JP2006269782A - Light-emitting diode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting diode provided with a substrate of a structure, capable of efficiently radiating the heat emitted from a light-emitting element to outside, without lowering the light-emitting characteristics of the light-emitting element. <P>SOLUTION: The light emitting diode 21 is provided with a flexible substrate 22 where an anode electrode 25a and a cathode electrode 25b are formed, and the light-emitting element 23 mounted on the surface of the flexible substrate 22. On the flexible substrate 22, a seating part 26 for the light-emitting element 23 which is obtained by making the flexible substrate 22 project from a rear face side toward the front face side is provided to form a recessed place 28 on the rear surface of the seating part 26, and the recessed place 28 is charged with a radiation member 31. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light emitting diode formed using a substrate having a heat dissipation effect.

  2. Description of the Related Art Conventionally, small light emitting diodes mounted on various electronic devices are composed of a resin substrate on which an electrode pattern is formed and a light emitting element mounted on the resin substrate. In such a light emitting diode, since the light emitting element is surface-mounted on a resin substrate, a through hole is provided from the surface on which the light emitting element of the resin substrate is mounted to the back surface on which the external connection electrodes are formed. Further, the through hole may be used as a thermal via for heat dissipation.

  FIG. 6 shows a light-emitting diode 1 having a structure using the through hole as a thermal via (Patent Document 1). The light emitting diode 1 includes a flat resin substrate 2 made of glass epoxy, a light emitting element 3 mounted on the surface of the resin substrate 2, and a through hole 4 penetrating the resin substrate 2. Yes. A pair of electrode patterns (anode electrode 7a and cathode electrode 7b) are formed on the resin substrate 2, and the light emitting element 3 is surface-mounted on the electrode pattern via bumps 8a and 8b. The anode electrode 7a and the cathode electrode 7b are connected to external connection electrodes 9a and 9b formed on the back surface of the resin substrate 2, respectively. The through hole 4 is formed so as to penetrate the resin substrate 2 from the front surface to the back surface, one bump 8b of the light emitting element 3 is bonded to the upper surface, and the heat radiation pattern 5 is provided on the lower surface.

In the light emitting diode 1 having the above structure, the light emitting element 3 is solder-mounted on the anode electrode 7a and the cathode electrode 7b via the bumps 8a and 8b. Further, since the bump 8b mounted on the cathode electrode 7b side is located above the through hole 4, the solder member 6 is also filled into the through hole 4 when soldered. As a result, the solder member 6 filled in the through hole 4 serves as a heat sink, and the heat generated from the light emitting element 3 can be radiated to the outside through the heat radiation pattern 5 connected to the through hole 4.
JP 2002-289923 A

  However, in the conventional light emitting diode 1, since the through hole 4 is provided inside the thin flat resin substrate 2, the volume of the through hole 4 is small, and the solder for obtaining a large heat dissipation effect The member 6 cannot be filled. In addition, the formation area of the heat radiation pattern 5 connected to the through hole 4 is limited. For this reason, there is a problem that an efficient heat dissipation effect cannot be obtained as a whole.

  Further, when the bump 8b located on the through hole 4 is joined by the solder member 6, the solder member 6 flows into the through hole 4, so that the joining position of the bump 8b is slightly smaller than the joining position of the bump 8a. Will sink down. For this reason, the light emitting element 3 is tilted with respect to the resin substrate 2, thereby causing a problem that the light emission characteristics are deteriorated.

  Accordingly, an object of the present invention is to provide a light emitting diode including a substrate having a structure capable of efficiently dissipating heat generated from the light emitting element to the outside without deteriorating the light emission characteristics of the light emitting element.

  In order to solve the above-described problems, a light-emitting diode according to the present invention includes a substrate on which an electrode pattern is formed and a light-emitting element mounted on the surface of the substrate. By providing a pedestal portion of the light emitting element that protrudes from the back surface side toward the front surface side, a recess is formed on the back surface of the pedestal portion, and a heat radiating member is filled in the recess.

  According to the light emitting diode of the present invention, the base portion from which the portion on which the light emitting element is mounted is projected is provided on the substrate, and the back surface of the base portion is a recess for filling the heat dissipation member. The heat generated from the light emitting element can be efficiently radiated through the heat radiating member filled in the recess.

  Moreover, while providing the hole part which leads to a recess from the upper surface of the said pedestal part, the back surface of a board | substrate is functioned as a heat sink with a large heat dissipation capacity by filling the heat radiating member from the said recess to the inside of a hole part. Can do.

  In addition, since a flexible substrate is used as the substrate, it is easy to form the recess, and the shape and size of the recess can be adjusted according to the shape of the light emitting element to be mounted and the heat dissipation effect.

  Hereinafter, embodiments of a light emitting diode according to the present invention will be described in detail with reference to the accompanying drawings. Here, FIG. 1 is a perspective view of the light emitting diode of the present invention, and FIG. 2 is a cross-sectional view taken along the line AA of the light emitting diode.

  As shown in FIGS. 1 and 2, the light emitting diode 21 of the present invention is mounted on a flexible substrate (hereinafter referred to as FPC) 22 on which an electrode pattern (anode electrode 25a, cathode electrode 25b) is formed, and the FPC 22. The light emitting element 23 is configured.

  The FPC 22 is formed with a pedestal 26 for mounting the light emitting element 23 at the center of the upper surface thereof. The pedestal portion 26 is formed by projecting into a trapezoidal cylindrical shape by hot pressing from the back surface of the FPC 22, and the upper surface is a mounting portion 27 on which the light emitting element 23 is surface-mounted. On the back surface side of the mounting portion 27, a space (recess) 28 raised by hot press processing is formed. The pedestal portion 26 is provided with holes (hereinafter referred to as through holes) 24 a, 24 b, 24 c that lead from the mounting portion 27 to the recess 28. The through holes 24a, 24b, and 24c are provided to serve as thermal vias for heat dissipation. An anode electrode 25a and a cathode electrode 25b are formed on the surface of the FPC 22 from the center portion of the pedestal portion 26 toward both left and right ends. Further, on the back surface of the FPC 22, an external connection electrode 29a that is electrically connected to the anode electrode 25a and an external connection electrode 29b that is electrically connected to the cathode electrode 25b are formed. The external connection electrode 29b is formed so as to cover the back surface of the pedestal portion 26 through which the through holes 24a, 24b, and 24c pass.

  The light emitting element 23 is a quadrangular chip having element electrode portions corresponding to the anode electrode 25a and the cathode electrode 25b on the lower surface, and emits light in a light emitting color such as blue or red by applying a voltage. To do. The element electrode part is solder-mounted on the anode electrode 25a and the cathode electrode 25b patterned on the pedestal part 26, respectively. This solder mounting is performed by a reflow process.

  The through holes 24a, 24b, and 24c are, for example, cylindrical through holes, and a conductive film such as gold or copper is formed on the inner peripheral surface thereof. The through holes 24a, 24b, and 24c are provided immediately below the light emitting element 23, and the opening on the upper surface is covered with an anode electrode 25a and a cathode electrode 25b made of a copper foil film having high thermal conductivity.

  The recess 28 on the back surface side of the pedestal portion 26 constitutes a heat sink, and is filled with a heat radiating member 31 having a high thermal conductivity. The heat radiating member 31 is preferably made of solder or a metal material, and is filled to fill the entire recess 28 and the through holes 24a, 24b, 24c completely.

  The through holes 24a, 24b, and 24c are preferably provided corresponding to effective light emitting regions of the light emitting element 23 in order to enhance the heat dissipation effect. In the present embodiment, an effective light emitting region of the light emitting element 23 is a region A indicated by hatching in FIG. Therefore, as shown in FIG. 4, an efficient heat dissipation effect can be obtained by forming the through holes 24a, 24b, and 24c immediately below the region A.

  FIG. 5 shows an example in which an L-shaped through hole 44 having a large opening along the planar shape of the region A is formed. Thus, by increasing the number of through holes or increasing the shape of the through holes, the heat dissipation capacity can be increased proportionally. In order to facilitate mounting of the light-emitting element 23 on the upper surfaces of the through holes 24a, 24b, 24c, and 44, it is desirable to form the anode electrode 25a and the cathode electrode 25b with a copper foil film.

  According to the light emitting diode 21 shown in FIGS. 1 and 2, when heat is generated as the light emitting element 23 emits light, most of the heat is directly in contact with the anode electrode 25a and the cathode electrode 25b via solder. Conducted quickly. And it is conducted to the heat radiating member 31 filled in the through holes 24a, 24b, 24c, and can be radiated to the outside through the heat radiating member 31 in the recess 28 having a large volume. Further, since the light emitting diode 21 is surface-mounted on the motherboard on the back side of the FPC 22, the heat dissipation member 31 filled in the recess 28 comes into contact with the motherboard together with the mounting of the FPC 22. As described above, the heat generated in the light emitting element 23 is conducted from the through holes 24a, 24b, 24c to the recesses 28 in the direction of increasing the heat radiation capacity, so that the heat conduction is performed quickly and efficiently. Can do. Further, since the recess 28 filled with the heat radiating member 31 covers the back surface of the FPC 22 centering on the light emitting element 23, the heat conducted to the FPC 22 can also be efficiently diffused.

  Further, since the upper surfaces of the through holes 24a and 24b are covered with the anode electrode 25a and the cathode electrode 25b made of a copper foil film, the conductive member can be reliably connected without sinking or leakage of the solder member. it can. For this reason, it becomes equal to the joining amount of the solder with other element electrode portions not mounted on the through holes 24a, 24b, and the balance of the light emitting element 23 can be kept constant. By maintaining the balance of the light emitting element 23 as described above, it is possible to obtain stable light emission over a long period of time without deteriorating the optical characteristics of the light emitting element 23.

  In the above-described embodiment, the FPC 22 in which the recess 28 can be easily formed is used for the substrate. However, the insulating member is not limited to such an FPC 22 as long as the recess 28 can be formed.

1 is a perspective view of a light emitting diode according to the present invention. It is AA sectional drawing of the said light emitting diode. It is a top view which shows the light emission area | region of a light emitting element. It is a top view of the board | substrate which provided the several through hole according to the light emission area | region. It is a top view of the board | substrate which has the through hole formed along the shape of the light emission area | region. It is sectional drawing of the conventional light emitting diode.

Explanation of symbols

21 Light-Emitting Diode 22 FPC (Flexible Board)
23 Light Emitting Elements 24a, 24b, 24c Through Hole 25a Anode Electrode 25b Cathode Electrode 26 Base Part 27 Mounting Part 28 Recess 29a, 29b External Connection Electrode 31 Heat Dissipation Member

Claims (9)

In a light emitting diode comprising a substrate on which an electrode pattern is formed and a light emitting element mounted on the surface of the substrate,
The substrate is provided with a pedestal portion of the light emitting element in which the substrate is projected from the back surface side to the front surface side, thereby forming a recess in the back surface of the pedestal portion, and filling the heat dissipation member in the recess. A light emitting diode characterized by that. The light emitting diode according to claim 1, wherein the substrate is made of a flexible substrate, and the pedestal and the recess are formed by press molding. The light emitting diode according to claim 1, wherein a hole portion that leads from the upper surface to the recess is provided in the pedestal portion, and the heat radiating member is filled in the hole portion. The light emitting diode according to claim 3, wherein the hole is provided directly below a light emitting region of the light emitting element. The light emitting diode according to claim 3, wherein the hole has an opening having a shape corresponding to a light emitting region of the light emitting element. The light emitting diode according to claim 3, wherein a plurality of the hole portions are formed in a light emitting region of the light emitting element. The light emitting diode according to claim 3, wherein the hole is a through hole or a thermal via. The light emitting diode according to claim 3, wherein the hole is covered with a copper foil film disposed on an upper surface of the pedestal. The light-emitting diode according to claim 1, wherein the heat radiating member is formed of a metal, solder, or resin having high thermal conductivity.

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