CN101268557A - Light-emitting apparatus - Google Patents

Abstract

A light emitting device includes a light emitting diode chip, a heat conductive plate mounting thereon the light emitting diode chip, a sub-mount member disposed between said light emitting diode chip and said heat conductive plate, a dielectric substrate stacked on the heat conductive plate and being formed with a through-hole through which the sub-mount member is exposed, an encapsulation member for encapsulation of said light emitting diode chip, and a lens superimposed on the encapsulation member. The sub-mount member is formed around a coupling portion of the light emitting diode chip with a reflective film which reflects a light emitted from a side face of the light emitting diode chip. The sub-mount member is selected to have a thickness such that the reflecting film has its surface spaced away from said heat conductive plate by a greater distance than said dielectric substrate.

Description

Light emitting device

Technical Field

The present invention relates to a light emitting device using an LED (light emitting diode) chip.

Background

Japanese unexamined patent application publication No. 2001-85748 (hereinafter referred to as patent document 1) and japanese unexamined patent application publication No. 2001-148514 (hereinafter referred to as patent document 2) propose a light-emitting device including an LED chip; a circuit board on which the LED chip is mounted; a metal frame (e.g., made of aluminum) surrounding the LED chip on the surface of the circuit board; an encapsulating member (for example, made of a transparent resin such as epoxy resin and silicone resin) filled in the frame to encapsulate the LED chip and the bonding wires connected to the LED chip. The frame disclosed inpatent documents 1 and 2 is shaped to have an open area which is larger the farther from the circuit board, and is polished to have an inner mirror surface (mirror interface) which functions as a reflector for reflecting light emitted from the LED chip. However, it was found that light could not be satisfactorily efficiently extracted from the above light-emitting device because light radiated from the side of the LED chip was absorbed by the circuit board or leaked through the joint between the frame and the circuit board.

Disclosure of Invention

The present invention has been made in view of the above problems, and has an object to provide a light emitting device capable of improving its light output.

The light emitting device according to the present invention includes: an LED chip; a heat conductive plate made of a heat conductive material so as to mount the LED chip thereon; a sub-mount member configured in a flat plate shape, the dimension of which is set to be larger than the LED chip and smaller than the heat conductive plate; a dielectric substrate stacked on the heat conductive member; a package member made of a transparent and elastic material so as to package the LED chip; and a lens stacked on the package member. The sub-mount member is disposed between the LED chip and the heat conductive plate to alleviate stress applied to the LED chip due to a difference in linear thermal expansion coefficient between the LED chip and the heat conductive plate. Further, the dielectric substrate is provided with a pair of lead patterns on a surface opposing the heat conductive plate for electrical connection with the electrodes of the LED chip, respectively. Further, the dielectric substrate is formed with a through hole through which the sub-mount component is exposed. The sub-mount member includes a reflective film disposed around a junction of the LED chip so as to reflect light emitted from a sidewall of the LED chip, and is selected to have a thickness of: the surface of the reflective film is spaced from the heat conductive plate by a distance greater than the distance from the dielectric substrate.

Since the light emitting device of the present invention is configured to include the sub-mount member with the reflective film, the sub-mount member has such a thickness: the distance between the surface of the reflective film and the heat conductive plate is made larger than the distance between the surface of the reflective film and the dielectric substrate, so that the absorption of light emitted from the side wall of the LED chip by the surface or the side wall of the dielectric substrate can be prevented, thereby improving the light extraction efficiency and consequently improving the light output accordingly.

In general, a color conversion member is disposed on a surface of a dielectric substrate so as to convert a color of light radiated from an LED chip or a metal frame that reflects the light of the LED chip. By selecting such thicknesses: making the surface of the reflective film a distance from the heat conductive plate greater than a distance from the dielectric substrate, even if the above color conversion member is provided on the surface of the dielectric substrate, it is possible to prevent light from leaking through the joint between the above color conversion member and the dielectric substrate.

Therefore, the light extraction efficiency can be improved, and color shading (colorshading) can also be reduced.

Preferably, the LED chip and the sub-mount member are each configured to have a square planar shape, and the LED chip is disposed at the center of the sub-mount member in such a manner that: the flat sides of the LED chips are made to intersect the corresponding diagonal lines of the sub-mount members, respectively.

In this case, the reflective film can efficiently reflect light radiated from each of the side walls of the LED chip toward the sub-mount member. Preferably, the light emitting device further includes a frame disposed on a surface of the dielectric substrate so as to surround the sub-mount member and the LED chip, and the encapsulation member is defined by a transparent material filled in the frame. The frame is molded from a transparent material.

The frame may be configured to determine the dimensions of the package component. Further, the frame molded from a transparent material can reduce the difference in linear thermal expansion coefficient between the frame and the package member, as compared with the conventional case where the frame is made of a metal material, so as to suppress the generation of voids under low temperature conditions during thermal cycle testing. Also, the frame itself can reduce light reflection loss, thereby improving light output efficiency.

Preferably, the LED chip is formed with one of the electrodes on one surface thereof and the other electrode on the other surface thereof. Of the electrodes, the electrode adjacent to the sub-mount member is connected to one bonding wire through the conductor pattern on the sub-mount member, and the other electrode remote from the sub-mount member is connected to a bonding wire extending along one of the diagonals of the LED chip.

In this case, the bonding wire has less chance of blocking light radiated from the side wall of the LED chip, and therefore, the decrease in light extraction efficiency due to the presence of the bonding wire can be reduced.

The light emitting device is preferably configured to further include a dome-shaped color conversion member provided on the dielectric substrate so as to cover the lens. The color conversion member is a molded member molded from a transparent material mixed with a fluorescent material that is emitted from the LED chip and is excited by light of the package member to radiate light having a color different from that of the LED chip. Further, the color conversion member is provided to form an air layer between the color conversion member and the light emission surface of the lens.

The provision of the color conversion member enables radiation of a color different from that of the LED chip. Further, the color conversion member is provided to form an air layer between the color conversion member and the light emission surface of the lens. The air layer can inhibit the color conversion member from transmitting stress to the LED chip through the lens and the encapsulating member when the color conversion member is subjected to an external force. Further, the amount of light guided and passed through the lens, that is, the portion of light radiated from the LED chip to be incident on the color conversion member through the lens and the encapsulating member and scattered by the fluorescent particles in the color conversion member can be reduced. Therefore, the light extraction efficiency of the entire device can be improved. In addition, the LED chip can be protected from moisture in the external environment. Since it is not necessary to bring the color conversion member into close contact with the lens, it is possible to reduce a decrease in yield due to the dimensional accuracy or positioning accuracy associated with the color conversion member.

Drawings

FIG. 1 is a cross-sectional view of a light emitting device according to one embodiment of the present invention;

FIG. 2 is an exploded perspective view, partially cut away, of the above device;

fig. 3 is a plan view illustrating a main part of the above apparatus;

FIG. 4 is a perspective view of a sub-mount member used in the above apparatus;

fig. 5A is a schematic view of a main part of the above apparatus;

fig. 5B is a schematic view of a main part of the above apparatus;

FIG. 6 is a cross-section of another configuration of the above apparatus; and

fig. 7 is a cross-section of a further configuration of the above device.

Detailed Description

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

As shown in fig. 1 and 2, thelight emitting device 1 according to the present embodiment includes: anLED chip 10; acircuit board 20 made of a heat conductive material to mount theLED chip 10 thereon; aframe 40 surrounding theLED chip 10 on the surface of thecircuit board 20; anencapsulation member 50 having elasticity and made of a translucent material (transparent resin) filled in theframe 40 so as to encapsulate theLED chip 10 and thebonding wires 14 connected to theLED chip 10; alens 60 stacked on thepackage member 50; and a dome-shapedcolor changing member 70, which is a molded member, molded of a transparent material mixed with a fluorescent material, and provided on thecircuit board 20 so as to cover thelens 60. Thelight emitting apparatus 1 of the present embodiment is suitable for use as, for example, a light source of a lighting device, and is mounted on a metal body 100 (for example, made of a high thermal conductivity metal such as aluminum or copper) of the device through adielectric layer 90 made of, for example, a green sheet. Since being mounted on themetal body 100 of the device, the thermal resistance from theLED chip 10 to themetal body 100 can be made small, thereby improving the heat dissipation capability. Further, since the temperature rise at the junction of the LED chip can be limited, the input power can be increased, thereby increasing the output power. In this connection it should be noted that when thelight emitting device 1 is used in a lighting apparatus, a plurality oflight emitting devices 1 may be mounted on themetal body 100 of the apparatus, the light emitting devices being connected to each other in series or in parallel in order to obtain a desired output optical power.

Thecircuit board 20 includes ametal plate 21 and adielectric substrate 22 made of a glass epoxy plate and stacked on themetal plate 21. Thedielectric substrate 22 is provided with a pair of lead patterns on a surface thereof opposite to themetal plate 21 for electrical connection with electrodes (not shown) of theLED chip 10, respectively, and is formed with throughholes 24 through whichsub-mount members 30 to be mentioned later are exposed. Although themetal plate 21 is made of copper (Cu) in the present embodiment, it may be made of another metal having high thermal conductivity such as aluminum (Al). Further, in the present embodiment, themetal plate 21 is made of a heat conductive material so as to define itself as a heat conductive plate on which theLED chip 10 is mounted. Themetal plate 21 is fixed to thedielectric substrate 22 by means of anadhesive member 25 made of a dielectric adhesive sheet film. Instead of theadhesive member 25, a coupling metal layer adjacent to themetal plate 21 may also be provided on thedielectric substrate 22 so as to fix thedielectric substrate 22 to themetal plate 21 by means of the coupling metal layer.

Each of thelead patterns 23 is realized by means of a laminate composed of a Ni layer and an Au layer, and defines aninner lead portion 23a by its portion located within theframe 40, and anouter lead portion 23b by its portion not covered with thecolor conversion member 70. Each of thelead patterns 23 is not limited to the lamination of the Ni layer and the Au layer, but may be realized by the lamination of the Cu layer, the Ni layer, and the Ag layer.

TheLED chip 10 is a blue LED chip based on GaN that radiates blue light, and is configured to have a square planar shape. TheLED chip 10 includes a conductive substrate as an epitaxial substrate, which is an n-type SiC substrate, has a larger lattice constant and crystal structure closer to GaN than to sapphire, and has conductivity. Alight emitting part 12, which is made of a GaN-based semiconductor material and obtained by epitaxial growth (e.g., MOVPE process), so as to have a laminated structure such as a double heterostructure, is also formed on the main surface of theconductive substrate 11. A cathode electrode (n-type electrode) (not shown) is formed as a cathode-side electrode on the back side of theconductive substrate 11. An anode electrode (p-type electrode) (not shown) is formed as an anode-side electrode on the surface of the light-emitting part 12 (the foremost surface of the main surface of the conductive substrate 11). In short, theLED chip 10 has an anode electrode on one surface thereof and a cathode electrode on the opposite surface.

It should be noted that, although the cathode electrode and the anode electrode of the present embodiment are each composed of a laminate composed of a Ni layer and an Au layer, the cathode electrode and the anode electrode are not limited to a specific material, but may be made of a material exhibiting good ohmic characteristics (e.g., Al). Further, the present embodiment shows that theLED chip 10 is mounted on themetal plate 21, wherein thelight emitting part 12 of theLED chip 10 is spaced farther from themetal plate 21 than theconductive substrate 11. However, it is also possible to mount theLED chip 10 on the metal plate 21: the light-emittingpart 12 is brought closer to the metal plate than to theconductive plate 11. Although it is desirable to separate the light-emittingpart 12 from themetal plate 21 from the viewpoint of light extraction efficiency, disposing the light-emittingpart 12 close to themetal plate 21 does not increase light extraction loss because, in the present embodiment, theconductive substrate 11 and the light-emittingpart 12 have the same level of refractive index.

TheLED chip 10 is mounted on themetal plate 21 through thesub-mount member 30 in the through-hole 24. Thesub-mount member 30 is shaped as a rectangular plate (a square planar plate in this example) whose dimension is set larger than theLED chip 10 and smaller than themetal plate 21, and alleviates stress applied to theLED chip 10 due to a difference in linear expansion coefficient between theLED chip 10 and themetal plate 21. In addition, in addition to alleviating the above-described stress, thesub-mount member 30 has a heat conduction function of conducting heat generated from theLED chip 10 to themetal plate 21 over a region wider than the chip size of theLED chip 10. The heat generated from theLED chip 10 is conducted to themetal plate 21 through thesub-mount member 30 without passing through thedielectric substrate 22.

In this connection, it should be noted that although AlN is employed as the material of thesub-mount member 30 because AlN has both high thermal conductivity and insulating property, the material of thesub-mount member 30 is not limited to AlN, and may be selected to have a linear expansion coefficient close to that of theconductive substrate 11 made of 6H — SiC and high thermal conductivity, such as composite SiC, Si, or the like.

As shown in fig. 4, thesub-mount member 30 includes aconductive pattern 31, theconductive pattern 31 being connected to the above-described cathode electrode on the surface of theLED chip 10, and further includes a reflective film 32 (e.g., a laminate of a Ni film and an Ag film, an Al film, or the like) that reflects the radiated light from the side of theLED chip 10. In short, thesub-mount member 30 includes thereflective film 32 which is provided around the bonding portion of theLED chip 10 to reflect the radiated light from the side of theLED chip 10. Further, theselector mounting part 30 has such a thickness: the surface of thereflection film 32 is made to be farther from the metal plate 21 (heat conductive plate) than from thedielectric substrate 22.

By selecting the thickness of thesub-mount member 30 in the above-described manner in addition to providing thereflection film 32 on thesub-mount member 30, absorption of the radiated light from the side wall of theLED chip 10 by the surface of thesub-mount member 30 and the side wall of thedielectric substrate 22 can be prevented, and leakage via the joint between thecolor conversion member 70 and thedielectric substrate 22 can also be prevented, thereby improving the light extraction efficiency. Further, the color unevenness can be reduced by preventing the radiation light from the side wall of theLED chip 10 from leaking through the above-described joint portion between thecolor conversion member 70 and thedielectric substrate 22.

TheLED chip 10 has a cathode electrode electrically connected to one of thelead patterns 23 through theconductive pattern 31 and through a bonding wire 14 (e.g., a thin gold wire, a thin aluminum wire); and has an anode electrode electrically connected to theother lead pattern 23 through abonding wire 14.

TheLED chip 10 is disposed at the center of thesub-mount member 30 in such a manner that: so that the flat sides of theLED chip 10 cross the corresponding diagonal lines of thesub-mount member 30. In the present embodiment, the central axis of theLED chip 10 is substantially aligned with the central axis of thesub-mount member 30 in the thickness direction thereof, and each of the flat sides of theLED chip 10 intersects with a corresponding one of the diagonal lines at an angle of about 45 °. With such an arrangement, the radiated light from each of the side walls of theLED chip 10 can be efficiently reflected at thereflective film 32. TheLED chip 10 is disposed at the center of thesub-mount member 30 in such a manner that: so that the flat sides of theLED chip 10 cross the corresponding diagonal lines of thesub-mount member 30.

In the present embodiment, the central axis of theLED chip 10 is substantially aligned with the central axis of thesub-mount member 30 in the thickness direction thereof, and each of the flat sides of theLED chip 10 intersects with a corresponding one of the diagonal lines at an angle of about 45 °. With such an arrangement, the radiated light from each of the side walls of theLED chip 10 can be efficiently reflected at thereflective film 32.

As shown in fig. 3, the light emitting device of the present embodiment is configured such that: each bondingwire 14 electrically coupled to theLED chip 10 is made to extend in a direction of a diagonal line of theLED chip 10 so as to reduce the chance of blocking the radiated light from each side of theLED chip 10. Therefore, by providing thebonding wire 14, a decrease in light extraction efficiency can be suppressed.

Although theLED chip 10 and thesub-mount member 30 may be bonded with solder such as SnPb, AuSn, SnAgCu or silver paste, they are preferably bonded by using lead-free solder such as AuSn, SnAgCu.

Silicone resin is used as a transparent material for theencapsulation member 50. However, the encapsulation member may be made of acrylic resin instead of silicone resin.

Theframe 40 is molded from a transparent resin into a cylindrical shape. Theframe 40 is disposed on thedielectric substrate 22 to surround theLED chip 10 and thesub-mount member 30. The present embodiment shows that theframe 40 is made of silicone, i.e., a transparent material having a linear thermal expansion coefficient almost equal to that of thepackage member 50. When acrylic resin is used for theencapsulation part 50 without using silicone resin, it is desirable to mold theframe 40 using acrylic resin. The present embodiment indicates that theencapsulation member 50 is defined by a transparent material filled in the frame and thermally cured after theframe 40 is bonded to thecircuit board 20.

Due to the provision of theframe 40, the size of thepackage component 50 may be determined by theframe 40. Further, theframe 40 molded from a transparent material can reduce the difference in linear thermal expansion coefficient between theframe 40 and thepackage member 50, compared to the conventional case where the frame is made of a metal material, thereby suppressing the generation of voids under low temperature conditions during thermal cycle testing. Also, theframe 40 can reduce light reflection loss, thereby improving light output efficiency.

Thelens 60 is configured as a biconvex lens having a convexlight incident surface 60a opposite thepackage 50 and a convexlight emitting surface 60 b. Thelens 60 is molded from silicone and has the same refractive index as thepackage 50. Thelens 60 is not limited to a silicone mold, but may be molded from an acrylic resin. Thelight emission surface 60b of the lens is outwardly convex so that the light reaching thelight incident surface 60a is not totally internally reflected at the interface between thelight emission surface 60b and theair layer 80. Further, thelens 60 is disposed so that the optical axis thereof is aligned with a center line of the light-emittingpart 12, which extends in the thickness direction thereof through theLED chip 10.

Thecolor conversion member 70 is molded of a mixture of a transparent material such as silicone resin and a particulate yellow fluorescent material that is emitted from theLED chip 10 and radiates broad yellow white light (blue white light) by being excited by blue light of thepackage 50. The light emitted from the side wall of theLED chip 10 reaches thecolor conversion member 70 via thepackage 50 and theair layer 80, excites the fluorescent material of thecolor conversion member 70, or passes through thecolor conversion member 70 without colliding with the fluorescent material. Thelight emitting device 1 of the present embodiment can give white light which is a combination of blue light emitted from theLED chip 10 and light emitted from a yellow fluorescent material.

Theinner surface 70a of thecolor conversion member 70 is shaped to conform to thelight emission surface 60b of thelens 60, so that a uniform normal distance between thelight emission surface 60b and theinner surface 70a of thecolor conversion member 70 is obtained over the entire surface of thelight emission surface 60 b. Further, thecolor conversion member 70 is shaped to have a uniform thickness in the normal direction.

Thecolor conversion member 70 is fixed on thedielectric substrate 22 on the periphery of the opening of thecolor conversion member 70 by means of a joint (not shown) provided by, for example, an adhesive (e.g., silicone, epoxy resin) so as to obtain anair layer 80 defined between thecolor conversion member 70 and thelight emission surface 60b of thelens 60 and theframe 40. The presence of theair layer 80 reduces the possibility of contact between thelens 60 and thecolor conversion member 70 when thecolor conversion member 70 is deformed by an external force. Therefore, stress generated at thecolor conversion member 70 due to an external force can be prevented from being transmitted to theLED chip 10 and thebonding wire 14, thereby reducing a decrease in light emitting performance of theLED chip 10 and breakage of thebonding wire 14, resulting in improved reliability. Further, since theair layer 80 is provided between thecolor conversion member 70 and thelens 60, theLED chip 10 can be protected from moisture in the external environment. Further, since it is not necessary to bring thecolor conversion member 70 into close contact with thelens 60 and theframe 40, it is possible to reduce a decrease in yield due to dimensional accuracy or positioning accuracy relating to thecolor conversion member 70. Since thecolor conversion member 70 is finally assembled, the color deviation can be reduced simply by selecting thecolor conversion member 70 in which the mixing ratio of the fluorescent material to the transparent material is adjusted for the wavelength of the light from theLED chip 10.

Moreover, since theair layer 80 is provided between thecolor conversion member 70 and thelens 60, the amount of light diffused from thecolor conversion member 70 back into thelens 60, that is, the portion of light emitted from theLED chip 10 and scattered by the yellow fluorescent particles in thecolor conversion member 70 after being incident on thecolor conversion member 70 via the encapsulatingmember 50 and thelens 60, can be reduced. Therefore, the light extraction efficiency of the entire device can be improved.

Description is made below with reference to fig. 5A and 5B in which the optical axis of thecolor conversion member 70 is aligned with the optical axis of the LED chip so that blue light radiated from theLED chip 10 is uniformly scattered from thecolor conversion member 70 in each direction along the center point P of the optical axis thereof. For the light scattered at the point P, thecolor conversion member 70 generates a selected cone (escape cone) ECa having an expansion angle of 2 θ a and an escape cone ECb having an expansion angle of 2 θ b on the inner side and the outer side of thecolor conversion member 70, respectively. As shown in fig. 5A, when the total internal reflection angles Φ a and Φ B are 40 °, the spread angle is represented as 2 θ a being 60 °, 2 θ B being 98 °, and as shown in fig. 5B, when the total internal reflection angles Φ a and Φ B are 50 °, 2 θ a being 76 °, 2 θ B being 134 °, wherein the total internal reflection angle Φ a is defined at the interface between thecolor conversion member 70 and the air layer, and the total internal reflection angle Φ B is defined at the interface between thecolor conversion member 70 and the air, i.e., the medium outside thecolor conversion member 70.

The blue light scattered at point P and guided through the escape cone ECa inside the color conversion component has a maximum emission efficiency η, denoted as η ═ (1/4 n)²) X 100 (%) where n is the refractive index of the transparent material forming thecolor conversion member 70. Therefore, when the silicone resin of n-1.4 is used as described above,

. In other words, when theair layer 80 is provided between thecolor conversion member 70 and thelens 60, only 13% of the blue light scattered at the point P is reflected back to thelens 60, and in the absence of theair layer 80, as much as about 50% of the blue light is reflected. Therefore, light extraction efficiency can be improved, and deterioration of thepackage member 50 due to blue light can be suppressed. It is desirable to use thecolor conversion member 70 with an increased thickness to reduceLess blue light is directed through the escape cone ECa.

The transparent material for thecolor conversion member 70 is not limited to silicone resin, and may also include, for example, acrylic resin, epoxy resin, glass. Further, the fluorescent material mixed into the transparent material for thecolor conversion member 70 is not limited to the yellow fluorescent material, and may be replaced with a mixture of a red fluorescent material and a green fluorescent material that generates white light.

The above embodiment shows that a SiC substrate is used as theconductive substrate 11 carrying theLED chip 10, wherein theLED chip 10 is a blue LED chip emitting blue light, however, thesubstrate 11 may be made of a GaN substrate instead. When SiC and GaN substrates are used, the epitaxial substrate has higher thermal conductivity than when a dielectric sapphire substrate is used, thereby reducing thermal resistance. TheLED chip 10 may be configured to emit red light or green light instead of blue light. The material of thelight emitting part 12 of theLED chip 10 is not limited to the GaN-based semiconductor composite material, but may include a GaAs-based semiconductor composite material or a GaP-based semiconductor composite material.

Theconductive substrate 11 is not limited to the SiC substrate, and may be selected from a GaAs substrate, a GaP substrate, and the like that are compatible with the material of thelight emitting part 12.

As discussed above, thelight emitting device 1 of the present embodiment is configured to include thereflective film 32 on thesub-mount member 30, and the thickness of the sub-mount member is selected such that the surface of thereflective film 32 is farther from the metal plate (heat conductive plate) 21 than from the surface of thedielectric substrate 22. With this configuration, light emitted from the side walls of theLED chip 10 can be prevented from being absorbed by the surface of thesub-mounting member 30 or the side walls of the dielectric substrate, and also from leaking via the joint between thecolor conversion member 70 and thedielectric substrate 22, thereby improving light output efficiency. The light output is also improved due to the improved output efficiency. It should be noted that although the present embodiment shows the light-emittingdevice 1 having theframe 40 made of transparent resin, the frame may be omitted as shown in fig. 6.

Further, thelight emitting device 1 of the present embodiment may use a frame 40' made of a conventional metal instead of theframe 40 made of a transparent resin. In this case, the thickness of thesub-mount member 30 is also selected so that the surface of thereflection film 32 is farther from the metal plate (heat conductive plate) 21 than from thedielectric substrate 22. Accordingly, it is possible to manufacture a light emitting device capable of preventing light radiated from the sidewalls of theLED chip 10 from being absorbed by the sidewalls of thedielectric substrate 32 and preventing light from leaking through the junction between the metal frame 40' and thedielectric substrate 22, thereby improving light extraction efficiency, with a corresponding increase in light output.

As discussed above, it is apparent that various embodiments can be conceived within the scope of the technical idea of the present invention, and therefore, the present invention should not be limited to a specific embodiment but should be defined by the claims.

Claims (5)

1. A light emitting device comprising:

a light emitting diode chip;

a heat conducting plate made of a heat conducting material so as to mount the light emitting diode chip thereon;

a flat sub-mount part having a size set larger than the light emitting diode chip and smaller than the heat conductive plate, the sub-mount part being disposed between the light emitting diode chip and the heat conductive plate so as to relieve stress acting on the light emitting diode chip due to a difference in linear thermal expansion coefficient between the light emitting diode chip and the heat conductive plate;

a dielectric substrate stacked on the heat conductive member, the dielectric substrate being provided with a pair of lead patterns on a surface opposite to the heat conductive plate for electrical connection with the electrodes of the light emitting diode chips, respectively, the dielectric substrate being formed with through-holes through which the sub-mount members are exposed;

an encapsulation part made of a transparent and elastic material so as to encapsulate the light emitting diode chip;

a lens stacked on the package member;

wherein,

the sub-mount section includes a reflection film provided around the bonding portion of the light emitting diode chip so as to reflect light emitted from the side surface of the light emitting diode chip; and

the sub-mount member is selected to have a thickness such that a surface of the reflection film is spaced from the heat conductive plate by a distance greater than a distance from the dielectric substrate.

2. The light emitting device according to claim 1,

the light emitting diode chip and the sub-mount section are each configured to have a square planar shape, and the light emitting diode chip is disposed at the center of the sub-mount section in such a manner that the flat sides of the light emitting diode chip respectively intersect with the corresponding diagonal lines of the sub-mount section.

3. The light emitting apparatus of claim 1, further comprising:

a frame provided on a surface of the dielectric substrate so as to surround the sub-mounting part and the light emitting diode chip, the encapsulation part being defined by a transparent material filled in the frame, and the frame being molded by a transparent resin.

4. The light emitting device according to claim 1,

the light-emitting diode chip is formed with one electrode on one surface thereof and another electrode on the other surface thereof, the electrode of the electrodes close to the sub-mount section being connected to one bonding wire through the conductor pattern on the sub-mount section, and the other electrode remote from the sub-mount section being connected to another bonding wire extending along one of the diagonals of the light-emitting diode chip.

5. The light emitting apparatus of claim 1, further comprising:

a dome-shaped color conversion member provided on the dielectric substrate so as to cover the lens, the color conversion member being a molded member molded from a transparent material mixed with a fluorescent material that is emitted from the light emitting diode chip and is excited by light of the encapsulating member to radiate light of a color different from that of the light emitting diode chip, the color conversion member being provided to form an air layer between the color conversion member and a light emitting surface of the lens.

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