Wiring board and method for manufacturing the same

Abstract

To provide a wiring board that can be made thinner and has excellent thermal conductivity.SOLUTION: The present disclosure provides a wiring board which has a ceramic substrate having a first surface and a second surface opposite the first surface, the first surface having a first flat area, a first recess, and a second recess, first wiring arranged in the first recess, and a reflective member arranged in the second recess.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a wiring board and a method for manufacturing the same.

Background Art

[0002] A wiring board for mounting a light-emitting element, in which a conductor pattern and a light reflection layer are provided on a substrate, is known.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An embodiment according to the present disclosure aims to provide a wiring board and a method for manufacturing the wiring board, which can be thinned and have excellent thermal conductivity.

Means for Solving the Problems

[0005] A wiring board according to an aspect of the present disclosure includes a ceramic substrate having a first surface and a second surface opposite to the first surface, the first surface having a first flat portion, a first recess, and a second recess, a first wiring disposed in the first recess, and a reflecting member disposed in the second recess.

[0006] A method for manufacturing a wiring board according to an aspect of the present disclosure includes the steps of preparing a ceramic substrate having a first surface and a second surface opposite to the first surface, removing a part of the first surface to form a first recess, disposing a first conductive paste in the first recess, firing the first conductive paste to form a first wiring, removing a part of the first surface to form a second recess adjacent to the first recess via the first flat portion, and disposing a reflecting member in the second recess.

Advantages of the Invention

[0007] According to one aspect of the present disclosure, it is possible to provide a wiring board capable of being thinned and having excellent thermal conductivity, and a method for manufacturing the wiring board.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 3E

Figure 3F

Figure 3G

Figure 3H

Figure 3I

Figure 4A

Figure 4B

Figure 4C

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Figure 9

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Figure 11A

Figure 11B

Figure 11C

Figure 11D

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. However, the embodiments described below are for embodying the technical idea according to the present disclosure, and the invention is not limited to the following unless specifically described. The content described in one embodiment is also applicable to other embodiments and modifications. Further, the drawings schematically show the embodiments, and in order to clarify the description, the scale, interval, positional relationship, etc. of each member are exaggerated, or a part of the member may be omitted, or an end view showing only the cut surface as a cross-sectional view may be used. The directions shown in each figure indicate the relative positions between the components and are not intended to indicate absolute positions. Note that the same names and reference numerals generally indicate the same or similar members, and detailed descriptions will be omitted as appropriate.

[0010] In this specification, viewing an object from the first surface side or the second surface side of a ceramic substrate is referred to as a plan view, and the surface of the object viewed from the first surface side of the ceramic substrate may be referred to as the upper surface, and the surface located opposite to the upper surface may be referred to as the lower surface.

[0011] In this specification or the claims, when there are a plurality of certain components and they are to be distinguished and expressed respectively, "first", "second", etc. may be appended to the heads of the components for distinction. Also, the objects to be distinguished may be different between this specification and the claims. Therefore, even if a component with the same appendix as in this specification is described in the claims, the object specified by this component may not match between this specification and the claims.

[0012] For example, in this specification, there are components marked as "first", "second", and "third" for distinction. When the components marked as "first" and "third" in this specification are described in the claims, or when the component marked as "first" and the component without a specific ordinal number are described in the claims, from the perspective of readability, in the claims, it may be marked as "first" and "second" to distinguish the components. In this case, the components marked as "first" and "second" in the claims respectively refer to the components marked as "first" and "third" in this specification or the component without a specific ordinal number. Note that the application of this rule is not limited to components, but can also be reasonably and flexibly applied to other objects.

[0013] (First Embodiment) The wiring board according to the first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic plan view showing the wiring board 1a. FIG. 2 is a schematic cross-sectional view showing the cross-section along the line II-II of FIG. 1.

[0014] The wiring board 1a according to the first embodiment of the present disclosure has a first surface 21 and a second surface 22 on the opposite side of the first surface 21. The first surface 21 has a first planar portion 21a, a first recess 21b, and a second recess 21c, a ceramic substrate 2, a first wiring 3 disposed in the first recess 21b, and a reflective member 4 disposed in the second recess 21c.

[0015] In the wiring board 1a, the first wiring 3 is disposed in the first recess 21b, the reflective member 4 is disposed in the second recess 21c of the ceramic substrate 2, and the upper surfaces of the first wiring 3 and the reflective member 4 are on the same plane as the first planar portion 21a of the ceramic substrate. Thereby, the wiring board 1a can be thinned. Further, the first wiring 3 is disposed in contact with the inner surface and the bottom surface defining the first recess 21b, and since the first wiring 3 is in contact with the ceramic substrate having high thermal conductivity, the heat from the first wiring 3 is released to the outside through the ceramic substrate 2. Therefore, the heat dissipation path is widened by the ceramic substrate 2, and the heat dissipation performance is improved.

[0016] The thickness of the wiring board 1a is, for example, 0.1 mm or more and 2 mm or less, preferably 0.15 mm or more and 1.5 mm or less, and more preferably 0.2 mm or more and 1.2 mm or less.

[0017] (Ceramic substrate) The ceramic substrate 2 is an insulating member that serves as a base for later disposing the first wiring 3, the reflecting member 4, and the second wiring 5.

[0018] The material of the ceramic substrate 2 is preferably nitride-based ceramics such as silicon nitride, aluminum nitride, and boron nitride, and oxide-based ceramics such as aluminum oxide, silicon oxide, calcium oxide, and magnesium oxide may also be used. The material of the ceramic substrate 2 is preferably AlN or SiN.

[0019] The ceramic substrate 2 is a fired substrate. When the first wiring 3 and the second wiring 5 are disposed using a green sheet before firing, the firing temperature of the green sheet is much higher than the melting points of the first wiring 3 and the second wiring 5, and the first wiring 3 and the second wiring 5 may melt, resulting in a decrease in the accuracy of the arrangement or difficulty in obtaining the desired metal characteristics. On the other hand, when a fired ceramic substrate is used, the first wiring 3 and the second wiring 5 having the desired metal characteristics can be accurately arranged.

[0020] The ceramic substrate 2 has a rectangular first surface 21, a rectangular second surface 22 on the opposite side of the first surface 21, and four side surfaces 23 between the first surface 21 and the second surface 22. The first surface 21 has a first flat portion 21a, a first recess 21b, and a second recess 21c. A first flat portion 21a exists between the first recess 21b and the second recess 21c. In other words, the first flat portion 21a can be said to be the upper surface of the convex portion with reference to the bottom surfaces of the first recess 21b and the second recess 21c. The second surface 22 has a second flat portion 22a and a third recess 22b. Each of the four side surfaces 23 is located between the first surface 21 and the second surface 22 and is adjacent to the four sides of the outer edge of the first surface 21 and the four sides of the outer edge of the second surface 22.

[0021] The thickness of the ceramic substrate 2 is preferably, for example, 0.08 mm or more and 2 mm or less. The thickness of the ceramic substrate 2 means the distance between the first flat portion 21a and the second flat portion 22a.

[0022] In the example shown in FIG. 1, the first recess 21b is rectangular having a long side and a short side in plan view. The ceramic substrate 2 has two first recesses 21b, and the long sides of the two first recesses 21b are arranged to face each other. A second recess 21c is arranged between the two first recesses 21b. The first recess 21b and the second recess 21c are arranged adjacent to each other with the first flat portion 21a interposed therebetween. The second recess 21c is arranged in plan view so as to surround the first recess 21b with the first flat portion 21a interposed therebetween. The second recess 21c arranged between the long sides of the two first recesses 21b is connected to the portion surrounding the two first recesses 21b together. In other words, a continuous single second recess 21c is arranged so as to surround the entire circumferences of the two first recesses 21b. The two first recesses 21b are surrounded by one second recess 21c, and the entire circumferences of the first recess 21b and the second recess 21c are each surrounded by the first flat portion 21a. That is, in plan view, the ceramic substrate 2 has two first recesses 21b arranged with their long sides facing each other, a first flat portion 21a arranged on the entire circumference of each first recess 21b, a second recess 21c arranged on the entire circumference of the first flat portion 21a, and a first flat portion 21a arranged on the entire circumference of the second recess 21c.

[0023] The distance between the first concave portion 21b and the second concave portion 21c adjacent via the first planar portion 21a is, for example, 1 μm or more and 100 μm or less, preferably 5 μm or more and 80 μm or less, more preferably 10 μm or more and 50 μm or less. Since the first concave portion 21b where the first wiring 3 is disposed and the second concave portion 21c where the reflecting member 4 is disposed are separated from each other, a large contact area between the first wiring 3 and the ceramic substrate 2 can be ensured. Thereby, heat dissipation performance is improved. Further, by setting the distance between the first concave portion 21b where the first wiring 3 is disposed and the second concave portion 21c where the reflecting member 4 is disposed within the above range, light from the light-emitting element absorbed by the first planar portion 21a of the ceramic substrate 2 can be reduced.

[0024] The depth of the first concave portion 21b may be, for example, 1 μm or more and 500 μm or less, 5 μm or more and 300 μm or less, 10 μm or more and 100 μm or less, or 15 μm or more and 50 μm or less.

[0025] The depth of the second concave portion 21c may be, for example, 1 μm or more and 500 μm or less, 5 μm or more and 300 μm or less, 10 μm or more and 100 μm or less, or 15 μm or more and 50 μm or less. When the volume of the second concave portion 21c where the reflecting member 4 is disposed increases, the volume occupied by the wiring substrate 1a increases. Thereby, since the volume of the ceramic substrate 2 becomes small, the heat dissipation performance of the wiring substrate 1a may decrease or the mechanical strength may decrease. In the present embodiment, by setting the depth of the second concave portion 21c within the above range, the heat dissipation performance and the mechanical strength of the wiring substrate 1a can be maintained high.

[0026] Preferably, the depth of the first concave portion 21b is greater than or equal to the depth of the second concave portion 21c. More preferably, the depth of the first concave portion 21b is deeper than the depth of the second concave portion 21c. The difference between the depth of the first concave portion 21b and the depth of the second concave portion 21c may be, for example, 0.1 μm or more and 50 μm or less, 0.5 μm or more and 20 μm or less, 1 μm or more and 10 μm or less, or 1 μm or more and 5 μm or less. By setting the difference between the depth of the first concave portion 21b and the depth of the second concave portion 21c within the above range, formation of a fine pattern of the first wiring 3 disposed in the first concave portion 21b can be facilitated, and a decrease in heat dissipation performance can be reduced.

[0027] In the example shown in FIG. 1, the first recess 21b is rectangular in plan view. The first recess 21b may have rounded corners in plan view, or may be entirely curved. In the example shown in FIG. 2, the inner surface defining the first recess 21b includes a curved surface. That is, the inner surface defining the first recess 21b includes a curved surface. In a cross-sectional view of the ceramic substrate 2 in the thickness direction, the first recess 21b is curved except for a part of the bottom surface that is flat. By the inner surface defining the first recess 21b being a curved surface, stress can be dispersed and the first wiring 3 can be prevented from peeling off from the ceramic substrate 2. Further, damage to the ceramic substrate 2 when it is subjected to a thermal shock can be reduced. Note that the first recess 21b may have a curved bottom surface continuous from the inner surface. For example, in a cross-sectional view of the ceramic substrate 2 in the thickness direction, the first recess 21b may be entirely curved.

[0028] The inner surface defining the second recess 21c includes a curved surface. That is, the inner surface in the thickness direction of the second recess 21c includes a curved surface. In a cross-sectional view of the ceramic substrate 2 in the thickness direction, the second recess 21c is curved except for a part of the bottom surface that is flat. By the inner surface defining the second recess 21c being a curved surface, stress can be dispersed and the reflecting member 4 can be prevented from peeling off from the ceramic substrate 2. Further, damage to the ceramic substrate 2 when it is subjected to a thermal shock can be reduced. Note that the second recess 21c may have a curved bottom surface continuous from the inner surface. For example, in a cross-sectional view of the ceramic substrate 2 in the thickness direction, the second recess 21c may be entirely curved.

[0029] The inner surfaces defining the first recess 21b and the second recess 21c are preferably rough surfaces. By roughening, it is possible to reduce the peeling of the first wiring 3 and the reflecting member 4 disposed in the first recess 21b and the second recess 21c from the ceramic substrate 2. The arithmetic mean roughness Ra of the inner surfaces defining the first recess 21b and the second recess 21c can be, for example, 200 nm or more and 2 μm or less, and preferably 300 nm or more and 800 nm or less. The arithmetic mean roughness Ra may be measured in accordance with JIS B 0601 using a stylus type surface roughness meter equipped with a diamond stylus having a tip curvature radius r of 2 μm (for example, SE3500 manufactured by Kosaka Laboratory Ltd.).

[0030] The third recess 22b is rectangular in plan view and has a long side and a short side. The two third recesses 22b are arranged with their long sides facing each other. The third recess 22b is disposed at a position overlapping the first recess 21b in plan view. The second flat portion 22a is disposed so as to surround the third recess 22b in plan view. Similar to the first recess 21b, the third recess 22b may have rounded corners in plan view, or the entire longitudinal end may be curved. Also, the inner surface defining the third recess 22b may include a curved surface, and the inner surface defining the third recess 22b is preferably roughened.

[0031] (Wiring) The first wiring 3 and the second wiring 5 are members for conducting electricity on the wiring substrate 1a. The first wiring 3 is disposed in the first recess 21b. The second wiring 5 is disposed in the third recess 22b. In the example shown in FIG. 2, the second wiring 5 is disposed at a position overlapping the first wiring 3 in plan view. The ceramic substrate 2 may have a through hole connecting the first recess 21b on the first surface 21 and the third recess 22b on the second surface 22. By providing a conductive member inside the through hole, the first wiring 3 and the second wiring 5 may be electrically connected.

[0032] The first wiring 3 and the second wiring 5 include at least one selected from Ag, Cu, Al, Zn, Sn, Ni, and Ag-Cu eutectic alloy. Among these, an Ag-Cu eutectic alloy (Ag 72 wt%, Cu 28 wt%) having high electrical conductivity and a low melting point is preferable. Thereby, since the thermal resistance of the wiring board 1a is lowered, the temperature rise of the light-emitting element mounted on the wiring board 1a is suppressed, and the life of the light-emitting element is extended.

[0033] The first wiring 3 and the second wiring 5 preferably further include at least one of Ti, Hf, Zr, Nb, Ce, and Mg. When the ceramic substrate 2 is a nitride-based ceramic, these metals can form a metal compound layer serving as a reaction layer such as TiN at the interface between the first wiring 3 and the second wiring 5 and the ceramic substrate 2. Thereby, the adhesion between the first wiring 3 and the second wiring 5 and the ceramic substrate 2 is improved.

[0034] The first wiring 3 is preferably formed so as to be in contact with the entire inner surface defining the first recess 21b and the upper surface of the first wiring 3 is flush with the first flat portion 21a. That is, the surface of the first wiring 3 in contact with the ceramic substrate 2 may have the same shape as the inner surface defining the first recess 21b.

[0035] The second wiring 5 is preferably formed so as to be in contact with the entire inner surface defining the third recess 22b and the lower surface of the second wiring 5 (that is, the surface on the lower side of the second wiring 5 in FIG. 2) is flush with the second flat portion 22a. That is, the surface of the second wiring 5 in contact with the ceramic substrate 2 may have the same shape as the inner surface defining the third recess 22b.

[0036] A first metal layer may be disposed on the upper surface of the first wiring 3. Also, a second metal layer may be disposed on the lower surface of the second wiring 5. Hereinafter, the first metal layer and the second metal layer may be collectively referred to as a metal layer.

[0037] The metal layer may contain at least one selected from, for example, Au, Pt, Pd, Rh, Ni, W, Mo, Cr, and Ti. The metal layer may be a single layer or two or more layers. The first metal layer and the second metal layer may have the same configuration or different configurations. For example, the first metal layer and the second metal layer may contain the same metal or different metals. Also, the first metal layer and the second metal layer may have the same layer configuration or different layer configurations.

[0038] (Reflection member) The reflection member 4 is a member that reflects light toward the wiring board 1a and is disposed in the second recess 21c.

[0039] The reflection member 4 is not particularly limited as long as its reflectivity is higher than that of the ceramic substrate 2.

[0040] The reflection member 4 may be, for example, a member in which a light diffusing material is contained in a resin, or a member in which a plurality of inorganic materials are contained. Also, for example, it may be a metal such as Pt, Ag, Rh, or Al, or a distributed Bragg reflector (DBR).

[0041] In the member in which a light diffusing material is contained in the resin, as the resin, for example, silicone resin, epoxy resin, or acrylic resin is used. Also, as the light diffusing material, for example, titanium oxide, silicon oxide, aluminum oxide, or zinc oxide is used.

[0042] The member in which the plurality of inorganic materials are mixed includes a light reflecting material and a support member that supports the light reflecting material.

[0043] The light reflecting material can be, for example, boron nitride or aluminum oxide.

[0044] The light reflecting material may be primary particles or secondary particles formed by aggregation of two or more primary particles. Further, the light reflecting material may contain primary particles and secondary particles.

[0045] The particles of the light reflecting material may preferably be plate-shaped or spherical particles.

[0046] The average particle size of the light reflecting material may preferably be 0.6 μm or more and 43 μm or less. When the light reflecting material is boron nitride, the average particle size of the primary particles of the light reflecting material is, for example, 6 μm or more and 43 μm or less. When the light reflecting material is aluminum oxide, the average particle size of the primary particles of the light reflecting material is, for example, 0.6 μm or more and 10 μm or less.

[0047] The average particle size of the light reflecting material is measured by using image analysis software for an image obtained by using a scanning electron microscope "TM3030Plus" manufactured by Hitachi High-Technologies Corporation.

[0048] First, one surface of a carbon double-sided tape is attached to the sample stage of the microscope, and then the light reflecting material is placed on the other surface of the double-sided tape. The pixel number of the microscope is set to 1.23 million pixels, the magnification is set from 1000 times to 2000 times, and images of 100 particles of the light reflecting material are acquired. Then, the particle size of each particle is measured by image analysis software. In this specification, the particle size of the light reflecting material is the maximum diameter among the diameters when viewed from one main surface of the light reflecting material. Next, the median diameter of the measured particles is calculated, and the calculated value is taken as the average particle size of the light reflecting material. The particle size of the light reflecting material is measured by extracting a cross section of the light-reflective member by SEM and measuring it with image analysis software.

[0049] The support member may preferably contain silicon oxide and an alkali metal.

[0050] The content ratio of silicon oxide and the light reflecting material contained in the reflecting member 4 is, for example, 1:4 to 1:1 by mass ratio. That is, the mass of the light reflecting material contained in the reflecting member 4 is, for example, 1 to 4 times the mass of the silicon oxide contained in the reflecting member 4. By setting the content ratio of silicon oxide and the light reflecting material to 1:4 to 1:1, shrinkage can be reduced while maintaining the curability during manufacturing.

[0051] The alkali metal contained in the reflecting member 4 can be, for example, one or both of potassium and sodium.

[0052] The reflecting member 4 may preferably further contain a light diffusing material. By including the light diffusing material in the reflecting member 4, the light reflectance of the reflecting member 4 is improved.

[0053] The light diffusing material contained in the reflecting member 4 can be, for example, a light diffusing material containing zirconium oxide or titanium oxide. The light diffusing material in the reflecting member 4 is dispersed and present in the silicon oxide of the support member.

[0054] When a light emitting element that emits ultraviolet light is mounted on the wiring board 1a, the light diffusing material may preferably contain zirconium oxide with little light absorption in the ultraviolet wavelength region. The zirconium oxide contained in the light diffusing material may be simple zirconium oxide, or may be one coated with a coating film composed of any one or two or more of organic materials such as silicon oxide, aluminum oxide, and resin on the surface of zirconium oxide. Also, the zirconium oxide contained in the light diffusing material may be stabilized zirconium oxide added with calcium, magnesium, yttrium, aluminum, etc., or partially stabilized zirconium oxide.

[0055] The titanium oxide contained in the light diffusing material may be simple titanium oxide, or may be one coated with a coating film composed of any one or two or more of silicon oxide, aluminum oxide, zirconium oxide, zinc, and organic on the surface of titanium oxide.

[0056] The average particle size of the light diffusing material is preferably smaller than that of the light reflecting material. By making the average particle size of the light diffusing material smaller than that of the light reflecting material, it becomes easier to arrange the light diffusing material in the gaps between the light reflecting materials, so that the light emitted from the light emitting element 20 can be reduced from passing through the reflection member 4 through the gaps between the light reflecting materials. The average particle size of the light diffusing material is measured by the laser diffraction method.

[0057] In the wiring board of the present disclosure, the reflection member 4 can also be replaced with a light absorbing member. The light absorbing member is a member in which a light absorbing material is contained in an organic material such as resin or an inorganic material containing an alkali metal silicate. The light absorbing member is different in that it contains a light diffusing material in the resin and contains a light absorbing material instead of the light diffusing material. As the light absorbing material, carbon black, graphite, etc. are used.

[0058] It is preferable that the reflection member 4 is in contact with the entire inner surface defining the second recess 21c and the upper surface of the reflection member 4 is formed to be flush with the first flat portion 21a. The surface of the reflection member 4 that contacts the ceramic substrate 2 of the second recess 21c may have the same shape as the inner surface defining the second recess 21c.

[0059] In the wiring board 1a, the first wiring 3 is rectangular in plan view and has a long side and a short side. Two first wirings 3 are arranged side by side with their long sides facing each other. A reflection member 4 is arranged between the two first wirings 3. The first wiring 3 and the reflection member 4 are arranged adjacent to each other via the first flat portion 21a. In the example shown in FIG. 1, one continuous reflection member 4 is arranged so as to surround the entire circumference of each of the two first wirings 3. The two first wirings 3 are surrounded by one reflection member 4, and the entire circumference of the first wiring 3 and the entire circumference of the reflection member 4 are each surrounded by the first flat portion 21a. That is, in plan view, the wiring board 1a has two first wirings 3 arranged side by side with their long sides facing each other, a first flat portion 21a arranged on the entire circumference of each first wiring 3, a reflection member 4 arranged on the entire circumference of the first flat portion 21a, and a first flat portion 21a arranged on the entire circumference of the reflection member 4.

[0060] The distance between the first wiring 3 and the reflecting member 4 adjacent via the first planar portion 21a is, for example, 1 μm or more and 100 μm or less, preferably 5 μm or more and 80 μm or less, and more preferably 10 μm or more and 50 μm or less. Since the first wiring 3 and the reflecting member 4 are separated from each other, the ceramic substrate 2 is disposed around the entire circumference of the first wiring 3, and a large area of contact between the first wiring 3 and the ceramic substrate 2 can be ensured. Thereby, the heat dissipation performance is improved. If the first wiring 3 and the reflecting member 4 are too far apart, the area of the first planar portion 21a of the ceramic substrate 2 becomes large, and the light from the light-emitting element absorbed by the ceramic substrate 2 increases. In the present embodiment, by setting the distance between the first wiring 3 and the reflecting member 4 within the above range, the light from the light-emitting element absorbed by the first planar portion 21a of the ceramic substrate 2 can be reduced.

[0061] (Method for manufacturing a wiring board) The method for manufacturing the wiring board 1a includes: (a) a step of preparing a ceramic substrate having a first surface and a second surface opposite to the first surface; (b) a step of removing a part of the first surface to form a first recess; (c) a step of disposing a first conductive paste in the first recess; (d) a step of firing the first conductive paste to form a first wiring; (e) a step of removing a part of the first surface to form a second recess adjacent to the first recess via a first planar portion; and (f) a step of disposing a reflecting member in the second recess.

[0062] (a) Step of preparing a ceramic substrate Prepare a ceramic substrate 2a having a first surface 21 and a second surface 22 opposite to the first surface 21 (FIG. 3A).

[0063] Such a ceramic substrate 2a becomes the ceramic substrate 2 by later forming a first recess 21b, a second recess 21c, and a third recess 22b. The ceramic substrate 2 may be formed by firing and molding ceramics, or a fired substrate may be prepared.

[0064] (b) Step of forming a first recess Remove a part of the first surface 21 to form a first recess 21b (FIGS. 3B and 3C).

[0065] In the example shown in FIGS. 3B and 3C, in the step of forming the first recess 21b, simultaneously, a part of the second surface 22 is removed to form a third recess 22b. Note that the first recess 21b and the third recess 22b may be formed in separate steps.

[0066] Before forming the first recess 21b and the third recess 22b, dispose a first mask 61 having a first opening 61a at a position overlapping the first recess 21b and the third recess 22b (FIG. 3B). For example, the first mask 61 is formed as follows.

[0067] Bond a dry film to the first surface 21 and the second surface 22 of the ceramic substrate. The dry film is a sheet-like photoresist. For example, use a negative-type photoresist in which the exposed area is cured.

[0068] Next, expose and develop the dry film. Before exposure, attach a mask over the dry film. The mask has a light-shielding pattern in the regions where the first recess 21b and the third recess 22b are to be formed. Subsequently, irradiate light for exposure. The light is, for example, ultraviolet light. The regions other than the light-shielding pattern transmit light, and the dry film at those positions is cured. In the subsequent development, remove the mask and dissolve and remove the uncured portion of the dry film with an alkaline aqueous solution or the like. The cured portion remains without being dissolved and removed, and the first mask 61 is formed. Note that the first mask 61 may be disposed by bonding a separately formed first mask 61 to the ceramic substrate 2a.

[0069] After forming the first mask 61, form the first recess 21b and the third recess 22b to obtain a ceramic substrate 2b (FIG. 3C).

[0070] The first recess 21b and the third recess 22b can be formed, for example, by etching, blasting, or laser processing. Note that etching, blasting, or laser processing may be performed using only one of these methods, or two or more of them may be combined.

[0071] Etching can be performed by wet etching or dry etching, and wet etching is preferred. Wet etching can form the first recess 21b and the third recess 22b whose inner surfaces include curved surfaces by etching using acidic or alkaline agents such as HF, NH4F, KOH, NaOH, CsOH, etc.

[0072] In blasting, the ceramic substrate 2a can be polished or ground from a direction perpendicular to the first surface 21 and the second surface 22 by impinging abrasive grains to form a desired shape, and the ceramic substrate 2b can be obtained.

[0073] When forming the first recess 21b and the third recess 22b by laser processing, the first mask 61 is not required.

[0074] For example, in the step of forming the first recess, it may include the step of disposing a photoresist on the first surface 21 of the ceramic substrate 2a, the step of performing exposure and development on the photoresist through a mask, the step of etching or blasting the ceramic substrate 2a through the first mask 61 formed in a predetermined pattern by performing exposure and development, and the step of forming the first recess 21b by etching or blasting to obtain the ceramic substrate 2b.

[0075] (c) Step of disposing the first conductive paste Through the first opening 61a, the first conductive paste 3a is disposed in the first recess 21b (Fig. 3D). The first conductive paste 3a becomes the first wiring 3 by being fired.

[0076] In the example shown in FIG. 3D, in the step of disposing the first conductive paste 3a, the first conductive paste 3a is disposed in the first recess 21b, and the second conductive paste 5a is disposed in the third recess 22b. In this case, the first conductive paste 3a is disposed in the first recess 21b by printing through the first opening 61a. When the first conductive paste contains a solvent described later, the solvent is dried. Next, the ceramic substrate 2a is inverted, and the second conductive paste 5a is disposed in the third recess 22b by printing. When the second conductive paste contains a solvent described later, the solvent is dried. Thereafter, the first conductive paste 3a and the second conductive paste 5a are fired. The first conductive paste 3a and the second conductive paste 5a become the first wiring 3 and the second wiring 5 by being fired.

[0077] The first conductive paste 3a is a member having fluidity and can be disposed by printing so as to adhere to the inner surface of the first recess 21b. Similarly, the second conductive paste 5a is a member having fluidity and can be disposed by printing so as to adhere to the inner surface of the third recess 22b. Hereinafter, the first conductive paste 3a and the second conductive paste 5a may be collectively referred to as a conductive paste.

[0078] The conductive paste contains a first metal powder. The first metal powder may contain at least one selected from Ag, Cu, Al, Zn, Sn, Ni, and Ag-Cu eutectic alloy. Among these, an Ag-Cu alloy (Ag 72 wt%, Cu 28 wt%) that can be fired at a relatively low temperature such as 780°C or higher and 950°C or lower is preferable. Also, pure Cu powder, pure Ag powder, etc. may be mixed with the Ag-Cu eutectic alloy. The pure Cu powder may be mixed up to 85% by weight fraction, and the pure Ag powder may be mixed up to 50% by weight fraction. This is because firing can be performed at a temperature lower than the melting points of Ag and Cu. When the conductive paste containing the first metal powder is disposed in the first recess 21b and the third recess 22b, the size of the first metal powder only needs to be smaller than the depths of the first recess 21b and the third recess 22b. For example, the median diameter of the first metal powder is preferably 1 μm or more and 50 μm or less, more preferably 2 μm or more and 40 μm or less, and particularly preferably 5 μm or more and 30 μm or less. The above median diameter can be measured by the laser diffraction scattering method. By setting the median diameter of the first metal powder to 5 μm or more, aggregation can be suppressed and the thermal conductivity can be increased. On the other hand, by setting the median diameter of the first metal powder to 10 μm or less, the filling property can be increased. Also, the shape of the first metal powder is preferably spherical or ellipsoidal from the viewpoint of fluidity, but may be flat or needle-shaped. This is because by making it flat or needle-shaped, the contact between particles can be increased, the thermal conductivity can be increased, and the electrical resistance can be decreased.

[0079] The conductive paste may contain at least one of Ti, Hf, Zr, Nb, Ce, and Mg. The above metals may be included as active metal powders. The active metal powder may be at least one selected from TiH2, HfH2, ZrH2, NbH2, CeH2, and MgH2. Among these, TiH2 is preferable. By containing TiH2, it reacts with the nitrogen contained in the ceramic substrate 2 to form a metal compound layer such as TiN as a reaction layer at the interface with the ceramic substrate 2. Thereby, the adhesion between the first wiring 3 and the second wiring 5 to which the conductive paste has hardened and the ceramic substrate 2 is improved.

[0080] The conductive paste may further contain an organic solvent. Examples of the organic solvent include those used in general conductive pastes. For example, glycol-based solvents, carbitol-based solvents, and terpineol-based solvents can be mentioned.

[0081] The conductive paste may further contain an organic resin binder. The viscosity of the conductive paste can be adjusted according to the type and amount of the organic resin binder. As the organic resin binder, for example, resin materials such as solvents, acrylic resins, epoxy resins, urethane resins, ethyl cellulose resins, silicone resins, phenol resins, polyimide resins, polyurethane resins, melamine resins, and urea resins that are generally used as conductive pastes may be used. Note that the organic resin binder is decomposed by firing described later and evaporated and removed.

[0082] The conductive paste may contain a plurality of inorganic fillers excluding metals. By containing the inorganic filler, the volume shrinkage during sintering of the conductive paste can be reduced. As the inorganic filler, for example, AlN, Si3N4, etc. can be used.

[0083] In this embodiment, the first conductive paste 3a and the second conductive paste 5a are made of the same material. However, the first conductive paste 3a and the second conductive paste 5a may be made of different materials.

[0084] After arranging the first conductive paste 3a and the second conductive paste 5a, the first mask 61 is removed. The first conductive paste 3a is not arranged on the upper surface of the first flat portion 21a but is arranged in the first concave portion 21b, and the second conductive paste 5a is not arranged on the lower surface of the second flat portion 22a but is arranged in the third concave portion 22b. Note that the first mask 61 may be removed before arranging the first conductive paste 3a and the second conductive paste 5a in the first concave portion 21b and the third concave portion 22b.

[0085] (d) Step of forming the first wiring The first conductive paste 3a is fired and polished to form the first wiring 3 (FIG. 3E).

[0086] In the example shown in FIG. 3E, in the step of forming the first wiring 3, at the same time, the second conductive paste 5a is fired to form the second wiring 5.

[0087] The firing temperature when firing the conductive paste can be 700°C or higher and 1000°C or lower, preferably 700°C or higher and 980°C or lower, and particularly preferably 750°C or higher and 970°C or lower. The firing atmosphere is preferably a vacuum atmosphere of 10 -5 Pa or lower, or an Ar atmosphere of 99.9% or more in a slightly reduced pressure state or a slightly increased pressure state. Here, the slightly reduced pressure state means a state in which the normal atmospheric pressure (about 100 kPa) is reduced to 500 Pa, and the slightly increased pressure state means a state in which a pressure of 1.0 MPa or less is applied to the normal atmospheric pressure (about 100 kPa). After firing the first conductive paste 3a and the second conductive paste 5a, by polishing each of them, as shown in FIG. 3E, the first wiring 3 substantially flush with the first surface 21 of the ceramic substrate 2b and the second wiring 5 substantially flush with the second surface 22 of the ceramic substrate 2b are obtained.

[0088] (e) Step of forming the second recess A part of the first surface 21 is removed to form a second recess 21c adjacent to the first recess 21b via the first flat portion 21a (FIGS. 3F and 3G).

[0089] The second recess 21c is formed between the recesses 21b. Before forming the second recess 21c, a second mask 62 having a second opening 62a at a position overlapping a part of the first flat portion 21a is disposed (FIG. 3F). The second mask 62 is also disposed on the second surface 22. The second mask 62 is provided on the first wiring 3 and the first flat portion 21a continuous with the first recess 21b of the ceramic substrate 2b. Note that the second mask 62 can be formed in the same manner as the first mask 61 described above.

[0090] After forming the second mask 62, a second recess 21c is formed to obtain the ceramic substrate 2 (FIG. 3G). By disposing the second mask 62 on the first planar portion 21a adjacent to the entire circumference of the first wiring 3, after forming the second recess 21c, the first planar portion 21a is formed on the entire circumference of the first wiring 3.

[0091] The second recess 21c can be formed in the same manner as the above-described first recess 21b.

[0092] (f) Step of disposing a reflective member The reflective member 4 is disposed in the second recess 21c (FIG. 3H).

[0093] When the reflective member 4 is a reflective member made of a mixture containing a light diffusing material in an organic material such as resin, after disposing this mixture in the second recess 21c by printing or dispensing, the organic material is heated and cured at a temperature of 50°C or higher and 300°C or lower. When the reflective member 4 is a reflective member made of a mixture containing a light diffusing material (for example, boron nitride or aluminum hydroxide) in an inorganic material containing an alkali metal silicate, this mixture can be produced by mixing a mixed powder of boron nitride powder and silicon oxide powder with an alkali solution (for example, potassium hydroxide), then disposing it in the second recess 21c and heating and curing it. When the alkali solution is potassium hydroxide, when heating and curing, silicon oxide and potassium hydroxide react to produce potassium silicate which is an alkali metal silicate. Boron nitride is a member capable of reducing the shrinkage of the mixture during heat curing. Here, both the reflective member before and after curing are referred to as the reflective member.

[0094] When disposing the reflective member 4, the reflective member 4 may have a recess in which the central region of the reflective member is recessed more than the outer peripheral region on the surface of the reflective member due to its surface tension. Due to the presence of the recess, the upper surface area of the reflective member 4 becomes larger compared to the case where the upper surface of the reflective member 4 is a flat surface. Therefore, when disposing other members on the reflective member 4, the adhesion is improved by the anchor effect. For example, in the light-emitting device 100 described below, the adhesion with the covering member 73 is improved.

[0095] After arranging the reflection member 4, the second mask 62 is removed. Thereby, the wiring board 1a is obtained (FIG. 3I). Note that the second mask 62 may be removed before arranging the reflection member 4.

[0096] (g) Polishing or grinding step The method for manufacturing a wiring board according to the present disclosure may further include a step of polishing or grinding the first wiring 3 and the reflection member 4 to expose the ceramic substrate 2 after the step of arranging the reflection member 4. By the polishing or grinding step, the wiring formed on the first flat surface portion 21a of the ceramic substrate 2 can be removed. It is preferable that the upper surface of the first wiring 3 and the first flat surface portion 21a are flush with each other by polishing or grinding. In the polishing or grinding step, it is not limited to a mode of polishing or grinding both the first wiring 3 and the reflection member 4, and only one of them may be polished or ground. Further, in the polishing or grinding step, the first surface 21 of the ceramic substrate 2 may be polished or ground. When the first surface 21 of the ceramic substrate 2 is polished or ground, the upper surface of the newly obtained ceramic substrate 2 is taken as the first surface 21. The first surface 21 of the ceramic substrate 2 after polishing or grinding may be the same as the first surface 21 of the ceramic substrate 2 before polishing or grinding.

[0097] (h) Step of forming a metal layer The method for manufacturing a wiring board according to the present disclosure may include at least one of a step of arranging a first metal layer on the first wiring 3 and a step of arranging a second metal layer on the second wiring 5 after the step of arranging the reflection member 4 or after the polishing or grinding step.

[0098] The metal layer can be formed, for example, by plating (electroplating or electroless plating), vapor deposition, sputtering, or the like. It is preferable that at least one of the first metal layer and the second metal layer is formed by plating. The formation of the metal layer may be performed through a mask.

[0099] The manufacturing method of the wiring board 1a described above is (b) In the step of forming the first recess 21b, a first mask 61 having a first opening 61a at a position overlapping the first recess 21b is formed on the first surface 21 of the ceramic substrate 2a to form the first recess 21b. Then, (c) in the step of disposing the first conductive paste 3a, the step of disposing the first conductive paste 3a into the first recess 21b through the first opening 61a is included. (e) In the step of forming the second recess 21c, a second mask 62 having a second opening 62a at a position overlapping a part of the first flat portion 21a is formed on the first wiring 3 and the first flat portion 21a continuous with the first recess 21b in the ceramic substrate 2b. Then, the step of forming the second recess 21c may be included.

[0100] (Alternative Method 1) Another method for manufacturing the wiring board 1a of the present disclosure is (c’) In the step of disposing the first conductive paste 3a, a third mask 63 having a third opening 63a through which the first recess 21b and the first flat portion 21a continuous with the first recess 21b are exposed is formed on the ceramic substrate 2b (FIG. 4A), and the step of disposing the first conductive paste 3a on the first recess 21b and the exposed first flat portion 21a continuous with the first recess 21b is included (FIG. 4B). (e’) In the step of forming the second recess 21c, a step of removing a part of the first surface 21 of the ceramic substrate 2b exposed from the first wiring 3 by using the first wiring 3b formed by firing the first conductive paste 3a as a fourth mask 64 (FIG. 4C). may be included.

[0101] In the example shown in FIG. 4B, in step (c’), there is a fourth opening 63b at a position overlapping the first flat portion 21a disposed around the entire circumference of the reflecting member 4. In this case, the first conductive paste 3a is also disposed in the fourth opening 63b.

[0102] In the example shown in FIG. 4C, in step (e’), the first conductive paste 3a disposed in the fourth opening 63b is fired to form a part of the fourth mask 64.

[0103] In the manufacturing method of deformation method 1, after the step of forming the second concave portion 21c (e), or after the step of arranging the reflecting member 4 (f), a step of polishing or grinding (g) is performed to remove the first wiring 3b formed on the first flat portion 21a in step (c).

[0104] Note that since the reflecting member 4 is not arranged on the second surface 22 of the ceramic substrate, the second surface may be processed in the same manner as the above steps (c) and (e).

[0105] (Second Embodiment) The wiring board 1b according to the second embodiment will be described with reference to FIGS. 5 and 6.

[0106] The wiring board 1b is rectangular in plan view. The side surface of the wiring board 1b has a first side surface 11, a second side surface 12 and a third side surface 13 adjacent to the first side surface 11, and a fourth side surface 14 on the opposite side of the first side surface 11 and adjacent to the second side surface 12 and the third side surface 13. In the wiring board 1b, the first wiring 3 constitutes a part of the first side surface 11 and a part of the fourth side surface 14, and further, the reflecting member 4 constitutes a part of the first side surface 11, a part of the second side surface 12, a part of the third side surface 13, and a part of the fourth side surface 14, which is different from the wiring board 1a according to the first embodiment. In the wiring board 1b, in plan view, the first wiring 3 is a rectangle extending in the directions of the first side surface 11 and the fourth side surface 14. The wiring board 1b has the first wiring 3 arranged not only on the first surface 21 side but also on the first side surface 11 and the fourth side surface 14, and has excellent heat dissipation performance because the heat spreads greatly in the horizontal direction of the first surface 21.

[0107] (Third Embodiment) The wiring board 1c according to the third embodiment will be described with reference to FIGS. 7 and 8.

[0108] The wiring board 1c is different from the wiring board 1a according to the first embodiment in that the reflecting member 4 constitutes a part of the first side surface 11, a part of the second side surface 12, a part of the third side surface 13, and a part of the fourth side surface 14. In the wiring board 1c, the reflecting member 4 is disposed on the entire circumference of the first surface 21. Since the area of the first surface 21 where the reflecting member 4 is disposed is large in the wiring board 1c, it has excellent light reflectivity.

[0109] (Light-emitting device) The light-emitting device 100 according to the embodiment will be described with reference to FIGS. 9 and 10. FIG. 9 is a schematic plan view showing the light-emitting device 100. FIG. 10 is a schematic cross-sectional view showing a cross-section taken along the line X-X in FIG. 9.

[0110] The light-emitting device 100 includes the wiring board 1 of the present disclosure and a light-emitting element 70 having an element electrode 71 disposed on the wiring board 1. The element electrode 71 and the first wiring 3 are electrically connected via a conductive member 81 and a first metal layer 6. Here, the light-emitting device 100 further includes a light-transmissive member 72 disposed on the upper surface of the light-emitting element 70 and a covering member 73 that exposes the upper surface of the light-transmissive member 72 and covers the light-emitting element 70 and the light-transmissive member 72.

[0111] The light-emitting device 100 has, as an example, one light-emitting element 70 and one light-transmissive member 72. Hereinafter, each component of the light-emitting device 100 will be described.

[0112] (Wiring board) The wiring board can be, for example, the wiring board 1. The wiring board 1 includes the wiring board 1a of the first embodiment. The wiring board 1a has a first surface 21 and a second surface 22 on the opposite side of the first surface 21. The first surface 21 has a first planar portion 21a, a first concave portion 21b, and a second concave portion 21c. The wiring board 1a has a ceramic substrate 2, a first wiring 3 disposed in the first concave portion 21b, and a reflective member 4 disposed in the second concave portion 21c. The second surface 22 has a second planar portion 22a and a third concave portion 22b. The wiring board 1a further has a second wiring 5 disposed in the third concave portion 22b. The wiring board 1 further includes a first metal layer 6 disposed on the first wiring 3 of the wiring board 1a and a second metal layer 7 disposed on the second wiring 5 of the wiring board 1a. The wiring board 1 has the first surface 21 side as the upper surface, and a light-emitting element 70 is disposed on the first surface 21 side. The first wiring 3 and the first metal layer 6 on the upper surface side have a size and shape capable of disposing the element electrode 71 of the light-emitting element 70.

[0113] (Light-emitting element) The light-emitting element 70 is a member that emits light when supplied with power. The planar shape of the light-emitting element 70 is, for example, rectangular. The light-emitting element 70 includes a semiconductor laminate. Here, a light-transmissive substrate such as sapphire or gallium nitride is disposed on the upper surface side of the semiconductor laminate, and a pair of positive and negative element electrodes 71 are provided on the lower surface side. As the semiconductor laminate, an arbitrary composition can be used according to the desired emission wavelength. For example, a nitride semiconductor (In x Al y Ga 1-x-y N, 0≦X, 0≦Y, X + Y≦1), GaP, or GaAlAs and AlInGaP capable of emitting red light can be used. Also, the size and shape of the light-emitting element 70 can be appropriately selected according to the purpose of use.

[0114] The planar shape of the pair of positive and negative element electrodes 71 is, for example, rectangular and is exposed on the lower surface 70a of the light-emitting element 70. The element electrode 71 can be formed of, for example, a single-layer film or a laminated film of a metal such as Au, Pt, Pd, Rh, Ni, W, Mo, Cr, Ti, or an alloy thereof.

[0115] Here, the element electrode 71 is connected to the first wiring 3 via the conductive member 81 and the first metal layer 6. That is, the element electrode 71 is indirectly electrically connected to the first wiring 3. The conductive member 81 can be a bump such as gold or solder, for example, and the element electrode 71 and the first metal layer 6 may be connected by disposing solder or the like over the entire electrode surface, for example, without providing a bump.

[0116] (Light-transmissive member) The light-transmissive member 72 is a member that protects the upper surface 70b of the light-emitting element 70. The upper surface of the light-transmissive member 72 is the main light extraction surface of the light-emitting device 100. Here, as an example, the light-transmissive member 72 has a rectangular shape and has a size and shape that enclose the light-emitting element 70 in plan view. The light-transmissive member 72 may have the same shape and size as the light-emitting element 70 in plan view.

[0117] The light-transmissive member 72 is made of, for example, a light-transmissive resin material, and an epoxy resin, a silicone resin, or a resin obtained by mixing these can be used. The light-transmissive member 72 may contain a phosphor. For example, by containing a phosphor that absorbs blue light from the light-emitting element 70 and emits yellow light, white light can be emitted from the light-emitting device 100. Further, the light-transmissive member 72 may contain a plurality of types of phosphors. For example, by containing a phosphor that absorbs blue light from the light-emitting element 70 and emits green light and a phosphor that emits red light, white light can also be emitted from the light-emitting device 100.

[0118] The light-transmissive member 72 may further contain a light-emitting material such as a phosphor or quantum dots. Examples of such phosphors include yttrium aluminum (gallium-doped) garnet activated with cerium, calcium aluminosilicate (strontium) nitride activated with europium, potassium fluorosilicate activated with manganese, and β-sialon-based phosphors. Specifically, as the phosphor, yttrium aluminum garnet-based phosphors (for example, (Y,Gd)3(Al,Ga)5O12 :Ce), lutetium-aluminum-garnet-based phosphor (e.g., Lu3(Al,Ga)5O 12 :Ce), terbium-aluminum-garnet-based phosphor (e.g., Tb3(Al,Ga)5O 12 :Ce), CCA-based phosphor (e.g., Ca 10 (PO4)6Cl2:Eu), SAE-based phosphor (e.g., Sr4Al 14 O 25 :Eu), chlorosilicate-based phosphor (e.g., Ca8MgSi4O 16 Cl2:Eu), silicate-based phosphor (e.g., (Ba,Sr,Ca,Mg)2SiO4:Eu), β-sialon-based phosphor (e.g., (Si,Al)3(O,N)4:Eu) or α-sialon-based phosphor (e.g., Ca(Si,Al) 12 (O,N) 16 :Eu) and other oxynitride-based phosphors, LSN-based phosphor (e.g., (La,Y)3Si6N 11 :Ce), BSESN-based phosphor (e.g., (Ba,Sr)2Si5N8:Eu), SLA-based phosphor (e.g., SrLiAl3N4:Eu), CASN-based phosphor (e.g., CaAlSiN3:Eu) or SCASN-based phosphor (e.g., (Sr,Ca)AlSiN3:Eu) and other nitride-based phosphors, KSF-based phosphor (e.g., K2SiF6:Mn), KSAF-based phosphor (e.g., K2(Si 1-x Al x )F 6-x :Mn, where x satisfies 0 < x < 1.) or fluoride-based phosphors such as MGF-based phosphor (e.g., 3.5MgO·0.5MgF2·GeO2:Mn) etc. can be mentioned. As quantum dots, quantum dots having a perovskite structure (e.g., (Cs,FA,MA)(Pb,Sn)(F,Cl,Br,I)3, where FA represents formamidinium and MA represents methylammonium.), II-VI group quantum dots (e.g., CdSe), III-V group quantum dots (e.g., InP), quantum dots having a chalcopyrite structure (e.g., (Ag,Cu)(In,Ga)(S,Se)2) etc. can be mentioned.

[0119] (Coating member) The covering member 73 is a member that is disposed on the upper surface of the wiring board 1 and covers and protects the side surface of the light-emitting element 70, as well as the side and lower surfaces of the light-transmissive member 72. In the example shown in FIG. 10, the covering member 73 is disposed between the light-emitting element 70 and the wiring board 1, and also covers the side and lower surfaces of the element electrode 71, and the side and upper surfaces of the conductive member 81.

[0120] The covering member 73 can be formed of a resin having light reflectivity, light transmissivity, light shielding property, etc., a resin containing a light-reflective substance in these resins, or the like. The covering member 73 preferably has at least one of light reflectivity and light shielding property. Examples of the resin include a resin containing one or more of a silicone resin, a modified silicone resin, an epoxy resin, a modified epoxy resin, an acrylic resin, or a hybrid resin. Examples of the light-reflective substance include titanium oxide, silicon oxide, zirconium oxide, potassium titanate, aluminum oxide, aluminum nitride, boron nitride, mullite, and the like. The covering member 73 may contain a phosphor, a light diffusing material, a coloring agent, or the like. The covering member 73 may be a member in which a light diffusing material is contained in the resin, as described for the reflective member of the wiring board. Further, the covering member 73 may be a light-reflective member made of an inorganic material containing, for example, boron nitride or an alkali metal silicate. In this case, it can further contain titanium oxide or zirconium oxide.

[0121] (Method for manufacturing a light-emitting device) The method for manufacturing the light-emitting device according to the embodiment will be described with reference to FIGS. 11A to 11E. FIGS. 11A to 11E are cross-sectional views for explaining the method for manufacturing the light-emitting device 100 shown in FIGS. 9 and 10.

[0122] The method for manufacturing a light-emitting device includes a step of preparing a wiring board obtained by the above-described method for manufacturing a wiring board, and a step of disposing a light-emitting element 70 having an element electrode 71 on a first metal layer 6. In the step of disposing the light-emitting element 70, the first metal layer 6 and the light-emitting element 70 are electrically connected directly or indirectly. Here, the method further includes a step of disposing a conductive member 81, a step of disposing a light-transmissive member 72 on the upper surface of the light-emitting element 70, and a step of forming a covering member 73 that exposes the upper surface of the light-transmissive member 72 and covers the light-emitting element 70 and the light-transmissive member 72. Hereinafter, each step of the method for manufacturing a light-emitting device will be described.

[0123] (Step of preparing a wiring board) As an example, a wiring board 1 is prepared (FIG. 11A). The wiring board 1 includes the wiring board 1a of the first embodiment, a first metal layer 6 disposed on the first wiring 3, and a second metal layer 7 disposed on the second wiring 5. The first metal layer 6 and the second metal layer 7 can be formed by the step (h) shown in the method for manufacturing a wiring board of the first embodiment described above. The wiring board 1 has the first surface 21 side on which the light-emitting element 70 is disposed as the upper surface. Further, the first wiring 3 and the first metal layer 6 are formed in accordance with the size, arrangement, and interval between a pair of element electrodes 71 of the light-emitting element 70.

[0124] (Step of disposing a light-emitting element) A conductive member 81 is disposed on the first metal layer 6 on the upper surface side of the wiring board 1. The conductive member may be a bump such as gold or solder. Next, with the element electrode 71 facing the wiring board 1 side, the light-emitting element 70 is disposed (FIG. 11B). The element electrode 71 of the light-emitting element 70 is indirectly electrically connected to the first wiring 3 via the conductive member 81 and the first metal layer 6.

[0125] (Step of disposing a light-transmissive member) Place a light-transmissive member 72 on the upper surface 70b of the light-emitting element 70 (FIG. 11C). The light-transmissive member 72 is a member formed in a sheet shape or a plate shape and is placed on the upper surface of the light-emitting element 70 via an adhesive. Note that the light-emitting element 70 on which the light-transmissive member 72 is previously placed may be placed on the wiring substrate 1. Note that the light-transmissive member 72 may be placed by, for example, performing application of a material of the uncured light-transmissive member 72 by potting, spraying, inkjet, printing, or the like, and then curing it.

[0126] (Place a covering member) Place a covering member 73 above the wiring substrate 1 so as to expose the upper surface 72a of the light-transmissive member 72 (FIG. 11D). The covering member 73 is placed so as to cover the side surface, the side surface, and the lower surface of the light-transmissive member 72 of the light-emitting element 70. It is preferable to also cover the lower surface of the light-emitting element 70 and the side surface and the upper surface of the conductive member 81. The covering member 73 can be placed, for example, by arranging a nozzle of a resin discharge device above the wiring substrate 1, moving the nozzle while discharging an uncured resin material from the tip of the nozzle, and then curing it. The application of the covering member 73 may be performed once or may be performed in a plurality of times. Note that the covering member 73 may be formed by compression molding or transfer molding.

[0127] The upper surface 73a of the covering member 73 is preferably formed to be flush with the upper surface 72a of the light-transmissive member 72. The upper surface 73a of the covering member 73 can be formed to be flush with the upper surface 72a of the light-transmissive member 72 by polishing, grinding, or the like the covering member 73 or the light-transmissive member 72.

[0128] The wiring board of the present disclosure is a wiring board that can be thinned and has excellent thermal conductivity. Therefore, it can be suitably applied to the wiring board used in light-emitting devices such as in-vehicle light sources, lighting light sources, various indicator light sources, display light sources, liquid crystal backlight light sources, traffic lights, etc., and the manufacturing process of the wiring board. However, the wiring board and the manufacturing method of the wiring board of the present disclosure are not limited to the wiring board used in the light-emitting device and its manufacturing process, but can be applied to the wiring board used in various applications and its manufacturing process.

[0129] Embodiments according to the present disclosure include the following items. [Item 1] A ceramic substrate having a first surface and a second surface opposite to the first surface, wherein the first surface has a first flat portion, a first concave portion, and a second concave portion; A first wiring disposed in the first concave portion; A reflecting member disposed in the second concave portion; A wiring board having the above. [Item 2] The wiring board according to Item 1, wherein the inner surface defining the first concave portion includes a curved surface. [Item 3] The wiring board according to Item 1 or Item 2, wherein the first wiring and the reflecting member are disposed adjacent to each other via the first flat portion. [Item 4] The wiring board according to Item 3, wherein the distance between the first wiring and the reflecting member adjacent to each other via the first flat portion is 1 μm or more and 100 μm or less. [Item 5] The wiring board according to any one of Items 1 to 4, wherein the first flat portion is disposed around the entire circumference of the first concave portion. [Item 6] The wiring board according to any one of Items 1 to 5, wherein the first flat portion is disposed around the entire circumference of the second concave portion. [Item 7] The wiring board according to any one of Items 1 to 6, having the second concave portion between two of the first concave portions. [Item 8] The wiring board according to claim 7, wherein the second recess is further connected to a portion surrounding the two first recesses together. [Claim 9] The two first recesses are surrounded by one second recess, The wiring board according to claim 7 or 8, wherein the entire circumferences of the first recess and the second recess are each surrounded by the first planar portion. [Claim 10] The wiring board according to any one of claims 1 to 9, wherein the depth of the first recess is deeper than the depth of the second recess. [Claim 11] The wiring board according to any one of claims 1 to 10, wherein the first wiring includes at least one of Ti, Hf, Zr, Nb, Ce, and Mg. [Claim 12] The wiring board according to any one of claims 1 to 11, wherein the reflective member includes a resin and a light diffusing material. [Claim 13] The wiring board according to any one of claims 1 to 12, wherein the ceramic substrate is AlN or SiN. [Claim 14] A step of preparing a ceramic substrate having a first surface and a second surface on the opposite side of the first surface; A step of removing a part of the first surface to form a first recess; A step of disposing a first conductive paste in the first recess; A step of firing the first conductive paste to form a first wiring; A step of removing a part of the first surface to form a second recess adjacent to the first recess via a first planar portion; A step of disposing a reflective member in the second recess; A method for manufacturing a wiring board, including: [Claim 15] The method for manufacturing a wiring board according to claim 14, wherein in the step of forming the second recess, the second recess is formed between the two first recesses. [Claim 16] The method for manufacturing a wiring board according to claim 14 or 15, wherein the first conductive paste contains at least one of Ti, Hf, Zr, Nb, Ce, and Mg. [Claim 17] In the step of forming the first recess, a first mask having a first opening at a position overlapping the first recess is formed on the first surface of the ceramic substrate to form the first recess. Then, in the step of disposing the first conductive paste, the first conductive paste is disposed in the first recess through the first opening. In the step of forming the second recess, a second mask having a second opening at a position overlapping a part of the first flat portion is formed on the first wiring and the first flat portion of the ceramic substrate continuous with the first recess in the first recess. Then, forming a second recess is included. The method for manufacturing a wiring board according to any one of claims 14 to 16. [Claim 18] In the step of disposing the first conductive paste, a third mask having a third opening through which the first recess and the first flat portion continuous with the first recess are exposed is formed on the ceramic substrate. And a step of disposing the first conductive paste on the first recess and the exposed first flat portion continuous with the first recess. In the step of forming the second recess, a step of removing a part of the first surface of the ceramic substrate exposed from the first wiring using the first wiring formed by firing the first conductive paste as a fourth mask is included. The method for manufacturing a wiring board according to any one of claims 14 to 16. [Claim 19] The method for manufacturing a wiring board according to any one of claims 14 to 18, further including polishing or grinding the first wiring and the reflective member after the step of disposing the reflective member to expose the ceramic substrate. [Claim 20] In the step of forming the first wiring, the firing temperature is 700°C or higher and 1000°C or lower. The method for manufacturing a wiring board according to any one of claims 14 to 19.

Description of Reference Numerals

[0130] 1, 1a, 1b, 1c... wiring board 2, 2a, 2b... ceramic substrate, 3... first wiring, 3a... first conductive paste 4... reflective member, 5... second wiring, 6... first metal layer, 7... second metal layer 5a... second conductive paste 11... first side, 12... second side, 13... third side, 14... fourth side 21... first surface, 21a... first flat portion, 21b... first recess, 21c... second recess 22... second surface, 22a... second flat portion, 22b... third recess, 22c... second recess 23... side surface of the ceramic substrate 61... first mask, 61a... first opening, 62... second mask, 62a... second opening 63... third mask, 63a... third opening, 63b... fourth opening, 64... fourth mask 70... light emitting element, 70a... lower surface of the light emitting element, 70b... upper surface of the light emitting element 71... element electrode, 72... light transmissive member, 72a... upper surface of the light transmissive member 73... covering member, 73a... upper surface of the covering member, 81... conductive member, 100... light emitting device

Claims

1. A ceramic substrate having a first surface and a second surface on the opposite side of the first surface, wherein the first surface has a first planar portion, a first concave portion, and a second concave portion; A first wiring disposed in the first concave portion; A reflecting member disposed in the second concave portion; A wiring board having the above.

2. The wiring board according to claim 1, wherein an inner surface defining the first concave portion includes a curved surface.

3. The wiring board according to claim 1, wherein the first wiring and the reflecting member are disposed adjacent to each other via the first planar portion.

4. The wiring board according to claim 3, wherein a distance between the first wiring and the reflecting member adjacent to each other via the first planar portion is 1 μm or more and 100 μm or less.

5. The wiring board according to claim 1 or 2, wherein the first planar portion is disposed around the entire circumference of the first concave portion.

6. The wiring board according to claim 1 or 2, wherein the first planar portion is disposed around the entire circumference of the second concave portion.

7. The wiring board according to claim 1 or 2, having the second concave portion between two of the first concave portions.

8. The wiring board according to claim 7, wherein the second concave portion is further connected to a portion surrounding the two first concave portions together.

9. The two first concave portions are surrounded by one second concave portion, The wiring board according to claim 7, wherein the entire circumference of the first concave portion and the entire circumference of the second concave portion are respectively surrounded by the first planar portion.

10. The wiring board according to claim 1 or 2, wherein a depth of the first concave portion is deeper than a depth of the second concave portion.

11. The wiring board according to claim 1 or 2, wherein the first wiring includes at least one of Ti, Hf, Zr, Nb, Ce, and Mg.

12. The wiring board according to claim 1 or 2, wherein the reflecting member includes a resin and a light diffusing material.

13. The wiring board according to claim 1 or 2, wherein the ceramic substrate is AlN or SiN.

14. A step of preparing a ceramic substrate having a first surface and a second surface on the opposite side of the first surface; A step of removing a part of the first surface to form a first concave portion; A step of disposing a first conductive paste in the first concave portion; A step of firing the first conductive paste to form a first wiring; A step of removing a part of the first surface to form a second concave portion adjacent to the first concave portion via a first planar portion; A step of disposing a reflecting member in the second concave portion; A method for manufacturing a wiring board, including

15. The method for manufacturing a wiring board according to claim 14, wherein in the step of forming the second recess, the second recess is formed between the two first recesses.

16. The manufacturing method according to claim 14 or claim 15, wherein the first conductive paste contains at least one of Ti, Hf, Zr, Nb, Ce, and Mg.

17. In the step of forming the first recess, a first mask having a first opening at a position overlapping the first recess is formed on the first surface of the ceramic substrate to form the first recess. Then, in the step of disposing the first conductive paste, the first conductive paste is disposed in the first recess through the first opening, In the step of forming the second recess, a second mask having a second opening at a position overlapping a part of the first flat portion is formed on the first wiring and the first flat portion continuous with the first recess of the ceramic substrate. Then, forming a second recess is included, The method for manufacturing a wiring board according to claim 14 or claim 15.

18. In the step of disposing the first conductive paste, a third mask having a third opening through which the first recess and the first flat portion continuous with the first recess are exposed is formed on the ceramic substrate. The step of disposing the first conductive paste on the first recess and the exposed first flat portion continuous with the first recess is included, In the step of forming the second recess, the step of removing a part of the first surface of the ceramic substrate exposed from the first wiring by using the first wiring formed by firing the first conductive paste as a fourth mask is included, The method for manufacturing a wiring board according to claim 14 or claim 15.

19. The manufacturing method according to any one of claim 14, further including polishing or grinding the first wiring and the reflective member after the step of disposing the reflective member to expose the ceramic substrate.

20. The manufacturing method according to any one of claim 14, wherein in the step of forming the first wiring, the firing temperature is 700 °C or higher and 1000 °C or lower.

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