JP2007294621A - Led lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of production of exfoliation due to a difference of coefficient of thermal expansion between each of projected parts and a resin attended with heat generation of LED chips because of bad adhesiveness between each of the projected parts and the resin for covering each of the LED chips when each LED chip is mounted on each projected part of a heat dissipation substrate in order to establish the compatibility between the heat dissipation and a light extraction efficiency. <P>SOLUTION: The LED lighting system includes the heat conductive substrate, the heat conductive projected parts formed on the heat conductive substrate, the LED chips each mounted on each heat conductive projected part, and a sealing material for covering the LED chips and the heat conductive projected parts, and an edge of each heat conductive projected part is rounded. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an illumination device using an LED chip or an LED chip and a phosphor.

  In recent years, LEDs (light-emitting diodes) have been frequently used as light sources for lighting devices. As a method of obtaining white light of an illumination device using LEDs, a method using three types of LEDs, a red LED, a blue LED, and a green LED, fluorescence that emits yellow light by converting excitation light emitted from the blue LED and the blue LED. There are methods using the body.

  As a light source for illumination, white light with sufficient luminance is required, and lighting devices using a plurality of LED chips have been commercialized. In that case, securing sufficient heat dissipation becomes a problem. In Patent Document 1, heat dissipation is improved by mounting an LED chip on a metal substrate.

  In order to achieve both improved heat dissipation and improved light extraction efficiency, Patent Document 2 has the following structure. FIG. 5A is a schematic cross-sectional view of the illumination device described in Patent Document 2. FIG. A plurality of columnar protrusions 10a protruding upward and a storage recess 10b for storing the LED chip 1 are formed on a metal plate 10 such as aluminum having excellent heat dissipation, and the LED chip 1 is mounted on the storage recess 10b. ing. A wiring substrate 11 is bonded on the metal plate 10. An Au wire 2 for electrical connection is connected between an electrode (not shown) formed on the LED chip 1 and a wiring substrate 11.

  FIG. 5B is a partially enlarged view of the schematic cross-sectional view. A silicone resin 6 in which a phosphor 9 is dispersed is formed so as to cover the protrusion 10a, the housing recess 10b, the LED chip 1 and the Au wire 2 arranged there. The light emitted from the LED chip 1 and the light (light ray P2) obtained by converting the light by the phosphor 9 are reflected upward by the projecting portion 10a functioning as a reflector, and the efficiency of external light extraction Has improved.

In the illuminating device having the configuration shown in FIG. 5, the heat generated by the LED chip 1 can be directly transmitted to the metal plate 10 on which the LED chip 1 is mounted, so that the heat dissipation efficiency can be increased. For this reason, it is said that it is possible to suppress a decrease in luminous efficiency due to temperature rise, a decrease in lifetime, deterioration of the silicone resin 6 covering the LED chip 1, and the like.
JP 2004-265986 A JP 2003-152225 A

  Adhesiveness between the metal plate 10 and the silicone resin 6 excellent in heat dissipation is originally insufficient. Moreover, since heat is generated when the LED chip 1 emits light, heat is also applied to the housing recess 10b and the protruding portion 10a and the silicone resin 6 disposed in the vicinity of the LED chip 1. Since these materials have different coefficients of thermal expansion, a difference in thermal expansion occurs when the LED chip 1 emits light, and when this is repeated, a gap (peeling) is likely to occur at the contact portions of each other. Furthermore, in the structure shown in FIG. 5, since the sharp shape of the peripheral part of the protrusion part 10a which functions as a reflector part is near the LED chip 1, the influence becomes large. In some cases, a sharp portion may crack, and as a result, an air layer is generated in the gap formed between the protruding portion 10a / housing recess 10b and the silicone resin 6, and the light beam P2 emitted from the LED chip 1 is efficient. The silicone resin 6 cannot be well traveled, resulting in a decrease in overall light emission luminance. Moreover, a crack may occur in the entire silicone resin 6 due to the peeling and cracking. When a crack occurs, it becomes impossible to ensure stable brightness as a lighting device, leading to a failure that makes the operation impossible. Even if the edge of the protruding portion is not a sharp shape shown in Patent Document 2 but a simple right angle, stress concentration generally occurs at a vertical corner portion, which causes peeling.

  The present invention provides a heat transfer substrate, a heat transfer protrusion formed on the heat transfer substrate, at least one LED chip mounted on the heat transfer protrusion, the LED chip, and the heat transfer protrusion. An LED lighting device, wherein the edge of the heat transfer protrusion is rounded.

  The LED lighting device according to the present invention is preferably characterized in that a radius of curvature of an edge of the heat transfer protrusion is 1/50 or more of a height of the heat transfer protrusion.

  It is preferable that the present invention is an LED lighting device in which a boundary between the heat conductive substrate and the heat conductive protrusion is rounded.

  According to the present invention, a wiring board is arranged in addition to the protruding portion on the heat conductive substrate and the vicinity thereof, and the upper surface of the heat conductive protruding portion is equal to or higher than the upper surface of the wiring substrate. It is preferable that it is the LED lighting apparatus characterized.

  It is preferable that the present invention is an LED lighting device in which the heat transfer protrusion is a metal.

  The LED lighting device according to the present invention is preferably characterized in that the heat conductive protrusion is formed by plating.

  The present invention is preferably an LED lighting device having a plurality of the heat transfer protrusions on the heat transfer substrate.

  The LED lighting device according to the present invention is preferably characterized in that the plurality of heat transfer protrusions are individually sealed with the sealing material.

  The LED lighting device according to the present invention is preferably characterized in that the plurality of heat transfer protrusions are arranged at the apexes of a substantially equilateral triangle.

  Preferably, the present invention is an LED lighting device in which a reflector portion is formed on the wiring board.

  The present invention is preferably an LED lighting device in which the reflector portion is not in contact with the sealing material.

  According to the present invention, it is possible to solve the problem of adhesion with a sealing material newly generated by making a portion on which an LED chip is mounted a good heat radiating material, and to provide a reliable LED lighting device. Can be realized.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of the LED lighting device of the first embodiment. A protrusion 23 having good heat conduction is formed on the heat conductive Al substrate 24 (thickness 1 mm) made of aluminum. Adjacent to the protrusion 23, a glass epoxy substrate 25 (thickness L2 = 0.5 mm) as a wiring substrate is disposed. The glass epoxy substrate 25 has holes formed in portions corresponding to the protrusions 23 and is bonded to the Al substrate 24. The surface height L1 of the protrusion 23 is formed to be substantially the same as or higher than the glass epoxy substrate 7 (height L1 = 0.5 to 0.6 mm).

  The LED chip 21 is bonded to the upper portion of the protruding portion 23 with a die bond paste 27. A wiring pattern (not shown) is formed on the upper surface of the glass epoxy substrate 25 by etching or the like, and between the p-side electrode and the n-side electrode (not shown) formed on the surface of the LED chip 21. Are electrically connected by an Au wire 22. Here, an InGaN blue LED is used as the LED chip 21. The thickness of the LED chip 21 is approximately 130 to 240 μm.

  A silicone resin 26, which is a sealing material, is formed so as to cover the protrusion 23, the LED chip 21, and the Au wire 22. The silicone resin 26 also serves to protect the LED chip 21 and the Au wire 22 from scratches, moisture, and the like. A phosphor 29 is dispersed in the silicone resin 26. The phosphor 29 converts blue light generated by passing a driving current through the LED chip 21 into yellow light, and white is generated by the yellow light and the blue light from the LED chip 21. As the phosphor 29, a Ce: YAG (cerium activated yttrium / aluminum / garnet) phosphor, Eu: BOSE or SOSE (europium activated strontium / barium / silicate) phosphor, a europium activated α-sialon phosphor, or the like is preferably used. Can do.

  By disposing the LED chip 21 on the protruding portion 23, the light beam P <b> 1 emitted in the side surface direction of the LED chip 21 is emitted to the outside without being blocked by the glass epoxy substrate 25.

  Here, by manufacturing the protruding portion 23 by Cu plating, the upper edge portion 23A is naturally rounded, for example, with a radius of curvature R1 = 10, 20 or 50 μm depending on the manufacturing conditions. In order to prevent peeling from the silicone resin 26, the radius of curvature of this roundness is preferably 1/50 or more of the height of the protrusion 23 (10 μm or more in the present embodiment), and about 1/10 ( In this embodiment, 50 μm) is considered more preferable. The reason why the radius of curvature is defined with respect to the height of the protruding portion 23 is that the amount of thermal expansion in the height direction is “L1 × thermal expansion coefficient difference × temperature change amount”. This curvature radius can be adjusted, for example, by adjusting the formation conditions of plating. The upper limit of the ratio of the radius of curvature to the height of the protruding portion may be 1 or less, but is preferably 1/2 or less in order to reduce the distance between the LED chip 21 and the glass epoxy substrate 25 for miniaturization.

  In addition, as a formation method of the protrusion part 23, normal electroplating may be sufficient and electroless plating may be sufficient. As a material for plating, Ni or the like may be used in addition to Cu. Also, a method other than plating, for example, a method of pressing the Al substrate 24 from the downward direction in FIG. 1 can make the portion corresponding to the edge 23A rounded. Further, as the protruding portion 23, a heat transfer material such as a metal material or a heat transfer ceramic material having a rounded portion corresponding to the edge portion 23A may be attached. In order to improve the reflectivity, it is preferable to thinly coat a material having a good reflectivity such as Ag by a method such as plating after the protrusion is formed.

  Further, in order to further suppress the peeling from the silicone resin 26, for example, the hem 23B is rounded (curvature radius R2) so that the hem of the protrusion 23, that is, the hem at the boundary with the Al substrate 24 becomes gentle. Is formed to be 10 μm to 50 μm.

  Thus, even if the operation test of the LED lighting device was performed by eliminating the acute angle portion in the protruding portion 23, the peeling from the silicone resin 26 as the sealing material did not occur.

  Regarding heat dissipation, since the projecting portion 23 made of a material having good thermal conductivity is selected and inserted directly under the LED chip 21, the heat generated in the LED chip 21 can be efficiently transmitted to the Al substrate 24. . The heat transmitted to the Al substrate 24 can be effectively dissipated from the back surface (the side opposite to the side where the LED chip or the like is disposed). If a heat radiation fold or the like (not shown) is arranged on the back surface, a further heat radiation effect can be obtained.

  Although the p-side electrode and the n-side electrode are formed on one surface of the LED chip 21 and two wires are bonded with the surface as the upper surface, the protruding portion 23 is shown with the electrode formation surface down. A so-called flip chip arrangement on the side may be employed. Further, a p-side electrode formed on one surface of the LED chip and an n-side electrode formed on the opposite surface may be used. In this case, one wire bonding may be performed on the upper electrode. . Although the LED chip 21 emits blue light, the emission color is not limited to this, and for example, ultraviolet light or green light may be used. Moreover, although the method of obtaining the white color by converting the light emitted from the LED chip 21 with the phosphor has been shown, it is possible to illuminate the white color by using, for example, three red, green, and blue LED chips without using the phosphor. You may get the color you want.

  Although the case where one LED chip 21 is mounted on the protruding portion 23 is illustrated, a plurality of LED chips are mounted on one protruding portion 23 in order to secure a light amount or use LED chips of a plurality of colors. May be.

(Arrangement of LED chip in Embodiment 1)
As shown in FIG. 2 which is a schematic top view, the protrusions 23 which are LED chip mounting portions are arranged at the vertices of an equilateral triangle at intervals of L3 = 2 mm (a plurality of LED chips are mounted on each protrusion 23. However, in this embodiment, one LED chip is mounted). When arranging LED chip mounting parts densely, in the case of an equilateral triangle arrangement, the distance from one LED chip mounting part to the adjacent LED chip mounting part is arranged concentrically and is constant, so the distance is By setting the necessary and sufficient value, it is difficult for the light emitted from each LED chip to be blocked by the resin including the adjacent LED chip. Therefore, in the LED lighting device in which the LED chips are mounted on the protruding portions, the LED chip mounting portions can be densely packed as compared with the lattice arrangement in which the distance to the adjacent LED chip mounting portion is non-uniform.

  In addition, a plurality of LED chips constituting the LED lighting device are not covered with a resin as a whole, but each LED chip mounting portion is covered with a resin containing a phosphor. In this method, the length of the light emitted from the LED chip 21 passing through the silicone resin 26 is not so long for the light emitted in the lateral direction as compared to the light emitted upward, so that the color non-uniformity is small. (When the light passes through the resin containing the phosphor for a long time, the amount of blue light converted into fluorescence increases, so the yellow component increases). Moreover, the amount of resin used can also be suppressed. Furthermore, by sealing the resin for each LED chip mounting portion, the difference in thermal expansion coefficient between the silicone resin 26 and the Al substrate 24 / projecting portion 23 is not added in the length direction, so both are difficult to peel off. It also has the advantage of becoming.

  At this time, the side wall surface of the silicone resin 26 in which the phosphor 29 is dispersed is preferably as vertical as possible. When the blue light and yellow light produced inside reach the substantially vertical side wall surface of the phosphor 29, it is refracted and travels substantially upward (light ray P1). The white light traveling upward is used as illumination light. In this way, by using the light emitted from the side surface, good light extraction efficiency can be obtained without using a reflector.

(Embodiment 2)
FIG. 3 shows a schematic cross-sectional view of the lighting apparatus according to Embodiment 2 of the present invention (the same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted). FIG. 3 shows the structure of the first embodiment shown in FIG. 1 in which a reflector 28 is arranged around each silicone resin 26 including the LED chip 21 and the like. The reflector 28 is made of a metal plate such as Al, and a plurality of holes are formed in a portion where the LED chip is disposed, and the wall surface is processed so as to form a reflector. By disposing the reflector 28, the blue light and yellow light transmitted through the side wall surface of the silicone resin 26 including the phosphor 29 are reflected upward (light ray P2), and the higher on-axis luminous intensity (outgoing light) is obtained as an illumination device. (Brightness in the direction) can be obtained.

  Here, since the reflector 28 is not in contact with the silicone resin 26, there is an advantage that the problem of peeling between the two does not occur. Also, from the point of light emission, since the light is once extracted from the side surface of the silicone resin 26 and then the direction is changed, the light extraction efficiency is superior to the case where the reflector is covered with the resin.

  FIG. 4 shows a schematic top view of the lighting device of the second embodiment. The protrusion 23 on which the LED chip 21 is mounted is disposed at the apex of an equilateral triangle when viewed from the top. Since there is the reflector 28, even if the interval between the LED chips 21 is narrower than that in the first embodiment, the light beam P2 does not enter the adjacent silicone resin 26 and cause a loss. Therefore, the LED chips 21 can be placed more densely. In the present embodiment, the distance L4 between the LED chips 21 is 1.2 mm.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. Embodiments are also included in the technical scope of the present invention.

It is a cross-sectional schematic diagram of the illuminating device which concerns on 1st Embodiment. It is an upper surface schematic diagram of the illuminating device which concerns on 1st Embodiment. It is a cross-sectional schematic diagram of the illuminating device which concerns on 2nd Embodiment. It is an upper surface schematic diagram of the illuminating device which concerns on 2nd Embodiment. It is the cross-sectional schematic diagram of the conventional illuminating device, and its enlarged view.

Explanation of symbols

21 LED chip 22 Au wire 23 Projection 23A Edge 23B Bottom 24 Al substrate 25 Glass epoxy substrate 26 Silicone resin 27 Die bond paste 28 Reflector 29 Phosphor P1 light P2 light

Claims (11)

A thermally conductive substrate;
A heat transfer protrusion formed on the heat transfer substrate;
At least one LED chip mounted on the heat transfer protrusion;
A sealing material covering the LED chip and the heat conductive protrusion,
The LED lighting device, wherein an edge of the heat transfer protrusion is rounded.   2. The LED lighting device according to claim 1, wherein a radius of curvature of an edge of the heat transfer protrusion is 1/50 or more of a height of the heat transfer protrusion.   The LED lighting device according to claim 1, wherein a boundary between the heat conductive substrate and the heat conductive protrusion is rounded. A wiring board is arranged in addition to the protrusion and its vicinity on the heat conductive substrate,
4. The LED lighting device according to claim 1, wherein an upper surface of the heat conductive protrusion is equal to or higher than an upper surface of the wiring board. 5.   The LED lighting device according to any one of claims 1 to 4, wherein the heat transfer protrusion is a metal.   The LED lighting device according to claim 5, wherein the heat transfer protrusion is formed by plating.   The LED lighting device according to claim 1, wherein the LED lighting device has a plurality of the heat transfer protrusions on the heat transfer substrate.   The LED lighting device according to claim 7, wherein the plurality of heat transfer protrusions are individually sealed with the sealing material.   The LED lighting device according to claim 7, wherein the plurality of heat transfer protrusions are arranged at the apexes of a substantially equilateral triangle.   The LED illumination device according to claim 4, wherein a reflector portion is formed on the wiring board.   The LED lighting device according to claim 10, wherein the reflector portion is not in contact with the sealing material.

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