LED package structure and preparation method thereof

Abstract

The application provides an LED packaging structure and a preparation method thereof, the method comprising the following steps: respectively pretreating an AlN / diamond composite substrate and an LED chip, and preparing a metallization layer on the AlN / diamond composite substrate; obtaining an Au-20Sn alloy solder piece with the same size as the LED chip, and performing hot-pressing eutectic welding on the three to obtain a first-stage packaging structure; preparing a fluorescent ceramic sheet, setting the fluorescent ceramic sheet on the side of the LED chip away from the Au-20Sn alloy solder piece through low-temperature glass powder, and forming a gap between the fluorescent ceramic sheet and the LED chip, and obtaining the LED packaging structure after solidification treatment. The hot-pressing eutectic welding reduces the cavity rate of the solder layer, and further reduces the thermal resistance of the core heat conduction path; another heat dissipation channel is constructed through the fluorescent ceramic sheet, the chip junction temperature is significantly reduced, and the light efficiency and service life of the LED packaging structure are improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to an LED packaging structure and its fabrication method. Background Technology

[0002] Current LED packaging solutions mainly include: 1. COB (Chemical-on-Board) packaging with phosphor mixed with silicone directly coated on the chip surface. Due to the extremely low thermal conductivity of silicone (approximately 0.18 W / m·K), it becomes the main thermal resistance, causing the heat generated by the chip to be unable to dissipate in time, resulting in severe light decay, color coordinate drift, and shortened lifespan. Its power density is usually limited to below 200 W / cm²; 2. Remote phosphor packaging, which physically separates the phosphor layer from the LED chip. Although it improves the thermal stability of the phosphor to some extent, it increases the optical path, leading to luminous efficiency loss. Moreover, the heat dissipation path is long, and the thermal management problem has not been fundamentally solved; 3. Conventional ceramic substrate packaging, which uses alumina (Al2O3) or aluminum nitride (AlN) ceramic as the substrate. Although the thermal conductivity of the substrate itself (20-30 W / m·K) is better than that of resin, if phosphor silicone is still used, the problem of poor heat dissipation of the phosphor layer still exists.

[0003] As LEDs upgrade to higher power density, traditional packaging processes, due to their high thermal resistance and susceptibility to aging, have limited power density (typically ≤200W), which can no longer meet the needs of kilowatt-level industrial and special lighting. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an LED packaging structure and its preparation method, thereby solving the technical problem that the power density is limited due to the high thermal resistance and easy aging of traditional packaging processes in the prior art.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing an LED packaging structure, comprising the following steps: AlN / diamond composite substrate and several LED chips were pretreated respectively, and a metallization layer was prepared on the pretreated AlN / diamond composite substrate. Obtain Au-20Sn alloy solder sheets of the same size as LED chips, and perform hot-press eutectic bonding on the AlN / diamond composite substrate, several LED chips and several Au-20Sn alloy solder sheets to obtain a first-stage packaging structure. A fluorescent ceramic sheet is prepared, and a low-temperature glass powder is obtained. The fluorescent ceramic sheet is then placed on the side of the LED chip facing away from the Au-20Sn alloy solder sheet using the low-temperature glass powder, and a gap is formed between the fluorescent ceramic sheet and the LED chip to obtain a second-stage packaging structure. The second-stage packaging structure is then cured to obtain an LED packaging structure.

[0006] Furthermore, the steps of pre-processing the AlN / diamond composite substrate and the plurality of LED chips respectively include: The AlN / diamond composite substrate was subjected to acetone ultrasonic cleaning, alcohol cleaning and nitrogen drying in sequence. The acetone ultrasonic cleaning time was 12 min to 16 min and the alcohol cleaning time was 8 min to 12 min. A number of LED chips are subjected to argon plasma cleaning, wherein the power of the argon plasma cleaning is 100W~150W and the cleaning time is 3min~5min.

[0007] Furthermore, the metallization layer includes a Ti layer, a Ni layer, and an Au layer sequentially disposed from bottom to top on the AlN / diamond composite substrate. The thickness of the Ti layer is 40nm~60nm, the thickness of the Ni layer is 140nm~160nm, and the thickness of the Au layer is 490nm~510nm.

[0008] Furthermore, the step of performing thermo-pressed eutectic bonding on the AlN / diamond composite substrate, the plurality of LED chips, and the plurality of Au-20Sn alloy solder sheets to obtain the first-stage packaging structure includes: A plurality of LED chip arrays are disposed on the metallization layer, and the spacing between adjacent LED chips is 0.5mm~1.0mm; An Au-20Sn alloy solder sheet is disposed between the LED chip and the metallization layer to form an initial package structure; The initial packaging structure is placed in a thermocompression welding machine, and nitrogen gas is introduced into the thermocompression welding machine. The temperature inside the thermocompression welding machine is adjusted to a preset temperature at a preset heating rate, and the pressure inside the thermocompression welding machine is adjusted to a first preset pressure. After a first preset time, the first-stage packaging structure is obtained.

[0009] Furthermore, the preset heating rate is 8℃ / min~10℃ / min, the preset temperature is 320℃~340℃, the first preset pressure is 7MPa~9MPa, and the first preset time is 12s~18s.

[0010] Furthermore, the step of preparing the fluorescent ceramic sheet includes: Y3Al5O 12 :Ce³ + Yttrium oxide, aluminum oxide, cerium oxide, and sintering aids are mixed to form a mixture, and the mixture is ball-milled to obtain a mixed powder. The mixed powder is filled and sealed into an elastic mold, the elastic mold is placed in a high-pressure container filled with hydraulic oil, the pressure in the high-pressure container is adjusted to a second preset pressure, and the pressure is maintained for a second preset time before the blank is obtained in the elastic mold. The blank is subjected to vacuum sintering and double-sided polishing, and then cut into fluorescent ceramic sheets.

[0011] Furthermore, the Y3Al5O 12 :Ce³ + Ce³ + The doping concentration is 5%~15%.

[0012] Furthermore, the second preset pressure is 200MPa~300MPa, and the second preset time is 5min~10min.

[0013] Furthermore, the gap is ≤0.1mm.

[0014] In a second aspect, the present invention provides an LED packaging structure, which is prepared by the LED packaging structure preparation method described in the first aspect above.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: By selecting the AlN / diamond composite substrate, its high thermal conductivity significantly reduces the thermal resistance of the substrate; by selecting the Au-20Sn alloy solder sheet and combining it with the LED chip and the AlN / diamond composite substrate for hot-pressing eutectic bonding, the molten solder fully wets and fills all microscopic irregularities between the chip and the metallization layer, significantly reducing the void ratio of the solder layer formed by the Au-20Sn alloy solder sheet; and establishing a dense and continuous metal thermal conductivity channel between the LED chip and the AlN / diamond composite substrate, thus optimizing the interface. The surface-to-thermal contact reduces the thermal resistance of the solder layer. The combination of these two factors reduces the thermal resistance of the core heat conduction path from the LED chip to the external heat sink, improving heat dissipation efficiency. By replacing the traditional fluorescent silicone with the fluorescent ceramic sheet, the high thermal conductivity of the fluorescent ceramic sheet no longer hinders heat transfer. The heat from the LED chip is conducted to the fluorescent ceramic sheet through the gap and dissipated into the external environment. The heat from the phosphor can also be dissipated through the fluorescent ceramic sheet itself. This creates an additional heat dissipation channel in the original heat dissipation system, significantly reducing the chip junction temperature and improving the luminous efficacy and lifespan of the LED packaging structure. Attached Figure Description

[0016] Figure 1 This is a flowchart of the method for preparing the LED packaging structure in Embodiment 1 of the present invention; The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0017] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0018] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] Please see Figure 1 In a first aspect, Embodiment 1 of the present invention provides a method for preparing an LED packaging structure, comprising the following steps: S10: Pre-treat the AlN / diamond composite substrate and several LED chips respectively, and prepare a metallization layer on the pre-treated AlN / diamond composite substrate. Step S10 includes: S110: The AlN / diamond composite substrate is sequentially subjected to acetone ultrasonic cleaning, alcohol cleaning and nitrogen drying. The acetone ultrasonic cleaning time is 12min~16min and the alcohol cleaning time is 8min~12min. In this embodiment, the ultrasonic cleaning time with acetone is 15 minutes, and the cleaning time with alcohol is 10 minutes.

[0021] S120: Perform argon plasma cleaning on several LED chips, wherein the power of the argon plasma cleaning is 100W~150W and the cleaning time is 3min~5min; In this embodiment, the argon plasma cleaning power is 120W, and the argon plasma cleaning time is 4 minutes. The argon plasma cleaning removes oxides and organic contaminants from the chip electrode surface.

[0022] A Ti layer, a Ni layer, and an Au layer are sequentially deposited on the surface of the AlN / diamond composite substrate by magnetron sputtering, forming the Ti, Ni, and Au layers sequentially from bottom to top on the AlN / diamond composite substrate. Preferably, the thickness of the Ti layer is 40nm~60nm, the thickness of the Ni layer is 140nm~160nm, and the thickness of the Au layer is 490nm~510nm. In this embodiment, the thickness of the Ti layer is 50nm, the thickness of the Ni layer is 150nm, and the thickness of the Au layer is 500nm. This metallization layer provides a solder layer for subsequent hot-pressing eutectic bonding.

[0023] S20: Obtain Au-20Sn alloy solder sheets of the same size as LED chips, and perform hot-press eutectic bonding on the AlN / diamond composite substrate, a number of LED chips and a number of Au-20Sn alloy solder sheets to obtain a first-stage packaging structure; The Au-20Sn alloy is cut to the size of the LED chip, and the cut alloy is vacuum baked to remove gas to obtain the Au-20Sn alloy solder sheet. Preferably, the thickness of the Au-20Sn alloy solder sheet is 15μm-30μm. In this embodiment, the thickness of the Au-20Sn alloy solder sheet is 20μm. It can be understood that the Au-20Sn alloy solder sheet refers to a solder sheet in which the weight ratio of Au to Sn is 80:20.

[0024] Step S20 includes: S210: A plurality of the LED chip arrays are disposed on the metallization layer, wherein the spacing between adjacent LED chips is 0.5mm~1.0mm; S220: The Au-20Sn alloy solder sheet is disposed between the LED chip and the metallization layer to form an initial package structure; S230: The initial packaging structure is placed in a thermocompression welding machine, and nitrogen gas is introduced into the thermocompression welding machine. The temperature inside the thermocompression welding machine is adjusted to a preset temperature at a preset heating rate, and the pressure inside the thermocompression welding machine is adjusted to a first preset pressure. After a first preset time, the first stage packaging structure is obtained. Preferably, the preset heating rate is 8℃ / min~10℃ / min. By controlling the heating rate, the temperatures of the LED chip, the Au-20Sn alloy solder sheet, and the AlN / diamond composite substrate can rise synchronously and uniformly, avoiding excessive instantaneous thermal stress caused by the different thermal expansion coefficients of the materials. This prevents the LED chip from cracking or the AlN / diamond composite substrate from warping. It also avoids the situation where the outer layer of the solder sheet melts rapidly while the inner layer has not yet reached the required temperature, causing the volatile substances inside to vaporize rapidly and resulting in solder "splatter," which could lead to voids or poor connections.

[0025] In this embodiment, the preset heating rate is 10℃ / min, the preset temperature is 330℃, the first preset pressure is 8MPa, and the first preset time is 15s. It should be noted that because several LED chips are operated on simultaneously, the pressure uniformity among the LED chips is ≤±0.5MPa, ensuring consistent welding quality.

[0026] S30: Prepare a fluorescent ceramic sheet and obtain low-temperature glass powder. Use the low-temperature glass powder to place the fluorescent ceramic sheet on the side of the LED chip facing away from the Au-20Sn alloy solder sheet, and form a gap between the fluorescent ceramic sheet and the LED chip to obtain a second-stage packaging structure. Perform a curing treatment on the second-stage packaging structure to obtain an LED packaging structure. The interconnect structure includes a copper interconnect layer and a buffer bonding layer.

[0027] Specifically, step S30 includes: S310: Y3Al5O 12 :Ce³ + Yttrium oxide, aluminum oxide, cerium oxide, and sintering aids are mixed to form a mixture, and the mixture is ball-milled to obtain a mixed powder. The Y3Al5O 12 :Ce³ + Ce³ + The doping concentration is 5%~15%, and the Ce³ content is controlled by... + The appropriate doping concentration avoids both insufficient luminescence intensity due to excessively low concentration and the "concentration quenching" effect caused by excessively high concentration. After ball milling, the particle size of the mixed powder is ≤1μm. After obtaining the mixed powder, it undergoes vacuum drying at 80℃ for 12 hours.

[0028] S320: The mixed powder is filled and sealed into an elastic mold, the elastic mold is placed in a high-pressure container filled with hydraulic oil, the pressure in the high-pressure container is adjusted to a second preset pressure, and the pressure is maintained for a second preset time, and then the blank is obtained in the elastic mold; Preferably, the second preset pressure is 200MPa~300MPa, and the second preset time is 5min~10min. In this embodiment, the second preset pressure is 250MPa, and the second preset time is 8min. Using hydraulic oil as the pressure transmission medium, the same pressure is applied uniformly to the powder within the elastic mold from different directions. This uniform pressure results in a denser powder buildup, achieving a higher initial density than unidirectional pressing. In this embodiment, the density of the green body is ≥65%. This lays the foundation for obtaining extremely high density (≥99.5%) during subsequent sintering, significantly reducing sintering shrinkage deformation and internal defects, eliminating stress concentration, and the isotropic pressure avoids deformation, warping, or cracking after sintering due to uneven density, resulting in higher quality fluorescent ceramic sheets. It should be noted that after obtaining the blank, the blank is subjected to a debinding process. In this embodiment, the debinding process is as follows: the blank is heated in an environment of 300℃~600℃ to slowly and uniformly decompose the organic binder in the blank, so as to avoid the subsequent vacuum sintering process causing the organic matter to burn or carbonize rapidly, generating a large amount of gas and pressure in the blank, which would cause the blank to bubble, crack or form pores.

[0029] S330: The blank is subjected to vacuum sintering and double-sided polishing, and then cut into fluorescent ceramic sheets; Preferably, the vacuum sintering temperature is 1750℃~1850℃. By controlling the vacuum sintering temperature, it is possible to avoid incomplete densification and turbidity of the obtained fluorescent ceramic sheet due to excessively low temperature, and to avoid abnormal grain growth, the formation of scattering centers, and reduced transparency due to excessively high temperature. The vacuum sintering time is 10h~15h. In this embodiment, the vacuum sintering temperature is 1800℃ and the vacuum sintering time is 12h. It should be noted that after the vacuum sintering process, nitrogen gas needs to be introduced for protection during the cooling stage to prevent oxidation. After the double-sided polishing process, the surface roughness of the blank is ≤0.1μm. Preferably, the thickness of the fluorescent ceramic sheet is 0.3mm to 0.8mm. By controlling the thickness of the fluorescent ceramic sheet, engineering optimization parameters such as light conversion efficiency, mechanical strength, and thermal resistance can be considered. If the thickness is too small, the fluorescence conversion is insufficient and the sheet is fragile; if the thickness is too large, the loss of light propagation inside (absorption and scattering) will increase, and thermal resistance may also increase. In this embodiment, the thickness of the fluorescent ceramic sheet is 0.5mm, and its density is ≥99.5%. The softening point of the low-temperature glass powder is 250℃ to 300℃. The low-temperature glass powder can be used to attach the fluorescent ceramic sheet to the substrate and form a gap between it and the LED chip. The curing temperature is 300℃, and the curing time is 30 minutes to achieve curing of the low-temperature glass powder. Preferably, the gap is ≤0.1mm. In this embodiment, the gap is 0.1mm. By setting the gap, rigid contact between the fluorescent ceramic sheet and the LED chip can be avoided, thereby reducing thermal stress.

[0030] By selecting the AlN / diamond composite substrate, its high thermal conductivity significantly reduces the substrate's thermal resistance. By selecting the Au-20Sn alloy solder sheet and performing hot-press eutectic bonding with the LED chip and the AlN / diamond composite substrate, the molten solder fully wets and fills all microscopic irregularities between the chip and the metallization layer, significantly reducing the void ratio of the solder layer formed by the Au-20Sn alloy solder sheet. This establishes a dense and continuous metal thermal conductivity channel between the LED chip and the AlN / diamond composite substrate, optimizing interfacial thermal contact and reducing the void ratio of the solder layer. The combination of these two factors reduces the thermal resistance of the core heat conduction path from the LED chip to the external heat sink, thus improving heat dissipation efficiency. By replacing the traditional fluorescent silicone with the fluorescent ceramic sheet, the high thermal conductivity of the fluorescent ceramic sheet no longer hinders heat transfer. The heat from the LED chip is conducted to the fluorescent ceramic sheet through the gap and dissipated into the external environment. The heat from the phosphor can also be dissipated through the fluorescent ceramic sheet itself. This creates an additional heat dissipation channel in the original heat dissipation system, significantly reducing the chip junction temperature and improving the luminous efficacy and lifespan of the LED packaging structure.

[0031] Embodiment 2 of the present invention provides a method for preparing an LED packaging structure, which differs from the method for preparing an LED packaging structure described in Embodiment 1 in that... The preset temperature is 320℃.

[0032] Embodiment 3 of the present invention provides a method for preparing an LED packaging structure, which differs from the method for preparing an LED packaging structure described in Embodiment 1 in that... The preset temperature is 340℃.

[0033] Embodiment 4 of the present invention provides a method for preparing an LED packaging structure, which differs from the method for preparing an LED packaging structure described in Embodiment 1 in that... The first preset pressure is 7 MPa.

[0034] Embodiment 5 of the present invention provides a method for fabricating an LED packaging structure, which differs from the method for fabricating an LED packaging structure described in Embodiment 1 in that... The first preset pressure is 9 MPa.

[0035] Embodiment 6 of the present invention provides a method for preparing an LED packaging structure, which differs from the method for preparing an LED packaging structure described in Embodiment 1 in that... The first preset time is 12 seconds.

[0036] Embodiment 7 of the present invention provides a method for fabricating an LED packaging structure, which differs from the method for fabricating an LED packaging structure described in Embodiment 1 in that... The first preset time is 18 seconds.

[0037] Comparative Example 1 of this invention provides a method for fabricating an LED packaging structure, which differs from the method for fabricating the LED packaging structure described in Example 1 in that... The preset temperature is 300℃.

[0038] Comparative Example 2 of this invention provides a method for fabricating an LED packaging structure, which differs from the method for fabricating an LED packaging structure described in Example 1 in that... The preset temperature is 360℃.

[0039] Comparative Example 3 of this invention provides a method for fabricating an LED packaging structure, which differs from the method for fabricating an LED packaging structure described in Example 1 in that... The first preset pressure is 5 MPa.

[0040] Comparative Example 4 of this invention provides a method for fabricating an LED packaging structure, which differs from the method for fabricating an LED packaging structure described in Example 1 in that... The first preset pressure is 11 MPa.

[0041] Comparative Example 5 of this invention provides a method for fabricating an LED packaging structure, which differs from the method for fabricating an LED packaging structure described in Example 1 in that... The first preset time is 10 seconds.

[0042] Comparative Example 6 of this invention provides a method for fabricating an LED packaging structure, which differs from the method for fabricating an LED packaging structure described in Example 1 in that... The first preset time is 20 seconds.

[0043] Comparative Example 7 of the present invention provides a method for fabricating an LED packaging structure, which differs from the method for fabricating an LED packaging structure described in Example 1 in that... The gap is 0.2 mm.

[0044] Comparative Example 8 of this invention provides a method for fabricating an LED packaging structure, which differs from the method for fabricating an LED packaging structure described in Example 1 in that... It uses fluorescent adhesive COB encapsulation.

[0045] Comparative Example 9 of this invention provides a method for fabricating an LED packaging structure, which differs from the method for fabricating an LED packaging structure described in Example 1 in that... It uses conventional ceramic substrate packaging.

[0046] LED packaging structures were prepared based on the LED packaging structure preparation methods described in Examples 1-7 and Comparative Examples 1-9 of this invention. Steady-state thermal resistance and chip junction temperature were tested (according to GB / 2423.1-2008 standard, temperature was measured after 12 hours of continuous operation at 1000W power using an infrared thermal imager (accuracy ±0.1℃) and a T3ster thermal resistance tester; the test points were the chip center and the substrate edge, and the data were averaged after three parallel tests). Light decay was also tested (according to IEC60068-2-2 standard, high-temperature aging test was conducted; after 2000 hours under extreme stress conditions of 150℃ and 1000W, the light decay rate was obtained through its luminous flux maintenance rate) and lifetime test (according to IES LM-80-20 standard, long-term luminous flux maintenance test was conducted; after 10000 hours of continuous operation at an ambient temperature of 85℃ and a drive current of 700mA, the luminous flux maintenance rate was obtained, and based on this data, according to IES... The L70 expected lifetime was calculated using the TM-21-19 recommended method under a typical application scenario (ambient temperature 40℃), and the test results are shown in Table 1 below: Table 1 , As can be seen from the table, by controlling the various process parameters, the prepared LED packaging structure can be ensured to have reduced thermal resistance and a longer service life. Compared with the traditional preparation method, the various indicators are significantly improved.

[0047] Secondly, Embodiment 8 of the present invention provides an LED packaging structure, which is prepared by the LED packaging structure preparation method described in the above embodiments.

[0048] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0049] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for fabricating an LED packaging structure, characterized in that, Includes the following steps: AlN / diamond composite substrate and several LED chips were pretreated respectively, and a metallization layer was prepared on the pretreated AlN / diamond composite substrate. Obtain Au-20Sn alloy solder sheets of the same size as LED chips, and perform hot-press eutectic bonding on the AlN / diamond composite substrate, several LED chips and several Au-20Sn alloy solder sheets to obtain a first-stage packaging structure. A fluorescent ceramic sheet is prepared, and a low-temperature glass powder is obtained. The fluorescent ceramic sheet is then placed on the side of the LED chip facing away from the Au-20Sn alloy solder sheet using the low-temperature glass powder, and a gap is formed between the fluorescent ceramic sheet and the LED chip to obtain a second-stage packaging structure. The second-stage packaging structure is then cured to obtain an LED packaging structure.

2. The method for preparing the LED packaging structure according to claim 1, characterized in that, The steps of pre-processing the AlN / diamond composite substrate and the LED chips respectively include: The AlN / diamond composite substrate was sequentially subjected to ultrasonic cleaning with acetone, cleaning with alcohol, and drying with nitrogen. The ultrasonic cleaning with acetone lasted for 12 to 16 minutes, and the cleaning with alcohol lasted for 8 to 12 minutes. A number of LED chips are subjected to argon plasma cleaning, wherein the power of the argon plasma cleaning is 100W~150W and the cleaning time is 3min~5min.

3. The method for preparing the LED packaging structure according to claim 1, characterized in that, The metallization layer includes a Ti layer, a Ni layer and an Au layer disposed sequentially from bottom to top on the AlN / diamond composite substrate. The thickness of the Ti layer is 40nm~60nm, the thickness of the Ni layer is 140nm~160nm, and the thickness of the Au layer is 490nm~510nm.

4. The method for preparing the LED packaging structure according to claim 1, characterized in that, The step of performing hot-pressing eutectic bonding on the AlN / diamond composite substrate, the plurality of LED chips, and the plurality of Au-20Sn alloy solder sheets to obtain the first-stage packaging structure includes: A plurality of LED chip arrays are disposed on the metallization layer, and the spacing between adjacent LED chips is 0.5mm~1.0mm; An Au-20Sn alloy solder sheet is disposed between the LED chip and the metallization layer to form an initial package structure; The initial packaging structure is placed in a thermocompression welding machine, and nitrogen gas is introduced into the thermocompression welding machine. The temperature inside the thermocompression welding machine is adjusted to a preset temperature at a preset heating rate, and the pressure inside the thermocompression welding machine is adjusted to a first preset pressure. After a first preset time, the first-stage packaging structure is obtained.

5. The method for preparing the LED packaging structure according to claim 4, characterized in that, The preset heating rate is 8℃ / min~10℃ / min, the preset temperature is 320℃~340℃, the first preset pressure is 7MPa~9MPa, and the first preset time is 12s~18s.

6. The method for preparing the LED packaging structure according to claim 1, characterized in that, The steps for preparing the fluorescent ceramic sheet include: Y3Al5O 12 :Ce³ + Yttrium oxide, aluminum oxide, cerium oxide, and sintering aids are mixed to form a mixture, and the mixture is ball-milled to obtain a mixed powder. The mixed powder is filled and sealed into an elastic mold, the elastic mold is placed in a high-pressure container filled with hydraulic oil, the pressure in the high-pressure container is adjusted to a second preset pressure, and the pressure is maintained for a second preset time before the blank is obtained in the elastic mold. The blank is subjected to vacuum sintering and double-sided polishing, and then cut into fluorescent ceramic sheets.

7. The method for preparing the LED packaging structure according to claim 6, characterized in that, The Y3Al5O 12 :Ce³ + Ce³ + The doping concentration is 5%~15%.

8. The method for preparing the LED packaging structure according to claim 6, characterized in that, The second preset pressure is 200MPa~300MPa, and the second preset time is 5min~10min.

9. The method for preparing the LED packaging structure according to claim 1, characterized in that, The gap is ≤0.1mm.

10. An LED packaging structure, characterized in that, The LED packaging structure is prepared according to the method for preparing the LED packaging structure as described in any one of claims 1 to 9.

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