Conductive particle and preparation method thereof, and conductive adhesive and preparation method thereof
By using a conductive polymer layer as a metal plated transition layer in conductive particles, the existing problems of poor morphology and complex preparation of conductive particles are solved, and the preparation of high-performance conductive particles and the bonding of high-precision circuits are realized.
Patent Information
- Application Number
- CN202411409811.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-10
- Publication Date
- 2025-02-18
AI Technical Summary
The existing conductive particles have poor morphology, low performance, complex preparation process and serious pollution.
Using conductive polymer layer as the transition layer for metal plating on the surface of the microspheres, the conductive polymer layer wraps the microspheres and uses the chelation of the metal ions to achieve electroless metal plating, replacing the coarsification and sensitivity in the traditional electroless plating process. Steps.
It reduces environmental pollution, simplifies the preparation process, improves the morphology and performance of conductive particles, and enables array anisotropic conductive adhesive to achieve high-precision circuit bonding and device miniaturization.
Smart Images
Figure CN119463218A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of microelectronic packaging, and in particular to a conductive particle and a preparation method thereof, a conductive adhesive and a preparation method thereof. Background Art
[0002] Many materials have been explored for conductive particles in anisotropic conductive films (ACF). There are two types of conductive particles generally used in ACF. The first type is composed of conductive materials such as pure metals, such as tin-bismuth alloy microspheres (Sn58Bi), silver-coated tin microspheres (Sn@Ag), gallium-indium-tin alloy microspheres (Ga-In-Sn), silver microspheres (Ag), and gold microspheres (Au). The second type is composed of metal-coated polymer microspheres or inorganic microspheres to form a core-shell structure, relying on the metal conductivity of the shell layer to achieve circuit conduction, such as nickel-coated polymer (Ni-Polymer), gold-coated polymer (Au-Polymer), silver-coated polymer (Ag-Polymer), copper-coated polymer (Cu-Polymer), nickel-coated silica microspheres (Ni-SiO2), etc. Generally, metal-coated polymer microspheres have more advantages than pure metal or alloy microspheres. For example, metal-coated polymer microspheres have moderate hardness and will not damage the circuit during hot pressing. The specific density is relatively low, and it is not easy to cause particle deposition when scraping the glue during the preparation of ACF film, resulting in inconsistent particle density between the bottom and upper layers of the film. The particle size of the microspheres can be more easily controlled to be monodisperse; and the cost is lower.
[0003] However, there are many limitations in the preparation of core-shell structured microspheres. 1. The complex synthesis steps hinder its use. 2. There are many highly toxic and highly polluting wastes generated during the preparation process. 3. The existing core-shell structured microspheres have poor morphology and low performance. Traditional chemical metal plating requires four main steps: roughening, sensitization, activation, and chemical plating to achieve metal plating on the surface of the microspheres. The surface of polymer microspheres is relatively smooth, which is not conducive to the deposition and growth of metal particles. Roughening is to etch rough metal growth sites on the surface of smooth polymer microspheres. Generally, highly polluting and highly toxic reagents such as potassium dichromate and concentrated sulfuric acid are used. Sensitized microspheres require high concentrations of stannous chloride (SnCl2) and hydrochloric acid to treat the microspheres. Activated microspheres require treatment with a dilute hydrochloric acid solution of the heavy metal salt PdCl2. Therefore, in the three steps of roughening, sensitization, and activation, highly polluting and highly toxic reagents are used, and the steps are cumbersome, which is not conducive to large-scale and green production.
[0004] Therefore, the prior art still needs to be improved and developed. Summary of the invention
[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a conductive particle and a preparation method thereof, a conductive adhesive and a preparation method thereof, aiming to solve the problems of poor morphology and low performance of the existing conductive particles.
[0006] The technical solution of the present invention is as follows:
[0007] A conductive particle comprises a microsphere, a conductive polymer layer wrapping the microsphere, and metal particles attached to the surface of the conductive polymer layer.
[0008] The conductive particles, wherein the material of the microspheres includes one or a copolymer of polystyrene, polymethyl methacrylate, polyurethane, phenolic resin, polydimethoxysiloxane, and silicon dioxide.
[0009] In the conductive particles, the material of the conductive polymer layer includes one or more of polyaniline, polyacetylene, polypyrrole, polythiophene, and polyethylenedioxythiophene.
[0010] The conductive particles, wherein the material of the metal particles includes one or more of gold, nickel, silver, tin, copper, cobalt, and palladium; and / or the size of the metal particles is 500nm-200μm.
[0011] A method for preparing conductive particles, comprising the steps of:
[0012] The microspheres, the conductive polymer monomer and the oxidant are mixed and stirred to obtain the microspheres coated with the conductive polymer layer;
[0013] The metal salt, the reducing agent and the microspheres coated with the conductive polymer layer are mixed and reacted to obtain conductive particles.
[0014] The method for preparing the conductive particles, wherein the mass ratio of the microspheres, the conductive polymer monomer and the metal salt is (4-5):(2-3):(9-11).
[0015] The method for preparing the conductive particles, wherein the oxidant includes one or more of ammonium persulfate, ferric chloride, ferrous sulfate, and hydrogen peroxide; and / or the reducing agent includes one or more of glucose, sodium hypophosphite, sodium borohydride, dimethylaminoborane, formaldehyde, and hydrazine hydrate; and / or the metal salt includes one or more of silver nitrate, silver sulfate, copper nitrate, copper sulfate, copper chloride, palladium chloride, cobalt sulfate, cobalt chloride, chloroauric acid, nickel sulfate, nickel chloride, nickel nitrate, tin tetrachloride, and stannous chloride.
[0016] A conductive adhesive comprises a first adhesive film layer, a second adhesive film layer arranged on one side of the first adhesive film layer, and a plurality of conductive particles embedded between the first adhesive film layer and the second adhesive film layer.
[0017] In the conductive adhesive, the conductive particles are arranged in an array between the first adhesive film layer and the second adhesive film layer; and the distance between two adjacent conductive particles is 1 μm-20 μm.
[0018] A method for preparing a conductive adhesive comprises the following steps:
[0019] Arranging a layer of adhesive film on the base film to obtain a base film with a first adhesive film layer;
[0020] Fill the conductive particles into the template by scraping with a rubber or dust-free cloth, cover the base film with the first adhesive film layer on one side of the template filled with conductive particles, press and peel off the template to obtain the first adhesive film layer with conductive particles;
[0021] A second adhesive film layer is arranged on the side of the first adhesive film layer coated with conductive particles to obtain a conductive adhesive.
[0022] Beneficial effects: The present invention provides a conductive particle and a preparation method thereof, a conductive adhesive and a preparation method thereof, wherein the conductive particle comprises a microsphere, a conductive polymer layer for wrapping the microsphere, and metal particles attached to the surface of the conductive polymer layer. The present invention uses a conductive polymer layer as a transition layer for metal plating on the surface of the microsphere, so that the conductive particle can roughen the surface of the microsphere by a simple method of wrapping the microsphere with a conductive polymer layer, and then successfully chemically plate metal on the surface of the conductive polymer layer by means of the chelation between the conductive polymer layer and metal ions, replacing the roughening and sensitization process in the traditional chemical plating process, reducing environmental pollution and simplifying the process of preparing conductive particles; at the same time, the conductive particles of the present invention have the characteristics of good morphology and excellent performance, so that the array-type anisotropic conductive adhesive obtained by using it can realize the bonding of high-precision circuits, realize higher-precision device connection, and realize device miniaturization; and provide production efficiency, suitable for large-scale assembly line operations. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 It is a structural schematic diagram of an array type anisotropic conductive adhesive of the present invention;
[0024] Figure 2 It is a schematic diagram of the structure of the template;
[0025] Figure 3 This is a characterization image after the particles are transferred to the film using the template transfer method;
[0026] Figure 4 Schematic diagram of the method for functionalizing the microsphere surface;
[0027] Figure 5 This is a diagram of the mechanism of chemical surface silver plating;
[0028] Figure 6 This is the SEM image of the microspheres functionalized with polyaniline after chemical silver plating;
[0029] Figure 7 This is the SEM image of the microspheres that were not functionalized with polyaniline after chemical silver plating. DETAILED DESCRIPTION
[0030] The present invention provides a conductive particle and a preparation method thereof, a conductive adhesive and a preparation method thereof. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.
[0031] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined as herein.
[0032] The growing demand for integration and miniaturization of electronic components has promoted the development of welding materials for high-precision circuits, such as the interconnection between stretchable electrodes, organic light-emitting diodes and driver ICs. Electronic packaging plays a vital role in establishing connections between electronic components. Compared with traditional wire bonding, through-hole and flip-chip bonding connection methods, anisotropic conductive adhesive is a competitive material due to its advantages of high-precision circuit connection, convenient operation and green environmental protection. ACF is mainly used for interconnection between high-precision circuits, which can achieve conductivity in the thickness direction and insulation in other directions. The conductive particles in ACF play a role in circuit conduction, and the condition of the conductive particles directly affects the conduction effect of the connection circuit.
[0033] The existing core-shell conductive particles composed of metal-wrapped polymer microspheres or inorganic microspheres have a preparation process that uses a roughening, sensitization, and activation process; the roughening process uses concentrated sulfuric acid, potassium dichromate and other highly polluting solvents to treat the polymer surface to achieve microsphere surface etching and provide metal growth sites for subsequent operations. The sensitization process uses high-concentration hydrochloric acid and stannous chloride to sensitize the microspheres, and the high-concentration hydrochloric acid is a great source of danger and pollution. The activation process uses high-concentration hydrochloric acid and palladium chloride to activate the surface of the microspheres, and the high-concentration hydrochloric acid and palladium chloride are high pollution sources during the experiment.
[0034] Based on this, the present invention provides a conductive particle, including a microsphere, a conductive polymer layer wrapping the microsphere, and metal particles attached to the surface of the conductive polymer layer.
[0035] In this embodiment, a conductive polymer layer is used as a transition layer for metal plating on the surface of the microspheres, so that the conductive particles can roughen the surface of the microspheres by a simple method of wrapping the microspheres with the conductive polymer layer, and then successfully chemically plate metal on the surface of the conductive polymer layer with the help of the chelation effect between the conductive polymer layer and the metal ions to form a conductive metal shell, which replaces the roughening and sensitization process in the traditional chemical plating process, reduces environmental pollution and simplifies the process of preparing conductive particles; at the same time, the conductive particles of the present invention have the characteristics of good morphology and excellent performance, so that the array-type anisotropic conductive adhesive obtained by using it can realize the bonding of high-precision circuits, realize higher-precision device connection, and realize device miniaturization; and provide production efficiency, suitable for large-scale assembly line operations.
[0036] In some embodiments, the material of the microspheres includes, but is not limited to, one of polystyrene, polymethyl methacrylate, polyurethane, phenolic resin, polydimethoxysiloxane, silicon dioxide, or a copolymer. Using these microspheres as the core of the conductive particles has moderate hardness and will not damage the circuit during hot pressing. The particle size of the microspheres can be more easily controlled to be monodisperse, and the cost is lower.
[0037] In a preferred embodiment, the microspheres are made of polystyrene.
[0038] In some embodiments, the material of the conductive polymer layer includes but is not limited to one or more of polyaniline, polyacetylene, polypyrrole, polythiophene, and polyethylenedioxythiophene. The above conductive polymer materials are used to form a conductive polymer layer on the surface of the microspheres, which can achieve microsphere functionalization, and then metal ions are attached under the chelation effect of the conductive polymer and metal cations, and then chemical metal plating is achieved under the action of a reducing agent, so that metal particles are attached to the surface of the conductive polymer layer.
[0039] In a preferred embodiment, the conductive polymer layer is made of polyaniline.
[0040] In some embodiments, the material of the metal particles includes, but is not limited to, one or more of gold, nickel, silver, tin, copper, cobalt, and palladium; and / or, the size of the metal particles is 500nm-200μm. The above metal particles can achieve a good conductive effect, and controlling the size of the metal particles between 500nm-200μm is conducive to further controlling the size of the conductive particles; the size of the conductive particles can determine the bonding accuracy of the circuit, the smaller the bonding accuracy, the higher the bonding accuracy, the larger the particles, the worse the bonding accuracy, when the particles are in contact with the circuit substrate for conduction, the thinner the circuit width, the higher the circuit accuracy, and the smaller the required particle size.
[0041] In some embodiments, the particle size of the conductive particles is 500nm-50μm, the particle size of the microspheres is 500nm-50μm, and the thickness of the conductive metal shell of the conductive particles is 5nm-5μm. The size of the conductive particles can determine the bonding accuracy of the circuit. The smaller the size, the higher the bonding accuracy. The larger the particle size, the worse the bonding accuracy. When the particles are in contact with the circuit substrate for conduction, the thinner the circuit width, the higher the circuit accuracy, and the smaller the required particle size. The conductivity increases with the thickness of the conductive metal shell. When the particles are in contact with the circuit substrate for conduction, the greater the power of the device connected to the circuit, the smaller the resistance at the circuit connection, and thus the thicker the thickness of the conductive particle metal shell.
[0042] In addition, the present invention also provides a method for preparing conductive particles, comprising the steps of:
[0043] Step S10: mixing the microspheres, the conductive polymer monomer and the oxidant, and stirring to obtain microspheres coated with the conductive polymer layer;
[0044] Step S20: mixing the metal salt, the reducing agent and the microspheres coated with the conductive polymer layer, and obtaining conductive particles after reaction.
[0045] In this embodiment, the microspheres are roughened by using a conductive polymer to form a conductive polymer layer on the surface of the microspheres, the microspheres are coated, and the microspheres are chemically plated with metal ions by means of the chelation effect of the conductive polymer. This can omit the sensitization and activation steps in traditional chemical metal plating, reduce pollution to the environment, and produce conductive particles with excellent morphology and high performance.
[0046] Specifically, taking aniline monomer (ANI) as a conductive polymer monomer, it is used to form a polyaniline conductive polymer layer on the surface of the microsphere. Since polyaniline contains aniline-like groups and quinoneimine groups, it can chelate metal ions. Compared with adsorbing metal cations on the surface of the microsphere, and then adding a reducing agent to plate the metal on the surface of the microsphere, the metal microspheres plated in this way have good appearance and good conductivity. Compared with other chemical plating processes, the step of forming a polyaniline conductive polymer layer on the surface of the microsphere can save the two complex steps of activation and activation.
[0047] In some embodiments, the mass ratio of the microspheres, the conductive polymer monomer and the metal salt is (4-5):(2-3):(9-11), and the conductive particles prepared according to this mass ratio have the characteristics of good appearance and excellent performance.
[0048] In a preferred embodiment, the mass ratio of the microspheres, the conductive polymer and the metal salt is 5:3:10.
[0049] In some embodiments, the oxidant includes, but is not limited to, one or more of ammonium persulfate, ferric chloride, ferrous sulfate, and hydrogen peroxide; the oxidant can be used to cause the conductive polymer monomer to undergo polymerization to form a conductive polymer layer.
[0050] In some embodiments, the reducing agent includes but is not limited to one or more of glucose, sodium hypophosphite, sodium borohydride, dimethylamino borane, formaldehyde, and hydrazine hydrate; the above reducing agents can play a role in reducing metal elements, that is, the reducing agent can reduce the metal ions chelated by the conductive polymer layer into conductive metal elements.
[0051] In some embodiments, the metal salt includes, but is not limited to, one or more of silver nitrate, silver sulfate, copper nitrate, copper sulfate, copper chloride, palladium chloride, cobalt sulfate, cobalt chloride, chloroauric acid, nickel sulfate, nickel chloride, nickel nitrate, tin tetrachloride, and stannous chloride. The metal salt is the source of the conductive metal particles in the conductive particles, and when used in conjunction with the modification of the conductive polymer layer, the metal corresponding to the metal salt can be plated on the surface of the conductive polymer layer. That is, the metal salt is used to provide chelated metal ions, the metal ions are fixed on the conductive polymer layer, and then reduced to a metal element by a reducing agent in a subsequent reaction.
[0052] In addition, if Figure 1 As shown, the present invention further provides a conductive adhesive, including a first adhesive film layer 10, a second adhesive film layer 20 disposed on one side of the first adhesive film layer 10, and a plurality of conductive particles 30 embedded between the first adhesive film layer 10 and the second adhesive film layer 20.
[0053] In this embodiment, the conductive particles play the role of conducting the circuit in the bonding circuit, and the conductive particles are in contact with the electrode / substrate to achieve the conductive effect; the adhesive film layer is the main part of the bonding circuit and is the medium for fixing the circuit, thereby protecting the conductive particles and the circuit to be stably connected. The conductive particles play the role of conducting the circuit when bonding the devices, and at the same time, the proper addition method can achieve the effect of filling the adjacent particles with resin, achieve the effect of lateral insulation, and improve the bonding accuracy.
[0054] In some embodiments, the conductive particles are arranged in an array between the first adhesive film layer and the second adhesive film layer; the spacing between two adjacent conductive particles is 1 μm-20 μm, so that the conductive particles are evenly distributed between the first adhesive film layer and the second adhesive film layer to form an array-type anisotropic conductive adhesive.
[0055] In some embodiments, the first adhesive film layer and the second adhesive film layer are both composed of resin and curing agent. The resin is the main component of the adhesive film and will bond the circuit. The curing agent is used to initiate the cross-linking reaction of the resin during the use of ACF (heating and pressurization). The cross-linking reaction of the resin is a necessary condition for bonding and fixing the circuit.
[0056] In some embodiments, the resin is a mixture of a curable resin and a thermoplastic resin; the curable resin will cross-link during use to improve the adhesive / resin bonding performance; the thermoplastic resin is conducive to the preparation of the adhesive film, and it is difficult to form a film with only curable resins, so the addition of thermoplastic resin can achieve the continuity of the adhesive film and facilitate film formation. The curing agent triggers the cross-linking reaction of the curable resin, and triggers the cross-linking reaction of the resin under a certain temperature / ultraviolet irradiation.
[0057] In some embodiments, thermosetting resins mainly include but are not limited to epoxy resins, acrylic resins, multifunctional polyurethanes, etc., and thermoplastic resins mainly include but are not limited to polyurethane, polyacrylate, polyvinyl alcohol, polyvinyl butyral, etc. The above resins can ensure the stability of the connector when the anisotropic conductive adhesive is bonded.
[0058] In some embodiments, the curable resin includes, but is not limited to, one or more of acrylate, epoxy resin, and methacrylate; a cross-linking reaction can be achieved by utilizing double bonds of acrylate, epoxy rings of epoxy resin, and double bonds of methacrylate.
[0059] In some embodiments, the thermoplastic resin includes, but is not limited to, one or more of polyurethane, polystyrene, polymethacrylate, polycaprolactone, polypropylene, and polyvinyl chloride. The thermoplastic resin is a flexible resin that can form a film.
[0060] In some embodiments, for epoxy resins, imidazoles, acid anhydrides, amines and other curing agents are mainly used, including but not limited to imidazole, dimethylimidazole, diphenylimidazole, dicyandiamide, phthalic anhydride, tetrahydrophthalic anhydride, etc. For acrylic acid / methacrylic acid resins, curing initiators mainly include azobisisobutyl cyanide, dibenzoyl peroxide, etc. The use of curing agents can trigger the cross-linking reaction of thermosetting resins during the bonding process, thereby achieving the effect of bonding devices.
[0061] In some embodiments, the curing agent includes but is not limited to one or more of imidazole, dimethylimidazole, diphenylimidazole, dicyandiamide, tetrahydrophthalic anhydride, and diethylamine, which can induce epoxidation reaction of unsaturated bonds to achieve crosslinking.
[0062] In some embodiments, a base film 40 is further provided on the side of the first adhesive film layer 10 facing away from the second adhesive film layer 20. The material of the base film includes but is not limited to one of polyethylene terephthalate, polyimide, polyvinyl chloride, and polypropylene. The base film plays a bearing role and is used to carry the first adhesive film layer, conductive particles, and the second adhesive film layer. The base film needs to be peeled off during the use of the conductive adhesive.
[0063] In a preferred embodiment, the base film is made of polyethylene terephthalate (PET), which has good friction resistance and mechanical properties, and can ensure the attachment and peeling of the anisotropic conductive film. The PET surface has a release force of 10 to 2000, which protects the anisotropic conductive film from contamination and facilitates packaging and storage.
[0064] In addition, the present invention also provides a method for preparing a conductive adhesive, comprising the steps of:
[0065] Step S100: a layer of adhesive film is provided on the base film to obtain a base film with a first adhesive film layer;
[0066] Step S200: Fill the conductive particles into the template by scraping with a rubber or dust-free cloth, cover the base film with the first adhesive film layer on one side of the template filled with conductive particles, press and then peel off the template to obtain the first adhesive film layer with conductive particles;
[0067] Step S300: a second adhesive film layer is provided on the side of the first adhesive film layer coated with conductive particles to obtain a conductive adhesive.
[0068] In some embodiments, the method of filling the conductive particles into the template by scraping with a rubber or a dust-free cloth so that the conductive particles are arranged periodically includes a template transfer method, which can realize the periodic arrangement of the conductive particles, leaving gaps between the conductive particles, and the particles are not in contact with each other, which greatly improves the connection of the bonding high-precision circuit. Compared with the traditional preparation method of mechanical stirring dispersion (uneven particle dispersion, inevitable particle agglomeration, etc.), it has higher advantages.
[0069] In some embodiments, Figure 2 As shown (where Figure 2 a is a template diagram, and b is a schematic diagram of a micro groove). The template of the template transfer method is provided with a micro groove. The shape of the micro groove includes but is not limited to a triangle, a circle, a hexagon, a quadrilateral, a parallelogram, etc. The depth of the micro groove is 1μm-20μm, and the wall of the micro groove is inclined at an angle of 1-90° to the bottom surface; the shape, depth and angle of the groove affect the filling effect, and the micro groove under this parameter can improve the filling effect of the conductive particles.
[0070] In a preferred embodiment, the depth of the micro groove is 4 μm, and the width of the micro groove is 6 μm.
[0071] Specifically, the characterization diagram after the particles were transferred to the film using the template transfer method is shown in the figure below: Figure 3 As shown (where Figure 3 (a is a SEM image, b is a metallographic microscope image of the bonding circuit, and c is an optical microscope image). It can be seen that the neatness of the microspheres and the state without impurities are very conducive to the preparation of arrayed anisotropic conductive adhesives by the template method. The particles are distributed on the adhesive film in an array arrangement.
[0072] The following examples are further given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention.
[0073] Example 1
[0074] In this embodiment, polyaniline is used to modify the surface of the microspheres. After 24 hours of redox reaction, the polyaniline is well coated on the surface of the microspheres. The schematic diagram of the method for functionalizing the surface of the microspheres is shown in FIG. Figure 4 As shown, the specific preparation steps are as follows:
[0075] Weigh 1g of PS (polystyrene) microspheres, put them into 50ml of water (H2O), disperse them with an ultrasonic machine for 5min, then add 0.6g of aniline monomer (ANI), stir them magnetically for 10min, then add 0.04g of ammonium persulfate (APS), continue stirring for 24h, centrifuge at 6000rpm and wash them with 50ml of clean water for three cycles after the reaction, and then dry them. The PS wrapped with polyaniline is recorded as PS-PANI. Use a scanning electron microscope to observe the particle morphology, and the clean ones are good.
[0076] Examples 2-7 and Comparative Examples 1-4
[0077] The methods for functionalizing the microsphere surfaces in Examples 2-7 and Comparative Examples 1-4 are the same as in Example 1, except for the amount of aniline monomer added, the amount of ammonium persulfate added, and the amount of polystyrene added, as shown in Table 1.
[0078] Table 1
[0079] ANI APS PS <![CDATA[H2O]]> state Example 1 0.6g 0.04g 1g 50mL good Example 2 0.6g 0.12g 1g 50mL good Example 3 0.6g 0.24g 1g 50mL good Example 4 0.15g 0.12g 1g 50mL good Example 5 0.3g 0.12g 1g 50mL good Example 6 1.2g 0.12g 1g 50mL good Example 7 2.4g 0.12g 1g 50mL good Comparative Example 1 0.6g 0.48g 1g 50mL There are particles Comparative Example 2 0.6g 0.96g 1g 50mL There are particles Comparative Example 3 0.6g 1.92g 1g 50mL More particle impurities Comparative Example 4 4.8g 0.12g 1g 50mL There are particles
[0080] Example 8
[0081] The PS-PANI prepared in Example 1 was subjected to chemical surface silver plating, and the mechanism is as follows: Figure 5 As shown, the silver ions are chelated by the quinone imine group, and then the silver plating on the surface of the microspheres is more easily achieved under the action of the reducing agent glucose. The specific steps are as follows:
[0082] Weigh 2g of silver sulfate (Ag2SO4) and put it in a 50ml water beaker A, then add 5ml of ammonia (NH3·H2O), then put 1g of PS-PANI (with good morphology) prepared in Example 1 in beaker A, then weigh 4g of glucose and put it in beaker B filled with 50ml of water, ultrasonically dissolve, then add beaker B to beaker A, and then stir for 1h. After the solution reacts, centrifuge at 6000rpm and wash three times with 50ml of clean water, and then dry. The silver-plated PS-PANI particles are recorded as PS-PANI-Ag.
[0083] Comparative Examples 5-7
[0084] The method for chemically silver-plating PS-PANI in Comparative Examples 5-7 is the same as that in Example 8, except that the amounts of ammonia water and silver sulfate added are different, as shown in Table 2:
[0085] Table 2
[0086]
[0087] Comparative Example 8
[0088] The chemical surface silver plating method in this comparative example is the same as that in Example 8, except that the chemical silver plating is performed on the microspheres that are not functionalized with polyaniline.
[0089] The conductive particles obtained in Example 8 and Comparative Example 8 were characterized. The SEM images of the microspheres functionalized with polyaniline after chemical silver plating in Example 8 are shown in FIG. Figure 6 As shown, the SEM image of the microspheres functionalized with polyaniline in Comparative Example 8 after chemical silver plating is as follows Figure 7 It can be seen that the silver coating effect of the microspheres without polyaniline modification is extremely poor, while the silver coating effect of the microspheres modified with polyaniline is better.
[0090] In summary, the present invention provides a conductive particle and a preparation method thereof, a conductive adhesive and a preparation method thereof, wherein the conductive particle includes a microsphere, a conductive polymer layer that wraps the microsphere, and metal particles attached to the surface of the conductive polymer layer. The present invention uses a conductive polymer layer as a transition layer for metal plating on the surface of the microsphere, so that the conductive particle can roughen the surface of the microsphere by a simple method of wrapping the microsphere with a conductive polymer layer, and then successfully chemically plate metal on the surface of the conductive polymer layer by means of the chelation between the conductive polymer layer and the metal ions, replacing the roughening and sensitization process in the traditional chemical plating process, reducing environmental pollution and simplifying the process of preparing conductive particles; at the same time, the conductive particles of the present invention have the characteristics of good morphology and excellent performance, so that the array-type anisotropic conductive adhesive obtained by using it can realize the bonding of high-precision circuits, realize higher-precision device connection, and realize device miniaturization; and provide production efficiency, suitable for large-scale assembly line operations.
[0091] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, 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 conductive particle, characterized in that: The invention comprises microspheres, a conductive polymer layer which wraps the microspheres, and metal particles attached to the surface of the conductive polymer layer.
2. The conductive particle according to claim 1, characterized in that The material of the microspheres includes one or a copolymer of polystyrene, polymethyl methacrylate, polyurethane, phenolic resin, polydimethoxysiloxane, and silicon dioxide.
3. The conductive particle according to claim 1, characterized in that The material of the conductive polymer layer includes one or more of polyaniline, polyacetylene, polypyrrole, polythiophene, and polyethylenedioxythiophene.
4. The conductive particle according to claim 1, characterized in that The material of the metal particles includes one or more of gold, nickel, silver, tin, copper, cobalt, and palladium; and / or the size of the metal particles is 500nm-200μm.
5. A method for preparing conductive particles according to any one of claims 1 to 4, characterized in that: Includes steps: The microspheres, the conductive polymer monomer and the oxidant are mixed and stirred to obtain the microspheres coated with the conductive polymer layer; The metal salt, the reducing agent and the microspheres coated with the conductive polymer layer are mixed and reacted to obtain conductive particles.
6. The method for preparing conductive particles according to claim 5, characterized in that: The mass ratio of the microspheres, the conductive polymer monomer and the metal salt is (4-5):(2-3):(9-11).
7. The method for preparing conductive particles according to claim 5, characterized in that: The oxidant includes one or more of ammonium persulfate, ferric chloride, ferrous sulfate, and hydrogen peroxide; and / or the reducing agent includes one or more of glucose, sodium hypophosphite, sodium borohydride, dimethylaminoborane, formaldehyde, and hydrazine hydrate; and / or the metal salt includes one or more of silver nitrate, silver sulfate, copper nitrate, copper sulfate, copper chloride, palladium chloride, cobalt sulfate, cobalt chloride, chloroauric acid, nickel sulfate, nickel chloride, nickel nitrate, tin tetrachloride, and stannous chloride.
8. A conductive adhesive, characterized in that: The invention comprises a first adhesive film layer, a second adhesive film layer arranged on one side of the first adhesive film layer, and a plurality of conductive particles as claimed in any one of claims 1 to 4 embedded between the first adhesive film layer and the second adhesive film layer.
9. The conductive adhesive according to claim 8, characterized in that: The conductive particles are arranged in an array between the first adhesive film layer and the second adhesive film layer; the distance between two adjacent conductive particles is 1 μm-20 μm.
10. A method for preparing the conductive adhesive according to any one of claims 8 to 9, characterized in that: Includes steps: Arranging a layer of adhesive film on the base film to obtain a base film with a first adhesive film layer; Fill the conductive particles into the template by scraping with a rubber or dust-free cloth, cover the base film with the first adhesive film layer on one side of the template filled with conductive particles, press and peel off the template to obtain the first adhesive film layer with conductive particles; A second adhesive film layer is arranged on the side of the first adhesive film layer coated with conductive particles to obtain a conductive adhesive.