JP3748355B2 - Light emitting diode - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light emitting diode (LED) chip and a light emitting diode combined with a phosphor for light emission wavelength conversion.
[0002]
[Prior art]
Since LEDs that emit light at a short wavelength of 430 nm or less have been developed, LED lamps have been developed that can emit white light by converting the emission wavelength by applying a phosphor on the surface of the LED chip.
[0003]
However, this phosphor has a large specific gravity, and when a resin such as an epoxy resin and the phosphor are mixed and applied to the surface of the LED chip, only the phosphor is settled, so a large amount of application is required. There is.
[0004]
Furthermore, there is only one type of secondary emission wavelength obtained by wavelength conversion using the phosphor applied to the surface of the LED chip, and it is expressed by a combination ratio of the secondary emission wavelength and the emission wavelength of the LED chip before excitation. Only possible color tones could be emitted.
[0005]
[Problems to be solved by the invention]
In the above-described conventional technology, it is necessary to use a large amount of very expensive phosphors, and there is a problem that the product cost increases.
[0006]
In addition, since the balance of the converted wavelengths varies depending on the variation in the amount of phosphor applied, there is also a problem that variations in the color of emitted light occur and the manufacturing yield decreases.
[0007]
Furthermore, with respect to the color tone expression represented by the color coordinates, it is impossible to express the color tone other than on the line connecting the emission wavelength of the LED itself and the emission wavelength obtained by exciting the emission wavelength with a phosphor and converting the wavelength.
[0008]
The present invention has been made to solve such problems of the prior art, and can efficiently perform emission wavelength conversion with a small amount of phosphor, and can improve the manufacturing yield. An object of the present invention is to provide a light emitting diode chip and a light emitting diode capable of increasing variations in color expression.
[0010]
[Means for Solving the Problems]
In the light emitting diode of the present invention, a semiconductor multilayer structure that emits light of a predetermined wavelength is formed on a substrate, and light emitted from the semiconductor multilayer structure is formed on a surface of the substrate opposite to the semiconductor multilayer structure. A light emitting diode chip in which one or more lower phosphor layers for wavelength conversion are formed is attached to the lead frame by a die-bonding adhesive provided between the lower phosphor layer and the lead frame. While being die- bonded, a pair of electrodes provided in the semiconductor laminated structure and the lead frame are each wire-bonded, and further, an upper phosphor layer in which one kind or two or more kinds of phosphors are mixed with a resin, Rutotomoni is applied so as to cover the surface and the respective electrode to the light emitting diode chip surface, the light emitting diode chip by said lower phosphor layer The so completely enveloping said being applied over a side surface of the semiconductor multilayer structure, the light emitting diode chip, wherein characterized in that it is molded by resin together with the lead frame, the object is achieved by the Is done.
[0011]
Phosphor of the upper phosphor layer, the wavelength of the light emitted from the semiconductor multilayer structure, may be one which is converted to a different wavelength from that of the lower phosphor layer.
The semiconductor multilayer structure may emit light having a wavelength of 430 nm or less.
[0012]
The operation of the present invention will be described below.
[0013]
In the present invention, the emission wavelength from the LED can be converted by providing the phosphor layer on the lower surface of the substrate substrate of the LED chip (the surface opposite to the semiconductor laminated structure). For this phosphor layer, an epoxy resin mixed with a phosphor is uniformly applied to the lower surface of the substrate, or a phosphor dispersed in a solid such as epoxy resin or glass is attached to the lower surface of the substrate. It can be formed by attaching. Therefore, unlike the conventional case, there is no problem that the coating amount varies or the phosphor settles on the resin and requires a large amount of phosphor.
[0014]
In addition, after the LED chip of the present invention is die-bonded to a lead frame or a conductive substrate to perform wire bonding, the phosphor is applied to the surface of the LED chip, whereby the phosphor provided on the lower surface of the phosphor coating layer and the substrate. With the layer, it becomes possible to completely envelop the light emitting layer of the LED chip. The upper part can be coated with a phosphor mixed with resin, and the lower part can be coated with a resin with dispersed phosphor, or a solid with dispersed resin phosphor can be attached to reduce the amount of phosphor required. Efficient wavelength conversion is possible with a small amount of phosphor. Therefore, unlike the prior art, it is not necessary to use a large amount of expensive phosphor, and there is no problem that the product cost increases.
[0015]
Furthermore, by making the type of phosphor applied to the LED chip surface different from that of the phosphor layer provided on the lower surface of the substrate, it is excited and converted by the emission wavelength of the LED itself and the lower phosphor layer. It is possible to emit three types of wavelengths: the emitted light wavelength and the light emission wavelength that is excited and converted by the upper phosphor coating layer. Therefore, variations in color tone that can be expressed more than before are increased at a stretch.
[0016]
By providing two or more phosphor layers having different emission wavelengths on the lower surface of the substrate, or by applying two or more types of phosphors on the surface of the LED chip, variations in color expression can be further increased.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0018]
FIG. 1 is a cross-sectional view showing a schematic configuration of an LED chip according to an embodiment of the present invention. In this LED chip, a semiconductor laminated structure including an N-GaN layer 4, a light emitting layer 3 and a P-GaN layer 2 is laminated on a sapphire substrate 5. The light emitting layer 3 and the P-GaN layer 2 are partially removed so that the underlying N-GaN layer 4 is exposed, and the electrode 1 is formed on the exposed portion of the N-GaN layer 4 and on the P-GaN layer 2. Is formed.
[0019]
Further, a lower phosphor layer 6 is provided on the lower surface of the sapphire substrate 5 in order to convert the wavelength of light emitted from the LED itself (blue (eg, 430 nm) or less (light emission wavelength of blue or less)).
[0020]
For example, before dicing a wafer, a phosphor in which a phosphor is uniformly dispersed in a resin and a mixture of the phosphor are uniformly applied to the lower surface of the sapphire substrate 5 and divided into chips, whereby the lower phosphor Layer 6 can be formed. Alternatively, before the wafer is diced, the lower phosphor layer 6 is also formed by attaching a phosphor dispersed in a solid such as resin or glass to the lower surface of the sapphire substrate 5 and dividing it one chip at a time. be able to.
[0021]
As this resin, an epoxy resin, glass or the like can be used, and as the phosphor, Ce (Y ₃ Al ₅ O ₁₂ : Ce ³⁺ ), CaGa ₂ S ₄ : Ce ³⁺ , SrCa ₂ S ₄ : Ce ^{3 +} , M ₂ SiO ₅ : Ce ³⁺ (where M is at least one metal element of calcium, strontium, and barium), Y ₂ SiO ₅ : Ce ^{3+, and the} like can be used.
[0022]
This LED chip is die-bonded to the lead frame 9 using a die-bonding adhesive 10 as shown in FIG. Then, among the metallic electrodes 1 existing on the LED chip surface, one of the anode side and the cathode side is wire-connected to the end of the die-bonded frame using a thin wire 8 such as gold or aluminum, and the other These electrodes are wire-connected to a counter electrode frame which is located away from the die-bonded frame. Thus, the die bonding and wire bonding steps are completed.
[0023]
The lead frame thus completed with wire bonding is usually molded into an arbitrary shape with a transparent or colored epoxy resin.
[0024]
In the present embodiment, after wire bonding, a resin mixed with a phosphor having a light emission wavelength different from that of the lower phosphor layer 6 is applied to the surface of the LED chip to form the upper phosphor coating layer 7 as shown in FIG. . As this phosphor, Ce (Y ₃ Al ₅ O ₁₂ : Ce ³⁺ ), CaGaS ₄ : Ce, CaGa ₂ S ₄ : Ce ³⁺ or the like can be used. Thereafter, it is further molded into an arbitrary shape with a resin.
[0025]
The emission wavelength distribution of the LED of this embodiment obtained in this way is shown in FIG. As shown in this figure, from the LED of this embodiment, the emission wavelength from the LED chip itself, the emission wavelength obtained by exciting the light emission from the LED chip itself with the lower phosphor layer, and the emission from the LED chip itself Light having three types of wavelengths, that is, an emission wavelength obtained by exciting light emission with the upper phosphor coating layer, is obtained. An arbitrary color tone can be expressed by controlling the height of the peak output of each wavelength light. The emission wavelength from the LED chip itself is controlled by current, and the emission wavelength obtained by exciting the light emission from the LED chip itself with the lower phosphor layer and the emission light from the LED chip itself are excited by the upper phosphor coating layer. The obtained emission wavelength can be controlled by the phosphor concentration.
[0026]
In FIG. 3, the light emission wavelength of the upper phosphor coating layer is set larger than the light emission wavelength of the lower phosphor layer, but the reverse is also possible. Further, two or more phosphor layers having different emission wavelengths may be formed as the lower phosphor layer, and two or more kinds of phosphors having different emission wavelengths may be applied as the upper phosphor coating layer.
[0027]
Furthermore, the present invention is not limited to LED chips made of GaN, but can also be applied to LED chips using other material systems, for example, ZnSe-based materials.
[0028]
【The invention's effect】
As described above in detail, according to the present invention, a phosphor layer in which phosphors are uniformly dispersed is provided in advance on the lower surface of the substrate substrate of the LED chip, and further, a lead frame or a conductive substrate is provided. After performing die bonding or wire bonding, it is possible to completely enclose the light emitting layer of the LED chip by applying a phosphor on the surface of the LED chip. Therefore, wavelength conversion can be performed efficiently with a small amount of phosphor, and the manufacturing cost can be reduced.
[0029]
In addition, the phosphor layer provided on the lower surface of the substrate uses a phosphor dispersed in a solid, thereby controlling the amount of phosphor by changing the concentration in the solid or changing the thickness of the solid. And variations can be prevented.
[0030]
Furthermore, by making the type of phosphor applied to the LED chip surface different from that of the phosphor layer provided on the lower surface of the substrate, it is excited by the emission wavelength of the LED itself and the lower phosphor layer. A light-emitting diode capable of emitting three types of wavelengths, the converted emission wavelength and the emission wavelength excited and converted by the upper phosphor coating layer, is obtained. Therefore, the color tone variations that can be expressed more than before can be greatly increased.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of an LED chip according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a configuration of an LED according to an embodiment of the present invention.
FIG. 3 is a graph showing an emission wavelength distribution in an LED according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 LED chip electrode 2 P-GaN layer 3 Light emitting layer 4 N-GaN layer 5 Sapphire substrate 6 Lower fluorescent substance layer 7 Upper fluorescent substance coating layer 8 Fine wire 9 which consists of gold wire or aluminum 9 Lead frame 10 Adhesive for die bonding

Claims (3)

A semiconductor multilayer structure that emits light of a predetermined wavelength is formed on a substrate, and a lower surface for converting the wavelength of light emitted from the semiconductor multilayer structure on a surface opposite to the semiconductor multilayer structure of the substrate A light emitting diode chip in which one or more phosphor layers are formed is die-bonded to the lead frame by a die-bonding adhesive provided between the lower phosphor layer and the lead frame, and the semiconductor a pair of electrodes provided in the multilayer structure and the lead frame are wire-bonded, respectively, further, one or more kinds of phosphors upper phosphor layer are mixed resin, said to the light emitting diode chip surface surface and the coated so as to cover the electrodes Rutotomoni, so as to enclose the complete light emitting diode chip by said lower phosphor layer, Serial are applied over a side surface of the semiconductor laminated structure, a light emitting diode the light emitting diode chip, characterized in that it is molded by resin together with the lead frame. The phosphor of the upper phosphor layer, light-emitting diode according to the wavelength of the light emitted from the semiconductor stacked structure, in claim 1 is intended to be converted to a different wavelength from that of the lower phosphor layer.   The light emitting diode according to claim 1, wherein the semiconductor multilayer structure emits light having a wavelength of 430 nm or less.

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