Substrate, module for x-ray detector, and x-ray detection unit

Abstract

Provided is a substrate used in an X-ray detector for a computed tomography device, said substrate comprising: a ceramic insulating substrate that has a first surface and a second surface; a first via conductor that is positioned inside the insulating substrate and that extends to the first surface; and a first pad that is electrically connected to the first via conductor. The first via conductor and the first pad have different types of metal as the main components thereof. The first pad includes a first glass material, and is directly bonded to the first surface.

Description

Substrate, Module for X-ray Detector, and X-ray Detection Unit

[0001] The present disclosure relates to a substrate, a module for an X-ray detector, and an X-ray detection unit.

[0002] Conventionally, with regard to a substrate for mounting electronic elements, techniques for improving heat transfer from the electronic elements have been proposed (see, for example, Patent Document 1).

[0003] Japanese Patent No. 7174046

[0004] The substrate according to one aspect of the present disclosure is a substrate used for an X-ray detector of a computed tomography apparatus, and includes a ceramic insulating substrate having a first surface on which an X-ray detection member is mounted and a second surface located on the opposite side of the first surface, a first via conductor located inside the insulating substrate, extending in the thickness direction of the insulating substrate and reaching the first surface, and a first pad provided on the first surface so as to be electrically connected to the first via conductor. The first via conductor and the first pad are different from each other in the type of metal as the main component. The first pad contains a first glass material and is directly bonded to the first surface.

[0005] A perspective view schematically showing an example of a CT apparatus to which the substrate according to an embodiment of the present disclosure is applied. A perspective view showing an example of a module for an X-ray detector including the substrate according to an embodiment of the present disclosure. A perspective view showing an example of the substrate according to an embodiment of the present disclosure. An enlarged cross-sectional view showing the peripheral configuration of the first pad of the substrate according to an embodiment of the present disclosure. An enlarged cross-sectional view showing the peripheral configuration of the second pad of the substrate according to an embodiment of the present disclosure. A cross-sectional view for explaining a multi-piece substrate before cutting out the substrate according to an embodiment of the present disclosure. An enlarged cross-sectional view showing the peripheral configuration of a plurality of first pads of the substrate according to an embodiment of the present disclosure. An enlarged cross-sectional view showing the peripheral configuration of a plurality of second pads of the substrate according to an embodiment of the present disclosure. A schematic diagram for explaining the substrate, the module for an X-ray detector, and the X-ray detection unit according to an embodiment of the present disclosure.

[0006] The technology described in Patent Document 1 reduces the expansion of electronic elements due to heat generated from those elements, thereby making it less likely for electronic elements mounted on a substrate to shift position. Incidentally, substrates are required to have various characteristics depending on their application. For substrates used in X-ray detectors of computed tomography scanners, precise positional accuracy of the pads connected to the electrodes of mounted components is required. Furthermore, each part of the substrate is also required to have high strength.

[0007] Hereinafter, one embodiment of the present disclosure will be described in detail with reference to the drawings. However, the following description is intended to provide a better understanding of the spirit of the invention and does not limit the present disclosure unless otherwise specified. For the sake of clarity, the drawings referenced in the following description show only the main components necessary to explain the embodiment, and for the sake of brevity, explanations of known technical matters will be omitted as appropriate.

[0008] To facilitate understanding of the substrate and other components in one embodiment of this disclosure, first, an overview of a computed tomography (CT) apparatus will be described with reference to Figure 1. The substrate in one embodiment of this disclosure is a substrate used in the X-ray detector of a CT apparatus, and more specifically, is a support substrate that supports an X-ray detection member and includes wiring for transmitting electrical signals. There are several types of CT apparatuses, but this disclosure focuses on medical X-ray CT apparatuses. Medical X-ray CT apparatuses include various types of X-ray CT apparatuses such as PET / CT. Furthermore, the substrate in one embodiment of this disclosure can be applied to detectors in various types of tomography imaging apparatuses such as PET and SPECT.

[0009] Figure 1 is a schematic perspective view showing an example of a CT apparatus to which the substrate in one embodiment of the present disclosure is applied. As shown in Figure 1, the CT apparatus 300 includes a gantry (frame) 310 having an opening 311. An X-ray generator 320 and an X-ray detector 1 are provided inside the housing of the gantry 310. The CT apparatus 300 is, of course, equipped with a console (computer), although this is not shown or described.

[0010] In the CT scanner 300, the X-ray generator 320 and the X-ray detector 1 are positioned within the housing of the gantry 310 so as to face each other across the opening 311. In the CT scanner 300, the X-ray generator 320 and the X-ray detector 1 are capable of rotating around the opening 311 within the housing of the gantry 310 while maintaining their opposing positional relationship. The subject H is, for example, lying on a bed (cradle) 400, and is moved horizontally into the opening 311 by the movable part of the bed 400.

[0011] In the CT scanner 300, the X-ray generator 320 and the X-ray detector 1 rotate at high speed around the subject H, emitting X-rays from the X-ray generator 320, and detecting the X-rays that have passed through the subject H with the X-ray detector 1. By processing the results with a computer, a cross-sectional image of the subject H can be obtained.

[0012] In the CT apparatus 300, the specific configuration of the rotation mechanism for rotating the X-ray generator 320 and the X-ray detector 1 is not particularly limited. For example, the X-ray generator 320 and the X-ray detector 1 may be mounted on a rotating frame driven by a rotation drive unit. The CT apparatus 300 may be equipped with multiple sets of X-ray generators 320 and X-ray detectors 1.

[0013] In the CT scanner 300, the X-ray generator 320 and the X-ray detector 1 rotate with a certain radius of rotation, for example, at a speed of about 1 revolution per second. As a result, a large centrifugal force is generated in the X-ray generator 320 and the X-ray detector 1. Therefore, each part of the X-ray detector 1 is required to have resistance to the centrifugal force generated when the CT scanner 300 is in operation. Furthermore, in order to improve the performance of the CT scanner 300, an improvement in the resolution of X-ray detection is required for the X-ray detector 1.

[0014] In the CT apparatus 300, the X-ray generator 320 may be a known device, and a detailed description of the X-ray generator 320 is omitted. The X-ray detector 1 includes an X-ray detector module, which includes a substrate according to one embodiment of the present disclosure. This X-ray detector module is described below. The X-ray detector 1 may have a known configuration in parts other than the X-ray detector module, and a detailed description is omitted.

[0015] Figure 2 is a perspective view showing an example of an X-ray detector module including a substrate in one embodiment of the present disclosure. In Figure 2, the various parts of the X-ray detector module are shown separately for clarity. Figure 3 is a perspective view showing an example of a substrate in one embodiment of the present disclosure.

[0016] Hereafter, the thickness direction of the X-ray detector module (the thickness direction of the substrate) will be defined as the Z-axis direction, and the XY-axis directions will be defined perpendicular to the Z-axis direction. The transverse direction of the main surface of the substrate will be defined as the X-axis direction, and the vertical direction will be defined as the Y-axis direction. The XYZ-axis directions will be defined similarly in the following explanation. For reference, the XYZ-axis coordinate system is shown in each figure as appropriate.

[0017] As shown in Figures 2 and 3, the X-ray detector module 50 included in the X-ray detector 1 comprises a substrate 100 in one embodiment of the present disclosure and an X-ray detection member 20 mounted on the substrate 100.

[0018] The substrate 100 has a first surface 110 on which the X-ray detection member 20 is mounted, and a second surface 120 located on the opposite side of the first surface 110. The substrate 100 may be a laminated substrate having multiple insulating layers laminated together and including wiring conductors. In the substrate 100, the multiple insulating layers are made of ceramic. The first surface 110 is provided with a first pad group 11G consisting of multiple first pads 11. The second surface 120 is provided with a second pad group 12G. The second pad group 12G consists of multiple second pads (see Figures 5 and 8, described later).

[0019] The X-ray detector module 50 may be, for example, an indirect conversion type flat panel detector (FPD). The X-ray detection member 20 may include, for example, an X-ray detection film 21 and a photodetector 22. The X-ray detection film 21 may be, for example, a CsI-based or GOS-based scintillator. The photodetector 22 may be, for example, an image sensor having a plurality of photodetectors (photodiodes, etc.). The photodetector 22 may be, for example, a photon counting detector capable of detecting photons.

[0020] In the X-ray detection member 20 having the above configuration, X-rays are converted into light by the X-ray detection film 21, and an analog electrical signal is generated when the photodetector 22 detects the photons. The photodetector 22 has a group of back electrodes (not shown) located on the surface facing the substrate 100. Each of the multiple back electrodes in the back electrode group of the photodetector 22 and each of the multiple first pads 11 in the first pad group 11G of the substrate 100 are electrically connected via a bonding material such as solder.

[0021] In the X-ray detector 1, the X-ray detector module 50 may be mounted on, for example, a mounting base (not shown). The second pad group 12G on the second surface 120 of the substrate 100 is connected to an external output member via, for example, a connector. A data acquisition circuit (DAS) may be connected to the X-ray detector 1 via a signal cable or the like. On the substrate 100, the second pads only need to be arranged so that connection to the external output member is possible, and the specific arrangement of the second pads in the second pad group 12G may be designed as appropriate.

[0022] The substrate 100 is required to have the following characteristics to accommodate its use in the X-ray detector 1. Specifically, when increasing the density of photodetectors in the photodetector 22 to improve the resolution of X-ray detection, multiple back electrodes in the back electrode group of the photodetector 22 are arranged closely together at a short pitch. The substrate 100 is required to have multiple first pads 11 arranged in a planar manner with high positional accuracy to correspond to the above back electrode group in order to mount the photodetector 22. In addition, for computer processing in the CT apparatus 300, it is required to synchronize multiple electrical signals transmitted from the back electrode group of the photodetector 22 with high precision. For this reason, it is required to make the transmission distance (electrical connection) between the back electrode group of the photodetector 22 and each of the multiple first pads 11 uniform, that is, to align the positions (height positions) of each of the multiple first pads 11 in the Z-axis direction. On the other hand, in the second pad group 12G, the number of pads is smaller than in the first pad group 11G because the electrical signals of the first pad group 11G are aggregated to some extent by the internal wiring of the substrate 100. In the second pad group 12G, the requirements regarding the positional accuracy of the multiple second pads are less than the requirements regarding the positional accuracy of the multiple first pads 11 in the first pad group 11G. Furthermore, each part of the substrate 100 is required to have resistance to the large centrifugal force generated in the X-ray detector 1, as described above.

[0023] The substrate 100 in one embodiment of this disclosure has been realized through diligent research by the inventors to satisfy the above-described characteristics and has the configuration described below.

[0024] Figure 4 is an enlarged cross-sectional view showing the peripheral configuration of the first pad of a substrate in one embodiment of the present disclosure. For convenience of explanation, Figure 4 shows a single first pad.

[0025] As shown in Figure 4, the substrate 100 includes a ceramic insulating substrate 130. The substrate 100 may be a laminated substrate as described above. The insulating substrate 130 may have a plurality of insulating layers. In the insulating substrate 130, the plurality of insulating layers may be made of, for example, an aluminum oxide sintered body (alumina ceramics), an aluminum nitride sintered body, a mullite sintered body, or a glass ceramic sintered body.

[0026] The substrate 100 is located inside the insulating substrate 130 and includes a first via conductor 111 that extends in the thickness direction (Z-axis direction) of the insulating substrate 130 to the first surface 110, and a first pad 11 provided on the first surface 110 so as to be electrically connected to the first via conductor 111. In the substrate 100, the first via conductor 111 and the first pad 11 have different types of main metal components. The first pad 11 contains a first glass material and is directly bonded to the first surface 110.

[0027] The substrate 100 can be manufactured in general terms as follows. The insulating substrate 130 and the first via conductor 111 are formed by co-firing (sometimes referred to as cofire). Hereinafter, for the sake of explanation, the firing process for manufacturing the insulating substrate 130 will be referred to as the first firing process. After the first firing process, the insulating substrate 130 is subjected to a planarization process such as polishing to form a flat first surface 110. Then, for example, a raw material paste is patterned on the first surface 110, and then the first pad 11 is formed by further firing (sometimes referred to as post-firing). Hereinafter, for the sake of explanation, the firing process for forming the first pad 11 will be referred to as the second firing process. The raw material paste that forms the basis of the first pad 11 includes a first glass material. Examples of the first glass material include silicon dioxide.

[0028] The first firing process described above is carried out at a high temperature capable of firing the ceramic insulating substrate 130. Therefore, the first via conductor 111 contains a metal with a high melting point. On the other hand, since the first pad 11 connected to the first via conductor 111 can be made of a different composition than the first via conductor 111, the second firing process described above can be carried out at a lower temperature than the first firing process described above. Thus, the degree of freedom in selecting the material for the first pad 11 can be increased.

[0029] In the substrate 100 of this embodiment, the first pads 11 are formed in a later step (the second firing step) than when the first via conductors 111 are formed (the first firing step). Therefore, multiple first pads 11 can be formed on the flat first surface 110 of the insulating substrate 130 so as to connect to each of the multiple first via conductors 111 on the substrate 100. As a result, multiple first pads can be formed at high density (short pitch) with high positional accuracy. This is because, after the insulating substrate 130 shrinks during firing in the first firing step, multiple first pads 11 are formed on the flat first surface 110 at a relatively low heating temperature during the second firing step.

[0030] In this embodiment, the substrate 100 includes a first glass material. As a result, when the first pad 11 is formed by the second firing process, the fixing of the first glass material contributes to the direct and strong bonding of the first pad 11 to the first surface 110. The first via conductor 111 may include a third glass material, and the insulating substrate 130 may include a fifth glass material. Examples of the third and fifth glass materials include alumina and silicon oxide. The third and fifth glass materials may be the same as or different from the first glass material.

[0031] In the substrate 100, the insulating substrate 130 and the first via conductor 111 are integrally formed by a first firing process performed with the raw material containing glass material. The substrate 100 may also have a first joint portion 11C between the first pad 11 and the first surface 110. Mutual fixing of the glass material occurs at the first joint portion 11C, and as a result, the bonding strength between the first pad 11 and the first surface 110 is improved.

[0032] As described above, the substrate 100 in this embodiment includes a ceramic insulating substrate 130 having high strength (rigidity). By forming the first pad 11 on the flat first surface 110 of the insulating substrate 130, the positional accuracy of the first pad 11 can be improved and high bonding strength can be easily ensured. Therefore, it is possible to accommodate high density of the back electrode group of the X-ray detection member 20 mounted on the first surface 110. Furthermore, in the substrate 100, the first pad group 11G and the first surface 110 are firmly bonded, making it easier to ensure the stability of the bond after mounting the X-ray detection member 20. Therefore, in the X-ray detector 1 using the substrate 100, resistance to centrifugal force (stress in the direction that presses the first pad 11 against the first surface 110) generated on the first surface 110 side of the substrate 100 can be effectively increased.

[0033] In the substrate 100, the first pad 11 may be a metal layer (metallized layer) formed by, for example, a metallization method. The first pad 11 may have copper as its main component, and the first via conductor 111 may have a metal with a higher melting point than copper as its main component. The first pad 11 may be a copper metallized layer containing a first glass material. The first via conductor 111 may contain a high-melting-point metal such as tungsten or molybdenum. The first via conductor 111 may be filled into a through-hole in the insulating substrate 130. There may also be a gap between the through-hole and the first via conductor 111.

[0034] In this specification, the main component refers to the component of the material that has the highest content (or, if the material has only one component, that component). The content may be expressed as, for example, weight percent (wt%).

[0035] By making the first pad 11 a copper metallized layer, thermal conductivity and electrical conductivity can be effectively increased. Therefore, the heat generated in the X-ray detection member 20 mounted on the substrate 100 can be efficiently transferred to the substrate 100.

[0036] Furthermore, the substrate 100 in this embodiment may include a bonding metal layer 15 located between the first via conductor 111 and the first pad 11. The bonding metal layer 15 has a higher bonding strength to the first via conductor 111 and the first pad 11 than when the first via conductor 111 and the first pad 11 are directly reacted.

[0037] As mentioned above, the first via conductor 111 and the first pad 11 have different types of main metal components. Therefore, depending on the compatibility between the dissimilar metals, it may be difficult to bond the first pad 11 to the first via conductor 111 when forming the first pad 11. By indirectly bonding the first pad 11 and the first via conductor 111 via the bonding metal layer 15, it is easier to ensure more reliable bonding stability. Furthermore, even when the first pad 11 is bonded to the first via conductor 111 via a glass component, it is required that it be electrically connected to the first via conductor 111. By providing the bonding metal layer 15 in the substrate 100, the first pad 11 and the first via conductor 111 can be electrically connected more reliably via the bonding metal layer 15.

[0038] The first pad 11, the first via conductor 111, and the bonding metal layer 15 can be a combination of metals that are compatible with each other. In one example of the substrate 100, the first pad 11 may have copper as its main component, the first via conductor 111 may have molybdenum as its main component, and the bonding metal layer 15 may have a bonding metal whose main component is different from that of the first via conductor 111. The bonding metal may be, for example, Cu, Au, or Ni. The bonding metal may be diffused in both the first pad 11 and the first via conductor 111 of the substrate 100.

[0039] For example, after the first firing process described above, more specifically after a planarization process such as polishing, a bonding metal layer 15 may be formed on the first via conductor 111 by plating with a bonding metal. After the formation of the bonding metal layer 15, a second firing process may be performed to form the first pad 11. In this case, during the second firing process, the bonding metal diffuses into both the first pad 11 and the first via conductor 111. The substrate 100 may have a pad diffusion portion 16, which is the portion in the first pad 11 where the bonding metal has diffused, and a via conductor diffusion portion 17, which is the portion in the first via conductor 111 where the bonding metal has diffused.

[0040] In the substrate 100, the first pad 11 has a lower surface 11B that is in contact with the bonding metal layer 15 and an upper surface 11T that is farther from the insulating substrate 130, and the bonding metal may be diffused from the lower surface 11B to the upper surface 11T. The pad diffusion portion 16 of the first pad 11 may be formed in cross-sectional view from the bonding portion between the first pad 11 and the first via conductor 111 to the upper surface 11T. In this embodiment, the pad diffusion portion 16 of the first pad 11 has a different color from the other parts. That is, when the bonding metal is diffused from the lower surface 11B to the upper surface 11T, the part with a different color (i.e., the pad diffusion portion 16) reaches the upper surface 11T in cross-sectional view.

[0041] Let L1 be the central axis of the first via conductor 111, and L2 be the central axis of the first pad 11. In Figure 4, central axes L1 and L2 are shown, but this does not necessarily mean that central axes L1 and L2 are located on the cross-section shown in Figure 4. As shown in Figure 4, central axes L1 and L2 may be misaligned on the substrate 100. This is because the position of the first via conductor 111 is shifted due to the effect of firing shrinkage, while the multiple first pads 11 in the first pad group 11G are formed on the first surface 110 with high positional accuracy to correspond to the multiple back electrodes in the back electrode group of the X-ray detection member 20 mounted on the substrate 100. The magnitude of the misalignment S12 may differ for each set of multiple first pads 11 and first via conductors 111. Note that central axis L2 is the central axis in the cross-section including the central axis L1 of the first via conductor 111.

[0042] FIG. 5 is an enlarged cross-sectional view showing the peripheral configuration of the second pad of the substrate in one embodiment of the present disclosure. In FIG. 5, for convenience of explanation, a single second pad is shown.

[0043] As shown in FIG. 5, the substrate 100 may include a second via conductor 121 that is located inside the insulating substrate 130 and extends in the thickness direction of the insulating substrate 130 to reach the second surface 120, and a second pad 12 that is continuous with the second via conductor 121 and is located on the second surface 120. The second pad 12 may contain a second glass material and may be directly bonded to the second surface 120.

[0044] The second via conductor 121 and the second pad 12 may be co-fired together with the insulating substrate 130 and the first via conductor 111 by the aforementioned first firing process. The second via conductor 121 may typically be connected to the first via conductor 111 through a wiring layer located inside the insulating substrate 130. In the substrate 100, in a plan view, the positions of the second via conductor 121 and the first via conductor 111 may be different from each other.

[0045] Examples of the second glass material contained in the second pad 12 include silicon oxide and the like. The second via conductor 121 may contain a fourth glass material. In the substrate 100, the insulating substrate 130, the second via conductor 121, and the second pad 12 are integrally formed by performing the first firing process with the glass material contained in the raw materials.

[0046] The second via conductor 121 contains a metal with a high melting point. The second via conductor 121 may have the same composition as the first via conductor 111 or may have a different composition. The second via conductor 121 may be, for example, a metal whose main component has a higher melting point than copper. The second via conductor 121 may contain a high melting point metal such as tungsten or molybdenum. The second via conductor 121 may be filled in the through hole of the insulating substrate 130 and may have voids in a part of the through hole.

[0047] The second pad 12 contains a metal with a high melting point. The second pad 12 may be, for example, a metal whose main component has a higher melting point than copper. The second pad 12 may contain a high melting point metal such as tungsten or molybdenum.

[0048] In the substrate 100, the second via conductor 121 and the second pad 12 may have the same type of metal as the main component. The second pad 12 may have a different composition from the second via conductor 121. The second pad 12 and the second via conductor 121 can control the firing shrinkage amount based on the composition. For example, the second via conductor 121 may have a composition with a higher molybdenum content than the second pad 12. Also, for example, the second pad 12 may have a composition with a higher tungsten content than the second via conductor 121.

[0049] In the manufacturing process of the substrate 100, the back surface side of the insulating substrate 130 is not subjected to a planarization process such as polishing. Therefore, the second pad 12 can be formed on the second surface 120 side in the first firing step.

[0050] As described above, in the substrate 100 according to the present embodiment, since the second pad 12 is integrally bonded to the second surface 120 and the second via conductor 121 in the first firing step, it has a high bonding strength. Therefore, in the X-ray detector 1 using the substrate 100, the resistance to the centrifugal force (the stress in the direction of pulling the second pad 12 away from the second surface 120) generated on the second surface 120 side of the substrate 100 can be effectively increased.

[0051] The substrate 100 may have a second bonding portion 12C between the second pad 12 and the second surface 120. In the second bonding portion 12C, mutual fixation of the glass material occurs, and as a result, the bonding strength between the second pad 12 and the second surface 120 is improved. The second bonding portion 12C has a stronger bonding force than the first bonding portion 11C on the first surface 110 side. The second pad 12 has a different stress direction due to the centrifugal force from the first pad 11 as described above, and a stronger bonding strength than the first pad 11 is required. In the substrate 100, by simultaneously firing the second pad 12, the insulating substrate 130, and the second via conductor 121 in the first firing step, a high bonding strength can be ensured for the second pad 12.

[0052] In the substrate 100, the second surface 120 may have curvature. In the substrate 100, the first surface 110 may be planar, and the second surface 120 may be curved. By electrically connecting a plurality of first pads 11 formed on the planar first surface 110 and the back electrode group of the photodetector 22 in the X-ray detection member 20 via a bonding material such as solder, the X-ray detection member 20 can be mounted on the first surface 110. This makes it easier to keep the solder thickness constant between the plurality of back electrodes in the back electrode group of the X-ray detection member 20 and each of the plurality of first pads 11 on the substrate 100. Therefore, it is easier to reliably synchronize the electrical signals transmitted from the X-ray detection member 20.

[0053] In the substrate 100, the surface roughness Ra of the first surface 110 may be smaller than that of the second surface 120. The first surface 110 may be a polished surface, and the second surface 120 may be an unpolished surface. In the substrate 100, at the second joint portion 12C, an anchoring effect is generated when a part of the second pad 12 fits into the irregularities of the second surface 120 of the insulating substrate 130. Therefore, the bonding strength of the second pad 12 can be further increased. Note that the relationship of surface roughness Ra is not limited to the relationship described above. For example, the surface roughness Ra of the first surface 110 may be greater than or equal to the surface roughness Ra of the second surface 120.

[0054] Figure 6 is a cross-sectional view illustrating a multi-cavity substrate before cutting in one embodiment of the present disclosure. The substrate 100 in this embodiment is typically manufactured by dividing a larger multi-cavity substrate 200 into individual pieces. Figure 6 shows the multi-cavity substrate 200 just before it is cut into pieces for substrate 100.

[0055] As shown in Figure 6, the multi-cavity substrate 200 has a first main surface 210 and a second main surface 220. The first main surface 210 corresponds to the first surface 110 of the substrate 100, and the second main surface 220 corresponds to the second surface 120 of the substrate 100. As shown in the diagram indicated by reference numerals 6001 and 6002 in Figure 6, the first main surface 210 has a planar shape, while the second main surface 220 may have a convex or concave shape. Figure 6 is a schematic diagram and does not mean that the multi-cavity substrate 200 has a curvature of the magnitude shown.

[0056] An example of a method for manufacturing the substrate 100 of this embodiment, using a multi-cavity substrate 200 as an intermediate product, is described below.

[0057] Through holes are formed in a ceramic green sheet containing alumina or the like before firing, and conductive paste is filled into the through holes. Conductive paste is also printed onto the surface of the ceramic green sheet. Multiple ceramic green sheets are stacked while undergoing such processing, and the first firing process is carried out. This forms an insulating substrate 130 with internal wiring, and at the same time forms multiple first via conductors 111, multiple second via conductors 121, and multiple second pads 12. The temperature in the first firing process may be, for example, 1800°C or higher.

[0058] After the first firing process, a planarization treatment is performed on the surface of the insulating substrate 130 on the side where the multiple second pads 12 are not formed. The planarization treatment may be, for example, a mechanical polishing treatment. This forms the first main surface 210. The surface of the insulating substrate 130 on the side where the multiple second pads 12 are formed becomes the second main surface 220. No planarization treatment is performed on the second main surface 220.

[0059] Next, after performing appropriate cleaning and other treatments, a bonding metal layer 15 is formed on the surface of the first via conductor 111 exposed on the first main surface 210. In one specific example, the bonding metal is pattern-plated onto the first main surface 210 using a resist as appropriate. After that, the conductor paste that will form the base of the first pad 11 is pattern-printed in a predetermined arrangement and overlapping with the bonding metal layer 15. In one specific example, the main component of the conductor paste is copper.

[0060] Next, the first pad 11 is formed by performing a second firing process. The temperature in the second firing process may be, for example, 1000°C or less. After the second firing process, the surface of the first pad 11 may be plated in order to suppress changes in the surface condition of the first pad 11.

[0061] This allows for the production of a multi-cavity substrate 200 as an intermediate product. Multiple substrates 100 can be manufactured by performing a slicing process on the multi-cavity substrate 200. The side surface connecting the first surface 110 and the second surface 120 of the substrate 100 (see Figure 9) may be a sliced ​​cut surface. This side surface may have a lower surface roughness Ra than the second surface 120. Generally, it is possible to distinguish by observation whether a side surface is a cut surface formed by a slicing process or a fracture surface caused by a break using a dividing groove.

[0062] The substrate 100 manufactured by the method described above may further have the configuration described below.

[0063] Figure 7 is an enlarged cross-sectional view showing the peripheral configuration of a plurality of first pads on a substrate in one embodiment of the present disclosure. As shown in Figure 7, the substrate 100 comprises a plurality of first pads 11 and a plurality of first via conductors 111. In the substrate 100, the distance P1 between the pads in the plurality of first pads 11 is constant or substantially constant, and the distance D between the vias in the plurality of first via conductors 111 may vary. In the example shown in Figure 7, the distances D1, D2, and D3 between each of the plurality of first via conductors 111 may be different.

[0064] Due to the effects of firing shrinkage in the first firing process, a discrepancy may occur between the position where the through-holes are formed in the ceramic green sheet (in other words, the position where the conductive paste is filled) and the respective positions (in other words, the distance and spacing) of the multiple first via conductors 111 on the substrate 100. On the other hand, as mentioned above, multiple first pads 11 can be arranged with high precision on the substrate 100.

[0065] Figure 8 is an enlarged cross-sectional view showing the peripheral configuration of a plurality of second pads on a substrate in one embodiment of the present disclosure. As shown in Figure 8, the substrate 100 is provided with a plurality of second pads 12, and there may be variations in the distance P2 between the pads in the plurality of second pads 12. In the example shown in Figure 7, the distances P21 and P22 between each of the plurality of second pads 12 may be different.

[0066] Due to the effects of firing shrinkage in the first firing process, a misalignment may occur between the position where the conductive paste that forms the base of the second pad 12 is printed on the ceramic green sheet and the respective positions (in other words, distance, spacing) of the multiple second pads 12 on the substrate 100. Even if there is a misalignment of the multiple second pads 12 on the substrate 100, or if the second surface 120 has curvature, the second pad group 12G can still be connected to an external output member. In the X-ray detector 1 using the substrate 100, a strong centrifugal force may be generated on the second pads 12, partly due to the connection of the external output member to the second pad group 12G. Therefore, in the substrate 100 of this embodiment, the bonding strength of the second pads 12 is given more importance than the positional accuracy of the second pads 12.

[0067] Figure 9 is a schematic diagram illustrating a substrate, an X-ray detector module, and an X-ray detection unit in one embodiment of the present disclosure. As shown in Figure 9, the X-ray detector module 50 is a module used in the X-ray detector 1 of a CT apparatus 300, and comprises a substrate 100 and an X-ray detection member 20.

[0068] The substrate 100 is manufactured by slicing a multi-cavity substrate 200 to form individual pieces. The substrate 100 may have a rectangular first surface 110 of the insulating substrate 130. The first surface 110 may be, for example, rectangular or square. The substrate 100 has sides 131 on all four sides. The sides 131 are the sliced ​​cut surfaces and have a surface roughness Ra smaller than that of the second surface 120. The corners where the sides 131 and the first surface 110 intersect may be right angles. On the other hand, the second surface 120 may have curvature.

[0069] The X-ray detector 1 may include an X-ray detection unit 60 in which a plurality of X-ray detector modules 50 are arranged. In the X-ray detection unit 60, each of the plurality of X-ray detector modules 50 has an insulating substrate 130 that is rectangular in plan view, and the four sides 131 connecting the first surface 110 and the second surface 120 of the insulating substrate 130 may be sliced ​​cross-sections. The plurality of X-ray detector modules 50 may have the same or substantially the same outer dimensions of the insulating substrate 130, and may be arranged in close contact with the outer edges of the insulating substrate 130 in contact with each other.

[0070] In the X-ray detector 1, the so-called slice direction is denoted as DS, and the channel direction as DC. For example, the Y-axis direction shown in Figure 2 may be aligned with the slice direction DS, and the X-axis direction may be aligned with the channel direction DC.

[0071] In each of the multiple X-ray detector modules 50, the outer dimensions of the insulating substrate 130 and the outer dimensions of the X-ray detection member 20 are the same. Therefore, the multiple X-ray detector modules 50 can be arranged closely together.

[0072] In the X-ray detection unit 60, multiple X-ray detector modules 50 are arranged in close contact to form a flat plate in the slice direction DS. In the X-ray detection unit 60, in the channel direction DC, the surfaces of the X-ray detection members 20 of the multiple X-ray detector modules 50 may form an arc so as to align with the rotation direction of the X-ray detector 1 in the CT apparatus 300 (see Figure 1). Since the sizes of the multiple X-ray detector modules 50 are the same, it is easy to arrange the multiple X-ray detector modules 50 densely in the channel direction DC.

[0073] (Alternative Configuration Example) (a) The X-ray detection member 20 only needs to be capable of detecting X-rays and be mountable on the substrate 100, and the specific configuration of the X-ray detection member 20 is not particularly limited. The X-ray detector module 50 may be, for example, a direct conversion type FPD. In this case, the X-ray detection member 20 does not need to have an X-ray detection film 21, and may have an X-ray detection unit having an X-ray detection element instead of a photodetector 22.

[0074] (b) As described above, the substrate 100 may further include a plating layer that covers the surface of the first pad 11. This makes it easier to store the substrate 100.

[0075] [Summary] The substrate in embodiment 1 of the present disclosure is a substrate used in an X-ray detector of a computed tomography apparatus, and comprises a ceramic insulating substrate having a first surface on which an X-ray detection member is mounted and a second surface located opposite to the first surface, a first via conductor located inside the insulating substrate and extending in the thickness direction of the insulating substrate to the first surface, and a first pad provided on the first surface so as to be electrically connected to the first via conductor, wherein the first via conductor and the first pad have different types of main metal components, and the first pad contains a first glass material and is directly bonded to the first surface.

[0076] In embodiment 2 of the present disclosure, the substrate is such that, in embodiment 1, the first pad is mainly composed of copper, and the first via conductor is mainly composed of a metal with a higher melting point than copper.

[0077] The substrate in embodiment 3 of the present disclosure further comprises, in embodiment 1 or 2, a second via conductor located inside the insulating substrate and extending in the thickness direction of the insulating substrate to the second surface, and a second pad continuous with the second via conductor and located on the second surface, wherein the second pad comprises a second glass material and is directly bonded to the second surface.

[0078] In embodiment 4 of the present disclosure, the substrate is such that, in any one embodiment of embodiments 1 to 3, the first surface is planar and the second surface is curved.

[0079] In embodiment 5 of the present disclosure, the substrate is such that, in any one embodiment of embodiments 1 to 4, the first surface has a surface roughness Ra smaller than that of the second surface.

[0080] The substrate in embodiment 6 of the present disclosure comprises a bonding metal layer located between the first via conductor and the first pad in any one embodiment of embodiments 1 to 5, wherein the bonding metal layer has a higher bonding strength to the first via conductor and the first pad than when the first via conductor and the first pad are directly reacted.

[0081] The substrate in embodiment 7 of the present disclosure comprises, in any one embodiment of embodiments 1 to 6, a plurality of first pads and a plurality of first via conductors, wherein the distance between the pads in the plurality of first pads is constant or substantially constant, and the distance between vias in the plurality of first via conductors is variable.

[0082] The substrate in embodiment 8 of the present disclosure comprises a plurality of the second pads in any one embodiment of embodiments 1 to 7, wherein the distance between the pads in the plurality of second pads varies.

[0083] The substrate in embodiment 9 of the present disclosure is, in any one embodiment of embodiments 1 to 8, the insulating substrate has a side surface connecting the first surface and the second surface, the side surface being a sliced ​​cut surface, and having a surface roughness Ra smaller than that of the second surface.

[0084] The substrate in embodiment 10 of the present disclosure further comprises a plating layer that covers the surface of the first pad, in any one embodiment of embodiments 1 to 9.

[0085] The X-ray detector module in embodiment 11 of the present disclosure is a module used in an X-ray detector of a computed tomography apparatus, comprising a substrate according to any one of embodiments 1 to 10, and an X-ray detection member mounted on the substrate.

[0086] The X-ray detection unit in embodiment 12 of the present disclosure is an X-ray detection unit in which a plurality of X-ray detector modules in embodiment 11 are arranged, wherein each of the plurality of X-ray detector modules has an insulating substrate that is rectangular in plan view, and the four sides connecting the first surface and the second surface of the insulating substrate are sliced ​​cross-sections, the outer dimensions of the insulating substrates are the same or substantially the same, and the plurality of X-ray detector modules are arranged in close contact with the outer edges of the insulating substrates in contact with each other.

[0087] Furthermore, the field of application of the technology disclosed herein is not limited to X-ray detector modules and X-ray detection units for computed tomography systems, or substrates used therein. For example, it can be broadly applied to ceramic substrates on which a pad made of a copper metallized layer is formed by a post-fire process on the surface of a polished ceramic substrate. Specifically, it can be applied to substrates on which high flatness is required for mounting electronic components such as sensors or actuators, and can be applied to substrates used on the light-receiving surface side of an image sensor or the support surface side of a MEMS mirror, or to modules including these substrates. In such applications as well, the technology disclosed herein can ensure high levels of pad positional accuracy and bonding strength.

[0088] Furthermore, the ceramic materials used in the technology of this disclosure are not limited to the configurations in the embodiments described above. For example, it is also applicable to insulating substrates mainly composed of aluminum oxide sintered bodies (alumina), silicon nitride sintered bodies, aluminum nitride sintered bodies, and other ceramic materials. This increases the freedom of material selection according to the required properties such as mechanical strength, thermal conductivity, and electrical insulation, and allows the technology of this disclosure to be effectively utilized in a variety of fields other than the medical field, such as industrial equipment, measuring instruments, and optical instruments.

[0089] [Additional Notes] The inventions described in this disclosure have been explained based on the drawings and embodiments. However, the inventions described in this disclosure are not limited to the embodiments described above. That is, the inventions described in this disclosure can be modified in various ways within the scope shown in this disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the inventions described in this disclosure. In other words, it should be noted that it is easy for those skilled in the art to make various modifications or alterations based on this disclosure. Furthermore, it should be noted that these modifications or alterations are included in the scope of this disclosure.

[0090] 1 X-ray detector 11 First pad 12 Second pad 20 X-ray detection member 21 X-ray detection film 22 Photodetector 50 Module for X-ray detector 100 Substrate 111 First via conductor 121 Second via conductor 130 Insulating substrate 300 CT apparatus 311 Aperture 310 Gantry 320 X-ray generator 400 Bed

Claims

1. A substrate used in an X-ray detector of a computed tomography apparatus, comprising: a ceramic insulating substrate having a first surface on which an X-ray detection member is mounted and a second surface located opposite to the first surface; a first via conductor located inside the insulating substrate and extending in the thickness direction of the insulating substrate to the first surface; and a first pad provided on the first surface so as to be electrically connected to the first via conductor, wherein the first via conductor and the first pad have different types of main metal components, and the first pad contains a first glass material and is directly bonded to the first surface.

2. The substrate according to claim 1, wherein the first pad is mainly composed of copper, and the first via conductor is mainly composed of a metal with a higher melting point than copper.

3. The substrate according to claim 1 or 2, further comprising: a second via conductor located inside the insulating substrate and extending in the thickness direction of the insulating substrate to the second surface; and a second pad continuous with the second via conductor and located on the second surface, wherein the second pad comprises a second glass material and is directly bonded to the second surface.

4. The substrate according to any one of claims 1 to 3, wherein the first surface is planar and the second surface is curved.

5. The substrate according to any one of claims 1 to 4, wherein the first surface has a surface roughness Ra smaller than that of the second surface.

6. The substrate according to any one of claims 1 to 5, comprising a bonding metal layer located between the first via conductor and the first pad, wherein the bonding metal layer has a higher bonding strength to the first via conductor and the first pad than when the first via conductor and the first pad are directly reacted.

7. A substrate according to any one of claims 1 to 6, comprising a plurality of first pads and a plurality of first via conductors, wherein the distance between the pads in the plurality of first pads is constant or substantially constant, and the distance between vias in the plurality of first via conductors is variable.

8. The substrate according to claim 3, comprising a plurality of the second pads, wherein the distance between the pads in the plurality of the second pads varies.

9. The substrate according to any one of claims 1 to 8, wherein the insulating substrate has a side surface connecting the first surface and the second surface, and the side surface is a sliced ​​cut surface having a surface roughness Ra smaller than that of the second surface.

10. The substrate according to any one of claims 1 to 9, further comprising a plating layer covering the surface of the first pad.

11. An X-ray detector module used in an X-ray detector of a computed tomography apparatus, comprising a substrate according to any one of claims 1 to 10 and an X-ray detection member mounted on the substrate.

12. An X-ray detection unit comprising a plurality of X-ray detector modules according to claim 11, wherein each of the plurality of X-ray detector modules has an insulating substrate that is rectangular in plan view, and the four sides connecting the first surface and the second surface of the insulating substrate are sliced ​​cross-sections, the outer dimensions of the insulating substrates are the same or substantially the same, and the plurality of X-ray detector modules are arranged in close contact with the outer edges of the insulating substrates in contact with each other.

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