WO2016000459A1

WO2016000459A1 - Led encapsulation structure

Info

Publication number: WO2016000459A1
Application number: PCT/CN2015/073470
Authority: WO
Inventors: 梁兴华; 卓佳利; 郑建森; 李佳恩; 夏德玲; 蔡培崧; 林素慧; 徐宸科
Original assignee: 厦门市三安光电科技有限公司
Priority date: 2014-07-04
Filing date: 2015-03-02
Publication date: 2016-01-07
Also published as: CN104091875A

Abstract

An LED encapsulation structure, comprising an encapsulation substrate (301) used for protecting and carrying an LED chip (302), a reflective layer (304) on the encapsulation substrate, a light conversion layer (303) on the reflective layer, and the LED chip on the light conversion layer, the LED chip being able to emit light of specific wavelengths in dual directions. The encapsulation structure is characterized in that if the light emission direction of the encapsulation structure is defined to be the front direction, then the light conversion layer is located in the back of the LED chip; the light emitted from the LED encapsulation structure consists of the light emitted by the LED chip and light of other wavelengths generated by the light conversion layer upon converting the light emitted by the LED chip. A part of the light does not pass the light conversion layer and is not absorbed, thereby reducing loss and enhancing light efficiency.

Description

LED package structure

The present application claims priority to Chinese Patent Application No. 201410316144.8, the entire disclosure of which is incorporated herein by reference.

Technical field

The present invention relates to a light emitting diode-based package structure and a method of fabricating the same, and more particularly to a package structure including a light conversion material.

Background technique

Solid-state lighting, especially light-emitting diodes (LEDs), is becoming a new generation of light sources because of its long life, no pollution, and high luminous efficiency. Since the LEDs produced by direct production are monochromatic light, in order to obtain white light, a plurality of colors must be mixed to form. The most common way to prepare a white LED is to use a blue/ultraviolet LED to excite the light conversion material, and the light emitted by the LED itself and the complementary light converted by the light conversion layer together form white light.

Figure 1 shows an LED package prepared using the prior art. The preparation process is generally as follows: an LED package substrate 101 is provided, and the LED chip 102 is crystallized on the package substrate, and then the light conversion layer 103 (such as phosphor) is coated on the chip, and finally baked. After the blue light R _1b emitted from the LED chip passes through the phosphor layer, part of it is absorbed by the phosphor and converted into yellow light (R _1yo and R _1yi ); the other part passes through the phosphor layer and does not convert the wavelength, still blue light (R _1bo and R _1bi ), when the unconverted blue light (R _1bo and R _1bi ) passes through the phosphor layer, although no wavelength conversion occurs, a part of the energy is absorbed by the phosphor layer to lower the light efficiency. At the same time, the unconverted blue light is scattered by the phosphor and then directed to the outer body of the package R _1bo and the package body R _1bi . The R _1bi that is directed into the package is again absorbed by the phosphor layer, and the energy is further lost.

Summary of the invention

It is an object of the present invention to improve the efficacy of a package structure comprising a light-converting material, primarily by reducing unnecessary absorption of the light-emitting material by the light-emitting diode.

To achieve this, the present invention provides an LED package structure comprising: a package substrate having relative upper and lower a surface; a reflective layer on the upper surface or the lower surface of the package substrate, reflecting light directed to the package substrate; a light conversion layer located on the reflective layer, absorbing light of a specific wavelength and converting into light of other wavelengths; a chip, located on the light conversion layer, bidirectionally emitting light of a specific wavelength in the upper and lower directions; the package structure is characterized in that: if the light emitting direction of the package structure is defined as positive, the light conversion layer is located on the back side of the LED chip; The light emitted by the LED package structure is composed of light emitted from the LED chip that has not passed through the light conversion layer and light passing through the light conversion layer. The light emitted from the LED chip does not pass through the light conversion layer and is not absorbed, thereby reducing losses and improving light efficiency.

In some embodiments, the LED package substrate contains a phosphor, and the LED chip is flip-chip bonded directly to the bump of the package substrate without a wire bonding process.

In some embodiments, the LED package substrate contains a phosphor, and the LED chip is a positive/vertical chip, and the solid crystal is attached to the phosphor, and is connected to the package substrate by wire bonding.

In some embodiments, the LED package substrate has a raised platform, and the LED chip is a positive/vertical chip. The solid crystal is bonded to the package substrate and is connected to the package substrate.

In some embodiments, the LED package substrate does not contain phosphors, and one side surface of the LED chip contains phosphor, and the phosphor is pre-deposited on the surface of the LED, and may be deposited by spin coating, spraying, electrophoresis or the like.

In some embodiments, the LED package substrate is free of phosphor, and the LED chip is formed by bonding a ceramic phosphor sheet and an LED chip.

In some embodiments, the LED package structure further includes a selective reflection lens that completely transmits light of a wavelength of 500 nm to 780 nm and partially reflects/transmits light of a wavelength of 400 nm to 500 nm.

The present invention also provides an LED package substrate comprising: a susceptor for carrying a remaining portion of the package substrate; a reflective layer on the pedestal; and a light conversion layer on the reflective layer. The light of the first wavelength emitted by the chip upward and the light of the second wavelength reflected by the reflective layer are mixed to form white light.

In some embodiments, the susceptor is a ceramic pedestal on which circuitry is pre-arranged for subsequent use with the LED chip; then a reflective material is applied to the surface of the ceramic pedestal for use as a reflective layer. Wherein, a conductive material such as silver or the like is plated on the susceptor circuit. The other part is coated with an insulating material, such as DBR; finally, the ceramic phosphor sheet is aligned and bonded to the ceramic base, and is sintered at 500 ° C - 1000 ° C; wherein the ceramic phosphor sheet is pre-drilled The hole is filled with a conductive material in the through hole.

In some embodiments, a ceramic phosphor sheet is first provided, a through hole is drilled therein, and a conductive material is filled in the through hole; a partition bar is formed on the back surface of the ceramic phosphor sheet with an insulating material to separate positive and negative Electrode through hole; plating a conductive reflective material on the back surface of the ceramic phosphor sheet as a reflective layer, such as silver; plating under the reflective layer on the back surface of the ceramic phosphor sheet A thick layer of conductive material is used to protect the supporting phosphor sheet and the reflective layer and function as a pedestal. The conductive reflective layer and the conductive material layer of the package substrate are both spaced apart from the positive and negative electrode through holes by the partition bar.

In some embodiments, a susceptor is provided on which the grooves, circuitry, and solder bumps are pre-arranged. The recess is for placing a phosphor layer; the circuit and the solder bump are used for forming an electrical connection with the LED chip; the reflective material is plated on the surface of the base for use as a reflective layer, wherein the circuit portion forms a conductive material such as silver, etc. The part is formed with an insulating material, such as DBR, etc.; the surface of the base is coated with a fluorescent glue, and baked at 100 ° C - 500 ° C; the surface of the fluorescent rubber is polished/cut to expose the solder bumps.

While the invention will be described in conjunction with the exemplary embodiments and the methods of the invention, it is understood that the invention is not intended to limit the invention. Rather, the invention is to cover all alternatives, modifications, and equivalents of the scope of the invention as defined by the appended claims.

DRAWINGS

The drawings are intended to provide a further understanding of the invention, and are intended to be a In addition, the drawing figures are a summary of the description and are not drawn to scale.

FIG. 1 is an LED package prepared by the prior art.

Figure 2 shows the reflectivity of metal materials commonly used in reflective layers in different wavelength bands.

3 to 5 are schematic cross-sectional views showing a first embodiment of the present invention.

Figure 6 is a schematic cross-sectional view showing a second embodiment of the present invention.

Figure 7 is a schematic cross-sectional view showing a third embodiment of the present invention.

Figure 8 is a schematic cross-sectional view showing a fourth embodiment of the present invention.

Figure 9 is a schematic cross-sectional view showing a fifth embodiment of the present invention.

10 to 11 are schematic cross-sectional views showing a sixth embodiment of the present invention.

Figure 12 is a schematic cross-sectional view showing a seventh embodiment of the present invention.

The numbers in the figure indicate:

R _1b : blue light emitted by the chip

R _1bo : blue light emitted by the chip after the phosphor layer

R _1bi : blue light emitted by the chip after the phosphor layer

R _1yo : the yellow light emitted by the chip after absorption and conversion by the phosphor layer

R _1yi : yellow light emitted by the chip after absorption and conversion by the phosphor layer

R _2b : blue light emitted by the chip upward

R _2y : yellow light emitted by the chip downwardly converted by the light conversion layer

101, 301, 401, 501, 601, 701, 801, 901: package substrate

102, 302, 402, 502, 602, 702: LED chip

103, 303, 403, 503, 603, 703, 803: light conversion layer

304, 404, 504, 604, 704, 804, 904: reflective layer

305, 405, 505, 705, 805: conductive column

301a: ceramic body

301b: circuit under the ceramic substrate

301c: circuit on ceramic substrate

301d: through-hole conductive pillar inside ceramic substrate

301e: Insulation block

302a: substrate

302b: n-type layer

302c: active layer

302d: p-type layer

304a, 804a: Ag reflective layer

304b, 804b: DBR reflective layer

406, 506, 606: wire

507: raised platform

605, 905: solder bumps of the package substrate

708: Selective reflective lens

901a: Insulating body

901b: circuit

903: fluorescent glue.

detailed description

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and embodiments, in which the present invention can be applied to the technical problems, and the implementation of the technical effects can be fully understood and implemented. Need to explain The various embodiments of the present invention and the various features of the various embodiments may be combined with each other, and the technical solutions formed are all within the scope of the present invention.

The following embodiment discloses an LED package substrate, which fixes an LED chip on a package substrate and then performs baking. If the light-emitting direction of the package structure is positive, a light conversion layer is located on the back surface of the LED chip. The light emitted by the structure consists of the light emitted by the LED chip and other wavelengths of light converted by the light conversion layer. Since a part of the light does not pass through the light conversion layer, it is not absorbed, thereby reducing the loss and improving the light efficiency.

Example 1

3 shows a cross-sectional view of an LED package structure including a substrate 301, an LED chip 302, a light conversion layer 303, and a reflective layer 304, in accordance with a first embodiment of the present invention.

Specifically, the package substrate 301 may be selected from one or more combinations of plastic, metal, and ceramic. Fig. 4 shows the structure of a ceramic substrate which can be applied to this embodiment. Referring to FIG. 4, the ceramic substrate 301 includes a ceramic body 301a, a lower surface circuit 301b, an upper surface circuit 301c, and a via-hole conductive post 301d inside the ceramic base connected to the upper and lower surface circuits, wherein the circuit of the same surface is separated by an insulating block 301e. open. The ceramic body 301a may be alumina, aluminum nitride or the like, and alumina is preferred. The material of the upper and lower surface circuits and the through-hole conductive pillars may be one of copper, silver, gold or an alloy thereof. Preferably, copper is used as the conductive material. The material used for the insulating block 301e is alumina.

The reflective layer 304 is formed on the package substrate 301 and may be combined with one or more of a metal mirror surface, a photonic crystal, and a reflective paint. When the ceramic substrate shown in FIG. 4 is used, the reflective layer 304 is divided into two parts, and the upper surface circuit 301c is plated with a conductive reflective material 304a (such as a high reflectivity metal material such as silver or aluminum), and the insulating block 301e is plated with an insulating material 304b. It is preferably a distributed Bragg reflection layer (abbreviated as DBR in English).

The light conversion layer 303 is located on the reflective layer 304 and has a through hole having a conductive material inside. The light conversion material of the light conversion layer 303 may be a combination of one or more of a phosphor, a quantum dot, and an organic fluorescent/phosphorescent material. In this embodiment, an integrally formed ceramic phosphor sheet is selected as the light conversion layer, and the conductive pillar 305 having the phosphor sheet is connected to the circuit of the package substrate. When the ceramic substrate 301 shown in Fig. 4 is used, the light conversion layer 303 is aligned and bonded to the ceramic substrate 301, and sintered at 500 ° C to 1000 ° C, preferably at 850 ° C. The package substrate 301 is integrally formed with the ceramic phosphor sheet, and the various parts are combined well, the structural strength is higher, and the electrical and thermal conductivity properties are better. At the same time, the phosphor coating method does not need to be coated on different package brackets separately, which solves the problem of large difference in color point of the conventional dispensing method, and is more suitable for mass production and production. In this embodiment, the blue light emitted by the LED in the back direction is twice the thickness in the phosphor sheet, so that more yellow light can be converted by the thinner phosphor, and the optimum thickness is less than 1 mm.

The LED chip 302 is located in the light conversion layer 303. In this embodiment, a flip chip LED chip with bidirectional illumination on the lower and upper surfaces is selected. The structure diagram is as shown in FIG. 5, and includes a sapphire substrate 302a, an n-type layer 302b, an active layer 302c, and P-type layer 302d. The chip 302 is electrically connected to the conductive pillars 305 of the light conversion layer 303 by eutectic method, and at the same time, by filling the gap between the LED chip 302 and the light conversion layer 303, a heat conduction path is formed between the LED chip and the package substrate, thereby realizing thermoelectric conduction. Separation to improve the efficiency of thermoelectric conduction. The LED chip 302 emits blue light having a wavelength of 450 nm to 460 nm and emits respectively in two directions, wherein the blue light emitted downward is converted into a yellow light R _{2y of a} wavelength of 570 nm to 580 nm by the light conversion layer 303, and is reflected by the reflective layer 304. The blue light R _2b emitted upward from the chip is mixed together into white light. Since the blue light R _2b emitted upward does not pass through the phosphor layer, energy is not absorbed, thereby reducing loss and improving light efficiency. At the same time, since the ceramic phosphor powder sheet has been prepared in advance on the package substrate, the dispensing and dispensing processes are omitted in the package section, which makes the packaging process easier and saves the manufacturing man-hour. Furthermore, the surface of the package substrate is provided with a reflective layer, and a common metal reflective layer (Au/Ag, as shown in FIG. 2) tends to become longer as the wavelength becomes longer, and the reflectance becomes higher, so that the blue light emitted by the LED chip 302 is emitted downward. The conversion layer 303 is converted into yellow light having a wavelength of 570 nm to 580 nm, and the reflectance is increased when it is incident on the package substrate, which further improves the light efficiency.

Example 2

6 is a cross-sectional view showing an LED package structure according to a second embodiment of the present invention. The difference between this embodiment and the embodiment 1 is that the front and bottom surfaces are bidirectionally lit by the LED chip 402, and the two electrodes pass through the wire 406 and the light. The conductive pillars 405 of the conversion layer 403 form an electrical connection.

Example 3

7 is a cross-sectional view showing an LED package structure according to a third embodiment of the present invention. The difference between this embodiment and the embodiment 1 is that the package substrate 501 has a raised platform 507, and the LED chip 502 is a positive/vertical chip. It is connected to the raised platform 507 and is isolated from the light conversion layer (phosphor layer) 503. In this embodiment, the heat generated by the LED chip does not affect the phosphor, so that the phosphor does not cause the quantum light-emitting efficiency to decrease due to the temperature being too high. The underside of the raised platform is a transparent/hollow design that facilitates the LED chip to emit light toward the phosphor.

Example 4

8 is a cross-sectional view showing an LED package structure according to a fourth embodiment of the present invention. The difference between this embodiment and the embodiment 1 is that the bottom of the LED chip 602 includes a phosphor layer 603, and the solder bumps of the bonding substrate 601 and the package substrate 601 are formed. Point 605 forms an electrical connection. The phosphor layer on the LED chip can be obtained by the following two methods: 1) spraying/spinning the phosphor layer on the entire surface of the epitaxial wafer, and cutting and cutting into chips after baking, and 2) ceramic phosphor sheet and epitaxial wafer bond After the combination, the cutting is further broken into chips.

Example 5

9 is a cross-sectional view showing an LED package structure according to a fifth embodiment of the present invention. The difference between this embodiment and the embodiment 1 is that the package body is covered with a selective reflection lens 708, which can completely transmit the wavelength of >500 nm. The red-yellow light, while partially reflecting the blue light <500nm, so that part of the blue light is reflected back to the phosphor layer through the selective reflection lens, and converted into more yellow light, the package structure is more suitable for applications with high ratio of yellow/blue light.

Example 6

10 is a cross-sectional view showing an LED package substrate according to a sixth embodiment of the present invention, the substrate comprising: a ceramic phosphor sheet 803, a conductive reflective layer 804a and a DBR reflective layer 804b formed on the back surface of the ceramic phosphor sheet 803, forming The conductive material layer 801 under the conductive reflective layer 804a has a thickness of 100 μm or more for protecting the supporting phosphor sheet and the reflective layer and functions as a susceptor. The DBR reflective layer 804b serves as a partition bar separating the positive and negative electrode through holes.

Figure 11 shows the preparation process of the LED package substrate. First, a pre-prepared ceramic phosphor sheet 803 is provided, which internally contains via via conductive posts 805. Next, the back surface of the ceramic phosphor sheet 803 is divided into a conductive region and an isolation region, and an insulating material is formed in the isolation region to form a partition column, and the positive and negative electrode through holes are separated. In this embodiment, a DBR reflective layer is used, and silicon oxide and In the combination of titanium oxide, an Ag layer is deposited as a reflective layer 803a in the conductive region of the ceramic phosphor sheet 803; finally, a layer of a conductive material is deposited on the back surface of the ceramic phosphor sheet 803 as a substrate 801 for protecting the phosphor sheet and The reflective layer, the material of the conductive material layer 801 may be copper silver gold or an alloy thereof, and has a thickness greater than 100 micrometers. Preferably, the total thickness of the conductive material layer 801 and the Ag light reflecting layer 803a is greater than the thickness of the DBR reflective layer. In this embodiment, a DBR reflective layer may be formed on the back surface of the entire ceramic phosphor sheet 803, and a photoresist is formed on the DBR reflective layer. The insulating region is blocked by the photoresist, and the conductive position is exposed. The conductive reflective layer 803a and the conductive material layer 801 are then formed using the same photoresist pattern.

This embodiment saves the ceramic pedestal and is more advantageous in terms of cost, and can be applied to any of the package structures disclosed in Embodiments 1 to 5.

Example 7

12 is a cross-sectional view showing an LED package substrate according to a seventh embodiment of the present invention, the substrate including an insulative housing 901a having a recess for filling the fluorescent paste 903, and the circuit 901b is distributed at the bottom of the recess And extending through the insulative housing 901a to the sidewall of the insulative housing 901a. The upper surface of the insulative housing 901a is selectively coated with a reflective varnish as the reflective layer 904 (other than the solder bumps 905). The fluorescent glue 903 is filled in the recess of the insulative housing 901a, and its surface is flat, exposing the solder bumps 905 for mounting the LED chips.

The package substrate is suitable for any of the package structures of the first to fifth embodiments.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and patent specification content of the present invention, All remain within the scope of the invention patent.

Claims

An LED package structure comprising:

a package substrate having opposite upper and lower surfaces;

a reflective layer on the upper surface or the lower surface of the package substrate, reflecting light directed to the package substrate;

a light conversion layer, located on the reflective layer, absorbing light of a specific wavelength and converting it into light of other wavelengths;

An LED chip, located on the light conversion layer, emitting light of a specific wavelength in both directions up and down;

The package structure is characterized in that: if the light-emitting direction of the package structure is positive, the light conversion layer is located on the back surface of the LED chip, and the light emitted by the LED package structure is emitted by the LED chip without passing through the light conversion layer. And its light passing through the light conversion layer.
The LED package structure according to claim 1, wherein the surface of the package substrate has positive and negative circuits separated by an insulating region.
The LED package structure according to claim 2, wherein the reflective layer is composed of a conductive reflective layer and a DBR reflective layer, wherein a conductive reflective layer is formed on the circuit of the package substrate, and the DBR reflective layer is formed. In the insulating region of the package substrate.
The LED package structure of claim 1 , wherein the package substrate has a raised platform that is higher than the light conversion layer, and the LED chip is mounted on the raised platform, not The light conversion layer is in direct contact.
The LED package structure of claim 1 , wherein the package substrate has an insulating body and a circuit, the insulating body has a recess, and the circuit is distributed at the bottom of the recess and passes through the insulating body. Extending to the sidewall of the insulative body.
The LED package structure according to claim 5, wherein the reflective layer is formed on an upper surface of the package substrate, the light conversion layer fills the recess, and forms a flat surface with the package substrate Overall.
The LED package structure according to claim 1, wherein the package substrate is composed of two conductive blocks separated by an insulator, and the reflective layer is formed on the two conductive layers and is isolated by the insulator. Two electrical areas.
The LED package structure according to claim 1, wherein the reflective layer is made of a metal mirror and a photonic crystal One or more combinations of body and reflective coatings.
The LED package structure according to claim 1, wherein the light conversion material of the light conversion layer is formed by combining one or more of a phosphor, a quantum dot, and an organic fluorescent/phosphorescent material.
The LED package structure according to claim 9, wherein the light conversion layer is made of a mixture of a phosphor and a silica gel.
The LED package structure according to claim 9, wherein the light conversion layer is a ceramic phosphor sheet.
The LED package structure according to claim 1, wherein the thickness of the light conversion layer is less than 1 mm.
The LED package structure according to claim 1, wherein said light conversion layer has a through hole filled with a conductive material.
The LED package structure according to claim 1, wherein the LED chip emits blue light having a wavelength of 400 nm to 500 nm, and the light conversion layer absorbs blue light emitted from the LED chip to emit light having a wavelength of 500 nm to 780 nm.
The LED package structure according to claim 1, further comprising a lens that completely transmits light of a wavelength of 500 nm to 780 nm and partially reflects/transmits light of a wavelength of 400 nm to 500 nm.