JP4820135B2 - Light emitting device - Google Patents

Description

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

Conventionally, an LED chip, a mounting substrate on which the LED chip is mounted, and an epoxy resin sealing the LED chip and a bonding wire connected to the LED chip on the mounting surface side of the LED chip on the mounting substrate There has been proposed a light emitting device that has a directivity of light emitted by forming a part of the sealing portion into a convex lens shape (for example, Patent Document 1). In Patent Document 1, an LED chip that emits blue light or ultraviolet light and a phosphor that emits light of a color different from the emission color of the LED chip when excited by the light emitted from the LED chip. A technique for obtaining mixed color light having a hue different from the emission color of the LED chip including white is disclosed.
JP 2003-243724 A

  However, in the case where an epoxy resin is used as the material of the sealing portion as in the light emitting device described in Patent Document 1, the weather resistance of the sealing portion is low, and the blue LED chip emits blue light. In this case, there is a problem that the sealing portion is easily deteriorated by blue light.

  The present invention has been made in view of the above-described reasons, and an object thereof is to provide a light emitting device capable of improving reliability and directivity.

The invention of claim 1 is an LED chip, a mounting substrate on which the LED chip is mounted, and a reflector that surrounds the LED chip on the mounting surface side of the LED chip on the mounting substrate and reflects light emitted from the LED chip. A reflector having a shape in which an opening area gradually increases as the distance from the mounting surface increases; a sealing portion that seals an LED chip and a bonding wire electrically connected to the LED chip inside the reflector; A molded product formed by molding together with a transparent material a lens arranged on the stopper and the reflector, and a phosphor that emits light of a color different from the emission color of the LED chip when excited by the light emitted from the LED chip. The lens is covered with the mounting surface side of the mounting substrate and an air layer is formed between the lens and the light emitting surface of the lens. And a sealing part is formed by filling the inside of the reflector with silicone resin, the lens is a convex lens, and the lens emits light incident from the light incident surface. A convex curved surface that is not totally reflected at the boundary between the surface and the air layer, is formed by a part of a spherical surface, and the center of the spherical surface is positioned on the center line of the light emitting unit along the thickness direction of the LED chip. The distance between the light emitting surface in the normal direction and the inner surface of the color conversion member is a substantially constant value regardless of the position of the light emitting surface of the lens. The reflector is molded so that the thickness along the normal direction is uniform, and the reflector has an annular positioning rib for positioning the color conversion member on the periphery of the surface opposite to the mounting board side. It is characterized in that it is projected .

According to the present invention, since the sealing portion is formed of the silicone resin, the reliability of the sealing portion can be increased, and the directivity can be increased because the lens is formed of a convex lens. Further, by providing a color conversion member disposed in such a manner that an air layer is formed between the light emitting surface of the lens, the light emitted from the LED chip and the phosphor of the color conversion member are emitted. In addition to being able to obtain mixed color light with the light to be transmitted, the lens can be protected, and the stress generated in the color conversion member when an external force is applied to the color conversion member is applied to the LED chip or the Since transmission to the bonding wire can be suppressed and fluctuations in the light emission characteristics of the LED chip and disconnection of the bonding wire due to the external force can be suppressed, reliability can be further improved. According to this invention, the lens is formed by a part of a spherical surface having a light exit surface that is a convex curved surface that does not totally reflect light incident from the light entrance surface at the boundary between the light exit surface and the air layer. The center of the spherical surface is arranged on the center line of the light emitting part along the thickness direction of the LED chip, and the light emitting surface and the color in the normal direction are independent of the position of the light emitting surface of the lens. Since the distance between the inner surface of the conversion member is a substantially constant value and the color conversion member is formed so that the thickness along the normal direction is uniform regardless of the position, the LED chip Emitted from the LED chip (the light emitted from the LED chip and reflected on the light incident surface of the lens without being reflected by the reflector) and the light emitted from the LED chip and reflected by the inner surface of the reflector and incident on the light incident surface of the lens Light) is the light exit surface and air layer Until the color conversion member without being totally reflected at the boundary tends to reach, it is possible to increase the total luminous flux. Further, according to the present invention, since the annular positioning rib for positioning the color conversion member is continuously and integrally provided on the peripheral portion of the surface opposite to the mounting substrate side, the reflector is colored with respect to the reflector. The conversion member can be positioned with high accuracy.

  In the invention of claim 1, there is an effect that reliability and directivity can be improved.

  Hereinafter, the light-emitting device of the present embodiment will be described with reference to FIGS.

  The light emitting device 1 of the present embodiment radiates from the LED chip 10, the LED chip 10, the mounting substrate 20 on which the LED chip 10 is mounted, the LED chip 10 on the mounting substrate 20 side of the mounting substrate 20. A frame-like reflector 40 that reflects light, and a transparent resin material filled inside the reflector 40 to seal the LED chip 10 and bonding wires 14 and 14 connected to the LED chip 10 and to provide elasticity. The sealing part 50 having the lens, the lens 60 disposed so as to overlap the sealing part 50 and the reflector 40, and the light emitted from the LED chip 10 to emit light of a color different from the emission color of the LED chip 10. A molded product obtained by molding a fluorescent material together with a transparent material, covering the lens 60 on the light emitting surface 60b side of the lens 60, and the light emitting surface 60 And a color conversion member 70 domed disposed in the form of an air layer 80 is formed between the. The light-emitting device 1 of the present embodiment is used as a light source of a lighting fixture such as a spotlight, for example, and has a metal (for example, Al, Cu or the like having a thermal conductivity through an insulating layer 90 made of a green sheet, for example. By mounting on the device body 100 made of a high metal), the thermal resistance from the LED chip 10 to the device body 100 can be reduced, the heat dissipation is improved, and the temperature rise of the junction temperature of the LED chip 10 can be suppressed. Therefore, the input power can be increased and the optical output can be increased. Here, in the case of a lighting fixture, a plurality of light emitting devices 1 are mounted on the fixture main body 100 so as to obtain a desired light output (in FIG. 5, ten light emitting devices 1 are bottomed). An example is shown in which the inner bottom surface of the bottom wall of the cylindrical instrument body 100 is arranged at equal intervals along the circumferential direction), and a plurality of light emitting devices 1 may be connected in series or in parallel.

  The mounting substrate 20 includes a metal plate 21 on which the LED chip 10 is mounted, and an insulating base material 22 made of a glass epoxy substrate laminated on the metal plate 21, and the metal plate in the insulating base material 22. A pair of lead patterns 23 that are electrically connected to both electrodes (not shown) of the LED chip 10 are provided on the surface opposite to the 21 side, and a window is formed at a portion corresponding to the LED chip 10 in the insulating substrate 22. A hole 24 is provided so that heat generated in the LED chip 10 can be transferred to the metal plate 21 without passing through the insulating base material 22. Here, Cu is employed as the material of the metal plate 21, but any metal material having a relatively high thermal conductivity may be used, and not only Cu but Al or the like may be employed. In addition, the metal plate 21 and the insulating base material 22 are fixed by a fixing material 25 made of an insulating sheet-like adhesive film. Each lead pattern 23 is composed of a laminated film of a Ni film and an Au film, and a portion not covered with the color conversion member 70 is an outer lead portion 23b. Further, the insulating base material 22 is formed with a reflection film 27 that reflects light emitted from the LED chip 10 around the window hole 24. Here, the reflection film 27 is formed of a laminated film of a Ni film and an Ag film.

  The LED chip 10 is a GaN-based blue LED chip that emits blue light, and is a conductive substrate made of an n-type SiC substrate that has a lattice constant and a crystal structure close to GaN as a crystal growth substrate and has conductivity compared to a sapphire substrate. The light emitting portion 12 formed of a GaN-based compound semiconductor material and having, for example, a double hetero structure is formed on the main surface side of the conductive substrate 11 by an epitaxial growth method (for example, MOVPE method). ), A cathode electrode (n electrode) which is a cathode side electrode (not shown) is formed on the back surface of the conductive substrate 11, and is shown on the surface of the light emitting unit 12 (the outermost surface on the main surface side of the conductive substrate 11). An anode electrode (p electrode) which is an electrode on the anode side that is not to be formed is formed. In short, the LED chip 10 has an anode electrode formed on one surface side and a cathode electrode formed on the other surface side. The cathode electrode and the anode electrode are composed of a laminated film of a Ni film and an Au film, but the material of the cathode electrode and the anode electrode is not particularly limited, and a material capable of obtaining good ohmic characteristics For example, Al or the like may be employed. In the present embodiment, the light emitting unit 12 of the LED chip 10 is mounted on the metal plate 21 so as to be on the side farther from the metal plate 21 than the conductive substrate 11. The conductive plate 11 may be mounted on the metal plate 21 so as to be closer to the metal plate 21 than the conductive substrate 11. In consideration of the light extraction efficiency, it is desirable to arrange the light emitting unit 12 on the side away from the metal plate 21, but in this embodiment, the conductive substrate 11 and the light emitting unit 12 have the same refractive index. Therefore, even if the light emitting unit 12 is disposed on the side close to the metal plate 21, the light extraction loss does not become too large.

  Further, the LED chip 10 is formed on the metal plate 21 in the shape of a rectangular plate having a size larger than the chip size of the LED chip 10, and the LED chip 10 is caused by the difference in linear expansion coefficient between the LED chip 10 and the metal plate 21. It is mounted via a submount member 30 that relieves stress acting on the chip 10. The submount member 30 has not only a function of relieving the stress, but also a heat conduction function of transferring heat generated in the LED chip 10 to a range wider than the chip size of the LED chip 10 on the metal plate 21. . In the present embodiment, AlN having a relatively high thermal conductivity and insulation is used as the material of the submount member 30, and the LED chip 10 has the cathode electrode on the LED chip 10 side of the submount member 30. Electrically connected to one lead pattern 23 via a bonding wire 14 provided on the surface and connected to the cathode electrode (see FIG. 2) and a metal wire (for example, a gold wire, an aluminum wire, etc.) The anode electrode is electrically connected to the other lead pattern 23 via the bonding wire 14. The LED chip 10 and the submount member 30 may be bonded using, for example, solder such as SnPb, AuSn, SnAgCu, or silver paste, but may be bonded using lead-free solder such as AuSn, SnAgCu. It is preferable.

  The material of the submount member 30 is not limited to AlN, and any material may be used as long as the linear expansion coefficient is relatively close to 6H—SiC that is the material of the conductive substrate 11 and the heat conductivity is relatively high. Si or the like may be employed.

  A silicone resin is used as the transparent resin material of the sealing portion 50 described above, and the sealing portion 50 is gel-like and has elasticity.

  The reflector 40 has a frame shape opened in a circular shape, and the shape of the inner side surface 40a is designed so that light emitted from the side surface of the LED chip 10 is reflected toward the lens 60 side. That is, the reflector 40 is formed in a shape in which the opening area increases as the distance from the LED chip 10 increases in the thickness direction of the LED chip 10 (that is, the shape in which the opening area gradually increases as the distance from the mounting surface increases). Here, as the material of the reflector 40, a material (for example, Al) having a relatively high reflectance with respect to light emitted from the LED chip 10 (here, blue light) is adopted, and the inner side surface 40a of the reflector 40 is used. What is necessary is just to make it a mirror surface, and the reflector 40 should just be formed, for example by drawing an aluminum base material. In addition, the reflector 40 is fixed to the mounting substrate 20 with a fixing material 26 made of an insulating sheet-like adhesive film. In the present embodiment, after the reflector 40 is fixed to the mounting substrate 20, the sealing portion 50 is formed by filling (potting) the transparent resin material inside the reflector 40 and thermosetting it.

  The lens 60 is configured by a convex lens in which the light incident surface 60a on the sealing portion 50 side is formed in a flat shape and the light emitting surface 60b is formed in a convex curved surface shape. Here, the lens 60 is formed of a molded product of silicone resin, and the refractive index is the same as that of the sealing portion 50. However, the lens 60 is not limited to the molded product of silicone resin. You may comprise by the molded article of resin.

  Incidentally, the lens 60 and the reflector 40 are arranged so that their optical axes coincide with each other and each optical axis passes through the LED chip 10, and the lens 60 has a light emitting surface 60b incident from the light incident surface 60a. It is formed in a convex curved surface shape that does not totally reflect light at the boundary between the light emitting surface 60b and the air layer 80 described above. Here, the lens 60 is formed such that the light emitting surface 60 b is formed by a part of a spherical surface, and the center of the spherical surface is positioned on the center line of the light emitting unit 12 along the thickness direction of the LED chip 10. Yes. Therefore, the light emitted from the LED chip 10 (the light emitted from the LED chip 10 and incident on the light incident surface 60a of the lens 60 without being reflected by the reflector 40, and the inner surface 40a of the reflector 40 emitted from the LED chip 10). The light that has been reflected by the light and incident on the light incident surface 60a of the lens 60 is not easily totally reflected at the boundary between the light emitting surface 60b and the air layer 80, and can easily reach the color conversion member 70, thereby increasing the total luminous flux. Can do.

  The color conversion member 70 is a molded article in which a transparent material such as a silicone resin and a particulate yellow phosphor that emits broad yellow light when excited by the blue light emitted from the LED chip 10 are mixed. It is comprised by. Therefore, in the light emitting device 1 of the present embodiment, the blue light emitted from the LED chip 10 and the light emitted from the yellow phosphor are emitted through the outer surface 70b of the color conversion member 70, and white light is obtained. Can do. Note that the transparent material used as the material of the color conversion member 70 is not limited to the silicone resin, and for example, an acrylic resin, an epoxy resin, glass, or the like may be employed. Further, the phosphor mixed with the transparent material used as the material of the color conversion member 70 is not limited to the yellow phosphor. For example, white light can be obtained by mixing a red phosphor and a green phosphor.

  Here, the color conversion member 70 has an inner surface 70 a formed in a shape along the light emitting surface 60 b of the lens 60. Therefore, the distance between the light emitting surface 60b and the inner surface 70a of the color conversion member 70 in the normal direction is a substantially constant value regardless of the position of the light emitting surface 60b of the lens 60. In addition, the color conversion member 70 is shape | molded so that the thickness along a normal line direction may become uniform irrespective of a position. The color conversion member 70 may be bonded to the reflector 40 at the periphery of the opening using, for example, an adhesive (for example, silicone resin, epoxy resin).

  By the way, in the reflector 40 described above, an annular positioning rib 41 that surrounds the color conversion member 70 and positions the color conversion member 70 is continuously and integrally provided on the periphery of the surface opposite to the mounting substrate 20 side. Therefore, in this embodiment, the color conversion member 70 can be positioned with high accuracy with respect to the reflector 40.

  In the light emitting device 1 of the present embodiment described above, the sealing portion formed by filling the inside of the reflector 40 with silicone resin and sealing the LED chip 10 and the bonding wires 14 and 14 connected to the LED chip 10. 50, the weather resistance of the sealing part 50 can be improved as compared with the conventional case where an epoxy resin is used as the material of the sealing part 50, and the deterioration due to the light emitted from the LED chip 10 Is less likely to occur.

  Further, in the light emitting device 1 of the present embodiment, since the lens 60 made of a convex lens formed separately from the sealing portion 50 is fixed to the sealing portion 50 in an overlapping manner, the directivity of the emitted light can be improved. In particular, it is suitable as a light source for a luminaire having a high directivity requirement such as a luminaire such as a spotlight.

  Further, in the light emitting device 1 of the present embodiment, the color conversion member 70 may be disposed in a form in which the air layer 80 is formed between the light emitting surface 60 b of the lens 60, and the color conversion member 70 is attached to the lens 60. Since it is not necessary to make it closely_contact | adhere, the fall of the yield resulting from the dimensional accuracy and positioning accuracy of the color conversion member 70 can be suppressed. Further, in the light emitting device 1 of the present embodiment, since the assembly of the color conversion member 70 is the final process at the time of assembly, the color conversion member 70 in which the blending of the phosphor with respect to the transparent material is adjusted according to the emission wavelength of the LED chip 10. By using, color variations can be reduced.

  Further, in the light emitting device 1 of the present embodiment, since the air layer 80 is formed between the color conversion member 70 and the lens 60 as described above, the color conversion member when an external force acts on the color conversion member 70. The possibility that the lens 70 is deformed and abutted against the lens 60 is reduced, and the stress generated in the color conversion member 70 due to the external force is transmitted to the LED chip 10 and the bonding wires 14 and 14 through the lens 60 and the sealing portion 50. Therefore, there is an advantage that reliability is improved because fluctuations in the light emission characteristics of the LED chip 10 due to the external force and disconnection of the bonding wires 14 and 14 are less likely to occur. In addition, since the air layer 80 is formed between the color conversion member 70 and the lens 60, there is an advantage that moisture in the external atmosphere hardly reaches the LED chip 10.

  In addition, since the air layer 80 is formed between the color conversion member 70 and the lens 60, the color conversion member 70 is emitted from the LED chip 10 and enters the color conversion member 70 through the sealing portion 50 and the lens 60. Among the light scattered by the yellow phosphor particles in 70, there is an advantage that the amount of light scattered to the lens 60 side and transmitted through the lens 60 can be reduced, and the light extraction efficiency to the outside as the entire apparatus can be improved. is there.

  Here, as shown in FIGS. 6A and 6B, the optical axis of the color conversion member 70 and the optical axis of the LED chip 10 coincide with each other, and the central position of the color conversion member 70 in the optical axis direction. It is assumed that the blue light from the LED chip 10 is scattered in all directions by P, the total reflection angle at the interface between the color conversion member 70 and the air layer 80 is φa, and the color conversion member 70 and the outside of the color conversion member 70 are outside. The total reflection angle at the interface with air, which is the medium, is φb, and the light scattered at the position P is 2θa, the spread angle of the escape cone ECa on the inner surface 70a side of the color conversion member 70, and the color is scattered with respect to the light scattered at the position P. If the spread angle of the escape cone ECb on the outer surface 70b side of the conversion member 70 is 2θb, as shown in FIG. 6A, when the total reflection angles φa and φb are 40 °, 2θa = 60 ° and 2θb = 98 °. As shown in FIG. 6B, the total reflection angle When φa and φb are 50 °, 2θa = 76 ° and 2θb = 134 °.

Here, if the refractive index of the transparent material used for the color conversion member 70 is n and the maximum emission efficiency of blue light scattered at the position P and emitted through the escape cone ECa on the inner surface 70a is η, η = ( ¼n ² ) × 100 [%], so that when silicone resin is used as the transparent material as described above, η≈13% when n = 1.4. Therefore, when the air layer 80 is not formed between the color conversion member 70 and the lens 60, 50% of the blue light scattered at the position P returns to the lens 60, whereas the air layer Since 80 is formed, only 13% of the blue light scattered at the position P returns to the lens 60, so that deterioration of the sealing portion 50 due to the blue light can be suppressed. In order to reduce the blue light emitted through the escape cone ECa, it is desirable to increase the thickness of the color conversion member 70.

  By the way, in the above-described embodiment, a blue LED chip whose emission color is blue is adopted as the LED chip 10, and a SiC substrate is adopted as the conductive substrate 11, but a GaN substrate is used instead of the SiC substrate. In the case of using a SiC substrate or a GaN substrate, the crystal growth substrate has a higher thermal conductivity than the case of using a sapphire substrate as an insulator as the crystal growth substrate. Thermal resistance can be reduced. Further, the light emission color of the LED chip 10 is not limited to blue, and may be, for example, red or green. That is, the material of the light-emitting portion 12 of the LED chip 10 is not limited to the GaN-based compound semiconductor material, and a GaAs-based compound semiconductor material, a GaP-based compound semiconductor material, or the like may be employed according to the emission color of the LED chip 10. Further, the conductive substrate 11 is not limited to the SiC substrate, and may be appropriately selected from, for example, a GaAs substrate and a GsP substrate according to the material of the light emitting unit 12.

It is a schematic sectional drawing which shows embodiment. It is a general | schematic disassembled perspective view which showed the same and partially fractured | ruptured. It is a principal part schematic plan view which shows the same as the above. The insulating base material same as the above is shown, (a) is a schematic plan view, (b) is a schematic cross-sectional view. The lighting fixture using the same is shown, (a) is a principal part schematic plan view, (b) is a principal part schematic sectional drawing. It is principal part explanatory drawing same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 LED chip 14 Bonding wire 20 Mounting board 21 Metal plate 22 Insulating base material 23 Lead pattern 30 Submount member 40 Reflector 50 Sealing part 60 Lens 60a Light incident surface 60b Light output surface 70 Color conversion member 80 Air layer

Claims (1)

An LED chip, a mounting substrate on which the LED chip is mounted, and a reflector that surrounds the LED chip on the mounting surface side of the LED chip on the mounting substrate and reflects light emitted from the LED chip, and opens as the distance from the mounting surface increases A reflector formed in a shape that gradually increases in area, a sealing portion in which the LED chip and a bonding wire electrically connected to the LED chip are sealed inside the reflector, and the sealing portion and the reflector are overlapped A molded product obtained by molding together with a transparent material a phosphor that emits light of a color different from the emission color of the LED chip when excited by the light emitted from the LED chip and the LED chip, and the mounting surface of the mounting substrate A dome-shaped color conversion member that covers the lens on the side and is disposed in a form in which an air layer is formed between the lens and the light exit surface of the lens. The sealing part is formed by filling the inside of the reflector with silicone resin, the lens is a convex lens, and the lens has a light exit surface that reflects light incident from the light entrance surface between the light exit surface and the air layer. And is formed by a part of a spherical surface that is not totally reflected, and is arranged so that the center of the spherical surface is located on the center line of the light emitting unit along the thickness direction of the LED chip. Regardless of the position of the light exit surface, the distance between the light exit surface in the normal direction and the inner surface of the color conversion member is a substantially constant value, and the color conversion member follows the normal direction regardless of the position. The reflector is molded so that the wall thickness is uniform, and the reflector is provided with an annular positioning rib for positioning the color conversion member on the periphery of the surface opposite to the mounting board side. A light emitting device characterized by the above.

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