JP2007194525A - Semiconductor light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make temperature dependency of coloring small as a device by reducing a decrease in efficiency of a phosphor due to heat generation accompanying light emission, by making a semiconductor light emitting element not directly touch a layer containing the phosphor. <P>SOLUTION: The semiconductor light emitting device has a heat insulating layer 11 formed around the semiconductor light emitting element 10 by a printing method with high precision, and a phosphor layer 12 is provided outside the heat insulating layer 11. Consequently, heat generated by the semiconductor light emitting element 10 is not conducted directly to the phosphor 110 to prevent deterioration of the phosphor 110 with time due to the heat generation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device that emits a phosphor by light from a semiconductor light emitting element and emits light obtained by synthesizing light from the semiconductor light emitting element and light from the phosphor. In particular, the present invention relates to a semiconductor light emitting device for high power consumption called a power LED (Light Emitting Device).

  Semiconductor light emitting devices capable of emitting blue light have been put into practical use, and light emitting devices of various colors can be designed. In other words, it is possible to emit various shades by combining the semiconductor light emitting element and phosphors emitting various colors. Hereinafter, a light emitting device in which a semiconductor light emitting element and a phosphor are combined is referred to as a “mixed light emitting device” or simply “light emitting device” in contrast to a “monochromatic light emitting device” composed of only semiconductor light emitting elements. Therefore, the mixed light emitting device is included in the semiconductor light emitting device.

  For example, a white light emitting device can be formed by combining a blue semiconductor light emitting element and a yellow phosphor. However, a slight mixing error between blue and yellow causes a difference in emission wavelength, and even in white, a difference in hue occurs. In order to achieve a certain color as a light emitting device, the color of the final product must be adjusted by adjusting the density and thickness of the phosphor portion (see Patent Document 1).

  As described above, in the mixed light emitting device, the hue is realized by a delicate balance between the semiconductor light emitting element and the phosphor portion. Therefore, it is necessary to devise such that the change in the characteristics of each part with time after production is minimized.

For example, as a countermeasure against the deterioration of the resin mixed with the phosphor with the lapse of time because the usable light-emitting element has been shortened, the resin composition is specified (see Patent Document 2), which is added at the time of sealing during manufacturing. There is a device (Patent Document 3 and Patent Document 4) in which a relaxation layer is provided in order to avoid malfunction of the light emitting element and peeling of the sealing portion from thermal strain.
JP 2005-56885 A JP 2002-374007 A JP 2004-241704 A JP 2001-168398 A

  Among mixed type light emitting devices, a type having a large amount of light emission called a power LED requires measures against heat generation in addition to the above problems. There is also a monochromatic semiconductor light-emitting device that does not use a phosphor in the power LED.

  The power LED generally refers to a semiconductor light emitting device that is used by flowing a large current of several hundred mA (milliampere) to 1 A (ampere) or more, and is mainly used for applications such as lighting and large displays. In order to obtain a large amount of light emission by flowing a large current, the entire device has heat due to Joule heat. In the case of a mixed light emitting device belonging to a power LED, a problem arises that the luminous efficiency of the phosphor is reduced by this heat. A decrease in the luminous efficiency of the phosphor brings about a change in the hue emitted by the phosphor, resulting in a change in the hue of the mixed light emitting device as a whole. In other words, after lighting, there is a problem that the color changes as the temperature of the light emitting device increases.

  Therefore, in order to avoid the temperature rise of the phosphor, it is necessary to insulate the semiconductor light emitting element. However, excessive heat insulation conversely causes thermal damage to the semiconductor light emitting element, leading to a reduction in life. Therefore, prevention of temperature rise of the phosphor layer and thermal damage to the semiconductor light emitting element must be balanced, and the thickness of the heat insulating layer needs to be precisely controlled.

  The present invention has been conceived in order to solve such problems.

  In order to solve this problem, the present invention provides a finely controlled heat insulating layer between the semiconductor light emitting element and the phosphor. Specifically, a heat insulating layer whose thickness is controlled with an accuracy of 1 mm or less is provided using a printing method. And a fluorescent substance layer is arrange | positioned on the outer side of the heat insulation layer.

  Further, the resin used for the phosphor layer has a high thermal conductivity. Specifically, a transparent filler with good thermal conductivity is mixed in the resin to increase the thermal conductivity.

  The present invention has a structure in which a phosphor-containing layer is not directly touched to a semiconductor light emitting element that generates heat by passing a large current. Accordingly, it is possible to alleviate the decrease in efficiency of the phosphor due to heat generated by light emission, and to reduce the temperature characteristic of color development as an apparatus.

(Embodiment 1)
FIG. 1 shows a cross-sectional view of a mixed light emitting device of the present invention (a surface obtained by cutting the mixed light emitting device along a surface perpendicular to the main light emitting surface).

  Note that the main light emitting surface side refers to the positive direction of the X axis in FIG. 1 with respect to the semiconductor light emitting element 10 (hereinafter, the same applies to the present specification).

  Prior to detailed description of each part of the mixed light emitting device 1, an outline of the mixed light emitting device 1 will be shown.

  The mixed light-emitting device 1 includes a semiconductor light-emitting element 10, a submount 15 on which the semiconductor light-emitting element 10 is mounted, and an electrode disposed on the top, and a heat insulating layer covering the periphery including the main light-emitting surface side of the semiconductor light-emitting element 10 11, a lead frame 16 electrically connected to the semiconductor light emitting element 10 through a conductive through hole 14 provided in the submount 15, a heat radiation member 17 formed integrally with the lead frame, and a heat insulating layer 11 is provided with a phosphor layer 12 provided around 11.

  In FIG. 1, the lead frame 16 and the heat radiating member 17 are shown as one body, but the heat radiating member 17 may be configured separately from the lead frame. When the lead frame 16 and the heat radiating member 17 are integrated, the heat radiating member 17 means including a portion of the lead frame 16 that is in contact with the submount 15. The same applies to the following embodiments.

  The mixed light emitting device 1 operates as follows. A current supplied from the outside flows from one side of the lead frame 16 to the PN junction in the semiconductor light emitting device 10 through the through hole 14. Then, the current flows to the other lead frame 16 through the other through hole 14. When the current passes through the PN junction in the semiconductor light emitting device 10, the semiconductor light emitting device 10 emits light. Part of the light emitted here is wavelength-converted by the phosphor 110 of the phosphor layer 12, and the mixed light appears to be emitted.

  When the amount of current is increased in order to increase the amount of light emission, the semiconductor light emitting element 10 mainly generates heat. This heat is dissipated by being transmitted from the submount 15 to the heat dissipating member 17. On the other hand, since the heat insulating layer 11 is disposed around the semiconductor light emitting element 10, heat is not easily transmitted directly to the phosphor layer 12. With this configuration, the phosphor layer 12 is unlikely to increase in temperature due to heat. That is, it is possible to obtain an effect that the light emission efficiency is hardly lowered and the hue is hardly changed.

  A method for manufacturing the mixed light-emitting device illustrated in FIG. 1 will be described. FIG. 2 illustrates a part of the manufacturing process.

  A submount base material 30 provided with through holes 14 imparted with conductivity to the material of the submount 15 is prepared (FIG. 2A). The semiconductor light emitting element 10 in which the bump electrode is formed is disposed at the position of the through hole 14 (FIG. 2B). A heat insulating layer 11 is applied by screen printing so as to cover the semiconductor light emitting element 10 (FIG. 2C). By using the printing method, the thickness of the heat insulating layer can be precisely controlled with an accuracy of 1 mm or less. Further, it can be produced in large quantities at a time, which is advantageous for cost reduction. Further, after the formation of the heat insulating layer, the upper portion may be polished with a polishing machine 50 or the like (FIG. 2D).

  Thereafter, the submount base material 30 is cut with a slicer 55 or the like, so that the semiconductor light emitting element is arranged on the submount and the light emitting element unit 20 covered with the heat insulating layer is obtained (FIG. 2E).

  According to this method, the area of the mounting portion of the semiconductor light emitting element of the submount 15 is equal to or larger than the cross-sectional area of the heat insulating layer 11 in the X direction. Note that the cross-sectional area in the X direction refers to a cross-sectional area when the X direction in FIG.

  The lead frame 16 is fixed to the mold in a predetermined positional relationship, and the molten material of the frame substrate 13a is poured therein. When the heat radiating member 17 is separated from the lead frame 16, the heat radiating member 17 is also molded integrally.

After arranging the lead frame 16 and the light emitting element unit 20 to be electrically conductive,
The periphery of the light emitting unit is sealed with a phosphor layer 12 in which the phosphor is dispersed in the resin by a transfer molding technique.

  After manufacturing in this way, a current is passed and a light emission test is performed to confirm whether the desired color tone is obtained. The amounts of the heat insulating layer 11 and the phosphor layer 12 are determined in advance as design values, but the amount of mixing varies due to errors in manufacturing. Variations in the phosphor layer 12 appear as variations in color tone.

  Therefore, the actual color tone is confirmed by the light emission test, and the phosphor layer 12 is shaved and adjusted so that the final desired color tone is obtained. Therefore, it is preferable to mold the phosphor layer 12 in advance so as to be slightly larger. The phosphor layer 12 is polished using a lapping machine or the like. As described above, the final color tone adjustment is completed, and the mixed light-emitting device 1 is obtained.

  (Configuration of Each Part) Hereinafter, each configuration of the mixed light-emitting device 1 will be described more specifically. Note that the description of each configuration is the same in other embodiments unless otherwise specified.

  (Semiconductor Light Emitting Element 10) The semiconductor light emitting element 10 is a blue LED using a semiconductor made of a gallium nitride compound. As shown in FIG. 3, the semiconductor light emitting device 10 includes, for example, a GaN n-type layer 101, an InGaN active layer 102, and a GaN p-type layer 103 on one surface of an element substrate 100 made of GaN. Are laminated in this order.

  Then, a part of the p-type layer 103 is exposed to the n-type layer 101 by etching, for example. An n-type electrode 104 is formed on the exposed surface of the n-type layer 101. A p-type electrode 105 is formed on the surface of the p-type layer 103. The semiconductor light emitting device 10 is a so-called single-sided electrode type having both a p-type electrode and an n-type electrode on one surface.

  The n-type electrode 104 and the p-type electrode 105 are electrically connected to the submount 15 having electrodes on the surface and through holes provided with conductivity through bumps 106, respectively. As the material of the bump 106, for example, Au can be used, but any conductive material may be used. The connection method using the bumps 106 is preferable because there is nothing to block the light output in the irradiation direction of the light emitting light source.

  In addition, as a structure of blue LED, it is not limited to the example given here. For example, as the element substrate 100, SiC or insulating sapphire may be used. Further, for example, as the n-type layer 101 and the p-type layer 103, AlGaN or InGaN may be used, and a buffer layer made of GaN or InGaN is used between the n-type layer 101 and the element substrate 100. Is also possible. For example, the active layer 102 may have a multilayer structure (quantum well structure) in which InGaN and GaN are alternately stacked.

  (Heat insulation layer 11) The heat insulation layer 11 consists of 1 type, or 2 or more types of combinations selected from a silicone resin, an epoxy resin, and a fluororesin. In particular, a silicone resin is more preferable because it has high elasticity, can protect the semiconductor light emitting element from external force, and is excellent in heat resistance and light resistance. The heat insulating layer 11 may be a siloxane-based resin.

  (Phosphor layer 12) The phosphor layer 12 is yellow light (light having a peak in a range from 540 nm to 600 nm) by the phosphor 110 containing a part of blue light emitted from the blue LED described above. Has been converted. Due to the color mixture of blue light and yellow light, the semiconductor light emitting device 1 as a whole emits white light.

  The phosphor layer 12 is configured by dispersing the phosphor 110 in a resin mainly composed of a silicone resin, an epoxy resin, and a fluororesin. In particular, as the non-silicone resin, a siloxane-based resin, a polyolefin, a silicone / epoxy hybrid resin, or the like is preferable.

The average particle shape of the phosphors 110 dispersed and arranged in the phosphor layer 12 is, for example, 3 μm to 15 μm, and is substantially spherical. The phosphor 110 is a yellow phosphor that absorbs blue light emitted from the semiconductor light emitting element 10 and emits yellow light after being excited. As such a yellow phosphor, a rare earth-doped nitride-based or rare earth-doped oxide-based phosphor is preferable. For example, (Y · Sm) ₃ (Al · Ga) ₅ O ₁₂ : Ce and (Y _0.39 Gd _0.57 Ce _0.03 Sm _0.01 ) ₃ Al ₅ O ₁₂ , rare earth doped alkaline earth metal orthosilicate, rare earth doped rare earth doped garnet Doped thiogallate, rare earth doped aluminate and the like can be suitably used.

  Moreover, the heat | fever which reached | attained the fluorescent substance layer 12 through the heat insulation layer 11 can be thermally radiated as early as possible by using resin with high heat conductivity for the fluorescent substance layer 12. FIG. This not only prevents the temperature of the phosphor layer 12 from rising, but also helps to dissipate heat from the semiconductor light emitting element 10 itself, and also has an effect of preventing thermal degradation of the semiconductor light emitting element 10.

  As a method for imparting thermal conductivity to the resin, by adding a transparent filler such as silica or a filler having a particle size smaller than the emission wavelength, the thermal conductivity can be increased without reducing the luminous efficiency.

  (Frame Substrate 13a) The frame substrate integrates the lead frame 16 and the heat dissipation member 17. As the member, for example, a thermoplastic resin such as LCP (Liquid Crystal Polymer) or polyphthalamide resin, a thermosetting resin, or the like can be used.

  (Submount 15) The submount 15 has a structure in which the semiconductor light emitting element 10 is placed on the upper surface and electrodes are provided on the surface.

  Referring to FIG. 3, submount 15 has a through hole 14, and the electrode on the surface is electrically connected to the through hole. Therefore, it is connected to the lead frame 16 through this through hole 14. That is, the semiconductor light emitting element 10 is flip-chip connected to the submount 15 having the through hole 14.

  The through hole 14 includes a conductive material made of, for example, copper, aluminum, gold, or the like.

  Further, the through hole 14 may be formed in any manner as long as it includes the submount 15. For example, it may be formed along the end surface of the submount 15. In this case, since the distance between the paired through holes 14 can be increased, a large cross-sectional area can be obtained even when the submount 15 is downsized. That is, the resistance to the lead frame 16 can be reduced.

  The submount 15 may be a Zener diode, Si (silicon) diode, Si, ceramic, or the like. The through hole 14 includes a conductive material made of, for example, copper, aluminum, gold, or the like.

  With such a configuration, since the semiconductor light emitting element 10 does not use a bonding wire, an electrode region for disposing the bonding wire on the submount 15 can be omitted.

  In addition, with this configuration, there is nothing to block light above the semiconductor light emitting element 10, so that the luminance can be improved. Furthermore, since the electrode of the semiconductor light emitting device 10 can be enlarged, the amount of reflected light is increased, and at the same time, the reliability of bonding can be improved.

  (Lead frame 16) The lead frame 16 is made of a metal having excellent conductivity and heat dissipation, such as a copper alloy.

  (Heat radiating member 17) The heat radiating member 17 is preferably made of a member having excellent heat radiating properties, for example, a heat sink, a cooling body, a PCB (Printed Circuit Board, printed wiring board), or the like. The heat radiating member 17 is exposed from the frame substrate 13a and releases heat to the outside of the light emitting device. The thick portion of the lead frame 16 may be integrally molded.

(Embodiment 2)
FIG. 4 shows another configuration of the mixed light-emitting device of the present invention. In the present embodiment, the phosphor layer 12 is also formed together with the heat insulating layer 11 by a printing method. According to this method, the light emitting device 1 itself can be formed very small. Further, by reducing the size of the device itself, the surface area per volume is increased and the heat dissipation effect is further enhanced.

  The production method will be briefly described. It is the same as FIG. 2 until the heat insulating layer 11 is formed. Before entering the cutting step in FIG. 2, the phosphor layer 12 is applied again by a printing method. After the formation, the light emitting element unit is formed by cutting and combining the phosphor layers. This is called a phosphor layer-attached light emitting element unit 24.

  As in the first embodiment, the phosphor layer-attached light emitting element unit 24 is bonded to a frame substrate in which a lead frame and a heat dissipation member are integrated to obtain a mixed light emitting device shown in FIG.

(Embodiment 3)
FIG. 5 shows the mixed light-emitting device of this embodiment. In the present embodiment, the light emitting element unit 20 (the instruction number is omitted in the drawing) is housed in the housing 13, and the inside of the housing 13 is filled with the phosphor layer 12. The configuration is almost the same as in the first embodiment. However, since the housing 13 is used, mass productivity like a transfer mold cannot be obtained, but stress when filling the phosphor layer 12 can be reduced. Therefore, connection by a method such as bonding becomes possible.

  Further, the light emitting efficiency of the entire light emitting device 1 is improved by providing the inclined portion 18 inside the housing 13 and applying a mirror finish to the portion of the inclined portion 18.

  In FIG. 5, the submount 15 does not have a through hole. Electrical connection from the electrodes provided on the submount 15 to the lead frame 16 is made directly by bonding wires 109.

  Further, since it is not an electrical connection by a through hole, one of the lead frames 16 is formed long, and the large heat radiating member 17 is formed integrally with the longer lead frame. By doing so, the efficiency is increased in terms of heat dissipation through the submount. As for the submount, a submount having a through hole 14 shown in FIG. 1 may be used. In that case, it is preferable to use the same lead frame shape as that in FIG.

  In addition, a diode described in a fourth embodiment described later can be used for the submount.

  A method for manufacturing the mixed light-emitting device of this embodiment will be briefly described. The light emitting element unit 20 is produced according to FIG. The light emitting element unit 20 is mounted on the housing 13 integrally molded together with the lead frame 16 molded integrally with the heat radiating member 17. The lead frame 16 is connected to the lead frame 16 by a bonding wire 109, and then the phosphor layer 12 is filled in the housing 13.

  As a member of the housing 13, for example, a thermoplastic resin such as LCP (Liquid Crystal Polymer) or polyphthalamide resin, a thermosetting resin, or the like can be used.

  Adhesion resin is used for adhesion between the light emitting element unit 20 and the heat dissipation member 17. When the submount 15 is formed of a diode, a conductive resin (hereinafter referred to as “conductive paste”) is used as the adhesive resin.

  For example, Ag paste is preferable for reflecting the downward light from the semiconductor light emitting element 10 toward the main light emitting surface and for imparting heat conductivity to transmit heat generated from the light emitting element unit 20 to the heat radiating member 17. However, the present invention is not particularly limited to the Ag paste, and may be a metal paste such as Cu, Au, Sn, Al, Ni having a relatively high thermal conductivity.

(Embodiment 4)
FIG. 6 shows the configuration of the mixed light-emitting device of this embodiment. The present embodiment is the same as the third embodiment in that the light emitting element unit 20 (the instruction number is omitted in the figure) is placed on the housing 13. However, the four sides other than the main light emitting surface of the light emitting element unit 20 are covered with a filler-containing resin having high thermal conductivity and reflectivity. A filler-filled resin having high thermal conductivity and reflectivity is referred to as a reflective resin layer 22.

  The phosphor layer 12 is filled on the main light emitting surface of the light emitting element unit 20.

  With such a configuration, heat generated from the light emitting element unit 20 through the heat insulating layer 11 can be effectively radiated. Moreover, since the filler which has reflectivity is contained, the luminous efficiency of the whole apparatus 1 does not fall.

  A method for manufacturing the mixed light-emitting device 1 of the present embodiment will be briefly described. The light emitting element unit 20 is formed according to FIG. The housing 13 in which the lead frame 16 and the heat radiating member 17 are integrated is manufactured, and the light emitting element unit 20 is placed on the heat radiating member 17 and connected to the lead frame 16 by the bonding wire 109. The conductive paste used in Embodiment 3 is used for bonding the light emitting element unit 20 and the heat dissipation member 17.

  In the case of FIG. 6, there is only one bonding wire 109, but the case where the submount 15 is a Zener diode is shown. Of course, it goes without saying that the submount 15 may be made of ceramic or the like and connected to the lead frame with two bonding wires.

  Further, a submount having a through hole shown in FIG. 1 can also be used.

  Thereafter, a reflective resin paste is poured so that the four sides of the light emitting element unit are immersed. The reflective resin paste is hardened to form the reflective resin layer 22. Thereafter, the phosphor layer 12 is filled to obtain the mixed light emitting device of the present embodiment.

  The specific example of the reflective resin layer 22 used for this Embodiment is shown. In addition, the following is an illustration and is not limited to this.

  In the present embodiment, since the reflective resin layer 22 is in contact with both the light emitting element unit 20 and the lead frame 16, insulation is an essential characteristic.

  Examples of the filler having reflectivity include those containing light reflecting particles containing Ca, Ti, Ba, Al, Si, Mg, K, and O in a composition such as barium sulfate, calcium carbonate, alumina, and silica. .

Specifically, an epoxy resin, an acrylic resin, or a silicone resin is used as a cloth, and insulating fine particles such as AlN, Al ₂ O ₃ , and TiO ₂ are mixed as fillers. The heat conductivity can be increased by mixing these fillers, and the light reflectance can also be increased by the white gloss on the filler surface.

Further, a combination of Al and SiO ₂ , Ag and SiO ₂ may be used as a filler, and by improving the component ratio of SiO ₂ , improvement in thermal conductivity and light reflectivity can be obtained.

  As described above, the present invention can provide a mixed light-emitting device (semiconductor light-emitting device) that reduces the decrease in efficiency of the phosphor due to heat generation and has less color characteristics of color to be developed, and is particularly suitable for power LEDs. Can be used.

Configuration diagram of mixed light-emitting device according to Embodiment 1 of the present invention The figure which shows the manufacturing process of a light emitting element unit The figure which shows the structure of a semiconductor light-emitting device Configuration diagram of mixed light-emitting device according to Embodiment 2 Configuration diagram of mixed light-emitting device according to Embodiment 3 Configuration diagram of mixed light-emitting device of Embodiment 4

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor light emitting element 11 Heat insulation layer 12 Phosphor layer 13 Housing 13a Frame board 14 Through hole 15 Submount 16 Lead frame 17 Heat radiating member 22 Reflective resin layer 110 Phosphor 109 Bonding wire

Claims (7)

A semiconductor light emitting device;
A phosphor-free layer covering the semiconductor light-emitting element;
A light emitting device unit including a submount on which the semiconductor light emitting device covered with a layer not containing the phosphor is placed;
The semiconductor light-emitting device which has the fluorescent substance layer arrange | positioned in contact with the layer which does not contain the said fluorescent substance. The semiconductor light emitting device according to claim 1, wherein the phosphor layer includes a filler. The semiconductor light emitting device according to claim 1, wherein the phosphor layer is on the submount. The semiconductor light emitting device according to claim 1, wherein the light emitting element unit is in a housing. The semiconductor light-emitting device according to claim 4, wherein there is a layer including a filler that reflects light around the light-emitting element unit. The semiconductor light emitting device according to claim 5, wherein the layer including a filler that reflects light around the light emitting element unit has high thermal conductivity. The semiconductor light emitting device according to claim 1, wherein the light emitting element unit is in contact with a heat radiating member.

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