JP2007205935A - Radiation detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation detector capable of maintaining satisfactory electric connection between a common electrode and a voltage supply pad. <P>SOLUTION: In this X-ray detector 1, a connection member 19 comprising a conductive resin is laid in the common electrode 18 and the voltage supply pad 15 to connect the common electrode 18 electrically to the voltage supply pad 15. The common electrode 18 is thereby prevented from being separated partially, since the common electrode 18 is not formed on an inclined face even when a side face 17b of a photoconductive layer 17 is an inclined face. Resultingly, not only the electric connection between the common electrode 18 and the voltage supply pad 15 is maintained favorably, but also the X-ray detector 1 is prevented from being affected unfavorably and variously with separated electrode chips formed into dust. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radiation detector for detecting radiation such as X-rays.

As a conventional radiation detector, a so-called direct conversion type is known. The direct conversion type radiation detector is, for example, a signal readout substrate in which a plurality of pixel electrodes are two-dimensionally arranged on a substrate, a photoconductive layer formed on the signal readout substrate, and a photoconductive layer And a common electrode formed. In such a radiation detector, an electrical connection between the common electrode and the voltage supply pad is achieved by extending a part of the edge of the common electrode to the voltage supply pad formed on the signal readout substrate. Is common (see, for example, Patent Documents 1 and 2).
JP 2000-241556 A JP 2002-303676 A

  However, the radiation detector as described above has the following problems. That is, when a photoconductive layer is deposited on a signal readout substrate using a mask, if the mask is brought into contact with the signal readout substrate, the mask is removed from the signal readout substrate and at the same time the edge of the photoconductive layer is also removed. Therefore, it is necessary to keep the mask away from the signal readout substrate. As a result, part of the material for forming the photoconductive layer goes under the mask, and as a result, the side surface of the photoconductive layer becomes an inclined surface. If a part of the edge of the common electrode is formed on such an inclined surface, the common electrode is likely to be partially peeled off, and the electrical connection between the common electrode and the voltage supply pad is not maintained well. Or, the peeled electrode pieces may become dust and have various adverse effects on the radiation detector.

  Therefore, the present invention has been made in view of such circumstances, and an object thereof is to provide a radiation detector capable of maintaining good electrical connection between the common electrode and the voltage supply pad. .

  In order to achieve the above object, a radiation detector according to the present invention is a radiation detector for detecting radiation, wherein a plurality of pixel electrodes are arranged one-dimensionally or two-dimensionally on one surface of a substrate. A signal readout substrate, a photoconductive layer formed on one surface of the signal readout substrate so as to include a pixel electrode when viewed from a direction orthogonal to one surface of the substrate, and orthogonal to one surface of the substrate A common electrode formed on one surface of the photoconductive layer so as to include the pixel electrode when viewed from the direction and included in one surface of the photoconductive layer, and a voltage supply pad formed on the signal readout substrate. And a connection member made of a conductive resin is stretched between the common electrode and the voltage supply pad.

  In this radiation detector, in order to electrically connect the common electrode and the voltage supply pad, a connection member made of a conductive resin is stretched over the common electrode and the voltage supply pad. Thereby, even if the side surface of the photoconductive layer is an inclined surface, the common electrode is not formed on the inclined surface, so that partial separation of the common electrode can be prevented, and the common electrode and the voltage supply pad can be prevented from being separated. It is possible to maintain a good electrical connection.

  In the radiation detector according to the present invention, the connecting member is preferably in contact with the side surface of the photoconductive layer. Thereby, since the installation of the connection member is improved, the stability of electrical connection between the common electrode and the voltage supply pad can be improved.

  In the radiation detector according to the present invention, the connection member is preferably made of a conductive resin having a shrinkage rate of 2% or less when cured. As a result, the stress generated in the connection member due to the shrinkage of the conductive resin during curing is reduced, so that the common electrode formed on one surface of the photoconductive layer is pulled by the connection member and partially peeled off. Can be prevented. The shrinkage ratio at the time of curing is a value representing a dimensional difference before / after curing as a percentage of the dimension before curing.

  In the radiation detector according to the present invention, the photoconductive layer is preferably made of a crystalline material. Thereby, the sensitivity of the photoconductive layer with respect to incident X-rays can be improved.

  According to the present invention, the electrical connection between the common electrode and the voltage supply pad can be favorably maintained.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted.

  As shown in FIGS. 1 to 3, an X-ray detector (radiation detector) 1 is for detecting X-rays incident from the front (upper in FIGS. 2 and 3), and is a signal readout board. 2 is provided. The signal readout substrate 2 is configured by arranging a large number of pixel units 4 in a two-dimensional matrix on a rectangular effective pixel region R defined on a front surface (one surface) 3a of a rectangular substrate 3 made of glass. Has been. A plurality of bonding pads 5 are formed along one side of the substrate 3 in a region outside the effective pixel region R on the front surface 3 a of the substrate 3, and two opposite sides of the substrate 3 are further formed in the same region. A plurality of bonding pads 6 are formed along each of them.

  As shown in FIG. 4, each pixel unit 4 includes a pixel electrode 7 for collecting charges, a storage capacitor 8 for storing charges collected in the pixel electrode 7, and a charge stored in the storage capacitor 8. Has a switching element 9 for reading out. As a result, in the signal readout substrate 2, a large number of pixel electrodes 7 are arranged in a two-dimensional matrix on the front surface 3 a of the substrate 3. The switching element 9 is, for example, a thin film transistor (TFT), and is, for example, a C-MOS transistor when the substrate 3 is made of silicon.

  Each switching element 9 is electrically connected to the bonding pad 5 by a signal line 11, and further electrically connected to a gate driver 12 for turning on / off the switching element 9 by a flexible printed circuit (FPC) or the like. ing. Each storage capacitor 8 is electrically connected to the bonding pad 6 by a signal line 13 through a switching element 9, and further, a charge amplifier 14 that amplifies the charge stored in the storage capacitor 8, an FPC, and the like. Electrically connected.

  As shown in FIGS. 1 to 3, a voltage supply pad 15 is formed in a region outside the effective pixel region R on the front surface 3 a of the substrate 3 so as to face the bonding pad 5 with the effective pixel region R interposed therebetween. ing. An insulating planarizing film is formed on the front surface 3a of the substrate 3 so that the front surfaces of the pixel electrode 7, the bonding pads 5 and 6, and the voltage supply pad 15 are exposed and the signal lines 11 and 13 are embedded. 16 is formed.

  The front surface (one surface) 2a of the signal readout substrate 2 includes the effective pixel region R as viewed from the front (that is, the direction orthogonal to the front surface 3a of the substrate 3) (that is, includes all the pixel electrodes 7). As described above, a crystalline photoconductive layer 17 made of a metal halide, for example, lead iodide, is formed, and is electrically connected to each pixel electrode 7. The photoconductive layer 17 is formed in a square frustum shape having a rectangular front surface (one surface) 17a including the effective pixel region R when viewed from the front and a side surface 17b which is an inclined surface. This is because when the photoconductive layer 17 is deposited on the front surface 2a of the signal readout substrate 2 using a mask, if the mask is brought into contact with the front surface 2a, the mask is peeled off from the front surface 2a and at the same time the photoconductive layer 17 is formed. This is because the edge part also peels off, so that the mask needs to be separated from the front surface 2a, and as a result, a part of lead iodide wraps around the mask.

  The front surface 17a of the photoconductive layer 17 includes the effective pixel region R as viewed from the front (that is, includes all the pixel electrodes 7), and the rectangular common electrode so as to be included in the front surface 17a of the photoconductive layer 17. 18 is formed. More specifically, the common electrode 18 is formed on the front surface 17 a of the photoconductive layer 17 so as not to reach the side surface 17 b that is the inclined surface of the photoconductive layer 17. A connection member 19 made of a conductive resin is stretched over the common electrode 18 and the voltage supply pad 15 so as to be in contact with the side surface 17 b of the photoconductive layer 17. As a result, the common electrode 18 and the voltage supply pad 15 are electrically connected. The contact point between the connection member 19 and the common electrode 18 is outside the effective pixel region R (specifically, an outer edge surrounding the effective pixel region R in the common electrode 18 when viewed from the front so as not to narrow the imaging region). Area).

  On the front surface 2 a of the signal readout substrate 2, the voltage supply pad 15, the planarizing film 16, and the connection member 19 are surrounded by the voltage supply pad 15 so as to be open and cover the entire connection member 19. A rectangular annular insulating convex portion 21 made of an insulating resin having good adhesiveness, for example, a UV curable acrylic resin (such as WORLD ROCK No. 801-SET2 manufactured by Kyoritsu Chemical Industry Co., Ltd.) is formed. One end of the voltage supply line 22 is fixed to a part (open portion) of the voltage supply pad 15 surrounded by the insulating convex portion 21 by soldering or with a conductive adhesive. As a result, the voltage supply pad 15 and the voltage power source 23 are electrically connected.

  Further, the front surface 2 a of the signal readout substrate 2 has an insulating resin having good adhesion to the planarizing film 16, for example, the insulating protrusions 21, so as to surround the photoconductive layer 17 and the insulating protrusions 21. A rectangular annular insulating convex portion 24 made of the same UV curable acrylic resin is formed. In the region inside the insulating convex portion 24, the protection reaching the tops of the insulating convex portions 21 and 24 so as to cover the photoconductive layer 17 and the common electrode 18 except for the region inside the insulating convex portion 21. Layer 25 is formed. The protective layer 25 is configured by sandwiching an inorganic film 26 with an organic film (insulating protective layer) 27. The inorganic film 26 is made of a material that has little X-ray absorption and shields visible light, such as aluminum. The organic film 27 is made of a material having insulating properties and excellent moisture resistance, for example, polyparaxylylene resin (trade name: Parylene, etc., manufactured by Three Bond Co., Ltd.). Therefore, the protective layer 25 is a combination of the inorganic film 26 and the organic film 27, thereby reducing noise by blocking visible light, improving ease of handling by ensuring insulation, and preventing water vapor and gas in the external atmosphere. An effect such as prevention of deterioration of characteristics of the photoconductive layer 17 due to the blocking is obtained.

  Inside the insulating convex portion 21, the insulating portion is higher than the organic film 27 so that the fixing portion between the voltage supply pad 15 and the voltage supply line 22 is sealed from the outside atmosphere, and the adhesive portion 21 is bonded to the insulating convex portion 21. An insulating sealing member 28 made of a resin having good properties, for example, silicone rubber (such as RTV-11 manufactured by GE Silicones) is filled. The insulating sealing member 28 reaches the top of the insulating protrusion 21 and covers the inner edge 25 a of the protective layer 25. As a result, the insulating sealing member 28 comes into contact with the inner edge of the organic film 27. In order to prevent the outer edge 25b of the protective layer 25 from being peeled off, the top of the insulating convex portion 24 is made of a material having good adhesion to the insulating convex portion 24 and the organic film 27, for example, An insulating fixing member 29 made of the same UV curable acrylic resin as the insulating convex portion 21 is arranged in a rectangular ring shape and covers the outer edge 25 b of the protective layer 25.

  The operation of the X-ray detector 1 configured as described above will be described. As shown in FIG. 4, when X-rays are incident on the photoconductive layer 17 from the front, the X-rays are absorbed in the photoconductive layer 17 and a charge proportional to the absorbed X-ray dose is generated. At this time, since the bias voltage Vb (a high voltage of about 500 V to 1000 V) is applied to the common electrode 18 by the voltage power supply 23, the charge generated in the photoconductive layer 17 flows through the photoconductive layer 17 in the electric field. And is collected by the pixel electrode 7 and accumulated in the storage capacitor 8. Then, each switching element 9 is sequentially turned on / off by the gate driver 12, and the charges accumulated in the respective storage capacitors 8 are sequentially read out and amplified by the charge amplifier 14, whereby a two-dimensional X-ray image is obtained. Is obtained.

  As described above, in the X-ray detector 1, in order to electrically connect the common electrode 18 and the voltage supply pad 15, the connection member 19 made of a conductive resin is connected to the common electrode 18 and the voltage supply pad 15. Is over. Thereby, even if the side surface 17b of the photoconductive layer 17 is an inclined surface, since the common electrode 18 is not formed on the inclined surface, partial peeling of the common electrode 18 can be prevented.

  This specifically solves the following problem.

  That is, when the connection member 19 is formed of a metal film as in the prior art, since the side surface 17b of the photoconductive layer 17 is an inclined surface, the thickness of the metal film formed on the side surface 17b is flat and flat. There is a difference in the film thickness of the metal film formed on the flat portion from the end of the side surface 17b to the voltage supply pad 15 on the conversion film 16. Therefore, particularly when the thickness of the metal film is increased, stress such as internal stress is likely to be applied to the thickness changing portion or the thick thickness portion, and peeling or the like is likely to occur.

  The X-ray detector 1 uses a crystalline photoconductive layer 17 made of a metal halide such as lead iodide. Therefore, the X-ray detector 1 is highly sensitive to X-rays, but has a connection member 19 and a photoconductive layer 17. Similarly to the front surface 17a including the effective pixel region R when viewed from the front, the side surface 17b, which is an inclined surface serving as a contact surface, is also made of a polycrystalline body having various crystal orientations. Therefore, since the surface form is uneven and not flat, when the connection member 19 is formed of a metal film as in the prior art, the film thickness tends to be non-uniform, especially when the film thickness is reduced. , Easy to break.

  Further, the metal film may be damaged due to a difference in coefficient of thermal expansion with the contact member.

  As described above, when the connection member 19 is formed of a metal film, it is difficult to maintain good electrical connection regardless of whether the film thickness is increased or decreased.

  On the other hand, according to the X-ray detector 1, since the conductive resin is used for the connecting member 19, the elasticity of the resin component suppresses the influence of stress such as internal stress. Therefore, it is possible not only to maintain a good electrical connection between the common electrode 18 and the voltage supply pad 15, but also the peeled electrode pieces become dust and have various adverse effects on the X-ray detector 1. Can be prevented.

  In the X-ray detector 1, the connection member 19 is in contact with the side surface 17 b of the photoconductive layer 17. Thereby, since the installation of the connection member 19 is improved, the stability of electrical connection between the common electrode 18 and the voltage supply pad 15 can be improved.

  In the X-ray detector 1, the connecting member 19 is made of a conductive resin having a shrinkage rate of 2% or less when cured. As a result, the stress generated in the connection member 19 due to the shrinkage of the conductive resin during curing is reduced, so that the common electrode 18 formed on the front surface 17a of the photoconductive layer 17 is pulled by the connection member 19 and partially peeled off. Can be prevented. In addition, conductive resin is resin (silver paste etc.) containing metal powder and carbon powder, for example, As a material of the connection member 19, "Fukuda metal foil powder industry Co., Ltd. conductive paste sill coat GL-10" Etc. are suitable.

  Furthermore, in the X-ray detector 1, the photoconductive layer 17 is formed of a crystalline material. Thereby, the sensitivity of the photoconductive layer 17 with respect to incident X-rays can be improved.

  Next, a method for manufacturing the above-described X-ray detector 1 will be described.

  First, as shown in FIG. 5, the front surface 2a of the signal readout substrate 2 on which the voltage supply pad 15 is formed includes the effective pixel region R as viewed from the front (that is, includes all the pixel electrodes 7). A) A photoconductive layer 17 is formed. Subsequently, as shown in FIG. 6, the common electrode 18 is formed on the front surface 17a of the photoconductive layer 17 so as to include the effective pixel region R when viewed from the front (that is, to include all the pixel electrodes 7). To do.

  After forming the common electrode 18, as shown in FIG. 7, a connection member 19 is spanned between the common electrode 18 and the voltage supply pad 15 in order to electrically connect the common electrode 18 and the voltage supply pad 15. . Subsequently, as shown in FIG. 8, an insulating convex portion 21 is formed on the front surface 2 a of the signal readout substrate 2 so as to surround a part of the voltage supply pad 15, and at the front surface 2 a of the signal readout substrate 2. Then, the insulating convex portion 24 is formed so as to surround the photoconductive layer 17 and the insulating convex portion 21.

After forming the insulating convex portions 21 and 24, as shown in FIG. 9, the photoconductive layer 17, the common electrode 18, the voltage supply pad 15, the insulating convex portions 21 and 24, and the signal readout substrate 2 are covered. A protective layer 25 is formed.
Subsequently, as shown in FIG. 10, the voltage surrounded by the insulating convex portion 21 by peeling the protective layer 25 inside the cutting 21 a by making a circular cut 21 a along the insulating convex portion 21. A part of the supply pad 15 is exposed. Further, the protective layer 25 outside the notch 24a is peeled off by making the notches 24a annularly along the insulating convex portions 24.

  After peeling a predetermined portion of the protective layer 25, as shown in FIG. 2, in order to electrically connect the voltage supply pad 15 and the voltage power source 23, a part of the exposed voltage supply pad 15 is applied. The voltage supply line 22 is fixed. Subsequently, an insulating sealing member 28 is filled inside the insulating convex portion 21 to cover the inner edge 25a of the protective layer 25, and an insulating fixing member 29 is formed in a rectangular ring shape on the top of the insulating convex portion 24. And the X-ray detector 1 is completed by covering the outer edge 25b of the protective layer 25.

  According to the manufacturing method of the X-ray detector 1 described above, it is possible to easily and reliably manufacture the X-ray detector 1 capable of suppressing the generation of noise in the electrical signal read from the pixel electrode 7. Become.

  The present invention is not limited to the embodiment described above.

  For example, the radiation detector according to the present invention is not limited to the X-ray detector, and may be for detecting electromagnetic waves (γ rays or the like) having different wavelength regions and other light.

  The signal readout substrate is not limited to one in which a plurality of pixel electrodes are two-dimensionally arranged on the front surface of the substrate, and may be one in which a plurality of pixel electrodes are one-dimensionally arranged on the front surface of the substrate. Good.

  The photoconductive layer is not limited to being formed directly on the front surface of the signal readout substrate, and an intermediate layer such as a charge injection blocking layer may be formed between the signal readout substrate and the photoconductive layer. Similarly, an intermediate layer such as a charge injection blocking layer may be formed between the common electrode and the photoconductive layer.

  In addition, the photoconductive layer is not limited to metal halides such as lead iodide, mercury iodide, and bismuth iodide, and other materials that exhibit conductivity and have crystallinity upon incidence of radiation may be used.

  In addition, the materials used for each of the insulating protrusions and the insulating sealing member may be a common material or different materials as long as the conditions such as insulation and adhesion to each contact member are satisfied. May be.

  Further, as shown in FIG. 11, the insulating fixing member 31 is arranged in a rectangular ring shape on the top of the insulating convex portion 21 to cover the inner edge 25 a of the protective layer 25, thereby providing an inner side of the protective layer 25. The edge 25a may be prevented from peeling off.

It is a top view of one embodiment of a radiation detector concerning the present invention. It is sectional drawing along the II-II line | wire shown by FIG. It is sectional drawing along the III-III line | wire shown by FIG. It is a conceptual diagram of the radiation detector shown by FIG. It is sectional drawing which shows the 1st manufacturing process of the radiation detector shown by FIG. It is sectional drawing which shows the 2nd manufacturing process of the radiation detector shown by FIG. It is sectional drawing which shows the 3rd manufacturing process of the radiation detector shown by FIG. It is sectional drawing which shows the 4th manufacturing process of the radiation detector shown by FIG. It is sectional drawing which shows the 5th manufacturing process of the radiation detector shown by FIG. It is sectional drawing which shows the 6th manufacturing process of the radiation detector shown by FIG. It is sectional drawing of other embodiment of the radiation detector which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... X-ray detector (radiation detector), 2 ... Signal reading board | substrate, 2a ... Front surface (one surface), 3 ... Substrate, 3a ... Front surface (one surface), 7 ... Pixel electrode, 15 ... Voltage supply pad 17 ... Photoconductive layer, 17a ... Front surface (one surface), 17b ... Side surface, 18 ... Common electrode, 19 ... Connection member.

Claims (4)

A radiation detector for detecting radiation,
A signal readout substrate in which a plurality of pixel electrodes are arranged one-dimensionally or two-dimensionally on one surface of the substrate;
A photoconductive layer formed on one surface of the signal readout substrate so as to include the pixel electrode when viewed from a direction orthogonal to the one surface of the substrate;
A common electrode formed on one surface of the photoconductive layer so as to include the pixel electrode as viewed from a direction orthogonal to the one surface of the substrate and to be included in one surface of the photoconductive layer;
A voltage supply pad formed on the signal readout substrate,
A radiation detector, wherein a connection member made of a conductive resin is stretched between the common electrode and the voltage supply pad.   The radiation detector according to claim 1, wherein the connection member is in contact with a side surface of the photoconductive layer.   The radiation detector according to claim 1, wherein the connection member is made of a conductive resin having a shrinkage rate of 2% or less when cured. The radiation detector according to claim 1, wherein the photoconductive layer is made of a crystalline material.

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