CN110681325A

CN110681325A - Method for manufacturing composite microspheres and core-shell type composite microspheres for EMI shielding

Info

Publication number: CN110681325A
Application number: CN201911013767.7A
Authority: CN
Inventors: 张伟军; 盛荆浩; 江舟
Original assignee: Hangzhou Jianwenlu Technology Co Ltd
Current assignee: Jianwenlu Zhejiang Semiconductor Co ltd
Priority date: 2019-10-23
Filing date: 2019-10-23
Publication date: 2020-01-14
Anticipated expiration: 2039-10-23
Also published as: CN110681325B

Abstract

The embodiment of the application discloses a method for manufacturing composite microspheres and core-shell type composite microspheres for EMI shielding, wherein metal particles are placed in deionized water for ultrasonic dispersion; adding a mixed solution containing a silane coupling agent for primary stirring; adding ammonia water and a mixed solution containing TEOS, and carrying out a closed reaction, wherein the mixed solution containing TEOS is added for multiple times; and finally, carrying out solid-liquid separation on the solution obtained after the reaction to obtain a final product. The final product has the advantages of small granularity, reasonable grain composition, good dispersibility, good corrosion resistance, good EMI resistance, capability of being filled in a radio frequency communication module product with small volume, capability of ensuring that each module in the product is free from the interference of an EM source on the premise of not changing the volume and the internal structure of the product, no additional device and not causing the short circuit of the internal module, simple process, suitability for mass production, lasting and reliable shielding effect and the like.

Description

Method for manufacturing composite microspheres and core-shell type composite microspheres for EMI shielding

Technical Field

The application relates to the field of composite materials, and mainly relates to a method for manufacturing composite microspheres and core-shell type composite microspheres for EMI shielding.

Background

With the rapid development of communication technology, electromagnetic wave pollution is increasingly serious, and the normal work of equipment is seriously interfered. When the radio frequency module product works, the radio frequency module product is interfered mutually due to the fact that frequency bands of internal parts of modules are close to each other except for external electromagnetic interference, the internal space is small, and all modules are highly concentrated. In order to ensure normal and effective work of radio frequency products, interference between an external EM (electromagnetic) source and other internal module EM sources needs to be shielded, and particularly low-frequency electromagnetic interference is shielded.

There are four kinds of existing EMI resistant materials, the first one is formed by combining a plurality of materials in the shapes of layers, pipes and the like. The laminated structure is mostly coated on the protected component in a film pasting mode, the manufacturing process and the operation mode are complex, and the laminated structure is not suitable for radio frequency products with compact internal structures; the tubular structure has a certain length-diameter ratio, and the void ratio is high after the filling due to the structural characteristics; the tip effect is easily generated due to the local curvature of the partial shape. The second is core-shell type composite microsphere with metal coated organic polymer or metal. The composite microsphere has relatively complex manufacturing process, is not suitable for mass production, and the electromagnetic shielding effect can be reduced due to easy oxidation of the outer layer metal. In addition, pure metal filling has the defect of overlarge density, and short circuit can be caused after the pure metal filling is filled between devices, so that the pure metal filling is suitable for covering the surface or filling a groove with a specific shape. And the third method is to adopt the EMI shielding paste to carry out sectional type EMI shielding, and cover a layer of EMI shielding paste on the surface of the device while arranging the sectional type shielding, and the method has complex process, and the EMI shielding paste can not shield the bottom of the device, so the shielding effect is poor. The fourth is to use an EMI filter, which is installed in a radio frequency product and is difficult to shield EM source from the internal module of the product.

In view of the above, it is one of the problems that needs to be solved urgently at present to develop a high-performance composite material with good EMI shielding effect, small particle size and reasonable particle size distribution.

Disclosure of Invention

Aiming at the problems that the EMI resistant material in the EMI shielding technology has complex manufacturing process and operation mode, is not suitable for mass production, has poor electromagnetic shielding effect and the like, the invention provides a method for manufacturing composite microspheres and core-shell composite microspheres to solve the problems.

In a first aspect, embodiments of the present application provide a method of manufacturing a composite microsphere, comprising the steps of:

s1: putting the metal particles into deionized water for ultrasonic dispersion;

s2: adding a mixed solution containing a silane coupling agent for primary stirring;

s3: adding ammonia water and a mixed solution containing TEOS, and then carrying out a closed reaction, wherein the mixed solution containing TEOS is added for multiple times;

s4: and (4) carrying out solid-liquid separation on the solution obtained after the reaction in the step S3 to obtain a final product.

In some embodiments, the metal particles are submicron metal particles. The submicron metal particles have small particle size and are easy to be dispersed uniformly.

In some embodiments, the metal particles have a diameter between 0.1um and 30 um. The metal particle composition is reasonable.

In some embodiments, the metal particles are single metal structures, alloy materials of multiple metals, or multilayer metal composite structures. The metal particles may be formed of a plurality of materials or structures such as a single metal structure, a composite structure formed of a plurality of layers of metals, or an alloy formed of a plurality of layers of metals.

In some embodiments, the metal particles are made of Ag, Au, Cu, NiFe, Ni, or Cr materials. The material source of the metal particles varies.

In some embodiments, the first stirring is performed at room temperature for 0.5 to 1 hour. The first stirring temperature and the modification time are controlled.

In some embodiments, the closed reaction comprises a second stirring, the reaction temperature is 20-40 ℃, and the reaction time is 4-5 hours. This step is specific to the reaction temperature and SiO₂The control of the coating time can obtain uniform SiO with good coating effect₂And (3) a layer.

In some embodiments, the volume fraction of ammonia in the solution obtained after the reaction of step S3 is 0.8% to 1.4%. Ammonia water as catalyst, its content is SiO₂The coating thickness of (2) has a certain influence. The content of ammonia water is controlled atIn this range, 100nm of SiO can be obtained₂The coating layer has good coating effect.

In some embodiments, the mixed solution containing the silane coupling agent includes the silane coupling agent, ethanol, and water. The silane coupling agent, alcohol and water are proportioned according to the hydrolysis method of the silane coupling agent so as to carry out good modification treatment on the metal particles.

In some embodiments, the silane coupling agent is KH-550 and the alcohol is ethanol. The KH-550 and ethanol are used for reaction, so that the metal particles are good in modification effect and low in cost.

In some embodiments, the TEOS-containing mixed solution includes TEOS and ethanol at a volume ratio of 1:9 to 1: 20. TEOS can be effectively dispersed in ethanol solution to react with the modified metal particles, so that the modified metal particles are uniformly coated with SiO with a certain thickness₂And (4) coating.

In some embodiments, the volume ratio of KH-550 to TEOS is 1:10 to 2: 5. The reasonable volume ratio can lead the silane coupling agent to play the roles of bridging and dispersing, and uniform and compact SiO can be easily obtained₂And (4) coating.

In some embodiments, the TEOS-containing mixed solution is added in two times, the volume ratio of the TEOS and the ethanol added in the first time is 1: 15-1: 20, and the volume ratio of the TEOS and the ethanol added in the second time is 1: 9-1: 14. The way in which TEOS is added will affect the SiO in the final product₂Formation of mononuclear, in this way SiO can be suppressed or reduced₂And (4) forming a mononuclear.

In some embodiments, the means for solid-liquid separation comprises centrifugation and vacuum drying. The SiO can be effectively obtained by centrifugal separation and vacuum drying₂The layer is uniformly coated with the core-shell type composite microsphere of the metal particles.

In a second aspect, embodiments of the present application also provide a core-shell composite microsphere, which is prepared by the method of the first aspect.

In a third aspect, embodiments of the present application also provide a core-shell composite microsphere for EMI shielding, including a submicron metal particle core, a silane coupling agent coated on the metal particle, and a silica insulating layer coated on the silane coupling agent.

The embodiment of the application discloses a method for manufacturing composite microspheres and core-shell type composite microspheres for EMI shielding, wherein metal particles are placed in deionized water for ultrasonic dispersion; adding a mixed solution containing a silane coupling agent for primary stirring; adding ammonia water and a mixed solution containing TEOS, and carrying out a closed reaction, wherein the mixed solution containing TEOS is added for multiple times; and finally, carrying out solid-liquid separation on the solution obtained after the reaction to obtain a final product. The final product is SiO₂The composite microspheres formed by the layer-coated metal particles have small granularity, reasonable particle grading, good dispersibility, good corrosion resistance and good anti-EMI effect, can be filled in a small-volume radio frequency communication module product, ensure that each module in the product is prevented from being interfered by an EM source on the premise of not changing the product volume and the internal structure, having no additional device and not causing short circuit of the internal module, and also play a certain degree of protection effect on the internal module. The process flow has the advantages of simple process, suitability for mass production, lasting and reliable shielding effect and the like.

Drawings

The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and together with the description serve to explain the principles of the invention. Other embodiments and many of the intended advantages of embodiments will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.

FIGS. 1 and 2 are schematic structural views of core-shell composite microspheres according to the prior art;

FIGS. 3 and 4 are schematic structural views of composite microspheres in examples of the present application;

FIG. 5 is a schematic flow chart of manufacturing composite microspheres in an example of the present application;

FIG. 6 is a schematic view I of the surface modification of metal particles by a silane coupling agent in an example of the present application;

FIG. 7 is a schematic view II of the surface modification of metal particles by a silane coupling agent in examples of the present application;

FIG. 8 shows the reaction temperature and SiO in example III of the present application₂A variation curve graph of the particle size;

FIG. 9 is a graph showing the reaction time and the quality of a SiO2 coating layer in example four of the present application;

FIG. 10 shows the concentration of ammonia in water versus SiO in example five of the present application₂A variation curve graph of the particle size;

FIG. 11 is a schematic representation of the use of EMI resistant composite microspheres;

FIG. 12 is a diagram illustrating the Shielding effect (SE: Shielding effect).

Detailed Description

The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the related invention are shown in the drawings.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

Fig. 1 and 2 show the structure of a composite microsphere in the prior art, and the inventors of the present application found that the preparation process of such a composite microsphere is relatively complex, and is not suitable for mass production, and the outer layer metal is easily oxidized, which easily reduces the electromagnetic shielding effect. And the pure metal filler has the defect of overlarge density, and is easy to cause short circuit when filled in a device. Therefore, the inventors of the present application prepared SiO shown in FIGS. 3 and 4 by a method of manufacturing composite microspheres according to examples of the present application₂The nanometer insulating layer is coated with the metal composite microspheres.

Example one

Fig. 5 illustrates a process flow of manufacturing a composite microsphere of an embodiment of the present application, including the steps of:

s1: putting the metal particles into deionized water for ultrasonic dispersion;

In a specific embodiment, the metal particles are submicron metal particles made of Ag, Au, Cu, NiFe, Ni or Cr materials. The submicron metal particles have small particle size and are easy to be dispersed uniformly. In a preferred embodiment, the metal particles have a diameter between 0.1um and 30 um. The metal particles can be selected from the same particle size or different particle sizes, and the prepared composite microsphere has reasonable particle size distribution. The metal particles can be selected from a single metal to form a single structure, can also be selected from alloy materials consisting of a plurality of metals, and can also be selected from metals of different materials to form a multilayer composite structure. The metal particles can be formed by a single metal structure, a composite structure formed by multiple layers of metals or multiple materials or structures such as an alloy formed by multiple layers of metals, and the metal particles can be effectively and uniformly dispersed in deionized water through ultrasonic dispersion.

In a specific embodiment, the mixed solution containing the silane coupling agent in step S2 includes the silane coupling agent, ethanol, and water. The silane coupling agent, alcohol and water are proportioned according to the hydrolysis method of the silane coupling agent so as to carry out good modification treatment on the metal particles. In a preferred embodiment, KH-550 is selected as the silane coupling agent, and ethanol is selected as the alcohol. Therefore, when a mixed solution containing a silane coupling agent was prepared, the volume ratios of KH-550, ethanol and water were 20%, 72% and 8%, respectively. In other alternative embodiments, the silane coupling agent may be other silane coupling agents such as methoxysilane, and the alcohol may be other alcohols such as methanol. In this case, the silane coupling agent may undergo a hydrolysis reaction, and may be uniformly attached to the surface of the metal particles by first stirring to modify the surface of the metal particles. Wherein the first stirring can be atStirring was carried out at room temperature. As shown in FIGS. 6 and 7, M represents a metal particle, and the silane coupling agent is represented by the general formula YRSIX3, and is used for surface modification of the metal particle M to form a metal M-silane coupling agent-SiO₂The bonding layer of (3). X represents a hydrolytic group, which is connected with the metal particle; r represents an alkyl group; y represents a functional group reactive with an organic polymer, such as a vinyl group, an epoxy group, an amino group, etc.

In a specific embodiment, the mixed solution containing TEOS of step S3 includes TEOS and ethanol, where TEOS is SiO₂The source is dispersed in an ethanol solution and then undergoes a hydrolysis reaction with KH-550, thereby forming SiO with a uniform texture on the surface of the silane coupling agent₂And (3) a layer. The closed reaction in the step S2 comprises a second stirring, and finally, SiO is obtained by a solid-liquid separation mode₂Composite microspheres coated with metal particles. The solid-liquid separation can adopt centrifugal separation and vacuum drying. The SiO can be effectively obtained by centrifugal separation and vacuum drying₂The layer is uniformly coated with the core-shell type composite microsphere of the metal particles.

Example two

The specific process flow is the same as that in the first embodiment, the first stirring time is set to be 0.2h, 0.5h, 1h and 1.5h respectively, the reaction temperature of the closed reaction is 30 ℃, the reaction time is 4h, the volume ratio of ammonia water in the solution obtained after the reaction in the step S3 is 1%, the volume ratio of TEOS to ethanol is 1:9, the volume ratio of KH-550 to TEOS is 1:5, the volume ratio of TEOS to ethanol added for the first time is 1:15, and the volume ratio of TEOS to ethanol added for the second time is 1: 9. The experimental data as given in table 1 below were obtained.

TABLE 1 coating effect of time of first stirring on composite microspheres and SiO₂Influence of thickness

As can be seen from the above table, the time for the first stirring is set between 0.5h and 1h, the prepared composite microspheres have good coating effect and high efficiency, and the SiO₂The thickness of the layer meets the requirements of EMI shielding, and SiO can be ensured in a short time₂The thickness of the layer is about 100nmAnd SiO₂The layer is uniformly and densely covered on the surface of the metal particles. At the moment, the silane coupling agent just completely reacts on the surface modification of the metal particles, so that a good modification effect can be obtained, and uniform silane coupling agent coating layers are formed on the surfaces of the metal particles.

EXAMPLE III

The specific process flow is the same as that in the first embodiment, the first stirring time is 1h, the reaction temperature of the closed reaction is respectively set to 20 ℃, 30 ℃, 40 ℃, 50 ℃, 60 ℃ and 70 ℃, the reaction time is 4h, the volume ratio of ammonia water in the solution obtained after the reaction in the step S3 is 1%, the volume ratio of KH-550 to TEOS is 1:5, the mixed solution containing TEOS is added twice, the volume ratio of TEOS and ethanol added for the first time is 1:15, and the volume ratio of TEOS and ethanol added for the second time is 1: 9. The reaction temperature and SiO as shown in FIG. 8 were obtained₂The variation curve of the particle size.

As can be seen from FIG. 8, the optimal reaction temperature for the sealing reaction is 20-40 deg.C, at which time SiO is present₂Small grain diameter, and can form uniform and compact SiO on the surface of metal particles₂And (3) a layer. The hydrolysis reaction is incomplete when the reaction temperature is too low, and the coating layer is formed by SiO when the reaction temperature is too high₂Large particle size and poor densification or self-phase nucleation.

Example four

The specific process flow is the same as that in the first embodiment, the first stirring time is 1h, the reaction temperature of the closed reaction is 30 ℃, the reaction time is set to be 1h, 2h, 3h, 4h, 5h and 6h, the volume ratio of ammonia water in the solution obtained after the reaction in the step S3 is 1%, the volume ratio of KH-550 to TEOS is 1:5, the mixed solution containing TEOS is added in two times, the volume ratio of TEOS to ethanol added in the first time is 1:15, the volume ratio of TEOS to ethanol added in the second time is 1:9, and the reaction time and SiO shown in FIG. 9 are obtained₂Profile of the coating mass.

As can be seen from FIG. 9, the optimal reaction time for the sealing reaction is 4-5 h. TEOS in this reaction time forms SiO on the silane coupling agent₂The reaction of the layers can be carried out completely, so that finally uniform SiO can be formed on the surface of the metal particles₂And (3) a layer. Too short reaction time can lead to incomplete hydrolysis reaction and too long reaction time of SiO₂The mass ratio of the coating layer is almost unchanged, but the reaction time is too long, so that the experiment efficiency is influenced, and the optimal reaction time is set to be 4-5 h.

EXAMPLE five

The specific process flow is the same as that in the first embodiment, the first stirring time is 1h, the reaction temperature of the closed reaction is 30 ℃, the reaction time is 4h, the volume ratio of ammonia water in the solution obtained after the reaction in the step S3 is respectively set to be 0.6%, 0.8%, 1%, 1.2%, 1.4% and 1.6%, the volume ratio of KH-550 to TEOS is 1:5, the mixed solution containing TEOS is added in two times, the volume ratio of TEOS and ethanol added in the first time is 1:15, and the volume ratio of TEOS and ethanol added in the second time is 1: 9. The ammonia concentration and SiO shown in FIG. 10 were obtained₂The variation curve of the particle size.

As can be seen from fig. 10, the optimal volume ratio of the ammonia water in the solution obtained after the reaction in step S3 is 0.8% to 1.4%. Ammonia water as catalyst, its content is SiO₂The coating thickness of (2) has a certain influence. The content of the ammonia water is controlled within the range, and uniform SiO can be obtained₂A coating layer and a good coating effect, and is used for forming SiO₂SiO of the coating layer₂The particle size is uniform and moderate, and when the proportion of ammonia water is 1.6 percent, the ammonia water is used for forming SiO₂SiO of the coating layer₂Large particle size of SiO formed₂The coating layer has loose texture and more gaps. TEOS can form SiO on silane coupling agent at the ammonia water content₂The reaction of the layer is completely carried out, so that finally uniform SiO can be formed on the surface of the metal particles₂And (3) a layer. Too little ammonia content leads to incomplete hydrolysis reaction, and too much ammonia content leads to SiO₂The grain diameter is too large, and the coating layer is loose and has a plurality of gaps.

EXAMPLE six

The specific process flow is the same as that in the first embodiment, the first stirring time is 1h, the reaction temperature of the closed reaction is 30 ℃, the reaction time is 4h, the volume ratio of ammonia water in the solution obtained after the reaction in the step S3 is 1%, the volume ratio of KH-550 to TEOS is 1:10, 2:10, 3:10, 4:10 and 5:10, the mixed solution containing TEOS is added twice, the volume ratio of TEOS to ethanol added for the first time is 1:15, and the volume ratio of TEOS to ethanol added for the second time is 1: 9. The experimental data as given in table 5 below were obtained.

TABLE 5 volume ratio of KH-550 to TEOS coating effect of composite microspheres and SiO₂Influence of thickness

As can be seen from the above table, the optimum volume ratio of KH-550 to TEOS is 1:10 to 2: 5. The reasonable volume ratio of KH-550 to TEOS can make the silane coupling agent play the role of bridging and dispersing, and can finally obtain uniform and compact SiO₂And (4) coating. The coating formed by the KH-550 and TEOS with too large volume ratio is unstable and has poor corrosion resistance; SiO with too small volume ratio of KH-550 to TEOS₂The growth rate is accelerated, and the large core covers the surface of the metal particle to cause more gaps.

EXAMPLE seven

The specific process flow is consistent with that of the first embodiment, the first stirring time is 1 hour, the reaction temperature of the closed reaction is 30 ℃, the reaction time is 4 hours, the volume ratio of ammonia water in the solution obtained after the reaction in the step S3 is 1%, the volume ratio of KH-550 to TEOS is 1:5, the mixed solution containing TEOS is added in one time and added in two times, the volume ratio of TEOS to ethanol is set to be low concentration within the range of 1: 9-1: 14, and the volume ratio of TEOS to ethanol is set to be high concentration within the range of 1: 15-1: 20. The experimental data as given in table 6 below were obtained.

TABLE 6 coating effect of TEOS addition on composite microsphere and SiO₂Influence of thickness

As can be seen from the above table, the content of the composite microspheres in the final product obtained by adding the TEOS mixed solution twice is higher than that obtained by adding the TEOS mixed solution once, and SiO is higher₂There are fewer single cores. Adding a mixed solution containing TEOS at first with low concentration and then with high concentrationSiO in the final product obtained after the addition of formula (II)₂And the number of single cores is less. When the concentration is too high when TEOS is added, SiO is generated due to the high local concentration of TEOS in the system₂Nucleation from the self phase, in addition due to SiO₂And after the growth rate is too high, the coating has more gaps. Therefore, the mixed solution containing TEOS can effectively inhibit or reduce SiO by adopting the adding mode₂Mononuclear formation.

The embodiment of the application also provides a core-shell composite microsphere which is prepared by the method. The SiO which can be uniformly and compactly covered on the surface of the metal particle is prepared by the method₂Composite microspheres of layers, SiO thereof₂The coating effect of the layer is good, the thickness is uniform, and as shown in fig. 12, the shielding effect of 40dB can be achieved in the frequency range of 500MHz and above.

The embodiment of the application also provides a core-shell composite microsphere for EMI shielding, which comprises a submicron metal particle core, a silane coupling agent covering the metal particle and a silicon dioxide insulating layer covering the silane coupling agent, as shown in fig. 11, a shielding material 1 containing the composite microsphere is coated on the surface of a device 2 to achieve a good shielding effect, and compared with a common shielding material, the core-shell composite microsphere has a better shielding effect and SiO₂And the insulating layer is not easy to cause short circuit between devices. The composite microsphere can be filled in a radio frequency communication module product with small volume, the volume and the internal structure of the product do not need to be changed, an additional device is not needed, and an insulating layer SiO is coated outside metal particles₂The modules are not connected or short-circuited, the modules in the product can be prevented from being interfered by EM (electromagnetic radiation) sources, and the internal modules are protected to a certain extent. In addition, a metal shielding layer 3 can be arranged on the outer side of the shielding material 1, so that the shielding effect is better.

The embodiment of the application provides a method for manufacturing composite microspheres and core-shell type composite microspheres for EMI shielding, wherein metal particles are placed in deionized water for ultrasonic dispersion; adding a mixed solution containing a silane coupling agent for primary stirring; adding ammonia water and a mixed solution containing TEOS, and carrying out a closed reaction, wherein the mixed solution containing TEOS is added for multiple times; and finally, carrying out solid-liquid separation on the solution obtained after the reaction to obtain the composite microsphere with the EMI shielding effect. The composite microspheres have good dispersibility and corrosion resistance, can be filled in a small-volume radio frequency communication module product, can ensure that each module in the product is prevented from being interfered by an EM source on the premise of not changing the volume and the internal structure of the product, having no additional device and not causing short circuit of the internal module, and simultaneously play a role in protecting the internal module. Has the advantages of simple process, suitability for mass production, lasting and reliable shielding effect and the like.

While the present invention has been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

In the description of the present application, it is to be understood that the terms "upper", "lower", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred devices or elements must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application. The word 'comprising' does not exclude the presence of elements or steps not listed in a claim. The word 'a' or 'an' preceding an element does not exclude the presence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims shall not be construed as limiting the scope.

Claims

1. A method of making a composite microsphere comprising the steps of:

s1: putting the metal particles into deionized water for ultrasonic dispersion;

2. The method of claim 1, wherein the metal particles are submicron metal particles.

3. The method of claim 2, wherein the metal particles have a diameter between 0.1um and 30 um.

4. The method of claim 1, wherein the metal particles are a single metal structure, an alloy material of multiple metals, or a multi-layer metal composite structure.

5. The method of claim 4, wherein the metal particles are made of Ag, Au, Cu, NiFe, Ni, or Cr materials.

6. The method according to claim 1, wherein the first stirring is performed at room temperature for 0.5-1 h.

7. The method according to claim 1, wherein the closed reaction comprises a second stirring, the reaction temperature is 20-40 ℃, and the reaction time is 4-5 hours.

8. The method according to any one of claims 1 to 7, wherein the aqueous ammonia is present in a volume ratio of 0.8% to 1.4% in the solution obtained after the reaction of step S3.

9. The method according to any one of claims 1 to 7, wherein the mixed solution containing a silane coupling agent comprises a silane coupling agent, an alcohol and water.

10. The method according to claim 9, wherein the silane coupling agent is KH-550 and the alcohol is ethanol.

11. The method according to claim 10, wherein the TEOS-containing mixed solution comprises TEOS and ethanol, and the volume ratio of TEOS to ethanol is 1:9 to 1: 20.

12. The method of claim 11, wherein the volume ratio of KH-550 to TEOS is 1:10 to 2: 5.

13. The method according to any one of claims 1 to 7, wherein the TEOS-containing mixed solution is added in two portions, the volume ratio of the TEOS and the ethanol added in the first portion is 1:15 to 1:20, and the volume ratio of the TEOS and the ethanol added in the second portion is 1:9 to 1: 14.

14. The method according to any one of claims 1 to 7, wherein the means of solid-liquid separation comprises centrifugation and vacuum drying.

15. A core-shell composite microsphere, characterized in that it is produced by the method according to any one of claims 1 to 14.

16. A core-shell type composite microsphere for EMI shielding, comprising a submicron-sized metal particle core, a silane coupling agent covering the metal particle, and a silica insulating layer covering the silane coupling agent.