JP3963188B2 - Light emitting device - Google Patents

Description

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

  Conventionally, a metal base plate on which a plurality of LED chips are directly mounted, and a printed wiring board on which a wiring pattern is formed so that both electrodes of each LED chip are connected to each other via bonding wires. And a sealing part in which the LED chip and a bonding wire connected to the LED chip are sealed with an epoxy resin or a silicone resin on the mounting surface side of the LED chip in the metal base plate, and the sealing part has a lens shape Thus, there has been proposed a light emitting device capable of obtaining a desired light distribution characteristic (for example, Patent Document 1).

Conventionally, a sapphire substrate has been used as a crystal growth substrate, and an LED chip that emits blue light or ultraviolet light is excited by light emitted from the LED chip and emits light of a color different from the emission color of the LED chip. A technique for obtaining mixed color light having a hue different from the emission color of the LED chip including white by combining with a radiating phosphor is widely known.
JP 2003-152225 A

  However, in the light emitting device described in Patent Document 1, since the LED chip is directly mounted on the metal base plate, the LED chip is damaged due to the difference in linear expansion coefficient between the metal base plate and the LED chip. In addition, when an external force is applied, the external force is transmitted to the LED chip and each bonding wire through the sealing portion, and there is a fear that the light emission characteristics of the LED chip may fluctuate or each bonding wire may be disconnected. .

  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 obtaining desired light distribution characteristics and improving reliability.

  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 formed in a shape in which the opening area gradually increases as the distance from the mounting surface increases, and a pair of LED chips and a pair of electrically connected to the LED chips formed by filling a transparent resin material inside the reflector A sealing portion in which the bonding wire is sealed, a lens arranged on the sealing portion and the reflector, and light emitted from the LED chip to emit light having a color different from that emitted from the LED chip. A molded product made of a phosphor with a transparent material, covering the lens and forming an air layer between the light exit surface of the lens. The mounting substrate is provided with a metal plate and a pair of lead patterns that are electrically connected to both electrodes of the LED chip on the surface opposite to the metal plate side. And an insulating base material provided with a window hole in a portion corresponding to the LED chip and laminated on the metal plate, and the LED chip has both electrodes formed on one surface side, and the LED chip and the metal plate A submount member that relieves stress acting on the LED chip due to a difference in linear expansion coefficient between them, and that is larger than the chip size of the LED chip and thermally couples the LED chip and the metal plate The one surface is mounted to face the metal plate via a member, and each electrode is different from each other via a conductor pattern and a bonding wire provided on the submount member. Characterized by comprising connected to the lead pattern.

  According to this invention, the LED chip is excited by the light emitted from the LED chip, the reflector that surrounds the LED chip on the mounting surface side of the LED chip on the mounting substrate, the lens that is placed on the sealing portion and the reflector, and the LED chip. The light emitted from the LED chip and the light emitted from the phosphor are provided with a color conversion member made of 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 A submount member that can obtain desired light distribution characteristics with respect to mixed color light and relaxes the stress acting on the LED chip due to the difference in linear expansion coefficient between the LED chip and the metal plate However, since the size of the LED chip is larger than the chip size of the LED chip, a submount member that thermally couples the LED chip and the metal plate is interposed. Due to the rate difference can be prevented from LED chip is damaged, it is possible to improve the reliability. In addition, since the color conversion member need only be disposed in a form that forms an air layer between the light emitting surface of the lens and does not need to be in close contact with the lens, the stress generated in the color conversion member when an external force is applied. Can be prevented from being transmitted to the LED chip and each bonding wire through the lens and the sealing portion, so that the emission characteristics of the LED chip can be prevented from changing or the bonding wires can be disconnected, thereby further improving the reliability. be able to. Further, the amount of light emitted from the LED chip and incident on the color conversion member through the sealing portion and the lens and scattered by the phosphor particles in the color conversion member is scattered toward the lens and transmitted through the lens. There is an advantage that the light extraction efficiency to the outside as the whole apparatus can be improved, and that moisture in the external atmosphere hardly reaches the LED chip.

  According to the first aspect of the invention, desired light distribution characteristics can be obtained and reliability can be enhanced.

  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 formed of a GaN-based compound semiconductor material on the main surface side of a crystal growth substrate 11 made of a sapphire substrate and has, for example, a laminated structure having a double hetero structure. The light emitting portion 12 composed of a portion is grown by an epitaxial growth method (for example, MOVPE method). Further, the LED chip 10 has a cathode electrode (n electrode) which is a cathode side electrode (not shown) and an anode electrode (p electrode) which is an anode side electrode (not shown) formed on one 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 portion 12 of the LED chip 10 is mounted on the metal plate 21 in a form closer to the metal plate 21 than the crystal growth substrate 11 (that is, mounted face-down). ).

  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 adopted as the material of the submount member 30, and the LED chip 10 mounting surface side of the submount member 30 is provided on the mounting surface side of the LED chip 10. A conductor pattern (not shown) is provided in which the cathode electrode and the anode electrode are electrically connected through bumps 13 and 13 made of a metal material (for example, gold, solder, etc.). In short, the LED chip 10 is electrically connected to lead patterns 23 different from each other via bonding wires 14 in which the cathode electrode and the anode electrode are each composed of a bump 13 and the conductor pattern and a fine metal wire (for example, a gold fine wire, an aluminum fine wire, etc.). Connected. The number of bumps 13 interposed between each of the anode electrode and the cathode electrode and the conductor pattern is not particularly limited. However, the larger the number of bumps 13, the greater the distance between the LED chip 10 and the metal plate 21. Therefore, the heat resistance can be reduced. In addition, the submount member 30 is formed with a reflective film (for example, a laminated film of a Ni film and an Ag film) that reflects light emitted from the LED chip 10 around the mounting portion of the LED chip 10.

  The material of the submount member 30 is not limited to AlN, and may be any material that has a linear expansion coefficient that is relatively close to that of sapphire that is the material of the crystal growth substrate 11 and a relatively high thermal conductivity. For example, composite SiC, Si Etc. may be adopted.

  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. In addition, as a transparent resin material of the sealing part 50, you may use not only a silicone resin but an acrylic resin.

  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 reflector 40 surrounding the LED chip 10 on the mounting surface side of the LED chip 10 on the mounting substrate 20, and the lens 60 disposed so as to overlap the sealing portion 50 and the reflector 40. A color conversion member 70 made of a molded product obtained by molding a phosphor that is excited by light emitted from the LED chip 10 and emits light of a color different from the emission color of the LED chip 10 together with a transparent material such as a silicone resin; Therefore, it is possible to obtain a desired light distribution characteristic for the mixed color light of the light emitted from the LED chip 10 and the light emitted from the phosphor.

  Further, in the light emitting device 1 of the present embodiment, a submount member that relaxes stress acting on the LED chip 10 due to the difference in linear expansion coefficient between the LED chip 10 and the metal plate 21 of the mounting substrate 20. Since the submount member 30 that is larger than the chip size of the LED chip 10 and thermally couples the LED chip 10 and the metal plate 21 is interposed, the LED chip 10 is damaged due to the difference in linear expansion coefficient. Can be prevented, and reliability can be improved.

  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 it is not necessary to closely contact the lens 60. The stress generated in the color conversion member 70 when an external force is applied to the color conversion member 70 can be suppressed from being transmitted to the LED chip 10 and the bonding wires 14 and 14 through the lens 60 and the sealing portion 50. Variations in the light emission characteristics of the LED chip 10 due to external force and disconnection of the bonding wires 14 and 14 are less likely to occur, and reliability is improved. 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.

  Further, in the light emitting device 1 of the present embodiment, the air layer 80 is formed between the color conversion member 70 and the lens 60, so that the color conversion is performed from the LED chip 10 through the sealing portion 50 and the lens 60. Of the light incident on the member 70 and scattered by the yellow phosphor particles in the color conversion member 70, the amount of light scattered to the lens 60 side and transmitted through the lens 60 can be reduced, so that the entire apparatus can be transmitted to the outside. There is an advantage that the light extraction efficiency can be improved.

  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-mentioned embodiment, the blue LED chip whose emission color is blue is adopted as the LED chip 10, and the sapphire substrate is adopted as the substrate 11 for crystal growth. A GaN substrate or the like may be used. 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. The crystal growth substrate 11 is not limited to the sapphire substrate, and may be appropriately selected from, for example, a SiC substrate, a GaN substrate, 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 13 Bump 14 Bonding wire 20 Mounting board 21 Metal plate 22 Insulating base material 23 Lead pattern 24 Window hole 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, and a sealed LED chip and a pair of bonding wires that are formed by filling a transparent resin material inside the reflector and electrically connected to the LED chip. Molded together with a transparent material, a stop portion, a lens placed on the sealing portion 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 Shaped dome that covers the lens and is arranged in the form of an air layer between the lens and the light exit surface The mounting board includes a metal plate and a pair of lead patterns that are electrically connected to both electrodes of the LED chip on the surface opposite to the metal plate side, and corresponds to the LED chip. The LED chip comprises an insulating base material provided with a window hole in a part and laminated on a metal plate, and both electrodes are formed on one surface side, and both wires are connected between the LED chip and the metal plate. Metal plate through a submount member that relieves stress acting on the LED chip due to a difference in expansion coefficient and is larger than the chip size of the LED chip and thermally couples the LED chip and the metal plate Are mounted with the one surface facing each other, and each electrode has a conductor pattern provided on the submount member and a lead pattern different from each other through a bonding wire. The light emitting device characterized by comprising been continued.

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