Mini / Micro LED and manufacturing method thereof

Abstract

The invention discloses a Mini / Micro LED (Light Emitting Diode) and a manufacturing method thereof. The manufacturing method comprises the following steps: preparing a metal conductive ball; putting the metal conductive balls into insulating glue, and stirring to form anisotropic conductive glue; printing anisotropic conductive adhesive on a bonding pad of the substrate by adopting a steel mesh coating process; and mounting a Mini / Micro LED chip on the anisotropic conductive adhesive, enabling bonding pads of the Mini / Micro LED chip to be in one-to-one correspondence with the bonding pads of the substrate, and performing hot pressing and curing to obtain the Mini / Micro LED. According to the technology, stable connection between the Mini / Micro LED chip and the substrate is formed through the anisotropic conductive adhesive, electrical connection is formed through the metal conductive balls, adhesion is formed through curing of the insulating glue, in this way, a reflow soldering technology does not need to be adopted, the curing temperature of the insulating glue does not exceed the junction temperature of the Mini / Micro LED, and the service life of the Mini / Micro LED chip is prolonged. Therefore, the stability and the reliability of the manufactured Mini / Micro LED are ensured, the service life and the performance of the product are effectively improved, and the display requirement is met.

Description

Technical Field

[0001] This application relates to the technical field of LED display, and particularly to a Mini / Micro LED and its manufacturing method. Background Art

[0002] The higher the resolution of a display screen, the more pixel points it has on the screen. For example, a 4K display screen has 8,294,400 pixel points, and an 8K display screen has 33,177,600 pixel points. And each pixel point requires 3 chips (red, green, and blue). In traditional processes, the positive and negative electrodes of each chip need to be soldered. Therefore, the number of chip solders reaches tens of millions or even is measured in billions.

[0003] In the prior art, the reflow soldering process is usually used to realize the soldering of Mini / Micro LEDs. During the reflow soldering process, the soldering temperature usually reaches 200°C to 250°C. Since the junction temperature Tj of red, green, and blue chips is generally between 125 and 150°C, if the soldering duration exceeds this temperature for a long time (more than 10 seconds), it will damage the chips and lead to unstable soldering quality. Summary of the Invention

[0004] The main purpose of this application is to provide a Mini / Micro LED and its manufacturing method, aiming to solve the problem that the process of using reflow soldering to connect LED chips to a substrate in the prior art is prone to unstable soldering quality due to excessive temperature.

[0005] To achieve the above purpose, this application provides a manufacturing method of a Mini / Micro LED. The manufacturing method of the Mini / Micro LED includes: Preparing metal conductive balls; Putting the metal conductive balls into insulating glue and stirring to form anisotropic conductive glue; Using a stencil printing process to print the anisotropic conductive glue on the pads of the substrate; Mounting Mini / Micro LED chips onto the anisotropic conductive glue, and making the pads of the Mini / Micro LED chips correspond to the pads of the substrate one by one, and hot-pressing and curing to obtain Mini / Micro LEDs.

[0006] In some embodiments, the preparation of metal conductive balls includes: Selecting a conductive metal material, where the conductive metal material includes tin, silver, nickel, gold, copper, or their alloys; Preparing metal conductive balls with a particle size of 10μm to 20μm by physical vapor deposition, chemical vapor deposition, electroplating, or ball milling processes.

[0007] In some embodiments, putting the metal conductive balls into the insulating glue and stirring to form the anisotropic conductive glue includes: Providing insulating glue; the insulating glue includes at least one of epoxy resin, silica gel, and polyimide; the viscosity of the insulating glue is between 120 and 180 Pa·s; Adding the metal conductive balls and the insulating glue into a stirring container and stirring to uniformly disperse the metal conductive balls in the insulating glue to obtain anisotropic conductive glue; the volume ratio of the metal conductive balls in the anisotropic conductive glue is between 10% and 20%.

[0008] In some embodiments, adding the metal conductive balls and the insulating glue into the stirring container further includes: Adding a dispersant into the stirring container synchronously to prevent the metal conductive balls from agglomerating; the dispersant includes polyethylene glycol, sodium dodecyl sulfate, sodium hexametaphosphate, and sodium oleate.

[0009] In some embodiments, after stirring to uniformly disperse the metal conductive balls in the insulating glue to obtain anisotropic conductive glue, it further includes: Performing a defoaming treatment on the obtained anisotropic conductive glue until there are no obvious bubbles in the appearance of the anisotropic conductive glue; Detecting the conductivity and viscosity of the anisotropic conductive glue to ensure that it meets the process requirements.

[0010] In some embodiments, it further includes the storage and activation of the anisotropic conductive glue that meets the process requirements, including: Before and after use, the anisotropic conductive glue is sealed and stored frozen, and the freezing temperature is between -15 and -20 °C; and, Before use, the anisotropic conductive glue is restored to room temperature and then unsealed, and the relative humidity of the use environment is lower than 60%.

[0011] In some embodiments, before printing the anisotropic conductive glue on the pads of the substrate by using a stencil printing process, it further includes: Providing a steel plate, and opening stencil holes according to the occupied size of a group of RGB chips on the substrate to form a stencil; Coating a nano-hydrophobic coating on the stencil to obtain a hydrophobic nano-stencil.

[0012] In some embodiments, mounting the Mini / Micro LED chips on the anisotropic conductive glue so that the pads of the Mini / Micro LED chips correspond to the pads of the substrate one by one, and thermally pressing and curing to obtain Mini / MicroLED includes: Mount the Mini / Micro LED chip onto the anisotropic conductive adhesive on the substrate through a chip mounter; Set the hot pressing and curing parameters. During hot pressing, make the metal conductive balls contact the pads on both sides, and cure the insulating glue to obtain a Mini / Micro LED.

[0013] In some embodiments, after setting the hot pressing and curing parameters, during which the metal conductive balls contact the pads on both sides and the insulating glue is cured to obtain a Mini / Micro LED, the following steps are further included: Conduct performance testing on the obtained Mini / Micro LED; the performance testing includes electrical performance testing, optical performance testing, and reliability testing.

[0014] This application also provides a Mini / Micro LED manufactured by the manufacturing method described above.

[0015] In the technical solution provided by this application, a Mini / Micro LED and its manufacturing method are proposed. The manufacturing method of this Mini / Micro LED includes: preparing metal conductive balls; putting the metal conductive balls into insulating glue and stirring to form anisotropic conductive adhesive; using a stencil printing process to print the anisotropic conductive adhesive on the pads of the substrate; mounting the Mini / Micro LED chip onto the anisotropic conductive adhesive, and making the pads of the Mini / Micro LED chip correspond to the pads of the substrate one by one, and obtaining the Mini / Micro LED through hot pressing and curing. In the technology of this application, it aims to form a stable connection between the Mini / Micro LED chip and the substrate through the anisotropic conductive adhesive, including forming an electrical connection through the metal conductive balls and forming an adhesion through the curing of the insulating glue. In this way, the reflow soldering process is not required, and the curing temperature of the insulating glue does not exceed the junction temperature of the Mini / Micro LED, thereby ensuring the stability and reliability of the Mini / Micro LED, effectively improving the service life and performance of the product, and meeting the display requirements. Description of the Drawings One or more embodiments are exemplarily illustrated by corresponding drawings. These exemplary illustrations do not limit the embodiments. Elements with the same reference numerals in the drawings represent similar elements. Unless otherwise stated, the drawings in the figures do not constitute a proportional limitation.

[0016] Figure 1 It is a schematic flow chart of the manufacturing method of the Mini / Micro LED in the embodiments of this application; Figure 2Schematic diagram of the preparation process of the anisotropic conductive adhesive in the embodiments of the present application; Figure 3 Partial enlarged view of the Mini / Micro LED in the embodiments of the present application. Detailed implementation manners

[0017] To facilitate the understanding of the present application, the present application will be described in more detail below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is expressed as "fixed to" another element, it can be directly on the other element, or there can be one or more intermediate elements therebetween. When an element is expressed as "connected to" another element, it can be directly connected to the other element, or there can be one or more intermediate elements therebetween. The terms "vertical", "horizontal", "left", "right", "inside", "outside" and similar expressions used in this specification are only for the purpose of illustration. In the description of the present application, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating relative importance or implicitly indicating the quantity of the indicated technical features. Thus, unless otherwise stated, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features; the meaning of "a plurality" is two or more. The term "comprising" and any deformation thereof mean non-exclusive inclusion, and there may be or be added one or more other features, integers, steps, operations, units, components and / or their combinations.

[0018] In addition, unless otherwise clearly specified and defined, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. All technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not used to limit the present application. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0019] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0020] For the convenience of understanding, the specific process of the embodiments of the present application will be described below. Please refer to Figure 1 , the present application provides a manufacturing method for a Mini / Micro LED. The manufacturing method for the Mini / Micro LED includes: Step S10, preparing metal conductive balls.

[0021] The metal conductive ball is used as a conductive medium in the anisotropic conductive adhesive to achieve electrical connection between the substrate and the Mini / Micro LED chip. The preparation of the metal conductive ball includes: Conductive metal materials are selected, including tin, silver, nickel, gold, copper or their alloys; and then physical vapor deposition, chemical vapor deposition, electroplating or ball milling are used to prepare metal conductive balls with a particle size of 10 μm to 20 μm.

[0022] Exemplarily, when the material of the metal conductive ball is a tin ball, the preparation process is as follows: a high-purity tin block (more than 99.9%) is heated to above the melting point (232°C) to form liquid tin. The liquid tin is injected into a high-temperature stable oil phase (such as silicone oil or mineral oil), and a surfactant (such as Span80) is added to prevent the tin droplets from agglomerating. The tin is dispersed into tiny droplets by high-speed stirring or homogenizer shear force. The stirring speed (usually thousands to ten thousand revolutions per minute) and the viscosity of the oil phase are controlled so that the droplet size falls within the target range (10 to 20 μm). The temperature is slowly lowered to below the melting point of tin, and the droplets solidify into spherical particles. The oil phase and surfactant are washed away with an organic solvent (such as acetone), and the tin balls are collected by centrifugation or filtration.

[0023] Among them, the particle size of the metal conductive ball is controlled within the range of 10μm to 20μm, and the particle size error can be further strictly controlled within ±0.5μm, which can ensure that when the pad size is small, it can also be set between the pad of the substrate and the pad of the Mini / MicroLED chip, avoiding poor contact or short circuit problems caused by too large or too small particles, thereby forming a stable electrical connection between the substrate and the Mini / MicroLED chip.

[0024] Furthermore, the precise particle size control can be achieved by optimizing the preparation process parameters, such as adjusting the rotation speed of the rotating disk, the vibration frequency and the cooling rate, to ensure the uniform size of the particles and improve the conductivity and reliability. Furthermore, the particle size can also be detected by a laser particle size analyzer.

[0025] Step S20, placing the metal conductive ball into the insulating glue and stirring to form anisotropic conductive glue.

[0026] This step aims to further prepare anisotropic conductive glue (ACG, full name Anisotropic Conductive Glue) based on the prepared metal conductive balls, that is, it conducts electricity in the Z-axis direction while remaining insulating in the X-axis and Y-axis directions.

[0027] See also Figure 2 As shown, the preparation of the anisotropic conductive adhesive may further comprise the following steps; Step S201, providing insulating glue.

[0028] The insulating glue includes at least one of epoxy resin, silicone, and polyimide. Among them, epoxy resin has excellent bonding strength and can firmly fix metal conductive balls and subsequently mounted Mini / MicroLED chips on the substrate. Silicone has excellent flexibility and can effectively release the thermal stress between the chip and the substrate. During the operation of Mini / MicroLED, due to temperature changes, thermal stress will be generated. The flexibility of silicone can prevent the chip or substrate from being damaged due to thermal stress. Polyimide has excellent electrical insulation performance and can effectively prevent current leakage in an unexpected direction, ensuring the anisotropic conductive characteristics of the anisotropic conductive adhesive.

[0029] In addition, control the viscosity of the insulating glue to be between 120 and 180 Pa·s. It can be understood that if the viscosity is too low, the metal conductive balls are prone to sedimentation during the stirring process, resulting in uneven distribution of the conductive balls in the conductive glue and affecting the conductive performance of the anisotropic conductive adhesive. If the viscosity is too high, it will make the stirring difficult, and the metal conductive balls are difficult to be evenly dispersed in the insulating glue. At the same time, it will also increase the difficulty of the subsequent coating process, possibly resulting in problems such as uneven coating or the appearance of bubbles.

[0030] Therefore, by precisely controlling the viscosity, ensure that the metal conductive balls are evenly distributed in the insulating glue to form a stable anisotropic conductive glue layer, thereby establishing a reliable electrical connection between the Mini / MicroLED chip and the substrate.

[0031] Step S202: Add the metal conductive balls and the insulating glue into a stirring container; and stir to evenly disperse the metal conductive balls in the insulating glue to obtain an anisotropic conductive adhesive.

[0032] In this step, further control the volume ratio of the metal conductive balls in the anisotropic conductive adhesive to be between 10% and 20%. That is, the density of the metal conductive balls in the anisotropic conductive adhesive is between 10% and 20%. A lower density is beneficial to the dispersion of the metal conductive balls, thereby preventing the adjacent metal conductive balls from contacting in the horizontal direction due to excessive density, ultimately resulting in the short-circuit phenomenon of adjacent pads.

[0033] Among them, the metal conductive balls can be evenly dispersed by setting up a stirring device and under specific stirring parameters. For example, a mechanical stirrer or a magnetic stirrer can be used. The mechanical stirrer has a strong stirring force and is suitable for high-viscosity insulating glue systems; the magnetic stirrer has the advantages of no pollution and uniform stirring, and is suitable for occasions with high cleanliness requirements. For metal conductive balls with a particle size of 10-20 μm and insulating glue with a viscosity of 120-180 Pa·s, the stirring speed can be set at 200-500 revolutions per minute. However, too long stirring time will not only increase production costs, but also may cause chemical reactions such as cross-linking of the insulating glue, affecting its performance. Usually, the stirring time can be controlled within 30-60 minutes. And during the stirring process, the insulating glue can also be appropriately heated (for example, epoxy resin glue can be heated to 40-60 °C) to reduce its viscosity and improve the dispersibility of the metal conductive balls.

[0034] And in some embodiments, adding the metal conductive balls and the insulating glue into the stirring container further includes synchronously adding a dispersant into the stirring container. The dispersant can adsorb on the surface of the metal conductive balls, increase the electrostatic repulsion or steric hindrance between the particles, effectively reduce the agglomeration phenomenon between the metal conductive balls, improve the dispersion uniformity, and ensure the stable conductivity.

[0035] During the stirring process, the dispersant is fully mixed with the insulating glue and the metal conductive balls to form a uniform conductive glue system. The dispersant includes polyethylene glycol, sodium dodecyl sulfate, sodium hexametaphosphate, and sodium oleate.

[0036] In a further solution, the preparation of the anisotropic conductive glue further includes the steps of: S203, performing a defoaming treatment on the anisotropic conductive glue obtained after stirring until there are no obvious bubbles in the appearance of the anisotropic conductive glue.

[0037] It can be understood that after the stirring is completed, there may be a large number of bubbles in the mixed system, which will affect the performance of the anisotropic conductive glue. The performance influence can be eliminated through the defoaming treatment.

[0038] Specifically, the defoaming treatment can be carried out by using a vacuum defoaming machine. By reducing the air pressure in the container, the bubbles expand and burst, so as to remove the bubbles in the conductive glue. Among them, the treatment time is generally controlled within 10-20 minutes to ensure that the anisotropic conductive glue is uniform and bubble-free.

[0039] S204, detecting the conductivity and viscosity of the anisotropic conductive glue to ensure that they meet the process requirements.

[0040] In this step, devices such as a four-probe tester can be used to detect the conductivity of the anisotropic conductive adhesive, including the resistivity in the vertical and horizontal directions. The vertical direction should have a lower resistivity to ensure good electrical conductivity; the horizontal direction should have a higher resistivity to prevent short circuits. Additionally, a rotational viscometer can be used to measure the viscosity of the anisotropic conductive adhesive, and the viscosity should be controlled within an appropriate range to enable uniform printing on the substrate in subsequent coating processes.

[0041] After the preparation of the conductive adhesive, the technical solution of this application further includes the storage and activation of the anisotropic conductive adhesive that meets the process requirements, including: The anisotropic conductive adhesive is stored sealed and frozen before and after use, and the freezing temperature is -15 to -20 °C. This storage setting can better balance the storage effect and equipment cost, effectively reduce the chemical reaction rate, slow down the aging process of the anisotropic conductive adhesive, and extend its service life. Also, The anisotropic conductive adhesive is restored to room temperature and then the seal is removed before use. This can avoid the problem of a rapid decrease in the adhesive force of the conductive adhesive caused by condensation on the surface of the conductive adhesive. Therefore, when removing the seal, it must be restored to room temperature before opening. It is recommended to warm up at 25 °C for at least 2 to 4 hours, and the number of warm-up times should not exceed three. In addition, the anisotropic conductive adhesive is sensitive to humidity, and the glue cannot be exposed to the air for a long time. The relative humidity of the use environment is less than 60%.

[0042] Under the above storage and activation conditions, the performance stability of the anisotropic conductive adhesive is ensured, and the further steps are as follows: Step S30: Using a stencil printing process, the anisotropic conductive adhesive is printed on the pads of the substrate.

[0043] In this step, compared with the dispensing or lithography process, using stencil printing for single forming is suitable for mass production and improves efficiency. Moreover, the stencil process has high precision and micro-refinement, which is suitable for the high-density pad layout of this application. A process step for uniformly coating the anisotropic conductive adhesive on the pads of the substrate is as follows: The stencil opening is aligned with the pads of the substrate through optical positioning, the anisotropic conductive adhesive is uniformly coated on the surface of the stencil, and the squeegee scrapes across the stencil at a constant speed (10 - 50 mm / s) and pressure (0.1 - 0.3 MPa) to make the colloid leak-print through the opening onto the pads. The stencil is slowly lifted vertically to avoid colloid drawing or offset. Then, the thickness and coverage uniformity of the glue layer are inspected by a microscope or AOI (Automated Optical Inspection).

[0044] It can be understood that before printing the anisotropic conductive adhesive on the pads of the substrate using the stencil printing process, it further includes: providing a steel plate, opening stencil holes according to the occupied size of a group of RGB chips on the substrate to form a stencil; and coating a nano-hydrophobic coating on the stencil to obtain a hydrophobic nano-stencil.

[0045] Among them, the steel mesh is opened according to the size of a group of RGB chips on the substrate to meet the layout requirements of smaller pads (8K, or even denser pixels). When the pad is smaller, the precision of the steel mesh cannot be so precise, and anisotropic conductive adhesive is difficult to brush in and contact the pad. Even if it is brushed in, it is easy to be brought out when it is separated from the steel mesh. Therefore, the steel mesh is customized according to the size of a group of RGB chips (including three LED chips: red, green, and blue). At this time, the size of the steel mesh will be relatively large, which can ensure that the anisotropic conductive adhesive is smoothly filled and fully contacted with the pad. And the nano-hydrophobic coating is applied on the steel mesh. Since the nano-material makes the surface of the steel mesh hole wall smooth, the adhesion between the anisotropic conductive adhesive and the hole wall is greatly reduced, thereby improving the demolding performance. During the printing process, the anisotropic conductive adhesive can be more completely transferred from the steel mesh hole to the substrate, reducing the occurrence of undesirable phenomena such as anisotropic conductive adhesive residue and pull-tip, and improving the printing quality.

[0046] Step S40, mounting the Mini / MicroLED chip onto the anisotropic conductive adhesive, and making the pads of the Mini / MicroLED chip correspond one by one to the pads of the substrate, and hot pressing and curing to obtain the Mini / MicroLED.

[0047] Specifically, it includes: mounting the Mini / MicroLED chip on the anisotropic conductive adhesive of the substrate through the patch equipment. Among them, the use of high-precision patch equipment, such as a die bonder, has a high-precision positioning system, which can accurately place the Mini / MicroLED chip at the specified position of the anisotropic conductive adhesive on the substrate, so that the pads on the substrate correspond to the pads of the Mini / MicroLED chip one by one. Compared with manual placement, its speed is increased by several times or even dozens of times, which greatly improves production efficiency and meets the needs of large-scale production (based on mass transfer process, large-scale transfer and precise placement).

[0048] Moreover, set the hot-press curing parameters. The hot press makes the metal conductive balls contact the pads on both sides and fully cures the insulating glue to obtain Mini / Micro LEDs. For example, the hot-press temperature is determined according to the curing characteristics of the anisotropic conductive adhesive, generally between 100 and 150 °C; the hot-press pressure is between 20 and 100 N; the hot-press time is 5 to 30 minutes. Appropriate hot-press parameters can enable the metal conductive balls to form good electrical connections with the pads of the Mini / Micro LED chips and the pads of the substrate, while fully curing the insulating glue and improving the bonding strength between the Mini / Micro LED chips and the substrate. After the hot-press curing is completed, let the product cool naturally or adopt forced cooling to fully cure the anisotropic conductive adhesive. The cooling rate should not be too fast, generally controlled at 5 to 10 °C per minute to avoid cracking of the Mini / Micro LED chips or the substrate due to thermal stress.

[0049] It should be noted that the particle size of the metal conductive balls is very small. Therefore, after screen printing and mounting the Mini / Micro LED chips through the stencil, there will be multiple metal conductive balls arranged between the pads of the Mini / Micro LED chips and the pads of the substrate. And only when both sides of one metal conductive ball contact the pads of the Mini / Micro LED chips and the pads of the substrate can normal electrical conductivity be achieved.

[0050] Furthermore, after fully curing the insulating glue to obtain Mini / Micro LEDs, it also includes: Perform performance testing on the obtained Mini / Micro LEDs. The performance testing includes appearance inspection, electrical performance inspection, and reliability inspection. Among them: Appearance inspection: Use a microscope or an automatic optical inspection device (AOI) to perform appearance inspection on the mounted Mini / Micro LEDs, check whether there are situations such as offset, tilt, and breakage of the Mini / Micro LED chips, and whether there are defects such as overflow and bubbles of the conductive glue.

[0051] Electrical performance inspection: Use testing equipment to detect the electrical performance of the product, including parameters such as resistance, current, and voltage, to ensure good electrical connection between the Mini / Micro LED chips and the substrate and meet the electrical performance requirements of the product.

[0052] Reliability inspection: Conduct reliability inspections such as high-temperature and high-humidity tests and thermal shock tests, simulate the environmental conditions during the actual use of the product, and test the stability and reliability of the product. For example, in the high-temperature and high-humidity test, place the product in an environment of 85 °C and 85% relative humidity for a certain period of time (such as 1000 hours), and observe whether the product shows performance degradation, short circuit, and other failures.

[0053] The present application also provides a Mini / Micro LED, which is manufactured by the above manufacturing method.

[0054] As Figure 3 shown, an embodiment of the present application also discloses a Mini / Micro LED. Among them, the Mini / Micro LED includes a substrate 10, an LED chip 20, and an anisotropic conductive adhesive 30. Among them, a plurality of first pads 11 are arranged in an array on the mounting surface of the substrate 10; the Mini / Micro LED chip 20 includes a second pad 21 corresponding to the first pad 11, and the Mini / Micro LED chip 20 is attached to the mounting surface of the substrate 10; the anisotropic conductive adhesive 30 is disposed between the first pad 11 and the second pad 21. The anisotropic conductive adhesive 30 is disposed between the first pad 11 and the second pad 21. The anisotropic conductive adhesive 30 includes an insulating adhesive 31 and metal conductive balls 32 uniformly dispersed in the insulating adhesive 31. Among them, both sides of the metal conductive balls 32 are respectively abutted against the first pad 11 and the second pad 21; and, the insulating adhesive 31 is filled between the substrate 10 and the Mini / Micro LED chip 20, and adheres and fixes the substrate 10 and the Mini / Micro LED chip 20.

[0055] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; under the idea of the present application, the technical features in the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order, and there are many other changes in different aspects of the present application as described above. For the sake of brevity, they are not provided in detail; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A manufacturing method of Mini / Micro LED, characterized in that, The manufacturing method includes: Preparing metal conductive balls; Putting the metal conductive balls into insulating glue and stirring to form anisotropic conductive glue; Using a stencil coating process to print the anisotropic conductive glue on the pads of the substrate; Mounting Mini / Micro LED chips onto the anisotropic conductive glue, and making the pads of the Mini / Micro LED chips correspond to the pads of the substrate one by one, and hot-pressing and curing to obtain Mini / Micro LED.

2. The manufacturing method according to claim 1, wherein The preparing of the metal conductive balls includes: Selecting a conductive metal material, which includes tin material, silver material, nickel material, gold material, copper material or their alloys; Preparing metal conductive balls with a particle size of 10μm - 20μm by physical vapor deposition, chemical vapor deposition, electroplating or ball milling process.

3. The manufacturing method according to claim 1, characterized in that, The putting the metal conductive balls into insulating glue and stirring to form anisotropic conductive glue includes: Providing insulating glue; the insulating glue includes at least one of epoxy resin, silica gel and polyimide; the viscosity of the insulating glue is between 120 - 180 Pa·s; Putting the metal conductive balls and the insulating glue into a stirring container and stirring to make the metal conductive balls evenly dispersed in the insulating glue to obtain anisotropic conductive glue; the volume ratio of the metal conductive balls in the anisotropic conductive glue is 10% - 20%.

4. The manufacturing method according to claim 3, characterized in that, The putting the metal conductive balls and the insulating glue into the stirring container further includes: Synchronously adding a dispersant into the stirring container to prevent the metal conductive balls from agglomerating; the dispersant includes polyethylene glycol, sodium dodecyl sulfate, sodium hexametaphosphate and sodium oleate.

5. The manufacturing method according to claim 3, characterized in that, After the stirring to make the metal conductive balls evenly dispersed in the insulating glue to obtain anisotropic conductive glue, it further includes: Performing a defoaming treatment on the stirred anisotropic conductive glue until there are no obvious bubbles in the appearance of the anisotropic conductive glue; Detecting the conductivity and viscosity of the anisotropic conductive glue to ensure that it meets the process requirements.

6. The manufacturing method according to any one of claims 1-5, characterized in that, It also includes the storage and activation of the anisotropic conductive glue that meets the process requirements, including: Before and after use, the anisotropic conductive glue is sealed and stored frozen, and the freezing temperature is -15°C to -20°C; and, Before use, the anisotropic conductive glue is restored to room temperature and then unsealed, and the relative humidity of the use environment is lower than 60%.

7. The manufacturing method according to claim 1, characterized in that, Before using the stencil coating process to print the anisotropic conductive glue on the pads of the substrate, it further includes: Providing a steel plate, and opening stencil holes according to the occupied size of a group of RGB chips on the substrate to form a stencil; Coating a nano-hydrophobic coating on the stencil to obtain a hydrophobic nano-stencil.

8. The manufacturing method according to claim 1, characterized in that, The mounting the Mini / Micro LED chips onto the anisotropic conductive glue to make the pads of the Mini / Micro LED chips correspond to the pads of the substrate one by one and hot-pressing and curing to obtain Mini / Micro LED includes: Mounting the Mini / Micro LED chips onto the anisotropic conductive glue of the substrate through a chip mounter; Set the hot pressing and curing parameters. Through hot pressing, the metal conductive balls are brought into contact with the pads on both sides, and the insulating glue is cured to obtain Mini / Micro LEDs.

9. The manufacturing method according to claim 8, characterized in that, After setting the hot pressing and curing parameters, through hot pressing, the metal conductive balls are brought into contact with the pads on both sides, and the insulating glue is cured to obtain Mini / Micro LEDs, the following steps are further included: Perform performance testing on the obtained Mini / Micro LEDs; the performance testing includes electrical performance testing, optical performance testing, and reliability testing.

10. A Mini / Micro LED, characterized in that, The Mini / Micro LEDs are manufactured by using the manufacturing method described in any one of claims 1 to 9.

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