JP2001024228A - Light emitting device - Google Patents

Abstract

(57) [Problem] To provide a light emitting device having sufficiently high reliability even under severe environmental conditions and excellent in optical characteristics. SOLUTION: The light emitting device includes a molded body formed by integrally molding a positive and negative lead electrode and a molding resin, and a light emitting element chip having positive and negative electrodes connected to the positive and negative lead electrodes, respectively. A light-emitting element in which a light-emitting element chip is sealed on a molded body with a light-transmitting resin, and the positive and negative lead electrodes are substantially except for portions connected to the positive and negative electrodes of the light-emitting element chip. It was made to be covered with molding resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-emitting device using an LED chip which can be used for various indicators, displays, writing light sources for optical printers, and light sources for liquid crystal backlights. It relates to the structure of the light-emitting device as intended.

[0002]

2. Description of the Related Art Today, light emitting devices using LED chips are widely used as various light sources. The LED chip is a semiconductor light-emitting element, and has characteristics of not being broken and having excellent ON / OFF drive characteristics, and thus is considered to be more widely used in the future. The LED chip is extremely small, about 300 μm square, and is usually used after being connected to a lead electrode and then molded with a resin. Recently, a chip type light emitting element that can be surface-mounted is often used. It is becoming.

In a chip type light emitting device, a package made of a liquid crystal polymer having a concave portion for accommodating an LED chip is used, and a lead electrode is embedded in the package. Further, the lead electrode is exposed at the bottom surface of the concave portion for connecting to the LED chip. The LED chip is fixed to the concave portion of the package manufactured as described above with a die bond resin or the like, and the exposed lead electrode and L
After connecting the electrodes of the ED chip with, for example, metal wires, the light emitting device is manufactured by covering the LED chip with a translucent epoxy resin to protect the LED chip. Thus, a light-emitting device having excellent optical characteristics can be obtained. The chip-type light-emitting device thus manufactured is surface-mounted in the same manner as other chip-type components, and current is supplied to the LED chip via a lead electrode, thereby causing the LED to emit light.
The chip emits light, and the emitted light is emitted directly from the LED chip or reflected on the side surface of the concave portion to the outside of the package.

[0004] In recent years, LED chips have been used for various purposes, and soldering methods have been diversified.
Even in a package of a chip type light emitting device, various devices have been devised to facilitate electrical connection and handling.

[0005]

However, as the light emitting device has been used under severe operating conditions as the field of use of the light emitting device has expanded, the light emitting device has higher reliability and excellent optical characteristics. Is required.

Accordingly, an object of the present invention is to provide a light emitting device which has sufficiently high reliability under severe environmental conditions and has excellent optical characteristics.

[0007]

That is, a light emitting device according to the present invention comprises a molded body in which positive and negative lead electrodes and a molding resin are integrally molded, and a molded body which is connected to the positive and negative lead electrodes, respectively. A light-emitting element chip having positive and negative electrodes, wherein the light-emitting element chip is sealed on the molded body with a transparent resin, wherein the positive and negative lead electrodes are respectively The light-emitting element chip is substantially covered with the molding resin except for portions connected to the positive and negative electrodes. With this configuration, in the light emitting device according to the present invention, the area of the interface between the positive and negative lead electrodes and the translucent resin can be made extremely small, and vaporization and expansion at the interface can be prevented. Also,
By reducing the area of the exposed part of the lead electrode in the molded body, when the light emitting chip is covered with a translucent resin,
Since the area of the interface between the molding resin and the translucent resin having relatively strong adhesion can be relatively increased, the adhesion between the molded body and the translucent resin can be increased. That is, in the light emitting device according to the present invention, it is possible to prevent vaporization and expansion at the interface between the positive and negative lead electrodes and the translucent resin, and to increase the adhesion between the molded body and the translucent resin. Separation of the interface between the molded article and the translucent resin can be effectively prevented, and the reliability can be extremely increased.

Further, in the light emitting device according to the present invention,
The molded body may have a concave portion for accommodating a light emitting chip, and the light emitting element chip may be provided in the concave portion and sealed with the translucent resin. Furthermore, in the light emitting device using the molded body in which the concave portion is formed, it is preferable that at least a part of the surface of the concave portion is treated so as to reflect light generated by the light emitting element chip. The light emitted from the light emitting chip can be effectively output upward.

Further, in the light emitting device according to the present invention, the light emitting element chip has both the positive and negative electrodes formed on the surface opposite to the light emitting surface, and the molded body has the positive and negative lead electrodes respectively. The light emitting element chip may be exposed so as to face the positive and negative electrodes, and the positive and negative lead electrodes may be joined so as to conduct with the positive and negative electrodes at the exposed portions. That is, in the present light emitting device, the light emitting element chip is mounted with a so-called flip chip with its electrode facing down. In this case, the interface between the positive and negative lead electrodes and the translucent resin is formed. Since the area of the light emitting device can be further reduced, the reliability can be further increased, and the thickness of the light emitting device can be reduced as compared with the method of connecting by wire bonding.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A light emitting device (chip type LED element) according to an embodiment of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2B, the light emitting device of the present embodiment has a concave portion 2 and a concave bottom surface 2 thereof.
The molded body package 1 is formed by exposing a part of the positive lead electrode 3 and a part of the negative lead electrode 4 to the LED b. Here, particularly in the light emitting device of the present embodiment, the positive and negative lead electrodes 3 and 4 are substantially covered with the molding resin 1a except for the portions connected to the positive and negative electrodes of the light emitting element chip. Thus, the light emitting device of the present embodiment has an excellent effect that high reliability can be ensured even in a severe use environment.

That is, according to the present invention, in the conventional light emitting device (shown in FIG. 7), the metal forming the lead electrodes 203 and 204 of the molded package 201 and the translucent resin 206 sealing the LED chip 5 are provided. The inventors have found that the following deterioration in reliability or deterioration in light emission characteristics occurs due to poor adhesion between the substrate and the substrate, and the present invention has been completed to solve the problems. Analysis of Causes of Deterioration of Reliability in Conventional Example (1) Moisture is easily absorbed at the interface between the metal of lead metals 203 and 204 and translucent resin 206 at the time of manufacture or the like. Exposure to a high temperature such as during attachment causes vaporization and expansion, and separation between the light-transmitting resin and the metal causes the formation of the space 210. (2) Optical properties change or the LED chip does not emit light due to separation between the light-transmitting resin and the metal.

On the other hand, in the light emitting device of the present embodiment, the positive and negative lead electrodes 3 and 4 are substantially formed by the molding resin 1a except for the end portions connected to the positive and negative electrodes of the light emitting element chip. The molded package 1 is configured to be covered. Therefore, in this light emitting device, after sealing with the translucent resin 6, the lead electrodes 3, 4
There is almost no interface between the resin and the light-transmitting resin 6, and the interface does not contain water that causes a problem. Therefore, the reliability and the light emission characteristics are not deteriorated by the vaporization and expansion of the moisture at the interface between the lead electrodes 3 and 4 and the translucent resin 6.

Hereinafter, each configuration of the light emitting device of the present embodiment will be described in detail. (Molded Body Package 1) The molded body package 1 is obtained by inserting the lead electrodes 3 and 4 into predetermined positions in the mold 507 shown in FIG. By injecting. The molten resin injected into the mold is taken out of the mold after cooling, and the lead electrodes 3 and 4 are each processed into a predetermined shape.

Here, as the molding resin 1a, an insulating support member such as a liquid crystal polymer, a polybutylene terephthalate (PBT) resin, a polyamide resin, an ABS resin, and a melamine resin can be used. In the present embodiment,
The molded package 1 was formed so as to have inclined side walls 2a in order to efficiently extract light from the LED chip 5. Further, in the present invention, the reflectance of light on the surface of the molding resin, in particular, the surface of the side wall 2a is improved by mixing the molding resin 1a with a white pigment such as barium titanate, titanium oxide, zinc oxide or barium sulfate. Preferably.

As described above, when the molded package 1 is molded in a mold by molding or the like, the lead electrodes 3 and 4 arranged inside the mold are exposed at the bottom surface of the concave portion of the molded package 1. Close the part to the mold,
By injecting the resin so as to cover the lead electrodes 3 and 4 except for the parts that have been brought into close contact with each other, the molded package 1 of the present embodiment can be formed relatively easily.

The mold 507 for molding the molded package 1 of the present embodiment includes
And a second portion for making the convex portion 502 further contact a part of the lead electrodes 3 and 4.
It has a convex part 503. The mold 5 thus formed
After arranging the lead electrodes 3 and 4 at predetermined positions at 07, a molded body package 1 is formed by injecting a liquid crystal polymer into a mold and curing it. Therefore, in the molded package 1 formed by molding, a part of the lead electrodes 3 and 4 is exposed only on the bottom surface of the second concave portion 2c formed on the concave bottom surface 2b corresponding to the second convex portion 503 of the mold. You. That is,
The electrode leads 3 and 4 located in the concave portion 2 other than the second concave portion 2c are all covered with the molding resin. Note that the package of the light emitting device of this embodiment is LE
In order to mount the D chip 5 in a flip-chip manner, the LED chip 5 is formed so that the connection portions of the positive lead electrode 3 and the negative lead electrode 4 are exposed at positions facing the positive and negative electrodes, respectively.

(Lead Electrodes 3, 4) The lead electrodes 3, 4 can be formed using an electric conductor such as phosphor bronze. Further, in order to improve the reflectance of light from the LED chip 5, the surfaces of the lead electrodes 3 and 4 can be plated with a metal such as silver, aluminum, copper or gold. Is preferably smoothed to improve the reflectance. In addition, it is preferable that the area of the lead electrodes 3 and 4 is large. In this case, the heat dissipation can be increased, so that the temperature rise of the LED chip can be effectively suppressed. As a result, a relatively large amount of current can flow through the LED chip, and the light output can be increased.

(Transparent sealing resin 6) Transparent sealing resin 6
Is filled in the recess of the package to protect the LED chip 5 from external force, dust and the like, and high light transmittance is required to efficiently transmit the light from the LED chip 5 to the outside. Incidentally, the structure in which the electrode of the LED chip and the lead electrode are connected by a wire also has a function of protecting the wire. Epoxy resin, silicone resin, acrylic resin, or the like is suitable as the material of the light-transmitting sealing resin 6, and the light-transmitting sealing resin 6 has a specific filter effect against light from the LED chip 5. A coloring dye or a coloring pigment can be added in order to have

(LED Chip 5) The LED chip 5 is made of a nitride semiconductor (In _x Ga _Y Al _{1 -XYN} , 0 ≦ X, 0 ≦
Y, 0 ≦ X + Y ≦ 1), and both positive and negative electrodes are formed on the opposite side of the substrate. That is, since a high-quality nitride semiconductor can be grown on an insulating sapphire substrate, a light-emitting element using a nitride semiconductor is formed using a sapphire substrate. In the light emitting element using this sapphire substrate, since the sapphire substrate is an insulator, no current can be supplied to the n or p side through the substrate, so that both the positive and negative electrodes are on the semiconductor layer. (On the same surface side). In this case, the emitted light can be extracted through the sapphire substrate, or can be extracted from the semiconductor layer side by forming a light-transmitting electrode. In this embodiment mode, the emitted light can be extracted through the sapphire substrate. It is configured to extract light.

More specifically, the LED chip 5
Are formed on a sapphire substrate 5s, an n-type nitride semiconductor layer 5e composed of one or more layers, an active layer (not shown), and a p-type nitride semiconductor layer 5d composed of one or more layers, Further, positive and negative electrodes are formed as follows. That is, the positive electrode is composed of the electrode 5c formed on almost the entire surface of the p-type nitride semiconductor layer 5d and the pad electrode 5a formed on a part of the electrode 5c, and the negative electrode is formed on the p-type nitride semiconductor layer. The electrode 5b is formed on the surface of the n-type nitride semiconductor layer 5e which is exposed by removing a part of 5d.

In order to efficiently inject a current into the active layer, the p-type nitride semiconductor layer 5d or the n-type nitride semiconductor layer 5
e and a metal that provides good ohmic contact,
Used as the electrode 5c and the electrode 5b. In the present embodiment, it is preferable to use a metal film that reflects light emitted from the active layer as the electrode 5c that covers the p-type nitride semiconductor layer 5d. Part of the light is reflected by the electrodes, and more light is output from the front surface (via the substrate).

LED chip 5 configured as described above
The flip-chip mounting can be performed by bonding the lead electrodes 3 and 4 exposed on the bottom surface of the second concave portion 2c of the molded package 1 to each other with the positive and negative electrodes facing each other using solder. The flip-chip mounted LED element can efficiently output light through the sapphire substrate due to the high transmittance of the light to the substrate.

As described above, in the light emitting device of the present embodiment, the positive and negative lead electrodes 3 and 4 are substantially covered with the molding resin 1a except for the portions connected to the positive and negative electrodes of the light emitting element chip. Have been done. As a result, the interface between the lead electrodes 3 and 4 and the translucent resin 6 can be made extremely small, so that the vaporization and expansion of moisture at the interface can be substantially eliminated, and high reliability is secured even in a severe use environment. be able to.

In the light emitting device of the present embodiment, the reflectance of the surface of the molding resin is improved by mixing the molding resin with a white pigment such as barium titanate, titanium oxide, zinc oxide or barium sulfate. In addition, light emitted from the electrode side or the end face of the light emitting element chip can be extracted forward, and the light emission luminance can be improved. More specifically, as shown in the schematic diagram of FIG. 6, light 608 incident from the light emitting point 612 of the LED chip to the surface 604 of the translucent sealing material at an angle θ equal to or greater than the critical angle is transmitted through the translucent sealing agent. Is reflected at the critical angle at the interface (surface 604) between
Numeral 9 reaches the surface of the package having diffuse reflection (the side surface of the concave portion in FIG. 6). The reflected light 609 is scattered and reflected on the surface of the package, and of the scattered light 610, light incident on the surface 604 at a critical angle or less is directly extracted from the light-transmitting sealant to the outside. Also, light having a critical angle or more at the critical angle of the scattered light is reflected at the critical angle at the interface between the transparent sealing material and the outside, arrives at the package surface again, is scattered and reflected in the same manner as described above, and a part of the light is radiated to the outside. Is done. In this manner, most of the emitted light can be extracted to the outside.

Modifications In the above embodiment, an example using a nitride semiconductor as the LED chip 5 has been described. However, the present invention is not limited to this. For example, the MOCVD method or the liquid phase growth method GaP, GaAlAs, GaAlInP
Alternatively, a chip formed using a semiconductor such as a semiconductor chip may be used. Further, in the present invention, MIS is used as the LED chip 5.
Various structures such as a homo structure, a hetero structure, and a double hetero structure having a junction, a PIN junction, a pn junction, or the like can be used. Further, in the present invention, the mounting of the LED chip is not limited to the flip chip mounting, and a mounting method of connecting the electrodes by wire bonding may be used. As described above, the present invention can be variously modified as described above, and even if modified in such a manner, the present invention has the same effect as the embodiment.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a light emitting device according to an embodiment of the present invention will be described. (Example 1) In Example 1, an LED chip having a nitride semiconductor capable of emitting blue light (470 nm) in a light emitting layer was used as the LED chip 5, and a light emitting device having the same configuration as the embodiment of FIG. It is an example of an apparatus. That is, the first embodiment
In FIG. 3, the molded package 1 is a mold 50 shown in FIG.
The lead electrodes 3 and 4 are arranged in advance as shown in FIG. 3 and are prepared by injecting and curing a liquid crystal polymer.
The liquid crystal polymer to be injected is obtained by mixing white titanium oxide powder as a filler into a white resin in an amount of about 40 wt%, so that the surface of the molded resin becomes blue (470 nm).
Has a high reflectance with respect to the light.

The molded package 1 produced as described above
Next, an LED chip capable of emitting blue light produced so as to output light through the sapphire substrate 5s is flip-chip bonded and sealed with the translucent resin 6, as shown in FIG. .

The chip type L manufactured as described above
1000 light emitting devices of Example 1 as ED elements
Leave at 0 ° C. and 90% relative humidity for 24 hours.
After reflow was performed at 0 ° C. for 10 seconds, when current was supplied, all 1000 light emitted blue light out of 1,000 light.

On the other hand, in order to compare with the embodiment 1, the chip type LED element of the embodiment 1 was manufactured in the same manner as the chip type LED element of the embodiment 1 except that the lead electrode was largely exposed on the bottom surface of the concave portion of the package. Chip type LE
A similar test was performed by fabricating a D element. As a result, 43 out of 1,000 chip type LED elements of the comparative example did not emit light. Inspection of the unlit products that did not emit light revealed that in all of them, the sealing resin was peeled off from the bottom surface of the concave portion of the package, and the connection between the LED chip and the lead electrode was disconnected.

When the light emitting device according to the first embodiment and the light emitting device according to the comparative example are compared with each other for the light emitting device after the test, the chip type LED element of the first embodiment emits blue light in the entire concave portion 2. In contrast, the chip-type LED element of the comparative example was observed to emit light remarkably near the LED chip. The average light emission luminance of the chip type LED element of the comparative example was 100
As a result, about 30% of the former chip type LEDs were observed to have high luminance. This is the chip type LED of Example 1.
In the element, the light emitted by the LED chip is
This shows that the light is effectively reflected at the concave portion 2 of the package and output efficiently.

As described above, the chip-type LED element according to the first embodiment of the present invention has almost all of the lead electrodes 3 and 4 of the molded package 1 except for the connection portion for connecting to the LED chip. Since the portion was covered with the molding resin, it was confirmed that peeling between the translucent resin 6 and the bottom surface of the concave portion of the package could be prevented, thereby improving reliability. Further, in the first embodiment, since the LED chip is flip-chip mounted, the boundary surface between the metal constituting the electrode of the LED chip and the light-transmitting resin can be made extremely small, and the lead electrodes 3 and 4 can be connected to the light-transmitting resin. In addition to preventing vaporization and expansion at the interface with the transparent resin 6, it is possible to further prevent vaporization and expansion at the boundary surface between the metal forming the electrodes of the LED chip and the translucent resin 6. Thereby, the adhesion between the surface of the light emitting element and the mold resin can be strengthened, and separation at the interface can be prevented, so that the reliability can be further improved. Further, the chip-type LED element of Example 1 according to the present invention has a white liquid crystal polymer further containing titanium oxide having a high reflectance in white to increase the reflectance and enable diffuse reflection.
It was confirmed that the light emitted from the LED chip could be output efficiently.

(Embodiment 2) A chip type LED element (light emitting device) according to Embodiment 2 of the present invention is a GaAs having a positive electrode formed on the front surface and a negative electrode formed on the back surface (lower surface of the substrate). An example in which the configuration of the present invention is applied using a system LED chip 105 is shown. In the chip type LED element of the second embodiment, the molded package 10
0 is the first in the concave portion 102 as shown in FIGS.
A part of the lead electrode 4 is exposed in the connection recess 102c, and a part of the lead electrode 3 is exposed in the second connection recess 102d.

In the second embodiment, the negative electrode formed on the back surface of the LED chip 105 configured as described above is opposed to the lead electrode 4 exposed in the connection recess 102c by a conductive adhesive, solder, or the like. The gold wire 1 is connected to the lead electrode 3 which has been joined and the positive electrode on the surface is exposed to the second connection recess 102d.
10 and connected by wire bonding.

The chip type LED device of Example 2 manufactured as described above had the same effect as that of Example 1. The chip type LED element of Example 2 was left at -40 ° C for 15 minutes,
When a gas phase thermal shock test was performed in which leaving for 1 minute was one cycle, the wire was not broken even at the time of 3000 cycles in the chip type LED element of Example 2, but it was prepared for comparison with the present invention. Chip type LED
In the device, wire breakage occurred in 5 out of 100 wires at 3000 cycles.

[0035]

As described in detail above, the light emitting device according to the present invention is substantially identical to the light emitting device except that the positive and negative lead electrodes are respectively connected to the positive and negative electrodes of the light emitting element chip. Because it is covered by the molding resin,
Evaporation and expansion at the interface between the positive and negative lead electrodes and the translucent resin can be prevented, and the adhesion between the molded body and the translucent resin can be enhanced. Thereby, the light emitting device according to the present invention can effectively prevent the interface between the molded body and the translucent resin from peeling off, and can achieve extremely high reliability.

In the light emitting device according to the present invention,
The molded body may have a concave portion for accommodating a light emitting chip, and the light emitting element chip may be provided in the concave portion and sealed with the translucent resin. Furthermore, in the light emitting device using the molded body in which the concave portion is formed, it is preferable that at least a part of the surface of the concave portion is treated so as to reflect light generated by the light emitting element chip. The light emitted from the light emitting chip can be effectively output upward, and the light extraction efficiency can be increased.

Also, in the light emitting device according to the present invention, the area of the interface between the positive and negative lead electrodes and the light transmitting resin can be reduced by mounting the light emitting element chip by flip chip mounting. In addition, the thickness of the light emitting device can be reduced as compared with a method of connecting by wire bonding.

[Brief description of the drawings]

FIG. 1 is a plan view of a light emitting device according to an embodiment of the present invention.

2A is a cross-sectional view taken along line AA ′ of FIG. 1, and FIG. 2B is an enlarged cross-sectional view showing a part of the LED chip 5 in FIG.

FIG. 3 is a cross-sectional view of a mold for producing a molded body package of the light emitting device according to the embodiment of the present invention.

FIG. 4 shows a chip type LED according to a second embodiment of the present invention.
It is a top view of an element (light emitting device).

FIG. 5 is a sectional view taken along line B-B ′ of FIG. 4;

FIG. 6 is a schematic diagram schematically showing reflection on a concave surface according to the embodiment of the present invention.

FIG. 7 is a cross-sectional view for explaining a problem of the conventional example.

[Explanation of symbols]

 1,100: molded package, 1a: molded resin, 2,102: concave, 2a: side wall, 2b: concave bottom, 2c: second concave, 3, 4: lead electrode, 5, 105: LED chip, 5a: Pad electrode, 5b, 5c: electrode, 5d: p-type nitride semiconductor layer, 5e: n-type nitride semiconductor layer, 5s: sapphire substrate, 6: translucent resin, 102c: first connection recess, 102d: second Connection recess, 110: gold wire, 507: mold.

Claims (4)

[Claims] 1. A molded body in which positive and negative lead electrodes and a molding resin are integrally molded, and a light emitting element chip having positive and negative electrodes connected to the positive and negative lead electrodes, respectively. A light-emitting element in which the light-emitting element chip is sealed on the molded body with a light-transmitting resin, wherein a portion where the positive and negative lead electrodes are respectively connected to the positive and negative electrodes of the light-emitting element chip A light emitting device characterized by being substantially covered with the molding resin except for the above. 2. The light emitting device according to claim 1, wherein the molded body has a concave portion, and the light emitting element chip is sealed in the concave portion with the translucent resin. 3. The light emitting device according to claim 2, wherein at least a part of the surface of the concave portion is treated so as to reflect light generated by the light emitting element chip. 4. The light emitting element chip has both the positive and negative electrodes formed on a surface opposite to a light emitting surface, and the molded body has the positive and negative lead electrodes respectively provided on the positive and negative electrodes of the light emitting element chip. The positive and negative lead electrodes are joined so as to be electrically connected to the positive and negative electrodes at the exposed portions.
The light emitting device according to any one of the above.