JP2003303999A - Surface-mounted light-emitting diode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of the life time of an LED element deteriorating, due to stresses applied to the LED element in accordance with the thermal expansion of configuring members. <P>SOLUTION: Two symmetrical metal cores are fixed through electrically insulating adhesive 14 so that the cross-sectional shape can be turned to be an inverted trapezoidal recessed part 12 to form an almost stereoscopic metal core substrate 11, while a sub-mount substrate 3, where a predetermined electrode pan formed on an insulating substrate is mounted with an LED element 15 with a solder bump 16, and a sub-mount 2 sealed with sealing resin 17 is formed so that the LED element 15 can be coated, and the sub-mount 2 is soldered by solder 5 across the adhesive 14 on a bottom face 12a of the recessed part 12 of the metal core substrate 11. A reflecting film 13, constituted by gloss silver plating, is formed on the recessed oblique face 12 of the metal core substrate. A glass ceramic substrate or a glass epoxy substrate, whose thermal expansion coefficients are set between the LED element and the metal core substrate, is used for the sub-mount substrate. Thus, stresses generated due to temperature are relaxed, and a high reliability surface-mounted LED can be realized. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface mount type light emitting diode.

[0002]

2. Description of the Related 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 electronic devices pursuing lightness, thinness and shortness. . The outline will be described below.

In FIG. 3, reference numeral 10 is a surface mount type LED. Reference numeral 11 denotes a metal core substrate formed by molding a metal core material such as Mg-based, Al-based, or Cu-based having high heat conductivity into a substantially cubic shape by injection molding or press molding. The metal core substrate 11 is formed so as to form a recess 12 having an inverted trapezoidal cross section. Bottom surface 12a of the recess 12
Also, the slope 12b is provided with a reflective film 13 such as gloss silver plating.

A slit 12c is formed so as to divide the metal core substrate 11 into two parts.
An electrically insulating adhesive 14 is filled therein. This is a state in which two metal cores having a symmetrical shape are integrated by the adhesive agent 14. The electrically insulating adhesive 14 has a thermal expansion coefficient of 40 to 80 ppm / ° of a general epoxy adhesive.
Although it is about C, basically, for example, an epoxy adhesive and a low expansion type adhesive having a thermal expansion coefficient of about 20 ppm / ° C are preferable.

On the metal core substrate 11, a pair of electrode patterns divided into two by an electrically insulating adhesive 14 is formed. Then, the light emitting diode 15 (LE
The bottom surface 12a of the recess 12 for mounting the D element) and the external connection terminal portion of the lower surface 11a of the metal core substrate 11 are each subjected to surface treatment such as gold plating necessary for rust prevention and bonding.

On the bottom surface 12a of the concave portion 12 of the metal core substrate 11, the LED element 15 with bumps, in which the solder bumps 16 are formed in advance on the LED element 15 on both electrode surfaces across the electrically insulating adhesive 14, is flipped. Chip mounted and joined. Then, the surface mount LED 10 is completed by sealing the LED element 15 with the sealing resin 17 made of a transparent resin.

When the surface mount type LED 10 is used, the surface mounting is realized by electrically fixing the external connection terminal portion of the lower surface 11a of the metal core substrate 11 to the printed wiring of the motherboard (not shown) with solder or the like. is there.

[0008]

However, the surface mount type light emitting diode described above is, for example, −40 ° C.
30min → + 100 ° C × 30min for 1 hour 10
Even if a low expansion type electrically insulating adhesive is used under an environmental test such as a heat cycle that guarantees operation after 00 cycles or more, the adhesive, LED element, metal core substrate, etc. have The stress due to the difference occurs,
There is a risk of defects such as solder cracks and bump peeling in the LED element portion, which shortens the life of the surface-mounted light emitting diode.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a highly reliable surface mount light emitting diode which is excellent in heat dissipation and has less stress generated by thermal expansion. .

[0010]

In order to achieve the above object, in a surface mount type light emitting diode according to the present invention, an insulating member is formed by arranging two symmetrical metal cores into a recess having an inverted trapezoidal cross section. Surface mount type light emitting diode in which a substantially three-dimensionally shaped metal core substrate is formed by fixing with, and a light emitting diode element is mounted on the bottom surface of the recess of the metal core substrate, and the light emitting diode element is covered with a sealing resin. In the above, a submount substrate is interposed between the light emitting diode element and the metal core substrate.

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.

Further, the present invention is characterized in that a reflective film is formed on at least the slope of the concave portion of the metal core substrate.

The electrode pattern is made of gold or silver.

Further, the reflective film is characterized in that it is a bright silver plating.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION A surface mount LED according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a surface mount LED according to a first embodiment of the present invention, and FIG. 2 is a sectional view of a submount shown in FIG.

In FIG. 1, the surface mount type LED 1 has a structure in which a submount 2 having an LED element 15 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 similar to that described in the related art, and two metal cores having a symmetrical shape are formed into a recess 12 having an inverted trapezoidal cross section.
To form a substantially three-dimensional shape by bonding with an electrically insulating adhesive 14. On the metal core substrate 11, a pair of electrode patterns divided into two parts by an electrically insulating adhesive 14 is formed, and the bottom surface 1 of the recess 12 is formed.
2a and the external connection terminal portions on the lower surface 11a of the metal core substrate 11 are subjected to surface treatment such as gold plating necessary for rust prevention and bonding. The bottom surface 12a and the sloped surface 12b of the recess 12 are provided with a reflective film 13 such as bright silver plating.

A submount mounted on the bottom surface of the recess of the metal core substrate will be described with reference to FIG. FIG. 2 is a sectional view of the submount. In FIG. 2, 3 is 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 formed by laminating a plating resist on the double-sided copper foil portion of the insulating substrate, exposing and developing it to form a predetermined wiring pattern, and further subjecting it to surface treatment such as gold plating or silver plating. 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.

Then, on the upper surface of the submount substrate 3, both electrode surfaces are astride the upper surface electrodes 4a, 5a,
The LED element 15 with bumps in which the solder bumps 16 are formed in advance on the LED element 15 are flip-chip mounted and joined. Then, the submount 2 is completed by sealing with the sealing resin 17 made of a transparent resin so as to cover the LED element 15.

On the bottom surface 12a of the recess 12 of the metal core substrate 11, the above submount 2 is mounted on both electrode surfaces across the electrically insulating adhesive 14 and die-bonded with silver paste and soldered with solder 5. Connect electrically.

The thermal expansion coefficient of the submount substrate 3 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. In the middle of.

The function and effect of the surface mount LED having the above-described structure will be described. Even under severe environmental tests such as the above-mentioned heat cycle, since the thermal expansion coefficient of the submount substrate is approximately in the middle between the LED element and the metal core substrate, the stress generated by the temperature is relaxed.
Fatal defects such as solder cracks and bump peeling in the D element portion are reduced.

[0022]

As described above, according to the present invention,
The metal core substrate that constitutes the package has excellent heat dissipation,
With the structure in which the submount substrate is interposed between the LED element and the metal core substrate, it is excellent in heat dissipation and is less likely to generate stress due to thermal expansion. A high surface mount light emitting diode can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a surface mount light emitting diode according to an embodiment of the present invention.

2 is a cross-sectional view of the submount of FIG.

FIG. 3 is a cross-sectional view of a conventional surface mount light emitting diode.

[Explanation of symbols]

1 Surface mount LED 2 submount 3 submount board 4a, 5a Top electrode 4b, 5b Side electrode 4c, 5c Bottom electrode 5 solder 11 Metal core substrate 12 recess 12a bottom 12b slope 13 Reflective film 14 Electrically insulating adhesive 15 LED element 16 Solder bump 17 Sealing resin

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Norihiro Sho             Yamanashi Prefecture Fujiyoshida City Kamigure 1-23-1             Citizen Electronics Co., Ltd. (72) Inventor Shinobu Nakamura             2 6663 Funatsu, Kawaguchiko Town, Minamitsuru District, Yamanashi Prefecture               Kawaguchiko Precision Co., Ltd. F-term (reference) 5F041 AA33 AA43 AA44 DA09 DA20                       DA43 DB09

Claims (5)

[Claims] 1. A two-dimensionally symmetrical metal core is fixed by an insulating member so as to form a recess having an inverted trapezoidal cross section to form a substantially three-dimensional metal core substrate, and light is emitted on the bottom surface of the recess of the metal core substrate. In a surface mount type light emitting diode in which a diode element is mounted and sealed with a sealing resin so as to cover the light emitting diode element, a submount substrate is interposed between the light emitting diode element and a metal core substrate. Surface mount type light emitting diode. 2. The surface mounting type light emitting diode according to claim 1, wherein the submount substrate is a wiring substrate in which a predetermined electrode tapan is formed on an insulating substrate made of glass epoxy resin or the like. 3. The surface-mount type light emitting diode according to claim 1, wherein a reflective film is formed on at least the slope of the concave portion of the metal core substrate. 4. The surface mount light emitting diode according to claim 2, wherein the electrode pattern is gold or silver. 5. The surface mount light emitting diode according to claim 3, wherein the reflective film is a bright silver plating.