JPH09298314A - Light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge a heat radiation part and improve the heat radiation, namely to suppress the temp. rise of a light emitting device by fixing a plurality of light emitting elements on electrodes in the same package through a common adhesive. SOLUTION: Electrodes 101 are inserted into a package 103 composed of a liq. crystal polymer molded item and the like, and light emitting elements 105 are fixed on the electrodes 101 through a common adhesive 102. This adhesive is pref. a good thermal-conductive one to transfer the heat from each light emitting element 105 to the identical electrode 101 and pref. a resin binder contg. a conductive member such as Ag, C, Cu, Au, Al and Pd. This allows the identical electrodes 101 with the adhered light emitting elements 105 and outer electrodes 107 to be large sized structures and hence the thermal resistance can be reduced to thereby reduce the temp. rise of the light emitting element assembly due to the increase of the heat radiation rate.

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 a light emitting element, and more particularly to a light emitting device which contains two or more light emitting elements, has stable semiconductor characteristics, and is excellent in color mixing during multicolor light emission. Is.

[0002]

2. Description of the Related Art In a chip part type LED assembly which is a light emitting device, a light emitting element is protected by a chip type protector so that it can be used like an element which is electrically and mechanically stabilized. Therefore, the outer shape is required to be smaller than the intended purpose. Such a chip component type LED assembly is constructed by fixing each LED chip as a light emitting element on a separate electrode in the package in order to individually supply electric power and emit light of a plurality of colors.

However, when the chip component type LED assembly is miniaturized, the heat radiation area for processing the heat emitted by the LED chip is also proportionally reduced. Further, in the multicolor light emitting chip component type LED assembly including a plurality of LED chips, the heat generation amount is remarkably increased as compared with the one including a single LED chip. For this reason, the temperature rise when the light emitting device is turned on is extremely large, and the operating characteristics of the semiconductor light emitting element may become unstable, or the light emitting device may be partially destroyed due to thermal stress. In order to prevent the temperature rise of the LED chip, it is considered that heat generated by the light emitting element is conducted to the package electrode or the like to which the light emitting element is fixed. Specifically, the heat generated by the LED chip emitting light is radiated into the atmosphere through the package electrode on the substrate on which the LED assembly is mounted and the external electrode fixed by soldering or the like. As a result, the temperature rise of the LED assembly is suppressed and the light emission characteristics are maintained in good condition.

That is, in order to further enhance the heat radiation effect, it is necessary to effectively utilize the package electrode and the external electrode as the heat radiation portion, and it is necessary to maximize the surface areas of the package electrode and the external electrode. Increasing the surface area of the external electrodes inevitably increases the size of the electrodes on which the LED chips are arranged. Therefore, the degree of freedom of the circuit layout on the substrate is reduced by the increase of the electrode width, and the space of the external circuit, that is, the size of the substrate is increased. Further, since the LED chip is arranged for each electrode, it is not possible to reduce the distance between the light emitting elements and the color mixing property at the time of multicolor lighting is deteriorated.

Further, in order to reduce the size of the chip part type LED assembly and improve the color mixing property, when the LED chips are arranged close to each other, the collet comes into contact with the LED chip previously mounted at the time of die bonding of the LED chips and each LED. It may damage the tip. On the other hand, if the LED chips are separated from each other to such an extent that they are not damaged, there is a problem that the color mixing property deteriorates. Even if the LED chips are arranged close to each other on the adhesive in order to improve the color mixing property, the LED chips move in the curing stage of the adhesive and the color mixing property cannot be improved. In particular, when the paste viscosity of the paste, which is the adhesive agent, decreases even when the light emitting elements are brought close to each other on the adhesive agent provided on separate electrodes, the surface tension of the paste causes the chip to be viewed planarly. Are attracted to the center of the paste, and the intervals between the chips after curing inevitably become larger than the paste application diameter.

[0006]

Therefore, in the present day when more excellent light emitting characteristics are required, the light emitting device having the above structure is not sufficient, and further improvement in characteristics is required.
In view of such a problem, the present invention is to provide a light emitting device having stable emission characteristics, no color shift, and high color mixing.

[0007]

DISCLOSURE OF THE INVENTION The invention of the present application has a package electrode for supplying electric power from the outside to the inside of the package, and at least two or more light emitting elements which are included in the package and connected to the package electrode. The device is a light emitting device in which the light emitting elements are fixed on the same package electrode via a common adhesive.

The common adhesive is a light emitting device in which a conductive paste is used, and the conductive paste is Ag, C,
The light emitting device is a resin binder containing at least one selected from Cu, Au, Al and Pd. Further, the light emitting element has three or more for each emission wavelength of RGB and has a semiconductor formed on a conductive substrate, and at least two or more light emission having a semiconductor formed on an insulating substrate. The element is also a light emitting device.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventor has conducted various experiments,
The present invention has been completed based on the finding that a light emitting device having excellent light emitting characteristics and color mixing can be obtained by fixing a plurality of light emitting elements on the same electrode with a common adhesive.

That is, the light emitting elements formed on the common adhesive on the same package electrode can be arranged close to each other and firmly fixed, and the heat radiation from the light emitting elements can be efficiently released to the outside. it can. By arranging the light emitting diodes on the same package electrode, it is sufficient to consider the heat radiation property only for the wiring pattern connected to the same package electrode, which facilitates the design of the wiring pattern and increases the heat radiation area. Furthermore, since each light emitting element is arranged on the same electrode, the temperature unevenness of the light emitting element is small and the semiconductor characteristics can be stabilized. Further, by using the common adhesive, the light emitting elements can be arranged densely without damage. When the emission colors are different, the color mixing property can be enhanced. Specifically, FIG. 5A and FIG.
A light emitting element 501 provided on an adhesive as described in (A),
Reference numeral 601 indicates the state of FIG. 5B and FIG.
As described above, the adhesive moves to the center of each of the adhesives 502 and 602. This reduces the paste viscosity during the curing of the adhesive,
It is considered that this occurs because the light emitting element is attracted to the central portion of the adhesive due to the surface tension of the adhesive. When the light emitting elements are arranged on the common adhesive as shown in FIG. 6, the central portion of the paste becomes one point, and therefore each light emitting element is attracted to the common one point by the surface tension of the paste when the paste is cured. Therefore, since the paste is cured while pulling all the chips to one common point, the positions of the respective light emitting elements after curing are brought into close contact with each other without damaging the respective light emitting elements to provide a light emitting device having excellent color mixing. You can

The present invention will be described below. FIG. 1 shows a schematic view of a light emitting element of the present invention, and FIG. 1 (A) shows a top view of the light emitting element. FIG.
It is a typical AA sectional view of (A). A package electrode 1 is provided in a package 103 made of a liquid crystal polymer molding or the like.
01 is inserted. Each LED chip is fixed on this package electrode by using silver paste or the like as a common adhesive. LED which is a light emitting element
Various types of chips can be used. Although various LED chips can achieve desired emission colors, RGB (red, green, blue) emission colors are preferably used for full-color display. Each LED chip is electrically connected from one electrode on the same polarity side to the same package electrode with a conductive wire such as gold or aluminum that is an electrical connection member, or is connected as a back electrode with silver. It is electrically connected via paste. The other electrode on the opposite polarity side of each LED chip is electrically connected to each of the other electrodes provided on the package by using an electrical connection member such as a metal wire.

The LED chip is protected from the external environment by molding in a recess containing the light emitting element of the package with a resin such as translucent silicone or epoxy. Further, the package electrodes are electrically connected and locked to external electrodes such as wiring patterns provided on the substrate on the outside of the package by soldering or the like. With such a structure, each package electrode other than the same package electrode needs to have a size such as a metal wire to be bonded, so that it can be downsized and the same package electrode to which the LED chip is fixed can be enlarged. Become. Further, the external electrodes connected to other than the package electrode to which the LED chip is fixed may have the minimum necessary size capable of supplying current to the LED chip, and the external electrode connected to the package can be enlarged accordingly. The main heat dissipation path in this structure is from the same package electrode to which the LED is fixed to the external electrode and to the atmosphere, and the same package electrode to which the LED chip is fixed and the external electrode can be upsized, so that the thermal resistance can be reduced. . Therefore, the temperature rise of the LED assembly is reduced with the increase of the heat radiation amount. Further, in designing the heat dissipation of the substrate, it is only necessary to consider the heat dissipation of the external electrode connected to the same package electrode to which the LED chip is fixed, so that the design is dramatically facilitated and the manufacture is facilitated. Further, since the front LED chip is mounted on one electrode, the light emitting elements can be arranged densely, and the color mixing property at the time of multicolor light emission is improved. Hereinafter, each configuration of the present invention will be described in detail.

(Package electrode) What is a package electrode?
It is used to supply electric power from the outside of the package 103 to the light emitting element 105 arranged inside. The package electrode can be formed in various sizes depending on heat dissipation, electrical conductivity, characteristics of the light emitting device, and the like. In the present invention, the same package electrode 101 means
The light emitting elements 105 are the same electrodes arranged close to each other. Therefore, all the light emitting elements and the same package electrode may be electrically connected, or at least one of them may be electrically connected. In order to fix each light emitting element on the same package electrode, the other electrodes can be made extremely small enough to be electrically connected to the light emitting element by a wire or the like. Further, it is particularly preferable that the same package electrode has good thermal conductivity in order to dispose the heat emitted from the light emitting element to the outside while disposing each light emitting element. Further, since the light emitting element is arranged on the package electrode, the reflectance is preferably high in order to effectively use the light emitted by the light emitting element. As such a package electrode, a copper or phosphor bronze plate surface plated with a noble metal such as silver or gold is preferably used.
Various types of such package electrodes can be used depending on the electrical conductivity and thermal conductivity, but from the viewpoint of workability, the plate thickness is preferably 0.1 mm to 2 mm.

(Common Adhesives 102, 602) The common adhesive 102 used in the present invention is the same package electrode 1
01 and each light emitting element 105 are fixed,
It means one adhesive agent in which the light emitting elements 105 to be fixed are connected and continuous. It is preferable that the common adhesive 102 has good thermal conductivity in order to conduct the heat radiation from the light emitting element 105 to the same package electrode 101. If desired, the same package electrode can be directly electrically connected as a conductive adhesive. In this case, good electrical conductivity is also required. As such a common adhesive, a resin binder containing a conductive member is preferable. Ag, C, C as a conductive member satisfying the above requirements
u, Au, Al, Pd, etc. may be mentioned. Preferable examples of the resin binder and the common adhesive itself include epoxy resins diluted with a solvent such as n-2-methylpyrrolidone and acetone, and thermosetting resins such as acrylic resin and imide resin. As the common adhesive, one having a large fluidity may be used in order to improve the coating property, or one having a small fluidity may be used in order to prevent a large movement of the LED chip. In any case, it is desirable that it has fluidity before curing and is fixed after curing.

(Package 103) Package 103
Has an electrode for fixing and protecting the light emitting element 105 in the concave portion and for enabling electrical connection to the outside.
That is, in the package 103, a translucent protective body or the like may be housed in the recess of the package in order to further protect the light emitting element 105 from the external environment. Therefore, the package is required to have good adhesiveness to the translucent protective body and higher rigidity than the translucent protective body. Further, in order to improve the adhesiveness with the translucent protective body and direct the force exerted by the translucent protective body at the time of thermal expansion to the outside, the cylindrical portion may be shaped like a sloping pot that expands toward the outside. Further, in order to accommodate and use a light emitting element having a spectral characteristic for visible light, it is preferable that the light emitting element is colored to have a light shielding function. Further, it is desired to have an insulating property in order to electrically shut off the light emitting element and the outside. Further, the package is preferably a package having a small coefficient of thermal expansion in consideration of the adhesion with the protective body when it is affected by heat from the light emitting element or the like. The inner surface of the package can be embossed to increase the adhesive area,
It is also possible to perform plasma treatment to improve the adhesion to the protector.

Resins such as polycarbonate resin, polyphenylene sulfide (PPS), liquid crystal polymer (LCP), ABS resin, epoxy resin, phenol resin, acrylic resin and PBT resin can be used for such a package.

The package has a package electrode on which a light emitting element can be placed in advance and can be electrically connected to one electrode of the light emitting element, and each electrode which can be connected to the other electrode of the light emitting element. Therefore, the package may be formed integrally with the electrode, or the package may be divided into a plurality of pieces and combined by fitting or the like. Such a package can be formed relatively easily by insert molding or the like.

(Light-Emitting Element 105) As the light-emitting element 105 used in the present invention, GaAlN, ZnS, ZnSe, Si is formed on a substrate by a liquid phase growth method, a MOCVD method or the like.
C, GaP, GaAlAs, AlInGaP, InGa
A light emitting layer formed of a semiconductor such as N, GaN, or AlInGaN is used. As a semiconductor structure,
Homo structure having MIS junction, PIN junction and PN junction,
Examples include a heterostructure or a double heterostructure. The emission wavelength can be selected from ultraviolet light to infrared light depending on the material of the semiconductor layer and its degree of mixed crystal. Furthermore, in order to have a quantum effect, the light emitting layer may have a single quantum well structure or a multiple quantum well structure.

A vacuum vapor deposition method or heat is applied to the semiconductor thus formed.
A desired electrode is formed by using various CVD methods utilizing light, discharge energy and the like. The semiconductor electrode may be provided on one side of the semiconductor or on both sides thereof. Directly full cut the semiconductor wafer on which the electrodes are formed with a dicing saw with a blade having a diamond blade tip, or after cutting a groove with a width wider than the blade edge width (half cut), the semiconductor wafer is cut by an external force. Break. Alternatively, an extremely thin scribe line (meridian line) is drawn on the semiconductor wafer by, for example, a grid pattern by a scriber in which a diamond needle at the tip moves reciprocally linearly, and then the wafer is split by external force to cut the semiconductor wafer into chips. Form chips.

In order to allow the light emitting device to emit full-color light, an LED chip that emits RGB light emission colors can be used. In particular, when using outdoors, it is preferable to use green and blue gallium nitride-based compound semiconductors as high-brightness semiconductor materials, and for red, gallium-aluminum-arsenic-based semiconductors and aluminum-indium-gallium. -It is preferable to use a phosphorus-based semiconductor, but various types can be used depending on the application. In addition,
In order to obtain a full-color emission color, the emission wavelength of R: red is 600 nm to 700 nm, and the emission wavelength of G: green is 49.
5 nm to 565 nm, B: blue emission wavelength is 430 n
It is preferably from m to 490 nm. Hereinafter, specific embodiments of the present invention will be described in detail, but it is needless to say that the present invention is not limited to only the specific embodiments.

(Translucent Protective Body 109) Transparent Protective Body 10
Reference numeral 9 is provided to protect each light emitting element 105, the wire 104 for electrical connection thereof, and the like from external force, dust, moisture, and the like. Therefore, the translucent protective body 109 and the light emitting element 105 may be formed in close contact with each other, or may not be in close contact with the light emitting element for heat dissipation and stress relaxation. Further, the light-transmitting protective body 109 may be divided into two or more layers as desired, such as a multilayer structure of layers having different transmittances. As a material for such a translucent protective body, specifically, a resin having excellent weather resistance such as an epoxy resin, a urea resin, a silicon resin, a fluororesin, a polycarbonate resin, or the like is preferably used.

[0022]

【Example】

[Example 1] As the light-emitting elements, three LED chips each having red, green, and blue emission colors and capable of full-color emission by each combination were used. As a semiconductor light emitting layer of the light emitting element, GaAlAs (emission wavelength 660
nm), InGaN (emission wavelength 525 nm), InGa
Each LED chip was constructed using N (emission wavelength 470 nm). Specifically, a semiconductor wafer for an LED chip that emits red light is a P-type GaA substrate on a P-type gallium arsenide substrate that is a conductive substrate continuously by a temperature difference liquid crystal growth method.
lAs is grown, N-type GaAlAs is grown on it,
P-type GaAlAs is formed. The semiconductor wafer that emits blue and green light has a thickness of 400 μm as an insulating substrate.
N-type and P-type gallium nitride compound semiconductors are deposited on the sapphire substrate of 5 .mu.m and 1 .mu.m respectively by MOCVD to form a heterostructure PN junction. The P-type gallium nitride semiconductor is formed by annealing after doping Mg which is a P-type dopant. Next, LE
After electrodes were formed by sputtering so as to be the electrodes of the D chip, a scribe line was drawn by a scriber to use each semiconductor wafer as an LED chip, and the semiconductor wafer was cut into a size of 350 μm square by an external force.

A package electrode having a phosphor bronze plate surface plated with silver was insert-molded in a liquid crystal polymer to form a package having a package electrode on the recess and the bottom of the package. Each LED chip is mounted on a package electrode provided in a recess in the package by a die bonder and Ag.
It was fixed using paste. On the package electrode on which the LED chips are stacked, many adhesives are formed by using a collet so that each LED chip can be arranged on a common Ag paste. After the LED chip is placed on the package electrode and the Ag paste is cured and fixed, the diameter is 0.03 using a wire-bonding device.
The Au wire of mm was wire-bonded to each electrode of the LED chip and the package electrode. Next, a non-colored epoxy resin as a translucent protective body was filled in the concave portion in the package and cured at 120 ° C. for 16 hours. In this way LE of three colors
100 light emitting devices in which D chips were enclosed were formed.

When the three light emitting devices thus formed were lit at a current of 10 mA, the temperature rise could be kept within 20 ° C. on average. In addition, even in the case of multicolor emission, color unevenness did not occur in the package.

[Comparative Example 1] The same package electrode as in Example 1 was formed in the same manner as in Example 1 except that the size of the electrode was changed and the light emitting element was fixed for each package electrode as shown in FIG. It was The formed light emitting device is 10 mA
The temperature rise when three lights are turned on with the current of
There was a temperature increase of 10 ° C or more as compared with. In addition, color mixing at the time of multicolor light emission causes color unevenness in the package.

[0026]

As described above, with the structure of claim 1 of the present invention, since the heat radiating portion can be made larger, the heat radiating property can be improved, that is, the temperature rise of the light emitting device can be suppressed.
Further, since the main heat radiation path is one, the heat design can be facilitated. Further, since the light emitting elements are arranged on the same electrode by using the common adhesive, the intervals between the light emitting elements can be made small without degrading the light emitting characteristics, and the color mixing property is improved.

With the structure according to the second aspect of the present invention, the intervals between the light emitting elements can be made smaller and the color mixture can be improved more easily without lowering the light emitting characteristics.

By adopting the structure of claim 3 of the present invention, a light emitting device having more excellent thermal conductivity and electrical conductivity can be obtained.

With the structure of claim 4 of the present invention, a full-color light emitting device with improved color mixing can be obtained.

[Brief description of drawings]

FIG. 1 shows a schematic view of a light emitting device of the present invention, and FIG.
FIG. 1A is a schematic top view of the light emitting device of the present invention.
1B is a sectional view taken along line AA of FIG.

FIG. 2 is a perspective view showing a package electrode structure of a light emitting device of the present invention.

3A and 3B are schematic diagrams of a light emitting device shown for comparison with the present invention, FIG. 3A is a schematic top view of a light emitting device for comparison, and FIG. 3 is a sectional view taken along line AA of FIG.

FIG. 4 is a perspective view showing a package electrode structure of a light emitting device shown for comparison with the present invention.

FIG. 5 is a schematic top view showing the movement of the light emitting element that occurs when the adhesive used in the light emitting element shown for comparison with the present invention is cured, and FIG. 5 (A) shows the light emitting element before curing. Are brought close to each other, and FIG. 5B is a diagram showing the state after the adhesive is cured.

FIG. 6 is a schematic top view showing the movement of the light emitting element that occurs when the adhesive used in the light emitting element for comparison with the present invention is cured, and FIG. 6 (A) shows the light emitting element before curing. 6A and 6B are brought close to each other, and FIG. 6B is a diagram showing the state after the adhesive is cured.

[Explanation of symbols]

 101 ... Same package electrode 102 ... Common adhesive 103 ... Package 104 ... Electrical connection member 105 ... Light emitting element 106 ... Solder 107 ... External electrode 108 ... Substrate 301 ... Electrode 302 ... Adhesive 303 ... Package 304 ... Electrical connection member 305 ... Light emitting element 306 ... Solder 307 ... External electrode 308 ... Substrate 501, 601, ... .Light emitting elements 502, 602 ... Adhesive

Claims (4)

[Claims] 1. A package electrode for supplying electric power from the outside to the inside of the package, and at least two or more light emitting elements that are included in the package and connected to the package electrode.
A light emitting device comprising: a light emitting device, wherein the light emitting elements are fixed on the same package electrode via a common adhesive. 2. The light emitting device according to claim 1, wherein the common adhesive is a conductive paste. 3. The conductive paste is Ag, C, Cu, A
The light emitting device according to claim 2, which is a resin binder containing at least one selected from u, Al, and Pd. 4. The light-emitting element has three or more for each emission wavelength of RGB and has a semiconductor formed on a conductive substrate, and at least two having a semiconductor formed on an insulating substrate. The light emitting device according to claim 2, which is the above light emitting element.