Anisotropic conductive adhesive film, magnetic conductive particle and preparation method

Abstract

The invention discloses an anisotropic conductive adhesive film, a magnetic conductive particle and a preparation method. The preparation method of the anisotropic conductive adhesive film comprises the following steps: providing a template, wherein the template is provided with grooves distributed in an array; using magnetic attraction to attract the magnetic conductive particles to fill the grooves, and forming the magnetic conductive particles distributed in an array; covering the magnetic conductive particles distributed in the array with a first resin adhesive film, and performing hot pressing treatment to transfer the magnetic conductive particles distributed in the array to the first resin adhesive film; and coating one side, containing the magnetic conductive particles distributed in the array, of the first resin adhesive film with a second resin dispersion liquid, and drying to obtain the anisotropic conductive adhesive film. According to the preparation method disclosed by the invention, the anisotropic conductive adhesive film internally containing the uniformly dispersed magnetic conductive particles in array distribution can be obtained, and the connection of an ultrahigh-precision circuit can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of anisotropic conductive adhesive films, and in particular to an anisotropic conductive adhesive film, magnetic conductive particles and a preparation method thereof. Background Art

[0002] Today, electronic products are increasingly miniaturized and require packaging technology to pack more circuit units into a limited space. However, the traditional use of lead-tin solder and tin-based solder as connection materials not only generates thermal stress that affects device stability but also makes it difficult to connect high-precision circuits. Anisotropic conductive films (ACFs), a material that can conduct electricity in the vertical direction and insulate in the planar direction, are not only environmentally friendly but also possess ultra-high circuit connection precision. These characteristics make ACFs a key technology for fine-pitch circuit connections.

[0003] However, conventional anisotropic conductive films are prepared by randomly mixing conductive particles within a resin. This randomly distributed conductive particle structure can lead to short circuits between adjacent electrodes during the bonding of ultra-high-precision circuits, resulting in circuit connection failure. Therefore, the development of new anisotropic conductive films capable of connecting higher-precision circuits is urgent. Logically, the most effective bonding method to prevent short circuits would be to periodically arrange the conductive particles within the resin, creating an anisotropic conductive adhesive with a periodic arrangement of conductive particles. However, achieving a periodic arrangement of conductive particles on the film is an extremely challenging process, and ensuring a uniform distribution of conductive particles on the film has always been a difficult problem in the field of anisotropic conductive films.

[0004] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide an anisotropic conductive adhesive film, magnetic conductive particles and a preparation method, aiming to solve the problem that the conductive particles in the existing anisotropic conductive adhesive film are unevenly distributed and cannot achieve high-precision circuit connection.

[0006] The technical solutions of the present invention are as follows:

[0007] A first aspect of the present invention provides a method for preparing an anisotropic conductive adhesive film, comprising the following steps:

[0008] Providing a template, wherein the template is provided with grooves distributed in an array;

[0009] Providing magnetic conductive particles, and using magnetic attraction to attract the magnetic conductive particles to fill the grooves to form an array of magnetic conductive particles;

[0010] Providing a first resin film, covering the arrayed magnetic conductive particles with the first resin film, and performing a hot pressing process to transfer the arrayed magnetic conductive particles to the first resin film;

[0011] A second resin dispersion is coated on the side of the first resin film containing the arrayed magnetic conductive particles, and dried to obtain the anisotropic conductive film.

[0012] Optionally, the magnetic conductive particles are spherical, and the depth of the grooves is 30% to 90% of the diameter of the magnetic conductive particles; and / or,

[0013] In the array-distributed magnetic conductive particles, the distance between two adjacent magnetic conductive particles is 1 to 20 μm.

[0014] Optionally, a magnetic field of 10 to 2800 mT is used to apply a continuous magnetic attraction force to the magnetic conductive particles to attract the magnetic conductive particles to fill the grooves; and / or,

[0015] The process parameters used in the hot pressing treatment are:

[0016] The temperature is 80°C, the pressure is 1kPa~1MPa, and the time is 1~10s.

[0017] Optionally, a magnet is placed on the side of the template away from the magnetic conductive particles, moved 3 to 5 times, and then kept stationary to attract the magnetic conductive particles to fill the grooves, and then the magnetic conductive particles not filled in the grooves are recovered; the magnetic field strength generated by the magnet is 10 to 2800 mT.

[0018] Optionally, the magnetic conductive particles include first composite microspheres and a magnetic metal coating layer coated on the surface of the first composite microspheres; the first composite microspheres include microspheres and a conductive polymer layer coated on the surface of the microspheres;

[0019] The material of the microspheres includes at least one of polystyrene, polymethyl methacrylate, polyurethane, phenolic resin, polydimethoxysiloxane and silicon dioxide; or the material of the microspheres includes a copolymer of at least two of polystyrene, polymethyl methacrylate, polyurethane, phenolic resin and polydimethoxysiloxane;

[0020] The diameter of the magnetic conductive particles is 500 nm to 50 μm; the thickness of the magnetic metal coating layer is 5 nm to 5 μm.

[0021] A second aspect of the present invention provides an anisotropic conductive adhesive film, which is prepared by the preparation method of the present invention as described above.

[0022] A third aspect of the present invention provides a method for preparing magnetic conductive particles, wherein the magnetic conductive particles are used to prepare the anisotropic conductive adhesive film of the invention as described above, and the method for preparing the magnetic conductive particles comprises the following steps:

[0023] The microspheres, the conductive polymer monomer and the oxidant are stirred to coat the surface of the microspheres with a conductive polymer layer to obtain first composite microspheres;

[0024] adding the first composite microspheres to an activation solution for activation, thereby forming catalytic particles on the surface of the first composite microspheres to obtain second composite microspheres, wherein the catalytic particles are used to catalyze the reduction of magnetic metal ions;

[0025] Providing a chemical plating solution, the chemical plating solution comprising a magnetic metal salt, a reducing agent, a complexing agent and water, wherein the pH of the chemical plating solution is 6.5 to 8.5;

[0026] The second composite microspheres are added to a chemical plating solution, and the mass ratio of the second composite microspheres, magnetic metal salt, reducing agent and complexing agent is 0.5:(0.1~0.4):(0.25~0.5):(0.25~0.5). After reacting at a temperature of 50~70°C for 0.5~2h, a magnetic metal coating layer is formed on the surface of the second composite microspheres to obtain the magnetic conductive particles.

[0027] Optionally, the mass ratio of the microspheres to the conductive polymer monomer is (4-5):(2-3); and / or,

[0028] The diameter of the magnetic conductive particles is 500 nm to 50 μm, and the thickness of the magnetic metal coating layer is 5 nm to 5 μm; and / or,

[0029] The material of the microspheres includes at least one of polystyrene, polymethyl methacrylate, polyurethane, phenolic resin, polydimethoxysiloxane and silicon dioxide, or the material of the microspheres includes a copolymer of at least two of polystyrene, polymethyl methacrylate, polyurethane, phenolic resin and polydimethoxysiloxane; and / or,

[0030] The conductive polymer in the conductive polymer layer includes at least one of polyaniline, polyacetylene, polypyrrole, polythiophene and polyethylenedioxythiophene.

[0031] Optionally, the oxidant comprises at least one of ammonium persulfate, ferric chloride, ferrous sulfate and hydrogen peroxide; and / or,

[0032] The reducing agent comprises at least one of glucose, sodium hypophosphite, sodium borohydride, dimethylamino borane, formaldehyde and hydrazine hydrate; and / or,

[0033] The complexing agent includes at least one of sodium citrate, citric acid, disodium edetate and ammonia water; and / or,

[0034] The magnetic metal salt includes one or more of palladium chloride, cobalt sulfate, cobalt chloride, nickel sulfate, nickel chloride and nickel nitrate; and / or,

[0035] The activation solution includes at least one of a palladium salt solution, a platinum nanoparticle solution, a silver salt solution, and a copper salt solution.

[0036] A fourth aspect of the present invention provides a magnetic conductive particle, wherein the magnetic conductive particle is prepared by the preparation method of the present invention as described above.

[0037] Beneficial effect: The present invention attracts magnetic conductive particles to fill the array-distributed grooves on the template through magnetic attraction to form array-distributed magnetic conductive particles, and then transfers the array-distributed magnetic conductive particles to the first resin film. Finally, a second resin dispersion is spin-coated on the surface of the first resin film containing the array-distributed magnetic conductive particles. After drying, an anisotropic conductive film containing array-distributed and uniformly dispersed magnetic conductive particles can be obtained, which can achieve ultra-high precision circuit connection. The preparation method provided by the present invention can effectively solve the problem that the conductive particles in the anisotropic conductive film prepared by the existing method are unevenly distributed and cannot achieve high-precision circuit connection, and can improve the production efficiency of the array-type anisotropic conductive film. The advantage of the anisotropic conductive film prepared by the present invention in bonding high-precision circuits is incomparable to the anisotropic conductive film in which the conductive particles are randomly distributed in the film (due to the random distribution of the conductive particles, the particles may aggregate, resulting in reduced bonding accuracy; there are no conductive particles in the film part, and the phenomenon of no conduction when the bonding circuit occurs) cannot be compared.

[0038] In addition, in the process of preparing anisotropic conductive films using magnetic conductive particles, when filling the grooves with magnetic conductive particles, the magnetic conductive particles can be effectively fixed in the grooves under the action of magnetic attraction. Therefore, compared with conductive particles, magnetic conductive particles are easier to enter the grooves. This fixing effect will reduce the groove depth of the template. The reduction in the groove depth is conducive to the full transfer of magnetic conductive particles to the first resin film. This is because the shallower the groove, the larger the area of ​​​​the magnetic conductive particles exposed in the groove, and the larger the contact area between the magnetic conductive particles and the first resin film, which is more conducive to the transfer of magnetic conductive particles to the first resin film. Therefore, the advantages of magnetic conductive particles play an important role in the preparation of array-type anisotropic conductive films. In addition, in the process of recovering excess magnetic conductive particles outside the groove, the magnetic conductive particles inside the groove can be fixed due to the existence of magnetic attraction. The magnetic conductive particles outside the groove have no external force to hinder their lateral movement, thus achieving the removal and recovery of magnetic conductive particles outside the groove. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a flowchart of the preparation process of anisotropic conductive adhesive film.

[0040] Figure 2 Schematic diagram of the structure of anisotropic conductive film.

[0041] Figure 3 Schematic diagram of the structure of the template groove.

[0042] Figure 4 This is a flowchart of the preparation process of magnetic conductive particles.

[0043] Figure 5 Schematic diagram of the preparation of magnetic conductive particles in Example 1.

[0044] Figure 6 These are SEM images of the substances in Example 1, where a is polystyrene microspheres, b is the first composite microspheres, c is the second composite microspheres, and d is the magnetic conductive particles.

[0045] Figure 7 1 is the XRD pattern of the polystyrene microspheres, the first composite microspheres, the second composite microspheres and the magnetic conductive particles in Example 1.

[0046] Figure 8 a is the hysteresis loop diagram of the magnetic conductive particles in Example 1, and b is a partially enlarged diagram of the hysteresis loop diagram of the magnetic conductive particles in Example 1.

[0047] Figure 9 Schematic diagram of filling of magnetic conductive particles in Example 8.

[0048] Figure 10Schematic diagram of the preparation of the anisotropic conductive film in Example 8.

[0049] Figure 11 This is a diagram of the filling effect of magnetic conductive particles on the template under different magnetic field strengths when the groove depth is 2.5 μm in Example 8, where a is 0 mT magnetic field strength, b is 88 mT magnetic field strength, c is 150 mT magnetic field strength, and d is 280 mT magnetic field strength.

[0050] Figure 12 This is a diagram of the filling effect of magnetic conductive particles on the template under different magnetic field strengths when the groove depth is 3.5 μm in Example 9, where a is 0 mT magnetic field strength, b is 88 mT magnetic field strength, c is 150 mT magnetic field strength, and d is 280 mT magnetic field strength.

[0051] Figure 13 These are the SEM images and metallographic microscope images after the magnetic conductive particles are filled in the template and transferred to the first resin film under the conditions of a groove depth of 3.5 μm and a magnetic field strength of 280 mT in Example 9, where a is the SEM image and b is the metallographic microscope image.

[0052] Figure 14 This is a diagram of the filling effect of magnetic conductive particles on the template under different magnetic field strengths when the groove depth is 6 μm in Example 10, where a is 0 mT magnetic field strength, b is 88 mT magnetic field strength, c is 150 mT magnetic field strength, and d is 280 mT magnetic field strength.

[0053] Figure 15 These are SEM images of the magnetic conductive particles after being transferred to the first resin film under groove conditions of different depths in Example 11, where a is 3.5 μm, b is 4 μm, c is 5 μm, and d is 6 μm.

[0054] Figure 16 This is a diagram showing the filling effect of magnetic conductive particles on the template under different magnetic field strengths and groove depths in Example 12. DETAILED DESCRIPTION

[0055] The present invention provides an anisotropic conductive adhesive film, magnetic conductive particles, and a preparation method. To clarify the objectives, technical solutions, and effects of the present invention, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0056] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0057] Terms such as “vertical,” “horizontal,” “upper,” “lower,” “left,” “right,” and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementations.

[0058] If there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features.

[0059] The embodiment of the present invention provides a method for preparing an anisotropic conductive adhesive film, wherein, Figure 1 As shown, the following steps are included:

[0060] S11. Providing a template, wherein the template is provided with grooves distributed in an array (for example, grooves distributed in a periodic array, and the specific array arrangement shape can be set according to actual needs);

[0061] S12, providing magnetic conductive particles, and using magnetic attraction to attract the magnetic conductive particles to fill the grooves to form an array of magnetic conductive particles;

[0062] S13, providing a first resin film, covering the arrayed magnetic conductive particles with the first resin film, and performing a hot pressing process to transfer the arrayed magnetic conductive particles to the first resin film;

[0063] S14, coating a second resin dispersion on the side of the first resin film containing the arrayed magnetic conductive particles, and drying to obtain the anisotropic conductive film.

[0064] The present invention uses magnetic attraction to attract magnetic conductive particles to fill the grooves distributed in an array on the template to form an array of magnetic conductive particles, and then transfers the array of magnetic conductive particles to a first resin film. Finally, a second resin dispersion is spin-coated on the surface of the first resin film containing the array of magnetic conductive particles. After drying, an anisotropic conductive film containing uniformly dispersed array-distributed magnetic conductive particles can be obtained, thereby achieving ultra-high-precision circuit connection. The preparation method provided by the present invention can effectively solve the problem of uneven distribution of conductive particles in anisotropic conductive films prepared by existing methods, which cannot achieve high-precision circuit connection, and can improve the production efficiency of array-type anisotropic conductive films. The advantage of the anisotropic conductive film prepared by the present invention in bonding high-precision circuits is incomparable to anisotropic conductive films in which conductive particles are randomly distributed in the film (due to the random distribution of conductive particles, particles may aggregate, resulting in reduced bonding accuracy; if there are no conductive particles in the film, there will be a phenomenon of no conduction when bonding the circuit).

[0065] In addition, in the process of preparing anisotropic conductive films using magnetic conductive particles, when filling the grooves with magnetic conductive particles, the magnetic conductive particles can be effectively fixed in the grooves under the action of magnetic attraction. Therefore, compared with conductive particles, magnetic conductive particles are easier to enter the grooves. This fixing effect will reduce the groove depth of the template. The reduction in the groove depth is conducive to the full transfer of magnetic conductive particles to the first resin film. This is because the shallower the groove, the larger the area of ​​​​the magnetic conductive particles exposed in the groove, and the larger the contact area between the magnetic conductive particles and the first resin film, which is more conducive to the transfer of magnetic conductive particles to the first resin film. Therefore, the advantages of magnetic conductive particles play an important role in the preparation of array-type anisotropic conductive films. In addition, in the process of recovering excess magnetic conductive particles outside the groove, the magnetic conductive particles inside the groove can be fixed due to the existence of magnetic attraction. The magnetic conductive particles outside the groove have no external force to hinder their lateral movement, thus achieving the removal and recovery of magnetic conductive particles outside the groove.

[0066] like Figure 2 As shown, the prepared anisotropic conductive film includes a first resin film layer 1, a second resin film layer 2 stacked in sequence, and an array of magnetic conductive particles 3 located at the interface between the first resin film layer 1 and the second resin film layer 2 and embedded in the first resin film layer and the second resin film layer.

[0067] In step S11, the present invention does not limit the specific shape and lateral size of the groove, as long as the groove can accommodate the magnetic conductive particles. More specifically, one groove can only accommodate one magnetic conductive particle. For example, in the horizontal direction, the cross-sectional shape of the groove includes but is not limited to a triangle, a circle, a hexagon, a quadrilateral, and a parallelogram. For example, Figure 3 As shown, the groove is cylindrical, that is, in the horizontal plane direction, the cross-sectional shape of the groove is circular, the depth of the cylindrical groove is h=4 μm, and the diameter of the cylindrical groove is Φ=6 μm.

[0068] In step S12, in some embodiments, the magnetic conductive particles include first composite microspheres and a magnetic metal coating layer coated on the surface of the first composite microspheres, the first composite microspheres include microspheres and a conductive polymer layer coated on the surface of the microspheres; the material of the microspheres includes at least one of polystyrene, polymethyl methacrylate, polyurethane, phenolic resin, polydimethoxysiloxane and silica; or, the material of the microspheres includes a copolymer of at least two of polystyrene, polymethyl methacrylate, polyurethane, phenolic resin and polydimethoxysiloxane.

[0069] In some embodiments, the conductive polymer layer includes at least one of polyaniline, polyacetylene, polypyrrole, polythiophene, and polyethylenedioxythiophene.

[0070] In some embodiments, the diameter of the magnetic conductive particles is 500 nm to 50 μm, for example, 500 nm, 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm. The size of the magnetic conductive particles can determine the bonding accuracy of the circuit. The smaller the size of the magnetic conductive particles, the higher the bonding accuracy, while the larger the size of the magnetic conductive particles, the lower the bonding accuracy. Therefore, when the magnetic conductive particles contact the circuit substrate for conduction, the finer the circuit width, the higher the circuit accuracy, and the smaller the particle size of the magnetic conductive particles required.

[0071] In some embodiments, the thickness of the magnetic metal coating layer is 5 nm to 5 μm, for example, 5 nm, 10 nm, 50 nm, 100 nm, 200 nm, 500 nm, 800 nm, 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm. The conductivity of the magnetic conductive particles increases with the thickness of the magnetic metal coating layer. When the magnetic conductive particles are in contact with the circuit substrate for electrical conduction, the higher the power of the circuit connected device, the lower the resistance at the circuit connection, and thus the thicker the magnetic metal coating layer.

[0072] In some embodiments, the magnetic conductive particles are spherical, and the depth of the grooves is 30% to 90% of the diameter of the magnetic conductive particles (for example, 30%, 40%, 50%, 60%, 70%, 80%, or 90%, etc.). In this embodiment, the use of magnetic attraction is more conducive to fixing the magnetic conductive particles in the grooves. Therefore, the magnetic conductive particles can be fixed in grooves with a smaller depth (i.e., the groove depth and the magnetic conductive particle diameter are in the above ratio). In this way, a larger area of ​​the magnetic conductive particles can be exposed outside the grooves, and the contact area between the magnetic conductive particles and the first resin film is larger (the first resin film can only contact the portion of the magnetic conductive particles exposed outside the grooves), which is conducive to the transfer of the magnetic conductive particles to the first resin film.

[0073] In some specific embodiments, the depth of the groove is 1 to 20 μm, for example, 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm or 20 μm.

[0074] In some embodiments, the distance between two adjacent magnetic conductive particles is 1 to 20 μm, for example, 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm or 20 μm.

[0075] In some embodiments, a magnetic field of 10 to 2800 mT (for example, 10 mT, 20 mT, 50 mT, 60 mT, 80 mT, 88 mT, 100 mT, 120 mT, 150 mT, 180 mT, 200 mT, 220 mT, 250 mT, 280 mT, 300 mT, 400 mT, 500 mT, 600 mT, 700 mT, 800 mT, 900 mT, 1000 mT, 1200 mT, 1500 mT, 1800 mT, 2000 mT, 2200 mT, 2500 mT, or 2800 mT, etc.) is used to apply a continuous magnetic attraction force to the magnetic conductive particles, so that the magnetic conductive particles are attracted and filled into the grooves.

[0076] In some embodiments, a magnet is placed on a side of the template away from the magnetic conductive particles, moved 3 to 5 times, and then kept stationary to attract the magnetic conductive particles to fill the grooves, and then the magnetic conductive particles not filled in the grooves are recovered; the magnetic field strength generated by the magnet is 10 to 2800 mT.

[0077] In some embodiments, the steps of providing magnetic conductive particles and using continuous magnetic attraction to attract the magnetic conductive particles to fill the grooves to form an array of magnetic conductive particles include:

[0078] dispersing magnetic conductive particles in an organic solvent (such as ethanol) to obtain a magnetic conductive particle dispersion;

[0079] A dispersion of magnetic conductive particles is dripped onto the surface of a template with grooves. A magnet is placed on the side of the template facing away from the magnetic conductive particles. After moving the magnet 3-5 times, it remains stationary, attracting the magnetic conductive particles to fill the grooves. After the organic solvent evaporates, the magnetic conductive particles that have not filled the grooves are recovered, leaving only the grooves on the template containing the magnetic conductive particles. A diameter of 500nm to 50μm for magnetic conductive particles makes monodispersion easier to control and reduces costs.

[0080] In step S13, in some embodiments, the process parameters used for the hot pressing treatment are:

[0081] The temperature is 80°C, the pressure is 1KPa~1MPa, and the time is 1~10s.

[0082] For example, the pressure may be 1 KPa, 2 KPa, 3 KPa, 5 KPa, 10 KPa, 50 KPa, 100 KPa, 200 KPa, 300 KPa, 400 KPa, 500 KPa, 600 KPa, 700 KPa, 800 KPa, 900 KPa, or 1 MPa, etc. The time may be 1 s, 2 s, 3 s, 4 s, 5 s, 6 s, 7 s, 8 s, 9 s, or 10 s, etc.

[0083] In some embodiments, the first resin film includes a first resin, which includes a thermoplastic resin or a thermosetting resin. The thermosetting resin includes, but is not limited to, at least one of epoxy resin, acrylic resin, and multifunctional polyurethane, and the thermoplastic resin includes, but is not limited to, at least one of polyurethane, polyacrylate, polyvinyl alcohol, and polyvinyl butyral. These resins can ensure the stability of the connector during bonding of the anisotropic conductive film.

[0084] In some embodiments, the first resin film may further include a curing agent, including but not limited to at least one of dicyandiamide, phthalic anhydride, tetrahydrophthalic anhydride imidazole, methylimidazole, and diphenylimidazole. These curing agents can cure and crosslink the thermosetting resin. In some embodiments, the first resin film may further include an initiator, including at least one of azobisisobutyl cyanide and dibenzoyl peroxide.

[0085] In some embodiments, the temperature used for the curing and crosslinking is 100-250°C (for example, it can be 100°C, 120°C, 150°C, 180°C, 200°C, 220°C or 250°C, etc.), the pressure is 1KPa-5.01MPa (for example, it can be 1KPa, 2KPa, 5KPa, 10KPa, 20KPa, 50KPa, 100KPa, 200KPa, 500KPa, 800KPa, 1MPa, 2MPa, 3MPa, 4MPa, 5MPa or 5.01MPa, etc.), and the time is 0.5-200s (for example, it can be 0.5s, 1s, 5s, 10s, 20s, 50s, 100s, 120s, 150s, 180s or 200s, etc.). When the prepared anisotropic conductive adhesive film is used, such as bonding a circuit, the anisotropic adhesive film can be cured using this temperature, pressure and time.

[0086] In some embodiments, the steps of providing a first resin film, covering the arrayed magnetic conductive particles with the first resin film, and performing a heat pressing process to transfer the arrayed magnetic conductive particles to the first resin film specifically include:

[0087] forming a first resin film on the base film to obtain a composite film;

[0088] The composite film is covered on the array-distributed magnetic conductive particles, and the first resin film is made to adhere to the array-distributed magnetic conductive particles. After hot pressing, the composite film is peeled off to transfer the array-distributed magnetic conductive particles to the first resin film of the composite film.

[0089] At this time, the anisotropic conductive film is prepared on the base film, such as Figure 2 As shown, an anisotropic conductive film is prepared on a base film 4, and the anisotropic conductive film includes a first resin film layer 1, a second resin film layer 2 stacked in sequence from bottom to top, and array-distributed magnetic conductive particles 3 located at the interface between the first resin film layer 1 and the second resin film layer 2 and embedded in the first resin film layer 1 and the second resin film layer 2 at the same time.

[0090] The base film serves as a carrier for the first resin film layer, the magnetic conductive particles, and the second resin film layer. During use, the anisotropic conductive film requires a release process, and its surface has a release force of 10 to 2000 g / mm. The base film also protects the anisotropic conductive film from contamination, facilitating packaging and storage.

[0091] In some embodiments, the material of the base film includes, but is not limited to, one of polyethylene terephthalate (PET), polyimide, polyvinyl chloride, and polypropylene.

[0092] In step S14, in some embodiments, the second resin film includes a second resin, which includes a thermoplastic resin or a thermosetting resin. The thermosetting resin includes, but is not limited to, at least one of epoxy resin, acrylic resin, and multifunctional polyurethane, and the thermoplastic resin includes, but is not limited to, at least one of polyurethane, polyacrylate, polyvinyl alcohol, and polyvinyl butyral. These resins can ensure the stability of the connector during bonding of the anisotropic conductive film.

[0093] In some embodiments, the second resin film may further include a curing agent, including but not limited to at least one of dicyandiamide, phthalic anhydride, tetrahydrophthalic anhydride imidazole, methylimidazole, and diphenylimidazole. These curing agents can cure and crosslink the thermosetting resin. In some embodiments, the second resin film may further include an initiator, including at least one of azobisisobutyl cyanide and dibenzoyl peroxide. In some embodiments, the temperature used for the curing and crosslinking is 100-250°C (for example, it can be 100°C, 120°C, 150°C, 180°C, 200°C, 220°C or 250°C, etc.), the pressure is 1KPa-5.01MPa (for example, it can be 1KPa, 2KPa, 5KPa, 10KPa, 20KPa, 50KPa, 100KPa, 200KPa, 500KPa, 800KPa, 1MPa, 2MPa, 3MPa, 4MPa, 5MPa or 5.01MPa, etc.), and the time is 0.5-200s (for example, it can be 0.5s, 1s, 5s, 10s, 20s, 50s, 100s, 120s, 150s, 180s or 200s, etc.). When the prepared anisotropic conductive adhesive film is used, such as bonding a circuit, the anisotropic adhesive film can be cured using this temperature, pressure and time.

[0094] An embodiment of the present invention further provides an anisotropic conductive adhesive film, which is prepared using the preparation method of the present invention as described above.

[0095] The traditional electroless nickel plating process usually involves the following steps: (1) roughening the microsphere surface with concentrated sulfuric acid or hydrofluoric acid; (2) sensitizing the microsphere with stannous chloride; (3) activating the microsphere with palladium chloride or platinum solution; and (4) electrolessly plating nickel on the microsphere surface with salts such as nickel sulfate. The traditional process is too long and complicated.

[0096] Based on this, an embodiment of the present invention further provides a method for preparing the magnetic conductive particles used in the above embodiment, wherein: Figure 4 As shown, the following steps are included:

[0097] S21, stirring the microspheres, the conductive polymer monomer, and the oxidant to coat the surface of the microspheres with a conductive polymer layer to obtain first composite microspheres;

[0098] S22, adding the first composite microspheres to an activation solution for activation, forming catalytic particles (such as catalytic atoms or catalytic particles) on the surface of the first composite microspheres to obtain second composite microspheres, wherein the catalytic particles are used to catalyze the reduction of magnetic metal ions;

[0099] S23, providing a chemical plating solution, wherein the chemical plating solution includes a magnetic metal salt, a reducing agent, a complexing agent and water, and the pH of the chemical plating solution is 6.5 to 8.5;

[0100] S24. Add the second composite microspheres to a chemical plating solution, and the mass ratio of the second composite microspheres, magnetic metal salt, reducing agent and complexing agent is 0.5:(0.1~0.4):(0.25~0.5):(0.25~0.5). After reacting at a temperature of 50~70°C for 0.5~2h, a magnetic metal coating layer is formed on the surface of the second composite microspheres to obtain the magnetic conductive particles.

[0101] In this embodiment, a conductive polymer layer is formed on the surface of the microspheres. That is, the present invention roughens the surface of the microspheres by a simple method of wrapping the microspheres with a conductive polymer layer. The conductive polymer layer is then used as a transition layer for metal plating on the surface of the microspheres. With the help of the chelation effect of the conductive polymer layer on the metal ions in the activation solution, the microspheres are activated in the activation solution. Then, a magnetic metal is chemically plated on the surface of the conductive polymer layer in an electroless plating solution to form a magnetic metal coating layer. This can omit the roughening and sensitization steps in traditional electroless metal plating and reduce pollution to the environment.

[0102] At the same time, the magnetic conductive particles prepared in this embodiment have the characteristics of good morphology, high conductivity, and high magnetism (can be attracted by magnets), so that the anisotropic conductive film prepared by it can achieve bonding of high-precision circuits, achieve higher-precision device connection, and achieve device miniaturization; improve production efficiency and be suitable for large-scale assembly line operations. In addition, the inventors found through research that the reaction conditions have a great influence on whether the final conductive particles are magnetic. Therefore, in this embodiment, by controlling the reaction conditions, that is, the pH of the chemical plating solution is 6.5-8.5, the mass ratio of the second composite microspheres, magnetic metal salts, reducing agents and complexing agents is 0.5: (0.1-0.4): (0.25-0.5): (0.25-0.5), and the reaction is carried out at 50-70°C for 0.5-2h to prepare conductive particles with magnetic properties. After changing the reaction conditions, conductive particles with magnetic properties cannot be prepared.

[0103] In step S21, in some embodiments, the mass ratio of the microspheres to the conductive polymer monomer is (4-5):(2-3), for example, it can be 4:2, 4:2.5, 4:3, 4.5:2, 4.5:2.5, 4.5:3, 5:2, 5:2.5 or 5:3, etc.

[0104] In some embodiments, the microspheres are made of at least one of polystyrene, polymethyl methacrylate, polyurethane, phenolic resin, polydimethoxysiloxane, and silicon dioxide; or a copolymer of at least two of these materials. Microspheres made of these materials serve as the core of the magnetic conductive particles, exhibiting moderate hardness and preventing damage to the circuit during hot pressing.

[0105] The conductive polymer in the conductive polymer layer includes at least one of polyaniline, polyacetylene, polypyrrole, polythiophene, and polyethylenedioxythiophene. The conductive polymer is used to form a conductive polymer layer on the surface of the microspheres, thereby functionalizing the microspheres. The conductive polymer then chelates with metal cations, allowing metal ions to attach and be reduced to metal particles (such as metal atoms) as a catalyst. Furthermore, the conductive polymer chelates with magnetic metal cations in an electroless plating solution, allowing the magnetic metal cations to adhere to the surface of the conductive polymer layer. The magnetic metal cations are then reduced under the action of a catalyst and a reducing agent, thereby electrolessly plating the magnetic metal onto the surface of the conductive polymer layer.

[0106] From a microscopic perspective, the conductive polymer layer is composed of magnetic metal particles, and the particle size thereof can be 5 nm to 5 μm.

[0107] In some embodiments, the oxidant includes at least one of ammonium persulfate, ferric chloride, ferrous sulfate, and hydrogen peroxide. These oxidants can better enable the conductive polymer monomer to undergo polymerization to form a conductive polymer layer.

[0108] In step S22 , the activation solution includes at least one of a palladium salt solution (eg, palladium chloride solution), a platinum nanoparticle solution, a silver salt solution, and a copper salt solution.

[0109] Taking the conductive polymer in the conductive polymer layer as polyaniline and the palladium salt solution as palladium chloride solution as an example, the first composite microspheres are placed in an activation solution, and the palladium ions are chelated on the surface of the polyaniline layer. That is, the palladium ions in the palladium chloride are adsorbed by the quinone-like groups and imino groups of the polyaniline and reduced to palladium atoms. The palladium atoms play a catalytic role in the chemical plating, reducing the difficulty of the reaction. During the chemical plating process of the magnetic metal, the magnetic metal ions will preferentially grow at the positions containing palladium atoms (i.e., as activation sites) on the conductive polymer layer under the action of the reducing agent.

[0110] In step S23, in some embodiments, the magnetic metal salt includes at least one of palladium chloride, cobalt sulfate, cobalt chloride, nickel sulfate, nickel chloride, and nickel nitrate. The magnetic metal salt is the source of the magnetic metal particles in the magnetic conductive particles. When used in conjunction with the modification of the conductive polymer layer, the surface of the conductive polymer layer can be coated with the magnetic metal corresponding to the magnetic metal salt. Specifically, the magnetic metal salt is used to chelate magnetic metal ions, which are then fixed to the conductive polymer layer and then reduced to a magnetic metal element by a reducing agent in a subsequent reaction. Therefore, the corresponding magnetic metal coating layer is made of at least one of palladium, cobalt, and nickel.

[0111] In some embodiments, the reducing agent includes but is not limited to at least one of glucose, sodium hypophosphite, sodium borohydride, dimethylamino borane, formaldehyde and hydrazine hydrate. These reducing agents can play a role in reducing magnetic metal ions, that is, the reducing agent can reduce the magnetic metal ions chelated by the conductive polymer layer into conductive magnetic metal elements.

[0112] In some embodiments, the complexing agent includes at least one of sodium citrate, citric acid, disodium edetate, and ammonia. The complexing agent functions to chelate the magnetic metal cations in the electroless plating solution, thereby controlling the rate of release of the magnetic metal cations and allowing them to be slowly reduced during the electroless plating process. This ensures the quality of the coating (i.e., the magnetic metal coating) and ensures a smooth coating. Failure to add the complexing agent can result in the large-scale reduction of the magnetic metal cations, leading to undesirable phenomena such as agglomeration or uneven coating.

[0113] In some embodiments, the method for preparing the chemical plating solution comprises the following steps:

[0114] Providing a mixed solution comprising a magnetic metal salt, a reducing agent, a complexing agent, and water;

[0115] A pH adjuster is added to the mixed solution, and the pH of the system is adjusted to 6.5-8.5 by using the pH adjuster to obtain a chemical plating solution.

[0116] In some embodiments, the pH adjuster includes but is not limited to at least one of dilute hydrochloric acid, acetic acid, phosphoric acid, dilute sulfuric acid, sodium hydroxide, and ammonia water.

[0117] An embodiment of the present invention further provides a magnetic conductive particle, wherein the magnetic conductive particle is prepared using the preparation method described above in the embodiment of the present invention.

[0118] In this embodiment, the magnetic conductive particles possess good morphology, high conductivity, and high magnetism (they can be attracted by magnets). These magnetic and conductive properties facilitate the process of filling the grooved template with the conductive particles during the preparation of an anisotropic conductive film. The depth of the grooved template can also be reduced, thereby improving the transfer efficiency of the magnetic conductive particles and, in turn, reducing the difficulty of preparing an array-type anisotropic conductive film. The anisotropic conductive film prepared using magnetic conductive particles in the present invention can achieve high-precision circuit bonding, higher-precision device connection, and device miniaturization, improving production efficiency and making it suitable for high-volume assembly line operations. The present invention is further illustrated below through specific examples.

[0119] Example 1

[0120] This embodiment provides a method for preparing magnetic conductive particles, such as Figure 5 As shown, the following steps are included:

[0121] 1 g of polystyrene (PS) microspheres, 0.6 g of aniline monomer (PANI), 0.12 g of ammonium persulfate, and 50 mL of deionized water were mixed and mechanically stirred at room temperature for 20 h to obtain polystyrene microspheres with a polyaniline layer on the surface, i.e., the first composite microspheres (which can be recorded as PS@PANI);

[0122] The first composite microspheres were immersed in a 0.1M palladium chloride solution (PdCl2) at 50°C for 30 minutes to activate their surfaces (the palladium in palladium chloride is adsorbed by quinone-like groups and imino groups and reduced to palladium atoms. Palladium plays a catalytic role in electroless plating. In electroless nickel plating, nickel ions, under the action of a reducing agent, will preferentially grow in locations containing palladium). The activated first composite microspheres were then separated from the solution, washed three times with deionized water, and dried in a 60°C oven for an appropriate time to form Pd atoms on the surface of the first composite microspheres, obtaining second composite microspheres (which can be recorded as PS@PANI&Pd).

[0123] A mixed solution was provided, which consisted of a magnetic metal salt (0.2 g NiSO4·6H2O), a reducing agent (0.25 g C2H7BN), water (50 mL) and a complexing agent (0.25 g C 10 H 14 N2O8Na2·2H2O).

[0124] NaOH was added to the mixed solution, and the pH value of the system was adjusted to 6.5 with NaOH to obtain an electroless plating solution;

[0125] The electroless plating solution was heated to 50°C, and then 0.5g of the second composite microspheres were added under mechanical stirring. The reaction was continued at 50°C for 60 minutes. Finally, the sample was washed with deionized water and ethanol, centrifuged at 6000 rpm, and dried in a 60°C oven. A Ni coating was formed on the surface of the second composite microspheres, resulting in magnetic conductive particles (referred to as PS@PANI&Pd@Ni). The prepared magnetic conductive particles were microspherical with a particle size of 4.64μm, good morphology, and magnetic properties.

[0126] The scanning electron microscope (SEM) images of the polystyrene microspheres, the first composite microspheres, the second composite microspheres and the magnetic conductive particles in this embodiment are shown in FIG. Figure 6 As shown in a, b, c and d, the X-ray diffraction (XRD) pattern is as follows Figure 7 The hysteresis loop of magnetic conductive particles is shown in Figure 8 shown.

[0127] Example 2

[0128] This embodiment provides a method for preparing magnetic conductive particles, which is different from the embodiment 1 only in that the chemical plating solution contains 0.4 g NiSO4·6H2O.

[0129] The prepared magnetic conductive particles are microspherical, with a particle size of 4.67 μm, good morphology and magnetic properties.

[0130] Example 3

[0131] This embodiment provides a method for preparing magnetic conductive particles, which is different from the embodiment 1 only in that the chemical plating solution contains 0.5 g of C2H7BN.

[0132] The prepared magnetic conductive particles are microspherical, with a particle size of 4.68 μm, good morphology and magnetic properties.

[0133] Example 4

[0134] This embodiment provides a method for preparing magnetic conductive particles, which differs from the embodiment 1 only in that: 10 H 14 The concentration of N2O8Na2·2H2O is 0.5g.

[0135] The prepared magnetic conductive particles are microspherical, with a particle size of 4.65 μm, good morphology and magnetic properties.

[0136] Example 5

[0137] This embodiment provides a method for preparing magnetic conductive particles, which differs from embodiment 1 only in that:

[0138] The pH value of the system was adjusted to 8.5 with NaOH.

[0139] The prepared magnetic conductive particles are microspherical, with a particle size of 4.67 μm, good morphology and magnetic properties.

[0140] Example 6

[0141] This embodiment provides a method for preparing magnetic conductive particles, which differs from embodiment 1 only in that:

[0142] The electroless plating solution was heated to 70° C. and reacted at 70° C. for 60 minutes.

[0143] The prepared magnetic conductive particles are microspherical, with a particle size of 4.65 μm, good morphology and magnetic properties.

[0144] Example 7

[0145] This embodiment provides a method for preparing magnetic conductive particles, which differs from embodiment 1 only in that:

[0146] The electroless plating solution contained 0.1 g of NiSO4·6H2O; the pH value of the system was adjusted to 8.5 with NaOH.

[0147] The prepared magnetic conductive particles are microspherical, with a particle size of 4.68 μm, good morphology and magnetic properties.

[0148] Comparative Example 1

[0149] This embodiment provides a method for preparing magnetic conductive particles, which differs from embodiment 1 only in that:

[0150] The electroless plating solution contained 1.6 g of NiSO4·6H2O.

[0151] The prepared magnetic conductive particles are microspheres with a particle size of 4.73 μm, with impurities, microspheres agglomerated, and magnetic

[0152] Comparative Example 2

[0153] This embodiment provides a method for preparing conductive particles, which differs from embodiment 1 only in that:

[0154] The electroless plating solution contained 0.05 g of C2H7BN.

[0155] The prepared conductive particles are microspherical, with a particle size of 4.59 μm, good morphology, and no magnetism.

[0156] Comparative Example 3

[0157] This embodiment provides a method for preparing conductive particles, which differs from embodiment 1 only in that:

[0158] The electroless plating solution contains C 10 H 14 N2O8Na2·2H2O is 1.0g.

[0159] The prepared conductive particles are microspherical, with a particle size of 4.58 μm, good morphology, and no magnetism.

[0160] Comparative Example 4

[0161] This embodiment provides a method for preparing conductive particles, which differs from embodiment 1 only in that:

[0162] The pH value of the electroless plating solution was adjusted to 2.5.

[0163] The prepared conductive particles are microspherical, with a particle size of 4.53 μm, good morphology, and no magnetism.

[0164] Comparative Example 5

[0165] This embodiment provides a method for preparing conductive particles, which differs from embodiment 1 only in that:

[0166] The electroless plating solution was heated to 25° C. and reacted at 25° C. for 60 minutes.

[0167] The conductive particles are micro-spherical with a particle size of 4.56 μm, good morphology and no magnetism.

[0168] Example 8

[0169] This embodiment provides four methods for preparing anisotropic conductive adhesive films, including the following steps:

[0170] (1) Filling of magnetic conductive particles

[0171] like Figure 9 As shown, a silicon template is provided, on which grooves distributed in an array are provided, and the depth of the grooves is 2.5 μm;

[0172] 0.05 g of PS@PANI&Pd@Ni prepared in Example 1 was dispersed in 1 mL of ethanol to obtain a magnetic conductive particle dispersion.

[0173] A dispersion of magnetic conductive particles was dropwise added to one side of a silicon template with grooves. A magnet was then moved beneath the template four times. The magnet was then fixed beneath the template (applying magnetic forces of 0mT, 88mT, 150mT, and 280mT to the bottom of the template) and held stationary, allowing the PS@PANI&Pd@Ni to be drawn into the grooves. After the ethanol evaporated, any remaining PS@PANI&Pd@Ni on the silicon template that had not yet filled the grooves (i.e., any excess PS@PANI&Pd@Ni on the surface of the silicon template) was removed with a brush, allowing the PS@PANI&Pd@Ni to be drawn into the grooves, forming an array of magnetic conductive particles (with a distance of 8.76μm between adjacent magnetic conductive particles).

[0174] (2) Preparation of anisotropic conductive adhesive film

[0175] like Figure 10 As shown, a first resin liquid (composed of the following components by mass percentage: thermoplastic polyurethane elastomer (TPU, Bayer 9385, Covestro, Germany) 33.6%, dibenzoyl peroxide (BPO) 0.3%, N,N-dimethylformamide 33.8%, bisphenol A epoxy acrylic resin (YC3382, Shanghai Yinchang New Materials Co., Ltd.) 31.7% and γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) 0.6%)) was spin-coated at a speed of 450 rpm for 5 seconds, then at a speed of 5000 rpm for 20 seconds on a PET film, and then placed at 60° C. for drying for 10 minutes to form a first resin film on the PET film to obtain a composite film;

[0176] The composite film is placed on a silicon template with an array of magnetic conductive particles on its surface, so that the first adhesive film adheres to the array of magnetic conductive particles. The film is then hot-pressed at 80°C and 3kPa for 10 seconds, and then the composite film is peeled off from the template. During this process, the magnetic conductive particles on the silicon template are successfully transferred to the surface of the first resin film, resulting in a composite film with an array of magnetic conductive particles on its surface.

[0177] The first resin liquid (process parameters are spin coating at 450 rpm for 5 seconds and then spin coating at 5000 rpm for 20 seconds) is applied to a composite film with array-distributed magnetic conductive particles on the surface, and the film is dried in an oven at 60°C for 10 minutes to finally obtain four anisotropic conductive adhesive films (prepared using different magnetic field intensities).

[0178] In this embodiment, the filling effect of magnetic conductive particles on the template under different magnetic field strengths with a groove depth of 2.5 μm is shown in the figure below. Figure 11 shown.

[0179] Example 9

[0180] This embodiment provides four methods for preparing anisotropic conductive adhesive films, which differ from embodiment 8 only in that:

[0181] The groove depth is 3.5 μm.

[0182] In this embodiment, the filling effect of magnetic conductive particles on the template under different magnetic field strengths with a groove depth of 3.5 μm is shown in the figure. Figure 12 shown.

[0183] Under the conditions of groove depth of 3.5μm and magnetic field strength of 280mT, the magnetic conductive particles are filled in the groove of the template and transferred to the first resin film. The SEM (scanning electron microscope) and metallographic microscope images are as follows: Figure 13 As shown, it can be seen that the magnetic conductive particles are neat and free of impurities, which is very conducive to the preparation of arrayed anisotropic conductive adhesive by the template method. The magnetic conductive particles are distributed on the first resin film in an array arrangement.

[0184] Example 10

[0185] This embodiment provides four methods for preparing anisotropic conductive adhesive films, which differ from embodiment 8 only in that:

[0186] The groove depth is 6 μm.

[0187] In this embodiment, the groove depth is 6 μm, and the filling effect of magnetic conductive particles on the template under different magnetic field strengths is shown in the figure below. Figure 14 shown.

[0188] The filling efficiency, transfer efficiency and arrangement state of the magnetic conductive particles in the anisotropic conductive adhesive film in Examples 8 to 10 are shown in Table 1.

[0189] Table 1. Filling efficiency, transfer efficiency and arrangement of magnetic conductive particles in anisotropic conductive adhesive films

[0190]

[0191]

[0192] Among them, filling efficiency: filling efficiency refers to the efficiency of magnetic conductive particles entering the grooves of the template, that is, the ratio of the number of magnetic conductive particles entering the grooves on the template to the total number of grooves.

[0193] Transfer efficiency: The transfer efficiency is the ratio of the number of magnetic conductive particles transferred from the grooves on the template to the first resin film to the total number of magnetic conductive particles in the grooves on the template (each groove can only accommodate one magnetic conductive particle).

[0194] Example 11

[0195] This embodiment provides four methods for preparing anisotropic conductive adhesive films, which differ from embodiment 8 only in that:

[0196] The groove depths are 3.5 μm, 4 μm, 5 μm and 6 μm respectively.

[0197] The magnetic field strength is 280mT.

[0198] Among them, the SEM picture of the magnetic conductive particles after being transferred to the first resin film is as follows: Figure 15 shown.

[0199] Example 12

[0200] This embodiment provides 21 methods for preparing anisotropic conductive adhesive films, which differ from embodiment 8 only in that:

[0201] (1) The groove depth is 1.0 μm; the magnetic field intensities are 0 mT, 88 mT, and 280 mT respectively;

[0202] (2) The groove depth is 2.0 μm; the magnetic field intensities are 0 mT, 88 mT, and 280 mT respectively;

[0203] (3) The groove depth is 2.5 μm; the magnetic field intensities are 0 mT, 88 mT, and 280 mT respectively;

[0204] (4) The groove depth is 3.5 μm; the magnetic field strengths are 0 mT, 88 mT, and 280 mT respectively;

[0205] (5) The groove depth is 4 μm; the magnetic field strengths are 0 mT, 88 mT, and 280 mT respectively;

[0206] (6) The groove depth is 5 μm; the magnetic field strengths are 0 mT, 88 mT, and 280 mT respectively;

[0207] (7) The groove depth is 6 μm; the magnetic field strengths are 0 mT, 88 mT, and 280 mT, respectively.

[0208] The filling effect of magnetic conductive particles on the template under different magnetic field strengths and different groove depths is shown in the figure. Figure 16 shown.

[0209] The above results show that:

[0210] Because magnetic conductive particles are attracted by magnetic attraction under the action of a magnetic field, the filling efficiency is improved. Therefore, under the action of a magnetic field, the magnetic conductive particles can be perfectly filled into the grooves of a template with shallow grooves, making the preparation of anisotropic conductive adhesive films more convenient. However, in the absence of a magnetic field (i.e., 0 mT), the filling efficiency of magnetic conductive particles on the template is severely reduced.

[0211] When transferring the magnetic conductive particles arrayed on the template to the first resin film, shallower grooves facilitate the transfer of the magnetic conductive particles, and the shallower the grooves, the higher the transfer efficiency. Therefore, the advantage of shallow grooves over deep groove templates is that the transfer efficiency is significantly improved.

[0212] Although the filling efficiency of the magnetic conductive particles on the template is higher when the groove is deeper, when the magnetic conductive particles are transferred to the first resin film, since the diameter of the magnetic conductive particles (4.64μm) is much smaller than the depth of the groove (6μm), the contact area between the magnetic conductive particles and the first resin film is reduced during the transfer of the magnetic conductive particles, thereby reducing the transfer efficiency and being unfavorable for the preparation of array-type anisotropic conductive adhesive.

[0213] In summary, the present invention provides an anisotropic conductive film, magnetic conductive particles, and a preparation method. Using magnetron array technology, the magnetic conductive particles are precisely positioned within a micro-grooved template with submicron precision. A pressure-assisted transfer process successfully achieves a two-dimensional periodic arrangement of the magnetic conductive particles on the surface of a first resin film. The proposed magnetic field-induced assembly process offers two major technical advantages: precise spacing control, avoiding the risk of short circuits caused by contact between adjacent magnetic conductive particles; and a scalable production process, which utilizes magnetic field filling and transfer methods, making them more suitable for industrial production.

[0214] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing an anisotropic conductive adhesive film, characterized in that: The steps include: Providing a template, wherein the template is provided with grooves distributed in an array; Providing magnetic conductive particles, and using magnetic attraction to attract the magnetic conductive particles to fill the grooves to form an array of magnetic conductive particles; Providing a first resin film, covering the arrayed magnetic conductive particles with the first resin film, and performing a hot pressing process to transfer the arrayed magnetic conductive particles to the first resin film; A second resin dispersion is coated on the side of the first resin film containing the arrayed magnetic conductive particles, and dried to obtain the anisotropic conductive film.

2. The preparation method according to claim 1, characterized in that The magnetic conductive particles are spherical, and the depth of the grooves is 30% to 90% of the diameter of the magnetic conductive particles; and / or, In the array-distributed magnetic conductive particles, the distance between two adjacent magnetic conductive particles is 1 to 20 μm.

3. The preparation method according to claim 1, characterized in that Using a magnetic field of 10 to 2800 mT, a continuous magnetic attraction force is applied to the magnetic conductive particles to attract the magnetic conductive particles to fill the grooves; and / or, The process parameters used in the hot pressing treatment are: The temperature is 80°C, the pressure is 1kPa~1MPa, and the time is 1~10s.

4. The preparation method according to claim 3, characterized in that Place a magnet on the side of the template away from the magnetic conductive particles, move it 3 to 5 times, and then keep it stationary to attract the magnetic conductive particles to fill the grooves, and then recover the magnetic conductive particles that are not filled in the grooves; the magnetic field strength generated by the magnet is 10 to 2800 mT.

5. The preparation method according to claim 1, characterized in that The magnetic conductive particles include a first composite microsphere and a magnetic metal coating layer coated on the surface of the first composite microsphere; the first composite microsphere includes a microsphere and a conductive polymer layer coated on the surface of the microsphere; The material of the microspheres includes at least one of polystyrene, polymethyl methacrylate, polyurethane, phenolic resin, polydimethoxysiloxane and silicon dioxide; or the material of the microspheres includes a copolymer of at least two of polystyrene, polymethyl methacrylate, polyurethane, phenolic resin and polydimethoxysiloxane; The diameter of the magnetic conductive particles is 500 nm to 50 μm; the thickness of the magnetic metal coating layer is 5 nm to 5 μm.

6. An anisotropic conductive film, characterized in that: The preparation method is described in any one of claims 1 to 5.

7. A method for preparing magnetic conductive particles, characterized in that: The magnetic conductive particles are used to prepare the anisotropic conductive adhesive film according to claim 6, and the magnetic conductive particles include the following steps: The microspheres, the conductive polymer monomer and the oxidant are stirred to coat the surface of the microspheres with a conductive polymer layer to obtain first composite microspheres; adding the first composite microspheres to an activation solution for activation, thereby forming catalytic particles on the surface of the first composite microspheres to obtain second composite microspheres, wherein the catalytic particles are used to catalyze the reduction of magnetic metal ions; Providing a chemical plating solution, the chemical plating solution comprising a magnetic metal salt, a reducing agent, a complexing agent and water, wherein the pH of the chemical plating solution is 6.5 to 8.5; The second composite microspheres are added to a chemical plating solution, and the mass ratio of the second composite microspheres, magnetic metal salt, reducing agent and complexing agent is 0.5:(0.1~0.4):(0.25~0.5):(0.25~0.5). After reacting at a temperature of 50~70°C for 0.5~2h, a magnetic metal coating layer is formed on the surface of the second composite microspheres to obtain the magnetic conductive particles.

8. The preparation method according to claim 7, characterized in that The mass ratio of the microspheres to the conductive polymer monomer is (4-5):(2-3); and / or, The diameter of the magnetic conductive particles is 500 nm to 50 μm, and the thickness of the magnetic metal coating layer is 5 nm to 5 μm; and / or, The material of the microspheres includes at least one of polystyrene, polymethyl methacrylate, polyurethane, phenolic resin, polydimethoxysiloxane and silicon dioxide, or the material of the microspheres includes a copolymer of at least two of polystyrene, polymethyl methacrylate, polyurethane, phenolic resin and polydimethoxysiloxane; and / or, The conductive polymer in the conductive polymer layer includes at least one of polyaniline, polyacetylene, polypyrrole, polythiophene and polyethylenedioxythiophene.

9. The preparation method according to claim 7, characterized in that The oxidant comprises at least one of ammonium persulfate, ferric chloride, ferrous sulfate and hydrogen peroxide; and / or, The reducing agent comprises at least one of glucose, sodium hypophosphite, sodium borohydride, dimethylamino borane, formaldehyde and hydrazine hydrate; and / or, The complexing agent includes at least one of sodium citrate, citric acid, disodium edetate and ammonia water; and / or, The magnetic metal salt includes at least one of palladium chloride, cobalt sulfate, cobalt chloride, nickel sulfate, nickel chloride and nickel nitrate; and / or, The activation solution includes at least one of a palladium salt solution, a platinum nanoparticle solution, a silver salt solution, and a copper salt solution.

10. A magnetic conductive particle, characterized in that: The magnetic conductive particles are prepared by the preparation method according to any one of claims 7 to 9.

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