Polymer composite conductive microsphere as well as preparation method and application thereof
By generating ferric hydroxide precipitate on the surface of polymer microspheres and adding graphene to form a composite coating, the problem of poor adhesion of metal coatings on conductive microspheres was solved, and polymer composite conductive microspheres with high bonding strength and high conductivity were realized.
Patent Information
- Application Number
- CN202511366340.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-23
- Publication Date
- 2025-12-12
AI Technical Summary
The metal coatings on existing conductive microspheres have poor adhesion, making it difficult to meet the requirements of high-end applications.
By reacting polymer microspheres with iron salts and alkalis to generate ferric hydroxide precipitate, active sites are provided. Graphene is added during the electroless plating process to form a composite coating of nickel and graphene, which improves the bonding strength and conductivity of the metal coating.
The bonding strength of the metal coating is improved, and the metal coating of the polymer composite conductive microspheres does not peel off under external force, thus maintaining high conductivity.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of conductive materials, and particularly relates to a polymer composite conductive microsphere and a preparation method and application thereof. BACKGROUND
[0002] Anisotropic conductive film (ACF) is widely used in liquid crystal display modules, flexible circuit boards, chip packaging, high-precision wiring and wearable devices due to its low curing temperature, good conductivity, high flexibility, and ultra-fine pitch connection. The conductive principle of ACF is to use conductive microspheres to connect the electrodes between the IC chip and the substrate to realize conduction, and to avoid short circuit between adjacent two electrodes, so as to realize vertical conduction and horizontal non-conduction. The conductive microsphere is the core technology of ACF and plays a decisive role in the performance of the product.
[0003] At present, the conductive microsphere is generally a composite conductive microsphere obtained by taking a polymer particle as a core and coating a high-conductive nickel or gold shell layer outside. It has become the mainstream product due to its elasticity, difficulty in breaking during compression, good conductivity and other advantages. However, the adhesion of the metal plating layer on the polymer microsphere is poor, which makes it difficult to meet the higher application requirements. Therefore, how to improve the conductive microsphere to improve the bonding strength of the metal plating layer has become a technical problem to be solved in the field. SUMMARY
[0004] The present application provides a polymer composite conductive microsphere and a preparation method and application thereof. The polymer composite conductive microsphere prepared by the preparation method provided by the present application has a metal plating layer with excellent bonding strength and high conductivity.
[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions: The present application provides a preparation method of a polymer composite conductive microsphere, comprising the following steps: (1) mixing monomers, stabilizers, initiators and solvents to perform a polymerization reaction to obtain a polymer microsphere dispersion liquid; (2) mixing the polymer microsphere dispersion liquid obtained in step (1), an iron salt solution and a base to perform activation to obtain activated polymer microspheres; (3) performing chemical nickel plating and graphene on the activated polymer microspheres obtained in step (2) to obtain polymer composite conductive microspheres.
[0006] Preferably, the monomers in step (1) include at least one of styrene, methyl methacrylate, ethyl methacrylate, vinyl propionate and vinyl butyrate.
[0007] Preferably, the temperature of the polymerization reaction in step (1) is 50-90℃, and the polymerization reaction time is 5-20h.
[0008] Preferably, the iron salt in the iron salt solution in step (2) comprises one of ferric chloride, ferric nitrate and ferric sulfate; and the mass concentration of the iron salt solution is 10-30%.
[0009] Preferably, the base in step (2) comprises sodium hydroxide and / or potassium hydroxide.
[0010] Preferably, the temperature of the activation in step (2) is 50-90℃, and the activation time is 1-5h.
[0011] Preferably, the composition of the plating solution used in the electroless plating in step (3) comprises 20-30g / L nickel salt, 40-80mg / L graphene, 10-20g / L complexing agent, 20-40g / L reducing agent, 20-30g / L surfactant and water.
[0012] Preferably, the temperature of the electroless plating in step (3) is 25-90℃, and the electroless plating time is 0.5-3h.
[0013] The application further provides the polymer composite conductive microspheres prepared by the preparation method.
[0014] The application further provides the application of the polymer composite conductive microspheres in an anisotropic conductive adhesive film.
[0015] The application provides a preparation method of polymer composite conductive microspheres, which comprises the following steps: mixing monomers, a stabilizer, an initiator and a solvent to perform a polymerization reaction to obtain a polymer microsphere dispersion liquid; mixing the polymer microsphere dispersion liquid, an iron salt solution and a base to perform activation to obtain activated polymer microspheres; and performing electroless plating of nickel and graphene on the activated polymer microspheres to obtain polymer composite conductive microspheres. In the application, the reaction of the iron salt and the base forms a ferric hydroxide precipitate, the generated ferric hydroxide precipitate particles can be adsorbed on the surface of the polymer microspheres to form active sites, thereby providing a carrier for the adsorption of metal nickel ions in the subsequent process, and the binding strength of the metal plating layer is improved; graphene is plated in the electroless plating process, and the excellent conductive performance of the graphene is utilized to further improve the conductive performance of the polymer composite conductive microspheres. Experimental results show that the polymer composite conductive microspheres prepared by the preparation method have high binding strength between the metal plating layer and the polymer microspheres, and the metal plating layer does not peel off under the action of external force; under a large pressure, the contact resistance of the polymer composite conductive microspheres prepared by the preparation method remains basically unchanged, and the resistance is 0.51-0.64Ω. DETAILED DESCRIPTION
[0016] The application provides a preparation method of polymer composite conductive microspheres, which comprises the following steps: (1) mixing monomers, stabilizers, initiators and solvents to perform a polymerization reaction to obtain a polymer microsphere dispersion liquid; (2) mixing the polymer microsphere dispersion liquid obtained in the step (1), an iron salt solution and a base to perform activation to obtain activated polymer microspheres; (3) performing nickel chemical plating and graphene on the activated polymer microspheres obtained in the step (2) to obtain polymer composite conductive microspheres.
[0017] Unless otherwise specified, the application does not have special limitations on the source of the raw materials, and commercially available products or well-known preparation methods known to those skilled in the art can be used.
[0018] The application mixes monomers, stabilizers, initiators and solvents to perform a polymerization reaction to obtain a polymer microsphere dispersion liquid.
[0019] In the application, the monomers preferably include at least one of styrene, methyl methacrylate, ethyl methacrylate, propionic acid vinyl ester and butyric acid vinyl ester; the stabilizers preferably include at least one of polyvinylpyrrolidone, polyvinyl alcohol and polyethylene glycol; the initiators preferably include at least one of azobisisobutyronitrile, azobisisoheptyl nitrile, dibenzoyl peroxide, cyclohexanone peroxide and tert-butyl hydroperoxide; and the solvent is preferably ethanol or a mixed solution of ethanol and water.
[0020] In the application, when the solvent is a mixed solution of ethanol and water, the volume percentage of the ethanol is preferably ≥80%. As an embodiment, the volume percentage of the ethanol can be 85%, 90% or 95%.
[0021] In the application, the mass of the monomers is preferably 1-30%, the mass of the stabilizers is preferably 1-5%, and the mass of the initiators is preferably 0.1-5%, based on 100% of the mass of the monomers, stabilizers and initiators. The application can further improve the degree of polymerization by controlling the mass of the monomers, stabilizers and initiators within the above range.
[0022] As an embodiment, the mass of the monomers can be 5%, 10%, 15%, 20% or 25%, the mass of the stabilizers can be 2%, 3% or 4%, and the mass of the initiators can be 0.5%, 1%, 2%, 3% or 4%.
[0023] The application does not have special limitations on the operation of mixing the monomers, stabilizers, initiators and solvents, and a technical solution for preparing a mixture known to those skilled in the art can be used.
[0024] In the present application, the temperature of the polymerization reaction is preferably 50-90°C; the time of the polymerization reaction is preferably 5-20h. As an embodiment, the temperature of the polymerization reaction can be 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or 85°C; the time of the polymerization reaction can be 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h or 19h. The present application can further improve the degree of polymerization reaction by limiting the temperature and time of the polymerization reaction within the above range.
[0025] In the present application, the polymerization reaction is preferably carried out in a protective atmosphere; the protective atmosphere is preferably nitrogen.
[0026] After obtaining the polymer microsphere dispersion, the present application mixes the polymer microsphere dispersion, the iron salt solution and the base to activate the polymer microsphere to obtain activated polymer microsphere.
[0027] In the present application, the iron salt in the iron salt solution preferably includes one of ferric chloride, ferric nitrate and ferric sulfate; the mass concentration of the iron salt solution is preferably 10-30%. As an embodiment, the mass concentration of the iron salt solution can be 15%, 20% or 25%. In the present application, the iron salt is used to provide trivalent iron ions.
[0028] In the present application, the base preferably includes sodium hydroxide and / or potassium hydroxide. In the present application, the base is used to provide hydroxyl ions so that the trivalent iron ions and the hydroxyl ions react to form iron hydroxide particles.
[0029] In the present application, the mass of the iron salt is preferably 30-150% of the mass of the monomer. As an embodiment, the iron salt can be 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130% or 140% of the mass of the monomer. The present application limits the mass of the iron salt within the above range to facilitate adsorbing sufficient iron hydroxide particles on the surface of the polymer microsphere, thereby improving the bonding strength of the metal plating layer.
[0030] The present application does not have special limitation on the amount of the base, as long as the pH value of the system is 11-12.
[0031] The present application does not have special limitation on the operation of mixing the polymer microsphere dispersion, the iron salt solution and the base, and the technical solution for preparing the mixture material known to those skilled in the art can be adopted.
[0032] In the present application, the iron salt solution is preferably added in the form of dropwise addition. The present application does not have special limitation on the rate of the dropwise addition, and the dropwise addition operation known to those skilled in the art can be adopted.
[0033] In the present application, the temperature of the activation is preferably 50-90℃; the time of the activation is preferably 1-5h. As an embodiment, the temperature of the activation can be 55℃, 60℃, 65℃, 70℃, 75℃, 80℃ or 85℃; the time of the activation can be 2h, 3h or 4h. The present application can further improve the degree of activation by limiting the temperature and time of the activation within the above range, thereby improving the bonding strength of the metal coating.
[0034] After the activation is completed, the present application preferably filters the product obtained by the activation to obtain filter residue, and then washes the filter residue with water to obtain activated polymer microspheres.
[0035] The present application does not have special limitations on the operation of the filtering, and the filter residue can be obtained by using the operation well known to those skilled in the art.
[0036] The present application does not have special limitations on the operation of the washing, and the operation well known to those skilled in the art can be used.
[0037] As an embodiment, the number of times of the washing can be 3.
[0038] After obtaining the activated polymer microspheres, the present application performs electroless nickel plating and graphene on the activated polymer microspheres to obtain polymer composite conductive microspheres.
[0039] In the present application, the composition of the plating solution used in the electroless plating preferably includes 20-30g / L nickel salt, 40-80mg / L graphene, 10-20g / L complexing agent, 20-40g / L reducing agent, 20-30g / L surfactant and water. The present application can further improve the uniformity of the coating by limiting the composition of the plating solution within the above range.
[0040] As an embodiment, the composition of the plating solution can be 22-28g / L nickel salt, 45-75mg / L graphene, 12-18g / L complexing agent, 25-35g / L reducing agent, 22-28g / L surfactant and water, or 24-26g / L nickel salt, 50-60mg / L graphene, 14-16g / L complexing agent, 28-30g / L reducing agent, 25-26g / L surfactant and water.
[0041] In the present application, the nickel salt is preferably at least one of nickel sulfate, nickel nitrate, nickel chloride and nickel acetate; the complexing agent is preferably at least one of sodium citrate, sodium tartrate, sodium acetate and sodium lactate; the reducing agent is preferably at least one of hypophosphite, borohydride, dimethylamine borate and hydrazine; the surfactant is preferably sodium dodecyl benzene sulfonate; and the particle size of the graphene is preferably 3-5μm.
[0042] In the present application, the mass of the activated polymer microspheres to the volume of the plating solution is preferably (1-10) g:(20-50) mL. As an embodiment, the mass of the activated polymer microspheres to the volume of the plating solution can be (2-8) g:(25-45) mL, and can also be (4-6) g:(30-35) mL. Limiting the mass of the activated polymer microspheres to the volume of the plating solution in the present application to the above range is advantageous for uniform coating of the metal plating layer.
[0043] In the present application, the plating solution is preferably subjected to ultrasonic stirring before use. The present application does not have special limitations on the operation of the ultrasonic stirring, and any operation known to those skilled in the art that ensures uniform dispersion of graphene can be used.
[0044] In the present application, the temperature of the electroless plating is preferably 25-90℃; the time of the electroless plating is preferably 0.5-3h. As an embodiment, the temperature of the electroless plating can be 30℃, 40℃, 50℃, 60℃, 70℃ or 80℃; the time of the electroless plating can be 1h, 2h or 3h. Limiting the temperature and time of the electroless plating in the present application to the above range is advantageous for uniform coating of the metal plating layer.
[0045] After the electroless plating is completed, the present application preferably filters the product obtained by the electroless plating to obtain filter residue, and then sequentially washes and dries the filter residue to obtain polymer composite conductive microspheres.
[0046] The present application does not have special limitations on the operation of the filtering, and any operation known to those skilled in the art that obtains filter residue can be used.
[0047] The present application does not have special limitations on the operation of the washing, and any operation known to those skilled in the art can be used.
[0048] As an embodiment, the number of times of washing can be 3 times.
[0049] The present application does not have special limitations on the operation of the drying, and any operation known to those skilled in the art that dries to a constant weight can be used.
[0050] In the present application, iron salt and alkali are reacted to form iron hydroxide precipitate, and the generated iron hydroxide precipitate particles can be adsorbed on the surface of the polymer microspheres to form active sites, providing a carrier for subsequent adsorption of metal nickel ions, thereby improving the bonding strength of the metal plating layer; graphene is added during the electroless plating process, which can form a composite plating layer of nickel and graphene, and the two synergistically act, thereby further improving the conductivity of the polymer composite conductive microspheres.
[0051] The present application also provides polymer composite conductive microspheres prepared by the preparation method of the above technical solution.
[0052] The application further provides application of the polymer composite conductive microspheres in the anisotropic conductive adhesive film.
[0053] The application of the polymer composite conductive microspheres in the anisotropic conductive adhesive film is not specially limited in the application, and the application operation known to those skilled in the art can be used.
[0054] The technical solutions in the application will be clearly and completely described below with reference to the embodiments in the application. Obviously, the described embodiments are only some of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.
[0055] Embodiment 1 A preparation method of the polymer composite conductive microspheres comprises the following steps: (1) mixing monomers, stabilizers, initiators and solvents, and then performing a polymerization reaction in a nitrogen atmosphere to obtain a polymer microsphere dispersion liquid; wherein the monomers are styrene; the stabilizers are polyvinylpyrrolidone; the initiators are azobisisobutyronitrile; and the solvents are ethanol; the mass of the monomers is 30% based on 100% of the mass of the monomers, stabilizers, initiators and solvents; the mass of the stabilizers is 5%; the mass of the initiators is 0.5%; the polymerization reaction is performed at a temperature of 80°C for 10 hours; (2) adding an iron salt solution into the polymer microsphere dispersion liquid obtained in the step (1) and adding alkali at the same time to perform activation, and then filtering the product obtained by the activation to obtain filter residue, and washing the filter residue with water for 3 times to obtain activated polymer microspheres; wherein the iron salt in the iron salt solution is ferric chloride; the mass concentration of the iron salt solution is 20%; the alkali is sodium hydroxide; the mass of the iron salt is 100% of the mass of the monomers, and the pH value of the system is 12; the activation is performed at a temperature of 70°C for 1 hour; (3) placing the activated polymer microspheres obtained in the step (2) in a plating solution to perform chemical nickel plating and graphene, and then filtering the product obtained by the chemical plating to obtain filter residue, and washing the filter residue with water for 3 times, and finally drying to obtain polymer composite conductive microspheres; wherein the composition of the plating solution is: 25 g / L of nickel sulfate, 60 mg / L of graphene, 15 g / L of sodium acetate, 30 g / L of hypophosphite, 25 g / L of sodium dodecylbenzenesulfonate and water; the particle size of the graphene is 3-5 μm; the mass of the activated polymer microspheres to the volume of the plating solution is 1 g:25 mL; the plating solution is ultrasonically stirred before use; the chemical plating is performed at a temperature of 80°C for 1 hour.
[0056] Comparative Example 1 On the basis of Example 1, graphene is omitted, that is, no graphene is added in the plating solution, and other conditions are the same as those in Example 1.
[0057] Example 2 On the basis of Example 1, only the mass of the iron salt is modified to 50% of the monomer mass, and other conditions are the same as those in Example 1.
[0058] Example 3 On the basis of Example 1, only the mass of the iron salt is modified to 120% of the monomer mass, and other conditions are the same as those in Example 1.
[0059] Example 4 On the basis of Example 1, only the mass of the iron salt is modified to 150% of the monomer mass, and other conditions are the same as those in Example 1.
[0060] Example 5 A preparation method of a polymer composite conductive microsphere comprises the following steps: (1) mixing a monomer, a stabilizer, an initiator and a solvent, and then performing a polymerization reaction in a nitrogen atmosphere to obtain a polymer microsphere dispersion liquid; wherein the monomer is styrene; the stabilizer is polyvinylpyrrolidone; the initiator is azobisisobutyronitrile; the solvent is ethanol; the mass of the monomer is 15% based on 100% of the mass of the monomer, the stabilizer, the initiator and the solvent; the mass of the stabilizer is 2%; the mass of the initiator is 0.2%; the temperature of the polymerization reaction is 80°C, and the polymerization reaction time is 15 h; (2) adding an iron salt solution dropwise in the polymer microsphere dispersion liquid obtained in the step (1), and simultaneously adding a base to perform activation, and then filtering the product obtained by the activation to obtain a filter residue, and washing the filter residue with water for 3 times to obtain activated polymer microspheres; wherein the iron salt in the iron salt solution is ferric chloride; the mass concentration of the iron salt solution is 30%; the base is sodium hydroxide; the mass of the iron salt is 130% of the mass of the monomer, and the pH value of the system is 12; the activation temperature is 60°C; and the activation time is 3 h; (3) placing the activated polymer microspheres obtained in step (2) into a plating solution, performing electroless nickel and graphene plating, filtering the product obtained by electroless plating to obtain filter residue, then washing the filter residue with water for 3 times, and finally drying to obtain polymer composite conductive microspheres; wherein the plating solution comprises 20 g / L nickel sulfate, 80 mg / L graphene, 10 g / L sodium acetate, 40 g / L hypophosphite, 20 g / L sodium dodecyl benzene sulfonate and water; the particle size of the graphene is 3-5 μm; the mass of the activated polymer microspheres to the volume of the plating solution is 1 g: 35 mL; the plating solution is ultrasonically stirred before use; the temperature of the electroless plating is 70°C; and the electroless plating time is 2 h.
[0061] Example 6 A polymer composite conductive microsphere preparation method comprises the following steps: (1) mixing monomers, stabilizers, initiators and solvents, and then performing polymerization reaction in a nitrogen atmosphere to obtain a polymer microsphere dispersion liquid; wherein the monomers are styrene; the stabilizers are polyvinylpyrrolidone; the initiators are azobisisobutyronitrile; and the solvents are ethanol; the mass of the monomers is 20% based on 100% of the mass of the monomers, stabilizers, initiators and solvents; the mass of the stabilizers is 1%; the mass of the initiators is 5%; the temperature of the polymerization reaction is 80°C; and the polymerization reaction time is 5 h; (2) adding an iron salt solution into the polymer microsphere dispersion liquid obtained in step (1) while adding alkali to perform activation, filtering the product obtained by the activation to obtain filter residue, washing the filter residue with water for 3 times, and obtaining activated polymer microspheres; wherein the iron salt in the iron salt solution is ferric chloride; the mass concentration of the iron salt solution is 10%; the alkali is sodium hydroxide; the mass of the iron salt is 80% of the mass of the monomers; the pH value of the system is 12; the activation temperature is 60°C; and the activation time is 5 h; (3) placing the activated polymer microspheres obtained in step (2) into a plating solution, performing electroless nickel and graphene plating, filtering the product obtained by electroless plating to obtain filter residue, then washing the filter residue with water for 3 times, and finally drying to obtain polymer composite conductive microspheres; wherein the plating solution comprises 20 g / L nickel sulfate, 80 mg / L graphene, 10 g / L sodium acetate, 40 g / L hypophosphite, 20 g / L sodium dodecyl benzene sulfonate and water; the particle size of the graphene is 3-5 μm; the mass of the activated polymer microspheres to the volume of the plating solution is 1 g: 35 mL; the plating solution is ultrasonically stirred before use; the temperature of the electroless plating is 70°C; and the electroless plating time is 2 h.
[0062] The ability of the metal plating layer to combine with the polymer microspheres in the polymer composite conductive microspheres prepared in Examples 1-6 was tested, and the results are shown in Table 1. The testing method was as follows: 0.1 g of the polymer composite conductive microspheres was dispersed in 20 mL of water to obtain a dispersion liquid, one drop of the dispersion liquid was dropped on a glass slide, 0.3 g of a cover glass was used to cover the dispersion liquid, 1 kg of an iron block was placed on the cover glass, and the cover glass was moved back and forth 20 times. Then the polymer composite conductive microspheres were observed under a microscope.
[0063] Table 1 Ability of the metal plating layer to combine with the polymer microspheres in the polymer composite conductive microspheres prepared in Examples 1-6
[0064] As can be seen from Table 1, the polymer composite conductive microspheres provided by the application have high bonding strength of the metal plating layer to the polymer microspheres, and the metal plating layer does not peel off under external force.
[0065] 30 g of the polymer composite conductive microspheres prepared in Examples 1-6 and Comparative Example 1, 100 g of an epoxy resin (EP1641, United Adhesive Inc.), 2 g of a curing agent T31, and 100 g of toluene were mixed and coated on a substrate, a thin coating was coated by using a coating thickness controller, and after drying, the coating thickness was 10 μm.
[0066] Conductivity test: The coating was cut into a 2 mm*2 mm sample. One piece of a 2 mm*5 mm printed circuit board with a 0.2 mm*1.0 mm electrode etched in advance was taken, and the end of the electrode was connected to a lead wire for measuring resistance. One piece of a 7 mm*5 mm copper foil was taken as an electrode. Before the conductivity test, the electrode was sequentially cleaned with hydrochloric acid and acetone. The sample was pasted on the 2 mm*5 mm printed circuit board, the release film was removed, and the copper foil electrode was pasted on the sample. Then the sample was heat-sealed and pasted for 20 s*170°C. After cooling, the resistance was tested, and the results are shown in Table 2.
[0067] Table 2 Conductivity of the coating prepared from the polymer composite conductive microspheres prepared in Examples 1-6 and Comparative Example 1
[0068] As can be seen from Table 2, under a larger pressure, the contact resistance of the polymer composite conductive microspheres prepared by the application basically remains unchanged, and has high conductivity; and omitting graphene will cause the resistance to increase and the conductivity to decrease.
[0069] As can be seen from the above examples and comparative examples, the metal plating layer in the polymer composite conductive microspheres prepared by the preparation method provided by the application has excellent bonding strength and high conductivity.
[0070] The above merely describes the preferred embodiments of the present application, and it should be pointed out that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.
Claims
1. A method for preparing polymer composite conductive microspheres, comprising the following steps: (1) Mix monomers, stabilizers, initiators and solvents and carry out polymerization reaction to obtain polymer microsphere dispersion; (2) The polymer microsphere dispersion obtained in step (1), iron salt solution and alkali are mixed and activated to obtain activated polymer microspheres; (3) The activated polymer microspheres obtained in step (2) are chemically plated with nickel and graphene to obtain polymer composite conductive microspheres.
2. The preparation method according to claim 1, characterized in that, The monomers in step (1) include at least one of styrene, methyl methacrylate, ethyl methacrylate, vinyl propionate, and vinyl butyrate.
3. The preparation method according to claim 1, characterized in that, The polymerization temperature in step (1) is 50~90℃ and the polymerization time is 5~20h.
4. The preparation method according to claim 1, characterized in that, The iron salt in the iron salt solution in step (2) includes one of ferric chloride, ferric nitrate and ferric sulfate; the mass concentration of the iron salt solution is 10~30%.
5. The preparation method according to claim 1, characterized in that, The alkali in step (2) includes sodium hydroxide and / or potassium hydroxide.
6. The preparation method according to claim 1, characterized in that, The activation temperature in step (2) is 50~90℃, and the activation time is 1~5h.
7. The preparation method according to claim 1, characterized in that, The composition of the plating solution used in step (3) includes: 20~30g / L nickel salt, 40~80mg / L graphene, 10~20g / L complexing agent, 20~40g / L reducing agent, 20~30g / L surfactant and water.
8. The preparation method according to claim 1, characterized in that, In step (3), the temperature of the electroless plating is 25~90℃ and the time of electroless plating is 0.5~3h.
9. Polymer composite conductive microspheres prepared by the preparation method according to any one of claims 1 to 8.
10. The application of the polymer composite conductive microspheres of claim 9 in anisotropic conductive adhesive films.