JP2001318155A - Radiation detector and x-ray ct device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation detector which can take a photograph of high resolution in a shorter photography time and a CT device which uses it. SOLUTION: At least photodiode arrays 4, 24, 34, and 44 or switching elements 8a to 8n, 28a to 28n, 38a to 38n, and 48a to 48n and wiring boards 7, 7a, 7b, and 7c or the photodiode arrays and switching elements are electrically connected through flexible substrates 9a to 9n, 39, or bumps 49a to 49n.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a radiation detector and a multi-slice X-ray CT apparatus using the radiation detector.

[0002]

2. Description of the Related Art With the advent of the helical scan method and the multi-slice method and the high-speed rotation of the X-ray generator and detector, the X-ray CT apparatus has realized a reduction in imaging time and a high-resolution tomographic image. I have. In particular, shortening the photographing time can reduce the patient's pain at the time of the examination. At the same time, the resolution of captured images has been improved, and it has become possible to find tumors that could not be seen by conventional X-ray CT and to capture organ images equivalent to those in a stationary state. Examples of the X-ray CT apparatus include, for example, JP-A-10-127617 and JP-A-10-127.
No. 73666, Japanese Patent Application Laid-Open No. H11-221207, and the like disclose the configuration. The X-ray detection device is an X-ray detector having an optical sensor (photoelectric converter) such as a photodiode.
The line detector module has a basic structure in which a plurality of lines are formed along the body axis direction (slice direction) of a subject.
That is, X-rays, which are radiation emitted from an X-ray tube and transmitted through a subject, are absorbed by a scintillator provided in an X-ray detector module, and fluorescence generated according to the amount of the absorbed light is detected by an optical sensor. Is converted into an electric signal by a photodiode and output. By the switching operation of the switch device, the signal output from the photodiode array is sequentially sent to a data collection device having an amplification function and an A / D conversion function.

FIG. 7A is a plan view showing an example of the configuration of a conventional radiation detector, and FIG. 7B is a side sectional view thereof. That is, the wiring board 91 is formed of a multilayer wiring board, and has a predetermined wiring pattern (not shown) on the surface. On the surface of the wiring board 91, a photodiode array 92 and switch elements 93a, 93b, 93c ... 9
3n are mounted, and the photodiode array 92 and the switching elements 93a, 93b, 93c... 93n are connected by bonding wires 94a, 94b, 94c. Also, switch elements 93a, 93b,
93c ... 93n are bonding wires 94a, 94b,
94n are connected to the wiring pattern of the wiring board 91 by the wiring patterns 94c.
95n are connected to connectors 96a, 96b, 96c... 96n on the back surface of the wiring board. The connectors 96a, 96b, 96c... 96n have electric wires 97a, 97b, 97c.
n, which is connected to a data collection device (not shown) outside the module to transmit and receive signals.
Note that a scintillator member 98 for converting X-rays as radiation into visible light is provided above the photodiode array 92.
a, 98b, 98c... 98n are mounted.

[0004]

In the structure of the X-ray detector, a medical site in recent years demands a further reduction in imaging time and high-resolution imaging. To improve the performance of the X-ray detector, it is effective to increase the number of slices. However, if the number of slices increases, the number of signals from the photodiode array increases significantly. The pitch and area of the bonding pads on the substrate become very small, and connection is impossible with the wire bonding method. For this reason, the conventional multi-slice X-ray CT has a limit of up to four slices, and development of a radiation detector having a new structure has been desired. The present invention has been made based on these circumstances, and an object of the present invention is to provide a radiation detector capable of reducing imaging time and performing high-resolution imaging, and an X-ray CT apparatus using the same. .

[0005]

In order to solve the above-mentioned problems, the present invention provides a photodiode array optically connected to a scintillator member on one surface of a wiring board, and an electrical connection between the photodiode array and the photodiode array. The connected switch element is mounted, and the other surface of the wiring board, in a radiation detector mounted with a data collection element that receives an electric signal from the photodiode array, the photodiode array or the switching element and A radiation detector is provided in which at least one of the connection with the wiring substrate and the connection between the photodiode array and the switching element is electrically connected using a flexible substrate. At this time, it is preferable that the electrical connection with the respective parts using the flexible substrate is made by an anisotropic conductive sheet or TAB.

Further, according to the present invention, a photodiode array in which a scintillator member and a photoelectric conversion surface are optically connected to one surface of a wiring board and a switch element electrically connected to the photodiode array are mounted. In a radiation detector in which a data collection element that receives an electric signal from the photodiode array is mounted on the other surface of the wiring board, the photodiode array is located on a main surface on which the photoelectric conversion surface is formed. A radiation detector is provided in which a through wiring penetrating the other main surface is formed, and which is mounted on the wiring substrate by a bump provided on the other main surface.

In this case, it is preferable that the through wiring is made of any one of polysilicon, W, Ni, and Cu.

[0008] The present invention also provides an X-ray CT apparatus equipped with these radiation detectors.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. An example of the configuration of an X-ray solid-state detection device constituted by integrating radiation detectors will be described with reference to FIGS. 1 (a) and 1 (b). FIG. 1A is a perspective view of a detection unit of the X-ray solid-state detection device.
(B) is a perspective view of a radiation detector which is a component thereof. A medical CT scanner device (not shown) detects an X-ray source as radiation and a plurality of X-rays arranged in a line in a direction (channel direction) perpendicular to the body axis direction of the subject and the X-ray incidence direction. Detector modules 1a, 1
By rotating b, 1c... 1n around the subject together with the gantry, data is obtained by scanning while constantly changing the angle at which the X-ray beam intersects the subject. Radiation detector modules 1a, 1b, 1c ... 1n
Is a plurality of rows arranged in a row in the channel direction, that is,
Eight or more rows, for example, 10 rows are provided, and detect projection data as X-ray attenuation measurement values of an X-ray fan beam (X-ray beam) emitted from an X-ray source.

That is, the radiation detector modules 1a, 1
.. 1n faithfully convert the X-ray dose transmitted through the subject into an electric charge, and each scintillator member 3a constituting each scintillator segment 2a, 2b, 2c. , 3b, 3c... 3n receive X-rays and emit fluorescence, and the photodiodes 4a, 4b, 4n
are converted into electric charges (currents) by the photodiode array 4 composed of 4n. Thus, the radiation detector module is also called a “scintillator module” because it is a module that photoelectrically converts visible light emitted by the scintillator block. The materials of the scintillator members 3a, 3b, 3c... 3n used for the CT scanner are inorganic crystals, Nal (Tl), Csl
(Tl), BGO (Bi4Ge3O14), CdWO4
Are often used.

That is, a radiation detector module (multi-slice) 1a, 1b, 1 provided in the radiation detector
c... 1n are two-dimensionally arranged individual scintillator members 3a, 3b, 3c that emit visible light when receiving X-rays.
.. 3n scintillator segments 2a, 2b, 2
c,... 2n, photodiodes 4a, 4b, 4c... 4n optically joined to receive light emitted in the scintillator segment and generate a signal current, and are disposed between the scintillator segment and the photodiode array. A stripe block (not shown) composed of a linear X-ray shield for hiding a positional displacement of the scintillator member in the direction along the channel;
A collimator 5 arranged on the X-ray source side perpendicular to the X-ray shield,
And a support member 6 for holding them together.

In order to construct such a radiation detector, first, the scintillator members 3a, 3b, 3c...
.. 2n are optically adhered onto the photodiode array 4 and then fixed so as to be electrically connected to the wiring board 7, thereby forming the radiation detector modules 1a, 1b,. 1c... 1n. Then, the radiation detector module 1 in which the photodiode array 4 is adhered to a collimator 5 made of a cobalt alloy incorporated so as to match the pitch of the scintillator member.
a, 1b, 1c... 1n are fixed to the support member 6 so as to be aligned. The support members 6 integrally hold each other so that the collimator 5 is maintained at a predetermined pitch. Note that the wiring board 7 is a multilayer wiring board, and a predetermined wiring pattern is also provided on the surface thereof. The photodiode array 4 and the switch element are mounted on the surface side of the wiring board 7, and the photodiode array 4 and the switch element are electrically connected. Further, this switch element is connected to the wiring board 7 through a through wiring formed in the wiring board 7.
It is electrically connected to a data collection element (described later) mounted on the back side of the wiring board 7.

Therefore, the radiation detector module 1
The radiation received by the scintillator blocks of a, 1b, 1c... 1n is photoelectrically converted into an electric signal having a power corresponding to the radiation dose. By extracting an electric signal from each photodiode element while selecting an element with a switch element, an electric signal output corresponding to radiation incident on the scintillator block can be obtained as detection data. This detection data is transferred to a DAS (Data Acquis) which is a data collection element formed of a semiconductor integrated circuit.
The data is collected and processed by an external device. FIG. 2 is a block diagram showing the processing contents of the DAS. That is, it indicates the processing order of the signal after the X-rays are converted into visible light by the scintillator block and photoelectrically converted. The radiation detector modules 1a, 1b, 1c...
S, the detection data is sent out, and the amplifier 11, the sample and hold 12, the multiplexer 13, the A / D converter 14
And output from the interface 15 to the computer 16 which is an external device. next,
Each embodiment of the radiation detector module fixed to the wiring board, that is, the radiation detector will be described in detail.

(Embodiment 1) FIG. 3A is a plan view of a radiation detector of the present invention, and FIG. 3B is a sectional side view thereof. The wiring board 7a is made of ceramics or glass epoxy material, is formed of multilayer wiring, and has a predetermined wiring pattern (not shown) on the surface. The photodiode array 24 and the switch elements 28a, 2
8n are mounted, and the photodiode array 24 and the switch elements 28a, 28b, 28c.
n is mounted on each element 24 and 28a, 28
The surface of each element 24 and 28a, 28b, 28c... 28n and the surface of the wiring board 7a are formed to have substantially the same height. On the photodiode array 24, scintillator members 23a, 23b, 23c for converting X-rays into light are provided.
23n are optically connected and mounted. Further, the data collecting elements 26a, 26b,
26n are mounted. The photodiode array 24 and the wiring board 7a are electrically connected to the wiring pattern of the wiring board 7a by flexible boards 9a, 9b, 9c,. 28b, 28c ... 2
8n and the input / output of the wiring board 7a, the flexible patterns 9a, 9b, 9c.
n. Therefore, each element 24 and 2
.., 28n are electrically connected to each other via a wiring pattern of the wiring board 7a.

These flexible substrates 9a, 9b, 9c
.. 9n and each element 2 and 28a, 28b, 28c.
n is connected to an ACF (An) using an anisotropic conductive sheet.
isotropic Conductive Fil
e) or a TAB method in which a protruding electrode such as a gold bump is formed in advance and bonding is performed. In this embodiment, a flexible substrate 7 having a copper wiring having a minimum wiring width of 35 μm, a wiring distance of 15 μm, and a wiring pitch of 50 μm formed on an insulating sheet made of a polyimide material.
Are connected using an anisotropic conductive sheet. Further, on the flexible substrate and the connection portion, a protective coat is applied with an epoxy resin (not shown) for improving the mechanical strength and the insulating property, so that the number of slices is 8 or more (for example, 10 rows). ) Can be connected correctly. On the other hand, in the case of the conventional wire bonding method, the bonding to a pad pitch of about 80 μm is practically limited. The number of signal lines extracted from each element of
Since connection to a pad pitch of 50 μm or less is required, it has been difficult to cope with it.

A method for manufacturing these radiation detector modules will be described with reference to FIGS. 3 (a) and 3 (b). First, packaged data collection elements 26a, 26a are mounted on the back surface of a wiring board 7a, which is a ceramic multilayer wiring board manufactured using the thick film wiring technique and the co-firing technique.
26n are mounted by soldering. Next, the photodiode array 24 and the switch element 28
a, 28b, 28c... 28n are bonded and fixed to the surface of the wiring board 7a using an epoxy resin. After that, the elements 24 and 28a, 28b, 28c... 28n mounted on the flexible substrates 9a, 9b, 9c... 9n were aligned with the wiring substrate 7a, and connected by an anisotropic conductive sheet. At this time, the curing temperature of the anisotropic conductive sheet is 18
Performed at 0 ° C. Finally, the scintillator members 23a, 23
23n were aligned with and bonded to the photodiode array 24 to form a radiation detector module.

(Embodiment 2) FIG. 4A is a plan view of the radiation detector of the present invention, and FIG. 4B is a sectional side view thereof. The structure of the radiation detector in this embodiment is the same as that of (Example 1) except for the shape of the flexible substrate that electrically connects the elements mounted on the surface of the wiring board.

That is, the wiring board 7b is made of a ceramic or glass epoxy material, is formed of multilayer wiring, and has a predetermined wiring pattern (not shown) on the surface. The photodiode array 34 and the switch elements 38a, 38b, 38c... 38n are mounted on the wiring board 7b.
The photodiode array 34 and the switch elements 38a, 3
The portions on which 8b, 38c... 38n are mounted are dug in accordance with the thickness of each element, and the elements 34 and 38a, 38
The surfaces of b, 38c... 38n and the surface of the wiring board 7 are configured to have substantially the same height. On the photodiode array 34, scintillator members 33a, 33b, 33c... 33n for converting X-rays into light are optically connected and mounted. Data collecting elements 36a, 36b, 36c... 36n are mounted on the back surface of the wiring board 7b.
Further, the photodiode array 34 and the wiring board 7b
It is electrically connected by a flexible substrate 39 provided with wiring, and includes switch elements 38a, 38b, 38c.
.. 38n and the input / output of the wiring board 7b are similarly connected by the flexible board 79. These flexible substrates 3
9 and each element 34 and 38a, 38b, 38c ... 38n
ACF (Anisotr) using an anisotropic conductive sheet
(Optical Conductive Film) method or TAB method in which a protruding electrode such as a gold bump is formed in advance and bonded.

Thus, each of the elements 34 and 38a, 3
8b, 38c... 38n are connected by one circuit.
Since it is formed on a single flexible substrate 39, the number and types of flexible substrates 39 are reduced, and the number of connection steps can be reduced, which is advantageous in terms of cost. However, in this case, the flexible substrate 3
9 are connected in such a manner that the electrodes of the photodiode array 34, the wiring board 7b, the switch elements 38a, 38b, 38c... 38n and the electrodes of the flexible board 39 are accurately aligned. ,
38n need to be bonded to the wiring board 7b. This alignment can be realized, for example, by using a double-sided alignment device (not shown) having a half mirror (not shown).

The method of manufacturing the radiation detector module shown in this embodiment is basically the same as that of (Example 1). First, the data collection element 36a packaged on the back surface of the wiring board 7b, which is a ceramic multilayer wiring board manufactured by using the thick film wiring technique and the co-firing technique,
36n are mounted by soldering. Next, the photodiode array 34 and the switch element 38
a, 38b, 38c... 38n are bonded and fixed to the surface of the wiring board 7b using an epoxy resin. Thereafter, the flexible substrate 39 and the mounted elements 34 and 38a,
38n, 38c... 38n and the wiring board 7b were aligned and connected by an anisotropic conductive sheet. The curing temperature of the anisotropic conductive sheet at that time was 180 ° C. Finally, the scintillator members 33a, 33b, 33c ... 33n
Was bonded to the photodiode array 34 after it was positioned, thereby forming a radiation detector module.

(Embodiment 3) FIG. 5A is a plan view of a radiation detector according to the present invention, and FIG. 5B is a sectional side view thereof. The structure of the radiation detector in this embodiment is the same as that of the first embodiment and the second embodiment in the components constituting the detector, such as a photodiode array and a switch element. And switch elements are flip-chip mounted on a wiring board using bumps. That is, the wiring board 7c is made of a ceramic or glass epoxy material, is formed of a multilayer wiring board, and has a predetermined wiring pattern (not shown) on the surface. On the wiring pattern on the wiring board 7c, the photodiode array 44 and the switch elements 48a, 48
b, 48c... 48n are bumps 49a, 49b, 49c
.. 49n. On the photodiode array 44, scintillator members 43a, 43b, 43c... 43n for converting X-rays into light are arranged. The data collecting element 48a is provided on the back side of the wiring board 7c.
48b, 48c ... 48n are bumps 49a, 49b, 4
9c... 49n.

In the method of manufacturing the radiation detector shown in this embodiment, first, the radiation detector is packaged on the back surface of a wiring board 7c which is a ceramic multilayer wiring board manufactured by using the thick film wiring technique and the co-firing technique. Data collection elements 46a, 4
.. 46n, and the switching elements 48a, 48b, 48c.
48n is mounted by soldering. In this case, the switch elements 48a, 48b, 48c... 48n and the data collection elements 46a, 46b, 46c... 46n are connected to the electrodes formed on the front surface of each chip by bumps 49a, 49b, 49c.
.. 49n are formed by, for example, an electroplating method and mounted by a flip chip method.

FIG. 6 is a schematic diagram showing a cross section of the photodiode array 44 of the present invention. Wiring 5 for extracting a signal from each diffusion layer 51 in which photodiodes 44a, 44b, 44c... 44n serving as the main body of the photoelectric conversion unit are formed.
2 is formed on the surface of the photodiode array 44. The wiring 52 extends so as to be connected to a through wiring 54 formed through the front and back of the Si wiring substrate 53. A bump 55 is formed on the back surface of the photodiode 44 in a state where the bump 55 is connected to the through wiring 54. The through wiring 54 is formed of polysilicon, W, Ni,
It can be formed of any of Cu. Also,
The insulating films 56a, 56b, 56c are formed between the wirings 52, 54 and the Si wiring substrate 53 by a silicon oxide film to be insulated. The through hole of the through wiring 54 can be easily formed by RIE dry etching, and the conductive material can be filled by a CVD method or an electroplating method. As the filling material, polysilicon or tungsten is effective in the CVD method, and nickel or copper is effective in the electroplating method in terms of electrical characteristics. Further, the bump-shaped electrodes and the copper bumps and the solder bumps formed by the electroplating method can be connected to the wiring board 7 with high reliability.

Usually, the photodiode array has electrodes formed on the same main surface as the photoelectric conversion surface for outputting a current obtained by photoelectric conversion. In such a photodiode array, the surface on which the photodiode body for detecting light is formed in principle cannot be mounted facing the multilayer wiring board side. The connection with the wiring pattern was made. In the present embodiment, the structure shown in FIG. 6 enables flip-chip mounting of the photodiode array.

As described above, the mounting structure of the radiation detector having a large number of slices includes a photodiode array and a wiring board, a photodiode array and a switching element, or at least one of a switching element and a wiring board. It is effective that the combination electrically connects the flexible substrate 7 by an anisotropic conductive sheet (ACF method) or TAB method. In addition, a through wiring 54 penetrating through the inside from the surface on which the photoelectric conversion units are arranged to the back surface.
So that the bumps 5 are connected to the through wirings 54.
5 was formed on the back surface to constitute a photodiode array. The structure in which the bumps are used to mount the flip-chip on the wiring board 7 contributes to the high density of the photoelectric conversion surface and is suitable for the mounting structure of a radiation detector having a large number of slices.

Also, these radiation detectors are shown in FIG.
X-ray C arranged in an arc shape as shown in FIG.
T devices are useful. X from the radiation source
The rays are absorbed by the radiation detector after passing through the human body, and processing of the transmission data by a computer makes it possible to obtain a precise and good image.

[0027]

According to the present invention, according to the prior art, it is possible to realize a radiation detector used in a multi-slice X-ray CT, which has high reliability and low cost cannot be realized. In addition, an X-ray CT apparatus using the same makes it possible to obtain a precise and good image.

[Brief description of the drawings]

FIG. 1A is a perspective view of an X-ray solid state detector, and FIG.
3 is a perspective view of a radiation detector.

FIG. 2 is a block diagram showing a path of signal processing in the DAS.

3A is a plan view of an embodiment of the radiation detector of the present invention, and FIG. 3B is a cross-sectional side view thereof.

4A is a plan view of an embodiment of the radiation detector according to the present invention, and FIG. 4B is a cross-sectional side view thereof.

FIG. 5A is a plan view of an embodiment of the radiation detector of the present invention, and FIG. 5B is a cross-sectional side view thereof.

FIG. 6 is a sectional side view showing an embodiment of the photodiode array of the present invention.

FIG. 7A is a plan view of an example of a conventional radiation detector, and FIG. 7B is a cross-sectional side view thereof.

[Explanation of symbols]

1a, 1b, 1c-1n ... radiation detector module, 2a, 2b, 2c-2n ... scintillator segment, 3a, 3b, 3c-3n ... scintillator member, 4, 24, 34, 44 ... photodiode array, 7, 7a , 7b, 7c ... wiring board, 8a to 8n, 28a to 28n, 38a to 38n, 48a
... 48n ... switch element, 9a, 9b, 9c-9n, 39 ... flexible board, 26a-26n, 36a-36n, 46a-46n ... data collection element, 49a, 49b, 49c-49n ... bump

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Machiko Ono 1385-1 Higashiyama, Shimoishikami, Otawara-shi, Tochigi Pref. Address F-term in Toshiba R & D Center (reference) 2G088 EE02 FF02 GG19 JJ02 JJ05 JJ33 4C093 AA22 BA10 CA02 CA18 CA27 EB12

Claims (5)

[Claims] 1. A photodiode array optically connected to a scintillator member and a switch element electrically connected to the photodiode array are mounted on one surface of a wiring board, and the other side of the wiring board is mounted on the other side of the wiring board. A radiation detector having a surface on which a data collection element receiving an electric signal from the photodiode array is mounted, wherein a connection between the photodiode array or the switching element and the wiring board, and the photodiode array and the switching A radiation detector, wherein at least one of the connections to the element is electrically connected using a flexible substrate. 2. The method according to claim 2, wherein the electrical connection with each of the parts using the flexible substrate is performed using an anisotropic conductive sheet or a T
The radiation detector according to claim 1, wherein the radiation detector is connected by AB. 3. A photodiode array in which a scintillator member and a photoelectric conversion surface are optically connected to one surface of a wiring board, and a switch element electrically connected to the photodiode array are mounted. In a radiation detector in which a data collection element for receiving an electric signal from the photodiode array is mounted on the other surface of the wiring board, the photodiode array is arranged such that the main surface on which the photoelectric conversion surface is formed is the other main surface. A radiation detector, wherein a penetrating wiring penetrating a surface is formed, and the radiation detector is mounted on the wiring substrate by a bump provided on the other main surface. 4. The semiconductor device according to claim 1, wherein the through wiring is formed of polysilicon, W, N
The radiation detector according to claim 3, wherein the radiation detector is made of one of i and Cu. 5. An X-ray CT apparatus comprising the radiation detector according to claim 1. Description: