KR20080001287A - Stacked light emitting diode and manufacturing method of the same - Google Patents

Abstract

A stacked light emitting diode and a method for manufacturing the same are provided to enhance the intensity of light and to reduce the mounting area by stacking at least two light emitting diode chips to up and down. A light emitting chip attached at a P-type electrode(202) is connected on a printed circuit board(201). At least one light emitting chip is vertically stacked on the light emitting chip. Wire bonding is performed to the top chip of the stacked light emitting diode chips. The stacked light emitting diode chips are then packaged to an EMC(Epoxy Molding Compound).

Description

Stacked Light Emitting Diode And Manufacturing Method Of The Same

1 is a side cross-sectional view schematically showing a light emitting device according to an embodiment of the prior art.

2 is a side cross-sectional view schematically showing a stacked light emitting diode according to an embodiment of the present invention.

3 is a schematic view showing a computer simulation of the heat generated from the stacked light emitting diode chip according to an embodiment of the present invention and a heat generation temperature table of each part.

4 and 5 are schematic diagrams showing the computer simulation of the heat generated from a single light emitting diode chip according to an embodiment of the prior art and the heat generation temperature table of each part.

6 is a graph schematically illustrating the results of FIGS. 3 to 5.

7 is a schematic diagram and graph showing an optical simulation of light emitted from a stacked LED chip according to an embodiment of the present invention.

           ｝ Explanation of symbols for main part of drawing

100: light emitting diode package

101, 102: red and blue light emitting diode chip

103: metal wire

104, 105, 106: red light, purple light, blue light

200: bottom surface of the LED package cup

201: Circuit Board (PCB)

202: reflector and P-type electrode

203: metal alloy layer

204: Indium gallium nitrogen (InGaN) layer or gallium nitride (GaN) layer

205 Au-Sn Bump

206: aluminum indium gallium phosphorus (AlGaInP) layer or gallium nitride (GaN) layer

207 gallium phosphorus (GaP) or silicon carbide (SiC) substrate

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stacked light emitting diode, wherein a light emitting device is amplified by stacking two or more light emitting diode chips vertically so that light output is amplified when the wavelengths are the same, and light is mixed effectively when the wavelengths are different.

Recently, light-emitting diodes (“LEDs”) are being used in display light sources for mobile phone backlight units (BLUs), LCD TV backlight units, and phototherapy, or have entered the market. In the future, it is said that the semiconductor lighting era is coming by gradually expanding its application fields to general lighting fields such as incandescent lamps and fluorescent lamps.

In general, LEDs are driven by applying a current to a single chip, and are arranged horizontally when driving a plurality of chips. A typical case is a backlight unit for a liquid crystal display (LCD), and since it is disposed horizontally, mixing of light has become the biggest technical problem.

On the other hand, therapeutic LEDs require high optical power in a small area, and even in this case, multiple chips are mounted to give high light output.

However, in the above-mentioned method, since several LED chips are horizontally arranged side by side, gathering light in one place becomes an important technical issue.

1 is a side cross-sectional view schematically showing a light emitting device according to an embodiment of the prior art. FIG. 1 illustrates a conventional light emitting method of a light emitting diode in a structurally understandable manner.

In this embodiment, the LED package structure includes a red LED chip 101, a blue LED chip 102, a metal wire 103 mainly made of gold (Au), and an LED package 100. The LED chip emits light, the LED package protects the chip, and the metal wire supplies power to the LED chip through the electrodes.

In the above embodiment, since the red LED chip and the blue LED chip are horizontally arranged in a general arrangement manner, the emitted light is emitted with the red light 104 from the red LED chip 101 and the blue LED chip 102. On the side, blue light 106 is emitted. Meanwhile, since the middle portion of the red light and the blue light is an area where both lights are mixed, the violet light 105 in which the red and blue are mixed is emitted.

Generally, such LEDs are used in LCD backlight units, car tail lights, indicator lights, and various lighting fixtures.

In particular, a backlight unit such as a mobile phone or an LCD TV can be classified into a direct light type and an edge light type according to the arrangement of the light source. In any case, the light emitted from the LED is used. Mixing and brightness are very important.

Conventional techniques for amplifying the light output emitted from the LED or to facilitate the mixing of light include a method of controlling the spreading angle of light by placing several chips in a package in a semicircle shape (US Patent Application No. US 2001-895354), a three-dimensional arrangement of side LED chips and surface LED chips to increase the optical power (US Patent No. US 6,452,217).

In the field of organic EL, a technology of a stacked organic light emitting device having a red-green-blue (RGB) tricolor emitting layer that can be used as a surface light source as a self-emission type using a field sequential color method that emits red, green, and blue colors sequentially (Domestic Patent) Application No. 2004-0027687.

An object of the present invention is to change the arrangement and structure of the light emitting diode in order to improve the optical power and the light mixing method of the conventional light emitting diode as described above, the light emitted is uniformly mixed or the light output is amplified It is to provide a light emitting diode.

Another object of the present invention is to provide a light emitting diode that can reduce the mounting area occupied by a light emitting diode in a light emitting device, and at the same time, provide a higher efficiency than combining two or more conventional light emitting devices with one light emitting device.

In order to achieve the above object, the stacked LED of the present invention includes two or more LED chips stacked vertically.

In the present invention, the LED chip on the top of the stacked LEDs includes a chip having a semiconductor layer formed on a transparent substrate.

In the present invention, preferably, the stacked light emitting diode chips are packaged in an encapsulant with or without phosphors.

In the present invention, the stacked light emitting diode chips each include the same or different wavelengths.

In the present invention, the stacked light emitting diode chips each include the same size or different.

In the present invention, the chips of the light emitting diode are preferably characterized in that the vertical junction of the P-N-P-N type or the vertical junction of the N-P-N-P type.

In the present invention, the light emitting die chips are selected from lead-tin (PbSn) alloy solder, gold-tin (AuSn) alloy solder, tin-silver-copper (SnAgCu) alloy solder, tin to bismuth, zinc, indium and nickel. Select one or more species and bond them to any one selected from the group consisting of mixed lead-free solder and conductive adhesive.

In order to achieve the above object, there is provided a method of manufacturing a stacked light emitting diode according to the present invention, comprising: connecting a light emitting diode chip having a P-type electrode attached to a lower portion on a circuit board, and having the same or different wavelength as that of the light emitting diode chip on the chip; Connecting at least one light emitting diode chip vertically, wire bonding the top chip of the stacked light emitting diode chip, and packaging the light emitting diode chip with an encapsulant.

In the present invention, the top chip of the stacked light emitting diode chip is a light emitting diode chip in which a semiconductor layer is formed on a transparent substrate, and includes bonding the transparent substrate upward.

In the present invention, the stacked light emitting diode chip includes a vertical junction of P-N-P-N type or a vertical junction of N-P-N-P type.

In the present invention, connecting the light emitting die chips include lead-tin (PbSn) alloy solder, gold-tin (AuSn) alloy solder, tin-silver-copper (SnAgCu) alloy solder, tin to bismuth, zinc, indium, It is selected and used in the group consisting of lead-free solder and conductive adhesive mixed with one or more selected from nickel.

In the present invention, the encapsulant may or may not include a phosphor.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In adding reference numerals to the components of the following drawings, it is known that the same components, even if displayed on the other drawings to have the same reference numerals as possible and determined to unnecessarily obscure the subject matter of the present invention Detailed description of functions and configurations will be omitted.

2 is a side cross-sectional view schematically showing a stacked light emitting diode according to an embodiment of the present invention.

Referring to FIG. 2, in the structure of the LED device according to the embodiment of the present invention, a light emitting diode chip having a lower color is bonded to the bottom surface 200 of the package cup with a conductive adhesive. The light emitting diode chip is formed by depositing a reflector and a P-type electrode portion 202 on a circuit board 201, forming a metal alloy layer 203 thereon, and then forming a semiconductor layer of indium gallium nitrogen layer 204 thereon. It consists of a deposited structure.

Referring to FIG. 2, light emitting diode chips emitting the same wavelength or different wavelengths are vertically stacked on the light emitting diode chips emitting monochromatic light. In the above embodiment, the LED chip of the upper layer includes an aluminum indium gallium phosphorus (AlGaInP) layer or a gallium nitride (GaN) layer 206 as a semiconductor layer, which is gallium phosphorus (GaP) or silicon carbide (a material of a transparent substrate). SiC) is formed on the substrate 110.

In the exemplary embodiment of the present invention according to FIG. 2, the stacked LED has a conductive adhesive material with the semiconductor layer 204 of the lower LED chip with the LED chip having the semiconductor layer 206 formed on the transparent substrate turned upside down. It is bonded by phosphor gold-tin bumps 205.

According to an exemplary embodiment of the present invention according to FIG. 2, a stacked light emitting diode may be wire-bonded to a top chip and packaged with an encapsulant including or without a phosphor to form a stacked light emitting device.

3 is a schematic view showing a computer simulation of the heat generated from the stacked light emitting diode chip according to an embodiment of the present invention and the heating temperature table of each part, Figures 4 and 5 is a single light emitting diode according to an embodiment of the prior art A schematic diagram showing a computer simulation of heat generated from a chip and a heat generation temperature table of each part.

6 is a graph showing an average heat generation temperature of a junction temperature (Tj) of a stacked light emitting diode chip and a conventional single blue light emitting diode chip according to an embodiment of the present invention. That is, FIG. 6 is a graph showing only results of Tj of the blue light emitting diode chip among the results of FIGS. 3 to 5.

Referring to FIG. 3, the distribution of heat generated when the stacked light emitting diode according to the exemplary embodiment of the present invention is driven at 0.1 W on the lower chip and 0.1 W on the upper chip is respectively simulated. The light emitting diode according to the exemplary embodiment of the present invention illustrated in FIG. 3 is laminated with two light emitting diode chips emitting blue and red light, respectively, and exhibits a temperature distribution of about 70 ° C. as a whole. In the stacked light emitting diode according to the exemplary embodiment of FIG. 3, a chip having an upper layer of an aluminum indium gallium phosphorus (AlGaInP) layer is formed, and a chip having a lower layer of a gallium nitride (GaN) layer is formed. No average 69.9 ° C. The average temperature of the metal alloy layer is 69.8 ° C., which is not significantly different from the temperature of the chip, but the average temperature of the circuit board is 64.3 ° C., which is slightly different.

Referring to FIG. 4, which shows a single light emitting diode according to an exemplary embodiment of the prior art, when driven at 0.1 W, the picture of the thermal computer simulation is significantly different from that of FIG. 3, which is an embodiment of the present invention. An exothermic distribution of about 50 ° C., which is about 20 ° C. lower than the average temperature of an embodiment of the present invention in which two chips are stacked, is shown.

Referring to FIG. 4, a gallium nitride (GaN) layer is used as the light emitting diode chip, and the average temperature is 51.0 ° C., indicating that the light emitting diode chip is significantly lower than the gallium nitride layer temperature of the stacked light emitting diode of FIG. 3. This is because 0.2W power is applied to all of the stacked light emitting diodes of FIG. 3, whereas 0.1W power is applied to the stacked light emitting diodes of FIG. 4.

However, when the same heating energy output is generated, the average temperature of the metal alloy layer of FIG. 4 is 51.0 ° C and the average temperature of the circuit board is 48.0 ° C. Able to know.

FIG. 5 shows a computer simulation of the heat distribution when a chip of a single light emitting diode according to an embodiment of the prior art is driven at 0.2W, and the overall average temperature is 71.1 ° C., so that it is 0.1W in a single light emitting diode chip. It can be seen that the heat generation is higher than when driven.

Referring to FIG. 5, it can be seen that when the input power is doubled on the chip of a single light emitting diode according to the related art, a distribution form similar to the heating distribution of the stacked light emitting diode according to the exemplary embodiment is shown.

As a graph in FIG. 6, heat dissipation distributions according to the three cases of FIGS. 3 to 5 are summarized. Referring to FIG. 6, it can be seen that the thermal difference between two types of chips is within an error range at the same input power, which indicates that there is no thermal loss problem even when the LED chips are stacked.

FIG. 7 is a schematic diagram and graph showing an optical simulation of light emitted from a light emitting diode in which a chip emitting red and blue light is stacked as a stacked light emitting diode according to an exemplary embodiment of the present invention.

Referring to FIG. 7, it can be seen from the optical side that red and blue light are well mixed and emitted as purple light. In this embodiment, since the light extraction efficiency of the stacked light emitting diode is about 86%, it can be seen that the optical loss is insignificant.

According to one embodiment of the present invention, the number of vertically stacked light emitting diode chips may be two or more. That is, the stacked light emitting diodes mainly include light emitting diodes emitting monochromatic light or polychromatic light, and may be stacked between light emitting diodes having the same wavelength of emitted light, or stacked between light emitting diodes emitting different colors with different wavelengths. It may be. When the wavelengths of the stacked chips are the same, there is an effect of improving the light output. When the wavelengths are different, the light is effectively mixed. In particular, as each light emitting diode that emits monochromatic, multicolored, or white light is stacked, it is possible to emit light of a unique color that has not been seen previously. In the stacked light emitting diode according to an embodiment of the present invention, when the chips emitting red light, green light and blue light are stacked, a light emitting diode having a structure in which all the light in the visible light region emits in an area occupied by one light emitting diode chip is obtained. Can be.

In one embodiment of the present invention, the light emitting diode includes a general lamp type or a surface mount device (SMD).

In the stacked light emitting diode according to the exemplary embodiment of the present invention, two or more chips may be stacked, but the chip stacked on the top thereof is preferably a transparent substrate. The transparent substrate is mainly a gallium phosphorus (GaP) substrate or a silicon carbide (SiC) substrate, but is not limited thereto and may be a known transparent substrate that can be easily understood by those skilled in the art. According to one embodiment of the present invention, when the substrate is made transparent and a light emitting diode having a semiconductor layer deposited thereon is stacked on top, light may be mixed to emit mixed color light to the outside. To this end, the LED chip stacked on the top is configured to be bonded to the lower chips while the transparent substrate is turned upside down.

The red light-emitting diode chip according to the exemplary embodiment of the present invention is bonded with a conductive material through which current can flow. In the above embodiment, it is preferable that the conductive adhesive material is plated and adhered to the edge of the surface to which the lower LED chip and the upper LED chip are bonded.

When two or more vertically stacked light emitting diode chips are bonded with a transparent conductive material to allow current to flow, they are connected in series between the stacked light emitting diode chips. The conductive adhesive material is mainly selected from lead-containing alloy solders, lead-free alloy solders containing no lead, conductive adhesives, and the like, but is not limited thereto. A conductive adhesive material known to those skilled in the art may be used.

In particular, solders are selected from lead-tin (PbSn) alloy solder, gold-tin (AuSn) alloy solder, tin-silver-copper (SnAgCu) alloy solder, tin, and at least one selected from bismuth, zinc, indium, and nickel. It is preferable to select one lead-free solder or the like, and other solders are possible.

The stacked LED according to the exemplary embodiment of the present invention is mainly configured to be electrically connected to the lowermost chip by metal wire bonding to the uppermost chip, so that power is supplied from the lower chip to the upper chip.

However, if each chip is wire bonded to each layer, each chip can be driven individually.

The stacked light emitting diode according to an embodiment of the present invention packages the light emitting diode chip into an encapsulant. In general, the encapsulant material is epoxy or ceramic material. In particular, a plastic epoxy resin is a silicone plastic made by adding amorphous silica (SiO ₂ ) to a silicone resin made of phenyl-methyl-silicon.

An embodiment of the present invention may or may not include a phosphor in the material of the encapsulation material in encapsulating the stacked light emitting diode. In particular, the phosphor may be a wavelength modified phosphor for changing the light emitted from the light emitting diode to a long wavelength.

Multi-layered light emitting diode according to an embodiment of the present invention can be easily applied to both a light emitting diode device having a common light emitting diode and a lamp-type structure of the type in which two wires are bonded to the upper surface or one wire is bonded to the upper surface. have.

Since the stacked light emitting diode according to the exemplary embodiment of the present invention requires only an area occupied by one chip since the vertical junction structure of the chips may be usefully used in light and small type electronic products. That is, the mounting area occupied by the stacked light emitting diode of the present invention is an area for one chip and at the same time can produce twice the optical power, thereby improving the light output with low disadvantages of the conventional light emitting diode. In addition, because of the stacked structure, it is easy to mix light emitted from individual chips.

As described above, the present invention has been described with reference to a preferred embodiment of the present invention, but those skilled in the art can vary the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. It will be appreciated that modifications and variations can be made.

As described above, according to the present invention, by stacking two or more light emitting diode chips vertically, the light of each wavelength emitted from the light emitting diode can be mixed in various ways and the mixing ratio is increased.

In addition, there is little heat loss and light loss of the stacked light emitting diode chips, and at the same time, the light output generated from the light emitting diode chip is amplified, so that the optical power is integrated.

In addition, compared with the conventional multi-chip light emitting device in which the light emitting diode chip is disposed, the effect of high light mixing and light output is exhibited even in a small area, which has the advantage that it can be efficiently used for light and small sized light emitting devices.

Claims (12)

Stacked light emitting diode, characterized in that two or more LED chips are stacked vertically. The stacked light emitting diode of claim 1, wherein the light emitting diode chip on the top of the stacked light emitting diode chips is a chip having a semiconductor layer formed on a transparent substrate. The multilayer light emitting diode of claim 1, wherein the stacked light emitting diode chips are packaged in an encapsulant including or not containing a phosphor. The stacked light emitting diode of claim 1, wherein the stacked light emitting diode chips emit the same or different wavelengths. The stacked light emitting diode of claim 1, wherein the stacked light emitting diode chips have the same or different sizes. The stacked light emitting diode of claim 1, wherein the chips of the light emitting diode are a vertical junction of P-N-P-N type or a vertical junction of N-P-N-P type. The method of claim 1, wherein the light emitting die chips are lead-tin (PbSn) alloy solder, gold-tin (AuSn) alloy solder, tin-silver-copper (SnAgCu) alloy solder, bismuth, zinc, indium, nickel on tin Multi-layered light emitting diodes, characterized in that the adhesion to any one selected from the group consisting of a lead-free solder and a conductive adhesive mixed with one or more selected. Connecting a light emitting diode chip attached to a lower portion of a P-type electrode on a circuit board; Vertically connecting at least one light emitting diode chip having the same wavelength as or different from the light emitting diode chip on the chip; Wire bonding a top chip of the stacked light emitting diode chips; And manufacturing the light emitting diode chip with an encapsulant. The method of claim 8, wherein the top chip of the stacked light emitting diode chip is a light emitting diode chip having a semiconductor layer formed on a transparent substrate, and the transparent substrate is bonded to face upward. 10. The method of claim 8, wherein the stacked light emitting diode chips are vertical junctions of P-N-P-N type or vertical junctions of N-P-N-P type. 10. The method of claim 8, wherein connecting the light emitting die chips comprises lead-tin (PbSn) alloy solder, gold-tin (AuSn) alloy solder, tin-silver-copper (SnAgCu) alloy solder, bismuth to zinc, zinc, A method for manufacturing a stacked light emitting diode, characterized in that it is selected and used in the group consisting of lead-free solder and conductive adhesive selected by mixing at least one of indium and nickel. The method of claim 8, wherein the encapsulant includes or does not include a phosphor.

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