KR100869640B1 - Light Emitting Diode - Google Patents

Abstract

Disclosed is a light emitting diode that reduces the luminance of emitted green light or blue light. In order to reduce the luminance of the diode chip that emits light with high luminance, the light emitting diode includes a luminance reduction unit. The brightness reduction part includes an electromagnetic wave shielding agent or a black pigment which is black powder. In addition, the luminance reducing unit is provided with a phosphor or a phosphor which is excited by blue or green light and emits green light. Part of the light emitted from the phosphor or the like and part of the light emitted from the diode chip are absorbed by an electromagnetic wave shielding agent or the like. Therefore, the problem of implementing low luminance by lowering the operating current by several hundred uA in the conventional light emitting diode is improved.

Description

Light Emitting Diode

1 is a cross-sectional view showing a green or blue light emitting diode according to a preferred embodiment of the present invention.

2 is a characteristic graph illustrating a range of an operating current of a light emitting diode according to an exemplary embodiment of the present invention.

3 is a cross-sectional view illustrating a package state of a light emitting diode according to an exemplary embodiment of the present invention.

4 is a cross-sectional view showing an example in the case of manufacturing a light emitting diode according to an embodiment of the present invention in a shell type package.

Explanation of symbols on the main parts of the drawings

110 substrate 130 diode chip

150: luminance reduction unit 151: phosphor

153: electromagnetic wave blocker

The present invention relates to a light emitting diode, and more particularly, to a light emitting diode performing a green to blue light emitting operation.

A light emitting diode is a device that performs a light emitting operation by flowing a forward current through a p-n junction of a semiconductor. Currently commercially available light emitting diodes are fabricated mainly using III-IV hybrid semiconductor materials. That is, GaAlAs, AlInGaP, InGaN or AlInGaN is used as the light emitting material.

Recently, due to advances in semiconductor epitaxial growth technology and process technology, light emitting diodes having very high light conversion efficiency have been developed. In particular, the GaN series, which is a nitride semiconductor, is a material capable of emitting green, blue, and violet light, and is a compound semiconductor device having a wide energy band structure of 3.4 eV, high thermal stability, and excellent electrical and optical properties. In particular, development of high-efficiency light emitting diodes has led to applications in various industrial fields such as mobile phones and large screen backlight units.

Recently, with the development of high efficiency blue light emitting diodes, various attempts have been made to use light emitting diodes as white light sources. There are two ways of obtaining white color using a light emitting diode of a specific color.

First, red, green, and blue (R, G, B) light emitting diodes are simultaneously turned on to realize white color. In the above method, the driving voltages and the light emitting characteristics of each light emitting diode are different from each other, and there are difficulties in practical use due to the difference in temperature or life of the device.

Second, a light emitting diode that emits light in the blue or near ultraviolet region is used as an excitation light source, and a phosphor is applied to the outside to realize white color. The above method has the advantage that only one type of device can be used, so that the design of the driving circuit is easy. Therefore, the above method is used in a conventional white light emitting diode.

Korean Patent No. 558080 discloses a phosphor and a method of manufacturing a light emitting diode MIG using the same. The patent uses a portion of light as an excitation source on a light emitting diode chip that emits blue light, and attaches a phosphor emitting blue to yellow light to form a white light emitting diode by mixing blue light emitting diodes with yellow green or yellow light emitting phosphors. It provides a way.

In addition, Korean Patent Publication No. 2006-55631 discloses a fluorescent material and a white light emitting device using the same. The patent forms a white light emitting device by coating a fluorescent material on the light emitting chip. In particular, the fluorescent material is a mixture of a dye and a resin, and the dye has a yellow or red color using a direct dye, an acid dye, a basic dye, an acid mordant dye, and a sulfur dye.

The two patents described above use a light of a specific color as an excitation source, pass a fluorescent material, and mix it with light of another color to form white light. In addition, recently studied light emitting diode technology has focused on the field of increasing the light efficiency. That is, the development of light emitting diodes having high brightness characteristics has been concentrated. In particular, in the case of the blue light emitting diode, due to the high applicability, the development of products having high brightness characteristics is being made.

However, when a light emitting diode is used for lighting, especially for automobile interiors, a situation arises in which not only high brightness characteristics but also low brightness characteristics are required. That is, a large number of blue light emitting diodes having low luminance characteristics are required for automotive interior lighting.

Efforts have been made to acquire low luminance characteristics using existing blue light emitting diodes, but this has many problems. That is, the method of artificially lowering the brightness by supplying a low current to the existing blue light emitting diode causes uneven brightness due to the limitation of the operating range of the blue light emitting diode. For example, when a low luminance is realized by lowering the operating current in uA units, it is out of the operating range of the conventional blue light emitting diode, and a nonuniformity of luminance having different luminance with respect to the same current is generated for each blue light emitting diode. .

An object of the present invention for solving the above problems is to provide a light emitting diode that can screen the non-uniformity of the luminance in the mass production process, and can ensure a low luminance characteristics uniformly.

The present invention for achieving the above object, a diode chip for emitting blue or green light; A lower substrate for supporting the diode chip; And it provides a light emitting diode comprising a brightness reduction unit for reducing the brightness of blue or green light emitted from the diode chip.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example

1 is a cross-sectional view showing a green or blue light emitting diode according to a preferred embodiment of the present invention.

Referring to FIG. 1, a green or blue light emitting diode according to the present exemplary embodiment has a lower substrate 110, a diode chip 130, and a brightness reduction unit 150.

The lower substrate 110 may have a different configuration depending on the package form of the green or blue light emitting diode. For example, when the package is a shell type, the lower substrate 110 is a lead frame. In addition, when the package form is surface mounted or integrated, the lower substrate 110 may be a predetermined structure formed by an injection molding or the like. That is, the lower substrate 110 supports the diode chip 130 and may be variously changed according to the shape of the package.

The diode chip 130 performs a light emitting operation. For example, the diode chip 130 may be a GaN-based light emitting diode chip. In addition, the GaN series may be formed using a thin film such as InGaN, AlGaN, AlInGaN. That is, any diode chip capable of performing the green light emitting operation or the blue light emitting operation may be used regardless of the type of the thin film.

The luminance reducing unit 150 includes a phosphor 151 and an electromagnetic wave blocking agent 153. The phosphor 151 and the electromagnetic wave shielding agent 153 are present in the form of powder in the epoxy 160 or the silicone resin. In addition, the phosphor 151 may be replaced with a phosphor. When the diode chip 130 performs the blue light emission operation, the blue light excites the phosphor 151 to form green light. The green light emitted from the phosphor 151 and the blue light emitted from the diode chip 130 are absorbed by the electromagnetic wave shield 153.

In particular, the electromagnetic wave shield 153 absorbs more green light emitted from the phosphor 151. This is because the phosphor 151 is present in the epoxy 160 in the form of a powder, and the electromagnetic wave shield 153 is also present in the epoxy 160 in the form of a powder, so that the phosphor 151 is adjacent to the electromagnetic wave shield 153. The absorbance of the generated light becomes higher than that of the blue light generated from the diode chip 130.

Therefore, the blue light emitting diode has a color of sky blue in which white color is added to blue.

In addition, the electromagnetic wave shield 153 is made of CuMnO or Co ₃ O ₄ having a black powder and having insulating properties. Instead of the electromagnetic wave shield 153, a black pigment having insulation may be used. The black pigment absorbs light emitted from the diode chip 130 and the phosphor 151 as Cu, Cr, Fe oxide.

In addition, the phosphor 151 may be a mixture of SrGa ₂ S ₄ , Y ₂ SiO ₂ and TiO ₂ , ZnS: Cu, Au, Al (doped with Cu, Au or Al in ZnS), and green excitation properties. Any fluorescent or phosphor having a compound may be used. In particular, the phosphor 151 forms green light. When blue light is generated from the diode chip 130, the blue light excites the phosphor 151. The excited phosphor 151 generates green light. Some of the generated green light is absorbed by the electromagnetic wave shield 153 located nearby.

In addition, the phosphor 151 may be configured to form green light by excitation even when the light emitted from the diode chip 130 is green light. In the above-described light emitting diode, the electromagnetic wave blocking agent 153 absorbs a part of the green light to emit green light.

Through the above-described process, the green or blue light emitting diode emits light with lower luminance than the blue light emitted from the diode chip 130. In addition, the blue light emitting diode is formed by the blue light emitting diode mixed with white light by the phosphor 151 excited by the blue light to form green light and the electromagnetic wave blocking agent 153 absorbing a part of the green light generated from the phosphor 151. It will emit light.

In addition, the same effect may be obtained by using a black pigment instead of the above-described electromagnetic wave shield 153.

The light emitting diode according to the present invention described above artificially reduces the luminance of the existing blue or green light emitting diode. Therefore, when the existing light emitting diode has an operating current of 20 mA, in order to perform a light emitting operation of low luminance, an operating current in units of uA must be supplied. However, this low operating current results in a difference in visibility between the light emitting diodes.

2 is a characteristic graph illustrating a range of an operating current of a light emitting diode according to an exemplary embodiment of the present invention.

Referring to FIG. 2, first, the characteristic lines A1 and B1 show characteristics of light emitting diodes before luminance is reduced. In general, a plurality of light emitting diodes must have a luminance difference within 30% in order to be visually recognized as exhibiting uniform luminance. In addition, in order to test a low luminance state and select a defective chip whose luminance is uneven due to the luminance difference, it is usually necessary to supply a current of several hundred uA.

However, in the case of low luminance, the low luminance cannot be measured due to limitations of an image sensor that senses the luminance, and the test is performed by flowing an operating current of ordinary brightness. That is, in the case of a GaN series light emitting diode, a product having a luminance difference of more than 30% is selected and shipped with a current of about 20 mA. However, in a typical GaN series light emitting diode, an operating point Q whose luminance difference is changed from each other is formed at 1 mA to 2 mA. Therefore, it would be impossible to select a product with a normal luminance difference of less than 30% at a lower operating current.

According to the present invention, the brightness of the diode chip is reduced to form an operating point in the range of several mA. That is, the A1 characteristic line moves to A2 and the B1 characteristic line moves to B2. Due to the movement of the characteristic line, the operating point for emitting the same brightness is moved from Q1 to Q2. That is, it moves from several hundred uA of operating current to several mA of operating current. Therefore, even if the light emitting diode is tested with an operating current of about 20 mA, very accurate test results can be obtained.

For example, in FIG. 2, when the luminance is not reduced, the luminance of A1 is higher than that of B1 because B1 has a higher luminance than A1 at the actual operating point Q1, but a current of about 20 mA flows during the test process. However, when the luminance is reduced, the situation where the luminance of A2 is high at the actual operating point Q2 is also reflected in the 20 mA test procedure. Thus, a higher accuracy test process can be ensured in the production process.

3 is a cross-sectional view illustrating a package state of a light emitting diode according to an exemplary embodiment of the present invention.

According to FIG. 3, the light emitting diode according to the present invention may be packaged in various forms such as a shell type or a surface mount type. In particular, FIG. 3 is a surface-mounted package of the light emitting diode according to the present invention.

Referring to FIG. 3, the surface mount package of the present invention includes a substrate 210, a fin 230, a diode chip 250, and a brightness reduction unit 270.

The substrate 210 is preferably made of an epoxy material.

In addition, the fin 230 is provided on the surface of the substrate 210. The fin 230 is made of copper foil, and the copper foil is formed over a portion of the upper surface of the substrate 210 and the back surface of the substrate 210. In addition, the copper foil is electrically connected to the diode chip 250 through the bonding wire 280.

The diode chip 250 emits blue or green light. In addition, power for performing the light emitting operation is supplied through the pin 230 electrically connected to the diode chip 250 through the bonding wire 280. In addition, the luminance of the blue or green light emitted is reduced by the luminance reduction unit 270. The brightness reduction unit 270 is composed of a phosphor 271 and an electromagnetic wave shielding agent 273.

The configuration and operation of the brightness reduction unit 270 are the same as those shown and described with reference to FIGS. 1 and 2. Therefore, the description of the configuration and operation of the brightness reduction unit 270 will be omitted in order to avoid duplicate description.

4 is a cross-sectional view showing an example in the case of manufacturing a light emitting diode according to an embodiment of the present invention in a shell type package.

Referring to FIG. 4, the shell type package includes a lead frame 310, a diode chip 330, a brightness reduction unit 350, and a molding unit 370.

The lead frame 310 is made of a conductive material electrically connected to the outside. In addition, a diode chip 330 is provided on one side of the lead frame 310.

The pads on the surface of the diode chip 330 are electrically connected to the respective lead frames 330 through wire bonding. That is, the lead frame 330 and the diode chip 330 are electrically connected through the bonding wire 360.

In addition, the brightness reduction unit 350 embeds the diode chip 330. The luminance reduction unit 350 has a phosphor 351 and an electromagnetic wave blocking agent 353 as shown in FIG. 1. The configuration and operation of the luminance reduction unit 350 are the same as described with reference to FIGS. 1 and 2. The upper part of the brightness reduction part 350 is provided with a molding part 370.

The molding part 370 discharges the light emitted from the brightness reducing part 350 to the outside.

According to the present invention described above, the luminance of the green light or the blue light emitted from the diode chip by the luminance reducing unit is reduced. That is, compared with the conventional method of reducing the luminance by reducing the operating current, when the luminance is reduced by the luminance reduction unit, more stable luminance distribution can be ensured.

According to the present invention as described above, in the conventional case, the low luminance characteristics can not be tested at the direct operating current due to the low operating current. Thus, the test is performed using a test current of tens of milliamps. In this case, it is impossible to test accurate characteristics due to the luminance distribution of the light emitting diode. In addition, even if the luminance is checked by applying a low current to confirm the low luminance characteristics, the measurement time of the luminance is prolonged due to the sensitivity problem, the actual measurement is impossible. Accordingly, the present invention provides a light emitting diode capable of emitting light at low luminance even at a somewhat high supply current by using the luminance reducing unit. In this case, it can be applied to the interior lighting of a car requiring low luminance characteristics, and even if a relatively high current is supplied during mass production, the luminance characteristics can be accurately tested.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (5)

A diode chip for emitting blue or green light; A lower substrate for supporting the diode chip; And A luminance reducing unit for reducing luminance of blue or green light emitted from the diode chip,  The brightness reduction unit, A phosphor that is excited by blue light or green light emitted from the diode chip to emit green light; And A light emitting diode comprising blue or green light emitted from the diode chip and an electromagnetic wave blocking agent which absorbs the green light emitted from the phosphor and is provided in powder form with CuMnO or Co ₃ O ₄ . The light emitting diode according to claim 1, wherein the phosphor is SrGa ₂ S ₄ , TiO ₂ mixture with Y ₂ SiO ₂ or ZnS: Cu, Au, Al. The light emitting diode of claim 1, wherein the electromagnetic wave blocking agent absorbs more green light emitted from the phosphor than light emitted from the diode chip. delete delete

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