JP2012248573A - Light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both insulation quality and heat radiation performance for a mounting method of a light emitting element using conductive adhesives.SOLUTION: An LED light source 10 includes: an LED chip 11; conductive adhesives 13a, 13b; an insulation structure 14; a substrate 16; and a resist layer 17. Two pieces of wiring 15a, 15b are provided on a surface of the substrate 16. Two electrode 12a, 12b are provided on a bottom surface of the LED chip 11. The bottom surface side of the LED chip 11 is mounted on the front surface side of the substrate 16 through the two conductive adhesives 13a, 13b. The insulation structure 14 is provided at an area which is disposed between the surface of the substrate 16 and the bottom surface of the LED chip 11 and is located between the two conductive adhesives 13a, 13b.

Description

  The present invention relates to a light emitting device. The present invention particularly relates to an LED light source in which an LED (light emitting diode) chip having an electrode on an adhesive surface is mounted on a wiring board.

  2. Description of the Related Art Conventionally, in some LED light sources, an LED chip mounting method in which an electrode is provided below a light emitting element and connected to a wiring board using a conductive adhesive is used. Since bonding at a low temperature is possible compared to metal eutectic bonding, there is an advantage that options for a wiring board on which an LED chip is mounted are widened (for example, see Patent Documents 1 and 2).

JP-A-11-168235 JP 2007-49045 A

  In the mounting form of Patent Document 1, the heat conductivity of the conductive adhesive is poor, and there are bumps for connection, and there is a problem in heat dissipation. Although the thermal conductivity is improved by increasing the density of the metal conductive particles of the conductive adhesive, it is necessary to consider the insulation between the electrodes, so that the blending amount cannot exceed a certain level.

  In the semiconductor device of Patent Document 2, the above problem is addressed by the structure of the LED chip, but the structure on the LED chip side is complicated. Furthermore, some distance between the electrodes is required, and there is room for improvement in heat dissipation.

  An object of the present invention is to achieve both insulation and heat dissipation in a method for mounting a light emitting element using a conductive adhesive, for example.

A light emitting device according to one embodiment of the present invention includes:
A substrate having a surface provided with two wirings;
A light-emitting element having a bottom surface provided with two electrodes, a conductive adhesive electrically connecting one of the two wirings and one of the two electrodes, the other of the two wirings, and the two electrodes A light emitting element whose bottom surface is mounted on the surface side of the substrate via two conductive adhesives and a conductive adhesive that electrically connects the other of
And an insulating member provided between the surface of the substrate and the bottom surface of the light emitting element and provided between the two conductive adhesives.

  According to one aspect of the present invention, it is possible to achieve both insulation and heat dissipation by a method for mounting a light emitting element using a conductive adhesive.

Sectional drawing of the LED light source which concerns on Embodiment 1. FIG. FIG. 3 is a perspective view of a substrate according to the first embodiment. Sectional drawing of the LED light source which concerns on Embodiment 2. FIG. FIG. 5 is a perspective view of a substrate according to Embodiment 2. FIG. 6 is a perspective view of a substrate according to Embodiment 3. 10 is a graph showing a relationship between a load and a displacement when an LED chip of the LED light source according to Embodiment 3 is mounted. Sectional drawing of the LED light source which concerns on Embodiment 4. FIG. FIG. 6 is a perspective view of a substrate according to Embodiment 4.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of each embodiment, directions such as “up”, “down”, “left”, “right”, “front”, and “rear” are shown as such for convenience of explanation. The arrangement and orientation of the devices, instruments, parts, etc. are not limited.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view of an LED light source 10 according to the present embodiment. FIG. 2 is a perspective view of the substrate 16 of the LED light source 10.

  As shown in FIG. 1, the LED light source 10 includes an LED chip 11, conductive adhesives 13 a and 13 b, an insulating structure 14, a substrate 16, and a resist layer 17. Two wirings 15 a and 15 b are provided on the surface of the substrate 16. Two electrodes 12 a and 12 b (an anode electrode and a cathode electrode) are provided on the bottom surface of the LED chip 11. The LED chip 11 is mounted on the surface side of the substrate 16 on the bottom surface side via two conductive adhesives 13a and 13b.

  The resist layer 17 reflects light that hits the surface side of the substrate 16 among the light emitted from the LED chip 11. Thereby, the luminous efficiency of the LED light source 10 increases.

  The conductive adhesive 13a electrically connects the electrode 12a and the wiring 15a. In addition, the conductive adhesive 13b electrically connects the electrode 12b and the wiring 15b. These two conductive adhesives 13a and 13b are both thermosetting adhesives containing conductive particles such as metal particles. Examples of the resin material include epoxy resin, acrylic resin, and silicone resin. As the metal particles, Ni, Au, Sn, Al, Ag, Cu, Fe or other metals or their alloys are used. In addition, it is also possible to use the particle | grains which covered resin with the said metal as electroconductive particle. Moreover, you may mix | blend combining multiple types of electrically-conductive particles, such as a metal particle and a resin particle.

  The insulating structure 14 (insulating member) is provided between the surface of the substrate 16 and the bottom surface of the LED chip 11, and is provided between the two conductive adhesives 13a and 13b. In the present embodiment, the insulating structure 14 is erected between the two wirings 15 a and 15 b on the surface of the substrate 16, and the tip (upper end) of the insulating structure 14 is two electrodes 12 a and 12 b on the bottom surface of the LED chip 11. It adheres between. Thereby, the conductive adhesives 13a and 13b can be separated to prevent a short circuit between the electrodes 12a and 12b.

  As a modification of the present embodiment, the insulating structure 14 protrudes from between the two electrodes 12 a and 12 b on the bottom surface of the LED chip 11, and the tip (lower end) of the two wirings 15 a and 15 b on the surface of the substrate 16. You may make it closely_contact | adhere between them. Also in this case, similarly to the above, the conductive adhesives 13a and 13b can be separated to prevent a short circuit between the electrodes 12a and 12b.

  As shown in FIG. 2, the insulating structure 14 is provided so as to cross the bottom surface of the LED chip 11. Specifically, the insulating structure 14 is formed in a substantially I shape (“one” shape) in plan view. The insulating structure 14 is formed so as to be sandwiched between the wirings 15a and 15b on the substrate 16 in the short direction. The insulating structure 14 is formed of polyimide resin, epoxy resin, urethane resin, acrylic resin, silicone resin, or the like. The thickness of the insulating structure 14 is desirably 100 μm (micrometers) or less. The width of the insulating structure 14 is desirably about 20 to 100 μm depending on the distance between the electrodes 12a and 12b.

  In the present embodiment, the insulating structure 14 has a width of the upper surface that is smaller than the width of the bottom surface in the short direction (front view) (for example, has a substantially trapezoidal shape in cross section). Therefore, the width of the tip portion of the insulating structure 14 (the portion that contacts the bottom surface of the LED chip 11) can be reduced without impairing the stability and rigidity of the insulating structure 14. Therefore, the distance between the electrodes 12a and 12b can be short, and the area of the electrodes 12a and 12b can be increased. If the area of the electrodes 12a and 12b is large, the light emitting layer of the LED chip 11 can be increased correspondingly, so that the output of the LED chip 11 can be increased.

  When the LED chip 11 is mounted on the substrate 16, first, conductive adhesives 13 a and 13 b are applied to a predetermined range on both the left and right sides of the insulating structure 14 on the substrate 16 shown in FIG. 2. Next, the LED chip 11 is mounted on the substrate 16 so that the upper end of the insulating structure 14 is in contact between the electrodes 12a and 12b on the bottom surface of the LED chip 11 and the electrodes 12a and 12b are in contact with the conductive adhesives 13a and 13b, respectively. Placed in. When the LED chip 11 is pressed in the direction (downward) of the substrate 16 with a certain force, the conductive adhesives 13a and 13b are appropriately compressed, and the LED chip 11 and the substrate 16 are bonded (physical connection). ) And conduction (electrical connection) between the electrodes 12a and 12b and the wirings 15a and 15b. Finally, a resist layer 17 is formed on the entire periphery of the LED chip 11 on the substrate 16.

  When the LED chip 11 is mounted on the substrate 16 in this manner, a current to the LED chip 11 input from the power supply device (not shown) to the substrate 16 is transmitted from the wirings 15a and 15b to the conductive adhesives 13a and 13b. After that, it can be supplied to the electrodes 12a and 12b of the LED chip 11.

  The LED chip 11 generates heat during light emission, and this heat is radiated from the electrodes 12a and 12b to the substrate 16 through the conductive adhesives 13a and 13b and the wirings 15a and 15b. At this time, by increasing the mixing amount of the conductive particles of the conductive adhesives 13a and 13b, the electrical resistance and the thermal resistance during heat dissipation are reduced, and the reliability of electrical connection is further improved. In calculation, the thermal resistance can be reduced to 1/10 by increasing the number of conductive particles of the conductive adhesives 13a and 13b 10 times. At the same time, as the number of connecting particles (conductive particles) increases, the circuit on the substrate 16 has redundancy and the reliability is improved.

  According to the present embodiment, since the insulating structure 14 is arranged so as to enter between the electrodes 12a and 12b, the electrodes 12a and 12b are not short-circuited even if the particle density of the conductive particles is increased. In the conventional mounting method, since the probability of occurrence of a short circuit due to conductive particles increases, it is necessary to increase the distance between the electrodes or decrease the density of the conductive particles. However, according to the structure of the present embodiment, a short circuit occurs. Without increasing the density of the conductive particles, the density of the conductive particles can be increased. At the same time, the distance between the electrodes 12a and 12b can be reduced.

  For example, the insulating structure 14 may include a filler made of an inorganic material in order to increase the light reflectance. In this way, by using a material having a high light reflectivity for the insulating structure 14, the light striking between the electrodes 12 a and 12 b and the periphery of the electrodes 12 a and 12 b is reflected, and the light utilization efficiency is improved as compared with the case without the insulating structure 14. Can be improved.

  The LED light source 10 is an example of a light emitting device, and may include a light emitting element other than the LED chip 11 (for example, organic EL (electroluminescence)).

  A plurality of LED chips 11 may be mounted on the substrate 16. In this case, an insulating structure 14 is provided for each LED chip 11.

  As described above, the LED light source 10 according to the present embodiment includes the LED chip 11, the substrate 16, the insulating structure 14 provided on the substrate 16, the conductive adhesives 13 a and 13 b including conductive particles, and the substrate 16. It is comprised from the reflecting material (resist layer 17). In the LED light source 10, an insulating structure 14 having a thickness of about 100 μm or less is used in which a protrusion formed of an insulating material separates the conductive adhesives 13a and 13b containing conductive particles to ensure insulation. In this embodiment, since the insulating structure 14 enters between the electrodes 12a and 12b on the lower surface of the LED chip 11 and separates the conductive adhesives 13a and 13b, the mixing amount of particles having high thermal conductivity and electrical conductivity is increased. Even if it is increased, short-circuit between the electrodes 12a and 12b due to particles does not occur, heat from the LED chip 11 during light emission can be efficiently radiated, and connection resistance can be reduced and connection reliability can be improved. become. At the same time, the luminous efficiency of the LED light source 10 is increased.

  According to the present embodiment, in the mounting method of the LED chip 11 with the conductive particles interposed, even when the density of the conductive particles is increased to reduce the electrical resistance and increase the heat dissipation, the lower part of the LED chip 11 is reduced. It avoids the occurrence of an electrical short circuit due to high density of conductive particles filled between the electrodes 12a and 12b, ensures insulation between the electrodes 12a and 12b, and causes ion migration and deterioration of insulating resin even in long-term use. The electrical short circuit resulting from this can be suppressed.

  Furthermore, when a material having a high light reflectance is used for the insulating structure 14, the insulating structure 14 can reflect light while reducing the distance between the electrodes 12a and 12b below the LED chip 11, In the LED chip 11 in which the light emitting layer is formed in a layer structure with the anode or cathode electrode, the ratio of the light emitting area within the chip area is designed to be large, and the amount of reflected light near the electrodes 12a and 12b is further increased. It becomes possible.

Embodiment 2. FIG.
In the present embodiment, differences from the first embodiment will be mainly described.

  FIG. 3 is a cross-sectional view of the LED light source 10 according to the present embodiment. FIG. 4 is a perspective view of the substrate 16 of the LED light source 10.

  As shown in FIG. 3, the LED light source 10 includes an LED chip 11, conductive adhesives 13 a and 13 b, an insulating structure 14, a substrate 16, and a resist layer 17, as in the first embodiment.

  In the present embodiment, as shown in FIG. 4, the insulating structure 14 extends along a part of the outer peripheral portion of the bottom surface of the LED chip 11, and the extended portion connects the LED chip 11 to the LED chip 11. It is supported from the bottom side. That is, the insulating structure 14 is also disposed at a portion surrounding the LED chip 11. Specifically, the insulating structure 14 is formed in a substantially H shape (“e” shape) in plan view. As described above, by extending the insulating structure 14 around the mounting position of the LED chip 11, it is possible to control (limit) the flow range of the conductive adhesives 13a and 13b. That is, the conductive adhesives 13 a and 13 b can be prevented from flowing around the LED chip 11. Thereby, the light from the LED chip 11 is emitted to the surroundings without being blocked by the conductive adhesives 13a and 13b, so that the light emission efficiency of the LED light source 10 is increased.

  As in the first embodiment, for example, the insulating structure 14 may include a filler composed of an inorganic material in order to increase the light reflectance. Since the light emission from the side surface of the LED chip 11 may reach a maximum of 20 to 30% from a few percent of the light emission of the LED chip 11 as a whole, if the reflectance around the LED chip 11 increases, the light emission efficiency of the LED light source 10 also increases. Increases significantly.

  As described above, in the LED light source 10 according to the present embodiment, as in the first embodiment, the LED chip 11 having the anode electrode and the cathode electrode on the bottom surface and the conductive particles are mixed with the insulating resin material. The structure is mounted on the substrate 16 by the conductive adhesives 13a and 13b. In this structure, the electrodes 12a and 12b on the bottom surface of the LED chip 11 are made as large as possible, the distance between the electrodes 12a and 12b is narrowed, and an insulating structure 14 having a high light reflectivity is provided on the substrate 16 in advance. The luminous efficiency of the LED light source 10 is improved while limiting the flow range of the adhesives 13a and 13b.

  In the present embodiment, the insulating structure 14 is extended around the LED chip 11 to limit the flow range of the conductive adhesives 13a and 13b. Thereby, it is possible to suppress the conductive adhesives 13a and 13b from flowing around the LED chip 11, and to irradiate the surroundings without disturbing the light emitted from the LED chip 11. Therefore, the luminous efficiency of the LED light source 10 is increased.

Embodiment 3 FIG.
The difference between the present embodiment and the second embodiment will be mainly described.

  FIG. 5 is a perspective view of the substrate 16 of the LED light source 10 according to the present embodiment.

  In the present embodiment, as shown in FIG. 5, the insulating structure 14 extends along the entire outer peripheral portion of the bottom surface of the LED chip 11, and the extended portion connects the LED chip 11 to the LED chip 11. It is supported from the bottom side. That is, the insulating structure 14 is disposed in the frame portion on the lower surface of the LED chip 11, and forms a gap corresponding to the height of the insulating structure 14 when the LED chip 11 is mounted. Specifically, the insulating structure 14 is formed in a substantially “day” shape in plan view. As described above, the flow range of the conductive adhesives 13a and 13b can be reliably controlled (restricted) by extending the insulating structure 14 around the entire mounting position of the LED chip 11.

  FIG. 6 is a graph showing the relationship between load and displacement when the LED chip 11 of the LED light source 10 is mounted.

  The load refers to the pressure applied to the LED chip 11, and when the insulating structure 14 is not present, the pressure at which the compressibility of the conductive particles contained in the conductive adhesives 13a and 13b is maximized is 100%. The displacement refers to the ratio of the pressure to the limit value when the limit value of the pressure applied to the LED chip 11 without destroying the LED chip 11 is 100%. In the present embodiment, it is assumed that a displacement of about 94 to 99% is desirable. When the displacement is less than 94%, the conductive particles contained in the conductive adhesives 13a and 13b are not sufficiently compressed, and the electrical connection between the electrodes 12a and 12b of the LED chip 11 and the wirings 15a and 15b of the substrate 16 is not good. May become stable. On the other hand, if the displacement exceeds 99%, the electrodes 12a and 12b and the light emitting layer of the LED chip 11 may be destroyed.

  As shown in FIG. 6, when the insulating structure 14 is not disposed on the lower surface of the LED chip 11, the load increases rapidly at the portion where the conductive particles are compressed as shown by the curve “without insulating structure”. For this reason, the load adjustment range when the LED chip 11 is mounted is the area A of the graph. At a load smaller than this region, the conductive particles are not sufficiently compressed, so that heat conduction and electric conduction to the LED chip 11 become unstable. On the other hand, when reaching the limit value indicated by 100% of the graph, the electrodes 12a and 12b and the light emitting layer on the lower surface of the LED chip 11 are destroyed.

  On the other hand, in the connection structure of the present embodiment, the insulating structure 14 is compressed, so that the rate of change of the compressive load with respect to the displacement is reduced as shown by the curve “with insulating structure” in the graph, which is suitable for mounting the LED chip 11 The applied load spreads as shown in the area B of the graph. For this reason, it is possible to compress the conductive adhesives 13a and 13b appropriately, achieve high thermal conductivity without destroying the LED chip 11, and realize highly reliable electrical connection. That is, in this embodiment, since a part of the insulating structure 14 enters the lower surface of the LED chip 11, the adjustment range of the load of the LED chip 11 is widened and it is easy to appropriately adjust the load. It becomes possible to suppress the destruction of the electrodes 12a and 12b and the light emitting layer of the chip 11 and the shortage of the partial conductive adhesives 13a and 13b.

  As described above, in this embodiment, the insulating structure 14 can insulate the electrodes 12a and 12b on the lower surface of the LED chip 11, and the gap between the LED chip 11 and the substrate 16 can be adjusted to be constant. Highly reliable adhesion can be realized as compared with the case of bonding only with the adhesives 13a and 13b.

  As described above, in the LED light source 10 according to the present embodiment, the insulating structure 14 is extended to the entire outer periphery of the LED chip 11, and the flow range of the conductive adhesives 13a and 13b is limited as in the second embodiment. However, since the peripheral portion further enters under the LED chip 11, the adjustment range of the applied pressure when the LED chip 11 is mounted is expanded.

  According to the present embodiment, the pressure adjustment range when the LED chip 11 is mounted is increased, so that highly reliable adhesion is possible by avoiding damage to the LED chip 11 and insufficient filling of the conductive adhesives 13a and 13b. become.

Embodiment 4 FIG.
The difference between the present embodiment and the third embodiment will be mainly described.

  FIG. 7 is a cross-sectional view of the LED light source 10 according to the present embodiment. FIG. 8 is a perspective view of the substrate 16 of the LED light source 10.

  As shown in FIG. 7, the LED light source 10 includes an LED chip 11, conductive adhesives 13 a and 13 b, an insulating structure 14, and a substrate 16. There is no resist layer 17 as in the first to third embodiments, and the insulating structure 14 also serves as the resist layer 17.

  In the present embodiment, as shown in FIG. 8, the insulating structure 14 extends outward from the outer peripheral portion of the bottom surface of the LED chip 11 to cover the substrate 16 and covers the substrate 16 (Embodiments 1 to 3). Corresponds to the resist layer 17). That is, the insulating structure 14 is applied to the entire surface of the substrate 16 on which the LED chip 11 is mounted (except for the place where the electrodes 12a and 12b of the LED chip 11 are disposed). Generally, in the LED light source, as in Embodiments 1 to 3, the mounting substrate is whitened with a resist material or the like in order to improve the usage rate of light from the LED. In the present embodiment, similarly to this, the insulating structure 14 is whitened and extended to the entire surface of the substrate 16, whereby the LED insulation effect and the light reflection effect can be obtained simultaneously. Further, since the formation of the insulating structure 14 and the whitening of the surface of the substrate 16 can be realized by the same process, the cost can be reduced.

  As described above, in the LED light source 10 according to the present embodiment, since the insulating structure 14 is enlarged and whitened over the entire substrate 16, a light reflection layer is simultaneously formed in the process of forming the insulating structure 14. Cost reduction.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these embodiment, A various change is possible as needed.

  10 LED light source, 11 LED chip, 12a, 12b electrode, 13a, 13b conductive adhesive, 14 insulating structure, 15a, 15b wiring, 16 substrate, 17 resist layer.

Claims (6)

A substrate having a surface provided with two wirings;
A light-emitting element having a bottom surface provided with two electrodes, a conductive adhesive electrically connecting one of the two wirings and one of the two electrodes, the other of the two wirings, and the two electrodes A light emitting element whose bottom surface is mounted on the surface side of the substrate via two conductive adhesives and a conductive adhesive that electrically connects the other of
A light emitting device comprising: an insulating member provided between a surface of the substrate and a bottom surface of the light emitting element and provided between the two conductive adhesives.   2. The light emitting device according to claim 1, wherein the insulating member is erected between the two wirings on a surface of the substrate, and a tip thereof is in close contact between the two electrodes on a bottom surface of the light emitting element.   The light-emitting device according to claim 1, wherein the insulating member is provided so as to cross a bottom surface of the light-emitting element.   The light-emitting device according to claim 1, wherein the insulating member extends along at least a part of an outer peripheral portion of a bottom surface of the light-emitting element.   5. The light emitting device according to claim 4, wherein a portion of the insulating member that extends along at least a part of an outer peripheral portion of the bottom surface of the light emitting element supports the light emitting element from the bottom surface side of the light emitting element. .   6. The light emitting device according to claim 4, wherein the insulating member extends outward from an outer peripheral portion of a bottom surface of the light emitting element to cover the substrate, and a portion covering the substrate reflects light.

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