JPH0968506A - X-ray inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray inspection device equipped with a function to exclude the influence of a supporting member for a stimulable phosphor upon the photographed image of back scattering X-rays. SOLUTION: X-rays 6 are applied on a base board (object to be inspected) 3, and the portion having passed through the board 3 is incident on a stimulable phosphor 4. A load plate (high shutoff material) 2 for X-rays is installed downstream in the X-ray irradiating direction of the phosphor 4, i.e., parallel with the surface opposite the X-ray incident surface. Because the X-rays having penetrated the phosphor 4 are shut off by the lead plate 2, they do not reach the structural member which supports the phosphor 4 in the specified position, and it is possible to prevent the X-rays having penetrated from being scattered by the structural member and put again incident on the phosphor 4. When other beams of X-rays than those having passed the base board 3 are incident on the phosphor 4, the resolution of the X-ray transmission image accumulated in the phosphor 4 may be degraded, but the above configuration well prevents it and precise X-ray inspection can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention accumulates X-rays transmitted through an object to be inspected on a stimulable phosphor, and accumulates the accumulated X-rays.
The present invention relates to an X-ray inspection apparatus that inspects a structure of an object to be inspected based on a line transmission image.

[0002]

2. Description of the Related Art When a certain kind of phosphor is irradiated with radiation such as X-rays, a part of this radiation energy is accumulated in the phosphor in correspondence with its intensity, and the radiation information is visible in the phosphor. It is known that the accumulated radiation information shows stimulated emission when irradiated with excitation light such as light rays. Phosphors exhibiting such properties are called stimulable phosphors, and are used not only for X-ray projection inspection of the human body but also for industrial use such as soldering inspection of printed wiring boards by X-ray transmission. It is attracting attention as an effective one. The stimulable phosphor has a high economical value because it can be repeatedly used by erasing the remaining information after the accumulated radiation information is read, and is highly useful as a means for accumulating image information. FIG. 3 shows an example of an inspection apparatus for a printed wiring board (hereinafter referred to as a board) using the above-mentioned stimulable phosphor. FIG. 3A is a front view showing the configuration of the X-ray inspection unit of the inspection apparatus 30, and FIG. 3B is a conveyance cycle of the stimulable phosphor in the inspection apparatus 30 in the cycle of imaging → reading → erasing → imaging. It is a top view of a fluorescent substance conveyance floor.

In FIG. 3A, the left side is an X-ray irradiation section A and the right side is an image reading section B. The substrate 3, which is the object to be inspected, is carried into the X-ray irradiation unit A from the position of the arrow, is conveyed by the conveyance elevator 14, and is set at a predetermined position on the X-ray irradiation stage 5. The stimulable phosphor 4 is arranged on the X-ray irradiation stage 5, and the X-ray source 10 is arranged vertically above the X-ray irradiation stage 5. When the X-ray 6 is emitted from the X-ray source 10, the X-ray 6 passes through the substrate 3 and an X-ray transmission image corresponding to the X-ray transmission amount distribution is stored in the stimulable phosphor 4. After this, the substrate 3 is transferred to the transport elevator 14
And is carried out of the apparatus by the carry-out conveyor 13. Further, the stimulable phosphor 4 that has accumulated the image is the X-ray irradiation part A.
To the image reading section B. The stimulable phosphor 4 that has accumulated the image is scanned by excitation light from an image reading device (not shown) in the image reading section B to read out the accumulated image, and the soldering inspection of the board or the like is performed based on this image. To be done. The stimulable phosphor 4 that has completed reading the accumulated image is the lifter 1 shown in FIG.
It is conveyed to the image erasing section C by 5a. In the image erasing section C, the stimulable phosphor 4 is moved from the lifter 15a to the lifter 15b.
The remaining image is erased by irradiating the fluorescent lamps 16, 16 ... While moving to. The image-erasable stimulable phosphor 4 is conveyed again to the X-ray irradiation stage 5 by the lifter 15b and used for the X-ray inspection of the substrate 3.

[0004]

As shown in the above-mentioned conventional example, the stimulable phosphor is characterized in that it can be repeatedly used in a cycle of imaging, reading and erasing. In order to make full use of this feature, a mechanism for transporting the stimulable phosphor and setting it at a predetermined position in each processing unit is required as in the above-described configuration example. FIG. 8 is an enlarged view of the X-ray irradiation stage 5 portion in the above configuration. As shown in the figure, an opening is provided in the center of a base plate 8 on which the stimulable phosphor 4 is placed, and a lift plate 9 is provided in the opening. The stimulable phosphor 4 is conveyed by the lifter 15b and set at a predetermined position on the base plate 8. When the imaging is completed, the lift plate 9 is raised by the cylinder 17 to lift the stimulable phosphor 4 from the mounting surface of the base plate 8, The sheet is conveyed to the image reading section B by a feeding mechanism (not shown). As described above, the stimulable phosphor 4 is
Base plate 8 and lift plate 9 during X-ray irradiation
Supported by. In this state, the X-rays that have passed through the substrate 3 enter the stimulable phosphor 4. When the X-rays transmitted through the stimulable phosphor 4 are reflected by the base plate 8 and the lift plate 9, the backscattered X-rays enter the stimulable phosphor 4. That is, the stimulable phosphor 4 reacts with the X-rays transmitted through the substrate 3 and the backscattered X-rays, and the image by the X-rays transmitted through the substrate 3 is affected by the backscattered X-rays. As a result, there is a problem that the transparent image is blurred and the image resolution is reduced. An object of the present invention is to provide an X-ray inspection apparatus having a configuration that eliminates the influence of backscattered X-rays on a captured image by a support member of a stimulable phosphor.

[0005]

In order to achieve the above object, the means adopted by the present invention is to irradiate an object to be inspected with X-rays by an X-ray irradiator and In an X-ray inspection apparatus for performing a structural inspection of the inspection object by storing as an X-ray transmission image on the stimulable phosphor and reading image information from the stimulable phosphor in which the X-ray transmission image is stored, The X-ray inspection apparatus is characterized in that an X-ray high shielding material parallel to the stimulable phosphor is provided on the downstream side of the stimulable phosphor in the X-ray irradiating section as viewed in the X-ray irradiating direction. ing. Then, X-rays are radiated from the X-ray source toward the inspection object, and the X-rays transmitted through the inspection object enter the stimulable phosphor. A high X-ray shielding material is provided on the downstream side of the stimulable phosphor in the X-ray irradiation direction, that is, parallel to the surface opposite to the X-ray incident surface. With this configuration, X-rays that have passed through the stimulable phosphor are shielded by the X-ray high shielding material,
The structural member that holds the stimulable phosphor in place cannot be reached,
The transmitted X-rays are prevented from being scattered by the structural member and entering the stimulable phosphor again. When X-rays other than the X-rays transmitted through the object to be inspected enter the stimulable phosphor, the resolution of the X-ray transmission image accumulated in the stimulable phosphor is lowered, but this is prevented by the configuration of the present invention. X-ray inspection can be performed accurately.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
The following embodiments are examples embodying the present invention and do not limit the technical scope of the present invention. Here, FIG. 1 shows the X-ray of the X-ray inspection apparatus according to the embodiment of the present invention.
A plan view (a) and a side view (b) showing the configuration of the radiation irradiating section, and FIG. 2 are X-ray transmission amount measurement graphs showing the effects of the configuration of the embodiment. The overall configuration of the X-ray inspection apparatus according to this embodiment is the same as that of the X-ray inspection apparatus shown in the conventional example, but the configuration of the X-ray irradiation unit is different. Therefore, the description of the components common to the conventional example is omitted, and the configuration of the embodiment of the X-ray irradiation unit will be described below. In FIG. 1, an X-ray irradiation stage 1 according to the present embodiment is provided with a lead plate (high X-ray shielding material) 2 on the upper surfaces of a base plate 8 and a lift plate 9, and accumulates on the lead plate 2. Fluorescent phosphor 4 is placed.

In the above structure, the X-ray 6 emitted from the X-ray source 10 (see FIG. 3) has a transmission amount distribution corresponding to the X-ray shielding degree of various members formed on the substrate (inspection object) 3. And enters the stimulable phosphor 4, and the stimulable phosphor 4 stores and stores an image corresponding to the X-ray transmission amount distribution. Stimulable phosphor 4
Although the X-rays 6 incident on the stimulable phosphor 4 further pass through the stimulable phosphor 4, the lead plate 2 is disposed downstream of the stimulable phosphor 4 in the X-ray irradiation direction as in the above-mentioned configuration, so that The X-ray transmitted through the body 4 is shielded by the lead plate 2. Therefore, the X-rays that have passed through the stimulable phosphor 4 are not scattered by the base plate 8 and the lift plate 9 and are incident on the stimulable phosphor 4 again, and the substrate 3 stored and stored in the stimulable phosphor 4 is prevented. It does not affect the X-ray transmission image.
FIG. 2 is a graph (a) in which the amount of X-rays transmitted through the soldering portion formed on the substrate 3 and accumulated in the stimulable phosphor 4 is measured without the lead plate 2 (conventional example configuration), and FIG. It is shown as a graph (b) measured with the plate 2 present (configuration of the embodiment). In the state without the lead plate shown in FIG. 2A, the X-rays transmitted through the stimulable phosphor 4 reach the base plate 8, and the backscattered X-rays generated on the base plate 8 enter the stimulable phosphor 4. , The apparent X-ray transmission amount increases and the gray level rises.

On the other hand, in the state with the lead plate shown in FIG. 2B, the backscattering X-rays do not occur, so the gray level shows the original value. The gray level becomes small in a portion having a small amount of X-ray transmission such as a soldering portion and is displayed white in the grayscale image. However, when it is affected by the backscattered X-ray, the gray level is actually as shown in FIG. 2 (a). Greater than the value,
The difference from the portion having a large amount of X-ray transmission becomes small, and the clarity of the grayscale image becomes low. In addition, the backscattered X-rays also affect the parts other than the transmission image of the soldering part to change the original gray level and reduce the resolution of the image. As shown in the actual measurement graph of the X-ray transmission amount, by disposing the lead plate 2, the X-ray transmission amount distribution proportional to the X-ray transmission degree of the soldered part formed on the substrate 3 and the mounted component is resolved. Since it is accumulated in the stimulable phosphor 4 as a well-defined gray image, the stimulable phosphor 4 that has been imaged in the X-ray irradiation section A is sent to the image reading section B. The image reading section B scans the stimulable phosphor 4 with excitation light to read the image information accumulated in the stimulable phosphor 4. Since stimulated emission light corresponding to the accumulated radiation image information is generated from the scanning point scanned by the excitation light, it is received by the photoelectric element through the filter that transmits the wavelength component of this stimulated emission light and photoelectrically converted. , It is possible to reproduce the accumulated radiation image information. Although the above-mentioned configuration is applied to the soldering inspection of the substrate 3, the stimulable phosphor 4
A similar configuration can be applied to the formation of the radiation image using the.

[0009]

EXAMPLES In the above embodiment, as shown in FIGS. 1 and 3, in order to mechanically transport the stimulable phosphor 4, the support portion of the stimulable phosphor 4 in the X-ray irradiation section A is the base plate 8 having the outer edge portion. And a lift plate 9 in the center. Then, the lift plate 9 moves up and down and receives the stimulable phosphor 4 conveyed by the lifter 15b from the image erasing section C from the lifter 15b. However, the above base plate 8
A plane-processed lead plate 2 is installed on the upper surface side of the lift plate 9 and the lift plate 9, and when X-ray imaging is performed by such a mechanism, there is a gap between the base plate 8 and the lift plate 9 as shown in FIG. For example, there may be a difference between the backscattered X-ray state of this portion and the backscattered X-ray state of the other portion, and there is a possibility that a detected concentration abnormal portion according to the shape of the gap occurs. Further, if there is a step between the base plate 8 and the lift plate 9, a so-called floating state in which the stimulable phosphor 4 does not adhere to the lead plate 2 occurs, and the backscattering X-ray level of this floating portion and the contact portion Since there is a difference from the level, the detected density abnormality part (floating part) may occur also in this case.

Further, the lead plate 2 is easily scratched, and a local abnormality such as a recess is likely to occur. Therefore, there is room for further improvement of the above embodiment. Therefore, as shown in FIGS. 5 and 6, the inventors of the present invention have integrated the base plate 8, the lift plate 9 and the lead plate 2 in the imaging region of the stimulable phosphor 4 during X-ray imaging into an integrated structure. In addition to forming the support body 8 ', the support body 8 "(sheet transfer frame) other than the imaging area has a different structure. Further, the stimulable phosphor 4 is a sheet frame 4'made of a hard resin such as vinyl chloride. The sheet transfer frame 8 ″ is provided with appropriate pins 8a ″, and the pin 8a ″ is engaged with the pin hole 4a ″ formed in the sheet frame 4 ′. 8 ″ is raised to receive the stimulable phosphor 4 together with the seat frame 4 ′ from the lifter 15b.

Then, an image was taken without a printed circuit board, and the X-ray transmission amounts of the above embodiment and this embodiment were measured. FIG. 7 shows the result. In the figure, the gray level of the whole is not the same in the embodiment and the present embodiment because the structure around the imaging unit is different, but the base plate 8 of the cross section A and the lift in the structure of the above embodiment are different. While the gray level change was observed in the gap and the step between the plate 9 and the plate 9, almost no change was observed in the cross section B in the structure of this example. By mounting the stimulable phosphor 4 on the support 8'having an integral structure as described above, the backscattered X-rays from the support 8'of the X-rays transmitted through the stimulable phosphor 4 are significantly reduced. Therefore, the entire imaging region can be maintained in a uniform state (a state in which there is a slight amount of backscattered X-rays). Therefore, it is possible to measure the X-ray transmission density level of thick solder in the entire imaging region without having position dependency.

Further, since the stimulable phosphor 4 is made of a flexible resin as a base material, the stimulable phosphor 4 may be bent and hindered during transportation or receiving by the lifters 15a and 15b. The sheet frame 4'provides the rigidity required for transportation and the like, and the stimulable phosphor 4 is tensioned to suppress the bending deformation of the central portion thereof. Further, the material of the seat frame 4'is made of resin to reduce the weight as much as possible, so that stable transportation can be performed. Furthermore, since the sheet frame 4'and the sheet transfer frame 8 "are engaged with the pin 8a" to receive the stimulable phosphor 4, the position reproducibility at the time of image pickup can be secured. In the above structure, the lead plate 2 is provided on the upper surface of the support 8 ', but the material of the support itself is a material other than lead having a high X-ray absorption efficiency and a small backscattered X-ray. By doing lead plate 2
Can be omitted. Further, since normal lead is easily scratched or dented, hard lead containing antimony in an amount of 2 to 8% may be used. Even in these cases, by using the support body having an integral structure, it is possible to eliminate the gap between the base plate and the lift plate as in the above-described embodiment, and suppress the occurrence of abnormal detection density of transmitted X-rays.

[0013]

As described above, according to the present invention, the X-ray irradiating surface of the stimulable phosphor which accumulates the X-rays transmitted through the object to be inspected as a transmission amount distribution image, that is, the X-ray incident surface. A high X-ray shielding material is provided parallel to the surface opposite to the surface. With this configuration, the X-rays that have passed through the stimulable phosphor are blocked by the high X-ray shielding material, so that they cannot reach the structural member that supports the stimulable phosphor at a predetermined position, and the transmitted X-rays are scattered by the structural member. Then, the light is prevented from entering the storage phosphor again. When X-rays other than the X-rays transmitted through the inspection object enter the stimulable phosphor, the X accumulated in the stimulable phosphor.
Although the resolution of the X-ray transmission image is reduced, this is prevented by the configuration of the present invention, and the X-ray inspection can be performed accurately.

[Brief description of drawings]

FIG. 1 shows an X of an X-ray inspection apparatus according to an embodiment of the present invention.
The top view (a) and side view (b) which show the structure of a radiation irradiation part.

FIG. 2 is a graph comparing accumulated data of an X-ray transmission amount according to the configuration of the embodiment of the present invention with a conventional example.

FIG. 3 is a front view (a) showing a configuration of a substrate X-ray inspection apparatus and a plan view (b) of a stimulable phosphor transport floor.

FIG. 4 is a partial enlarged view of a support portion of the stimulable phosphor in the configuration of the embodiment of the present invention.

FIG. 5 is a partially enlarged view of a support portion of the stimulable phosphor in the constitution of the embodiment of the present invention.

FIG. 6 is a structural diagram of a sheet frame of the stimulable phosphor in the configuration of the example of the present invention.

FIG. 7 is a graph comparing the accumulated data of the X-ray transmission amount according to the configuration of the example of the present invention with the accumulated data of the X-ray transmission amount according to the configuration of the embodiment.

FIG. 8 is a side view showing a configuration of an X-ray irradiation stage according to a conventional configuration.

[Explanation of symbols]

 1 ... X-ray irradiation stage 2 ... Lead plate (high X-ray shielding material) 3 ... Substrate (inspection object) 4 ... Accumulable phosphor 6 ... X-ray 30 ... X-ray inspection apparatus A ... X-ray irradiation part B ... Image Reading unit C ... Image erasing unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hirofumi Shono Inventor Hirobumi Shono 2-3-1, Niihama, Arai-cho, Takasago-shi, Hyogo Kobe Steel Works Takasago Works (72) Inventor Shoichi Mure 2-chome, Niihama, Arai-cho, Takasago-shi, Hyogo No. 3-1 Takasago Works, Kobe Steel, Ltd.

Claims (1)

[Claims] 1. An X-ray irradiating section irradiates an object to be inspected with X-rays, and X-rays transmitted through the object to be inspected are X-rayed onto a stimulable phosphor.
In an X-ray inspection apparatus for inspecting the structure of an object to be inspected by storing and storing as a ray transmission image, and reading image information from the stimulable phosphor in which the X-ray transmission image is stored, An X-ray inspection apparatus, wherein an X-ray high shielding material parallel to the stimulable phosphor is provided on the downstream side of the stimulable phosphor as viewed in the X-ray irradiation direction.