TWI462344B - A package structure of white light led with high efficiency - Google Patents

Description

High efficiency white LED package structure

The present invention relates to a light emitting diode package structure, and more particularly to a high efficiency white light emitting diode package structure in which a nano metal layer is coated on a phosphor layer.

Light Emitting Diodes (LEDs) are light source systems made of solid materials such as semiconductors. They are different from traditional light sources such as heat lamps or various gas discharge lamps that operate under vacuum or with a small amount of special gas. Compared with traditional light sources, white LED light sources have many advantages, such as low power consumption, small size, fast response, high efficiency, environmental protection and flat packaging. In addition, in terms of energy saving, they can be used. It has a lifespan of 60 years and is 100 times that of traditional light bulbs. In terms of energy consumption, white LEDs are only 10% of conventional light bulbs. Therefore, since the successful development of high-power and high-brightness LEDs, white LEDs have been recognized as the most promising environmentally friendly lighting source in the 21st century. At present, the luminous efficiency of white LEDs has reached 60-80 lm/W or more, and has reached 100 lm/W in academic experiments. Up to now, the development of light-emitting diodes has two major directions, one is to provide high uniformity of white light, and the other is to require high brightness. However, since the brightness of a single LED is lower than the general lighting requirement, it is desirable to improve the photoelectric conversion efficiency and the external light extraction rate by the improvement of epitaxial growth, die fabrication, and packaging technology, so that the application range of the LED is wider.

The conventional LED package structure 100, as shown in FIG. 1 , shows a conventional LED package structure 100. The light-emitting element 130 is fixed in a reflective concave cup 110 whose inner wall is coated with the reflective metal layer 120, and is connected to the positive and negative electrodes of the light-emitting element by a metal wire (not shown), and the outer layer is an epoxy resin (Epoxy) layer. The 140 encapsulation package is formed by mixing a phosphor powder 150. Since this design cannot concentrate the light and the light emission angle is dispersed, many light rays are not fully utilized, and the effect of improving the brightness is limited.

U.S. Patent No. 8,030,843, entitled "Quantum dot phosphors for solid-state lighting devices", discloses a special optical property of a quantum dot phosphor and borrows The size of the quantum dot phosphor powder is controlled to improve the luminous efficiency. However, this kind of quantum dot phosphor powder is complicated to produce, and its effect of improving brightness is limited.

In view of this, the inventors of the present invention have carefully studied and proposed a high-efficiency white LED package structure, mainly by applying a nano metal layer on a phosphor layer to form a high-efficiency white LED. Wherein the nano metal layer is used to generate a plasma effect, thereby increasing the light-emitting intensity of the phosphor layer, and the phosphor layer is formed by a coating method, a transfer method, a screen printing method, and a spray method. One surface of the light-transmissive substrate is used to achieve a uniform phosphor layer, and the reflective light source collecting the reflective layer can be mixed with the phosphor layer to form a high-efficiency white LED. It should be noted that the lens layer of the present invention has the property of dissipating heat.

The object of the present invention is to provide a high efficiency white LED package structure for improving the luminous efficiency, heat dissipation and life of a conventional white LED package structure.

For the purpose of the present invention, the present invention provides a high efficiency white LED package structure comprising: a phosphor layer; a nano metal layer; a light emitting chip; a first conductive support; a second conductive support; a first bonding wire; a second bonding wire; a package base; a reflective layer; and a lens layer. Wherein the phosphor layer is coated on one side of a transparent substrate; the nano metal layer is coated on the other side of the phosphor layer to generate a surface plasma effect to increase the brightness of the phosphor layer The strength, wherein the nano metal layer has a crystal particle size of between 5 nm and 60 nm, and the thickness thereof is between 2 nm and 30 nm; the light emitting chip is fixed on the light transmissive substrate The other side of the first conductive support is disposed on one side of the transparent substrate; the second conductive support is disposed on the other side of the transparent substrate; the first bonding wire is used Electrically connecting the first conductive support to the positive electrode of the light-emitting chip; the second bonding wire is for electrically connecting the second conductive support and the negative electrode of the light-emitting chip; the package base has a semi-circular groove And the side of the first conductive support and the second conductive support are connected to encapsulate the light-emitting chip; the reflective layer is coated on the inner wall of the semi-circular groove to enhance the light-emitting chip Light usage, wherein the reflective layer can reflect light emitted by the luminescent wafer, To react with the fluorescent layer, to form white light; and a lens system for layer fills the groove and provides a good thermal effect.

According to one feature of the package structure of the present invention, the extinction coefficient of the nanometal layer is between 1.5 and 6.5 in the visible range.

The effect of the invention:

1. Use the material characteristics of the nano metal layer such as different thickness, crystal particles, carrier concentration and resistivity to produce different surface plasma effects.

2. Using the optical reaction of the nano metal layer, the light is effectively utilized, and the reflective light source collecting the reflective layer is mixed with the fluorescent glue layer to form a high-efficiency white LED, thereby improving the heat dissipation of the conventional white LED package structure. And life issues.

3. By combining the nano metal layer and the phosphor layer, the light-emitting intensity of the phosphor layer is increased to improve the luminous efficiency of the conventional white LED package structure.

4. Increasing the brightness and increasing the light projection distance: the high-efficiency white LED package structure of the invention enhances the light-emitting brightness of the light-emitting chip by using the reflection effect of the reflective layer, and then concentrates the light beam emitted by the light-emitting chip by the concentrated beam effect of the lens layer. In turn, the effect of increasing the brightness and increasing the light projection distance is achieved.

5. Wide application level: The high-efficiency white LED package structure of the present invention not only has the effect of improving the external light extraction rate of the package, but also is suitable for the surface adhesion process, manual and mechanical assembly process. Therefore, it can be connected with existing packaging technologies, thus expanding its application level.

6. Using a simple coating method, the nano metal layer is coated on one side of the phosphor layer, in addition to the surface plasma effect, the surface plasma effect can be effectively used to make the fluorescent The light-emitting intensity of the glue layer is increased.

7. The nano metal layer proposed by the present invention does not affect the light transmittance of the white LED package structure.

The above and other objects, features, and advantages of the present invention will become more apparent and understood.

While the invention may be embodied in various forms, the embodiments illustrated in the drawings It is not intended to limit the invention to the particular embodiments illustrated and/or described.

Referring now to Figure 2, there is shown a schematic diagram of a high efficiency white LED package structure 200 in accordance with an embodiment of the present invention. The high efficiency white LED package structure 200 of the present invention comprises: a transparent substrate 210; a phosphor layer 220; a nano metal layer 221; a first conductive bracket 230; a first bonding wire 240; a layer 250; a lens layer 260; an illuminating wafer 270; a package pedestal 280; a second bonding wire 290; and a second conductive support 231. The first conductive support 230 and the second conductive support 231 are respectively grouped by a metal having good conductivity such as gold, silver, copper, iron, aluminum and a conductive metal alloy, and are respectively fixed on both sides of the transparent substrate 210. Used to connect with other conductive materials. In addition, the material of the transparent substrate 210 may be one of a glass material and a plastic material.

The phosphor layer 220 is formed by mixing a phosphor material and a gel, covering one surface of the transparent substrate 210, and performing a heat treatment process to enable the phosphor layer 220 and the transparent substrate 210 to be tightly coupled. The absorption and emission bands of the fluorescent material are between 254 nm and 570 nm, and are yellow yttrium aluminum garnet (YAG), yellow yttrium aluminum garnet (TAG), and a yellow silicate (Silicate). Any combination of Sulfate and Nitrate.

The illuminating chip 270 is fixed on the other surface of the transparent substrate 210, and includes positive and negative poles, and is electrically connected to the anode of the first conductive bracket 230 and the illuminating wafer 270 by a first bonding wire 240, and the second bonding wire 290 is It is used to electrically connect the second conductive support 231 and the negative electrode of the light-emitting chip 270. In addition, the illuminating wafer 270 further includes a carrier substrate, and the material used for the substrate may be one of a sapphire substrate, a glass substrate, and a plastic substrate.

The package base 280 of the present invention has a semi-circular recess inside, and the side of the package base 280 is connected to the first conductive bracket 230 and the second conductive bracket 231. In order to increase the light usage of the luminescent wafer 270, a reflective layer 250 is applied over the inner wall of the semi-circular recess and the recess is filled with the lens layer 260 to provide a good thermal conductivity. The reflective layer 250 can react with the phosphor layer 220 to reflect white light by reflecting the light emitted by the light-emitting chip 270.

It should be noted that the reflective layer 250 is sputtered with a metal material having a high reflectivity on the inner wall of the semicircular recess, which is selected from one of silver, gold, aluminum, and a metal alloy. The portion of the lens layer 260 is formed by injecting a thermally conductive resin having high light transmittance into the inner wall of the semicircular recess of the package base 280, which is selected from the group consisting of thermosetting plastics and thermoplastic plastics. One. The material of the lens layer 260 is selected from the group consisting of epoxy resin (Epoxy), polystyrene (PS), Acrylonitrile-Butadene-Styrene (ABS), polymethyl methacrylate Polymethl methacylate (PMMA), Acrylic Resin, Silicone or any combination of the above. It should be noted that the material of the lens layer 260 needs to be subjected to a heat treatment process so that the package base 280, the light-emitting chip 270, and the light-transmitting substrate 210 can be tightly joined. In addition, the refractive index of the transparent substrate 210, the fluorescent adhesive layer 220, and the lens layer 260 should be as close as possible, the main reason is that the relatively close refractive index can avoid the loss of light in the package, thereby improving the external light extraction of the package. rate.

Preferably, the fluorescent material selected for use in the present invention is (Y _2.95-a Ce _0.05 Gda)(Al _5-b Ga _b )O ₁₂ , wherein Y, Ce, Gd, Al, Ga, O are respectively represented as钇, 锗, 釓, aluminum, gallium and oxygen. It should be noted that the Gd(釓) substitution amount a is between 0 and 3, the Ga (gallium) substitution amount b is between 0 and 5, and the phosphor material has a particle size of 1 to 3 μm. between. In addition, the material used for the phosphor layer 220 needs to have an excitation spectrum in the range of 240 to 500 nm, and the excitation main peak position is 430 nm; the emission spectrum is in the range of 450 to 600 nm, and the emission main peak position is At 512 nm, the luminous efficiency obtained was 60%.

Next, the phosphor material which has been treated with the decane coupling agent is kneaded in an appropriate amount in an epoxy resin in various ratios, and is spray-coated on one side of the light-transmitting substrate 210 to form a uniform phosphor layer. 220. In order to enable the phosphor layer 220 to be tightly bonded to the transparent substrate 210, the coated phosphor layer 220 is placed in an oven at 80 ° C for 30 minutes to obtain a thickness of between 80 μm and 100 μm. The fluorescent glue layer 220.

Further, after the epoxide adhesive was printed on the other surface of the light-transmitting substrate 210 by Surface Mount Technology (SMT), the light-emitting wafer 270 having an emission wavelength of 430 nm was placed on the epoxy adhesive. Next, the epoxide is irradiated with 365 nm of UV light to cure the luminescent wafer 270, and the luminescent wafer 270 is fixed to the transparent substrate 210.

It should be noted that the nano metal layer 221 of the present invention is coated on the other side of the phosphor layer 220 to increase the light-emitting intensity of the phosphor layer 220 by the surface plasma effect, wherein the nano metal The crystalline particles of layer 221 are between 5 nm and 60 nm and have a thickness between 2 nm and 30 nm. Preferably, the nano metal layer 221 has a carrier concentration of 10 ²² cm ^-3 to 10 ²³ cm ^-3 , and the extinction coefficient of the nano metal layer 221 is between 1.5 and 6.5 in the visible light range. Further, the nano metal layer 221 is composed of nano metal particles.

Among them, the thermodynamic characteristics of nano metal particles, such as melting point, specific heat, etc., as well as electronic structure, electrical properties, optical properties, magnetic properties, chemical reactivity, and self-assembly of nano metal particles are all different in size. And change. Wherein the nano metal particles are selected from one of nickel, gold, cobalt, copper, aluminum, titanium and alloys thereof. In addition, because nanoparticle is a transition product between atoms, molecules and bulk materials. In this size range, many physical and chemical properties are related to size, which is an important controlling factor in the science and application of nanomaterials.

In addition, as the diameter of the nanoparticle becomes smaller, the specific surface area will increase significantly, that is, the percentage of the number of surface atoms will increase significantly, and about 15% of the particles with a diameter of 10 nm are on the surface of the particle. While almost all atoms on the 1 nm diameter nanoparticle are surface atoms, generally higher surface area nanoparticles have higher chemical reactivity. The high atomic number on the surface of the nanoparticles causes an increase in surface activity and can be applied to develop catalyst particles and high efficiency catalysts. In the heterogeneous reaction catalyst in which the nano metal particles are used as a catalyst, since the metal surface is the reactive site, the smaller the particle size, the higher the surface area of the reaction, and the higher the reactivity.

For example, as the particle size of the nano-gold particles becomes smaller and smaller, the proportion of surface atoms greatly increases. Glittering gold is a golden yellow metal with a metallic color. When it exists in the form of nanometers, the optical properties will change dramatically. As the particle size shrinks, the color change can be clearly seen by the naked eye, from black (about 10 nm) to dark red (about 30 nm) to a clear purple solution (about 100 nm).

Can be divided into physical methods and chemical methods. In terms of physical methods, there are:

1. Laser ablation:

The method is simple in preparation and the prepared metal colloid solution is relatively clean, but it is difficult to control the shape and size of the nano metal particles, and it is impossible to estimate the yield of the nano metal particles. It is made by immersing the metal in a solvent and then bombarding the surface of the gold with a laser.

2. Evaporation and sputtering

The metal source is heated by the electrode, so that the metal atom evaporated by the vapor deposition metal is deposited on the substrate as evaporation; if the gold target is bombarded with argon ions, the surface is glow discharge, and the surface gold atom is ejected. Depositing on a substrate is called sputtering.

There are many types of chemical preparation methods for nano metal particles. Taking nano gold particles as an example, the chemical preparation method is as follows:

1. Direct reduction method, directly adding a reducing agent to reduce the chloroauric acid in the solution under appropriate conditions.

2. Chemical vapor deposition, which thermally decomposes volatile gold compounds to deposit gold on the substrate.

3. Electrochemical method, using a gold wire as an anode, reacting in an electrolyte containing a surfactant, and depositing gold particles at the cathode.

4. Photochemical method, which decomposes water by ultraviolet light or gamma ray to generate electrons to reduce chloroauric acid.

5. Ultrasonic method, using ultrasonic waves to reduce the chloroauric acid by hydrogen radicals generated by water decomposition.

According to an embodiment of the present invention, the nano metal particles are formed by direct reduction to form gold nuggets, but it should be noted that the other metal may also form nano metal particles. The drugs used are all above the purity of the reagent grade, so the purification step is not used before use, and the reduction steps are:

1. Take 1 ml of HNO ₃ (70% concentration) and 3 ml of HCl (37% concentration) to make aqua regia.

2. Dissolve 0.2089 g of gold ingot in the prepared aqua regia and completely dissolve by ultrasonic vibration.

3. Dilute the solution with one liter of deionized water.

4. Finally, the diluted solution is heated, and an appropriate amount of sodium citrate (Na ₃ (C ₆ H ₅ O ₇ ) is added as a reducing agent, followed by vigorous stirring to reduce.

5. The reduced nano gold particle solution is dropped onto the phosphor layer 220, and the nano gold particle solution is completely plated on the phosphor layer 220, and dispersed by the self-assembly property of the nano gold particles to the firefly. On the surface of the photoresist layer 220.

6. Dry the nano gold particles that have been spin coated onto the phosphor layer 220.

Wherein, the package base 280 is formed by injection molding, and has a semicircular groove inside. In a preferred embodiment, the selected reflective layer 250 is made of silver and is primarily formed by sputtering in a semi-circular recess as the reflective layer 250. The material of the lens layer 260 is epoxy resin, and the epoxy resin is injected into the semicircular groove by dispensing.

Finally, the prepared luminescent wafer 270, the phosphor layer 220 and the transparent substrate 210 are assembled onto the package pedestal 280. After the packaging and testing in the back section, the entire white LED device can be completed. In this embodiment, the light is mainly reflected by the metal reflection effect of the reflective layer 250, and the light is concentrated in the radius of the lens layer 260, and the white light is emitted to the outside through the reaction of the mixed phosphor layer 220. Therefore, the high-efficiency white LED package structure of the present invention not only allows the light to be uniformly concentrated in the central portion, but also increases the overall light output of the white LED device.

Referring now to Figure 3, there is shown another embodiment of a high efficiency white LED package structure 200 in accordance with an embodiment of the present invention. The difference from the above embodiment is that the nano metal layer 221 and the phosphor layer 220 further comprise a polymer film for separating the nano metal layer 221 and the phosphor layer 220, and The polymer film can be used to help the nano metal layer 221 to be coated on the uniformity of the phosphor layer 220. Wherein, the distance between the nano metal layer 221 and the phosphor layer 220 is between 2 nm and 20 nm.

<Example 1>

The thickness of the nano metal layer 221 is about 5 nm, and when the number of the nano metal particles is controlled to a small range, the light-emitting effect of the phosphor layer 220 can be increased by 1.2 times, thereby improving the efficiency of the white LED. 1 times.

<Embodiment 2>

The thickness of the nano metal layer 221 is about 10 nm, and when the number of the nano metal particles is controlled to a small range, the light-emitting effect of the phosphor layer 220 can be increased by 1.5 times, even beyond the phosphor layer. 220 original quantum efficiency, which in turn makes the efficiency of white LEDs 1.3 times.

<Example 3>

The thickness of the nano metal layer 221 is about 15 nm, and the thickness of the polymer film is 2 nm. The thickness of the polymer film is used to determine the amount of the nano metal particles, and the uniformity of the coating on the phosphor layer 220, thereby increasing the light-emitting effect of the phosphor layer 220 by a factor of two. In order to increase the efficiency of white LEDs by 1.6 times.

It will be apparent from the above-described preferred embodiments of the present invention that the application of the present invention has the following advantages.

1. Using the material characteristics of the nano metal layer 221 such as different thicknesses, crystal particles, carrier concentration, and resistivity to produce different surface plasma effects.

2. Using the optical reaction of the nano metal layer 221, the light is effectively utilized, and the reflective light source collecting the reflective layer 250 is mixed with the fluorescent glue layer 220 to form a high-efficiency white LED, thereby improving the conventional white LED package. The heat dissipation and life of the structure 100.

3. By combining the nano metal layer 221 and the phosphor layer 220, the light-emitting intensity of the phosphor layer 220 is increased to improve the luminous efficiency of the conventional white LED package structure 100.

4. Increasing the brightness and increasing the light projection distance: the high efficiency white LED package structure 200 of the present invention enhances the light emission brightness of the light emitting chip 270 by the reflection effect of the reflective layer 250, and then the light emitting chip 270 is made by the concentrated beam effect of the lens layer 260. The beam of light is concentrated, thereby achieving the effect of increasing brightness and increasing the distance of light projection.

5. Wide application level: The high-efficiency white LED package structure 200 of the present invention has the effects of improving the external light extraction rate of the package, and is also suitable for surface adhesion process, manual and mechanical assembly processes. Therefore, it can be connected with existing packaging technologies, thus expanding its application level.

While the present invention has been described in its preferred embodiments, it is not intended to limit the scope of the invention, and various modifications and changes can be made without departing from the spirit and scope of the invention. As explained above, various modifications and variations can be made without departing from the spirit of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

100. . . Traditional LED package structure

110. . . Reflection concave cup

120. . . Reflective metal layer

130. . . Light-emitting element

140. . . Epoxy layer

150. . . Fluorescent powder

200. . . High efficiency white LED package structure

210. . . Light transmissive substrate

220. . . Fluorescent layer

221. . . Nano metal layer

222. . . Polymer film

230. . . First conductive bracket

240. . . First wire bond

231. . . Second conductive bracket

250. . . Reflective layer

260. . . Lens layer

270. . . Light emitting chip

280. . . Package base

290. . . Second wire

The above and other objects, features, and advantages of the present invention will become more apparent from the <RTIgt;

Figure 1 shows a schematic diagram of a conventional LED package structure;

2 is a schematic view showing the structure of a high efficiency white LED package of the present invention;

FIG. 3 shows another embodiment of the high efficiency white LED package structure of the present invention.

200. . . High efficiency white LED package structure

210. . . Light transmissive substrate

220. . . Fluorescent layer

230. . . First conductive bracket

240. . . First wire bond

250. . . Reflective layer

221. . . Nano metal layer

260. . . Lens layer

270. . . Light emitting chip

280. . . Package base

290. . . Second wire

231. . . Second conductive bracket

Claims (10)

A high-efficiency white LED package structure comprising: a phosphor layer coated on one side of a transparent substrate; and a nano metal layer coated on the other side of the phosphor layer to generate a surface The plasma effect increases the light-emitting intensity of the phosphor layer, wherein the nano-metal layer has a crystal particle size between 5 nm and 60 nm, and the thickness is between 2 nm and 30 nm. An illuminating chip is fixed on the other side of the transparent substrate and has positive and negative poles; a first conductive bracket is disposed on one side of the transparent substrate; and a second conductive bracket is disposed on the side The other side of the light-transmissive substrate; a first bonding wire for electrically connecting the first conductive support and the positive electrode of the light-emitting chip; and a second bonding wire for electrically connecting the second conductive support and the light-emitting a negative electrode of the chip; a package base having a semi-circular recess, and a side thereof is connected to the first conductive bracket and the second conductive bracket for encapsulating the light-emitting chip; a reflective layer is coated on the substrate The inner wall of the semicircular groove can increase the light usage rate of the illuminating chip, The reflective layer can reflect the light emitted by the light-emitting chip to react with the phosphor layer to form white light; and a lens layer for filling the groove and providing a good heat conduction effect; The polymer layer between the nano metal layer and the phosphor layer further comprises a polymer film. The nano metal layer and the phosphor layer are separated. The high-efficiency white LED package structure according to claim 1, wherein the phosphor layer is a mixture of a fluorescent material and a gel. The high-efficiency white LED package structure according to claim 1, wherein the nano metal layer has a carrier concentration of 10 ²² cm ^-3 to 10 ²³ cm ^-3 . The high efficiency white LED package structure according to claim 1, wherein the nano metal layer is composed of nano metal particles. The high-efficiency white LED package structure according to claim 1, wherein the material of the transparent substrate is selected from one of a glass material and a plastic material. The high efficiency white LED package structure according to claim 1, wherein the reflective layer is formed of a metal material having high reflectivity selected from one of silver, gold, aluminum and a metal alloy. The high efficiency white LED package structure according to claim 1, wherein the lens layer is formed by a heat conductive resin having high light transmittance, which is selected from the group consisting of thermosetting plastics and thermoplastic plastics. One. The high-efficiency white LED package structure according to claim 1, wherein the material of the lens layer is selected from the group consisting of epoxy resin (polypoxy), polystyrene (PS), and acrylonitrile-butadiene-benzene. Acrylonitrile-Butadene-Styrene (ABS), Polymethl methacylate (PMMA), Acrylic Resin, Silicone or any combination of the above. The high efficiency white LED package structure according to claim 1, wherein the polymer film can be used to help the nano metal layer to be coated on the uniformity of the phosphor layer. The high efficiency white LED package structure according to claim 1, wherein the nano metal layer has an extinction coefficient ranging from 1.5 to 6.5 in the visible light range.