JP2002208740A - Light emitting diode and forming method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting diode and a forming method thereof which has a granular fluorescent substance for emitting a converted light using a light emitted from an LED chip, and reduces the color nonuniformity in all directions. SOLUTION: The light emitting diode comprises an LED chip on a support and a granular fluorescent substance which absorbs at least a part of a light emitted from the LED chip, and emits a wavelength-converted light. Especially, the thickness of a coating having the granular fluorescent substance disposed on the LED chip is approximately equal to that of a coating having a granular fluorescent substance disposed on the support except the LED chip thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an LED display,
The present invention relates to a light emitting device used for a backlight light source, a traffic light, an illuminated switch, various sensors and various indicators, and in particular, in a light emitting diode having a phosphor capable of emitting light by wavelength conversion of light emitted from a light emitting element, a light emitting direction, The present invention relates to a light emitting diode with improved color tone unevenness and mass productivity and a method for forming the same.

[0002]

2. Description of the Related Art Light emitting diodes (hereinafter referred to as L) are light emitting devices.
Also called ED. ) Are small, efficient and emit bright colors. In addition, since it is a semiconductor element, there is no fear of breaking the ball. It has excellent drive characteristics and is resistant to vibration and repeated ON / OFF lighting. Therefore, it is used as various indicators and various light sources. However, LEDs have an excellent monochromatic peak wavelength, and therefore cannot emit light of a wavelength such as white.

[0003] The applicant of the present invention has proposed a light emitting diode capable of emitting light of another color by converting the color of light emitted from the blue light emitting diode by using a blue light emitting diode and a fluorescent substance. 7-993
No. 45 has developed a light emitting diode. By these light emitting diodes, one kind of LED
Other luminescent colors such as white or green using a blue LED chip can be emitted using the chip.

[0004] Specifically, an LED chip or the like capable of emitting blue light is arranged on a cup provided at the tip of a lead frame. The LED chip is electrically connected to a metal stem or a metal post provided with the LED chip. Further, a fluorescent substance that absorbs light from the LED chip and converts the wavelength is contained in a resin mold member that covers the LED chip. By selecting a blue light emitting diode and a fluorescent substance that absorbs the emitted light and emits a yellow light, a white light can be emitted by using color mixture. This can be used as a white light emitting diode that emits sufficient luminance.

[0005]

However, this light emitting diode tends to be hardly formed in a desired color.
When the light emitting diodes are mass-produced, it is difficult to form each light emitting diode in a desired chromaticity range, and the yield tends to decrease. Further, there is a problem that color unevenness is slightly generated on a light emission observation surface of the light emitting diode.

Specifically, when viewed from the light emission observing surface side, the central portion where the LED chip, which is the light emitting element, is arranged is blue,
A yellow, green or reddish portion may be seen in a ring shape in the peripheral direction. Human tone perception is particularly sensitive in white. Therefore, even with a slight color difference, reddish white,
Feel greenish white, yellowish white, etc.

[0007] Such color unevenness caused by looking directly at the light emission observation surface is not only unfavorable in quality, but also causes color unevenness on the display surface when used in a display device and errors in precision equipment such as an optical sensor. Also. Further, as a more severe condition, the luminance of the light emitting diode tends to decrease when the device is used for a long time with high luminance. An object of the present invention is to solve the above-mentioned problems and to form a light emitting diode with excellent mass productivity, in which color tone unevenness on a light emission observation surface and variation among light emitting diodes are extremely small.

[0008]

The present invention comprises an LED chip disposed on a support, and a particulate phosphor that absorbs at least a part of the light emitted from the LED chip and converts the wavelength to emit light. It is a light emitting diode. In particular, in the present invention, the thickness of the coating portion having the particulate phosphor disposed on the LED chip and the thickness of the coating portion having the particulate phosphor disposed on a support other than the LED chip are different. The light emitting diodes are substantially equal.

According to a second aspect of the present invention, in the light emitting diode according to the second aspect of the present invention, the coating portion includes at least one of Si, Al, Ga, Ti, Ge, P, B and an alkaline earth element together with the particulate phosphor. A light-emitting diode comprising an oxide having at least one species.

According to a third aspect of the present invention, the light emitting layer of the LED chip is a nitride-based compound semiconductor, and the particulate phosphor is an yttrium-aluminum-garnet-based phosphor activated with cerium. It is.

According to the light emitting diode of the present invention, the main emission peak of the LED chip is from 400 nm to 53 nm.
0 nm and the main emission wavelength of the particulate phosphor is LED
The light emitting diode is longer than the main light emission peak of the chip.

According to a fifth aspect of the present invention, in the light emitting diode of the present invention, the light emitting layer of the LED chip is a nitride compound semiconductor and the particulate phosphor is (Re1-xSmx) 3 (Al1-yG).
ay) 5O12: Ce. (However, 0 ≦ x <1, 0 ≦
y ≦ 1, Re is at least one element selected from Y, Gd, and La. According to a sixth aspect of the present invention, there is provided a method for forming a light emitting diode comprising: an LED chip; and a phosphor that absorbs at least a part of the light emitted from the LED chip and converts the wavelength to emit light. In particular,
This is a method for forming a light emitting diode in which a coating portion containing a particulate phosphor is formed on an LED chip by sedimentation of the particulate phosphor dispersed in a gas phase or a liquid phase.

[0013]

According to the present invention, the thickness of the coating portion containing the particulate phosphor is substantially equal on both the LED chip and the substrate on which the LED chip is disposed. The light emitted from the LED chip has a relatively equal optical path length difference and uniform light emission characteristics can be obtained. In addition, color unevenness on the light emitting surface and variations among the light emitting diodes can be extremely reduced. Furthermore, a large amount of light emitting diodes can be formed at once with good productivity by depositing and depositing the particulate phosphor on a package on which a plurality of LED chips are arranged. Even when the amount of the particulate phosphor disposed on the LED is extremely small, the amount of the particulate phosphor (the thickness of the coating portion) can be controlled uniformly.
Therefore, a light emitting diode with less variation can be formed.

The coating part is made of Si, Al, Ga, T
The particulate phosphor is bound with an inorganic substance that is an oxide having one or more of i, Ge, P, B and an alkaline earth element. Thus, even when relatively high energy light from the LED chip is irradiated at a high density, the coating portion does not deteriorate in color. Therefore, it is possible to provide a light emitting diode in which the luminance does not decrease even when the light is emitted with high luminance for a long time.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have obtained L
By distributing the particle phosphors arranged on the ED chip and the particle phosphors arranged on other supports almost evenly, the color tone unevenness on the emission observation surface and the variation of each light emitting device are improved. The inventors have found out what can be done and have accomplished the present invention.

It is considered that the uneven color tone and the variation of each light emitting diode on the light emission observation surface are caused by the inclination in the planar distribution of the particulate phosphor contained in the coating portion when the coating portion is formed. That is, the coating portion can be disposed on a desired cup by discharging the resin containing the particulate phosphor from a tube such as a thin nozzle.

However, it is extremely difficult to apply the particulate phosphor contained in the binder uniformly and at high speed on the LED chip. Further, due to the viscosity of the binder and the surface tension with the package surface in contact with the coating portion, the shape of the finally formed coating portion is not constant. Coating thickness (amount of particulate phosphor)
Are partially different, and the amount of light from the LED chip and the amount of light from the particulate phosphor are partially different.

For this reason, L
The color of light emitted from the ED chip becomes strong, and the color of light emitted from the phosphor becomes strong, causing uneven color tone. Further, it is considered that variations occur for each light emitting diode. In the present invention, uneven color tone and directivity can be improved by uniformly disposing the particulate phosphors formed on the LED chip and other portions. Hereinafter, the constituent members of the present invention will be described in detail.

(Coating Parts 111 and 112) The coating parts 111 and 112 used in the present invention are provided in a cup of a mount lead or an opening of a package separately from a mold member. Examples include a particulate phosphor that converts light emission, and a resin or glass that binds the particulate phosphor. In the coating parts 111 and 112 of the present invention, the thickness of the coating part 111 provided on the LED chip 103 is substantially equal to the thickness of the coating part 112 provided on the support other than the LED chip. The thickness of the coating portion 111 provided on the LED chip 103 and the thickness of the coating portion 112 provided on the surface of the opening of the package serving as a support are such that the particulate phosphor dispersed in the gas phase or the liquid phase can be statically dispersed. It is relatively easy to form substantially the same by placing and settling.

In the coating part, L
High-density light emitted from the ED chip is also reflected, so that the density becomes high. Furthermore, the coating may be exposed to high-density high-energy light by being reflected and scattered by the particulate phosphor. Therefore, a nitride-based semiconductor that emits high-energy light
When used as a chip, Si, Al, Ga, Ti, Ge,
It is preferable to use an oxide having one or more of P, B and an alkaline earth metal as the binder.

One of the specific main materials of the coating portion is a light-transmitting inorganic member such as SiO 2, Al 2 O 3, MSiO 3 (M is Zn, Ca, Mg, Ba, Sr, etc.). The one containing a particulate phosphor is preferably used. The particulate phosphor is bound by these translucent inorganic members and deposited in layers on the LED chip or the support. The coating portion may contain an ultraviolet absorber together with the particulate phosphor.

Such coating sections 111 and 121
Is obtained by thoroughly mixing the particulate fluorescent substance and the binder, which are the materials of the coating portions 111 and 121, and ejecting the mixture into the container 202 from the nozzle of the discharging means 201. In the container 202,
A package 105 having an LED chip is provided. The material ejected from the nozzle is converted into a suspension
Collect in 02. When the container 202 is left standing, the phosphor particles settle, and a phosphor film 204 is formed on the bottom of the container 202. After discharging the supernatant, heated air discharged from the drying device 205 is blown and dried. Thereafter, by taking out each package 105, a light emitting diode having a particulate phosphor can be obtained.

(Particulate Phosphor) The phosphor used in the present invention is a particulate phosphor that emits light when excited by at least light emitted from the semiconductor light emitting layer of the LED chip 103. When the light emitted by the LED chip 103 and the light emitted by the particulate phosphor have a complementary color relationship, white light can be emitted by mixing the respective lights. Specifically, the case where the light from the LED chip 103 and the light of the particulate phosphor excited and emitted by the LED chip 103 correspond to the three primary colors of light (red, green, and blue), respectively, The emitted blue light and the yellow light of the particulate phosphor that is excited and emits light by the emitted blue light are exemplified.

The emission color of the light-emitting diode is determined by the ratio of the particulate phosphor to the inorganic member such as a resin or glass serving as a binder for the particulate phosphor, the settling time of the particulate phosphor,
Various adjustment of the shape of particulate phosphor and LED
By selecting the emission wavelength of the chip, an arbitrary white color tone such as a bulb color can be provided. It is preferable that the light from the LED chip and the light from the phosphor pass through the mold member efficiently outside the light emitting diode.

Specific examples of the particulate phosphor include cadmium zinc sulfide activated by copper and yttrium aluminum garnet-based phosphor activated by cerium. In particular, when used for a long time with high brightness, (Re
1-xSmx) 3 (Al1-yGay) 5O12: Ce (0≤x <
1, 0 ≦ y ≦ 1, where Re is at least one element selected from the group consisting of Y, Gd, and La. Is preferred. Especially as a particulate phosphor (Re1-xSm
When x) 3 (Al1-yGay) 5O12: Ce is used,
Even when the irradiance is (Ee) = 3 W · cm −2 or more and 10 W · cm −2 or less and is arranged in contact with or close to the LED chip, a light emitting diode having sufficient light resistance with high efficiency can be obtained.

(Re1-xSmx) 3 (Al1-yGay) 5 O1
2: Since the Ce phosphor has a garnet structure, it is resistant to heat, light and moisture, and can have an excitation spectrum peak near 470 nm. Also, the emission peak is 530.
A broad emission spectrum that is near nm and extends to 720 nm can be provided. Moreover, the composition A
By substituting a part of 1 with Ga, the emission wavelength shifts to a shorter wavelength, and by substituting a part of Y of the composition with Gd,
The emission wavelength shifts to longer wavelengths. By changing the composition in this way, the emission color can be continuously adjusted. Therefore, there is provided an ideal condition for converting the blue light emission of the nitride semiconductor to white light emission such that the intensity on the long wavelength side can be continuously changed by the composition ratio of Gd.

Such phosphors include Y, Gd, Ce, S
An oxide or a compound which easily becomes an oxide at a high temperature is used as a raw material of m, Al, La and Ga, and these are sufficiently mixed in a stoichiometric ratio to obtain a raw material. Or Y, Gd, C
e, a co-precipitated oxide obtained by co-precipitating a solution obtained by dissolving a rare earth element of Sm in an acid at a stoichiometric ratio with oxalic acid, aluminum oxide, and gallium oxide to obtain a mixed raw material. obtain. An appropriate amount of a fluoride such as ammonium fluoride is mixed into the crucible as a flux and packed in a crucible.
It is fired in a temperature range of 50 to 1450 ° C for 2 to 5 hours to obtain a fired product. Next, the fired product is ball-milled in water, washed, separated, dried, and finally passed through a sieve to obtain a desired particulate phosphor.

In the light emitting diode of the present invention, two or more kinds of particulate phosphors may be mixed. That is, two or more kinds of (Re1-xSmx) 3 (Al1-yG) having different contents of Al, Ga, Y, La, Gd and Sm.
ay) The wavelength components of RGB can be increased by mixing 5O12: Ce phosphor. Further, at present, there are some emission wavelengths of the semiconductor light emitting elements, and therefore, a desired white light or the like can be obtained by mixing and adjusting two or more kinds of phosphors. Specifically, by adjusting and including the amount of phosphors having different chromaticity points according to the emission wavelength of the light emitting element, an arbitrary point on the chromaticity diagram connected between the phosphors and the light emitting element is emitted. be able to.

Such a particulate phosphor can be dispersed in a gas phase or a liquid phase and uniformly emitted. The particulate phosphor in a gas phase or a liquid phase sediments by its own weight. In particular, by allowing the suspension to stand still in the liquid phase, a layer having more uniform particulate phosphor can be formed. By repeating a plurality of times as desired, a desired amount of the particulate phosphor can be formed.

(LED Chip 103) The LED chip 103 used in the present invention can excite the particulate phosphor. The LED chip 103 which is a light emitting element has M
GaAs, InP, GaAs on the substrate by OCVD
lAs, InGaAlP, InN, AlN, GaN, I
A semiconductor such as nGaN, AlGaN, and InGaAlN is formed as a light emitting layer. The structure of the semiconductor is MIS
Homo-structure, hetero-structure or double-hetero structure having a junction, PIN junction, PN junction or the like. Various emission wavelengths can be selected depending on the material of the semiconductor layer and the degree of mixed crystal thereof. Also, a single quantum well structure or a multiple quantum well structure in which the semiconductor active layer is formed as a thin film in which a quantum effect occurs can be used. Preferably, a nitride-based compound semiconductor (general formula: IniGajAlk) capable of efficiently emitting a relatively short wavelength capable of efficiently exciting a particulate phosphor.
N, where 0 ≦ i, 0 ≦ j, 0 ≦ k, i + j + k =
1).

When a gallium nitride-based compound semiconductor is used, sapphire, spinel, SiC, S
Materials such as i, ZnO, and GaN are preferably used. In order to form gallium nitride having good crystallinity, it is more preferable to use a sapphire substrate. When a semiconductor film is grown on a sapphire substrate, it is preferable to form a buffer layer such as GaN or AlN and form a gallium nitride semiconductor having a PN junction thereon. GaN selectively grown on a sapphire substrate using SiO2 as a mask
The single crystal itself can be used as a substrate. In this case, the light emitting element and the sapphire substrate can be separated by etching and removing SiO2 after forming each semiconductor layer. Gallium nitride-based compound semiconductors exhibit N-type conductivity without being doped with impurities. When a desired N-type gallium nitride semiconductor is formed, for example, to improve luminous efficiency, Si, Ge, Se,
It is preferable to appropriately introduce Te, C, and the like. On the other hand, in the case of forming a P-type gallium nitride semiconductor, P-type dopants such as Zn, Mg, Be, Ca, Sr, and Ba are doped.

The gallium nitride-based compound semiconductor is hardly converted into a P-type by doping only with a P-type dopant, so that after the P-type dopant is introduced, the gallium nitride-based compound semiconductor is annealed by heating in a furnace, low-speed electron beam irradiation, plasma irradiation, or the like. Is preferred. As a specific layer structure of the light-emitting element, a gallium nitride semiconductor N-type contact layer, an aluminum gallium nitride semiconductor, and a sapphire substrate having a buffer layer formed of gallium nitride, aluminum nitride, or the like at a low temperature or silicon carbide are used. An N-type cladding layer, an active layer of an indium gallium nitride semiconductor doped with Zn and Si, a P-type cladding layer of an aluminum-gallium nitride semiconductor, and a P-type contact layer of a gallium nitride semiconductor are laminated. Preferred examples are given. In order to form the LED chip 103, in the case of the LED chip 103 having a sapphire substrate, P
After the exposed surfaces of the type semiconductor and the N-type semiconductor are formed, each electrode having a desired shape is formed on the semiconductor layer by using a sputtering method, a vacuum evaporation method, or the like. In the case of a SiC substrate, a pair of electrodes can be formed using the conductivity of the substrate itself.

Next, the formed semiconductor wafer or the like is directly full-cut by a dicing saw in which a blade having a diamond cutting edge is rotated, or after a groove having a width larger than the cutting edge width is cut (half cut). The semiconductor wafer is broken by external force. Alternatively, an extremely thin scribe line (meridian) is drawn on the semiconductor wafer, for example, in a checkerboard pattern by a scriber in which a diamond needle at the tip reciprocates linearly, and then the wafer is cut by an external force and cut into chips from the semiconductor wafer. Thus, the LED chip 103 which is a nitride-based compound semiconductor can be formed.

In the case where the light emitting diode of the present invention emits white light, the main emission wavelength of the LED chip 103 is 400 nm or more in consideration of the complementary color with the particulate phosphor.
0 nm or less is preferable, and 420 nm or more and 490 nm or less are more preferable. In order to further improve the efficiency of the LED chip 103 and the efficiency of the particulate phosphor, respectively, 450 nm
It is more preferably at least 475 nm.

(Package 102) Package 102
Functions as a support for fixing and protecting the LED chip 103 in the recess. In addition, an external electrode 104 which can be electrically connected to the outside is provided. The package 102 may have a plurality of openings in accordance with the number and size of the LED chips 103. Further, it is preferable that the package 102 be colored in a dark color such as black or gray to have a light shielding function, or the light emission observation surface side of the package 102 be colored in a dark color.
The package 102 includes coating portions 111 and 112 to further protect the LED chip 103 from the external environment.
In addition, a mold member 106 which is a light-transmitting protective body can be provided. The package 102 preferably has good adhesion to the coating portions 111 and 112 and the mold member 106 and high rigidity. It is desired that the LED chip 103 has an insulating property in order to electrically disconnect the LED chip 103 from the outside. Further, the package 102 includes the LED chip 1
03, etc., the mold member 1
A material having a small coefficient of thermal expansion is preferable in consideration of the adhesiveness to the film.

The inner surface of the concave portion of the package 102 can be embossed to increase the bonding area, or can be plasma-treated to improve the adhesion to the mold member. The package 102 may be formed integrally with the external electrode 104, or the package 102 may be divided into a plurality of parts and combined by fitting or the like. Such a package 102 can be formed relatively easily by insert molding or the like. Polycarbonate resin, polyphenylene sulfide (P
PS), a liquid crystal polymer (LCP), an ABS resin, an epoxy resin, a phenol resin, an acrylic resin, a resin such as a PBT resin, or a ceramic. Also,
Various dyes and pigments are suitably used as a coloring agent for coloring the package 102 in a dark color system. Specifically, C
Preferred are r2O3, MnO2, Fe2O3, carbon black and the like.

The bonding between the LED chip 103 and the package 102 can be performed with a thermosetting resin or the like.
Specifically, an epoxy resin, an acrylic resin, an imide resin, and the like can be given. In order to dispose and fix the LED chip 103 and electrically connect the LED chip 103 to the external electrode 104 in the package 102, an Ag paste, a carbon paste, an ITO paste, a metal bump, or the like is preferably used.

(External Electrode 104) The external electrode 104 is used to supply power from outside the package 102 to the LE
This is to be used for supplying to the D chip 103. Therefore, there are various types such as those using a conductive pattern provided on the package 102 and a lead frame. Further, the external electrode 104 can be formed in various sizes in consideration of heat dissipation, electric conductivity, characteristics of the LED chip 103, and the like. It is preferable that the external electrode 104 has good thermal conductivity for disposing the LED chips 103 and radiating heat emitted from the LED chips 103 to the outside. External electrode 104
Is preferably 300 μΩ · cm or less, more preferably 3 μΩ · cm or less. The specific thermal conductivity is 0.01 cal / (s) (cm
2) (° C./cm) or more is preferable, and more preferably 0.5
cal / (s) (cm 2) (° C./cm) or more.

As the external electrode 104, a copper or phosphor bronze plate whose surface is plated with a metal such as silver, palladium or gold, or a solder plating is preferably used. When a lead frame is used as the external electrode 104, it can be variously used depending on the electric conductivity and the heat conductivity, but the thickness is preferably 0.1 mm to 2 mm from the viewpoint of workability. As the external electrode 104 provided on a support such as glass epoxy resin or ceramic, a copper foil or a tungsten layer can be formed. When using a metal foil on a printed circuit board, the thickness of the copper foil or the like should be 18 to 7
Preferably, it is 0 μm. Also, gold on copper foil etc.
You may give solder plating etc.

(Conductive Wire 105) The conductive wire 105 is required to have good ohmic contact with the electrodes of the LED chip 103, good mechanical connection, good electrical conductivity and good thermal conductivity. The thermal conductivity is 0.01 cal /
It is preferably at least (s) (cm 2) (° C./cm), more preferably at least 0.5 cal / (s) (cm 2) (° C./cm).
The diameter of the conductive wire 105 is preferably Φ10 μm or more and Φ45 μm or less in consideration of workability and the like. Specific examples of such conductive wires 105 include conductive wires using metals such as gold, copper, platinum, and aluminum and alloys thereof. Such a conductive wire 105 can easily connect an electrode of each LED chip 103 to an inner lead, a mount lead, and the like by a wire bonding device.

(Mold member 106) Mold member 10
Reference numeral 6 can be provided to protect the LED chip 103, the conductive wire 105, and the coating portions 111 and 112 containing the particulate phosphor from the outside according to the application of the light emitting diode. Mold member 106
Can be formed using various resins, glass, or the like. As a specific material of the mold member 106, a transparent resin having excellent weather resistance, such as an epoxy resin, a urea resin, or a silicone resin, or glass is preferably used.
Further, by including a diffusing agent in the mold member, the directivity from the LED chip 103 can be reduced and the viewing angle can be increased. Such a mold member 106
May be the same material as the binder of the coating portion, or may be a different material. Hereinafter, examples of the present invention will be described, but it goes without saying that the present invention is not limited to only specific examples.

[0042]

(Example 1) An In0.2Ga0.8N semiconductor having a main emission peak of 460 nm was used as an LED chip. L
The ED chip is TMG on a cleaned sapphire substrate.
A (trimethyl gallium) gas, a TMI (trimethyl indium) gas, a nitrogen gas and a dopant gas were flowed together with a carrier gas, and a gallium nitride-based compound semiconductor was formed by MOCVD. By switching between SiH4 and Cp2Mg as a dopant gas, a gallium nitride based semiconductor having N-type conductivity and P
A gallium nitride based semiconductor having mold conductivity is formed to form a PN junction. As a semiconductor light emitting device, a contact layer made of a gallium nitride semiconductor having N-type conductivity, a cladding layer made of a gallium aluminum nitride semiconductor having P-type conductivity, and a contact layer made of a gallium nitride semiconductor having P-type conductivity are formed. I let it. An active layer of non-doped InGaN having a thickness of about 3 nm and a single quantum well structure was formed between a contact layer having N-type conductivity and a cladding layer having P-type conductivity. (Note that a gallium nitride semiconductor is formed on a sapphire substrate at a low temperature to serve as a buffer layer. A semiconductor having P-type conductivity is annealed at 400 ° C. or more after film formation.) Sapphire by etching After exposing the surface of each PN semiconductor on the substrate, each electrode was formed by sputtering. After a scribe line was drawn on the semiconductor wafer thus completed, the wafer was divided by external force to form LED chips of 350 μm square as light emitting elements.

On the other hand, a chip type LED package was formed by insert molding using a polycarbonate resin. LE inside the chip type LED package
It has an opening in which the D chip is arranged. In the package, a silver-plated copper plate is arranged as an external electrode. The LED chip is fixed using an epoxy resin or the like inside the package. LE wire is a conductive wire
Each electrode of the D chip and each external electrode provided on the package are electrically connected by wire bonding. Thus, 8280 packages on which the LED chips were arranged were formed. A resist film is formed on the surface of each package excluding the opening. The package in which the 8280 LED chips are placed is placed in a container containing the pure electrolyte.

On the other hand, as the particulate phosphor, a solution obtained by dissolving rare earth elements of Y, Gd and Ce in an acid at a stoichiometric ratio was coprecipitated with oxalic acid. This is mixed with a coprecipitated oxide obtained by calcination and aluminum oxide to obtain a mixed raw material. This was mixed with ammonium fluoride as a flux, packed in a crucible, and fired in air at a temperature of 1400 ° C. for 3 hours to obtain a fired product. Ball-mill the baked product in water, wash, separate,
Dried and finally formed through a sieve. (Y0.
The 8Gd0.2) 3Al5O12: Ce phosphor is dispersed in the SiO2 sol.

Next, after adjusting the pH to 5.0 with acetic acid,
Immediately in the container where the package is placed (Y0.8Gd0.
2) 3Al5O12: Ce phosphor and SiO2 sol are injected at once (FIG. 2 (A)). After standing (Y0.8Gd0.2) 3Al
The 5O12: Ce phosphor sediments and settles on the package (FIG. 2 (B)). The waste liquid in the container is removed, and the package in which the particulate phosphor is deposited on the LED chip is dried with air heated to 120 degrees (FIG. 2 (C)). Thereafter, each light-emitting diode is taken out of the container, and the particulate phosphor adhered to the non-light-emitting portion of the light-emitting diode is removed together with the resist mask, so that the film thickness on both the LED chip and the package bottom is substantially equal to about 40 μm. A part can be formed. Further, a translucent epoxy resin was formed as a mold member in the package opening where the coating was formed in order to protect the LED chip and the particulate phosphor from external stress, moisture, dust and the like. After mixing the translucent epoxy resin, the mixture was cured at 150 ° C. for 5 hours.
Thus, a light emitting diode as a light emitting device as shown in FIG. 1 was formed.

By supplying power to the obtained light emitting diode, white light can be emitted. The color temperature and the color rendering were measured from the front of the light emitting diode. Color temperature 8090K, Ra (color rendering index) = 87.5
showed that. The luminous efficiency was 10.8 lm / w. Further, x, y = (0.305,
0.315) Within a range surrounded by ± 0.03, about 811
Four light emitting diodes were distributed, and the yield was about 98%.

(Comparative Example 1) In an epoxy resin, (Y0.8G
d0.2) A light emitting diode was formed in the same manner as in Example 1 except that a coating was formed by mixing a 3Al5O12: Ce phosphor and projecting from a nozzle. In the cross section of the formed light emitting diode, the end face of the coating portion was raised and the amount of the particulate phosphor was not uniform. The chromaticity point of the light emitting diode thus formed was measured in the same manner as in Example 1. The chromaticity point of the formed light emitting diode was substantially located on a line connecting the main light emission peak of the LED chip and the main light emission wavelength of the phosphor, but the yield was about 6%.
It was only 1%.

[0048]

According to the light emitting diode of the present invention having a uniform coating thickness, a chromaticity shift in each direction is extremely small, and a light emitting diode having no color tone shift from the light emission observation surface can be obtained. Further, a light-emitting diode with a high yield can be obtained.

In particular, by adopting the structure according to the first aspect of the present invention, color shift can be achieved even with high luminance and long time use.
A light-emitting diode with a very small decrease in the luminous efficiency can be obtained.

According to the configuration of the second aspect of the present invention, a light emitting diode having higher light resistance and higher luminous efficiency can be obtained.

By adopting the structure of the third aspect of the present invention, a light emitting diode capable of emitting white light with less decrease in luminance and less color shift even when used at high luminance for a long time can be obtained.

According to the configuration of the fourth aspect of the present invention, a light emitting diode capable of emitting white light and having higher luminous efficiency can be obtained.

By adopting the structure of claim 5 of the present invention, it is possible to obtain a light emitting diode capable of emitting white light with less decrease in luminance and less color shift even when used for a long time with high luminance.

According to the method of claim 6 of the present invention, it is possible to form a light-emitting diode capable of emitting a large amount of light uniformly without emission unevenness with a high yield.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a chip type LED which is a light emitting device of the present invention.

FIG. 2 is a schematic view showing a forming apparatus for forming a light emitting diode of the present invention.

[Explanation of symbols]

111 Coating portion on LED chip 112 Coating portion on support 102 Package 103 LED chip 104 External electrode 105 Conductive wire 106 Mold member 201 ... Ejecting means for ejecting the material of the coating portion 202 ... Container 203 ... Material of the coating portion ejected from the nozzle 204 ... Phosphor film 205 ... Drying device that can blow heated air

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[Procedure amendment]

[Submission date] February 12, 2002 (2002.2.1
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

Patent application title: Light emitting diode and method for forming the same

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an LED display,
The present invention relates to a light emitting device used for a backlight light source, a traffic light, an illuminated switch, various sensors and various indicators, and in particular, in a light emitting diode having a phosphor capable of emitting light by wavelength conversion of light emitted from a light emitting element, a light emitting direction, The present invention relates to a light emitting diode with improved color tone unevenness and mass productivity and a method for forming the same.

[0002]

2. Description of the Related Art Light emitting diodes (hereinafter referred to as L) are light emitting devices.
Also called ED. ) Are small, efficient and emit bright colors. In addition, since it is a semiconductor element, there is no fear of breaking the ball. It has excellent drive characteristics and is resistant to vibration and repeated ON / OFF lighting. Therefore, it is used as various indicators and various light sources. However, LEDs have an excellent monochromatic peak wavelength, and therefore cannot emit light of a wavelength such as white.

[0003] The applicant of the present invention has proposed a light emitting diode capable of emitting light of another color by converting the color of light emitted from the blue light emitting diode by using a blue light emitting diode and a fluorescent substance. 7-993
No. 45 has developed a light emitting diode. By these light emitting diodes, one kind of LED
Other luminescent colors such as white or green using a blue LED chip can be emitted using the chip.

[0004] Specifically, an LED chip or the like capable of emitting blue light is arranged on a cup provided at the tip of a lead frame. The LED chip is electrically connected to a metal stem or a metal post provided with the LED chip. Further, a fluorescent substance that absorbs light from the LED chip and converts the wavelength is contained in a resin mold member that covers the LED chip. By selecting a blue light emitting diode and a fluorescent substance that absorbs the emitted light and emits a yellow light, a white light can be emitted by using color mixture. This can be used as a white light emitting diode that emits sufficient luminance.

[0005]

However, this light emitting diode tends to be hardly formed in a desired color.
When the light emitting diodes are mass-produced, it is difficult to form each light emitting diode in a desired chromaticity range, and the yield tends to decrease. Further, there is a problem that color unevenness is slightly generated on a light emission observation surface of the light emitting diode.

Specifically, when viewed from the light emission observing surface side, the central portion where the LED chip, which is the light emitting element, is arranged is blue,
A yellow, green or reddish portion may be seen in a ring shape in the peripheral direction. Human tone perception is particularly sensitive in white. Therefore, even with a slight color difference, reddish white,
Feel greenish white, yellowish white, etc.

[0007] Such color unevenness caused by looking directly at the light emission observation surface is not only unfavorable in quality, but also causes color unevenness on the display surface when used in a display device and errors in precision equipment such as an optical sensor. Also. Further, as a more severe condition, the luminance of the light emitting diode tends to decrease when the device is used for a long time with high luminance. An object of the present invention is to solve the above-mentioned problems and to form a light emitting diode with excellent mass productivity, in which color tone unevenness on a light emission observation surface and variation among light emitting diodes are extremely small.

[0008]

According to the present invention, there is provided an LED chip disposed on a support, and a particulate phosphor which absorbs at least a part of light emitted from the LED chip and converts the wavelength to emit light. A light emitting diode having the LED
On the chip and on the support, there is provided a coating layer containing an oxide containing at least one of Si, Al, Ga, Ti, Ge, P, B and an alkaline earth element together with the particulate phosphor. It is a light emitting diode characterized by the above.

According to a second aspect of the present invention, in the light emitting diode of the present invention, the support has an external electrode capable of being electrically connected to the outside, and the LED chip is disposed on the external electrode. The light emitting diode according to claim 1, wherein

According to a third aspect of the present invention, there is provided the light emitting diode of the present invention, wherein the light emitting layer of the LED chip is a nitride-based compound semiconductor, and the particulate phosphor is a yttrium-aluminum-garnet-based phosphor activated with cerium. 3. The light emitting diode according to claim 1, which is a phosphor.

In the light emitting diode according to the present invention, the main emission peak of the LED chip is from 400 nm to 530 nm, and the main emission wavelength of the particulate phosphor is higher than the main emission peak of the LED chip. Long claim 3
It is a light emitting diode as described.

[0012] The light-emitting diode of the present invention described in claim 5 is a light emitting layer is a nitride-based compound semiconductor of the LED chip, and said particulate phosphor (Re _1-x Sm _{x)
3 (Al 1-y Ga y} ) 5 O 12: Claim 1 is Ce
3. A light emitting diode according to any one of claims 1 to 2.

Where 0 ≦ x <1, 0 ≦ y ≦ 1, Re
Is a light-emitting diode according to claim 1 or 2, which is at least one element selected from Y, Gd and La.

According to a sixth aspect of the present invention, there is provided the method for forming
On a support on which an ED chip is arranged, at least Si, Al, Ga, together with a particulate phosphor that absorbs at least a part of light emitted from the LED chip and converts the wavelength to emit light.
A method for forming a light-emitting diode having a coating layer containing an oxide having one or more of Ti, Ge, P, B, and an alkaline earth element, wherein the coating layer includes the particles in the oxide sol. A first step of suspending and injecting the dispersed phosphor in a lump on the support, and a second step of drying the support after the first step. This is a method for forming a light emitting diode.

According to a seventh aspect of the present invention, in the first step, the particulate phosphor is dispersed in the oxide sol and ejected from a nozzle onto the support. 7. The method for forming a light emitting diode according to claim 6, wherein the suspension is injected at once.

The method of the present invention according to claim 8, wherein in the second step, the drying is performed by blowing heated air at 120 ° C. This is a method for forming a light emitting diode.

According to the present invention, the thickness of the coating portion containing the particulate phosphor is substantially equal on both the LED chip and the substrate on which the LED chip is disposed. The light emitted from the LED chip has a relatively equal optical path length difference and uniform light emission characteristics can be obtained. In addition, color unevenness on the light emitting surface and variations among the light emitting diodes can be extremely reduced. Furthermore, a large amount of light emitting diodes can be formed at once with good productivity by depositing and depositing the particulate phosphor on a package on which a plurality of LED chips are arranged. Even when the amount of the particulate phosphor disposed on the LED is extremely small, the amount of the particulate phosphor (the thickness of the coating portion) can be controlled uniformly.
Therefore, a light emitting diode with less variation can be formed.

The coating part is made of Si, Al, Ga, T
The particulate phosphor is bound with an inorganic substance that is an oxide having one or more of i, Ge, P, B and an alkaline earth element. Thus, even when relatively high energy light from the LED chip is irradiated at a high density, the coating portion does not deteriorate in color. Therefore, it is possible to provide a light emitting diode in which the luminance does not decrease even when the light is emitted with high luminance for a long time.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have obtained L
By distributing the particle phosphors arranged on the ED chip and the particle phosphors arranged on other supports almost evenly, the color tone unevenness on the emission observation surface and the variation of each light emitting device are improved. The inventors have found out what can be done and have accomplished the present invention.

It is considered that the uneven color tone on the light emission observation surface and the variation among the light emitting diodes are caused by the inclination in the planar distribution of the particulate phosphor contained in the coating portion when the coating portion is formed. That is, the coating portion can be disposed on a desired cup by discharging the resin containing the particulate phosphor from a tube such as a thin nozzle.

However, it is extremely difficult to apply the particulate phosphor contained in the binder on the LED chip in a uniform amount at a high speed. Further, due to the viscosity of the binder and the surface tension with the package surface in contact with the coating portion, the shape of the finally formed coating portion is not constant. Coating thickness (amount of particulate phosphor)
Are partially different, and the amount of light from the LED chip and the amount of light from the particulate phosphor are partially different.

For this reason, L
The color of light emitted from the ED chip becomes strong, and the color of light emitted from the phosphor becomes strong, causing uneven color tone. Further, it is considered that variations occur for each light emitting diode. In the present invention, uneven color tone and directivity can be improved by uniformly disposing the particulate phosphors formed on the LED chip and other portions. Hereinafter, the constituent members of the present invention will be described in detail. (Coating portions 111 and 112) The coating portions 111 and 112 used in the present invention are provided in a cup of a mount lead or an opening of a package separately from the mold member, and convert the light emission of the LED chip 103. And a resin or glass that binds the particulate phosphor. Coating part 11 of the present invention
In Nos. 1 and 112, the thickness of the coating portion 111 provided on the LED chip 103 is substantially equal to the thickness of the coating portion 112 provided on the support other than the LED chip. The thickness of the coating portion 111 provided on the LED chip 103 and the thickness of the coating portion 112 provided on the surface of the opening of the package serving as a support are such that the particulate phosphor dispersed in the gas phase or the liquid phase can be statically dispersed. It is relatively easy to form substantially the same by placing and settling.

In the coating part, L
High-density light emitted from the ED chip is also reflected, so that the density becomes high. Furthermore, the coating may be exposed to high-density high-energy light by being reflected and scattered by the particulate phosphor. Therefore, a nitride-based semiconductor that emits high-energy light
When used as a chip, Si, Al, Ga, Ti, Ge,
It is preferable to use an oxide having one or more of P, B and an alkaline earth metal as the binder.

One of the specific main materials of the coating part is SiO ₂ , Al ₂ O ₃ , MSiO ₃ (M is Zn, Ca, Mg, Ba, Sr, etc.). A translucent inorganic member containing a particulate phosphor is preferably used. The particulate phosphor is bound by these translucent inorganic members and deposited in layers on the LED chip or the support. The coating portion may contain an ultraviolet absorber together with the particulate phosphor.

Such coating sections 111 and 121
Is obtained by thoroughly mixing the particulate fluorescent substance and the binder, which are the materials of the coating portions 111 and 121, and ejecting the mixture into the container 202 from the nozzle of the discharging means 201. In the container 202, L
A package 105 having an ED chip is provided. The material ejected from the nozzle is converted into a suspension
Collect in 02. When the container 202 is left standing, the phosphor particles settle, and a phosphor film 204 is formed on the bottom of the container 202. After discharging the supernatant, heated air discharged from the drying device 205 is blown and dried. Thereafter, by taking out each package 105, a light emitting diode having a particulate phosphor can be obtained. (Particle Phosphor) The phosphor used in the present invention includes:
It refers to a particulate phosphor that emits light when excited by light emitted from at least the semiconductor light emitting layer of the LED chip 103. L
When the light emitted by the ED chip 103 and the light emitted by the particulate phosphor have a complementary color relationship or the like, white light can be emitted by mixing the respective lights. Specifically, the case where the light from the LED chip 103 and the light of the particulate phosphor excited and emitted by the LED chip 103 correspond to the three primary colors of light (red, green, and blue), respectively, The emitted blue light and the yellow light of the particulate phosphor that is excited and emits light by the emitted blue light are exemplified.

The emission color of the light-emitting diode is determined by the ratio of the particulate phosphor to an inorganic member such as a resin or glass that acts as a binder for the particulate phosphor, the settling time of the particulate phosphor,
Various adjustment of the shape of particulate phosphor and LED
By selecting the emission wavelength of the chip, an arbitrary white color tone such as a bulb color can be provided. It is preferable that the light from the LED chip and the light from the phosphor pass through the mold member efficiently outside the light emitting diode.

Specific examples of the particulate phosphor include cadmium zinc sulfide activated by copper and yttrium aluminum garnet phosphor activated by cerium. In particular, when used for a long time with high brightness, (Re
_{1-x Sm x) 3 (} Al 1-y Ga y) 5 O 12: Ce
(0 ≦ x <1, 0 ≦ y ≦ 1, where Re is Y, Gd,
At least one element selected from the group consisting of La. Is preferred. In particular, (R
_{e 1-x Sm x) 3} (Al 1-y Ga y) 5 O 1 2: C
When e is used, it is arranged in contact with or close to the LED chip, and the irradiance is (Ee) = 3 W · cm ^−2.
Even at a value of 10 W · cm ⁻² or less, a light-emitting diode having sufficient light resistance can be obtained with high efficiency.

[0027] _{(Re 1-x Sm x)} 3 (Al 1-y Ga
_y ) Since the ₅ O ₁₂ : Ce phosphor has a garnet structure,
Resistant to heat, light and moisture, the peak of the excitation spectrum is 47
It can be set to around 0 nm. Further, the emission peak is around 530 nm, and a broad emission spectrum with a tail extending to 720 nm can be provided. In addition, the emission wavelength shifts to a short wavelength by substituting a part of the Al in the composition with Ga, and the emission wavelength shifts to a long wavelength by substituting a part of the Y in the composition with Gd. By changing the composition in this way, the emission color can be continuously adjusted. Therefore, there is provided an ideal condition for converting the blue light emission of the nitride semiconductor to white light emission such that the intensity on the long wavelength side can be continuously changed by the composition ratio of Gd.

Such phosphors include Y, Gd, Ce, S
An oxide or a compound which easily becomes an oxide at a high temperature is used as a raw material of m, Al, La and Ga, and these are sufficiently mixed in a stoichiometric ratio to obtain a raw material. Or Y, Gd, C
e, a co-precipitated oxide obtained by co-precipitating a solution obtained by dissolving a rare earth element of Sm in an acid at a stoichiometric ratio with oxalic acid, aluminum oxide, and gallium oxide to obtain a mixed raw material. obtain. An appropriate amount of a fluoride such as ammonium fluoride is mixed into the crucible as a flux and packed in a crucible.
It is fired in a temperature range of 50 to 1450 ° C for 2 to 5 hours to obtain a fired product. Next, the fired product is ball-milled in water, washed, separated, dried, and finally passed through a sieve to obtain a desired particulate phosphor.

In the light emitting diode of the present invention, two or more kinds of particulate phosphors may be mixed. That, Al, Ga, Y, the content of La and Gd and Sm are two or more kinds of _{(Re 1-x Sm x)} 3 (Al
_{1-y Ga y) 5 O} 12: by mixing Ce phosphor RG
The wavelength component of B can be increased. Further, at present, there are some emission wavelengths of the semiconductor light emitting elements, and therefore, a desired white light or the like can be obtained by mixing and adjusting two or more kinds of phosphors. Specifically, by adjusting and including the amount of phosphors having different chromaticity points according to the emission wavelength of the light emitting element, an arbitrary point on the chromaticity diagram connected between the phosphors and the light emitting element is emitted. be able to.

Such a particulate phosphor can be dispersed in a gas phase or a liquid phase and uniformly emitted. The particulate phosphor in a gas phase or a liquid phase sediments by its own weight. In particular, by allowing the suspension to stand still in the liquid phase, a layer having more uniform particulate phosphor can be formed. By repeating a plurality of times as desired, a desired amount of the particulate phosphor can be formed. (LED Chip 103) The LED chip 103 used in the present invention can excite the particulate phosphor.
The LED chip 103 serving as a light emitting element is formed on a substrate by GaAs, InP, GaAlAs, InAl by MOCVD or the like.
GaAlP, InN, AlN, GaN, InGaN, A
A semiconductor such as lGaN or InGaAlN is formed as a light emitting layer. Semiconductor structures include MIS junction, PIN
Examples include a homostructure, a heterostructure, and a double heterostructure having a junction or a PN junction. Various emission wavelengths can be selected depending on the material of the semiconductor layer and the degree of mixed crystal thereof. Also, a single quantum well structure or a multiple quantum well structure in which the semiconductor active layer is formed as a thin film in which a quantum effect occurs can be used. Preferably, a nitride-based compound semiconductor capable of efficiently emitting a relatively short wavelength capable of efficiently exciting the particulate phosphor (general formula: In _i Ga _j Al _k N;
0 ≦ i, 0 ≦ j, 0 ≦ k, i + j + k = 1).

When a gallium nitride-based compound semiconductor is used, sapphire, spinel, SiC, S
Materials such as i, ZnO, and GaN are preferably used. In order to form gallium nitride having good crystallinity, it is more preferable to use a sapphire substrate. When a semiconductor film is grown on a sapphire substrate, it is preferable to form a buffer layer such as GaN or AlN and form a gallium nitride semiconductor having a PN junction thereon. GaN selectively grown on a sapphire substrate using SiO ₂ as a mask
The single crystal itself can be used as a substrate. In this case, it is also possible to separate the light emitting element and the sapphire substrate by the formed after SiO ₂ each semiconductor layer removed by etching. Gallium nitride-based compound semiconductors exhibit N-type conductivity without being doped with impurities. When a desired N-type gallium nitride semiconductor is formed, for example, to improve luminous efficiency, Si, Ge, Se,
It is preferable to appropriately introduce Te, C, and the like. On the other hand, in the case of forming a P-type gallium nitride semiconductor, P-type dopants such as Zn, Mg, Be, Ca, Sr, and Ba are doped.

The gallium nitride-based compound semiconductor is hardly converted into a P-type by doping only with a P-type dopant, so that after the P-type dopant is introduced, the gallium nitride-based compound semiconductor is annealed by heating in a furnace, low-speed electron beam irradiation, plasma irradiation, or the like. Is preferred. As a specific layer structure of the light-emitting element, a gallium nitride semiconductor N-type contact layer, an aluminum gallium nitride semiconductor, and a sapphire substrate having a buffer layer formed of gallium nitride, aluminum nitride, or the like at a low temperature or silicon carbide are used. An N-type cladding layer, an active layer of an indium gallium nitride semiconductor doped with Zn and Si, a P-type cladding layer of an aluminum-gallium nitride semiconductor, and a P-type contact layer of a gallium nitride semiconductor are laminated. Preferred examples are given. In order to form the LED chip 103, in the case of the LED chip 103 having a sapphire substrate, P
After the exposed surfaces of the type semiconductor and the N-type semiconductor are formed, each electrode having a desired shape is formed on the semiconductor layer by using a sputtering method, a vacuum evaporation method, or the like. In the case of a SiC substrate, a pair of electrodes can be formed using the conductivity of the substrate itself.

Next, the formed semiconductor wafer or the like is directly full-cut by a dicing saw in which a blade having a diamond cutting edge is rotated, or after a groove having a width larger than the cutting edge width is cut (half cut). The semiconductor wafer is broken by external force. Alternatively, an extremely thin scribe line (meridian) is drawn on the semiconductor wafer, for example, in a checkerboard pattern by a scriber in which a diamond needle at the tip reciprocates linearly, and then the wafer is cut by an external force and cut into chips from the semiconductor wafer. Thus, the LED chip 103 which is a nitride-based compound semiconductor can be formed.

In the case where the light emitting diode of the present invention emits white light, the main emission wavelength of the LED chip 103 is 400 nm or more in consideration of the complementary color with the particulate phosphor.
0 nm or less is preferable, and 420 nm or more and 490 nm or less are more preferable. In order to further improve the efficiency of the LED chip 103 and the efficiency of the particulate phosphor, respectively, 450 nm
It is more preferably at least 475 nm. (Package 102) The package 102 functions as a support for fixing and protecting the LED chip 103 in the recess. In addition, an external electrode 104 which can be electrically connected to the outside is provided. The package 102 may have a plurality of openings in accordance with the number and size of the LED chips 103.
Further, it is preferable that the package 102 be colored in a dark color such as black or gray to have a light shielding function, or the light emission observation surface side of the package 102 be colored in a dark color. Package 10
2, a mold member 106, which is a light-transmitting protective body, may be provided in addition to the coating portions 111 and 112 to further protect the LED chip 103 from the external environment. The package 102 includes coating portions 111 and 11
2 and a member having high rigidity and good adhesion to the mold member 106 are preferable. It is desired that the LED chip 103 has an insulating property in order to electrically disconnect the LED chip 103 from the outside. Further, when the package 102 is affected by heat from the LED chip 103 or the like, it is preferable that the package 102 has a small coefficient of thermal expansion in consideration of adhesion to the mold member 106.

The inner surface of the concave portion of the package 102 can be embossed to increase the bonding area, or can be plasma-treated to improve the adhesion to the mold member. The package 102 may be formed integrally with the external electrode 104, or the package 102 may be divided into a plurality of parts and combined by fitting or the like. Such a package 102 can be formed relatively easily by insert molding or the like. Polycarbonate resin, polyphenylene sulfide (P
PS), a liquid crystal polymer (LCP), an ABS resin, an epoxy resin, a phenol resin, an acrylic resin, a resin such as a PBT resin, or a ceramic. Also,
Various dyes and pigments are suitably used as a coloring agent for coloring the package 102 in a dark color system. Specifically, C
r ₂ O ₃ , MnO ₂ , Fe ₂ O ₃ , carbon black and the like are preferred.

The bonding between the LED chip 103 and the package 102 can be performed with a thermosetting resin or the like.
Specifically, an epoxy resin, an acrylic resin, an imide resin, and the like can be given. In order to dispose and fix the LED chip 103 and electrically connect the LED chip 103 to the external electrode 104 in the package 102, an Ag paste, a carbon paste, an ITO paste, a metal bump, or the like is preferably used. (External electrode 104) The external electrode 104 is
(2) LED chip 10 in which electric power from outside is arranged inside
3 for use. Therefore, there are various types such as those using a conductive pattern provided on the package 102 and a lead frame. Further, the external electrode 104 can be formed in various sizes in consideration of heat dissipation, electric conductivity, characteristics of the LED chip 103, and the like. External electrode 104
It is preferable that the LED chips 103 have good thermal conductivity in order to dispose the LED chips 103 and radiate the heat emitted from the LED chips 103 to the outside. The specific electric resistance of the external electrode 104 is preferably 300 μΩ · cm or less, more preferably 3 μΩ · cm or less. The specific thermal conductivity is 0.01 cal / (s) (cm ² ) (° C./c
m) or more, more preferably 0.5 cal /
(s) (cm ² ) (° C./cm) or more.

As the external electrode 104, a copper or phosphor bronze plate whose surface is plated with a metal such as silver, palladium or gold, or a solder plating is preferably used. When a lead frame is used as the external electrode 104, it can be variously used depending on the electric conductivity and the heat conductivity, but the thickness is preferably 0.1 mm to 2 mm from the viewpoint of workability. As the external electrode 104 provided on a support such as glass epoxy resin or ceramic, a copper foil or a tungsten layer can be formed. When using a metal foil on a printed circuit board, the thickness of the copper foil or the like should be 18 to 7
Preferably, it is 0 μm. Also, gold on copper foil etc.
You may give solder plating etc. (Conductive Wire 105) The conductive wire 105 is required to have good ohmic properties, mechanical connectivity, electrical conductivity, and thermal conductivity with the electrodes of the LED chip 103. The thermal conductivity is 0.01 cal / (s) (cm ² )
(° C./cm) or more, more preferably 0.5 c
al / (s) (cm ² ) (° C./cm) or more. The diameter of the conductive wire 105 is preferably Φ10 μm or more and Φ45 μm or less in consideration of workability and the like. Specifically, as such a conductive wire 105, gold,
Conductive wires using metals such as copper, platinum and aluminum and alloys thereof are exemplified. Such a conductive wire 105 can easily connect an electrode of each LED chip 103 to an inner lead, a mount lead, and the like by a wire bonding device. (Mold member 106) The mold member 106 is provided to protect the LED chip 103, the conductive wire 105, the coating portions 111 and 112 containing the particulate phosphor from the outside according to the use application of the light emitting diode. Can be. The mold member 106 can be formed using various resins, glass, or the like. As a specific material of the mold member 106, a transparent resin having excellent weather resistance, such as an epoxy resin, a urea resin, or a silicone resin, or glass is preferably used. Further, by including a diffusing agent in the mold member, the directivity from the LED chip 103 can be reduced and the viewing angle can be increased. Such a mold member 106 may use the same material as the binder of the coating portion or may use a different material. Hereinafter, examples of the present invention will be described, but it goes without saying that the present invention is not limited to only specific examples.

[0038]

(Embodiment 1) A main light emitting chip is used as an LED chip.
460 nm In_0.2Ga_0.8Using N semiconductor
Was. The LED chip is placed on a cleaned sapphire substrate
MG (trimethyl gallium) gas, TMI (trimethyl
Indium gas, nitrogen gas and dopant gas
Gallium nitride based on MOCVD
It was formed by depositing a compound semiconductor. Do
SiH as a punt gas₄And Cp ₂Switch between Mg and
Gallium nitride based semiconductor with N-type conductivity
Gallium nitride based semiconductor with P-type conductivity
A PN junction is formed. N-type semiconductor light emitting device
Gallium nitride semiconductor contact layer having electrical conductivity
And gallium aluminum nitride semiconductor having P-type conductivity
Gallium nitride having P-type conductivity
A contact layer, which is a semiconductor, was formed. N-type conductivity
Contact layer and cladding layer having p-type conductivity
Is about 3 nm thick and has a single quantum well structure
An active layer of non-doped InGaN was formed. (Note that
Gallium nitride semiconductor formed on sapphire substrate at low temperature
And a buffer layer. Also has P-type conductivity
Semiconductors are annealed at 400 ° C or higher after film formation.
You. ) Each PN semiconductor surface on sapphire substrate by etching
After exposing each electrode,
Formed. The completed semiconductor wafer
After drawing scribe line, split by external force and emit light
An LED chip of 350 μm square was formed as an element.

On the other hand, a chip type LED package was formed by insert molding using a polycarbonate resin. LE inside the chip type LED package
It has an opening in which the D chip is arranged. In the package, a silver-plated copper plate is arranged as an external electrode. The LED chip is fixed using an epoxy resin or the like inside the package. LE wire is a conductive wire
Each electrode of the D chip and each external electrode provided on the package are electrically connected by wire bonding. Thus, 8280 packages on which the LED chips were arranged were formed. A resist film is formed on the surface of each package excluding the opening. The package in which the 8280 LED chips are placed is placed in a container containing the pure electrolyte.

On the other hand, as the particulate phosphor, a solution in which rare earth elements of Y, Gd, and Ce were dissolved in an acid at a stoichiometric ratio was coprecipitated with oxalic acid. This is mixed with a coprecipitated oxide obtained by calcination and aluminum oxide to obtain a mixed raw material. This was mixed with ammonium fluoride as a flux, packed in a crucible, and fired in air at a temperature of 1400 ° C. for 3 hours to obtain a fired product. Ball-mill the baked product in water, wash, separate,
Dried and finally formed through a sieve. Formed (Y
_0.8 Gd _0.2 ) ₃ Al ₅ O ₁₂ : Ce phosphor is Si
Disperse in the O ₂ sol.

Next, after adjusting the pH to 5.0 with acetic acid,
Immediately in the container where the package is placed (Y _0.8 Gd
_0.2 ) ₃ Al ₅ O ₁₂ : Ce phosphor and SiO ₂ sol are suspended and injected at once (FIG. 2 (A)). After standing (Y _0.8
Gd _0.2 ) ₃ Al ₅ O ₁₂ : Ce phosphor sediments and settles on the package (FIG. 2 (B)). The waste liquid in the container is removed, and the package in which the particulate phosphor is deposited on the LED chip is dried with air heated to 120 degrees (FIG. 2 (C)). Thereafter, each light-emitting diode is taken out of the container, and the particulate phosphor adhered to the non-light-emitting portion of the light-emitting diode is removed together with the resist mask, so that the film thickness on both the LED chip and the package bottom is substantially equal to about 40 μm. A part can be formed. Further, a translucent epoxy resin was formed as a mold member in the package opening where the coating was formed in order to protect the LED chip and the particulate phosphor from external stress, moisture, dust and the like. After mixing the translucent epoxy resin, the mixture was cured at 150 ° C. for 5 hours. Thus, a light emitting diode as a light emitting device as shown in FIG. 1 was formed.

By supplying power to the obtained light emitting diode, white light can be emitted. The color temperature and the color rendering were measured from the front of the light emitting diode. Color temperature 8090K, Ra (color rendering index) = 87.5
showed that. The luminous efficiency was 10.8 lm / w. Further, x, y = (0.305,
0.315) Within a range surrounded by ± 0.03, about 811
Four light emitting diodes were distributed, and the yield was about 98%. (Comparative Example 1) (Y _0.8 Gd _0.2 ) in epoxy resin
_A light emitting diode was formed in the same manner as in Example 1 except that ₃ Al ₅ O ₁₂ : Ce phosphor was mixed and projected from the nozzle to form a coating portion. In the cross section of the formed light emitting diode, the end face of the coating portion was raised and the amount of the particulate phosphor was not uniform.
The chromaticity point of the light emitting diode thus formed was determined in Example 1.
It measured similarly to. The chromaticity point of the formed light emitting diode was substantially located on a line connecting the main light emission peak of the LED chip and the main light emission wavelength of the phosphor, but the yield was about 61%.
It was just nothing.

[0043]

According to the light emitting diode of the present invention having a uniform coating thickness, a chromaticity shift in each direction is extremely small, and a light emitting diode having no color tone shift from the light emission observation surface can be obtained. Further, a light-emitting diode with a high yield can be obtained.

In particular, by adopting the structure according to the first aspect of the present invention, color shift can be achieved even with high luminance and long time use.
A light-emitting diode with a very small decrease in the luminous efficiency can be obtained. That is, the configuration according to claim 1 of the present invention prevents the coating portion from being colored and deteriorated even when a relatively high energy light from the LED chip is irradiated at a high density. Therefore, it is possible to provide a light emitting diode in which the luminance does not decrease even when the light is emitted with high luminance for a long time.

According to the configuration of the second aspect of the present invention, it is possible to radiate the heat emitted from the LED chip to the outside.

By adopting the structure of the third aspect of the present invention, a light emitting diode capable of emitting white light with less decrease in luminance and less color shift even when used for a long time with high luminance can be obtained.

According to the structure of the fourth aspect of the present invention, a light emitting diode capable of emitting white light and having higher luminous efficiency can be obtained.

By adopting the structure of claim 5 of the present invention, it is possible to obtain a light emitting diode capable of emitting white light with less decrease in luminance and less color shift even when used at high luminance for a long time.

By adopting the method according to the sixth aspect of the present invention, it is possible to form a light emitting diode capable of emitting a large amount of light uniformly without any uneven light emission with a high yield.

According to the method of the present invention, a layer having a more uniform particulate phosphor can be formed, and the desired phosphor can be formed by repeating a plurality of times as required. Quantity can be formed.

By adopting the method according to the eighth aspect of the present invention, it is possible to form a light-emitting diode capable of emitting a large amount of light uniformly without emission unevenness with higher yield.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a chip type LED which is a light emitting device of the present invention.

FIG. 2 is a schematic view showing a forming apparatus for forming a light emitting diode of the present invention.

[Description of Signs] 111 ·· Coating portion on LED chip 112 ··· Coating portion on support 102 ··· Package 103 ··· LED chip 104 ··· External electrode 105 ··· Conductive wire 106 · ··· Mold member 201 ··· Ejecting means for ejecting the material of the coating portion 202 ··· Container 203 ··· Material of the coating portion ejected from the nozzle 204 ··· Phosphor film 205 ··· Heating air Spray drying equipment

Claims (6)

[Claims] 1. A light-emitting diode comprising: an LED chip disposed on a support; and a particulate phosphor that absorbs at least a part of light emitted from the LED chip and converts the wavelength to emit light. The thickness of the coating portion having the particulate phosphor disposed on the LED chip is substantially equal to the thickness of the coating portion having the particulate phosphor disposed on the support other than the LED chip. Light emitting diode. 2. The coating part comprises an oxide containing at least one of Si, Al, Ga, Ti, Ge, P, B and an alkaline earth element together with the particulate phosphor. A light-emitting diode as described. 3. The light-emitting diode according to claim 1, wherein the light-emitting layer of the LED chip is a nitride-based compound semiconductor, and the particulate phosphor is an yttrium-aluminum-garnet-based phosphor activated with cerium. . 4. The main emission peak of the LED chip is 400
The light emitting diode according to claim 3, wherein the main emission wavelength of the particulate phosphor is longer than the main emission peak of the LED chip. 5. The light emitting layer of the LED chip is a nitride-based compound semiconductor, and the particulate phosphor is (Re1-xS
The light emitting diode according to claim 1, wherein mx) 3 (Al1-yGay) 5O12: Ce. However, 0 ≦ x <1, 0 ≦ y ≦
1, Re is at least one element selected from Y, Gd, and La. 6. A method for forming a light emitting diode, comprising: an LED chip; and a phosphor that absorbs at least a part of light emitted from the LED chip and converts the wavelength to emit light. A method for forming a light emitting diode, comprising forming a coating portion containing a particulate phosphor on the LED chip by sedimentation of the dispersed particulate phosphor.