JP2008108836A - Semiconductor light emitting device and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized and low cost semiconductor light emitting device ensuring higher heat radiating property and also provide a method for manufacturing the same semiconductor light emitting device. <P>SOLUTION: The semiconductor light emitting device is provided with a light emitting element 10, a lead frame 20 where the light emitting element 10 is mounted on a main surface thereof, a first resin part 40 forming a reflecting surface 41 for reflecting the light beam from the light emitting element 10, and a second resin part 50 for fixing the lead frame 20. The first resin part 40 and the second resin part 50 are respectively constituted with inclusion of the "first and second resins". A light reflection coefficient for a visible light of the "firsts resin" constituting the first resin part 40 is higher than that for a visible light of the "second resin" constituting the second resin part 50 and a heat conductive coefficient of the "second resin" constituting the second resin part 50 is higher than that of the "first resin" constituting the first resin part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device and a method for manufacturing the same, and more particularly to a semiconductor light emitting device used for a liquid crystal backlight, an illumination device, an image reading device, and the like that require high heat dissipation characteristics and a method for manufacturing the same.

  In recent years, a white LED obtained by applying a phosphor to a blue LED to make it pseudo white or using a red / green / blue LED to become white has been provided, and the demand has increased. ing. A white LED used for a liquid crystal backlight or illumination is required to have a very large luminous intensity. For this reason, taking into account the light emission efficiency as well as the increase in the size of the light emitting element, the current of a small light emitting element is increased or many are used. For example, in the past, a current of about 20 mA was passed through a light emitting element of about 0.3 mm square, but in recent years, a current of about 50 mA has been passed through a light emitting element of the same magnitude. When this is converted into electric power, the input power (about 0.18 W) in recent light emitting elements is more than twice the input power (about 0.07 W) in conventional light emitting elements. In addition, when the size of the light emitting element is 0.5 mm to 0.6 mm square, a current of about 150 mA is passed. In this way, diversification of elements with a slightly smaller input power (for example, about 0.3 W to 1 W) is attempted instead of a large power that causes a current of 350 mA to flow through an element of about 1 mm square.

  As a general characteristic of a light-emitting element, in a light-emitting diode, a semiconductor laser, or the like, as the light output increases, the light output and the lifetime decrease with increasing device temperature. For this reason, a package with high heat dissipation characteristics is required from the viewpoint of suppressing the light output and the life reduction.

  In a surface-mount type LED package, as described in Japanese Patent Application Laid-Open No. 2006-49442 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2004-214436 (Patent Document 2), lead a metal having high heat dissipation characteristics. A method of placing the frame under the frame is known.

  Japanese Laid-Open Patent Publication No. 2003-115615 (Patent Document 3) describes a method of releasing heat to the reflector by connecting the lead terminal and the reflector with a high thermal conductive resin.

  In Japanese Patent Laid-Open No. 2006-13323 (Patent Document 4), a gel-like heat conduction member having a high thermal conductivity is provided between a lead frame on which a semiconductor element that generates heat is mounted and a lead frame that generates little heat. A method for reducing the temperature distribution bias of the entire mold resin by transferring heat is disclosed.

Japanese Patent Application Laid-Open No. 2006-514434 (Patent Document 5) has a partial area where the surface of the package body is metallized and a partial area where the surface is not metallized, and the package body is made of at least two different plastics. A device is disclosed that has one of the plastics that is not metallizable and the other is made of a metallizable plastic. Here, the metal coating is used for electrical conductivity and light reflection.
JP 2006-49442 A JP 2004-214436 A JP 2003-115615 A JP 2006-13323 A JP 2006-514434 A

  In general, in a semiconductor light emitting device that does not have a large input power, heat of the light emitting element is radiated to the circuit board through a lead frame to which the light emitting element is die-bonded and a lead terminal exposed to the outside. However, while the thickness of the lead frame is about 0.3 to 0.4 mm, the length to the lead end is about several mm to 10 mm. Thus, the thickness of the lead frame is small with respect to its length, and even if the lead frame is made of copper or copper alloy having very high thermal conductivity, heat cannot be transferred effectively. From the viewpoint of improving the heat transfer efficiency through the lead frame, the lead frame can be made thicker, but for complex shapes such as mounting multiple light emitting devices in a small package, the thickness of the lead frame should be reduced. It cannot be larger than the gap between the lead frames, and the thickness of the lead frame is limited.

  For this reason, in Patent Documents 1 and 2, a heat radiating member made of a highly heat conductive metal or ceramic is incorporated in a resin package in order to increase the thermal conductivity. In this structure, there is a problem that the reliability of the package may not be sufficient because there is a combination with a large difference in thermal expansion coefficient such as resin and metal or resin and ceramic. On the other hand, in the structures described in Patent Documents 1 and 2, in order to ensure the reliability of the package, the package size tends to increase or the structure becomes complicated. As a result, it becomes difficult to manufacture the package at a low cost. In particular, when a plurality of light emitting elements are mounted on a lead frame, it is very difficult to manufacture a heat dissipation member that can insulate each element. Furthermore, since the area of the heat radiating member exposed to the outside is small with respect to the size of the package, improvement in heat transfer efficiency from the package to a substrate outside the package is limited. As described above, even if a heat radiating member having a heat conductivity of 100 W / m · K or higher is used, the heat radiating efficiency to the outside of the package cannot always be effectively improved.

  Further, the methods described in Patent Documents 3 and 4 cannot effectively conduct heat because the contact area and volume of the heat conducting member that is thermally connected to the lead frame are small. Here, when a resin having a thermal conductivity that is an order of magnitude smaller than that of metal is used for the heat conducting member, the small contact area greatly affects.

  In Patent Document 5, it is described that a package is manufactured with two kinds of resins, but only the metal-covered portion contributes to heat dissipation, and sufficient heat dissipation characteristics cannot always be obtained.

  As described above, the method of incorporating metal or ceramic in the package can be expected to be effective in terms of heat dissipation and cost, for example, when a high-power element having a size of 1 mm square is used and, for example, an input power of 1 W or more is used. Manufacturing a smaller package (for example, a package that uses a plurality of light emitting elements with a size of about 0.3 mm to 0.6 mm and has an input power of about 0.3 W to 1 W, for example) at low cost while ensuring reliability. Not enough to do.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a small-sized semiconductor light-emitting device with low cost and high heat dissipation characteristics and a method for manufacturing the same.

  A semiconductor light-emitting device according to the present invention includes a light-emitting element, a main surface, a lead frame on which the light-emitting element is mounted, and a first resin that forms a reflective surface that reflects light from the light-emitting element. And a second resin part for fixing the lead frame, the first resin part includes a first resin, and the second resin part includes a second resin different from the first resin. Is done.

  According to the above configuration, both the first resin portion that forms the reflecting surface and the second resin portion that fixes the lead frame can be formed of the resin, and the thermal expansion coefficient of both can be made closer. The reliability of the device is improved. On the other hand, the heat dissipation characteristics of the semiconductor light emitting device can be improved by appropriately selecting the resin material of the second resin portion for fixing the lead frame. Here, it is suppressed that the structure of the semiconductor light emitting device is complicated or enlarged. Therefore, according to the above configuration, a small-sized semiconductor light emitting device with low cost and high heat dissipation characteristics can be obtained.

  In the semiconductor light emitting device, preferably, the thermal conductivity of the second resin is higher than the thermal conductivity of the first resin. Preferably, the thermal conductivity of the second resin is 2 W / m · K or more and 20 W / m · K or less. Thereby, the heat dissipation characteristics of the semiconductor light emitting device can be effectively improved.

  In the semiconductor light emitting device, preferably, the light reflectance of the first resin with respect to visible light is higher than the light reflectance of the second resin with respect to visible light. Preferably, the light reflectance of the first resin with respect to visible light is 85% or more. Thereby, the optical characteristics of the semiconductor light emitting device can be effectively improved.

  In the semiconductor light emitting device, as one example, the first and second resins are non-conductive.

  The method for manufacturing a semiconductor light emitting device according to the present invention includes a step of forming a resin portion for fixing a lead frame, and a step of mounting a light emitting element on the main surface of the lead frame, and the step of forming the resin portion includes: A first resin portion that includes a first resin and forms a reflective surface that reflects light from the light emitting element; and a second resin portion that includes a second resin different from the first resin and fixes the lead frame. Forming.

  According to the above method, both the first resin part that forms the reflecting surface and the second resin part that fixes the lead frame can be formed of the resin, and the thermal expansion coefficient of both can be made closer. The reliability of the device is improved. On the other hand, the heat dissipation characteristics of the semiconductor light emitting device can be improved by appropriately selecting the resin material of the second resin portion for fixing the lead frame. Here, it is suppressed that the structure of the semiconductor light emitting device is complicated or enlarged. Therefore, according to the above method, a small-sized semiconductor light-emitting device with low cost and high heat dissipation characteristics can be obtained.

  In one aspect, the step of forming the first and second resin portions includes a step of integrally molding the first and second resin portions. In another aspect, the step of forming the first resin portion and the second resin portion includes a step of joining the first resin portion and the second resin portion that are separately molded.

  In any of the above aspects, it is possible to obtain a small-sized semiconductor light emitting device with low cost and high heat dissipation characteristics.

  In the semiconductor light emitting device manufacturing method, in one aspect, the first and second resin portions are joined by welding using ultrasonic waves. In another aspect, joining of the 1st and 2nd resin parts is performed by adhesion using an adhesive.

  According to the present invention, a small semiconductor light emitting device having high heat dissipation characteristics can be obtained at low cost.

  Embodiments of the present invention will be described below. Note that the same or corresponding portions are denoted by the same reference numerals, and the description thereof may not be repeated.

  Note that in the embodiments described below, when referring to the number, amount, and the like, the scope of the present invention is not necessarily limited to the number, amount, and the like unless otherwise specified. In the following embodiments, each component is not necessarily essential for the present invention unless otherwise specified. In addition, when there are a plurality of embodiments below, it is planned from the beginning to appropriately combine the features of each embodiment unless otherwise specified.

(Embodiment 1)
FIG. 1 is a top view of the semiconductor light emitting device according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view taken along the line II-II in FIG.

  1 and 2, the semiconductor light emitting device according to the present embodiment includes a light emitting element 10, a lead frame 20 on which the light emitting element 10 is mounted on the main surface, a wire 30, and first and first elements. 2 resin parts 40 and 50 and the sealing resin part 60 are comprised.

  The light emitting device 10 mounted on the lead frame 20 is, for example, an LED (Light Emitting Diode). More specifically, the lead frame 20 includes two lead frames 21 and 22. The light emitting element 10 is mounted on a lead frame 21, and the light emitting element 10 and the lead frame 22 are electrically connected via a wire 30 made of Au or the like. A first resin portion 40 is provided on the main surface of the lead frame 20 so as to surround the light emitting element 10, and a reflective surface 41 is formed on the side facing the light emitting element. By doing in this way, the light radiate | emitted from the light emitting element 10 is reflected by the reflective surface 41, and adjustment of an emission angle is performed. A second resin portion 50 is formed around and under the lead frame 20. Portions exposed to the outside from the second resin portion 50 in the lead frame 20 become lead terminals 21A and 22A.

As the lead frame 20, for example, a copper alloy in which a Fe—Ni—P compound is finely dispersed and precipitated can be used. By doing in this way, the lead frame 20 excellent in strength and heat resistance can be obtained. Further, when the above material is used, the thermal conductivity of the lead frame is about 310 (W / m · K). This thermal conductivity is inferior to that of copper (about 400 W / m · K) and silver (about 420 W / m · K), but is about the same as gold (about 310 W / m · K). is there. The thermal conductivity is about 150 to 200 (W / m · K) of aluminum nitride (AlN), which is ceramic, and about 20 to 40 (W / m · K) of alumina (Al ₂ O ₃ ). Is very good compared to

  Although the thickness of the lead frame 20 (21, 22) can be changed as appropriate, it can be considered to be, for example, about 0.2 mm or more and 0.4 mm or less. In general, when a plurality of light emitting elements 10 are mounted on a package, the pattern of the lead frame 20 tends to be complicated. When the pattern of the lead frame 20 is complicated, it is necessary to form the lead frame 20 thinly.

  Further, from a viewpoint different from the above, it is required to reduce the size of the package. In order to sufficiently secure the bending workability of the lead frame 20, it is required to reduce the thickness of the lead frame 20.

  On the main surface (the upper surface in FIG. 2) of the lead frame 20, Ag plating or the like is applied. Thereby, the light emitted from the light emitting element 10 is efficiently reflected toward the front (the upper side in FIG. 2).

  Examples of the brazing material for forming the conductive layer that joins the lead frame 20 and the light emitting element 10 include a solder, a Ag paste mixed with a resin, a compound containing gold and tin (hereinafter referred to as “AuSn”). .) Etc. can be used.

  As the resin constituting the second resin portion 50 located around the lead frame 20, a resin having high thermal conductivity is used. In order to increase heat conduction, a member having high heat conduction is made into a fine powder and mixed as a filler in a resin as a base material. Therefore, the thermal conductivity is determined by the filler material and the amount of filling. The thermal conductivity of the high thermal conductive resin used here is about 2 to 20 (W / m · K). On the other hand, in the resin in which the filler having high thermal conductivity is not mixed, it is about 0.2 to 0.5 (W / m · K), which is about 1/10 of the value of the high thermal conductive resin. is there. However, in general, when a filler or the like is mixed into the resin, the choice of resin as a base material is limited, and as a result of taking into consideration the influence of filler mixing, the reflectance tends to be low.

  In the present embodiment, the first resin portion 40 that constitutes the reflective surface 41 to which the light emitted from the light emitting element 10 hits is molded with a resin having a high visible light reflectance (for example, 85% or more). As the resin having high reflectance, polyphthalamide (PPA), semi-aromatic polyamide (Genesta (registered trademark)) or the like is used. Thus, in this embodiment, two resin parts (first and second resin parts) having different thermal conductivities are molded together with the lead frame by a two-color molding method.

  The heat generated in the light emitting element 10 is transmitted to the lead frame 21 through the brazing material. However, when the lead frame 21 is thin, even if its thermal conductivity is high, heat is not easily transmitted to the lead terminals 21A and 22A outside the package. Further, the lead frame 22 on which the light emitting element 10 is not mounted tends to be hardly used for heat dissipation.

  On the other hand, in this embodiment, the heat dissipation efficiency to the outside of the package is improved by covering the periphery of the lead frame 20 with a resin having high thermal conductivity. Here, the thermal conductivity of the second resin part 50 is about 1/10 of the thermal conductivity of the lead frame 20, but if the thickness of the second resin part 50 is about 10 times that of the lead frame 20, the second resin The part 50 has substantially the same heat transfer characteristics as the lead frame 20. Further, as shown in FIG. 2, by configuring the entire lower surface of the package with the second resin portion 50 and the lead frame 20 having high thermal conductivity, the heat radiation area to the substrate on which the semiconductor light emitting device is mounted is increased. Effective heat transfer can be performed.

  According to the semiconductor light emitting device according to the present embodiment, both the first resin portion 40 that forms the reflection surface 41 and the second resin portion 50 that fixes the lead frame 20 can be formed of resin. Since the expansion coefficient can be made closer, the reliability of the semiconductor light emitting device is improved. Further, the heat radiation characteristics of the semiconductor light emitting device can be improved by configuring the second resin portion 50 for fixing the lead frame 20 with a resin having a relatively high heat transfer coefficient. Furthermore, the optical characteristics of the semiconductor light emitting device can be improved by configuring the first resin portion 40 forming the reflective surface 41 with a resin having a relatively high reflectance. In the semiconductor light-emitting device according to the present embodiment, the structure of the device is prevented from becoming complicated or enlarged. Therefore, according to the present embodiment, it is possible to obtain a small-sized semiconductor light emitting device with low cost and high heat dissipation characteristics.

  The above contents are summarized as follows. That is, the semiconductor light emitting device according to the present embodiment has a light emitting element 10, a main surface, a lead frame 20 on which the light emitting element 10 is mounted, and light from the light emitting element 10. A first resin portion 40 as a “first resin portion” that forms the reflective surface 41 and a second resin portion 50 that fixes the lead frame 20 are provided. The first resin portion 40 is a light for visible light. The second resin portion 50 is configured to include a resin (first resin) having a reflectance of about 85% or more, and the second resin portion 50 is different from the first resin in that the heat transfer coefficient is 2 W / m · K or more and 20 W / It is configured to include a resin (second resin) that is about m · K or less. The light reflectance of the “first resin” constituting the first resin part 40 with respect to the visible light is the light reflectance of the “second resin” constituting the second resin part 50 with respect to the visible light. The thermal conductivity of the “second resin” constituting the second resin part 50 is higher than the reflectance, and is higher than the thermal conductivity of the “first resin” constituting the first resin part.

  The method for manufacturing a semiconductor light emitting device according to the present embodiment includes a step of forming a resin portion for fixing the lead frame 20 and a step of mounting the light emitting element 10 on the main surface of the lead frame 20. The step of forming the portion includes the first resin, the first resin portion 40 that forms the reflection surface 41 that reflects the light from the light emitting element 10, and the second resin that is different from the first resin. Forming a second resin portion 50 for fixing the frame 20. In the present embodiment, the first and second resin portions 40 and 50 are integrally molded.

(Embodiment 2)
FIG. 3 is a cross-sectional view of the semiconductor light emitting device according to Embodiment 2 of the present invention. Referring to FIG. 3, the semiconductor light emitting device according to the present embodiment is a modification of the semiconductor light emitting device according to the first embodiment, and is relatively relative to first resin portion 40 having a relatively high reflectance. The second resin portion 50 having a high thermal conductivity is separately molded, and then the first and second resin portions 40 and 50 are joined by ultrasonic welding or an adhesive.

  Generally, two-color molding with one mold may be difficult when the characteristics of the resin, particularly the molding temperature and fluidity, are greatly different. For this purpose, the first resin part with high reflectivity 41 and the second resin part 50 with high thermal conductivity for fixing the lead frame are made of different molds and bonded while applying ultrasonic waves later. Two molded products are joined by a method of fusing the surfaces with heat or a method of using an adhesive. The bonding timing may be after the light emitting element 10 is mounted on the lead frame 20 and wire bonding is performed.

(Embodiment 3)
FIG. 4 is a top view of the semiconductor light emitting device according to the third embodiment of the present invention. Referring to FIG. 4, the semiconductor light emitting device according to the present embodiment is a modification of the semiconductor light emitting device according to the first and second embodiments, and a plurality of light emitting elements are mounted in one package. Features. In the example of FIG. 4, three light emitting elements 11, 12, and 13 that are blue, green, and red light emitting elements are provided in one package.

  When white is produced by the blue, green, and red light emitting elements 11, 12, and 13, currents flowing through the respective elements are different, and driving voltages are greatly different depending on materials used for the elements. In addition, since each of the light emitting elements 11, 12, and 13 has two electrodes of anode / cathode, six terminals (lead terminal portions 21A to 26A) are required to drive the light emitting elements 11, 12, and 13 independently. is required. Note that there may be a case where only one of the anode and the cathode is used, so that four terminals are sufficient.

  When a plurality of light emitting elements 11, 12, and 13 are mounted on one package as in the present embodiment, not only the input power is increased and the amount of heat generated is increased, but also the lead frame 20 (21 to 26). The pattern becomes fine and complicated. For this reason, the thickness of the lead frame 20 must be reduced, and the heat dissipation efficiency tends to be lowered only by heat dissipation through the leadframe. On the other hand, in the semiconductor light emitting device according to the present embodiment, similarly to the first and second embodiments, heat is radiated from the package by forming a resin portion having high thermal conductivity around and under the lead frame 20. Improves efficiency.

  Although the embodiment of the present invention has been described above, the embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a top view of a semiconductor light emitting device according to a first embodiment of the present invention. It is II-II sectional drawing in FIG. It is sectional drawing of the semiconductor light-emitting device concerning Embodiment 2 of this invention. It is a top view of the semiconductor light-emitting device concerning Embodiment 3 of this invention.

Explanation of symbols

  10-13 light emitting element, 20-23 lead frame, 21A-26A lead terminal part, 30 wire, 40 1st resin part, 41 reflective surface, 50 2nd resin part, 60 sealing resin part, 70 joint part.

Claims (11)

A light emitting element;
A lead frame having a main surface on which the light emitting element is mounted;
A first resin portion that forms a reflection surface that reflects light from the light emitting element;
A second resin portion for fixing the lead frame;
The semiconductor light emitting device, wherein the first resin portion includes a first resin, and the second resin portion includes a second resin different from the first resin.   2. The semiconductor light emitting device according to claim 1, wherein a thermal conductivity of the second resin is higher than a thermal conductivity of the first resin.   3. The semiconductor light emitting device according to claim 1, wherein a thermal conductivity of the second resin is 2 W / m · K or more and 20 W / m · K or less.   4. The semiconductor according to claim 1, wherein a light reflectance of the first resin with respect to visible light is higher than a light reflectance of the second resin with respect to visible light. 5. Light emitting device.   The semiconductor light-emitting device according to claim 1, wherein the first resin has a light reflectance of 85% or more with respect to visible light.   The semiconductor light emitting device according to claim 1, wherein the first and second resins are non-conductive. Forming a resin portion for fixing the lead frame;
A step of mounting a light emitting element on the main surface of the lead frame,
The step of forming the resin portion includes a first resin, a first resin portion that forms a reflection surface that reflects light from the light emitting element, and a second resin that is different from the first resin, A method for manufacturing a semiconductor light emitting device, comprising: forming a second resin portion for fixing the lead frame.   The method of manufacturing a semiconductor light emitting device according to claim 7, wherein the step of forming the first and second resin portions includes a step of integrally molding the first and second resin portions.   The method of manufacturing a semiconductor light emitting device according to claim 7, wherein the step of forming the first and second resin portions includes a step of joining the first resin portion and the second resin portion that are separately molded. .   The method for manufacturing a semiconductor light emitting device according to claim 9, wherein the joining of the first and second resin parts is performed by welding using ultrasonic waves.   The method of manufacturing a semiconductor light emitting device according to claim 9, wherein the joining of the first and second resin parts is performed by adhesion using an adhesive.

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