JP2005243658A - Light emitting diode package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting diode package which has a good light reflecting face for reflecting luminous light flux from an LED element to an outer part, whose manufacture is easy, and manufacture variation of luminance and angle of visibility is small, and which is superior in heat dissipation. <P>SOLUTION: In the light emitting diode package, the mounting region of the LED element is formed on a ceramic substrate, a metal ring is brazed on the ceramic substrate along a route surrounding the LED element, and the light reflecting face reflecting luminous light flux from the LED element in a prescribed direction is formed on the ring. The ring is brazed on a metallized layer formed along the route on the surface of the ceramic substrate. A cavity with bottom is formed which is opened to one main surface of the ceramic substrate, the mounting region of the LED element is formed at the base of the cavity, and the metallized layer is formed at an outer peripheral edge part of the base. The ring having an outer peripheral face whose size is almost the same as an inner peripheral face of the cavity is brazed on the metallized layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a light emitting diode package.

  In recent years, attention has been focused on light emission diodes (hereinafter also referred to as LED elements). In particular, since high-intensity blue light-emitting diodes can be manufactured, high-intensity white light can be obtained using red, green and blue LED elements, and these LED elements can be used as light bulbs and car headlights. Development for use is underway. Since the LED element consumes less electric power, the battery load is reduced when used as a car headlight. In addition, since it has a long life, fluorescent lamps and light bulbs used indoors are being replaced by LED elements. These LED elements are being developed in order to improve light characteristics such as light emission luminance and spectrum in order to satisfy the user's requirements.

  The characteristics such as the emission spectrum and the luminance are mainly determined by the compound semiconductor constituting the LED element. However, characteristics such as luminance and viewing angle are greatly affected by the package on which the LED element is mounted. For this reason, a light emitting diode package has attracted attention as a means for obtaining brightness and viewing angle desired by the user. As such a light emitting diode package, one mounted on a ceramic substrate has been conventionally used. An example is shown in FIG. The LED element 1 is placed on the first ceramic substrate 20 and is electrically connected to the metal wirings 23a and 23b. A cavity 24 for accommodating the LED element 1 is formed. The cavity 24 is formed so as to penetrate the second ceramic substrate 21, and the first ceramic substrate 20 and the second ceramic substrate 21 are bonded together. The size of the light emitting diode package is about several millimeters, and a desired amount of light can be obtained by collecting a large number. A metal layer 22 is formed on the inner peripheral surface of the cavity 24, and is configured to reflect the emitted light beam from the LED element 1.

  The light emitting diode package is manufactured by, for example, a green sheet lamination method. A metallized paste to be the metal wirings 23a and 23b is applied to the ceramic green sheet to be the first ceramic substrate 20, and the second ceramic substrate 21 is punched to form a cavity 24. A metal is formed on the inner peripheral surface of the cavity 24. A metallized paste to be the layer 22 is applied. Thereafter, the ceramic substrates 20 and 21 are bonded and sintered at a high temperature to obtain a sintered body in which the ceramic substrates 20 and 21 are integrated. Then, a nickel plating layer, a gold plating layer, or the like is deposited on the metal layer 22 by a known electroless plating method or electrolytic plating method.

However, since the cavity 24 is formed by punching the second ceramic substrate 21, the angle θ becomes a right angle, the luminous flux from the LED element 1 is not emitted to the outside, and the desired viewing angle and brightness cannot be obtained. there were. Therefore, as described in Patent Document 1 below, the angle θ is 55 ° to 70 °, the center line average roughness Ra of the metal layer is 1 to 3 μm, and the light reflectance is 80% or more. Thus, a light emitting diode package capable of obtaining high luminous efficiency has been proposed.
Japanese Patent Laid-Open No. 2002-232017

Further, in Patent Document 2 below, a metal reflector is provided in the cavity, a hooking claw is formed on the upper part of the metal reflector and hooked on the upper stage of the second ceramic substrate 21, or a silicon-based bonding with high thermal conductivity. A light emitting diode package in which a metal reflector is attached to a second ceramic substrate using a material has been proposed. The reason why the bonding material having high thermal conductivity is used is to efficiently dissipate heat from the LED element.
JP 2003-197974 A

  However, as in Patent Document 1, it is difficult to perforate so that the angle θ is always a constant angle, and there is a problem that the angle θ varies when it is mass-produced. Further, when a metallized paste is applied to a green sheet and a metal layer is formed by simultaneous firing with ceramic, the surface is likely to be bent, and it is difficult to form a high-quality light reflecting surface. Therefore, there has been a problem that variations in luminance and viewing angle become large. In addition, as in Patent Document 2, the method of hooking the metal reflector on the ceramic substrate with the hooking claws is unstable because the metal reflector may come off. There is also a method of bonding the metal reflector with a silicon-based bonding material having high thermal conductivity, but there remains room for improving the heat dissipation efficiency.

  The present invention has been made in view of the above circumstances, and in particular, has a high-quality light reflecting surface for reflecting the emitted light beam from the LED element to the outside, is easy to manufacture, has a brightness and a visual field. An object of the present invention is to provide a light emitting diode package with small manufacturing variation of corners and excellent heat dissipation.

Means for Solving the Problems and Effects of the Invention

  In order to solve the above-described problems, the LED package of the present invention has a LED element mounting region formed on a ceramic substrate, and a metal ring is brazed on the ceramic substrate along a path surrounding the LED element. The ring is mainly characterized in that a light reflecting surface for reflecting the luminous flux from the LED element in a predetermined direction is formed.

  The ring is brazed to the metallized layer formed along the path on the surface of the ceramic substrate. In the light emitting diode package of the present invention, a bottomed cavity opened on one main surface of the ceramic substrate is formed, a mounting region for the LED element is formed on the bottom surface of the cavity, and an outside of the bottom surface is formed. The metallized layer is formed on a peripheral edge, and the ring having an outer periphery substantially the same size as the inner periphery of the cavity is brazed to the metallized layer.

  The ring is brazed to the metallized layer with an Ag-based brazing material. The light reflecting surface is formed so as to be wide in the opening direction. Further, in the light emitting diode package of the present invention, the mounting area of the LED element is formed on the first ceramic substrate, the cavity is formed to penetrate the second ceramic substrate, and the cavity is the LED. The first ceramic substrate and the second ceramic substrate are bonded so as to accommodate the element.

  Furthermore, the light emitting diode package of the present invention is formed by laminating first, second, and third ceramic substrates in this order, and a mounting region for the LED element is formed on the first ceramic substrate. A through hole is formed in the third ceramic substrate, the two through holes are connected to form the cavity, and a metal pad connected to the LED element is formed on one main surface of the second ceramic substrate. The pad is exposed from the cavity.

  The through hole has a cylindrical shape, and the diameter of the through hole formed in the third ceramic substrate is larger than the diameter of the through hole formed in the third ceramic substrate. The through hole is formed by vertically punching the second and third ceramic substrates.

  Since the light reflecting surface used in the present invention is formed on a metal ring, the surface is smooth and has high light reflectance. Metal rings can be produced stably in shape. Therefore, when the light emitting diode package is manufactured, the variation in viewing angle and luminance can be reduced. Since the metal ring is brazed using a brazing material with good thermal conductivity, it has excellent heat dissipation. The type of brazing material may be anything such as Ag, nickel or aluminum, but Ag brazing is particularly preferred.

  The cavity can be cylindrical, for example. The bottom surface is circular, and an LED element mounting region is formed in the center. A metallized layer made of a metal such as Mo or W is formed on the outer peripheral edge of the bottom surface. The outer ring of the metal ring has substantially the same size as the inner periphery of the cavity, and enters the cavity with almost no gap. As the material of such a ring, any metal that can be brazed, such as KOVAR, 42Ni, and Cu, can be used.

  The ring is brazed as follows, for example. First, an Ag-based brazing ball is placed on the metallized layer and subjected to a heat treatment at about 800 ° C. for reflow. After cooling to room temperature, place the ring on the brazing material and apply heat treatment again. Then, the Ag-based brazing material melts and adheres to the ring. Thereafter, if necessary, a plating layer such as Ag may be formed on the ring surface.

Hereinafter, embodiments of the light emitting diode package of the present invention will be described with reference to the drawings.
FIG. 1A is a cross-sectional view of a main part showing an embodiment of a light emitting diode package of the present invention, and FIG. 1B is a perspective view of the same. The ceramic substrate 15 is a substantially rectangular flat plate made of a ceramic material such as aluminum oxide or aluminum nitride, and has a bottomed cavity 3 on one main surface. Further, the mounting area 25 of the LED element 1 is provided on the cavity bottom surface 16 and functions as a support substrate for the LED element 1. Metal pads 8 a and 8 b are formed on the cavity bottom surface 16. The LED element 1 is bonded to the mounting region 25 and is electrically connected to the metal pads 8a and 8b via the bonding wires 2. The metal pads 8a and 8b are electrically connected to the external terminals 26a and 26b on the back surface of the ceramic substrate 15, and a driving current for the LED element 1 flows from here.

  A metallized layer 7 made of, for example, Mo—Mn, Mo, W, W—Mn, or the like is formed on the outer peripheral edge of the cavity bottom surface 16 along a path surrounding the LED element 1. A metal ring 5 is brazed to the metallized layer 7 with an Ag-based brazing material 27. The outer peripheral surface of the ring 5 is approximately the same size as the inner peripheral surface 4 of the cavity 3. The ring 5 is fitted in the cavity 3, and there is substantially no gap between the ring outer peripheral surface and the cavity inner peripheral surface. A light reflecting surface 6 is formed on the ring 5 so as to be wide in the opening direction. Therefore, the light reflecting surface 6 has an antenna type structure, and efficiently reflects the emitted light beam from the LED element to the outside.

  FIG. 1C is an enlarged cross-sectional view of the ring 5. The angle θ formed between the cavity bottom surface 16 and the light reflecting surface 6 is an important parameter that affects the viewing angle and the luminance. Particularly in mass production, variation in θ becomes a problem, but the ring 5 can be manufactured with high accuracy. Therefore, the light emitting diode package using the ring 5 can be manufactured with a stable viewing angle and brightness. Further, in the present invention, since the ring 5 is brazed with the Ag-based brazing material 27, there is a feature that heat dissipation is good.

  It is desirable that the ring 5 is disposed on the circumference centering on the LED element 1. The reason is that if the ring 5 is substantially circular, the light-reflecting light beam from the LED element 1 can be uniformly reflected by the light reflecting surface 6 and emitted to the outside.

  Next, another embodiment will be described. FIG. 2A is a schematic sectional view showing another embodiment of the light emitting diode package of the present invention, and FIG. 2B is a perspective view of the same. The light emitting diode package of FIG. 2 is formed by laminating a first ceramic substrate 10, a second ceramic substrate 11, and a third ceramic substrate 12. The second ceramic substrate 11 and the third ceramic substrate 12 have a hole penetrating the plate, and the two through holes constitute a cavity 3.

  A metallized layer 7 and a metal mounting region 14 are formed on the main surface of the first ceramic substrate 10. The metallized layer 7 and the mounting region 14 are made of a metal such as Mo—Mn, Mo, W, and W—Mn, for example. The LED element 1 is bonded to the mounting region 14.

  On one main surface of the second ceramic substrate 11, metal pads 8a and 8b and a metal wiring 13 connected to the metal pads 8a and 8b are formed. The metal pads 8 a and 8 b are connected to the LED element 1 through the bonding wires 2. Electric power for driving the LED element is supplied from an external terminal (not shown) through the metal pads 8 a and 8 b and the metal wiring 13. The third ceramic substrate 12 is bonded to the second ceramic substrate so as to cover the metal wiring 13. Further, the through hole of the third ceramic substrate 12 is formed larger than the through hole of the second ceramic substrate 11, and the metal pads 8a and 8b are exposed. If it does in this way, since the 3rd ceramic substrate 12 protects the metal wiring 13, problems, such as peeling of the metal wiring 13 during use, can be avoided.

  The light emitting diode package of the present invention can also be mounted with a plurality of LED elements as shown in FIG. In the embodiment of FIG. 3, three LED elements are mounted. One terminal of each LED element is connected to the metal pads 8 a, 8 b, 8 c by the bonding wire 2. The other terminal is connected to the metal pad 8d as a common terminal. White light can be obtained by using red, blue, and green LED elements.

  Next, an embodiment relating to a method of manufacturing a light emitting diode package according to the present invention will be described with reference to FIGS. First, as shown in FIG. 4A, green sheets 10a, 11a, and 12a to be first to third ceramic substrates are prepared. Such a green sheet is produced by making a mixed slip of ceramic fine powder and an organic binder, a plasticizer, a solvent, etc. into a thin plate shape by a well-known doctor blade method or calendar method.

  Next, as shown in FIG. 4B, a metallized paste for the metallized layer 7 and the mounting region 14 is printed on the green sheet 10a for the first ceramic substrate by a screen printing method. The metallized layer 7 is printed in a substantially circular shape along a path surrounding the mounting area 14. Further, the through hole 3a is formed in the green sheet 11a for the second ceramic substrate, and the metal pads 8a and 8b and the metallized paste for the metal wiring 13 connected thereto are printed on the upper surface of the green sheet 11. Further, the through hole 3b is also formed in the green sheet 12a for the third ceramic substrate. The through holes 3a and 3b are substantially cylindrical and are formed by punching each green sheet vertically. In the prior art, a method of punching at an angle has been adopted. However, in the present invention, since punching is performed vertically, it can be easily manufactured.

  Then, as shown in FIG.4 (c), the green sheets 10a, 11a, and 12a which should become a 1st-3rd ceramic substrate are laminated | stacked, and it adhere | attaches. Then, the through holes 3a and 3b are connected to form a cavity 3 for housing the LED element. Thereafter, when the green sheet is fired, the ceramic substrates 10 to 12 are integrated, and a sintered body having the cavity 3 is obtained.

  Next, as shown in FIG. 5 (d), Ag-based brazing balls 27 a are placed on the metallized layer 7. In this step, for example, the ball 5a is placed in the cavity 3, and the ceramic substrate itself is inclined and placed. Thereafter, for example, when a high temperature treatment of about 800 ° C. is performed, the ball 5a is melted, and the Ag brazing material 27 is reflowed on the metallized layer 7 as shown in FIG. After cooling to room temperature, the ring 5 is placed on the metallized layer 7 and subjected to high temperature treatment again. Then, the ring 5 is bonded by the melted Ag-based brazing material, as shown in FIG. Thereafter, if necessary, a plating layer (not shown) such as Ag may be formed on the surface of the ring 5. For example, when Cu is used as the material of the ring, the light reflecting surface has a color peculiar to Cu. Such a problem can be solved by applying Ag plating to the surface. In the present invention, it is desirable that there is no gap between the ring 5 and the cavity inner peripheral surface. The reason is that when the plating process is performed, the plating solution may enter the gap, and the plating solution may gradually leak out over time, causing the light reflecting surface 6 to be discolored.

Schematic sectional view (a) and perspective view (b) showing an embodiment of the present invention Schematic sectional view (a) and perspective view (b) showing another embodiment of the present invention A perspective view of a light emitting diode package having a plurality of LED elements mounted thereon Process diagram of light emitting diode package of the present invention Process diagram following FIG. Sectional view showing a conventional example of a light emitting diode package

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 LED element 3 Cavity 4 Cavity inner peripheral surface 5 Ring 6 Light reflection surface 7 Metallized layer 8 Metal pad 13 Metal wiring 14 Mounting area 16 Cavity bottom

Claims (1)

  An LED element mounting region is formed on the ceramic substrate, and a metal ring is brazed on the ceramic substrate along a path surrounding the LED element, and a luminous flux from the LED element is given to the ring. A light-emitting diode package, wherein a light reflecting surface that reflects in the direction of is formed.

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