Flip LED chip and its grinding method and grinding system
By applying a wax layer to protect the metal bumps during the polishing process of flip-chip LEDs, the problem of chip cracking during the polishing process of flip-chip LEDs was solved, achieving high yield and low cost production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGXI ZHAO CHI SEMICON CO LTD
- Filing Date
- 2024-11-26
- Publication Date
- 2026-06-12
AI Technical Summary
In the existing process of polishing flip-chip LEDs, the large number and narrow spacing of metal bumps make it easy for chips to crack during polishing, which makes it difficult to meet the production requirements of high yield.
By applying wax to the wafer, the diffusion and filling of the wax are controlled to form a wax layer that protects the metal bumps. The wax layer disperses stress and controls the outward expansion distance, thereby reducing the breakage rate during the grinding process.
This significantly reduced the chip breakage rate during grinding, improved product yield, and lowered production costs.
Smart Images
Figure CN119427195B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of LED chip fabrication methods, and more particularly to a flip-chip LED chip and its polishing method and system. Background Technology
[0002] Flip-chip LEDs are manufactured by bonding the electrodes to a package substrate, typically using metal bonding. However, as LED chips become increasingly functional and miniaturized, metal bonding is no longer sufficient. This has led to the development of a newer process called bump bonding, where multiple metal bumps are formed on the pads of the flip-chip for later connection to the package substrate. However, this bump bonding process presents significant challenges to subsequent chip fabrication processes (thinning, polishing, etc.). In particular, existing flip-chip LEDs have a large number of bumps with very narrow spacing. For example, a 4-inch wafer with a diameter of 50mm can accommodate 8988 flip-chips, while the number of metal bumps is 35952, with adjacent bumps only 10μm to 20μm apart. This results in poor stress uniformity during masking, making the wafer highly susceptible to cracking. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to provide a method for grinding flip-chip LEDs, which can significantly reduce the chip breakage rate and improve the yield.
[0004] The technical problem that this invention also aims to solve is to provide a polishing system for flip-chip LEDs, which can significantly reduce the chip breakage rate and improve the yield.
[0005] Another technical problem that this invention aims to solve is to provide a flip-chip LED.
[0006] To address the above problems, this invention discloses a method for grinding flip-chip LEDs, comprising:
[0007] A wafer is loaded onto a first carrier, wherein the wafer includes a first side and a second side opposite to each other, the first side is provided with a plurality of flip-chip LEDs, each flip-chip LED having at least two metal bumps formed thereon, and the second side of the wafer contacts the first carrier;
[0008] Wax is applied to the first side; during waxing, the first carrier is driven to remain stationary for a first preset time, and then rotated for a second preset time, so that the wax diffuses on the first side and the cross-sectional area of the diffused wax is smaller than the cross-sectional area of the wafer, thus obtaining a waxed wafer;
[0009] The waxed wafer is loaded onto a second carrier and a preset pressure is applied at a preset temperature to fill the gaps between the metal bumps with wax and to extend the wax beyond the outer edge of the wafer by a preset distance. The wafer is then cooled to form a wax layer, resulting in a wafer to be ground. The preset temperature is greater than the melting point of the wax.
[0010] The wafer to be ground is ground.
[0011] As an improvement to the above technical solution, in the step of applying wax to the first side; during waxing, the first carrier is driven to remain stationary for a first preset time, and then rotated for a second preset time, so that the wax diffuses on the first side and the cross-sectional area of the diffused wax is smaller than the cross-sectional area of the wafer, to obtain a waxed wafer, the amount of wax applied is calculated according to the following formula:
[0012] M=k1πρh(R+l) 2 -ρNV
[0013] Where M is the amount of wax applied to a single wafer, ρ is the density of the wax, R is the radius of the wafer, l is the preset distance by which the wax extends beyond the outer edge of the wafer, N is the total number of metal bumps on a single wafer, V is the volume of a single metal bump, and k1 is a constant with a value ranging from 0.95 to 0.99.
[0014] As an improvement to the above technical solution, in the step of loading the waxed wafer onto a second carrier and applying a preset pressure at a preset temperature to fill the gaps between the metal bumps with wax and to extend the wax beyond the outer edge of the wafer by a preset distance, cooling to form a wax layer, and obtaining the wafer to be ground, the preset distance is calculated according to the following formula:
[0015] l=k2R 0.15
[0016] Where l is the preset distance of the wax extending beyond the outer edge of the wafer, R is the radius of the wafer, and k2 is a constant with a value ranging from 1.7 to 1.8.
[0017] As an improvement to the above technical solution, in the step of applying wax to the first side; during waxing, the first carrier is driven to remain stationary for a first preset time, and then rotated for a second preset time, so that the wax diffuses on the first side, and the cross-sectional area of the diffused wax is smaller than the cross-sectional area of the wafer, to obtain a waxed wafer:
[0018] When applying wax, first keep the first carrier stationary for 1 to 3 seconds, and then drive the first carrier to rotate at a speed of 50 to 80 rpm for 15 to 20 seconds.
[0019] After the waxing is stopped, the first carrier is driven to rotate at a speed of 5 rpm to 20 rpm for 1 to 5 seconds to allow the wax to spread on the first side.
[0020] As an improvement to the above technical solution, in the step of applying wax to the first side; when applying wax, the first carrier is driven to remain stationary for a first preset time, and then rotated for a second preset time, so that the wax diffuses on the first side and the cross-sectional area of the diffused wax is smaller than the cross-sectional area of the wafer to obtain a waxed wafer: the temperature of the wax is 80℃~120℃, and the wax is sprayed in the central area of the first side.
[0021] As an improvement to the above technical solution, in the step of loading the waxed wafer onto the second carrier and applying a preset pressure at a preset temperature to fill the gaps between the metal bumps with wax and to extend the wax beyond the outer edge of the wafer by a preset distance, cooling to form a wax layer, and obtaining the wafer to be ground, the preset pressure is 15MPa to 25MPa, the preset temperature is 100℃ to 150℃, and the time for applying the preset pressure is 150s to 250s.
[0022] As an improvement to the above technical solution, in the step of applying wax to the first side; during waxing, the first carrier is driven to remain stationary for a first preset time, and then rotated for a second preset time, so that the wax diffuses on the first side and the cross-sectional area of the diffused wax is smaller than the cross-sectional area of the wafer to obtain a waxed wafer: the cross-sectional area of the diffused wax is 20% to 45% of the cross-sectional area of the wafer.
[0023] As an improvement to the above technical solution, the first carrier is a vacuum carrier disk, and the second carrier is a ceramic carrier disk.
[0024] Accordingly, the present invention also discloses a polishing system for flip-chip LEDs, comprising:
[0025] A wafer providing unit is used to provide a wafer, the wafer including a first side and a second side opposite to each other, the first side having a plurality of flip-chip LEDs, each flip-chip LED having at least two metal bumps formed thereon;
[0026] A first carrier is used to carry the wafer and drive the wafer to rotate or remain stationary; a second side of the wafer contacts the first carrier;
[0027] A waxing unit is used to apply wax to the first side of the wafer. During waxing, the first carrier is driven to remain stationary for a first preset time and then rotate for a second preset time so that the wax diffuses on the first side and the cross-sectional area of the diffused wax is smaller than the cross-sectional area of the wafer, thus obtaining a waxed wafer.
[0028] A second carrier is used to hold the waxed wafer and apply a preset pressure at a preset temperature to fill the gaps between the metal bumps with wax, and to extend the wax beyond the outer edge of the wafer by a preset distance, thus obtaining a wafer to be ground; and
[0029] A grinding unit is used to grind the wafer to be ground.
[0030] Accordingly, the present invention also discloses a flip-chip LED, which is ground by the above-described flip-chip LED grinding method.
[0031] Implementing this invention has the following beneficial effects:
[0032] In one embodiment of the present invention, a method for polishing flip-chip LEDs involves first applying wax to the first side of a flip-chip LED on a wafer. The wax is then diffused by controlling the stationary and rotating motion of a first carrier, ensuring the diffused cross-sectional area is smaller than the wafer's cross-sectional area. A preset pressure is then applied at a preset temperature to fill the gaps between the metal bumps, extending the wax beyond a preset distance from the wafer's outer edge. Finally, the wafer is polished. Based on this polishing method, firstly, by controlling the movement of the first carrier during wax application and by controlling the pressure and temperature on the waxed wafer on the second carrier, the wax can fully coat the metal bumps, providing effective protection, dispersing stress, reducing the damage to the wafer caused by cutting forces during polishing, and lowering the breakage rate. Secondly, by controlling the wax to extend beyond the wafer's outer edge by a preset distance, the wax expands outwards, reducing damage to the wafer's outer edge during polishing, significantly lowering the breakage rate, improving product yield, and reducing production costs. Attached Figure Description
[0033] Figure 1 This is a flowchart of a method for grinding flip-chip LEDs according to an embodiment of the present invention. Detailed Implementation
[0034] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Furthermore, it should be understood that the specific embodiments described herein are merely for explaining this application and are not intended to limit this application.
[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.
[0036] The following disclosure provides numerous different embodiments or examples for implementing various structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.
[0037] See Figure 1 This invention discloses a method for grinding flip-chip LEDs, which includes the following steps:
[0038] S1: Load the wafer into the first carrier;
[0039] S2: Apply wax to the first side; when applying wax, drive the first carrier to stand still for a first preset time, and then rotate for a second preset time, so that the wax diffuses on the first side and the cross-sectional area of the diffused wax is smaller than the cross-sectional area of the wafer, thus obtaining a waxed wafer;
[0040] S3: The waxed wafer is loaded onto the second carrier and a preset pressure is applied at a preset temperature to fill the gaps between the metal bumps with wax and to extend the wax beyond the outer edge of the wafer by a preset distance. The wafer is then cooled to form a wax layer, and the wafer to be ground is obtained.
[0041] S4: Grind the wafer to be ground.
[0042] Specifically, the wafer includes a first side and a second side opposite to each other. A plurality of flip-chip LEDs are disposed on the first side, and each flip-chip LED has at least two metal bumps formed on it. Preferably, each flip-chip LED has four metal bumps. In this embodiment, the wafer has a large number of metal bumps with small spacing, making grinding difficult.
[0043] Specifically, based on the aforementioned polishing method, firstly, by controlling the movement of the first carrier during waxing and controlling the pressure and temperature on the waxed wafer on the second carrier, the wax can effectively coat the metal bumps, forming a good protective wax layer after cooling. This results in a more uniform stress distribution during polishing, reducing the damage to the wafer caused by cutting forces and significantly lowering the breakage rate. Secondly, by controlling the wax to extend beyond a predetermined distance from the outer edge of the wafer, i.e., wax expansion, damage to the outer edge of the wafer can be reduced during polishing, significantly lowering the breakage rate, improving product yield, and reducing production costs.
[0044] Specifically, in step S1, the second side of the wafer contacts the first carrier to apply wax to the flip-chip LED on the first side. Specifically, the first carrier can be a vacuum carrier disk commonly used in the art, but is not limited thereto.
[0045] Specifically, in step S2, the amount of wax applied can be determined based on common knowledge known to those skilled in the art. For example, for a 2-inch wafer (50mm in diameter), the amount of wax applied is 0.32g to 0.4g, but it is not limited to this. Preferably, in one embodiment, the amount of wax applied is calculated according to the following formula:
[0046] M=k1πρh(R+l) 2 -ρNV
[0047] Where M is the amount of wax applied to a single wafer, ρ is the density of the wax, R is the radius of the wafer, l is the preset distance by which the wax extends beyond the outer edge of the wafer, N is the total number of metal bumps on a single wafer, V is the volume of a single metal bump, and k1 is a constant with a value ranging from 0.95 to 0.99.
[0048] It should be noted that existing technologies for polishing flip-chip LEDs with metal bumps often apply wax using the same amount as conventional flip-chip LEDs (without metal bumps). Through extensive research, the inventors discovered that the conventional, empirically applied wax amount is generally too small, resulting in insufficient wax penetration of the metal bumps and a high breakage rate. Conversely, blindly increasing the wax amount can lead to several issues: too little wax application results in insufficient penetration of the metal bumps and inadequate expansion; too much wax application leads to excessive expansion, causing insufficient contact between the polishing device and the wafer during polishing, reducing polishing accuracy, and increasing wax waste. Therefore, this invention employs the method described above to precisely control the wax application amount, significantly reducing the breakage rate.
[0049] Specifically, in one embodiment, the temperature of the wax is controlled to be between 80°C and 120°C to give the wax suitable fluidity. This not only facilitates the application of the wax to the wafer in the form of spray wax, but also allows the wax to diffuse within a controllable range through the stationary and rotating motion of the first carrier, providing a good foundation for the subsequent full wetting of the metal bumps by thermal pressure. Exemplarily, the wax temperature is 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, or 115°C, but is not limited thereto. Preferably, it is between 90°C and 110°C, more preferably between 95°C and 105°C.
[0050] Specifically, in one embodiment, in step S2, wax can be applied to the first side of the wafer by processes such as spin coating or spray coating, but is not limited thereto. Preferably, in one embodiment, wax is applied to the first side of the wafer by a wax spraying process, and the wax is sprayed in the central area of the first side.
[0051] Specifically, in one embodiment, in step S2, the first preset time for the first carrier to remain stationary is 1s to 10s, exemplarily 1s, 3s, 5s, 8s, or 9s, but not limited thereto. The second preset time for the first carrier to rotate is 10s to 30s, exemplarily 12s, 14s, 16s, 18s, 20s, 22s, 24s, 26s, or 28s, but not limited thereto. Based on the above time control, the wax can be partially diffused on the wafer surface, but not beyond the edge of the wafer.
[0052] Preferably, in one embodiment, in step S2: when applying wax, the first carrier is first made to stand still for 1s to 3s, and then the first carrier is driven to rotate at a speed of 50rpm to 80rpm for 15s to 20s; after the waxing is stopped, the first carrier is driven to rotate at a speed of 5rpm to 20rpm for 1s to 5s, so that the wax can spread on the first side.
[0053] Specifically, by controlling the amount of wax applied, the temperature of the wax, and the motion state of the first carrier during the waxing process, the cross-sectional area of the diffused wax can be 20% to 45% of the cross-sectional area of the wafer, thereby creating favorable conditions for the subsequent hot pressing to fully wet the metal bumps and form an outward expansion.
[0054] Specifically, in one embodiment, in step S3, the preset temperature applied to the waxed wafer is higher than the melting point of the wax, causing the wax to flow. A preset pressure is applied to ensure the wax flows sufficiently, filling the gaps between the metal bumps and achieving thorough wetting of the metal bumps, resulting in outward expansion. Specifically, the preset temperature can be 100℃ to 150℃, exemplarily 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, or 145℃, but is not limited to these. Preferably, it is 110℃ to 130℃. The preset pressure is 15MPa to 25MPa, exemplarily 15.5MPa, 17MPa, 18.5MPa, 20MPa, 21.5MPa, 23MPa, or 24.5MPa, but is not limited to these. Preferably, it is 18MPa to 21MPa. Specifically, the hot pressing time is 150s to 250s, exemplarily 160s, 180s, 200s, 220s or 240s, but not limited thereto. Preferably it is 180s to 220s.
[0055] Specifically, the second carrier may be a ceramic carrier plate, but is not limited to this.
[0056] Specifically, in one embodiment, in step S3, the preset distance by which the wax extends beyond the outer edge of the wafer is calculated according to the following formula:
[0057] l=k2R 0.15
[0058] Where l is the preset distance of the wax extending beyond the outer edge of the wafer in mm, R is the radius of the wafer in mm, and k2 is a constant with a value ranging from 1.7 to 1.8.
[0059] It should be noted that if the expansion is too small, the pressure on the wafer edge will be relatively high, making it prone to breakage. If the expansion is too large, the grinding (thinning, polishing) process will reduce the grinding effect of the grinding device on the wafer, resulting in uneven grinding and decreased grinding efficiency. Therefore, based on extensive research, this invention rationally calculates the preset expansion distance to meet the calculation requirements of different wafer sizes, further improving yield, reducing wax waste, and lowering production costs.
[0060] Specifically, in step S4, grinding may include, but is not limited to, grinding thinning, polishing processes, etc. Those skilled in the art can select the appropriate process based on the specific requirements.
[0061] The present invention will be further described below with reference to specific embodiments:
[0062] Example
[0063] This embodiment provides a method for grinding flip-chip LEDs, which includes the following steps:
[0064] (1) Load the wafer onto the vacuum carrier disk. The wafer is a 4-inch wafer with a radius of 50 mm. Its first side has 8988 flip-chip LEDs, and the flip-chip LEDs have 35952 metal bumps. Make the second side of the wafer contact with the vacuum carrier disk.
[0065] (2) Spray wax on the central area of the first side;
[0066] The amount of wax sprayed is M = k1πρh(R+l). 2 -ρNV=0.98×π×0.9g / cm 3 ×0.007cm×(5cm+0.307cm) 2 -0.9g / cm 3 ×39592×1.99×10 -6 cm -3 =0.483g
[0067] l=k2R 0.15 =1.73 × 50 0.15 =3.11mm =0.311mm
[0068] During wax spraying, the ceramic carrier plate is first allowed to remain stationary for 2 seconds, then rotated at 60 rpm for 20 seconds. After stopping the wax spraying, the ceramic carrier plate is rotated at 10 rpm for 2 seconds. After this step, the cross-sectional area of the diffused wax is 35.5% of the cross-sectional area of the wafer.
[0069] (3) Load the waxed wafer onto the ceramic disk and pressurize it at 120℃ and 20MPa for 200s so that the wax fills the gap between the metal bumps and extends 3.11mm beyond the outer edge of the wafer. Cool to form a wax layer and obtain the wafer to be ground.
[0070] (4) Grind the wafer to be ground.
[0071] Comparative Example 1
[0072] This comparative example provides a method for grinding a flip-chip LED, which includes:
[0073] (1) Load the wafer onto the vacuum carrier disk. The wafer is a 4-inch wafer with a radius of 50 mm. Its first side has 8988 flip-chip LEDs, and the flip-chip LEDs have 35952 metal bumps. Make the second side of the wafer contact with the vacuum carrier disk.
[0074] (2) Spray wax on the central area of the first side;
[0075] The amount of wax sprayed is 0.35g. During wax spraying, the vacuum tray does not rotate; after wax spraying, it rotates at 3000rpm for 20s.
[0076] (3) Grind the wax-sprayed wafer.
[0077] Comparative Example 2
[0078] This comparative example provides a method for grinding a flip-chip LED, which includes:
[0079] (1) Load the wafer onto the vacuum carrier disk. The wafer is a 4-inch wafer with a radius of 50 mm. Its first side has 8988 flip-chip LEDs, and the flip-chip LEDs have 35952 metal bumps. Make the second side of the wafer contact with the vacuum carrier disk.
[0080] (2) Spray wax in the central area of the first side to obtain a waxed wafer;
[0081] The amount of wax sprayed is 0.35g. During wax spraying, the vacuum tray does not rotate; after wax spraying, it rotates at 3000rpm for 20s.
[0082] (3) Load the waxed wafer onto the second carrier and pressurize it at 30°C for 80s to obtain the wafer to be polished;
[0083] (4) Grind the wafer to be ground.
[0084] According to statistics, the fragmentation rate in the example was 0%, the fragmentation rate in Comparative Example 1 was 57.14%, and the fragmentation rate in Comparative Example 2 was 14.29%. Therefore, it can be seen that the present invention significantly reduces the fragmentation rate.
[0085] In the description of this specification, the 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 the described embodiment or example is included in at least one embodiment or example of this application. 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.
[0086] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.
Claims
1. A method for grinding flip-chip LEDs, characterized in that, include: A wafer is loaded onto a first carrier, wherein the wafer includes a first side and a second side opposite to each other, the first side is provided with a plurality of flip-chip LEDs, each flip-chip LED having at least two metal bumps formed thereon, and the second side of the wafer contacts the first carrier; Wax is applied to the first side; during waxing, the first carrier is driven to remain stationary for a first preset time, and then rotated for a second preset time, so that the wax diffuses on the first side and the cross-sectional area of the diffused wax is smaller than the cross-sectional area of the wafer, thus obtaining a waxed wafer; The waxed wafer is loaded onto a second carrier and a preset pressure is applied at a preset temperature to fill the gaps between the metal bumps with wax and to extend the wax beyond the outer edge of the wafer by a preset distance. The wafer is then cooled to form a wax layer, resulting in a wafer to be ground. The preset temperature is greater than the melting point of the wax. Grind the wafer to be ground. In the step of applying wax to the first side, during waxing, the first carrier is driven to remain stationary for a first preset time, and then rotated for a second preset time to allow the wax to diffuse on the first side, such that the cross-sectional area of the diffused wax is smaller than the cross-sectional area of the wafer, thus obtaining a waxed wafer, the amount of wax applied is calculated according to the following formula: Where M is the amount of wax applied to a single wafer, ρ is the density of the wax, R is the radius of the wafer, l is the preset distance of the wax extending beyond the outer edge of the wafer, N is the total number of metal bumps on a single wafer, V is the volume of a single metal bump, and k1 is a constant with a value ranging from 0.95 to 0.
99.
2. The method for grinding flip-chip LEDs as described in claim 1, characterized in that, In the step of loading the waxed wafer onto a second carrier and applying a preset pressure at a preset temperature to fill the gaps between the metal bumps with wax and to extend the wax beyond the outer edge of the wafer by a preset distance, and then cooling to form a wax layer to obtain the wafer to be ground, the preset distance is calculated according to the following formula: Where l is the preset distance of the wax extending beyond the outer edge of the wafer, R is the radius of the wafer, and k2 is a constant with a value ranging from 1.7 to 1.
8.
3. The method for grinding flip-chip LEDs as described in claim 1, characterized in that, In the step of applying wax to the first side, during waxing, the first carrier is driven to remain stationary for a first preset time, and then rotated for a second preset time, so that the wax diffuses on the first side and the cross-sectional area of the diffused wax is smaller than the cross-sectional area of the wafer, thus obtaining a waxed wafer: When applying wax, first keep the first carrier stationary for 1 to 3 seconds, and then drive the first carrier to rotate at a speed of 50 to 80 rpm for 15 to 20 seconds. After the waxing is stopped, drive the first carrier to rotate at a speed of 5 rpm to 20 rpm for 1 to 5 seconds to allow the wax to spread on the first side.
4. The method for grinding flip-chip LEDs as described in claim 1, characterized in that, In the step of applying wax to the first side, during waxing, the first carrier is driven to remain stationary for a first preset time, and then rotated for a second preset time, so that the wax diffuses on the first side and the cross-sectional area of the diffused wax is smaller than the cross-sectional area of the wafer to obtain a waxed wafer: the temperature of the wax is 80℃~120℃, and the wax is sprayed in the central area of the first side.
5. The method for grinding flip-chip LEDs as described in any one of claims 1, 3, or 4, characterized in that, In the step of applying wax to the first side, during waxing, the first carrier is driven to remain stationary for a first preset time, and then rotated for a second preset time, so that the wax diffuses on the first side and the cross-sectional area of the diffused wax is smaller than the cross-sectional area of the wafer to obtain a waxed wafer: the cross-sectional area of the diffused wax is 20% to 45% of the cross-sectional area of the wafer.
6. The method for grinding flip-chip LEDs as described in claim 1, characterized in that, In the step of loading the waxed wafer onto a second carrier and applying a preset pressure at a preset temperature to fill the gaps between the metal bumps with wax and extend the wax beyond a preset distance from the outer edge of the wafer, cooling to form a wax layer, and obtaining the wafer to be ground, the preset pressure is 15MPa~25MPa, the preset temperature is 100℃~150℃, and the time for applying the preset pressure is 150s~250s.
7. The method for grinding flip-chip LEDs as described in claim 1, characterized in that, The first carrier is a vacuum carrier, and the second carrier is a ceramic carrier.
8. A polishing system for flip-chip LEDs, used to implement the polishing method for flip-chip LEDs as described in any one of claims 1 to 7, characterized in that, include: A wafer providing unit is used to provide a wafer, the wafer including a first side and a second side opposite to each other, the first side having a plurality of flip-chip LEDs, each flip-chip LED having at least two metal bumps formed thereon; A first carrier is used to carry the wafer and drive the wafer to rotate or remain stationary; a second side of the wafer contacts the first carrier; A waxing unit is used to apply wax to the first side of the wafer. During waxing, the first carrier is driven to remain stationary for a first preset time and then rotate for a second preset time so that the wax diffuses on the first side and the cross-sectional area of the diffused wax is smaller than the cross-sectional area of the wafer, thus obtaining a waxed wafer. The second carrier is used to carry the waxed wafer and apply a preset pressure at a preset temperature so that the wax fills the gaps between the metal bumps and extends beyond the outer edge of the wafer by a preset distance to obtain the wafer to be ground. as well as A grinding unit is used to grind the wafer to be ground.
9. A flip-chip LED, characterized in that, It is ground by the grinding method of the flip-chip LED as described in any one of claims 1 to 7.