JPS6076178A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To obtain an element with good heat dissipating property as well as high reliability by interposing a submount of composite structure including a second material having thermal expansivity identical with that of the semiconductor light emitting pellet between the pellet and the package. CONSTITUTION:A light emitting diode pellet 3 is fixed on a stem body 1 of the package through a submount 10 consisting of two different submount members 8 and 9. The first member 8 directly under the light emitting diode is made of a material having good heat conductivity (e.g. copper). The second member 9 of the submount is made of a material having a thermal expansivity equivalent to that of InP which is a main material of the light emitting diode pellet 3, for example of copper-tungsten alloy. By such a construction, heat dissipation directly under the diode pellet can be maintained in a preferably state. Although copper has a thermal expansivity approximately three times larger than that of InP, expansion of copper can be controlled by the alloy layer surrounding it in the construction as described above, and the thermal expansion directly under the substrate is sharply reduced. Thus, a stress due to difference of thermal expansivities, which would deteriorate the reliability, can be minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to improvements in heat dissipation characteristics and reliability of semiconductor light emitting devices.

(Problems with the Prior Art) One of the major problems with semiconductor light emitting devices lies in the heat dissipation design of the light emitting element pellets.

In general, semiconductor light-emitting devices such as light-emitting diodes and semiconductor lasers are driven with large currents of several tens of milliamps for microscopic elements (1,1 mm3 or less), which generates a high density of heat. Therefore, appropriate heat dissipation is required. If the design is not done properly, there is a risk that performance may deteriorate due to heat generation during energized use, the life of the device may be reduced, or the light emitting device itself may be destroyed.

However, semiconductor light emitting devices are generally compact and are often packaged in high density to take advantage of their characteristics, which places great restrictions on the use of heat sinks. Therefore, it is necessary to improve the heat dissipation characteristics of the device itself.

FIGS. 1(a) and Φ) are respectively a top view and a central sectional view of a semiconductor light emitting device using a so-called TO-46 type package, which has been widely used in the past. In the figure, a light emitting element pellet 3 is fixed to a stem body 1 via a submount 2. In terms of heat dissipation characteristics, it is desirable to use a material with as good thermal conductivity as possible for the submount l-2.

However, metal materials with good thermal conductivity generally have a coefficient of thermal expansion different from that of semiconductor crystals, which are the main materials of semiconductor light emitting devices. Therefore, if the semiconductor light emitting device pellets generate even a small amount of heat, stress is generated due to the difference in thermal expansion coefficients, which adversely affects reliability. For this reason, although it is disadvantageous in terms of heat dissipation characteristics, the semiconductor light emitting element pellet itself and the heat 1 bonito elongation are relatively close to each other, such as Si, as a submount.
Fees are used bX.

(Disclosure of the Invention) The present invention has been made to solve the above-mentioned problems, and allows the use of materials with good thermal conductivity for free TVs, and also avoids the adverse effects of stress caused by differences in thermal expansion coefficients. By using a submount with a structure that does not generate heat, it is possible to provide a semiconductor light emitting device with good heat dissipation characteristics and high reliability.

The semiconductor light emitting device of the present invention has a thermal conductivity of 20 W/m'C.
A submount having a composite structure consisting of the first material as described above and a second material that is annularly fixed to the outer periphery of the first material and has the same coefficient of thermal expansion as the semiconductor light emitting device pellet is used as a semiconductor light emitting device. It is characterized by being interposed between the pellet and the package.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings, taking as an example a light emitting diode for communication mainly made of InP, which is one of semiconductor light emitting devices.

FIGS. 2(a) and 2(b) are a top view and a central sectional view similar to FIG. 1, respectively, showing an embodiment of the present invention.

In the figure, a light emitting diode pellet 3 is fixed to the stem body 1 of the package via a submount IO having a composite structure consisting of two types of submount members 8 and 9 as shown in FIG. The first member 8 directly below the light emitting diode is made of a material with good thermal conductivity (for example, copper). The second part 9 of the submount is made of a material with a thermal expansion coefficient similar to that of InP, which is the main material of the light emitting diode pellet 3.
For example, use a copper-tungsten alloy. According to the above structure, heat dissipation directly below the light emitting diode pellet is maintained well. The coefficient of thermal expansion of copper is about three times higher than that of InP, but with the above structure, the expansion of copper goes up to the alloy layer on the outer periphery and is suppressed, and the thermal expansion in the horizontal direction is suppressed directly below the substrate. Significantly lower filtration. Therefore, the stress caused by the difference in thermal expansion coefficient, which causes reliability deterioration, can be suppressed to a minimum.

Depending on the expansion coefficient of the main material of the light emitting diode, other materials such as alloys such as Yuval can be used as the material for the second part 449 used for the outer peripheral part, or materials with a smaller coefficient of thermal expansion can be used. In this case, it may be possible to use an iron-nickel alloy such as Imphal.

(Example) A light emitting diode shown in FIG. 1 was manufactured using a crystal in which InGaAsP was epitaxially grown on InP.
When Si is used as the submount, the temperature of the light emitting diode pellet increases by about 63° C. relative to the outside air when the light emitting diode is driven at 100 mW, especially when no cooler is used.

- When the submount of the present invention with a thickness of 0.8 mm is used directly under the substrate by the method of Riki's invention, the temperature rise can be suppressed to 60"C or less, according to approximate theoretical calculations. Due to the drop, the device life can be improved by about 30%, and the emission power can be improved by about 3%.

(Possibilities for industrial use) As mentioned above, the present invention has 13 reliability, has a fire effect on life, and is useful for communications as taken as an example in the detailed explanation above. This is extremely effective in fields that require reliability, such as light-emitting diodes. However, it is of course not necessary to limit the use to light-emitting devices for communications; it can also be used for light-emitting devices for display, and it goes without saying that similar effects can be expected, as well as the development of electronics technology that includes light-emitting and light-receiving elements called optoelectronics. It greatly contributes to

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) respectively show a top view and a sectional view of the central part of a conventionally widely used light emitting diode. FIGS. 2(a) and 2(b) are a top view and a side view of a light emitting diode showing an embodiment of the present invention. ■...Package stem body 2...Zub mount 3...Light emitting element pellet 4...Lead wire 5...First lead wire 6...Insulating glass 7...Second lead drawer Line 8: A first submount material having good thermal conductivity; a first submount member made of a blank material; 9: a second submount made of a second submount material having a coefficient of thermal expansion equal to that of the light emitting element pellet; Member 10: Composite structure submount head 1 Figure 2

Claims (1)

[Claims] (1) When fixing a semiconductor light-emitting device pellet to a package, a first material having a thermal conductivity of 20 W/m'C or more and a semiconductor A semiconductor light emitting device characterized in that a submount having a composite structure made of a second material having the same coefficient of thermal expansion as the light emitting element pellet is interposed between the semiconductor light emitting element pellet and the cage.