AgNP / organic silicon conductive nano-microsphere, preparation method thereof and conductive adhesive

Abstract

The invention relates to the technical field of electronic-grade silica powder functional fillers and the technical field of conductive adhesives, in particular to an AgNP / organosilicon conductive nano-microsphere, a preparation method thereof and a conductive adhesive, the preparation method comprises the following steps: preparing a silver source, 3-aminopropyltriethoxysilane and second organosilane into a mixed aqueous solution to form a silver-amine complex precursor; the preparation method comprises the following steps: carrying out co-hydrolysis and co-condensation reaction on a silver-amine complex precursor and tetraethoxysilane in a first mixed solvent, carrying out first-stage reaction, adding a silver-ammonia solution, and carrying out second-stage reaction to form silver ion-loaded organic silicon microspheres; according to the preparation method, the silver ion-loaded organic silicon microspheres are subjected to reduction treatment, the silver ions are reduced into silver nano particles, the AgNP / organic silicon conductive nano microspheres are obtained, and the nano microspheres prepared by the method provide a new method for preparing nano materials with excellent conductivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic-grade silicon micro-powder functional fillers and the technical field of conductive adhesives, in particular to AgNP / organic silicon conductive nanomicrospheres, a preparation method thereof and a conductive adhesive. BACKGROUND

[0002] With the development of electronic devices towards miniaturization, ultra-thinness and flexibility, traditional welding technology has been difficult to meet the needs of some applications. The traditional welding technology needs to be assisted by a high-temperature environment, which is easy to cause the deformation of the substrate and the damage of the components, thereby affecting the service life of the device. As a material that can be cured at low temperature, the conductive adhesive can realize the connection of components while avoiding the damage caused by the high-temperature environment. The traditional conductive adhesive is obtained by uniformly dispersing conductive fillers (such as silver, copper, carbon, etc.) into a resin matrix to form a conductive path, thereby imparting the resin matrix with conductive properties.

[0003] Silver nanoparticles, as a kind of nanomaterial with excellent conductive properties, are often used in the research and production of conductive adhesives. However, due to its large surface energy, silver nanoparticles are prone to agglomeration when dispersed into the resin matrix, thereby affecting the conductive properties of the conductive adhesive. Moreover, with the long-term use of the conductive adhesive, silver nanoparticles will be lost under the action of temperature, humidity and other environments, further reducing the conductive properties of the conductive adhesive. Loading silver nanoparticles onto nanomicrospheres (such as organic silicon nanomicrospheres) is an effective method. The presence of organic groups on the nanomicrospheres can prevent the agglomeration and loss of silver nanoparticles, and can also reduce the addition content of silver nanoparticles, thereby reducing the material preparation cost. The preparation of ordinary organic silicon microspheres requires chemical modification of silica microspheres to carry organic groups (such as amino groups and hydroxyl groups), which can complex with silver ions. The organic silicon microspheres loaded with silver nanoparticles are prepared by in-situ reduction method. However, this method requires more steps and high-temperature environment, increasing the complexity and cost of preparation. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides AgNP / organic silicon conductive nanomicrospheres with excellent conductive properties, a preparation method thereof and a conductive adhesive. The nanomicrospheres prepared by the method provide a new method for preparing nanomaterials with excellent conductive properties.

[0005] According to a first aspect of the present application, a preparation method of AgNP / organic silicon conductive nanomicrospheres is provided, comprising the following steps: The silver source, 3-aminopropyl triethoxysilane (APTES) and a second organosilane are prepared into a mixed aqueous solution to form a silver-amine complex precursor; the second organosilane is gamma-(2,3-epoxypropoxy) propyl trimethoxysilane (GPTMS) or 3-mercaptopropyl triethoxysilane (MPTMS); The silver-amine complex precursor and tetraethoxysilane (TEOS) are subjected to a co-hydrolysis and co-condensation reaction in a first mixed solvent, and after a first-stage reaction, a silver-ammonia solution is added to perform a second-stage reaction to form organic silicon microspheres loaded with silver ions; The organic silicon microspheres loaded with silver ions are subjected to a reduction treatment to reduce the silver ions into silver nanoparticles, thereby obtaining the AgNP / organic silicon conductive nanomicrosphere (AgNP@o-SiO2).

[0006] The pre-synthesized citrate-protected silver nanoparticles are used as a "core" and are pre-mixed with APTES and a second organosilane (GPTMS or MPTMS). The amino group of APTES replaces the citric acid layer through ligand exchange, thereby achieving silanization of the silver nanoparticles, which not only improves the stability of the silver nanoparticles but also provides a firm chemical anchoring point for subsequent wrapping of the silver nanoparticles in the silicon sphere.

[0007] APTES provides an amino group for complexing silver ions, GPTMS provides an epoxy group that can react with the resin matrix, and MPTMS provides a sulfur group that has a strong affinity for silver. The two are co-condensed with TEOS to achieve the introduction of multiple organic functional groups in one step while constructing an inorganic skeleton. This design enables the final microspheres to firmly fix the silver nanoparticles from the inside and form a strong interface with the resin matrix from the outside, thereby solving the problem of difficult compatibility and load.

[0008] According to an embodiment of the present application, the silver source is pre-synthesized citrate-protected silver nanoparticles, and the particle size of the silver source is 10-30 nm. The molar ratio of the 3-aminopropyl triethoxysilane to the tetraethoxysilane is 3:5-1:5. The mass ratio of the 3-aminopropyl triethoxysilane to the second organosilane is 2.5:1-1:1. The molar ratio of the silver source to the 3-aminopropyl triethoxysilane is 1:2-1:6.

[0009] The initial silver nanoparticles are wrapped in the organic silicon microsphere embryo in the first stage through co-hydrolysis and condensation, and then the silver-ammonia solution is added in the second stage. The timing control ensures that the newly introduced silver ions are reduced inside the microsphere network that has been formed and is rich in amino groups / sulfur groups.

[0010] The newly generated silver atoms will preferentially nucleate and grow on the surface of the existing silver nanoparticles with larger size rather than self-nucleate due to the steric hindrance and the demand for reducing the interface energy. This process spontaneously and accurately constructs the large-small silver nanoparticle multi-level structure. The structure densely fixes a large number of silver nanoparticles with small size (3-8 nm) around the large-size 'core', creating a very high internal conductive contact density, while avoiding the migration and agglomeration of small-size silver nanoparticles.

[0011] According to the embodiment of the present application, the silver source, 3-aminopropyl triethoxysilane and the second organic silane are formulated into a mixed aqueous solution to form a silver-amine complex precursor, including: The mixed aqueous solution is stirred at 40°C under light-proof conditions to form a silver-amine complex precursor.

[0012] According to the embodiment of the present application, the silver-amine complex precursor and tetraethoxysilane are subjected to a co-hydrolysis and co-condensation reaction in a first mixed solvent, after the first-stage reaction, a silver-ammonia solution is added to perform a second-stage reaction to form a silver ion-loaded organic silicon microsphere, including: The silver-amine complex precursor is slowly added to the first mixed solvent, and the first mixed solvent is a mixed solvent of water and ethanol with a volume ratio of 1:6-1:15; The tetraethoxysilane is added at a uniform speed after stirring to uniformity at 20-60°C to perform the first-stage reaction; The silver-ammonia solution is slowly added thereto to perform the second-stage reaction, and the silver ion-loaded organic silicon microsphere is obtained after centrifugal washing.

[0013] According to the embodiment of the present application, the reaction time of the first-stage reaction is 1-2h; The reaction time of the second-stage reaction is 1-6h; The concentration of the silver-ammonia solution is 0.05M-0.15M, and the mass ratio of the silver-ammonia solution to the silver source is 1:5-1:2.

[0014] According to the embodiment of the present application, the silver ion-loaded organic silicon microsphere is subjected to a reduction treatment to reduce the silver ions into silver nanoparticles to obtain the AgNP / organic silicon conductive nanomicrosphere, including: The silver ion-loaded organic silicon microsphere is dispersed into a second mixed solvent to obtain a microsphere dispersion liquid, and the second mixed solvent is a mixed solvent of ethanol and water with a volume ratio of 1:2-1:6; A first reducing agent is added to the microsphere dispersion liquid to perform a first-stage reduction at room temperature; A second stage reduction is carried out by adding a second reducing agent to the microsphere dispersion at room temperature, and the AgNP / silicone conductive nanospheres are obtained after washing and centrifugation.

[0015] According to an embodiment of the present application, the first reducing agent is sodium ascorbate or trisodium citrate, and the molar ratio of the first reducing agent to the silver ion-loaded silicone microspheres is 1:1-1.5:1. The second reducing agent is sodium borohydride, and the molar ratio of the second reducing agent to the silver ion-loaded silicone microspheres is 2:1-5:1.

[0016] The first reducing agent (such as ascorbic acid) is used for mild reduction, mainly acting on the silver ions introduced by the silver ammine solution, controlling the slow nucleation and preliminary growth of the silver ions, and being conducive to the formation of small-sized silver nanoparticles with uniform size. The second reducing agent (such as sodium borohydride) is used as a strong reducing agent to ensure that all residual silver ions are completely reduced and to promote the lattice reorganization of silver atoms, thereby improving the crystallinity of the silver nanoparticles. The two-step reduction achieves the simultaneous optimization of the size uniformity and the crystallinity of the silver nanoparticles, and provides the microspheres with excellent and stable intrinsic conductivity.

[0017] According to a second aspect of the present application, an AgNP / silicone conductive nanosphere prepared by the above preparation method is provided, and the particle size of the AgNP / silicone conductive nanosphere is 100-300 nm. The core of the large-sized silver nanoparticles in the AgNP / silicone conductive nanosphere, and the small-sized silver nanoparticles attached to the surface of the core; The particle size of the large-sized silver nanoparticles is 10-50 nm. The particle size of the small-sized silver nanoparticles is 3-8 nm.

[0018] The "core" with a particle size of 10-50 nm serves as a primary conductive unit and a stable carrier. The "satellite" with a particle size of 3-8 nm provides a large number of low-potential barrier electron transmission points due to its extremely high specific surface area and activity. The combination of the two forms a high-efficiency, stable, and high-density three-dimensional internal conductive network in the microsphere. The electrons can be transmitted through the "core" or jump between the dense "satellites" through tunneling effect, realizing the conductive synergistic effect of 1+1 greater than 2. In addition, the structure is tightly wrapped by the silicone network, fundamentally solving the problems of migration, agglomeration, and oxidation of silver nanoparticles.

[0019] According to a third aspect of the present application, a conductive adhesive is provided, which contains the AgNP / silicone conductive nanosphere of claim 8, silver nanowires, and a resin matrix. The mass ratio of the silver nanowires (Ag NW) to the AgNP / silicone conductive nanomicrosphere is 1:2-1:6. The mass ratio of the AgNP / silicone conductive nanomicrosphere to the resin matrix is 1:5-1:15.

[0020] According to the embodiment of the present application, the resin matrix is an epoxy resin or an epoxy resin-polyurethane hybrid system (DA-PU); The epoxy resin-polyurethane hybrid system (DA-PU) is a mixed solution comprising a bisphenol A type epoxy resin and a DA-polyurethane prepolymer, wherein the mass ratio of the bisphenol A type epoxy resin to the DA-polyurethane prepolymer is 7:3-6:4. The DA-polyurethane prepolymer is obtained by reacting a terminal hydroxyl polyurethane prepolymer with a furan-maleimide type DA adduct.

[0021] The AgNP / silicone microsphere serves as a conductive node and pivot. The silver nanowire (Ag NW) serves as a conductive skeleton and bridge. When the two are compounded in a preferred mass ratio of 1:2-1:6, the Ag NW can bridge multiple AgNP / silicone microspheres at a long distance, forming a long-range conductive path throughout the resin matrix. This mixed-dimensional conductive network has a lower percolation threshold, higher electrical conductivity, and stronger anti-cracking and anti-fatigue ability compared to a single filler system. When local stress causes partial microsphere contact failure, electrons can still bypass through the Ag NW, ensuring the redundancy and reliability of the conductive path.

[0022] The bisphenol A type epoxy resin in the epoxy resin-polyurethane hybrid system provides rigidity, strength, and thermal stability, constituting the skeleton of the material. The DA-polyurethane prepolymer introduces a dynamic and reversible Diels-Alder (DA) bond, which forms an interpenetrating or semi-interpenetrating structure with the epoxy network, thereby providing excellent toughening effect and simultaneously releasing internal stress. The PU segment can effectively induce shear bands to absorb impact energy, overcoming the brittleness of pure epoxy resin. When the material is damaged, heating to 120°C can trigger the reverse DA reaction, causing the chemical bonds at the crack interface to break and recombine, achieving crack healing. After cooling, the DA bond is reformed, repairing the strength. The presence of dynamic bonds helps to release internal stress generated during curing and thermal cycling, protecting the internal brittle conductive network from being damaged, achieving the best balance point of maintaining sufficient rigidity and strength, while simultaneously obtaining significant toughening effect and self-repairing ability.

[0023] The application provides a kind of silver ion loaded organic silicon microspheres prepared by sol-gel method, and silver nanoparticles loaded organic silicon composite microspheres are prepared by using chemical reduction method, which is used as filler to obtain conductive adhesive with excellent conductivity by uniformly dispersing in resin matrix. This method uses the mixed solution of silver source and APTES to form sol in ethanol aqueous solution, and then TEOS and APTES are added to prepare 100-300 nm organic silicon microspheres by co-dewatering condensation reaction at a certain temperature. Two different sizes of silver nanoparticles can be doped in the microspheres by silver source and silver ammonia solution, and the silver nanoparticles loaded organic silicon composite microspheres are obtained by reduction of reducing agent. The prepared nanometer microspheres provide a new method for preparing nanometer materials with excellent conductivity, and provide a new nanometer material for the preparation of conductive adhesive. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 TEM image of AgNP@o-SiO2 prepared in Example 1 of the application; Figure 2 Infrared spectrum of AgNP@o-SiO2 prepared in Example 1 of the application; Figure 3 XRD spectrum of AgNP@o-SiO2 prepared in Example 1 of the application; Figure 4 Infrared spectrum of conductive adhesive prepared in Example 1 of the application; Figure 5 Percolation threshold curve of conductive adhesive prepared in Example 1 of the application. DETAILED DESCRIPTION

[0025] The application provides an AgNP / organic silicon conductive nanometer microsphere, a preparation method thereof and conductive adhesive.

[0026] Example 1 A preparation method of AgNP / organic silicon conductive nanometer microsphere, comprising the following steps: S1: configure silver source into silver source solution, add 3-aminopropyl triethoxysilane and γ-(2,3-epoxypropoxy) propyl trimethoxysilane to the silver source solution, the molar ratio of silver source to 3-aminopropyl triethoxysilane is 1:3, and the mass ratio of 3-aminopropyl triethoxysilane to the second organosilane is 1:1, to prepare a mixed aqueous solution, and the mixed aqueous solution is stirred at 40 DEG C under light shielding condition to form a silver-amine complex precursor; The silver source is citrate-protected silver nanoparticles synthesized in advance, and the particle size of the silver source is 10 nm.

[0027] S2: The silver-amine complex precursor is slowly added to the first mixed solvent, which is 50 ml of a mixed solvent of water and ethanol with a volume ratio of 1:12. At 30°C, after stirring until homogeneous, tetraethoxysilane was added at a uniform rate to carry out the first stage reaction. The molar ratio of 3-aminopropyltriethoxysilane to tetraethoxysilane was 3:10, and the reaction time was 2 hours. Silver ammonia solution was slowly added to the mixture. The concentration of the silver ammonia solution was 0.15M, and the mass ratio of the silver ammonia solution to the silver source was 1:3. After the second stage reaction was carried out for 2 hours, the mixture was centrifuged and washed to obtain organosilicon microspheres loaded with silver ions. S3: Disperse the silver ion-loaded organosilicon microspheres in a second mixed solvent to obtain a microsphere dispersion. The second mixed solvent is a mixture of ethanol and water with a volume ratio of 1:4. A first reducing agent was added to the microsphere dispersion to carry out the first stage of reduction at room temperature. The first reducing agent was sodium ascorbate or trisodium citrate, and the molar ratio of the first reducing agent to the organosilicon microspheres loaded with silver ions was 1:1. A second reducing agent, sodium borohydride, was added to the microsphere dispersion to carry out a second-stage reduction at room temperature. The molar ratio of the second reducing agent to the silver ion-loaded organosilicon microspheres was 2:1. After washing and centrifugation, AgNP / organosilicon conductive nanospheres were obtained.

[0028] Characterization: The morphology of the organosilicon support (AgNP@o-SiO2) was observed using transmission electron microscopy (TEM), such as... Figure 1 As shown, the particles are spherical with a diameter of approximately 200 ± 30 nm. The infrared spectrum (FTIR, Bruker TENSORII) of the product is as follows. Figure 2 As shown, Ag + 1590 cm⁻¹ in the @o-SiO₂ spectrum -1 The peak at 1385 cm⁻¹ represents the bending vibration of amino groups. -1 The peak at 1385 cm⁻¹ represents the stretching vibration peak of NO in nitrate ions in silver ammonia solution. After reduction, AgNP@o-SiO₂ is obtained at 1385 cm⁻¹. -1 The stretching vibration peak of NO in nitrate disappears. The X-ray diffraction pattern (XRD, SmartLab) of the product is shown below. Figure 3 As shown, the characteristic peaks of AgNP@o-SiO2 correspond to AgNP, indicating that Ag... + It has been reduced to AgNP. 10 mg AgNP@o-SiO2 was dispersed in 10 ml of deionized water, and excess dilute nitric acid was slowly added dropwise until AgNP reacted completely with the nitric acid. After centrifugation and filtration to remove impurities, the product contained AgNP. +AgNP@o-SiO2, and the loading of AgNP in AgNP@o-SiO2 is 26.5% by ICP test and calculation. The conductivity of AgNP@o-SiO2 is 10 4 S / m by four-probe method.

[0029] Preparation of conductive adhesive encapsulating AgNP@o-SiO2 1 g of AgNP@o-SiO2 and 0.5 g of silver nanowires were weighed and uniformly dispersed into 10 g of epoxy resin and stirred uniformly, the mass ratio of AgNP / organic silicon conductive nanomicrospheres to resin matrix was 1:5, and the mass ratio of silver nanowires to AgNP / organic silicon conductive nanomicrospheres was 1:2, and the bubbles were removed by ultrasonic treatment and vacuum pumping.

[0030] The epoxy resin was cured at low temperature of 40℃ for 4h to finally obtain the conductive adhesive encapsulating AgNP@o-SiO2.

[0031] Characterization: The infrared spectrum (FTIR, Bruker TENSORII) of the conductive adhesive is shown in Figure 4 The characteristic absorption peak of C=O is at 1726 cm -1 , and the characteristic absorption peaks of C-O-C are at 1230 cm -1 and 1072 cm -1 . Different contents of AgNP@o-SiO2 were added to the conductive adhesive, and the conductivity of different content samples was calculated after complete curing, and the percolation threshold was 16%, as shown in Figure 5

[0032] Example 2 A preparation method of AgNP / organic silicon conductive nanomicrospheres, comprising the following steps: S1: preparing a mixed aqueous solution of a silver source, 3-aminopropyl triethoxysilane and γ-(2,3-epoxypropoxy) propyl trimethoxysilane, stirring the mixed aqueous solution under light-proof conditions at 40℃ to form a silver-amine complex precursor; The silver source is a pre-synthesized citrate-protected silver nanoparticle, and the particle size of the silver source is 20 nm; The mass ratio of the 3-aminopropyl triethoxysilane to the γ-(2,3-epoxypropoxy) propyl trimethoxysilane is 1.8:1; The molar ratio of the silver source to the 3-aminopropyl triethoxysilane is 1:4.

[0033] S2: slowly adding the silver-amine complex precursor into a first mixed solvent, and the first mixed solvent is a mixed solvent of water and ethanol with a volume ratio of 1:10, and the volume of the first mixed solvent is 50 ml; ​The first stage reaction was carried out at 50°C by stirring until uniform, then adding tetraethoxysilane at a uniform rate, the molar ratio of 3-aminopropyl triethoxysilane to tetraethoxysilane being 3:7.5, and the reaction time being 1.5h; The second stage reaction was carried out by slowly adding a silver ammine solution into the mixture, the concentration of the silver ammine solution being 0.1M, the mass ratio of the silver ammine solution to the silver source being 1:3, and the reaction time being 4h, to obtain the silver ion loaded silicone microspheres after centrifugal washing; S3: The silver ion loaded silicone microspheres were dispersed into a second mixed solvent to obtain a microsphere dispersion, the second mixed solvent being a mixed solvent of ethanol and water in a volume ratio of 1:4; The first stage reduction was carried out by adding sodium ascorbate into the microsphere dispersion at room temperature, the molar ratio of sodium ascorbate to the silver ion loaded silicone microspheres being 1.2:1; The second stage reduction was carried out by adding sodium borohydride into the microsphere dispersion at room temperature, the molar ratio of sodium borohydride to the silver ion loaded silicone microspheres being 3:1, to obtain the AgNP / silicone conductive nanomicrospheres after washing and centrifugal separation. The particle size of the prepared AgNP / silicone conductive nanomicrospheres was about 300nm, the AgNPs were uniformly distributed, and the conductivity was about 1.2×10 4 S / m.

[0034] Example 3 A method for preparing AgNP / silicone conductive nanomicrospheres, compared with Example 2, the difference was that the second organosilane was 3-mercaptopropyl triethoxysilane, and the mass ratio of 3-aminopropyl triethoxysilane to 3-mercaptopropyl triethoxysilane was 1.5:1. The particle size of the prepared AgNP / silicone conductive nanomicrospheres was smaller due to the strong coordination of the mercapto group, the AgNPs were more tightly anchored, and the conductivity was increased to 1.5×10 4 S / m.

[0035] Example 4 A method for preparing AgNP / silicone conductive nanomicrospheres, compared with Example 2, the difference was that the molar ratio of 3-aminopropyl triethoxysilane to tetraethoxysilane was 3:15. The mechanical strength of the prepared AgNP / silicone conductive nanomicrospheres was improved, but the Ag loading was slightly reduced, and the conductivity was about 9×10 3 S / m.

[0036] Example 5 A method for preparing AgNP / silicone conductive nanomicrospheres, compared with Example 2, the difference was that the molar ratio of the silver source to 3-aminopropyl triethoxysilane was 1:6; the mass ratio of the silver ammine solution to the silver source was 1:5.

[0037] The prepared AgNP / silicone conductive nanospheres have a reduced Ag content and a conductivity of about 6 x 10 3 S / m, which is suitable for low-cost application scenarios.

[0038] Example 6 A method for preparing AgNP / silicone conductive nanospheres, which is different from that of Example 2 in that The reaction temperature in S2 is 25℃, and the reaction time of the first stage is 2h.

[0039] The prepared AgNP / silicone conductive nanospheres have a complete microsphere morphology, slightly larger AgNPs (about 35nm), and a conductivity of about 10 4 S / m, which is suitable for thermal sensitive substrate composite.

[0040] Example 7 A method for preparing AgNP / silicone conductive nanospheres, which is different from that of Example 2 in that The concentration of the silver ammine solution is 0.15M; The mass ratio of the silver ammine solution to the silver source is 1:2.

[0041] The prepared AgNP / silicone conductive nanospheres have a significantly increased Ag loading amount and a conductivity of about 1.8 x 10 4 S / m, but part of the AgNPs precipitates on the surface, so the reduction rate needs to be controlled.

[0042] Example 8 The conductive adhesive encapsulating AgNP@o-SiO2 prepared in Example 2 is used 1g of AgNP@o-SiO2 and 0.5g of silver nanowires are uniformly dispersed into 10g of epoxy resin and stirred uniformly, the mass ratio of the AgNP / silicone conductive nanospheres to the resin matrix is 1:5, and the mass ratio of the silver nanowires to the AgNP / silicone conductive nanospheres is 1:2, and then the mixture is subjected to ultrasonic treatment and vacuum pumping to remove bubbles.

[0043] The epoxy resin is low-temperature cured at 60℃ for 4h to finally obtain the conductive adhesive encapsulating AgNP@o-SiO2, and the conductivity of the conductive adhesive is about 1.7 x 10 4 S / m.

[0044] Example 9 The conductive adhesive encapsulating AgNP@o-SiO2 prepared in Example 2 was used, and different from Example 8, 1 g of AgNP@o-SiO2 and 0.25 g of silver nanowires were uniformly dispersed into 10 g of an epoxy-polyurethane hybrid system and stirred uniformly, wherein the mass ratio of bisphenol A type epoxy resin to DA-polyurethane prepolymer was 7:3, and finally the conductive adhesive encapsulating AgNP@o-SiO2 was obtained, and the conductivity of the conductive adhesive was about 1.4 x 10 4 S / m, the elongation at break was greater than 15%, and after heating at 90°C for 30 min, the self-repairing was achieved, and the resistance recovery rate was greater than 90%.

[0045] Example 10 The conductive adhesive encapsulating AgNP@o-SiO2 prepared in Example 2 was used, and different from Example 8, 1 g of AgNP@o-SiO2 and 0.25 g of silver nanowires were uniformly dispersed into 10 g of an epoxy-polyurethane hybrid system and stirred uniformly, wherein the mass ratio of bisphenol A type epoxy resin to DA-polyurethane prepolymer was 7:3, and finally the conductive adhesive encapsulating AgNP@o-SiO2 was obtained, and the conductivity of the conductive adhesive was about 1.4 x 10 3 S / m.

[0046] Example 11 The conductive adhesive encapsulating AgNP@o-SiO2 prepared in Example 2 was used, and different from Example 8, 1 g of AgNP@o-SiO2 and 0.25 g of silver nanowires were uniformly dispersed into 10 g of an epoxy-polyurethane hybrid system and stirred uniformly, wherein the mass ratio of bisphenol A type epoxy resin to DA-polyurethane prepolymer was 7:3, and finally the conductive adhesive encapsulating AgNP@o-SiO2 was obtained, and the conductivity of the conductive adhesive was about 1.4 x 10 4 S / m.

[0047] In summary, the AgNP / organic silicon conductive nanosphere with unique "core-satellite" internal structure is successfully prepared by ingenious molecular design and process flow control, and the conductive adhesive with high conductivity, high stability, excellent mechanical properties and self-repairing function is developed based on the same. The deep synergistic enhancement effect is generated between the components, and the multiple bottleneck problems in the prior art are solved, and the conductive adhesive has a broad application prospect in the fields of high-end electronic packaging, flexible electronics, aerospace and the like.

[0048] Although the preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to the embodiments once they know the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including all changes and modifications falling within the scope of the present application.

[0049] Obviously, many modifications and variations of the present application are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A method for preparing AgNP / organosilicon conductive nanospheres, characterized in that, Includes the following steps: A silver source, 3-aminopropyltriethoxysilane and a second organosilane were prepared into a mixed aqueous solution to form a silver-amine complex precursor; the second organosilane was γ-(2,3-epoxypropoxy)propyltrimethoxysilane or 3-mercaptopropyltriethoxysilane. The silver-amine complex precursor and tetraethoxysilane were subjected to co-hydrolysis and co-condensation reactions in a first mixed solvent. After the first stage reaction, silver ammonia solution was added to carry out the second stage reaction to form organosilicon microspheres loaded with silver ions. The silver ion-loaded organosilicon microspheres were subjected to a reduction treatment to reduce the silver ions to silver nanoparticles, thereby obtaining the AgNP / organosilicon conductive nanospheres.

2. The preparation method according to claim 1, characterized in that, The silver source is pre-synthesized citrate-protected silver nanoparticles with a particle size of 10-30 nm. The molar ratio of 3-aminopropyltriethoxysilane to tetraethoxysilane is 3:5-1:5; The mass ratio of the 3-aminopropyltriethoxysilane to the second organosilane is 2.5:1 to 1:1; The molar ratio of the silver source to 3-aminopropyltriethoxysilane is 1:2:1:

6.

3. The preparation method according to claim 1, characterized in that, The process of preparing a mixed aqueous solution of a silver source, 3-aminopropyltriethoxysilane, and a second organosilane to form a silver-amine complex precursor includes: The mixed aqueous solution was stirred at 40°C under light-protected conditions to form a silver-amine complex precursor.

4. The preparation method according to claim 1, characterized in that, The silver-amine complex precursor and tetraethoxysilane are subjected to co-hydrolysis and co-condensation reactions in a first mixed solvent. After the first stage reaction, a silver ammonia solution is added to carry out a second stage reaction, forming silver ion-loaded organosilicon microspheres, comprising: The silver-amine complex precursor is slowly added to the first mixed solvent, which is a mixture of water and ethanol with a volume ratio of 1:6 to 1:

15. Under conditions of 20-60 °C, after stirring until homogeneous, tetraethoxysilane is added at a uniform rate to carry out the first stage reaction; The silver ammonia solution was slowly added to the solution to carry out the second stage reaction. After centrifugation and washing, organosilicon microspheres loaded with silver ions were obtained.

5. The preparation method according to claim 4, characterized in that, The reaction time for the first stage reaction is 1-2 hours; The reaction time for the second stage reaction is 1-6 hours. The concentration of the silver ammonia solution is 0.05M-0.15M, and the mass ratio of the silver ammonia solution to the silver source is 1:5-1:

2.

6. The preparation method according to claim 1, characterized in that, The reduction treatment of the silver-ion-loaded organosilicon microspheres, reducing the silver ions to silver nanoparticles to obtain the AgNP / organosilicon conductive nanospheres, includes: The silver-loaded organosilicon microspheres were dispersed in a second mixed solvent to obtain a microsphere dispersion. The second mixed solvent was a mixture of ethanol and water with a volume ratio of 1:2 to 1:

6. A first reducing agent is added to the microsphere dispersion to carry out a first-stage reduction at room temperature; A second reducing agent was added to the microsphere dispersion to carry out a second-stage reduction at room temperature. After washing and centrifugation, the AgNP / organosilicon conductive nanospheres were obtained.

7. The preparation method according to claim 6, characterized in that: The first reducing agent is sodium ascorbate or trisodium citrate, and the molar ratio of the first reducing agent to the organosilicon microspheres loaded with silver ions is 1:1-1.5:1; The second reducing agent is sodium borohydride, and the molar ratio of the second reducing agent to the organosilicon microspheres loaded with silver ions is 2:1-5:

1.

8. An AgNP / organosilicon conductive nanosphere prepared by any one of claims 1-7, characterized in that, The AgNP / organosilicon conductive nanospheres have a particle size of 100-300 nm; The AgNP / organosilicon conductive nanospheres form a core of large-diameter silver nanoparticles and small-diameter silver nanoparticles attached to the surface of the core. The large-diameter silver nanoparticles have a particle size of 10-50 nm. The small-diameter silver nanoparticles have a particle size of 3-8 nm.

9. A conductive adhesive, characterized in that, It contains the AgNP / organosilicon conductive nanospheres, silver nanowires, and resin matrix as described in claim 8; The mass ratio of the silver nanowires to the AgNP / organosilicon conductive nanospheres is 1:2-1:

6. The mass ratio of the AgNP / organosilicon conductive nanospheres to the resin matrix is ​​1:5-1:

15.

10. The conductive adhesive according to claim 9, characterized in that: The resin matrix is ​​epoxy resin or an epoxy resin-polyurethane hybrid system; The epoxy resin-polyurethane hybrid system is a mixed solution comprising bisphenol A type epoxy resin and DA-polyurethane prepolymer, wherein the mass ratio of the bisphenol A type epoxy resin to the DA-polyurethane prepolymer is 7:3-6:

4. The DA-polyurethane prepolymer is obtained by reacting a hydroxyl-terminated polyurethane prepolymer with a furan-maleimide type DA adduct.

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