Ceramic substrates and light-emitting devices, and methods for manufacturing the same.

Abstract

To provide ceramic substrates and light-emitting devices that are less prone to cracking on the surface, as well as methods for manufacturing them. Also, from another perspective, to provide ceramic substrates and light-emitting devices that are less prone to short circuits when mounting electronic components, as well as methods for manufacturing them. [Solution] A method for manufacturing a ceramic substrate 100 according to one embodiment of the present disclosure includes: preparing a ceramic plate 1 having a first surface 1a and a second surface 1b opposite to the first surface 1a, having a through hole 2 connecting the first surface 1a and the second surface 1b, wherein the maximum diameter B1 of the second opening 4 of the through hole 2 formed on the second surface 1b is less than 0.90 times the maximum diameter A1 of the first opening 3 of the through hole 2 formed on the first surface 1a; bringing the inner surface defining the through hole 2 of the ceramic plate 1 into contact with an etching solution; blasting the through hole 2 from the second surface 1b side; placing a first conductive paste 6 in the blasted through hole 2; and sintering the first conductive paste 6.

Description

[Technical Field]

[0001] This disclosure relates to ceramic substrates and light-emitting devices, as well as methods for manufacturing the same. [Background technology]

[0002] In recent years, in order to miniaturize, enhance the functionality, and integrate electronic devices and components, substrates have been proposed in which through-holes (also called "holes" or "vias") are formed in an insulating substrate, and conductive materials such as copper and silver are placed inside the through-holes to electrically connect both sides of the substrate.

[0003] For example, one known method for forming through-holes in such an insulating substrate is to form the through-holes with a laser and then plate the inside of the through-holes (see Patent Document 1).

[0004] Furthermore, it has been described that the diameter of the opening of the through-hole in an insulating substrate formed by laser irradiation decreases in the direction of laser irradiation (see Patent Document 2). That is, it is known that the through-hole becomes tapered in cross-sectional view in the thickness direction of the insulating substrate.

[0005] Furthermore, a method is known in which through holes are created in a ceramic green sheet using a laser, metal paste is embedded in the through holes, and then the ceramic green sheet and metal paste are sintered simultaneously (see Patent Document 3). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 63-196094 [Patent Document 2] Japanese Patent Publication No. 2022-13766 [Patent Document 3] Japanese Patent Publication No. 2015-162575 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] This disclosure aims to provide ceramic substrates and light-emitting devices that are less prone to cracking on their surfaces, as well as methods for manufacturing them. From another perspective, it also aims to provide ceramic substrates and light-emitting devices that are less prone to short circuits when mounting electronic components, as well as methods for manufacturing them. [Means for solving the problem]

[0008] A method for manufacturing a ceramic substrate according to one embodiment of the present disclosure includes: preparing a ceramic plate having a first surface and a second surface opposite to the first surface, having a through hole connecting the first surface and the second surface, wherein the maximum diameter B1 of the second opening of the through hole formed on the second surface is less than 0.90 times the maximum diameter A1 of the first opening of the through hole formed on the first surface; bringing the inner surface defining the through hole of the ceramic plate into contact with an etching solution; blasting the through hole from the second surface side; placing a first conductive paste in the blasted through hole; and sintering the first conductive paste.

[0009] Furthermore, a method for manufacturing a light-emitting device according to one embodiment of the present disclosure includes preparing a ceramic substrate manufactured by the method for manufacturing a ceramic substrate of the present disclosure, and arranging a light-emitting element equipped with electrodes on the ceramic substrate.

[0010] Furthermore, a ceramic substrate according to one embodiment of the present disclosure is a ceramic plate having a first surface and a second surface opposite to the first surface, with a through hole connecting the first surface and the second surface, and a conductive member disposed inside the through hole, wherein the maximum diameter of the first opening of the through hole formed in the first surface is A2, the maximum diameter of the second opening of the through hole formed in the second surface is B2, and the average length between the first surface and the second surface is L, the maximum diameter of the through hole in a cross section in a direction substantially perpendicular to the thickness direction of the ceramic substrate at a position L / 4 from the first surface is C1, the maximum diameter of the through hole in a cross section in a direction substantially perpendicular to the thickness direction of the ceramic substrate at a position L / 2 from the first surface is C2, and the maximum diameter of the through hole in a cross section in a direction substantially perpendicular to the thickness direction of the ceramic substrate at a position 3L / 4 from the first surface is C3, and C1>C2>C3, A2>C1, and B2>C3 are satisfied.

[0011] Furthermore, a light-emitting device according to one embodiment of the present disclosure comprises the ceramic substrate of the present disclosure and a light-emitting element having electrodes disposed on the ceramic substrate. [Effects of the Invention]

[0012] According to one embodiment of this disclosure, it is possible to provide a ceramic substrate and a light-emitting device that are less prone to cracking on the surface, as well as a method for manufacturing the same. From another viewpoint, it is possible to provide a ceramic substrate and a light-emitting device that are less prone to short circuits when mounting electronic components, as well as a method for manufacturing the same. [Brief explanation of the drawing]

[0013] [Figure 1] This is a flowchart showing an example of a method for manufacturing a ceramic substrate according to the first embodiment. [Figure 2A] This is a schematic cross-sectional view showing an example of a ceramic plate used in the manufacturing method of a ceramic substrate according to the first embodiment. [Figure 2B] Figure 2A is a schematic top view of the ceramic plate. [Figure 2C] It is a schematic bottom view of the ceramic plate of Fig. 2A. [Figure 3] It is a schematic cross-sectional view showing an example of a contacting step in the method for manufacturing a ceramic substrate according to the first embodiment. [Figure 4A] It is a schematic cross-sectional view showing an example of a blasting step in the method for manufacturing a ceramic substrate according to the first embodiment. [Figure 4B] It is a schematic cross-sectional view showing the sizes of respective parts in Fig. 4A. [Figure 5A] It is a schematic cross-sectional view showing an example of disposing a first conductive paste in the method for manufacturing a ceramic substrate according to the first embodiment. [Figure 5B] It is an enlarged cross-sectional view schematically showing an enlarged view of a region VB in Fig. 5A. [Figure 6A] It is a schematic cross-sectional view showing an example of a sintering step in the method for manufacturing a ceramic substrate according to the first embodiment. [Figure 6B] It is an enlarged cross-sectional view schematically showing the state of a conductive member obtained by enlarging a region VIB in Fig. 6A. [Figure 7A] It is a schematic cross-sectional view showing an example of a blasting step in the method for manufacturing a ceramic substrate according to the fourth embodiment. [Figure 7B] It is a schematic cross-sectional view showing the sizes of respective parts in Fig. 7A. [Figure 8] It is a flowchart showing an example of preparing a ceramic plate in the method for manufacturing a ceramic substrate according to the fifth embodiment. [Figure 9] It is a schematic cross-sectional view showing an example of preparing a ceramic plate having no through-holes in the method for manufacturing a ceramic substrate according to the fifth embodiment. [Figure 10A] It is a schematic cross-sectional view showing an example of forming through-holes in the method for manufacturing a ceramic substrate according to the fifth embodiment. [Figure 10B] It is a schematic top view of the ceramic plate of Fig. 10A. [Figure 10C] It is a schematic bottom view of the ceramic plate of Fig. 10A. [Figure 11A] This is a schematic cross-sectional view showing an example of a case in which an etching solution containing an alkaline solution is used for contact in the manufacturing method of a ceramic substrate according to the fifth embodiment. [Figure 11B] This is a schematic cross-sectional view showing an example of a case in which an etching solution containing an acidic solution is used when contacting a ceramic substrate in the manufacturing method according to the fifth embodiment. [Figure 12] This is a flowchart showing an example of preparing a ceramic plate according to the method for manufacturing a ceramic substrate according to the sixth embodiment. [Figure 13A] This is a schematic cross-sectional view showing an example of arranging the first coating member and the second coating member in the method for manufacturing a ceramic substrate according to the sixth embodiment. [Figure 13B] This is a schematic cross-sectional view showing an example of placing the second conductive paste in the method for manufacturing a ceramic substrate according to the sixth embodiment. [Figure 14] This is a schematic cross-sectional view showing an example of sintering in the manufacturing method of a ceramic substrate according to the sixth embodiment. [Figure 15] This is a flowchart showing an example of preparing a ceramic plate according to the method for manufacturing a ceramic substrate according to the seventh embodiment. [Figure 16A] This is a schematic cross-sectional view showing an example of polishing or grinding in the method for manufacturing a ceramic substrate according to the seventh embodiment. [Figure 16B] This is a schematic cross-sectional view showing an example of a ceramic substrate after polishing or grinding according to the manufacturing method of the ceramic substrate according to the 7th embodiment. [Figure 16C] This is a schematic cross-sectional view showing another example of a ceramic substrate after polishing or grinding, as described in the manufacturing method of a ceramic substrate according to the fourth embodiment. [Figure 17A] This is a schematic cross-sectional view showing an example of a ceramic substrate according to the eighth embodiment. [Figure 17B] Figure 17A is a schematic top view of the ceramic substrate. [Figure 17C]Figure 17A is a schematic cross-sectional view of the ceramic substrate at position L1, in a direction substantially perpendicular to the thickness direction of the ceramic substrate. [Figure 17D] Figure 17A is a schematic cross-sectional view of the ceramic substrate at position L2, in a direction approximately perpendicular to the thickness direction of the ceramic substrate. [Figure 17E] Figure 17A is a schematic cross-sectional view of the ceramic substrate at position L3, in a direction substantially perpendicular to the thickness direction of the ceramic substrate. [Figure 17F] Figure 17A shows a schematic cross-sectional view in a direction approximately perpendicular to the thickness direction of the ceramic substrate, at the position L3 between the first surface of the ceramic substrate and position L3, where the maximum diameter of the through-hole in a cross-section in a direction approximately perpendicular to the thickness direction of the ceramic substrate is smallest. [Figure 17G] Figure 17A is a schematic bottom view of the ceramic substrate. [Figure 17H] This is a magnified view of region XVIIH in Figure 17A. [Figure 18A] Figure 18A is a schematic cross-sectional view showing an example of a ceramic substrate according to the ninth embodiment. [Figure 18B] This is a magnified view of region XVIIB in Figure 18A. [Figure 19] This is a schematic cross-sectional view showing an example of a light-emitting device according to the embodiment. [Figure 20A] This is a perspective view showing an application example of the light-emitting device according to the embodiment. [Figure 20B] Figure 20A is a cross-sectional view along the line XXB-XXB. [Figure 21] This is a flowchart showing an example of a method for manufacturing a light-emitting device according to an embodiment. [Figure 22A] This is a cross-sectional SEM image of the through-hole 2 observed at a magnification of 500x in Example 1, after contacting it (S32). [Figure 22B] This is an SEM cross-sectional view of the entire ceramic plate 1 after contacting it in Example 1 (S32). [Figure 23A]This is a cross-sectional SEM image of the through-hole 2 after blast treatment S33 in Example 1, observed at a magnification of 500x. [Figure 23B] This is an SEM cross-sectional view of the entire ceramic plate 1 after blast treatment S33 in Example 1. [Figure 23C] This is a magnified partial image of the SEM cross-sectional view of the through-hole 2 after blast treatment S33 in Example 1. [Figure 23D] This is a magnified partial image of the FBI-SEM (focused ion beam-SEM) cross-sectional observation of the through-hole 2 after blast treatment S33 in Example 1. [Figure 24A] This is a top view of the design drawing for ceramic plate 1. [Figure 24B] This graph shows the simulation condition values ​​for part number (1) and part number (2) in Figure 24A. [Figure 24C] This is a cross-sectional view along the XXIVCD-XXIVCD line in Figure 24A, based on "Design 1". [Figure 24D] This is a cross-sectional view along the XXIVCD-XXIVCD line in Figure 24A, based on "Design 2". [Figure 24E] Figure 24D is an enlarged cross-sectional view of region XXIVE. [Figure 24F] This graph shows the temperature conditions of the simulation. [Figure 25A] This shows the stress results for the top view of ceramic plate 1 based on "Design 1". [Figure 25B] This shows the stress results in the cross-sectional view of ceramic plate 1 based on "Design 1". [Figure 25C] This is the stress result for the cross-sectional view of ceramic plate 1 based on "Design 2". [Modes for carrying out the invention]

[0014] A ceramic substrate and a light-emitting device according to the embodiments of this disclosure, as well as a method for manufacturing them, will be described in detail with reference to the drawings. However, the embodiments described below are illustrative examples of ceramic substrates and light-emitting devices and methods for manufacturing them that embody the technical concept of this disclosure, and are not limited to those described below.

[0015] Furthermore, the dimensions, materials, shapes, and relative arrangements of the components described in the embodiments are merely illustrative examples and not intended to limit the scope of this disclosure unless otherwise specified. Note that the size and positional relationships of the components shown in each drawing may be exaggerated for clarity. Also, in the following description, the same name and reference numeral indicate the same or identical components, and detailed explanations are omitted as appropriate. To avoid overly complex drawings, schematic diagrams may be used with some elements omitted, or end views showing only the cross-section may be used as cross-sectional views.

[0016] Furthermore, in this disclosure, the term "polygon" refers to polygons such as rectangles, triangles, and quadrilaterals, including shapes where the corners of the polygon have been rounded, chamfered, or otherwise modified. Similarly, shapes where modifications have been made not only to the corners (ends of the sides) but also to the middle parts of the sides will also be referred to as polygons. In other words, shapes that retain the shape of a polygon but have been partially modified are included in the interpretation of "polygon" as described in this disclosure.

[0017] Furthermore, the same applies not only to polygons but also to terms describing specific shapes such as trapezoids, circles, and convex shapes. The same also applies when dealing with each side that forms such a shape. In other words, even if a side has been processed at a corner or in the middle, the interpretation of "side" includes the processed part. When distinguishing a "polygon" or "side" without partial processing from a processed shape, the term "strictly" should be added, for example, "strictly quadrilateral."

[0018] Furthermore, the following description uses terms to indicate specific directions or positions as needed (e.g., "up," "down," "side," "top surface," "bottom surface," "side," "X," "Y," "Z," and other terms including these terms). However, the use of these terms is solely to facilitate understanding of the invention with reference to the drawings, and the meaning of these terms does not excessively limit the technical scope of the present invention. For example, if "top surface" is mentioned, the invention does not necessarily have to be used in a way that it always faces upwards. Also, in the embodiments, "covering" is not limited to direct contact, but also includes indirect covering, for example, through other components.

[0019] In each drawing, the Z-axis direction is defined as the thickness direction of the ceramic plate 1 or ceramic substrate 100, the direction approximately perpendicular to the Z-axis direction is defined as the X-axis direction, and the direction approximately perpendicular to both the Z-axis and X-axis directions is defined as the Y-axis direction. The X-axis, Y-axis, and Z-axis are mutually orthogonal.

[0020] Furthermore, in this specification or the claims, when there are multiple components and each is to be expressed separately, the components may be distinguished by adding "first," "second," etc., to their names.

[0021] [Method for manufacturing ceramic substrates] <First Embodiment> Figure 1 is a flowchart showing an example of a method for manufacturing a ceramic substrate according to the first embodiment. The method for manufacturing a ceramic substrate according to the first embodiment will be explained with reference to Figures 2A to 6B. Here, we show a method for manufacturing one ceramic substrate 100, but multiple ceramic substrates 100 may be manufactured simultaneously.

[0022] A method for manufacturing a ceramic substrate 100 according to the first embodiment includes: preparing a ceramic plate 1 having a first surface 1a and a second surface 1b opposite to the first surface 1a, having a through hole 2 connecting the first surface 1a and the second surface 1b, wherein the maximum diameter B1 of the second opening 4 of the through hole 2 formed on the second surface 1b is less than 0.90 times the maximum diameter A1 of the first opening 3 of the through hole 2 formed on the first surface 1a; bringing the inner surface defining the through hole 2 of the ceramic plate 1 into contact with an etching solution; blasting the through hole 2 from the second surface 1b side; placing a first conductive paste 6 in the blasted through hole 2; and sintering the first conductive paste 6. The method for manufacturing the ceramic substrate may further include other processes as necessary.

[0023] In the method for manufacturing the ceramic substrate, an embodiment in which the first etching solution contains an alkaline solution will be described. In this case, the first etching solution will not contain an acidic solution.

[0024] (S1) Prepare ceramic plate 1. Figure 2A is a schematic cross-sectional view showing an example of a ceramic plate used in the manufacturing method of a ceramic substrate according to the first embodiment. Figure 2B is a schematic top view of the ceramic plate in Figure 2A. Figure 2C is a schematic bottom view of the ceramic plate in Figure 2A. Note that Figure 2A is a schematic cross-sectional view taken along the line IIA-IIA in Figures 2B and 2C.

[0025] In preparing the ceramic plate 1 S1, the ceramic plate 1 is provided with a first surface 1a and a second surface 1b opposite to the first surface 1a, and has a through hole 2 connecting the first surface 1a and the second surface 1b, wherein the maximum diameter B1 of the second opening 4 of the through hole 2 formed on the second surface 1b is less than 0.90 times the maximum diameter A1 of the first opening 3 of the through hole 2 formed on the first surface 1a. That is, the condition B1 / A1 < 0.90 is satisfied.

[0026] The ceramic plate 1 is an insulating material. The ceramic plate 1 may be a ceramic precursor in a softened state before sintering, or it may be a sintered ceramic, but it is preferable that it be a sintered ceramic because there is no dimensional change due to sintering, through holes 2 can be accurately formed at the desired position, and the size of the through holes 2 can be adjusted to a constant desired size.

[0027] There are no particular restrictions on the material of the ceramic plate 1, and it can be appropriately selected according to the purpose, but it is preferable that it contains aluminum nitride (AlN) as the main material, and other auxiliary materials may also be included as needed. Here, "main material" means the material that makes up the largest amount of material in the materials constituting the ceramic plate 1. As materials for the ceramic plate 1 other than aluminum nitride, for example, silicon nitride (Si3N4), aluminum oxide (Al2O3), silicon carbide (SiC), etc. can be used, but white aluminum nitride and silicon nitride, which have excellent heat resistance, light resistance, and high thermal conductivity, are preferred. Commercially available ceramic plates 1 can be used.

[0028] There are no particular restrictions on the auxiliary materials used in ceramic plate 1, but examples include ceramics other than aluminum nitride, glass, etc. These may be used individually or in combination of two or more types.

[0029] Other ceramics besides aluminum nitride are not particularly limited and include, for example, nitride-based ceramics such as silicon nitride and boron nitride; oxide-based ceramics such as aluminum oxide, silicon oxide, calcium oxide, and magnesium oxide; silicon carbide; mullite; and borosilicate glass. These may be used individually or in combination of two or more.

[0030] The ceramic plate 1 is preferably a plate-shaped member whose outer shape in plan view is rectangular. This rectangle may be a rectangle with a long side and a short side. Unless otherwise specified, a square may also be included in the definition of a rectangle. Furthermore, the outer shape of the ceramic plate 1 in plan view is not limited to a rectangle; it may also be a circle, an ellipse, a polygon, or the like.

[0031] The first surface 1a may or may not be flat, but it is preferable that it be flat when the ceramic substrate 100 is used in a light-emitting device, as this allows for a suitable arrangement of light-emitting elements.

[0032] The second surface 1b is the surface of the ceramic plate 1 opposite to the first surface 1a. The second surface 1b may be flat or not, but it is preferable that it be flat, as this allows for suitable placement on the mounting substrate when the ceramic substrate 100 is used in a light-emitting device.

[0033] In Figure 2A, the surface of the ceramic plate 1 in the upper Z-axis direction is shown as the first surface 1a, and the surface of the ceramic plate 1 in the lower Z-axis direction is shown as the second surface 1b. However, this is merely for convenience, and when the ceramic substrate 100 is used in a light-emitting device, the mounting substrate may be placed on the first surface 1a and the light-emitting element on the second surface 1b.

[0034] The first surface 1a and the second surface 1b are, for example, parallel. Here, when describing the surfaces of the ceramic plate 1 as "parallel," a difference of ±5 degrees is permitted.

[0035] The through-hole 2 connects the first surface 1a and the second surface 1b. The through-hole 2 is, for example, a via hole.

[0036] In a plan view of the ceramic plate 1, the shape of the first opening 3 of the through hole 2 formed on the first surface 1a and the shape of the second opening 4 of the through hole 2 formed on the second surface 1b are preferably circular or elliptical. However, the shapes of the first opening 3 and the second opening 4 of the through hole 2 in a plan view of the ceramic plate 1 are not limited to circular or elliptical, but may also be polygons including rectangles.

[0037] The maximum diameter A1 of the first opening 3 of the through hole 2 formed on the first surface 1a and the maximum diameter B1 of the second opening 4 of the through hole 2 formed on the second surface 1b in a plan view of the ceramic plate 1 are not particularly limited, as long as the maximum diameter B1 of the second opening 4 of the through hole 2 formed on the second surface 1b is less than 0.90 times the maximum diameter A1 of the first opening 3, and can be appropriately selected according to the purpose. For example, the maximum diameter A1 of the first opening 3 is preferably 110 μm or more and 150 μm or less, and more preferably 125 μm or more and 135 μm or less. The maximum diameter B1 of the second opening 4 is preferably 60 μm or more and 90 μm or less, and more preferably 65 μm or more and 75 μm or less.

[0038] If the shapes of the first opening 3 and the second opening 4 of the through hole 2 are circular, "maximum diameter A1" and "maximum diameter B1" shall be the diameters of the first opening 3 and the second opening 4, respectively. If the shapes of the first opening 3 and the second opening 4 of the through hole 2 are elliptical, they shall be the longest diameters of the first opening 3 and the second opening 4, respectively. Furthermore, if the shapes of the first opening 3 and the second opening 4 of the through hole 2 in a plan view of the ceramic plate 1 are rectangular, "maximum diameter A1" and "maximum diameter B1" shall be the maximum diagonal lengths of the first opening 3 and the second opening 4, respectively.

[0039] There are no particular restrictions on the number of through holes 2 in the ceramic plate 1; there may be one or multiple holes, but from the viewpoint of mounting it in a light-emitting device, it is preferable to have multiple holes.

[0040] The inner surface of the through hole 2 has a damaged layer 5, which is damaged during the processing to form the through hole 2, resulting in cracks or brittleness. In this disclosure, the damaged layer 5 means an area in the ceramic plate 1 that has cracks and / or has deteriorated, such as having reduced strength.

[0041] (S2) Make contact Figure 3 is a schematic cross-sectional view showing an example of contact in the manufacturing method of a ceramic substrate according to the first embodiment.

[0042] In contact S2, the inner surface defining the through-hole 2 of the ceramic plate 1 is brought into contact with the etching solution. At this time, the damage layer 5 disposed on the inner surface of the through-hole 2 comes into contact with the etching solution. As a result, the damage layer 5 can be removed in contact S2. In the manufacturing method of the ceramic substrate according to the first embodiment, the etching solution contains an alkaline solution.

[0043] Examples of etching solutions containing an alkaline solution include etching solutions containing one or more pH adjusting agents selected from the group consisting of potassium hydroxide, sodium hydroxide, lithium hydroxide, calcium hydroxide, and magnesium hydroxide.

[0044] The concentration of the pH adjusting agent contained in the etching solution containing the alkaline solution is not particularly limited as long as it can remove the damaged layer 5, and can be appropriately selected according to the purpose, but it is preferably 1.5 mol / L or more and 3.5 mol / L or less, and more preferably 2.5 mol / L or more and 3.5 mol / L or less. When the concentration of the pH adjusting agent contained in the etching solution containing the alkaline solution is 1.5 mol / L or more, the inner surface defining the through-holes 2 of the ceramic plate 1 can be efficiently etched, and the damaged layer 5 can be removed. Furthermore, when the concentration of the pH adjusting agent contained in the etching solution containing the alkaline solution is 3.5 mol / L or less, the etching rate of the ceramic plate 1 does not become too fast, making it easy to adjust the opening diameter and shape of the through-holes 2 to the desired size.

[0045] There are no particular limitations on the method of bringing the inner surface defining the through-holes 2 of the ceramic plate 1 into contact with an etching solution containing an alkaline solution, and any method can be appropriately selected depending on the purpose. For example, methods include immersing the ceramic plate 1 having the through-holes 2 in an etching solution containing an alkaline solution, or applying the etching solution to the ceramic plate 1 so that the first surface 1a, the second surface 1b, and the inside of the through-holes 2 of the ceramic plate 1 come into contact with the etching solution containing an alkaline solution. Among these, the method of immersing the ceramic plate 1 having the through-holes 2 in an etching solution containing an alkaline solution is efficient and preferred for bringing the inner surface defining the through-holes 2 of the ceramic plate 1 into contact with the etching solution containing an alkaline solution.

[0046] In contact S2, the temperature at which the etching solution containing the alkaline solution is brought into contact with the inner surface defining the through-holes 2 of the ceramic plate 1 is not particularly limited as long as the damaged layer 5 can be removed, and can be appropriately selected according to the purpose, but 50°C or more and less than 100°C is preferred, and 70°C or more and 95°C or less is more preferred. If the temperature at which the etching solution containing the alkaline solution is brought into contact with the inner surface defining the through-holes 2 of the ceramic plate 1 is 50°C or higher, the inner surface defining the through-holes 2 of the ceramic plate 1 can be efficiently etched. Also, if the temperature at which the etching solution containing the alkaline solution is brought into contact with the inner surface defining the through-holes 2 of the ceramic plate 1 is less than 100°C, it is possible to prevent the etching solution containing the alkaline solution from boiling.

[0047] In contact S2, the contact time between the etching solution containing the alkaline solution and the inner surface defining the through-hole 2 of the ceramic plate 1 is not particularly limited as long as the damage layer 5 can be removed, and can be appropriately selected according to the purpose, but 5 minutes or more and 60 minutes or less is preferred. If the contact time between the etching solution containing the alkaline solution and the inner surface defining the through-hole 2 of the ceramic plate 1 is 60 minutes or more, the inner surface defining the through-hole 2 of the ceramic plate 1 can be efficiently etched and the damage layer 5 can be removed. Furthermore, if the contact time between the etching solution containing the alkaline solution and the inner surface defining the through-hole 2 of the ceramic plate 1 is 180 minutes or less, it is easier to adjust the opening diameter and shape of the through-hole 2 to the desired size, and it is possible to prevent the thickness of the ceramic plate 1 from being reduced by etching.

[0048] There are no particular restrictions on the atmospheric conditions for bringing the etching solution containing the alkaline solution into contact with the inner surface defining the through-hole 2 of the ceramic plate 1 in contact S2, and it can be carried out under atmospheric pressure conditions.

[0049] Among these, in the contacting step S2, the contacting is preferably performed under atmospheric pressure conditions of less than 100°C for 5 minutes or more and 60 minutes or less, and more preferably performed under atmospheric pressure conditions of 70°C or more and less than 100°C for 10 minutes or more and 30 minutes or less.

[0050] (S3) Blasting treatment Figures 4A and 4B are schematic cross-sectional views showing an example of the blasting treatment in the method for manufacturing a ceramic substrate according to the first embodiment. Figure 4B is a schematic cross-sectional view showing the size of each part in Figure 4A.

[0051] In the blasting treatment step S3, the abrasive 10 is applied from the second surface 1b side to perform blasting on the through-hole 2. As a result, in the second opening 4 of the through-hole 2 formed on the second surface 1b, the ceramic plate 1 that defines the second opening 4 is scraped. In addition, the surfaces of the second surface 1b and the inner surface of the through-hole 2 are roughened.

[0052] When the maximum diameter of the first opening 3 of the through-hole 2 formed on the first surface 1a is A2, the maximum diameter of the second opening 4 of the through-hole 2 formed on the second surface 1b is B2, and the average length between the first surface 1a and the second surface 1b is L after the blasting treatment step S3: let C1 be the maximum diameter of the through-hole 2 in a cross section in a direction substantially perpendicular to the thickness direction of the ceramic plate 1 at a position of L / 4 from the first surface 1a side, that is, position L1; let C2 be the maximum diameter of the through-hole 2 in a cross section in a direction substantially perpendicular to the thickness direction of the ceramic plate 1 at a position of L / 2 from the first surface 1a side, that is, position L2; let C3 be the maximum diameter of the through-hole 2 in a cross section in a direction substantially perpendicular to the thickness direction of the ceramic plate 1 at a position of 3L / 4 from the first surface 1a side, that is, position L3. Then, the relationships C1 > C2 > C3, A2 > C1, and B2 > C3 are satisfied. In the present embodiment, A2 < B2 is satisfied. Accordingly, the pitch distance between adjacent through-holes 2 on the first surface 1a side can be made smaller than the pitch distance between adjacent through-holes 2 on the second surface 1b side, and the degree of freedom in design when mounting a light-emitting element or the like can be increased. In addition, by increasing the opening area of B2, the thermal conductivity to the second surface 1b side can be improved.

[0053] The maximum diameter B2 of the second opening 4 of the through hole 2 formed in the second surface 1b of the ceramic plate 1 in a plan view is increased by at least 10 μm, and in some cases by 200 μm or more, compared to the initial maximum diameter B1 of the second opening 4, by contact S2 and blast treatment S3.

[0054] Preferably, the area near the second opening 4 of the through hole 2 on the second surface 1b has a tapered shape in cross-sectional view such that the opening diameter decreases from the second surface 1b side toward the thickness direction of the ceramic plate 1.

[0055] In blast treatment S3, there are no particular restrictions on the type of abrasive 10, and it can be appropriately selected from known abrasives 10.

[0056] There are no particular restrictions on the blasting method used in S3; it may be a dry blasting method or a wet blasting method.

[0057] In blast treatment S3, there are no particular restrictions on the arithmetic mean roughness Ra of the inner surface defining the through-hole 2, and it can be appropriately selected according to the purpose, but it is preferably 0.5 μm or more and 2.0 μm or less. The arithmetic mean roughness Ra of the inner surface defining the through-hole 2 is measured in accordance with JIS B 0601 using a stylus-type surface roughness meter (for example, SE3500 manufactured by Kosaka Laboratory Co., Ltd.) equipped with a diamond stylus with a tip radius of curvature r of 2 μm.

[0058] (S4) Place the first conductive paste. Figure 5A is a schematic cross-sectional view showing an example of placing the first conductive paste in the manufacturing method of a ceramic substrate according to the first embodiment. Figure 5B is an enlarged cross-sectional view schematically showing an enlarged version of region VB in Figure 5A.

[0059] In step S4, the first conductive paste is placed in the blast-treated through-hole 2.

[0060] The first conductive paste can be placed in S4 by filling the through-hole 2 with the first conductive paste 6, for example, by screen printing, metal mask printing, or injection using a nozzle, so that the surface height is approximately the same as that of the first surface 1a and the second surface 1b of the ceramic plate 1.

[0061] In step S4, when placing the first conductive paste, it is preferable to place the first conductive paste 6 not only to fill the through hole 2 with the first conductive paste 6, but also to place the first conductive paste 6 so as to cover at least a portion of either the first opening 3 or the second opening 4 of the through hole 2, and the first surface 1a or the second surface 1b of the ceramic plate 1. This prevents a decrease in dimensional accuracy due to volume shrinkage when the first conductive paste 6 is sintered in step S5, and allows the thickness of the first conductive member 7a to be sufficient.

[0062] As a specific example, in the step S4 of placing the first conductive paste, when filling the through-hole 2 with the first conductive paste 6, the first conductive paste 6 can be filled into the through-hole 2 from the first surface 1a of the ceramic plate 1 using a squeegee, for example, a tool used in screen printing, and then the first conductive paste 6 can be filled into the through-hole 2 from the second surface 1b of the ceramic plate 1 using a squeegee in the same way as the first surface 1a, thereby placing the first conductive paste 6 so as to cover at least a portion of at least one of the first surface 1a and the second surface 1b of the ceramic plate 1. In other words, the first conductive paste 6 can be placed so as to continuously cover at least a portion of at least one of the first surface 1a and the second surface 1b of the ceramic plate 1 from the through-hole 2.

[0063] Furthermore, when placing the first conductive paste S4, it is preferable to further dry the first conductive paste 6 and pressurize the dried first conductive paste 6 before sintering. To dry the first conductive paste 6, for example, it may be dried by placing it in an electric furnace where the atmosphere is higher than room temperature but lower than 100°C. It is also preferable to perform drying and pressurizing at the same time by using a pressurizing mold when placing the ceramic plate 1 with the first conductive paste 6 into the electric furnace. By drying and pressurizing here, the first conductive paste 6 becomes less susceptible to volume shrinkage during sintering S5. In the thickness direction of the ceramic plate 1, it is preferable to place the first conductive paste 6 so as to protrude outward from the ceramic plate 1. Because the first conductive paste 6 is prone to volume shrinkage during sintering, shrinkage is likely to occur on the surface of the first conductive member 7a. Therefore, if the first conductive paste 6 is filled to a height flush with the thickness of the ceramic plate 1, the first conductive member 7a may be recessed compared to the first surface 1a of the ceramic plate 1, making it difficult to make the first conductive member 7a and the first surface 1a of the ceramic plate 1 flush.

[0064] <<First conductive paste 6>> The first conductive paste 6 preferably contains an activated metal brazing material, as this allows for the suitable formation of a nitride coating 16b on the inner surface defining the through-hole 2, thereby improving the adhesion between the ceramic plate 1 and the first conductive member 7a. The activated metal brazing material preferably contains a eutectic powder 11 of silver and copper, an activated metal powder 12, and a solvent 13, and further preferably contains an inorganic filler 14, and may also contain other components as needed.

[0065] Furthermore, the activated metal brazing material is fluid and can be freely filled into through holes 2 of any shape, and can be positioned by applying it to any shape and thickness and then curing it.

[0066] -Eutectic powder 11- The eutectic powder 11 is a eutectic powder of silver and copper. The melting point of the eutectic powder of silver and copper is approximately 780°C.

[0067] There are no particular restrictions on the content of the eutectic powder 11 in the first conductive paste 6, but it is preferable that the content is 40% by mass or more and 95% by mass or less, when the total amount of the eutectic powder 11, activated metal powder 12, and inorganic filler 14 is taken as 100% by mass.

[0068] -Active metal powder 12- After sintering, the activated metal powder 12 becomes a metal compound 16 that is distributed on the inner surface defining the through-hole 2 and on at least a portion of the surface of the inorganic filler 14.

[0069] There are no particular restrictions on the active metal powder 12, and examples include titanium hydride (TiH2), cerium hydride (CeH2), zirconium hydride (ZrH2), and magnesium hydride (MgH2). These may be used individually or in combination of two or more. Among these, it is preferable that the active metal powder 12 contains titanium hydride. When the active metal powder 12 contains titanium hydride, if aluminum nitride is exposed on the inner surface defining the through hole 2, it can react with this aluminum nitride to form titanium nitride (TiN) as the metal compound 16. Titanium nitride is known as a barrier metal. Therefore, migration of the metal in the first conductive member 7a can be suppressed, and a highly reliable ceramic substrate 100 can be obtained.

[0070] There are no particular restrictions on the content of the activated metal powder 12 in the first conductive paste 6, but it is preferable that it be 2% by mass or more and 15% by mass or less when the total amount of the eutectic powder 11, activated metal powder 12, and inorganic filler 14 is 100% by mass. When the content of the activated metal powder 12 is 2% by mass or more relative to the total amount of the eutectic powder 11, activated metal powder 12, and inorganic filler 14, a nitride film 16b of a suitable thickness can be formed. In addition, the hydrogen derived from the activated metal powder 12 can create a reducing atmosphere in the reaction phase, allowing the first conductive paste 6 to be sintered suitably. When the content of the activated metal powder 12 is 15% by mass or less relative to the total amount of the eutectic powder 11, activated metal powder 12, and inorganic filler 14, the possibility that the generated hydrogen will not escape and will remain in the first conductive member 7a as voids can be reduced.

[0071] -Solvent 13- There are no particular restrictions on the solvent 13, but an organic binder is preferred. There are no particular restrictions on the organic binder, and examples include thermosetting resins and thermoplastic resins. Specific examples of organic binders include epoxy resins, silicone resins, acrylic resins, urethane resins, polyvinyl resins, ethylcellulose resins, phenolic resins, polyimide resins, polyurethane resins, melamine resins, and polyurea resins. Alternatively, the organic binder may be a solvent or resin material commonly used as a via material. These may be used individually or in combination of two or more. Since the organic binder functions as a sintering binder, it is decomposed and removed by evaporation during sintering S5.

[0072] There are no particular restrictions on the content of the solvent 13 in the first conductive paste 6, and it can be appropriately selected depending on the content of the eutectic powder 11, activated metal powder 12, and inorganic filler 14. The content of the solvent 13 may be from 0.5% by mass to 20% by mass or less, preferably from 1% by mass to 15% by mass or less, and more preferably from 2% by mass to 10% by mass or less.

[0073] -Inorganic Filler 14- There are no particular restrictions on the inorganic filler 14, and examples include ceramic fillers such as silica filler, metal fillers, and glass fillers. These may be used individually or in combination of two or more. Among these, ceramic fillers are preferred as the inorganic filler 14. When the first conductive paste 6 contains the inorganic filler 14, the thermal conductivity and heat dissipation characteristics of the first conductive member 7a can be improved.

[0074] There are no particular restrictions on the ceramic filler, and examples include aluminum nitride (AlN), silicon nitride (Si3N4), aluminum oxide (Al2O3), and silicon carbide (SiC).

[0075] Furthermore, the inorganic filler 14 is preferably made of a material with a coefficient of linear expansion of 8 ppm or less. This makes it possible to lower the linear coefficient of the first conductive member 7a and improve the thermal shock characteristics.

[0076] There are no particular restrictions on the median diameter of the inorganic filler 14, but it is preferably 1 μm or more and 50 μm or less, and more preferably 2 μm or more and 15 μm or less.

[0077] Furthermore, the inorganic filler 14 is preferably a material having a coefficient of linear expansion of 5 ppm or less and a high thermal conductivity of 100 W / m·K or more. Examples of such materials include the ceramic fillers mentioned above. By dispersing such materials in the first conductive member 7a, the difference in coefficients of linear expansion can be mitigated, and reliability such as thermal shock characteristics can be improved.

[0078] There are no particular restrictions on the thermal conductivity of the inorganic filler 14, but it is preferably 20 W / (m / K) or higher, and more preferably 30 W / (m / K) or higher, at a measurement temperature of 300 K.

[0079] There are no particular restrictions on the content of the inorganic filler 14 in the first conductive paste 6, but it is preferable that the content is 4% by mass or more and 50% by mass or less, when the total amount of the eutectic powder 11, activated metal powder 12, and inorganic filler 14 is taken as 100% by mass.

[0080] -Other ingredients-- Other components in the first conductive paste 6 are not particularly limited and include, for example, reducing agents such as organic acids and other eutectic alloy powders other than the silver-copper eutectic powder 11. These may be used individually or in combination of two or more.

[0081] Other eutectic alloy powders besides the silver-copper eutectic powder 11 include, for example, a copper-zinc eutectic alloy and a copper-tin eutectic alloy. These may be used individually or in combination of two or more.

[0082] While there are no particular restrictions on the melting point of other eutectic alloy powders, a melting point of 700°C to 1,200°C is preferred, 720°C to 1,100°C is more preferred, and 780°C to 850°C is even more preferred. Lowering the melting point of the eutectic alloy powder reduces the thermal load on the material to the ceramic plate 1, etc., thereby reducing discoloration.

[0083] There are no particular restrictions on the content of other eutectic alloy powders, as long as they do not impair the effects of this disclosure.

[0084] (S5) Sintering Figure 6A is a schematic cross-sectional view showing an example of sintering in the manufacturing method of a ceramic substrate according to the first embodiment. Figure 6B is an enlarged cross-sectional view schematically showing the state of the conductive member by enlarging region VIB in Figure 6A.

[0085] In sintering S5, the first conductive paste 6 is sintered. Sintering S5 yields a ceramic substrate 100 having a second surface 100b opposite to the first surface 100a, a through hole 2 connecting the first surface 100a and the second surface 100b, and a first conductive member 7a placed in the through hole 2.

[0086] Specifically, sintering S5 involves sintering the first conductive paste 6 that was filled into the through-hole 2 of the ceramic plate 1 in placing the first conductive paste S4, thereby forming the first conductive member 7a. In the case where the first conductive paste 6 is placed in placing the first conductive paste S4 so as to cover at least a portion of the first surface 1a and the second surface 1b of the ceramic plate 1, the first conductive paste 6 is sintered in the same manner to form the first conductive member 7a.

[0087] In sintering S5, it is preferable to dry the first conductive paste 6 after placing the first conductive paste S4 but before sintering it. There are no particular restrictions on the drying temperature, for example, a temperature lower than the sintering temperature of the first conductive paste 6.

[0088] There are no particular restrictions on the sintering atmosphere when sintering the first conductive paste 6, but an Ar atmosphere of 99.9% or more or 10 -5 A vacuum atmosphere of Pa or less is preferable.

[0089] The sintering temperature when sintering the first conductive paste 6 should be a temperature at which at least a portion of the first conductive paste 6 melts, and is particularly preferably a temperature at which the eutectic powder 11 contained in the first conductive paste 6 melts, and is below the melting point of the inorganic filler 14. The sintering temperature when sintering the first conductive paste 6 is preferably 700°C or more and 1,200°C or less, more preferably 720°C or more and 1,000°C or less, and even more preferably 750°C or more and 900°C or less.

[0090] There are no particular restrictions on the sintering time when sintering the first conductive paste 6, but it is preferably 5 minutes or more and 90 minutes or less, more preferably 10 minutes or more and 60 minutes or less, and even more preferably 15 minutes or more and 30 minutes or less.

[0091] The first conductive member 7a, prepared using the first conductive paste 6, includes, for example, a metal 15, a metal compound 16, and an inorganic filler 14. The solvent 13 is removed by evaporation when the first conductive paste 6 is sintered.

[0092] The first conductive member 7a preferably contains, for example, when the total content of metal 15, metal compound 16, and inorganic filler 14 is 100% by mass, the metal 15 is preferably 40% to 95% by mass, the metal compound 16 is preferably 1% to 10% by mass, and the inorganic filler 14 is preferably 5% to 50% by mass. The first conductive member 7a can reduce volume shrinkage by containing inorganic filler 14 in a predetermined proportion. Furthermore, the first conductive member 7a can disperse the inorganic filler 14 in continuous metal 15 by containing metal 15 in a predetermined proportion.

[0093] The metal 15 is a metal component that, together with the inorganic filler 14, forms the core of the first conductive member 7a. The metal 15 is arranged in a state in which the inorganic filler 14 is dispersed.

[0094] During sintering S5, the eutectic powder 11 in the first conductive paste 6 is sintered to become metal 15. Therefore, the type of metal in the eutectic powder 11 can be identified from the type of metal in metal 15. Examples include silver, copper, silver-copper eutectic alloy, copper-zinc eutectic alloy, and copper-tin eutectic alloy. Among these, silver and copper are preferred for metal 15 due to their good thermal and electrical conductivity.

[0095] In the first conductive member 7a, the inorganic filler 14 is arranged in a dispersed state with multiple particles. Here, "multiple inorganic fillers 14" indicates that the inorganic filler 14 consists of multiple particles, not just one particle.

[0096] Furthermore, the inorganic filler 14 has a thickness of 100 μm in the cross-sectional view in the thickness direction of the ceramic substrate 100 of the first conductive member 7a. 2 Per inch, 10 μm2 More than 75μm 2 It is preferable that they be arranged within the following range.

[0097] The metal compound 16 is formed by sintering the activated metal powder 12. By sintering the first conductive paste 6, a reaction layer of the inorganic filler 14 and the activated metal powder 12 is formed on the surface of the inorganic filler 14. The metal compound 16 is mainly disposed on at least a part or all of the surface of the inorganic filler 14 and on at least a part of the inner wall of the through hole 2 in the ceramic plate 1. The metal compound 16 consists of a filler surface metal compound 16a disposed on the surface of the inorganic filler 14 and a nitride film 16b disposed on at least a part of the inner wall of the through hole 2 in the ceramic plate 1. Preferably, the filler surface metal compound 16a and the nitride film 16b are disposed as reactants by sintering the activated metal powder 12 and the components of the inorganic filler 14 and the inner wall of the through hole 2 in the ceramic plate 1.

[0098] The filler surface metal compound 16a is a metal compound 16, and is arranged to cover at least a part or all of the surface of the inorganic filler 14. For example, if the inorganic filler 14 is AlN or Si3N4, the filler surface metal compound 16a reacts with TiH2 in the active metal powder 12 before sintering to form TiN on the surface of the inorganic filler 14. The filler surface metal compound 16a then forms a continuous, jagged pattern of irregularities on its surface, and the surface of the inorganic filler 14 also forms a jagged pattern of irregularities. The inorganic filler 14 with the filler surface metal compound 16a on its surface is then dispersed within the continuous first conductive member 7a.

[0099] The nitride film 16b is disposed as a metal compound 16 on at least a portion of the inner wall of the through-hole 2 in the ceramic plate 1. For example, if the ceramic plate 1 is at least one selected from silicon nitride, aluminum nitride, and boron nitride, and the active metal powder 12 before sintering is, for example, TiH2, the nitride film 16b generates the reactant TiN and is formed as a compound on the inner wall of the through-hole 2 in the ceramic plate 1. The nitride film 16b creates a continuous jagged pattern of irregularities on the inner wall of the through-hole 2 in the ceramic plate 1, improving the connection strength between the inner wall of the through-hole 2 in the ceramic plate 1 and the first conductive member 7a.

[0100] The manufacturing method for the ceramic substrate according to the first embodiment can suppress the occurrence of cracks on the second surface 100b of the ceramic substrate 100 by removing the damage layer 5 by contacting it S2. In addition, by blasting it S3, the area around the second opening 4 of the through hole 2 on the second surface 1b of the ceramic plate 1 becomes tapered in cross-sectional view, with the opening diameter decreasing from the second surface 1b side toward the thickness direction of the ceramic plate 1. This makes it easier to distribute stress on the ceramic substrate 100, and further suppresses the occurrence of cracks on the second surface 100b of the ceramic substrate 100. By reducing the occurrence of cracks, the adhesion between the first conductive member 7a and the ceramic plate 1 can be improved, and the reliability of conductivity can be increased.

[0101] <Second Embodiment> The method for manufacturing a ceramic substrate according to the second embodiment differs from the method for manufacturing a ceramic substrate according to the first embodiment in that, in contact S2, the etching solution contains an acidic solution as a pH adjusting agent. In this case, the etching solution does not contain an alkaline solution.

[0102] Examples of etching solutions containing an acidic solution include etching solutions containing one or more pH adjusting agents selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, citric acid, and acetic acid.

[0103] The concentration of the pH adjusting agent contained in the etching solution containing the acidic solution is not particularly limited as long as it can remove the damaged layer 5, and can be appropriately selected according to the purpose, but it is preferably 8.0 mol / L or higher, and more preferably 10.0 mol / L or higher. When the concentration of the pH adjusting agent contained in the etching solution containing the acidic solution is 8.0 mol / L or higher, the inner surface defining the through-holes 2 of the ceramic plate 1 can be efficiently etched, and the damaged layer 5 can be removed.

[0104] In contact S2, the temperature at which the etching solution containing the acidic solution is brought into contact with the inner surface defining the through-holes 2 of the ceramic plate 1 is not particularly limited as long as the damaged layer 5 can be removed, and can be appropriately selected according to the purpose, but it is preferably less than 100°C, and more preferably between 20°C and 80°C. If the temperature at which the etching solution containing the acidic solution is brought into contact with the inner surface defining the through-holes 2 of the ceramic plate 1 is less than 100°C, it is possible to prevent the etching solution containing the acidic solution from boiling. Also, if the temperature at which the etching solution containing the acidic solution is brought into contact with the inner surface defining the through-holes 2 of the ceramic plate 1 is 20°C or higher, the inner surface defining the through-holes 2 of the ceramic plate 1 can be etched efficiently.

[0105] In contact S2, the contact time between the etching solution containing the acidic solution and the inner surface defining the through-hole 2 of the ceramic plate 1 is not particularly limited as long as the damage layer 5 can be removed, and can be appropriately selected according to the purpose, but 5 minutes or more and 90 minutes or less is preferred, and 10 minutes or more and 60 minutes or less is more preferred. If the contact time between the etching solution containing the acidic solution and the inner surface defining the through-hole 2 of the ceramic plate 1 is 5 minutes or more, the inner surface defining the through-hole 2 of the ceramic plate 1 can be efficiently etched. Also, if the contact time between the etching solution containing the acidic solution and the inner surface defining the through-hole 2 of the ceramic plate 1 is 60 minutes or less, it is easier to adjust the opening diameter and shape of the through-hole 2 to the desired size, and it is possible to prevent the thickness of the ceramic plate 1 from being reduced by etching.

[0106] <Third Embodiment> The method for manufacturing a ceramic substrate according to the third embodiment differs from the method for manufacturing a ceramic substrate according to the first embodiment in that the first conductive paste 6 used in placing the first conductive paste S4 further contains at least one powder 17 selected from the group consisting of copper powder, silver powder, silver-copper alloy powder, and ceramic powder.

[0107] Furthermore, the step S4 of placing the first conductive paste in the ceramic substrate manufacturing method according to the third embodiment can also be applied to the step S4 of placing the first conductive paste in the ceramic substrate manufacturing method according to the second embodiment.

[0108] The content of at least one powder 17 selected from the group consisting of copper powder, silver powder, silver-copper alloy powder, and ceramic powder in the first conductive paste 6 is not particularly limited as long as it does not impair the effects of this disclosure. However, it is preferable that the content is 5% by mass or more and 20% by mass or less when the total amount of eutectic powder 11, activated metal powder 12, inorganic filler 14, and powder 17 is 100% by mass.

[0109] Copper powder, silver powder, and silver-copper alloy powder have superior conductivity compared to the silver-copper eutectic powder 11. Furthermore, since copper powder has a melting point of 1,084°C and silver powder has a melting point of 962°C, they are less likely to melt in the first conductive paste 6 during sintering in S5 and can remain dispersed as powder in the first conductive member 7a. This further improves the conductivity of the ceramic substrate 100.

[0110] Furthermore, because the ceramic powder also has a high melting point, it is difficult for it to melt into the first conductive paste 6 during sintering in S5, and it can remain dispersed as powder in the first conductive member 7a. This reduces the difference in the coefficient of thermal expansion between the ceramic plate 1 and the first conductive member 7a, further improving the reliability of the ceramic substrate 100.

[0111] <Fourth Embodiment> The method for manufacturing a ceramic substrate according to the fourth embodiment differs from the method for manufacturing a ceramic substrate according to the first embodiment in that, in the blasting process S3, the through-hole 2 is blasted from the first surface 1a side.

[0112] Furthermore, the blasting process S3 in the method for manufacturing a ceramic substrate according to the fourth embodiment can also be applied to the blasting process S3 in the method for manufacturing a ceramic substrate according to the second embodiment and the method for manufacturing a ceramic substrate according to the third embodiment.

[0113] Figure 7A is a schematic cross-sectional view showing an example of blast treatment in the manufacturing method of a ceramic substrate according to the fourth embodiment. Figure 7B is a schematic cross-sectional view showing the size of each part in Figure 7A.

[0114] In the method for manufacturing a ceramic substrate according to the fourth embodiment, in blast treatment S3, abrasive 10 is applied from the second surface 1b side and the first surface 1a side, and the second surface 1b, the first surface 1a, and the through hole 2 are blasted. As a result, the ceramic plate 1 defining the second opening 4 of the through hole 2 formed in the second surface 1b is abraded, and the ceramic plate 1 defining the first opening 3 of the through hole 2 formed in the first surface 1a is also abraded. In addition, the inner surfaces of the second surface 1b, the first surface 1a, and the through hole 2 become rough.

[0115] In the method for manufacturing a ceramic substrate according to the fourth embodiment, when the maximum diameter of the first opening 3 of the through hole 2 formed in the first surface 1a is A2, the maximum diameter of the second opening 4 of the through hole 2 formed in the second surface 1b is B2, and the average length between the first surface 1a and the second surface 1b is L, when the maximum diameter of the through hole 2 in a cross section at a position L / 4 from the first surface 1a, i.e., position L1, in a direction substantially perpendicular to the thickness direction of the ceramic plate 1 is C1, when the maximum diameter of the through hole 2 in a cross section at a position L / 2 from the first surface 1a, i.e., position L2, in a direction substantially perpendicular to the thickness direction of the ceramic plate 1 is C2, and when the maximum diameter of the through hole 2 in a cross section at a position 3L / 4 from the first surface 1a, i.e., position L3, in a direction substantially perpendicular to the thickness direction of the ceramic plate 1 is C3, the following conditions are met: C1>C2>C3, A2>B2, A2>C1, and B2>C3.

[0116] Preferably, the area near the first opening 3 of the through hole 2 on the first surface 1a has a tapered shape in cross-sectional view such that the opening diameter decreases from the first surface 1a side toward the thickness direction of the ceramic plate 1.

[0117] The method for manufacturing a ceramic substrate according to the fourth embodiment can suppress the occurrence of cracks on both the first surface 100a and the second surface 100b of the ceramic substrate 100. In addition, by performing blast treatment S3, the area near the first opening 3 on the first surface 1a of the ceramic plate 1 and the area near the second opening 4 of the through hole 2 on the second surface 1b of the ceramic plate 1 take on a tapered shape in cross-sectional view, such that the opening diameter decreases toward the thickness direction of the ceramic plate 1 from the first surface 1a side and the second surface 1b side, respectively. This makes it easier to distribute stress on the ceramic substrate 100, and further suppresses the occurrence of cracks on the first surface 100a and the second surface 100b of the ceramic substrate 100.

[0118] <Fifth Embodiment> The method for manufacturing a ceramic substrate according to the fifth embodiment differs from the method for manufacturing a ceramic substrate according to the first embodiment or the method for manufacturing a ceramic substrate according to the second embodiment in that, in the step of preparing the ceramic plate 1 in S1, instead of using a commercially available ceramic plate 1, the method is changed to preparing a ceramic plate 1 that does not have through holes 2 by processing the through holes 2 in the following way, such that the maximum diameter B1 of the second opening 4 of the through hole formed on the second surface 1b is less than 0.90 times the maximum diameter A1 of the first opening 3 of the through hole 2 formed on the first surface 1a. The changes to the contact step S22 that accompany the change to preparation step S21 will also be explained below.

[0119] Furthermore, the preparation step S21 in the method for manufacturing a ceramic substrate according to the fifth embodiment may be a modification of the preparation step S1 in the method for manufacturing a ceramic substrate according to the third embodiment and the method for manufacturing a ceramic substrate according to the fourth embodiment.

[0120] Figure 8 is a flowchart showing an example of preparing a ceramic plate according to the manufacturing method of a ceramic substrate according to the fifth embodiment.

[0121] (S21) Preparations (S21-1) Prepare a ceramic plate that does not have through holes. Figure 9 is a schematic cross-sectional view showing an example of preparing a ceramic plate without through holes in a method for manufacturing a ceramic substrate according to the fifth embodiment.

[0122] In preparing the ceramic plate S21, a ceramic plate 1 having a first surface 1a and a second surface 1b opposite to the first surface 1a is prepared. The ceramic plate 1 in preparing the ceramic plate S21 is the same as the ceramic plate 1 in the manufacturing method of the ceramic substrate according to the first embodiment or the manufacturing method of the ceramic substrate according to the second embodiment, except that it does not have through holes 2.

[0123] (S21-2) Forming through holes Figure 10 is a schematic cross-sectional view showing an example of forming through holes in a ceramic substrate manufacturing method according to the fifth embodiment. Figure 10B is a schematic top view of the ceramic plate shown in Figure 10A. Figure 10C is a schematic bottom view of the ceramic plate shown in Figure 10A. Note that Figure 10A is a schematic cross-sectional view taken along the line XA-XA in Figures 10B and 10C.

[0124] In forming the through-hole S21-2, the through-hole 2 is formed in the ceramic plate 1 such that the maximum diameter B1 of the second opening 4 of the through-hole formed on the second surface 1b is less than 0.90 times the maximum diameter A1 of the first opening 3 of the through-hole 2 formed on the first surface 1a. There is no particular lower limit for the maximum diameter B1 of the second opening 4 of the through-hole formed on the second surface 1b relative to the maximum diameter A1 of the first opening 3 of the through-hole 2 formed on the first surface 1a of the ceramic plate 1, but it is preferably 0.5 times or more, and more preferably 0.6 times or more. This makes it possible to reduce the maximum diameter of the second opening 4. In addition, the angle between the inner surface defining the through-hole 2 and the second surface 1b in a cross-sectional view can be 45 degrees or more, preferably 60 degrees or more, and more preferably 75 degrees or more. This makes it possible to reduce the occurrence of cracks when forming the through-hole 2.

[0125] In forming through holes (S21-2), methods for forming through holes 2 of a predetermined shape in the ceramic plate 1 include irradiating with laser light Z and drilling. These may be used individually or in combination of two or more. Among these, the method of irradiating with laser light Z is preferred because it allows for the easy formation of small through holes 2 even when using a sintered ceramic plate 1.

[0126] In forming a through hole S21-2, when using a method of irradiating with laser light Z, the laser light Z is irradiated from the first surface 1a to the second surface 1b to form a through hole 2 in the ceramic plate 1. Specifically, by irradiating a predetermined area of ​​the first surface 1a of the ceramic plate 1 with laser light Z in the Z-axis direction and performing thermal processing, the ceramics on the first surface 1a of the ceramic plate 1 are removed mainly by melting and sublimation in the irradiated area that absorbed the irradiated laser light Z. As a result, a through hole 2 connecting the first surface 1a to the second surface 1b is formed.

[0127] The through-hole 2 may be formed by a single irradiation of laser light Z, or it may be formed by gradually removing the ceramics by irradiating with laser light Z multiple times, but it is preferable to irradiate the same location with laser light Z only once.

[0128] The laser beam Z is not particularly limited as long as it can form through holes 2 such that the maximum diameter B1 of the second opening 4 of the through hole formed on the second surface 1b is less than 0.90 times the maximum diameter A1 of the first opening 3 of the through hole formed on the first surface 1a of the ceramic plate 1. However, a laser beam Z capable of thermal processing is preferred, and a laser beam having an oscillation wavelength of 750 nm or more or an output of 200 W or more is more preferred.

[0129] There are no particular restrictions on the pulse width of the laser beam Z, but it is preferable to include a continuous wave (CW). A continuous wave is defined as a laser beam Z with a pulse width that is maximized during the pulse repetition period.

[0130] Specific examples of laser light Z include Nd:YAG laser light, Nd:YVO4 laser light, CO2 laser light, and high-power fiber laser light or disk laser light regardless of wavelength. These may be used individually or in combination of two or more types. Among these, fiber laser light is preferred as the laser light Z.

[0131] There are no particular restrictions on the atmospheric conditions when irradiating with laser light Z; for example, a vacuum atmosphere or an inert gas atmosphere can be used. Examples of inert gases include N2 and CO2. These may be used individually or in combination of two or more.

[0132] There are no particular restrictions on the pulse width, power output, and wavelength of the laser light Z. For example, processing can be performed using fiber laser light (wavelength: 1070 nm, power output: 1000 W, frequency: 100 Hz, irradiation time: 1.5 mm seconds). However, it is sufficient to form a through-hole 2 where the maximum diameter B1 of the second opening 4 of the through-hole 2 formed on the second surface 1b is less than 0.90 times the maximum diameter A1 of the first opening 3 of the through-hole 2 formed on the first surface 1a. The process is not limited to these conditions.

[0133] When a laser beam Z is irradiated onto the ceramic plate 1, irregularities are formed on the inner surface near the irradiated area of ​​the ceramic plate 1, that is, on the surface defining the through-hole 2, resulting in a roughened surface. The recesses on the inner surface defining the through-hole 2 have an irregular microstructure. In this disclosure, the irregular microstructure of the recesses on the inner surface defining the through-hole 2 may be referred to as, for example, dendritic or tree-like.

[0134] When using a ceramic plate 1 containing aluminum nitride as the main material, an aluminum layer 8 may precipitate continuously or fragmentarily on the inner surface defining the through-hole 2, i.e., the area irradiated by the laser beam Z on the ceramic plate 1. The aluminum layer 8 is formed in a state where it is embedded in the irregularities of the inner surface defining the through-hole 2. This is because, when the aluminum layer 8 is formed, the irradiation of the laser beam Z causes a rapid temperature rise in the aluminum nitride, resulting in a phase change in which a portion of the aluminum nitride melts and sublimes, causing ablation. In other words, the material constituting the ceramic plate 1 exists within the dendritic depressions on the lower surface of the aluminum layer 8. Thus, the lower surface of the aluminum layer 8 on the side where the ceramic plate 1 is placed contains both the material constituting the ceramic plate 1 and the precipitated aluminum.

[0135] When a ceramic plate 1 is irradiated with laser light Z, the heat generated by the irradiation of the laser light Z spreads not only to the irradiated area but also to the surrounding area. Therefore, the deposition of the aluminum layer 8 from the ceramic plate 1 occurs not only at the irradiated area of ​​the laser light Z but also in the surrounding area inside the ceramic plate 1 in the Z-axis direction from the irradiated area. At this time, the heat generated by the irradiation of the laser light Z that has spread to the surrounding area degrades the ceramic plate 1, and a damaged layer 5 is also formed. Thus, a damaged layer 5 is formed between the aluminum layer 8 and the ceramic plate 1.

[0136] (S22) Make contact In the contact step S22 of the ceramic substrate manufacturing method according to the fifth embodiment, the inner surface defining the through hole 2 of the ceramic plate 1 is brought into contact with the etching solution. At this time, the aluminum layer 8 disposed on the inner surface of the through hole 2 comes into contact with the etching solution, and the damaged layer 5 also comes into contact with the etching solution. As a result, the aluminum layer 8 and the damaged layer 5 are removed in the same manner as in the ceramic substrate manufacturing method according to the first embodiment or the ceramic substrate manufacturing method according to the second embodiment.

[0137] <<Aspects using an etching solution containing an alkaline solution>> Figure 11A is a schematic cross-sectional view showing an example of a case in which an etching solution containing an alkaline solution is used for contact in the manufacturing method of a ceramic substrate according to the fifth embodiment.

[0138] Here, when using an etching solution containing an alkaline solution, it is preferable to use an etching solution whose etching reaction rate with respect to aluminum nitride is faster than its etching reaction rate with respect to aluminum. An example of such an alkaline solution contained in an etching solution is the alkaline solution exemplified in the method for manufacturing a ceramic substrate according to the first embodiment.

[0139] When an etching solution containing an alkaline solution in which the etching reaction rate for aluminum nitride is faster than the etching reaction rate for aluminum is brought into contact with the laser-processed ceramic plate 1, the aluminum layer 8 inside the through hole 2 is difficult to etch, while the aluminum nitride, the main material of the ceramic plate, is easily etched. Therefore, the damage layer 5 around the first opening 3 and the damage layer 5 around the second opening 4 of the through hole 2 are the easiest to etch, and the ceramic plate 1 is gradually etched from the first opening 3 and the second opening 4. Consequently, the aluminum layer 8 is also removed from the first opening 3 side and the second opening 4 side along with the etching of the aluminum nitride of the ceramic plate 1. On the other hand, the inner surface of the through hole 2 is difficult to etch because the ceramic plate 1 is covered with the aluminum layer 8. As a result, during the etching reaction process, the ceramic plate 1 defining the first opening 3 of the through hole 2 is scraped away, and a tapered shape is formed such that the opening diameter decreases in the thickness direction of the ceramic plate 1 from the first surface 1a side before the blast treatment S23 is performed. Similarly, during the etching reaction process, the ceramic plate 1 defining the second opening 4 of the through hole 2 is shaved, and before the blast treatment S23 is performed, a tapered shape is formed such that the opening diameter decreases in the thickness direction of the ceramic plate 1 from the second surface 1b side.

[0140] Therefore, when using an etching solution containing an alkaline solution as the etching solution for the laser-processed ceramic plate 1, compared to the manufacturing method of the ceramic substrate according to the first embodiment, it is possible to more efficiently achieve a shape that satisfies C1>C2>C3, A2>B2, A2>C1, and B2>C3 during the blasting process S23.

[0141] <> Figure 11B is a schematic cross-sectional view showing an example of a case in which an etching solution containing an acidic solution is used for contact in the manufacturing method of a ceramic substrate according to the fifth embodiment.

[0142] When using an etching solution containing an acidic solution, it is preferable to use an etching solution whose etching reaction rate with respect to aluminum is faster than its etching reaction rate with respect to aluminum nitride. An example of such an acidic solution contained in an etching solution is the acidic solution exemplified in the method for manufacturing a ceramic substrate according to the second embodiment.

[0143] When an etching solution containing an acidic solution, whose etching reaction rate for aluminum is faster than that for aluminum nitride, is brought into contact with a laser-processed ceramic plate 1, the aluminum layer 8 inside the through-hole 2 is easily etched, while the aluminum nitride, the main material of the ceramic plate, is not easily etched. As a result, the aluminum layer 8 on the inner surface of the through-hole 2 and the etching solution containing the acidic solution react uniformly, removing both the aluminum layer 8 and the damaged layer 5.

[0144] When the ceramic plate 1 is irradiated with a laser L, burrs of the aluminum layer 8 may form on the first surface 1a of the ceramic plate 1 defining the first opening 3 and on the second surface 1b of the ceramic plate 1 defining the second opening 4. When these burrs come into contact with the etching solution containing an acidic solution, the ceramic plate 1 defining the first opening 3 and the ceramic plate 1 defining the second opening 4 are easily removed, and in the etching reaction process, the ceramic plate 1 defining the first opening 3 of the through hole 2 is scraped away, and a tapered shape may be formed such that the opening diameter decreases in the thickness direction of the ceramic plate 1 from the first surface 1a side before the blast treatment S23 is performed. Similarly, in the etching reaction process, the ceramic plate 1 defining the second opening 4 of the through hole 2 is scraped away, and a tapered shape may be formed such that the opening diameter decreases in the thickness direction of the ceramic plate 1 from the second surface 1b side before the blast treatment S23 is performed. However, the curve radius (R) of the tapered shape is gentler compared to when using an etching solution containing an alkaline solution.

[0145] The method for manufacturing a ceramic substrate according to the fifth embodiment includes processing through holes 2 in the ceramic plate 1, and therefore, compared to the method for manufacturing a ceramic substrate according to the first embodiment or the method for manufacturing a ceramic substrate according to the second embodiment, it is possible to increase the design freedom of the ceramic substrate. In particular, when a laser beam Z is used to process the through holes 2, it is easy to make the through holes 2 small in diameter, to accurately form the through holes 2 at a desired position, and furthermore, the size of the through holes 2 can be adjusted to a certain desired size.

[0146] <Sixth Embodiment> The method for manufacturing a ceramic substrate according to the sixth embodiment differs from the method for manufacturing a ceramic substrate according to the first embodiment in that, after placing the first conductive paste 6 and before sintering, it further includes S35, which involves placing the first coating member 18a on the first surface 1a, placing the second coating member 18b on the second surface 1b, and placing the second conductive paste 19 on the surface of the first conductive paste 6.

[0147] In the method for manufacturing a ceramic substrate according to the sixth embodiment, the first conductive paste 6 and the second conductive paste 19 may be sintered separately or simultaneously, but it is more efficient and preferable to sinter the first conductive paste 6 and the second conductive paste 19 simultaneously by sintering S36.

[0148] Furthermore, the step of placing the second conductive paste S35 in the method for manufacturing a ceramic substrate according to the sixth embodiment may further include placing the second conductive paste S35 in the method for manufacturing a ceramic substrate according to the second embodiment, the method for manufacturing a ceramic substrate according to the third embodiment, the method for manufacturing a ceramic substrate according to the fourth embodiment, and the method for manufacturing a ceramic substrate according to the fifth embodiment.

[0149] Figure 12 is a flowchart showing an example of preparing a ceramic plate in the manufacturing method of a ceramic substrate according to the sixth embodiment.

[0150] (S35) Place the second conductive paste. Figure 13A is a schematic cross-sectional view showing an example of arranging the first coating member and the second coating member in the method for manufacturing a ceramic substrate according to the sixth embodiment. Figure 13B is a schematic cross-sectional view showing an example of arranging the second conductive paste in the method for manufacturing a ceramic substrate according to the sixth embodiment.

[0151] Examples of the first covering member 18a and the second covering member 18b include a metal mask, a screen mask, and an insulating film (e.g., a resist). The first covering member 18a and the second covering member 18b may be the same or different. Among these, a metal mask is preferred.

[0152] When resist is used as the first coating member 18a and the second coating member 18b, the area and shape in which the second conductive paste 19 is to be placed is exposed and developed using photolithography or etching.

[0153] There are no particular restrictions on the method of arranging the second conductive paste 19. For example, the second conductive paste 19 can be placed on the surface of the first conductive paste 6 by filling the openings of the first covering member 18a and the second covering member 18b with the second conductive paste 19 by screen printing, metal mask printing, injection with a nozzle, etc.

[0154] Furthermore, the process of placing the second conductive paste S35 may be similar to the process of placing the first conductive paste S4, but after placing the second conductive paste 19 and before sintering, the second conductive paste 19 may be dried and the dried second conductive paste 19 may be pressurized.

[0155] There are no particular restrictions on the second conductive paste 19, and it can be appropriately selected from known conductive pastes. The composition of the second conductive paste 19 may be the same as that of the first conductive paste 6, or it may have a different composition. Among these, it is preferable to use the same second conductive paste 19 as the first conductive paste 6 containing the activated metal brazing material described in the first embodiment for manufacturing a ceramic substrate, and it is more preferable to use the same second conductive paste 19 as the first conductive paste 6 containing the activated metal brazing material described in the third embodiment for manufacturing a ceramic substrate, and at least one powder 17 selected from the group consisting of copper powder, silver powder, silver-copper alloy powder, and ceramic powder.

[0156] (S36) Sintering Figure 14 is a schematic cross-sectional view showing an example of sintering in the manufacturing method of a ceramic substrate according to the sixth embodiment.

[0157] In sintering S36, the first conductive paste 6 and the second conductive paste 19 are sintered. Sintering S36 yields a ceramic substrate 100 having a second surface 100b opposite to the first surface 100a, a through hole 2 connecting the first surface 100a and the second surface 100b, a first conductive member 7a with the first conductive paste 6 sintered into it, and a second conductive member 7b with the second conductive paste 19 sintered into it, with the first conductive member 7a on the first surface 100a and the second conductive member 7a on the second surface 100b being the surfaces of the first conductive member 7a.

[0158] In sintering S36, the sintering conditions, such as the sintering temperature and sintering time, can be the same as those used in sintering S5 in the manufacturing method of the ceramic substrate according to the first embodiment.

[0159] Furthermore, if the composition of the second conductive paste 19 is the same as that of the first conductive paste 6, the first conductive member 7a and the second conductive member 7b after sintering are not distinguishable. Also, even if the composition of the second conductive paste 19 is different from that of the first conductive paste 6, the first conductive member 7a and the second conductive member 7b after sintering will both function as conductive members. For this reason, the first conductive member 7a and the second conductive member 7b may collectively be referred to as "conductive member 7" below.

[0160] In the manufacturing method of the ceramic substrate according to the sixth embodiment, even if the volume of the first conductive member 7a shrinks due to sintering S36, the second conductive member 7b made of the second conductive paste 19 is in contact with the surface of the first conductive member 7a and is arranged convexly on the first surface 100a and the second surface 100b, so a decrease in dimensional accuracy can be prevented and the thickness of the conductive member 7 can be made to a sufficient thickness.

[0161] <Seventh Embodiment> The method for manufacturing a ceramic substrate according to the seventh embodiment differs from the method for manufacturing a ceramic substrate according to the sixth embodiment in that, after sintering, it further includes polishing or grinding the first coating member 18a, the second coating member 18b, and the conductive member 7 so that the first surface 1a and the second surface 1b of the ceramic plate 1 in the portion covered by the first coating member 18a, the second coating member 18b, and the conductive member 7 formed by sintering the first conductive paste 6 and the second conductive paste 19 are exposed.

[0162] Figure 15 is a flowchart showing an example of preparing a ceramic plate in the manufacturing method of a ceramic substrate according to the seventh embodiment.

[0163] (S47) Polishing or grinding Figure 16A is a schematic cross-sectional view showing an example of polishing or grinding in the method for manufacturing a ceramic substrate according to the seventh embodiment. Figure 16B is a schematic cross-sectional view showing an example of a ceramic substrate after polishing or grinding in the method for manufacturing a ceramic substrate according to the seventh embodiment. Figure 16C is a schematic cross-sectional view showing another example of a ceramic substrate after polishing or grinding in the method for manufacturing a ceramic substrate according to the seventh embodiment, in the method for manufacturing a ceramic substrate according to the fourth embodiment.

[0164] The first coating member 18a and the second coating member 18b can be removed by polishing or grinding in S47.

[0165] In polishing or grinding S47, the ceramic plate 1 is polished or ground so that the first surface 1a and the second surface 1b are exposed. This polishing or grinding may be done to remove only the first coating member 18a and the second coating member 18b, or a portion of the first surface 1a and the second surface 1b may be polished or ground. For example, the first surface 1a and the second surface 1b may be polished or ground with an XVIB-XVIB wire. This makes the first surface 100a and the second surface 100b of the ceramic substrate 100 smoother, and when the ceramic substrate 100 is used in a light-emitting device, the light-emitting elements can be arranged more favorably.

[0166] Furthermore, polishing or grinding in S47 allows for adjustment of the area of ​​the conductive member 7 exposed on the first surface 100a and the second surface 100b. Since the conductive member 7 has a cross-sectional shape of the through hole 2 formed by blasting in S43, the conductive member 7 has a tapered shape in cross-section such that the opening diameter decreases from the second surface 1b side toward the thickness direction of the ceramic plate 1. When polishing or grinding is performed from the second surface 1b side, the area of ​​the conductive member 7 exposed on the second surface 1b gradually decreases.

[0167] In polishing or grinding S47, in order not to impair the effects of the present disclosure, after polishing or grinding S47, the first surface 1a and the second surface 1b are polished or ground such that C1>C2>C3, A2>C1, and B2>C3 are satisfied.

[0168] The relationship between A2 and B2 may change depending on the position where polishing or grinding is performed in polishing or grinding S47, that is, where the XVIB-XVIB line is set in the thickness direction (Z-axis direction) of the ceramic substrate 100. If only the second surface 1b side is blasted, A2 <B2となることがある。

[0169] In the manufacturing method of the ceramic substrate according to the seventh embodiment, peeling S4 is performed by polishing or grinding, so when the ceramic substrate 100 is used in a light-emitting device, the light-emitting elements can be more suitably arranged on the first surface 100a of the ceramic substrate 100.

[0170] [Ceramic substrate] <Eighth Embodiment> Figure 17A is a schematic cross-sectional view showing an example of a ceramic substrate according to the eighth embodiment. Figure 17B is a schematic top view of the ceramic substrate of Figure 17A. Figure 17C is a schematic cross-sectional view of the ceramic substrate of Figure 17A at position L1, in a direction substantially perpendicular to the thickness direction of the ceramic substrate. Figure 17D is a schematic cross-sectional view of the ceramic substrate of Figure 17A at position L2, in a direction substantially perpendicular to the thickness direction of the ceramic substrate. Figure 17E is a schematic cross-sectional view of the ceramic substrate of Figure 17A at position L3, in a direction substantially perpendicular to the thickness direction of the ceramic substrate. Figure 17F is a schematic cross-sectional view of the ceramic substrate of Figure 17A at the position between the first surface of the ceramic substrate and position L3, in a direction substantially perpendicular to the thickness direction of the ceramic substrate, at the position where the maximum diameter of the through-hole in the cross-section in a direction substantially perpendicular to the thickness direction of the ceramic substrate is smallest. Figure 17G is a schematic bottom view of the ceramic substrate of Figure 17A. Note that Figure 17A is a schematic cross-sectional view taken along the line XVIIA-XVIIA from Figures 17B to 17G. Figure 17H ​​is an enlarged view of region XVIIH in Figure 17A.

[0171] The ceramic substrate 100 according to the eighth embodiment is a ceramic plate 1 having a first surface 100a and a second surface 100b opposite to the first surface 100a, and a through hole 2 connecting the first surface 100a and the second surface 100b, and a conductive member 7 disposed inside the through hole 2, wherein the maximum diameter of the first opening 3 of the through hole 2 formed in the first surface 100a is A2, the maximum diameter of the second opening 4 of the through hole 2 formed in the second surface 100b is B2, and the average length between the first surface 100a and the second surface 100b is L. When the maximum diameter of the through-hole 2 in a cross-section in a direction substantially perpendicular to the thickness direction of the ceramic substrate 100 at a position L / 4 from the first surface 100a is C1, the maximum diameter of the through-hole 2 in a cross-section in a direction substantially perpendicular to the thickness direction of the ceramic substrate 100 at a position L / 2 from the first surface 100a is C2, and the maximum diameter of the through-hole 2 in a cross-section in a direction substantially perpendicular to the thickness direction of the ceramic substrate 100 at a position 3L / 4 from the first surface 100a is C3, then C1>C2>C3, A2>C1, and B2>C3 are satisfied. The ceramic substrate 100 may further have other configurations as needed. The ceramic substrate 100 can be used by appropriately referring to the configuration of the manufacturing method of the ceramic substrate 100 according to the first embodiment described above.

[0172] The maximum diameter A2 is preferably 120 μm to 300 μm, and more preferably 120 μm to 180 μm. The maximum diameter B2 can also be approximately the same size as the maximum diameter A2. "Approximately the same" means that the maximum diameter B2 is 0.9 times to 1.1 times the maximum diameter A2. This makes it possible to make the surface area of ​​the first opening 3 and the second opening 4 approximately the same, which simplifies the design of mounting the light-emitting element, etc. On the other hand, even if the surface area of ​​the first opening 3 and the second opening 4 is approximately the same, a constriction occurs on the side of the conductive member 7, which prevents the conductive member 7 from falling out of the ceramic plate 1.

[0173] There are no particular restrictions on the average length L between the first surface 100a and the second surface 100b, and it can be appropriately selected according to the purpose, but it is preferably 200 μm or more and 600 μm or less, and more preferably 300 μm or more and 500 μm or less.

[0174] C4 is defined as the maximum diameter of the through-hole 2 in a cross-section in a direction substantially perpendicular to the thickness direction of the ceramic substrate 100, between the first surface 100a and position L3, at which point the maximum diameter of the through-hole 2 is smallest. The average length L is preferably 2.5 times or more, and more preferably 3 times or more, than C4.

[0175] Preferably, in a cross-sectional view of the ceramic substrate 100 in the thickness direction, the internal angle R1 between the second surface 1b extending from the second surface 1b to the through hole 2 and the imaginary line V1 that passes through the point of contact M1 between the second surface 1b and the inner surface defining the through hole 2, and extends the inner surface defining the through hole 2 from the second surface 1b, is less than 90 degrees. Also, in a cross-sectional view of the ceramic substrate 100 in the thickness direction, the external angle R2 on the opposite side of the inner surface of the through hole 2 at the intersection of the imaginary line V2 passing through L2 and L3 and the imaginary line V1 is greater than 90 degrees. By satisfying these internal and external angles R1 and R2, the area near the second opening 4 of the through hole 2 on the second surface 1b has a tapered shape in a cross-sectional view such that the opening diameter decreases from the second surface 1b side toward the thickness direction of the ceramic substrate 100.

[0176] When there are multiple through holes 2, there are no particular restrictions on the arrangement of the multiple through holes 2 in a plan view of the ceramic substrate 100, or the pitch between one through hole 2 and other adjacent through holes 2, and these can be appropriately selected according to the purpose. However, since the maximum diameter B2 of the second opening 4 is between 0.90 and 1.1 times the maximum diameter A2 of the first opening 3, the pitch between a through hole 2 formed on the first surface 100a and other adjacent through holes 2 can be made approximately equal to the pitch between a through hole 2 formed on the second surface 100b and other adjacent through holes 2. As a result, the distance between adjacent through holes 2 in the ceramic substrate 100 can be kept constant, and the design of the ceramic substrate 100 has a high degree of freedom.

[0177] <Ninth Embodiment> Figure 18A is a schematic cross-sectional view showing an example of a ceramic substrate according to the ninth embodiment. Figure 18B is an enlarged view of region XVIIIB in Figure 18A.

[0178] The ceramic substrate 100 according to the ninth embodiment differs from the ceramic substrate 100 according to the first embodiment in that, in cross-sectional view, the shape of the conductive member 7 is tapered such that the length in the X-axis direction (the length of the conductive member 7 in a direction perpendicular to the thickness direction of the ceramic substrate 100 or the width of the conductive member 7 in cross-sectional view) decreases from the first surface 100a side toward the thickness direction of the ceramic substrate 100.

[0179] Preferably, in a cross-sectional view of the ceramic substrate 100 in the thickness direction, the internal angle R3 between the imaginary line V3, which passes through the point of contact M2 between the first surface 100a and the inner surface defining the through-hole 2 and extends from the first surface 100a along the inner surface defining the through-hole 2, is less than 90 degrees. Also, in a cross-sectional view of the ceramic substrate 100 in the thickness direction, the external angle R4 on the opposite side of the inner surface of the through-hole 2 at the intersection of the imaginary line V4, which passes through L2 and L1, and the imaginary line V3, is greater than 90 degrees. By satisfying these internal angle R3 and external angle R4, the area near the first opening 3 of the through-hole 2 on the first surface 100a has a tapered shape in a cross-sectional view such that the opening diameter decreases from the first surface 100a side toward the thickness direction of the ceramic plate 1.

[0180] [Light-emitting device] Figure 19 is a schematic cross-sectional view showing an example of a light-emitting device according to the embodiment. The various components of the light-emitting device 200 will be described below.

[0181] The light-emitting device 200 according to the embodiment includes a ceramic substrate 100 according to the embodiment, and a light-emitting element 202 having an electrode 205 disposed on the ceramic substrate 100.

[0182] The light-emitting device 200 is a device that emits light by arranging light-emitting elements 202 on a ceramic substrate 100. The number of light-emitting elements 202 may be one or multiple. Furthermore, if there are multiple light-emitting elements 202, there are no particular restrictions on their arrangement; for example, they may be arranged in a row.

[0183] The light-emitting device 200, as an example, includes a light-transmitting member 203 that covers the light-extracting surface of the light-emitting element 202, a light-reflecting member 204 that covers the side surface of the light-emitting element 202 and the first surface 100a of the ceramic substrate 100, and a metal bump 206 that electrically connects the light-emitting element 202 and the conductive member 7 of the ceramic substrate 100.

[0184] While various wiring patterns can be formed on the ceramic substrate 100 depending on the application, in the light-emitting device 200 according to this embodiment, the light-emitting element 202 has a pair of electrodes 205 on the same side, and is face-down mounted with the side having the electrodes 205 facing the first surface 100a of the ceramic substrate 100.

[0185] In addition, the light-emitting device 200 according to this embodiment may be a face-up mounting in which the pair of electrodes 205 of the light-emitting element 202 are placed on the side opposite to the surface in contact with the ceramic substrate 100 and connected to the conductive member 7 of the ceramic substrate 100 by wire.

[0186] (Light-emitting element 202) The light-emitting element 202 includes a pair of electrodes 205, a semiconductor laminate 207, and an element substrate 208.

[0187] As an example, the light-emitting element 202 includes a semiconductor laminate 207 on the bottom side of the element substrate 208, and has a pair of electrodes 205 on the semiconductor laminate 207 side.

[0188] The semiconductor laminate 207 can be any composition depending on the desired emission wavelength, for example, a nitride semiconductor (In) capable of emitting blue or green light. x Al y Ga 1-x-y N, 0≦X, 0≦Y, X+Y≦1) or GaP, or GaAlAs or AlInGaP capable of emitting red light can be used. These may be used individually or in combination of two or more. The size and shape of the light-emitting element 202 can be appropriately selected depending on the purpose of use.

[0189] The element substrate 208 may, for example, be a sapphire substrate or a silicon substrate.

[0190] The electrode 205 is connected to the conductive member 7 of the ceramic substrate 100 via the bonding member 209 by the metal bump 206. One of the electrodes 205 is a p-electrode, and is arranged while maintaining a distance that does not cause an electrical short circuit with the other n-electrode. As an example, the electrode 205 has a configuration in which one p-electrode and one n-electrode are arranged respectively, but a configuration in which one of them is arranged at two positions and the other is arranged at one position may also be adopted.

[0191] (Translucent member 203) The translucent member 203 is arranged on the plane side that serves as the light extraction surface of the element substrate 208. The translucent member 203 is made of, for example, a translucent resin material, and an epoxy resin, a silicone resin, or a resin obtained by mixing these can be used. The translucent member 203 may contain a phosphor. For example, by containing a phosphor that absorbs blue light from the light-emitting element 202 and emits yellow light, white light can be emitted. Further, the translucent member 203 may contain a plurality of types of phosphors. For example, it can also emit white light from the light-emitting element 202 by including a phosphor that absorbs blue light from the semiconductor laminate 207 and emits green light, and a phosphor that emits red light.

[0192] As the phosphor to be contained in the translucent member 203, those that can be excited by the light emitted from the light-emitting element 202 are used. For example, one of the specific examples shown below can be used alone, or two or more can be used in combination. Specific examples of phosphors excitable by a blue light-emitting element or an ultraviolet light-emitting element include cerium-activated yttrium-aluminum-garnet phosphors (e.g., Y3(Al,Ga)5O 12 :Ce), cerium-activated lutetium-aluminum-garnet phosphors (e.g., Lu3(Al,Ga)5O 12 :Ce), europium and / or chromium activated nitrogen-containing calcium aluminosilicate phosphors (e.g., CaO-Al2O3-SiO2:Eu), terbium-aluminum-garnet phosphors (e.g., Tb3(Al,Ga)5O 12:Ce), silicate phosphors activated with europium (for example, (Sr,Ba)2SiO4:Eu), β-sialon phosphors (for example, Si 6-z Al z O z N 8-z :Eu (0<Z<4.2), α-sialon phosphors (for example, Mz(Si,Al) 12 (O,N) 16 (where 0<z≦2, and M is Li, Mg, Ca, Y and lanthanide elements excluding La and Ce)), nitride phosphors such as CASN phosphors (for example, CaAlSiN3:Eu), SCASN phosphors (for example, (Sr,Ca)AlSiN3:Eu), potassium fluorosilicate phosphors activated with manganese (for example, K2SiF6:Mn, K2(Si,Al)F6:Mn, 3.5MgO·0.5MgF2·GeO2:Mn), sulfide phosphors, quantum dot phosphors (for example, perovskite, chalcopyrite), and the like. By combining these phosphors with a blue light-emitting element or an ultraviolet light-emitting element, light-emitting devices of various colors (for example, white-based light-emitting devices) can be manufactured. When a light-emitting device capable of emitting white light is provided, the color is adjusted to be white depending on the type and concentration of the phosphor contained in the translucent member 203. When such a phosphor is contained in the translucent member 203, the concentration of the phosphor is preferably about 5% or more and 50% or less.

[0193] (Metal bump 206) Metal bump 206 is a member that electrically connects the electrode 205 and the conductive member 7. The metal bump 206 may be disposed either on the electrode 205 side or on the conductive member 7 side. Furthermore, the shape, size, and number of the metal bumps 206 can all be appropriately set as long as they can be arranged within the range of the electrode 205. In addition, the size of the metal bump 206 can be appropriately adjusted according to the size of the semiconductor laminate 207, the required light emission output of the light-emitting element, etc. For example, the diameter may be about several tens of μm to several hundreds of μm.

[0194] The metal bump 206 can be formed from, for example, Au, Ag, Cu, Al, Sn, Pt, Zn, Ni, or alloys thereof. The metal bump 206 can be formed from, for example, stud bumps known in the art. Stud bumps can be formed from stud bump bonders, wire bonding equipment, etc. Alternatively, the metal bump 206 may be formed from, for example, electroplating, electroless plating, vapor deposition, sputtering, or other methods known in the art.

[0195] As an example, the metal bumps 206 are joined here via a joining member 209. Examples of the joining member 209 used here include solders such as tin-bismuth, tin-copper, tin-silver, and gold-tin; eutectic alloys such as alloys mainly composed of Au and Sn, alloys mainly composed of Au and Si, and alloys mainly composed of Au and Ge; paste materials such as silver, gold, and palladium; anisotropic conductive materials such as ACP and ACF; brazing materials of low-melting-point metals; conductive adhesives and conductive composite adhesives that combine these materials.

[0196] (Light-reflecting member 204) The light-reflecting member 204 is a member that has light-reflecting properties. The light-reflecting member 204 is positioned to cover the first surface 100a of the ceramic substrate 100 and to cover the side surface of the light-emitting element 202. Furthermore, the light-reflecting member 204 is positioned to expose the light extraction surface of the light-emitting element 202 and is positioned to be coplanar with the light-reflecting member 204 of the light-emitting element 202. As an example, the light-reflecting member 204 is also positioned between the lower surface of the light-emitting element 202 and the first surface 100a of the ceramic substrate 100.

[0197] The light-reflecting member 204 preferably has a high reflectivity in order to effectively utilize the light from the light-emitting element 202. The light-reflecting member 204 is preferably white. The reflectivity of the light-reflecting member 204 is preferably 90% or more, and more preferably 94% or more, at the wavelength of light emitted by the light-emitting element 202.

[0198] The light-reflecting member 204 can be made of a thermoplastic resin such as acrylic resin, polycarbonate resin, cyclic polyolefin resin, polyethylene terephthalate resin, polyethylene naphthalate resin, or polyester resin, or a thermosetting resin such as epoxy resin or silicone resin. As a light-diffusing material, known materials such as titanium dioxide, silicon dioxide, aluminum oxide, zinc oxide, or glass can be used.

[0199] The light-emitting device 200 uses one light-emitting element 202 as a unit for controlling brightness and on / off states, but the number of light-emitting elements 202 included in one unit may be one or multiple. For example, one unit can consist of four light-emitting elements 202 arranged in 1 row and 4 columns or 2 rows and 2 columns, or nine light-emitting elements 202 arranged in 3 rows and 3 columns, and the number of light-emitting elements 202 is not limited.

[0200] In the light-emitting device according to the embodiment of this disclosure, the ceramic substrate 100 satisfies the condition A2 > B2 between the maximum diameter A2 of the first opening 3 of the through hole 2 formed on the first surface 100a and the maximum diameter B2 of the second opening 4 of the through hole 2 formed on the second surface 100b. Conductive material 7 is filled into the through hole 2. Therefore, the exposed portions of the conductive material 7 on the first surface 100a and the second surface 100b of the ceramic substrate 100 also satisfy the condition A2 > B2. As a result, when a light-emitting element is mounted on the first surface 100a, the distance between terminals on the second surface 100b can be increased, thereby suppressing the occurrence of short circuits in commonly used solder connections.

[0201] <Application examples of light-emitting devices> Figure 20A is a perspective view showing an application example of the light-emitting device according to the embodiment. Figure 20B is a cross-sectional view taken along the line XXB-XXB in Figure 20A. Note that Figure 20B omits some of the components of Figure 20A.

[0202] The light-emitting device 200 may be arranged in a row in a light-emitting module 300 (11 in Figure 20A), or 11 light-emitting devices 200 may be mounted on a single ceramic substrate 100. The configuration when it is a light-emitting module 300 will be described below.

[0203] The light-emitting module 300 comprises 11 light-emitting devices 200 in a row, with light-reflecting members 204 on the outer circumference of the light-emitting devices 200, a frame 301 on the outside of the light-reflecting members 204, and a module substrate 302 connected to the side of the ceramic substrate 100 opposite to the first surface 100a.

[0204] The frame 301 is a member that surrounds the light-reflecting members 204 that cover the multiple light-emitting devices 200. The frame 301 is formed in a rectangular ring shape, for example, which is rectangular in plan view, and is arranged to surround the light-reflecting members 204.

[0205] The frame 301 can be formed using a frame-shaped member made of metal, alloy, or ceramic. Examples of metals include Fe, Cu, Ni, Al, Ag, Au, Al, Pt, Ti, W, and Pd. Examples of alloys include alloys containing at least one selected from the group consisting of Fe, Cu, Ni, Al, Ag, Au, Al, Pt, Ti, W, and Pd.

[0206] Furthermore, a resin material may be used for the frame 301. In this case, the metal, alloy, or ceramic member may be embedded in the frame 301 formed of the resin material, or a part of the frame 301 may be made of resin material and the other part of it may be made of metal, alloy, or ceramic member.

[0207] The module substrate 302 is a component on which the light-emitting device 200 is mounted and electrically connects the light-emitting device 200 to the outside. The module substrate 302 is formed, for example, in a substantially rectangular shape in plan view. The module substrate 302 comprises a substrate portion 303 and a wiring board portion 304.

[0208] As the material for the substrate portion 303, it is preferable to use an insulating material, and also a material that does not easily transmit light emitted from the light-emitting element 202 or ambient light. For example, ceramics such as aluminum oxide, aluminum nitride, and mullite; thermoplastic resins such as polyamide, polyphthalamide, polyphenylene sulfide, and liquid crystal polymer; and resins such as epoxy resin, silicone resin, modified epoxy resin, urethane resin, and phenolic resin can be used. Among these, it is preferable to use ceramics, which have excellent heat dissipation properties, as the material for the substrate portion 303.

[0209] Furthermore, the wiring board portion 304 is formed on the substrate portion 303 at a position facing the conductive member 7 on the side of the ceramic substrate 100 of the light-emitting device 200 that is opposite to the first surface 100a. Examples of materials for the wiring board portion 304 include those exemplified as materials used for the conductive member 7.

[0210] The module substrate 302 is joined to the frame 301 via a conductive adhesive 305, and is arranged so that the conductive member 7 and the wiring board portion 304 are joined. For the conductive adhesive 305, for example, eutectic solder, conductive paste, or bumps may be used. In addition, in the light-emitting device 200, a protective element 306 is arranged on the ceramic substrate 100 in parallel with each light-emitting element 202.

[0211] As the light-emitting module 300 is configured as described above, when it is driven, the following occurs. Specifically, current is supplied from an external power source to the light-emitting element 202 via the wiring board section 304, the conductive member 7, and the electrode 205, causing the light-emitting element 202 to emit light. The light emitted by the light-emitting element 202, if traveling upward, is taken out to the outside of the light-emitting device 200 via the light-transmitting member 203. Light traveling downward is reflected by the ceramic substrate 100 and taken out to the outside of the light-emitting device 200 via the light-transmitting member 203. Light traveling between the light-emitting element 202 and the frame 301 is reflected by the light-reflecting member 204 and the frame 301 and taken out to the outside of the light-emitting device 200 via the light-transmitting member 203. Light traveling between the light-emitting elements 202 is reflected by the light-reflecting member 204 and taken out to the outside of the light-emitting device 200 via the light-transmitting member 203. In this case, by narrowing the distance between the light-transmitting members 203 (for example, 0.2 mm or less), the optical system configuration can be made simpler and more compact, for example, when the light-emitting module 300 is used as a light source for a vehicle's headlight.

[0212] When manufacturing the light-emitting module 300, the light-emitting devices 200 are arranged on a sheet material, a frame 301 is placed around them, and the light-reflecting members 204 are placed in the space enclosed by the frame 301 and the sheet material. Subsequently, the light-emitting devices 200 supported by the frame 301 and the light-reflecting members 204 are placed on a module substrate 302 on which the wiring board portion 304 and conductive adhesive 305 are arranged, and the light-emitting module 300 is manufactured by electrically connecting the conductive member 7 and the wiring board portion 304.

[0213] [Method for manufacturing a light-emitting device] A method for manufacturing a light-emitting device according to an embodiment includes preparing a ceramic substrate 100 manufactured by the method for manufacturing a ceramic substrate 100 according to an embodiment, and arranging a light-emitting element 202 equipped with an electrode 205 on the ceramic substrate 100. The electrode 205 and the conductive member 7 are electrically connected.

[0214] Figure 21 is a flowchart showing an example of a method for manufacturing a light-emitting device according to the embodiment. Note that, as an example, the method for manufacturing a light-emitting device according to the embodiment includes arranging a light-reflecting member.

[0215] (S51) Prepare a ceramic substrate. In preparing the ceramic substrate 100 in S51, the ceramic substrate 100 according to the embodiment is prepared.

[0216] Furthermore, the ceramic substrate 100 has multiple areas for arranging the light-emitting elements 202, and after arranging the light-reflecting members 204, it may be sized to be a single piece for each light-emitting device 200, or it may be sized to be the size of a single light-emitting device 200.

[0217] (S52) Arrange the light-emitting element. In S52, the placement of the light-emitting element involves placing a light-emitting element 202, which has electrodes 205, on the ceramic substrate 100. In S42, the placement of the light-emitting element involves connecting the electrodes 205 of the light-emitting element 202 to a bonding member 209 placed on the conductive member 7 using metal bumps 206. The light-emitting element 202 is placed with the translucent member 203 already connected to the element substrate 208. When bonding the translucent member 203 to the element substrate 208, a translucent bonding material is used.

[0218] (S53) Arrange light-reflecting members. In S53, when arranging the light-reflecting member, the light-reflecting member 204 is positioned to cover the first surface 100a of the ceramic substrate 100 and the side surface of the light-emitting element 202. The light-reflecting member 204 is positioned on the ceramic substrate 100 so as to surround the light-emitting element 202 and expose the upper surface of the translucent member 203, which is the light extraction surface of the light-emitting element 202. The light-reflecting member 204 is positioned to form a rectangle in plan view.

[0219] In the manufacturing method of the light-emitting device according to the embodiment, after arranging the light-reflecting members in S53, individualization work is performed as needed. One unit of the light-emitting device 200 is predetermined by the number of light-emitting elements 202 used. Therefore, when multiple light-emitting devices 200 are manufactured together, individualization work is performed. When individualization work is performed, multiple light-emitting devices 200 are manufactured by cutting in a grid pattern. Examples of cutting methods include using a disc-shaped rotating blade, an ultrasonic cutter, a laser beam irradiation blade, etc. [Examples]

[0220] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way to these examples.

[0221] (Example 1) The ceramic substrate 100 of Example 1 was manufactured by applying step 21, which is the preparation of the ceramic substrate shown in Figure 8, which is the manufacturing method of the ceramic substrate according to the fifth embodiment, to the flowchart shown in Figure 12, which is the manufacturing method of the ceramic substrate according to the sixth embodiment.

[0222] <(S21-1) Prepare a ceramic plate that does not have through holes.> In S21-1, a flat ceramic plate 1 with a thickness of 370 μm and no through holes, mainly composed of aluminum nitride, was prepared.

[0223] <(S21-2) Forming a through hole> In forming the through hole (S21-2), a fiber laser beam Z (wavelength: 1070 nm, output: 1000 W, frequency: 100 Hz, irradiation time: 3 mm seconds) was irradiated from the first surface 1a of the ceramic plate 1 to form the through hole 2.

[0224] <(S32) Make contact> In contact step S32, the ceramic plate 1 with through-holes 2 formed on it was immersed in a 3.0 mol / L potassium hydroxide solution as the etching solution and left at 80°C under atmospheric pressure for 90 minutes.

[0225] <(S33) Blast treatment> The blast treatment S33 was performed in accordance with the blast treatment S3 described in the fourth embodiment. Specifically, the abrasive 10 was applied to the second surface 1b and the first surface 1a of the ceramic plate 1, and the through hole 2 was blast-treated.

[0226] <(S34) Place the first conductive paste> In step S34, when the first conductive paste is placed, an activated brazing material containing a eutectic powder of silver and copper 11, activated metal powder 12, solvent 13, and inorganic filler 14 is used as the first conductive paste 6. The first conductive paste 6 is filled into the through-holes 2 by screen printing, and the first conductive paste 6 is placed so that it has approximately the same surface height as the first surface 1a and the second surface 1b of the ceramic plate 1. The activated brazing material used consisted of 75% by mass of eutectic powder 11, 10% by mass of activated metal powder 12, 10% by mass of solvent 13, and 5% by mass of inorganic filler 14, relative to the total mass of the activated brazing material.

[0227] <(S35) Place the second conductive paste> In step S35, when the second conductive paste is placed, metal masks serving as the first covering member 18a and the second covering member 18b are placed on the first surface 1a and the second surface 1b of the ceramic plate 1, respectively, and the second conductive paste 19, having the same composition as the first conductive paste 6 used in step S34, is placed by metal mask printing. After that, the first conductive paste 6 and the second conductive paste 19 are placed in an electric furnace set to 100°C and dried for 15 minutes.

[0228] <(S25) Sintering> In sintering S36, the ceramic plate 1 after placing the second conductive paste S35 is 10 -6Sintering was performed under the condition of holding at a maximum temperature of 850°C for 15 minutes in a Pa vacuum furnace.

[0229] [Evaluation 1] Observation of ceramic plate 1 and through-hole 2 In Example 1, the ceramic plate 1 after performing the contacting step S32 and the ceramic plate 1 after performing the blasting step S33 were each cut in the thickness direction by laser beam irradiation, and observed with a scanning electron microscope (SEM).

[0230] FIG. 22A is a SEM cross-sectional observation image of the through-hole 2 after performing the contacting step S32 in Example 1 observed at a magnification of 500×. The scale bar is 100 μm. FIG. 22B is a SEM cross-sectional observation image showing the entire ceramic plate 1 after performing the contacting step S32 in Example 1. The scale bar is 200 μm.

[0231] Further, FIG. 23A is a SEM cross-sectional observation image of the through-hole 2 after performing the blasting step S33 in Example 1 observed at a magnification of 500×. The scale bar is 100 μm. FIG. 23B is a SEM cross-sectional observation image showing the entire ceramic plate 1 after performing the blasting step S33 in Example 1. The scale bar is 200 μm. FIG. 23C is a partially enlarged image of a SEM cross-sectional observation image of the through-hole 2 after performing the blasting step S33 in Example 1. The scale bar is 50 μm. FIG. 23D is a partially enlarged image of an FBI-SEM (focused ion beam-SEM) cross-sectional observation image of the through-hole 2 after performing the blasting step S33 in Example 1. The scale bar is 5 μm.

[0232] From FIGS. 22A and 22B, it was found that after performing the contacting step S32, cracks occurred in the ceramic plate 1 near the inner surface that defines the through-hole 2, causing damage (a damaged layer 5 exists). In contrast, from FIGS. 23A to 23D, it can be seen that after performing the blasting step S33, the damaged layer 5 is removed, whereby a ceramic plate 1 free of cracks was obtained. Further, after performing the blasting step S33, C1>C2>C3 was satisfied, A2>C1 was satisfied, and B2>C3 was satisfied.

[0233] [Evaluation 2] Simulation of stress on ceramic plate 1 in sintering step S36 A simulation was performed under the following analysis conditions based on the ceramic plates 1 of Design 1 and Design 2 below. (Design 1) Ceramic plate 1 after step S21-2 of forming a through-hole (Design 2) Ceramic plate 1 after blasting step S33 in Example 1 (Analysis conditions) The temperature is raised from 25°C to 790°C over 1 hour, the first conductive paste is fired at 790°C, and then the temperature is returned to 25°C over 1 hour.

[0234] The melting point of the eutectic of silver and copper is approximately 780°C, and in a completely meltable paste, the paste solidifies as the temperature decreases from 780°C. Based on this, when returning the temperature from 780°C to 25°C, the eutectic of silver and copper was assumed to be solid, and the stress due to the difference in coefficient of linear expansion from aluminum nitride, which is the main material of the ceramic plate 1, was calculated.

[0235] Figure 24A is a top view of the design drawing of ceramic plate 1. In Figure 24A, (1) and (2) indicate part numbers for simulation. Figure 24B is a graph showing the simulation condition values ​​for part numbers (1) and (2) in Figure 24A. Figure 24C is a cross-sectional view of Figure 24A along the XXIVCD-XXIVCD line based on "Design 1". Figure 24D is a cross-sectional view of Figure 24A along the XXIVCD-XXIVCD line based on "Design 2". Figure 24E is an enlarged cross-sectional view of region XXIVE in Figure 24D. Figure 24F is a graph showing the temperature conditions for the simulation. It shows that the temperature rises from 25°C to 780°C in 1 hour and then returns to 25°C in 1 hour.

[0236] In the simulation, it was assumed that polishing or grinding of the first surface 1a and the second surface 1b of the ceramic plate 1 (S47) would not be performed. Furthermore, the conductive member 7 was assumed to be a eutectic of silver and copper, and theoretical values ​​for copper were used in the calculations. That is, the TiN layer (nitride coating 16b) and the Ag layer were omitted from the theoretical values. Also, creep was assumed to be absent, and heat dissipation analysis was not performed.

[0237] The simulation results are shown in Figures 25A to 25C. Figure 25A shows the stress results for the top view of ceramic plate 1 based on "Design 1". Figure 25A corresponds to Figure 24A. From this, it can be seen that the stress is slightly higher around part number (1).

[0238] Figure 25B shows the stress results for a cross-sectional view of ceramic plate 1 based on "Design 1". Figure 25B corresponds to Figure 24C. Figure 25C shows the stress results for a cross-sectional view of ceramic plate 1 based on "Design 2". Figure 25C corresponds to Figures 24D and 24E. Note that in Figures 25B and 25C, the second conductive member 7b based on the second conductive paste 19 is not related to the shape of the first conductive member 7a and is a common structure, so it is omitted in Figures 25B and 25C.

[0239] In Figure 25B, the stress was highest near the through-hole 2 on the second surface 1b, that is, in the ceramic plate 1 defining the second opening 4 of the through-hole 2 on the second surface 1b. In contrast, a comparison of Figure 25B and Figure 25C shows that by performing blast treatment S33 according to design 2, the cross-sectional shape on the second surface 1b side was tapered so that the opening diameter decreases from the second surface 1b side toward the thickness direction of the ceramic plate 1, thereby relieving the stress on the ceramic plate 1 defining the second opening 4 of the through-hole 2 on the second surface 1b.

[0240] Furthermore, as described above, the second conductive member 7b based on the second conductive paste 19 is omitted, but in reality, the second conductive member 7b based on the second conductive paste 19 is present on the first surface 1a and the second surface 1b. Therefore, in Figure 25C, the first opening 3 on the first surface 1a does not have a tapered shape like the second opening 4 on the second surface 1b. Consequently, the stress was highest near the through hole 2 of the first surface 1a, that is, in the ceramic plate 1 defining the first opening 3 of the through hole 2 on the first surface 1a.

[0241] The simulation results in these two evaluations were consistent with the crack occurrence locations in the first evaluation.

[0242] As described above, the present invention has been explained based on specific embodiments, but these are merely examples, and the present invention is not limited to the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, additions, modifications, etc., are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0243] In addition to the embodiments described above, the following further notes are disclosed. (Note 1) To prepare a ceramic plate having a first surface and a second surface opposite to the first surface, having a through hole connecting the first surface and the second surface, wherein the maximum diameter B1 of the opening of the through hole formed on the second surface is less than 0.90 times the maximum diameter A1 of the opening of the through hole formed on the first surface, Bringing the inner surface defining the through hole of the ceramic plate into contact with the etching solution, The through hole is blast-treated from the second surface side, The first conductive paste is placed in the blast-treated through hole, Sintering the first conductive paste, This is a method for manufacturing ceramic substrates, including [the specified element]. (Note 2) The method for manufacturing a ceramic substrate as described in Appendix 1, wherein, in the preparation described above, a laser is irradiated from the first surface toward the second surface to form the through hole in the ceramic plate. (Note 3) In the preparation described above, the ceramic plate contains aluminum nitride, which is the method for manufacturing a ceramic substrate as described in Appendix 1 or Appendix 2. (Note 4) In the preparation described above, the ceramic plate is a sintered ceramic plate, as described in any one of the appendices 1 to 3. (Note 5) In the aforementioned contact, the etching solution contains an alkaline solution containing one or more selected from the group consisting of potassium hydroxide, sodium hydroxide, lithium hydroxide, calcium hydroxide, and magnesium hydroxide as a pH adjusting agent, as described in any one of the methods for producing a ceramic substrate according to Appendix 1 to Appendix 4. (Note 6) In the aforementioned contact, the etching solution contains one or more acidic solutions selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, citric acid, and acetic acid as a pH adjusting agent, as described in the method for producing a ceramic substrate according to any one of the appendices 1 to 4. (Note 7) The method for manufacturing a ceramic substrate according to any one of Supplementary Notes 1 to 6, wherein the blasting treatment includes blasting the through-hole from the first surface side. (Supplementary Note 8) After the blasting treatment, let A2 be the maximum diameter of an opening of the through-hole formed on the first surface, let B2 be the maximum diameter of an opening of the through-hole formed on the second surface, when L is an average length between the first surface and the second surface, let C1 be the maximum diameter of the through-hole in a cross-section in a direction substantially orthogonal to the thickness direction of the ceramic substrate at a position of L / 4 from the first surface side, let C2 be the maximum diameter of the through-hole in a cross-section in a direction substantially orthogonal to the thickness direction of the ceramic substrate at a position of L / 2 from the first surface side, and let C3 be the maximum diameter of the through-hole in a cross-section in a direction substantially orthogonal to the thickness direction of the ceramic substrate at a position of 3L / 4 from the first surface side, C1 > C2 > C3 is satisfied, A2 > C1 is satisfied, and B2 > C3 is satisfied, The method for manufacturing a ceramic substrate according to any one of Supplementary Notes 1 to 7. (Supplementary Note 9) The method for manufacturing a ceramic substrate according to any one of Supplementary Notes 1 to 8, wherein in the step of disposing the first conductive paste, the first conductive paste is an active metal brazing material. (Supplementary Note 10) The method for manufacturing a ceramic substrate according to any one of Supplementary Notes 1 to 9, wherein the active metal brazing material contains a eutectic powder of silver and copper, an active metal powder, and a solvent. (Supplementary Note 11) The method for manufacturing a ceramic substrate according to Supplementary Note 10, wherein the active metal brazing material further contains at least one powder selected from the group consisting of copper powder, silver powder, powder of an alloy of silver and copper, and ceramic powder. (Supplementary Note 12) The method for manufacturing a ceramic substrate as described in Appendix 10 or Appendix 11, wherein the content of the active metal powder in the active metal brazing material is 2% by mass or more and 15% by mass or less. (Note 13) A method for manufacturing a ceramic substrate according to any one of the appendices 1 to 12, further comprising placing a first coating member on the first surface, a second coating member on the second surface, and a second conductive paste on the surface of the first conductive paste, after placing the first conductive paste and before sintering. (Note 14) The method for manufacturing a ceramic substrate as described in Appendix 13, wherein the second conductive paste is an activated metal brazing material. (Note 15) The method for manufacturing a ceramic substrate as described in Appendix 13 or Appendix 14, wherein, after placing the second conductive paste, the second conductive paste is also sintered simultaneously during the sintering process. (Note 16) The method for manufacturing a ceramic substrate as described in any one of the appendices 1 to 15, wherein the sintering temperature is 700°C or higher and 1,200°C or lower. (Note 17) The method for manufacturing a ceramic substrate according to Appendix 15 or Appendix 16, further comprising polishing or grinding the first coating member, the second coating member, and the conductive member in the portion covered by the first coating member, the second coating member, and the conductive member formed by sintering the first conductive paste and the second conductive paste, after sintering, so as to expose the first and second surfaces of the ceramic plate. (Note 18) The process involves preparing the ceramic substrate manufactured by the method for manufacturing the ceramic substrate described in any one of the appendices 1 to 17, The ceramic substrate is used to arrange light-emitting elements that have electrodes, This is a method for manufacturing a light-emitting device, including [the specified element]. (Note 19) A ceramic plate having a first surface and a second surface opposite to the first surface, and having a through hole connecting the first surface and the second surface, A conductive member disposed inside the through hole, A ceramic substrate having, Let A2 be the maximum diameter of the opening of the through hole formed on the first surface. Let B2 be the maximum diameter of the opening of the through hole formed on the second surface. When the average length between the first surface and the second surface is L, the maximum diameter of the through-hole in a cross-section approximately perpendicular to the thickness direction of the ceramic substrate at a position L / 4 from the first surface is C1, the maximum diameter of the through-hole in a cross-section approximately perpendicular to the thickness direction of the ceramic substrate at a position L / 2 from the first surface is C2, and the maximum diameter of the through-hole in a cross-section approximately perpendicular to the thickness direction of the ceramic substrate at a position 3L / 4 from the first surface is C3, Satisfying C1 > C2 > C3, A2 > C1 is satisfied, and Satisfying B2 > C3, It is a ceramic substrate. (Note 20) When C4 is the maximum diameter of the through-hole at which the maximum diameter of the through-hole in a cross-section in a direction substantially perpendicular to the thickness direction of the ceramic substrate is smallest between the first surface and position L3, The ceramic substrate is as described in Appendix 19, wherein L is 2.5 times or more than C4. (Note 21) A ceramic substrate as described in Appendix 19 or Appendix 20, wherein A2 is 120 μm or more and 300 μm or less, and B2 is 100 μm or more and 280 μm or less. (Note 22) A ceramic substrate as described in any one of the appendices 19 to 21, wherein L is 200 μm or more and 600 μm or less. (Note 23) In a cross-sectional view of the ceramic substrate in the thickness direction, The interior angle R1 between the second surface and the imaginary line V1 extending from the second surface and defining the through-hole, passing through the contact point M1 between the second surface and the inner surface defining the through-hole in a cross-sectional view in the thickness direction of the ceramic substrate, is less than 90 degrees. In a cross-sectional view of the ceramic substrate in the thickness direction, on the inner surface defining the through-hole, the outer angle R2 on the opposite side from the inner surface of the through-hole at the intersection of a virtual line V2 passing through L2 and L3 and the virtual line V1 is greater than 90 degrees. A ceramic substrate as described in any one of the items from Appendix 19 to Appendix 22. (Note 24) In a cross-sectional view of the ceramic substrate in the thickness direction, The interior angle R3 between the first surface and the imaginary line V3 that passes through the contact point M2 between the first surface and the inner surface defining the through hole in a cross-sectional view in the thickness direction of the ceramic substrate, and extends from the first surface along the inner surface defining the through hole, is less than 90 degrees. In the inner surface defining the through-hole in a cross-sectional view in the thickness direction of the ceramic substrate, the outer angle R4 on the opposite side from the inner surface of the through-hole at the intersection of a virtual line V4 passing through L2 and L1 and the virtual line V3 is greater than 90 degrees. A ceramic substrate as described in any one of the items from Appendix 19 to Appendix 23. (Note 25) A ceramic substrate according to any one of the appendices 19 to 24, wherein the arithmetic mean roughness Ra of the inner surface defining the through-hole is 0.5 μm or more and 2.0 μm or less. (Note 26) The ceramic substrate described in any one of the appendices 19 to 25, A light-emitting element having electrodes is disposed on the ceramic substrate, A light-emitting device having the following features. [Explanation of symbols]

[0244] 1. Ceramic plate 1a 1st page 1b 2nd side 2 through holes 3. First opening 4. Second opening 5 Damage Layers 6. First conductive paste 7. Conductive members 7a First conductive member 7b Second conductive member 8 Aluminum layer 10 Abrasives 11 Eutectic powder 12 Active metal powder 13 Solvents 14 Inorganic fillers 15 metal 16 Metal compounds 16a Filler surface metal compound 16b Nitride coating 17 Powder 18a First covering member 18b Second covering member 19. Second conductive paste 100 ceramic substrates 100a, Page 1 100b 2nd side 200 Light-emitting devices 202 Light-emitting element 203 Translucent material 204 Light-reflecting member 205 Electrode 206 Metal Bump 207 Semiconductor Stack 208-element substrate 209 Joining member 300 Light-Emitting Modules 301 Frame 302 Module board 303 Circuit board section 304 Wiring board section 305 Conductive adhesive 306 Protective element Z laser light

Claims

1. To prepare a ceramic plate having a first surface and a second surface opposite to the first surface, having a through hole connecting the first surface and the second surface, wherein the maximum diameter B1 of the second opening of the through hole formed on the second surface is less than 0.90 times the maximum diameter A1 of the first opening of the through hole formed on the first surface, Bringing the inner surface defining the through hole of the ceramic plate into contact with the etching solution, The through hole is blast-treated from the second surface side, The first conductive paste is placed in the blast-treated through-hole, Sintering the first conductive paste, A method for manufacturing ceramic substrates, including [the specified element].

2. The method for manufacturing a ceramic substrate according to claim 1, wherein, in the preparation described above, a laser is irradiated from the first surface toward the second surface to form the through hole in the ceramic plate.

3. The method for manufacturing a ceramic substrate according to claim 1, wherein the ceramic plate contains aluminum nitride in the preparation described above.

4. The method for manufacturing a ceramic substrate according to claim 1, wherein the ceramic plate is a sintered ceramic plate in the preparation described above.

5. The method for producing a ceramic substrate according to claim 1, wherein, in the contact described above, the etching solution contains an alkaline solution containing one or more selected from the group consisting of potassium hydroxide, sodium hydroxide, lithium hydroxide, calcium hydroxide, and magnesium hydroxide as a pH adjusting agent.

6. The method for producing a ceramic substrate according to claim 1, wherein, in the contact described above, the etching solution contains one or more acidic solutions selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, citric acid, and acetic acid as a pH adjusting agent.

7. The method for manufacturing a ceramic substrate according to claim 1, wherein the blast treatment includes blasting the through hole from the first surface side.

8. After the aforementioned blasting treatment, Let A2 be the maximum diameter of the first opening of the through hole formed on the first surface. Let B2 be the maximum diameter of the second opening of the through hole formed on the second surface. When the average length between the first surface and the second surface is L, the maximum diameter of the through-hole in a cross-section in a direction substantially perpendicular to the thickness direction of the ceramic substrate at a position L / 4 from the first surface is C1, the maximum diameter of the through-hole in a cross-section in a direction substantially perpendicular to the thickness direction of the ceramic substrate at a position L / 2 from the first surface is C2, and the maximum diameter of the through-hole in a cross-section in a direction substantially perpendicular to the thickness direction of the ceramic substrate at a position 3L / 4 from the first surface is C3, Satisfying C1 > C2 > C3, A2 > C1 is satisfied, and Satisfying B2 > C3, A method for manufacturing a ceramic substrate according to claim 1.

9. The method for manufacturing a ceramic substrate according to claim 1, wherein the first conductive paste is an activated metal brazing material.

10. The method for manufacturing a ceramic substrate according to claim 9, wherein the activated metal brazing material contains a eutectic powder of silver and copper, an activated metal powder, and a solvent.

11. The method for manufacturing a ceramic substrate according to claim 10, wherein the activated metal brazing material further contains at least one powder selected from the group consisting of copper powder, silver powder, powder of a silver-copper alloy, and ceramic powder.

12. The method for manufacturing a ceramic substrate according to claim 10, wherein the content of the active metal powder in the active metal brazing material is 2% by mass or more and 15% by mass or less.

13. A method for manufacturing a ceramic substrate according to claim 1, further comprising: placing a first coating member on the first surface, placing a second coating member on the second surface, and placing a second conductive paste on the surface of the first conductive paste, after placing the first conductive paste and before sintering.

14. The method for manufacturing a ceramic substrate according to claim 13, wherein the second conductive paste is an activated metal brazing material.

15. The method for manufacturing a ceramic substrate according to claim 13, wherein, after placing the second conductive paste, the second conductive paste is also sintered at the same time as the sintering.

16. The method for manufacturing a ceramic substrate according to claim 1, wherein the sintering temperature is 700°C or higher and 1,200°C or lower.

17. A method for manufacturing a ceramic substrate according to claim 15, further comprising polishing or grinding the first coating member, the second coating member, and the conductive member in the portion covered by the first coating member, the second coating member, and the conductive member formed by sintering the first conductive paste and the second conductive paste, after the sintering, so as to expose the first and second surfaces of the ceramic plate.

18. The process involves preparing the ceramic substrate manufactured by the method for manufacturing the ceramic substrate described in any one of claims 1 to 17, The ceramic substrate is used to arrange light-emitting elements that have electrodes, A method for manufacturing a light-emitting device, including the method described above.

19. A ceramic plate having a first surface and a second surface opposite to the first surface, and having a through hole connecting the first surface and the second surface, A conductive member disposed inside the through hole, A ceramic substrate having, Let A2 be the maximum diameter of the first opening of the through hole formed on the first surface. Let B2 be the maximum diameter of the second opening of the through hole formed on the second surface. When the average length between the first surface and the second surface is L, the maximum diameter of the through-hole in a cross-section in a direction substantially perpendicular to the thickness direction of the ceramic substrate at a position L / 4 from the first surface is C1, the maximum diameter of the through-hole in a cross-section in a direction substantially perpendicular to the thickness direction of the ceramic substrate at a position L / 2 from the first surface is C2, and the maximum diameter of the through-hole in a cross-section in a direction substantially perpendicular to the thickness direction of the ceramic substrate at a position 3L / 4 from the first surface is C3, Satisfying C1 > C2 > C3, A2 > C1 is satisfied, and Satisfying B2 > C3, Ceramic substrate.

20. The ceramic substrate according to claim 19, wherein, between the first surface and position L3, when the maximum diameter of the through-hole in a cross-section in a direction substantially perpendicular to the thickness direction of the ceramic substrate is smallest, C4 is the maximum diameter of the through-hole, and L is 2.5 times or more C4.

21. The ceramic substrate according to claim 19, wherein A2 is 120 μm or more and 300 μm or less, and B2 is 100 μm or more and 280 μm or less.

22. The ceramic substrate according to claim 19, wherein L is 200 μm or more and 600 μm or less.

23. In a cross-sectional view of the ceramic substrate in the thickness direction, The interior angle R1 between the second surface and the imaginary line V1 that passes through the contact point M1 between the second surface and the inner surface defining the through-hole in a cross-sectional view in the thickness direction of the ceramic substrate, and extends from the second surface along the inner surface defining the through-hole, is less than 90 degrees. In a cross-sectional view of the ceramic substrate in the thickness direction, on the inner surface defining the through-hole, the outer angle R2 on the opposite side from the inner surface of the through-hole at the intersection of a virtual line V2 passing through L2 and L3 and the virtual line V1 is greater than 90 degrees. The ceramic substrate according to claim 19.

24. In a cross-sectional view of the ceramic substrate in the thickness direction, The interior angle R3 between the first surface and the imaginary line V3 that passes through the contact point M2 between the first surface and the inner surface defining the through hole in a cross-sectional view in the thickness direction of the ceramic substrate, and extends from the first surface along the inner surface defining the through hole, is less than 90 degrees. In the inner surface defining the through-hole in a cross-sectional view in the thickness direction of the ceramic substrate, the outer angle R4 on the opposite side from the inner surface of the through-hole at the intersection of a virtual line V4 passing through L2 and L1 and the virtual line V3 is greater than 90 degrees. The ceramic substrate according to claim 19.

25. The ceramic substrate according to claim 19, wherein the arithmetic mean roughness Ra of the inner surface defining the through hole is 0.5 μm or more and 2.0 μm or less.

26. The ceramic substrate according to any one of claims 19 to 25, A light-emitting element having electrodes is disposed on the ceramic substrate, A light-emitting device having the following features.

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