Micro-LED chip flow magnetic self-assembly method and device

Abstract

The invention discloses a Micro-LED chip flow magnetic self-assembly method and device, and belongs to the technical field of semiconductors, and the method comprises the steps: manufacturing RGB LED chips with different shapes and sizes; applying a ferrite magnetic powder layer of 2-5 [mu] m to a pin layer of the chip, and magnetizing the chip; grooves are formed in the transfer glass substrate, and each pixel point corresponds to three grooves of the RGB three LED chips; moving the magnetic needle to enable the needle point of the magnetic needle to directly face the lower part of the groove of the substrate, and adjusting the height between the magnetic needle and the substrate; enabling the chip to fall into the flow field pool, and enabling the chip to be completely infiltrated in the solvent; grabbing a corresponding chip into a corresponding groove through a magnetic needle, and opening a flow field to finely adjust the posture of the chip; adjusting the position of the magnetic needle and the flow velocity of the flow field, retaining the chips in the groove and washing away the redundant chips; the substrate is taken out, dried and fixed, and transferring is completed. By the adoption of the method, a large number of Micro-LED chips can be accurately transferred at a time, self-assembly is achieved, the transfer efficiency is improved, the structure is simple, and the transfer cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method and device for self-assembly of a Micro-LED chip flux magnetic field. Background Art

[0002] Micro-LED display chips are considered to be the next generation of display technology after liquid crystal displays (LCDs) and organic light-emitting diode displays (OLEDs) due to their small size, self-luminous source characteristics, excellent efficiency, outstanding brightness, fine resolution, and long service life. In order to produce high-resolution and high-pixel-density Micro-LED displays, it is necessary to use mass transfer technology to accurately transfer millions of Micro-LED chips to the driving substrate and ensure that the transfer process has a high yield rate.

[0003] At present, a variety of different methods have been developed for mass transfer technology in the Micro-LED field, including precise pick-and-place technology, laser stripping technology, roll-to-roll printing technology, and self-assembly technology. Among the many technologies, fluid magnetic self-assembly technology stands out due to its unique advantages. It uses the principles of fluid dynamics to automatically position semiconductor light-emitting diodes to a predetermined position in the fluid. This technology can reduce transfer costs and improve transfer efficiency, and is particularly suitable for the manufacture of large-screen display devices.

[0004] Publication No. CN202310975987.8 proposes a self-assembly and mass transfer method and device for Micro-LED chips, which realizes the self-assembly process by matching RGB Micro-LED chips with specific shapes and electrode structures with the grooves of a special substrate. However, this technology faces challenges in precise alignment and bonding technology. The patent does not elaborate on how to adapt to chips of different sizes and shapes, and only relies on the fluid and the tilt angle of the substrate to put the chip into the groove, so the upper limit of the transfer efficiency is low.

[0005] Publication No. CN202211665819.0 proposes a method for transferring magnetic LED chips. By adjusting the thickness of the magnetic film and precisely controlling the magnetic field strength, the precise adsorption and transfer of LED core particles of different colors are achieved. However, the transfer yield and repeatability using only the interaction between the magnetic field and the magnetic chip need to be improved, and the posture of the transferred chip cannot be precisely controlled.

[0006] Publication No. CN202211483927.6 proposes a laser-assisted rapid transfer method for Micro-LED chips. By precisely controlling the laser parameters and the microstructure groove design of the intermediate template, the precise alignment and transfer of Micro-LED chips can be achieved. However, it requires precise control of the laser irradiation conditions and the corrosion process, which has high requirements for equipment and technology, and the bonding and cleaning steps after the transfer may require additional processing and verification. Summary of the invention

[0007] The purpose of the present invention is to provide a method and device for self-assembly of Micro-LED chips by fluid magnetism, which realizes the mass transfer of RGB chips by means of the combination of fluid and magnet and groove design.

[0008] To achieve the above object, the present invention provides a method for self-assembly of a Micro-LED chip by magnetic flux, comprising the following steps:

[0009] S1. Manufacture three kinds of LED chips with different shapes and sizes: RGB;

[0010] S2, applying a 2-5 μm ferrite powder layer on the chip pin layer and magnetizing the chip;

[0011] S3, opening grooves on the transfer glass substrate, each pixel point corresponds to three grooves of the three RGB LED chips;

[0012] S4, move the magnetic needle so that its needle tip is directly below the groove of the substrate, and adjust the height between the magnetic needle and the substrate;

[0013] S5, dropping the chip into the flow field pool to completely soak the chip in the solvent;

[0014] S6, grab the corresponding chip by the magnetic needle and put it into the corresponding groove, and turn on the flow field to fine-tune the chip posture;

[0015] S7, adjusting the position of the magnetic needle and the flow rate of the flow field to retain the chips in the groove and flush away the excess chips;

[0016] S8, take out the substrate and dry and fix it, and the transfer is completed.

[0017] Preferably, the shapes of the three RGB LED chips are all rectangular, wherein the dimensions of the R-type chip are 200 μm in length and 100 μm in width, the dimensions of the G-type chip are 150 μm in length and 150 μm in width, and the dimensions of the B-type chip are 225 μm in length and 75 μm in width, and the height of the three chips are all 80 μm.

[0018] Preferably, the material of the ferrite magnetic powder layer is selected from at least one of Fe3O4, manganese-zinc ferrite Mn-ZnFe2O4 or nickel-zinc ferrite Ni-ZnFe2O4, the magnetic powder particle diameter is 0.5μm-2μm, and is applied to the chip pin layer by deposition.

[0019] Preferably, the groove size on the transfer glass substrate is: the groove corresponding to the R-type chip is 215μm long and 115μm wide, the groove corresponding to the G-type chip is 165μm long and 165μm wide, the groove corresponding to the B-type chip is 225μm long and 90μm wide, the groove depth is 20μm-40μm, and the spacing between each group of grooves is 2mm.

[0020] Preferably, the magnetic needle is made of aluminum-nickel permanent magnetic alloy, iron-chromium-cobalt permanent magnetic alloy, permanent magnetic ferrite or rare earth permanent magnetic material, the diameter of the magnetic needle is 1 mm, and the distance between adjacent magnetic needles is 2 mm; the tip of the magnetic needle is a stepped structure, the upper cone has a diameter of 0.1 mm and a height of 0.1 mm, and the lower cone has a diameter of 1 mm and a height of 1 mm.

[0021] Preferably, the magnetic field generated by the magnetic needle has a peak-to-valley distribution in the horizontal direction, with a peak value of ≥50mT and a valley value of ≤10mT, and the upper magnetic pole of the magnetic needle is opposite to the magnetic pole of the chip pin layer.

[0022] Preferably, the solvent in the flow field pool is an alcohol, ketone or fluorocarbon solvent with low surface tension and low viscosity, and the chip that is not transferred is recycled with the solvent.

[0023] The present invention also provides a Micro-LED chip flow magnetic self-assembly device, comprising:

[0024] Permanent magnetic needle array, used to grab and locate chips through magnetic field;

[0025] A flow field cell module, which has a solvent flow channel and a water inlet / outlet inside;

[0026] The transfer substrate is embedded in the bottom of the flow field pool and is provided with a groove matching the RGB chip;

[0027] The three-dimensional motion platform is used to adjust the relative position of the magnetic needle array and the transfer substrate.

[0028] Preferably, the groove depth of the transfer substrate is 20 μm-40 μm, and the distance between the three grooves of each pixel is 2 mm.

[0029] Preferably, the magnetic needle head of the permanent magnetic needle is a double-layer coaxial frustum structure, the magnetic field strength at the needle tip is ≥50mT, and the magnetic field strength at the lower part is ≤10mT.

[0030] Therefore, the present invention adopts the above-mentioned Micro-LED chip flow magnetic self-assembly method and device, which has the following technical effects:

[0031] (1) By using LED chips of specific shapes and sizes and matching substrate grooves, the chips can be accurately placed in the target position.

[0032] (2) Utilizing magnetic-assisted self-assembly, specific magnetic needle design and magnetic field distribution ensure that the chip can be accurately captured and placed, improving the efficiency and speed of the assembly process. Precise magnetic control and flow field adjustment help reduce errors in the assembly process and improve transfer yield.

[0033] (3) Strong compatibility, suitable for the transfer and assembly of RGB primary color chips, which helps to realize the application of full-color display technology.

[0034] (4) High automation potential. The magnetic needle operation and flow field control in the method make automated production possible, which helps to improve production efficiency and large-scale manufacturing.

[0035] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the main structure of the device according to an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the structure of a hole-digging transfer substrate according to an embodiment of the present invention;

[0038] Figure 3 A schematic diagram of the positions of the array magnetic needles and the transfer substrate according to an embodiment of the present invention;

[0039] Figure 4 It is a cross-sectional schematic diagram of the positions of the array magnetic needles and the transfer substrate according to an embodiment of the present invention;

[0040] Figure 5 This is a schematic diagram of magnetic density distribution 0.5 mm above the array magnetic needles according to an embodiment of the present invention;

[0041] Figure 6 A schematic diagram of a chip entering a pit process according to an embodiment of the present invention;

[0042] Figure 7 A schematic diagram of a special case process of chip entering a pit according to an embodiment of the present invention;

[0043] Figure 8 A flow chart of a transfer method is disclosed for one embodiment of the present invention;

[0044] Reference numerals

[0045] 1. Flow field pool; 101. Water inlet and outlet holes; 102. Transfer substrate groove; 2. Transfer substrate; 201. A group of pixel grooves; 201a. R-type chip groove; 201b. G-type chip groove; 201c. B-type chip groove; 3. Array magnetic needle block; 301. Magnetic needle body; 301a. Magnetic needle tip; 301b. Lower part of magnetic needle; 4. Magnetic chip; 401. Magnetic powder layer; 4a. Chip flip position 1; 4b. Chip flip position 2; 4c. Chip flip position 3; 4d. Chip flip position 4; 5. Carrier solvent. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0047] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0048] Embodiment 1

[0049] Device construction; Figure 1 As shown, the Micro-LED chip flow magnetic self-assembly device of this embodiment is mainly composed of three parts, namely a flow field pool 1, a transfer substrate 2 and an array magnetic needle block 3.

[0050] The flow field pool 1 is located at the top of the device and is the space carrier for chip transfer. It is equipped with an inlet and outlet 101, which can be opened as needed to provide flow power for the core carrier solvent 5 and build a stable flow field environment. The hollowed-out area at the bottom of the flow field pool 1 is precisely fitted with the transfer substrate 2 and sealed with the help of a vacuum system to effectively prevent solvent leakage and ensure the stability of the transfer process.

[0051] like Figure 2As shown, the transfer substrate 2 is in the middle of the device, and its upper surface is carefully designed and processed into a group of pixel grooves 201 according to the size and layout requirements of the three RGB chips. Each pixel corresponds to three grooves, namely the R-type chip groove 201a, the G-type chip groove 201b and the B-type chip groove 201c. Among them, the groove 201a corresponding to the R-type chip is 215μm long and 115μm wide, the groove 201b corresponding to the G-type chip is 165μm long and 165μm wide, and the groove 201c corresponding to the B-type chip is 225μm long and 90μm wide. The depth of all grooves is controlled at 30μm (satisfying the range requirement of 20μm-40μm). The spacing between each group of grooves is 2mm, and the total thickness of the transfer substrate 2 is 0.5mm. Such a design not only ensures the precise matching of the chip and the groove, but also provides a reliable basis for the subsequent chip transfer and fixation.

[0052] like Figure 1 , Figure 3 , Figure 4 As shown, the bottom layer of the device is the array magnetic needle block 3, and the magnetic needle body 301 is made of aluminum-nickel permanent magnetic alloy (at least one of iron-chromium-cobalt permanent magnetic alloy, permanent magnetic ferrite, rare earth permanent magnetic material or composite permanent magnetic material can also be selected). The diameter of the magnetic needle body 301 is 1mm, and the distance between adjacent magnetic needles is also 2mm, which is convenient for uniform distribution of the magnetic field and precise control of the chip. The magnetic needle body 301 adopts a unique two-layer coaxial circular step ladder structure. The upper frustum, i.e., the magnetic needle tip 301a, has a diameter of 0.1mm and a height of 0.1mm, and the lower frustum, i.e., the lower part of the magnetic needle 301b, has a diameter of 1mm and a height of 1mm. The lower frustum is firmly fixed on the top of the permanent magnetic needle. As shown Figure 5 As shown, the permanent magnetic field generated by the permanent magnetic needle 301a and the magnetic needle tip 301b is distributed in peak and valley in the horizontal direction. At 0.5mm above the array magnetic needle, the peak value of the magnetic field is greater than or equal to 50mT, and the valley value is less than or equal to 10mT. In addition, the device is equipped with a three-dimensional motion platform for accurately adjusting the relative position of the magnetic needle array and the transfer substrate 2, ensuring that the magnetic needle tip 301a can be accurately aligned with the bottom of the substrate groove, and the height between the magnetic needle and the substrate can be flexibly adjusted to meet the transfer requirements at different stages.

[0053] Chip preparation: manufacture rectangular LED chips of three different shapes and sizes: RGB. Among them, the R-type chip is 200μm long, 100μm wide, and 80μm high; the G-type chip is 150μm long, 150μm wide, and 80μm high; the B-type chip is 225μm long, 75μm wide, and 80μm high. By precisely controlling the chip size, it can be accurately matched with the transfer substrate groove 102 to reduce assembly errors.

[0054] A ferrite magnetic powder layer with a thickness of 3 μm (within the range of 2-5 μm) is applied to the chip pin layer by a deposition method. In this embodiment, Fe3O4 magnetic powder is selected (manganese-zinc ferrite Mn-ZnFe2O4 or nickel-zinc ferrite Ni-ZnFe2O4, etc. can also be selected), and its particle diameter is 1 μm (within the range of 0.5 μm-2 μm). After applying the magnetic powder layer, the chip is magnetized to make the chip magnetic so that it can be transferred and positioned by magnetic force later.

[0055] Chip transfer; Figure 3 , Figure 4 As shown, the transfer substrate 2 is tightly fitted and installed at the bottom of the flow field pool 1 and sealed and fixed by a vacuum system. With the help of a three-dimensional motion platform, the spatial position of the array magnetic needle block 3 and the transfer substrate 2 is carefully adjusted to ensure that the magnetic needle tip 301a is precisely aligned with the bottom of each group of pixel point grooves 201, and the height between the magnetic needle and the substrate is adjusted to a suitable state.

[0056] Slowly introduce the core solvent 5 from the water inlet of the flow field pool 1. In this embodiment, an alcohol solvent is selected (a ketone or fluorocarbon solvent may also be used, which must meet the requirements of low surface tension and low viscosity). After the solvent fills the flow field pool 1, gently place the magnetic chip 4 into the flow field pool 1 to ensure that the chip is completely soaked in the solvent and sinks naturally. Figure 6 The low surface tension and low viscosity of the solvent allow the chip to move freely in it, providing convenient conditions for subsequent magnetic needle grasping and posture adjustment.

[0057] Since the magnetic polarity of the magnetic powder layer 401 of the magnetic chip 4 is opposite to that of the magnetic needle body 301, the chip will fall to the vicinity of the magnetic needle body 301 under the action of the magnetic field. Figure 6 As shown. The magnetic density at the magnetic needle tip 301a is relatively high (greater than or equal to 50mT), and the magnetic force on the chip is stronger, which can firmly attract the chip. After the chip is close to the magnetic needle tip 301a, it is guided by the magnetic force and the chip electrode faces downward into the corresponding groove. At this time, the inlet (outlet) 101 of the flow field pool 1 is opened to allow the core carrier solvent 5 to flow slowly, and the fluid force is used to fine-tune the chip's pit posture to ensure that the chip can fall into the groove neatly and accurately, as shown in FIG. Figure 6 shown.

[0058] After the chip initially falls into the groove, the height of the magnetic needle array and the transfer substrate 2 is adjusted again with the help of the three-dimensional motion platform, and the flow field flow rate is precisely controlled, such as Figure 6 By properly adjusting the position of the magnetic needle and the flow field parameters, the magnetic field force on the chip in the groove and the flow field force are balanced, ensuring that the chip in the groove is stably fixed and will not be washed away; while the excess chips around the groove and on the upper layer are all washed away under the action of the flow field, thereby achieving accurate screening and positioning of the chips.

[0059] When only the required chip is left in the groove, close the water inlet (inlet) 101 of the flow field pool 1 to stop the flow of solvent. Collect the core carrier solvent 5 in the flow field pool 1 and the chips that have not been transferred therein. These chips can be recycled together with the solvent to reduce production costs. Carefully take out the transfer substrate 2 and dry it so that the chip is firmly fixed in the groove, completing the transfer process of the Micro-LED chip. Figure 8 shown.

[0060] Special case handling; during the chip transfer process, there may be a small number of magnetic chips 4 close to the groove 201, the magnetic powder layer 401 of the pin layer side facing up special situation, such as Figure 7 At this time, since the magnetic powder layer 401 of the chip has the same magnetic polarity as the magnetic needle 301, a repulsive force will be generated, causing the chip to flip, as shown in FIG. Figure 7 The chip is continuously flipped under the repulsive force, as shown in FIG. Figure 7 Until the electrode surface and the side with the magnetic powder layer face downward, the magnetic needle 301 can re-attract the chip and make it fall into the pit, ensuring that the chip is correctly transferred to the groove and the integrity and accuracy of the transfer process. Figure 7 As shown in chip 4d.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for self-assembly of a Micro-LED chip by magnetic flux, characterized in that: The following steps are involved: S1. Manufacture three kinds of LED chips with different shapes and sizes: RGB; S2, applying a 2-5 μm ferrite powder layer on the chip pin layer and magnetizing the chip; S3, opening grooves on the transfer glass substrate, each pixel point corresponds to three grooves of the three RGB LED chips; S4, move the magnetic needle so that its needle tip is directly below the groove of the substrate, and adjust the height between the magnetic needle and the substrate; S5, dropping the chip into the flow field pool to completely soak the chip in the solvent; S6, grab the corresponding chip by the magnetic needle and put it into the corresponding groove, and turn on the flow field to fine-tune the chip posture; S7, adjusting the position of the magnetic needle and the flow rate of the flow field to retain the chips in the groove and flush away the excess chips; S8, take out the substrate and dry and fix it, and the transfer is completed.

2. The method for self-assembly of Micro-LED chips by magnetic flux according to claim 1, characterized in that: The shapes of the three RGB LED chips are all rectangular, among which the dimensions of the R-type chip are 200μm long and 100μm wide, the dimensions of the G-type chip are 150μm long and 150μm wide, and the dimensions of the B-type chip are 225μm long and 75μm wide. The height of the three chips is 80μm.

3. The method for self-assembly of Micro-LED chips by magnetic flux according to claim 1, characterized in that: The material of the ferrite magnetic powder layer is selected from at least one of Fe3O4, manganese-zinc ferrite Mn-ZnFe2O4 or nickel-zinc ferrite Ni-ZnFe2O4, the magnetic powder particle diameter is 0.5μm-2μm, and is applied to the chip pin layer by deposition.

4. The method for self-assembly of Micro-LED chips by magnetic flux according to claim 1, characterized in that: The groove sizes on the transfer glass substrate are: the groove corresponding to the R-type chip is 215μm long and 115μm wide, the groove corresponding to the G-type chip is 165μm long and 165μm wide, the groove corresponding to the B-type chip is 225μm long and 90μm wide, the groove depth is 20μm-40μm, and the spacing between each group of grooves is 2mm.

5. The method for self-assembly of Micro-LED chips by magnetic flux according to claim 1, characterized in that: The magnetic needle is made of aluminum-nickel permanent magnetic alloy, iron-chromium-cobalt permanent magnetic alloy, permanent magnetic ferrite or rare earth permanent magnetic material, the diameter of the magnetic needle is 1mm, and the distance between adjacent magnetic needles is 2mm; the tip of the magnetic needle is a stepped structure, the upper frustum has a diameter of 0.1mm and a height of 0.1mm, and the lower frustum has a diameter of 1mm and a height of 1mm.

6. The method for self-assembly of Micro-LED chips by magnetic flux according to claim 5, characterized in that: The magnetic field generated by the magnetic needle is distributed in peak and valley in the horizontal direction, with a peak value of ≥50mT and a valley value of ≤10mT, and the upper magnetic pole of the magnetic needle is opposite to the magnetic pole of the chip pin layer.

7. The method for self-assembly of Micro-LED chips by magnetic flux according to claim 1, characterized in that: The solvent in the flow field pool is an alcohol, ketone or fluorocarbon solvent with low surface tension and low viscosity, and the chip that is not transferred is recycled with the solvent.

8. A Micro-LED chip flow magnetic self-assembly device, characterized in that: include: Permanent magnetic needle array, used to grab and locate chips through magnetic field; A flow field cell module, which has a solvent flow channel and a water inlet / outlet inside; The transfer substrate is embedded in the bottom of the flow field pool and is provided with a groove matching the RGB chip; The three-dimensional motion platform is used to adjust the relative position of the magnetic needle array and the transfer substrate.

9. The Micro-LED chip magnetic flux self-assembly device according to claim 8, characterized in that: The groove depth of the transfer substrate is 20 μm-40 μm, and the distance between the three grooves of each pixel is 2 mm.

10. The Micro-LED chip magnetic flux self-assembly device according to claim 8, characterized in that: The magnetic needle head of the permanent magnetic needle is a double-layer coaxial frustum structure, the magnetic field strength at the needle tip is ≥50mT, and the magnetic field strength at the lower part is ≤10mT.

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