operator will fail to detect defects in the form of a missing or misinserted component. Also, visual inspection by human operators must be performed at a relatively slow speed and may be affected by the operators susceptibility to fatigue.

Because of the difficulties associated with visual inspection of printed circuit boards, much effort has been devoted to developing automatic equipment for performing this task. Although these automatic systems work well, these systems incorporate line scan vision cameras or television cameras which are extremely expensive and complicated.

U.S. Pat. No. 4,005,939 Aby Stavalone, U.S. Pat. No. 4,105,340 by Kempf and U.S. Pat. No. 4,379,647 by Kempf disclose apparatuses for optically comparing a manufactured board with a master board to identify a discrepancy on the manufactured board because of its different appearance from the master board. The image comparison is made by an observer who scans the alternately presented images. The effectiveness of this comparison is dependant on the skills of the observer and the observer's susceptibility to fatigue. This method differs from the present invention because it relies on an observer and because this method cannot be automated or otherwise performed by mechanical or electrical means.

U.S. Pat. No. 4,295,198 by Copeland et al. describes a method and an apparatus of optically recognizing particular features of a printed circuit board (PCB) and then display that information on a CRT screen so an operator may create machine instructions for those features at specific locations. The instructions are then used to direct the operations of a numerically operated machine such as a gang drill. The present invention differs from this patent in that the present invention illuminates the PCB and uses unique materials in different patterns to uniquely characterize the sensed reflected radiation to permit either visual, optical or mechanical identification of a components presence, absence or orientation.

U.S. Pat. No. 4,549,206 by Suzuki et al. and U.S. Pat. No. 4,811,410 by Amir et al. disclose inspection systems for printed circuit boards. The systems illuminate the board and analyze the reflected light to determine various defects. The present invention is similar to these patents only in the fact that the present invention utilizes a means of illuminating the PCB and uses the reflected light. This is the same procedure used for any type of visual inspection. The present invention differs in that it employs unique materials in differing patterns to characterize the sensed light to permit either visual, optical or mechanical identification of component presence, absence, orientation or identity.

Because of the problems stated above, a method has been developed which minimizes the possibilities for error and also allows the inspector to increase the number of printed circuit boards inspected over a period of time, or to permit the use of automatic equipment to perform this task.

SUMMARY OF THE INVENTION

The present invention provides a method for detecting the presence, absence, orientation, or polarity of required components on a printed circuit board (PCB) (or other type of component assembly) as the PCB traverses the various stages of the manufacturing process. The present invention is accomplished by adding a pattern of marks or dots in such a manner to the printed circuit board so that the marks would be either partially or totally obscured when a component is placed in its intended location.

These marks, added to the surface of the PCB, can be used to accomplish several objectives. The marks can be used to provide identification of any location that is not occupied with its intended component. The marks can also provide other information, such as component polarity reversals, and/or component orientation depending upon the spacing permitted on the PCB.

The marks can be easily and economically applied during PCB manufacturing by silk screening, printing, decals or any method used for marking and the marks may be of any material which can be easily detected by mechanical, visual, optical, electrical or some other means. In one embodiment, a mark may only appear when a PCB is scanned by ultraviolet light and a component is missing or improperly installed.

BRIEF DESCRIPTION OF THE DRAWINGS

1. FIG. 1 illustrates a top view of a fully populated printed circuit board.

2. FIG. 2 illustrates a top view of a printed circuit board with several components missing.

3 FIG. 3 illustrates a top view of a printed circuit board with several components missing, however, one embodiment of the present is utilized.

4. FIG. 4 illustrates a top view of a printed circuit board with several components misinserted.

5. FIG. 5 illustrates a top view of a printed circuit board with several components misinserted, however, one embodiment of the present invention is utilized.

DETAILED DESCRIPTION OF THE DRAWINGS

As is shown in FIG. 1, printed circuit board (PCB) 11 contains a heavy population of components 12. Components 12 may be semiconductor elements, resistor elements, capacitor elements, heat sinks or/and any other board mounted components. Among the components 12 mounted on printed circuit board 11 are resistors 21, 22, 23, capacitors 24, 25, 26 and integrated circuits (ICs) 27, 28, 29, 30. Because of the density of printed circuit board 11 and the variety of shapes and sizes of components 12, visual inspection of printed circuit board 11 by a human operator is very difficult and the time it takes to inspect printed circuit board 11 is excessive.

Illustrated in FIG. 2, is the same printed circuit board 11 as illustrated in FIG. 1, however, in FIG. 2, several components are missing. The missing components (from FIG. 1) are resistor 21, capacitors 25, 26 and ICs 27, 29. The empty locations of the missing components are identified in FIG. 2 as 21, 25, 26, 27 and 29. As discussed above, because of the density of printed circuit board 11 it is difficult to quickly establish that components are missing. The purpose of this invention is to provide a rapid, efficient and reliable means to inspect the printed circuit board 11.

FIG. 3 illustrates one embodiment of the present invention wherein marks 13 are utilized to draw attention to the missing components when printed circuit board 11 is viewed from its top side 14. The marks 13 can provide a variety of information such as part number, availability, etc. A simple color code may be utilized to provide various types of information or a more complex marking technique such as a bar code may be utilized. The marks 13 may be designed to be discernable by the human eye or by optical scanners, as are known in the art. The marks may also appear to be invisible to the human eye until scanned by ultraviolet light.

FIG. 4 illustrates a printed circuit board 11 having components misinserted. The misinserted components are resistor 22, and ICs 28, 30. Because of the density of printed circuit board 11, it is difficult to quickly establish that any components are misinserted.

FIG. 5 illustrates one embodiment of the present invention wherein marks 13 are utilized to draw attention to the misinserted components. The misinserted components are resistor 22 and ICs 28, 30. As discussed above, these marks 13 can provide a variety of information such as part number, availability, etc. It is obvious that without these marks 13 it would be much more difficult to notice the components that are misinserted. Also illustrated in FIG. 5 are means for scanning 41, means for detecting 42, and means for illuminating 43.

It is not intended that this invention be limited to the arrangement, or operational procedures shown disclosed. This invention includes all of the alterations and variations thereto as encompassed within the scope of the claims as follows.

Claims

1. An apparatus for providing an empty location identification of component parts located on a printed circuit board or other type of component assembly, said apparatus comprising:

a pattern of marks located on said printed circuit board or said other type of component assembly at predetermined locations, said predetermined locations defined so that said pattern of marks would be totally obscured when said component parts are in their intended locations and positions;

means for scanning said printed circuit board or said other type of component assembly; and,

means for detecting said pattern of marks on said printed circuit board or said other type of component assembly.

2. An apparatus for providing an empty location identification of component parts as claimed in claim 1 wherein:

said pattern of marks comprises material only observable by ultraviolet light; and,

said means for scanning comprises utilizing ultraviolet light.

3. An apparatus for providing an empty location identification of component parts as claimed in claim 1 further comprising:

means for illuminating said printed circuit board or said other type of component assembly.

4. An apparatus for providing an empty location identification of component parts as claimed in claim 1 wherein:

said means for detecting said pattern of marks on said printed circuit board or said other type of component assembly comprises means for checking if said component parts are correctly mounted in a predetermined position on said printed circuit board or said other type of component assembly.

5. An apparatus for providing an empty location identification of component parts as claimed in claim 1 wherein:

said means for detecting said pattern of marks on said printed circuit board or said other type of component assembly comprises means for establishing pressence, absence, orientation, polarity or identification of said component parts on said printed circuit board or said other type of component assembly.

6. An apparatus for providing an empty location identification of component parts as claimed in claim 1 wherein:

said means for detecting said pattern of marks on said printed circuit board or said other type of component assembly comprises mechanical means.

7. An apparatus for providing an empty location identification of component parts as claimed in claim 1 wherein:

said means for detecting said pattern of marks on said printed circuit board or said other type of component assembly comprises electrical means.

8. An apparatus for providing an empty location identification of component parts as claimed in claim 1 wherein:

said means for detecting said pattern of marks on said printed circuit board or said other type of component assembly comprises optical means.

9. A method of inspecting component parts located on a printed circuit board, said method comprising the steps of:

adding a pattern of marks to said printed circuit board at predetermined locations, said predetermined locations defined so that said pattern of marks would be totally obscured when said component parts are properly mounted;

scanning at least one surface of said printed circuit board; and,

detecting defects associated with the mounting of components on said printed circuit board.

10. A method of inspecting mounting of component parts on a printed circuit board or other type of component assembly comprising the steps of:

adding a pattern of marks to said printed circuit board or said other type of component assembly at predetermined locations, said predetermined locations defined so that said pattern of marks would be totally obscured when said component parts are properly mounted;

illuminating said printed circuit board or said other type of component assembly;

viewing said printed circuit board or said other type of component assembly from above; and,

detecting said pattern of marks on said printed circuit board or said other type of component assembly if said component parts are improperly mounted.