JP2007142476A - Light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve light reflection characteristics on the light reflection surface of a package; and to reduce a change in light intensity, a light radiation angle, and light intensity distribution due to a temperature change. <P>SOLUTION: A light-emitting device comprises a light-emitting element 5, the package 1 for mounting the light-emitting element 5, and a heat sink 6 provided on the lower surface of the package 1. The package 1 comprises a mount 2a of the light-emitting element 5, and a light reflection surface for surrounding the light-emitting element 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light emitting device on which a light emitting element is mounted.

  Conventionally, light-emitting devices using light-emitting elements such as light-emitting diodes (LEDs) and semiconductor lasers (LDs) have been attracting attention because they are expected to further reduce power consumption and extend their lifetime in the future. It has begun to be used in various fields such as various indicators, optical sensors, displays, photocouplers, backlights, and optical printer heads. A cross-sectional view of a light emitting element storage package (hereinafter also simply referred to as a package) for mounting a conventional light emitting element is shown in FIG.

  As shown in FIG. 2, the conventional package 11 has a base 12 generally made of a material such as various resins or ceramics. A metallized layer is formed on the substrate 12 by applying and baking a conductive paste containing tungsten, molybdenum-manganese, or the like, and a wiring conductor 13 is formed on which a Ni plating layer or an Au plating layer is applied by plating. Has been.

  The wiring conductor 13 is electrically connected to the mounting portion 12a on which the light emitting element 15 is mounted via a solder bump 17 made of gold (Au), tin (Sn) -lead (Pn) alloy, or the like. The drive current is supplied from the outside to the light emitting element 15 in the package 11 through the wiring conductor 13 and the solder bump 17.

  The base body 12 is provided with a frame body 14 made of various resins and ceramics having a through hole 14a penetrating the upper and lower surfaces in the center portion on one main surface inside the package 11. The frame body 14 is fixed to the base 12 by a brazing material such as silver (Ag) -copper (Cu) having a melting point of 700 to 900 ° C., a resin adhesive, a low melting point glass melting at 500 ° C. or less, and the like.

  Further, in order to protect the light emitting element 15, a transparent resin (not shown) is provided inside the frame 14 so as to cover the light emitting element 15. This transparent resin is formed by heat-curing a thermosetting epoxy resin or silicone resin. Further, by mixing at least one phosphor that absorbs light of the light emitting element 15 and converts the wavelength into the transparent resin, light of a desired color can be extracted. Further, the transparent resin also has a function of firmly attaching the light emitting element 15 to the package 11. As a result, a light-emitting device that houses the light-emitting element 15 is obtained.

  In this light emitting device, the light emitting element 15 emits light by a drive current supplied from an external electric circuit. Applications include various indicators, optical sensors, displays, photocouplers, backlights, and optical printer heads.

  In recent years, this light-emitting device has been used for illumination, and a device having higher characteristics in terms of high luminance and heat dissipation is required. In addition, when used for illumination, the lifetime is an important issue, and thus a long-life light emitting device is required.

  Therefore, recently, in order to improve the light emission luminance of the light emitting device, the frame body 14 and the base body 12 are often made of a material having a higher reflectance. For example, by using a highly reflective metal such as Ag or Al as the material of the frame body 14 that reflects the light of the light emitting element 15, or by depositing these metals on the inner peripheral surface of the frame body 14, It has been proposed to provide a light emitting device with brightness.

  Although the conventional package 11 can sufficiently cope with high brightness, if the input power of the light emitting element 15 is increased to increase the brightness, the light intensity stabilized by the heat emitted from the light emitting element 15, the light emission angle, the light There is a new problem that the intensity distribution cannot be obtained. Further, when the heat dissipation is deteriorated, the temperature of the light emitting element 15 is increased, and the extraction efficiency of light emitted from the active layer of the light emitting element 15, that is, so-called internal quantum efficiency is remarkably deteriorated. Further, the light emitting element 15 and the package 11 are distorted, and the light emission angle and the light intensity distribution measured at a certain distance from the package 11 deviate from desired values and patterns. The light intensity distribution is represented by a single light beam (light beam) or an aggregate thereof, and the pattern of the light beam becomes unstable due to distortion of the package 11 and becomes unstable. As described above, when the light-emitting device is used for local illumination or the like, the light emission angle and the light intensity distribution are important problems.

  Therefore, the present invention has been completed in view of such conventional problems, and its purpose is to improve the light reflection characteristics on the light reflection surface of the package, and to improve the light intensity due to temperature change, the light emission angle, It is to reduce the change of the light intensity distribution.

  The present invention includes a light emitting element, a package on which the light emitting element is mounted, and a heat dissipation plate provided on the lower surface of the package. The package has a light emitting element mounting portion and a light reflecting surface surrounding the light emitting element.

  The present invention includes a light emitting element, a package on which the light emitting element is mounted, and a heat sink provided on the lower surface of the package, so that light generated by the light emitting element can be favorably reflected on the light reflecting surface of the package. Reflecting and radiating uniformly and efficiently to the outside, changes in light intensity, light emission angle, and light intensity distribution due to temperature changes are reduced.

  The light emitting element storage package of the present invention will be described in detail below. FIG. 1 is a cross-sectional view showing an example of an embodiment of the package of the present invention. In FIG. 1, 2 is a base, 4 is a frame, and 6 is a heat radiating plate. The package 1 is mainly configured.

  A package 1 according to the present invention includes a base 2 made of an insulator having a mounting portion 2a on which a light emitting element 5 is mounted at the center of the upper main surface, and a wiring conductor 3 led out from the mounting portion 2a to the outside. A frame 4 made of a metal attached to an outer peripheral portion of the upper main surface of the base body 2 so as to surround the mounting portion 2a and having an inner peripheral surface that is an inclined surface extending outward and upward; And a heat sink 6 made of metal joined to the center of the lower main surface.

  The substrate 2 in the present invention is an insulator made of ceramics such as an aluminum oxide sintered body (alumina ceramic), an aluminum nitride sintered body, a mullite sintered body, a glass ceramic, or a resin such as an epoxy resin. In addition to functioning as a support member for supporting and mounting the light emitting element 5, a mounting portion 2a for mounting the light emitting element 5 is provided at the center of the upper main surface thereof.

  The substrate 2 is a wiring conductor 3 made of a metallized layer such as tungsten (W), molybdenum (Mo), manganese (Mn), copper (Cu), etc., which conducts electrical conduction from the vicinity of the mounting portion 2a to the outside of the package. Is formed. For this wiring conductor 3, for example, a metal paste obtained by adding and mixing an organic solvent and a solvent to a powder such as W is printed and applied in a predetermined pattern on a ceramic green sheet to be a base 2, and a plurality of ceramic green sheets are laminated. And then fired. On the surface of the wiring conductor 3, in order to prevent oxidation and to firmly connect the light emitting element 5 with solder bumps 7 such as a low melting point brazing material, a Ni (nickel) layer having a thickness of 0.5 to 9 μm and a thickness of 0.5 to It is preferable to deposit a metal layer such as a 5 μm Au layer by a plating method.

  In addition, the upper main surface of the substrate 2 is not short-circuited to the wiring conductor 3 in order to effectively suppress the transmission of light to the lower main surface of the substrate 2 and to reflect light efficiently above the substrate 2. Thus, it is preferable to form a metal reflective layer such as Al, Ag, Au, Cu, Pt by vapor deposition or various plating methods.

  The wiring conductor 3 of the present invention has electrode pads that are electrically connected to the light emitting element 5 by solder bumps 7 made of a low melting point solder such as Au or Sn—Pb solder, and the light emitting element 5 and the package 1. Conduct electrical continuity with the outside. When the light emitting element 5 is activated, heat generated in the vicinity of the electrodes of the light emitting element 5 is transferred to the wiring conductor 3 through the solder bumps 7 and also through the wiring conductor 3 formed in the inner layer of the base 2. And diffused throughout the substrate 2. As a result, the heat transmitted through the inside of the base 2 is sufficiently diffused, the thermal resistance of the base 2 is lowered, and the heat is distributed over the entire lower main surface of the base 2 and efficiently transferred to the heat sink 6. .

  The heat sink 6 of the present invention is made of a metal such as iron (Fe) -nickel (Ni) -cobalt (Co) alloy or Cu-W alloy, and the ingot is subjected to conventionally known metal processing such as rolling or punching. By applying, it is formed into a predetermined shape and manufactured. In particular, in order to enhance the heat dissipation effect, it is preferable to be made of a Cu—W alloy having excellent thermal conductivity. Further, the heat sink 6 is successively plated with a metal having excellent corrosion resistance and wettability with the brazing material, specifically, a Ni layer having a thickness of 0.5 to 9 μm and an Au layer having a thickness of 0.5 to 9 μm. It is preferable to deposit it by the method, and it is possible to effectively prevent the heat sink 6 from being oxidized and corroded.

  The heat dissipation plate 6 preferably has a thermal conductivity of 100 W / m · K or more. Thereby, the heat dissipation from the light emitting element 5 to the external circuit board via the heat sink 6 is improved, and the drive current that can be input to the light emitting element 5 can be increased.

  That is, at 100 W / m · K or higher, the junction temperature of the light-emitting element 5 (the lower the maximum temperature of the light-emitting element 5 when a predetermined drive current is input is better) even when the drive current is as large as 20 mA. The temperature is 50 ° C. or lower, and it is possible to emit light while ensuring normal and high luminance over 10,000 hours, and it is possible to input a large driving current and improve the luminance of the light emitting element 5. Further, the temperature rise of the entire package 1 when the light emitting element 5 operates is effectively suppressed, and deformation and distortion due to the difference in thermal expansion between the base 2 and the frame 4 are effectively suppressed. As a result, the positional deviation between the central axis of the base 2 and the frame 4 and the optical axis at which the light intensity of the light emitting element 5 is maximized is suppressed, and the light of the light emitting element 5 is reflected by the inner peripheral surface of the frame 4. The light is efficiently emitted to the outside of the package 1 with a desired radiation angle and intensity distribution, and the luminance is improved. Furthermore, the thermal stress caused by the difference in thermal expansion coefficient generated at the bonding interface between the base body 2 and the frame body 4 is reduced, and cracks and peeling generated at the bonding interface between the base body 2 and the frame body 4 can be effectively suppressed. In addition, since the temperature rise of the light emitting element 5 is effectively suppressed, a decrease in light extraction efficiency from the active layer of the light emitting element 5 accompanying the temperature rise is suppressed, and the light emitting device can operate normally and stably over a long period of time. .

  Note that the chip junction temperature is the temperature of the chip (light-emitting element 5) when a predetermined drive current (20 mA or the like) is input, and is preferably as low as possible. That is, if the heat dissipation property is not increased, heat is accumulated in the light emitting element 5 and the chip junction temperature does not decrease. Therefore, if the heat dissipation property is increased and the chip junction temperature is decreased, a drive current can flow accordingly. In general, it is said that when the temperature is 65 ° C. or higher, the limit of the light-emitting element 5 is exceeded, and no further drive current can be input.

  When the heat conductivity of the heat sink 6 is less than 100 W / m · K, for example, when the driving current is 20 mA, the chip junction temperature of the light-emitting element 5 is 65 ° C. or more, and the light-emitting efficiency of the light-emitting element 5 is significantly deteriorated and the heat is reduced. The light transmittance of a transparent resin such as an epoxy resin or a silicone resin that covers the light emitting element 5 is deteriorated due to a mechanical load, and it becomes difficult to ensure high luminance over 10,000 hours and stably emit light.

  Moreover, it is preferable that the heat sink 6 has a thermal expansion coefficient difference of 5 × 10 −6 / ° C. or less with respect to the frame body 4. As a result, when the base 2, the frame body 4, and the heat radiating plate 6 are joined via the brazing material such as silver brazing in the manufacturing process of the package 1, when the brazing material is cooled to normal temperature and cured. The bending moment applied to the base body 2 due to the contraction of the frame body 4 can be reduced by the heat radiating plate 6.

  The frame 4 is made of metal such as Al, Ag, Cu, Au, Pt, Fe—Ni—Co alloy, Fe—Ni alloy, etc., and Al is preferable because it has a high light reflection effect and can be manufactured at low cost. . This frame body 4 is formed with a through-hole 4a whose inner peripheral surface extends outwardly upward by applying conventionally known metal processing such as cutting, rolling and punching to the metal ingot. It is attached to the outer peripheral portion of the upper main surface of the base 2 so as to surround the mounting portion 2a.

  Further, the through hole 4 a of the frame body 4 is preferably formed such that its inner peripheral surface extends outward at an angle of 35 to 60 degrees with respect to the upper main surface of the base 2. Then, the light of the light emitting element 5 accommodated in the through hole 4a is reflected by the inner peripheral surface of the inclined through hole 4a, so that the light is radiated to the outside of the package 1 within a range of 20 degrees or less with respect to the optical axis. be able to. As a result, the luminance of the light emitting device using the package 1 of the present invention can be made extremely high.

  When the angle formed by the inner peripheral surface of the through hole 4a and the upper main surface of the base 2 is less than 35 degrees, the light emission angle is dispersed to 20 degrees or more, and high-power light having directivity cannot be emitted. On the other hand, when the angle exceeds 60 degrees, the light from the light emitting element 5 is not efficiently radiated to the outside of the package 1, and the inside of the package 1 is irregularly reflected to increase the loss.

  The light emission angle is as seen in a longitudinal section as shown in FIG. 1, and if the cross-sectional shape in a cross section perpendicular to the optical axis of the light beam is circular, the radiation angle is constant, and the light beam If the cross section of the cross section perpendicular to the optical axis has a deviation such as an elliptical shape, the radiation angle is the maximum value.

  The arithmetic average roughness Ra of the inner peripheral surface of the through hole 4a of the frame 4 is preferably 0.004 to 4 μm. When it exceeds 4 μm, it becomes difficult to uniformly reflect the light of the light emitting element 5 accommodated in the through hole 4a, and the intensity of the reflected light tends to be biased. If it is less than 0.004 μm, it tends to be difficult to form such a smooth surface stably and efficiently. In order to set Ra of the inner peripheral surface of the through hole 4a within the above range, it can be processed by a conventionally known chemical etching method or cutting method. Alternatively, a transfer processing method using the surface accuracy of the mold may be used.

  Further, a step 4b is formed between the upper main surface and the inner peripheral surface of the frame body 4, and the translucent member made of glass, sapphire, plastic, quartz or the like having a function of a condenser lens or the like is formed on the step 4b. It is preferable that the end portion of 8 is locked and bonded. In this case, the optical coupling state between the light emitting element 5 and the translucent member 8 can be stably maintained, and a light emitting device with stable optical characteristics can be obtained.

  In the present invention, the base 2 and the frame 4 are joined by a resin adhesive such as a silicone resin or an epoxy resin, a brazing material such as Ag-Cu brazing, or a Pb-Sn alloy, Au-Sn alloy, Au -It is performed with a bonding material such as solder such as Si alloy. The bonding material may be appropriately selected in consideration of the material of the base body 2 and the frame body 4, the thermal expansion coefficient, and the like, and is not particularly limited, but when high reliability of bonding is required. A brazing material or solder is preferred.

  In the present invention, the base 2 made of alumina ceramic or the like having a thermal expansion coefficient of about 7 × 10 −6 to 8 × 10 −6 / ° C. and the thermal expansion coefficient bonded to the outer peripheral portion of the upper main surface thereof are about The coefficient of thermal expansion bonded to the central portion of the lower main surface of the base body 2 and the frame 4 made of aluminum or the like at 23 × 10 −6 / ° C. is about 6 × 10 −6 to 10 × 10 −6 / ° C. In order to suppress the occurrence of cracks and the like in the base 2 due to the difference in thermal expansion between the heat sink 6 made of Fe-Ni-Co alloy or the like, the outer peripheral end of the heat sink 6 is the lower surface of the frame 4 It is preferable that it exists in the outer peripheral side of the lower main surface of the board | substrate 2 rather than just under the inner peripheral end of this. Thereby, the base | substrate 2 is reinforced by the heat sink 6 which has a thermal expansion coefficient comparable as it, and it can suppress effectively that a crack etc. generate | occur | produce in the base | substrate 2. FIG. Furthermore, it is more preferable that the outer peripheral end of the heat radiating plate 6 is on the outer peripheral side of the lower main surface of the substrate 2 than the central portion of the lower surface of the frame body 4. Thereby, the reinforcement effect of the base 2 is further enhanced, and the occurrence of cracks and the like in the base 2 can be further effectively suppressed.

  Since the wiring conductor 3 is exposed at the outer peripheral portion of the lower main surface of the base 2, the outer peripheral end of the heat sink 6 should not reach the outer peripheral end of the lower main surface of the substrate 2.

  Thus, in the package of the present invention, the light emitting element 5 is mounted on the mounting portion 2a of the base 2, the electrodes of the light emitting element 5 and the wiring conductor 3 are electrically connected via the solder bumps 7, and then the light emitting element 5 is covered with a transparent resin such as a silicone resin, or a transparent resin is filled in the through hole 4a in which the light emitting element 5 is accommodated to seal the light emitting element 5, and the light of the light emitting element 5 above the frame 4 By installing the translucent member 8 on the step 4b on the upper main surface of the frame 4 while being installed on the shaft, a light emitting device is obtained.

  It should be noted that the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the scope of the present invention.

It is sectional drawing which shows an example of embodiment about the light emitting element accommodation package of this invention. It is sectional drawing of the conventional package for light emitting element accommodation.

Explanation of symbols

1: Light emitting element storage package 2: Base body 2a: Mounting portion 3: Wiring conductor 4: Frame body 5: Light emitting element 6: Heat sink 8: Translucent member

Claims (3)

A light emitting element;
A package having a mounting portion of the light emitting element and a light reflecting surface surrounding the light emitting element;
A heat sink provided on the lower surface of the package;
A light emitting device comprising:   The light-emitting device according to claim 1, further comprising a translucent member disposed on the light-emitting element.   The light-emitting device according to claim 1, wherein the light reflecting surface extends outward and upward.

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