CN113845863A

CN113845863A - Conductive adhesive, preparation method thereof and conductive film

Info

Publication number: CN113845863A
Application number: CN202111201909.XA
Authority: CN
Inventors: 田颜清; 蔡少勇; 曹戈
Original assignee: Southern University of Science and Technology
Current assignee: Southern University of Science and Technology
Priority date: 2021-10-15
Filing date: 2021-10-15
Publication date: 2021-12-28

Abstract

The application provides a conductive adhesive, a preparation method thereof and a conductive film, wherein the conductive adhesive comprises the following components in percentage by mass of 100% of the total mass of the conductive adhesive: 1-10% of AZO nano particles, 22-42% of adhesive and 50-70% of silver powder. The conductive adhesive is composed of AZO nanoparticles, an adhesive and silver powder, wherein the spherical AZO nanoparticles are good in dispersibility in different solvents and have good affinity with silver, Ag and the AZO nanoparticles are mutually crosslinked and stacked together under the action of the adhesive, the AZO can connect the silver and the silver with each other like a bridge, and meanwhile, electrons are enabled to be rapidly transferred between the silver and the silver based on the good conductivity of the AZO, so that the resistance of the conductive adhesive can be greatly reduced, and the conductivity of the conductive adhesive can be improved.

Description

Conductive adhesive, preparation method thereof and conductive film

Technical Field

The application relates to the technical field of adhesive materials, in particular to a conductive adhesive, a preparation method thereof and a conductive film.

Background

Conductive paste is a bonding solution proposed as a substitute for conventional tin-lead solder. Compared with the traditional lead material connection method, the conductive adhesive is used as an adhesive with certain conductive performance after being cured or dried, and the adhesion process has the remarkable advantages of mild conditions, simple process, less pollution, low cost and the like.

The conductive paste may be classified into an isotropic conductive paste (ICA) and an anisotropic conductive paste (ACA) according to a conductive direction. ACA and ICA are distinguished by whether the percentage of filler exceeds the percolation threshold, which is about 10-20% of the volume fraction of the conductive adhesive in silver conductive adhesives commonly available on the market. For isotropic conductive pastes, the conductive filler loading exceeds the percolation threshold (typically between 20-60%) and is thus conductive in the x, y and z directions. In contrast, the loading of the conductive filler used in anisotropic conductive adhesives is well below the percolation threshold (typically between 5-10%), and is insufficient to achieve mutual contact between the conductive particles and impair the conductivity in the x-y plane. Under the heating and pressurizing state, the conductive fillers are mutually contacted under the action of external force, so that the capability of conducting electricity in a single direction in the vertical direction is obtained.

For isotropic conductive adhesives, the conductivity is one of the important criteria for evaluating the quality of the conductive adhesives. In order to improve the conductivity of conductive adhesives, researchers often choose to have a conductivity of approximately 10⁶S/m nano metal material with extremely high conductivity, such as silver nano crystal and the like, is used as the conductive filler. However, the conductive adhesive of this scheme has high production cost, and thus is not suitable for industrial production.

Disclosure of Invention

The application aims to provide a conductive adhesive with high conductivity and low silver content, a preparation method thereof and a conductive film.

In order to achieve the above purpose, the invention provides the following technical scheme:

a conductive paste comprising, based on 100% of the total mass of the conductive paste: 1-10% of AZO (aluminum-doped zinc oxide) nano particles, 22-42% of adhesive and 50-70% of silver powder.

In some embodiments, the adhesive comprises at least one of TPU (thermoplastic polyurethane elastomer), epoxy, polyvinyl alcohol, polyethylene, polyvinyl chloride, and polymethyl acrylate.

In some embodiments, the silver powder has a particle size of 1 to 3 μm.

In some embodiments, the method of synthesizing AZO nanoparticles comprises:

mixing components including a zinc source, an aluminum source and a solvent, and carrying out a solvothermal reaction;

and carrying out solid-liquid separation on the product after the solvothermal reaction.

In some embodiments, the solvothermal reaction is carried out at a temperature of 180-220 ℃ for a period of 24-48 h;

preferably, the synthesis method further comprises drying the solid obtained by solid-liquid separation.

In some embodiments, the zinc source comprises Zn (CH)₃COO)₂·2H₂O and Zn (NO)₃)₂·6H₂At least one of O;

preferably, the aluminum source comprises AlCl₃、Al(CH₃CO₂)₃And Al (NO)₃)₃·9H₂At least one of O;

preferably, the solvent is a mixed solvent of a first organic solvent and water, and the first organic solvent includes diethylene glycol or hexamethylenetetramine;

preferably, the mass ratio of the zinc source to the aluminum source is 1 (0.006-0.024);

preferably, the zinc source and solvent are used in an amount of 1: (50-70) g/ml.

The application also provides a preparation method of the conductive adhesive, wherein the conductive adhesive is the conductive adhesive;

the preparation method comprises the following steps: the components including AZO nanoparticles, a binder, and silver powder were mixed.

In some embodiments, the method of making comprises: dissolving the adhesive in a second organic solvent at 60-100 ℃ to obtain a mixed solution;

dispersing AZO nano particles in the mixed solution to obtain a suspension;

dispersing silver powder in the suspension to obtain conductive adhesive;

preferably, the second organic solvent comprises at least one of 1, 4-dioxane, acetone, and ethyl acetate;

preferably, the dosage ratio of the adhesive to the second organic solvent is (0.22-0.42) g/(15-30) ml;

preferably, the preparation method further comprises adjusting the viscosity of the conductive adhesive;

preferably, the viscosity of the conductive adhesive is adjusted by heating and evaporating, and more preferably, the heating and evaporating temperature is 70-100 ℃ and the time is 1-3 h.

The application also provides a conductive film, which is obtained by coating the conductive adhesive on a substrate and drying.

In some embodiments, the drying temperature is 120-170 ℃ for 1-4 h.

The beneficial effect of this application:

(1) the conductive adhesive is composed of AZO nano-particles, an adhesive and silver powder, wherein the spherical AZO nano-particles have good dispersibility in different solvents and have good affinity with silver, Ag and the AZO nano-particles are mutually crosslinked and stacked together under the action of the adhesive, the AZO can mutually connect the silver and the silver like a bridge, and meanwhile, electrons are promoted to be quickly transferred between the silver and the silver based on the good conductivity of the AZO, so that the resistance of the conductive adhesive can be greatly reduced, and the conductivity of the conductive adhesive can be improved; the conductive adhesive can be widely applied to the fields of conductive connection, flexible circuit construction, electromagnetic shielding device construction and the like.

(2) The conductive adhesive prepared by the preparation process is simple in preparation process and low in production cost, is excellent in conductivity and the like, and is suitable for industrial mass production.

Drawings

To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments are briefly described below, and it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope of the present application.

FIG. 1 is an XRD pattern of AZO nanoparticles prepared in example 1 and commercially available ZnO nanoparticles;

FIG. 2a is an SEM topography of AZO nanoparticles;

FIG. 2b is a graph of the particle size distribution of AZO nanoparticles;

FIG. 3 is a diagram of a colloidal suspension of AZO nanoparticles in water and an organic solvent;

FIG. 4 is an SEM topography of the conductive film prepared in example 1;

FIG. 5a is a comparative statistical chart of the resistivity of the conductive films prepared in examples 3, 6 to 7 and 1 to 3 after heat treatment at 100 ℃;

fig. 5b is a linear graph of the resistivity of the conductive film with different doping amounts of AZO nanoparticles.

Detailed Description

The terms as used herein:

"prepared from … …" is synonymous with "comprising". The terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

The conjunction "consisting of … …" excludes any unspecified elements, steps or components. If used in a claim, the phrase is intended to claim as closed, meaning that it does not contain materials other than those described, except for the conventional impurities associated therewith. When the phrase "consisting of … …" appears in a clause of the subject matter of the claims rather than immediately after the subject matter, it defines only the elements described in the clause; other elements are not excluded from the claims as a whole.

When an amount, concentration, or other value or parameter is expressed as a range, preferred range, or as a range of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when the range "1 ~ 5" is disclosed, the ranges described should be construed to include the ranges "1 ~ 4", "1 ~ 3", "1 ~ 2 and 4 ~ 5", "1 ~ 3 and 5", and the like. When a range of values is described herein, unless otherwise stated, the range is intended to include the endpoints thereof and all integers and fractions within the range.

In these examples, the parts and percentages are by mass unless otherwise indicated.

"part by mass" means a basic unit of measure indicating a mass ratio of a plurality of components, and 1 part may represent any unit mass, for example, 1g or 2.689 g. If we say that the part by mass of the component A is a part by mass and the part by mass of the component B is B part by mass, the ratio of the part by mass of the component A to the part by mass of the component B is a: b. alternatively, the mass of the A component is aK and the mass of the B component is bK (K is an arbitrary number, and represents a multiple factor). It is unmistakable that, unlike the parts by mass, the sum of the parts by mass of all the components is not limited to 100 parts.

"and/or" is used to indicate that one or both of the illustrated conditions may occur, e.g., a and/or B includes (a and B) and (a or B).

The application provides a conductive adhesive, which comprises the following components in percentage by mass based on the total mass of the conductive adhesive as 100 percent:

AZO (aluminum doped zinc oxide) nanoparticles 1-10%, such as 1%, 2%, 4%, 6%, 8%, or 10%, etc.;

binder 22-42%, such as 22%, 25%, 30%, 33%, 35%, 39%, or 42%, etc.;

50-70% of silver powder, such as 50%, 55%, 60%, 65%, 68% or 70%.

In some embodiments, the adhesive includes, but is not limited to, at least one of TPU (thermoplastic polyurethane elastomer), epoxy, polyvinyl alcohol, polyethylene, polyvinyl chloride, and polymethyl acrylate.

In some embodiments, the particle size of the silver powder is 1-3 μm, that is, the adopted micro silver sheet enables AZO nanoparticles to be well distributed on the micro silver sheet and play a role of a bridge, the thickness of the insulating layer is reduced, and the transmission of electrons between the micro silver sheets can be well promoted, so that the conductivity of the conductive adhesive is improved.

In some embodiments, the method of synthesizing AZO nanoparticles comprises:

s10, mixing components including a zinc source, an aluminum source and a solvent, and carrying out a solvothermal reaction;

s20, carrying out solid-liquid separation on the product after the solvothermal reaction.

In some embodiments, the zinc source comprises Zn (CH)₃COO)·2H₂O and Zn (NO)₃)₂·6H₂At least one of O; the aluminum source comprises AlCl₃、Al(CH₃CO₂)₃And Al (NO)₃)₃·9H₂At least one of O; the solvent is a mixed solvent of a first organic solvent and water, and the first organic solvent comprises diethylene glycol or hexamethylenetetramine.

In some embodiments, the mass ratio of the zinc source to the aluminum source is 1 (0.006-0.024); the dosage of the zinc source and the solvent is 1: (50-70) g/ml.

When the first organic solvent is diethylene glycol, the volume ratio of diethylene glycol to water is (7-9): (1-3); when the first organic solvent is hexamethylenetetramine, the volume ratio of the hexamethylenetetramine to the water is 50: (1-20), and the molar mass of the Zn source is the same as that of the hexamethylene tetramine.

The solid-liquid separation process comprises the following steps: and (3) carrying out centrifugal washing on the product after the solvothermal reaction by adopting water and ethanol, and collecting the precipitate.

In some embodiments, the method of making comprises:

s100, dissolving the adhesive in a second organic solvent at 60-100 ℃ to obtain a mixed solution; preferably, the second organic solvent comprises 1, 4-dioxane; the dosage ratio of the adhesive to the second organic solvent is as follows;

s200, dispersing AZO nano particles in the mixed solution to obtain a suspension;

and S300, dispersing silver powder in the suspension to obtain the conductive adhesive.

In some embodiments, the method further comprises adjusting the viscosity of the conductive paste to achieve a desired optimal viscosity; preferably, the viscosity of the conductive adhesive is adjusted by heating and evaporating, and more preferably, the heating and evaporating temperature is 70-100 ℃ and the time is 1-3 h.

The application also provides a conductive film, which is obtained by coating the conductive adhesive on a substrate such as a polytetrafluoroethylene plate and drying.

In some embodiments, the drying temperature is 120-170 ℃ for 1-4 h.

It should be noted that the inventors of the present application found that the conductivity of the conductive paste depends on the degree of closeness of the silver micro-scale plate; when the solvent remains in the conductive film, the micro silver flakes will be dispersed in the binder and the conductive path cannot be formed; as the solvent evaporates and the adhesive cures, the gaps (insulating layers) between the silver flakes decrease, tunneling occurs, which makes it possible for the free electrons in the silver flakes to penetrate the insulating layers, so that directional motion occurs, i.e., the film begins to exhibit electrical conductivity; however, due to the difficulty of eliminating the insulating layer, resistance is always present in the conductive thin film, in other words, the conductivity of the conductive film is closely related to the thickness of the insulating layer, the moving speed of free electrons increases with the attenuation of the insulating layer, and finally one conductive layer is formed. According to the method, the thickness of the insulating layer is reduced by filling gaps of the micro silver sheets with the AZO nano particles, and the AZO nano particles are used as a bridge to promote the transfer of free electrons between the micro silver sheets; based on this, the conductive performance of the conductive film is greatly improved.

Embodiments of the present application will be described in detail below with reference to specific examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present application and should not be construed as limiting the scope of the present application. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

Example 1

(1) Synthesis of AZO nanoparticles: 1g of Zn (CH)₃COO)₂·2H₂O and 0.006g AlCl₃Dissolving in a mixed solvent of 45ml of diethylene glycol and 5ml of deionized water, and then carrying out solvent heating at 180 ℃ for 48 hours; and then, centrifugally washing the product after the solvent thermal reaction by water and ethanol in sequence, collecting the precipitate, and drying the precipitate overnight to obtain the AZO nano-particles.

(2) Synthesizing a conductive adhesive: 0.28g of TPU was dissolved well in 20ml of 1, 4-dioxane solution at 60 ℃, then 0.02g of AZO nanoparticles was dispersed ultrasonically in the above solution, then 0.70g of silver micro-flakes (diameter 1-3 μm) were added to the suspension under vigorous stirring, and then heated at 70 ℃ for 2 hours to remove part of the solvent to adjust the viscosity, to obtain a conductive adhesive.

(3) Preparing a conductive film: and pouring the conductive adhesive onto a polytetrafluoroethylene plate, drying at 120 ℃ for 2h, and removing the obtained flexible film, namely the conductive film, from the polytetrafluoroethylene plate.

Example 2

(1) Synthesis of AZO nanoparticles: 1g of Zn (CH)₃COO)₂·2H₂O and 0.012g AlCl₃Dissolving in a mixed solvent of 48ml of diethylene glycol and 12ml of deionized water, and then carrying out solvent heating at 200 ℃ for 36 h; and then, centrifugally washing the product after the solvent thermal reaction by water and ethanol in sequence, collecting the precipitate, and drying the precipitate overnight to obtain the AZO nano-particles.

(2) Synthesizing a conductive adhesive: 0.31g of TPU was dissolved well in 24ml of 1, 4-dioxane solution at 70 ℃, then 0.04g of AZO nanoparticles were dispersed ultrasonically in the above solution, then 0.65g of silver micro-flakes (diameter 1-3 μm) were added to the suspension under vigorous stirring, then heated at 80 ℃ for 1.5h to remove part of the solvent to adjust the viscosity, and conductive paste was obtained.

(3) Preparing a conductive film: and pouring the conductive adhesive onto a polytetrafluoroethylene plate, drying at 150 ℃ for 1.5h, and removing the obtained flexible film, namely the conductive film, from the polytetrafluoroethylene plate.

Example 3

(1) Synthesis of AZO nanoparticles: 1g of Zn (CH)₃COO)₂·2H₂O and 0.024g AlCl₃Dissolving in a mixed solvent of 42ml of diethylene glycol and 18ml of deionized water, and then carrying out solvent heating for 30h at 200 ℃; and then, centrifugally washing the product after the solvent thermal reaction by water and ethanol in sequence, collecting the precipitate, and drying the precipitate overnight to obtain the AZO nano-particles.

(2) Synthesizing a conductive adhesive: 0.42g of TPU was dissolved well in 30ml of 1, 4-dioxane solution at 60 ℃, then 0.08g of AZO nanoparticles was dispersed ultrasonically in the above solution, then 0.50g of silver micro-flakes (diameter 1-3 μm) were added to the suspension under vigorous stirring, and then heated at 90 ℃ for 1 hour to remove part of the solvent to adjust the viscosity, to obtain a conductive adhesive.

Example 4

(1) Synthesis of AZO nanoparticles: 1g of Zn (NO)₃)₂·6H₂O and 0.018g Al (CH)₃CO₂)₃Dissolving in a mixed solvent of 45ml of diethylene glycol and 5ml of deionized water, and then carrying out solvent heating at 220 ℃ for 24 hours; and then, centrifugally washing the product after the solvent thermal reaction by water and ethanol in sequence, collecting the precipitate, and drying the precipitate overnight to obtain the AZO nano-particles.

(2) Synthesizing a conductive adhesive: 0.32g of polyvinyl alcohol was sufficiently dissolved in 20ml of an ethyl acetate solution at 90 ℃, then 0.06g of AZO nanoparticles was ultrasonically dispersed in the above solution, then 0.62g of a micro silver plate (diameter 1 to 3 μm) was added to the suspension under strong stirring, and then heated at 100 ℃ for 1 hour to remove a part of the solvent to adjust the viscosity, to obtain a conductive adhesive.

(3) Preparing a conductive film: and pouring the conductive adhesive onto a polytetrafluoroethylene plate, drying at 170 ℃ for 1h, and then removing the obtained flexible film, namely the conductive film, from the polytetrafluoroethylene plate.

Example 5

(1) Synthesis of AZO nanoparticles: 1g of Zn (NO)₃)₂·6H₂O and 0.038g Al (CH)₃CO₂)₃Dissolving in a mixed solvent of 49ml of diethylene glycol and 14ml of deionized water, and then carrying out solvent heating for 38 hours at 180 ℃; and then, centrifugally washing the product after the solvent thermal reaction by water and ethanol in sequence, collecting the precipitate, and drying the precipitate overnight to obtain the AZO nano-particles.

(2) Synthesizing a conductive adhesive: 0.38g of polyvinyl alcohol was sufficiently dissolved in 28ml of an ethyl acetate solution at 100 ℃, then 0.1g of AZO nanoparticles was ultrasonically dispersed in the above solution, then 0.52g of a micro silver plate (diameter 1 to 3 μm) was added to the suspension under strong stirring, and then heated at 70 ℃ for 2 hours to remove a part of the solvent to adjust the viscosity, to obtain a conductive paste.

Example 6

The present embodiment 6 differs from embodiment 3 in that: in the step (2): replacing 0.42g of TPU with 0.32g, and replacing 0.50g of micron silver sheet with 0.60 g; otherwise, the same procedure as in example 1 was repeated.

Example 7

The present embodiment 7 differs from embodiment 3 in that: in the step (2): replacing 0.42g of TPU with 0.22g, and replacing 0.50g of micron silver sheet with 0.70 g; otherwise, the same procedure as in example 1 was repeated.

Comparative example 1

Comparative example 1 differs from example 3 in that: in the step (2): AZO nanoparticles are not added (namely the using amount of the AZO nanoparticles is 0), and 0.42g of TPU is replaced by 0.50 g; otherwise, the same procedure as in example 1 was repeated.

Comparative example 2

Comparative example 2 differs from example 3 in that: in the step (2): AZO nano particles are not added (namely the dosage of the AZO nano particles is 0), 0.42g of TPU is replaced by 0.40g, and 0.50g of micro silver sheet is replaced by 0.60 g; otherwise, the same procedure as in example 1 was repeated.

Comparative example 3

Comparative example 3 differs from example 3 in that: in the step (2): the AZO nano particles are not added (namely the dosage of the AZO nano particles is 0), the dosage of the TPU is 0.42g instead of 0.30g, and the dosage of the micro silver sheet is 0.50g instead of 0.70 g; otherwise, the same procedure as in example 1 was repeated.

FIG. 1 is an XRD pattern of AZO nanoparticles prepared in example 1 and commercially available ZnO nanoparticles; as can be seen from the figure, ZnO shows (100), (002), (101), (102), (110), (103), (200), (112) and (201) crystal planes associated with the hexagonal wurtzite structure at 2 θ of 31 °, 34 °, 36 °, 47 °, 56 °, 62 °, 66 °, 67 ° and 69 °, respectively; the AZO nanoparticles and the ZnO nanoparticles have the same peak position on the spectrum, but the intensity, the half-peak width (FWHM) and the peak position are changed. This is probably due to Al³⁺(53pm) ion radius ratio Zn²⁺(74pm) is small, so that the doped Al ions replace the positions of Zn ions in the crystal lattice but do not change the whole structure of the crystal lattice; furthermore, according to the Scherrer formula, the crystal size of the nanoparticles was significantly increased after doping, which reflects that the presence of the foreign atom Al may improve the crystal growth; thus, the results of this XRD demonstrate the successful preparation of AZO nanoparticles.

FIG. 2a is an SEM topography of AZO nanoparticles, and FIG. 2b is a particle size distribution diagram of AZO nanoparticles; as can be seen from fig. 2a and 2 b: AZO nanoparticles appear as nanospheres with an average particle size of about 40.48 nm.

FIG. 3 is a diagram of a colloidal suspension of AZO nanoparticles in water and organic solvent (1-water, 2-methanol, 3-ethanol, 4-acetone, 5-methylisobutylketone, 6-1, 4-dioxane, 7-ethyl acetate); the results of this figure 3 show that: the AZO nano-particles can form stable colloidal suspension in water and most organic solvents, which is beneficial to preparing a conductive adhesive material with high performance.

It should be noted that the XRD patterns and SEM morphology patterns of the AZO nanoparticles prepared in examples 2-5 are substantially the same as those of example 1.

FIG. 4 is an SEM topography of the conductive film prepared in example 1; as can be seen from the figure, the micro silver flakes and AZO nanoparticles are stacked on top of each other under the action of the TPU, and AZO is mainly present in the voids between the silver flakes. This phenomenon indicates that AZO can link adjacent micron silver sheets like a "bridge" and promote the rapid transfer of electrons between different silver sheets based on its own good conductivity.

The SEM topography of the conductive films prepared in examples 2-5 was substantially the same as example 1.

Fig. 5a is a comparative statistical chart of resistivity after heat treatment at 100 ℃ for the conductive films prepared in examples 3 and 6 to 7 (the amount of AZO is 8 wt% and the silver content is 50 wt%, 60 wt%, 70 wt%, respectively) and the conductive films prepared in comparative examples 1 to 3 (the amount of AZO is 0 and the silver content is 50 wt%, 60 wt%, 70 wt%, respectively) (wherein examples with the same silver content are compared with comparative examples, i.e., example 3 is compared with comparative example 1, example 6 is compared with comparative example 2, and example 7 is compared with comparative example 3). As can be seen from fig. 5a, the resistivity of the conductive film prepared in example 3 reached 2338.8 × 10^-5Ω · cm, which is about 1/1.02 of the conductive film prepared in comparative example 1 with the same silver content; the resistivity of the conductive film prepared in example 6 reached 8.5 × 10^-5Ω · cm, about 1/196 for the conductive film prepared in comparative example 2 with the same silver content; the resistivity of the conductive film prepared in example 7 reached 13.3 × 10^-5Ω · cm, is about 1/24 for the conductive film prepared in comparative example 3 with the same silver content. The conductivity test result proves that the bridge action of the AZO can well promote the transmission of electrons between different micron silver sheets, so that the conductivity of the conductive adhesive is improved.

In addition, by using example 6 in which the addition amount of the micro silver flakes is 60 wt% as a control, after the doping amounts of the AZO nanoparticles (0 wt%, 2 wt%, 5 wt%, and 10 wt%, respectively) are changed, the resistivity of the conductive film of the AZO nanoparticles with different doping amounts, in which the addition amount of the micro silver flakes is 60 wt%, is characterized, and the result is shown in fig. 5 b. From this fig. 5b, it can be understood that when the doping amount of the AZO nanoparticles is 0 wt%, the resistivity of the resulting conductive film is as high as 1638.8 × 10^-5Ω·cm，After a small amount of AZO nano-particles are added, the resistivity of the obtained conductive film is reduced sharply, and when the doping amount of the AZO nano-particles is increased to 8 wt%, the resistivity of the obtained conductive film is reduced to 8.5 multiplied by 10^-51/196 at about 0% Ω · cm; when the doping amount of the AZO nano particles is further increased by 10%, the resistivity of the conductive film is increased to 50.2 multiplied by 10%^-5Ω · cm, which is probably because the excess accumulation of AZO results in larger gaps between silver flakes and voids of varying degrees, resulting in a decrease in conductivity.

Therefore, under the condition of the same silver content, the conductive adhesive is added with AZO with the content of 1-10 wt% and has lower resistivity (namely higher conductivity) compared with a conductive film prepared without AZO; moreover, the doping amount of the AZO nanoparticles is the optimal doping amount at 8 wt%, and the resistivity of the obtained conductive adhesive is the lowest (i.e. the conductivity is the highest).

Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present application.

Moreover, those skilled in the art will appreciate that while some embodiments herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the application and form different embodiments. For example, in the claims above, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is only for enhancement of understanding of the general background of the application and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Claims

1. A conductive paste comprising, based on 100% by mass of the paste: 1-10% of AZO nano particles, 22-42% of adhesive and 50-70% of silver powder.

2. The conductive paste of claim 1, wherein the binder comprises at least one of TPU, epoxy, polyvinyl alcohol, polyethylene, polyvinyl chloride, and polymethyl acrylate.

3. The conductive paste according to claim 1, wherein the silver powder has a particle size of 1 to 3 μm.

4. The conductive paste according to claim 1, wherein the AZO nanoparticles are synthesized by a method comprising:

5. The conductive adhesive as claimed in claim 4, wherein the temperature of the solvothermal reaction is 180-220 ℃ and the time is 24-48 h;

6. The conductive paste of any one of claims 1-4, wherein the zinc source comprises Zn (CH)₃COO)₂·2H₂O and Zn (NO)₃)₂·6H₂At least one of O;

preferably, the mass ratio of the zinc source to the aluminum source is 1: (0.006-0.024);

7. A method for preparing a conductive adhesive, characterized in that the conductive adhesive is the conductive adhesive according to any one of claims 1 to 6;

8. The method for preparing the conductive paste according to claim 7, comprising: dissolving the adhesive in a second organic solvent at 60-100 ℃ to obtain a mixed solution;

dispersing the AZO nano particles in the mixed solution to obtain a suspension;

dispersing silver powder in the suspension to obtain the conductive adhesive;

9. A conductive film obtained by applying the conductive paste according to any one of claims 1 to 6 to a substrate and drying the applied conductive paste.

10. The conductive film of claim 9 wherein the drying temperature is 120-170 ℃ for 1-4 h.