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

Abstract

The present invention discloses a packaging process for a single-sided light-emitting CSP LED, which includes the following steps: providing a wafer, the wafer includes a plurality of LED direct-mounted chips with electrodes on the top surface, and planting conductive posts on the electrodes; covering a layer of high thermal conductivity and high reflectivity layer on the top surface of the LED direct-mounted chips, the high thermal conductivity and high reflectivity layer covers the area on the top surface of the LED direct-mounted chips where the conductive posts are not planted; performing thermal pressing on the conductive posts; cutting the wafer and performing reverse molding to obtain single LED flip-chip structure chips; providing a die placement board, attaching a layer of fluorescent film on the surface of the die placement board, and fixing the LED flip-chip structure chips on the fluorescent film; arranging a reflective layer between adjacent LED flip-chip structure chips, the reflective layer fills the gap between adjacent LED flip-chip structure chips and is connected to the high thermal conductivity and high reflectivity layer; performing cutting between adjacent LED flip-chip structure chips and performing reverse molding to obtain single products of single-sided light-emitting CSP LEDs.

Description

Technical Field

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

[0002] A light-emitting diode is abbreviated as LED (Light Emitting Diode), which is made of compounds containing atoms such as gallium (Ga), arsenic (As), phosphorus (P), nitrogen (N), etc. Since visible light can be radiated when electrons and holes recombine, it can be used to make a light-emitting diode. Among them, a gallium arsenide diode emits red light, a gallium phosphide diode emits green light, a silicon carbide diode emits yellow light, and a gallium nitride diode emits blue light. Initially, it was mostly used as an indicator light, a display light-emitting diode board, etc.; with the emergence of white LEDs, it has gradually been used for lighting. At present, white LEDs have been widely used in various lighting fields, such as mobile lighting, backlighting, flashlights, automotive lighting, etc.

[0003] At present, many LED packaging structures made by existing packaging processes are flip-chip packaging structures. In these flip-chip structures, gold wires are mostly used to connect the PN junctions of the chips to the positive and negative electrodes of the brackets. However, with the continuous increase in output power, failure problems such as large light decay and optical quenching that restrict the development of high-power LEDs have emerged one after another.

[0004] The main reason for quenching failure is the breakage of the gold wire. During the gold wire lead connection process, affected by multiple factors such as gold purity, bonding temperature, gold wire curvature, soldering machine accuracy, and bonding process, the gold wire is disconnected and quenched. Secondly, the silica gel mixed with phosphor powder is coated on the chip surface, which plays a dual role of light conversion and protecting the gold wire. When the chip is powered on and the temperature rises, due to reasons such as the thermal expansion and contraction of the silica gel, it will impact the gold wire and solder joints, and the solder joints will be desoldered, resulting in quenching.

[0005] The main reason for large light decay failure is the yellowing or reduced transmittance of the silica gel. The p and n electrodes of the flip-chip structure LED 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 silica gel, resulting in a large attenuation of the light output power.

[0006] Therefore, in order to improve problems such as easy breakage of the gold wire and poor heat dissipation of flip-chip packaged LEDs, researchers in the industry have developed flip-chip structure LEDs. At present, flip-chip chips have been around for a long time, but their cost has always been more than 50% higher than that of flip-chip chips. Moreover, under the same size and small current conditions, flip-chip chips have a light efficiency 20% higher than that of traditional flip-chip chips. Summary of the Invention

[0007] The main object of the present invention is to propose a packaging process for a single-sided light-emitting CSP LED, aiming to solve the above technical problems.

[0008] To achieve the above object, the packaging process for a single-sided light-emitting CSP LED proposed by the present invention includes the following steps:

[0009] S1: Provide a wafer, the wafer includes a plurality of LED flip-chip chips with electrodes on the top surface, and grow conductive posts on the electrodes of the LED flip-chip chips;

[0010] S2: Cover a layer of highly thermally conductive and highly reflective layer with a height lower than that of the conductive posts on the top surface of the LED flip-chip chips, and the highly thermally conductive and highly reflective layer covers the area on the top surface of the LED flip-chip chips where the conductive posts are not grown;

[0011] 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;

[0012] S4: Cut between adjacent LED flip-chip chips, and perform reverse molding to obtain single LED flip-chip structure chips;

[0013] S5: Provide a die placement board, attach a layer of fluorescent film on the surface of the die placement board, and fix a plurality of the fabricated LED flip-chip structure chips with the electrodes facing up at intervals on the fluorescent film;

[0014] S6: Spray reflective glue between adjacent LED flip-chip structure chips to form a reflective layer, and the reflective layer fills the gap between adjacent LED flip-chip structure chips and is connected to the highly thermally conductive and highly reflective layer as a whole;

[0015] S7: Cut between adjacent LED flip-chip structure chips, and perform reverse molding to obtain single single-sided light-emitting CSP LEDs.

[0016] In one embodiment, before the step S6, the following steps are further included: filling glue at the corners where the fluorescent film and the LED flip-chip structure chips meet, and the filled glue is cured into an oblique angle shape and adsorbed on the peripheral sides of the LED flip-chip chips to form a filling layer.

[0017] In one embodiment, 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 flip-chip chip is covered by the conductive post.

[0018] In one embodiment, in step S3, the protruding part of the conductive column is deformed into a cake shape and embedded with the high thermal conductivity and high reflectivity layer by placing the whole wafer into a planar hot press for hot pressing.

[0019] In one embodiment, the high thermal conductivity and high reflectivity 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;

[0020] And / or, the 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.

[0021] In one embodiment, the weight ratio of transparent silica gel to white oxide in the high thermal conductivity and high reflectivity layer is 1:0.3, and the particle size of the white oxide is 0.1 - 10 um;

[0022] And / or, the weight ratio of transparent silica gel to white oxide in the reflective layer is 1:0.3, and the particle size of the white oxide is 0.1 - 10 um.

[0023] In one embodiment, the fluorescent film includes silica gel and phosphor, and the particle size of the phosphor is 1 - 30 um.

[0024] In one embodiment, the manufacturing steps of the fluorescent film include: mixing silica gel and phosphor and stirring by means of vacuum stirring, and then forming a fluorescent film with a uniform cured thickness on the release paper by means of scraping heating or lamination heating, and the thickness of the fluorescent film is 15 - 300 um.

[0025] In one embodiment, the LED flip-chip is a blue light chip, including a gallium nitride layer and a sapphire substrate layer.

[0026] In one embodiment, the conductive column is made of metallic gold.

[0027] In the technical solution of the present invention, by encapsulating multiple single-sided light-emitting CSP LEDs simultaneously, the encapsulation efficiency is greatly improved; by encapsulating the LED direct-mounted chip 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; and, by planting conductive posts on the electrodes of the LED direct-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 layer of high thermal conductivity and high reflectivity layer on the top surface of the LED direct-mounted chip, on the one hand, the connection between the conductive post and the LED direct-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, further improving the heat dissipation performance of the LED flip-chip structure chip. The single-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 traditional encapsulation process of directly encapsulating a direct-mounted chip into a single-sided light-emitting CSP LED structure, in the encapsulation process of the present invention, the LED direct-mounted chip is first encapsulated into the LED flip-chip structure chip, and then the LED flip-chip structure chip is encapsulated into a single-sided light-emitting CSP LED structure. The luminous efficiency of the single-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 single-sided light-emitting LED CSP structure directly encapsulated by the traditional direct-mounted chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 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 drawings in the following description 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.

[0029] Figure 1 is Figure 1 a schematic flow chart of the encapsulation process of the single-sided light-emitting CSP LED of the present invention in an embodiment;

[0030] Figure 2 a schematic flow chart of the encapsulation process of the single-sided light-emitting CSP LED of the present invention in another embodiment;

[0031] Figure 3 a schematic structural diagram of the wafer of the present invention in an embodiment;

[0032] Figure 4It is a schematic structural diagram of the LED flip-chip structure chip of the present invention;

[0033] Figure 5 It is a schematic structural diagram of the single-sided light-emitting CSP LED prepared by the packaging process of the present invention;

[0034] Figure 6 It is a schematic flow diagram of the packaging process of the LED flip-chip structure chip of the present invention in an embodiment;

[0035] Figure 7 It is a schematic flow diagram of the packaging process of the single-sided light-emitting CSP LED of the present invention in an embodiment.

[0036] Explanation of the reference numerals in the drawings:

[0037] 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 pillar 02 Single-sided lighting CSP LED 20 Fluorescent film 40 Reflective layer 50 Filling layer 60 Wafer 70 UV film 80 Die pad

[0038] The realization, functional features and advantages of the object of the present invention will be further described with reference to the embodiments and the accompanying drawings. Specific embodiments

[0039] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to 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. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0040] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) 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.

[0041] In addition, if there are descriptions such as "first" and "second" in the embodiments of the present invention, the descriptions of "first" and "second" are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the 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, solution B, or a solution that satisfies both A and B at the same time. In addition, the technical solutions between the embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0042] In the examples where specific techniques or conditions are not indicated, they shall be in accordance with the techniques or conditions described in the literature in this field or in accordance with the product specifications. For the reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0043] The LED chip is made of compounds containing gallium (Ga), arsenic (As), phosphorus (P), nitrogen (N), etc. When electrons and holes recombine, visible light can be emitted. Among them, the gallium arsenide type LED chip emits red light, the gallium phosphide type LED chip emits green light, the silicon carbide type LED chip emits yellow light, and the gallium nitride type LED chip emits blue light. The positive and negative electrodes of the LED flip-chip 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 the gold wire bonding method. A typical one is the blue flip-chip. The structure of the blue flip-chip from top to bottom is a metal electrode, P-GaN (P-type gallium nitride), N-GaN (N-type gallium nitride), and sapphire substrate in sequence. When the blue flip-chip is directly packaged into a flip-chip type single-sided light-emitting CSP LED structure through the traditional packaging process, the light directly transmits 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 the output of light; moreover, since it mainly dissipates heat through the substrate connected to the sapphire substrate, and the sapphire substrate has poor thermal conductivity, it seriously affects the heat dissipation effect.

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

[0045] Please refer to Figure 1 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 LED flip-chips 100 with electrodes on the top surface, the plurality of LED flip-chips 100 are arranged in a matrix, the flip-chip has a relatively arranged substrate surface 130 and an electrode surface 110, the electrode surface 110 is provided with electrodes, and the electrodes include a positive electrode and a negative electrode arranged at intervals. Use a wire bonding machine to plant a conductive column 300 on the positive electrode and the negative electrode of the LED flip-chip 100 respectively.

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

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

[0049] S3: 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 a part of the top surface of the high thermal conductivity and high reflectivity layer 200.

[0050] More specifically, by placing the whole 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 whole wafer 60, cut between adjacent flip-chip LEDs 100, and demould to obtain single flip-chip LED structures 10.

[0053] S5: Provide a die placement board 80, attach a fluorescent film 20 on the surface of the die placement board 80, and fixedly place multiple fabricated flip-chip LED structures 10 with their electrodes facing up at intervals on the fluorescent film 20.

[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 fluorescent film 20 is attached to the adhesive layer, and the flip-chip LED structure 10 is connected to the carrier board through the adhesive layer.

[0055] S6: Spray a reflective glue between adjacent flip-chip LED structures 10 to form a reflective layer 40 with a flush top surface. The reflective layer 40 has excellent light reflection performance. The reflective layer 40 fills the gap between adjacent flip-chip LED structures 10 and is connected to the high thermal conductivity and high reflectivity layer 200 as a whole;

[0056] S7: Use a cutting tool to cut between adjacent flip-chip LED structures 10, and demould to obtain single-sided emitting CSP LEDs 02.

[0057] Compared with the single-sided light-emitting CSP LED structure of the flip-chip type directly encapsulated by a traditional packaging process using a flip-chip, the single-sided light-emitting CSP LED 02 encapsulated by the packaging process of the present invention has better heat dissipation performance and higher light transmission efficiency. For the convenience of detailed description, taking a blue light chip as an example, in the single-sided light-emitting CSP LED 02 encapsulated by 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 single-sided light-emitting CSP LED structure encapsulated by the packaging process of the present invention, the total reflection critical angle θ of light 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 is 57.4°. In the single-sided light-emitting CSP LED structure of the flip-chip type directly encapsulated by a traditional packaging process using a flip-chip, the light is directly transmitted from the GaN layer to the fluorescent layer, and its total reflection critical angle θ is 36.2°, which is smaller than the critical angle of the light transmission interface of the single-sided light-emitting CSP LED structure encapsulated by the packaging process of the present invention. Since a larger critical angle can output more light, therefore, compared with the single-sided light-emitting CSP LED structure of the flip-chip type directly encapsulated by a traditional packaging process using a flip-chip, the single-sided light-emitting CSP LED structure encapsulated by 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 flip-chip 100 is an LED red light chip, an LED green light chip or an LED yellow light chip, the single-sided light-emitting CSP LED 02 prepared by the packaging process of the present invention also has the above characteristics, which will not be elaborated one by one here.

[0058] In the technical solution of the present invention, by encapsulating multiple single-sided light-emitting CSP LEDs 02 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; and, 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. 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 made 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, so that the heat dissipation performance of the LED flip-chip structure chip 10 is further improved. The single-sided light-emitting CSP LED 02 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 single-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 single-sided light-emitting CSP LED structure. The luminous efficiency of the CSP LED 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 LED CSP structure directly encapsulated by traditional direct-mounted chips.

[0059] Please refer to Figure 4 , in the above embodiment, the material of the conductive post 300 can be selected from metal tin, metal gold or other conductive metals; preferably, the material of the conductive post 300 is selected from metal gold or an alloy including metal gold. The conductive post 300 made of gold has good ductility, is not easily expanded and broken by heat, and has good electrical conductivity and plasticity. Since the price of pure gold is relatively expensive, gold alloy can be used instead of pure gold. In one embodiment, by putting the whole wafer 60 into a planar hot press for hot pressing, the protruding part of the conductive post 300 is deformed into a cake shape and embedded with the high thermal conductivity and high reflectivity layer 200. On the one hand, the thickness of the LED flip-chip structure chip 10 can be reduced as much as possible, and on the other hand, the surface area of the end of the conductive post 300 can be increased as much as possible to further improve the heat dissipation performance and the connection stability with the substrate.

[0060] In the above embodiments, in the single-sided light-emitting LED CSP 02 prepared by the above packaging process, the inner wall surface of the reflective layer 40 is perpendicular to the fluorescent layer or forms an acute angle with the fluorescent layer. When the inner wall surface of the reflective layer 40 is perpendicular to the fluorescent layer, in the LED flip-chip structure chip 10, only the light transmitted towards the electrode surface 110 located at the top and the substrate surface 130 located at the bottom can be output to the outside, and the light transmitted towards the surrounding side surfaces cannot be output to the outside air; when the angle between the inner wall surface of the reflective layer 40 and the fluorescent layer is acute, in the LED flip-chip structure chip 10, not only the light transmitted towards the electrode surface 110 located at the top and the substrate surface 130 located at the bottom can be output to the outside, but also the light transmitted towards the surrounding side surfaces of the LED flip-chip structure chip 10 is reflected by the inner wall surface of the reflective layer 40 towards the direction of the fluorescent layer, and then can be successfully output to the outside; obviously, setting the angle between the inner wall surface of the reflective layer 40 and the fluorescent layer to be acute is more conducive to increasing the light transmission efficiency, thereby improving the luminous brightness of the single-sided light-emitting CSP LED 02.

[0061] Please refer to Figure 2 、 Figure 5 and Figure 6 ,Furthermore, in another embodiment of the present invention, before performing the above step S6, the following steps are further included: injecting a filling adhesive at the corner where the fluorescent film 20 and the LED flip-chip structure chip 10 are joined, and the filling adhesive is cured into an oblique angle shape and adsorbed on the surrounding side surfaces of the LED direct-chip 100 to form a filling layer 50. In this embodiment, in the single-sided light-emitting LED CSP 02 prepared by the packaging process of the present invention, the angle between the inner wall surface of the reflective layer 40 and the fluorescent layer is acute, and the refractive index of the transmission medium between the reflective layer 40 and the direct-chip is greater than the refractive index of air, which is more conducive to improving the light transmission efficiency. When the transmission medium between the reflective layer 40 and the direct-chip is air, the loss rate of the light transmitted towards the surrounding side surfaces of the LED flip-chip structure chip 10 is very high, and by introducing the filling layer 50, the loss of light during transmission can be greatly reduced. In one embodiment, the material of the light-transmitting layer is selected as transparent silicone, and the refractive index of the light-transmitting layer is designed to be 1.4 - 1.5. In order to increase the light transmission efficiency, the filling layer 50 can also be a film layer structure of other materials with a refractive index higher than air, and is not limited to selecting transparent silicone material.

[0062] In this embodiment, the reflective layer 40 also has high thermal conductivity, such that the fabricated single-sided light-emitting CSP LED 02 can dissipate heat not only from one side of the high thermal conductivity and high reflectivity layer 200, but also from the reflective layer 40 side. The composition of the reflective layer 40 can be the same as that of the high thermal conductivity and high reflectivity layer 200.

[0063] In one 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 inside the high thermal conductivity and high reflectivity layer 200 can be 75 um, 125 um, 150 um, 200 um, or any value therebetween; within this value range, the conductive post 300 does not affect the light-emitting area of the chip while being not easily bent or broken.

[0064] After the conductive post 300 is 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 post 300. The part of the conductive post 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. Designing the covering area to be not less than 50% enables the conductive post 300 to 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, and the relatively large surface area is conducive to the LED flip-chip structure chip 10 dissipating heat through the conductive post 300; designing the covering area to be not higher than 80% can avoid the situation where adjacent CSP LED structures affect each other due to the too-close solder joint positions when multiple five-sided light-emitting CSP LEDs 02 are welded to the substrate together.

[0065] 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 therebetween. 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. Additionally, since the part of the conductive post 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 cause 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, and 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.

[0066] In one embodiment, the high thermal conductivity and high reflectivity layer 200 includes transparent silica gel and white oxide. 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 alumina, zirconia, titanium dioxide or silica. The particle size of the white oxide is 0.1 - 10 μm, that is, the particle size of the white oxide can be 0.1 μm, 1 μm, 5 μm, 10 μm or any value between them. 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. Through a solenoid valve injector, the high thermal conductivity and high reflectivity glue is integrally coated 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 is connected into a whole on the wafer 60, and then dried and cured 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.

[0067] In step S5, it is necessary to first make the fluorescent film 20. The made fluorescent film 20 can be directly attached to the crystal mounting plate 80, and then multiple made LED flip-chip structures 10 are arranged on the fluorescent film 20 at intervals with the electrodes facing up. After heating, under the action of heat, the fluorescent film 20 will become soft and bond with the LED flip-chip structures 10, and then the fluorescent film 20 is cured again, and the LED flip-chip structures 10 will be tightly combined with the fluorescent film 20.

[0068] In one embodiment, the fluorescent film 20 includes transparent silica gel and phosphor. The fluorescent layer can be composed of a composite of a transparent silica gel layer and a phosphor layer, that is, the phosphor is coated on the surface of a cured transparent silica gel layer; or, the fluorescent layer is a film layer structure with a uniform thickness formed by uniformly mixing a proper proportion of transparent silica gel and phosphor and then curing. Preferably, the transparent silica gel in the fluorescent layer is a transparent secondary-cured silica gel. Compared with the primary-cured silica gel, the secondary-cured silica gel has stronger mechanical properties, such as higher hardness, which is more conducive to protecting the chip structure.

[0069] In one embodiment, the fluorescent film 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 to 30 μm, that is, the particle size of the phosphor powder can be 1 μm, 15 μm, 30 μm, or any value therebetween. If 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; if 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.

[0070] The manufacturing steps of the fluorescent film 20 include: mixing silica gel and phosphor powder and then stirring them by means of vacuum stirring, and then forming a fluorescent film 20 with a uniform cured thickness on the release paper by means of knife coating heating or pressing heating molding. The thickness of the fluorescent film 20 is 15 to 300 μm.

[0071] 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 virtue of 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 with 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.

[0072] The foregoing examples are merely illustrative and are used to explain some features of the method of the present invention. The appended claims are intended to claim the broadest scope possible, and the embodiments presented herein are merely illustrative of the 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 interpreted as being covered by the appended claims whenever possible.

Claims

1. Encapsulation process of a single-sided light-emitting CSP LED, characterized in that, it includes the following steps: S1: Provide a wafer, the wafer includes a number of LED flip-chip devices with electrodes on the top surface, and conductive posts are planted on the electrodes of the LED flip-chip devices; S2: Cover a top surface of the LED flip-chip device with a highly thermally conductive and highly reflective layer having a height lower than that of the conductive post, and the highly thermally conductive and highly reflective layer covers an area on the top surface of the LED flip-chip device where the conductive post is not planted; S3: Thermally press a 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; S4: Cut between adjacent LED flip-chip devices, and perform die casting to obtain single-chip LED flip-chip structure devices; S5: Provide a die placement board, attach a fluorescent film on the surface of the die placement board, and fixedly place multiple fabricated LED flip-chip structure devices with electrodes facing up at intervals on the fluorescent film; S6: Spray a reflective adhesive between adjacent LED flip-chip structure devices to form a reflective layer, and the reflective layer fills a gap between adjacent LED flip-chip structure devices and is connected to the highly thermally conductive and highly reflective layer as a whole; S7: Cut between adjacent LED flip-chip structure devices, and perform die casting to obtain a single-chip single-sided light-emitting CSP LED; wherein, the highly thermally conductive and highly reflective layer includes transparent silica gel and white oxide, the white oxide is selected from one or more of aluminum oxide, zirconium oxide, titanium dioxide or silicon dioxide, and the thickness of the highly thermally conductive and highly reflective layer is 20-50um; the reflective layer includes transparent silica gel and white oxide, the white oxide is selected from one or more of aluminum oxide, zirconium oxide, titanium dioxide or silicon dioxide; after the conductive post is thermally 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, and the axial cross-sectional diameter of the conductive post before being thermally pressed is 75-200um.

2. The encapsulation process according to claim 1, characterized in that, before the step S6, the following step is further included: spraying a filling adhesive at a corner where the fluorescent film and the LED flip-chip structure device are in contact, and the filling adhesive is in an oblique angle shape after curing and adsorbs on the peripheral side surfaces of the LED flip-chip device to form a filling layer.

3. The encapsulation process according to claim 1, characterized in that, in the step S3, by putting the whole wafer into a planar hot press for thermal pressing, the protruding part of the conductive post is deformed into a cake shape and is inlaid with the highly thermally conductive and highly reflective layer.

4. The encapsulation process according to claim 1, characterized in that, the weight ratio of transparent silica gel and white oxide in the highly thermally conductive and highly reflective layer is 1:0.3, and the particle size of the white oxide is 0.1-10um; and / or, the weight ratio of transparent silica gel and white oxide in the reflective layer is 1:0.3, and the particle size of the white oxide is 0.1-10um.

5. The encapsulation process according to claim 1, characterized in that, The fluorescent film comprises silica gel and phosphor powder, and the particle size of the phosphor powder is 1 to 30 μm.

6. The encapsulation process according to claim 5, characterized in that the manufacturing steps of the fluorescent film include: mixing silica gel and phosphor powder and stirring them by means of vacuum stirring, and then forming a fluorescent film with a uniform curing thickness on the release paper by means of scraping coating heating or pressing and heating forming, and the thickness of the fluorescent film is 15 to 300 μm.

7. The encapsulation process according to any one of claims 1 to 6, characterized in that the LED flip-chip is a blue light chip and comprises a gallium nitride layer and a sapphire substrate layer.

8. The encapsulation process according to any one of claims 1 to 6, characterized in that the conductive column is made of metal gold.

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