JPH11248648A - X-ray tomographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a clear tomographic image in real time by irradiating a rotating object with X-rays, then rotating a transmisive X-ray image by an X-ray image sensor synchronously with the rotation of object, and performing addition processing. SOLUTION: The X-ray tomographic device comprises an X-ray detection system composed of an X-ray image intensifier 40, image rotator 42 and CCD 45. An X-ray 27 passes through a object 2 and is made incident the intensifier 40, and then converted into an optical image thereat. The image is rotated synchrously with the rotation of object 2 on a rotation stage 38. When the image is read out for every rotation thereof under the condition where the accumulation time of the CCD 45 is for example the time when the stage 28 rotates once, the images except on a focus face 4 rotate on the surface of CCD 45 and mage vague, so that only the tomographic image on the focus face 4 can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray tomography apparatus using transmission X-rays, and more particularly to an X-ray tomography apparatus suitable for inspecting and measuring the internal structure of a multilayer circuit board.

[0002]

2. Description of the Related Art Conventionally, laminography has been known as a technique for detecting a tomographic image at a certain focal plane inside a target object using transmitted X-rays. In this technique, two of three elements, an X-ray source, an object, and a detector, are moved in synchronization to detect a tomographic image.

As this kind of technology, for example, Japanese Patent Laid-Open No. 59-1
The thing described in No. 16040 is known. This technique involves illuminating an object with a fixed radiation source,
The object and a surface sensitive to radiation and located next to the object with respect to the radiation source and contained in one plane are synchronously rotated in the same direction around a first axis and a second axis, respectively. Rotating so that the first axis and the second axis are parallel to each other, and the first axis is converted to a second axis by a similarity transformation of positive ratio and the center of the radiation source. Wherein the radiation source, the object and the sensitive surface are arranged such that they remain exposed to radiation during their rotation, and the plane containing the cross-section of the object extends the first axis through the second axis.
A stage in which the surface is converted into a surface including the sensitive surface by a similarity conversion into an axis;
Forming an image of the same value of degrees or greater and less than 90 degrees to form an image of at least a portion of the cross-section on the sensitive surface, thereby forming one surface. It is configured to perform tomographic imaging of the object along the cross section of the object contained therein. This technology simply relates to a method of synchronously rotating an object and a film to perform cross-sectional imaging.

Further, in the known example described in Japanese Patent Application Laid-Open No. 2-501411, an X-ray source is moved in a circular pattern by rotating and deflecting an electron beam so that a fluorescent screen is moved along a circular path. By doing so, tomographic imaging is performed.

[0005]

However, in the first prior art, since a film is used for the detecting section, the detected image cannot be viewed in real time. Further, since the image moves in parallel on the film surface, the linear structure extending in the moving direction has a drawback that the image is clearly detected without blurring even on a surface other than the focal plane.

In the second prior art, since the electron beam is rotationally deflected, aberration occurs in the electron optical system, and a fine electron beam cannot be obtained. For this reason, a microfocus X-ray source cannot be obtained, and the detection resolution is low.

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation of the prior art, and an object thereof is to provide an X-ray image forming apparatus capable of blurring an image of a linear structure on a plane other than the focal plane. An object of the present invention is to provide a line tomography method and apparatus. It is another object of the present invention to provide an X-ray tomography apparatus capable of displaying a tomographic image in real time without using a film. It is a further object of the present invention to provide an X-ray tomography apparatus with high resolution. In addition, another object of the present invention is to realize an apparatus for automatically inspecting a circuit connection portion such as a soldered portion on a circuit board having a multilayer structure.

[0008]

In order to achieve the above-mentioned object, an X-ray tomography apparatus according to the present invention comprises an X-ray source,
Means for rotating an object to be imaged, means for detecting an image of X-rays emitted from the X-ray source and transmitted through the object, and transmitting X-ray images detected by the detecting means. Means for performing rotation processing in synchronization with the rotation of the object, addition means for adding the image rotated by the rotation processing means in real time, and image information added in real time by the addition means And a display means for displaying the information as. Further, it is configured such that the means for rotating the object comprises a rotating stage, and the means for detecting the X-ray image comprises an X-ray image sensor. Further, the means for detecting the X-ray image includes an X-ray image intensifier for converting the X-ray image into an optical image, and an imaging tube for detecting the optical image, and the means for rotating the image includes a raster of the imaging tube. It is configured to comprise a circuit that rotates the scan. The means for detecting the X-ray image is constituted by an imaging tube. In addition, a microfocus X-ray tube having a unit for decentering and rotating a transmission target is used as the X-ray source. Further, the transmission type target included in the microfocus X-ray tube is configured to include at least two layers of an X-ray generation layer and a support layer. The image processing apparatus further includes an image processing circuit that detects a defect of the target object from the video information.

The principle of X-ray tomography according to the present invention will be described with reference to FIG. As can be seen from this figure, X-rays 27 are generated radially from the fixed X-ray source 1, and the object 2 to be imaged rotates around the rotation axis 5 inclined with respect to the optical axis 7. The detector 3 has a rotating shaft 6 parallel to the rotating shaft 5.
Around the object 2 in synchronization with the object 2. A plane including the intersection of the optical axis 7 and the rotation axis 5 and perpendicular to the rotation axis 5 (hereinafter, referred to as a plane)
The projected image of the focal plane 4 is detected as a stationary image by the detector 3, but the projected image other than the focal plane 4 is blurred because it is detected as a rotating image. Therefore, the image of the structure outside the focal plane 4 can be blurred, and only the X-ray tomographic image of the focal plane 4 can be obtained clearly.

FIG. 2 shows the basic configuration of the X-ray tomography apparatus according to the present invention. As can be seen from this figure, X-rays 27 are generated radially from the fixed X-ray source 1, and the object 2 to be imaged rotates around the rotation axis 5 inclined with respect to the optical axis 7. The X-ray detection system includes a unit 8 for converting an X-ray image into an optical image, a unit 9 for rotating the optical image, and a unit 10 for converting the optical image into an electric signal serving as a video signal. Means 12 and 13 for transmitting an optical image as means
Is provided. Means for rotating the optical image 9
The object 11 is rotated in synchronization with the object 2, and an X-ray tomographic image is obtained in real time by the means 11 for displaying an electric signal as image information.

FIG. 3 shows the basic configuration of a microfocus X-ray source according to the present invention. This means is for improving the resolution. In order to improve the resolution, it is necessary to reduce the penumbra of the projected image, and an X-ray source having a minute focal spot size is required. The operation principle of this X-ray source is as follows.

That is, the electron beam 2 generated from the cathode 20
When 1 is focused by the lens 22 and irradiated on the target 23, X-rays 27 are generated. Target 23 is a heavy metal X
It is composed of a line generating layer 24 and a light element support layer 25.
In this case, for example, tungsten is selected as the heavy metal, and beryllium is selected as the light element. At this time, by focusing the electron beam 21 sufficiently small and making the X-ray generation layer 24 thin, a minute focal spot size can be realized. Further, in order to prevent the target 23 from being damaged by heat generated when the electron beam 21 collides, the target 23 is rotated around a rotation axis 26.

FIG. 4 shows the basic configuration of an automatic inspection apparatus to which the X-ray tomography apparatus according to the present invention is applied. As shown in FIG. 4, a sample stage 31 for holding the X-ray source 1 and the circuit board 30 and a detection unit 32 for detecting an X-ray tomographic image of the circuit board 30
And a defect determination unit 33. Sample stage 31
Has a rotation function of driving the circuit board 30 to rotate about the rotation axis 5 and a function of sending the circuit board 30 for changing the detection field of view to step-and-repeat. In the inspection procedure, first, a focal plane is focused on a cross section of a soldered portion or the like to be inspected, and a tomographic image is detected. Next, the detected image is processed by the defect determination unit 33 to extract a defective portion. Next, the sample stage 31 is sent to change the detection visual field,
A tomographic image in the changed detection field of view is detected, and a defective portion is extracted. The same operation is repeated to inspect the entire surface of the circuit board 30. The detection unit 32 has the configuration shown in FIG.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In the following description, components that can be regarded as the same as the components described so far are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 5 is a diagram showing an example of a tomographic apparatus according to the present invention. This tomography apparatus basically includes an X-ray detection system, a sample stage system, and a display system. The sample stage system includes an XY stage 37, a rotary stage 38, and a Z stage 39.
An object 2 such as a circuit board is held on a chuck 7 via a chuck 36. Each of the stages 37, 38, and 39 is of a transmission type that does not block the optical axis 7. The X-ray detection system includes an X-ray image intensifier 4 from the X-ray tube 35 which is an X-ray source.
0, lens 41, image rotator 42, lens 44
And a solid-state imaging device (CCD) 45. The display system comprises a display 46.

In the tomographic apparatus generally constructed as described above, the X-rays 27 generated from the X-ray tube 35 are emitted to the object 2 side, pass through the object 2 and enter the X-ray image intensifier 40. I do. The X-ray image is amplified in brightness by an X-ray image intensifier 40 and is converted into an optical image. This optical image is subjected to CC by the lens 41 and the lens 44.
An image is formed on D45, converted into an electric signal as image information by the CCD 45, and displayed on the display 46.

The procedure for obtaining a tomographic image will be described below. Object 2
And the X-ray image intensifier 40 are positioned so that the rotation axes 5 and 6 are parallel to each other, and the optical axis 7 is inclined with respect to the rotation axis 5. The object 2 is rotated by the rotating stage 38, and the image rotator 42 is simultaneously rotated by the rotating stage 43.

The image rotator 42 includes a Dove prism (image rotating prism) and an image rotating mirror composed of three mirrors, and both can be used. When a Dove prism is used, light rays incident on the Dove prism must be parallel to suppress the occurrence of aberration. The light collimated by the lens 41 is made incident on the Dove prism, and is imaged on the CCD 45 by the lens 44. FIG. 5 shows an example using a Dove prism. When using an image rotation mirror, it is not always necessary to make parallel light. Since the optical image rotates twice when the image rotator 42 makes one rotation, the driver 47 controls the speed of the rotating stage 43 to be half the speed of the rotating stage 38 to rotate the object 2 and the optical image synchronously. As this control, for example, a stepping motor is used to control the frequency of the drive pulse at 2: 1 or a motor with an encoder is used to monitor the rotation and control the motor rotation so as to be synchronized. It is also possible.

Next, the accumulation time of the CCD 45 is set as the time required for the rotation stage 38 to make one rotation, and the image is read out every time the image makes one rotation. Therefore, the image other than the focal plane 4 is rotated and blurred on the surface of the CCD 45, so that the focal plane 4
Only an X-ray tomographic image can be obtained. Of course, the read cycle of the CCD 45 can be made longer than one rotation of the image, but thermal noise increases when used in long-time exposure, so it is effective to cool the CCD 45 to reduce the thermal noise. Since the focal plane 4 is a plane including the intersection of the optical axis 7 and the rotation axis 5 of the rotation stage 38, a tomographic image of the object 2 on an arbitrary plane can be obtained by moving the Z stage 39 that moves in the vertical direction up and down Is obtained. Further, the visual field can be arbitrarily changed by moving the XY stage 37. Thereby, even a circuit board having a multilayer structure can inspect a tomographic plane at an arbitrary position.

The X-ray tube 35 is preferably a micro focus type in order to improve the detection resolution. X-ray tube 3
By making the sample stage 5, the sample stage, and the X-ray detection system movable, it is possible to change the detection magnification and adjust the focus range of the tomographic image. In this case, the magnification becomes higher when the sample stage is brought closer to the X-ray tube 35, and becomes lower when the sample stage is separated. The optical axis 7
When the angle between the rotation axis 5 and the rotation axis 5 is increased, the focusing range becomes narrower, and when the angle is decreased, the focusing range becomes wider.

FIG. 6 shows an embodiment in which an image rotating mirror composed of three mirrors is used as the image rotator 42.
The image rotation mirror 94 is composed of three mirrors 95. Unlike the Dove prism, the image rotation mirror does not need to convert incident light into parallel light, so it is necessary to divide the optical system that forms the output image of the X-ray image intensifier 40 on the CCD 45 into a collimator lens and an imaging lens. And can be realized by one lens 41.

As for the X-ray detection system used in the X-ray tomography apparatus, there are several embodiments in addition to the above-described embodiment. Next, another embodiment of the X-ray detection system will be described. Note that an embodiment of the X-ray detection system described below is as follows.
By exchanging the corresponding components with the X-ray detection system shown in FIG. 5 (hereinafter also referred to as a first embodiment of the X-ray detection system), an X-ray tomography apparatus can be obtained as it is.

FIG. 7 shows a second embodiment of the X-ray detection system.
In this embodiment, an X-ray image is converted into an optical image by an X-ray image intensifier 40, and the optical image is converted into a lens 41,
At 44, an image is formed on the detection surface of the image pickup tube 50. An image rotator 42 is inserted in the middle of the optical path,
3, the image rotator 42 can be rotated. As a result, the converted optical image rotates. The rotation stage 43 for rotating the image rotator 42 is controlled by a driver 47 so as to rotate at half the speed of the rotation stage 38 for rotating an object. Further, the optical image is converted by the image pickup tube 50 into an electric signal (video signal) serving as video information. Since the image pickup tube 50 outputs an image at a TV rate, that is, every 1/30 second, the addition circuit 51 adds the image of the time during which the optical image makes one rotation. For example, if the rotation cycle is 0.5 seconds, 15 images are added. The addition circuit 51 can be realized by, for example, converting an image signal into a digital signal by an A / D converter, sampling the image signal, adding 15 images to a frame memory, and returning the image signal to a video signal by a D / A converter. The displayed image is displayed on the display 46.

FIG. 8 shows a third embodiment of the X-ray detection system.
In this embodiment, the X-ray image is converted into an optical image by the fluorescent screen 52. The X-ray image intensifier 40 used in the first and second embodiments has an image distortion of about 5%.
And the resolution is about 5 lp (line pair) / m
m and low. However, the fluorescent screen 52 has no image distortion and a resolution of up to about 20 lp / mm. As the fluorescent screen 52, a single-crystal scintillator, for example, CsI (Tl) (thallium-activated cesium iodide) or CaF ₂ (Eu) is polished to a thickness of about 0.4 mm in order to improve the resolution. Are preferred.
Further, since the light excited by the X-ray irradiation is weak, an optical image with a sufficient light quantity cannot be obtained. Therefore, the image of the fluorescent screen 52 is formed on the image intensifier 54 by the lens 53, and the brightness is amplified by the image intensifier 54. Image intensifier 54
Is preferably a proximity image intensifier having no image distortion. Here, it goes without saying that an image fiber may be used instead of the lens 53.
The optical image amplified by the image intensifier 54 is formed on the CCD 45 by the lens 41 and the lens 44, and the image is rotated by the image rotator 42 in the optical path. Then, it is converted into an electric signal (video signal) by the CCD 45 and displayed on the display 46. The configuration after the image intensifier 54 is the same as that of the first embodiment (FIG. 5) of the X-ray detection system. In this case, CC
Instead of D45, it is also possible to use an image pickup tube as shown in the second embodiment of the X-ray detection system (FIG. 7).

FIG. 9 shows a fourth embodiment of the X-ray detection system.
In this embodiment, an X-ray image is converted into an optical image by the fluorescent screen 52 as in the third embodiment (FIG. 8) of the X-ray detection system. The fluorescent screen 52 is configured to be rotatable by a rotary stage 55, and is controlled by a driver 47 to rotate at the same speed as the object 2. Fluorescent screen 5
By rotating the object 2 and the object 2 synchronously, the object 2
The image of the focal plane 4 is stopped on the fluorescent screen 52. Therefore, by using a material having a long afterglow time for the fluorescent screen 52, the image on the focal plane 4 is detected brightly. The optical image on the fluorescent screen 52 is formed on the CCD 45 by the lens 41 and the lens 44, and the image is rotated by the image rotator 42 inserted in the optical path. The CCD 45 displays the detected electric signal (video signal) on the display 46 with the time required for one rotation of the image as the exposure time. The structure after the lens 41 is the same as the structure of the first embodiment (FIG. 5) of the X-ray detection system. Also,
Insert an image intensifier in the middle of the optical path,
It is also possible to amplify the brightness. In addition, CCD45
Instead of this, it is also possible to use an image pickup tube as shown in the third embodiment (FIG. 7) of the X-ray detection system. A high-sensitivity imaging tube is suitable. For example, SIT (Silic)
on Intensified Target) tube, avalanche multiplication type imaging tube, or ICCD (Imag)
e Intensified CCD) camera and the like.

FIG. 10 shows a fifth embodiment of the X-ray detection system. This embodiment does not use an image rotator,
This is an example in which an image is rotated by image processing. The X-ray detection system in this embodiment includes an X-ray image sensor 56, an A / D
Converter 57, image processing unit 58, frame memory 59
And a D / A converter 60.

In such an X-ray detection system, first, an X-ray image is converted into an electric signal (video signal) by the X-ray image sensor 56. The X-ray image sensor 56 outputs an electric signal (video signal) every TV rate, that is, every 1/30 second. This video signal is converted into a digital signal by the A / D converter 57, whereby a digital image is obtained. next,
The obtained digital image is rotated by an angle synchronized with the rotation of the object by the image processing unit 58, and the image for one rotation is added to the frame memory 59. For example, when rotating an object at a cycle of 2 seconds, a 6 ° image rotates in 1/30 seconds. Therefore, the first detected image is rotated by 0 °, the second detected image is rotated by 6 °, and the nth detected image is rotated by 6 °.
X (n-1) degrees. Then, the image up to the 60th detected image is added to the frame memory 59. The digital image integrated in this manner is converted into an analog video signal by the D / A converter 60, and
6 is displayed. The X-ray image sensor 56 in this embodiment can be replaced with, for example, an X-ray vidicon, a system combining an X-ray image intensifier and an imaging tube, a system combining a fluorescent screen and an imaging tube, and the like.

FIG. 11 shows a sixth embodiment of the X-ray detection system. This embodiment is an embodiment using an image pickup tube for rotary raster scanning. The X-ray detection system in this embodiment includes an X-ray image intensifier 40, a lens 9
0, an imaging tube 50, a rotating raster waveform generating circuit 91, a clock generating circuit 92, an adding circuit 51, and a driver 47.

In this embodiment, an X-ray image is converted into an optical image by an X-ray image intensifier 40, and the optical image is formed on a detection surface of a tube 50 by a lens 90. The image pickup tube 50 is subjected to rotary raster scanning by the drive waveform generated by the rotating raster waveform generation circuit 91. Therefore, the rotated image is detected as a still image. In order to synchronize the rotation speed of the rotary stage 38 for rotating the object 2 shown in the first embodiment (FIG. 5) of the X-ray detection system with the speed of the rotary raster scanning of the imaging tube 50, a clock generation circuit 9 is provided.
The rotation raster waveform generating circuit 91 and the driver 47 are driven according to the clock signal from the second. An image detected by the image pickup tube 50 is added with an image for a time equal to or more than one rotation of the image by an adding circuit 51 and displayed on the display 46. In this embodiment, instead of the X-ray image intensifier 40, a fluorescent screen or a combination of a fluorescent screen and an image intensifier can be used.

FIG. 12 shows a seventh embodiment of the X-ray detection system. The X-ray detection system in this embodiment is an X-ray vidicon 9
3. It basically comprises an adding circuit 51, a clock generating circuit 92, a rotating raster waveform generating circuit 91 and a driver 47.

In this embodiment, first, an X-ray image is detected by the X-ray vidicon 93. At this time, the rotating image is detected as a still image by performing a rotary raster scan using the drive waveform generated by the rotating raster waveform generating circuit 91.
In order to synchronize the rotation speed of the rotation stage 38 (FIG. 5) with the speed of the rotary raster scanning of the image pickup tube 50, the rotation raster waveform generation circuit 91 and the driver 47 are driven according to the clock signal from the clock generation circuit 92. The image detected by the image pickup tube 50 is added with an image for a time equal to or more than one rotation of the image by an adding circuit 51 and displayed on the display 46.

In order to improve the detection resolution of the X-ray tomography apparatus according to the present invention, it is necessary to miniaturize the X-ray source. For this purpose, it is necessary to reduce the size of the irradiated electron beam and to make the target a thin film transmission type.

FIG. 13 shows X for obtaining a fine focal spot size.
1 shows an embodiment of a wire tube. The X-ray tube mainly includes a filament 61, a Wehnelt 62, an electric field lens 63, an X-ray generation layer 24, a support layer 25, and a target 23, and is housed in a glass bulb 64. The X-rays 27 can be emitted from an X-ray transmission window 69 provided in the glass bulb 64 facing the target 23.

That is, in the X-ray tube, the filament 61
Is focused on the target 23 by the Wehnelt 62 and the electric field lens 63. Target 23
Has a structure in which the periphery is fixed to a bearing shaft 68 and is rotatable by a bearing 67. A stator 65 is provided outside the glass bulb 64, and when the stator 65 is excited, a rotor 66 inside the glass bulb 64 rotates.
Rotates. The X-rays 27 generated in the target 23 by the irradiation of the electron beam 21 are emitted to the outside from the X-ray transmission window 69 and extracted as described above.

In order to reduce the diameter of the X-ray source, the beam diameter of the electron beam 21 irradiated on the target 23 must be reduced. For this reason, the filament 61 is preferably a high-luminance material, and a LaB ₆ (lanthanum hexaborite) filament is more suitable than a conventionally used tungsten filament, and has an advantage of a long life. Alternatively, a field emission type filament may be used. In addition, when the number of the electric field lenses 63 for focusing the electron beam 21 is plural, a fine electron beam diameter can be easily obtained.

The electrons incident on the target 23 collide with and scatter with atoms, and spread inside the target. Tube voltage 100
The magnitude of the spread at kV is said to be about 5 μm, and therefore, even if the electron beam is focused at one point (spread is 0), the X-ray source diameter becomes 5 μm or more. In order to reduce the X-ray source diameter, it is necessary to use a thin film target to limit the electron scattering region. In the present invention, the target 23 has a multilayer structure of the X-ray generation layer 24 and the support layer 25. The X-ray generation layer 24 is optimally made of tungsten or an alloy of tungsten and rhenium, and its thickness depends on the target X-ray source diameter.
m. Beryllium, which is a light element, is optimal for the support layer 25, and may be about 10 μm. The support layer 25 has the function of increasing the mechanical strength of the target 23 and at the same time releasing heat generated by the irradiation of the electron beam 21. Furthermore, the target 23 is rotated by the stator 65 and the rotor 66 so as not to irradiate the electron beam 21 to one location of the target 23, thereby increasing the strength against heat and preventing breakage.

The embodiment shown in FIG. 13 (hereinafter also referred to as the first embodiment of the X-ray tube) is an embodiment using an electric field lens for an electron lens, but shows an embodiment using an electromagnetic lens. It is shown in FIG. In this embodiment, the electron beam 21 generated from the filament 61 is focused on the target 23 by the Wehnelt 62 and the magnetic lens 70. The periphery of the target 23 is fixed to a bearing shaft 68 and is rotatable by a bearing 67.
Similarly, the embodiment is driven to rotate by the stator 65 and the rotor 66. The inside of the glass bulb 64 is under a high vacuum. Although the electric field lens 63 of the first embodiment of the X-ray tube was inside the glass bulb 64, in this embodiment, the glass bulb 64 passes through the center of the electromagnetic lens 70. Therefore, when the life of the filament 61 or the target 23 has expired, the glass bulb 64 need only be replaced, and the electromagnetic lens 70 can be used as it is.

As in the first embodiment of the X-ray tube, a plurality of electromagnetic lenses 70 can easily obtain a fine focal size.

In the above two embodiments, the glass bulb 64 is used.
FIG. 15 shows an embodiment of an X-ray tube of an open type, which is an embodiment of a sealed tube type X-ray tube in which various elements are enclosed. This embodiment of the X-ray tube is of the open type, and instead of the glass bulb 64 in the first embodiment of the X-ray tube, a vacuum vessel 71 is used.
Is used to suck the air in the container with a vacuum pump 74 to maintain a vacuum state, and replace the combination of the stator 65 and the rotor 66 with the combination of the motor 72 and the gear 75,
Further, a magnetic lens 70 is used instead of the electric lens 63.

In this embodiment, the electron beam 21 generated from the filament 61 is applied to the Wehnelt 62 and the magnetic lens 70.
To focus on the target 23. The periphery of the target 23 is fixed to a bearing shaft 68,
It has a rotatable structure. Target 23
Is driven by rotating a motor 72 outside the vacuum vessel 71 and via a rotation introducing shaft 73 and a gear 75. It is needless to say that the target 23 may be rotated by a stator and a rotor similarly to the first embodiment of the X-ray tube. The X-rays 27 generated in the target 23 by the irradiation of the electron beam 21 are extracted to the outside through the X-ray transmission window 69. The vacuum container 71 is maintained at a vacuum by a vacuum pump 74. The structure of the target 23 is the same as that of the first embodiment of the X-ray tube shown in FIG.

It is also possible to increase the detection resolution by using synchrotron radiation (SR light) as an X-ray source. In this case, since the SR light is a parallel light, penumbra does not occur, and therefore the resolution does not decrease.

Next, FIG. 16 shows an embodiment of an automatic inspection apparatus for a soldered portion and a circuit connection portion of a circuit board using the X-ray tomography apparatus according to the present invention. In this automatic inspection apparatus, the portion of the X-ray tomography apparatus from the X-ray tube 35 to the CCD 45 is the same as the embodiment of the first X-ray detection system described with reference to FIG. The configuration is such that a converter 57, an image processing unit 80, a result output unit 81, and a control computer 82 are added.

In this automatic inspection apparatus, a video signal output from the CCD 45 is converted into a digital image by the A / D converter 57, a defective portion is extracted by the image processing unit 80, and the position and type of the defect are output from the result output unit 81. I do. The control computer 82 controls the operation of the entire inspection apparatus and manages the inspection procedure.

Hereinafter, the inspection procedure will be described.

(1) The circuit board 30 is set on the stage.

(2) XY stage 37 and Z stage 39
To bring the inspection area into view.

(3) Rotating stage 38 and rotating stage 4
3 is rotated to expose the CCD 45 to obtain a tomographic image of the inspection portion.

(4) The Z stage 39 is moved to obtain a second tomographic image of the inspection portion. Further, the Z stage 39 is gradually moved to obtain a required number of tomographic images. If only one tomographic image is sufficient, this operation is not necessary.

(5) From the n tomographic images, the image processing unit 80 determines whether the product is good or defective. Since the solder has a high X-ray absorption, it is detected as a dark shadow. Defect determination is performed by comparing the detected shadow with a non-defective shadow, comparing the detected shadow with a shadow calculated based on design data, and calculating a feature amount of the detected shadow.

(6) The XY stage 37 is moved to change the inspection part. Then, the operations from (3) to (5) are repeated. Further, the XY stage 37 is moved, and the circuit board 30 is moved.
Inspect the entire surface of

(7) Output the position and type of the defect.

(8) The circuit board 30 is removed.

By performing such an inspection procedure, an X-ray tomographic image of the circuit board 30 to be inspected is obtained.
Even with a multilayer structure, the position and type of the defect can be reliably grasped.

[0054]

As apparent from the above description, the present invention has the following effects. That is, an X-ray source, a unit for rotating an object to be imaged, a unit for detecting an X-ray image emitted from the X-ray source and transmitted through the object, and a transmission detected by the detecting unit. Means for rotating the X-ray image in synchronization with the rotation of the object, adding means for adding the image rotated by the means for rotating processing in real time, and adding in real time by the adding means. X-ray tomography apparatus having display means for displaying the image as video information, the image of the linear structure on a plane other than the focal plane is detected as blurred, and only the detection target plane is sharply detected. It becomes possible to detect. In addition, this detection can be performed by displaying the video information in real time by the display means.

Further, when a microfocus X-ray tube having a means for eccentrically rotating the transmission type target is used as the X-ray source, the diameter of the X-ray source is reduced, and the electron beam is irradiated to one location of the target. Since it is not performed, the thermal intensity increases, and high-resolution detection can be stably performed.

Further, when the transmission type target included in the microfocus X-ray tube is composed of at least two layers of the X-ray generation layer and the support layer, the X-ray generation layer is thinned to limit the electron scattering region. Since the X-ray source diameter can be reduced, the mechanical strength of the target can be secured by the support layer, and the heat generated by electron beam irradiation can be radiated from the support layer, so that high-resolution detection can be performed stably. Becomes possible.

If an image processing circuit for detecting a defect of the object to be inspected from an electric signal serving as image information is further provided, a tomographic image of an arbitrary cross section of the object to be inspected can be obtained. Accordingly, the image processing circuit can automatically detect a defect in a complicated internal structure of the object, and can automatically inspect a circuit connection portion such as a soldered portion of the multilayer substrate.

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle of an X-ray tomography method according to the present invention.

FIG. 2 is a diagram showing a basic configuration of an X-ray tomography apparatus according to the present invention.

FIG. 3 is a diagram showing a basic configuration of a micro X-ray source according to the present invention.

FIG. 4 is a diagram showing a principle configuration of an automatic inspection device inside a circuit board having a multilayer structure according to the present invention.

FIG. 5 is a diagram showing a configuration of an embodiment of an X-ray tomography apparatus according to the present invention.

FIG. 6 is a diagram showing another example of the image rotator.

FIG. 7 is a diagram showing a configuration of a second embodiment of the X-ray detection system.

FIG. 8 is a diagram showing a configuration of a third embodiment of the X-ray detection system.

FIG. 9 is a diagram showing a configuration of a fourth embodiment of the X-ray detection system.

FIG. 10 is a diagram showing a configuration of a fifth embodiment of the X-ray detection system.

FIG. 11 is a diagram showing a configuration of a sixth embodiment of the X-ray detection system.

FIG. 12 is a diagram showing a configuration of an X-ray detection system according to a seventh embodiment.

FIG. 13 is a view showing a configuration of a first embodiment of a microfocal X-ray tube according to the present invention.

FIG. 14 is a diagram showing a configuration of a second embodiment of the microfocal X-ray source according to the present invention.

FIG. 15 is a diagram showing the configuration of a third embodiment of the microfocal X-ray source according to the present invention.

FIG. 16 is a view showing a configuration of an embodiment of an automatic automatic inspection apparatus for a circuit board according to the present invention.

[Description of Signs] 1 X-ray source 2 Object 4 Focal plane 5 Rotation axis 6 Rotation axis 7 Optical axis 27 X-ray 35 X-ray tube 37 XY table 38 Rotation stage 39 Z-stage 40 X-ray image intensifier 42 Image rotator (Dove prism) 43 Rotating stage 45 Solid-state imaging device (CCD) 46 Display 47 Driver

Claims (7)

[Claims] 1. An X-ray source, means for rotating an object to be imaged, means for detecting an X-ray image emitted from the X-ray source and transmitted through the object, and means for detecting the X-ray image Means for rotating the transmitted X-ray image detected by the means in synchronization with the rotation of the object, adding means for adding the image rotated by the means for rotating in real time, and adding means An X-ray tomography apparatus having display means for displaying an image added in real time as video information. 2. An X-ray tomography apparatus according to claim 1, wherein said means for rotating said object comprises a rotating stage, and said means for detecting said X-ray image comprises an X-ray image sensor. 3. An X-ray image intensifier for converting an X-ray image into an optical image and an image pickup tube for detecting an optical image, wherein the means for rotating the image includes an image pickup device. 2. The apparatus according to claim 1, further comprising a circuit for rotating a raster scan of the tube. 4. The X-ray tomography apparatus according to claim 1, wherein the means for detecting the X-ray image comprises an image pickup tube. 5. The X-ray tomography apparatus according to claim 1, wherein a microfocus X-ray tube having a unit for decentering and rotating a transmission type target is used as the X-ray source. 6. The X-ray tomography apparatus according to claim 5, wherein the transmission target included in the microfocus X-ray tube includes at least two layers: an X-ray generation layer and a support layer. 7. The X-ray tomography apparatus according to claim 1, further comprising an image processing circuit for detecting a defect of the object from the video information.