JP2006024480A - X-ray tube, x-ray generating device, and x-ray inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray tube with a reduced size, securing an insulation distance between a metallic envelope 12 and a cathode 1. <P>SOLUTION: The X-ray tube comprises a cathode 1 irradiating thermion beam from a filament, to which a prescribed power is supplied; an anode 2, with which the thermion beam emitted from the cathode collides; a high-voltage power source for X-ray generation 19 impressing a prescribed field between the anode 2 and the cathode 1, and making a target 7 generate X-ray by accelerating the thermion discharged from the cathode 1 and making the thermion collide on the target 7 of the anode 2; and an envelope 3 and the metallic envelope 12 housing the anode 2 and the cathode 1 in an airtight vacuum state. The high-voltage power source for X-ray generation 19 sets the voltage to be impressed respectively on the anode 2 and on the cathode 1 in compliance with the insulation distance between the position of a charged part of positive potential of a direct current impressed on the anode 2 and the metallic envelope 12, and the insulation distance between the position of a charged part of negative potential of a direct current impressed on the cathode 1 and the metallic envelope 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an X-ray tube for generating X-rays by accelerating and emitting a thermoelectron beam from a filament supplied with power by a predetermined accelerating electric field and colliding the radiated accelerated thermoelectron beam with a target. In particular, the present invention relates to an X-ray tube in which the X-ray tube main body is miniaturized by arranging electrodes that generate an acceleration electric field.
The present invention also relates to an X-ray generator having the X-ray tube.
Furthermore, the present invention relates to an X-ray inspection apparatus having the X-ray generator.

In recent years, a microfocus X-ray tube having a focus of several microns has attracted attention. The microfocus X-ray tube is expected to obtain high-resolution X-ray transmission images down to the cell level such as fine structure inspection of bonding wires and solder balls of semiconductor integrated circuits and tissue inspection of rat brain.
However, since the enlargement ratio for imaging must be much larger than the popular X-ray tube with a focal point of several millimeters, we devised insulation avoidance of the cathode, anode and the high voltage circuit applied to them. Otherwise, a larger structure than the popular X-ray tube is required.

  Therefore, in order to cope with such a problem, Patent Document 1 adopts a microfocus X-ray tube as a neutral point grounding method, and grid voltages applied to a plurality of grid electrodes arranged to form a microfocus. Generated by the grid voltage generation circuit using the voltage divided from the negative high voltage generation unit of the high voltage generation circuit, the grid voltage generation circuit is controlled by the optical signal from the grid voltage control unit of the control unit, the grid voltage The generator circuit and the grid voltage control unit are connected by an optical cable, and the X-ray tube has a neutral point grounding system, so the distance between the focal point and the X-ray radiation window (envelope) can be reduced. In addition, what enables high-magnification shooting is disclosed.

Patent Document 2 discloses an inverter type X-ray apparatus for supplying to an X-ray tube using a metal envelope.
JP2003-317996A JP-A-5-316085

  However, Patent Document 1 makes no mention of securing an insulation distance from the grid electrode (acceleration electrode) when the envelope is made of a conductive material such as stainless steel or copper.

  Further, Patent Document 2 does not destroy a rectifier or the like of a high-voltage circuit that keeps the anode ground voltage and cathode ground voltage of a power source supplied to an X-ray tube having a metal envelope in balance. Rather, the present invention employs a power supply that takes into account the imbalance.

An X-ray tube apparatus of the present invention includes a cathode part that emits a thermoelectron beam from a filament supplied with a predetermined power source, an anode part that has a target that collides the thermoelectron beam emitted by the cathode part, Acceleration that generates X-rays from the target by applying a predetermined electric field to the anode part and the cathode part, accelerating the thermal electrons emitted from the cathode by the applied electric field and colliding with the target of the anode In an X-ray tube comprising an electric field generation unit and an envelope that accommodates the acceleration electric field generation unit, the anode unit, and the cathode unit in a vacuum-tight manner, the acceleration electric field generation unit is applied to the anode. Depending on the insulation distance between the position of the DC positive potential charging part and the envelope and the insulation distance between the position of the DC negative potential charging part applied to the cathode and the envelope. The anode or It includes a voltage setting means for setting a voltage applied to each of the serial cathode.
As a result, it is possible to secure an insulation distance between the metal envelope and the acceleration electrode and to reduce the size of the X-ray tube.

The X-ray generator of the present invention includes an X-ray tube that generates X-rays, a container that accommodates the X-ray tube so as to be oil-tight with an insulating medium, and a high voltage to the X-ray tube in the container. A high-voltage power supply for supplying an X-ray generator, wherein the X-ray tube emits a thermoelectron beam from a filament to which a predetermined power supply is supplied, and is emitted by the cathode unit. An anode part having a target that collides with a thermionic beam, a predetermined electric field is applied to the anode part and the cathode part, and the thermoelectrons emitted by the cathode are accelerated by the applied electric field to X-rays comprising: an accelerating electric field generating unit that generates X-rays from the target by colliding with the target; and an envelope that accommodates the accelerating electric field generating unit, the anode unit, and the cathode unit in a vacuum-tight manner In the generator, the acceleration electric field generator is The insulation distance between the position of the DC positive potential charging portion applied to the anode and the envelope, and the position of the DC negative potential charging portion applied to the cathode and the envelope. Voltage setting means for setting a voltage applied to each of the anode and the cathode according to the insulation distance.
As a result, the insulation distance between the metal envelope of the X-ray tube and the acceleration electrode can be secured and the X-ray generator can be downsized.

The X-ray inspection apparatus of the present invention is an X-ray generator that irradiates an inspection object with X-rays, an X-ray detector that is disposed opposite to the X-ray generator and detects transmitted X-rays of the inspection object, A display that outputs the transmitted X-rays detected by the X-ray detector as an image. The X-ray generator includes an X-ray tube that generates X-rays, and the X-ray tube is oiled by an insulating medium. An X-ray generator comprising: a container that is housed in a sealed manner; and a high-voltage power supply that supplies a high voltage to the container to the X-ray tube, wherein the X-ray tube has a predetermined power source. A cathode part that emits a thermoelectron beam from the supplied filament, an anode part that has a target that collides the thermoelectron beam emitted by the cathode part, and a predetermined electric field is applied to the anode part and the cathode part. Accelerating thermionic electrons emitted by the cathode by the applied electric field to target the anode X-rays comprising: an accelerating electric field generating unit that generates X-rays from the target by colliding with a target; and an envelope that accommodates the accelerating electric field generating unit, the anode unit, and the cathode unit in a vacuum-tight manner In the generator, the accelerating electric field generating unit is configured to charge a negative DC potential applied to the cathode and an insulation distance between a position of a DC positive potential charged portion applied to the anode and the envelope. Voltage setting means is provided for setting a voltage applied to each of the anode and the cathode according to an insulation distance between the position of the portion and the envelope.
As a result, the insulation distance between the metal envelope of the X-ray tube and the acceleration electrode can be secured and the X-ray inspection apparatus can be downsized.

According to still another preferred embodiment of the present invention, the voltage setting means includes a position of the charged portion having the positive potential and the envelope, and a position of the charged portion having the negative potential and the envelope. The voltage applied to each of the anode or the cathode is set so as to be shorter than the insulation distance.
This makes it easy to set an enlargement ratio from the X-ray focal point to the object to be inspected, particularly in a microfocus X-ray tube.

   According to the present invention, an insulation distance between the metal envelope 12 and the cathode 1 can be ensured.

A first embodiment of the present invention will be described with reference to the drawings. In the first embodiment, an X-ray tube and an X-ray generator having the X-ray tube will be described.
FIG. 1 is a diagram showing a configuration example of an X-ray tube employed in the present invention. FIG. 1 (a) shows a structural example of a rotating anode type microfocus X-ray tube, and FIG. 1 (b) shows a structural example of a fixed anode type microfocus X-ray tube.

  As shown in FIG. 1, the microfocus X-ray tube common to both types includes a cathode 1, an anode 2 disposed opposite to the cathode 1, an envelope 3 that accommodates the cathode 1 and the anode 2, have.

   The cathode 1 is a source of thermionic electrons 4. Specifically, the cathode 1 is composed of a filament (cathode) 5 serving as a source for emitting thermoelectrons 4 and a grid electrode 6 for converging the emitted thermoelectrons 4. The entire cathode 1 has a negative potential compared to the anode 2, and this potential is the reference potential of the cathode 1. In contrast, the grid electrode 6 is adjusted to have a positive potential of several kilovolts relative to the reference potential of the cathode 1, and the heat released from the cathode 5 due to the difference between the adjusted potential and the reference potential. Convergence electron 4. A high voltage (hereinafter referred to as “tube voltage”) is applied between the cathode 1 and the anode 2 in order to accelerate the thermal electrons emitted from the cathode 5 by the high-voltage power supply 19 for X-ray generation. The applied high voltage accelerates the thermoelectrons emitted from the filament before reaching the anode 2, and the thermoelectrons 4 collide with the anode 2 to generate X-rays 10.

  The anode 2 has a target 7 with which the thermoelectrons 4 collide. In the rotating anode type (FIG. 1 (a)), a rotating mechanism 8 for rotating the target 7 is provided. The accelerated thermoelectrons 4 collide with the target 7. This collision surface is said to be the focal point 9 of X-rays.

  In the fixed anode type (FIG. 1 (b)), the target 7 is fixed without rotating. The difference between the two is that the rotating type in which the collision surface moves is higher than the fixed type in which the surface where the accelerated thermoelectrons collide with the target is always constant. This is advantageous for generating X-rays.

  The envelope 3 contains a cathode 1 and an anode 2. Since a potential difference of several hundred kilovolts is generated between the cathode 1 and the anode 2 when X-rays are generated, the inside of the envelope 3 is almost the same from the necessity of preventing discharge in the envelope 3. It is kept in a vacuum.

  The envelope 3 is provided with a radiation window 11 made of beryllium for emitting X-rays 10, and a metal portion is provided in a part of the envelope 3 in order to fix the radiation window 11. This metal part is called a metal envelope 12.

Next, an X-ray generator including the microfocus X-ray tube 13 of FIG. 1 (a) will be described with reference to FIG.
FIG. 2 is a diagram showing a configuration example of an X-ray generator including the rotating anode type microfocus X-ray tube of FIG. 1 (a).

  As shown in FIG. 2, the X-ray generator 22 is a stator that is attached so that the microfocus X-ray tube 12 shown in FIG. 1 (a) and the anode 2 of the microfocus X-ray tube 12 can rotate. A coil 14 and a tube support member 15 for attaching the microfocus X-ray tube 13 to the storage container 17 are provided.

The stator coil 14 is supplied with electric power to rotate like an induction motor about the anode 2 as a rotation axis.
The tube support member 15 attaches the microfocus X-ray tube 13 in a storage container 17 filled with an electrically insulating medium such as insulating oil 16 or Fluorinert.
In addition, X-rays 10 from other than the radiation window are covered with lead 18 inside the storage container 17 in order to prevent leakage.

In addition, the storage container 17 may contain a high-voltage power supply 19 for X-ray generation and a power supply 20 for X-ray control, and the X-ray tube and power supply may be integrated to facilitate handling as a so-called mono tank. is there.
In addition, when the rotating anode type microfocus X-ray tube 13 is mounted on the storage container 17, the starter power source 21 for the stator coil is stored.

Here, the tube voltage applied between the cathode 1 and the anode 2 is 150 kV. The tube voltage is set based on a predetermined insulation distance, and a positive potential of 100 kV is applied to the anode 2 and a negative potential of 50 kV is applied to the cathode 1 based on the result of the voltage setting. When this application condition is adopted for the tube voltage of 150 kV, the reference potential of the cathode 1 is reduced from 75 kV to 50 kV as compared with the case where it is divided into two equal parts of 75 kV. For this reason, the insulation distance between the position where the negative potential of the cathode 1 is charged and the metal envelope 12 can be reduced to 67%.
As a result, the distance between the cathode 1 and the metal envelope 12 in the arrangement direction of the target 7 can be shortened, and the arrangement direction of the target 7 having the dimensions of the metal envelope 12 can be reduced. It can contribute to.
The application conditions to the positive potential and the negative potential here are only examples, and any combination is possible as long as it excludes the bisection.

  Also, in this case, the insulation distance between the position of the positively charged part of the anode 2 and the metal envelope 12 is shorter than the insulation distance between the position of the negatively charged part of the cathode 1 and the metal envelope 12. I have to. As a result, if the insulation distance between the metal envelope 12 and the anode 2 is increased, the target 7 is disposed at the lower side of the drawing, and the distance between the target 7 and the X-ray radiation window 11 is increased. Therefore, in particular, in a microfocus X-ray tube, the magnification rate from the X-ray focal point to the inspection object can be easily set.

  According to this embodiment, the cathode 1 that emits a thermionic beam from a filament supplied with a predetermined power source, the anode 2 that has the target that collides the thermionic beam emitted by the cathode portion, and the anode 2 X-ray generation that generates a X-ray from the target 7 by applying a predetermined electric field to the cathode 1 and accelerating the thermal electrons emitted from the cathode 1 by the applied electric field and colliding with the target 7 of the anode 2 X-ray generation in an X-ray tube comprising a high-voltage power supply 19 for use, an envelope 3 for housing the anode 2 and the cathode 1 in a vacuum-tight manner, and a metal envelope 12 The high-voltage power supply 19 is used for the insulation distance between the position of the DC positive potential charging portion applied to the anode 2 and the metal envelope 12, and the position of the DC negative potential charging portion applied to the cathode 1. So that the insulation distance between the metal envelope 12 and the metal envelope 12 is located differently What I setting the voltage applied to each of the electrode 2 or the cathode 1, the metal envelope 12 and the miniaturization of the insulation distance ensured and X-ray tube the cathode 1 can be achieved.

  The X-ray tube 13, a storage container 17 for storing the X-ray tube 13 so as to be oil-tight with an insulating medium, and a high-voltage power supply for supplying a high voltage to the X-ray tube 13 in the storage container 17 are provided. In addition, the X-ray generator can secure the insulation distance between the metal envelope 12 and the cathode 1 and can reduce the size of the X-ray generator.

Next, a second embodiment of the present invention will be described with reference to the drawings. In the first embodiment, an X-ray inspection apparatus having the X-ray generator of the first embodiment will be described.
FIG. 3 is a diagram showing a configuration example of an X-ray inspection apparatus employing the X-ray generator of FIG.

  As shown in FIG. 3, the X-ray inspection apparatus 29 includes an X-ray generator 22 including a microfocus X-ray tube 13 that irradiates the inspection object 24 with X-rays, and an X-ray generator 22 disposed opposite to the X-ray generator 22. An X-ray detector 23 that detects transmitted X-rays of the inspection object 24, a shield 26 that shields the X-ray generator 22 and the X-ray detector 23 from X-rays, and the X-ray detector 23 are electrically connected. The monitor unit 27 includes an X-ray generator 22, an X-ray detector 23, and a control unit 28 that controls the monitor unit 27.

  The X-ray generator 22 irradiates the inspection object 24 on the observation table 25 with X-rays. The X-ray detector 23 detects transmitted X-rays of the inspection object 24 and is detected by an image intensifier, a flat panel detector, or the like. The subject 24 is a semiconductor integrated circuit. The observation table 25 has a structure like a turntable on which the subject 24 is placed and can move the subject 24 to an arbitrary position and angle, and observation is possible from various angles. The shield 26 accommodates these X-ray generator 22, X-ray detector 23, and observation table 25, and performs X-ray protection to the surroundings. The monitor unit 27 displays and outputs the image signal detected by the X-ray detector 23. The control unit 28 controls the X-ray conditions of the X-ray generator 22 and the position of the observation table 25.

The magnification used in the X-ray inspection apparatus 29 is an optical magnification. This is because the enlargement ratio obtained by image processing is enlarged based on the image signal obtained by the X-ray detector 23, which causes deterioration of the image. On the other hand, the optical magnification is determined by the focal point 9 of the X-ray 10, the inspection object 24, and the geometric shape of the X-ray detector 23.
Here, the distance between the focal point and the object to be inspected (Focus Object Distance: hereinafter referred to as “FOD”) 30 and the distance between the focal point 9 and the X-ray detector 23 (Focus Detector Distance: hereinafter referred to as “FDD”) 31 are assumed. The optical magnification is determined by dividing FDD31 by FOD30.
In order to increase the optical magnification, it is necessary to make the FOD 30 as small as possible. However, when the FOD 30 is reduced, the cathode 1 and the anode 2 of the X-ray tube have a metal envelope 12 including a radiation window 11. Will approach. Since the metal envelope 12 is normally fixed at the ground potential, the FOD 30 is within the range where the insulation is maintained by the electric field strength of the electric field formed by the cathode 1, the anode 2 and the metal envelope 12. Become.

  According to the present embodiment, the X-ray generator 22 of the first embodiment for irradiating the inspection object 24 with X-rays, and the transmitted X-rays of the inspection object 24 that are arranged opposite to the X-ray generator 22 are detected. X-ray detector 23 and monitor unit 27 that outputs the transmitted X-rays detected by X-ray detector 23 as an image, so that the insulation distance between the metal envelope of the X-ray tube and the acceleration electrode can be increased. Secure and miniaturize X-ray inspection equipment.

  Further, in addition to what has been described in the above embodiment, any configuration capable of realizing the technology described in the claims is included in the technical idea of the present invention.

The figure which shows the structural example of the X-ray tube employ | adopted by this invention. FIG. 2 is a diagram showing a configuration example of an X-ray generator including the rotating anode type microfocus X-ray tube of FIG. FIG. 3 is a diagram showing a configuration example of an X-ray inspection apparatus employing the X-ray generator of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Cathode 2 ... Anode 3 ... Envelope 11 ... Radiation window 12 ... Metal envelope 13 ... Micro focus X-ray tube

Claims (6)

A cathode part that emits a thermoelectron beam from a filament supplied with a predetermined power source, an anode part having a target that collides the thermoelectron beam emitted by the cathode part, and a predetermined part on the anode part and the cathode part Accelerated electric field generator for generating X-rays from the target by applying an electric field, accelerating the thermal electrons emitted from the cathode by the applied electric field and colliding with the target of the anode, and generation of the accelerated electric field An X-ray tube comprising: an envelope, an envelope containing the anode part and the cathode part in a vacuum-tight manner;
The accelerating electric field generator includes an insulation distance between the position of a DC positive potential charging portion applied to the anode and the envelope, and a position of a DC negative potential charging portion applied to the cathode. An X-ray tube comprising voltage setting means for setting a voltage applied to each of the anode and the cathode according to an insulation distance from the envelope.   The voltage setting means sets the voltage applied to each of the anode or the cathode so that an insulation distance from the positive potential envelope is shorter than an insulation distance from the negative potential envelope. The X-ray tube according to claim 1, wherein the X-ray tube is set. An X-ray tube that generates X-rays, a container that accommodates the X-ray tube so as to be oil-tight with an insulating medium, and a high-voltage power source that supplies the container with a high voltage to the X-ray tube. X-ray generator,
The X-ray tube includes a cathode part that emits a thermoelectron beam from a filament supplied with a predetermined power source, an anode part that has a target that causes the thermoelectron beam emitted by the cathode part to collide, and the anode part. An accelerating electric field generation unit that generates a X-ray from the target by applying a predetermined electric field to the cathode, accelerating the thermal electrons emitted from the cathode by the applied electric field and colliding with the target of the anode And an X-ray generator comprising the accelerating electric field generating unit, the anode unit, and the envelope containing the cathode unit in a vacuum-tight manner,
The accelerating electric field generator includes an insulation distance between the position of a DC positive potential charging portion applied to the anode and the envelope, and a position of a DC negative potential charging portion applied to the cathode. An X-ray generator comprising voltage setting means for setting a voltage applied to each of the anode and the cathode according to an insulation distance from the envelope.   The voltage setting means sets the voltage applied to each of the anode or the cathode so that an insulation distance from the positive potential envelope is shorter than an insulation distance from the negative potential envelope. The X-ray generator according to claim 3, wherein the X-ray generator is set. An X-ray generator for irradiating the inspection object with X-rays, an X-ray detector disposed opposite to the X-ray generator for detecting transmitted X-rays of the inspection object, and detected by the X-ray detector A display that outputs transmitted X-rays as an image;
The X-ray generator includes an X-ray tube that generates X-rays, a container that accommodates the X-ray tube so as to be oil-tight with an insulating medium, and supplies a high voltage to the X-ray tube. An X-ray generator comprising:
The X-ray tube includes a cathode part that emits a thermoelectron beam from a filament supplied with a predetermined power source, an anode part that has a target that causes the thermoelectron beam emitted by the cathode part to collide, and the anode part. Accelerated electric field generator for generating X-rays from the target by applying a predetermined electric field to the cathode, accelerating the thermal electrons emitted from the cathode by the applied electric field and colliding with the target of the anode And an X-ray generator comprising the accelerating electric field generating unit, the anode unit, and the envelope containing the cathode unit in a vacuum-tight manner,
The accelerating electric field generator includes an insulation distance between the position of a DC positive potential charging portion applied to the anode and the envelope, and a position of a DC negative potential charging portion applied to the cathode. An X-ray inspection apparatus comprising voltage setting means for setting a voltage applied to each of the anode and the cathode according to an insulation distance from the envelope.   The voltage setting means sets the voltage applied to each of the anode or the cathode so that an insulation distance from the positive potential envelope is shorter than an insulation distance from the negative potential envelope. The X-ray inspection apparatus according to claim 5, wherein the X-ray inspection apparatus is set.

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