JP6311887B2 - Light emitting element substrate and light emitting device - Google Patents

Description

  The present invention relates to a light emitting element substrate and a light emitting device, and more particularly to a light emitting element substrate on which a light emitting element is mounted and a light emitting device using the light emitting element substrate.

Patent Document 1 includes a mounting substrate that is formed of alumina, AlN, and Si and on which a light emitting element is mounted, and a heat dissipation substrate that supports the mounting substrate, and the heat dissipation substrate includes a metal having a lower thermal expansion coefficient than Cu and There is disclosed a light emitting module which is formed of a composite material made of Cu and the mounting substrate is bonded to the heat dissipation substrate by solder or an adhesive.
Patent Document 2 discloses a light emitting element mounting substrate in which a hollow layer made of a hollow material in which alumina is added to the surface of a core metal is provided.

  Patent Document 3 discloses a light source substrate on which a light source element is mounted, a base substrate, an insulating layer formed on a surface of the base substrate on which the light source element is mounted, A wiring pattern formed on the mounting surface side through an insulating layer; and a heat dissipation layer formed on a surface opposite to the mounting surface side of the base substrate. The base substrate is made of aluminum or an aluminum alloy. Copper, a copper-based alloy metal substrate, the insulating layer is formed of any one of ceramic, alumina, aluminum nitride, and aluminum alumite, and the heat dissipation layer is formed of any of alumina, aluminum nitride, and aluminum alumite The insulating layer and the heat dissipation layer are formed of a light source substrate formed by any one of plasma spraying, anodizing, spin coating, CVD, PVD, and vapor deposition. It is shown.

JP 2011-103353 A JP 2006-165029 A Japanese Patent No. 4880358

In the technology of Patent Document 1, due to the difference in the linear expansion coefficient between the mounting board and the heat dissipation board, a problem that a shear stress is applied to the mounting board, solder, or adhesive causes cracks, or the outer peripheral edge of the heat dissipation board warps. There is a problem of peeling from the mounting substrate.
The technique of Patent Document 2 has a problem that the manufacturing process is complicated and the manufacturing cost is high because the enamel layer is formed.

  In the technique of Patent Document 3, the insulating layer and the heat dissipation layer are formed by any one of plasma spraying, anodic oxidation, spin coating, CVD, PVD, and vapor deposition. There is a problem that the strength of the insulating layer and the heat dissipation layer is low.

The present invention has been made to solve the above problems, and has the following objects.
(1) A substrate for a light-emitting element that has high strength, is free from cracks and warps, and has excellent heat dissipation is provided at low cost.
(2) A light emitting device using the light emitting element substrate of (1) is provided.

  As a result of intensive studies in order to solve the above-mentioned problems, the present inventors have arrived at each aspect of the present invention as follows.

<First aspect>
The first aspect is
A light-emitting element substrate on which the light-emitting element is mounted,
A metal substrate;
A first ceramic layer formed on a mounting surface on which the light emitting element is mounted on the metal substrate;
A wiring layer formed on a surface opposite to the surface in contact with the metal substrate in the first ceramic layer and connected to the light emitting element;
A second ceramic layer formed on the opposite surface of the mounting surface of the metal substrate,
The metal substrate and the ceramic layers are bonded by diffusion bonding.

In the first aspect, since the metal substrate and each ceramic layer are bonded by diffusion bonding, the strength of each ceramic layer can be increased, and the light emitting element substrate can be manufactured at low cost.
In particular, a laminate in which a green sheet for forming each ceramic layer is bonded to a metal substrate is heated and pressurized, and the green sheet is fired to form each ceramic layer. If diffusion bonding is used, the manufacturing process can be simplified and the manufacturing cost can be reduced.

  In the first aspect, since the ceramic layers are formed on both the front and back surfaces of the metal substrate, even if the difference between the linear expansion coefficient of the metal substrate and the linear expansion coefficient of each ceramic layer is large, Since the shear stress generated between the ceramic layer and the ceramic layer is suppressed, it is possible to prevent the occurrence of cracks in each ceramic layer, and it is possible to prevent each ceramic layer from peeling off due to the metal substrate being warped.

In addition, in the first aspect, since a metal substrate having high thermal conductivity is provided, heat dissipation is superior to the case where a single ceramic substrate is used, and thus heat generated by the light emitting element can be quickly dissipated. Thus, failure of the light emitting element can be prevented and the life can be extended.
Further, in the first aspect, since the difference between the linear expansion coefficient of the first ceramic layer and the linear expansion coefficient of the light emitting element is small, the shear stress generated between the first ceramic layer and the light emitting element is also small. The connection between the light emitting element and the wiring layer can be prevented from being hindered.

<Second aspect>
According to a second aspect, in the first aspect, the light emitting device substrate further includes a fixing portion for fixing the light emitting element substrate to an attachment using an attachment member, and a portion of the fixing portion that contacts the attachment member. The first ceramic layer is not formed, and the metal substrate is exposed.
In the second aspect, since the mounting member does not contact the first ceramic layer, it is possible to prevent the first ceramic layer from being cracked by the applied force from the mounting member.

<Third aspect>
The third aspect is the second aspect,
The fixing portion is arranged and symmetrically arranged with respect to the center line of the light emitting element substrate, and includes a notch formed in opposite sides of the light emitting element substrate.
The peripheral edge of the notch is a part that contacts the mounting member,
The first ceramic layer is formed on the entire mounting surface of the metal substrate except for the peripheral edge of the notch.

In the third aspect, since a male screw, a rivet, a snap, a split pin or the like is used as an attachment member, and the attachment member can be inserted into the notch of the fixing portion and fixed to the attachment object, The situation can be easily realized.
In addition, in the third aspect, since the fixing portions are arranged symmetrically with respect to the center line of the light emitting element substrate, a uniform force is applied to the entire surface of the light emitting element substrate to fix it to the attachment. Therefore, unnecessary deformation of the light emitting element substrate can be avoided, and cracks and peeling can be prevented from occurring in each ceramic layer.

<Fourth aspect>
The fourth aspect is the second aspect,
The fixing portion is arranged to be symmetrical with respect to the center line of the light emitting element substrate, and includes a through hole formed to penetrate in the plate thickness direction of the light emitting element substrate
The peripheral portion of the through hole is a portion that comes into contact with the mounting member,
The first ceramic layer is formed on the entire surface of the mounting surface of the metal substrate except for the peripheral edge of the through hole.

In the fourth aspect, since a male screw, a rivet, a snap, a split pin, or the like is used as the mounting member, and the mounting member can be inserted into the through hole of the fixing portion and fixed to the object to be attached, This aspect can be easily realized.
In addition, in the fourth aspect, since the fixing portions are arranged symmetrically with respect to the center line of the light emitting element substrate, a uniform force is applied to the entire surface of the light emitting element substrate and fixed to the attachment. Therefore, unnecessary deformation of the light emitting element substrate can be avoided, and cracks and peeling can be prevented from occurring in each ceramic layer.

<5th aspect>
According to a fifth aspect, in the third or fourth aspect, the second ceramic layer is formed on the entire surface of the metal substrate opposite to the mounting surface including the peripheral edge.
In the fifth aspect, the entire back surface (second ceramic layer) of the light emitting element substrate can be brought into close contact with the attachment object, and the mounting strength and heat dissipation of the light emitting element substrate can be improved. .

<Sixth aspect>
According to a sixth aspect, in the first to fifth aspects, the metal substrate is formed of any one metal selected from the group consisting of copper, a copper-based alloy, aluminum, and an aluminum-based alloy. If the metal material of this is used, the said effect | action and effect of the 1st-5th aspect will be acquired reliably.

<Seventh aspect>
In a seventh aspect, in each of the first to sixth aspects, each ceramic layer is formed of any one metal selected from the group consisting of aluminum oxide, aluminum nitride, silicon nitride, and silicon carbide. If these ceramic materials are used, the operations and effects of the first to sixth aspects can be reliably obtained.

<Eighth aspect>
In the eighth aspect, a light emitting device including the light emitting element substrate of the first to seventh aspects and the light emitting element mounted on the light emitting element substrate can be provided.

The top view of the light-emitting device 10 of 1st Embodiment which actualized this invention. The top view which shows the state which attached and fixed the light-emitting device 10 to the heat sink 51 with which the headlamp of a motor vehicle is equipped with the external screws 50a and 50b. 3 is an end view of a longitudinal section of the light emitting device 10, and is an end view of a section taken along the line XX shown in FIGS. 1 and 2. FIG. FIG. 3 is an end view of a longitudinal section for explaining a method for manufacturing the light emitting device 10. The top view of the light-emitting device 100 of 2nd Embodiment which actualized this invention. The top view which shows the state which attached and fixed the light-emitting device 100 to the heat sink 51 with the external screws 50a and 50b.

Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In each embodiment, the same constituent members and constituent elements are denoted by the same reference numerals, and redundant description of the same contents is omitted.
Moreover, in each drawing, in order to make the explanation easy to understand, the dimensional shape and arrangement location of the constituent members of each embodiment are schematically illustrated in an exaggerated manner, and the dimensional shape and arrangement location of each constituent member are the real thing. May not always match.

<First Embodiment>
As shown in FIGS. 1 to 3, the light emitting device 10 of the first embodiment includes a light emitting element substrate 20 (light emitting portion mounting area 20 a), a metal substrate 21, fixing portions 22 a and 22 b (peripheral portion 22 c), a first portion. Reference hole 23, second reference hole 24, first ceramic layer 25, second ceramic layer 26, wiring layer 27, solder resist layer 28, light emitting unit 30, LED (Light Emitting Diode) chip 31, bump 32, phosphor plate 33, a sealing frame portion 34, a sealing resin portion 35, a thermistor 41, resistors 42a and 42b, a connector 43 (connection surface 43a), and the like, and an automobile headlamp using male screws 50a and 50b (seat surface 50c). Is mounted and fixed to the heat sink 51 (flat surface 51a, female screw holes 52a and 52b, reference projections 53 and 54).

The light emitting element substrate 20 includes a metal substrate 21, fixing portions 22a and 22b, a first reference hole 23, a second reference hole 24, a first ceramic layer 25, a second ceramic layer 26, a wiring layer 27, a solder resist layer 28, and the like. Are formed symmetrically with respect to the center line L of the light emitting device 10 (light emitting element substrate 20).
The metal substrate (base substrate) 21 has a rectangular shape and is formed of a thin metal plate material.
The fixing portions 22a, 22b are arranged and formed symmetrically with respect to the center line L of the light emitting device 10 (light emitting element substrate 20), and are formed on opposite sides of the light emitting element substrate 20 (metal substrate 21). A substantially U-shaped notch is provided.
The first reference hole 23 is a circular through hole formed in the vicinity of the fixing portion 22b in the thickness direction of the light emitting element substrate 20.
The second reference hole 24 is an oval through-hole formed in the vicinity of the fixing portion 22a in the thickness direction of the light emitting element substrate 20.

The first ceramic layer 25 is formed on the surface (mounting surface) of the metal substrate 21 at a portion excluding the peripheral portion 22c of the notches of the fixing portions 22a and 22b.
The second ceramic layer 26 is formed on the entire back surface of the metal substrate 21.
The wiring layer 27 is formed on the surface of the first ceramic layer 23 and constitutes a wiring pattern (not shown).
The solder resist layer 28 includes, on the surfaces of the second ceramic layer 26 and the wiring layer 27, the light emitting portion mounting area 20a, the peripheral edge portion 22c of each of the fixing portions 22a and 22b, the wiring layer 27, and each electronic component (thermistor 41). , Resistors 42a and 42b, and a connector 43).

The light emitting unit 30 includes an LED chip 31, a bump 32, a phosphor plate 33, a sealing frame portion 34, a sealing resin portion 35, and the like, and is lined with respect to the center line L of the light emitting device 10 (light emitting element substrate 20). It is formed symmetrically and is mounted on the light emitting portion mounting area 20a disposed between the fixing portions 22a and 22b of the light emitting element substrate 20.
The four LED chips 31 having the same configuration are substantially rectangular parallelepiped, and are arranged in a line between the fixing portions 22a and 22b of the light emitting element substrate 20.
An anode electrode and a cathode electrode (not shown) are formed on the lower surface of each LED chip 31, and these electrodes and the wiring layer 27 are flip-chip bonded via bumps 32.

The phosphor plate 33 has a rectangular flat plate shape, and is attached and fixed to the upper surface of each LED chip 31 using an adhesive (not shown).
The sealing frame portion (dam material) 34 has a rectangular annular shape (frame shape), is disposed so as to surround each LED chip 31, and is formed on the surface of the first ceramic layer 25 of the light emitting element substrate 20.
The sealing resin portion 35 includes a sealing frame portion 34 and each member (LED chip 31, bump 32, phosphor plate 33, first ceramic layer 25, wiring layer 27) provided inside the sealing frame portion 34. Each of the members is sealed by being filled in between.
The surface of the phosphor plate 33 is exposed from the sealing resin portion 35.

The thermistor 41 is a chip component, is disposed between the reference holes 23 and 24 in the vicinity of the light emitting unit 30 on the center line L of the light emitting device 10, and is connected to the wiring layer 27.
Each of the registers 42 a and 42 b is a chip component, and is arranged in line symmetry with respect to the center line L of the light emitting device 10 between the reference holes 23 and 24 in the vicinity of the thermistor 41 and connected to the wiring layer 27. Yes.
The connector 43 has a rectangular parallelepiped shape and is connected to the wiring layer 27. The connection surface 43a of the connector 43 is disposed adjacent to a side different from the side where the fixing portions 22a and 22b of the light emitting element substrate 20 are formed. Yes.

[Mounting structure of light emitting device 10]
As shown in FIGS. 2 and 3, a flat surface 51 a for mounting and fixing the light emitting device 10 is formed on the heat sink 51 provided in the headlamp of the automobile.
On the flat surface 51a of the heat sink 51, two female screw holes 52a and 52b are screwed and two reference projections 53 and 54 are projected.
The reference protrusion 53 is a protrusion having a circular cross section, and the reference protrusion 53 has a cross sectional dimension corresponding to a cross sectional dimension of the first reference hole 23 of the light emitting element substrate 20.
The reference protrusion 54 is a protrusion having an oval cross section, and the cross sectional dimension of the reference protrusion 54 corresponds to the cross sectional dimension of the second reference hole 24 of the light emitting element substrate 20.

In order to attach and fix the light emitting device 10 to the heat sink 51, first, the light emitting element substrate 20 with the back surface side (second ceramic layer 26 side) of the light emitting element substrate 20 facing the flat surface 51 a of the heat sink 51. The light emitting device 10 is positioned with respect to the heat sink 51 by fitting the reference holes 23 and 24 to the reference protrusions 53 and 54 of the heat sink 51, respectively.
Then, the cutouts of the fixing portions 22a and 22b in the light emitting element substrate 20 and the female screw holes 52a and 52b of the heat sink 51 are brought into a match state.
Accordingly, the male screws 50a and 50b are inserted into the notches of the fixing portions 22a and 22b, and the male screws 50a and 50b are screwed into the female screw holes 52a and 52b, thereby attaching the light emitting device 10 to the heat sink 51. Fix it.
Here, as shown in FIG. 3, the seat surface 50 c of the screw head of each male screw 50 a, 50 b is formed on the metal substrate 21 exposed from the peripheral portion 22 c of the notch of each fixing portion 22 a, 22 b in the light emitting element substrate 20. It is in close contact with the surface.
When the light emitting device 10 is attached and fixed to the heat sink 51, heat radiation grease is applied between the second ceramic layer 26 and the flat surface 51a of the heat sink 51, or a heat radiation sheet is sandwiched. Preferably, the heat generated by the light emitting device 10 can be efficiently radiated through the heat radiating grease or the heat radiating sheet.

When an automobile wire harness (not shown) is connected to the connection surface 43a of the connector 43, the DC power applied to the connector 43 from the wire harness passes through the wiring pattern formed of the wiring layer 27 and the thermistor 41 and each register 42a. , 42b and each LED chip 31 is supplied, and each LED chip 31 is turned on.
In the light emitting device 10, primary light (blue light) emitted from each LED chip 31 and secondary light in which a part of the primary light is wavelength-converted by exciting the phosphor contained in the phosphor plate 33. (Yellow light) is mixed, and white light generated by the mixed color is emitted from the surface of the phosphor plate 33 which is a light emitting surface of the light emitting device 10.

[Manufacturing Method of Light-Emitting Device 10]
Step 1 (see FIG. 4A): Using the press work, the fixing portions 22a and 22b and the reference holes 23 and 24 (not shown in FIG. 4) are punched and formed in the metal substrate 21.
Further, a thin film of insert metal M is attached to one side of each of the green sheets Ga and Gb for forming the ceramic layers 25 and 26.
Then, the fixing portions 22a and 22b and the reference holes 23 and 24 are punched and formed in the green sheets Ga and Gb and the insert metal M using press working.
The green sheet is prepared by mixing a raw material powder made of a sintering aid such as a ceramic material and glass, an organic binder, a plasticizer and a solvent to produce a slurry (liquid mixture), and the slurry is a doctor blade molding machine. Is processed into a flexible sheet material.

  Process 2 (refer FIG. 4 (B)): Each fixing | fixed part 22a, 22b and each reference hole 23,24 of the metal substrate 21, Each green sheet Ga, Gb, each fixing | fixed part 22a, 22b of each insert metal M, and each The positions of the reference holes 23 and 24 are aligned, and the green sheet Ga is adhered to the surface of the metal substrate 21 with the insert metal M interposed therebetween, and the green sheet Gb is adhered to the back surface of the metal substrate 21 with the insert metal M interposed therebetween. To do.

Step 3 (see FIG. 4C): A laminate of the metal substrate 21, the green sheets Ga and Gb, and the insert metals M is heated and pressurized in a vacuum or an inert gas atmosphere.
Thereby, the green sheets Ga and Gb are fired (sintered) to form the ceramic layers 25 and 26, and at the same time, the metal substrate 21 and the ceramic layers 25 and 26 are bonded to each other by a diffusion bonding method (thermocompression bonding method). To join.
In addition, in the definition of JIS standard, diffusion bonding means “diffusion of atoms generated between bonding surfaces by pressing the base material in close contact and pressurizing the base material to the extent that plastic deformation does not occur as much as possible. It is said that it is a method of joining using.

  Here, the insert metal M sandwiched between the metal substrate 21 and the green sheets Ga and Gb is diffused after being temporarily melted by TLP (Transient Liquid Phase Diffusion Bonding). The metal substrate 21 and the ceramic layers 25 and 26 are bonded by isothermal solidification and bonded to the metal substrate 21 and the ceramic layers 25 and 26, and the bonding surfaces of the metal substrate 21 and the ceramic layers 25 and 26 are cleaned. Promote diffusion bonding.

Step 4 (see FIG. 4D): A wiring layer 27 is formed on the entire surface of the first ceramic layer 25 using a plating method.
Then, unnecessary portions of the wiring layer 27 are removed using a photolithography method and an etching method to form a wiring pattern.
Step 5 (see FIG. 4E): When the solder resist layer 28 is formed on the surfaces of the first ceramic layer 25 and the wiring layer 27 using a printing method, the light emitting element substrate 20 is completed.

Process 6 (refer FIG. 2): The light emission part 30 is formed in the board | substrate 20 for light emitting elements. First, each LED chip 31 is flip-chip bonded to the wiring layer 27 by the bump 32, and then the phosphor plate 33 is attached and fixed to each LED chip 31, and then a sealing frame is formed on the surface of the first ceramic layer 25. When the portion 34 is formed and then the sealing resin portion 35 is formed, the light emitting portion 30 is completed.
Then, when each electronic component (thermistor 41, resistors 42a and 42b, connector 43) is connected to the wiring layer 27 using reflow soldering, the light emitting device 10 is completed.

  By the way, after Step 3, it is conceivable that the fixing portions 22a and 22b and the reference holes 23 and 24 are formed by punching the metal substrate 21 and the ceramic layers 25 and 26, respectively. In that case, the ceramic layers 25 and 26 having high hardness and brittleness may be cracked, which is not suitable.

[Constituent Members of Light-Emitting Device 10]
The metal substrate 21 of the light emitting element substrate 20 is formed of a metal material having high thermal conductivity and sufficient strength. For example, copper, a copper alloy, aluminum, an aluminum alloy, or the like may be used.

Among these metal materials, copper is most suitable because it has high thermal conductivity and can be easily diffusion bonded to the ceramic layers 25 and 26.
Aluminum and aluminum-based alloys can reduce the weight of the light-emitting device 10 because of their low specific gravity, but their thermal conductivity is inferior to copper or copper-based alloys, and diffusion bonding with the ceramic layers 25 and 26 is difficult.

The metal substrate 21 of the first embodiment uses copper, has a planar dimension of 18 × 19 mm, and a plate thickness of 1 mm.
When copper is used for the metal substrate 21, the thickness range is suitably 0.5 to 3 mm, and preferably 1 to 2 mm.

  If the thickness of the metal substrate 21 is larger than this range, the thermal resistance increases and the heat dissipation decreases, and the cost increases.

Further, when the thickness of the metal substrate 21 is smaller than this range, the metal substrate 21 is likely to be warped, and in addition to the ceramic layers 25 and 26 being peeled, a gap is generated between the metal substrate 21 and the heat sink 51. Thermal conductivity will decrease. When the metal substrate 21 is warped, the stress applied to the light emitting element substrate 20 from the male screws 50a and 50b when the light emitting device 10 is screwed to the heat sink 51 by the male screws 50a and 50b increases. This promotes the occurrence of cracks and peeling in the ceramic layers 25 and 26.
Note that a copper plate having a thickness of 1 mm is particularly inexpensive because it has a large amount of circulation, so that the cost of the light emitting device 10 can be reduced.

In the first embodiment shown in FIG. 1, the cutout dimensions of the fixing portions 22a and 22b in the light emitting element substrate 20 are a width t = 3.2 mm and a depth d = 3.6 mm.
The dimensions of the notches of the fixing portions 22a and 22b may be set corresponding to the screw diameters of the male screws 50a and 50b so that sufficient strength can be obtained when the light emitting device 10 is attached and fixed to the heat sink 51.

  Each ceramic layer 25, 26 is formed of a ceramic material having high insulation and sufficient strength. For example, aluminum oxide (alumina), aluminum nitride, silicon nitride, silicon carbide, or the like may be used.

Among these ceramic materials, aluminum oxide has high hardness and is inexpensive, and also has a linear expansion coefficient = 7.2 ppm / ° C., and the linear expansion coefficient of the LED chip 31 is close to 3.6 ppm / ° C. Since the shear stress generated between the ceramic layer 25 and each LED chip 31 is reduced, it is possible to reliably prevent the bump 32 from being cracked or peeled, and it is most suitable because it is inexpensive. .
Aluminum nitride has a linear expansion coefficient of 4.6 ppm / ° C. and is closer to the linear expansion coefficient of the LED chip 31 than aluminum oxide, so that it is possible to reliably prevent cracks and peeling from occurring in the ceramic layers 25 and 26. The thermal conductivity is 150 W / (m · K), and the thermal conductivity of aluminum oxide is higher than 32 W / (m · K), so that the heat dissipation is excellent, but there is a disadvantage that it is expensive.

  Since silicon nitride has a linear expansion coefficient of 2.8 ppm / ° C. and is closer to the linear expansion coefficient of the LED chip 31 than aluminum oxide, it is possible to reliably prevent the ceramic layers 25 and 26 from cracking and peeling. Yes, thermal conductivity = 27 W / (m · K), equivalent to aluminum oxide, toughness = 7 Mpa√m, and aluminum oxide toughness = higher than 4-5 Mpa√m. It can be done, but it has the disadvantage of being expensive.

  Since silicon carbide is substantially the same as the LED chip 31 at a linear expansion coefficient of 3.7 ppm / ° C., it is possible to more reliably prevent the ceramic layers 25 and 26 from being cracked or peeled off, and the thermal conductivity = Since it is higher than aluminum oxide at 200 W / (m · K), it has excellent heat dissipation, but it also has the disadvantage of being expensive.

The ceramic layers 25 and 26 of the first embodiment use aluminum oxide, and the layer thickness is 0.3 mm.
When aluminum oxide is used for the first ceramic layer 25, the range of the layer thickness is suitably 0.1 to 0.5 mm, desirably 0.2 to 0.4 mm, and particularly desirably 0.3 mm.

If the thickness of each ceramic layer 25, 26 is larger than this range, in addition to an increase in thermal resistance and a decrease in heat dissipation, the cost increases, and a displacement difference in linear expansion due to the thickness increases. Therefore, there is a concern that intra-layer fracture occurs in each ceramic layer 25, 26, and that each ceramic layer 25, 26 breaks in the lateral direction (direction intersecting with the thickness).
Further, if the thickness of each ceramic layer 25, 26 is thinner than this range, in addition to the decrease in insulation, cracks are likely to occur during firing.

When the ceramic layers 25 and 26 have different materials and layer thicknesses, the ceramic layers 25 and 26 have different linear expansions. Therefore, the ceramic layers 25 and 26 are warped due to the difference in linear expansion. As a result, the ceramic layers 25 and 26 are cracked or peeled off.
Therefore, the materials and layer thicknesses of the ceramic layers 25 and 26 need to be substantially the same.

  As described above, the insert metal M promotes effects such as diffusion in the joint, adhesion between the joint surfaces, and destruction and removal of the oxide film generated on the joint surface. For example, titanium, titanium-based alloy, etc. Titanium and titanium-based alloys are most suitable because they form a compound through covalent bonds with both metals and ceramics.

  The wiring layer 27 is formed of a multi-layered metal layer. As the layer structure, for example, a layer structure in which titanium or nickel, platinum, and gold are laminated from the first ceramic layer 25 side, copper, nickel, low-purity gold, and high A layer structure in which pure gold is stacked may be used.

  If a black solder resist is used for the solder resist layer 28, the light emitted from the light emitting section 30 is unnecessarily reflected on the surface of the light emitting element substrate 20, and the reflected light is prevented from becoming stray light that is not optically controlled. Therefore, it is possible to prevent the stray light from being emitted to an unintended region via a headlight lens (not shown).

The bumps 32 are gold / tin alloy solder bumps, and the gold / tin alloy solder bumps have a high melting point of about 300 ° C., and therefore can sufficiently withstand the heat generation of the LED chips 31.
The phosphor plate 33 is formed of a transparent material (for example, synthetic resin material, glass material, etc.) containing fine particles of a phosphor (for example, YAG (Yttrium Aluminum Garnet) type), and wavelength conversion is performed as described above. It functions as a member (wavelength conversion layer).
The sealing frame portion 34 is a white synthetic resin material (for example, a silicone resin, an epoxy resin, or the like) containing fine particles of a highly light-reflective material (for example, titanium oxide or aluminum oxide), or a light-reflective ceramic material. (For example, aluminum oxide), a light-reflective metal material (for example, aluminum alloy) or the like.
The sealing resin portion 35 is formed of a synthetic resin material containing fine particles of a material having high light reflectivity similar to the fine particles of the sealing frame portion 34.

[Operations and effects of the first embodiment]
According to the first embodiment, the following actions and effects can be obtained.

  [1] Each LED chip 31 (each LED chip 31) is mounted on the light emitting element substrate 20, and a metal substrate 21 and a first surface formed on the mounting surface of the metal substrate 21 on which the LED chips 31 are mounted. The ceramic layer 25, the wiring layer 27 formed on the surface opposite to the surface of the first ceramic layer 25 in contact with the metal substrate 21 and connected to each LED chip 31, and the surface opposite to the mounting surface of the metal substrate 21 are formed. The second ceramic layer 26 is provided, and the metal substrate 21 and the ceramic layers 25 and 26 are joined by diffusion bonding.

Therefore, the strength of the ceramic layers 25 and 26 can be increased, and the light emitting element substrate 20 can be manufactured at low cost.
In particular, a laminate in which green sheets Ga and Gb for forming the ceramic layers 25 and 26 are bonded to the metal substrate 21 is heated and pressurized, and the green sheets Ga and Gb are fired to form the ceramic layers 25 and 26. At the same time, if the metal substrate 21 and the ceramic layers 25 and 26 are diffusion bonded, the manufacturing process can be simplified and the manufacturing cost can be reduced.

  In the light emitting element substrate 20, the ceramic layers 25 and 26 are formed on both the front and back surfaces of the metal substrate 21. Therefore, the linear expansion coefficient of the metal substrate 21 and the linear expansion coefficient of the ceramic layers 25 and 26 are different from each other. Even if the difference is large, since the shear stress generated between the metal substrate 21 and the ceramic layers 25 and 26 is suppressed, it is possible to prevent the ceramic layers 25 and 26 from being cracked and to prevent the metal substrate 21. It is possible to prevent the ceramic layers 25 and 26 from peeling off and peeling off.

In addition, since the light emitting element substrate 20 includes the metal substrate 21 having high thermal conductivity, the heat dissipation is superior to that in the case of using a single ceramic substrate, and thus the heat generated by each LED chip 31 is quickly dissipated. The failure of each LED chip 31 can be prevented and the life can be extended.
Further, in the light emitting element substrate 20, since the difference between the linear expansion coefficient of the first ceramic layer 25 and the linear expansion coefficient of each LED chip 31 is small, it occurs between the first ceramic layer 25 and each LED chip 31. Since the shear stress is also reduced, it is possible to prevent the connection between each LED chip 31 and the wiring layer from being hindered.

[2] The light emitting element substrate 20 includes fixing portions 22a and 22b for mounting and fixing to the heat sink 51 (attachment) provided in the headlamp of the automobile using male screws 50a and 50b (attachment members).
The fixing portions 22 a and 22 b are arranged and formed symmetrically with respect to the center line L of the light emitting element substrate 20, and are provided with notches formed on opposite sides of the light emitting element substrate 20.

The peripheral portion 22c of the notch of the fixing portions 22a and 22b is a portion in contact with the seating surface 50c of the male screws 50a and 50b. The first ceramic layer 25 is not formed on the peripheral portion 22c and the metal substrate 21 is exposed. doing.
Therefore, since the seating surface 50c of the male screws 50a and 50b does not contact the first ceramic layer 25, it is possible to prevent the first ceramic layer 25 from being cracked by the applied force from the male screws 50a and 50b.
Then, the male screws 50 a and 50 b can be inserted into the notches of the fixing portions 22 a and 22 b and fixed to the heat sink 51.

  Further, since the fixing portions 22 a and 22 b are arranged and formed symmetrically with respect to the center line L of the light emitting element substrate 20, a uniform force is applied to the entire surface of the light emitting element substrate 20 to fix it to the heat sink 51. It is possible to prevent unnecessary deformation of the light emitting element substrate 20 and prevent the ceramic layers 25 and 26 from cracking or peeling.

[3] The second ceramic layer 26 is formed on the entire back surface (opposite surface of the mounting surface) of the metal substrate 21 including the peripheral portion 22c of the notches of the fixing portions 22a and 22b.
Therefore, the entire back surface (second ceramic layer 26) of the light emitting element substrate 20 can be brought into close contact with the heat sink 51, and the mounting strength and heat dissipation of the light emitting element substrate 20 can be increased.

Second Embodiment
As shown in FIGS. 5 and 6, the light emitting device 100 according to the second embodiment includes a light emitting element substrate 20 (light emitting portion mounting area 20a), a metal substrate 21, fixing portions 22a and 22b (peripheral portion 22c), a first portion. Reference hole 23, second reference hole 24, first ceramic layer 25, second ceramic layer 26, wiring layer, solder resist layer 28, light emitting portion 30, LED chip 31, bump, phosphor plate 33, sealing frame portion 34 , A sealing resin portion 35, a thermistor 41, resistors 42a and 42b, a connector 43 (connection surface 43a) and the like, and a heat sink 51 (flat surface) included in a headlamp of an automobile using male screws 50a and 50b (seat surface 50c). 51a, female screw holes 52a and 52b, and reference projections 53 and 54).

The light emitting device 100 of the second embodiment differs from the light emitting device 10 of the first embodiment in the following matters.
[A] The fixing portions 22a and 22b include circular through-holes that are formed through the light emitting element substrate 20 in the thickness direction in the vicinity of the opposing sides of the light emitting element substrate 20 (metal substrate 21).
[A] The first ceramic layer 25 is formed on the surface (mounting surface) of the metal substrate 21 except for the peripheral portion 22c of the through holes of the fixing portions 22a and 22b.
[C] The light emitting unit 30 is mounted on the light emitting unit mounting region 20 a disposed between the reference holes 23 and 24 in the light emitting element substrate 20.

As shown in FIG. 6, in order to attach and fix the light emitting device 100 to the heat sink 51, first, the back surface side (second ceramic layer 26 side) of the light emitting element substrate 20 is opposed to the flat surface 51a of the heat sink 51. Thus, the light emitting device 100 is positioned with respect to the heat sink 51 by fitting the reference holes 23 and 24 of the light emitting element substrate 20 to the reference protrusions 53 and 54 of the heat sink 51, respectively.
Then, the through holes of the fixing portions 22 a and 22 b in the light emitting element substrate 20 and the female screw holes 52 a and 52 b of the heat sink 51 are brought into a match state.
Therefore, the male screws 50a and 50b are inserted into the through holes of the fixing portions 22a and 22b, and the male screws 50a and 50b are screwed into the female screw holes 52a and 52b, whereby the light emitting device 100 is attached to the heat sink 51. Mount and fix.
Here, the bearing surface 50c of the screw head of each male screw 50a, 50b is in close contact with the surface of the metal substrate 21 exposed from the peripheral edge portion 22c of the through hole of each fixing portion 22a, 22b in the light emitting element substrate 20. .

[Operation and Effect of Second Embodiment]
According to the second embodiment, the effects [1] and [3] of the first embodiment can be obtained.
And in 2nd Embodiment, the peripheral part 22c of the through-hole of fixing | fixed part 22a, 22b is a part contact | abutted with the seat surface 50c of external thread 50a, 50b, and the 1st ceramics layer 25 is formed in the peripheral part 22c. The metal substrate 21 is exposed.
Therefore, since the seating surface 50c of the male screws 50a and 50b does not contact the first ceramic layer 25, it is possible to prevent the first ceramic layer 25 from being cracked by the applied force from the male screws 50a and 50b.
The male screws 50 a and 50 b can be inserted into the through holes of the fixing portions 22 a and 22 b and fixed to the heat sink 51.
In addition, in the second embodiment, the light emitting unit 30 can be positioned with higher accuracy by the above [c], and thus the utilization efficiency of the light emitted from the light emitting unit 30 can be increased.

<Another embodiment>
The present invention is not limited to the above-described embodiments, and may be embodied as follows. Even in this case, operations and effects equivalent to or higher than those of the above-described embodiments can be obtained.

  [A] The LED chip 11 may be replaced with any semiconductor light emitting element (for example, LD (Laser Diode)).

  [B] The light-emitting devices 10 and 100 are not limited to the heat sink 51 provided in the headlamp of an automobile, but are attached to any attachments (for example, a headlamp case (housing), indoor / outdoor lighting fixtures, etc.). Also good.

  [C] The male screws 50a and 50b may be any attachment member (for example, a rivet, etc.) as long as the light-emitting devices 10 and 100 can be attached and fixed through the notches or through holes of the fixing portions 22a and 22b. Snap, split pin, etc.) may be substituted.

  [D] Each LED chip 31 may be connected to the wiring layer 27 not only by flip chip bonding but also by wire bonding.

  [E] Rather than sticking the green sheets Ga and Gb to be the ceramic layers 25 and 26 to the metal substrate 21, the ceramic layers 25 and 26 are prepared by firing in advance, The ceramic layers 25 and 26 and the metal substrate 21 may be diffusion bonded.

  [F] Using a low temperature co-fired ceramics (LTCC) technology, a paste containing a conductor such as silver is printed on the surface of each green sheet Ga, Gb by screen printing, At the same time as the ceramic layers 25 and 26 and the metal substrate 21 are diffusion-bonded, the paste may be fired to form the wiring layer 27.

DESCRIPTION OF SYMBOLS 10 ... Light-emitting device 20 ... Light-emitting element substrate 21 ... Metal substrate 22a, 22b ... Fixed part 22c ... Peripheral part 25 ... 1st ceramic layer 26 ... 2nd ceramic layer 27 ... Wiring layer 28 ... Solder resist layer 30 ... Light-emitting part 31 ... LED chip (light emitting element)
50a, 50b ... Male thread (mounting member)
51 ... Heat sink (attachment) provided in the headlamp of an automobile

Claims (8)

A light-emitting element substrate on which the light-emitting element is mounted,
A metal substrate;
A first ceramic layer formed on a mounting surface on which the light emitting element is mounted on the metal substrate;
A wiring layer formed on a surface opposite to the surface in contact with the metal substrate in the first ceramic layer and connected to the light emitting element;
A second ceramic layer formed on the opposite surface of the mounting surface of the metal substrate,
The light emitting element substrate in which the metal substrate and the ceramic layers are bonded by diffusion bonding. Further comprising a fixing portion for fixing the light emitting element substrate to an attachment using an attachment member,
The first ceramic layer is not formed on the portion of the fixed portion that contacts the mounting member, and the metal substrate is exposed.
The light emitting element substrate according to claim 1. The fixing portion is arranged and symmetrically arranged with respect to the center line of the light emitting element substrate, and includes a notch formed in opposite sides of the light emitting element substrate.
The peripheral edge of the notch is a part that contacts the mounting member,
The first ceramic layer is formed on the entire surface of the mounting surface of the metal substrate except for a peripheral edge of the notch.
The light emitting element substrate according to claim 2. The fixing portion is arranged to be symmetrical with respect to the center line of the light emitting element substrate, and includes a through hole formed to penetrate in the plate thickness direction of the light emitting element substrate
The peripheral portion of the through hole is a portion that comes into contact with the mounting member,
The first ceramic layer is formed on the entire surface of the mounting surface of the metal substrate except for the peripheral edge of the through hole.
The light emitting element substrate according to claim 2. The second ceramic layer is formed on the entire surface of the metal substrate opposite to the mounting surface including the periphery.
The substrate for a light emitting device according to claim 3 or 4. The metal substrate is formed of any one metal selected from the group consisting of copper, a copper-based alloy, aluminum, and an aluminum-based alloy.
The light emitting element use substrate according to any one of claims 1 to 5. Each ceramic layer is formed of any one metal selected from the group consisting of aluminum oxide, aluminum nitride, silicon nitride, silicon carbide,
The light emitting element use substrate according to any one of claims 1 to 6. A substrate for a light emitting device according to any one of claims 1 to 7,
A light emitting device comprising: a light emitting element mounted on the light emitting element substrate.

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