Light emitting device, light emitting module, and method for manufacturing light emitting device

A light emitting device includes a light emitting element, a first terminal, a second terminal, and a light reflecting member. The first terminal and the second terminal each have a substantially spherical shape and are electrically connected to the light emitting element. The light reflecting member holds the light emitting element, the first terminal, and the second terminal. The light reflecting member includes a bottom surface, an upper surface, a first side surface, a second side surface, a front surface, a back surface, a first terminal exposure surface, and a second terminal exposure surface. The light emitting device is to be placed via the bottom surface. The first terminal is exposed from the first terminal exposure surface to provide a first exposed portion. The second terminal is exposed from the second terminal exposure surface to provide a second exposed portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U. S. C. §119 to Japanese Patent Application No. 2014-198639, filed Sep. 29, 2014. The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND

Technical Field

The present disclosure relates to a light emitting device, a light emitting module, and a method for manufacturing a light emitting device.

Discussion of the Background

A light emitting diode (LED) has many features of low power consumption, long lifetime, high reliability, and the like, so that as an LED light emitting device which emits white light by combining a blue LED and a phosphor is put to practical use, the LED is widely used for various purposes in various kinds of lights, a light source for backlight, and the like.

Japanese Unexamined Patent Application Publication No. 2013-69815 discloses a chip size package (CSP) type light emitting device. In the CSP type light emitting device, an LED chip is directly covered with a light reflective resin or the like, so that a small and thin light emitting device can be formed. The light emitting device described in Japanese Unexamined Patent Application Publication No. 2013-69815 is a side-surface light emission type semiconductor light emitting device including a semiconductor layer having a light emitting layer, an electrode and a wiring portion connected to the semiconductor layer, and a sealing portion covering the wiring portion. In this semiconductor light emitting device, the positive and negative wiring portions are exposed from a plurality of surfaces of the sealing portion, as terminal surfaces. According to this configuration, since a large terminal surface can be ensured, the semiconductor light emitting device can be small in size and great in mountability to a mounting substrate.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a light emitting device includes a light emitting element, a first terminal, a second terminal, and a light reflecting member. The light emitting element has a light emitting surface to emit a light. The first terminal and the second terminal each have a substantially spherical shape and are electrically connected to the light emitting element. The light reflecting member holds the light emitting element, the first terminal, and the second terminal. The light reflecting member includes a bottom surface, an upper surface, a first side surface, a second side surface, a front surface, a back surface, a first terminal exposure surface, and a second terminal exposure surface. The light emitting device is to be placed via the bottom surface. The upper surface is opposite to the bottom surface in a height direction of the light emitting device. The first side surface is provided between the bottom surface and the upper surface on a first side in a width direction of the light emitting device perpendicular to the height direction. The second side surface is provided between the bottom surface and the upper surface on a second side opposite to the first side in the width direction. The front surface is provided between the bottom surface and the upper surface and between the first side surface and the second side surface on a front side in a depth direction of the light emitting device perpendicular to the height direction and the width direction. The light emitting surface of the light emitting element is exposed from the front surface. The back surface is provided between the bottom surface and the upper surface and between the first side surface and the second side surface on a back side opposite to the front side in the depth direction. The first terminal is exposed from the first terminal exposure surface to provide a first exposed portion. The second terminal is exposed from the second terminal exposure surface to provide a second exposed portion. The first and the second exposed portions are provided inside a bottom region defined by the first side surface, the second side surface, the front surface, and the back surface of the light reflecting member when viewed from a bottom surface side of the light reflecting member in the height direction, are provided inside a side region defined by the upper surface, the bottom surface, the front surface, and the back surface of the light reflecting member when viewed from the first side or the second side of the light reflecting member in the width direction, and are provided inside a back region defined by the first side surface, the second side surface, the upper surface, and the bottom surface of the light reflecting member when viewed from the back side of the light reflecting member in the depth direction.

According to another aspect of the present invention, a light emitting module includes the light emitting device. The light emitting device is mounted on a mounting substrate.

According to further aspect of the present invention, a method for manufacturing a light emitting device includes connecting a first terminal and a second terminal to a light emitting element having a light emitting surface to emit a light. The first terminal and the second terminal each have a substantially spherical shape. A light reflecting member is provided to hold the light emitting element, the first terminal, and the second terminal and to include a bottom surface via which the light emitting device is to be placed, an upper surface opposite to the bottom surface in a height direction of the light emitting device, a first side surface provided between the bottom surface and the upper surface on a first side in a width direction of the light emitting device perpendicular to the height direction, a second side surface provided between the bottom surface and the upper surface on a second side opposite to the first side in the width direction, a front surface from which the light emitting surface of the light emitting element is exposed and which is provided between the bottom surface and the upper surface and between the first side surface and the second side surface on a front side in a depth direction of the light emitting device perpendicular to the height direction and the width direction, and a back surface provided between the bottom surface and the upper surface and between the first side surface and the second side surface on a back side opposite to the front side in the depth direction. The light reflecting member is partially removed so that a first terminal exposure surface is provided and the first terminal is partially exposed from the first terminal exposure surface to provide a first exposed portion, so that a second terminal exposure surface is provided and the second terminal is partially exposed from the second terminal exposure surface to provide a second exposed portion, and so that the first and the second exposed portions are provided inside a bottom region defined by the first side surface, the second side surface, the front surface, and the back surface of the light reflecting member when viewed from a bottom surface side of the light reflecting member in the height direction, are provided inside a side region defined by the upper surface, the bottom surface, the front surface, and the back surface of the light reflecting member when viewed from the first side or the second side of the light reflecting member in the width direction, and are provided inside a back region defined by the first side surface, the second side surface, the upper surface, and the bottom surface of the light reflecting member when viewed from the back side of the light reflecting member in the depth direction.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments will be described with reference to the drawings. However, a light emitting device which will be described below is only provided to embody a technical idea of the present disclosure, and the present invention is not limited to the following light emitting device. Specifically, dimensions, materials, shapes, relative arrangement of the components which will be described below do not limit a technical range of the present invention unless otherwise described, and they are only examples for the description. In addition, sizes and positional relation of the members shown in each drawing are sometimes exaggerated to make clear the description. Furthermore, as for each component in the embodiments, a plurality of components may be composed of one member so that one member serves as a plurality of components, or conversely, function of one member may be realized by a plurality of members. In addition, each configuration can be appropriately combined to be applied in the embodiments described below also unless otherwise specified.

First Embodiment

FIG. 1is a schematic perspective view of a light emitting device10according to a first embodiment viewed from a front surface side.FIG. 2is a schematic view of the light emitting device10viewed from a side surface side.FIG. 3Ais a schematic perspective view of the light emitting device10viewed from a back surface side. The light emitting device10according to the first embodiment is suited for being used mainly as a side-surface light emission type light emitting device. The light emitting device10includes a light emitting element1, a first terminal2and a second terminal3electrically connected to the light emitting element1, and a light reflecting member4holding the above components. The light emitting element1may include a semiconductor layer1a, an n-side electrode1b, and a p-side electrode1c. A light emitting surface of the light emitting element1(surface opposite to an electrode formation surface of the semiconductor layer1a) is exposed from the light reflecting member4. The first terminal2and the second terminal3each has a substantially spherical shape, and are electrically connected to the n-side electrode1bor the p-side electrode1cof the light emitting element1respectively. The first terminal2and the second terminal3are partially exposed from the light reflecting member4as exposed portions2aand3a, respectively.

In the first embodiment, the light reflecting member4forms external surfaces of the light emitting device10. The light reflecting member4may include a bottom surface4aserving as a mounting surface of the light emitting device10, side surfaces4b, a back surface4c, a front surface4d, and an upper surface4e. According to the first embodiment, the side surfaces4beach abuts on the bottom surface4asubstantially vertically. In addition, the side surfaces4bare arranged substantially parallel to each other, and the bottom surface4aand the upper surface4eare arranged substantially parallel to each other. The front surface4dof the light reflecting member4covers the electrode formation surface side of the light emitting element1. The back surface4cof the light reflecting member4is the surface opposite to the front surface4dthat serves as the light emitting surface of the light emitting device10, where the light emitting element1is exposed. In addition, in the description below, it is assumed that a substantially perpendicular direction from the front surface4dto the back surface4cis referred to as a “depth direction”, a direction substantially perpendicular from the bottom surface4ato the upper surface4eis referred to as a “height direction”, and a direction substantially perpendicular to the side surfaces4bis referred to as a “width direction”.

The light reflecting member4further includes terminal exposure surfaces4fin addition to the surfaces described above. The exposed portions2aand3aare exposed from the terminal exposure surfaces4frespectively.

The exposed portions2aand3aare formed at an inner side with respect to an outermost surface of the light reflecting member4, seen from the bottom surface side, either of the side surfaces side, and the back surface side of the light reflecting member4. In the specification, the term an “outermost surface” refers to a surface with an outermost periphery when viewed from the bottom surface side, the side surface side, and the back surface side of the light reflecting member4(as to what surface is the outermost surface when viewed from each surface side, will be described below), respectively. In addition, the term “inner side” refers to a state within the periphery of the outermost surface, but the exposed portions2aand3amay substantially align with the periphery of the outermost surface or may be partially outside of the outermost surface.

In the configuration described above, the first terminal2and the second terminal3in a spherical shape which are provided in advance are used, so that compared with a case where the terminals of a desired thickness are formed by plating or the like, a processing cost and a time can be reduced. Furthermore, with the use of spherical first terminal2and second terminal3, the exposed portions2aand3ahaving an outwardly round surface can be respectively exposed from the terminal exposure surfaces4fprovided by partially removing the light reflecting member4, so that a large surface area can be obtained. In addition, each of the outwardly rounded exposed portions2aand3ais positioned at an inner side with respect to the outermost surface when viewed from each surface side of the light reflecting member4, so that a reduction in the connection strength between the light emitting device10and a mounting substrate20can be avoided. In addition, absorption of light by the bonding agent6that connects the light emitting device10and the mounting substrate20can be suppressed by the terminal exposure surfaces4f. Therefore, while the light extraction can be sufficiently maintained, the light emitting device can be high in connection strength and mounting applicability to the mounting substrate20.

Hereinafter, each component of the light emitting device10according to the first embodiment will be described in detail. In addition, a configuration of each component which will be described below is shown as an example, and the present invention is not limited to that configuration.

The light emitting element1may include the semiconductor layer1ahaving an n-type semiconductor layer11, an active layer12, and a p-type semiconductor layer13, the n-side electrode1bformed on the n-type semiconductor layer11, and the p-side electrode1cformed on the p-type semiconductor layer13. In the first embodiment, the n-type semiconductor layer11, the active layer12, and the p-type semiconductor layer13of the semiconductor layer1aare formed in this order in the depth direction. For example, the semiconductor layer1acan be made of ZnSe, a nitride semiconductor (InXAlYGa1-X-YN (0≦X, 0≦Y, X+Y≦1)), GaAlAs, AlInGaP or the like. Each semiconductor layer may have a single-layer structure or may have a stacked-layer structure composed of layers having different compositions and/or different thicknesses, or a super lattice structure. The active layer12preferably has a single quantum well structure or multiple quantum well structure. The light emitting element1may have a substrate in addition to the semiconductor layer1a. In order to efficiently extract the light from the light emitting element1, a substrate made of a component having high light transmissivity such as sapphire can be used. In the case of the light emitting device in which the semiconductor layer1ais formed on the substrate, the semiconductor layer1acan be exposed from the light reflecting member4by removing the substrate. Thus, the light extraction from the light emitting element1can be improved. The substrate can be easily removed by using a laser lift-off (LLO) method.

The n-side electrode1bcan be formed, for example, by using a RIE method using a resist, on a portion which has been exposed in the n-type semiconductor layer11by partially removing the active layer12and the p-type semiconductor layer13in the semiconductor layer1a. Meanwhile, the p-side electrode1cis formed on the p-type semiconductor layer13. Each electrode may be made of a material such as Au, Ag, an Ag alloy, Al, an Al alloy, or ITO. Each electrode may be formed by using a sputtering method, a vapor deposition method, or the like. The upper surfaces of the n-side electrode1band the p-side electrode1cpreferably have substantially the same height, so that the first terminal2and the second terminal3having substantially the same size can be easily connected thereto.

The first terminal2and the second terminal3each has a substantially spherical shape, and are electrically connected to the n-side electrode1bor the p-side electrode of the light emitting element1, respectively. The first terminal2and the second terminal3each preferably has a substantially spherical shape having a circular cross-sectional surface, but may have a substantially spherical shape having an elliptical cross-sectional surface. In the first embodiment, the first terminal2and the second terminal3are connected in a row in the width direction of the light emitting element1. Since each of the first terminal2and the second terminal3has the spherical shape, each of the exposed portions2aand3ahas the outwardly round surface as will be described below, so that mounting of the light emitting device having good mounting applicability can be obtained.

As for the first terminal2and the second terminal3connected to the light emitting element1, their end portions are preferably arranged on substantially the same plane in the depth direction. In a case where there is a step difference between the n-side electrode1band the p-side electrode1c, the first terminal2and the second terminal3having different sizes are used so that their end portions can be arranged on substantially the same plane in the depth direction.

The substantially spherical first terminal2and second terminal3are covered with the light reflecting member4which will be described below, and they are partially exposed from the terminal exposure surfaces4fof the light reflecting member4, as the exposed portions2aand3a, respectively. Accordingly, each of the exposed portions2aand3ahas the outwardly round surface exposed from the terminal exposure surface4f, and its surface is a covering portion B which will be described below. However, in the case where the first terminal2and the second terminal3are also partially removed at the time of partially removing the light reflecting member4, the surface of each of the exposed portions2aand3amay be flat or not flat, and the surface may be partially a core A. The exposed portions2aand3aeach serves as an external terminal to be electrically connected to a wiring21of the mounting substrate20as shown inFIG. 8.

The exposed portions2aand3acan be provided in the end portions in the width direction of the light emitting device10. With this arrangement, the exposed portions2aand3acan be prevented from causing a short circuit. In the case where the first terminal2and the second terminal3have a diameter of about 40 μm to about 200 μm, the exposed portions2aand3aare preferably exposing about 10% to about 80% of their respective terminals. With this arrangement, connection strength with the mounting substrate20can be improved.

FIG. 4is a schematic cross-sectional view of the first terminal or the second terminal according to the first embodiment. The first terminal2and the second terminal3are preferably made of an electrically-conductive material which allows for easy bonding to the electrodes of the light emitting element1and to the wirings of the mounting substrate20by heating or the like, and which allows for maintaining of their predetermined shapes after the heating. For example, as shown inFIG. 4, each may have a configuration composed of the electrically-conductive core A and the electrically-conductive covering portion B which covers the core A.

Hereinafter, a description will be given to the first terminal2and second terminal3each composed of the electrically-conductive core A and the covering portion B.

The core A is a member to determine the shapes of the first terminal and the second terminal, and preferably made of a material which can maintain the predetermined shape during and after the heating operation. The core A is preferably made of a material containing Cu as its major component (e.g. Cu content is 50% by mass or more). Especially, the core A is preferably made of a material whose Cu content is 99% by mass or more, or Cu alloyed with one or more metals selected from Zn, Sn, P, Ni, Au, Mo, and W, because good thermal and electrical conductivity can be provided. The core A preferably has a substantially spherical shape, so that the first terminal2and the second terminal3can be easily formed into a substantially spherical shape. The core A preferably has a diameter of about 1 μm to about 1000 μm, and more preferably has a diameter of about 40 μm to about 200 μm.

The covering portion B is preferably made of a solder which can bond the core A to the light emitting element and/or the mounting substrate. More specifically, the covering portion B is preferably made of Au alloyed with at least one of Si, Ge, and Sn. In addition, the covering portion B may be made of Ni, Ni—B, or Ni—P. Especially, the covering portion B which has a Sn-based multilayer structure can be preferably used as a bonding agent to connect the light emitting device to the mounting substrate. The Sn-based covering portion B may have a single-layer structure composed of a Sn-based alloy, or may have a multi-layer structure composed of Sn and another alloy, or of a plurality of Sn alloys.

In the case where the covering portion B is made of Sn, the covering portion B may have a thickness of about 1 μm to about 50 μm, and more preferably about 1 μm to about 10 μm. With the covering portion B of the above thickness, good connection to the electrode of the light emitting element1and to the wiring of the mounting substrate20can be obtained, and occurrence of short circuit between the first terminal2and the second terminal3can be prevented.

As described above, in the case where the terminal is composed of the core A and the covering portion B, the material of the core A preferably has a melting temperature higher than that of the covering portion B. For example, as described above, in the case where each of the first terminal2and the second terminal3includes the core A made of Cu and the covering portion B made of Sn, the light emitting element1can be easily bonded to the first terminal2and the second terminal3by placing the terminals on the electrodes of the light emitting element1which are made of a metal and applying heat thereto. Furthermore, in the case of exposing the covering portion B at each of the exposed portions2aand3a, the light emitting device10can be bonded to the mounting substrate20by heating the exposed portions of the covering portion B.

In the above, the description has been given to the first terminal2and the second terminal3each including the core A and the covering portion B, but the configuration is not limited to this. The light emitting element1may be connected to the first terminal2and the second terminal3by using a method other than the eutectic bonding. For example, they may be connected by Ag paste. Furthermore, a plurality of first terminals2and second terminals3may be connected to respective electrodes of the light emitting device1, and/or a plurality of exposed portions2aor3amay be formed.

Light Reflecting Member4

The light reflecting member4holds the light emitting element1, the first terminal2, and the second terminal3. More specifically, the light reflecting member covers the electrode formation surface side of the light emitting element1, and the first terminal2and the second terminal3except for the exposed portions2aand3a. The light reflecting member4electrically insulates the first terminal2from the second terminal3, and reflects the light from the semiconductor layer1atoward the light emitting surface of the light emitting device10.

As described above, the light reflecting member4has the bottom surface4a(mounting surface), the side surfaces4b, the back surface4c, the front surface4d, and the upper surface4e. The bottom surface4a, the side surfaces4b, and the back surface4cof the light reflecting member4are formed so that the first terminal2and the second terminal3are respectively within the outer most surfaces of those surfaces. Further, in the first embodiment, the terminal exposure surfaces4frespectively connected to the bottom surface4a, the side surface4b, and the back surface4cand expose the exposed portions2aand3aare provided. In the specification, the expression “connected to the bottom surface, the side surface, and the back surface” means connected to all of the bottom surface, the side surface, and the back surface.

The terminal exposure surfaces4fare each formed by partially removing the light reflecting member, and may be composed of one or more surfaces. The terminal exposure surfaces4fin the first embodiment are each formed by removing a portion around a corner of the substantially cuboidal light reflecting member so as to have a recessed shape composed of a plurality of surfaces. With the terminal exposure surfaces4fhaving such a recessed shape, a large surface area can be provided for the exposed portions2aand3a. In addition, this configuration is also preferable in that an increased amount of the bonding agent to connect the light emitting device10and the mounting substrate can be accommodated. In addition, each of the terminal exposure surfaces4fmay be a flat surface or a curved surface.

The shapes of the surfaces of the light reflecting member4other than the terminal exposure surface4fcan be determined according to the shape of the terminal exposure surfaces4fthat have been formed. For example, as shown inFIGS. 3A and 5, each of the bottom surface4a(mounting surface) and the back surface4chas a substantially T shape, the side surface4bhas a substantially pentagonal shape, and the upper surface4ehas a substantially rectangular shape. However, the shape of each surface of the light reflecting member4is not limited to the above shape.

Hereinafter, relationships between the surfaces of the light reflecting member4and the exposed portions2aand3awill be described with reference toFIGS. 5 to 7.FIG. 5is a schematic view of the light emitting device10viewed from the bottom surface side.FIG. 6is a schematic view of the light emitting device10viewed from the side surface side.FIG. 7is a schematic view of the light emitting device10viewed from the back surface side.

Each of the exposed portions2aand3ais formed at an inner side with respect to the outermost surfaces of the light reflecting member4when viewed from the bottom surface side, the side surface side, and the back surface side. As shown inFIG. 5, when the light reflecting member4is viewed from the bottom surface4aside, the outermost surfaces of the light reflecting member4are the side surfaces4band the back surface4c, and the exposed portions2aand3aare respectively at an inner side with respect to the side surfaces4band the back surface4c. Similarly, as shown inFIG. 6, when the light reflecting member4is viewed from the side surface4bside, the outermost surfaces of the light reflecting member4are the bottom surface4aand the back surface4c, and the exposed portion2ais at an inner side with respect to the bottom surface4aand the back surface4c. Furthermore, as shown inFIG. 7, when the light reflecting member4is viewed from the back surface4cside, the outermost surfaces of the light reflecting member4are the bottom surface4aand the side surfaces4b, and the exposed portions2aand3aare respectively at an inner side with respect to the bottom surface4aand the side surface4b. Therefore, the exposed portions2aand3ado not project from the outermost surfaces of the light reflecting member4when viewed from each surface of the light reflecting member4. In the case where the bottom surface4aof the light reflecting member4and a portion of the exposed portions2aand3aare on substantially the same plane, the light emitting device10can be more stably mounted on the mounting substrate20.

According to the configuration as described above, while a large surface area can be provided for the exposed portions2aand3a, the mounting surface (the bottom surface4aof the light reflecting member4) of the light emitting device10can be stably mounted on the mounting substrate. Also, the providing of the exposed portions2aand3arespectively at an inner side with respect to the outermost surfaces of the light reflecting member4when viewed from the bottom surface side, the side surface side, and the back surface side of the light reflecting member4allows for preventing absorption of the light emitted from the light emitting device10by the bonding agent6in a light emitting module. Accordingly, the light emitting device10that has a high bonding strength with the mounting substrate20and allows for stable mounting on the mounting substrate20, and has good light extraction efficiency can be obtained.

The material of the light reflecting member4is not specifically limited as long as the material can electrically insulate the first terminal2from the second terminal3, and can reflect the light emitted from the semiconductor layer1atoward the light emitting surface of the light emitting device10. For example, the material in which a light reflecting material is contained in a base material can be employed.

Examples of the base material include ceramic, resin, glass, dielectric material, pulp, and a composite material containing two or more kinds of these. Particularly, it is preferably a resin which can be easily molded into a desired shape. Examples of such a resin include, a silicone resin, a modified silicone resin, an epoxy resin, a modified epoxy resin, a phenol resin, an acrylic resin, an unsaturated polyester resin, a polycarbonate resin, a polynorbornene resin, and a hybrid resin containing two or more kinds of these resins.

Examples of the light reflecting material includes, titanium oxide, zinc oxide, titanium dioxide, silicon dioxide, zirconium dioxide, potassium titanate, alumina, aluminum nitride, boron nitride, mullite, niobium oxide, barium sulfate, carbon black, and various rare-earth oxides (e.g., yttrium oxide, and gadolinium oxide). The base material may also contain a diffusing agent, a coloring agent, and/or a filler for the purpose of enhancing the strength and heat releasing property of the light reflecting member, and adjusting a coefficient of thermal expansion.

A reflectivity of the light reflecting member4for the light from the light emitting element1is preferably about 60% or greater, and more preferably about 70% to about 90% or greater.

The light emitting surface side of the light emitting element1(that is, the semiconductor layer1awhich is exposed from the light reflecting member4) is preferably covered with the wavelength conversion layer5. The wavelength conversion layer5is, for example, made of a base material which can transmit the light emitted from the light emitting element1and contains a wavelength conversion member which can convert a wavelength of the light emitted from the light emitting element1into a desirable wavelength. Examples of the base material include a silicone resin, a modified silicone resin, an epoxy resin, a modified epoxy resin, a phenol resin, an acrylic resin, a polycarbonate resin, a polynorbornene resin, or a hybrid resin containing two or more kinds of these resins, and glass. For the wavelength conversion member, an appropriate phosphor can be employed. Also, for the wavelength conversion member, a light emitting material, so-called called nanocrystal or quantum dot may be employed. Further, the wavelength conversion layer5may contain a diffusing agent or the like.

Examples of the phosphor include, a nitride-based phosphor and an oxynitride-based phosphor which are activated mainly with a lanthanoid-based element such as europium or cerium. More specific examples include, an α-sialon or β-sialon type phosphor and various kinds of alkali earth metal nitride silicate phosphors activated with europium, an alkali earth metal halogen apatite phosphor, an alkali earth halosilicate phosphor, an alkali earth metal silicate phosphor, an alkali earth metal halogen borate phosphor, an alkali earth metal aluminate phosphor, an alkali earth metal silicate, an alkali earth metal sulfide, an alkali earth metal thiogallate, an alkali earth metal silicon nitride, and a germanate, which are mainly activated with a lanthanoid-based element such as europium and/or a transition metal-based element such as manganese, a rare earth aluminate and a rare earth silicate which are mainly activated with a lanthanoid-based element such as cerium, and an organic substance and an organic complex which are mainly activated with a lanthanoid-based element such as europium. Especially, a YAG-based phosphor which is a yellow phosphor, KSF (K2SiF6:Mn) which is a red phosphor, and a β-SiAlON phosphor and a LAG-based phosphor which are green phosphors are favorably used. In addition, other than above, a phosphor which exhibits similar performance and effect can be appropriately used. The phosphor may be used alone or two or more kinds may be mixed to be used.

As the quantum dot, more specifically, nano-size high dispersible particles such as CdSe, core-shell type CdSXSe1-X/ZnS, GaP, InP, AgInS, or CuInS may be used.

FIG. 8is a schematic view of a light emitting module100in which the light emitting device10is mounted on the mounting substrate20. The mounting substrate20is a substrate on which the light emitting device10is mounted, and includes the wirings21and a base member22. The wirings21are electrically connected to the exposed portions2aand3aof the light emitting device10, respectively. In addition, the mounting substrate20may be only composed of the wirings21.

The wirings21can be made of a material having high electroconductivity such as copper, nickel, palladium, tungsten, chrome, titanium, aluminum, silver, gold, or an alloy of them. Particularly, the wirings21are preferably made of copper or a copper alloy, in view of a heat releasing property of the heat generated in the light emitting device10. Also, a film composed of silver, platinum, tin, gold, copper, rhodium, or an alloy of those may be formed on a surface of the wiring made of an appropriate material. Also, a film of silver oxide or silver alloy oxide may be formed on a surface of the wiring by oxidizing the surface of the wiring made of silver or silver alloy.

The base member22can be made of an insulating material such as ceramics, a glass epoxy, or a resin. It is particularly preferably made of ceramics having high heat resistance and weather resistance. As the ceramics material, alumina, aluminum nitride, or mullite is preferably, and a low temperature co-fired ceramics (LTCC) may also be used. Other than the above, the base member22may be an insulating base member provided by covering a surface of a metal material with an insulating material.

The light emitting module100is provided such that the light emitting device10is mounted on the mounting substrate20. The mounting surface (i. e., the bottom surface4aof the light reflecting member4) of the light emitting device10is mounted on the wirings21of the mounting substrate20, and the exposed portions2aand3aexposed from the terminal exposure surfaces4fof the light reflecting member4can be respectively electrically connected to the wirings21with the bonding agent6(made of an electrically-conductive bonding material such as a solder, or an anisotropically-conductive member such as an anisotropic conductive paste (ACP)). In the first embodiment, the bonding agent6which rose up along the exposed portions2aand3acan be prevented from absorbing the light emitted from the light emitting surface due to the terminal exposure surfaces4f. Therefore, it is possible to prevent the bonding agent36from absorbing the light more than a light emitting device30and a light emitting module200in which a light reflecting member34and exposed portions32aand33aare provided on substantially the same plane (or the exposed portions32aand33aproject outward from the light reflecting member34), as shown in a comparative example inFIGS. 3B and 13.

Method for Manufacturing Light Emitting Device10

Hereinafter, a method for manufacturing the light emitting device10according to the first embodiment will be described with reference toFIGS. 9A to 11.FIGS. 9A and 9Bare schematic views showing the step of connecting the terminals in the method for manufacturing the light emitting device10.FIGS. 10A and 10Bare schematic views showing the step of providing the light reflecting member.FIG. 11is a schematic view showing the step of partially removing the light reflecting member. In addition, the following description illustrates an example, so that another method and step order may be appropriately used.

Connecting Terminals

In the step of connecting the terminals, the substantially spherical first terminal2and second terminal3are respectively connected to the light emitting element1. First, a plurality of light emitting elements1each including the semiconductor layer, the n-side electrode, and the p-side electrode are provided, and disposed on a sheet8. For example, the sheet8may include a base member made of a polyimide and a bonding layer made of an acrylic-based resin disposed on the base member, and the light emitting elements1are disposed on the upper surface of the sheet8at intervals of about 0.4 mm to about 2.3 mm. Subsequently, a flux is appropriately applied on the n-side electrode and the p-side electrode of the light emitting element1. The method of applying the flux can be appropriately selected from printing, transfer printing, and the like.

Subsequently, the first terminal2and the second terminal3are set on the respective electrodes of the light emitting element1. According to the first embodiment, each of the first terminal2and the second terminal3having a diameter of about 110 μm is provided by previously covering the Cu core A of about 100 μm in diameter with the covering portion B made of Sn of about 5 μm in thickness, and then, with the use of a suction jig, place the first terminal2and the second terminal3on the electrodes of the light emitting element1respectively. At this time, a temporary fixing material may be used. As the temporary fixing material, an appropriate known material may be used. In addition, the first terminal2and the second terminal3can be disposed with high accuracy by previously forming a holding portion having a recess corresponding to the shape of the terminal, in each electrode of the light emitting element1(or forming the electrode itself into a recessed shape corresponding to the shape of the terminal).

Then, the light emitting elements1each having the first terminal2and the second terminal3are heated together with the sheet8in an oven or on a heating plate at about 280° C. or more for about one minute or more. Accordingly, the covering portion B made of Sn is melted and cured, and the light emitting element1and the electrically-conductive core A are bonded, so that the first terminal2and the second terminal3are fixed to the light emitting element1. Alternatively, the light emitting element1may be connected to the first terminal2and the second terminal3with a different solder, an Ag paste, or the like.

Providing Light Reflecting Member

Subsequently, in the step of providing the light reflecting member, the light reflecting member4is formed to hold the light emitting element1, the first terminal2, and the second terminal3. According to the first embodiment, the sheet8having the light emitting elements1connected to the first terminals2and the second terminals3(hereinafter, these are collectively referred to as a sheet aggregate80) is set in a mold90, and a silicone resin containing a light reflecting material such as titanium oxide is filled in the mold90and cured to form the light reflecting member4. In addition, the light reflecting member4may be formed by a desired method such as injection molding, extrusion molding, transfer molding, printing, or coating.

Subsequently, the sheet8is removed from the sheet aggregate80after the light reflecting member4has been formed, and the wavelength conversion layer5is appropriately formed so as to cover the light emitting surface of the light emitting element1. Thus, the wavelength of the light from the light emitting element1can be converted to a wavelength of light having a desired color. The wavelength conversion layer5can be formed, for example, by applying a silicone resin which contains a phosphor by using a desired method such as spraying, coating, or printing. The wavelength conversion layer5may have a thickness of about 30 μm to about 300 μm.

Subsequently, the light reflecting member4is singulated. Each of the singulated light reflecting members4at least has the bottom surface4awhich is to serve as the mounting surface of the light emitting device10, the side surfaces4b, and the back surface4c. According to the first embodiment, the singulated light reflecting member4has a substantially cuboidal shape, with the dimensions about 2.0 mm in width, about 0.5 mm in height, and about 0.5 mm in depth. In addition, there is no limitation on when to remove the sheet8in particular, but it is preferably removed before the light reflecting member4is singulated.

Partially Removing the Light Reflecting Member

In the step of partially removing the light reflecting member, the terminal exposure surfaces4fare formed by partially removing the light reflecting member4which has been singulated in the step of providing the light reflecting member. Further, the substantially spherical first terminal2and the second terminal3are partially exposed from the terminal exposure surfaces4f, respectively, thus, the exposed portions2aand3aare formed. In the first embodiment, the terminal exposure surfaces4fare each formed by removing a portion around the corner C between the bottom surface4a, the side surface4b, and the back surface4cof the substantially cuboidal light reflecting member4shown inFIG. 10B. For example, after the step of providing the light reflecting member, a mask9is formed on the light reflecting member4except for the portion in which the terminal exposure surface4fis to be formed (that is, the portion around the corner C between the bottom surface4a, the side surface4b, and the back surface4c). More specifically, in the first embodiment, a substantially T-shaped mask is formed on each of the bottom surface4aand the back surface4cto expose the corner C, and a substantially pentagonal mask is formed on the side surface4bto expose the corner C. Then, a blast treatment is performed so that the first terminal2and the second terminal3are exposed to a desired extent, whereby the terminal exposure surfaces4fand the exposed portions2aand3aare formed.

It is preferable that at the time of partially removing the light reflecting member4, the first terminal2and the second terminal3are not removed. However, the covering portions B (and cores A) of the first terminal2and the second terminal3may be partially removed together with the part of the light reflecting member4.

In addition, the light reflecting member4may be removed by laser processing. For example, in the laser processing, CO2laser, excimer laser, or solid-state laser such as YAG laser (fundamental wave, second harmonic wave, triple harmonic wave, or fourfold harmonic wave) can be used. Thus, the light reflecting member4can be partially removed with high precision.

As described above, in the step of partially removing the light reflecting member, the exposed portions2aand3a, and the terminal exposure surface4fcan be simultaneously formed. Each of the exposed portions2aand3ais formed so as to be positioned at an inner side with respect to the outermost surface of the light reflecting member4when viewed from the bottom surface4aside, the side surface4bside, and the back surface4cside of the light reflecting member4, respectively.

Through the steps as described above, there is provided the side-surface light emission type light emitting device10in which the exposed portions2aand3aeach having a round surface are exposed (projected) from the terminal exposure surfaces4fof the light reflecting member4respectively, and are positioned at an inner side with respect to the outermost surface of the light reflecting member4when viewed from the bottom surface side, the side surface side, and the back surface side of the light reflecting member4, respectively.

In addition, according to the first embodiment, the one terminal is connected to one electrode of the light emitting element, but the configuration is not limited to this. For example, as for a light emitting device10A shown inFIG. 14A, a plurality of first terminals and/or second terminals may be connected to each electrode of the light emitting element. Along with this, a plurality of terminal exposure surfaces4Af, and exposed portions2Aa and3Aa may be provided. In such a case, some of the plurality of terminals may be used as a heat releasing terminal which is not electrically connected to the light emitting element.

In addition, as shown inFIG. 14B, a light emitting device may include the exposed portion2Aa or3Aa of the first terminal or the second terminal (or the heat releasing terminal) which is provided outside the outermost surface of the light reflecting member4A when viewed from a bottom surface side, a side surface side, and a back surface side of the light reflecting member4A.

The side-surface light emission type (side view type) light emitting device10has been described in the first embodiment, but the present invention is not limited to this. For example, as shown inFIG. 15, the embodiment of the present invention may be applied to an upper-surface light emission type (top view type) light emitting device10B in which an upper surface serves as a light emitting surface while a bottom surface serves as a mounting surface. In the case of the upper-surface light emission type (top view type) light emitting device10B, a back surface4Bc at an opposite (opposed) side of the light emitting surface is a bottom surface4Ba, that serves as the mounting surface.

Method for Forming Light Emitting Module100

The light emitting module100is formed by mounting the light emitting device10formed through the steps as described above is mounted on the previously prepared mounting substrate20. Hereinafter, a method for forming the light emitting module100will be described. The description below is one example, and a desired method and a desired step order may be appropriately used.

First, a bonding agent6is applied on the wirings21of the mounting substrate20. For example, a solder which is a bonding agent6can be applied by using a screen printing method using a metal mask. It is preferable that the solder melts at a temperature lower than the temperature at which the solder that connects the light emitting element1and the first terminal and the second terminal melts. As for the bonding agent6, an Ag paste may be used. Subsequently, the light emitting device10is set on the bonding agent6. In this state, the bonding agent6is melted and cured, thus, the light emitting device10is electrically connected to the mounting substrate20, and the light emitting module100is obtained. In addition, as described above, in the case where each of the first terminal2and the second terminal3is composed of the spherical Cu core A covered with the covering portion B made of Sn, the light emitting device10can be connected to the mounting substrate20without using the bonding agent6. That is, the exposed portions2aand3aof the light emitting device10are placed on the wiring21of the mounting substrate20and heated, thus, eutectic bonding can be provided between the light emitting device10and the mounting substrate20, with Sn of the covering portion B formed on the surfaces of the exposed portions2aand3a.

Second Embodiment

FIG. 12is a schematic perspective view of the light emitting device50according to a second embodiment, viewed from a back surface side. The light emitting device50differs from the light emitting device10of the first embodiment, in the shape of the terminal exposure surfaces4f. The terminal exposure surfaces4fof the light emitting device50each has a substantially flat surface, and a light reflecting member4is provided thicker in the depth direction than that of the light emitting device10of the first embodiment. Other than that, the light emitting device50is configured substantially similar to the light emitting device10of the first embodiment, so that its description may be omitted appropriately.

The substantially flat terminal exposure surfaces4faccording to the second embodiment can be formed, for example, in the step of providing the light reflecting member by forming a mask having a shape different from that of the first embodiment, on the substantially cuboidal light reflecting member4before forming the terminal exposure surfaces4f. More specifically, according to the second embodiment, a hexagonal mask is formed on each of the bottom surface4aand a back surface4c, and a pentagonal mask is formed on a side surfaces4bof the light reflecting member4to expose a corner C. After that, a blast treatment is performed, whereby the substantially flat terminal exposure surface4fcan be formed.

With such flat terminal exposure surfaces4f, similar to the light emitting device10in the first embodiment, the light emitting device50of small in size, high in connection strength and mounting applicability with respect to the mounting substrate, and great in light extraction efficiency can be obtained. Furthermore, the light reflecting member4becomes possible to have a relatively large thickness in the depth direction, so that the light of the light emitting element1can be prevented from leaking from the light reflecting member4. Furthermore, a light emitting module equipped with the light emitting device50mounted on a mounting substrate can exhibit similar effects as described above.

Some embodiments have been illustrated in the above, but the present invention is not limited to the above embodiments, and can be modified within the scope of the present invention as a matter of course.

A light emitting device according to an embodiment includes:

a light emitting element;

a first terminal and a second terminal each having a substantially spherical shape and being electrically connected to the light emitting element; and

a light reflecting member for holding the light emitting element, the first terminal, and the second terminal, in which

the light reflecting member includes a bottom surface serving as a mounting surface, a side surface adjacent to the bottom surface, a back surface opposite to a light emitting surface of the light emitting element, and a terminal exposure surface for exposing the first terminal and the second terminal as exposed portions, and

the exposed portions are provided inside outermost surfaces of the light reflecting member when viewed from a bottom surface side, a side surface side, and a back surface side of the light reflecting member.

In addition, a method for manufacturing a light emitting device according to an embodiment includes:

a first step of connecting substantially spherical first terminal and second terminal to a light emitting element;

a second step of forming a light reflecting member to hold the light emitting element, the first terminal, and the second terminal; and

a third step of forming a terminal exposure surface by partially removing the light reflecting member, to partially expose the first terminal and the second terminal from the terminal exposure surface, in which

in the second step, the light reflecting member is formed into a shape having a bottom surface serving as a mounting surface, a side surface adjacent to the bottom surface, and a back surface opposite to a light emitting surface of the light emitting element, and

in the third step, the light reflecting member is partially removed so that exposed portions of the first terminal and the second terminal are positioned inside outermost surfaces of the light reflecting member when viewed from a bottom surface side, a side surface side, and a back surface side of the light reflecting member.

According to the light emitting device in the embodiments, the light emitting device can be small in size and great in mountability. In addition, according to the method for manufacturing a light emitting device in the embodiment, the light emitting device which is small in size and great in mountability can be manufactured with no difficulty.