Substrate for light-emitting element and method for manufacturing substrate for light-emitting element

Abstract

This substrate for a light-emitting element comprises: a base body having a first surface and a second surface opposing each other and a through-hole extending from the first surface to the second surface; and a heat dissipator filled in the through-hole of the base body. The first surface of the base body includes a mounting portion in which the light-emitting element is installed. In the substrate for a light-emitting element, when viewed from the first surface side, the area So in which the heat dissipator overlaps the mounting portion is 50% or more.

Description

Technical Field

[0001] The present invention relates to a substrate for a light-emitting element.

Background Art

[0002] Light-emitting elements such as light-emitting diodes (LEDs) and semiconductor laser diodes (LDs) are widely used in automotive lamps, displays, street lamps, and the like. The light-emitting element is installed on a substrate for a light-emitting element and used as a light-emitting device.

[0003] Generally, a through-hole is provided in the substrate for a light-emitting element from the upper surface (the surface on which the light-emitting element is installed) to the lower surface, and this through-hole is filled with a heat sink. By providing a heat sink in the substrate for a light-emitting element, the heat generated by the light-emitting element can be dissipated to the outside of the device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, as a configuration of a light-emitting device that replaces the wire bond type, a structure called the flip chip bond type has been adopted (for example, Patent Document 1).

[0006] In the flip chip bond type, electrical connection is made by each bump provided on the bottom surface of the light-emitting element and each pad provided on the upper surface of the substrate for a light-emitting element. Therefore, compared with a wire bond type light-emitting device, the wiring length can be shortened, and miniaturization and high efficiency of the light-emitting device can be achieved.

[0007] However, in the flip chip bond type, there is a problem that it is difficult to increase the area of the heat sink filled in the substrate for the light-emitting element. This is because, in the case of the flip chip bond type, it is necessary to embed a plurality of heat sinks in the substrate for the light-emitting element. If the distance between each heat sink approaches, cracks are likely to occur in the manufacturing process of the substrate for the light-emitting element.

[0008] For this reason, in the flip chip bond type, heat generation of the light-emitting element tends to become a problem again. In particular, if the miniaturization of the light-emitting device further progresses in the future, this heat generation problem is expected to become more prominent.

[0009] The present invention has been made in view of such a background, and an object of the present invention is to provide a substrate for a light-emitting element having better heat dissipation than conventional ones.

Means for Solving the Problems

[0010] In the present invention, there is provided a substrate for a light-emitting element, which has a first surface and a second surface facing each other, and a substrate body having a through hole extending from the first surface to the second surface; a heat sink filled in the through hole of the substrate body; and the first surface of the substrate body has a mounting portion on which the light-emitting element is installed, when viewed from the side of the first surface, the area S o of the portion where the heat sink overlaps with the mounting portion is 50% or more. A substrate for a light-emitting element is provided.

Effects of the Invention

[0011] In the present invention, it is possible to provide a substrate for a light-emitting element having better heat dissipation than conventional ones.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] (Regarding a flip-chip bond type light-emitting device) First, in order to better understand the configuration and characteristics of a substrate for a light-emitting element according to an embodiment of the present invention, a general flip-chip bond type light-emitting device will be described.

[0015] FIG. 1 schematically shows a cross-sectional configuration of a general flip-chip bond type light-emitting device.

[0016] As shown in FIG. 1, this light-emitting device 1 includes a substrate 2 for a light-emitting element and a light-emitting element 60.

[0017] The substrate 2 for a light-emitting element has an upper surface 4 and a lower surface 6, and the light-emitting element 60 is installed on the side of the upper surface 4 of the substrate 2 for a light-emitting element.

[0018] The substrate 2 for a light-emitting element includes a base body 10 and a plurality of heat radiators 18. The base body 10 has a plurality of through holes penetrating from the upper surface 14 to the lower surface 16, and the heat radiators 18 are filled in the respective through holes. Note that the upper surface 14 and the lower surface 16 of the base body 10 respectively correspond to the upper surface 4 and the lower surface 6 of the substrate 2 for a light-emitting element.

[0019] The light-emitting device 1 further includes a plurality of upper electrodes 25 formed on the upper surface 4 of the substrate 2 for a light-emitting element and a lower conductor 35 formed on the lower surface 6. The upper electrodes 25 and the lower conductor 35 are arranged so as to be electrically connected to the target heat radiator 18.

[0020] Also, the light-emitting device 1 has a plurality of electrode bumps 65 at the bottom 62 of the light-emitting element 60. Each electrode bump 65 is connected to the respective upper electrode 25.

[0021] In the light-emitting device 1 having such a structure, different from a wire-bond type device, energization can be performed at an arbitrary position of the light-emitting element 60. Therefore, in the light-emitting device 1, the wiring length can be shortened and the device can be miniaturized.

[0022] Here, the heat radiator 18 has a role of dissipating the heat generated in the light-emitting element 60 to the outside through the lower conductor 35. Therefore, from the viewpoint of heat dissipation efficiency, when the heat radiator 18 is viewed from the upper side (the side of the light-emitting element 60) of the light-emitting device 1 (hereinafter referred to as "top view"), it is desirable that the area of each heat radiator 18 be as large as possible.

[0023] However, the substrate 2 for the light-emitting element is usually manufactured by heat-treating the green sheet in a state where the paste for the heat sink 18 is filled in the through-holes provided in the green sheet that forms the base of the substrate 10. Since the green sheet (or the substrate 10) and the heat sink paste (or the heat sink 18) have different coefficients of thermal expansion, stress is generated at the interface between the two during the heat treatment. In particular, when the area of the heat sink 18 is expanded, the influence of this stress cannot be ignored, and cracks are generated at the interface between the substrate 10 and the heat sink 18 during the heating / cooling process of the substrate 10.

[0024] Thus, there is a problem that there is a limit to the expansion of the area of the heat sink 18, and as a result, it is difficult to further improve the heat dissipation characteristics of the light-emitting device 1.

[0025] On the other hand, in one embodiment of the present invention, as will be described in detail hereinafter, the area of the heat sink 18 can be further expanded. For example, in one embodiment of the present invention, in a top view, the total area (hereinafter referred to as the "overlap area") S o where the heat sink 18 overlaps with the light-emitting element 60 can be made 50% or more.

[0026] Therefore, in one embodiment of the present invention, it is possible to significantly improve the heat dissipation characteristics of the light-emitting device 1.

[0027] (Substrate for Light-Emitting Element According to One Embodiment of the Present Invention) Next, with reference to FIGS. 2 to 3, a configuration example of a substrate for a light-emitting element according to one embodiment of the present invention will be described.

[0028] FIG. 2 shows a schematic top view of a substrate for a light-emitting element according to one embodiment of the present invention. Further, FIG. 3 schematically shows a cross section along the line A-A of the substrate for a light-emitting element shown in FIG. 2.

[0029] As shown in FIGS. 2 and 3, a substrate for a light-emitting element (hereinafter referred to as "first substrate") 100 according to an embodiment of the present invention has a first surface 104 and a second surface 106 facing each other. Further, the first substrate 100 has a base body 130 and a plurality of heat radiators 158. In the examples shown in FIGS. 2 and 3, two heat radiators 158 are shown, and hereinafter, these are represented by 158a and 158b, respectively.

[0030] The base body 130 has an upper surface 134 and a lower surface 136 facing each other. Further, the base body 130 has a plurality of through holes 148a, 148b extending from the upper surface 134 to the lower surface 136.

[0031] The heat radiators 158a, 158b are filled in the respective through holes 148a, 148b of the base body 130, and thus extend from the upper surface 134 to the lower surface 136.

[0032] The first surface 104 of the first substrate 100 corresponds to the side of the upper surface 134 of the base body 130, and the second surface 106 of the first substrate 100 corresponds to the side of the lower surface 136 of the base body 130.

[0033] The first surface 104 of the first substrate 100 has a mounting portion 165 on which a light-emitting element (not shown) is installed. In FIG. 2, the mounting portion 165 is indicated by a square dashed line.

[0034] Here, when the first substrate 100 is viewed from the side of the first surface 104, that is, in a top view of the first substrate 100, the area of the portion where the heat radiators 158a, 158b overlap with the mounting portion 165, that is, the overlap area S o has a feature that it is 50% or more.

[0035] The overlap area S o is, for example, 60% or more, and preferably 65% or more.

[0036] When a light-emitting element is installed on the first substrate 100 having such characteristics to form a light-emitting device, the heat generated by the light-emitting element can be effectively dissipated to the outside through the heat radiators 158a and 158b.

[0037] Therefore, in such a light-emitting device, it is possible to improve the heat dissipation characteristics as compared with the conventional ones.

[0038] In the examples shown in FIGS. 2 and 3, the first substrate 100 has two rectangular heat radiators 158a and 158b in a top view. However, this is merely an example, and the number of the heat radiators 158 is not particularly limited as long as it is plural. Also, the shape of the heat radiator 158 is not particularly limited.

[0039] For example, the shape of the heat radiator 158 may be substantially circular, substantially elliptical, or substantially n-sided (where n is an integer of 3 or more). Also, the heat radiator 158 may have a shape with rounded corners. Further, each heat radiator 158 does not necessarily have to be of the same shape and may have mutually different shapes.

[0040] Similarly, in the example shown in FIG. 2, the mounting portion 165 has a rectangular form. However, the shape of the mounting portion 165 is not particularly limited, and the mounting portion 165 may have a shape such as substantially circular, substantially elliptical, or substantially n-sided (where n is an integer of 3 or more), for example. Also, the mounting portion 165 may have a shape with rounded corners.

[0041] (Each component member) Next, each component member included in the substrate for a light-emitting element according to an embodiment of the present invention will be described.

[0042] Here, for the sake of clarity, the first substrate 100 shown in FIGS. 2 and 3 will be taken as an example to describe its component members. Therefore, the reference numerals shown in FIGS. 2 and 3 are used to represent each member.

[0043] (Base body 130) The substrate 130 is made of, for example, a glass-based material. The substrate 130 may be made of a mixed material of glass and ceramics.

[0044] The composition of the glass is not particularly limited, but for example, a composition containing SiO2, B2O3, CaO, and Al2O3 is preferable. The glass may further contain at least one of K2O and Na2O.

[0045] By adopting such a composition, the adhesion between the substrate 130 and the heat sink 158 is improved.

[0046] Among these, SiO2 is a substance that forms the network former of the glass. SiO2 is preferably contained in the glass in the range of 57 mol% to 65 mol%.

[0047] When the content of SiO2 is less than 57 mol%, it becomes difficult to obtain a stable glass, and there is a possibility that the chemical durability may decrease. On the other hand, when the content of SiO2 exceeds 65 mol%, there is a possibility that the glass melting temperature and the glass transition temperature Tg may become excessively high. The content of SiO2 is preferably 58 mol% or more, more preferably 59 mol% or more, and particularly preferably 60 mol% or more. Also, the content of SiO2 is preferably 64 mol% or less, more preferably 63 mol% or less.

[0048] B2O3 is a substance that forms the network former of the glass. B2O3 is preferably contained in the glass in the range of 13 mol% to 18 mol%.

[0049] When the content of B2O3 is less than 13 mol%, there is a possibility that the glass melting temperature and the glass transition temperature Tg may become excessively high. On the other hand, when the content of B2O3 exceeds 18 mol%, it becomes difficult to obtain a stable glass, and there is a possibility that the chemical durability may decrease. The content of B2O3 is preferably 14 mol% or more, more preferably 15 mol% or more. Also, the content of B2O3 is preferably 17 mol% or less, more preferably 16 mol% or less.

[0050] CaO is added to enhance the stability of the glass and the precipitation property of crystals, and to lower the glass melting temperature and the glass transition temperature Tg. CaO is preferably contained in the glass in the range of 9 mol% to 23 mol%.

[0051] When the content of CaO is less than 9 mol%, the glass melting temperature may become excessively high. On the other hand, when the content of CaO exceeds 23 mol%, the glass may become unstable. The content of CaO is preferably 12 mol% or more, more preferably 13 mol% or more, and particularly preferably 14 mol% or more. Also, the content of CaO is preferably 22 mol% or less, more preferably 21 mol% or less, and particularly preferably 20 mol% or less.

[0052] Al2O3 is added to enhance the stability, chemical durability, and strength of the glass. Al2O3 is preferably contained in the glass in the range of 3 mol% to 8 mol%.

[0053] When the content of Al2O3 is less than 3 mol%, the glass may become unstable. On the other hand, when the content of Al2O3 exceeds 8 mol%, the glass melting temperature and the glass transition temperature Tg may become excessively high. The content of Al2O3 is preferably 4 mol% or more, more preferably 5 mol% or more. Also, the content of Al2O3 is preferably 7 mol% or less, more preferably 6 mol% or less.

[0054] K2O and Na2O lower the glass transition temperature Tg. K2O and Na2O are preferably contained in the glass in a total range of 0.5 mol% to 6 mol%.

[0055] When the total content of K2O and Na2O is less than 0.5 mol%, the glass melting temperature and the glass transition temperature Tg may become excessively high. On the other hand, when the total content of K2O and Na2O exceeds 6 mol%, the chemical durability, especially the acid resistance, may decrease, and the electrical insulation may also decrease. The total content of K2O and Na2O is preferably 0.8 mol% or more and 5 mol% or less.

[0056] Note that the composition of the glass is not necessarily limited to only the above components, and other components may be contained. When other components are contained, the total content thereof is preferably 10 mol% or less.

[0057] When the substrate 130 contains ceramics, examples of the ceramics include, but are not limited to, alumina, zirconia, or a mixture of both.

[0058] The amount of glass contained in the substrate 130 is, for example, in the range of 35% to 75% by mass based on the entire substrate 130. The amount of glass is preferably in the range of 40% to 70% by mass based on the entire substrate 130.

[0059] The thickness of the substrate 130 is not particularly limited, and is, for example, in the range of 200 μm to 1200 μm.

[0060] The upper surface 134 and / or the lower surface 136 of the substrate 130 preferably has a surface roughness Ra of 0.5 μm or less. In this case, the concentration of local stress applied to the upper surface 134 and / or the lower surface 136 of the substrate 130 is suppressed, and the generation of cracks can be further suppressed.

[0061] (Heat sink 158) The heat sink 158 has thermal conductivity and electrical conductivity and contains a metal. The heat sink 158 may contain, for example, at least one of copper, silver, and gold.

[0062] In a top view of the first substrate 100, the total area S of the heat sink 158 h is, for example, 0.5 mm2 ~1.5 mm 2 is in the range of

[0063] Here, the total area S h is represented by the sum of the areas of the respective heat radiators 158. For example, in the examples shown in FIGS. 2 and 3, the total area S h is represented by the sum of the area of the heat radiator 158a and the area of the heat radiator 158b in a top view of the first substrate 100.

[0064] When the first substrate 100 has a plurality of heat radiators 158, the distance d (see FIG. 2) between adjacent heat radiators 158 in a top view is, for example, 0.50 mm or less. The distance d is preferably 0.40 mm or less, and more preferably 0.35 mm or less.

[0065] In the present application, the distance d is defined as the minimum dimension between adjacent heat radiators in a top view.

[0066] (Mounting portion 165) As described above, the shape of the mounting portion 165 is not particularly limited, and various shapes can be adopted as the mounting portion 165.

[0067] The area S of the mounting portion 165 a is not particularly limited, but for example, 0.15 mm 2 ~4.00 mm 2 is in the range of. The area S of the mounting portion 165 a is preferably in the range of 0.50 mm 2 ~2.00 mm 2 and more preferably in the range of 0.75 mm 2 ~1.25 mm 2 is more preferably in the range of.

[0068] (First substrate 100) In the above description, the first substrate 100 is composed of a base body 130 and a heat radiator 158.

[0069] However, the first substrate 100 may further have a plurality of upper electrodes 25 as shown in FIG. 1. The upper electrodes 25 are installed on the upper surface 134 of the substrate 130 so as to cover the upper portions of the respective heat sinks 158a and 158b.

[0070] Further, the first substrate 100 may further have a plurality of lower conductors 35 as shown in FIG. 1. The lower conductors 35 are installed on the lower surface 136 of the substrate 130 so as to cover the bottom surfaces of the respective heat sinks 158a and 158b.

[0071] The upper electrodes 25 and the lower conductors 35 may be installed by any conventionally known method. For example, the upper electrodes 25 and the lower conductors 35 may be formed by firing the substrate 130 with a conductive paste installed on the upper surface 134 and the lower surface 136 of the substrate 130.

[0072] Also, in the above description, the first substrate 100 is provided as a substrate for a single light-emitting element. That is, the first substrate 100 has only a set of heat sinks 158 for one light-emitting device.

[0073] However, separately from this, the first substrate 100 may be provided as a substrate for a plurality of light-emitting devices. For example, the first substrate 100 may have a substrate 130 portion and a heat sink 158 portion for a first light-emitting device and a substrate 130 portion and a heat sink 158 portion for a second light-emitting device. In this case, the first substrate 100 is later cut at a predetermined position and used for each light-emitting device.

[0074] In addition to this, various modifications and additions can be assumed by those skilled in the art.

[0075] (Application Example of Substrate for Light-Emitting Element According to One Embodiment of the Present Invention) The substrate for a light-emitting element according to one embodiment of the present invention is used, for example, as a substrate for a light-emitting element for a flip-chip bond type light-emitting device 1 as shown in FIG. 1.

[0076] In the light-emitting device 1, the light-emitting element 60 may be of any type. The light-emitting element 60 may be, for example, an LED element, an LD, or a surface-emitting laser diode (VCSEL), etc.

[0077] In the light-emitting device 1 including a substrate for a light-emitting element according to an embodiment of the present invention, the heat dissipation characteristics can be significantly enhanced.

[0078] (Manufacturing method of a substrate for a light-emitting element according to an embodiment of the present invention) Next, with reference to FIGS. 4 to 9, an example of a manufacturing method of a substrate for a light-emitting element according to an embodiment of the present invention will be described.

[0079] FIG. 4 schematically shows the flow of a method for manufacturing a substrate for a light-emitting element according to an embodiment of the present invention.

[0080] As shown in FIG. 4, a method for manufacturing a substrate for a light-emitting element according to an embodiment of the present invention (hereinafter referred to as the "first manufacturing method") includes a step (S110) of forming a plurality of through holes in a green sheet having an upper surface and a lower surface, a step (S120) of filling each through hole with a paste for a heat sink, a step (S130) of installing a relaxation paste layer on the upper surface and the lower surface of the green sheet, a step (S140) of heat-treating the green sheet to form a sintered substrate, a step (S150) of polishing the upper and lower surfaces of the sintered substrate to obtain a substrate for a light-emitting element, and has.

[0081] Hereinafter, each step will be described in more detail with reference to FIGS. 5 to 9.

[0082] Here, the manufacturing method of the above-described first substrate 100 will be described as an example. Therefore, when representing each member, the reference numerals used in FIGS. 2 and 3 are used.

[0083] (Step S110) First, a green sheet is prepared. The green sheet is composed of a material mainly based on glass. The green sheet may further contain ceramics and / or an organic binder.

[0084] The green sheet is produced, for example, through the following steps.

[0085] (Production of glass powder) The glass powder can be prepared by pulverizing glass having a predetermined composition. The glass powder may have the composition as described above.

[0086] For the pulverization of glass, either a dry pulverization method or a wet pulverization method can be used.

[0087] In the wet pulverization method, the glass is pulverized in a solvent. It is preferable to use water as the solvent. For the pulverization, a pulverizer such as a roll mill, a ball mill, or a jet mill can be used.

[0088] The 50% average particle size (D 50 ) of the glass powder obtained after the pulverization treatment is preferably 0.5 μm or more and 2 μm or less.

[0089] In the present application, the 50% average particle size (D 50 ) refers to the value obtained by a particle size measuring device using the laser diffraction scattering method.

[0090] When D 50 of the glass powder is 0.5 μm or more, the glass powder is less likely to aggregate, easy to handle, and can be uniformly dispersed. On the other hand, when D 50 of the glass powder is 2 μm or less, an increase in the glass softening temperature and insufficient sintering are suppressed. The adjustment of the particle size is performed by classification or the like.

[0091] (Production of ceramic powder) As the ceramic powder, those used in the production of general glass ceramics can be used. As the ceramic powder, for example, alumina powder, zirconia powder, or a mixture of alumina powder and zirconia powder can be preferably used.

[0092] The D of the ceramic powder 50 is preferably, for example, 0.5 μm or more and 4 μm or less.

[0093] (Production of green sheet) Next, the aforementioned glass powder, ceramic powder, and organic binder are mixed at a predetermined ratio to prepare a slurry for a green sheet.

[0094] As the organic binder, polyvinyl butyral and / or acrylic resin, etc. can be used.

[0095] To the slurry for a green sheet, a plasticizer, a dispersant, and / or a solvent, etc. may be further added. As the plasticizer, dibutyl phthalate, dioctyl phthalate, and / or butyl benzyl phthalate, etc. can be used. Also, as the solvent, organic solvents such as toluene, xylene, 2-propanol, and / or 2-butanol can be used.

[0096] In the prepared slurry for a green sheet, the mass ratio of the glass powder to the ceramic powder (glass: ceramic) is preferably in the range of 35:65 to 75:25.

[0097] The obtained slurry for a green sheet is formed into a sheet shape by the doctor blade method or the like.

[0098] Thereafter, the slurry for a green sheet is dried to form a green sheet. The green sheet may be provided to the next through-hole forming step in a state where a plurality of sheets are laminated. Note that after the next through-hole forming step, both a single green sheet and a green sheet composed of a plurality of laminated sheets are simply referred to as "green sheet".

[0099] Next, a plurality of through holes are formed in the green sheet. The method of forming the through holes is not particularly limited and may be formed by a conventional general method.

[0100] FIG. 5 schematically shows a top view of the green sheet in which through holes are formed. Further, FIG. 6 schematically shows a cross-sectional view taken along line B-B of the green sheet shown in FIG. 5.

[0101] The green sheet 210 has an upper surface 214 and a lower surface 216. Further, through holes 230a and 230b are provided in the green sheet 210. The through holes 230a and 230b each penetrate from the upper surface 214 to the lower surface 216 of the green sheet 210.

[0102] The thickness of the green sheet 210, that is, the total length of the through holes 230a and 230b, may be, for example, in the range of 200 μm to 1200 μm.

[0103] (Step S120) Next, a heat sink paste is prepared.

[0104] The heat sink paste is prepared, for example, by mixing metal particles and a vehicle.

[0105] The metal particles may contain at least one of copper, silver, and gold. The metal particles are, for example, D 50 coarse particles in the range of 2 μm to 7 μm and D 50 fine particles in the range of 0.02 μm to 1 μm.

[0106] The vehicle contains a resin such as acrylic and / or ethyl cellulose and an organic solvent. The organic solvent may be, for example, α-terpineol.

[0107] The prepared heat sink paste may be filled into the through holes 230a and 230b by, for example, the screen printing method.

[0108] FIG. 7 schematically shows a state in which the through holes 230a and 230b are filled with the heat sink pastes 240a and 240b, respectively.

[0109] (Step S130) Next, a first relaxation paste layer is provided on the upper surface 214 of the green sheet 210 so as to cover the heat sink pastes 240a and 240b. Also, a second relaxation paste layer is provided on the lower surface 216 of the green sheet 210 so as to cover the heat sink pastes 240a and 240b.

[0110] The first relaxation paste layer and the second relaxation paste layer have a form of a paste containing glass.

[0111] Note that the glass contained in the first relaxation paste layer and the second relaxation paste layer has a coefficient of thermal expansion belonging to the range between the coefficient of thermal expansion of the glass contained in the green sheet 210 and the coefficient of thermal expansion of the metal contained in the heat sink pastes 240a and 240b.

[0112] The method for providing the first relaxation paste layer and the second relaxation paste layer is not particularly limited. For example, the first relaxation paste layer and the second relaxation paste layer may be provided by a printing method.

[0113] FIG. 8 schematically shows a cross section of an assembly 290 configured such that a first relaxation paste layer 272 is provided on the upper surface 214 of the green sheet 210 and a second relaxation paste layer 274 is provided on the lower surface 216 of the green sheet 210.

[0114] (Step S140) Next, the assembly 290 formed in Step S130 is heat-treated in the air.

[0115] The temperature of the heat treatment varies depending on the components included in the assembly 290, but is, for example, in the range of 800°C to 1000°C.

[0116] FIG. 9 schematically shows a cross section of a sintered member (hereinafter referred to as "sintered substrate 292") obtained after heat treatment.

[0117] By heat treatment, the powders contained in the green sheet 210 are sintered to form the substrate 130. Also, the heat sink pastes 240a and 240b filled in the through holes 230a and 230b are sintered to form heat sinks 258a and 258b, respectively. Further, the first relaxation paste layer 272 and the second relaxation paste layer 274 are sintered to form the first relaxation layer 282 and the second relaxation layer 284, respectively.

[0118] (Step S150) Next, by polishing the upper and lower surfaces of the sintered substrate 292, the first relaxation layer 282 and the second relaxation layer 284 are removed.

[0119] After polishing, the upper and lower surfaces of the sintered substrate 292 preferably have a surface roughness Ra of 0.5 μm or less.

[0120] Through the above steps, the first substrate 100 as shown in FIGS. 2 and 3 is manufactured.

[0121] Here, in the first manufacturing method, the first relaxation paste layer 272 is installed on the upper surface 214 of the green sheet 210, and the second relaxation paste layer 274 is installed on the lower surface 216 of the green sheet 210, and the assembly 290 is heat-treated.

[0122] In this case, since the first relaxation paste layer 272 and the second relaxation paste layer 274 are arranged along the in-plane direction of the green sheet 210, the in-plane contraction of the green sheet 210 (substrate 130) is hindered during the cooling process of the assembly 290. Similarly, the heat sink pastes 240a, 240b (heat sinks 258a, 258b) are hindered from contracting in the in-plane direction.

[0123] Therefore, in a top view, the total area S of the heat sinks 158a and 158b hEven when it is relatively large, during the cooling process of the assembly 290, it is possible to make it difficult for cracks to occur at the interfaces between the base 130 and the heat radiators 158a and 158b.

[0124] Also, it becomes possible to reduce the distance d between the heat radiators 158a and 158b.

[0125] As a result, in the first manufacturing method, a light-emitting element substrate including a heat radiator having a large area can be appropriately manufactured.

[0126] Specifically, as described above, it becomes possible to obtain a light-emitting element substrate having an overlap area S of 50% or more in a top view. o The distance d between the heat radiators 158a and 158b may be, for example, in the range of 0.35 mm to 0.50 mm.

Example

[0127] Next, specific examples of the present invention will be described. In the following description, Examples 1 to 13 are examples, and Example 21 is a comparative example.

[0128] (Example 1) Based on the above-described first manufacturing method, a light-emitting element substrate was fabricated.

[0129] The light-emitting element substrate was fabricated by heat-treating an assembly including a green sheet, a heat radiator paste, and a relaxation paste layer in the air to form a sintered substrate, and then removing the relaxation layers (thermal expansion coefficient = 15.0 ppm / °C) on both sides. The relaxation paste layer was installed by printing a paste containing glass ceramics. The thickness of the relaxation layer was approximately 10 μm on each surface.

[0130] FIG. 10 schematically shows a top view of the fabricated light-emitting element substrate (hereinafter referred to as "Sample 1").

[0131] The base 310 was made of a mixed material of glass and ceramics. The base 310 has a longitudinal (L 1ais set to) 1.95 mm, horizontal (L 1b is set to) 1.45 mm, and the thickness is 0.5 mm. The thermal expansion coefficient of the substrate 310 is about 6 ppm / °C.

[0132] For the heat sink 358, silver (thermal expansion coefficient = 19.7 ppm / °C) was used.

[0133] In FIG. 10, the shape of the mounting portion 365 on the upper surface of the substrate 310 is shown by a dashed line. The mounting portion 365 has a vertical (L 2a is set to) 1.00 mm, horizontal (L 2b is set to) 1.00 mm.

[0134] Also, each heat sink 358 has a vertical (L 3a is set to) of 0.92 mm and a width W of 0.36 mm. The distance d between both heat sinks 358 was set to 0.38 mm. Also, each heat sink 358 was arranged such that the outer side edges protruded 0.05 mm from the mounting portion 365.

[0135] The total area S of the heat sink 358 h is 0.60 mm 2 On the other hand, the area S of the mounting portion 365 a is 1.00 mm 2 The overlap area S o is 0.57 mm 2 is.

[0136] (Examples 2 to 13) A substrate for a light-emitting element was fabricated in the same manner as in Example 1. However, in Examples 2 to 13, the thickness of the relaxation layer, the total area S of the heat sink h , the distance d, and the overlap area S o etc. were varied.

[0137] The substrates for light-emitting elements manufactured in Examples 2 to 13 are respectively referred to as Samples 2 to 13.

[0138] (Example 21) A substrate for a light-emitting element was fabricated in the same manner as in Example 1. However, in this Example 21, unlike the case of Example 1, the relaxation paste layer was not provided. Therefore, the sintered substrate obtained after heat treatment of the assembly was used as the substrate for the light-emitting element as it was.

[0139] Also, in Example 21, the overlap area S o was set to 35 mm 2 and the distance between the two heat sinks was set to 0.55 mm.

[0140] The substrate for the light-emitting element manufactured in Example 21 is referred to as Sample 21.

[0141] The characteristics of each sample are summarized in Table 1 below.

[0142]

Table 1

[0143] (Evaluation of crack generation rate) The generation rate of cracks extending from the upper surface to the lower surface of the sample was evaluated visually.

[0144] The number of observations was 120 for each sample.

[0145] (Measurement of thermal resistance) An LED element was placed on the mounting portion of each sample to fabricate a light-emitting device.

[0146] First, two upper electrodes were formed on the upper surface of each sample so as to cover the respective heat sinks. The upper electrodes were formed by depositing copper by electrolytic plating.

[0147] Next, the LED element was fixed on the upper electrode of each sample using a die bond material. Thereby, a light-emitting device was configured.

[0148] The thermal resistance of each light-emitting device was measured using a thermal resistance measuring instrument (TH-2167; manufactured by Mineo Sound Electric Co., Ltd.).

[0149] The evaluation results obtained for each sample are summarized in Table 2 below.

[0150]

Table 2

[0151] On the other hand, it was confirmed that in Samples 1 to 13, where the relaxation layer was used during production, the generation of cracks at the interface between the substrate and the heat sink was significantly suppressed.

[0152] Also, it was confirmed that in Samples 1 to 13, the thermal resistance was significantly reduced.

[0153] This application claims priority based on Japanese Patent Application No. 2020-121684 filed on July 15, 2020, and incorporates the entire contents of the Japanese application by reference herein.

Explanation of Reference Numerals

[0154] 1 Flip-chip bond type light-emitting device 2 Substrate for light-emitting element 4 Upper surface 6 Lower surface 10 Substrate 14 Upper surface 16 Lower surface 18 Heat sink 25 Upper electrode 35 Lower conductor 60 Light-emitting element 62 Bottom 65 Electrode bump 100 Substrate for light-emitting element (first substrate) 104 First surface 106 Second surface 130 Substrate 134 Upper surface 136 Lower surface 148a, 148b Through-holes 158, 158a, 158b Heat sinks 165 Mounting portion 210 Green sheet 214 Upper surface 216 Lower surface 230a, 230b Through-holes 240a, 240b Heat sink paste 258a, 258b Heat sinks 272 First relaxation paste layer 274 Second relaxation paste layer 282 First relaxation layer 284 Second relaxation layer 290 Assembly 292 Sintered substrate 310 Substrate 358 Heat sink 365 Mounting portion

Claims

1. A substrate for a light-emitting element, comprising: a substrate having a first surface and a second surface facing each other, and at least two through-holes extending from the first surface to the second surface; a first heat sink and a second heat sink filled in each of the at least two through-holes of the substrate; wherein the distance between the first heat sink and the second heat sink is 0.5 mm or less; the first surface of the substrate has a mounting portion on which a light-emitting element is installed; when viewed from the side of the first surface, the heat sinks overlap with the mounting portion; and a part of each heat sink protrudes from the mounting portion.

2. The substrate for a light-emitting element according to claim 1, wherein the first surface and / or the second surface has a surface roughness Ra of 0.5 μm or less. The area S of the conforming portion ｏ is 50% or more of the area of the mounting portion,

3. The substrate for a light-emitting element according to claim 1 or 2, wherein the substrate contains glass.

4. The substrate for a light-emitting element according to claim 3, wherein the substrate contains ceramics.

5. The substrate for a light-emitting element according to any one of claims 1 to 4, wherein the heat sink contains metal.

6. A method for manufacturing a substrate for a light-emitting element, comprising: forming a plurality of through-holes in a green sheet having an upper surface and a lower surface; filling each of the through-holes with a paste for a heat sink; installing a first relaxation paste layer on the upper surface of the green sheet so as to cover the paste for the heat sink; installing a second relaxation paste layer on the lower surface of the green sheet so as to cover the paste for the heat sink; heat-treating the green sheet to form a sintered substrate; polishing the upper and lower surfaces of the sintered substrate to remove the sintered bodies of the first relaxation paste layer and the second relaxation paste layer. ​ ​ ​ ​ ​

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