KR100712876B1 - Light emitting diode capable of improving color uniformity and a manufacturing method thereof - Google Patents

Abstract

Disclosed are a light emitting diode capable of improving color uniformity and a method of manufacturing the same. In the light emitting diode according to the present invention, a light emitting diode chip is mounted on a printed circuit board on which a thin film pattern is formed, and a transparent resin layer is formed to cover the light emitting diode chip. At this time, the transparent resin layer has a thickness and shape proportional to the amount of light emitted from the light emitting diode chip, and phosphors are uniformly dispersed therein. As a result, the light emitting diode can prevent color uniformity degradation caused by total reflection of light, chromatic aberration, phosphor distribution, and the like, and as a result, it is possible to improve the brightness of the light emitting diode and increase the product yield.

Light Emitting Diode, Total Reflection, Chromatic Aberration, Phosphor Distribution, Color Uniformity

Description

Light emitting diode capable of improving color uniformity and a manufacturing method

1 is a view for explaining the total reflection,

2 is a diagram illustrating chromatic aberration;

3 is a view showing an example of a resin accommodating light emitting diode according to the prior art;

4 is a view showing an embodiment of a light emitting diode according to the present invention;

5 is a view showing another embodiment of a light emitting diode according to the present invention;

6 is a view illustrating a flip chip method;

7 is a flowchart illustrating an embodiment of a method of manufacturing a light emitting diode according to the present invention; and

8 is a flowchart illustrating another embodiment of a method of manufacturing a light emitting diode according to the present invention.

Explanation of symbols on the main parts of the drawings

7, 25: light emitting diode chip 12, 28: phosphor

14, 27: transparent resin layer 29: the lens

The present invention relates to a light emitting diode and a method of manufacturing the same, and more particularly, to a light emitting diode and a method of manufacturing the same that can improve color uniformity (color uniformity) and reduce color variation.

In general, a light emitting diode (LED) is an electronic component that generates a small number of carriers (electrons or holes) injected by using a pn junction structure of a semiconductor and emits light by recombination thereof. . In other words, a light emitting diode is a device made of a compound semiconductor that emits light of a specific wavelength while electrons move from a high energy level to a low energy state through electricity. Such a light emitting diode can be irradiated with high efficiency light at low voltage, and thus is widely used in electronic devices such as home appliances, electronic displays, and displays.

A light source system using a light emitting diode chip is formed by mounting a light emitting diode chip emitting light according to a intended use in various types of packages. In particular, according to the trend toward miniaturization and slimming of information and communication devices, various components such as resistors, capacitors, and noise filters are becoming more miniaturized. Accordingly, a light emitting diode package also includes a light emitting diode on a printed circuit board (PCB). It is made of Surface Mount Device (SMD) type in order to mount it directly.

When light is incident from an optically dense medium (a material having a high refractive index) to a small medium (a material having a small refractive index), as shown in FIG. The reflection of all light at the interface of the medium occurs. This phenomenon is called total reflection, and the incident angle of the limit at which total reflection of light occurs is called a critical angle. This total reflection is generated inside the lens of the light emitting diode as shown in FIG. 1B, but the total reflection generated inside the lens is a major factor that lowers the color uniformity of the light emitting diode.

In addition, the position of the image generated when the image of the object is made through the lens depends on the color coming from the object, which is called chromatic aberration. In the case of glass, the index of refraction gradually decreases as the wavelength of light increases. When the image is formed through the lens, the position or magnification of the image varies depending on the color of the object (wavelength of light). When white light is seen through a prism or a lens having chromatic aberration, as shown in FIG. 2A, the longer the wavelength is closer to the red, the farther the focus is from the lens, and the shorter the wavelength is closer to the violet, the closer the lens is. Such chromatic aberration is also generated through the lens of the light emitting diode as shown in Fig. 2b, which causes a decrease in color uniformity of the light emitting diode.

3 is a view showing an example of a resin accommodating light emitting diode according to the prior art. Referring to the drawings, the resin accommodating light emitting diode is mounted on the metal base part 1 by the die bonding 5 and the metal base parts 1 and 3 constituting a lead frame for connection to the outside. The light emitting diode chip 7, the wire bonding 9 for electrically connecting the metal base 1 and the light emitting diode chip 7, and the light emitted from the light emitting diode chip 7 to reflect upwardly. It consists of a white package 10 configured to release.

As shown in FIG. 3, the white package 10 has a recess at the bottom thereof to enable mounting of the light emitting diode chip 7, and the recess has a light transmissive epoxy resin in which the phosphor 12 is dispersed. 14 or silicone resin 14 is filled. At this time, the epoxy resin 14 or the silicone resin 14 should have good permeability, excellent light resistance, moisture resistance and heat resistance, and be suitable for use in a mass production apparatus in a production line.

In addition, the white package 10 should have high light reflectivity and low light absorption at its surface 16. In general, the resin containing light emitting diode of the related art having the structure of FIG. 3 uses a light emitting diode chip 7 made of a nitride compound semiconductor.

As a color conversion layer for realizing white color using blue light emitted from the light emitting diode chip 7, the fluorescent material dispersed in the resin 14 layer is yttrium-aluminum-garnet (Y ₃ Al ₅ ), which is an inorganic fluorescent material. O ₁₂ : Ce, YAG: Ce) compounds have been widely used. However, white light emitting diodes using YAG: Ce phosphors tend to be converted to silicate or TAG series phosphors due to their low color temperature and color rendering index.

However, in the conventional method, the fluorescent material was mixed during the heating of the powdered resin, and the inorganic phosphor 12 was locally aggregated due to the viscosity difference between the fluorescent material and the resin powder and the size difference of the granules (for example, For example, A) emission characteristics of FIG. 3 occur unevenly distributed over the entire area of the color conversion layer. In addition, there is a problem that the fluorescent material having a higher specific gravity than the transparent resin sinks while the powdered resin is melted by heat and the resin 14 is molded into the recessed portion in which the light emitting diode chip 7 is mounted (FIG. 3, S). Such a phenomenon lowers the color conversion efficiency in the resin, and consequently becomes a major factor in lowering the color uniformity of the light emitting diode.

The present invention has been made to solve the above problems, by improving the color uniformity of the light emitting diode, thereby providing a light emitting diode and a method of manufacturing the same that can improve the brightness of the light emitting diode and increase the product yield For the purpose of

A light emitting diode according to the present invention for achieving the above object, a printed circuit board formed with a thin film pattern; A light emitting diode chip mounted on the printed circuit board; And a transparent resin layer formed to cover the light emitting diode chip, forming a thickness and shape proportional to the amount of light emitted from the light emitting diode chip, and having phosphors uniformly dispersed therein.

Here, the transparent resin layer is preferably formed by a transfer molding method or an encapsulation printing method.

In addition, the transparent resin layer, the transparent resin layer is preferably formed by mixing the phosphor while applying heat in the process of mixing the main epoxy component or silicone component.

Preferably, the light emitting diode chip is implemented by a flip chip method.

Preferably, the transparent resin layer forms a convex lens shape and is formed such that an incident angle of light emitted from the light emitting diode chip toward the surface of the transparent resin layer is within about 40 °.

Alternatively, the lens may further include a lens bonded on the transparent resin layer such that light emitted from the light emitting diode chip is incident within about 40 °. Here, the lens is made of a material having a low light dispersion rate, the lens is preferably implemented by any one of fluorite glass or fluoride phosphate glass.

On the other hand, the light emitting diode according to the present invention comprises the steps of mounting a light emitting diode chip on a printed circuit board formed with a thin film pattern; And molding a transparent resin layer to cover the light emitting diode chip, wherein the transparent resin layer has a thickness and shape proportional to the amount of light emitted from the light emitting diode chip, and emits light in which phosphors are uniformly dispersed therein. Provided is a diode manufacturing method.

The light emitting diode manufacturing method includes the steps of mixing a phosphor in at least one water support material; Thermosetting the resin mixed with the phosphor to form a solid state; Powder grinding of the solid state molding; And forming a tablet from the powdered resin powder, wherein the molding step is preferably implemented using the formed tablet.

As a result, the light emitting diode and the manufacturing method thereof according to the present invention can improve the color uniformity of the light emitting diode, and as a result, it is possible to improve the brightness of the light emitting diode and increase the product yield.

Hereinafter, a light emitting diode and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

4 is a view showing an embodiment of a light emitting diode according to the present invention. Referring to the drawings, a light emitting diode is mounted on a printed circuit board (PCB) 21, 23 having a thin film pattern, the light emitting diode chip 25 is mounted, the transparent resin layer 27 is a light emitting diode chip 25 ) Is formed by covering. At this time, the transparent resin layer 27 has a thickness and shape proportional to the amount of light emitted from the light emitting diode chip 25, and the phosphor 28 is uniformly dispersed therein. Alternatively, the light emitting diode may have a structure in which convex lenses are bonded to the transparent resin layer 27 in which the phosphor 28 is uniformly dispersed therein, as shown in FIG. 5.

In order to omit wire bonding between the light emitting diode chip 25 and the printed circuit boards 21 and 23, the light emitting diode chip 25 may be implemented in a flip chip method.

FIG. 6 is a cross-sectional view of a gallium nitride (GaN) light emitting diode chip as shown to explain a flip chip method. Referring to the drawings, a GaN light emitting diode chip is basically formed in a predetermined region above the n-type GaN cladding layer 32 and the n-type GaN cladding layer 32 formed on the sapphire substrate 31 and the sapphire substrate 31. A current injection area is formed on the active layer 33 having a multi-quantum well structure, the p-type GaN cladding layer 34 and the p-type GaN cladding layer 34 formed on the active layer 33. Bonding B-electrode made of a conductive material formed at a predetermined position on the T-electrode 35 and a T-electrode 35 made of a transparent transparent material so as not to decrease the brightness characteristic of the light while increasing 36, an N-electrode 37 formed in a predetermined region on the n-type GaN cladding 32 and used for bonding and voltage application, on the B-electrode 36 and the N-electrode 37 After the bumps 38 are formed, the substrates 21 and 23 and the light emitting diodes are formed through the bumps 38 without the need for wire bonding. The chip 25 is directly bonded. Here, the T-electrode 35 may be omitted as necessary.

Of the light emitted from the active layer 33 of the flip chip bonded GaN LED chip 25, the light emitted upward is radiated as it is, but some of them are also emitted toward the substrates 21 and 23. Therefore, in order to improve the brightness characteristic of the diode, a reflective layer is first formed on the T-electrode 35 before the B-electrode 36 is formed to reflect the light emitted toward the substrates 21 and 23 upwards. Let's do it. As the reflective layer, Ag, Al, or the like having high reflectance is used.

 The transparent resin layer 27 is preferably embodied in the shape of a convex lens such that the incident angle of light emitted from the light emitting diode chip 25 to the surface of the transparent resin layer 27 is within about 40 °. However, as shown in FIG. 5, when the convex lens 29 is bonded on the transparent resin layer 27, the convex lens 29 is incident so that light emitted from the light emitting diode chip 25 is incident within about 40 °. It is preferable to form a curved surface. In addition, the lens to be bonded on the transparent resin layer 27 is preferably made of a material having a low dispersion rate of light in order to prevent the color uniformity decrease due to chromatic aberration. Examples of low light dispersion include fluorite glass and fluoride phosphate glass.

The reason for limiting the incident light angle to be within about 40 ° is as follows.

When the refractive index of air is 1, the refractive index of the transparent resin layer 27 may be about 1.52. When light is incident on a material having a large refractive index and a material having a small refractive index, total reflection of light occurs at a specific angle or more, and the critical angle at this time may be calculated by Equation 1 below.

n ₁ sinθ ₁ = n ₂ sinθ ₂

Where n ₁ = 1.52, n ₂ = 1, θ ₂ = 90 °,

1.52sinθ ₁ = 1.0sin90 ° = 1

Therefore sinθ ₁ = 1 / 1.52 = 0.658,

θ ₁ = 41.15 °.

On the other hand, the transparent resin layer 27 is preferably formed by a transfer molding method or an encapsulation printing method. The transfer molding method, also called transfer molding, transforms a plastic material into a cured state by injecting the material into a closed heating mold and then transferring the material. The operation is performed in the order of preforming-> preheating-> mold closing-> material supply-> hardening-> mold opening-> ejecting the molded product. This molding method is characterized by the use of brittle inserts (metal inserts in the resin), which are suitable for complex shapes and are not possible with normal compression molding.The parts of the product become homogeneous, especially in thick products. . In addition, products with precise dimensions can be obtained, and particularly thin and long products can be formed, and thin and long tubes can be formed.

The encapsulation printing method is a method of preventing the deformation of an element by forming a transparent resin layer 27 on a light emitting diode substrate and isolating the substrate from moisture, oxygen, and the like.

7 is a flowchart illustrating an embodiment of a method of manufacturing a light emitting diode according to the present invention. Referring to the drawings, the light emitting diode chip 25 is mounted on the printed circuit board or the lead frames 21 and 23 (S100), and the transparent resin layer 27 is provided to protect and seal the light emitting diode chip 25. Molding on the light emitting diode 25 (S300).

In the above, the light emitting diode chip 25 is mounted on a printed circuit board (PCB), and the light emitting diode chip 25 has been described as being implemented in a flip chip method, but is not limited thereto. That is, the light emitting diode chip 25 may be formed in the lead frame, or may be electrically connected to the printed circuit board or the lead frame by wire bonding. When the light emitting diode chip 25 is connected by wire bonding, gold (Au) is generally used as the material. Of course, the flip chip method eliminates the need for wire bonding.

In addition, a zener diode may be mounted on the mounting portions 21 and 23 to supply an appropriate current of the light emitting diode chip 25. This is required for stable operation and control of the white light emitting device.

In the process of molding the transparent resin layer 27, the transparent resin layer 27 is formed to have a thickness and shape proportional to the amount of light emitted from the light emitting diode chip 25. In addition, the transparent resin layer 27 is embodied in the shape of a convex lens such that the incident angle of light emitted from the light emitting diode chip 25 and directed to the surface of the transparent resin layer 27 is within about 40 °. Alternatively, as described above, the lens 29 is bonded on the transparent resin layer 27 covering the light emitting diode chip 25 so that the light emitted from the light emitting diode chip 25 is incident within about 40 °. It may be formed.

As the method of manufacturing the transparent resin layer 27 (S200), the phosphor 28 is mixed while applying heat during the process of mixing the main epoxy component or the silicone component (S210) (S220). Here, the main epoxy component or the silicone component is preferably blended in an appropriate ratio in consideration of transparency, color uniformity, etc. of the transparent resin layer 27, and is preferably blended so as to occupy 50% to 80% of the total components. . In addition, the phosphor 28 is preferably blended to account for 20% to 50% of the total components. However, the mixing ratio of the main component and the phosphor 28 is not limited thereto and may vary depending on the specifications of the manufacturer and the package. At this time, antioxidants, UV absorbers, modifiers and the like are used as additives.

In the resin in which the phosphor 28 is mixed, a curing agent epoxy component or a silicone component is mixed and solidified (S230). As the curing agent component, a liquid type such as MHHPA or MTHPA, or a solid type such as THPA or HHPA may be used. At this time, an antioxidant, a UV absorber, a catalyst, or the like may be further added to the main epoxy component or the silicone component. By addition of an additive, the heat resistance and moisture resistance of the transparent resin layer 27 improve, and moldability improves.

More specifically, the epoxy resin and the curing of the epoxy resin, generally, the epoxy resin is the molecular weight of bisphenol A [2,2-bis (4'-oxyphenol) propane] and epichlorohydrin in the presence of sodium hydroxide 300-4,000 primary resin (prepolymer) is produced. Since the primary resin can be obtained from an oil-like one to a solid-like one having a softening point of 160 ° C. depending on the mixing conditions of the raw materials, the reaction conditions can be selected according to the later use.

When an acid such as amine or phthalic anhydride such as m-phenylenediamine or phthalic anhydride is added to the primary resin, ring opening of epoxy group and reaction with hydroxy group occur to form a bridging bond, and the type and reaction of curing agent. Depending on the conditions, resins having different properties are produced.

Epoxy resin has a specific gravity of 1.230 to 1.189 and is excellent in mechanical properties such as bending strength and firmness. There is no generation of volatiles and shrinkage of the volume at the time of curing, and it has a great adhesion to the material surface at the time of curing. It is flammable and chemically resistant, but is slightly eroded by strong acids and strong bases. By adding a pigment, coloring can be made at will, and also daylight resistance is large. It has excellent workability such as casting, embedding and encapsulation.

By using the above-mentioned performance, the use of such adhesives, paints, lining materials, casting materials, laminated plates, and stabilizers of vinyl chloride resins is various.

In addition, one of the advantages of the epoxy resin is that it can easily be made of a thermosetting material at room temperature, this phenomenon (curing) is called curing of the epoxy resin. In order to cure this, a so-called hardener is used, and a hardener is used for materials that are easily reacted with epoxy. The curing agent is generally different from the catalyst. The catalyst causes a reaction, but the catalyst reacts directly with the reactant and does not exist as part of the polymer. The curing agent becomes a part of the reactant directly through the reaction.

The curing reaction is exothermic and heat is generated from the start of the reaction. However, in order to make a reaction, heating may be required.

In general, heating can shorten the time required to complete the curing reaction in proportion to the heating temperature. However, when hardening in the state where temperature is too high, the physical property of hardened | cured material tends to fall. That's why choosing the right temperature is so important.

Generally, high purity epoxy resins exist as chemically very stable compounds below 200 ° C, and have thermoplastic properties. It has a three-dimensional (network) structure through the curing reaction.

Therefore, as the transparent resin layer 27 of the white light emitting device, the mixing of the fluorescent material for uniform color distribution is not mixed in the process of forming the resin powder and applying the heat to form a tablet of a certain shape as in the prior art. In addition, by mixing the light-transmissive epoxy resin and the fluorescent substance 28, and thermosetting it to form a solid state, the fluorescent substance is evenly distributed throughout the transparent resin layer 27.

As described above, the curing degree of epoxy resin is proportionally determined according to the heat curing time and temperature, and the fluorescent material is mixed in the process of mixing the liquid epoxy resin raw material. You will be prevented from sitting down.

That is, there is no time for the fluorescent material to settle downward, and since it is in the process of hardening, the viscosity difference with the fluorescent material is reduced, so that its dispersibility is improved, and the fluorescent material is evenly distributed throughout the transparent resin layer 27. Will be done.

Solid-state resin is pulverized into a powder is converted into a powder state (S240), by applying heat to the powder of the powder (S250) to melt, to form a tablet of a certain form (S260).

In the molding of the transparent resin layer 27 (S300), it is preferable to use a transfer molding method or an encapsulation printing method, which is a printed circuit board or lead frame 21 on which the light emitting diode chip 25 is mounted. 23) is arranged on a transfer molding press equipped with a suitable mold, and the molding compound tablet formed in step S260 is placed, so as to cover the light emitting diode chip 25 electrically connected to the outside at a predetermined pressure, temperature, and time. By molding, a fluorescent material layer (transparent resin layer) 27 is formed.

8 is a flowchart illustrating another embodiment of a method of manufacturing a light emitting diode according to the present invention. Referring to the drawings, the steps S100 to S300 are the same as the steps S100 to S300 of FIG. 7, and therefore, the same reference numerals are assigned to the same members.

In FIG. 8, instead of forming the transparent resin layer 27 into a convex lens shape having a thickness and shape proportional to the amount of light emitted from the light emitting diode chip 25, the light emitting diode is formed in the above-described process as in the case of FIG. 7. It can be implemented by bonding the convex lens 29 on the transparent resin layer 27 formed by (S400). In this case, the convex lens 29 bonded on the transparent resin layer 27 has approximately 40 degrees of light emitted from the light emitting diode chip 25. It is desirable to have a curvature to be incident within. In this case, the lens 29 is preferably made of a material having a low light dispersion rate in order to prevent color uniformity degradation due to chromatic aberration, such as fluorite glass, fluoride phosphate glass, and the like.

Although the preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and the present invention is not limited to the specific embodiments of the present invention without departing from the spirit of the present invention as claimed in the claims. Anyone skilled in the art can make various modifications, as well as such modifications are within the scope of the claims.

As a result, the light emitting diode and its manufacturing method according to the present invention can prevent color uniformity degradation caused by total reflection of light, chromatic aberration, phosphor distribution, etc., and as a result, improve the brightness of the light emitting diode and increase the product yield. You can do it.

In addition, according to the present invention, since there is no restriction on phosphor coating and wire loops, various types of packages can be designed, resulting in the development of a very small package.

In addition, according to the present invention, since the burden of color deviation is reduced, various types of lenses can be designed and bonded to the transparent resin layer.

Claims (12)

delete delete A printed circuit board having a thin film pattern formed thereon; A light emitting diode chip mounted on the printed circuit board; And It is formed to cover the light emitting diode chip, forms a thickness and shape proportional to the amount of light emitted from the light emitting diode chip, and includes a transparent resin layer in which phosphors are uniformly dispersed therein, The transparent resin layer is a light emitting diode, characterized in that formed by mixing the mixture while applying heat in the process of mixing the epoxy component or silicone component. A printed circuit board having a thin film pattern formed thereon; A light emitting diode chip mounted on the printed circuit board; And It is formed to cover the light emitting diode chip, forms a thickness and shape proportional to the amount of light emitted from the light emitting diode chip, and includes a transparent resin layer in which phosphors are uniformly dispersed therein, The transparent resin layer is a light emitting diode, characterized in that the surface is implemented in the shape of a convex lens so that the incident angle of light emitted from the light emitting diode chip to the surface of the transparent resin layer is within 40 °. A printed circuit board having a thin film pattern formed thereon; A light emitting diode chip mounted on the printed circuit board; And It is formed to cover the light emitting diode chip, forms a thickness and shape proportional to the amount of light emitted from the light emitting diode chip, and includes a transparent resin layer in which phosphors are uniformly dispersed therein, The light emitting diode chip is a light emitting diode, characterized in that implemented in a flip chip (flip chip) method. A printed circuit board having a thin film pattern formed thereon; A light emitting diode chip mounted on the printed circuit board; A transparent resin layer formed to cover the light emitting diode chip, having a thickness and a shape proportional to the amount of light emitted from the light emitting diode chip, and having phosphors uniformly dispersed therein; And And a convex lens joined to the transparent resin layer such that light emitted from the light emitting diode chip is incident within 40 °. delete The method of claim 6, The lens is a light emitting diode, characterized in that implemented by any one of fluorite glass or fluoride phosphate glass. delete Mounting a light emitting diode chip on a printed circuit board on which a thin film pattern is formed; Molding a transparent resin layer to cover the light emitting diode chip; Mixing the phosphor with at least one support material; Thermosetting the resin mixed with the phosphor to form a solid state; Powder grinding of the solid state molding; And Forming a tablet from the powdered resin powder; The transparent resin layer has a thickness and shape proportional to the amount of light emitted from the light emitting diode chip, the phosphor is uniformly dispersed therein, The molding step is a light emitting diode manufacturing method, characterized in that implemented using the formed tablet. Mounting a light emitting diode chip on a printed circuit board on which a thin film pattern is formed; Molding a transparent resin layer to cover the light emitting diode chip; And Bonding a lens on the transparent resin layer such that light emitted from the light emitting diode chip is incident within 40 °; The transparent resin layer has a thickness and shape in proportion to the amount of light emitted from the light emitting diode chip, and the phosphor is uniformly dispersed therein. The method of claim 11, The lens is a light emitting diode manufacturing method, characterized in that implemented in any one of fluorite glass or fluoride phosphate glass.

Images