KR20070117527A - Method for manufacturing light emitting diode - Google Patents

Abstract

A method for fabricating an LED(light emitting diode) is provided to improve the moisture stability of phosphor and prevent the fluorescent characteristic of phosphor from being deformed by avoiding a reaction of the phosphor and moisture. A body includes a groove part in its upper part. An LED chip(20) is installed in the groove part of the body. A mixture of resin and phosphor(90) is injected into the groove part of the body. After th body is reversed, the mixture is hardened to form a molding part(70,80). The phosphor is deposited in a direction separated from the LED chip to be concentrated in the upper part of the molding part. The body can be one of a substrate(10), a heat sink mounted on a housing or a lead terminal.

Description

Method for manufacturing light emitting diodes

The present invention relates to a light emitting diode manufacturing method, and more particularly, to a light emitting diode manufacturing method that can improve the moisture stability of the phosphor and improve the reliability.

A light emitting diode (LED) refers to a device that makes a small number of carriers (electrons or holes) injected by using a pn junction structure of a semiconductor and emits a predetermined light by recombination thereof. It can be installed in a long, narrow space, and also provides vibration resistance. Recently, in addition to single color components, for example, red, blue, or green light emitting diodes, white light emitting diodes have been released, and demand for them is rapidly increasing.

The light emitting diode may implement white light using a single chip or multiple chips. In the case of a single chip, white light is realized by combining a light emitting diode chip of a compound semiconductor and a phosphor. That is, the phosphor is disposed on the light emitting diode chip so that a part of the first light emission of the light emitting diode chip and the secondary light emission wavelength-converted by the phosphor are mixed to realize white. White light emitting diodes of this structure are widely used because of their low cost and very simple in principle and structure.

In general, a blue light emitting diode chip and a yellow light emitting phosphor that can be excited from blue light are combined to realize white light. For example, white light may be realized by mixing blue light having a wavelength of 450 to 470 nm and yellow light of a yellow phosphor such as YAG: Ce or (Ba, Sr, Ca) ₂ SiO ₄ : Eu. In addition, a blue light emitting diode chip and a red and green light emitting phosphor capable of excitation from blue light are combined to realize white light. For example, white light can be realized by a mixture of blue light having a wavelength of 450 to 470 nm, red light of a red phosphor represented by (Sr, Ca) S: Eu, and green light of a green phosphor represented by SrGa ₂ S ₄ : Eu. have.

Sulfide-based phosphors have excellent excitation efficiency and excellent optical properties in the visible light region. However, sulfide-based phosphors are easily reacted with moisture to change into oxides or carbonates, and there is a problem of causing a change in chemical properties of the phosphors. For example, a CaS: Eu phosphor, which is a representative red phosphor of a sulfide-based phosphor, causes the following reaction.

CaS + H ₂ O + CO ₂ → CaO or CaCO ₃ + H ₂ S

The H ₂ S gas generated by the phosphor and the water reaction modifies the fluorescent property of the phosphor, accompanied by a change in color coordinates, and causes a sudden decrease in luminous intensity. In addition, the H ₂ S gas has a problem of reducing the reliability of the light emitting diode by black corrosion of Ag or Au formed as an electrode.

On the other hand, in general, by distributing the above-mentioned phosphor in a certain form in a transparent resin surrounding the LED chip, the phosphor can emit light using the light of the LED chip as an excitation source. FIG. 1 illustrates a light emitting diode having such a structure, wherein the light emitting diode chip 2 is mounted on a substrate 1 and electrically connected thereto, and then the light emitting diode chip 2 is formed using a transparent resin including a phosphor 8. Mold. However, in the light emitting diode having such a structure, precipitation of the phosphor 8 occurs in the molding part 7 made of a mixture of resin and phosphor. In particular, since the viscosity of the resin is sharply lowered during curing of the molding part 7, most of the phosphors 8 are precipitated and the upper surface of the light emitting diode chip 2 or the electrodes 3 and 4 made of Ag or Au. It will settle on the top. In addition, in the light emitting diode having such a structure, moisture is easily introduced between the molding part 7 and the substrate 1 or between the molding part 7 and the electrodes 3 and 4, and the introduced moisture reacts with the phosphor 8 to react with the phosphor. Causes modification of its chemical properties. In particular, the sulfide-based phosphor easily reacts with moisture to cause severe brightness degradation and optical property changes, and to corrode electrodes to deteriorate reliability.

The present invention is to solve the above problems, to improve the stability of the sulfide-based phosphor to the moisture has a superior light emission characteristics, to improve the stability for color temperature, color coordinates, etc., and to improve the reliability of the LED manufacturing method The purpose is to provide.

According to an exemplary embodiment of the present invention, the method includes: providing a body including a groove part at an upper portion to surround a light emitting diode chip; Mounting a light emitting diode chip in a groove portion of the body; Injecting a mixture of a resin and a phosphor into a groove of the body; Inverting the body and curing the mixture to form a molding part; And the phosphor is precipitated in a direction spaced apart from the light emitting diode chip, and concentrated in the upper portion of the molding part.

The phosphor includes a sulfide-based phosphor.

The phosphor includes (Ca, Sr) S: Eu, SrGa ₂ S ₄ : Eu, ZnS: Cu, Al or (Zn, Cd) S: Ag, Cl.

The body may be any one of a heat sink or a lead terminal mounted on a substrate, a housing.

The present invention can block the reaction of the phosphor with the water, thereby improving the moisture stability of the phosphor to prevent the modification of the fluorescent characteristics of the phosphor, improve the light emission characteristics, it is possible to prevent the corrosion of the electrode. In addition, it is possible to improve the stability of the color temperature, color coordinates, and the like, and to improve the light emission characteristics.

Hereinafter, with reference to the accompanying drawings will be described in more detail with respect to the present invention. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention, and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you. Like numbers refer to like elements in the figures.

Figure 2 shows a first embodiment of a light emitting diode according to the invention.

Referring to FIG. 2, the light emitting diode includes a substrate 10, electrodes 30 and 40 formed on the substrate 10, a light emitting diode chip 20 mounted on the first electrode 30, and a substrate ( The reflector 50 is formed on the top of the 10 to surround the light emitting diode chip 20. In addition, a first molding part 70 and a second molding part 80 encapsulating the light emitting diode chip 20 are formed in a central hole of the reflector 50, and inside the second molding part 80. A phosphor 90 uniformly distributed.

The electrodes 30 and 40 are composed of first and second electrodes 30 and 40 for connecting to the positive terminal and the negative terminal of the light emitting diode chip 20 on the substrate 10. The first and second electrodes 30 and 40 may be formed through a printing technique. The first and second electrodes 30 and 40 are formed of a metal material including copper or aluminum having excellent conductivity, but the first electrode 30 and the second electrode 40 are formed to be electrically disconnected.

The light emitting diode chip 20 uses a light emitting diode chip 20 emitting blue light of GaN, InGaN, AlGaN or AlGaInN. This embodiment uses a light emitting diode chip that emits blue light in the range of 420 to 480 nm. However, the present invention is not limited thereto, and a light emitting diode chip that emits ultraviolet light (UV) as well as blue light may be used. In addition, the number of light emitting diode chips 20 may be one, or may be configured in plural as desired.

The LED chip 20 is mounted on the first electrode 30 and is electrically connected to the second electrode 40 through a wire 60. Although the present embodiment is directly mounted on the electrodes 30 and 40 using the light emitting diode chip 20 having positive and negative electrodes on the upper and lower planes of the light emitting diode chip 20 as shown, When the light emitting diode chip 20 having a positive electrode and a negative electrode in the upper plane of the chip 20 is formed on the substrate 10 instead of being mounted on the electrode, the first through the two wires 60, It may be connected to the electrode 30 or the second electrode 40.

A reflector 50 including a central hole is formed on the substrate 10 so as to surround the light emitting diode chip 20. The reflector 50 may be manufactured integrally with the substrate 10 or separately manufactured and then combined with the substrate 10. As shown in FIG. 3, the inner surface of the reflector 50, that is, the inner circumferential surface forming the central hole, may have a predetermined slope to maximize reflection of light emitted from the LED chip 20 and increase luminous efficiency. have. In order to further increase the reflectance of the light, a light reflection material including aluminum (Al) or silver (Ag) may be coated on the inner circumferential surface of the central hole, or a reflecting plate may be added.

First and second molding parts 70 and 80 are formed in the central hole of the reflector 50 to encapsulate the LED chip 20. The light emitting diode chip 20 of the present embodiment is encapsulated by a first molding part 70 made of epoxy or silicon transparent resin, and a second molding part made of a mixture of transparent resin and phosphor 90 on top thereof. 80) is formed. This is to prevent the reaction of the phosphor 90 and the water flowing between the molding part and the substrate 10 or between the molding part and the electrodes 30 and 40, and is particularly preferable when a sulfide-based phosphor easily reacts with water. Do. That is, the phosphor 90 distributed inside the second molding part 80 due to the first molding part 70 is prevented from directly depositing on the upper surface of the LED chip 20 or the electrodes 30 and 40, and the phosphor It can block the reaction between (90) and moisture. Accordingly, it is possible to prevent the fluorescence property deformation of the phosphor 90 and to improve the luminescence property, and to prevent corrosion of the electrodes 30 and 40.

The phosphor 90 uses a sulfide-based phosphor that retains excellent fluorescence properties but easily reacts with moisture. The sulfide-based phosphor includes (Ca, Sr) S: Eu, SrGa ₂ S ₄ : Eu, ZnS: Cu, Al or (Zn, Cd) S: Ag, Cl. This embodiment uses a red phosphor of (Ca, Sr) S: Eu and a green phosphor of SrGa ₂ S ₄ : Eu for the implementation of white light. However, the present invention is not limited thereto, and various phosphors for realizing a desired color may be used, and the combination of the first and second molding parts may be variously configured. That is, the present embodiment includes a first molding part made of a transparent resin, and a second molding part made of a mixture of the red and green sulfide-based phosphors and the transparent resin, but is not limited thereto. It may also include a first molding part made of a mixture of phosphors and transparent resins of different composition with less reactivity, and a second molding part made of a mixture of sulfide-based phosphors and transparent resin with high reactivity with water.

The second molding part is not limited to the form shown in the drawings, and may be configured in, for example, a convex lens shape or various shapes for obtaining desired light condensing properties.

In the light emitting diode of this embodiment, primary light is emitted from the LED chip 20, and the phosphor emits wavelength-converted secondary light by the primary light, thereby realizing a color of a desired spectral region by mixing them. .

That is, blue light is emitted from the blue light emitting diode chip 20, and the red and green phosphors inside the second molding part 80 emit red light and green light by the blue light emitted through the first molding part 70. Thus, a part of the blue light, which is the primary light, and the red light and the green light, which are the secondary light, may be mixed to implement white light.

The manufacturing method of the light emitting diode according to the first embodiment described above may be very diverse, but the manufacturing method is briefly described as follows.

First, a substrate on which electrodes are formed is prepared, and a reflector including a central hole is formed. The LED chip is mounted on one electrode of the substrate exposed through the central hole of the reflector, and the other electrode and the LED chip are electrically connected through a wire. The first molding part may be formed by injecting a transparent epoxy or silicone resin into the volume of 1/3 to 1/2 of the entire molding part and curing the center hole of the reflector. Next, a mixture of a transparent epoxy or silicone resin and a phosphor is injected onto the first molding part and cured to form a second molding part to fabricate a light emitting diode.

In addition, the present embodiment is not limited to the above description, but the groove is formed in a predetermined region of the substrate on which the LED chip is mounted, the LED chip is mounted on the lower plane thereof, and then the first and second moldings are formed in the groove. Wealth can be formed. This will be described with reference to FIG. 4, and a description overlapping with the above-described example will be omitted.

Referring to FIG. 4, the light emitting diode may include a substrate 15 having a groove, electrodes 30 and 40 formed on the substrate 15, and an LED chip 20 mounted on the first electrode 30. A phosphor formed in the groove and including a first molding part 70 and a second molding part 80 encapsulating the light emitting diode chip 20, and being uniformly distributed in the second molding part 80. (90). Although not shown, a predetermined slope is formed on the sidewall surface of the groove to maximize the reflection of the light emitted from the light emitting diode chip and increase the luminous efficiency.

In addition, the present embodiment removes a predetermined area of the substrate on which the light emitting diode chip is mounted to form a through hole, inserts a heat sink into the through hole, inserts a heat sink into the through hole, and then heats the sink. A light emitting diode chip may be mounted on the top. This will be described with reference to FIG. 5, and a description overlapping with the above-described example will be omitted.

Referring to FIG. 5, the light emitting diode includes a housing 110 in which electrodes 30 and 40 are formed at both sides and includes a through hole, a heat sink 120 mounted in the through hole of the housing 110, and a heat. A light emitting diode chip 20 mounted on the sink 120 and first and second molding parts 70 and 80 encapsulating the light emitting diode chip 20, and the second molding part 80. It includes a phosphor 90 uniformly distributed therein.

The housing 110 may selectively use a resin suitable for conditions such as hardness, chemical resistance, and thermal conductivity, and may use PPA, LCP, or thermally conductive resin. As the heat sink 120 mounted in the through hole of the housing 110, a metal material having excellent thermal conductivity and electrical conductivity may be used, or a resin having excellent thermal conductivity may be used. By using such a material having excellent thermal conductivity, heat emitted from the light emitting diode chip 20 may be effectively released and thermal burden may be reduced. In addition, the heat dissipation effect can be further enhanced by additionally combining an external heat sink.

As described above, the first embodiment may double-mould the light emitting diode chip by the first and second molding parts, thereby preventing the phosphor from directly depositing on the top surface of the light emitting diode chip or the electrode and blocking the reaction between the phosphor and water. . As a result, it is possible to prevent the fluorescence property deformation of the phosphor and to improve the luminescence property, and to prevent corrosion of the electrode.

6 shows a second embodiment of a light emitting diode according to the invention.

Referring to FIG. 6, the light emitting diode includes a substrate 10, electrodes 30 and 40 formed on the substrate 10, a light emitting diode chip 20 mounted on the first electrode 30, and a substrate ( The reflector 50 is formed on the top of the 10 to surround the light emitting diode chip 20. In addition, a molding unit 100 encapsulating the light emitting diode chip 20 in a central hole of the reflector 50, and a phosphor 90 uniformly distributed in the molding unit 100. The present embodiment is characterized in that the phosphor 90 is uniformly distributed so that the phosphor 90 is not precipitated when the molding part 100 formed of a mixture of the transparent resin and the phosphor 90 is formed. Description is omitted. In addition, the present embodiment is not limited to the illustration, and can be applied to the various structures described in the case of the first embodiment.

The manufacturing method of the light emitting diode according to the second embodiment described above is as follows.

First, a substrate on which electrodes are formed is prepared, and a reflector including a central hole is formed. The LED chip is mounted on one electrode of the substrate exposed through the central hole of the reflector, and the other electrode and the LED chip are electrically connected through a wire. A molding portion is formed by injecting a mixture of a transparent epoxy or silicone resin and a phosphor into the central hole of the reflector. At this time, the light emitting diode is rotated so that the phosphor contained in the molding part is uniformly distributed without precipitation. That is, a mixture of a resin and a phosphor is injected into the central hole of the reflector to place the light emitting diode in the oven, and then the molding part is cured while rotating the light emitting diode in the oven or the oven at a speed of 1 to 100 RPM.

As described above, the second embodiment rotates the light emitting diode when forming the molding part of the light emitting diode, thereby preventing the phosphor from directly depositing on the upper surface of the LED chip or the electrode so as to be uniformly distributed, and blocking the reaction between the phosphor and water. have. As a result, it is possible to prevent the fluorescence property deformation of the phosphor and to improve the luminescence property, and to prevent corrosion of the electrode.

7 shows a third embodiment of a light emitting diode according to the invention.

Referring to FIG. 7, the light emitting diode includes a substrate 10, electrodes 30 and 40 formed on the substrate 10, a light emitting diode chip 20 mounted on the first electrode 30, and a substrate ( The reflector 50 is formed on the top of the 10 to surround the light emitting diode chip 20. In addition, a molding unit 100 encapsulating the light emitting diode chip 20 in a central hole of the reflector 50, and includes a phosphor 90 concentrated and distributed over the molding unit 100. . The present embodiment is characterized in that the phosphor 90 is distributed to be concentrated in the upper portion when forming the molding part 100 made of a mixture of a transparent resin and the phosphor 90, and the first and second embodiments described above Duplicate explanations are omitted. In addition, the present embodiment is not limited to the illustration, and can be applied to the various structures described in the case of the first embodiment.

The manufacturing method of the light emitting diode according to the third embodiment described above is as follows.

First, a substrate on which electrodes are formed is prepared, and a reflector including a central hole is formed. The LED chip is mounted on one electrode of the substrate exposed through the central hole of the reflector, and the other electrode and the LED chip are electrically connected through a wire. A molding portion is formed by injecting a mixture of a transparent epoxy or silicone resin and a phosphor into the central hole of the reflector. At this time, the mixture of the resin and the phosphor is injected into the central hole of the reflector, and then inverted and cured in the shape as shown. That is, by placing and curing the LED chip facing downward, the phosphor contained in the molding portion is precipitated downward, and is concentrated and distributed over the molding portion in the shape as shown. In order to form the molding part, it may be cured using a partition wall for maintaining the shape of the molding part. As shown in the drawing, to form a plate-shaped molding, the mixture of the resin and the phosphor injected into the center hole of the reflector is pressed with a plate-shaped partition wall, and then the LED is inverted and cured. Partition walls for various shapes of the molding part may be used.

As described above, the third embodiment injects the resin and the phosphor in the formation of the molding part of the light emitting diode, and then inverts and cures the light emitting diode, thereby preventing the phosphor from being concentrated on the upper part of the molding part and being directly deposited on the upper surface of the LED chip or the electrode. In addition, the reaction between the phosphor and water can be blocked. As a result, it is possible to prevent the fluorescence property deformation of the phosphor and to improve the luminescence property, and to prevent corrosion of the electrode.

The present invention is not limited to the above description, and various modifications and variations are possible, and may be applied to products of various structures. For example, even when encapsulating a light emitting diode chip mounted on a lead terminal, the reaction between the phosphor and water may be blocked by double molding, rotation when forming the molding part, or inverted and hardened as described above.

8 is a graph showing changes in optical characteristics of the comparative example according to the related art and the first and second embodiments as described above. That is, the comparative example, the first example and the second example were maintained for 3000 hours under the condition of 90% relative humidity at a temperature of 60 ° C., and the emission intensity was changed. Here, the first embodiment was formed by encapsulating the light emitting diode chip by the second molding part including the first molding part and the phosphor, and the second embodiment was formed by rotating and curing the molding part of the light emitting diode.

As can be seen in the drawing, the comparative example in which the phosphor precipitates in the molding portion surrounding the light emitting diode chip has a significant decrease in luminescence intensity due to deterioration of the phosphor caused by the reaction of the phosphor with the moisture penetrates over time. . On the other hand, in the first and second embodiments according to the present invention, it can be seen that there is little change in the emission intensity by blocking the reaction between the phosphor and water.

As mentioned above, although this invention was demonstrated in detail using the preferable Example, the scope of the present invention is not limited to a specific Example and should be interpreted by the attached Claim. In addition, those skilled in the art should understand that many modifications and variations are possible without departing from the scope of the present invention.

1 is a cross-sectional view showing a conventional light emitting diode.

2 to 5 are cross-sectional views showing a first embodiment of a light emitting diode according to the present invention.

6 is a sectional view showing a second embodiment of a light emitting diode according to the present invention;

7 is a sectional view showing a second embodiment of a light emitting diode according to the present invention;

8 is a graph showing changes in optical characteristics of Comparative Example, First Example and Second Example.

<Explanation of symbols for the main parts of the drawings>

10 substrate 20 light emitting diode chip

30, 40: electrode 50: reflector

60: wire 70, 80, 100: molding part

90 phosphor 110 housing

120: heat sink

Claims (4)

Providing a body including a groove at an upper portion to surround the LED chip; Mounting a light emitting diode chip in a groove portion of the body; Injecting a mixture of a resin and a phosphor into a groove of the body; Inverting the body and curing the mixture to form a molding part; And The phosphor is precipitated in a direction away from the light emitting diode chip, characterized in that it comprises the step of intensively distributed on the molding portion. The method of claim 1, The phosphor is a light emitting diode manufacturing method comprising a sulfide-based phosphor. The method according to claim 1 or 2, The phosphor includes (Ca, Sr) S: Eu, SrGa ₂ S ₄ : Eu, ZnS: Cu, Al or (Zn, Cd) S: Ag, Cl. The method according to claim 1 or 2, The body is a method of manufacturing a light emitting diode, characterized in that any one of a heat sink or a lead terminal mounted on the substrate, the housing.

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