Patent Number: 051134250
Section: description

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawing and more particularly to FIG. 1, reference numeral 10 denotes an X-ray cabinet for an X-ray inspection system for industrial applications and utilized, for example, in the inspection of electronic components and circuit boards therefor, castings and, when desirable, even biological specimens. The X-ray cabinet 10 is comprised of a lead lined steel structure including a generally vertical tower, typically having a height, for example, of 31 inches which sits above an inspection chamber or housing 14. The tower 12 contains an X-ray tube in the top portion thereof which generates a collimated X-ray beam 20. The beam 20 is directed downwardly into the top of the inspection chamber 14 as shown in FIG. 2. A slide-out support member 22 comprised of a drawer or shelf is mounted generally horizontally within the inspection chamber 14 by means of a slide rail assembly, or the like, 24 so that it can be manually moved back and forth for the loading and unloading of objects, not shown, to be inspected. As shown, a hinged door 16 is adapted to close the front of inspection chamber 14. When desirable, however, this could be deleted in favor of a flat vertical panel or front piece attached to the support member. The shelf 22 includes a generally flat top surface where X-ray film can be placed beneath the object to be inspected during a routine shadowgraph imaging mode in a well known manner. The shelf 22, moreover, includes an aperture 26 therethrough, shown in FIG. 1 as being a generally circular opening for the location of apparatus for performing "real time" or fluoroscopic inspection as will be explained hereinater. The aperture 26, however, can be completely eliminated, if desired, as long as this particular area of the shelf or the whole shelf member 22 is completely X-ray transparent. Additionally, the X-ray cabinet 10 has a control panel 28 mounted on the front side wall 30 of the tower 12 and includes one or more manually operable devices 32 for controlling the X-ray tube 18 in a well known manner for performing both filming and fluoroscopic inspection of objects placed on the shelf 22. This configuration provides a compact X-ray cabinet structure which has particular utility for the X-ray inspection of multi-layer printed circuit boards including the multi-layer lamination registration thereof, drilling registration and failure analysis thereof including both populated and unpopulated boards. Because printed circuit board and electronic fabrication requires rapid X-ray inspection cabability with good resolution, the present invention contemplates providing, during either original equipment manufacture or at a later date, as a retrofit either in the factory or on site, the inclusion of a microchannel plate image intensifier 34 which, as shown in FIG. 2, is mounted on the underside of the shelf 22 at the location of the opening 26. The device 34 includes an X-ray phosphor element 36 coupled to a fiber optic face plate 38 located adjacent a microchannel plate multiplier 40 within a housing element 42. The housing element 42 also includes a visible light phosphor element 44 positioned between the microchannel plate 40 and a fiber optic output face plate 46. The microchannel plate device 34 comprises a well known X-ray imaging device of the type disclosed, for example, in U.S. Pat. No. 4,142,101, issued to L. I. Yin on Feb. 27, 1979. It is also available commercially as a Model 3603-2 microchannel plate image intensifier from the Varo Corporation. What is necessary, however, is that the phosphor element 36 be sufficiently thin in coating thickness so that it is capable of producing a light image of high resolution. The microchannel plate multiplier 40, however, amplifies the light energy so that it can be utilized in connection with a closed circuit TV camera. Accordingly, and as shown in FIG. 2, the output of the image intensifier device 34 is directed to an aluminized prism or mirror 48 located directly beneath the image intensifier device 34 on a flat base 50 located at the bottom of the inspection housing 14. The visible image is reflected from the prism 48 and directed to the lens 52 of a closed circuit TV camera 54 mounted on a support bracket 56 secured to the base 50. The video output from the camera 54 is coupled to a monitor 58 by means of a cable 60 as shown in FIG. 1 where the object under inspection can be viewed in real time. When desirable, the image intensifier device 34 can be detached from the underside of the shelf 22 and secured directly on the surface of the base 50 over the prism 48. Thus the microchannel plate image intensifier embodiment of the subject invention provides a high resolution image which can be displayed. The image intensifier, moreover, is compact and can be powered by batteries which can be attached to the sliding shelf 22 without restraining it or requiring any physical or electrical connection to the base 50. The overall combination of elements results in a relatively low cost and compact multi-function, i.e. both film and real time capability, industrial X-ray system available with resolution suitable for MLB inspection. Having thus shown and described what is at present considered to be the preferred embodiment of the invention, it should be noted that the same has been made by way of illustration and not limitation. Accordingly, all modifications, alterations and changes coming within the spirit and scope of the invention are herein meant to be included.