Substrate manufacturing method

Abstract

To provide a substrate manufacturing method capable of forming a hole penetrating a ceramic substrate with high precision.SOLUTION: A substrate manufacturing method includes a step of preparing a ceramic substrate having a first surface and a second surface located on the opposite side to the first surface, a first processing step of irradiating a first region of the first surface with a first laser beam having a first pulse width to ablate the first region of the ceramic substrate, and a second processing step of irradiating a second region with a second laser beam having a second pulse width longer than the first pulse width, the second region being spaced apart from the first region on any one of the first surface and the second surface in plan view, thereby thermally processing a third region including the first region and the second region. In the second processing step, the third region and a region surrounded by the third region form a hole penetrating from the first surface through the second surface.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a substrate. [Background technology]

[0002] Conventionally, there is known a substrate provided with wiring on which light emitting elements and various electric elements can be mounted. Patent Document 1 discloses a technique for forming via holes penetrating a ceramic base material by laser processing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2019-511115 Summary of the Invention [Problem to be solved by the invention]

[0004] Ceramic substrates are harder than substrates made of other materials, and therefore more difficult to process with high precision than substrates made of other materials. On the other hand, in order to realize high-precision mounting and wiring of light-emitting elements and various electric elements on the substrate, high precision is required for the position and shape of holes penetrating the substrate.

[0005] An object of an embodiment of the present disclosure is to provide a method for manufacturing a substrate that is capable of forming holes penetrating a ceramic substrate with high accuracy. [Means for solving the problem]

[0006] A method for manufacturing a substrate according to one embodiment of the present disclosure includes a step of preparing a ceramic substrate having a first surface and a second surface located opposite the first surface, a first processing step of ablation processing a first region of the ceramic substrate by irradiating a first laser having a first pulse width to the first region of the first surface, and a second processing step of thermally processing a third region including the first region and the second region by irradiating a second laser having a second pulse width longer than the first pulse width to a second region separated from the first region on either the first surface or the second surface in a planar view, wherein in the second processing step, a hole is formed that penetrates the third region and a region surrounded by the third region from the first surface to the second surface. Effect of the Invention

[0007] According to an embodiment of the present disclosure, it is possible to provide a manufacturing method for a substrate that is capable of forming holes penetrating a ceramic substrate with high accuracy. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic top view illustrating a configuration of a light emitting device including a substrate according to an embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. [Diagram 3] 3A to 3C are schematic top views showing a step of preparing a ceramic substrate which is a target of the substrate manufacturing method according to the embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view taken along line IV-IV in FIG. [Diagram 5] 3A to 3C are schematic top views of a ceramic substrate illustrating a first processing step in a method for manufacturing a substrate according to an embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view taken along line VI-VI in FIG. [Figure 7] 4A to 4C are first schematic top views of the ceramic substrate illustrating a second processing step in the substrate manufacturing method according to the embodiment. [Figure 8] 8 is a first schematic cross-sectional view taken along line VIII-VIII in FIG. 7. [Figure 9] 5A is a second schematic top view of the ceramic substrate, illustrating a second processing step in the substrate manufacturing method according to the embodiment. FIG. [Figure 10] 10 is a second schematic cross-sectional view taken along line XX in FIG. 9. [Figure 11A] 5A and 5B are schematic top views showing holes formed by the substrate manufacturing method according to the embodiment. [Figure 11B] 4 is a schematic bottom view showing a hole formed by the substrate manufacturing method according to the embodiment. FIG. [Figure 12] 12 is a schematic cross-sectional view taken along line XII-XII in FIG. 11A. [Figure 13] 5A to 5C are schematic top views of the ceramic substrate illustrating a second processing step in the substrate manufacturing method according to the first modified example. [Figure 14] 14 is a schematic cross-sectional view taken along line XIV-XIV in FIG. 13. [Figure 15] 13 is a schematic top view of a ceramic substrate showing a first region in a substrate manufacturing method according to a second modified example. FIG. [Figure 16] 16 is a schematic cross-sectional view taken along line XVI-XVI in FIG. 15. [Figure 17] 13 is a first schematic top view of a ceramic substrate showing a second region and a third region in a substrate manufacturing method according to a second modified example. FIG. [Figure 18] 18 is a first schematic cross-sectional view taken along line XVIII-XVIII in FIG. 17. [Figure 19] 13 is a second schematic top view of the ceramic substrate, illustrating a second region and a third region, in a substrate manufacturing method according to a second modified example. FIG. [Figure 20] 20 is a second schematic cross-sectional view taken along line XX-XX in FIG. 19. [Figure 21A] 13 is a schematic top view of a substrate showing holes formed by a substrate manufacturing method according to a second modified example. FIG. [Figure 21B] 13 is a schematic bottom view of the substrate showing holes formed by a substrate manufacturing method according to a second modified example. FIG. [Figure 22A] FIG. 21B is a schematic cross-sectional view taken along line XXII-XXII in FIG. 21A. [Figure 22B] FIG. 11 is a schematic cross-sectional view showing the configuration of a light emitting device including a substrate according to a second modified example. [Figure 23A] 1 is a graph showing the reflectance of a ceramic substrate and glass. [Figure 23B] 4 is a top view photograph of a hole formed by the substrate manufacturing method according to the first embodiment. [Figure 24] 4 is a bottom photograph of a hole formed by the substrate manufacturing method according to the first embodiment. [Diagram 25] 13 is a top view photograph of a hole formed by the substrate manufacturing method according to Example 2. [Figure 26] 13 is a bottom photograph of a hole formed by the substrate manufacturing method according to Example 2. [Figure 27] 11 is a top view photograph of a hole formed by a substrate manufacturing method according to a reference example. [Figure 28] 11 is a bottom photograph of a hole formed by a substrate manufacturing method according to a reference example. [Figure 29] 13 is a top view photograph of a hole formed by a substrate manufacturing method according to a comparative example. [Diagram 30] 13 is a bottom photograph of a hole formed by a substrate manufacturing method according to a comparative example. [Diagram 31] FIG. 4 is a schematic diagram illustrating the interval between a first region and a second region. [Diagram 32] 11 is a diagram showing the relationship between the distance between the first region and the second region and the misalignment of formation positions. FIG. [Diagram 33] Photographs of the first and second surfaces taken after the first processing step and the second processing step, respectively. [Diagram 34] 4 is a cross-sectional view of a hole for explaining a first example of the shape of the inner side surface of the hole. FIG. [Diagram 35] 11 is a cross-sectional view of a hole for explaining a second example of the shape of the inner side surface of the hole. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A method for manufacturing a substrate according to an embodiment of the present disclosure will be described in detail with reference to the drawings. However, the embodiments shown below are merely illustrative of a method for manufacturing a substrate for embodying the technical ideas of the present disclosure, and are not limited to the following. Furthermore, unless otherwise specified, the dimensions, materials, shapes, and relative arrangements of the components described in the embodiments are merely illustrative examples, and are not intended to limit the scope of the present disclosure to those alone. Note that the size, positional relationship, etc. of the components shown in each drawing may be exaggerated to clarify the explanation. In addition, in the following explanation, the same names and symbols indicate the same or similar components, and detailed explanations will be omitted as appropriate. An end view showing only a cut surface may be used as a cross-sectional view.

[0010] In the drawings shown below, directions may be indicated by the X-axis, Y-axis, and Z-axis, but the X-axis, Y-axis, and Z-axis are mutually orthogonal directions. The X-direction along the X-axis and the Y-direction along the Y-axis indicate directions along a first surface of a ceramic substrate that is the target of the substrate manufacturing method according to the embodiment. The Z-direction along the Z-axis indicates a direction orthogonal to the first surface. That is, the first surface of the ceramic substrate is parallel to the XY plane, and the Z-axis is orthogonal to the XY plane.

[0011] The direction in which the arrow points in the X direction is written as the +X side, and the opposite side of the +X direction is written as the -X side. The direction in which the arrow points in the Y direction is written as the +Y side, and the opposite side of the +Y direction is written as the -Y side. The direction in which the arrow points in the Z direction is written as the upward or +Z side, and the opposite side of the +Z direction is written as the -Z side.

[0012] Planar view in the terms of the embodiment refers to viewing the object from the +Z side or the -Z side. In the embodiment, the surface of the object when viewed from the +Z side is the "upper surface", and the surface of the object when viewed from the -Z side is the "lower surface". Of the first and second surfaces of the ceramic substrate that is the manufacturing target of the substrate manufacturing method according to the embodiment, the first surface corresponds to the "upper surface", and the second surface corresponds to the "lower surface". However, these do not limit the orientation when using the substrate manufacturing method according to the embodiment. In the embodiments described below, along the X-axis, Y-axis, and Z-axis includes the object having a tilt within a range of ±10° with respect to these axes. In the embodiments, the orthogonal may include an error of ±10° with respect to 90°.

[0013] In addition, in this specification or claims, when there are multiple elements of a certain type and each element is to be expressed with a distinction, the elements may be distinguished by adding "first," "second," etc. to the beginning of the element. In addition, the objects to be distinguished may differ between this specification and the claims. Therefore, even if the claims describe an element with the same notation as this specification, the object identified by this element may not match between this specification and the claims.

[0014] For example, when there are elements distinguished by the notation "first", "second", and "third" in this specification, and the elements to which "first" and "third" are attached in this specification are described in the claims, or when the elements to which "first" is attached and the elements to which no specific ordinal number is attached are described in the claims, the elements may be distinguished by the notation "first" and "second" in the claims from the viewpoint of readability. In this case, the elements to which "first" and "second" are attached in the claims refer to the elements to which "first" and "third" are attached in this specification, or the elements to which no specific ordinal number is attached, respectively. Note that this rule is not limited to the application of elements, and can be applied rationally and flexibly to other objects as well.

[0015] [Embodiment] <Configuration Example of Light Emitting Device 100 Including Substrate 2> First, the configuration of a light emitting device including a substrate according to an embodiment will be described with reference to Fig. 1 and Fig. 2. In the example shown in Fig. 1 and Fig. 2, a case where a substrate including ceramics is used in a light emitting device will be described as an example. Fig. 1 is a schematic top view showing an example of the configuration of a light emitting device 100 including a substrate 2. Fig. 2 is a schematic cross-sectional view taken along line II-II in Fig. 1.

[0016] 1 and 2, the light emitting device 100 has a plurality of light emitting units 1, a substrate 2, and a mounting substrate 3. Each of the plurality of light emitting units 1 is disposed on the +Z side surface of the substrate 2. The substrate 2 is disposed on the +Z side surface of the mounting substrate 3.

[0017] In the example shown in FIG. 1 and FIG. 2, the light emitting device 100 has 15 light emitting sections 1. The 15 light emitting sections 1 include three light emitting sections 1a, six light emitting sections 1b, and six light emitting sections 1c. As shown in FIG. 1, the shape of each of the 15 light emitting sections 1 in a plan view is approximately rectangular. The area of ​​the light emitting section 1b is equal to the area of ​​the light emitting section 1c. The area of ​​the light emitting section 1a is larger than the area of ​​each of the light emitting sections 1b and the light emitting section 1c. The six light emitting sections 1b are arranged in a line in the Y direction on the -X side of the three light emitting sections 1a in a plan view. The six light emitting sections 1c are arranged in a line in the Y direction on the +X side of the three light emitting sections 1a in a plan view. However, in the multiple light emitting sections 1, the number, the combination of light emitting sections 1 having different areas, the shapes in a plan view, the arrangement in a plan view, and the like can be appropriately changed.

[0018] The light emitted by the light-emitting section 1 is preferably white light, but may be monochromatic light. The wavelength of the light emitted by the light-emitting section 1 can be appropriately selected depending on the application of the light-emitting device 100.

[0019] 2, the light-emitting unit 1 is placed on the +Z side surface of the substrate 2, i.e., the first surface 21, with the +Z side surface being the light-emitting surface 11 and the surface opposite to the light-emitting surface 11 being the mounting surface. The light-emitting unit 1 includes a light-emitting element 12, a translucent member 13 provided on the +Z side surface of the light-emitting element 12, and a covering member 14 that covers the side surfaces of the light-emitting element 12 and the side surfaces of the translucent member 13 except for the +Z side surface of the translucent member 13. Note that the configuration of each of the 15 light-emitting units 1 is the same.

[0020] It is preferable that at least a pair of positive and negative electrodes are provided on the surface of the light-emitting element 12 opposite to the light-emitting surface 11. In the example shown in Figures 1 and 2, the shape of the light-emitting surface 11 in a plan view is substantially rectangular. However, the shape of the light-emitting surface 11 in a plan view may be substantially circular or elliptical, or may be a polygon such as substantially triangular or substantially hexagonal.

[0021] The light emitting element 12 includes various semiconductors such as III-V group compound semiconductors and II-VI group compound semiconductors. The light emitting element 12 may be an LED (Light Emitting Diode) or an LD (Laser Diode). X Al Y Ga 1-X-Y It is preferable to use a nitride semiconductor such as InN (0≦X, 0≦Y, X+Y≦1), and InN, AlN, GaN, InGaN, AlGaN, InGaAlN, etc. can also be used. The emission peak wavelength of the light emitting element 12 is preferably 400 nm or more and 530 nm or less, more preferably 400 nm or more and 490 nm or less, and even more preferably 440 nm or more and 475 nm or less, from the viewpoints of luminous efficiency, excitation of a wavelength conversion substance described later, and color mixing relationship with the emission thereof.

[0022] The light-transmitting member 13 is, for example, a substantially rectangular member in a plan view, and is provided so as to cover the upper surface of the light-emitting element 12. The light-transmitting member 13 can be formed using a light-transmitting resin material or an inorganic material such as ceramics or glass. As the resin material, a thermosetting resin such as a silicone resin, a silicone-modified resin, an epoxy resin, an epoxy-modified resin, or a phenolic resin can be used. In particular, a silicone resin or a modified resin thereof, which has excellent light resistance and heat resistance, is preferable. The light-transmitting property here is preferably such that 60% or more of the light from the light-emitting element 12 is transmitted. In addition, the light-transmitting member 13 can be a thermoplastic resin such as a polycarbonate resin, an acrylic resin, a methylpentene resin, or a polynorbornene resin. Furthermore, the light-transmitting member 13 may contain a light diffusing material or a wavelength conversion material that converts the wavelength of at least a part of the light from the light-emitting element 12. For example, the light-transmitting member 13 may be a resin material, a ceramic, a glass, or the like containing a wavelength conversion material, or a sintered body of a wavelength conversion material. Furthermore, the light-transmitting member 13 may be a multi-layer member in which a resin layer containing a wavelength converting material or a light diffusing material is disposed on the ±Z side surfaces of a molded body of resin, ceramics, glass, or the like.

[0023] The wavelength conversion material is yttrium-aluminum-garnet phosphor (e.g., (Y,Gd)3(Al,Ga)5O 12 :Ce), lutetium aluminum garnet phosphors (e.g., Lu3(Al,Ga)5O 12 :Ce), terbium aluminum garnet phosphors (e.g., Tb3(Al,Ga)5O 12 :Ce), CCA phosphors (e.g., Ca 10 (PO4)6Cl2:Eu), SAE phosphors (e.g., Sr4Al 14 O 25 :Eu), chlorosilicate phosphors (e.g., Ca8MgSi4O 16 Cl2:Eu), silicate phosphors (e.g., (Ba,Sr,Ca,Mg)2SiO4:Eu), β-sialon phosphors (e.g., (Si,Al)3(O,N)4:Eu) or α-sialon phosphors (e.g., Ca(Si,Al) 12(O,N) 16 : Nitride-based phosphors such as oxynitride phosphors (e.g., (La,Y)3Si6N 11 :Ce), BSESN-based phosphors (e.g., (Ba,Sr)2Si5N8:Eu), SLA-based phosphors (e.g., SrLiAl3N4:Eu), CASN-based phosphors (e.g., CaAlSiN3:Eu), or SCASN-based phosphors (e.g., (Sr,Ca)AlSiN3:Eu), KSF-based phosphors (e.g., K2SiF6:Mn), KSAF-based phosphors (e.g., K2(Si 1-x Al x )F 6-x :Mn where 0 < x < 1. ) or fluoride-based phosphors such as MGF-based phosphors (e.g., 3.5MgO·0.5MgF2·GeO2:Mn), quantum dots having a perovskite structure (e.g., (Cs,FA,MA)(Pb,Sn)(F,Cl,Br,I)3 where FA and MA represent formamidinium and methylammonium, respectively), II-VI group quantum dots (e.g., CdSe), III-V group quantum dots (e.g., InP), or quantum dots having a chalcopyrite structure (e.g., (Ag,Cu)(In,Ga)(S,Se)2) can be used.

[0024] In the examples shown in FIGS. 1 and 2, the light emitting unit 1 uses a blue LED as the light emitting element 12, and the wavelength conversion material contained in the translucent member 13 wavelength-converts a part of the blue light emitted by the light emitting element 12 into yellow, and white light is emitted by mixing (i.e., color mixing) the blue light and the yellow light. As the light diffusing material contained in the translucent member 13, for example, titanium oxide, barium titanate, aluminum oxide, silicon oxide, etc. can be used.

[0025] The covering member 14 is disposed so as to cover the side surfaces of the light emitting element 12 and the light transmissive member 13. The covering member 14 covers the side surfaces of the light emitting element 12 and the light transmissive member 13 directly or indirectly. The upper surface of the light transmissive member 13 is exposed from the covering member 14 and is the light emitting surface 11 of the light emitting unit 1. In the example shown in FIG. 1 and FIG. 2, the covering member 14 is disposed between adjacent light emitting units 1 and integrally covers 15 light emitting units 1. The covering member 14 may be spaced apart between adjacent light emitting units among the 15 light emitting units 1. The covering member 14 is preferably made of a material having a high light reflectance in order to improve the light extraction efficiency. For example, the covering member 14 may be an organic material such as a resin containing a light reflective substance such as a white pigment. The covering member 14 may also be a light reflective member made of an inorganic material containing, for example, boron nitride or an alkali metal silicate. In this case, it may further contain titanium oxide or zirconium oxide.

[0026] Examples of light-reflecting substances include titanium oxide, zinc oxide, magnesium oxide, magnesium carbonate, magnesium hydroxide, calcium carbonate, calcium hydroxide, calcium silicate, magnesium silicate, barium titanate, barium sulfate, aluminum hydroxide, aluminum oxide, zirconium oxide, silicon oxide, etc., and it is preferable to use one of these alone or two or more of these in combination. In addition, as the resin material among the organic materials, it is preferable to use a resin material containing a thermosetting resin such as epoxy resin, epoxy-modified resin, silicone resin, silicone-modified resin, or phenolic resin as the main component. Note that the covering member 14 may be composed of a member that is transparent or absorbent to visible light as necessary.

[0027] The substrate 2 is a plate-like member having a substantially rectangular shape in a plan view. The substrate 2 is made of silicon nitride, silicon carbide, aluminum nitride, aluminum oxide, etc. The shape of the substrate 2 in a plan view is not limited to a substantially rectangular shape, and may be a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape, etc.

[0028] The substrate 2 is made of a ceramic substrate 20 as described below, and has a first surface 21 and a second surface 22 located on the opposite side to the first surface 21. In the example shown in Fig. 2, the substrate 2 has at least a pair of positive and negative first electrodes 24 arranged on the first surface 21, and at least a pair of positive and negative second electrodes 25 arranged on the second surface 22. Furthermore, the substrate 2 has a plurality of holes 23 formed therein, penetrating from the first surface 21 to the second surface 22. The holes 23 are, for example, via holes.

[0029] The substrate 2 has a first electrode 24 and a second electrode 25 corresponding to each of the 15 light-emitting units 1. In addition, holes 23 are formed in the substrate 2 corresponding to each of the 15 light-emitting units 1. The first electrode 24 is electrically connected to the light-emitting element 12 via a first conductive adhesive member 26. The second electrode 25 is electrically connected to a pair of positive and negative third electrodes 31 provided on the upper surface of the mounting substrate 3 via a second conductive adhesive member 27. The first electrode 24 and the second electrode 25 are electrically connected by a conductive member 28. In the substrate 2, the first electrode 24 of the substrate 2 and the electrode of the light-emitting element 12 are connected via the first conductive adhesive member 26, thereby electrically connecting the substrate 2 and the light-emitting unit 1.

[0030] The conductive member 28 is a sintered conductive paste containing a conductive material, and is disposed in the hole 23. For example, when the ceramic substrate 20 is configured to contain silicon nitride, the conductive paste preferably contains at least one of Ti, Hf, Zr, Nb, Ce, and Mg. In addition, a layer of Ag, Pt, Al, Rh, Au, or an alloy thereof may be provided on the surface of the conductive member 28 from the viewpoint of wettability and light reflectivity of the first conductive adhesive member 26 and the second conductive adhesive member 27. The configuration, size, etc. of the hole 23 in which the conductive member 28 is disposed in the substrate 2 are appropriately set according to the configuration and size of the first electrode 24 and the second electrode 25 of the light-emitting unit 1.

[0031] The mounting board 3 is a plate-like member having a substantially rectangular shape in a plan view. The mounting board 3 includes wiring 32 arranged on the surface (the surface on the +Z side and the surface on the -Z side). The mounting board 3 may also include wiring 32 inside. In the example shown in FIG. 2, the mounting board 3 includes wiring 32 arranged inside, a third electrode 31 provided on the surface on the +Z side of the mounting board 3 and connected to the wiring 32, and a fourth electrode 33 provided on the surface on the -Z side of the mounting board 3 and connected to the wiring 32. In the mounting board 3, the second electrode 25 of the board 2 and the third electrode 31 of the mounting board 3 are connected to each other via the second conductive adhesive member 27, thereby electrically connecting the board 2 and the mounting board 3. The configuration, size, and the like of the wiring 32 of the mounting board 3 are set according to the configuration and size of the second electrode 25 of the board 2. The shape of the mounting board 3 in a plan view is not limited to a substantially rectangular shape, and may be a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape, or the like.

[0032] The mounting substrate 3 preferably uses an insulating material as a base material, and preferably uses a material that is difficult to transmit light emitted from the light emitting unit 1 and external light, and preferably uses a material having a certain strength. Specifically, the mounting substrate 3 can be configured using ceramics such as aluminum oxide, aluminum nitride, mullite, and silicon nitride, and resins such as phenol resin, epoxy resin, polyimide resin, BT resin (bismaleimide triazine resin), and polyphthalamide as a base material.

[0033] <Example of a manufacturing method for a substrate according to an embodiment> Next, a method for manufacturing a substrate according to an embodiment will be described with reference to Fig. 3 to Fig. 12. The method for manufacturing a substrate according to an embodiment is, for example, a method for manufacturing the substrate 2 shown in Figs.

[0034] The method for manufacturing the substrate 2 according to the embodiment includes (a) a step of preparing a ceramic substrate 20 having a first surface 21 and a second surface 22, and (b) a first processing step of ablation processing a first region in the ceramic substrate 20 by irradiating a first region of the first surface 21 with a first laser having a first pulse width. The method for manufacturing the substrate according to the embodiment also includes (c) a second processing step of irradiating a second region separated from the first region in either the first surface 21 or the second surface 22 with a second laser having a second pulse width longer than the first pulse width in a plan view, thereby thermally processing a third region including the first region and the second region. In the method for manufacturing the substrate according to the embodiment, in the second processing step, a hole 23 is formed that penetrates the third region and a region surrounded by the third region from the first surface 21 to the second surface 22.

[0035] In this embodiment, by performing ablation processing, which is processing with a small thermal effect, in the first processing step, the part of the ceramic substrate 20 that absorbs the irradiated first laser 51 can be removed mainly by sublimation. In this embodiment, ablation processing refers to processing that does not involve thermal melting. As a result, the thermal effect of the laser can be reduced and processing can be performed with high accuracy. In this embodiment, a manufacturing method of a substrate that can form a hole 23 penetrating the ceramic substrate 20 with high accuracy can be provided by processing a desired region such as the first region with high accuracy by ablation processing. On the other hand, since the influence of heat is reduced in ablation processing, the processing time may be longer than that of thermal processing. In contrast, in this embodiment, the thermal processing in the second processing step removes the region of the ceramic substrate 20 that has been affected by the heat of the second laser 52 mainly by melting, and processes the third region with higher efficiency than the first processing step. As a result, the processing time for processing the hole 23 as a whole can be shortened, and the productivity of manufacturing the substrate 2 can be improved. Note that the "accuracy" here includes at least one of the accuracy of the position and the shape. The details of the operation and effect of the method for manufacturing a substrate according to the embodiment will be described separately with reference to Figures 7 to 12. Each step will be described in detail below.

[0036] (a) A step of preparing a ceramic substrate 20 Fig. 3 is a schematic top view of a ceramic substrate showing a step of preparing a ceramic substrate 20 which is a target of the substrate manufacturing method according to the embodiment. Fig. 4 is a schematic cross-sectional view taken along line IV-IV in Fig. 3.

[0037] In the example shown in FIG. 3 and FIG. 4, the ceramic substrate 20 prepared in this step has a first surface 21 and a second surface 22 located on the opposite side of the first surface 21, and is a plate-like member in a state in which holes 23, first electrodes 24, second electrodes 25, etc. are not provided. The first surface 21 and the second surface 22 of the ceramic substrate 20 coincide with the first surface 21 and the second surface 22 of the substrate 2 described above. The ceramic substrate 20 may also include wiring on the first surface 21, the second surface, and at least a part of the inside. If the ceramic substrate 20 is too thick, it may be difficult to form the holes 23. Therefore, the thickness of the ceramic substrate 20 is preferably 100 μm or more and 500 μm or less.

[0038] (b) A first processing step of ablation processing a first region. Fig. 5 is a schematic top view of a ceramic substrate showing a first processing step in a method for manufacturing a substrate according to an embodiment of the present invention Fig. 6 is a schematic cross-sectional view taken along line VI-VI in Fig. 5 .

[0039] As shown in FIG. 5 and FIG. 6, in this step, the first region 201 of the first surface 21 is irradiated with a first laser 51 having a first pulse width, thereby ablation-processing the first region 201 of the ceramic substrate 20. In the example shown in FIG. 5 and FIG. 6, the first region 201 is a linear, substantially rectangular region formed continuously with the Y direction as a longitudinal direction in a plan view. The first region 201 is a bottomed hole that does not penetrate from the first surface 21 to the second surface 22 in the Z direction. The first region 201 includes not only a region in the XY plane, but also a region in the Z direction. In the method for manufacturing a substrate according to the embodiment, the first region 201 can be ablation-processed by irradiating the first surface 21 of the ceramic substrate 20 with the first laser 51 while changing the relative position between the irradiation position of the first laser 51 and the ceramic substrate 20.

[0040] The shape of the first region 201 in plan view is not limited to a substantially rectangular shape. For example, in the first processing step, the first region 201 may be a ring shape in plan view that includes straight and arc-shaped lines, such as a substantially circular, semicircular, sector-shaped, elliptical, or semi-elliptical shape, or a polygonal ring shape such as a substantially square or polygonal shape (hereinafter, sometimes referred to as an annular region). The annular region may be formed either continuously or intermittently. In the first processing step, the first region 201 processed by ablation includes a portion that is mainly removed by sublimation and a portion that is altered in the periphery or depth direction. The altered portion includes a plurality of microcracks. In the ablation processing, the occurrence of the removed portion causes a sudden volume change in the ceramic and residual stress associated with the volume change. The microcracks are generated by these mechanical changes. The portion that is mainly removed by sublimation does not reach the second surface in the Z direction. In the Z direction, the altered portion of the ceramic substrate 20 may reach from the first surface 21 to the second surface 22. When the first region 201 reaches from the first surface 21 to the second surface 22, a smoother inner side surface can be formed in the hole 23 from the first surface 21 to the second surface 22.

[0041] The ablation process can achieve higher accuracy than the thermal process. However, it may take more time to process than the thermal process. For this reason, it is preferable to form the first region 201 by the ablation process in the portion of the hole 23 that requires particularly high accuracy.

[0042] In the ablation process using the first laser 51, the first pulse width of the first laser 51 can be set to either the femtosecond range or the picosecond range.

[0043] A fiber laser, a titanium sapphire laser, or the like can be used as a light source that emits the first laser 51. From the viewpoint of increasing the processing accuracy, the first pulse width of the first laser 51 is preferably in the femtosecond region, and more preferably 1 femtosecond or more and 10 picoseconds or less.

[0044] In the example shown in FIG. 5 and FIG. 6, the maximum width of the first region 201 in the X direction is about 20 μm. In the first region 201, the surface of the ceramic irradiated with the first laser 51 is removed. The first region 201 may be irradiated with the first laser 51 once to remove the ceramic, or may be irradiated with the first laser 51 multiple times to gradually remove the ceramic. In the example shown in FIG. 6, the ceramic substrate 20 has a V-shaped recess in the first region 201 with a depth of about 30 μm to about 50 μm in the Z direction where the ceramic has been removed. Since the first region 201 is processed by ablation, the ceramic is not thermally melted, and for example, the width of the processing in the X direction is smaller than that of the thermal processing described later. In addition, the width of the region where the ceramic substrate 20 is altered due to the ablation processing is about one tenth smaller than that of the processing involving thermal melting, around the first region 201.

[0045] 5 and 6, an altered region 201a is formed on the -Z side of the first region 201, i.e., the side of the ceramic substrate 20 opposite to the side irradiated with the first laser 51. The altered region 201a indicates a region in which the ceramic substrate 20 has been altered by irradiation with the first laser 51. The altered region 201a extends from the lower end of the V-shaped recess of the first region 201 to the -Z side and reaches the -Z side surface of the ceramic substrate 20. The alteration refers to a state in which the strength of the material is reduced by about 30% to 50% from its original value.

[0046] (c) a second processing step of irradiating the second region with a second laser to thermally process a third region; FIG. 7 is a first schematic top view of the ceramic substrate 20 showing a second processing step in the method for manufacturing a substrate according to the embodiment. FIG. 8 is a first schematic cross-sectional view taken along line VIII-VIII in FIG. 7. FIG. 9 is a second schematic top view of the ceramic substrate 20 showing a second processing step in the method for manufacturing a substrate according to the embodiment. FIG. 10 is a second schematic cross-sectional view taken along line XX in FIG. 9. FIG. 11A is a schematic top view showing a hole formed by the method for manufacturing a substrate according to the embodiment. FIG. 11B is a schematic bottom view showing a hole formed by the method for manufacturing a substrate according to the embodiment. FIG. 12 is a schematic cross-sectional view taken along line XII-XII in FIG. 11A.

[0047] In the second processing step, a second laser 52 having a second pulse width longer than the first pulse width is irradiated to a second region 202 separated from the first region 201 on either the first surface 21 or the second surface 22 in a plan view to thermally process a third region 203 including the first region 201 and the second region 202. In this embodiment, the pulse width of the second pulse width maximized in the pulse repetition period is a continuous wave, and the second pulse width includes a continuous wave. As shown in Figs. 11A, 11B, and 12, in the second processing step, the third region 203 and a fourth region 204 surrounded by the third region 203 form a hole 23 penetrating from the first surface 21 to the second surface 22. When the area surrounded by the second region 202 is small, the region surrounded by the second region 202 may be composed of only the third region 203. At this time, only the third region 203 is removed, and a hole 23 penetrating from the first surface 21 to the second surface 22 can be formed.

[0048] In this embodiment, a case where the second laser 52 is irradiated from the second surface 22 side will be described. As shown in Figs. 7 to 10, in the second processing step, the second laser 52 is irradiated from the second surface 22 side to the second region 202. In the example shown in Figs. 7 and 8, the second laser 52 is irradiated to the second region 202 separated from the first region 201 on the second surface 22 in a plan view. That is, the second region 202 is located on the second surface 22. In addition, the second region 202 is an annular region of a substantially semi-elliptical shape obtained by cutting an ellipse with the X direction as the major axis direction in substantially half in the major axis direction in a plan view. The second region 202 includes not only a region in the XY plane but also a region in the Z direction. In the substrate manufacturing method according to the embodiment, the second laser 52 can be irradiated to the second surface 22 of the ceramic substrate 20 while changing the relative position between the irradiation position of the second laser 52 and the ceramic substrate 20.

[0049] In the ceramic substrate 20 irradiated with the second laser 52, heat generated by the irradiation with the second laser 52 is not only generated in the second region 202 but also spreads from the second region 202 to the periphery.

[0050] In the second region 202, the ceramic is mainly melted and removed. In the example shown in Figs. 7 to 10, the width of the second region 202 in the X direction is not less than approximately 50 µm and not more than approximately 60 µm. In the second region 202, the ceramic is gradually removed by irradiating the second laser 52 multiple times. Note that in the second region 202, the ceramic may be removed in one go by irradiating the second laser 52 once.

[0051] On the other hand, in the vicinity of the second region 202 where the second laser 52 is not irradiated, the ceramic substrate 20 is altered by heat (hereinafter, sometimes referred to as thermal alteration). In the example shown in Figs. 9 and 10, the third region 203 is a region around the second region 202 where the second laser 52 is not irradiated, and is a region where the ceramic substrate 20 is thermally altered. In the third region 203, the ceramic substrate 20 is altered by heat, and the mechanical strength is reduced and the ceramic substrate 20 becomes brittle. The mechanical strength of the third region 203 gradually decreases toward the second region 202. In the example shown in Figs. 9 and 10, the thermally altered third region 203 is represented by dot hatching, and the higher the dot density (the smaller the interval between adjacent dots), the lower the mechanical strength. In this specification, thermal processing of the ceramic substrate 20 includes the ceramic being primarily melted and removed in the area irradiated with the second laser 52, and the ceramic being thermally altered around the area irradiated with the second laser 52.

[0052] In the second processing step, the region around the fourth region 204 surrounded by the third region 203 whose mechanical strength has been reduced in the ceramic substrate 20 becomes separable from the outside of the third region 203 (the region whose mechanical strength has not been reduced). Thereafter, by applying slight vibration or impact, such as lifting the ceramic substrate 20, the substrate 2 from which the region surrounded by the third region 203 has been removed is obtained. The region to be separated may include a part of the third region 203. In the example shown in FIG. 9 and FIG. 10, the entire periphery of the fourth region 204 is surrounded by the third region 203. As a result, as illustrated in FIG. 11A, FIG. 11B, and FIG. 12, a hole 23 is formed through the fourth region 204 from the first surface 21 to the second surface 22. In the example shown in FIG. 11A, FIG. 11B, and FIG. 12, the shape of the hole 23 in a plan view is approximately semi-elliptical.

[0053] Since the mechanical strength is not uniform within the third region 203, when the region around the fourth region 204 is separated from the outside of the third region 203 (the region where the mechanical strength is not reduced), the end positions of the separated region around the fourth region 204 vary. The end positions of the region around the fourth region 204 vary, causing the inner side surface of the hole 23 to become rough. In the example shown in FIG. 12, the region of the inner side surface of the hole 23 other than the region where the V-shaped recess is formed in the first region 201 is rough, and rough surface region 202a and rough surface region 202c are formed. In the rough surface region 202a, the smoothness of the inner side surface of the hole 23 is less precise than in the rough surface region 202c.

[0054] In this embodiment, the influence of the variation in the end position of the separated fourth region 204 is small in the region of the inner side of the hole 23 where the first region 201 is formed. Also, as described above, the region where the ceramic substrate 20 is altered is smaller around the first region 201 than around the second region 202. Therefore, a smooth surface is obtained in the smooth region 202b corresponding to the V-shaped recess in the first region 201 among the inner side of the hole 23. In the smooth region 202b, the accuracy of smoothing of the inner side of the hole 23 is high. Also, the surface roughness of the rough region 202c in the first region 201 can be reduced. In the example shown in FIG. 11A, the outline of the hole 23 viewed from the first surface 21 is an approximately straight line approximating the designed straight line shape in the region where the first region 201 is formed, and is processed with high accuracy. In the region where the second region 202 is formed, the shape is semi-elliptical as a whole, but includes multiple bent and curved lines, and is processed into a shape that is difficult to say is highly accurate, compared to the shape that is similar to the designed semi-ellipse. In the example shown in Fig. 11B, the outline of the hole 23 viewed from the second surface 22 is a line that is close to the designed straight line shape in the region where the first region 201 is formed, and is processed with relatively high accuracy. In the region where the second region 202 is formed, as in Fig. 11A, the shape is semi-elliptical as a whole, but includes multiple bent and curved lines, and is processed into a shape that is difficult to say is highly accurate, compared to the shape that is similar to the designed semi-ellipse.

[0055] 11A and 12, the area of ​​the first region 201 to be ablated is smaller than the areas of the second region 202 and the third region 203 to be thermally processed. Therefore, the processing time is shorter than when the entire annular region of the hole 23 is ablated.

[0056] As described above, in the method for manufacturing a substrate according to the embodiment, hole 23 can be formed in a short time compared to ablation of the entire annular region of hole 23, and the accuracy of hole 23 can be increased in desired regions such as smooth region 202b. The position, size, number, etc. of smooth region 202b in hole 23 can be appropriately changed depending on the desired position for forming conductive member 28. The smaller the size of smooth region 202b in hole 23 or the fewer the number of smooth regions 202b, the shorter the processing time for hole 23 can be.

[0057] In the substrate manufacturing method according to the embodiment, the second region 202 is annular in the second processing step. This allows the third region 203 and the fourth region 204 to form the hole 23 penetrating from the first surface 21 to the second surface 22, and allows the hole 23 to be formed more efficiently than when the second laser 52 is irradiated to both the second region 202 and the fourth region 204.

[0058] The shape of the second region 202 in plan view is not limited to a substantially semi-elliptical shape. For example, in the second processing step, the shape of the second region 202 in plan view may be a ring shape including a straight line and an arc-shaped line, such as a substantially circular, substantially semicircular, substantially sector-shaped, or substantially elliptical ring shape, or a polygonal ring shape such as a substantially square, substantially rectangular, or substantially polygonal ring shape (hereinafter, sometimes referred to as an annular region). The annular region may be formed either continuously or discontinuously as long as the third region 203 is continuous with the ceramic substrate 20, and the second region 202 may be formed either continuously or discontinuously. As long as the thermal alteration of the ceramic substrate 20 penetrates the third region 203 from the first surface 21 to the second surface 22 in the Z direction, the thermal alteration of the ceramic substrate 20 does not necessarily penetrate the second region 202 from the first surface 21 to the second surface 22. The third region 203 is a region that spreads out from the second region 202 to the periphery, and therefore has shapes similar to the inner and outer sides of the ring-shaped second region 202 in a plan view.

[0059] Thermal processing using the second laser 52 can be performed by making the second pulse width of the second laser 52 longer than the first pulse width, that is, by making it in the nanosecond range or longer.

[0060] A CO2 laser light source or the like can be used as a light source for emitting the second laser 52. In this embodiment, the second laser 52 is a laser emitted from a CO2 laser light source. From the viewpoint of increasing the processing efficiency, it is preferable that the second pulse width of the second laser 52 is 700 nanoseconds or more and 70 microseconds or less.

[0061] The method for manufacturing a substrate according to the embodiment may further include a conductive member forming step of disposing a conductive paste in hole 23 and firing the conductive paste to form conductive member 28 shown in Fig. 2. By including the conductive member forming step in the method for manufacturing a substrate according to the embodiment, it is possible to electrically connect light-emitting elements and various electric elements disposed on substrate 2 to substrate 2.

[0062] For example, when the ceramic substrate 20 contains silicon nitride, the conductive paste preferably contains at least one of Ti, Hf, Zr, Nb, Ce, and Mg. When the conductive paste is sintered, a nitrogen compound containing at least one of Ti, Hf, Zr, Nb, Ce, and Mg is formed at the interface between the conductive member 28 and the inner side of the hole 23, and the adhesion between the conductive member 28 and the inner side of the hole 23 can be improved. On the other hand, when the ceramic substrate 20 contains aluminum nitride, aluminum may precipitate on the irradiated surface when the ceramic substrate 20 is irradiated with a laser to form the hole 23. Therefore, when the ceramic substrate 20 is configured to contain aluminum nitride and a conductive paste containing at least one of Ti, Hf, Zr, Nb, Ce, and Mg is used as the material of the conductive member 28, a nitrogen compound containing at least one of Ti, Hf, Zr, Nb, Ce, and Mg is formed at the interface between the conductive member 28 and the inner surface of the hole 23 by sintering the conductive paste after removing the precipitated aluminum, thereby improving the adhesion between the conductive member 28 and the inner surface of the hole 23. In addition, the heat conducted from the conductive member 28 to the ceramic contained in the substrate 2 via the inner surface of the hole 23 can be efficiently released.

[0063] <Modification> Next, a method for manufacturing a substrate according to a modified example will be described. Note that the same names and symbols as those in the above-described embodiment indicate the same or similar members, and detailed descriptions will be omitted as appropriate. This also applies to the examples shown below.

[0064] (First Modification) The first modified example differs from the above-described embodiment in that the first surface 21 is irradiated with a second laser 52 in the second processing step.

[0065] Fig. 13 is a schematic top view of a ceramic substrate 20 illustrating a second processing step in a substrate manufacturing method according to a first modified example. Fig. 14 is a schematic cross-sectional view taken along line XIV-XIV in Fig. 13. In the cross-sectional view of Fig. 14, the third region 203 is represented by the same hatching as in the top view of Fig. 13 for ease of understanding.

[0066] As shown in Figs. 13 and 14, in this modification, the second laser 52 is irradiated to a second region 202 separated from the first region 201 on the first surface 21. In the example shown in Figs. 13 and 14, the second region 202 is an annular region of a substantially semi-elliptical shape obtained by cutting an ellipse with the X direction as the major axis direction in substantially half in the major axis direction in a plan view. The second region 202 reaches from the first surface 21 to the second surface 22 in the Z direction. The second region 202 includes not only a region in the XY plane but also a region in the Z direction. Note that, as long as the third region 203 reaches from the first surface 21 to the second surface 22 in the Z direction, the second region 202 may penetrate from the first surface 21 to the second surface 22.

[0067] As in this modification, when the second laser 52 is irradiated onto the second region 202 on the first surface 21, the laser light of the second laser 52 travels from the first surface 21 to the second surface 22. Since the processing energy of the laser light decreases in the traveling direction, the opening diameter of the hole 23 on the second surface 22 becomes smaller than the opening diameter of the hole 23 on the first surface 21. However, this modification also provides the same effects as the above-mentioned embodiment. That is, the hole 23 including the contour processed with high accuracy is obtained on the first surface 21.

[0068] (Second Modification) The second modified example differs from the above-described embodiment mainly in that the first region 201, the second region 202, the third region 203 and the holes 23 have a substantially rectangular shape in plan view.

[0069] Fig. 15 is a schematic top view of ceramic substrate 20 showing first region 201 in a substrate manufacturing method according to Modified Example 2. Fig. 16 is a schematic cross-sectional view taken along line XVI-XVI in Fig. 15.

[0070] In the example shown in FIG. 15 and FIG. 16, the first region 201 is a substantially rectangular annular region formed continuously in a plan view. The first region 201 is a bottomed hole that does not penetrate from the first surface 21 to the second surface 22 in the Z direction. The first region 201 includes not only a region in the XY plane but also a region in the Z direction. In the manufacturing method of the substrate according to this modification, the first region 201 can be ablated by irradiating the first surface 21 of the ceramic substrate 20 with the first laser 51 while varying the relative position between the irradiation position of the first laser 51 and the ceramic substrate 20. The first region 201 may be a substantially rectangular annular region formed intermittently so that the first region 201 is separated at the four corners of the substantially rectangular shape in a plan view. By forming the first region 201 intermittently, the processing time can be shortened.

[0071] In the method for manufacturing a substrate according to the embodiment, since the first region 201 is annular in the first processing step, the entire outer edge of the hole 23, i.e., the end face of the hole 23, can be formed with high precision by ablation processing. Also, in the method for manufacturing a substrate according to the embodiment, since the shape of the first region 201 is rectangular in a plan view, the hole 23 having a rectangular shape in a plan view can be formed.

[0072] FIG. 17 is a first schematic top view of the ceramic substrate 20 showing the second region 202 and the third region 203 in the manufacturing method of the substrate according to the second modification. FIG. 18 is a first schematic cross-sectional view taken along the line XVIII-XVIII in FIG. 17. FIG. 19 is a second schematic top view of the ceramic substrate 20 showing the second region 202 and the third region 203 in the manufacturing method of the substrate according to the second modification. FIG. 20 is a second schematic cross-sectional view taken along the line XX-XX in FIG. 19. FIG. 21A is a schematic top view of the substrate showing the hole 23 formed by the manufacturing method of the substrate according to the second modification. FIG. 21B is a schematic bottom view of the substrate showing the hole formed by the manufacturing method of the substrate according to the second modification. FIG. 22A is a schematic cross-sectional view taken along the line XXII-XXII in FIG. 21A. In the cross-sectional view of FIG. 20, the third region 203 is represented by the same hatching as in the top view of FIG. 19 for ease of understanding. FIG. 22B is a schematic cross-sectional view showing the configuration of a light emitting device 200 including a substrate according to a second modified example.

[0073] In the example shown in FIG. 17 and FIG. 18, the second region 202 is a substantially rectangular annular region in a plan view. The second region 202 is located inside the first region 201. The second region 202 penetrates from the first surface 21 to the second surface 22 in the Z direction. The second region 202 includes not only a region in the XY plane but also a region in the Z direction. In the manufacturing method of the substrate according to the embodiment, the second region 202 can be thermally processed by irradiating the second surface 22 of the ceramic substrate 20 with the second laser 52 while changing the relative position between the irradiation position of the second laser 52 and the ceramic substrate 20. In the example shown in FIG. 22A, a smooth region 202b is obtained on the +Z side of both sides (for example, the +X side and the -X side) of the inner surface of the hole 23. A rough surface region 202c with reduced surface roughness is obtained on the -Z side of both sides of the inner surface of the hole 23.

[0074] By thermally processing the second region 202 and the third region 203, the region surrounded by the first region 201 in the ceramic substrate 20 becomes separable from the surrounding region. Thereafter, by applying slight vibration or impact, such as lifting the ceramic substrate 20, the substrate 2 from which the region surrounded by the first region 201 has been removed is obtained. That is, as shown in FIG. 21A, FIG. 21B, and FIG. 22A, a hole 23 penetrating from the first surface 21 to the second surface 22 is formed. Note that, when the area surrounded by the second region 202 is small, the region surrounded by the second region 202 may be composed only of the third region 203. In this case, only the third region 203 is removed. In the example shown in FIG. 21A, FIG. 21B, and FIG. 22A, the shape of the hole 23 in a plan view is substantially rectangular. In the example shown in Fig. 21A, the outline of hole 23 viewed from first surface 21 is a rectangle including substantially straight lines that is similar to the designed rectangle in the region where first region 201 is formed, and is machined with high precision. Also, in the example shown in Fig. 21B, the outline of hole 23 viewed from second surface 22 is a line that is close to the designed rectangle in the region where first region 201 is formed, and is machined with relatively high precision.

[0075] Here, since the second pulse width of the second laser is longer than the first pulse width of the first laser, the second region 202 irradiated with the second laser is wider than the first region 201 irradiated with the first laser. Therefore, in this modification, in the second processing step, the second region 202 is located inside the first region 201, so that the end position of the second region 202 spreading from the inside to the outside can be aligned with the end position of the first region 201 located outside the second region 202. As a result, for example, the end face of the hole 23 can be formed with high accuracy by making the end position of the first region 201 the end face of the hole 23. For example, as shown in FIG. 22B, when the conductive member 28 is disposed in the hole 23 whose end face is formed with high accuracy and used as wiring, a light emitting device 200 can be obtained with improved mounting accuracy of the light emitting unit 1 mounted on the first surface 21 side of the hole 23. The other effects of this modification are the same as those of the above-mentioned embodiment.

[0076] [Example] Below, a comparative experiment of reflectance between a ceramic substrate and glass, Example 1, Example 2, Reference Example, and Comparative Example will be described, although the present disclosure is not limited to these examples in any way.

[0077] First, an experiment was conducted to confirm the difference in reflectance between the ceramic substrate and the glass. The ceramic substrate used in this experiment was silicon nitride with a thickness of 0.32 mm. The glass was 5 mm thick and contained silica (SiO2), soda ash (Na2O), and lime (CaO) as main components. In this experiment, the ceramic substrate had a first surface and a second surface located on the opposite side to the first surface. The first surface of the ceramic substrate corresponds to the "upper surface". The second surface of the ceramic substrate corresponds to the "lower surface". The glass had a first surface and a second surface located on the opposite side to the first surface. The first surface of the glass corresponds to the "upper surface". The second surface of the glass corresponds to the "lower surface". The reflectance of the ceramic substrate and the glass was measured by focusing on the first surface of each of them using SpectraMagic (manufactured by Konica Minolta, Inc.) and measuring the reflectance of laser light with a wavelength of 360 nm to 740 nm. The results are shown in FIG. 23A.

[0078] As shown in FIG. 23A, the light transmittance of glass was about 10% in the range of 360 nm to 680 nm, and about 26% in the range of 680 nm to 740 nm, both of which were low values. On the other hand, the light reflectance of the ceramic substrate was 30% or more at all wavelengths. This result shows that the light reflectance of the ceramic substrate is higher than that of glass. In other words, it can be said that the light transmittance of the ceramic substrate is lower than that of glass. From this, it is considered that it is difficult to focus the laser light at a specific position inside the ceramic substrate. Therefore, it can be said that irradiating the first laser and the second laser with the first surface or the second surface focused as in the above embodiment has good utilization efficiency in laser processing of the ceramic substrate.

[0079] Table 1 shows the main specifications of the first laser 51 and the second laser 52 used in the substrate manufacturing methods according to Example 1, Example 2, Reference Example, and Comparative Example. The ceramic substrate used in the substrate manufacturing methods according to Example 1, Example 2, Reference Example, and Comparative Example is a silicon nitride substrate having a thickness of 150 μm.

[0080] [Table 1]

[0081] In Example 1, the first laser 51 and the second laser 52 were combined to form 50 holes 23 by the substrate manufacturing method according to the embodiment described above. Specifically, the first laser 51 was irradiated onto the first surface 21 of the ceramic substrate 20 to perform ablation processing of the first region 201, and then the second laser 52 was irradiated onto the second surface 22 of the ceramic substrate 20 to perform thermal processing of the third region 203 including the first region 201 and the second region 202. As a result, the third region 203 and the fourth region 204 surrounded by the third region 203 were separated from the ceramic substrate 20. A hole 23 was formed in which the third region 203 and the fourth region 204 surrounded by the third region 203 penetrate from the first surface 21 to the second surface 22.

[0082] In Example 2, 50 holes 23 were formed by combining the first laser 51 and the second laser 52 using the substrate manufacturing method according to the first modified example described above. Specifically, the first laser 51 was irradiated onto the first surface 21 of the ceramic substrate 20 to perform ablation processing of the first region 201, and then the second laser 52 was irradiated onto the first surface 21 of the ceramic substrate 20 to perform thermal processing of the third region 203 including the first region 201 and the second region 202. As a result, the third region 203 and the fourth region 204 surrounded by the third region 203 were separated from the ceramic substrate 20. The third region 203 and the fourth region 204 surrounded by the third region 203 formed holes 23 penetrating from the first surface 21 to the second surface 22.

[0083] In the reference example, 50 holes 23 were formed using only the first laser 51. Specifically, the first surface 21 of the ceramic substrate 20 was irradiated with the first laser 51, and annular regions corresponding to the outer edges of the holes 23 were penetrated from the first surface 21 to the second surface 22 by ablation processing, thereby separating the region surrounded by the annular region from the ceramic substrate 20. The holes 23 were formed by the annular region and the region surrounded by the annular region.

[0084] In the comparative example, 50 holes 23 were formed using only the second laser 52. Specifically, the first surface 21 of the ceramic substrate 20 was irradiated with the second laser 52, and annular regions corresponding to the outer edges of the holes 23 were penetrated from the first surface 21 to the second surface 22 by thermal processing, thereby separating the region surrounded by the annular region from the ceramic substrate 20. The holes 23 were formed by the annular region and the region surrounded by the annular region.

[0085] <Results of forming hole 23> With reference to Figs. 23B to 30, the results of forming the hole 23 by the manufacturing method of the substrate according to each of Example 1, Example 2, Reference Example, and Comparative Example will be described. Figs. 23B and 24 are photographs of the hole 23 formed by the manufacturing method of the substrate according to Example 1. Fig. 23B is a photograph of the top of the hole 23, showing the first surface 21. Fig. 24 is a photograph of the bottom of the hole 23, showing the second surface 22. Figs. 25 and 26 are photographs of the hole 23 formed by the manufacturing method of the substrate according to Example 2. Fig. 25 is a photograph of the top of the hole 23, and Fig. 26 is a photograph of the bottom of the hole 23. Figs. 27 and 28 are photographs of the hole 23 formed by the manufacturing method of the substrate according to the Reference Example. Fig. 27 is a photograph of the top of the hole 23, and Fig. 28 is a photograph of the bottom of the hole 23. Figs. 29 and 30 are photographs of the hole 23 formed by the manufacturing method of the substrate according to the Comparative Example. Fig. 29 is a photograph of the top of the hole 23, and Fig. 30 is a photograph of the bottom of the hole 23. Each of FIG. 23B to FIG. 30 shows an image of the hole 23 formed in the ceramic substrate 20 captured by a camera.

[0086] In the examples shown in each of Figs. 23B to 30, six holes 23 out of 50 holes 23 formed by the substrate manufacturing method according to each of Example 1, Example 2, Reference Example, and Comparative Example are shown. As shown in Figs. 23B to 28, the outline of the hole 23 was clearly formed in Example 1, Example 2, and Reference Example. In particular, the outline of the hole 23 on the first surface 21 subjected to ablation processing by the first laser 51 was clearer. In detail, the straight line portion of the hole 23 on the first surface 21 was formed with excellent straightness. In addition, the corners of the hole 23 on the first surface 21 were formed at approximately right angles. On the other hand, in the Comparative Example, the straight line portion of the hole 23 was bent, and the straightness was inferior to that of Example 1, Example 2, and Reference Example. In addition, the corners of the hole 23 were formed on a curved surface.

[0087] Table 2 below shows a list of the evaluation of the formation results of the multiple holes 23 in each example.

[0088] [Table 2]

[0089] In the evaluation of Table 2, a plurality of holes 23 including holes having a substantially circular shape and a substantially rectangular shape in plan view were formed by the substrate manufacturing method according to each of Example 1, Example 2, Reference Example, and Comparative Example. The size of the holes 23 in plan view was 0.1 mm or more and 0.4 mm or less in the case of substantially rectangular holes, and the diameter was 0.06 mm or more and 0.3 mm or less in the case of substantially circular holes. The number of the plurality of holes 23 was 50.

[0090] In the evaluation results in Table 2, "◎" indicates an excellent level. "◯" indicates a level at which it can be used as a substrate. "×" indicates a level at which it cannot be used as a substrate. These notations for the evaluation results are the same for the evaluation results shown hereinafter.

[0091] In the evaluation items in Table 2, "corner shape" refers to the shape of the corners of the hole 23, and the closer it is to a right angle, the better it is. "Straight line shape" refers to the shape of the straight line of the hole 23, and the better the linearity, the better it is. The "corner shape" and "straight line shape" were evaluated by visually observing the appearance using a microscope. "Front-rear dimension difference" refers to the difference between the dimensions of the first surface 21 (front) side and the second surface 22 (back) side of the hole 23. "Front-rear dimension difference" is expressed as the ratio of the error to the design value of the dimension, with a positive value indicating a larger error than the design value and a negative value indicating a smaller error than the design value. "Processing time" refers to the time required to form all of the multiple holes 23.

[0092] As shown in Table 2, in the reference example, good results were obtained in the evaluation items of corner shape, straight line shape, front and back dimensional difference, and substrate damage. On the other hand, the processing time was 14.0 seconds, which was longer than in the other examples. From these, it was found that the reference example can form multiple holes 23 with high precision, and is useful, for example, when there is no constraint on processing time.

[0093] In the comparative example, the processing time was 1.2 seconds, which was shorter than the other examples. On the other hand, the evaluation items of the corner shape, the straight part shape, the difference in dimensions between the front and back, and the damage to the substrate were at a level that could not be used as a substrate. Specifically, the radius of curvature of the corner was about 25 μm. Also, the meandering width in the straight part was a maximum of 12 μm. From these, it was found that, in the comparative example, the multiple holes 23 can be formed with excellent productivity, but the formation accuracy of the multiple holes 23 is lower than that of the other examples. Here, the level that cannot be used as a substrate refers to a case where, assuming that a conductive member is placed in a hole formed in the substrate and a light emitting element is mounted on the hole, there is a high possibility that the light emitting element will be displaced from the intended mounting position.

[0094] In Examples 1 and 2, good results were obtained in all of the evaluation items, including the corner shape, the straight line shape, the difference in dimensions between the front and back sides, and the damage to the substrate. The processing time was 3.8 seconds, which was about 1 / 4 of the reference example and was close to the level of the comparative example. From these results, it was found that in Examples 1 and 2, the multiple holes 23 can be formed with high precision, and the multiple holes 23 can be formed with excellent productivity. In other words, it was found that in Examples 1 and 2, both high precision and excellent productivity can be achieved in forming the holes 23.

[0095] <Example of results of forming holes 23 by the substrate manufacturing method according to Example 1> The results of forming the holes 23 by the substrate manufacturing method according to the first embodiment will now be described in more detail.

[0096] First, with reference to Samples 1 to 5 in FIG. 31 and FIG. 32, the effect of the distance between the first region 201 and the second region 202 on the formation accuracy of the holes 23 will be described.

[0097] FIG. 31 is a schematic diagram for explaining the interval between the first region 201 and the second region 202. FIG. 31 shows, in a plan view, a first laser 51 irradiated onto the surface on the +Z side of the ceramic substrate 20 (the first surface 21 shown in FIG. 4) and a second laser 52 irradiated onto the surface on the -Z side of the ceramic substrate 20 (the second surface 22 shown in FIG. 4). The first laser 51 and the second laser 52 each represent the diameter of a laser beam on the irradiated ceramic substrate 20. The laser beam diameter of the first laser 51 was set to 15 μm. The beam spot diameter of the second laser 52 was set to 50 μm.

[0098] In FIG. 31, the first movement axis C1 represents the movement trajectory of the center of the laser light of the first laser 51 with the relative movement with respect to the ceramic substrate 20. The second movement axis C2 represents the movement trajectory of the center of the second laser 52 with the relative movement with respect to the ceramic substrate 20. The interval Δ is the interval between the first movement axis C1 and the second movement axis C2. This interval Δ corresponds to the distance between the first region formed by the first laser 51 and the second region formed by the second laser 52. The interval Δ also corresponds to the third region 203. The interval Δ can also be said to be the shortest distance between the center of the first region and the center of the second region. In the manufacturing method of the substrate according to the embodiment, a plurality of holes 23 are formed, and the center-to-center distance between adjacent holes 23 can be set to 100 μm or more and 500 μm or less.

[0099] 31, the first end face E1 indicates the end face that is ablated by the first laser 51. The second end face E2 indicates the end face that is thermally processed by the second laser 52. In thermal processing using the second laser 52, the processed area expands due to heat, compared to ablation processing using the first laser 51. For this reason, the second distance d2 between the second movement axis C2 and the second end face E2 is longer than the first distance d1 between the first movement axis C1 and the first end face E1.

[0100] FIG. 32 is a diagram showing the relationship between the interval Δ between the first region 201 and the second region 202 and the formation position deviation. As shown in FIG. 32, samples 1 to 5 were irradiated with the first laser 51 and the second laser 52 at different intervals Δ. The "photographed image of the first surface" is an image of the holes 23 formed in the ceramic substrate 20 at the interval Δ of each sample, photographed from the first surface 21 side. The "formation position deviation" means the maximum amount of deviation of the end face positions of the holes 23 formed in the ceramic substrate 20 at the interval Δ of each sample from the designed positions of the holes 23, i.e., the maximum error in the formation of the end faces of the holes 23.

[0101] 32, in the ceramic substrate 20, when the interval Δ was in the range of 25.0 μm or more and 32.5 μm or less, the formation position deviation was +5.0 μm or less, and the evaluation was "◎" or "◯." From this, it was found that from the viewpoint of forming the holes 23 with high precision, the interval Δ is preferably in the range of 25.0 μm or more and 32.5 μm or less, more preferably in the range of 30.0 μm or more and 32.5 μm or less, and particularly preferably 32.5 μm.

[0102] Fig. 33 shows photographs of ceramic substrate 20 after the first processing step taken from the first surface 21 side and the second surface 22 side in the substrate manufacturing method according to Example 1. Fig. 33 also shows photographs of hole 23 formed after the second processing step taken from the first surface 21 side and the second surface 22 side in the substrate manufacturing method according to Example 1. In the example shown in Fig. 33, the interval Δ shown in Fig. 31 was set to 32.5 μm.

[0103] 33, in the first processing step, a first region 201 was formed on the first surface 21 by ablation processing. As can be seen from the photograph of the second surface 22 of the ceramic substrate 20 taken after the first processing step, the deterioration of the ceramic substrate due to the ablation processing of the first surface 21 extended to the second surface 22. However, in the state after the first processing step, the area surrounded by the first region 201 was not separated from its surrounding areas.

[0104] In the second processing step, holes 23 were formed in the ceramic substrate 20 by thermal processing. In the example shown in FIG. 33, the thermal processing was performed by irradiating the second laser from the second surface 22 side. Therefore, as shown in the all-focus image of the hole 23 in FIG. 33 and the image of the hole 23 taken from an oblique direction, the end face of the hole 23 on the second surface 22 was rough and had large irregularities compared to the end face of the hole 23 on the first surface 21. From this, it can be seen that the shape accuracy of the first region 201 formed by the ablation processing is higher than that of the second region 202 and the third region 203 formed by thermal processing and shown in FIG. 9 and FIG. 10, etc.

[0105] For the hole 23 formed by the manufacturing method of the substrate according to the embodiment 1, the surface roughness of the smooth region 202b corresponding to the V-shaped recess in the first region 201 and the rough region 202c in which the surface roughness is reduced on both sides of the inner surface of the hole 23 on the -Z side were measured by a scanning electron microscope (SEM). The hole 23 used was cleaned by wet blasting before the surface roughness measurement. As a result, in the smooth region 202b of the inner surface of the hole 23, Sa=1.08 μm and Sz=5.71 μm. On the other hand, in the rough region 202c, Sa=2.45 μm and Sz=20.08 μm. Here, Sa is the arithmetic mean height, and Sz is the maximum height. As a result, a difference in surface roughness was observed between the smooth region 202b and the rough region 202c, and it was found that the surface roughness of the smooth region 202b was smaller than that of the rough region 202c.

[0106] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0107] For example, the shape of the inner side surface of hole 23 can be various shapes. Figures 34 and 35 are cross-sectional views of hole 23 illustrating the shape of the inner side surface of hole 23. Fig. 34 shows a first example, and Fig. 35 shows a second example. Note that Figs. 34 and 35 show cross sections of hole 23 along the Z direction cut by a virtual plane including central axis 230 of hole 23.

[0108] 34 and 35, the first inner side surface 231 is the inner side surface with the largest opening among the inner sides of the hole 23. The second inner side surface 232 is the inner side surface with the smallest opening among the inner sides of the hole 23.

[0109] In the example shown in FIG. 34, the first inner side surface 231 is on the first surface 21 side. The second inner side surface 232 is located between the first surface 21 and the second surface 22. In the hole 23, the surface roughness of the first inner side surface 231 is lower and smoother than the surface roughness of the second inner side surface 232. The hole 23 shown in FIG. 34 can be formed by irradiating the second region of the second surface 22 with the second laser 52 in the second processing step. When the second region 202 in the second surface 22 is irradiated with the second laser 52, the laser light of the second laser 52 travels from the second surface 22 toward the first surface 21. The processing energy of the laser light decreases in the traveling direction. On the second surface 22 irradiated with the second laser 52, the processing energy of the laser light is sufficiently large, but between the first surface 21 and the second surface 22, where the processing energy of the laser light is small, a second inner surface 232 having a larger surface roughness than the first inner surface 231 and including a convex portion is formed. In the hole 23 shown in FIG. 34, the second inner surface 232 is located at a position away from the first surface 21 and the second surface 22, so that the contour (i.e., the processing accuracy) of the hole 23 on the first surface 21 and the second surface 22 is not affected. Therefore, when it is desired to obtain a hole 23 having a contour processed with high accuracy on both the first surface 21 and the second surface 22, it is preferable to irradiate the second laser 52 from the second surface 22 side.

[0110] On the other hand, in the example shown in FIG. 35, the first inner side surface 231 is on the first surface 21 side. Also, the second inner side surface 232 is on the second surface 22 side. Therefore, in the example shown in FIG. 35, the opening of the hole 23 on the first surface 21 is larger than the opening of the second surface 22. In the hole 23, the surface roughness of the first inner side surface 231 is lower and smoother than the surface roughness of the second inner side surface 232. The hole 23 shown in FIG. 35 can be formed by irradiating the second region of the first surface 21 with the second laser 52 in the second processing step. When the second region 202 on the first surface 21 is irradiated with the second laser 52, the laser light of the second laser 52 travels from the first surface 21 toward the second surface 22. Since the processing energy of the laser light decreases in the traveling direction, the opening diameter at second surface 22 of hole 23 becomes smaller than the opening diameter at first surface 21 of hole 23, and in a cross-sectional view of hole 23 including first surface 21 and second surface 22, second inner surface 232 of hole 23 on the second surface 22 side has a convex portion formed thereon that has a greater surface roughness than first inner surface 231. However, even in the hole 23 shown in Fig. 35, a hole 23 including an outline processed with high precision at first surface 21 is obtained.

[0111] The substrate manufacturing method of the present disclosure is capable of forming holes penetrating a ceramic substrate with high accuracy, and therefore can be suitably applied to manufacturing processes of ceramic substrates used in light emitting devices such as in-vehicle light sources, lighting light sources, light sources for various indicators, light sources for displays, light sources for liquid crystal backlights, traffic lights, in-vehicle parts, channel letters for signboards, etc. However, the substrate manufacturing method of the present disclosure is not limited to manufacturing processes of ceramic substrates used in light emitting devices, and can be applied to manufacturing processes of ceramic substrates used for various purposes.

[0112] Aspects of the present disclosure are, for example, as follows. <Item 1> A method for manufacturing a substrate, comprising: a step of preparing a ceramic substrate having a first surface and a second surface located opposite to the first surface; a first processing step of irradiating a first region of the first surface with a first laser having a first pulse width to ablate the first region of the ceramic substrate; and a second processing step of irradiating a second region on either the first surface or the second surface, the second laser having a second pulse width longer than the first pulse width, in a plan view, away from the first region, to thermally process a third region including the first region and the second region, wherein in the second processing step, a hole penetrating the third region and a region surrounded by the third region is formed from the first surface to the second surface. <Item 2> The method for manufacturing a substrate according to <Item 1>, wherein in the first processing step, the first region is annular. <Item 3> The method for manufacturing a substrate according to <Item 2>, wherein in the second processing step, the second region is located inside the first region. <Item 4> The method for manufacturing a ceramic substrate according to <Item 3>, wherein in the ceramic substrate, a distance between the first region and the second region is 25.0 μm or more and 32.5 μm or less. <Item 5> The method for manufacturing a substrate according to any one of <Item 1> to <Item 4>, wherein the second region is located on the second surface. <Item 6> The method for manufacturing a substrate according to any one of <Item 1> to <Item 5>, wherein, in the first processing step, the first region processed by ablation reaches from the first surface to the second surface. <Item 7> The method for manufacturing a substrate according to any one of <Item 1> to <Item 6>, wherein in the second processing step, the second region is annular. <Item 8> The method for manufacturing a substrate according to any one of <Item 1> to <Item 7>, wherein the first region has a rectangular shape in a plan view. <Item 9> The method for manufacturing a substrate described in any one of <Item 1> to <Item 8>, wherein the first laser is a laser having a pulse width in the femtosecond range, and the second laser is a laser emitted from a CO2 laser light source. <Item 10> The method for manufacturing a substrate according to any one of <Item 1> to <Item 9>, wherein the ceramic substrate has a thickness of 100 μm or more and 500 μm or less. <Item 11> The method for manufacturing a substrate according to any one of <Item 1> to <Item 10>, wherein the ceramic substrate is made of silicon nitride. <Item 12> The method for manufacturing a substrate according to any one of <Item 1> to <Item 11>, further comprising a conductive member forming step of placing a conductive paste in the hole and firing the conductive paste to form a conductive member. <Item 13> The method for producing a substrate according to <Item 12>, wherein the conductive paste contains at least one of Ti, Hf, Zr, Nb, Ce, and Mg. [Explanation of symbols]

[0113] 1, 1a, 1b, 1c Light emitting part 11 Light-emitting surface 12 Light emitting element 13 Translucent material 14 Covering material 2. Board 20 Ceramic Substrate 21 Page 1 22 Side 2 23 holes 230 Center axis 231 1st inner surface 232 2nd inner surface 24 1st electrode 25 2nd electrode 26 First conductive adhesive member 27 Second conductive adhesive member 28 Conductive materials 3. Mounting Board 31 3rd electrode 32 Wiring 33 4th electrode 51 First Laser 52nd laser 100 Light emitting device 201 First region 202 Second region 203 Third region 204 Fourth region C1 First moving axis C2 Second moving axis d1 First distance d2 Second distance E1 First end face E2 Second end face Δ Interval

Claims

1. providing a ceramic substrate having a first surface and a second surface opposite the first surface; a first processing step of ablation-processing the first region of the ceramic substrate by irradiating a first laser having a first pulse width onto the first region of the first surface; a second processing step of irradiating a second region, in a plan view, on either the first surface or the second surface, the second region being spaced from the first region, with a second laser having a second pulse width longer than the first pulse width, to thermally process a third region including the first region and the second region; A method for manufacturing a substrate, wherein in the second processing step, a hole is formed that penetrates the third region and a region surrounded by the third region from the first surface to the second surface.

2. The method for manufacturing a substrate according to claim 1 , wherein in the first processing step, the first region is annular.

3. The method for manufacturing a substrate according to claim 2 , wherein in the second processing step, the second region is located inside the first region.

4. The method for manufacturing a substrate according to claim 3 , wherein in the ceramic substrate, a distance between the first region and the second region is not less than 25.0 μm and not more than 32.5 μm.

5. The method for manufacturing a substrate according to claim 1 , wherein the second region is located on the second surface.

6. 3. The method for manufacturing a substrate according to claim 1, wherein in the first processing step, the first region processed by ablation extends from the first surface to the second surface.

7. The method for manufacturing a substrate according to claim 1 or 2, wherein in the second processing step, the second region is annular.

8. The method for manufacturing a substrate according to claim 1 , wherein the first region has a rectangular shape in a plan view.

9. the first laser is a laser having a pulse width in the femtosecond range, The second laser is a CO ２ The method for manufacturing a substrate according to claim 1 or 2, wherein the laser is emitted from a laser light source.

10. 3. The method for manufacturing a substrate according to claim 1, wherein the ceramic substrate has a thickness of 100 μm or more and 500 μm or less.

11. 3. The method for manufacturing a substrate according to claim 1, wherein the ceramic substrate is made of silicon nitride.

12. The method for manufacturing a substrate according to claim 1 or 2, further comprising a conductive member forming step of disposing a conductive paste in the hole and firing the conductive paste to form a conductive member.

13. The method for manufacturing a substrate according to claim 12, wherein the conductive paste contains at least one of Ti, Hf, Zr, Nb, Ce, and Mg.

Images