A method and device for controlling Micro-LED arrangement by guiding capillary force based on laser processing

Abstract

The present invention relates to the intersection of ultrafast laser micro-nano processing and semiconductor optoelectronic technology, and discloses a method for regulating the arrangement of Micro-LEDs by guiding capillary forces based on laser processing, comprising the following steps: Step 1, surface modification of a circuit substrate to change the hydrophilicity and hydrophobicity of the substrate surface; Step 2, laser processing; placing the circuit substrate on a stage, designing laser processing parameters, and using laser processing to induce a uniform periodic groove microstructure on the surface of the circuit substrate so that its surface has super-hydrophobic properties; the present invention overcomes the drawback that fluid self-assembly can only be achieved on a uniform substrate surface. Through the selective regulation of the hydrophilicity and hydrophobicity of the material surface by ultrafast laser, micro-nano chip self-assembly can be achieved on a substrate with uneven materials and complex surface patterns, and the arrangement of microchips is completed with low-cost, high-throughput technology, thereby realizing the mass transfer of Micro-LEDs.

Description

Technical Field

[0001] The present invention belongs to the intersection of ultrafast laser micro-nano processing and semiconductor optoelectronic technology, and specifically relates to a method and device for regulating Micro-LED arrangement based on capillary force guided by laser processing. Background Art

[0002] In recent years, Micro-LED display technology, with its significant advantages such as high image quality, low energy consumption, and long life, has rapidly become a research hotspot in the display field and has become the mainstream direction of next-generation display technology. A key technical challenge in new Micro-LED display products is mass transfer technology. This technology requires transferring a large number of Micro-LED chips onto the substrate of the driver circuit and achieving precise positioning and arrangement. Currently, mainstream Micro-LED mass transfer technology solutions include contact micro-transfer, non-contact laser transfer, and fluid self-assembly technology.

[0003] 1. Contact transfer technology relies on multiple forces, such as van der Waals forces, electrostatic forces, and physical contact methods such as precise pick-and-place, to move microchips from the original substrate to the target circuit board. The elastic stamping solution based on van der Waals forces is simple to operate and has good selectivity, but the force control is difficult and requires an extremely flat stamp surface. The adsorption transfer solution based on electrostatic forces requires each Micro-LED position to be precisely aligned, and electrostatic forces can easily damage the chip, placing high demands on chip manufacturing. The selective suction transfer solution based on electromagnetic forces has high requirements for the uniformity of magnetic materials. The precise picking solution is time-consuming, inefficient, and expensive. Furthermore, the electrostatic and mechanical forces used in the contact micro-transfer process may damage the microchip, requiring very precise control of the magnitude of the electrostatic adsorption or mechanical force generated. Furthermore, the flatness of the LED chip substrate is highly required, and during the chip transfer process, strict requirements are placed on the smooth operation of the equipment and the accuracy of the alignment process.

[0004] 2. Existing non-contact micro-transfer technologies, such as the laser transfer process, avoid the drawbacks of contact transfer technology. They use high-energy lasers to ablate the photoresponsive material between the substrate and the chip, causing a photochemical reaction that allows the chip to fall onto the target substrate. The microchip is grown on a transparent substrate and needs to be transferred to the target substrate, a process achieved by laser irradiation. There is a layer of photochemically responsive material between the microchip and the transparent substrate. When the laser irradiates the corresponding layer of material above the chip, depending on the characteristics of the material, it can be ablated (direct transfer), causing the chip to fall off the substrate to the target substrate, or the material can expand due to heat to produce a protruding bubble (indirect transfer), and the microchip falls to the target location under the action of mechanical force. The non-contact laser transfer solution uses laser ablation of the response layer between the substrate and the chip, causing the chip to fall off to the target location on the substrate. This solution has the advantages of fast response and high selectivity, but requires precise control of the laser energy to avoid affecting the Micro-LED.

[0005] The current laser transfer process has the following disadvantages: (1) the alignment accuracy between the transparent substrate and the target substrate needs to be strictly guaranteed; (2) the laser power and frequency need to be strictly and accurately controlled. Excessive laser power may burn the microchip, and too low power may not achieve successful microchip transfer; (3) the cost is too high. The material of the response layer is a disposable consumable. It will be ablated or produce protrusions after a single laser irradiation and cannot be used anymore. The time and efficiency of the photochemical response need to be considered. Both contact transfer and non-contact laser transfer require a large amount of repeated precision alignment, which greatly increases the difficulty and cost of the process. As the size of display devices increases, improving efficiency will become more difficult.

[0006] 3. Self-assembly transfer utilizes fluid dynamics or magnetic fields to guide LED chips with specific microstructures to automatically align and position themselves on target electrodes during movement. Under the influence of fluid, LED chips with specialized microstructures can achieve self-assembly, with electrodes in contact with the target substrate. During liquid flow, the wider side of the microstructure with the electrode allows for stable landing in the LED pit on the target substrate.

[0007] However, existing fluid self-assembly technology has specific requirements for the morphology and materials of Micro-LED chips and circuit substrates. It is difficult to achieve microchip self-assembly for circuit substrates with complex surface patterns, and precise control of fluid and magnetic force is required. This is still a technical difficulty for technical personnel in this field. Summary of the Invention

[0008] To address the shortcomings of previous mass transfer methods, a new approach has been proposed that utilizes laser processing combined with capillary self-assembly technology to achieve precise positioning and arrangement of micro-objects, with potential application in the field of Micro-LED mass transfer. This approach specifically involves using ultrafast lasers to selectively manipulate the hydrophobicity of a material's surface. The capillary forces generated by the liquid's interface during flow and evaporation then induce the self-assembly of micro-objects. This approach addresses the challenges of previous mechanical alignment methods, including low efficiency, complex and difficult processes, and the high cost and consumables required.

[0009] The present invention adopts the following technical solution to achieve: a method for controlling Micro-LED arrangement based on laser processing-guided capillary force, comprising the following steps:

[0010] Step 1: Modify the surface of the circuit substrate to change the hydrophilicity and hydrophobicity of the substrate surface.

[0011] Step 2: Perform laser processing; place the circuit substrate on a stage, design laser processing parameters, and use laser processing to induce a uniform periodic groove microstructure on the surface of the circuit substrate, so that the surface has superhydrophobic properties.

[0012] Step 3: Hydrophilicity test: perform a hydrophilicity test on the sample processed in step 2.

[0013] Step 4: Processing the micro-baffle: Spin-coat a layer of negative photoresist on the surface of the tested circuit substrate, and use photolithography technology to process the micro-baffle at the chip pre-assembly position to prevent the microchip from moving forward. After the micro-baffle is formed, use a developer to remove the unexposed part of the photoresist.

[0014] Step 5: Regulate the interface contact line. Utilize the difference in wettability of the two regions to regulate the interface contact line. By changing the waterline morphology, the direction of the capillary force is controlled, thereby achieving capillary force edge position regulation of the Micro-LED chip.

[0015] Step 6: Construct a uniform magnetic field. The direction of the magnetic field is from bottom to top to control the direction of the Micro-LED electrodes, so that the two ends of the electrode of the chip always remain perpendicular to the substrate during the flow of liquid, avoiding the reversal of the positive and negative poles.

[0016] Step 7: Interface capillary self-assembly; the chip flows with the liquid to the target position on the substrate and is isolated by the micro-baffle at the chip pre-assembly location.

[0017] Specifically, in step 1, if the circuit substrate is made of a hydrophilic material, a layer of hydrophobic material is first sprayed on the processing position of the circuit substrate. The hydrophobic material can be polydimethylsiloxane (PDMS).

[0018] Specifically, in step 3, a contact angle meter is used to measure the contact angle of the droplet. A surface having a contact angle greater than 150° is considered to be super-hydrophobic.

[0019] Specifically, the model of the negative photoresist solution is SZ2080, and the spin coating thickness of the negative photoresist is 20 μm, and the photoresist is dried after spin coating.

[0020] Specifically, it is characterized in that the specific process of step 5 is:

[0021] A large number of micro-nano chips are dispersed in deionized water to form a uniformly mixed Micro-LED fluid.

[0022] Slowly drip liquid on the side of the processed circuit board to accumulate chips.

[0023] The mixed liquid forms a thin water film and flows in a preset direction.

[0024] Due to the difference in wettability between the hydrophilic and hydrophobic regions, the liquid will naturally avoid the hydrophobic region and flow only in the hydrophilic region.

[0025] The present invention discloses a device for controlling the arrangement of Micro-LEDs by capillary force guided by laser processing. The device utilizes ultrafast lasers to selectively control the hydrophobicity of the material surface. The capillary force generated by the liquid interface contact line during flow and evaporation induces the self-assembly of micro-objects. The device comprises:

[0026] substrate;

[0027] Femtosecond laser processing system, which is used to precisely focus the output energy on the pre-processing area of ​​the substrate material;

[0028] Computer software operating system, which uses the SAMLight marking system to achieve the desired processing by drawing the laser scanning path pattern within the software and setting parameters such as processing power, scanning speed, and number of cycles;

[0029] The magnetic field control system includes an energized solenoid and a constant temperature base plate located in the magnetic field of the energized solenoid.

[0030] Preferably, the femtosecond laser processing system includes a laser source, a laser optical path, an XY scanning galvanometer and a three-dimensional mobile platform, wherein the three-dimensional mobile platform is provided with a stage for carrying a substrate, and the XY scanning galvanometer can realize the deflection and focusing of the laser, and the laser is precisely focused on the processing workpiece through software interface control, and processing is realized according to a pre-set path.

[0031] Preferably, the laser light path includes a reflector, a half-wave plate, an aperture, and a Glan-Taylor prism. The reflector is used to adjust the direction of the light path, the half-wave plate and the Glan-Taylor prism jointly adjust the laser pulse energy, and the aperture is used to limit the light beam and field of view size.

[0032] Preferably, the substrate may be made of silicon dioxide, glass, or silicon wafer; and the laser source may be a femtosecond pulse laser, a nanosecond laser, or a continuous laser.

[0033] Preferably, the magnetic field control system further comprises a movable scraper, which contacts the sample surface to form a water film that continuously flows forward on the sample surface.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The assembly method proposed in the present invention does not require strict alignment, avoids the requirements for chip materials and shapes, requires less consumables, has high structural universality, and greatly simplifies the process steps; the present invention overcomes the disadvantage that fluid self-assembly can only be achieved on a uniform substrate surface. Through the selective regulation of the hydrophilicity and hydrophobicity of the material surface by ultrafast laser, it can achieve micro-nano chip self-assembly on substrates with uneven materials and complex surface patterns, and complete the arrangement of microchips with low-cost and high-throughput technology, thereby realizing the mass transfer of Micro-LEDs. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a flow chart of the Micro-LED arrangement method proposed in the present invention;

[0037] Figure 2 Schematic diagram of femtosecond laser processing in the present invention; Figure 2 (a) shows the surface of the hydrophobic material processed by laser; Figure 2 (b) shows laser processing of hydrophilic materials after low surface energy modification; Figure 2 (c) is a comparison of the droplet states in the processed area and the unprocessed area;

[0038] Figure 3 Schematic diagram of the change in contact angle between the hydrophobic and hydrophilic surfaces of the droplet;

[0039] Figure 4 It is a structural diagram of the shape of the water film edge;

[0040] Figure 5 The schematic diagram shows the principle of controlling the direction of Micro-LED electrodes by applying a magnetic field from bottom to top.

[0041] Figure 6 A schematic diagram of the structure of the microchip as it flows with the liquid to the target position on the substrate and is isolated by a micro baffle at the chip pre-assembly location;

[0042] Figure 7 Schematic diagram of the structure of the Micro-LED chip after self-assembly;

[0043] Figure 8 This is the experimental optical path diagram based on femtosecond laser processing;

[0044] Figure 9 Schematic diagram of the structure between the Micro-LED chip and the micro baffle under the action of the magnetic field;

[0045] Figure 10 Schematic diagram of the structure when the Micro-LED chip is isolated by the micro baffle when the laser path is curved;

[0046] Figure 11 Schematic diagram of the structure of the microchip when it stays in the hydrophilic grid area after scanning and processing several hydrophilic grid areas on the substrate surface to control the hydrophilicity and hydrophobicity using ultrafast laser for contact line control;

[0047] Figure 12 This is a schematic diagram of the installation layout of the scraper in this scheme. DETAILED DESCRIPTION

[0048] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0049] Example 1

[0050] Please combine Figure 1 This solution proposes a method for controlling Micro-LED arrangement based on laser processing-guided capillary force, including the following steps:

[0051] Step one: Surface modification of the circuit substrate. Since the hydrophilicity and hydrophobicity treatment of the substrate is a preliminary preparation for chip packaging, its surface wettability may affect the performance of the entire chip, and the hydrophilicity of the substrate surface needs to be changed according to the specific materials and processes. Super-hydrophobic surfaces have a very wide range of uses and have a series of excellent properties such as self-cleaning, anti-oxidation, and anti-corrosion. Therefore, it is comprehensively considered to use laser processing to perform super-hydrophobic treatment on the surface of the material, which can improve the surface performance of the substrate while realizing chip self-assembly by capillary force at the interface. For hydrophobic materials, it is only necessary to process rough micro-nano structures on their surface, while for hydrophilic materials, low surface energy modification is required first, such as spraying a layer of hydrophobic material polydimethylsiloxane (PDMS) at the processing position, and then combining the surface micro-nano structure for subsequent processing to obtain a super-hydrophobic effect;

[0052] More specifically, the circuit substrate surface pretreatment method described above is interchangeable. This experiment, to further differentiate the hydrophilic and hydrophobic properties of the material surface and enhance the substrate's self-cleaning properties, applied super-hydrophobic treatment to the unassembled area of ​​the chip. However, according to the principle of this device, only the hydrophobicity of the material surface needs to be classified, thus omitting the step of modifying the material's low surface energy. For hydrophilic materials, laser hydrophobicity control is required only at the pre-processed area. For hydrophobic materials, laser processing is performed to make the unassembled area more hydrophobic.

[0053] Step 2: Laser processing. First, place the sample on the stage and design the laser processing parameters, such as laser power, scanning direction, scanning speed, structural parameters, structural period, etc. The specific processing parameters need to be designed and regulated according to the material being processed. Use femtosecond laser to process and induce a uniform periodic groove microstructure on the surface of the material, so that the surface has super-hydrophobic properties. The comparison diagram of super-hydrophobic processing of hydrophobic materials and hydrophilic materials is shown in the figure. Figure 2 As shown in the figure, the laser scans along a preset path, making the processed area super-hydrophobic, with extremely low adhesion to droplets. The unprocessed area, on the other hand, retains the material's original hydrophilic properties, allowing droplets to quickly spread and wet the surface.

[0054] Figure 2 Schematic diagram of femtosecond laser processing: a) Laser processing of hydrophobic material surface; b) Laser processing of hydrophilic material after low surface energy modification; c) Comparison of droplet states in processed and unprocessed areas.

[0055] Step 3: Hydrophilicity and hydrophobicity test. Due to the selective regulation of the material surface by femtosecond laser, the contact angle of the droplet in the hydrophilic and hydrophobic contact area will have significant differences, such as Figure 3 As shown in the figure, the contact angle of the droplet in the processed area (superhydrophobic surface) is greater than 150°, which is very easy to roll, while the contact angle in the unprocessed area (hydrophilic area) is less than 60°, showing good wettability and fluidity. In order to ensure the subsequent chip assembly effect, it is necessary to test the wettability difference of the substrate surface after processing.

[0056] Step 4: Fabricating the micro-baffles. A layer of negative photoresist is spin-coated on the laser-selective controlled substrate surface. Using photolithography, micro-baffles are fabricated at the chip pre-assembly location to prevent the microchip from moving forward. Because the exposed portions of the negative photoresist undergo a chemical polymerization reaction, while the unexposed portions are dissolved during the development process, a developer is required to remove the unexposed portions of the photoresist after the micro-baffles are formed.

[0057] Step 5: Control the interface contact line. Utilizing the difference in wettability of the two regions to water, the interface contact line is controlled. By changing the waterline morphology, the direction of the capillary force is controlled, thereby achieving control of the capillary force edge position of the Micro-LED chip. The specific process is as follows:

[0058] 1. Disperse a large number of micro-nano chips into deionized water to form a uniformly mixed Micro-LED fluid. 2. Slowly drip liquid (i.e., Micro-LED fluid) onto the side of the processed substrate to accumulate the chips.

[0059] 3. The mixed liquid forms a thin water film and flows in the preset direction; this is achieved by the following structure: Figure 12 At the same time, a plastic scraper is placed on one side of it. The plastic scraper is installed on a fixture, and the fixture is installed on a two-dimensional mobile platform. The scraper can be driven to move by the two-dimensional mobile platform, and the sample surface has a slight contact with the scraper for subsequent experimental operations.

[0060] 4. Due to the difference in wettability between hydrophilic and hydrophobic areas, the liquid will naturally avoid the hydrophobic area and flow only in the hydrophilic area, e.g. Figure 4 As shown, the shape of the water film edge is determined by the path of laser processing.

[0061] Step 6: Add a uniform magnetic field outside the system. Figure 5 As shown, the direction of the magnetic field from bottom to top is used to regulate the direction of the Micro-LED electrodes, so that the two ends of the electrode of the chip always remain perpendicular to the substrate during the flow of liquid, avoiding the reversal of the positive and negative poles and facilitating subsequent conductive operations.

[0062] Step 7: Interface capillary self-assembly. The chip flows with the liquid to the target position on the substrate and is isolated by the micro-baffle at the chip pre-assembly location, such as Figure 6 As shown, a micro baffle isolates one chip, and the remaining chips continue to move forward in the liquid.

[0063] As the liquid slowly evaporates, the capillary force at the solid-liquid interface contact line becomes greater than the liquid flow force, which pulls the Micro-LED chip and regulates its position. Then, when the liquid completely evaporates, the van der Waals force between the chip and the micro baffle takes effect, which makes the microchip firmly adsorbed at the target position and achieve self-assembly. The final assembly diagram is shown below. Figure 7 As shown in the figure, due to the sufficient number of chips and the slow and uniform liquid flow rate, most baffles can successfully intercept the microchips, thus completing the arrangement of microchips on the substrate efficiently and cost-effectively, showing good prospects for the field of mass transfer of Micro-LEDs. This fluid self-assembly solution is applicable to chips of various shapes and has no additional requirements for the materials and structures of the substrate and chips.

[0064] Example 2

[0065] This solution proposes a device for controlling the arrangement of Micro-LEDs by guiding capillary force based on laser processing. As an optional embodiment of the present invention, the experimental optical path diagram based on femtosecond laser processing is shown in the figure below. Figure 8 As shown:

[0066] Relevant experimental components and materials include: femtosecond laser processing system, computer software operating system, silicon dioxide wafer (circuit substrate), polydimethylsiloxane (PDMS), photoresist (SZ2080), deionized water, micro LED chip with magnetic electrodes, and energized solenoid.

[0067] As an optional embodiment of the present invention, the femtosecond laser in the femtosecond laser processing system can precisely focus its output energy on the pre-processed area, offering advantages such as minimal thermal effects, high processing precision, and flexible processing methods. The present invention utilizes vertical laser processing. The entire femtosecond laser processing system consists of a laser source (pulse width of 104 fs, repetition rate of 1000 Hz, central wavelength of 800 nm), a laser optical path, an XY scanning galvanometer (SAMLight, Germany), and a three-dimensional motion platform. The laser optical path includes optical components such as a reflector, a half-wave plate, an aperture, and a Glan-Taylor prism. The reflector is used to control the direction of the optical path, the half-wave plate and Glan-Taylor prism jointly control the laser pulse energy, and the aperture is used to limit the beam and field of view. The XY scanning galvanometer can achieve laser deflection and focusing. Through software interface control, the laser is precisely focused on the workpiece, achieving processing according to the pre-defined path. The three-dimensional moving platform consists of an XY moving stage and a Z lifting stage. The travel range of the XY moving stage is 110 mm × 75 mm, and its maximum scanning speed can reach 250 mm / s. The Z lifting stage adjusts the height of the sample by a knob.

[0068] In this solution, the computer software operating system uses the SAMLight marking system to achieve the desired processing by drawing the laser scanning path pattern within the software and setting parameters such as processing power, scanning speed, and number of cycles.

[0069] In this protocol, silicon dioxide wafers were selected as the substrate material, and polydimethylsiloxane (PDMS) was used as a superhydrophobic pretreatment material to modify the substrate processing area to a low surface energy. Photoresist (SZ2080) was used as the experimental material for subsequent microplate processing, and micro-LED chips were used as micro-nanodevices for self-assembly.

[0070] In this solution, the energized solenoid is composed of an energized coil, which will generate a relatively uniform magnetic field during the energization process, and the direction of its external magnetic field starts from the N pole and returns to the S pole.

[0071] The specific experimental process of this proposal is a device based on laser processing to guide capillary force to control Micro-LED arrangement as follows:

[0072] The first step is to use scissors or other tools to cut the circuit substrate to the appropriate size (approximately 50 mm × 50 mm). Turn on the laser processing system, adjust the laser processing parameters, draw the required laser scanning path in the SAMLight marking system, set the marking speed, laser frequency, fill type and other parameters according to the material of the processing sample, and rotate the half-wave plate to adjust the laser power.

[0073] The second step is to place the sample substrate on the three-dimensional moving platform. Adjust the XY moving platform to place the sample in the laser processing area. Rotate the Z-axis lifting knob to place the sample at the laser focus. At this time, the laser spot reaches its brightest. Click the processing button to start processing. After processing is completed, remove the sample for subsequent experiments.

[0074] In the third step, a plastic mask is applied to the processed sample substrate, leaving the pre-processed area exposed and the liquid flow area (hydrophilic area) covered by the mask. A layer of pure PDMS solution is sprayed onto the mask to modify the pre-processed area to a low surface energy, making it superhydrophobic.

[0075] The fourth step is to test the hydrophobicity of the processed area on the sample substrate. Specifically, a contact angle meter (produced by Chongqing Sanke Instrument Co., Ltd., model SK-CKA / B) can be used to measure the contact angle of the droplet. A contact angle greater than 150° is considered a super-hydrophobic surface.

[0076] Step 5: Apply negative photoresist solution (SZ2080) to the processed sample surface and spin-coat it to a thickness of approximately 20 μm, ensuring a level surface. Bake the sample in a hot dryer at 60°C for 15 minutes and then at 90°C for 60 minutes to completely evaporate the solvent (the photoresist's organic solvent, such as toluene or isopropyl alcohol).

[0077] In the sixth step, the rectangular pattern (30 μm × 20 μm) on the mask is transferred to the substrate using UV lithography. The entire lithography process takes approximately 6 minutes. After exposure, the sample is developed using an ethanol solution to remove the unexposed and cured photoresist. After the alcohol evaporates, the sample substrate with micro-baffles is obtained.

[0078] Step 7: The sample, after being modulated by the femtosecond laser, is fixed on a base plate at a constant temperature of 50°C. The base plate is placed in the uniform magnetic field generated by the energized solenoid, and the magnetic field direction is from bottom to top.

[0079] Reference Figure 12At the same time, a plastic scraper is placed on one side of it. The plastic scraper is installed on a fixture, and the fixture is installed on a two-dimensional mobile platform. The scraper can be driven to move by the two-dimensional mobile platform, and the sample surface has a slight contact with the scraper for subsequent experimental operations.

[0080] Step 8: Mix a large number of Micro-LED chips in water to form a microchip dispersion. Use a pipette to slowly drip the solution (microchip dispersion) onto one side of the sample substrate. Then, turn on the motor to drive the scraper to slowly spread the accumulated solution toward the other side. Surface tension forces the liquid to form a thin film only on the hydrophilic area and continue to flow forward.

[0081] Step 9. The entire solution flow process is carried out on a bottom plate with a constant temperature of 50°C. As the liquid flows forward, the liquid at the rear is also constantly evaporating. Under the action of the magnetic field, the direction of the Micro-LED chip electrode will always remain vertically upward. During the movement, most of the Micro-LED chip particles will be blocked when they encounter the baffle, and some may cross the micro-baffle due to the flow force of the water. However, because there are many Micro-LED chips, the Micro-LED chips at the rear will fill the gap. At the same time, during the evaporation of water, the capillary force of the interface will pull the Micro-LED chip, and eventually the Micro-LED chip will be retained in front of the baffle. As the water evaporates completely, the van der Waals force between the Micro-LED chip and the micro-baffle comes into play. In the absence of external force, the two will not be easily separated. The entire device is shown in the figure below. Figure 9 shown.

[0082] Step 10. Finally, observe the assembly using an optical microscope after the solution has completely evaporated.

[0083] Example 3

[0084] Alternative solutions in the present invention

[0085] As an optional embodiment of the present invention, the material of the circuit substrate is replaceable. In this experiment, a silicon dioxide wafer is used, and the material can also be selected according to the specific circuit substrate required, such as a glass wafer, a silicon wafer, etc.

[0086] As an optional embodiment of the present invention, the laser light source is replaceable. The present invention adopts femtosecond pulse laser due to its advantages of low thermal effect and high precision. The laser source can also be replaced by nanosecond laser or continuous laser to regulate the surface hydrophobicity.

[0087] As an optional embodiment of the present invention, the laser processing pattern can be replaced. In the present invention, the laser path is set to a straight line, and the control software can also be used to import the desired scanning path, such as Figure 10As shown, true 3D scanning can be achieved due to the flexibility of laser processing.

[0088] In addition, ultrafast laser can be used to control the contact line, and small grids can be scanned and processed when controlling the hydrophilicity and hydrophobicity of the substrate surface, such as Figure 11 The laser-controlled area becomes hydrophobic. Due to the surface tension of the liquid, a liquid meniscus forms at the hydrophilic and hydrophobic boundary. This causes the microchip to tend to enter the hydrophilic grid area formed by the hydrophobic lines as the liquid flows. During the subsequent evaporation of the liquid, capillary forces at the contact lines come into play, "pulling" the microchip and hindering its movement, fixing it in the hydrophilic area to achieve a regular arrangement.

[0089] As an optional embodiment of the present invention, the photolithography technology in this solution is replaceable. In addition to non-contact photolithography technology, there are also electron beam lithography technology, focused ion beam lithography technology, laser direct writing technology, etc.

[0090] As an optional embodiment of the present invention, the step of photolithography of the microplate can be replaced by using laser to process hydrophobic lines at preset positions. When the microchip moves to the hydrophobic lines with the liquid, it will be separated. As the liquid evaporates, the microscopic interface capillary force between the chip and the hydrophobic lines comes into play, inducing the chip to self-assemble at the target position.

[0091] As an optional embodiment of the present invention, the liquid is replaceable. The solvent used in the present invention is deionized water, and the solvent can be replaced according to the specific properties of the substrate, such as silicone oil.

[0092] In addition, the liquid heating method is replaceable. The present invention adopts a constant temperature heating method to evaporate water, and can also use photothermal control, electric heating control and other methods to accelerate fluid evaporation.

[0093] As an optional embodiment of the present invention, the fluid control method is replaceable. The present invention uses a scraper to drive the flow of liquid and chips, and can use a micro turbine or a water vortex speed control system to drive the water flow.

[0094] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A method for controlling Micro-LED arrangement based on capillary force guided by laser processing, characterized in that: The steps include: Step 1: Modifying the surface of the circuit substrate to change the hydrophilicity and hydrophobicity of the substrate surface; Step 2: performing laser processing; placing the circuit substrate on a stage, designing laser processing parameters, and using laser processing to induce a uniform periodic groove microstructure on the surface of the circuit substrate, so that the surface has superhydrophobic properties; Step 3: hydrophilicity test: perform a hydrophilicity test on the sample processed in step 2; Step 4: Processing micro baffles; A layer of negative photoresist is spin-coated on the surface of the tested circuit substrate, and a micro-baffle is processed at the chip pre-assembly position using photolithography technology to prevent the microchip from moving forward. After the micro-baffle is formed, the unexposed part of the photoresist is removed using a developer. Step 5: Regulating the interface contact line: Utilizing the difference in wettability of the two regions to water, the interface contact line is regulated. By changing the waterline morphology, the direction of the capillary force is controlled, thereby achieving capillary force edge position regulation of the Micro-LED chip. Step 6: Construct a uniform magnetic field from bottom to top to control the orientation of the Micro-LED electrodes, so that the electrodes at both ends of the chip always remain perpendicular to the substrate during the flow of liquid, avoiding the reversal of the positive and negative poles. Step 7: Interface capillary self-assembly; the chip flows with the liquid to the target position on the substrate and is isolated by the micro-baffle at the chip pre-assembly location.

2. The method for controlling Micro-LED arrangement based on capillary force guided by laser processing according to claim 1, characterized in that: In step 1, if the circuit substrate is made of a hydrophilic material, a layer of hydrophobic material is first sprayed on the processing position of the circuit substrate. The hydrophobic material can be polydimethylsiloxane.

3. The method for controlling Micro-LED arrangement based on capillary force guided by laser processing according to claim 1, characterized in that: In step 3, a contact angle meter is used to measure the contact angle of the droplet. A contact angle greater than 150° is considered a super-hydrophobic surface.

4. The method for controlling Micro-LED arrangement based on capillary force guided by laser processing according to claim 1, characterized in that: The model of the negative photoresist solution is SZ2080, and the spin coating thickness of the negative photoresist is 20 μm, and the photoresist is dried after spin coating.

5. The method for controlling Micro-LED arrangement based on capillary force guided by laser processing according to claim 1, characterized in that: The specific process of step 5 is as follows: Disperse a large number of micro-nano chips into deionized water to form a uniformly mixed Micro-LED fluid; Slowly drip liquid on the side of the processed circuit substrate to accumulate chips; The mixed liquid forms a thin water film and flows in a preset direction; Due to the difference in wettability between the hydrophilic and hydrophobic regions, the liquid will naturally avoid the hydrophobic region and flow only in the hydrophilic region.

6. The method for controlling Micro-LED arrangement based on capillary force guided by laser processing according to claim 1, wherein: The processing equipment includes: substrate; Femtosecond laser processing system, which is used to precisely focus the output energy on the pre-processing area of ​​the substrate material; Computer software operating system, which uses the SAMLight marking system to achieve the desired processing by drawing the laser scanning path pattern within the software and setting the processing power, scanning speed, and number of cycles; The magnetic field control system includes an energized solenoid and a constant temperature base plate located in the magnetic field of the energized solenoid.

7. The method for controlling Micro-LED arrangement based on capillary force guided by laser processing according to claim 6, characterized in that: The femtosecond laser processing system includes a laser source, a laser optical path, an XY scanning galvanometer and a three-dimensional mobile platform. The three-dimensional mobile platform is provided with a stage for carrying a substrate. The XY scanning galvanometer can realize the deflection and focusing of the laser. Through the control of the software interface, the laser can be precisely focused on the processing workpiece, and processing is performed according to a predetermined path.

8. The method for controlling Micro-LED arrangement based on capillary force guided by laser processing according to claim 7, characterized in that: The laser light path includes a reflector, a half-wave plate, an aperture, and a Glan Taylor prism. The reflector is used to adjust the direction of the light path. The half-wave plate and the Glan Taylor prism jointly adjust the laser pulse energy. The aperture is used to limit the light beam and field of view.

9. The method for controlling Micro-LED arrangement based on capillary force guided by laser processing according to claim 7, characterized in that: The material of the substrate can be silicon dioxide, glass, silicon wafer, copper plate; the laser source can be femtosecond pulse laser, nanosecond laser, or continuous laser.

10. The method for controlling Micro-LED arrangement based on capillary force guided by laser processing according to claim 6, wherein: The magnetic field control system further comprises a movable scraper, which contacts the sample surface to form a water film that continuously flows forward on the sample surface.

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