JP2005210056A - LED ceramic package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic package for LED which has a high-quality light reflecting surface for reflecting a luminous flux from an LED element to the outside, is easy to manufacture, and has small manufacturing variations in luminance and viewing angle. The purpose is to do.
In order to solve the above-described problems, in an LED ceramic package of the present invention, a cavity 3 having an opening on one main surface of the package and a substantially center of the bottom surface 16 serving as a mounting region 25 of the LED element 1 is provided. And metallization layers 7a and 7b formed on the bottom and side surfaces of the cavity so as to surround the mounting region 25, and a metal material having a melting point lower than the firing temperature of the ceramic constituting the package, and on the metallization layers 7a and 7b. The fillet 5 includes a light reflecting surface 6 that reflects the emitted light flux from the LED element 1 in a predetermined direction.
[Selection] Figure 1

Description

  The present invention relates to an LED ceramic 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. Therefore, LED ceramic packages are attracting attention as a means for obtaining the brightness and viewing angle desired by the user. A ceramic package has advantages such as excellent durability, heat resistance, and corrosion resistance and good heat dissipation as compared with, for example, an organic package. As such a ceramic package for LED, what is conventionally mounted on a ceramic substrate is 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 LED ceramic 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 ceramic package for LED 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 ceramic package for LED that can obtain high luminous efficiency has been proposed.

Japanese Patent Laid-Open No. 2002-232017

  However, 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.

  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 ceramic package for an LED having small manufacturing variations.

Means for solving the problems / effects of the invention

  In order to solve the above-described problems, in the LED ceramic package of the present invention, an opening is formed on one main surface of the package, and a substantially central portion of the bottom surface surrounds a cavity that is an LED element mounting region and the mounting region. The metallization layer formed on the bottom and side surfaces of the cavity, and a fillet made of a metal material having a melting point lower than the firing temperature of the ceramic constituting the package, and the fillet formed on the metallization layer, It has the light reflection surface which reflects the emitted light beam from an LED element in a predetermined direction, It is characterized by the above-mentioned.

  Further, in the method for manufacturing an LED ceramic package of the present invention, in order to manufacture the LED ceramic package, a metal material having a melting point lower than the firing temperature of the ceramic constituting the package is melted, and the bottom surface and side surfaces of the cavity are formed. A fillet is formed by flowing over the formed metallized layer.

According to the present invention, by forming the fillet on the metallized layer formed on the bottom surface and side surface of the cavity, the luminous flux from the LED element can be favorably reflected by the light reflecting surface of the fillet. Moreover, a fillet can be easily formed by melting a metal material and flowing on the metallized layer. In order to form such a fillet, it is necessary to use a metal material having a melting point lower than the firing temperature of the ceramic so that the ceramic constituting the package does not deteriorate. Here, the firing temperature of a typical ceramic used for the package is exemplified by about 1550 ° C. for Al ₂ O _{3 and} about 1750 ° C. for AlN. Specifically, the fillet is preferably composed of a metal material having a melting point of 780 ° C to 1080 ° C.

  The fillet is preferably made of a metal material having a melting point lower than the melting point of the metallized layer so as not to melt the metallized layer. In forming the fillet, it is convenient to place a metal material in the cavity and melt the metal material by heating the entire package.

  Next, the surface of the metallized layer is plated with Ni, and the fillet is preferably made of a metal material having a wetting angle of 30 ° to 70 ° with respect to the Ni plated surface. By using such a metal material, a fillet having a shape capable of favorably reflecting the luminous flux from the LED element can be obtained.

  Specifically, the fillet can be composed of a metal material mainly composed of Ag or Cu. In addition, a metal material mainly composed of Au, Pt, Al, Ni, Zn, Mg, or the like can be used. Of these, Ag brazing material or Cu brazing material is preferably used. Here, the Ag-based brazing material refers to an alloy containing silver as a main component and adding a metal such as copper, zinc, cadmium or the like. The Cu-based brazing material refers to an alloy containing copper as a main component and a metal such as silver, zinc, cadmium, etc. added thereto.

  Next, it is possible to use a fillet surface for the light reflecting surface. However, in order to further improve the reflectance with respect to the luminous flux, metal plating is applied to the surface of the fillet, and the surface of the metal plating is applied to the light reflecting surface. It is preferable that In particular, since Ag plating has a good reflectance, it is more preferable that the metal plating is constituted by Ag plating.

  Further, it is preferable that a barrier layer is interposed between the fillet and the metal plating to prevent the fillet components from diffusing into the metal plating forming the light reflecting surface. For example, Ni plating can be used for the barrier layer. Among these, the smoothness of the light reflecting surface can be further improved by using glossy Ni plating. The glossy Ni plating refers to plating formed using a Ni plating bath to which a brightener is added.

  In order to solve the above-described problems, a ceramic package for LED according to the present invention has a mounting area for an LED element formed on a ceramic substrate, and a fillet portion made of an Ag-based brazing material along a path surrounding the LED element on the ceramic substrate. And a light reflecting surface that reflects the luminous flux from the LED element in a predetermined direction is formed on the fillet portion.

  The fillet portion is disposed on the metallized layer formed along the path on the surface of the ceramic substrate. In the LED ceramic package of the present invention, a bottomed cavity is formed on one main surface of the ceramic substrate. A mounting region for the LED element is formed on the bottom surface of the cavity. The metallized layer is formed on the outer peripheral edge and the inner peripheral surface of the cavity, and the fillet is formed so as to straddle the two metallized layers.

  The light reflecting surface is formed to be wide in the opening direction. Further, an Ag plating layer for increasing the light reflectance is formed on the light reflecting surface. Further, in the LED ceramic package of the present invention, the mounting region of the LED element is formed on the first ceramic substrate, the cavity is formed so as to penetrate the second ceramic substrate, and the cavity is formed as described above. The first ceramic substrate and the second ceramic substrate are bonded so as to accommodate the LED element.

  The LED ceramic package of the present invention is formed by laminating first, second, and third ceramic substrates in this order, and the LED element mounting region is formed on the first ceramic substrate. Through holes are formed in the second and third ceramic substrates, 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 metal 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 second ceramic substrate. The through hole is formed by vertically punching the second and third ceramic substrates.

  In the LED ceramic package of the present invention, a light reflecting surface is formed on a fillet portion made of an Ag-based brazing material. Since the surface is smooth, the luminous flux from the LED element is reflected to the outside, and high luminous efficiency is obtained. The Ag-based brazing material refers to an alloy containing silver as a main component and added with a metal such as copper, zinc or cadmium. As will be described later, since the shape of the fillet portion can be manufactured with high accuracy, the ceramic package for LED of the present invention can be mass-produced so that the variation in viewing angle and luminance is reduced. Furthermore, a silver plating layer can be formed on the surface of the light reflecting surface, and the light reflectance can be further increased.

  The LED element is placed at substantially the center of the bottom surface of the cavity, and a metallized layer is formed on the outer peripheral edge portion of the bottom surface of the cavity and the inner peripheral surface of the cavity. The fillet portion is formed by pouring Ag-based brazing material into the metallized layer and performing a high temperature treatment of about 800 ° C., for example. The brazing material is reflowed by the high temperature, and a smooth light reflecting surface is formed. Since the light reflecting surface is formed so as to be wide in the opening direction, it has an antenna type structure and efficiently reflects the emitted light beam from the LED element to the outside.

  In the structure of the fillet part, the angle between the bottom surface of the cavity and the light reflecting part is an important parameter. If the angle variation is large in mass production, the viewing angle is not stable. In the conventional technology, the ceramic green sheet was punched at an angle, so the variation was large. On the other hand, in the present invention, since the shape of the metallized layer can be manufactured with high accuracy, the variation in the angle can be reduced.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an LED ceramic package according to the present invention will be described with reference to the drawings.
Fig.1 (a) is principal part sectional drawing which shows one Embodiment of the ceramic package for LED of this invention, FIG.1 (b) is a front view similarly. 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.

  Metallized layers 7 b and 7 a made of, for example, Mo—Mn, Mo, W, W—Mn, or the like are formed on the outer peripheral edge portion of the cavity bottom surface 16 and the cavity inner peripheral surface 4 along the path surrounding the LED element 1, respectively. Has been. A fillet portion 5 made of an Ag brazing material is formed so as to straddle these two metallized layers. The fillet portion 5 has a smooth light reflecting surface 6 because it is formed by placing an Ag-based brazing ball and reflowing it by applying a heat treatment at about 800 ° C. The light reflecting surface 6 reflects the emitted light beam from the LED element 1 to the outside.

  The angle θ between the metallized layer 7b and the light reflecting surface 6 is determined by the height A of the metallized layer 7a and the width B of the metallized layer 7b, and is an important parameter that affects the viewing angle and the luminance. In particular, in mass production, variation in θ becomes a problem, but mass production can be performed so that the dimensional variation in A and B can be reduced, so variation in θ can also be suppressed. The angle θ is designed to satisfy the viewing angle and brightness required by the user. For example, when it is desired to set the angle θ to 30 °, A and B may be determined so as to satisfy the relationship of B≈1.73A.

  When the surface of the light reflecting surface 6 is plated with nickel, silver, platinum, palladium, or the like by electrolytic plating or electroless plating, the light reflectance can be further increased. In particular, when the surface is plated with silver, high reflection efficiency can be obtained.

  It is desirable that the fillet portion 5 is disposed on a circumference around the LED element 1. The reason is that if the fillet portion 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.2 (a) is a schematic sectional drawing which shows another embodiment of the ceramic package for LED of this invention, FIG.2 (b) is a front view similarly. The LED ceramic 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 b and a metal mounting region 14 are formed on the main surface of the first ceramic substrate 10. The metallized layer 7b and the mounting region 14 are made of a metal such as Mo—Mn, Mo, W, 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.

  A metallized layer 7a is formed on the cavity inner peripheral surface 4, and the first ceramic substrate 10 and the second ceramic substrate 11 are bonded so that the metallized layers 7a and 7b are vertically coupled. As a result, the metallized layers 7a and 7b are formed along the path surrounding the LED element 1 on the outer peripheral edge portion of the cavity bottom surface 16 and the cavity inner peripheral surface 4.

  The fillet portion 5 made of an Ag-based brazing material is formed so as to straddle the metallized layers 7a and 7b. The fillet portion 5 is formed, for example, by adhering the ceramic substrates 10, 11, and 12 to form a sintered body, placing Ag-based brazing particles thereon, and applying a heat treatment of about 800 ° C. to reflow. Is. The light reflecting surface 6 is plated with a nickel plating layer and a silver plating layer (not shown) so that the silver plating layer becomes the surface, and a device for increasing the reflectance of light is devised. Further, as shown in FIG. 2 (b), the fillet portion 5 is along the circle surrounding the LED element 1 and is formed so as to be wide in the opening direction. Reflects efficiently.

  The LED ceramic package of the present invention can be mounted with a plurality of LED elements as shown in FIG. In the embodiment of FIG. 3, three LED elements 1a, 1b, and 1c 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 related to a method for manufacturing an LED ceramic package of 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, the metallized layer 7b and the metallized paste for the mounting region 14 are printed on the green sheet 10a for the first ceramic substrate by a screen printing method. The metallized layer 7 b is printed in a substantially circular shape along a path that surrounds the mounting region 14. Furthermore, the through hole 3a is formed in the green sheet 11a for the second ceramic substrate, the metallized paste for the metallized layer 7a is printed on the inner peripheral surface 4 of the through hole 3a, and the metal pads 8a, 8b and the metallized paste for the metal wiring 13 connected thereto are printed. 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, a nickel plating layer (not shown) is formed on the surfaces of the metallized layers 7a and 7b by a known electrolytic plating method or electroless plating method. The nickel plating layer is used to improve the adhesiveness with the Ag-based brazing material. Thereafter, as shown in FIG. 5 (d), Ag-based brazing balls 5a are placed on the metallized layers 7a and 7b. 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 reflowed, and as shown in FIG. 5E, the fillet portion 5 of the Ag-based brazing material is formed so as to straddle the metallized layers 7a and 7b. . The light reflection surface 6 is formed by reflow, and the emitted light flux from the LED element 1 can be efficiently reflected to the outside. Further, a nickel plating layer and a silver plating layer (not shown) may be formed on the light reflecting surface 6 in this order. By forming a silver plating layer on the surface, the light reflectance can be further increased.

  Hereinafter, a detailed cross-sectional structure around the fillet portion 5 common to the above-described embodiments will be described. As shown in FIG. 7, a Ni plating layer 71 is formed on the surfaces of the metallized layers 7a and 7b. The Ag brazing material has good wettability on the surface of the Ni plating layer 71, and the fillet portion 5 is formed by melting and flowing on the surface.

  An Ni plating layer 62 and an Ag plating layer 61 are formed in this order on the surface of the fillet portion 5, and the surface of the Ag plating layer 61 having a good reflectance forms the light reflecting surface 6. Further, since the Ni plating layer 62 is made of bright Ni plating, the surface (light reflection surface) of the Ag plating layer 61 formed thereon has good smoothness.

  Further, the Ni plating layer 82 and the Ag plating layer 81 are also formed in this order on the surfaces of the pads 8a and 8b. Thereby, the bonding property of the bonding wire 2 is good. Here, the Ni plating layer 82 and the Ag plating layer 81 can have the same composition as the Ni plating layer 62 and the Ag plating layer 61 formed on the surface of the fillet portion 5, that is, can be formed simultaneously.

  In addition, the configuration and form of the LED ceramic package of the above-described embodiment can be variously modified without departing from the gist of the present invention, and can be appropriately modified and implemented. For example, not only the LED element 1 but also, for example, an element for driving the LED element 1 can be mounted in the mounting region 14 at the substantially center of the cavity bottom surface 16.

Schematic sectional view (a) and front view (b) showing an embodiment of the present invention Schematic sectional view (a) and front view (b) showing another embodiment of the present invention Front view of LED ceramic package with multiple LED elements Process diagram of ceramic package for LED of the present invention Process diagram following FIG. Sectional view showing a conventional example of a ceramic package for LED Schematic diagram showing the detailed cross-sectional structure around the fillet

Explanation of symbols

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

Claims (15)

A cavity having an opening in one main surface of the package, and a substantially center of the bottom surface being a mounting region of the LED element;
A metallization layer formed on the bottom and side surfaces of the cavity so as to surround the mounting region;
A fillet formed of a metal material having a melting point lower than the firing temperature of the ceramic constituting the package, and formed on the metallized layer,
With
The ceramic package for LED, wherein the fillet has a light reflecting surface for reflecting a luminous flux from the LED element in a predetermined direction.   The LED ceramic package according to claim 1, wherein the fillet is made of a metal material having a melting point lower than that of the metallized layer.   The LED ceramic package according to claim 1 or 2, wherein the fillet is made of a metal material having a melting point of 780 ° C to 1080 ° C.   The surface of the metallized layer is Ni-plated, and the fillet is made of a metal material having a wetting angle of 30 ° to 70 ° with respect to the Ni-plated surface. The ceramic package for LED according to claim 1.   5. The LED ceramic package according to claim 1, wherein the fillet is made of a metal material containing Ag or Cu as a main component. 6.   6. The LED ceramic package according to claim 1, wherein the fillet is made of an Ag-based brazing material.   6. The LED ceramic package according to claim 1, wherein the fillet is made of a Cu-based brazing material.   8. The LED ceramic package according to claim 1, wherein a metal plating is applied to a surface of the fillet, and the surface of the metal plating forms the light reflecting surface. 9.   The LED ceramic package according to claim 8, wherein the metal plating is Ag plating.   9. A barrier layer is interposed between the fillet and the metal plating to prevent the fillet component from diffusing into the metal plating forming the light reflecting surface. Or a ceramic package for LED according to 9;   The ceramic package for an LED according to claim 10, wherein the barrier layer is made of Ni plating.   12. The LED ceramic package according to claim 11, wherein the barrier layer is made of bright Ni plating.   To manufacture the LED ceramic package according to any one of claims 1 to 12, a metal material having a melting point lower than a firing temperature of the ceramic constituting the package is melted and formed on the bottom and side surfaces of the cavity. A method of manufacturing a ceramic package for an LED, wherein the fillet is formed by flowing on the metallized layer.   14. The method of manufacturing a ceramic package for LED according to claim 13, wherein the metal material is disposed in the cavity and the metal material is melted by heating the entire package. A mounting region of the LED element is formed on the ceramic substrate, a fillet portion made of an Ag-based brazing material is formed on the ceramic substrate along a path surrounding the LED element, and the fillet portion is formed from the LED element. A ceramic package for LED, wherein a light reflecting surface for reflecting a luminous flux in a predetermined direction is formed.

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