Wiring board and method for manufacturing a wiring board

Abstract

When multiple light-emitting elements are arranged on a substrate, this method achieves light focusing and shielding between the light-emitting elements while suppressing damage to the partition plates between the substrate and the light-emitting elements. [Solution] The wiring substrate on which the light-emitting element is arranged is a flat substrate made of metal and having a pair of main surfaces, wherein one of the pair of main surfaces has a recess formed in the thickness direction of the substrate on which the light-emitting element is arranged, and the other main surface is a flat substrate.

Description

【Technical Field】 【0001】 The present invention relates to a wiring board and a method for manufacturing the wiring board. 【Background Art】 【0002】 There is known a light-emitting device in which a plurality of light-emitting elements are arranged on a substrate (see, for example, Patent Documents 1 and 2). In Patent Document 1, a metal layer is provided as a partition portion for condensing and blocking light between adjacent light-emitting elements on the substrate. Patent Document 2 describes a light-emitting device in which semiconductor elements are arranged in recesses formed on the surface of a substrate. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Unexamined Patent Application Publication No. 2023-148970 【Patent Document 2】 International Publication No. 03 / 030274 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 In the light-emitting device described in Patent Document 1, since there is an interface between the substrate and the metal layer provided on the substrate, the bonding reliability of the metal layer with respect to the substrate may not be sufficient. Further, if the materials of the substrate and the metal layer are different, a difference in thermal expansion coefficient occurs, and there is a risk that the substrate or the metal layer may be damaged due to the difference in thermal expansion coefficient caused by a temperature change of the light-emitting element. In the light-emitting device described in Patent Document 2, semiconductor elements are arranged in recesses formed on the surface of the substrate. The recesses are formed by pressing. In pressing, the accuracy of the shape and dimensions of the formed recesses is not good, and there is room for improvement. 【0005】 The present invention has been made to solve at least some of the above-mentioned problems, and aims to achieve light focusing and light shielding between light-emitting elements when multiple light-emitting elements are arranged on a substrate, while suppressing damage to the partition plate present between the substrate and the light-emitting elements. [Means for solving the problem] 【0006】 The present invention was made to solve at least some of the problems described above, and can be realized in the following forms. 【0007】 (1) According to one embodiment of the present invention, a wiring substrate on which light-emitting elements are arranged is provided. The wiring substrate is a flat substrate made of metal and having a pair of main surfaces, wherein one of the pair of main surfaces has a recess formed in the thickness direction of the substrate on which the light-emitting elements are arranged, and the other main surface is a flat substrate. 【0008】 In this configuration, light-emitting elements are placed in recesses formed on one main surface of the substrate. Therefore, the inner surface forming the recesses functions as a partition plate separating multiple recesses with respect to the bottom surface of the recesses, thereby enabling light focusing and shielding of the light-emitting elements placed in each of the recesses. Since the partition plate is part of the substrate, the difference in thermal expansion coefficients between the partition plate and the substrate is the same, suppressing damage to the partition plate and the substrate caused by the difference in thermal expansion coefficients. Furthermore, since the main surface opposite to the main surface on which the recesses are formed is flat, the wiring board of this configuration is easily positioned relative to other components and devices. 【0009】 (2) In the wiring board of the above form, one main surface of the substrate has a plurality of recesses and a flat portion formed between the plurality of recesses, and the substrate has an inclined surface among the surfaces that define the recesses that is connected to the flat portion, and the angle formed between the inclined surface that defines some of the recesses and the flat portion may be different from the angle formed between the inclined surface that defines other recesses and the flat portion. In this configuration, the angles formed by the slopes of the multiple recesses on one main surface of the substrate differ from those of the flat surface. Depending on the position and type of light-emitting element on the substrate, the required light-gathering and light-blocking capabilities may vary. In this configuration, the different angles of the slopes of the recesses allow the capabilities of the light-emitting elements placed in each recess to be fully realized. 【0010】 (3) In the wiring board of the above form, a plurality of the light-emitting elements may be arranged in one of the recesses. This configuration allows for the placement of one or more light-emitting elements in a single recess, depending on the application, thus improving the usability of the wiring board. 【0011】 (4) In the above-described wiring board, the substrate comprises a first substrate made of metal and having a flat plate shape, and a second substrate made of metal and having through holes that penetrate in the thickness direction, and disposed on the first substrate, wherein the arithmetic mean roughness (Ra) of the opposing surface of the second substrate that is exposed from the through holes of the first substrate is 0.2 μm or less, and the flatness of the opposing surface is 0.1 mm or less, and the recess may be formed by the opposing surface and the through holes. In this configuration, a second substrate with through-holes is placed on the first substrate, thereby forming recesses between the opposing surface of the first substrate and the through-holes of the second substrate. The arithmetic mean roughness of the opposing surface of the first substrate is 0.2 μm or less, and the flatness of the opposing surface is 0.1 mm or less. Therefore, there is little difference in the height position of the opposing surface on the first substrate, which serves as the bottom surface, in multiple recesses. As a result, the brightness of the light-emitting elements placed in each recess is stable. 【0012】 Furthermore, the present invention can be realized in various forms, for example, in the form of a wiring board, electronic components, lighting devices, semiconductor packages, and systems comprising these, or a method for manufacturing a wiring board, and systems comprising these. [Brief explanation of the drawing] 【0013】 [Figure 1]Schematic cross-sectional view of a wiring board and a light-emitting element as an embodiment of the present invention. [Figure 2] Schematic cross-sectional view of a wiring board according to the second embodiment. [Figure 3] Schematic cross-sectional view of a wiring board according to the third embodiment. [Figure 4] Schematic cross-sectional view of a wiring board according to the fourth embodiment. [Figure 5] Schematic cross-sectional view of a wiring board according to the fifth embodiment. [Figure 6] Schematic cross-sectional view of a wiring board according to the sixth embodiment. [Figure 7] Flowchart of a manufacturing method of a wiring board according to the sixth embodiment. [Figure 8] Schematic cross-sectional view of a second substrate on which an insulating film and an electrode are formed. [Figure 9] Schematic cross-sectional view of a base material on which a second substrate is disposed on a first substrate. [Figure 10] Schematic cross-sectional view of a wiring board and a light-emitting element according to the seventh embodiment. [Figure 11] Flowchart of a manufacturing method according to the seventh embodiment. [Figure 12] Schematic cross-sectional view of a first substrate on which an insulating film and an electrode are formed. [Figure 13] Schematic cross-sectional view of a wiring board on which a second substrate is disposed on a first substrate. [Figure 14] Explanatory drawing about a method for specifying a flat portion on the upper surface of a base material. [Figure 15] Explanatory drawing about a method for specifying the position of a recess in a base material. [Figure 16] Explanatory drawing about a method for specifying the position of a recess in a base material of a modification. 【Mode for Carrying Out the Invention】 【0014】 <First Embodiment> Figure 1 is a schematic cross-sectional view of a wiring board 100 and a light-emitting element 200 as one embodiment of the present invention. Figure 1 shows a schematic cross-section of the wiring board 100 and the light-emitting element 200 disposed in a recess 11 of the wiring board 100. As shown in Figure 1, the wiring board 100 comprises a flat substrate 10 with a recess 11 formed in the thickness direction, an insulating film 20 covering a part of the bottom surface 11B of the recess 11, an electrode 40 formed on the insulating film 20, a reflective film 30 disposed on the inclined surface 11S of the recess 11, and a joint 60. The light-emitting element 200 is disposed on the electrode 40. The light-emitting element 200 in this embodiment is an LED (Light Emitting Diode) chip. The light-emitting element 200 is disposed on the electrode 40 via the joint 60. The joint 60 is formed of a bonding member used for soldering or the like. Note that Figure 1 shows a Cartesian coordinate system CS. The Cartesian coordinate system CS has two X and Y axes perpendicular to the Z-axis direction, with the thickness direction of the substrate 10 as the Z-axis direction. The X and Y axes are mutually orthogonal axes parallel to the horizontal direction of the base material 10. The Cartesian coordinate system CS shown in Figure 1 corresponds to the Cartesian coordinate system CS shown in Figures 2 and later. The dimensional relationships of each component shown in Figure 1 are approximate and differ from the actual dimensional relationships. 【0015】 As shown in Figure 1, the base material 10 has a top surface 10T and a bottom surface 10U as a pair of main surfaces. The top surface 10T of the base material 10 has a plurality of recesses 11 formed in the thickness direction of the base material 10. In other words, the top surface 10T of the base material 10 has a plurality of recesses 11 and a flat portion 10PL formed between the plurality of recesses 11. The recesses 11 are formed from a surface that demarcates the recess 11, a sloped surface 11S that connects to the flat portion 10PL, and a bottom surface 11B that is parallel to the flat portion 10PL and connects to the sloped surface 11S at the deepest position. In Figure 1, the flat portion 10PL, which is a virtual surface, is shown by a dashed line. The angle θ between the flat portion 10PL and the sloped surface 11S is 60 degrees (°) in this embodiment. The bottom surface 10U of the base material 10 is formed as a flat surface. The base material 10 of this embodiment is made of Cu (copper). The base material 10 of this embodiment has a rectangular shape when viewed from the thickness direction. 【0016】 The insulating film 20 covering a portion of the recess 11 is made of insulating AlN (aluminum nitride). The reflective film 30 positioned on the inclined surface 11S of the recess 11 is made of Al (aluminum). The reflective film 30 reflects light emitted from the light-emitting element 200. The electrodes 40 formed on the insulating film 20 are formed in a predetermined pattern according to the light-emitting element 200. Because the insulating film 20 is insulating, the electrodes 40 and the substrate 10 are electrically isolated. The electrodes 40 are electrically connected to the light-emitting element 200 via a junction 60. The light-emitting element 200 emits light in accordance with the power supplied from the electrodes 40. 【0017】 As described above, the wiring board 100 of this embodiment includes a base material 10 having an upper surface 10T and a lower surface 10U as a pair of main surfaces. Multiple recesses 11 are formed on the upper surface 10T of the base material 10, recessed in the thickness direction of the base material 10. The lower surface 10U of the base material 10 is formed as a flat surface. The base material 10 of this embodiment is made of Cu. With this configuration, light-emitting elements 200 are arranged in the recesses 11 formed on the upper surface 10T of the base material 10. Therefore, the inclined surface 11S, which is the inner circumferential surface forming the recesses 11, functions as a partition plate that separates the multiple recesses 11 with respect to the bottom surface 11B of the recesses 11, thereby achieving light-gathering and light-shielding of the light-emitting elements 200 arranged in each of the multiple recesses 11. Since the partition plate is part of the base material 10, the difference in thermal expansion coefficients between the partition plate and the base material 10 is the same, and damage to the partition plate and the base material 10 due to the difference in thermal expansion coefficients is suppressed. Furthermore, since the lower surface 10U opposite to the upper surface 10T where the recess 11 is formed is flat, the wiring board 100 of this embodiment is easily positioned relative to other components and devices. 【0018】 <Second Embodiment> Figure 2 is a schematic cross-sectional view of the wiring board 100a of the second embodiment. The wiring board 100a of the second embodiment differs from the wiring board 100 of the first embodiment in that it does not have a reflective film 30. The reflective film 30 does not have to be placed in the recesses 11 as in the wiring board 100a of the second embodiment, or the reflective film 30 may be placed in some of the recesses 11 and not in the other recesses 11. Furthermore, the shape, material, and placement position of the reflective film 30 may differ for each of the recesses 11. 【0019】 <Third Embodiment> Figure 3 is a schematic cross-sectional view of the wiring board 100b of the third embodiment. The wiring board 100b of the third embodiment differs from the wiring board 100 of the first embodiment in that the insulating film 20 and electrodes 40 are arranged on the flat portion 10PL of the upper surface 10T instead of in the recess 11, the light-emitting element 200b and electrodes 40 are electrically connected by current-carrying wires 50, and a bonding layer 70 is provided. 【0020】 As shown in Figure 3, in the wiring board 100b of the third embodiment, the insulating film 20 is formed on the flat portion 10PL of the upper surface 10T of the substrate 10. The electrode 40 is placed on the insulating film 20 and is not electrically connected to the substrate 10. The electrode 40 and the light-emitting element 200b are connected by a current-carrying wire 50. The bonding layer 70 is placed between the bottom surface 11B and the light-emitting element 200b. The bonding layer 70 is formed of a die attach agent. The die attach agent used as the bonding layer 70 may be insulating or a conductive material such as Ag paste. 【0021】 <Fourth Embodiment> Figure 4 is a schematic cross-sectional view of the wiring board 100c of the fourth embodiment. In the wiring board 100c of the fourth embodiment, compared to the wiring board 100 of the first embodiment, the angles θ and θc formed between the inclined surfaces 11S and 11Sc that form the recesses 11 and 11c and the flat portion 10PL are different among the multiple recesses 11 and 11c formed in the base material 10c. In the fourth embodiment, the shapes and other features that differ from those of the first embodiment will be described, and the descriptions of the shapes and other features that are the same as those of the first embodiment will be omitted. 【0022】 As shown in Figure 4, in the fourth embodiment, recesses 11 and 11c are formed on the upper surface 10Tc of the base material 10c, with different inclination angles θ and θc of the inclined surfaces 11S and 11Sc. Recess 11 is composed of an inclined surface 11S and a bottom surface 11B, similar to the first embodiment. Recess 11c is composed of an inclined surface 11Sc that forms an angle θc with the flat portion 10PLc of the base material 10c and a bottom surface 11B. Note that the angle θc in the fourth embodiment is 45°, but it may be a different angle in other embodiments. 【0023】 The same insulating film 20 and electrode 40 are formed on the bottom surface 11B of recess 11 and the bottom surface 11B of recess 11c. A light-emitting element 200 is also placed within recesses 11 and 11c. A reflective film 30c is placed on the inclined surface 11Sc of recess 11c. The reflective film 30c is made of the same material as the reflective film 30 placed on the inclined surface 11S of recess 11. 【0024】 As described above, in the wiring board 100c of the fourth embodiment, as shown in Figure 4, among the multiple recesses 11, 11c formed in the base material 10c, the angles θ, θc formed by the inclined surfaces 11S, 11Sc and the flat portion 10PLc are different. In this embodiment, the required light-collecting and light-shielding capabilities may differ depending on the position where the light-emitting element 200 is arranged on the base material 10c. In this embodiment, the different angles of the inclined surfaces 11S, 11Sc of the recesses 11, 11c allow the capabilities of the light-emitting element 200 arranged in each recess 11, 11c to be fully realized. 【0025】 <Fifth Embodiment> Figure 5 is a schematic cross-sectional view of the wiring board 100d of the fifth embodiment. In the fifth embodiment, two light-emitting elements 200d are arranged in some of the recesses 11D1 among the plurality of recesses 11D1, 11D2. Therefore, in the wiring board 100d of the fifth embodiment, the configuration and shape of the electrodes 40d arranged on the insulating film 20 covering the bottom surface 11B of the recess 11D1 where the two light-emitting elements 200d are arranged are different. Note that recesses 11D1 and 11D2 have the same shape as recess 11 of the first embodiment. 【0026】 As shown in Figure 5, an insulating film 20 is placed on the bottom surface 11B of the recess 11D1 formed in the substrate 10d. Two electrodes 40d are placed on the insulating film 20 placed in the recess 11D1. The two electrodes 40d are spaced apart from each other. A light-emitting element 200d is placed on each electrode 40d. The light-emitting element 200d is placed on the electrode 40d via a junction 60d. The two light-emitting elements 200d are spaced apart from each other. 【0027】 As described above, in the wiring board 100d of the fifth embodiment, two light-emitting elements 200d are arranged in some of the recesses 11D1 among the multiple recesses 11D1, 11D2. Therefore, in this embodiment, one or more light-emitting elements 200d are arranged in one recess 11D1 or recess 11D2 depending on the application, thus improving the usability of the wiring board 100d. 【0028】 <Sixth Embodiment> Figure 6 is a schematic cross-sectional view of the wiring board 100e of the sixth embodiment. The wiring board 100e of the sixth embodiment differs from the wiring board 100b of the third embodiment shown in Figure 3 in that the base material 10e is composed of a first substrate 12 and a second substrate 13, and that the reflective film 30 is not arranged. Therefore, in the sixth embodiment, the different configuration and shape from the third embodiment will be described, and the same configuration and shape as the third embodiment will be omitted. 【0029】 As shown in Figure 6, the substrate 10e of the sixth embodiment comprises a flat first substrate 12 and a second substrate 13 disposed on the upper surface 12T (opposing surface) of the first substrate 12. The first substrate 12 and the second substrate 13 are made of the same metal, Cu. The upper surface 12T of the first substrate 12 faces the lower surface 13U of the second substrate 13. In the sixth embodiment, the arithmetic mean roughness (Ra) of the upper surface 12T of the first substrate 12 is 0.2 μm or less. The flatness of the upper surface 12T is 0.1 mm or less. The second substrate 13 has a plurality of through holes 14 that penetrate in the thickness direction. The inner circumferential surface of the through holes 14 forms the same slope as the slope 11S of the recess 11 in the third embodiment. Therefore, as shown in Figure 6, when the second substrate 13 is placed on the upper surface 12T of the first substrate 12, the region of the upper surface 12T of the first substrate 12 located within the through hole 14 formed in the second substrate 13 functions as the bottom surface 11B of the recess 11 in the third embodiment. In other words, the recess 11 in the third embodiment is formed by the upper surface 12T within the through hole 14 of the first substrate 12 and the inner circumferential surface within the through hole 14 of the second substrate 13 in the sixth embodiment. 【0030】 Figure 7 is a flowchart of the manufacturing method for the wiring board 100e according to the sixth embodiment. In the manufacturing flow of the wiring board 100e shown in Figure 7, first, a flat Cu plate which will be the basis for the first substrate 12 is prepared (step S1). A polishing process is performed in which both sides of the flat Cu plate are polished (step S2). Both sides of the Cu plate are polished until the arithmetic mean roughness (Ra) of the upper surface 12T is 0.2 μm or less and the flatness of the upper surface 12T is 0.1 mm or less. 【0031】 Next, a flat Cu plate, which will be the basis for the second substrate 13, is prepared (step S3). A through-hole forming process is performed on the flat Cu plate to form through-holes 14 that penetrate in the thickness direction (step S4). The through-holes 14 are processed in the second substrate 13 so that the inner surface of the through-holes 14 becomes the inclined surface 11S of the recess 11 of the base material 10e. Next, an insulating film 20 is formed at a predetermined position on the upper surface 13T of the second substrate 13 (step S5). After that, electrodes 40 are formed on the insulating film 20 (step S6). Figure 8 is a schematic cross-sectional view of the second substrate 13 on which the insulating film 20 and electrodes 40 have been formed. 【0032】 When the process in step S6 of Figure 7 is performed, a placement process is carried out in which the second substrate 13, in which the through hole 14 is formed, is joined to the upper surface 12T of the first substrate 12 (step S7). Figure 9 is a schematic cross-sectional view of the substrate 10e in which the second substrate 13 is placed on the first substrate 12. As shown in Figure 9, the recess 11 in the third embodiment is formed by the through hole 14 formed in the second substrate 13 and the upper surface 12T of the first substrate 12 that is exposed within the through hole 14. 【0033】 When the process in step S7 of Figure 7 is performed, the light-emitting element 200b is placed on the upper surface 12T that is exposed within the through-hole 14 of the second substrate 13 and within the through-hole 14 of the first substrate 12 (step S8). Then, the electrode 40 and the light-emitting element 200b are connected by the energizing wire 50 (step S9), and the manufacturing flow of the wiring board 100e is completed. When the energizing wire 50 connects the electrode 40 and the light-emitting element 200b, the wiring board 100e shown in Figure 6 is manufactured. 【0034】 As described above, in the wiring board 100e of the sixth embodiment, the base material 10e comprises a flat first substrate 12 and a second substrate 13 disposed on the upper surface 12T of the first substrate 12. The upper surface 12T of the first substrate 12 faces the lower surface 13U of the second substrate 13. The arithmetic mean roughness (Ra) of the upper surface 12T of the first substrate 12 is 0.2 μm or less, and the flatness of the upper surface 12T is 0.1 mm or less. In the sixth embodiment, the upper surface 12T exposed within the through hole 14 of the first substrate 12 and the inner circumferential surface within the through hole 14 of the second substrate 13 constitute the recess 11 in the third embodiment. In this embodiment, the recess 11 is formed by the upper surface 12T of the first substrate 12 and the through hole 14 of the second substrate 13 when the second substrate 13, which has the through hole 14 formed thereon, is disposed on the first substrate 12. The arithmetic mean roughness of the top surface 12T of the first substrate 12 is 0.2 μm or less, and the flatness of the top surface 12T is 0.1 mm or less. Therefore, there is little deviation in the height position of the top surface 12T of the first substrate 12, which is the bottom surface 11B, in the multiple recesses 11. As a result, the brightness of the light-emitting elements 200 placed in each recess 11 is stable. 【0035】 <Seventh Embodiment> Figure 10 is a schematic cross-sectional view of the wiring board 100f and light-emitting element 200 of the seventh embodiment. The wiring board 100f of the seventh embodiment differs from the wiring board 100a of the second embodiment in that the base material 10e is composed of a first substrate 12 and a second substrate 13, as in the sixth embodiment. Therefore, in the seventh embodiment, the configurations that differ from those of the sixth embodiment will be described, and the configurations that are the same as those of the second embodiment will be omitted. 【0036】 As shown in Figure 10, the base material 10e of the wiring board 100f in the seventh embodiment comprises a flat first substrate 12 and a second substrate 13 disposed on the upper surface 12T of the first substrate 12. Therefore, the upper surface 12T within the through hole 14 of the first substrate 12 in the seventh embodiment and the inner circumferential surface within the through hole 14 of the second substrate 13 constitute the recess 11 in the second embodiment. 【0037】 Figure 11 is a flowchart of the manufacturing method of the seventh embodiment. In the manufacturing flow of the wiring board 100f shown in Figure 11, first, a flat Cu plate which will be the basis of the first substrate 12 is prepared (step S11). A polishing process is performed in which both sides of the flat Cu plate are polished (step S12). An insulating film 20 is formed at a predetermined position on the upper surface 12T of the first substrate 12 (step S13). An electrode 40 having a predetermined pattern is formed on the insulating film 20 (step S14). Figure 12 is a schematic cross-sectional view of the first substrate 12 on which the insulating film 20 and the electrode 40 are formed. 【0038】 Next, a flat Cu plate, which will be the basis for the second substrate 13, is prepared (step S15). A through-hole forming process is performed on the flat Cu plate in which through-holes 14 that penetrate in the thickness direction are formed (step S16). A placement process is performed in which the second substrate 13 with the through-holes 14 formed is joined to the upper surface 12T of the first substrate 12 (step S17). Figure 13 is a schematic cross-sectional view of a wiring board 100f in which the second substrate 13 is placed on the first substrate 12. 【0039】 When the process in step S17 of Figure 11 is performed, the light-emitting element 200 is placed on the electrode 40 (step S18), and the manufacturing flow of the wiring board 100f is completed. Once the light-emitting element 200 is placed on the electrode 40, the wiring board 100f with the light-emitting element 200 mounted on it, as shown in Figure 10, is manufactured. 【0040】 <Modified form of this embodiment> The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit, for example, the following modifications are also possible. 【0041】 In the embodiments from the first to the seventh embodiment described above, an example of a wiring board was explained. However, the wiring board is deformable within the range in which a light-emitting element 200 is arranged in a recess 11 formed on the upper surface 10T, the lower surface 10U is flat, and the substrate 10 is made of metal Cu. For example, the substrate 10 may be made of a metal other than Cu. The substrate 10 is preferably made of a metal with high thermal conductivity in order to improve heat dissipation. The wiring board 100 only needs to include a substrate 10 in which the recess 11 is formed, and does not need to include an insulating film 20, electrodes 40, reflective film 30, etc. The insulating film 20 arranged in the recess 11 may cover a part of the recess 11, or it may cover the entire recess 11 including the slope 11S. The material forming the insulating film 20 may be other than AlN, and may be a well-known material such as Al2O3 or SiN. The cross-sectional shape of the recess 11 does not have to be trapezoidal as shown in Figure 1, and is deformable within the range in which the light-emitting element 200 can be arranged. For example, the recess 11 may not have a bottom surface 11B and may have a triangular cross-section with its vertex on the lower side. Also, the shape of the recess 11 when viewed from the vertical direction may be a shape other than a rectangle, such as a circle. 【0042】 In the fourth embodiment described above, recesses 11, 11c having inclined surfaces 11S, 11Sc that form different angles θ, θc with respect to the flat portion 10PL were described. However, the angles that the inclined surfaces 11S, 11Sc of the recesses 11, 11c formed in the base material 10c make with respect to the flat portion 10PLc, and the number of different angles, are deformable. 【0043】 In the fifth embodiment described above, two light-emitting elements 200d were arranged in recess 11D1, one of the multiple recesses 11D1, 11D2. However, the number and type of light-emitting elements 200d arranged in a single recess 11D1 can be varied. For example, recess 11D1 may have a wider bottom surface than recess 11D2, and light-emitting elements 200 and 200d of different sizes may be arranged within recess 11D1. Alternatively, three or more light-emitting elements 200d may be arranged within recess 11D1. 【0044】 In the sixth embodiment described above, the base material 10e was formed by joining two substrates, a first substrate 12 and a second substrate 13. However, the base material 10e may be formed from three or more substrates. The upper surface 12T of the first substrate 12 was polished to an arithmetic mean roughness of 0.2 μm or less and a flatness of 0.1 mm or less. However, the upper surface 12T may be polished to a roughness greater than 0.2 μm in arithmetic mean roughness, and the flatness may be greater than 0.1 mm, and at least one of the surface roughness and flatness may be controlled by a method other than polishing. Furthermore, polishing is not necessarily required, and a metal plate as the first substrate 12 with a surface roughness of the upper surface 12T of less than or equal to a predetermined value may be prepared. 【0045】 Figure 14 is an explanatory diagram illustrating the method for identifying the flat portion 10PL on the upper surface 12T of the substrate 10. To identify the flat portion 10PL, the cross section shown in Figure 14 is mirror-polished after the substrate 10 is filled with resin. Subsequently, the flat portion 10PL is measured using an image measuring instrument on the mirror-polished cross section shown in Figure 14. In the measurement, first, a virtual plane LN1, represented by a dashed line in Figure 14, is arbitrarily determined from the edge of the upper surface 12T of the substrate 10. In the example shown in Figure 14, the edge of the upper surface 12T is shown as the edge on the negative X-axis side of the substrate 10. From the determined position P0 on the negative X-axis side of the virtual plane LN1, nine positions P1 to P9 on the upper surface 12T are identified, separated by 0.1 mm along the virtual plane LN1. The plane (a straight line in Figure 14) used by the least squares method for the 10 positions P0 to P9, which are the determined position P0 and the 9 identified positions P1 to P9, is identified as the planar section 10PL. 【0046】 Figures 15 and 16 are explanatory diagrams illustrating the method for identifying the locations of recesses 11 and 11g in the substrates 10 and 10g. Figure 15 shows a schematic cross-section of the substrate 10 of the first embodiment. To identify the location of the recesses 11, the cross-section shown in Figure 15 is mirror-polished after the substrate 10 is filled with resin. Subsequently, the shape of the recesses 11 is measured on the mirror-polished cross-section shown in Figure 15 using an image measuring instrument. In the measurement, first, the X1 axis parallel to the flat portion 10PL and the Z1 axis perpendicular to the X1 axis are determined. If the angle α (Figure 15) made with respect to the X1 axis in the negative direction of the Z1 axis is between 10° and 90°, the surface making angle α is identified as the inclined surface 11S of the recess 11. 【0047】 Figure 16 shows a schematic cross-section of a modified substrate 10g. As shown in Figure 16, when the inclined surface 11Sg of the recess 11g is a curved surface rather than a straight plane, the position on the surface of the recess 11g that is furthest from the X1 axis, i.e., the deepest position P20 on the surface of the recess 11g, is identified. The identified position P20 and the position P10 on the X1 axis are divided into 10 equal intervals along the Z1 axis, and nine positions P11 to P19 on the surface of the recess 11g corresponding to the 10 divided positions are identified. A virtual circle C1 is identified using the three positions P10 to P12, which are the position P10 on X1 and the two positions P11 and P12 closest to position P10 among the 10 divided positions P11 to P19. The angle αg between the tangent of the virtual circle C1 at the intersection of the virtual circle C1 and the X1 axis is used as the angle to identify the recess 11g. In Figure 16, the virtual circle C1 is partially shown with a dashed line. 【0048】 The embodiments of this specification have been described above based on the embodiments and modifications described above. The embodiments described above are for the purpose of facilitating understanding of this specification and do not limit it. This specification may be modified and improved without departing from its spirit and the scope of the claims, and equivalents thereof are included in this specification. Furthermore, any technical features that are not described as essential in this specification may be deleted as appropriate. 【0049】 The present invention can also be realized in the following forms. [Application Example 1] A wiring board on which light-emitting elements are arranged, A base material formed of metal, having a flat plate shape with a pair of main surfaces, wherein one of the pair of main surfaces has a recess formed in the thickness direction of the base material where the light-emitting element is arranged, and the other main surface is a flat surface. A wiring board characterized by the following features. [Application Example 2] The wiring board described in Application Example 1, The main surface of the substrate has a plurality of recesses and a flat portion formed between the plurality of recesses, The substrate has a surface that defines the recess, and among the surfaces that define the recess, it has a sloped surface that connects to the flat portion. The angle formed by the inclined surface and the planar portion that demarcates some of the recesses among the plurality of recesses is different from the angle formed by the inclined surface and the planar portion that demarcates other recesses among the plurality of recesses. A wiring board characterized by the following features. [Application Example 3] A wiring board as described in Application Example 1 or Application Example 2, Multiple light-emitting elements are arranged in one of the recesses. A wiring board characterized by the following features. [Application Example 4] A wiring board described in any one of Application Examples 1 to 3, The aforementioned substrate is A first substrate, formed of metal and in the shape of a flat plate, A second substrate is formed of metal, has through holes extending through it in the thickness direction, and is placed on the first substrate, It has, Of the first substrate, the arithmetic mean roughness (Ra) of the opposing surface exposed from the through hole of the second substrate is 0.2 μm or less, and the flatness of the opposing surface is 0.1 mm or less. The recess is formed by the opposing surface and the through hole. A wiring board characterized by the following features. [Application Example 5] A method for manufacturing a wiring substrate on which light-emitting elements are arranged, A polishing step in which one surface of a first flat plate-shaped substrate made of metal is polished until the arithmetic mean roughness (Ra) is 0.2 μm or less and the flatness is 0.1 mm or less, A through-hole forming step in which through-holes are formed in the thickness direction of a second flat plate-shaped substrate made of metal, A placement step of placing the second substrate, on one side of the first substrate, in which the through hole is formed, Equipped with, The light-emitting element is arranged on one surface of the first substrate and within the through-hole of the second substrate. A manufacturing method characterized by the following features. [Explanation of Symbols] 【0050】 10,10c,10d,10e,10f,10g…Base material 10PL,10PLc…Plane part 10T, 10Tc... Top surface (main surface) of the substrate 10U…Bottom surface (main surface) of the substrate 11, 11c, 11D1, 11D2, 11g…recessed 11B...Bottom surface of the recess 11S, 11Sc, 11Sg... slope 12…First circuit board 12T…Top surface (opposite side) of the first circuit board 13…Second circuit board 13U…Bottom surface of the second circuit board 14…Through hole 20…Insulating film 40,40d…electrode 30,30c…Reflection film 50...Electrified wire 60,60d…Joint part 70...Joining layer 100, 100a, 100b, 100c, 1000d, 100e, 100f… Wiring board 200, 200b, 200d… light-emitting elements θ, θc, α, αg… angles

Claims

[Claim 1] A wiring board on which light-emitting elements are arranged, A base material formed of metal, having a flat plate shape with a pair of main surfaces, wherein one of the pair of main surfaces has a recess formed in the thickness direction of the base material where the light-emitting element is arranged, and the other main surface is a flat surface. A wiring board characterized by the following features. [Claim 2] A wiring board according to claim 1, The main surface of the substrate has a plurality of recesses and a flat portion formed between the plurality of recesses, The substrate has a surface that defines the recess, and among the surfaces that define the recess, it has a sloped surface that connects to the flat portion. The angle formed by the inclined surface and the planar portion that demarcates some of the recesses among the plurality of recesses is different from the angle formed by the inclined surface and the planar portion that demarcates other recesses among the plurality of recesses. A wiring board characterized by the following features. [Claim 3] A wiring board according to claim 1, Multiple light-emitting elements are arranged in one of the recesses. A wiring board characterized by the following features. [Claim 4] A wiring board according to any one of claims 1 to 3, The aforementioned substrate is A first substrate, formed of metal and in the shape of a flat plate, A second substrate is formed of metal, has through holes extending through it in the thickness direction, and is placed on the first substrate, It has, Of the first substrate, the arithmetic mean roughness (Ra) of the opposing surface exposed from the through hole of the second substrate is 0.2 μm or less, and the flatness of the opposing surface is 0.1 mm or less. The recess is formed by the opposing surface and the through hole. A wiring board characterized by the following features. [Claim 5] A method for manufacturing a wiring substrate on which light-emitting elements are arranged, A polishing step in which one surface of a first flat substrate made of metal is polished until the arithmetic mean roughness (Ra) is 0.2 μm or less and the flatness is 0.1 mm or less, A through-hole forming step in which through-holes are formed in the thickness direction of a second flat substrate made of metal, A placement step of placing the second substrate, on one side of the first substrate, in which the through hole is formed, Equipped with, The light-emitting element is arranged on one surface of the first substrate and within the through-hole of the second substrate. A manufacturing method characterized by the following features.

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