JP4023723B2 - Surface mount type light emitting diode - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface mount type light emitting diode.
[0002]
[Prior art]
Conventionally, for example, a light emitting diode (LED) shown in FIG. 3 is known as a typical conventional structure of a surface mount type light emitting diode provided for an electronic device pursuing lightness and smallness. The outline will be described below.
[0003]
In FIG. 3, 10 is a surface-mounted LED. Reference numeral 11 denotes a metal core substrate in which a metal core material such as Mg, Al, or Cu having high thermal conductivity is formed into a substantially cubic shape by injection molding or press molding. The metal core substrate 11 is formed so as to be a recess 12 having an inverted trapezoidal cross section. The bottom surface 12a and the inclined surface 12b of the recess 12 are provided with a reflective film 13 such as bright silver plating.
[0004]
A slit 12c is formed so as to divide the metal core substrate 11 into two, and an electrically insulating adhesive 14 is filled in the slit 12c. In this state, two metal cores having a symmetrical shape are integrated with an adhesive 14. The electrical insulating adhesive 14 has a thermal expansion coefficient of about 40 to 80 ppm / ° C. of a general epoxy adhesive, but is basically an epoxy adhesive, for example. A low expansion type adhesive having a coefficient of about 20 ppm / ° C is preferable.
[0005]
The metal core substrate 11 is formed with a pair of electrode patterns that are divided into two by an electrically insulating adhesive 14. The bottom surface 12a of the recess 12 for mounting the light emitting diode 15 (LED element) and the external connection terminal portion of the bottom surface 11a of the metal core substrate 11 are each subjected to surface treatment such as gold plating necessary for rust prevention and bonding. ing.
[0006]
On the bottom surface 12 a of the concave portion 12 of the metal core substrate 11, the LED element 15 with a bump in which the solder bump 16 is previously formed on the LED element 15 is flip-chip mounted on both electrode surfaces across the electrically insulating adhesive 14. Are joined. Then, the surface-mounted LED 10 is completed by sealing with a sealing resin 17 made of a transparent resin so as to cover the LED element 15.
[0007]
When the surface-mounted LED 10 is used, surface mounting is realized by electrically fixing the external connection terminal portion of the lower surface 11a of the metal core substrate 11 to a printed wiring of a mother board (not shown) with solder or the like.
[0008]
[Problems to be solved by the invention]
However, the surface-mounted light emitting diode described above is low in an environmental test such as a heat cycle in which operation is ensured after one cycle of −40 ° C. × 30 min → + 100 ° C. × 30 min is performed for 1000 cycles or more. Even if an expansion-type electrically insulating adhesive is used, stress due to the difference in thermal expansion coefficient between the adhesive, LED element, metal core substrate, etc. is generated, and defects such as cracks in solder and bump peeling off of the LED element part occur. There is a danger that it will occur, and the life of the surface-mounted light emitting diode will be shortened.
[0009]
The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a highly reliable surface-mounted light-emitting diode that has excellent heat dissipation and generates less stress due to thermal expansion.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the surface-mounted light-emitting diode according to the present invention has a substantially three-dimensional metal core, in which two metal cores having a symmetric shape are fixed with an insulating member so that the cross-sectional shape is an inverted trapezoidal recess. forming a substrate, said metal core and mounting the light emitting diode element in the recess bottom surface of the substrate, the light emitting diode by encapsulating with a sealing resin so as to cover the element surface mounted light emitting diode, wherein said light emitting diode element metal core which the sub-mount substrate is interposed between the substrate Rutotomoni, characterized in that the thermal expansion coefficient of the submount substrate form an intermediate thermal expansion coefficient of the metal core substrate and the thermal expansion coefficient of the light emitting diode element It is.
[0011]
Further, the submount substrate is a wiring substrate in which a predetermined electrode pattern is formed on an insulating substrate made of glass epoxy resin or the like.
[0012]
In addition, a reflective film is formed on at least the concave slope of the metal core substrate.
[0013]
Further, the electrode pattern is subjected to surface treatment by gold plating or silver plating .
[0014]
Further, the reflective film is a bright silver plating.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the surface-mounted LED according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a surface-mount LED according to the first embodiment of the present invention, and FIG. 2 is a cross-sectional view of the submount of FIG.
[0016]
In FIG. 1, the surface mount type LED 1 is configured such that a submount 2 in which an LED element 15 is mounted on a submount substrate 3 is electrically fixed with solder 5 in a recess of a metal core substrate 11. The metal core substrate 11 is the same as that described in the prior art, and two metal cores having a symmetric shape are bonded with an electrically insulating adhesive 14 so as to form a recess 12 having a reverse trapezoidal cross-sectional shape. A substantially three-dimensional shape is formed. The metal core substrate 11 is formed with a pair of electrode patterns that are divided into two parts by an electrically insulating adhesive 14. The bottom surface 12 a of the recess 12 and the external connection terminal portions of the bottom surface 11 a of the metal core substrate 11 are respectively Surface treatment such as gold plating necessary for rust prevention and bonding is applied. The bottom surface 12a and the inclined surface 12b of the recess 12 are provided with a reflective film 13 such as glossy silver plating.
[0017]
The submount mounted on the bottom surface of the concave portion of the metal core substrate will be described with reference to FIG. FIG. 2 is a sectional view of the submount. In FIG. 2, reference numeral 3 denotes a submount substrate (wiring substrate) in which a predetermined wiring pattern is formed on an insulating substrate made of glass epoxy resin or the like. The submount substrate 3 is obtained by laminating a plating resist on both side copper foil portions of an insulating substrate, exposing and developing to form a predetermined wiring pattern, and further performing surface treatment such as gold plating or silver plating thereon. The wiring pattern is composed of a pair of upper surface electrodes 4a and 5a, lower surface electrodes 4c and 5c, and side surface electrodes 4b and 5b connecting the upper and lower electrodes.
[0018]
Then, on the upper surface of the submount substrate 3, the LED elements 15 with bumps, in which the solder bumps 16 are previously formed on the LED elements 15, are flip-chip mounted and bonded to both electrode surfaces across the upper surface electrodes 4a and 5a. ing. And the submount 2 is completed by sealing with the sealing resin 17 which consists of transparent resin so that the said LED element 15 may be covered.
[0019]
On the bottom surface 12a of the recess 12 of the metal core substrate 11, the above-described submount 2 is mounted on both electrode surfaces across the electrically insulating adhesive 14, die-bonded with silver paste, and soldered with solder 5 to be electrically connected. Connect to.
[0020]
The thermal expansion coefficient of the submount substrate 3 described above is approximately 10 ppm / ° C, the thermal expansion coefficient of the LED element is approximately 5.3 ppm / ° C, and the thermal expansion coefficient of the metal core substrate is approximately 20 ppm / ° C. is there.
[0021]
The effects of the surface-mounted LED having the above-described configuration will be described. Even under severe environmental tests such as the heat cycle described above, since the thermal expansion coefficient of the submount substrate is approximately between the LED element and the metal core substrate, the stress generated by the temperature is relieved. Fatal defects such as solder cracks and bump peeling are reduced.
[0022]
【The invention's effect】
As described above, according to the present invention, the metal core substrate constituting the package is excellent in heat dissipation, and the structure in which the submount substrate is interposed between the LED element and the metal core substrate is excellent in heat dissipation. In addition, it is most suitable for an in-vehicle LED that generates less stress due to thermal expansion, and can provide a highly reliable surface-mounted light-emitting diode.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a surface-mounted light emitting diode according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the submount of FIG.
FIG. 3 is a cross-sectional view of a conventional surface mount type light emitting diode.
[Explanation of symbols]
1 Surface-mount LED
2 Submount 3 Submount substrate 4a, 5a Upper surface electrode 4b, 5b Side electrode 4c, 5c Lower surface electrode 5 Solder 11 Metal core substrate 12 Recess 12a Bottom surface 12b Slope 13 Reflective film 14 Electrical insulating adhesive 15 LED element 16 Solder bump 17 Sealing resin

Claims (5)

An approximately three-dimensional metal core substrate is formed by fixing two symmetrical metal cores with an insulating member so that the cross-sectional shape is an inverted trapezoidal concave portion, and a light emitting diode element is mounted on the bottom surface of the concave portion of the metal core substrate. in the light emitting diode by encapsulating with a sealing resin so as to cover the element surface mounted light emitting diodes, said light emitting diode element and the metal core Rutotomoni submount substrate is interposed between the substrate, of the sub-mount substrate A surface mount type light emitting diode characterized in that a thermal expansion coefficient is intermediate between a thermal expansion coefficient of the light emitting diode element and a thermal expansion coefficient of the metal core substrate .   2. The surface mount light emitting diode according to claim 1, wherein the submount substrate is a wiring substrate in which a predetermined electrode pattern is formed on an insulating substrate made of glass epoxy resin or the like. 2. The surface mount light emitting diode according to claim 1, wherein a reflective film is formed on at least the concave slope of the metal core substrate. 3. The surface mount type light emitting diode according to claim 2, wherein the electrode pattern is surface-treated by gold plating or silver plating .   4. The surface mount type light emitting diode according to claim 3, wherein the reflective film is a bright silver plating.

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