JP2009021259A - X-ray device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray device with a rotary positive electrode type X-ray tube suppressing enlargement of an effective focus. <P>SOLUTION: This device includes a rotary positive electrode type X-ray tube having an X-ray radiation surface 22 radiating fine-focusing X-rays to photograph a subject, a rotor 25 with the X-ray radiation surface coupled thereto, a stator 31 fit into the rotor and having a liquid metal lubricant supplied sliding bearing formed between it and the rotor and a vacuum envelope 41 containing the X-ray radiation surface, the rotor and the stator, a coil 46 generating a rotating magnetic field exerting rotating force to the rotor, and a controller stopping generation of the rotating magnetic field by the coil to radiate X-rays from the X-ray radiation surface during inertial rotation of the rotor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an X-ray apparatus equipped with a rotating anode type X-ray tube with reduced fluctuation in the X-ray emission direction.

  As one of inspection apparatuses using X-rays, there is an apparatus for inspecting disconnection of a wiring pattern of an integrated circuit. This apparatus irradiates a circuit board on which a wiring pattern is formed with X-rays, and inspects whether or not the wiring pattern is disconnected based on an X-ray image transmitted through the circuit board. In such a disconnection inspection apparatus, an X-ray tube having a small effective focus is used because the wiring pattern of the integrated circuit has a fine structure.

  Conventionally, a microfocus X-ray tube has been used as an X-ray tube having a small effective focus. Here, the microfocus X-ray tube will be described with reference to FIG.

  Reference numeral 51 denotes a vacuum envelope constituting a microfocus X-ray tube, and an anode 52 is arranged in the vacuum envelope 51. The tip of the anode 52 is a cylindrical part 52a, and an opening 52b is provided in a part of the cylindrical part 52a. An inclined X-ray emission surface 52c is provided inside the cylindrical portion 52a. And the cathode 53 is arrange | positioned in the position facing the opening 52b of the cylindrical part 52a. A heater 54 is provided behind the cathode 53, and a grid 55 for controlling the electron beam is disposed between the cathode 53 and the opening 52b. In the above configuration, the electron beam e is emitted from the cathode 53 by heating by the heater 54. The electron beam e is applied to the X-ray emission surface 52c through the opening 52b, and X-rays are emitted from the X-ray emission surface 52c. The emitted X-rays are output to the outside through the output window 51a of the envelope 51.

  The effective focus of the microfocus X-ray tube is as small as about 10 μm. However, since the anode is fixed, a large output cannot be obtained, and there is a limit to the X-ray output. Therefore, it is not suitable for photographing a moving subject that irradiates a large output X-ray in a short time.

  Therefore, in order to solve the drawbacks of the microfocus X-ray tube with the anode fixed, an anode was rotated using a ball bearing and an X-ray tube having a small effective focal point was prototyped and evaluated. As a result, the structure of a conventional rotating anode X-ray tube, for example, a disk-shaped rotating body on which an X-ray emission surface is formed and a rotating body that supports the disk-shaped rotating body are processed independently, and then the disk In the structure in which the rotator and the rotator are integrated, the X-ray emitting surface that emits X-rays and the rotation axis of the rotator cannot be sufficiently secured, and as the anode rotates, It was found that shake occurred in the discharge direction.

  When the X-ray emission direction is swung within a certain angle range, the effective focus is substantially increased, and the effective focus of about 10 μm is, for example, about 30 μm. For this reason, the conventional rotary anode X-ray tube cannot obtain an effective focus having a dimension of about 10 μm, which is necessary for inspection of disconnection of the wiring pattern of the integrated circuit.

  The rate at which the effective focus increases due to fluctuations in the X-ray emission direction increases as the focal spot size decreases. For example, when the focal size is about 100 μm, the deviation is a size that cannot be ignored. Further, when the focal spot size is 50 μm or less, the deviation becomes noticeable. Further, when operating for a long time, the average output power does not reach that of a conventional fixed anode type microfocus X-ray tube in which the anode is water-cooled.

  An object of the present invention is to solve the above-described drawbacks and to provide an X-ray apparatus equipped with a rotary anode X-ray tube in which an increase in effective focus is suppressed.

  The present invention relates to an X-ray emitting surface that emits a microfocus X-ray for photographing a subject, a rotating body coupled with the X-ray emitting surface, a liquid metal fitted between the rotating body and the rotating body. A rotary anode type X-ray tube having a fixed body formed with a sliding bearing to which a lubricant is formed, the X-ray emission surface, the rotating body, and a vacuum envelope housing the fixed body, and the rotating body A coil that generates a rotating magnetic field for applying a rotational force to the coil, and a control device that stops generation of the rotating magnetic field by the coil and emits X-rays from the X-ray emitting surface during inertial rotation of the rotating body. It is characterized by doing.

  An X-ray apparatus equipped with a rotating anode X-ray tube that suppresses an increase in effective focus can be obtained.

  An embodiment of the present invention will be described with reference to FIG. 1 by taking as an example a case where the present invention is applied to a disconnection inspection apparatus for inspecting disconnection of a wiring pattern of an integrated circuit.

  Reference numeral 11 denotes a housing constituting the disconnection inspection device, and a lead shield layer 11 a is provided on the inner surface of the housing 11. An X-ray tube 12 that emits microfocus X-rays is disposed below the housing 11. Above the X-ray tube 12, an object to be inspected 13 such as a circuit board for inspecting a subject, for example, the presence or absence of disconnection of a wiring pattern is arranged. An X-ray multiplier 14 and an imaging tube 15 are sequentially disposed above the inspection object 13. A viewing window 16 is provided in a part of the housing 11 so that the inside can be monitored.

  In the above-described configuration, the X-ray tube 12 is operated by the control device 90 and emitted X-rays are irradiated onto the object 13 to be inspected. Then, the X-ray image on which the inspection object 13 is projected is input to the X-ray multiplier 14 and amplified. The X-ray image amplified by the X-ray multiplier 14 is converted into an enlarged electrical image by projecting a subject in the imaging tube 15. Further, the electrical image output from the imaging tube 15 is converted into a visible image by a picture tube (not shown) or the like, and the disconnection of the wiring pattern of the inspected object 13 is inspected.

  Here, the X-ray tube 12 used in the above-described disconnection detection apparatus will be described with reference to the cross-sectional views of FIGS. In FIG. 2 to FIG. 4, the corresponding parts are denoted by the same reference numerals, and a duplicate description is partially omitted.

  First, as shown in FIG. 2, the rotating part 20 of the X-ray tube is assembled. Reference numeral 21 denotes a disk-shaped rotating body, and an X-ray emitting surface 22 that emits X-rays by irradiation of an electron beam is provided on the upper surface of the disk-shaped rotating body 21. A blackening film 23 is formed on the lower surface of the disk-shaped rotating body 21 in order to enhance the heat dissipation effect.

  The disc-shaped rotating body 21 provided with the X-ray emission surface 22 is mechanically coupled to a bottomed cylindrical rotating body 25 via a rotating shaft 24. The rotating body 25 has, for example, a three-layer structure of an outer cylinder 25a, an intermediate cylinder 25b, and a bottomed inner cylinder 25c, and a portion of the intermediate cylinder 25b is connected to the rotating shaft 24. The outer cylinder 25a is made of copper, and the intermediate cylinder 25b and the bottomed inner cylinder 25c are in contact with each other by a plurality of protrusions 26, and a heat insulating gap 27 is provided between them.

  As described above, the disk-shaped rotating body 21 provided with the X-ray emission surface 22 and the like and the three-layered rotating body 25 are integrated via the rotating shaft 24. And the finishing process of the X-ray radiation surface 22 is performed in a state where the disk-shaped rotating body 21 and the rotating body 25 are integrated. At this time, the processing is performed so that the X-ray emission surface 22 and the rotation axis of the rotating body 25 are in a coaxial relationship. That is, when the X-ray emitting surface 22 rotates, the entire annular region on the X-ray emitting surface irradiated with the electron beam is processed so as to have the same angle with respect to the rotation axis of the rotating body.

  By such processing, the shake in the X-ray emission direction, that is, the shake in the extending direction of the rotating shaft (vertical direction in the figure) is reduced. For example, compared to a conventional structure in which the disk-shaped rotating body 21 and the rotating body 25 are individually processed and then coupled together by the rotating shaft 24, the X-ray radiation surface 22 and the rotating shaft of the rotating body 25 are coaxial. The degree is improved.

  Next, as shown in FIG. 3, the rotating mechanism portion 30 of the X-ray tube is assembled using the integrated disk-shaped rotating body 21 and the rotating body 25. At this time, the fixed body 31 is fitted in the internal space of the rotating body 25 while maintaining a narrow bearing gap.

  In addition, helical grooves 32 a and 32 b are formed on the side surface of the fixed body 31, and a radial dynamic pressure type plain bearing is formed between the fixed body 31 and the rotating body 25. In addition, spiral grooves 33 a and 33 b are formed on the upper and lower end faces of the fixed body 31, and a dynamic pressure type sliding bearing in the thrust direction is formed between the rotating body 25 and the rotating body 25. In addition, a lubricant accommodating chamber 34 is provided in the central portion of the fixed body 31. A liquid metal lubricant is stored in the lubricant storage chamber 34. Further, a passage 35 is provided between the lubricant containing chamber 34 and the dynamic pressure type slide bearing, and the liquid metal lubricant stored in the lubricant containing chamber 34 is supplied to the dynamic pressure type slide bearing through the passage 35. ing. The lower end of the rotating body 25 is sealed with a sealing body 36.

  Next, as shown in FIG. 4, the rotating mechanism portion of the X-ray tube is housed in a vacuum envelope, and a rotating anode X-ray tube is assembled.

  Reference numeral 41 denotes a vacuum envelope constituting an X-ray tube. The vacuum envelope 41 includes a large-diameter portion 41a having a large diameter and a small-diameter portion 41b having a small diameter. An output window 42 is provided in a part of the large diameter portion 41a. Then, the rotating mechanism portion (FIG. 3) is accommodated so that the disk-shaped rotating body 21 is positioned in the large diameter portion 41a and the fitting portion of the rotating body 25 and the fixed body 31 is positioned in the small diameter portion 41b. Is done. Further, a cathode 43 is disposed at a position facing the X-ray emission surface 22 of the disk-shaped rotating body 21.

  In this case, the end of the fixed body 31 is sealed to the small-diameter portion 41 b by the auxiliary metal ring 44 and the metal sealing 45. A coil 46 that generates a rotating magnetic field is disposed outside the small-diameter portion 41b.

  When the rotary anode X-ray tube having the above-described configuration is operated, a high voltage is applied to the anode configured by the disk-shaped rotating body 21 or the like. Further, a current is passed through the coil 46 to generate a rotating magnetic field. The rotating body 25 is rotated by the rotating magnetic field. As the rotating body 25 rotates, the disk-shaped rotating body 21 rotates and the X-ray emission surface 22 rotates. After the rotary body 25 is driven to rotate by the coil 46, the coil operation is stopped and the inertial rotation is performed. In this state, the X-ray emission surface 22 is irradiated with an electron beam from the cathode 43, and X-rays are emitted from the X-ray emission surface 22. The emitted X-rays are output to the outside through the output window 42.

  According to the above-described configuration, after the disk-shaped rotating body 21 and the rotating body 25 are integrated, the X-ray radiation surface 22 and the rotation axis of the rotating body 25 are coaxially connected to each other on the disk-shaped rotating body 21. The X-ray emission surface 22 is finished. Therefore, a good coaxial relationship is obtained between the X-ray emission surface 22 and the rotation axis of the rotating body 25. Further, inertial rotation is performed to generate X-rays.

  For this reason, even if the anode rotates, the shake of the emitted X-rays becomes small. As a result, an X-ray tube having a substantial focal point as viewed from the output window 42 side, that is, a so-called effective focal point is realized. In addition, since the anode rotates, a large output can be obtained, which is effective for shooting a moving subject that is shot in a short time using the large output.

  For example, even when the effective focal point on the X-ray emitting surface that emits X-rays has dimensions of 100 μm or less in the vertical direction and the horizontal direction, the increase in effective focal point is small. In addition, when the fitting part between the rotating body and the fixed body is constituted by a dynamic pressure type slide bearing, the effective focal point on the X-ray radiation surface is effective even if the vertical and horizontal dimensions are 50 μm or less respectively. The increase in focus is kept small.

  Next, another example of the X-ray tube 12 used in the disconnection detection device and the like will be described with reference to cross-sectional views of FIGS. In FIG. 5 to FIG. 7, corresponding parts are denoted by the same reference numerals, and a part of overlapping description is omitted.

  First, the rotating part 61 of the X-ray tube having the structure as shown in FIG. 5 is assembled. In the rotating portion 61, for example, an anode target portion 62 and a bottomed cylindrical portion 63 are directly coupled together. The upper surface of the anode target portion 62 has a flat center and a slope around the center. An X-ray emission surface 62 a that emits X-rays when irradiated with an electron beam is provided on the slope of the anode target portion 62. A copper outer cylinder 64 is attached to the outer peripheral side wall portion of the bottomed cylindrical portion 63.

  Then, finishing of the X-ray emission surface 62a is performed in a state where the anode target portion 62 and the bottomed cylindrical portion 63 are integrated. At this time, the processing is performed so that the X-ray emission surface 62a and the rotation axis of the bottomed cylindrical portion 63 are in a coaxial relationship. For example, when the X-ray emission surface 62a rotates, the entire annular region on the X-ray emission surface 62a irradiated with the electron beam is at the same angle with respect to the rotation axis mm of the bottomed cylindrical portion 63. To be processed. By such processing, the shake in the X-ray emission direction, that is, the shake in the extending direction (vertical direction in the figure) of the rotation axis mm is reduced. Therefore, after processing the X-ray emission surface, the coaxiality between the X-ray emission surface and the rotation axis mm is improved compared to the conventional structure in which the anode target portion and the bottomed cylindrical portion are coupled by a rotating shaft or the like. To do.

  Next, as shown in FIG. 6, the rotating mechanism portion 71 of the X-ray tube is assembled using the rotating portion 61 in which the anode target portion 62 and the bottomed cylindrical portion 63 are integrated. At this time, the fixed body 72 is fitted into the inner space of the bottomed cylindrical portion 63 while maintaining a narrow bearing gap. The fixed body 72 has a bottomed cylindrical shape, and a columnar space 72a is provided therein. The bottom end of the bottomed cylindrical portion 63 is sealed with a sealing body 73.

  On the side surface portion of the fixed body 72, for example, spiral grooves 73a and 73b are provided in pairs at two locations on the upper and lower sides, respectively, and a hydrodynamic slide bearing in the radial direction is formed between the bottomed cylindrical portion 63. In addition, spiral grooves 74a and 74b are provided in the end face on the fixed body 72 and the sealing body 73, and a dynamic pressure type sliding bearing in the thrust direction is formed.

  Next, as shown in FIG. 7, the rotating mechanism portion 71 of the X-ray tube is housed in a vacuum envelope and assembled into a rotating anode X-ray tube. Reference numeral 81 denotes a vacuum envelope constituting an X-ray tube, and the vacuum envelope 81 includes a large diameter portion 81a having a large diameter and a small diameter portion 81b having a small diameter. An output window 82 is provided in a part of the large diameter portion 81a. Then, the rotating mechanism portion 71 (FIG. 6) is accommodated so that the anode target portion 62 is positioned in the large diameter portion 81a and the fitting portion of the rotating portion 61 and the fixed body 72 is positioned in the small diameter portion 81b. Is done. Further, a cathode 83 is disposed at a position facing the X-ray emission surface 62 a of the anode target portion 62.

  In this case, the end 72 b of the fixed body 72 is sealed to the small-diameter portion 81 b by the auxiliary metal ring 84 and the metal sealing 85. A coil 86 that generates a rotating magnetic field is disposed outside the small-diameter portion 81b. A cylindrical member 87 for forming a cooling path is disposed in the space 72 a inside the fixed body 72. The lower end of the cylindrical member 87 in the figure extends to the outside of the vacuum envelope 81. Then, a cooling medium, for example, cooling water, is introduced in the direction of the arrow Y1 from the central portion of the lower end of the cylindrical member 87. The cooling water travels upward, enters the gap between the cylindrical member 87 and the fixed body 72 along the direction of the arrow Y2 at the upper end, and is led out in the direction of the arrow Y3.

  When operating the rotary anode X-ray tube having the above-described configuration, the controller 90 applies a high voltage to the anode formed of the anode target portion 62 and the like. Further, a current is passed through the coil 86 to generate a rotating magnetic field. The rotating part 61 is rotated by this rotating magnetic field. By the rotation of the rotating portion 61, the anode target portion 62 rotates and the X-ray emission surface 62a rotates. In this state, the electron beam is irradiated from the cathode 83 onto the X-ray emission surface 62a, and X-rays are emitted from the X-ray emission surface 62a. The emitted X-rays are output to the outside through the output window 82.

  According to the configuration described above, after the anode target portion 62 formed with the X-ray emission surface 62a and the bottomed cylindrical portion 63 are integrated, the X-ray emission surface 62a and the rotation axis mm of the rotation portion 61 are obtained. The X-ray radiation surface 62a is finished so as to have a coaxial relationship. Therefore, a good coaxial relationship can be obtained between the X-ray emission surface 62a and the rotation axis mm of the rotating portion 61.

  For this reason, even if the X-ray emission surface 62a rotates, the shake of the emitted X-rays becomes small. As a result, an X-ray tube having a substantial focal point as viewed from the output window 82 side, that is, a so-called effective focal point is realized. Moreover, since the anode rotates such as the X-ray emission surface 62a, a large output can be obtained. Therefore, it is effective for shooting a moving subject that is shot in a short time using a large output.

  For example, even when the effective focal point on the X-ray emission surface that emits X-rays has dimensions of 100 μm or less in the vertical direction and the horizontal direction, the increase in effective focal point is small. In addition, when the fitting part between the rotating body and the fixed body is constituted by a dynamic pressure type slide bearing, the effective focus on the X-ray radiation surface is effective even if the vertical and horizontal dimensions are 50 μm or less respectively. The increase in focus is kept small.

  Further, since the anode rotates, the maximum output is increased. For this reason, it is effective when shooting a moving subject that requires a large output, or when zooming in on a fine structure. For example, the present invention is suitable for a disconnection inspection apparatus that in-line inspects whether or not a wiring pattern of an integrated circuit is disconnected.

  Further, the heat of the X-ray emission surface is transmitted to the fixed body via the liquid metal lubricant, and is radiated by the cooling medium flowing inside the fixed body. For this reason, even when operating for a long time, an average output required for practical use can be obtained.

  Next, another example of the X-ray tube 12 (FIG. 1) used in the disconnection detection device will be described with reference to FIG. In FIG. 8, parts corresponding to those in FIGS. 5 to 7 are denoted by the same reference numerals, and overlapping description is partially omitted.

  In this embodiment, when compared with the embodiment of FIGS. 5 to 7, the flat portion at the center of the upper surface of the rotating portion 61 is widely formed, and the X-ray emission surface 62 a is integrated with an annular inclined surface located in the periphery thereof. Is provided directly. Further, the angle θ between the X-ray emission surface 62a and the rotation axis mm is smaller than that in the embodiment of FIGS. For example, the angle θ is set to 45 ° or less. An output window 82 is provided in the direction of the rotation axis mm with respect to the X-ray emission surface 62a, and a cathode 83 is disposed in a direction substantially perpendicular to the rotation axis mm.

  In this case, the electron beam emitted from the cathode 83 travels in a direction substantially perpendicular to the rotation axis mm, and is irradiated on the X-ray emission surface 62a. Then, X-rays are emitted from the X-ray emission surface 62a, and the emitted X-rays are output to the outside through the output window 82.

  In the case of the embodiment of FIG. 8, the distance between the X-ray emission surface 62a and the output window 82 can be reduced. Therefore, the distance between the focal point on the X-ray emission surface 62a and the subject can be reduced, and a further enlarged high-definition X-ray transmission image can be obtained.

  In each of the above-described embodiments, when the X-ray emitting surface emits X-rays, a current is passed through the coil to generate a rotating magnetic field, and a rotating force is applied to the rotating portion. A switch circuit is connected to this coil. For example, the switch circuit is opened during at least a part of the period during which X-rays are emitted, the current flowing through the coil is cut off, and the rotating part such as the X-ray radiation surface rotates with inertia. Let In this case, since there is no influence by the rotating magnetic field, the fluctuation in the X-ray emission direction is reduced, and a smaller effective focus can be realized.

  Further, when the current flowing through the coil is interrupted and the generation of the rotating magnetic field by the coil is stopped, the rotational force of the rotating portion gradually decreases. For this reason, when the rotational force of the rotating portion falls below a certain value, the current is again supplied to the coil, and control is performed so that the rotating force of the rotating portion increases. Such control is sequentially repeated, and, for example, X-rays are emitted from the X-ray emission surface during a period in which generation of a rotating magnetic field by the coil is stopped.

  In the above-described embodiment, a helical groove is formed in the fixed body in order to form a hydrodynamic slide bearing. However, a spiral groove may be formed on the rotating body, or a spiral groove may be formed on both the rotating body and the fixed body.

  As described above, according to the present invention, it is possible to realize a rotary anode X-ray tube with less fluctuation in the X-ray emission direction. Further, since the anode rotates, a large output can be obtained. For this reason, it is effective for photographing a moving subject requiring a large output and a fine structure, and is suitable for, for example, a disconnection inspection apparatus for inspecting disconnection of a wiring pattern of an integrated circuit. Further, when the cooling device is provided in the internal space of the fixed body, the heat of the X-ray emission surface can be easily released, and the average output power increases.

1 is a schematic structural diagram for explaining a disconnection inspection apparatus to which the present invention is applied. FIG. 1 is a schematic structural diagram for explaining an embodiment of the present invention, and shows a rotating portion. FIG. 1 is a schematic structural diagram for explaining an embodiment of the present invention, and shows a rotation mechanism portion. 1 is a schematic structural diagram for explaining an embodiment of the present invention, and shows a state assembled in an X-ray apparatus. FIG. FIG. 6 is a schematic structural diagram for explaining another embodiment of the present invention, in which a rotating portion is shown. FIG. 6 is a schematic structural diagram for explaining another embodiment of the present invention, and shows a rotation mechanism portion. FIG. 5 is a schematic structural diagram for explaining another embodiment of the present invention, and shows a state assembled in an X-ray apparatus. FIG. 5 is a schematic structural diagram for explaining another embodiment of the present invention, and shows a state assembled in an X-ray apparatus. It is a general | schematic structural diagram for demonstrating a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 ... Disc-shaped rotary body 22 ... X-ray radiation surface 23 ... Blackening film 24 ... Rotary shaft 25 ... Rotary body 31 ... Fixed body 41 ... Vacuum envelope 42 ... Output window 43 ... Cathode 46 ... Coil 90 ... Control device

Claims (4)

  An X-ray emitting surface that emits a microfocus X-ray for photographing a subject, a rotating body coupled with the X-ray emitting surface, and a liquid metal lubricant is supplied between the rotating body and the rotating body. A rotating anode type X-ray tube having a fixed body formed with a sliding bearing and the X-ray emitting surface, the rotating body, and a vacuum envelope that accommodates the fixed body, and a rotational force applied to the rotating body. A coil for generating a rotating magnetic field to be applied, and a control device for stopping generation of the rotating magnetic field by the coil and emitting X-rays from the X-ray emitting surface during inertial rotation of the rotating body. X-ray equipment.   The said control apparatus repeats generation | occurrence | production of the rotating magnetic field by the said coil, and the stop of generation | occurrence | production of the rotating magnetic field by a coil, and discharge | releases X-ray | X_line from the said X-ray radiation surface during the inertial rotation of the said rotary body. The X-ray apparatus according to 1.   2. The X-ray apparatus according to claim 1, further comprising control means for stopping generation of a rotating magnetic field of the coil during at least a part of a period during which the X-ray emitting surface emits X-rays.   The X-ray apparatus according to claim 1, wherein the finishing of the X-ray emission surface is performed in a state where the X-ray emission surface and the rotating body are coupled.

Images