Flip LED chip and grinding method and grinding system thereof

Abstract

The invention relates to the field of LED chip preparation methods, and particularly discloses a flip LED chip and a grinding method and a grinding system thereof. The grinding method comprises the steps that a wafer is loaded to a first carrier, the wafer comprises a first side and a second side which are opposite, a flip LED chip is arranged on the first side, metal protruding points are formed on the flip LED chip, and the second side of the wafer makes contact with the first carrier; waxing on the first side; during waxing, the first carrier is driven to be static for a first preset time and then rotate for a second preset time, so that wax is diffused on the first side, the cross sectional area of the diffused wax is smaller than that of the wafer, and a waxed wafer is obtained; loading the waxed wafer to a second carrier, and applying a preset pressure at a preset temperature, so that gaps between the metal bumps are filled with wax, the wax exceeds the outer edge of the wafer by a preset distance, and a to-be-ground wafer is obtained; and grinding the wafer to be ground. According to the invention, the fragment rate of the ground flip LED chip can be greatly reduced.

Description

Technical Field

[0001] The invention relates to the field of LED chip preparation methods, and in particular to a flip-chip LED chip and a grinding method and a grinding system thereof. Background Art

[0002] The flip-chip LED chip is to weld the electrode as a whole to the package bracket. The common process at present is the metal bonding process. However, as the LED chip further develops towards functionalization and miniaturization, the common metal bonding process can no longer meet the use requirements, so a new bump (metal bump) process has emerged, that is, multiple metal bumps are formed on the pads of the flip-chip LED chip for later connection with the package bracket. However, after the metal bump process is adopted, it brings huge challenges to the subsequent process of the chip (thinning-grinding, etc.). In particular, the number of bumps of the existing flip-chip LED chip is extremely large, and the spacing is very narrow. For example, a 4-inch wafer has a diameter of 50mm, and the number of flip-chip LED chips that can be arrayed on the wafer is 8988, while the number of metal bumps is 35952, and the distance between adjacent metal bumps is only 10μm to 20μm. This makes the stress distribution uniformity of the metal wafer poor during the masking process, and it is very easy to crack. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a grinding method for flip-chip LED chips, which can significantly reduce the grinding cracking rate and improve the yield.

[0004] Another technical problem to be solved by the present invention is to provide a grinding system for flip-chip LED chips, which can significantly reduce the grinding cracking rate and improve the yield.

[0005] Another technical problem to be solved by the present invention is to provide a flip-chip LED chip.

[0006] In order to solve the above problems, the present invention discloses a grinding method for a flip-chip LED chip, which comprises:

[0007] Loading a wafer onto a first carrier, wherein the wafer comprises a first side and a second side opposite to each other, a plurality of flip-chip LED chips are disposed on the first side, each flip-chip LED chip is formed with at least two metal bumps, and the second side of the wafer contacts the first carrier;

[0008] Apply wax on the first side; when applying wax, drive the first carrier to first be 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, thereby obtaining a waxed wafer;

[0009] The waxed wafer is loaded onto a second carrier, and a preset pressure is applied 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, and is cooled to form a wax layer to obtain a wafer to be ground; wherein the preset temperature is greater than the melting point of the wax;

[0010] The wafer to be ground is ground.

[0011] As an improvement of the above technical solution, in the step of applying wax on the first side, when applying wax, the first carrier is driven to be 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. In the step of obtaining the waxed wafer, the amount of wax applied is calculated according to the following formula:

[0012] M=k1πρh(R+l) 2 -ρNV

[0013] Among them, 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 that the wax exceeds 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 whose value range is 0.95 to 0.99.

[0014] As an improvement of 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 so that the wax fills the gaps between the metal bumps and the wax exceeds the outer edge of the wafer by a preset distance, cooling to form a wax layer, and obtaining a wafer to be ground, the preset distance is calculated according to the following formula:

[0015] l=k2R 0.15

[0016] Wherein, l is the preset distance that the wax exceeds the outer edge of the wafer, R is the radius of the wafer, and k2 is a constant whose value range is 1.7 to 1.8.

[0017] As an improvement of the above technical solution, in the step of applying wax on the first side; when applying wax, driving the first carrier to first be stationary for a first preset time and then rotating 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 the waxed wafer:

[0018] When applying wax, the first carrier is first made to stand still for 1s to 3s, and then driven to rotate at a speed of 50rpm to 80rpm for 15s to 20s;

[0019] After the wax application is stopped, the first carrier is driven to rotate at a speed of 5 rpm to 20 rpm for 1 second to 5 seconds to spread the wax on the first side.

[0020] As an improvement of the above technical solution, wax is applied on the first side; when applying wax, the first carrier is driven to first be stationary for a first preset time, and then rotated for a second preset time, so that the wax can diffuse 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 the waxed wafer: the temperature of the wax is 80°C to 120°C, and the wax is sprayed on the central area of ​​the first side.

[0021] As an improvement of 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 so that the wax fills the gaps between the metal bumps and extends beyond the outer edge of the wafer by a preset distance, cooling to form a wax layer, and obtaining a 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 of the above technical solution, wax is applied on the first side; when applying wax, the first carrier is driven to first be stationary for a first preset time, and then rotate for a second preset time, so that the wax can diffuse on the first side, and the cross-sectional area of ​​the wax after diffusion is smaller than the cross-sectional area of ​​the wafer, to obtain the step of waxing the wafer: the cross-sectional area of ​​the wax after diffusion is 20% to 45% of the cross-sectional area of ​​the wafer.

[0023] As an improvement of the above technical solution, the first carrier is a vacuum carrier, and the second carrier is a ceramic carrier.

[0024] Correspondingly, the present invention also discloses a grinding system for a flip-chip LED chip, which comprises:

[0025] A wafer providing unit, used for providing a wafer, wherein the wafer comprises a first side and a second side opposite to each other, wherein a plurality of flip-chip LED chips are arranged on the first side, and each flip-chip LED chip is formed with at least two metal bumps;

[0026] A first carrier is used to carry the wafer and drive the wafer to rotate or remain stationary; the second side of the wafer contacts the first carrier;

[0027] A wax applying unit, used for applying wax to the first side of the wafer; when applying wax, the first carrier is driven to be stationary for a first preset time, and then rotated for a second preset time, so that the wax is diffused on the first side, and the cross-sectional area of ​​the diffused wax is smaller than the cross-sectional area of ​​the wafer, so as to obtain a waxed wafer;

[0028] A 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 the wax exceeds the outer edge of the wafer by a preset distance to obtain a wafer to be ground; and

[0029] The grinding unit is used for grinding the wafer to be ground.

[0030] Correspondingly, the present invention also discloses a flip-chip LED chip, which is ground by the above-mentioned flip-chip LED chip grinding method.

[0031] The implementation of the present invention has the following beneficial effects:

[0032] In the grinding method of the flip-chip LED chip in one embodiment of the present invention, wax is first applied to the first side of the flip-chip LED chip on the wafer, and the wax is diffused by the static and rotation control of the first carrier, and the cross-sectional area after diffusion is smaller than the cross-sectional area of ​​the wafer, and then a preset pressure is applied to it at a preset temperature, so that the wax fills the gaps between the metal bumps, and the wax exceeds the preset distance of the outer edge of the wafer, and finally it is ground. Based on the above-mentioned grinding method, firstly, by controlling the movement mode of the first carrier during the waxing process, and controlling the pressure and temperature of the waxed wafer on the second carrier, the wax can fully wrap the metal bumps, forming an effective protection, dispersing the stress, reducing the damage of the cutting force to the wafer during the grinding process, and reducing the fragmentation rate. Secondly, by controlling the wax to exceed the preset distance of the outer edge of the wafer, that is, the wax expands outward, the damage to the outer edge of the wafer during the grinding process can be reduced, the fragmentation rate is greatly reduced, the product yield is improved, and the production cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a flow chart of a grinding method for a flip-chip LED chip in one embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below 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 throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. In addition, it should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0036] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, and itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides various specific examples of processes and materials, but those of ordinary skill in the art can appreciate the application of other processes and / or the use scenarios of other materials.

[0037] See also Figure 1 The present invention discloses a grinding method for a flip-chip LED chip, which comprises the following steps:

[0038] S1: loading the wafer into the first carrier;

[0039] S2: applying wax on the first side; when applying wax, driving the first carrier to first be stationary for a first preset time, and then rotating 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, thereby obtaining a waxed wafer;

[0040] S3: loading the waxed wafer onto a second carrier, and applying 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, and cooling to form a wax layer to obtain a wafer to be ground;

[0041] S4: grinding 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 LED chips are arranged on the first side, and at least two metal bumps are formed on each flip-chip LED chip. Preferably, four metal bumps are arranged on each flip-chip LED chip. In this embodiment, the number of metal bumps on the wafer is large, the spacing is small, and the grinding difficulty is high.

[0043] Specifically, based on the above-mentioned grinding method, firstly, by controlling the movement mode of the first carrier during the waxing process, and controlling the pressure and temperature of the waxed wafer on the second carrier, the wax can effectively wrap the metal bumps, and then form a good protective wax layer after cooling, so that the stress distribution during the grinding process is more uniform, reducing the damage to the wafer caused by the cutting force during the grinding process, and greatly reducing the fragmentation rate. Secondly, by controlling the wax to exceed the preset distance of the outer edge of the wafer, that is, the wax expands outward, the damage to the outer edge of the wafer during the grinding process can be reduced, the fragmentation rate can be greatly reduced, the product yield is improved, and the production cost is reduced.

[0044] Specifically, in step S1, the second side of the wafer contacts the first carrier to apply wax to the flip-chip LED chip on the first side. Specifically, the first carrier can be a common vacuum carrier in the art, but is not limited thereto.

[0045] Specifically, in step S2, the amount of wax applied can be determined according to the common knowledge of those skilled in the art. For example, for a 2-inch wafer (with a diameter of 50 mm), the amount of wax applied is 0.32 g to 0.4 g, but is not limited thereto. Preferably, in one embodiment, the amount of wax applied is calculated according to the following formula:

[0046] M=k1πρh(R+l) 2 -ρNV

[0047] Among them, 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 that the wax exceeds 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 whose value range is 0.95 to 0.99.

[0048] It should be noted that, when the prior art grinds flip-chip LED chips with metal bumps, wax is often applied with the wax application amount of conventional flip-chip LED chips (without metal bumps). After a lot of research, the inventors found that the conventional empirical wax application amount is generally relatively small, resulting in the inability of the wax to fully infiltrate the metal bumps, resulting in a high fragmentation rate; and if the wax application amount is blindly increased, if it is increased too little, it is still difficult to accurately achieve accurate infiltration of the metal bumps and achieve external expansion; if it is increased too much, the external expansion amount is too large, and the grinding device will not be in sufficient contact with the wafer during the grinding process, the grinding accuracy is reduced, and the waste of wax will also increase. Therefore, in the present invention, the wax application amount is accurately controlled by the above method, which greatly reduces the fragmentation rate.

[0049] Specifically, in one embodiment, the temperature of the wax is controlled to be 80°C to 120°C so that the wax has suitable fluidity, which not only facilitates the wax to be applied to the wafer in the form of spray wax, but also allows the wax to be allowed to diffuse within a controllable range by standing and rotating the first carrier, providing a good foundation for the subsequent full infiltration of the metal bumps by thermal pressure. Exemplarily, the temperature of the wax is 85°C, 90°C, 95°C, 100°C, 105°C, 110°C or 115°C, but is not limited thereto. Preferably, it is 90°C to 110°C, and more preferably, it is 95°C to 105°C.

[0050] Specifically, in one embodiment, in step S2, the wax may be applied to the first side of the wafer by spin coating, spray coating, etc., but is not limited thereto. Preferably, in one embodiment, the wax is applied to the first side of the wafer by a wax spraying process, and the wax is sprayed on the central area of ​​the first side.

[0051] Specifically, in one embodiment, in step S2, the first preset time for the first carrier to be 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 surface of the wafer, but not beyond the edge of the wafer.

[0052] Preferably, in one embodiment, in step S2: when applying wax, first make the first carrier stationary for 1s to 3s, and then drive the first carrier to rotate at a speed of 50rpm to 80rpm for 15s to 20s; after stopping the wax application, drive the first carrier to rotate at a speed of 5rpm to 20rpm for 1s to 5s to allow the wax to diffuse on the first side.

[0053] Specifically, by controlling the amount of wax applied, the temperature of the wax, and the movement state of the first carrier during the wax application process, the cross-sectional area of ​​the diffused wax can be 20% to 45% of the cross-sectional area of ​​the wafer, thereby creating good conditions for the subsequent hot pressing to allow the wax to fully infiltrate the metal bumps and form outward expansion.

[0054] Specifically, in one embodiment, in step S3, the preset temperature applied to the waxed wafer is greater than the melting point of the wax, so that the wax flows, and by applying a preset pressure, the wax fully flows and fills the gaps between the metal bumps, forming a full infiltration of the metal bumps and forming an outward expansion. Specifically, the preset temperature can be 100°C to 150°C, exemplarily 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C or 145°C, but not limited thereto. Preferably 110°C to 130°C. The preset pressure is 15MPa to 25MPa, exemplarily 15.5MPa, 17MPa, 18.5MPa, 20MPa, 21.5MPa, 23MPa or 24.5MPa, but not limited thereto, preferably 18MPa to 21MPa. Specifically, the hot pressing time is 150s to 250s, exemplarily 160s, 180s, 200s, 220s or 240s, but not limited thereto, preferably 180s to 220s.

[0055] Specifically, the second carrier may be a ceramic carrier, but is not limited thereto.

[0056] Specifically, in one embodiment, in step S3, the preset distance of the wax beyond the outer edge of the wafer is calculated according to the following formula:

[0057] l=k2R 0.15

[0058] Among them, l is the preset distance that the wax exceeds the outer edge of the wafer, the unit is mm, R is the radius of the wafer, the unit is mm, and k2 is a constant, and its value range is 1.7 to 1.8.

[0059] It should be noted that if the outward expansion is too little, the pressure on the edge of the wafer is relatively large and it is still easy to break. If the outward expansion is too much, the grinding (thinning, polishing) process reduces the grinding effect of the grinding device on the wafer, resulting in uneven grinding and reduced grinding efficiency. To this end, the present invention is based on a large amount of research and reasonably calculates the preset distance of the outward expansion, which meets the calculation of the outward expansion distance of wafers of different specifications, further improves the yield rate, reduces wax waste, and reduces production costs.

[0060] Specifically, in step S4, grinding may include grinding thinning, polishing, etc., but is not limited thereto. Those skilled in the art may select the specific process according to the specific process.

[0061] The present invention will be further described below with specific embodiments:

[0062] Example

[0063] This embodiment provides a method for grinding a flip-chip LED chip, which includes the following steps:

[0064] (1) Loading a wafer onto a vacuum carrier, wherein the wafer is a 4-inch wafer with a radius of 50 mm, and a first side thereof is provided with 8988 flip-chip LED chips, and 35952 metal bumps are formed on the flip-chip LED chips. The second side of the wafer is brought into contact with the vacuum carrier;

[0065] (2) spraying wax on the central area of ​​the first side;

[0066] Among them, the wax spraying amount 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] When spraying wax, the ceramic carrier is first kept still for 2 seconds, then driven to rotate at 60 rpm for 20 seconds; after stopping the wax spraying, the ceramic carrier is driven to rotate 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) loading the waxed wafer onto a ceramic plate and pressurizing it at 120° C. and 20 MPa for 200 s so that the wax fills the gaps between the metal bumps and the wax extends 3.11 mm beyond the outer edge of the wafer. Cooling forms a wax layer to obtain a wafer to be ground;

[0070] (4) Grinding the wafer to be ground.

[0071] Comparative Example 1

[0072] This comparative example provides a grinding method for a flip-chip LED chip, which comprises:

[0073] (1) Loading a wafer onto a vacuum carrier, wherein the wafer is a 4-inch wafer with a radius of 50 mm, and a first side thereof is provided with 8988 flip-chip LED chips, and 35952 metal bumps are formed on the flip-chip LED chips. The second side of the wafer is brought into contact with the vacuum carrier;

[0074] (2) spraying wax on the central area of ​​the first side;

[0075] The wax spraying amount was 0.35 g. During wax spraying, the vacuum carrier did not rotate. After wax spraying, it rotated at 3000 rpm for 20 seconds.

[0076] (3) Grinding the wax-sprayed wafer.

[0077] Comparative Example 2

[0078] This comparative example provides a grinding method for a flip-chip LED chip, which comprises:

[0079] (1) Loading a wafer onto a vacuum carrier, wherein the wafer is a 4-inch wafer with a radius of 50 mm, and a first side thereof is provided with 8988 flip-chip LED chips, and 35952 metal bumps are formed on the flip-chip LED chips. The second side of the wafer is brought into contact with the vacuum carrier;

[0080] (2) spraying wax on the central area of ​​the first side to obtain a waxed wafer;

[0081] The wax spraying amount was 0.35 g. During wax spraying, the vacuum carrier did not rotate. After wax spraying, it was rotated at 3000 rpm for 20 seconds.

[0082] (3) loading the waxed wafer onto a second carrier and pressing at 30° C. for 80 seconds to obtain a wafer to be polished;

[0083] (4) Grinding the wafer to be ground.

[0084] According to statistics, the fragmentation rate in the embodiment is 0%, the fragmentation rate in comparative example 1 is 57.14%, and the fragmentation rate in comparative example 2 is 14.29%. It can be seen that the present invention greatly reduces the fragmentation rate.

[0085] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0086] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A method for grinding a flip-chip LED chip, characterized in that: include: Loading a wafer onto a first carrier, wherein the wafer comprises a first side and a second side opposite to each other, a plurality of flip-chip LED chips are disposed on the first side, each flip-chip LED chip is formed with at least two metal bumps, and the second side of the wafer contacts the first carrier; Apply wax on the first side; when applying wax, drive the first carrier to first be 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, thereby obtaining a waxed wafer; The waxed wafer is loaded onto a second carrier, and a preset pressure is applied 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, and is cooled to form a wax layer to obtain a wafer to be ground; wherein the preset temperature is greater than the melting point of the wax; The wafer to be ground is ground.

2. The method for grinding a flip-chip LED chip according to claim 1, wherein: In the step of applying wax on the first side; when applying wax, driving the first carrier to first be stationary for a first preset time and then rotating 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, and obtaining the waxed wafer, the amount of wax applied is calculated according to the following formula: M=k1πρh(R+l) 2 -ρNV Among them, 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 that the wax exceeds 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 whose value range is 0.95 to 0.

99.

3. The method for grinding a flip-chip LED chip according to claim 1 or 2, characterized in that: In the step of loading the waxed wafer onto a second carrier and applying a preset pressure at a preset temperature so that the wax fills the gaps between the metal bumps and extends the wax beyond the outer edge of the wafer by a preset distance, cooling to form a wax layer, and obtaining a wafer to be ground, the preset distance is calculated according to the following formula: l=k2R 0.15 Wherein, l is the preset distance that the wax exceeds the outer edge of the wafer, R is the radius of the wafer, and k2 is a constant whose value range is 1.7 to 1.

8.

4. The method for grinding a flip-chip LED chip according to claim 1, wherein: In the step of applying wax on the first side; when applying wax, driving the first carrier to first be stationary for a first preset time and then rotating 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: When applying wax, the first carrier is first made to stand still for 1s to 3s, and then driven to rotate at a speed of 50rpm to 80rpm for 15s to 20s; After the wax application is stopped, the first carrier is driven to rotate at a speed of 5 rpm to 20 rpm for 1 second to 5 seconds to spread the wax on the first side.

5. The method for grinding a flip-chip LED chip according to claim 1, wherein: The wax is applied on the first side; when applying the wax, the first carrier is driven to be 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 the waxed wafer: the temperature of the wax is 80°C to 120°C, and the wax is sprayed on the central area of ​​the first side.

6. The method for grinding a flip-chip LED chip according to any one of claims 1, 2, 4 or 5, characterized in that: The wax is applied on the first side; when applying the wax, the first carrier is driven to first be 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 wax after diffusion is smaller than the cross-sectional area of ​​the wafer, to obtain the step of waxed wafer: the cross-sectional area of ​​the wax after diffusion is 20% to 45% of the cross-sectional area of ​​the wafer.

7. The method for grinding a flip-chip LED chip according to claim 1, wherein: In the step of loading the waxed wafer onto a second carrier and applying 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, cooling to form a wax layer, and obtaining a 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.

8. The method for grinding a flip-chip LED chip according to claim 1, wherein: The first carrier is a vacuum carrier, and the second carrier is a ceramic carrier.

9. A flip-chip LED chip grinding system, characterized in that: include: A wafer providing unit, used for providing a wafer, wherein the wafer comprises a first side and a second side opposite to each other, wherein a plurality of flip-chip LED chips are arranged on the first side, and each flip-chip LED chip is formed with at least two metal bumps; A first carrier is used to carry the wafer and drive the wafer to rotate or remain stationary; the second side of the wafer contacts the first carrier; A wax applying unit, used for applying wax to the first side of the wafer; when applying wax, the first carrier is driven to be stationary for a first preset time, and then rotated for a second preset time, so that the wax is diffused on the first side, and the cross-sectional area of ​​the diffused wax is smaller than the cross-sectional area of ​​the wafer, so as to obtain a waxed wafer; A 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 the wax exceeds the outer edge of the wafer by a preset distance to obtain a wafer to be ground; as well as The grinding unit is used for grinding the wafer to be ground.

10. A flip-chip LED chip, characterized in that: The method is ground by the flip-chip LED chip grinding method as claimed in any one of claims 1 to 8.

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