JPH01137655A - Optical device - Google Patents

Abstract

PURPOSE:To prevent an optical output from deteriorating by forming a package for sealing an LED chip or the like into a double structure of an inner layer made of low stress resin and an outer layer made of normal resin for optical elements. CONSTITUTION:A LED chip 6 having a cathode electrode 7 and an anode electrode 8 in a semispherical state is placed on a submount 5, and connected to a cathode electrode pattern 10 and an anode electrode pattern 11. The submount 5 is placed on a central lead 2, and electrode patterns 9, 10 are connected by wirings 13, 14 to right and left leads 2. A package 1 is formed of an undermolding 3 directly and completely covering the inner ends of the leads 2, the chip 6, and the wirings 13, 14, and a finish molding 4 covering the outside of the molding 3. The molding 3 is made of low stress resin having low Young's modulus and glass transition temperature, and operated as a buffer. Then, since a large stress is not applied to the chip, the deterioration of an optical output at the time of energizing for a long period of time can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to optical devices, such as light emitting diodes (LE
D) Concerning techniques that are effective when applied to devices.

[Conventional technology]

2. Description of the Related Art Light-emitting diode chips (light-emitting diodes) are often used as a light-emitting source for display devices or optical communications. For example, ``Electronic Materials J 1974'' published by Kogyo Research Association.
November issue, published November 1, 1970, P69-P72
describes an LED package-like resin. This document states that the characteristics required for the LED sealing resin are (1) moisture resistance, (2) similar to the case of -S semiconductors.
insulation, (3) heat resistance, (4) moldability and workability.

(5) Mechanical strength, (6) purity, and (7) chemical resistance are required, but it is also stated that (8) light transmittance is added as an optical property. Further, this document states that in order to improve the light transmittance, a filler or the like cannot be mixed. Furthermore, it is also described that casting or transfer molding is performed when a metal frame is used.

[Problems to be Solved by the Invention] When a dome-shaped LED chip is sealed with the transparent resin for optical devices as described above, the light output deterioration during long-term energization of the light-emitting diode device reaches several tens of percent. I understand. This is because transparent resin for optical devices requires a light transmittance of 99% or more, and because filler is not mixed in, the black resin used in -a semiconductor device packages is This seems to be due to the relatively large spiral flow and linear expansion coefficient α. For example, black resin has a spiral flow of 61 cm to 86 cm (1
80°C), linear expansion coefficient α is 2. 2X10-'(1/
'C), whereas the transparent resin for optical devices has a spiral flow of 120cm to 180cm (150°CL).
Both have a linear expansion coefficient α of 6.5×10 −′ (1/′C), which is significantly large. Therefore, thermal stress acts on the light emitting diode chip, reducing the light emitting output.

Therefore, the applicant has developed an LE method using transfer molding.
In order to prevent deterioration of the optical output of D, we adopted an undercoat structure in which the LED chip is covered with silicone, which is often applied to -C semiconductor devices. but,
It has been found that this undercoat structure causes a new problem.

That is, gel-type silicone resins have a glass transition point T0 lower than room temperature, so they are soft at room temperature. As a result, this silicone resin serves to relieve the mechanical stress on the chip of the transparent resin for optical elements made of epoxy resin, and it is possible to reduce the deterioration of the optical output during long-term energization. . However, this type of gel-type silicone resin has a coefficient of linear expansion α that is an order of magnitude higher than the epoxy resin, and when it is applied thickly onto a chip, it peels off at the interface with the epoxy resin due to thermal stress, creating a gap that causes optical properties. The inventor has made clear that the condition deteriorates. In addition, in order to eliminate this drawback, it is possible to apply silicone resin thinly and uniformly on the chip, but it is difficult to apply silicone resin thinly and uniformly due to the small size of the chip. Workability is also poor.

An object of the present invention is to provide a light emitting diode device with excellent characteristics that hardly cause deterioration of optical output.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Means for solving problems]

A brief overview of typical inventions disclosed in this application is as follows.

That is, in the light emitting diode device of the present invention, the package that seals the LED chip, the wires, the inner ends of the leads, etc. has a double structure. The under-mold part of the inner layer is made of a low-stress resin (epoxy resin) with a Young's modulus of 298 kg/cm'' and a glass transition temperature T of 104°C, which are lower than ordinary resins. The finished mold part of the exterior covering has a Young's modulus of 315 kg/cm" and a glass transition temperature Tr of 125°C.
It is made of transparent resin (epoxy resin) for ordinary optical devices. Furthermore, the resins constituting the under-mold part and the finishing mold part have substantially the same characteristic, characterized by a refractive index n, except for the Young's modulus and the glass transition point.

[Effect]

According to the above-mentioned means, the light emitting diode device of the present invention has a package for sealing an LED chip etc., which has a double structure including an under mold part of the inner layer and a finishing mold part of the outer layer, and the under mold part is The resin is made of a low-stress resin with a Young's modulus and a glass transition point T lower than that of ordinary transparent resins for optical devices, so the under-mold part acts as a buffer, so large stress does not act on the chip. Therefore, the deterioration rate ΔP0 of optical output during long-term energization can be suppressed to within 25% (1000 hours). Further, the finished mold part has a Young's modulus and a glass transition temperature T. The higher the moisture resistance, the higher the reliability of the device.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of a light emitting diode device according to an embodiment of the present invention, FIG. 2 is a front view showing the external appearance, and FIG.
This figure is a plan view showing a lead frame used for assembling the light emitting diode device, and FIG. 4 is a perspective view showing the same LED chip and a submount on which the LED chip is mounted.

As shown in FIG. 2, the light emitting diode device according to the present invention consists of a rectangular package 1 made of transparent resin and three glue sticks 2 protruding from one side of the package 1. There is.

In such a light emitting diode device, by applying a predetermined voltage to two of the three leads on both sides, the light emitting diode chip (LED) sealed in the package 1 can be activated.
chip) is designed to emit light. As shown in FIG. 1, the package 1 consists of an inner under-mold part 3 and an outer finish mold part 4 covering the under-mold part 3.

On the other hand, inside the puff cage 1, as shown in FIG. 1, a light emitting diode chip (LED chip) 6 is fixed to the top surface of the tip of the central glue 2 via a submount 5. As shown in FIG. 4, the light emitting diode chip 6 has a hemispherical (dome-like) shape, and has a cathode electrode 7 and an anode electrode 8 on a flat main surface (lower surface in the figure). There is. The cathode electrode 7 is located at the center of the main surface and is a point electrode with a diameter of several tens to several hundred μm. Further, the anode electrode 8 is a horseshoe-shaped electrode that concentrically surrounds the cathode electrode 7, which is a point electrode.

On the other hand, the submount 5, as also shown in FIG.
It has an anode electrode pattern and a cathode electrode pattern 10 on its main surface (upper surface). The anode electrode pattern 9 has a pattern corresponding to the anode electrode 8 of the light emitting diode chip 6, and a part thereof extends to one end side of the submount 5 to form a bonding pad 11 for connecting a wire. ing. Further, the cathode electrode pattern 10 has a pattern corresponding to the cathode electrode 7 of the light emitting diode chip 6, and a part of the cathode electrode pattern 10 extends to the other end side of the submount 5, and has a bonding pad 12 for connecting a wire. It consists of Since the submount 5 has an electrode pattern on its main surface, the entire submount 5 or the surface layer of its main surface is an insulator.

Therefore, the light emitting diode chip 6 is positioned and fixed to the submount 5 by face-down bonding. Further, the bonding pads 11.12 of the submount 5 and the inner ends of the leads 2 extending on both sides of the central lead 2 are electrically connected by wires 13.14.

Further, the under mold part 3 that directly and completely covers the inner end portion of the lead 2, the submount 5, the light emitting diode chip 6, and the bonding pads 11 and 12 is made of a low stress resin made of epoxy resin. . In addition to having the characteristics of general transparent resin for optical devices, this under-mold part 3 has a Young's modulus of 298.
kg/cmt, glass transition point T6 is 104'C
It has low characteristics. Further, the finishing mold part 4 covering the under-mold part 3 is made of epoxy resin as described above. The resin constituting the finishing mold part 4 is a commonly used transparent resin for optical devices, and has a specific gravity of 1.25, a hardness (Shore D) of 85, a water absorption rate of 0.13 wt%, and a linear expansion. Rate α is 6.5x
lO(1/'c), glass transition point T, 125°C, bending strength 12 kg/mm2, flexural modulus (Young's modulus) 315 kg/mm'', conductivity 3.6, refractive index 1.
It is 55.

In this way, the under-mold part 3 has other characteristics, except for the Young's modulus and the glass transition point T6°, that are in line with the finished mold part 4. The under-mold part 3 has a Young's modulus several tens of kg/cm" lower than that of ordinary resin and a glass transition point T several tens of degrees Celsius lower, so it acts as a buffer. As a result, the light-emitting diode chip 6 has a large Since no mechanical force is applied, the optical output deterioration rate ΔP0 during long-term energization can be suppressed to within 25% (1000 hours).

On the other hand, simply sealing the light emitting diode chip 6 and the like with the low stress resin will result in poor reliability in temperature cycle tests, pressure cook tests, and high temperature high temperature tests. Therefore, in this embodiment, the reliability is increased by covering the under-mold part 3 with the finishing mold part 4.

Next, a method for manufacturing such a light emitting diode device will be explained.

In manufacturing this light emitting diode device, the third
A lead frame 16 as shown in the figure is prepared.

This lead frame 16 is formed by punching out a metal plate with a thickness of several mm using a press. The lead frame 16 has a structure in which a plurality of leads 2 project from one side of an elongated frame 17 in parallel at regular intervals. In addition, the frame 1
A dam 18 is provided parallel to the lead 7 and connecting each lead 2. The unit lead frame is composed of three leads 2, as shown in FIG. In addition, in the lead 2, the center glue 2 has a wide tab 19 at its tip (inner end), and the side glue 2 has a wide band 20 at its tip (inner end). ing.

Next, in such a lead frame 16, the submount 5 is fixed onto the tab 19. At this time of fixation, the anode electrode pattern 9. Cathode electrode pattern 10
The fixing is done so that the surface provided with is the upper surface, that is, the exposed surface. Thereafter, the light emitting diode chip is positioned on the submount 5 and fixed by face down bonding. Next, the bonding pads 11 and 12 of the anode electrode pattern 9 and the cathode electrode pattern 10 of the submount 5 are connected to the pads 20 of the leads 2 on both sides by wires 13 and 14. In FIG. 1, for convenience of explanation, the bonding pads 11 and 12 of the anode electrode pattern 9 and the cathode electrode pattern 10 are depicted as extending in the width direction of the tab 19.

Next, this lead frame 16 is molded twice, as shown by the two-dot chain line in FIG. A package 1 is formed. In this mold, transparent resin is used so that the light emitted from the light emitting diode 6 to be sealed can be emitted outside the package 1. Young's modulus is 298k in order not to reduce the deterioration rate of optical output when energized.
g/cm" and a glass transition point T6 of 104°C, which is lower than ordinary transparent resin for optical devices. In addition, the second mold has a Young's modulus of 315 kg/cm".
A highly reliable resin is used for thermal cycle tests and high-temperature tests with a glass transition point T of 125°C.

Next, the cup I9 and the frame 17 connecting the leads 2 are cut and removed from the lead frame 16, and a light emitting diode device as shown in FIG. 1 is manufactured.

According to such an embodiment, the following effects can be obtained.

(1) In the light-emitting diode device of the present invention, the package that covers the light-emitting diode chip has a double structure, and the inner under-mold part is formed of a low-stress resin that does not apply large force to the light-emitting diode chip. Therefore, it is possible to suppress the decrease in the rate of deterioration of the optical output during long-term energization and to improve the characteristics.

(2) The light emitting diode device of the present invention has a double-structured pancage, and the resin constituting the finishing mold part of the outer layer is subjected to thermal cycle tests and high temperature high temperature tests of the low stress resin constituting the under mold part of the inner layer. Since the resin is highly reliable and serves to compensate for low reliability in tests and the like, it is possible to improve the reliability of the light emitting diode device.

(3) Although the package of the light emitting diode device of the present invention has a double structure, both the resins constituting the inner layer and the outer layer have the same coefficient of linear expansion α. This results in the effect that peeling does not occur at the interface with the substrate, and optical loss can also be prevented.

(4) Although the package of the light emitting diode device of the present invention has a double structure, both the resins constituting the inner layer and the outer layer have the same refractive index n, so there is no loss in light emission output. The effect is that it can be taken out without any problems.

(5) According to the above (1) to (4), according to the present invention, a synergistic effect is obtained in that a light emitting diode device with stable light output characteristics and high reliability can be provided with good reproducibility.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor. That is, the numerical values of the specifications of each resin are not limited to those in the examples.

In the above description, the invention made by the present inventor was mainly applied to a light emitting diode device, which is the background field of application, but the invention is not limited thereto. For example, it can also be applied to techniques for sealing other light-emitting elements and light-receiving elements within transparent resin.

The present invention is applicable to at least optical device manufacturing technology.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions among the inventions disclosed in this application is as follows.

In the light emitting diode device of the present invention, the package for sealing the LED chip, etc. has a double structure including an under mold part of the inner layer and a finishing mold part of the outer layer, and the resin constituting the under mold part has a Young's modulus. Since the chip is made of low-stress resin whose glass transition point T6 is lower than that of ordinary transparent resin for optical devices, large stress does not act on the chip, and the optical output deterioration rate ΔP when energized for a long period of time.
O can be suppressed to within 25% (1000 hours). Moreover, since the finished mold part has a high Young's modulus and a high glass transition point T6, moisture resistance is improved and reliability is increased.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the main parts of a light emitting diode device according to an embodiment of the present invention, Fig. 2 is a front view showing the external appearance, and Fig. 3 is a lead frame used for assembling the light emitting diode device. The plan view shown in Fig. 4 is the same <LED
FIG. 2 is a perspective view showing a submount on which a chip and an LED chimp are mounted. DESCRIPTION OF SYMBOLS 1... Pan cage, 2... Lead, 3... Under mold part, 4... Finish mold part, 5... Submount, 6... Light emitting diode chip, 7...
Cathode electrode, 8... Anode electrode, 9... Anode electrode pattern, 10... Cathode electrode pattern,
11.12...Bonding band, 13.14...
・Wire, 16・ ・Lead frame, 17・ ・
・Frame, 18...Dam, I9...Tab, 20...
band. M I Kuni notification Z father 5-LET) も7+ '54'' Xie 4 figure

Claims (1)

[Claims] 1. A substrate, an optical element attached to this substrate, a lead electrically connected to an electrode of this optical element, and a resin covering a part of the optical element, the substrate, and the lead. What is claimed is: 1. An optical device comprising: a package consisting of a double layer structure; 2. The under-mold part that covers the finished mold part of the package exterior is formed of a low-stress resin that has a low Young's modulus and a low glass transition temperature, and other resin properties including the optical refractive index are the same as those of the finished mold part. 2. The optical device according to claim 1, wherein the optical device has similar characteristics.