JP2019212658A - Light-emitting device - Google Patents

Abstract

To provide a light-emitting device that suppresses a difference in temperature in a light-emitting area.SOLUTION: A light-emitting device includes a mounting board 11 having a mounting area 11A, a plurality of light-emitting elements 20 arranged in the mounting area 11A, a plurality of bonding portions 60 that bond the mounting substrate 11 and the plurality of light emitting elements 20, a frame 40 arranged around the light-emitting element 20, and a sealing member 50 disposed inside the frame so as to seal the plurality of light-emitting elements 20, and the thickness of the bonding portion 60 for mounting the light-emitting element 20 on the mounting substrate 11 at the peripheral portion of the mounting area 11A is set to be greater than the thickness of the bonding portion 60 for mounting the light-emitting element 20 on the mounting substrate 11 at the center of the mounting area 11A.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light emitting device.

  Light emitting devices using light emitting elements such as LED (light-emitting diode) elements are widely used for illumination and the like.

  For example, Patent Document 1 describes a light-emitting device that mounts a plurality of LED chips on a mounting substrate with high density using a COB (Chip On Board) method.

Japanese Unexamined Patent Publication No. 2017-5135

  In the COB light emitting device, heat generated from a plurality of light emitting elements is generally more easily radiated in the peripheral portion than in the central portion of the mounting region. For this reason, when the light-emitting device is continuously turned on, the light-emitting element disposed in the central portion of the mounting region tends to have a higher temperature than the light-emitting element disposed in the peripheral portion. The temperature difference between the light emitting elements caused by the difference in the position in the mounting region causes uneven color and / or cracks of the sealing member disposed around the light emitting element, and is preferably reduced.

  An object of the present invention is to provide a light emitting device that reduces a temperature difference between light emitting elements.

  A light-emitting device according to the present invention includes a mounting substrate having a mounting region, a plurality of light-emitting elements arranged in the mounting region, a plurality of bonding portions that bond the mounting substrate and each of the plurality of light-emitting elements, A frame body disposed around the frame body and a sealing member disposed inside the frame body so as to seal the plurality of light emitting elements, and the light emitting element is mounted on the mounting substrate in a peripheral portion of the mounting region. Therefore, the thickness of the bonding portion is set so as to be thicker than the thickness of the bonding portion for mounting the light emitting element on the mounting substrate in the central portion of the mounting region.

  According to the light emitting device of the present invention, it is possible to reduce the temperature difference between the light emitting elements.

(A) is a top view of an example of the light-emitting device 1, (B) is the sectional view on the AA 'line of (A), (C) is the elements on larger scale of (B). It is a graph which shows the relationship between the position of the adhesion part 60, and thickness. 3 is a schematic diagram showing a state of heat transfer in the light emitting device 1. FIG. 6 is a graph showing experimental results regarding the temperature of the light emitting element 20.

  Hereinafter, a light emitting device according to the present invention will be described in detail with reference to the accompanying drawings. However, it should be noted that the technical scope of the present invention is not limited to these embodiments, but extends to the invention described in the claims and equivalents thereof.

<Embodiment>
1A is a plan view of an example of the light-emitting device 1, FIG. 1B is a cross-sectional view taken along the line AA ′ of FIG. 1A, and FIG. 1C is FIG. 2 is a partially enlarged view of a portion indicated by an arrow A in FIG. In FIG. 1A, the display of the sealing member is omitted.

  The light emitting device 1 includes a substrate 10, a light emitting element 20, a frame body 40, a sealing member 50, an adhesive portion 60, and the like.

  The substrate 10 includes a mounting substrate 11 and a circuit substrate 12. The mounting substrate 11 is a metal substrate having a square shape and having a mounting region 11A in which the light emitting element 20 is mounted at the center of the upper surface thereof. Since the mounting substrate 11 also functions as a heat dissipation substrate that dissipates heat generated by the light emitting element 20, it is made of aluminum having excellent heat resistance and heat dissipation, and its thermal conductivity is 236 (W / m * K). It is.

  The mounting substrate 11 may have a shape other than a square (for example, a rectangle, a circle, etc.). If the material of the mounting substrate 11 is excellent in heat resistance and heat dissipation, for example, copper or the like may be used. Any metal may be used.

  The circuit board 12 has the same shape and the same size as the mounting board 11, and a circular opening 12A is formed at the center thereof. The circuit board 12 is fixed by attaching the back surface of the circuit board 12 onto the mounting board 11 with an adhesive member such as an adhesive sheet. The mounting area 11A of the mounting substrate 11 is exposed from the opening 12A, and the opening 12A defines the outer edge of the mounting area 11A. A pair of wiring patterns 13A and 13B is formed on the surface of the circuit board 12 so as to surround the opening 12A. A pair of connection electrodes 17A and 17B for connecting the light emitting device 1 to an external power source are formed at two corners diagonally located on the surface of the circuit board 12, and are connected to the wiring patterns 13A and 13B, respectively. doing. One connection electrode 17A is an anode, and the other connection electrode 17B is a cathode. The circuit board 12 and the pair of wiring patterns 13A and 13B are covered and protected by a resist 14 that is an insulating film.

  The light emitting elements 20A to 20D (collectively simply referred to as the light emitting elements 20) are blue semiconductor light emitting elements (hereinafter also referred to as blue LED elements) formed in a rectangular shape, and are mounted on the mounting region 11A. A plurality are arranged. The four light emitting elements 20A are arranged in the central part 11C of the mounting region 11A, and the ten light emitting elements 20B are arranged in the donut-shaped first peripheral part 11D adjacent to the outside of the central part 11C. The 16 light emitting elements 20C are arranged in a donut-shaped second peripheral part 11E adjacent to the outside of the first peripheral part 11D, and the 18 light-emitting elements 20D are a donut type adjacent to the outside of the second peripheral part 11E. The third peripheral portion 11F is disposed. The boundary between the central portion 11C and each peripheral portion has a circular shape centering on the central point 11B of the mounting region 11A. The upper surface of the light emitting element 20 is disposed in parallel with the surface of the mounting substrate 11, and the lower surface is bonded to the mounting substrate 11 by the bonding portion 60. Although the InGaN-based compound semiconductor having an emission wavelength range of 440 to 455 nm is used for the light emitting element 20, the light emitting element 20 may be an element that emits light other than blue light.

  The total number of the light emitting elements 20 is an example, and may be another number. In that case, the series and the parallel can also be changed according to the specifications required for the light emitting device.

  The light emitting element 20 has a pair of element electrodes 21 and 22 on the surface, and the element electrode 21 and the element electrode 22 of the adjacent light emitting element 20 are electrically connected by a wire 30. The wire 30 connects the light emitting element 20 positioned on the outer peripheral side of the opening 12A and the wiring pattern 13A or 13B of the circuit board 12, and the plurality of light emitting elements 20 are connected to the connection electrode 17A via the wiring patterns 13A and 13B. And 17B are connected in series. Between the wiring patterns 13A and 13B, four sets of twelve light emitting elements connected in series by wires 30 are connected in parallel. When a direct current voltage is applied to the connection electrodes 17A and 17B from an external power source (not shown), the plurality of light emitting elements 20 are supplied with a direct current via the wiring patterns 13A and 13B and the wires 30 and emit light.

  The frame 40 is a frame-shaped member formed by curing a silicon resin mixed with white powder on the substrate 10 and is disposed so as to surround the plurality of light emitting elements 20. The cross-sectional shape of the frame 40 is a convex shape with a high center and a low periphery. The frame body 40 is a dam material for preventing the sealing member 50 from flowing out, and reflects the light emitted from the light emitting element 20 toward the frame body 40 to be emitted above the light emitting device 1.

  The sealing member 50 is a member in which a phosphor is contained in a translucent silicon resin, and is disposed inside the frame body 40 to integrally seal the plurality of light emitting elements 20. As the phosphor, YAG (yttrium aluminum garnet) that absorbs the blue light emitted from the light emitting element 20 and converts the wavelength into yellow light is used, and the blue light and the yellow light wavelength-converted by the phosphor are mixed. Thus, white light is emitted from the light emitting device 1. The sealing member 50 may be a member in which a phosphor is contained in another resin such as an epoxy resin instead of the silicon resin. The thermal conductivity of the sealing member 50 is 0.15 (W / m * K). The surface of the sealing member 50 having the frame body 40 as an outer edge may be referred to as a light emitting region 50A.

  The bonding portion 60 is a member obtained by curing a die bonding material for bonding the light emitting element 20 to the mounting substrate 11. The die bond agent is an insulating resin paste. The thermal conductivity of the bonding portion 60 is 0.15 (W / m * K). The thickness of the bonding portion 60 is a thickness after the die bonding material is cured, and is gradually increased from the central portion 11C of the mounting region 11A toward the third peripheral portion 11F. The thickness of the adhesion part 60 is implement | achieved by adjusting the viscosity, thixotropy, etc. of a die-bonding material.

  FIG. 2 is a graph showing the relationship between the position and thickness of the bonded portion 60.

  The thickness of the bonding portion 60 that bonds each light emitting element 20 is set according to the distance from the center point 11B of the mounting region 11A to the center of each light emitting element 20 and the relationship shown in FIG. The thickness of the bonding portion 60 is shown as a relative thickness when the thickness h1 of the bonding portion 60A is 1. In the embodiment, the thickness h1 of the bonding portion 60A that bonds the light emitting element 20A is 2 μm, and the thickness h2 of the bonding portion 60B that bonds the light emitting element 20B is 6 μm. The thickness h3 of the bonding portion 60C for bonding the light emitting element 20C is 22 μm, and the thickness h4 of the bonding portion 60D for bonding the light emitting element 20D is 50 μm.

  Note that the relationship between the distance from the center point 11B of the mounting region 11A shown in FIG. 2 to the center of each light emitting element 20 and the thickness of the adhesive portion 60 is an example, and the distance and thickness are proportional to each other. The relationship may be

<Operational Effect of Light Emitting Device According to Embodiment>
FIG. 3 is a schematic diagram illustrating a state of heat transfer in the light emitting device 1.

  The main heat generated in the light emitting device 1 is heat directly generated from the light emitting element 20 and heat generated when the phosphor included in the sealing member 50 converts the wavelength of light. The heat generated directly from the light emitting element 20 will be mainly discussed.

  In the light emitting device 1 according to the embodiment, heat generated when the light emitting element 20 emits light is transmitted to the mounting substrate 11 mainly through the bonding portion 60 and is radiated from the mounting substrate 11 to the outside of the light emitting device 1. . Further, since the adhesive portion 60B in the first peripheral portion 11D is thicker than the adhesive portion 60A in the central portion 11C of the mounting region 11A, the thermal resistance of the adhesive portion 60B is larger than the thermal resistance of the adhesive portion 60A. Due to the difference in thermal resistance between the bonding portions 60A and 60B, the amount of heat transferred from the light emitting element 20B to the mounting substrate 11 via the bonding portion 60B is the amount of heat transferred from the light emitting element 20A to the mounting substrate 11 via the bonding portion 60A. Less. The heat that is not transferred from the light emitting element 20B to the mounting substrate 11 raises the temperature of the light emitting element 20B. However, since the temperature of the light emitting element 20B is lower than the temperature of the light emitting element 20A, the temperature difference between the light emitting element 20B and the light emitting element 20A is Decrease.

  Since the temperature difference between the light emitting element 20B and the light emitting element 20A is reduced, the degree of discoloration due to heat of the sealing member 50 in the vicinity of each light emitting element is made uniform, so that the sealing in the vicinity of the light emitting elements 20A and 20B is performed. The uneven color of the light emitted through the stop member 50 is reduced. Further, since the temperature difference between the light emitting element 20B and the light emitting element 20A is reduced, the occurrence of cracks in the sealing member 50 is reduced in the vicinity of the light emitting elements 20A and 20B.

  The relationship between the light emitting elements 20A and 20B described above is similarly established for the light emitting elements 20A and 20C and 20A and 20D. For this reason, the color unevenness of the light emitted from the entire light emitting region 50A is reduced, and the occurrence of cracks in the sealing member 50 is reduced.

<Experimental result>
FIG. 4 is a graph showing experimental results regarding the temperature of the light emitting element 20. The light-emitting device 1 shown in FIG. 1 was used for the experiment. Table 1 shows the main conditions of the experiment.

  In general, if the temperature difference between the light emitting elements 20A to 20D is within 2 ° C., the color unevenness of the sealing member 50 can be within an allowable range. Can be within an allowable range. Here, the occurrence of color unevenness within an allowable range means a range where the color difference ΔE ≦ 0.8 in the CIELAB color space or the CIELV color space. As a result of the experiment, as shown in FIG. 4, the average temperature of the four light emitting elements 20A is about 140 ° C., the average temperature of the ten light emitting elements 20B is about 138 ° C., and the average temperature of the sixteen light emitting elements 20C is about 135. The average temperature of 18 light emitting elements 20D was about 131 ° C. Since the maximum value of the temperature difference is about 9 ° C. of the temperature difference between the light emitting element 20 </ b> A and the light emitting element 20 </ b> D, the light emitting device 1 can keep the uneven color and cracks of the sealing member 50 within the allowable range. did it.

  In the light emitting device 1 shown in FIG. 1, four levels of adhesive are used according to the distance from the center point 11B of the mounting region 11A, but other floors may be used.

  As described above, by thickening the bonding portion for bonding the light emitting element and the mounting substrate at the peripheral portion, the bonding portion for bonding the light emitting element and the mounting substrate at the peripheral portion is made thicker in the light emitting region. The temperature difference between the light emitting elements can be reduced.

DESCRIPTION OF SYMBOLS 1 Light-emitting device 11 Mounting board 11A Mounting area 20, 20A, 20B, 20C, 20D Light emitting element 40 Frame body 50 Sealing member 60, 60A, 60B, 60C, 60D Bonding part

Claims (2)

A mounting board having a mounting area;
A plurality of light emitting elements arranged in the mounting region;
A plurality of bonding portions for bonding the mounting substrate and each of the plurality of light emitting elements;
A frame disposed around the light emitting element;
A sealing member disposed inside the frame so as to seal the plurality of light emitting elements,
The thickness of the adhesive portion for mounting the light emitting element on the mounting substrate in the peripheral portion of the mounting area is the same as the thickness of the adhesive portion for mounting the light emitting element on the mounting substrate in the central portion of the mounting area. Set to be thicker than the thickness,
A light emitting device characterized by that.   2. The light emitting device according to claim 1, wherein a thickness of the adhesive portion is set so as to gradually increase from the central portion of the mounting region toward the peripheral portion.

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