JP2004239815A - X-ray inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray inspection device for generating two-dimensional X-ray transmission image by fixing an X-ray source and a line detector, using a simple mechanism, in particular, an inexpensive X-ray inspection device which observes a specimen while setting it in an optional posture and position in an X-ray image by radial X-ray irradiation such as a microfocus X-ray source. <P>SOLUTION: The X-ray radiation source 1 is opposed to the line detector 4, they are fixed to make the X-ray radiation get surely incident into the line detector, a sample table 3 wherein a stage 2 for mounting the specimen is reciprocated along a direction perpendicular to a shaft of the line detector is interposed therebetween, the specimen is reciprocated along a direction crossing the fixed line detector, a one-dimensional X-ray transmission profile is acquired thereby in every position adjacent to the specimen, and one-dimensional X-ray measurement results are integrated and compounded to generate the two-dimensional X-ray transmission image. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a detector for acquiring an X-ray absorption image, and more particularly to a sample stage of an X-ray detector that generates a two-dimensional image using a one-dimensional detector.
[0002]
[Prior art]
2. Description of the Related Art X-ray detectors for nondestructively and precisely inspecting small defects in electronic parts and automobile parts have displayed planar images obtained using a precise and expensive two-dimensional detector such as an imaging intensifier. .
In particular, an inspection apparatus that inspects a semiconductor board or the like using a microfocus X-ray source and a small two-dimensional detector can inspect an image of an object by enlarging it. In this apparatus, when the inspection position or the inspection angle of the object is changed, an apparatus configured to adjust the position and orientation of the two-dimensional detector in accordance with the change of the irradiation axis of the X-ray source is used.
[0003]
Since the dose is inversely proportional to the square of the distance from the X-ray source, the use of a large-area two-dimensional detector for the microfocus X-ray source not only makes the detector extremely expensive, but also makes the X-rays at the center and edge of the screen difficult. Since the distance from the source is different, a difference occurs in the received dose, and the captured image does not accurately reflect the X-ray absorption image. When changing the inspection angle, it is necessary to change the X-ray emission direction of the X-ray source with respect to the fixed inspection object. However, if the distance from the X-ray source to the detector is different, the received dose changes and the image magnification also increases. Therefore, if the detector is moved on a straight line, correct observation cannot be performed.
Therefore, usually, a small two-dimensional detector is used, and the position and orientation of the two-dimensional detector are adjusted to follow the X-ray irradiation axis when changing the inspection angle. This device can adjust the position on a spherical surface centered around the focus position of the X-ray so that the two-dimensional detector does not change the distance from the X-ray source.
[0004]
When an enlarged image is to be obtained for X-ray inspection of a minute component such as an electronic component, it is difficult to optically expand the image with X-rays. Geometric magnification refers to moving an object placed between an X-ray tube and an imaging device in the optical axis direction to enlarge an X-ray image projected on the imaging device, and the object approaches an X-ray source. An image with a larger enlargement ratio is obtained.
However, since a blur called a penumbra proportional to the size of the focal point for emitting X-rays occurs in the geometrically enlarged image, using a normal X-ray tube having a focal size of several hundred μm will increase the magnification. Is large, the image is blurred and a good image cannot be obtained. The microfocus X-ray tube has a focus size narrowed to 10 μm or less to reduce blur, and a clear image can be obtained even at a magnification of 100 times or more.
[0005]
In addition, the inspection apparatus using a microfocus X-ray source can freely enlarge and reduce the X-ray image by adjusting the position of the inspection object. The object to be inspected set on the sample stage is brought closer to the X-ray source side, a small-scale image is generated by a small two-dimensional detector, and the operator observes this image while operating the sample stage to confirm the position for detailed observation. Once the observation position is determined, a method of using the inspection object closer to the detector side for close inspection is possible.
However, an inspection apparatus that adjusts the position and orientation of a small two-dimensional detector according to the irradiation axis of a microfocus X-ray source only requires a complicated mechanism for coupling the X-ray source and the X-ray detector. In addition, for example, it takes several tens of seconds to incline the X-ray irradiation axis by 60 degrees.
[0006]
On the other hand, the line detector in which the X-ray detecting elements are arranged in a line can observe the X-ray absorption state on the line in which the detecting elements are arranged at once, and is relatively inexpensive. Often used for loose inspection.
Patent Literature 1 discloses an X-ray imaging apparatus that obtains a planar image using a line detector, wherein an X-ray intensity detected is substantially constant regardless of the magnitude of the X-ray transmittance of the subject. There is disclosed an apparatus in which the same quality of imaging data can be obtained for an imaging part.
The X-ray line detector has an ion chamber in which electrodes are arranged inside a long and narrow vacuum tube, and xenon gas is sealed so that X-rays passing between the electrodes ionize the gas and determine the X-ray dose from the current flowing. There is a formula line detector. As a non-ion chamber type, there is a semiconductor line detector or the like in which a semiconductor that generates an electric signal in response to X-rays is incorporated on the surface.
[0007]
In the ion chamber type X-ray line detector, when the incident angle of the X-ray becomes large, the X-ray becomes difficult to pass between the electrodes, so that the sensitivity is reduced, and the X-ray incident at a few degrees or less in a direction perpendicular to the line in which the elements are arranged is arranged. Has stable sensitivity only to For this reason, it is necessary for the line detector so that the plane of incidence on the detection element row always faces the direction facing the X-ray source, and the X-ray source and the line detector are used in a relatively fixed manner. In order to observe a two-dimensional image using a line detector, a mechanism for scanning in a direction perpendicular to the axis of the line detector may be provided. Therefore, as shown in FIG. 5, for example, an X-ray transmission image of an object moving on a belt conveyor provided between an X-ray source and a detector is continuously photographed and converted into a plane image to perform a content inspection. Or a structure such as a medical X-ray detector, in which the X-ray source and the detector are assembled together so that the angle of incidence on the detector is always vertical, and the X-ray source and the detector are synchronized separately. An X-ray photograph is taken and combined while moving the mechanism to be driven across the object, and the two-dimensional image is observed.
[0008]
[Patent Document 1]
JP-A-9-10191
[0009]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide an X-ray inspection apparatus that fixes an X-ray source and a line detector and generates a two-dimensional X-ray transmission image using a simple mechanism. It is an object of the present invention to provide an inexpensive X-ray inspection apparatus capable of observing a subject with an arbitrary posture and position set in an X-ray image obtained by radial X-ray irradiation of an X-ray source or the like.
[0010]
[Means for Solving the Problems]
In the X-ray detection apparatus of the present invention, while the X-ray radiation source and the line detector are opposed to each other and the X-ray radiation is surely incident on the line detector and fixed, the stage is in a direction perpendicular to the axis of the line detector. A one-dimensional X-ray transmission profile is obtained for each position adjacent to the subject by reciprocating the subject in a direction crossing the fixed line detector by interposing a sample stage that reciprocates The one-dimensional X-ray measurement results are integrated and combined to generate a two-dimensional X-ray transmission image.
[0011]
In the apparatus of the present invention, instead of moving the X-ray radiation source and the line detector integrally or synchronously, they are fixed at an optimal position and a stage that reciprocates between them is provided. An expensive and cumbersome drive mechanism for driving an X-ray radiation source or the like is not required, the apparatus can be manufactured at low cost, and the observation position and posture of the subject can be easily changed. The posture of the subject can be adjusted by changing the position of the subject in the horizontal direction under the X-ray source to change the incident direction of the X-rays without actually changing the inclination. .
[0012]
Also, unlike a conventional X-ray inspection apparatus in which a part that temporarily passes on a conveyor is inspected with an X-ray line detector that is fixed, the subject is fixed on a stage like a normal microscope and passes therethrough. It does not go. Since the stage reciprocates at an appropriate speed, measurement can be repeated as many times as necessary. For example, if the screen is updated each time scanning is performed, the shape of the subject or observation position changes. It is possible to simulate real-time measurement of a subject or a subject whose posture is being changed.
[0013]
The sample stage preferably has a mechanism capable of moving a stage on which the subject is mounted within a range of X-ray radiation incident on the line detector. The moving mechanism is preferably a three-dimensional driving mechanism.
The magnification can be adjusted by changing the distance from the X-ray source by moving the sample table along the line connecting the X-ray radiation source and the line detector, and by changing the incident angle of the X-ray. Can be changed. Furthermore, for a large subject, an observation portion can be selected using a moving mechanism.
[0014]
When a long line detector is used, it is preferable to use a line detector formed in an arc shape so as to be almost the same distance to the X-ray radiation source.
Since the X-ray radiation source radially emits X-rays having almost the same intensity in all directions, if a linear line detector is inserted into the X-ray radiation, the distance to the source changes depending on the position of the line detector. Since the X-ray dose is inversely proportional to the square of the distance from the source, it decreases rapidly as the distance from the foot of the perpendicular dropped from the source to the line detector increases. descend.
Therefore, by arranging the line detectors such that the perpendiculars dropped from the X-ray radiation sources are almost at the center of the line detectors, it is possible to reduce the deviation of the detection capability.
In addition, by arranging the line detector formed in an arc shape such that the center of curvature is substantially at the source position, the X-ray dose at each detection element of the line detector becomes substantially equal, and the X-ray transmission state of the subject can be accurately determined. Will be detected.
[0015]
The stage driving mechanism may include a ball screw connected to the stage and a motor for driving the ball screw, and the motor may be configured to drive the motor forward and reverse.
In addition, a hole was drilled in the stage body in the direction perpendicular to the line detector, a guide pole was passed through this hole, and the stage was moved only in the direction perpendicular to the line detector, and the tip of the ball screw was pressed from one side of the stage. Alternatively, the stage may be biased by the action of a spring member, and the ball screw may be connected to a forward / reverse rotating motor to reciprocate the stage in a direction perpendicular to the line detector.
[0016]
The X-ray radiation source is preferably a microfocus X-ray source. If a microfocus X-ray source is used, X-rays are emitted from an extremely small area, so that a clear X-ray image with less blur can be obtained. Further, in the conventional microfocus X-ray detector, it took several tens of seconds or more to move the two-dimensional detector by, for example, 60 degrees with respect to a fixed semiconductor board or the like. Since the observation can be performed with the detector fixed, the operation is simple.
Further, it is preferable that the whole of the acquired X-ray transmission image is displayed on the monitor, and the selected part can be enlarged and displayed on the monitor. If the entire screen and the partially enlarged screen can be recognized at the same time, the search for the part to be confirmed and the posture of the part can be easily understood, which is convenient for observation.
Also, a moving image can be created by updating the X-ray transmission image obtained by scanning the line detector for each scan. Further, if the scan speed of the line detector is increased, a smooth moving image similar to that of an apparatus using a large two-dimensional detector can be obtained in a pseudo manner.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the X-ray inspection apparatus of the present invention will be described in detail with reference to examples.
FIG. 1 is a conceptual diagram of the X-ray inspection apparatus of the present embodiment, FIG. 2 is a side view for explaining the concept, FIG. 3 is a perspective view for explaining a stage driving mechanism, and FIG. 4 shows another aspect of the stage driving mechanism. It is a perspective view.
[0018]
As shown in FIGS. 1 and 2, the X-ray inspection apparatus according to the present embodiment includes an X-ray source 1, a stage 2 on which a sample is mounted, a sample stage 3 on which the stage is mounted to adjust a three-dimensional position, and an X-ray inspection apparatus. It comprises an X-ray line detector 4 for measuring the amount of transmitted light and an image processing terminal 5 for processing the measurement signal and displaying the result.
The image processing device 5 may be a personal computer 8 having a display 6 and a keyboard 7.
[0019]
The X-ray source 1 is a microfocus ray source configured to emit X-rays from an extremely small focal point, and is fixed to an apparatus main body (not shown).
The X-ray line detector 4 is formed in an arc shape having an X-ray detection element array 11 provided inside, and is arranged along a circumference centered on a radiation point of the X-ray source 1. The distance from the source is almost the same.
Further, the X-ray detecting element array 11 is similarly fixed to the apparatus main body so as to accurately face the radiation point of the X-ray source. Therefore, all of the elements of the X-ray detecting element array 11 receive almost uniform X-ray dose from the X-ray source 1.
A large number of relatively short linear line detectors are arranged at the same distance from the X-ray source so that their perpendicular legs are almost at the center positions of the rain detectors, respectively, and have approximately the same performance as the arc detector. It is also possible to give.
[0020]
The sample stage 3 incorporating the stage 2 includes a base 12, an X-axis moving board 13, and a Y-axis moving board 14, and is arranged in a space between the X-ray source 1 and the line detector 4. The base 12 is vertically movably supported by a linear guide 15 and can be moved up and down by a driving motor 17 via a ball screw 16. The X-axis moving platen 13 is movably supported by a linear guide 18 provided on the base 12 in the X-axis direction, and can be moved in one horizontal axis direction by a drive motor 19 for pushing and pulling in the X-axis direction. it can. The Y-axis moving board 14 is supported by a linear guide 20 provided on the X-axis moving board 13 in the Y-axis direction orthogonal to the moving direction, and can be moved in one horizontal axis direction by a drive motor 21. The stage 2 is mounted on the Y-axis moving board 14.
Therefore, the stage 2 is three-dimensionally moved between the X-ray source 1 and the line detector 4 according to the movement of the base 12, the X-axis moving board 13, and the Y-axis moving board 14, and is fixed at an appropriate position. Is possible.
[0021]
The stage 2 has a structure in which a movable plate 23 reciprocates in a direction perpendicular to the line detector of FIG. 1 with respect to a frame 22 as shown in FIG. 3, for example. A guide hole is formed in the movable platen 23 in the horizontal direction, and a guide pole 24 is passed through the guide hole. The guide pole is fixed to the frame. Further, the ball screw 25 penetrates into the movable platen 23 and is fitted with an internal rotating female screw. When the ball screw 25 is rotated by a drive motor 26 connected to the ball screw 25 and the belt, the movable platen 23 is rotated in the direction of the rotation. To move forward or backward.
An object 27 to be observed by irradiating with X-rays is placed on the movable platen 23. As the movable platen 23 advances and retreats, the object 27 reciprocates during X-ray emission.
[0022]
FIG. 4 is a perspective view showing a stage of a system different from that of FIG.
The stage 2 in FIG. 4 uses a push rod 30 and a spring 28 which are externally threaded, instead of being reciprocated by a ball screw in the stage in FIG.
A guide pole 24 is passed through each of two guide holes provided in the movable plate 23 of the stage 2, and one end of the guide pole 24 is a direction in which a gap is widened between the movable plate 23 and the frame 22. The movable platen 23 is pressed against one side. A flange 29 is provided on the side surface of the movable platen 23, and the tip of the push rod 30 is in contact with a surface of the flange opposite to the spring 28.
[0023]
The push rod 30 is externally threaded, and is connected to the drive shaft of the drive motor 31 by a rack and a pinion so that forward and reverse rotation can be performed. A subject 27 is placed on the movable platen 23.
When the push rod 30 moves upward in the drawing, the movable platen 23 moves forward against the spring 28, and when the push rod 30 moves backward, the movable platen 23 moves backward by the urging force of the spring 28, so that the subject 27 emits X-rays. Reciprocate inside.
[0024]
In the X-ray inspection apparatus of this embodiment, the sample 27 is placed and fixed at a fixed position on the movable platen 23 of the stage 2, and the base 12 is set at an appropriate position between the X-ray source 1 and the line detector 4. The positions of the X-axis moving plate 13 and the Y-axis moving plate 14 are adjusted so that the X-ray transmitted through the sample 27 is incident on the X-ray detecting element of the line detector 4.
After the position adjustment, the movable platen 23 is driven to reciprocate the sample 27 so as to cross the plane including the X-ray emission point and the X-ray detection element array 11. Since the line detector 4 detects a one-dimensional X-ray transmission profile, a profile is obtained for a number of lines that cut the sample 27, and these are superimposed and synthesized in the image processing terminal 5, whereby an X-ray transmission image of the entire sample is obtained. Form.
[0025]
The X-ray transmission image may be formed only while the movable platen 23 is driven in one direction, or may be formed on both the outward path and the return path.
The X-ray transmission image can be displayed on the monitor 6 for observation. However, not only the whole image but also an appropriately designated part can be enlarged and displayed by software. As described above, if the entire image and the image of the target portion can be viewed together, the state of the desired portion, such as the posture and the position in the whole, can be clearly checked, so that the X-ray transmission state can be accurately determined. You can judge.
[0026]
When the magnification of the image is changed, the distance between the sample 27 and the X-ray source 1 may be adjusted. Therefore, the height of the base 12 is changed by driving the base drive motor 17.
Further, when the positions of the X-axis moving board 13 and the Y-axis moving board 14 are adjusted to change the horizontal position of the sample 27 under the X-ray source 1, the incident direction of the X-ray to the sample 27 changes. Changing the X-ray incident direction is the same as changing the line of sight for observing X-ray transmission, so that observation from any direction is possible.
[0027]
If the scan speed of the line detector is sufficiently high, it is possible to pseudo-real-time monitor by sequentially updating the acquired images. Therefore, real-time observation, which would have been difficult without using a two-dimensional detector, can be performed over a large area and a wide angle range that cannot be realized with a two-dimensional detector. By monitoring in real time, it is possible to directly observe the changing state of the subject. Further, it is possible to observe a change in the X-ray transmission image while moving the sample in the apparatus.
In this way, when observing a semiconductor board at different angles, it is possible to easily change the attitude of the sample and the X-ray incident direction, and there is no need to move the X-ray source or line detector, and handling is easy. It becomes remarkably easy.
[0028]
Needless to say, the driving device such as the stage can use various methods commonly used in addition to the above-mentioned means.
Further, in the embodiment, the bow-shaped line detector is used. However, it is needless to say that a linear line detector may be used when measuring in a narrower range or when not requiring much accuracy. Nor. In a practical level, an arc-shaped line detector should be used if the X-ray emission angle exceeds 60 degrees.
[0029]
【The invention's effect】
As described above, according to the present invention, the stage for reciprocating the subject is set on the sample stage capable of three-dimensionally adjusting the position and arranged between the X-ray source and the line detector. Providing an inexpensive X-ray inspection apparatus that can observe the X-ray transmission image by radial X-ray irradiation such as a microfocus X-ray source while arbitrarily setting the posture and magnification of the subject with the line detector and the line detector fixed. can do.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram illustrating a configuration of an embodiment of an X-ray inspection apparatus according to the present invention.
FIG. 2 is a side view illustrating the concept of the present embodiment.
FIG. 3 is a perspective view showing a stage used in the present embodiment.
FIG. 4 is a perspective view showing still another stage used in the present embodiment.
FIG. 5 is a conceptual diagram showing an example of a conventional X-ray detection device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 X-ray source 2 Stage 3 Sample stand 4 X-ray line detector 5 Image processing terminal 6 Display 7 Keyboard 8 Personal computer 11 X-ray detector row 12 Base 13 X-axis moving board 14 Y-axis moving board 15 Linear guide 16 Ball screw 17 For base Drive motor 18 Linear guide 19 for X-axis 19 Drive motor 20 for X-axis 20 Linear guide 21 for Y-axis Drive motor 22 for Y-axis Frame 23 Movable platen 24 Guide pole 25 Ball screw 26 for stage Drive for stage Motor 27 Subject 28 Spring 29 Flange 30 Push rod 31 Drive motor for push rod

Claims (10)

A line detector having a row of detector elements along an axis and a fixed X-ray radiation source are provided. Based on an X-ray transmission image, an object mounted on a stage provided between the line detector and the X-ray radiation source An X-ray inspection apparatus for inspecting, wherein the X-ray radiation source and the line detector are fixed to face each other so that X-ray radiation is surely incident on the line detector, and the stage is perpendicular to an axis of the line detector. A sample stage provided with a drive mechanism that reciprocates in the direction is interposed between the X-ray radiation source and the line detector, and the subject is reciprocated with respect to the line detector. An X-ray inspection apparatus characterized in that a one-dimensional X-ray transmission profile is acquired for each adjacent position, and a two-dimensional X-ray transmission image is generated by integrating and combining the one-dimensional X-ray measurement results. The X-ray inspection apparatus according to claim 1, wherein the sample stage includes a moving mechanism that can select a position of the stage within a range of X-ray radiation incident on the line detector. The X-ray inspection apparatus according to claim 1 or 2, wherein the magnification of an image is adjusted by moving the sample stage along a line connecting the X-ray radiation source and the line detector. 4. The apparatus according to claim 1, wherein at least one line detector is provided, and each of the line detectors is arranged substantially perpendicular to a straight line connecting a center and the X-ray radiation source. The X-ray inspection apparatus according to claim 1. The X-ray inspection apparatus according to any one of claims 1 to 3, wherein the line detector is formed in an arc shape so as to be substantially equidistant from the X-ray radiation source. 6. The device according to claim 1, wherein the driving mechanism includes a ball screw connected to the stage and a motor driving the ball screw, and reciprocates the stage in a direction perpendicular to the line detector. The X-ray inspection apparatus according to claim 1. A guide pole for moving the stage in a direction perpendicular to the line detector through a hole drilled in a direction perpendicular to the line detector through the body of the stage, and pressing the stage from one of the stages; A ball screw, a spring member for urging the stage from the other side, and a motor for reciprocatingly driving the ball screw, the stage being reciprocated in a direction perpendicular to the line detector. The X-ray inspection apparatus according to any one of 1 to 5. The X-ray inspection apparatus according to any one of claims 1 to 7, wherein the X-ray radiation source is a microfocus X-ray source. The X-ray inspection apparatus according to any one of claims 1 to 8, wherein a selected part is enlarged and displayed on a monitor in addition to the entirety of the acquired X-ray transmission image. The X-ray inspection apparatus according to any one of claims 1 to 9, wherein an X-ray transmission image obtained by scanning the line detector is updated for each scan to create a moving image.

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