Packaging process of a five-sided light-emitting CSP LED

Abstract

The present invention discloses a packaging process for a five-sided light-emitting CSP LED, which includes the following steps: providing a wafer, the wafer includes a number of LED flip-chip devices with electrodes on the top surface, and planting conductive posts on the electrodes; covering a layer of high thermal conductivity and high reflectivity on the top surface of the LED flip-chip device, and the high thermal conductivity and high reflectivity layer covers the area on the top surface of the LED flip-chip device where the conductive posts are not planted; performing thermal pressing on the conductive posts; cutting the wafer and obtaining single LED flip-chip structure chips by reverse molding; providing a die placement board, and fixedly placing multiple fabricated LED flip-chip structure chips on the die placement board at intervals, with the electrodes of the LED flip-chip structure chips facing downwards, covering a layer of fluorescent layer on the surfaces of multiple LED flip-chip structure chips and the surface of the die placement board, and the fluorescent layer covers the four side surfaces and the top surface of the LED flip-chip structure chips; cutting between adjacent LED flip-chip structure chips to obtain a product of a single five-sided light-emitting CSP LED.

Description

Technical Field

[0001] The present invention relates to the technical field of LED packaging, and particularly to a packaging process for a five-sided emitting CSP LED. Background Art

[0002] As a new type of LED packaging form, CSP has the following advantages: ① better stability, removing the gold wires and brackets in traditional packaging, making it safer and more reliable during transportation, storage, and installation, and reducing the product damage probability; ② smaller size, increasing the number of chips per unit area, increasing the current density, and being beneficial for use in high-power products; ③ simpler structure, reducing the number of layers of materials at the bottom of the chip, simplifying the heat conduction path, and making the thermal resistance lower; ④ the overall small size makes it more flexible, and it can be arbitrarily combined into various powers and series-parallel numbers, being beneficial for use in products with special requirements; ⑤ the LED changes from a surface light source with a 120-degree light-emitting angle on one surface to a volume light source with five-sided emission and a 180-degree light-emitting angle, increasing the light extraction efficiency and providing convenience for the product design that requires a large light-emitting angle; ⑥ in the packaging process, the usage of brackets and silicone is reduced, removing the machine-by-machine dispensing link in traditional pin-type and surface-mount packaging, and reducing the overall cost.

[0003] Currently, many of the five-sided emitting CSP LED packaging structures made by existing packaging processes are front-mounted packaging structures. For front-mounted structure LEDs, the p and n electrodes are on the same side of the LED, and the current must flow horizontally through the n-GaN layer, resulting in current crowding and high local heat generation, which limits the drive current. Secondly, due to the poor thermal conductivity of the sapphire substrate, the heat dissipation is seriously hindered. During long-term use, the high temperature caused by poor heat dissipation affects the performance and transmittance of the silicone, resulting in a large attenuation of the light output power.

[0004] In order to improve the problem of poor heat dissipation of front-mounted packaging LEDs, researchers in the industry have developed flip-chip structure CSP LEDs. However, currently, flip-chip chips have been around for a long time, and the cost has always been more than 50% higher than that of front-mounted chips. Moreover, under the same size and small current conditions, front-mounted chips have a light efficiency 20% higher than that of traditional flip-chip chips. Summary of the Invention

[0005] The main object of the present invention is to propose a packaging process for a five-sided emitting CSP LED, aiming to solve the above technical problems.

[0006] To achieve the above object, the packaging process for a five-sided emitting CSP LED proposed by the present invention includes the following steps:

[0007] S1: Provide a wafer, which includes a number of LED flip-chip devices with electrodes on their top surfaces, and grow conductive posts on the electrodes of the LED flip-chip devices;

[0008] S2: Cover the top surface of the LED flip-chip device with a highly thermally conductive and highly reflective layer that is lower in height than the conductive post, and the highly thermally conductive and highly reflective layer covers the area on the top surface of the LED flip-chip device where the conductive post is not grown;

[0009] S3: Hot-press the part of the conductive post protruding from the highly thermally conductive and highly reflective layer into a flat shape, so that the conductive post covers at least a part of the top surface of the highly thermally conductive and highly reflective layer;

[0010] S4: Cut between adjacent LED flip-chip devices, and perform reverse molding to obtain single LED flip-chip structure chips;

[0011] S5: Provide a die bonding plate, and fixedly bond multiple fabricated LED flip-chip structure chips on the die bonding plate at intervals, with the electrodes of the LED flip-chip structure chips facing downwards. Cover a fluorescent layer on the surfaces of the multiple LED flip-chip structure chips and the surface of the die bonding plate, and the fluorescent layer covers the peripheral sides and the top surface of the LED flip-chip structure chips;

[0012] S6: Cut between adjacent LED flip-chip structure chips to obtain single five-sided emitting CSP LEDs.

[0013] In one embodiment, after the conductive post is hot-pressed, 50%-80% of the surface of the highly thermally conductive and highly reflective layer covering the surface of the LED flip-chip device is covered by the conductive post.

[0014] In one embodiment, the axial cross-sectional diameter of the conductive post before hot-pressing is 75-200 um, and / or the height of the conductive post before hot-pressing is 60-300 um.

[0015] In one embodiment, the highly thermally conductive and highly reflective layer includes transparent silica gel and white oxide, and the white oxide is selected from one or more of aluminum oxide, zirconium oxide, titanium dioxide or silicon dioxide.

[0016] In one embodiment, the manufacturing steps of the highly thermally conductive and highly reflective layer include: using a solenoid valve spraying machine to integrally coat the highly thermally conductive and highly reflective glue on the area of the wafer where the conductive post is not grown, so that all the highly thermally conductive and highly reflective glue is connected into a whole on the wafer, and then drying and curing to form a highly thermally conductive and highly reflective layer covering the area on the top surface of the LED flip-chip device where the conductive post is not grown.

[0017] In one embodiment, the manufacturing steps of the fluorescent layer include:

[0018] Mix silica gel and phosphor and stir them under vacuum. Then, form a cured fluorescent glue film with a uniform thickness on the release paper by means of scraping coating and heating or pressing and heating. The thickness of the fluorescent glue film is 15 - 300 um.

[0019] Place the fluorescent glue film above multiple LED flip - chip structure chips arranged at intervals, and heat it in a vacuum chamber to make the fluorescent glue film soften and adsorb on the peripheral sides and the top surface of the multiple LED flip - chip structure chips. Then, perform secondary curing on the fluorescent glue film to form a fluorescent layer covering the peripheral sides and the top surface of the LED flip - chip structure chips.

[0020] In one embodiment, before S6, the following steps are further included: cover a light - enhancing layer on the surface of the fluorescent layer, and the refractive index of the light - enhancing layer is lower than that of the fluorescent layer.

[0021] In one embodiment, the surface of the light - enhancing layer is set to be uneven and frosted.

[0022] In one embodiment, the die - mounting plate includes a carrier plate and an adhesive layer coated on the upper surface of the carrier plate. In S5, the bottom surface of the LED flip - chip structure chip after die - bonding is covered by the adhesive layer, and the LED flip - chip structure chip is connected to the carrier plate through the adhesive layer.

[0023] In one embodiment, the material of the conductive column is selected as metallic gold.

[0024] In the technical solution of the present invention, by encapsulating multiple five-sided light-emitting CSP LEDs simultaneously, the encapsulation efficiency is greatly improved; by encapsulating the LED front-mounted chip into a flip-chip, the problems of poor heat dissipation performance of the front-mounted chip and too high cost of the flip-chip are solved simultaneously; and, by planting conductive posts on the electrodes of the LED front-mounted chip, the problem of easy breakage of gold wires is solved. By hot-pressing the part of the conductive post protruding from the high thermal conductivity and high reflectivity layer into a flat shape, the chip is more convenient for welding with the substrate and is more conducive to dissipating heat; by covering a high thermal conductivity and high reflectivity layer on the top surface of the LED front-mounted chip, on the one hand, the connection between the conductive post and the LED front-mounted chip is more stable, and on the other hand, the heat inside the LED flip-chip can be dissipated more quickly through the high thermal conductivity and high reflectivity layer, so that the heat dissipation performance of the LED flip-chip structure chip is further improved. The five-sided light-emitting CSP LED prepared by the encapsulation process of the present invention has the advantages of low cost, no need for additional welding wires, good heat dissipation effect, high light output efficiency, and stable product performance; compared with the five-sided light-emitting CSP LED structure directly encapsulated by traditional front-mounted chips, in the encapsulation process of the present invention, the LED front-mounted chip is first encapsulated into the LED flip-chip structure chip, and then the LED flip-chip structure chip is encapsulated into the five-sided light-emitting CSP LED structure. The luminous efficiency of the five-sided light-emitting LED CSP structure prepared by the encapsulation process of the present invention can be increased by 20-30% on the basis of the luminous efficiency of the five-sided light-emitting LED CSP structure directly encapsulated by traditional front-mounted chips. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0026] Figure 1 It is a schematic flow chart of the encapsulation process of the five-sided light-emitting CSP LED of the present invention in an embodiment;

[0027] Figure 2 It is a schematic flow chart of the encapsulation process of the five-sided light-emitting CSP LED of the present invention in another embodiment;

[0028] Figure 3 It is a schematic structural diagram of the wafer of the present invention in an embodiment;

[0029] Figure 4 It is a schematic structural diagram of the LED flip-chip structure chip of the present invention;

[0030] Figure 5 is the front view of the five-sided light-emitting CSP LED fabricated by the packaging process of the present invention;

[0031] Figure 6 is Figure 5 the top view of

[0032] Figure 7 is the process flow diagram of the packaging process of the LED flip-chip structure chip of the present invention in an embodiment;

[0033] Figure 8 is the process flow diagram of the packaging process of the five-sided light-emitting CSP LED of the present invention in an embodiment.

[0034] Explanation of the reference numerals in the drawings:

[0035] Label Name Label Name 10 Flip-chip LED structure chip 100 Surface-mount LED chip 110 Electrode surface 130 Substrate surface 200 High thermal conductivity and high reflectivity layer 300 Conductive post 01 Five-sided emitting CSP LED 20 Fluorescent layer 30 Anti-reflection layer 60 Wafer 70 UV film 80 Die placement board

[0036] The realization, functional features and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the accompanying drawings. Specific embodiments

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0038] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0039] In addition, if the embodiments of the present invention involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are for descriptive purposes only, and should not be construed as indicating or implying their relative importance or implicitly indicating the quantity of the technical features indicated. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the meaning of "and / or" appearing throughout the text is that it includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0040] The raw materials and equipment used in the present invention, unless otherwise specified, are common raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are conventional methods in the art. Unless otherwise specified, the meanings of the terms in this specification are the same as those generally understood by those skilled in the art, but in case of conflict, the definitions in this specification shall prevail.

[0041] As used herein, "comprising", "including", "containing", "having" or other variants are intended to cover non-closed inclusion, and no distinction is made between these terms. The term "including" means that other steps and components can be added without affecting the final result. The term "including" also includes the terms "consisting essentially of" and "consisting mainly of". The compositions and methods / processes of the present invention comprise, consist of, and consist essentially of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps or limitations described herein.

[0042] For those technical or conditions not specified in the examples, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product specifications. For the reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0043] LED chips are made of compounds containing gallium (Ga), arsenic (As), phosphorus (P), nitrogen (N), etc., and can emit visible light when electrons and holes recombine. Among them, gallium arsenide-based LED chips emit red light, gallium phosphide-based LED chips emit green light, silicon carbide-based LED chips emit yellow light, and gallium nitride-based LED chips emit blue light. The positive and negative electrodes of a flip-chip LED are both located on the same side of the chip, and its circuit connection is connected to the corresponding positive and negative positions on the package shell through wire bonding. A typical one is a blue flip-chip LED. The structure of a blue flip-chip LED from top to bottom is a metal electrode, P-GaN (P-type gallium nitride), N-GaN (N-type gallium nitride), and a sapphire substrate. When a blue flip-chip LED is directly packaged into a flip-chip type five-sided light-emitting CSP LED structure through traditional packaging technology, light is directly transmitted from the gallium nitride layer to the packaging silicone layer or the fluorescent layer, and the critical angle of its transmission interface is small, which is not conducive to light output; moreover, since it mainly dissipates heat through the substrate connected to the sapphire substrate, and the sapphire substrate has poor thermal conductivity, the heat dissipation effect is seriously affected.

[0044] To solve the above technical problems, the present invention proposes a packaging process for a five-sided light-emitting CSP LED.

[0045] Please refer to Figure 1 、 Figure 2 and Figure 3 In the embodiment of the present invention, the packaging process includes the following steps:

[0046] S1: Provide a wafer 60, the wafer 60 includes a plurality of flip-chip LED chips 100 with electrodes on the top surface, the plurality of flip-chip LED chips 100 are arranged in a matrix, the flip-chip has a relatively arranged bottom surface 130 and electrode surface 110, the electrode surface 110 is provided with electrodes, the electrodes include a positive electrode and a negative electrode arranged at intervals, the electrodes face upward, and a conductive column 300 is planted on the electrodes of the flip-chip LED chip 100 using a wire bonder.

[0047] Among them, the flip-chip LED chip 100 can be any one of a blue chip, a red chip, a green chip, or a yellow chip. Of course, the flip-chip LED chip 100 can also be other types of chips, and can be appropriately selected according to user needs and application scenarios.

[0048] S2: Cover a high thermal conductivity and high reflectivity layer 200 with a height lower than the conductive column 300 on the top surface of the flip-chip LED chip 100. The high thermal conductivity and high reflectivity layer 200 has high thermal conductivity and high reflectivity properties, and the high thermal conductivity and high reflectivity layer 200 covers the area on the top surface of the flip-chip LED chip 100 where the conductive column 300 is not planted.

[0049] S3: Hot-press the part of the conductive post 300 protruding from the high thermal conductivity and high reflectivity layer 200 into a flat shape, so that the conductive post 300 covers at least part of the top surface of the high thermal conductivity and high reflectivity layer 200.

[0050] More specifically, by placing the entire wafer 60 into a planar hot press, applying a certain pressure and heat to the end of the conductive post 300 facing away from the electrode surface 110 using the planar hot press, the end of the conductive post 300 facing away from the electrode surface 110 is deformed into a large pancake shape; of course, the end of the conductive post 300 away from the electrode can also be pressed into a flat shape by other means, which will not be elaborated here one by one.

[0051] After the conductive post 300 is hot-pressed, its upper end can be a regular cylindrical shape, a prismatic shape or other irregular cylindrical shapes, and its lower end can be a flat cylindrical shape, a flat prismatic shape, a hemispherical shape, a semi-elliptical shape, a semi-elliptical-like shape or other flat shapes.

[0052] S4: Cut the entire wafer 60, cut between adjacent LED flip-chip devices 100, and perform reverse molding to obtain single LED flip-chip structure chips 10.

[0053] S5: Provide a die placement board 80, fixedly place multiple fabricated LED flip-chip structure chips 10 on the upper surface of the die placement board 80 at intervals, with the electrodes of the LED flip-chip structure chips 10 facing downwards, and cover a layer of phosphor layer 20 on the surfaces of the multiple LED flip-chip structure chips 10 and the surface of the die placement board 80. The phosphor layer 20 covers the four side surfaces and the top surface of the LED flip-chip structure chips 10.

[0054] The die placement board 80 includes a carrier board and an adhesive layer coated on the upper surface of the carrier board. The adhesive layer has adhesiveness. The bottom surface of the LED flip-chip structure chip 10 is covered by the adhesive layer. The adhesive layer seals the bottom surfaces of the conductive post 300 and the high thermal conductivity and high reflectivity layer 200. The LED flip-chip structure chip 10 is connected to the carrier board through the adhesive layer.

[0055] S6: Use a cutting tool to cut between adjacent LED flip-chip structure chips 10 to obtain a product of single five-sided emitting CSP LEDs.

[0056] Compared with the front-mounted five-sided light-emitting CSP LED structure directly formed by packaging a front-mounted chip using a traditional packaging process, the five-sided light-emitting CSP LED structure packaged by using the packaging process of the present invention has better heat dissipation performance and higher light transmission efficiency. For the convenience of understanding, taking a blue light chip as an example, in the five-sided light-emitting CSP LED 01 packaged by using the packaging process of the present invention, the light emitted by the electrons in the gallium nitride layer is transmitted towards the sapphire substrate layer, and the internal heat is mainly dissipated through the high thermal conductivity and high reflectivity layer 200. Different from the sapphire substrate, the high thermal conductivity and high reflectivity layer has excellent thermal conductivity, which greatly improves the heat dissipation performance of the CSP LED. And based on the excellent light reflection performance of the high thermal conductivity and high reflectivity layer 200, since the light emitted by the electrons towards the electrode surface 110 will be reflected back to the sapphire substrate layer by the high thermal conductivity and high reflectivity layer 200 and then transmitted into the air through the substrate surface 130, the light output efficiency is further improved. On the other hand, according to Snell's law, in the five-sided light-emitting CSP LED 01 packaged by using the packaging process of the present invention, the total reflection critical angle θ from the GaN layer to the sapphire substrate layer is 44.5°, and the critical angle θ from the sapphire substrate layer to the fluorescent layer 20 is 57.4°; in the front-mounted five-sided light-emitting CSP LED structure directly formed by packaging a front-mounted chip using a traditional packaging process, the light is directly transmitted from the GaN layer to the fluorescent layer 20, and its total reflection critical angle θ is 36.2°, which is smaller than the critical angle of the light transmission interface of the five-sided light-emitting CSP LED structure packaged by using the packaging process of the present invention. Since a larger critical angle can output more light, therefore, compared with the front-mounted five-sided light-emitting CSP LED structure directly formed by packaging a front-mounted chip using a traditional packaging process, the five-sided light-emitting CSP LED 01 packaged by using the packaging process of the present invention has a higher external quantum efficiency, and thus a higher luminous efficiency. It can be understood that when the LED front-mounted chip 100 is an LED red light chip, an LED green light chip or an LED yellow light chip, the five-sided light-emitting CSP LED structure prepared by using the packaging process of the present invention also has the above characteristics, which will not be elaborated here one by one.

[0057] In the technical solution of the present invention, by encapsulating multiple five-sided light-emitting CSP LEDs 01 simultaneously, the encapsulation efficiency is greatly improved; by encapsulating the LED direct-mounted chip 100 into a flip-chip, the problems of poor heat dissipation performance of the direct-mounted chip and high cost of the flip-chip are solved simultaneously; moreover, by planting conductive posts 300 on the electrodes of the LED direct-mounted chip 100, the problem of easy breakage of the gold wires is solved, and by hot-pressing the part of the conductive post 300 protruding from the high thermal conductivity and high reflectivity layer 200 into a flat shape, the chip is more convenient for welding with the substrate and is more conducive to dissipating heat; by covering a high thermal conductivity and high reflectivity layer 200 on the top surface of the LED direct-mounted chip 100, on the one hand, the connection between the conductive post 300 and the LED direct-mounted chip 100 is more stable, and on the other hand, the heat inside the LED flip-chip can be dissipated more quickly through the high thermal conductivity and high reflectivity layer 200, further improving the heat dissipation performance of the LED flip-chip structure chip 10. The five-sided light-emitting CSP LED 01 prepared by the encapsulation process of the present invention has the advantages of low cost, no need for additional welding wires, good heat dissipation effect, high light output efficiency and stable product performance; compared with the five-sided light-emitting CSP LED structure directly encapsulated by traditional direct-mounted chips, in the encapsulation process of the present invention, the LED direct-mounted chip 100 is first encapsulated into the LED flip-chip structure chip 10, and then the LED flip-chip structure chip 10 is encapsulated into a five-sided light-emitting CSP LED structure. The luminous efficiency of the LED CSP structure prepared by the encapsulation process of the present invention can be increased by 20-30% based on the luminous efficiency of the LED CSP structure directly encapsulated by traditional direct-mounted chips.

[0058] In the above embodiment, the material of the conductive post 300 can be selected from metallic tin, metallic gold or other conductive metals; preferably, the material of the conductive post 300 is selected from metallic gold or an alloy including metallic gold. The conductive post 300 made of gold has good ductility, is not easily expanded and broken by heat, and has good electrical conductivity. Since the price of pure gold is relatively high, gold alloy can be used instead of pure gold.

[0059] Please refer to Figure 4 , in an embodiment, the axial cross-sectional diameter of the conductive post 300 before hot pressing is 75-200 um, that is, the axial cross-sectional diameter of the guiding section of the conductive post 300 embedded in the high thermal conductivity and high reflectivity layer 200 can be 75 um, 125 um, 150 um, 200 um or any value between them; within this value range, the conductive post 300 is not easy to bend and break while not affecting the light-emitting area of the chip.

[0060] Please refer to Figure 5 and Figure 6After the conductive posts 300 are hot-pressed, 50%-80% of the surface of the high thermal conductivity and high reflectivity layer 200 covering the surface of the LED flip-chip 100 is covered by the conductive posts 300. The portion of the conductive posts 300 protruding from the surface of the high thermal conductivity and high reflectivity layer 200 is used as a connection site for connecting to the substrate. The covering area is designed to be not less than 50%, so that the conductive posts 300 can provide a relatively large connection site for the metal substrate to improve the connection stability between the LED flip-chip structure chip 10 and the substrate. Moreover, the relatively large surface area is conducive to the LED flip-chip structure chip 10 dissipating heat through the conductive posts 300. And the covering area is designed to be not higher than 80%, so that when multiple five-sided light-emitting CSP LEDs 01 are welded to the substrate together, the situation that adjacent CSP LED structures affect each other due to the too-close solder joint positions can be avoided.

[0061] The thickness of the high thermal conductivity and high reflectivity layer 200 is 20-50 um, that is, the thickness of the high thermal conductivity and high reflectivity layer 200 can be 20 um, 30 um, 40 um, 50 um or any value between them. When the thickness of the high thermal conductivity and high reflectivity layer 200 is less than 20 um, the thermal conductivity and reflectivity of the high thermal conductivity and high reflectivity layer 200 itself will be affected. In addition, since the portion of the conductive posts 300 protruding from the high thermal conductivity and high reflectivity layer 200 is too close to the circuit layer on the flip-chip, it may have an adverse effect on the circuit layer of the LED flip-chip structure chip 10. When the thickness of the high thermal conductivity and high reflectivity layer 200 is greater than 50 um, on the one hand, it will increase the thickness of the LED flip-chip structure chip 10 and increase the difficulty of its packaging. On the other hand, the thermal conductivity and reflectivity of the high thermal conductivity and high reflectivity layer 200 itself will also be adversely affected.

[0062] In one embodiment, the high thermal conductivity and high reflectivity layer 200 comprises transparent silica gel and white oxide, and the weight ratio of the transparent silica gel to the white oxide is 1:0.3. The white oxide is selected from one or more of aluminum oxide, zirconium oxide, titanium dioxide or silicon dioxide, and the particle size of the white oxide is 0.1 - 10 um, that is, the particle size of the white oxide can be 0.1 um, 1 um, 5 um, 10 um or any value therebetween; when the particle size of the white oxide is too small, the white oxide will be too fluffy, which is not conducive to the mixing of the transparent silica gel and the white oxide; when the particle size of the white oxide is too large, the white oxide is likely to agglomerate into a paste, making it difficult to mix the transparent silica gel and the white oxide evenly. The preparation steps of the high thermal conductivity and high reflectivity layer 200 include: mixing the transparent silica gel and the white oxide and performing vacuum stirring to prepare a high thermal conductivity and high reflectivity glue, and through a solenoid valve spraying machine, coating the high thermal conductivity and high reflectivity glue integrally on the area of the wafer 60 where the conductive posts 300 are not planted, so that all the high thermal conductivity and high reflectivity glue forms a whole on the wafer 60, and then drying and curing to form the high thermal conductivity and high reflectivity layer 200 covering the area of the top surface of the LED flip chip 100 where the conductive posts 300 are not planted. It should be noted that this embodiment only provides one of the formula components and preparation methods of the high thermal conductivity and high reflectivity layer 200, and the components and preparation methods of the high thermal conductivity and high reflectivity layer 200 can be adaptively adjusted according to the requirements of the product and the corresponding preparation environment.

[0063] In one embodiment, the phosphor layer 20 comprises transparent silica gel and phosphor powder. The phosphor layer 20 can be composed of a composite of a transparent silica gel layer and a phosphor powder layer, that is, coating the phosphor powder on the surface of a cured transparent silica gel layer; or, the phosphor layer 20 is formed by uniformly mixing a proper proportion of transparent silica gel and phosphor powder and then curing to form a film layer structure with a uniform thickness. Preferably, the transparent silica gel in the phosphor layer 20 is selected as transparent secondary-cured silica gel. Compared with the once-cured silica gel, the secondary-cured silica gel has stronger mechanical properties, such as stronger hardness, which is more conducive to protecting the chip structure.

[0064] In one embodiment, the phosphor layer 20 is formed by uniformly mixing a proper proportion of transparent secondary-cured silica gel and phosphor powder and then curing to form a film layer structure with a uniform thickness. The thickness of the phosphor powder is 1 - 30 um, that is, the particle size of the phosphor powder can be 1 um, 15 um, 30 um or any value therebetween. When the particle size of the phosphor powder is too small, the phosphor powder will be too fluffy, which is not conducive to the mixing of the transparent secondary-cured silica gel and the phosphor powder; when the particle size of the phosphor powder is too large, the phosphor powder is likely to agglomerate into a paste, making it difficult to mix the transparent secondary-cured silica gel and the phosphor powder evenly.

[0065] The manufacturing steps of the fluorescent layer 20 include: mixing silica gel and phosphor and stirring under vacuum, and then forming a cured fluorescent glue film with a uniform thickness on a release paper by means of doctor blade coating heating or lamination heating molding. The thickness of the fluorescent glue film is 15 - 300 um; placing the fluorescent glue film above a plurality of neatly arranged LED flip-chip structure chips 10, heating in a vacuum chamber to make the fluorescent glue film soften and adsorb on the peripheral sides and top surface of the plurality of LED flip-chip structure chips 10, and then performing secondary curing on the fluorescent glue film to form a fluorescent layer 20 covering the peripheral sides and top surface of the LED flip-chip structure chips 10.

[0066] Please refer to Figure 8 , in another embodiment of the present invention, before performing step S6, the following steps are further included: covering a surface of the fluorescent layer 20 with an antireflection layer 30, and the refractive index of the antireflection layer 30 is lower than that of the fluorescent layer 20. In the five-sided emitting CSP LED 01 prepared by using the packaging process of the present invention, the light emitted by the electrons inside the chip passes through the fluorescent layer 20 and the antireflection layer 30 successively, and then enters the air. Generally speaking, the refractive index of the fluorescent layer 20 is 1.55 - 1.6. If the light directly passes through the fluorescent layer 20 and is transmitted into the air, the critical angle of total reflection will be relatively small, resulting in a low light transmittance. However, if an antireflection layer 30 with a refractive index lower than that of the fluorescent layer 20 is formed outside the fluorescent layer 20, the critical angle of total reflection when the light passes through the fluorescent layer 20 and the antireflection layer 30 and is transmitted into the air will be slightly larger, thereby increasing the light transmittance, and thus further improving the luminous brightness of the prepared five-sided emitting CSP LED packaging structure.

[0067] In one embodiment, the material of the antireflection layer 30 is selected as transparent silica gel, and the refractive index of the antireflection layer 30 is designed to be 1.4 - 1.5. In order to increase the above-mentioned critical angle of total reflection, a film layer structure made of other materials with a refractive index lower than that of the fluorescent layer 20 can also be coated on the peripheral sides and the surface corresponding to the bottom surface 130 of the fluorescent layer 20, and it is not limited to selecting transparent silica gel material.

[0068] Furthermore, the surface of the antireflection layer 30 is set to be uneven and frosted; in order to simplify the packaging process, the antireflection layer 30 can be formed by one-time film pressing using a mold. Of course, a smooth-surface antireflection layer 30 can also be first coated, and then the surface of the antireflection layer 30 is frosted.

[0069] Please refer to Figure 7, in one embodiment, before performing step S4, the following steps are further included: placing the hot-pressed wafer 60 on the UV film 70, and the UV film 70 fastens the wafer 60 by its own adhesive property. At this time, the electrodes of the LED flip-chip 100 face upward; in this embodiment, in step S4, after continuous irradiation of UV light, the adhesive property of the UV film 70 is greatly reduced, and the LED flip-chip structure 10 can be separated from the UV film 70 with a relatively small force, so that a single LED flip-chip structure 10 can be obtained by easy film inversion without damaging the chip.

[0070] The foregoing examples are illustrative only and are used to explain some features of the method of the present invention. The appended claims are intended to claim the broadest scope conceivable, and the embodiments presented herein are merely illustrative of selected embodiments from all possible combinations of embodiments. Therefore, the applicant's intention is that the appended claims are not limited by the selection of examples that illustrate the features of the present invention. Some of the numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be construed as being covered by the appended claims where possible.

Claims

1. A packaging process for a five-sided light-emitting CSP LED, characterized in that, It includes the following steps: S1: Provide a wafer, which includes a number of LED flip-chip on board (FOB) chips with electrodes on the top surface, and grow conductive posts on the electrodes of the LED FOB chips; S2: Cover the top surface of the LED FOB chips with a highly thermally conductive and highly reflective layer whose height is lower than that of the conductive posts, and the highly thermally conductive and highly reflective layer covers the area on the top surface of the LED FOB chips where the conductive posts are not grown; S3: Hot-press the part of the conductive post protruding from the highly thermally conductive and highly reflective layer into a flat shape, so that the conductive post covers at least part of the top surface of the highly thermally conductive and highly reflective layer; S4: Cut between adjacent LED FOB chips, and obtain single-piece LED flip-chip structure chips by casting; S5: Provide a die placement board, fixedly place multiple fabricated LED flip-chip structure chips on the die placement board at intervals, with the electrodes of the LED flip-chip structure chips facing downwards, cover a fluorescent layer on the surfaces of the multiple LED flip-chip structure chips and the surface of the die placement board, the fluorescent layer covers the peripheral sides and the top surface of the LED flip-chip structure chips, cover an anti-reflection layer on the surface of the fluorescent layer, and the surface of the anti-reflection layer is set to be uneven and frosted; S6: Cut between adjacent LED flip-chip structure chips to obtain single-piece five-sided emitting chip scale package (CSP) LEDs.

2. The encapsulation process according to claim 1, wherein After the conductive post is hot-pressed, 50%-80% of the surface of the highly thermally conductive and highly reflective layer covered on the surface of the LED FOB chip is covered by the conductive post.

3. The encapsulation process according to claim 2, characterized in that The axial cross-sectional diameter of the conductive post before hot-pressing is 75-200 um, and / or the height of the conductive post before hot-pressing is 60-300 um.

4. The encapsulation process according to claim 1, characterized in that, The highly thermally conductive and highly reflective layer includes transparent silica gel and white oxide, and the white oxide is selected from one or more of aluminum oxide, zirconium oxide, titanium dioxide or silicon dioxide.

5. The encapsulation process according to claim 1, characterized in that The manufacturing steps of the highly thermally conductive and highly reflective layer include: through a solenoid valve spraying machine, overall fill and coat the highly thermally conductive and highly reflective glue in the area on the wafer where the conductive posts are not grown, so that all the highly thermally conductive and highly reflective glue is connected into a whole on the wafer, and then bake and cure to form a highly thermally conductive and highly reflective layer covering the area on the top surface of the LED FOB chip where the conductive posts are not grown.

6. The encapsulation process according to claim 1, characterized in that, The manufacturing steps of the fluorescent layer include: Mix silica gel and phosphor and stir them in vacuum, and then form a cured fluorescent glue film with a uniform thickness on a release paper by means of scraping heating or pressing heating molding, and the thickness of the fluorescent glue film is 15-300 um; Place the fluorescent glue film above multiple spaced-apart LED flip-chip structure chips, heat it in a vacuum chamber, so that the fluorescent glue film becomes soft and adheres to the peripheral sides and the top surface of the multiple LED flip-chip structure chips, and then perform secondary curing on the fluorescent glue film to form a fluorescent layer covering the peripheral sides and the top surface of the LED flip-chip structure chips.

7. The encapsulation process according to any one of claims 1 to 6, characterized in that, Before S6, the following step is also included: the refractive index of the anti-reflection layer is lower than that of the fluorescent layer.

8. The encapsulation process according to any one of claims 1 to 6, characterized in that, The die placement board includes a carrier board and an adhesive layer coated on the upper surface of the carrier board. In step S5, the bottom surface of the LED flip-chip structure chip after die bonding is coated by the adhesive layer, and the LED flip-chip structure chip is connected to the carrier board through the adhesive layer.

9. The encapsulation process according to any one of claims 1 to 6, characterized in that, The conductive post is made of metallic gold.

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