Transfer method of mini-led and backlight device

Abstract

The present application relates to a kind of Mini-LED transfer method and a kind of backlight device, it is related to semiconductor display technical field.The first annular groove and the second annular groove are formed on the upper surface of Mini-LED unit, and the first annular magnetic bump and the second annular magnetic bump are formed in the first annular groove and the second annular groove respectively, wherein the magnetic field polarity of the upper surface of the first annular magnetic bump is opposite with the magnetic field polarity of the upper surface of the second annular magnetic bump, corresponding third annular magnetic bump and fourth annular magnetic bump are formed on the driving substrate, and then in the process that multiple Mini-LED units are transferred to the driving substrate using transfer substrate, each first annular magnetic bump is magnetically adsorbed with corresponding third annular magnetic bump, and each second annular magnetic bump is magnetically adsorbed with corresponding fourth annular magnetic bump.

Description

Technical Field

[0001] This invention relates to the field of semiconductor display technology, specifically to a method for transferring Mini-LEDs and a backlight device. Background Technology

[0002] Mini-LEDs are light-emitting diodes with a chip size of 100-300μm, falling between conventional LEDs and Micro-LEDs. Mini-LEDs can replace traditional LCD backlight modules and are mainly used in smart TVs, computer monitors, laptops, automotive displays, shopping mall advertising screens, and medical imaging displays. In the current fabrication process of Mini-LED backlight devices, tens of thousands of Mini-LED chips need to be transferred onto a driving substrate. Improving the transfer accuracy of Mini-LED chips is a key technological focus that the industry continues to pay attention to. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for transferring Mini-LEDs and a backlight device.

[0004] To achieve the above objectives, the present invention proposes a method for transferring Mini-LEDs, comprising: A light-emitting epitaxial wafer is provided, the light-emitting epitaxial wafer comprising a growth substrate and an epitaxial functional layer.

[0005] The epitaxial functional layer is cut to form multiple Mini-LED units arranged in an array.

[0006] Next, a first electrode is formed on each of the Mini-LED units.

[0007] Next, a first passivation layer is formed on the upper surface and side surface of each Mini-LED unit.

[0008] Each of the first passivation layers is patterned to form a first annular groove and a second annular groove in each of the first passivation layers, wherein the first annular groove surrounds the first electrode and the second annular groove surrounds the first annular groove.

[0009] Next, a first annular magnetic bump and a second annular magnetic bump are formed in the first annular groove and the second annular groove, respectively, wherein the magnetic field polarity of the upper surface of the first annular magnetic bump is opposite to that of the upper surface of the second annular magnetic bump.

[0010] Next, each of the first passivation layers is opened to expose each of the first electrodes, and conductive bumps are formed on each of the first electrodes.

[0011] Next, the growth substrate of the light-emitting epitaxial wafer is cut to form multiple separate Mini-LED units.

[0012] A driving substrate is provided, on which a plurality of pixel electrodes are formed, a third annular magnetic bump is formed around each of the pixel electrodes, and a fourth annular magnetic bump is formed around each of the third annular magnetic bumps, wherein the magnetic field polarity of the upper surface of the third annular magnetic bump is opposite to that of the upper surface of the fourth annular magnetic bump.

[0013] Multiple Mini-LED units are transferred to the driving substrate using a transfer substrate, such that each first annular magnetic bump is magnetically attracted to the corresponding third annular magnetic bump, and each second annular magnetic bump is magnetically attracted to the corresponding fourth annular magnetic bump.

[0014] As a preferred technical solution, the method further includes: heat-treating the conductive bumps so that the first electrode of each Mini-LED unit is fixedly connected to the corresponding pixel electrode.

[0015] As a preferred technical solution, the method further includes: forming a first encapsulation layer on the driving substrate, then removing the growth substrate of each Mini-LED unit, and then forming a common electrode, wherein the common electrode is electrically connected to a plurality of Mini-LED units.

[0016] As a preferred technical solution, the thickness of the first passivation layer is greater than the thickness of the first electrode, and a portion of the upper surface of the first electrode is covered by the first passivation layer.

[0017] As a preferred technical solution, the conductive bumps protrude from the first passivation layer, and the upper surface of each pixel electrode has a recessed accommodating area.

[0018] As a preferred technical solution, during the process of transferring multiple Mini-LED units to the driving substrate, the portion of the conductive bump protruding from the first passivation layer is embedded into the recessed accommodating area.

[0019] As a preferred technical solution, a magnetic layer is formed by spin coating or slot coating, and the first annular magnetic bump and the second annular magnetic bump are formed by patterning.

[0020] As a preferred technical solution, a third annular groove and a fourth annular groove are formed on the surface of the driving substrate, and then a magnetic layer is formed by spin coating or slot coating process, and the third annular magnetic bump and the fourth annular magnetic bump are formed by patterning process.

[0021] The present invention also proposes a backlight device, which is fabricated using the aforementioned Mini-LED transfer method.

[0022] The beneficial effects of this invention are as follows: In the Mini-LED transfer method of the present invention, a first annular groove and a second annular groove are formed on the upper surface of the Mini-LED unit, and a first annular magnetic bump and a second annular magnetic bump are formed in the first annular groove and the second annular groove, respectively. The magnetic field polarity of the upper surface of the first annular magnetic bump is opposite to that of the upper surface of the second annular magnetic bump. Correspondingly, a third annular magnetic bump and a fourth annular magnetic bump are formed on the driving substrate. In the process of transferring multiple Mini-LED units to the driving substrate using the transfer substrate, each first annular magnetic bump is magnetically attracted to the corresponding third annular magnetic bump, and each second annular magnetic bump is magnetically attracted to the corresponding fourth annular magnetic bump. Through the above configuration, the transfer accuracy of the Mini-LED chip can be improved, thereby improving the transfer yield of the Mini-LED chip and greatly reducing the production cost of the Mini-LED backlight module.

[0023] Secondly, by forming the first, second, third, and fourth annular magnetic bumps through spin coating or slot coating processes, the fabrication process of the magnetic bumps is effectively simplified, and the magnetic field direction of each magnetic bump can be easily adjusted. The Mini-LED transfer method of the present invention can improve the transfer efficiency and simplify the process difficulty of mass transfer. Attached Figure Description

[0024] Figure 1 The diagram shown is a schematic diagram of the structure forming a Mini-LED unit in an embodiment of the present invention.

[0025] Figure 2 The diagram shows a structure in which a first annular magnetic bump and a second annular magnetic bump are formed in the first passivation layer according to an embodiment of the present invention.

[0026] Figure 3 The diagram shows a structural schematic of the cutting process of the growth substrate of the light-emitting epitaxial wafer in an embodiment of the present invention.

[0027] Figure 4 The diagram shows a structure in which a third annular magnetic bump and a fourth annular magnetic bump are formed on a driving substrate in an embodiment of the present invention.

[0028] Figure 5The diagram shows a structure in which multiple Mini-LED units are transferred to a driving substrate in an embodiment of the present invention.

[0029] Figure 6 The diagram shown is a schematic representation of the structure forming the first encapsulation layer and the common electrode in an embodiment of the present invention. Detailed Implementation

[0030] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0031] like Figures 1-6 As shown, this embodiment provides a method for transferring Mini-LEDs, including: like Figure 1 As shown, a light-emitting epitaxial wafer 100 is provided, the light-emitting epitaxial wafer 100 including a growth substrate 101 and an epitaxial functional layer 102.

[0032] In a specific embodiment, the growth substrate 101 can be any suitable substrate such as a sapphire substrate. Then, an N-type semiconductor layer, a quantum well light-emitting layer, and a P-type semiconductor layer are epitaxially grown using the MOCVD process to serve as the epitaxial functional layer 102. More specifically, before growing the epitaxial functional layer 102, a buffer layer (not shown) can be pre-grown on the growth substrate 101.

[0033] In a specific embodiment, the N-type semiconductor layer and the P-type semiconductor layer are respectively an n-type gallium nitride layer and a p-type gallium nitride layer, while the quantum well light-emitting layer is an alternating InGaN quantum well layer and a GaN quantum barrier layer.

[0034] like Figure 1 As shown, the epitaxial functional layer 102 is cut to form a plurality of Mini-LED units 200 arranged in an array, and then a first electrode 103 is formed on each Mini-LED unit 200.

[0035] In a specific embodiment, multiple Mini-LED units 200 arranged in an array are formed by mechanical cutting or laser cutting.

[0036] In a specific embodiment, during the process of forming the first electrode 103 on each Mini-LED unit 200, photoresist can be formed on the light-emitting epitaxial wafer 100 in advance, and a photoresist mask can be formed by exposure and development process. Then, the first electrode 103 can be formed by thermal evaporation, magnetron sputtering, electroplating or chemical plating process. The material of the first electrode 103 is one or more of copper, aluminum, silver, titanium, gold and palladium. Then, the photoresist mask is removed. The first electrode 103 is located in the central region of the upper surface of the epitaxial functional layer 102 of the Mini-LED unit 200.

[0037] like Figure 2 As shown, a first passivation layer 201 is then formed on the upper surface and side surface of each Mini-LED unit 200.

[0038] In a specific embodiment, the thickness of the first passivation layer 201 is greater than the thickness of the first electrode 103.

[0039] In a specific embodiment, silicon oxide, silicon nitride, silicon oxynitride, or aluminum oxide is deposited using a PECVD or ALD process to serve as the first passivation layer 201, which covers the first electrode 103.

[0040] like Figure 2 As shown, each of the first passivation layers 201 is patterned to form a first annular groove 2011 and a second annular groove 2012 in each of the first passivation layers 201, wherein the first annular groove 2011 surrounds the first electrode 103 and the second annular groove 2012 surrounds the first annular groove 2011.

[0041] In a specific embodiment, the first annular groove 2011 and the second annular groove 2012 are formed by a wet etching process or a dry etching process. More specifically, the depth of the second annular groove 2012 is greater than the depth of the first annular groove 2011, and the bottom surface of the first annular groove 2011 is at the same level as the top surface of the first electrode 103. With the above settings, on the one hand, the magnetic strength of the first annular magnetic bump formed subsequently can be ensured, and on the other hand, the formation process of the first annular groove 2011 will not damage the conductivity stability of the first electrode 103.

[0042] like Figure 2 As shown, a first annular magnetic bump 301 and a second annular magnetic bump 302 are then formed in the first annular groove 2011 and the second annular groove 2012, respectively, wherein the magnetic field polarity of the upper surface of the first annular magnetic bump 301 is opposite to the magnetic field polarity of the upper surface of the second annular magnetic bump 302.

[0043] In a specific embodiment, a magnetic resin layer is formed by spin coating or slot coating, and the first annular magnetic bump 301 and the second annular magnetic bump 302 are formed by patterning.

[0044] In a specific embodiment, the specific process for forming the first annular magnetic bump 301 and the second annular magnetic bump 302 is as follows: a magnetic resin layer is formed on the surface of the first passivation layer 201 by spin coating or slot coating. The magnetic resin layer contains hard magnetic particles or semi-hard magnetic particles, more specifically, it may contain neodymium iron boron particles, cobalt-platinum alloy particles, or ferrite particles. Then, the first annular magnetic bump 301 and the second annular magnetic bump 302 are formed in the first annular groove 2011 and the second annular groove 2012 respectively by photolithography. Then, a pre-curing treatment is performed so that the first annular magnetic bump 301 and the second annular magnetic bump 302 are in a semi-cured state. Then, the first annular magnetic bump 301 is directionally magnetized under a first magnetic field, and the second annular magnetic bump 302 is directionally magnetized under a second magnetic field. The magnetic fields are in opposite directions. Then, while maintaining the opposite magnetic fields of the first and second magnetic fields, the first annular magnetic bump 301 and the second annular magnetic bump 302 are cured. The curing process is as follows: first, pre-curing at 90-110°C for 5-10 minutes, then high-temperature curing at 160-200°C in a nitrogen atmosphere for 40-100 minutes. More specifically, first, pre-curing at 100°C for 8 minutes, then high-temperature curing at 180°C in a nitrogen atmosphere for 70 minutes, so that the resin materials of the first annular magnetic bump 301 and the second annular magnetic bump 302 are completely cross-linked and cured. Then, while maintaining the first and second magnetic fields, the material is naturally cooled to room temperature, and then the first and second magnetic fields are removed, so that the magnetic field polarity of the upper surface of the first annular magnetic bump 301 is opposite to that of the upper surface of the second annular magnetic bump 302.

[0045] like Figure 2 As shown, each of the first passivation layers 201 is then made into an opening to expose each of the first electrodes 103, and a conductive bump 104 is formed on each of the first electrodes 103, the conductive bump 104 protruding from the first passivation layer 201.

[0046] In a specific embodiment, after each of the first passivation layers 201 is made into an opening, a portion of the upper surface of the first electrode 103 is covered by the first passivation layer 201.

[0047] In a specific embodiment, the opening process is performed by laser etching, and the conductive bump 104 can be conductive solder or conductive adhesive, which is then formed by ball-planting or dispensing processes.

[0048] like Figure 3 As shown, the growth substrate 101 of the light-emitting epitaxial wafer 100 is then cut to form a plurality of separate Mini-LED units 200.

[0049] In a specific embodiment, multiple separate Mini-LED units 200 are formed by mechanical cutting or laser cutting processes.

[0050] like Figure 4 As shown, a driving substrate 400 is provided, on which a plurality of pixel electrodes 401 are formed. Then, a third annular magnetic bump 402 is formed around each pixel electrode 401. Then, a fourth annular magnetic bump 403 is formed around each third annular magnetic bump 402. The magnetic field polarity of the upper surface of the third annular magnetic bump 402 is opposite to that of the upper surface of the fourth annular magnetic bump 403.

[0051] In a specific embodiment, the upper surface of each pixel electrode 401 has a recessed accommodating region 4011.

[0052] In a specific embodiment, the pixel electrode 401 is formed by thermal evaporation, magnetron sputtering, electroplating or chemical plating processes. The pixel electrode 401 is made of one or more of copper, aluminum, silver, titanium, gold and palladium. The recessed accommodating region 4011 is then formed by wet etching or dry etching processes.

[0053] In a specific embodiment, a third annular groove (not shown) and a fourth annular groove (not shown) are formed on the surface of the driving substrate 400. Then, a magnetic resin layer is formed by spin coating or slot coating process, and the third annular magnetic bump 402 and the fourth annular magnetic bump 403 are formed by patterning process.

[0054] In a specific embodiment, the third annular groove and the fourth annular groove are formed by a wet etching process or a dry etching process.

[0055] In a specific embodiment, the third annular magnetic bump 402 and the fourth annular magnetic bump 403 can be formed using the same process as that used to form the first annular magnetic bump 301 and the second annular magnetic bump 302, such that each first annular magnetic bump 301 and the corresponding third annular magnetic bump 402 can be magnetically attracted together, and each second annular magnetic bump 302 and the corresponding fourth annular magnetic bump 403 can be magnetically attracted together.

[0056] like Figure 5 As shown, a plurality of Mini-LED units 200 are transferred to the driving substrate 400 using a transfer substrate (not shown), such that each first annular magnetic bump 301 is magnetically attracted to the corresponding third annular magnetic bump 402, and each second annular magnetic bump 302 is magnetically attracted to the corresponding fourth annular magnetic bump 403, thereby improving the precise alignment between the first electrode 103 of the Mini-LED unit 200 and the pixel electrode 401 of the driving substrate 400.

[0057] In a specific embodiment, during the process of transferring the plurality of Mini-LED units 200 to the driving substrate 400, the portion of the conductive bump 104 protruding from the first passivation layer 201 is embedded in the recessed accommodating area 4011.

[0058] In a specific embodiment, the conductive bump 104 is heat-treated so that the first electrode 103 of each Mini-LED unit 200 is fixedly connected to each corresponding pixel electrode 401.

[0059] In a specific embodiment, the conductive bump 104 is heat-treated to melt or soften it, thereby fixing and bonding the first electrode 103 of each Mini-LED unit 200 to the corresponding pixel electrode 401.

[0060] like Figure 6 As shown, it further includes: forming a first encapsulation layer 500 on the driving substrate 400, then removing the growth substrate 101 of each Mini-LED unit 200, and then forming a common electrode 600, the common electrode 600 being electrically connected to the plurality of Mini-LED units 200.

[0061] In a specific embodiment, the first encapsulation layer 500 is a resin material and is formed by a molding process. The common electrode 600 is a transparent conductive electrode, which can be any suitable transparent conductive material such as ITO, FTO, or IZO, and is formed by processes such as magnetron sputtering.

[0062] like Figure 6 As shown, the present invention also proposes a backlight device, which is fabricated using the aforementioned Mini-LED transfer method.

[0063] In other preferred technical solutions, the present invention proposes a method for transferring Mini-LEDs, comprising: A light-emitting epitaxial wafer is provided, the light-emitting epitaxial wafer comprising a growth substrate and an epitaxial functional layer.

[0064] The epitaxial functional layer is cut to form multiple Mini-LED units arranged in an array.

[0065] Next, a first electrode is formed on each of the Mini-LED units.

[0066] Next, a first passivation layer is formed on the upper surface and side surface of each Mini-LED unit.

[0067] Each of the first passivation layers is patterned to form a first annular groove and a second annular groove in each of the first passivation layers, wherein the first annular groove surrounds the first electrode and the second annular groove surrounds the first annular groove.

[0068] Next, a first annular magnetic bump and a second annular magnetic bump are formed in the first annular groove and the second annular groove, respectively, wherein the magnetic field polarity of the upper surface of the first annular magnetic bump is opposite to that of the upper surface of the second annular magnetic bump.

[0069] Next, each of the first passivation layers is opened to expose each of the first electrodes, and conductive bumps are formed on each of the first electrodes.

[0070] Next, the growth substrate of the light-emitting epitaxial wafer is cut to form multiple separate Mini-LED units.

[0071] A driving substrate is provided, on which a plurality of pixel electrodes are formed, a third annular magnetic bump is formed around each of the pixel electrodes, and a fourth annular magnetic bump is formed around each of the third annular magnetic bumps, wherein the magnetic field polarity of the upper surface of the third annular magnetic bump is opposite to that of the upper surface of the fourth annular magnetic bump.

[0072] Multiple Mini-LED units are transferred to the driving substrate using a transfer substrate, such that each first annular magnetic bump is magnetically attracted to the corresponding third annular magnetic bump, and each second annular magnetic bump is magnetically attracted to the corresponding fourth annular magnetic bump.

[0073] In a more preferred technical solution, the conductive bumps are further subjected to heat treatment, such that the first electrode of each Mini-LED unit is fixedly connected to the corresponding pixel electrode.

[0074] In a more preferred technical solution, the method further includes: forming a first encapsulation layer on the driving substrate, then removing the growth substrate of each Mini-LED unit, and then forming a common electrode, wherein the common electrode is electrically connected to a plurality of Mini-LED units.

[0075] In a more preferred technical solution, the thickness of the first passivation layer is greater than the thickness of the first electrode, and a portion of the upper surface of the first electrode is covered by the first passivation layer.

[0076] In a more preferred embodiment, the conductive bumps protrude beyond the first passivation layer, and the upper surface of each pixel electrode has a recessed accommodating area.

[0077] In a more preferred technical solution, during the process of transferring multiple Mini-LED units to the driving substrate, the portion of the conductive bump protruding from the first passivation layer is embedded into the recessed accommodating area.

[0078] In a more advanced technical solution, a magnetic layer is formed by spin coating or slot coating, and the first and second annular magnetic bumps are formed by patterning.

[0079] In a more preferred technical solution, a third annular groove and a fourth annular groove are formed on the surface of the driving substrate, and then a magnetic layer is formed by spin coating or slot coating, and the third annular magnetic bump and the fourth annular magnetic bump are formed by patterning.

[0080] In a more preferred technical solution, the present invention also proposes a backlight device, which is fabricated using the aforementioned Mini-LED transfer method. In the Mini-LED transfer method of the present invention, a first annular groove and a second annular groove are formed on the upper surface of the Mini-LED unit, and a first annular magnetic bump and a second annular magnetic bump are formed in the first annular groove and the second annular groove, respectively. The magnetic field polarity of the upper surface of the first annular magnetic bump is opposite to that of the upper surface of the second annular magnetic bump. Correspondingly, a third annular magnetic bump and a fourth annular magnetic bump are formed on the driving substrate. In the process of transferring multiple Mini-LED units to the driving substrate using the transfer substrate, each first annular magnetic bump is magnetically attracted to the corresponding third annular magnetic bump, and each second annular magnetic bump is magnetically attracted to the corresponding fourth annular magnetic bump. Through the above configuration, the transfer accuracy of the Mini-LED chip can be improved, thereby improving the transfer yield of the Mini-LED chip and greatly reducing the production cost of the Mini-LED backlight module.

[0081] Secondly, by forming the first, second, third, and fourth annular magnetic bumps through spin coating or slot coating processes, the fabrication process of the magnetic bumps is effectively simplified, and the magnetic field direction of each magnetic bump can be easily adjusted. The Mini-LED transfer method of the present invention can improve the transfer efficiency and simplify the process difficulty of mass transfer.

[0082] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for transferring Mini-LEDs, characterized in that: include: A light-emitting epitaxial wafer is provided, the light-emitting epitaxial wafer comprising a growth substrate and an epitaxial functional layer; The epitaxial functional layer is cut to form multiple Mini-LED units arranged in an array; Next, a first electrode is formed on each of the Mini-LED units; Next, a first passivation layer is formed on the upper surface and side surface of each Mini-LED unit; Each of the first passivation layers is patterned to form a first annular groove and a second annular groove in each of the first passivation layers, wherein the first annular groove surrounds the first electrode and the second annular groove surrounds the first annular groove. Next, a first annular magnetic bump and a second annular magnetic bump are formed in the first annular groove and the second annular groove, respectively, wherein the magnetic field polarity of the upper surface of the first annular magnetic bump is opposite to the magnetic field polarity of the upper surface of the second annular magnetic bump. Next, each of the first passivation layers is made into an opening to expose each of the first electrodes, and a conductive bump is formed on each of the first electrodes; Next, the growth substrate of the light-emitting epitaxial wafer is cut to form multiple separate Mini-LED units; A driving substrate is provided, on which a plurality of pixel electrodes are formed, and then a third annular magnetic bump is formed around each of the pixel electrodes, and then a fourth annular magnetic bump is formed around each of the third annular magnetic bumps, wherein the magnetic field polarity of the upper surface of the third annular magnetic bump is opposite to the magnetic field polarity of the upper surface of the fourth annular magnetic bump. Multiple Mini-LED units are transferred to the driving substrate using a transfer substrate, such that each first annular magnetic bump is magnetically attracted to the corresponding third annular magnetic bump, and each second annular magnetic bump is magnetically attracted to the corresponding fourth annular magnetic bump.

2. The method for transferring Mini-LEDs according to claim 1, characterized in that: Further includes: The conductive bumps are heat-treated so that the first electrode of each Mini-LED unit is fixedly connected to the corresponding pixel electrode.

3. The method for transferring Mini-LEDs according to claim 2, characterized in that: Further includes: A first encapsulation layer is formed on the driving substrate, then the growth substrate of each Mini-LED unit is removed, and then a common electrode is formed, which is electrically connected to multiple Mini-LED units.

4. The method for transferring Mini-LEDs according to claim 2, characterized in that: The thickness of the first passivation layer is greater than the thickness of the first electrode, and a portion of the upper surface of the first electrode is covered by the first passivation layer.

5. The method for transferring Mini-LEDs according to claim 2, characterized in that: The conductive bumps protrude from the first passivation layer, and the upper surface of each pixel electrode has a recessed accommodating area.

6. The method for transferring Mini-LEDs according to claim 5, characterized in that: During the process of transferring multiple Mini-LED units to the driving substrate, the portion of the conductive bump protruding from the first passivation layer is embedded into the recessed accommodating area.

7. The method for transferring Mini-LEDs according to claim 2, characterized in that: The magnetic resin layer is formed by spin coating or slot coating, and the first and second annular magnetic bumps are formed by patterning.

8. The method for transferring Mini-LEDs according to claim 2, characterized in that: A third annular groove and a fourth annular groove are formed on the surface of the driving substrate. Then, a magnetic resin layer is formed by spin coating or slot coating. The third annular magnetic bump and the fourth annular magnetic bump are formed by patterning.

9. A backlight device, characterized in that: The backlight device is fabricated using the Mini-LED transfer method described in any one of claims 2-8.

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