Conductive silver paste and its preparation method

Abstract

The present disclosure provides a conductive silver paste and a preparation method thereof, relating to the technical field of electronic pastes. The conductive silver paste includes: conductive silver powder, a gallium-based liquid metal-based composite functional material, an organic resin binder phase, a curing agent, an organic solvent, and an auxiliary agent, wherein: the weight parts of the conductive silver powder are 55 parts - 75 parts; the weight parts of the gallium-based liquid metal-based composite functional material are 5 parts - 25 parts; the weight parts of the organic resin binder phase are 4 parts - 10 parts; the weight parts of the curing agent are 1 part - 3 parts; the weight parts of the organic solvent are 2 parts - 10 parts; the weight parts of the auxiliary agent are 0.1 part - 10 parts; the gallium-based liquid metal-based composite functional material includes a gallium-based liquid metal, a conductive polymer, and few-layer two-dimensional materials, the gallium-based liquid metal includes one or more of gallium, a gallium-tin alloy, a gallium-indium alloy, a gallium-indium-tin alloy, or a gallium-indium-tin-zinc alloy; the conductive polymer includes one or more of polypyrrole, polydopamine, or polyaniline; the few-layer two-dimensional materials include graphene or transition metal carbides.

Description

Technical Field

[0001] The present disclosure relates to the technical field of electronic pastes, and more particularly, to a conductive silver paste and a preparation method thereof. Background Art

[0002] Due to advantages such as high conductivity, high antioxidant property, and high stability, conductive silver paste has become one of the commonly used representative functional electronic pastes in the field of flexible electronic printing. However, during the service process of current conductive silver paste for flexible printing in China, there are problems of conductive layer failure and interface mismatch caused by mechanical deformation strains such as repeated bending / stretching, which easily lead to unstable electrical connection and even equipment failure.

[0003] It should be noted that the information disclosed in the above background art section is only used to enhance the understanding of the background of the present disclosure, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0004] The present disclosure provides a conductive silver paste and a preparation method thereof, which can improve problems such as conductive layer failure and interface mismatch, enhance the stability of electrical connection, and reduce the risk of equipment failure.

[0005] According to one aspect of the present disclosure, there is provided a conductive silver paste, which comprises the following components: conductive silver powder, gallium-based liquid metal-based composite functional material, organic resin binder, curing agent, organic solvent, and additives, wherein: the weight parts of the conductive silver powder are 55 parts - 75 parts; the weight parts of the gallium-based liquid metal-based composite functional material are 5 parts - 25 parts; the weight parts of the organic resin binder are 4 parts - 10 parts; the weight parts of the curing agent are 1 part - 3 parts; the weight parts of the organic solvent are 2 parts - 10 parts; the weight parts of the additives are 0.1 part - 10 parts;

[0006] The gallium-based liquid metal-based composite functional material comprises gallium-based liquid metal, conductive polymer, and few-layer two-dimensional material. The gallium-based liquid metal includes one or more of gallium, gallium-tin alloy, gallium-indium alloy, gallium-indium-tin alloy, or gallium-indium-tin-zinc alloy; the conductive polymer includes one or more of polypyrrole, polydopamine, or polyaniline; the few-layer two-dimensional material includes graphene or transition metal carbide.

[0007] In an exemplary embodiment of the present disclosure, the conductive silver powder comprises silver nanowires, flaky metallic silver powder, and nano-spherical silver powder, and the silver nanowires are synthesized by the polyol method.

[0008] In an exemplary embodiment of the present disclosure, the organic resin binder is one or more of hydroxyl-terminated polyester resin, epoxy-modified acrylic resin, and polyurethane resin.

[0009] In an exemplary embodiment of the present disclosure, the curing agent is a blocked isocyanate curing agent.

[0010] In an exemplary embodiment of the present disclosure, the organic solvent includes two or more of xylene, alkylbenzene, butyl carbitol, terpineol, N-methylpyrrolidone, butyl carbitol acetate, and mixed binary esters.

[0011] In an exemplary embodiment of the present disclosure, the additives include two or three of modified urea, polysiloxane, and thixotropic agent.

[0012] According to one aspect of the present disclosure, there is provided a method for preparing a conductive silver paste for preparing the conductive silver paste described in any one of the above, and the preparation method includes:

[0013] Preparing a gallium-based liquid metal-based composite functional material, the gallium-based liquid metal-based composite functional material including gallium-based liquid metal, a conductive polymer, and few-layer two-dimensional materials, the gallium-based liquid metal including one or more of gallium, gallium-tin alloy, gallium-indium alloy, gallium-indium-tin alloy, or gallium-indium-tin-zinc alloy; the conductive polymer including one or more of polypyrrole, polydopamine, or polyaniline; the few-layer two-dimensional materials including graphene or transition metal carbides;

[0014] Preparing a silver nanowire dispersion by a polyol synthesis method;

[0015] Weighing an organic resin binder phase and an organic solvent by weight and adding them to the silver nanowire dispersion, and stirring until a homogeneous state is formed to form an organic carrier;

[0016] Adding the gallium-based liquid metal-based composite functional material, flaky metallic silver powder, and nano-spherical silver powder to the organic carrier in small amounts and multiple times, and continuously stirring in a planetary mixer to prepare a homogeneous slurry;

[0017] Adding additives and a curing agent to the homogeneous slurry, and continuously stirring to adjust the viscosity and thixotropic properties of the slurry to form an initial conductive silver paste;

[0018] Adjusting the fineness of the initial conductive silver paste through a three-roll grinder, and after double filtration, obtaining the target conductive silver paste.

[0019] In an exemplary embodiment of the present disclosure, the preparation of the gallium-based liquid metal-based composite functional material includes:

[0020] Weighing gallium-based liquid metal by weight and adding it to a special ultrasonic crushing vessel containing an aqueous solution of sodium dodecylbenzenesulfonate at 10 ml, and performing ultrasonic crushing at a constant temperature of 20 °C to form suspension one;

[0021] Weighing Ti by weight 3 AlC2 Powder and lithium fluoride powder are added to hydrochloric acid solution, and few-layer Ti with dark green color is obtained by using lithium fluoride-hydrochloric acid etching process and ultrasonic stripping process 3 C 2 T x aqueous dispersion of nanosheets as suspension two;

[0022] Mix the suspension one and the suspension two by weight parts and ultrasonicate for 10 min. Based on the electrostatic repulsion between negatively charged Ti 3 C 2 T x and liquid metal, a uniform mixed solution of gallium-based liquid metal and two-dimensional material is obtained;

[0023] Add the reactant conductive polymer monomer - polypyrrole into the mixed solution, mix and stir, add the oxidant ferric chloride hexahydrate, and a black suspension is obtained after fully reacting for 1 h;

[0024] The black suspension is washed, vacuum filtered and vacuum dried for multiple times to obtain a gallium-based liquid metal-based composite functional material.

[0025] In an exemplary embodiment of the present disclosure, the preparation of the silver nanowire dispersion by the polyol synthesis method includes:

[0026] Add 0.3 parts of sodium chloride, 1.2 parts of silver nitrate and 1.2 parts of polyvinylpyrrolidone into a reaction kettle containing ethylene glycol, and prepare a silver nanowire dispersion by microwave reaction at 140 °C.

[0027] In an exemplary embodiment of the present disclosure, the curing agent is a blocked isocyanate curing agent; the organic solvents include two or more of xylene, alkylbenzene, butyl carbitol, terpineol, N-methylpyrrolidone, butyl carbitol acetate and mixed binary esters; the additives include two or three of modified urea, polysiloxane and thixotropic agent; the organic resin binder phase is one or more of hydroxyl-terminated polyester resin, epoxy-modified acrylic resin and polyurethane resin.

[0028] The conductive silver paste of the present disclosure and its preparation method significantly improve the application performance of the conductive silver paste in the field of flexible electronic printing by incorporating a gallium-based liquid metal-based composite functional material. In particular, a breakthrough has been made in solving the problems of conductive layer failure and interface mismatch caused by mechanical deformations such as repeated bending / stretching. For example, the gallium-based liquid metal (such as gallium, gallium-tin alloy, gallium-indium alloy, gallium-indium-tin alloy, or gallium-indium-tin-zinc alloy) in the gallium-based liquid metal-based composite functional material acts as a self-flowing crack repair agent. Its high conductivity and self-healing properties can quickly repair cracks when they appear after the silver paste layer is bent or stretched, thus greatly extending the service life of the conductive silver paste. The addition of conductive polymers (such as polypyrrole, polydopamine, or polyaniline) and few-layer two-dimensional materials (such as graphene or transition metal carbides) effectively improves the interfacial wettability between the liquid metal particles, conductive silver powder, and the substrate. The high flexibility and good interfacial compatibility of these materials can enhance the matching of the rigid-flexible interface, contributing to improving the repair effect. At the same time, the conductive polymers and two-dimensional materials in the gallium-based liquid metal-based composite functional material can also form additional conductive channels, which helps to enhance the stability and reliability of the conductive network. In addition, in the present disclosure, by precisely controlling the weight parts of each component, the conductive silver paste can achieve good adhesion and processing performance while maintaining high conductivity. The synergistic effect of the organic resin binder phase, curing agent, and additives ensures that the silver paste can form a dense and uniform conductive layer after curing. The finally obtained conductive silver paste not only has high bend resistance and strong adhesion but also exhibits high reliability, effectively solving the problems of conductive layer failure and interface mismatch caused by mechanical deformations (such as cracks) in flexible electronic printing.

[0029] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure. Brief Description of the Drawings

[0030] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present disclosure, and are used together with the specification to explain the principles of the present disclosure. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 It is a flowchart of the preparation method of the conductive silver paste in the embodiments of the present disclosure.

[0032] Figure 2 It is for few-layer Ti 3 C 2 T x SEM image of the nanosheets.

[0033] Figure 3SEM images of the gallium-based liquid metal-based composite functional material in the embodiments of the present disclosure.

[0034] Figure 4 SEM images of the distribution of gallium elements in the gallium-based liquid metal-based composite functional material in the embodiments of the present disclosure.

[0035] Figure 5 SEM images of the distribution of tin elements in the gallium-based liquid metal-based composite functional material in the embodiments of the present disclosure.

[0036] Figure 6 SEM images of the distribution of titanium elements in the gallium-based liquid metal-based composite functional material in the embodiments of the present disclosure.

[0037] Figure 7 SEM images of the distribution of nitrogen elements in the gallium-based liquid metal-based composite functional material in the embodiments of the present disclosure.

[0038] Figure 8 X-ray photoelectron spectroscopy of the gallium-based liquid metal-based composite functional material in the embodiments of the present disclosure.

[0039] In the figure: 1. Few-layer Ti 3 C 2 T x nanosheets; 2. Gallium-based liquid metal-based composite functional material. Detailed implementation manners

[0040] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. Like reference numerals in the figures denote like or similar structures, and thus their detailed descriptions will be omitted.

[0041] Although relative terms such as "upper" and "lower" are used in this specification to describe the relative relationship of one component of the icon to another component, these terms are used in this specification only for convenience, for example, according to the directions of the examples described in the accompanying drawings. It can be understood that if the device of the icon is turned upside down, the component described as "upper" will become the component "lower". When a structure is "on" another structure, it may mean that a structure is integrally formed on another structure, or that a structure is "directly" disposed on another structure, or that a structure is "indirectly" disposed on another structure through another structure.

[0042] The terms "a", "an", "the", and "said" are used to indicate the presence of one or more elements / components / etc.; the terms "comprising" and "having" are used to mean an open inclusion and refer to the possible existence of additional elements / components / etc. in addition to the listed elements / components / etc.

[0043] Gallium-based liquid metals have high metallic conductivity, thermal conductivity, and fluidity at room temperature. As a fluid, they have characteristics such as low viscosity, high surface tension, and deformability, enabling their wide application in fields such as stretchable electronics, wearable devices, soft robots, and reconfigurable circuit manufacturing. At the same time, different from traditional rigid materials (e.g., ultra-thin aluminum), the complex processes, poor flexibility, and electronic system breakdown caused by easy fatigue damage faced in the preparation of flexible electronics, the preparation method of gallium-based liquid metals is simple and has sufficient flexibility, mechanical stability, and reworkability, which can improve the durability of electronic devices. Therefore, by virtue of its conductivity and fluidity, it can be introduced as a self-healing material into the conductive silver paste system to enhance the crack self-healing ability of the silver paste and improve the fatigue life, service reliability, and stability of flexible electronic devices.

[0044] However, an insulating oxide layer is easily formed on the surface of gallium-based liquid metals, and the surface tension is relatively large, making it difficult to directly introduce them into the conductive silver paste system and prompt them to exert specific repair functions.

[0045] Based on this, embodiments of the present disclosure provide a conductive silver paste, which may include the following components: conductive silver powder, gallium-based liquid metal-based composite functional material, organic resin binder phase, curing agent, organic solvent, and additives; wherein, the weight parts of each component are: the weight part of the conductive silver powder is 55 parts - 75 parts; the weight part of the gallium-based liquid metal-based composite functional material is 5 parts - 25 parts; the weight part of the organic resin binder phase is 4 parts - 10 parts; the weight part of the curing agent is 1 part - 3 parts; the weight part of the organic solvent is 2 parts - 10 parts; the weight part of the additives is 0.1 part - 10 parts;

[0046] The gallium-based liquid metal-based composite functional material includes gallium-based liquid metal, conductive polymer, and few-layer two-dimensional material. The gallium-based liquid metal includes one or more of gallium, gallium-tin alloy, gallium-indium alloy, gallium-indium-tin alloy, or gallium-indium-tin-zinc alloy; the conductive polymer includes one or more of polypyrrole, polydopamine, or polyaniline; the few-layer two-dimensional material includes graphene or transition metal carbide.

[0047] The conductive silver powder includes silver nanowires, flaky metallic silver powder, and nano-spherical silver powder. The silver nanowires are synthesized by the polyol method.

[0048] The conductive silver paste of the present disclosure uses multi-dimensional micro-nano conductive silver powder (including silver nanowires with high aspect ratio, flaky metallic silver powder, and nano-spherical silver particles). Through multi-dimensional interfacial contact, a three-dimensional network conductive path is constructed inside the paste, effectively improving the conductive stability of the device during the flexible deformation process and ensuring the continuity of electrical connection. By incorporating a gallium-based liquid metal-based composite functional material, the application performance of the conductive silver paste in the field of flexible electronic printing is significantly improved, especially achieving a breakthrough in solving the problems of conductive layer failure and interfacial mismatch caused by mechanical deformations such as repeated bending / stretching. For example, the gallium-based liquid metal in the gallium-based liquid metal-based composite functional material (such as gallium, gallium-tin alloy, gallium-indium alloy, gallium-indium-tin alloy, or gallium-indium-tin-zinc alloy), as a self-flowing crack repair agent, its high conductivity and self-healing characteristics can quickly repair the cracks that occur after the silver paste layer is bent or stretched, thus greatly extending the service life of the conductive silver paste. The addition of conductive polymers (such as polypyrrole, polydopamine, or polyaniline) and few-layer two-dimensional materials (such as graphene or transition metal carbides) effectively improves the interfacial wettability between the liquid metal particles, the conductive silver powder, and the substrate. The high flexibility and good interfacial compatibility of these materials can enhance the matching of the rigid-flexible interface and contribute to improving the repair effect. At the same time, the conductive polymers and two-dimensional materials in the gallium-based liquid metal-based composite functional material can also form additional conductive channels, further enhancing the stability and reliability of the conductive network. In addition, in the present disclosure, by precisely controlling the weight parts of each component, the conductive silver paste can achieve good adhesion and processing performance while maintaining high conductivity. The synergistic effect of the organic resin binder phase, curing agent, and additives ensures that the silver paste can form a dense and uniform conductive layer after curing, making the finally obtained conductive silver paste not only have high bend resistance, strong adhesion, but also exhibit high reliability, effectively solving the problems of conductive layer failure and interfacial mismatch caused by mechanical deformations (such as cracks) in flexible electronic printing.

[0049] The following details each part of the conductive silver paste in the embodiments of the present disclosure and its specific details:

[0050] In an exemplary embodiment of the present disclosure, the conductive silver powder may include silver nanowires, flaky metallic silver powder, and nano-spherical silver powder. Among them, the silver nanowires can be synthesized by the polyol method. The length of the silver nanowires can be 20 μm - 50 μm. For example, the length can be 20 μm, 30 μm, 40 μm, or 50 μm. The diameter of the silver nanowires is 30 nm - 100 nm. For example, the diameter can be 30 nm, 50 nm, 70 nm, 90 nm, or 100 nm. Of course, the length and diameter of the silver nanowires can also be other values, which will not be listed one by one here. The particle size of the flaky metallic silver powder can be 2.0 μm - 8.0 μm. For example, the particle size can be 2.0 μm, 4.0 μm, 6.0 μm, or 8.0 μm. Of course, the particle size of the flaky metallic silver powder can also be other values, which will not be listed one by one here. The particle size of the nano-spherical silver powder can be 5 nm - 300 nm. For example, the particle size can be 5 nm, 50 nm, 100 nm, 200 nm, or 300 nm. Of course, the particle size of the nano-spherical silver powder can also be other values, which will not be listed one by one here.

[0051] In an exemplary embodiment of the present disclosure, the proportion of silver nanowires in the conductive silver powder can be 2% - 15%. For example, the proportion of silver nanowires can be 2%, 5%, 8%, 11%, 13%, or 15%. The proportion of nano-spherical silver powder in the conductive silver powder can be 2% - 30%. For example, the proportion of nano-spherical silver powder can be 2%, 5%, 10%, 20%, or 30%. The rest is flaky metallic silver powder.

[0052] The weight parts of the conductive silver powder can be 55 parts - 75 parts. For example, it can be 55 parts, 60 parts, 70 parts, or 75 parts. Of course, the conductive silver powder can also be other parts, which will not be listed one by one here.

[0053] The weight parts of the gallium-based liquid metal-based composite functional material can be 5 parts - 25 parts. For example, it can be 5 parts, 10 parts, 15 parts, 20 parts, or 25 parts. Of course, the weight parts of the gallium-based liquid metal-based composite functional material can also be other parts, which will not be listed one by one here.

[0054] In an exemplary embodiment of the present disclosure, the gallium-based liquid metal-based composite functional material may include gallium-based liquid metal, conductive polymer, and few-layer two-dimensional materials. Among them, the gallium-based liquid metal includes one or more of gallium, gallium-tin alloy, gallium-indium alloy, gallium-indium-tin alloy, or gallium-indium-tin-zinc alloy. The conductive polymer includes one or more of polypyrrole, polydopamine, or polyaniline. The few-layer two-dimensional materials include graphene or transition metal carbides.

[0055] In an exemplary embodiment of the present disclosure, the organic resin binder phase may be one or more of a hydroxyl-terminated polyester resin, an epoxy-modified acrylic resin, and a polyurethane resin. The weight parts of the organic resin binder phase may be 4 parts to 10 parts; for example, it may be 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, or 10 parts. Of course, it may also be other parts, which will not be listed one by one here.

[0056] In an exemplary embodiment of the present disclosure, the curing agent may be a blocked isocyanate curing agent. The weight parts of the curing agent may be 1 part to 3 parts; for example, it may be 1 part, 1.5 parts, 2 parts, 2.5 parts, or 3 parts. Of course, it may also be other parts, which will not be listed one by one here. The deblocking temperature of the curing agent may be 90°C to 130°C; for example, its deblocking temperature may be 90°C, 100°C, 110°C, 120°C, or 130°C.

[0057] In an exemplary embodiment of the present disclosure, the organic solvent may include two or more of xylene, alkylbenzene, butyl carbitol, terpineol, N-methylpyrrolidone, butyl carbitol acetate, and mixed binary esters. The weight parts of the organic solvent may be 2 parts to 10 parts; for example, it may be 2 parts, 4 parts, 6 parts, 8 parts, or 10 parts, or it may also be other parts, which will not be listed one by one here.

[0058] The additives may include modified urea, polysiloxane, and thixotropic agent. Among them, the addition amount of modified urea may be 0-3% of the total of all components in the conductive silver paste; the addition amount of polysiloxane may be 0%-5% of the total of all components in the conductive silver paste; the addition amount of thixotropic agent may be 0%-2% of the total of all components in the conductive silver paste. The weight parts of the additives may be 0.1 part to 10 parts; for example, it may be 0.1 part, 2 parts, 4 parts, 6 parts, 8 parts, or 10 parts. Of course, it may also be other parts, which will not be listed one by one here.

[0059] The present disclosure also provides a method for preparing a conductive silver paste, which is used to prepare the conductive silver paste in any of the above embodiments, as Figure 1 shown, the preparation method includes step S110-step S160, wherein:

[0060] Step S110, preparing a gallium-based liquid metal-based composite functional material, the gallium-based liquid metal-based composite functional material includes gallium-based liquid metal, a conductive polymer, and few-layer two-dimensional materials. The gallium-based liquid metal includes one or more of gallium, gallium-tin alloy, gallium-indium alloy, gallium-indium-tin alloy, or gallium-indium-tin-zinc alloy; the conductive polymer includes one or more of polypyrrole, polydopamine, or polyaniline; the few-layer two-dimensional materials include graphene or transition metal carbides;

[0061] Step S120, preparing a silver nanowire dispersion by a polyol synthesis method;

[0062] Step S130: Weigh the organic resin binder phase and organic solvent by weight parts and add them to the silver nanowire dispersion liquid, and stir until it reaches a homogeneous state to form an organic carrier.

[0063] Step S140: Add the gallium-based liquid metal-based composite functional material, flaky metallic silver powder, and nano-spherical silver powder to the organic carrier in small amounts and multiple times, and continue to stir in a planetary mixer to prepare a homogeneous slurry.

[0064] Step S150: Add additives and curing agents to the homogeneous slurry, and continue to stir to adjust the viscosity and thixotropic properties of the slurry to form an initial conductive silver paste.

[0065] Step S160: Adjust the fineness of the initial conductive silver paste through a three-roll grinder, and after double filtration, obtain the target conductive silver paste.

[0066] In the preparation method of the conductive silver paste of the present disclosure, by incorporating the gallium-based liquid metal-based composite functional material, the application performance of the conductive silver paste in the field of flexible electronic printing is significantly improved. Especially, a breakthrough has been made in solving the problems of conductive layer failure and interface mismatch caused by mechanical deformations such as repeated bending / stretching. For example, the gallium-based liquid metal (such as gallium, gallium-tin alloy, gallium-indium alloy, gallium-indium-tin alloy, or gallium-indium-tin-zinc alloy) in the gallium-based liquid metal-based composite functional material acts as a self-flowing crack repair agent. Its high conductivity and self-healing characteristics can quickly repair the cracks that appear after the silver paste layer is bent or stretched, thus greatly extending the service life of the conductive silver paste. The addition of conductive polymers (such as polypyrrole, polydopamine, or polyaniline) and few-layer two-dimensional materials (such as graphene or transition metal carbides) effectively improves the interfacial wettability between the liquid metal particles, conductive silver powder, and the substrate. The high flexibility and good interfacial compatibility of these materials can enhance the matching of the rigid-flexible interface and contribute to improving the repair effect. At the same time, the conductive polymers and two-dimensional materials in the gallium-based liquid metal-based composite functional material can also form additional conductive channels, which helps to enhance the stability and reliability of the conductive network. In addition, in the present disclosure, by precisely controlling the weight parts of each component, the conductive silver paste can achieve good adhesion and processing performance while maintaining high conductivity. The synergistic effect of the organic resin binder phase, curing agent, and additives ensures that the silver paste can form a dense and uniform conductive layer after curing. The finally obtained conductive silver paste not only has high bend resistance and strong adhesion, but also shows high reliability, effectively solving the problems of conductive layer failure and interface mismatch caused by mechanical deformations (such as cracks) in flexible electronic printing.

[0067] In an exemplary embodiment of the present disclosure, the preparation of the gallium-based liquid metal-based composite functional material (i.e., step S110) may include steps S210 - S250, where:

[0068] Step S210: Weigh gallium-based liquid metal by weight parts and add it to a special ultrasonic crushing vessel containing 10 ml of an aqueous solution of sodium dodecylbenzenesulfonate, and perform ultrasonic crushing at a constant temperature of 20 °C to form suspension one.

[0069] In some embodiments of the present disclosure, the gallium-based liquid metal can be one of gallium indium, gallium tin, gallium indium tin, and gallium indium tin zinc. Sodium dodecylbenzenesulfonate can be used as a dopant and stabilizer, and the addition amounts of sodium dodecylbenzenesulfonate and polypyrrole to be added later are added according to the molar ratio of sodium dodecylbenzenesulfonate / polypyrrole of 0.2 - 0.8:1.

[0070] In some embodiments of the present disclosure, the duration of ultrasonic crushing can be 5 min - 10 min. For example, the duration of ultrasonic crushing can be 5 min, 6 min, 7 min, 8 min, 9 min, or 10 min; of course, the duration of ultrasonic crushing can also be other durations, which will not be listed one by one here. The ultrasonic amplitude of the ultrasonic crushing process is: 60%; the ultrasonic time interval is 2 s or 3 s.

[0071] Step S220: Weigh Ti 3 AlC 2 powder and lithium fluoride powder and add them to a hydrochloric acid solution, and obtain a deep green aqueous dispersion of few-layer Ti 3 C 2 T x nanosheets 1 by using the lithium fluoride-hydrochloric acid etching process and the ultrasonic exfoliation process as suspension two. In the present disclosure, the prepared few-layer Ti 3 C 2 T x The scanning electron microscope image of nanosheets 1 is as Figure 2 shown.

[0072] In some embodiments of the present disclosure, the hydrochloric acid in the lithium fluoride-hydrochloric acid etching process can be a 6 mol / L hydrochloric acid solution. During the ultrasonic exfoliation process, the beaker can be placed in an ice bath to reduce the ultrasonic temperature and Ar can be introduced to prevent Ti 3 C 2 T x from oxidizing.

[0073] Step S230: Mix suspension one and suspension two by weight parts and ultrasonically mix for 10 min, and based on the electrostatic repulsion between negatively charged Ti 3 C 2 T x and the liquid metal, obtain a uniform mixed solution of gallium-based liquid metal - two-dimensional material.

[0074] Step S240: Add the reactant conductive polymer monomer - polypyrrole into the mixed solution, stir for 2 min - 5 min, add the oxidant ferric chloride hexahydrate, and obtain a black suspension after fully reacting for 1 h.

[0075] In some embodiments of the present disclosure, the addition amount of ferric chloride hexahydrate (i.e., FeCl 3 ·6H 2 O) is added in a ratio of 1:1 in terms of the molar ratio of oxidant / polypyrrole.

[0076] Step S250: After washing the black suspension multiple times, performing vacuum filtration, and vacuum drying, a gallium-based liquid metal-based composite functional material is obtained.

[0077] In some embodiments of the present disclosure, the multiple washings in step S250 include; washing 3 times with deionized water and ethanol respectively. In the present disclosure, the scanning electron microscope image of the gallium-based liquid metal-based composite functional material 2 obtained after drying is as Figure 3 shown. Meanwhile, the scanning electron microscope images of the important constituent elements (for example, gallium (Ga), tin (Sn), titanium (Ti), and nitrogen (N)) in the gallium-based liquid metal-based composite functional material 2 are as Figures 4 - 7 shown. It should be noted that Figures 4 - 7 the colored area in is the element distribution area corresponding to this figure. The X-ray photoelectron spectrum of the gallium-based liquid metal-based composite functional material 2 is as Figure 8 shown.

[0078] The preparation method of the liquid metal-based composite functional material of the present disclosure is simple. A highly conductive and highly flexible self-healing agent is successfully obtained through electrostatic self-assembly, and it has good interfacial wettability and adhesiveness with silver paste and the substrate, ensuring its application reliability in the field of flexible electronics.

[0079] In an exemplary embodiment of the present disclosure, the preparation of the silver nanowire dispersion by the polyol synthesis method (i.e., step S120) may include: weighing 0.3 parts of sodium chloride, 1.2 parts of silver nitrate, and 1.2 parts of polyvinylpyrrolidone by weight, and adding the weighed sodium chloride, silver nitrate, and polyvinylpyrrolidone into a beaker in a reaction kettle containing ethylene glycol, and preparing the silver nanowire dispersion by microwave reaction at 140°C. The method for preparing the silver nanowire dispersion is the polyol method. After the reaction, the beaker can be quickly placed in ice for cooling, and after adding acetone and centrifuging multiple times, the silver nanowire dispersion is obtained.

[0080] In step S130, the organic resin binder phase and the organic solvent are weighed by weight parts and added to the prepared silver nanowire dispersion liquid, and are stirred at a constant temperature in a high-speed dispersing ax until a homogeneous state is achieved. During this process, the rotation speed of the high-speed dispersing ax is 1000 revolutions per minute - 5000 revolutions per minute, the dispersion temperature is controlled at 55°C - 85°C, and the stirring and mixing time is 10 minutes - 30 minutes; the revolution speed of the mixer is 1000 revolutions per minute - 2200 revolutions per minute, and the rotation speed of the mixer is 700 revolutions per minute - 1400 revolutions per minute.

[0081] In step S160, the distance between adjacent rollers in the three-roll grinder is 2μm - 20μm, and the rotation speed of the three-roll grinder is 300 revolutions per minute - 500 revolutions per minute. The curing temperature of the target conductive silver paste prepared in the present disclosure is 90°C - 130°C, and the curing time is 10 min - 20 min.

[0082] Next, the preparation method of the conductive silver paste described in the exemplary embodiments of the present disclosure will be further explained and illustrated in conjunction with specific embodiments.

[0083] Example 1

[0084] The raw materials include the following components by weight parts: 25 parts of gallium-based liquid metal-based composite functional material, 55 parts of conductive silver powder, 4 parts of organic resin binder phase, 1 part of blocked isocyanate curing agent, 5 parts of organic solvent, and 10 parts of auxiliary agent. Among them, the gallium-based liquid metal-based composite functional material is prepared by self-assembly of gallium-based liquid metal, polypyrrole, and transition metal carbide. The conductive silver powder includes 30 parts of flaky metallic silver powder with D50 (D50 is the particle size corresponding to when the cumulative particle size distribution percentage of the sample reaches 50%) of 7.5μm; 15 parts of spherical ultrafine silver powder with D50 of 200nm and 10 parts of self-made silver nanowires (length 30μm, diameter 50nm); the organic resin binder phase includes 1 part of hydroxyl-terminated polyester resin and 3 parts of epoxy group-modified acrylic resin; the blocked curing agent is HDI (aliphatic polyisocyanate), and the deblocking temperature is 90°C; the organic solvent includes 2 parts of butyl carbitol, 1 part of xylene, and 2 parts of mixed binary ester; the auxiliary agent includes 3 parts of modified urea, 5 parts of polysiloxane, and 2 parts of thixotropic agent.

[0085] The specific preparation process is as follows:

[0086] Preparation of gallium-based liquid metal-based composite functional material: 200mg of gallium-tin alloy liquid metal and 10mL of sodium dodecylbenzenesulfonate (the molar ratio of sodium dodecylbenzenesulfonate / polypyrrole is 0.5:1) are added to a special ultrasonic crushing vessel (such as a flask) filled with deionized water, and are ultrasonically crushed at a constant temperature of 20°C for 5 min to obtain a gallium-tin nanoparticle dispersion liquid (i.e., suspension one), and argon can be used to remove the air in the flask.

[0087] Weigh Ti by weight parts 3 AlC 2 powders and lithium fluoride powder are added to hydrochloric acid solution, and few-layer Ti 3 C 2 T x nano-sheet 1's dispersed aqueous solution (i.e., suspension two); Mix suspension one and suspension two by weight parts and ultrasonicate for 10 min to obtain mixed solution one; Add 40 μL of polypyrrole to mixed solution one to obtain mixed solution two, and stir for 5 min; According to the molar ratio of oxidant to polypyrrole (i.e., FeCl 3 ·6H 2 O / Py) of 1:1, dissolve the corresponding mass of oxidant in 2 mL of deionized water respectively, and then quickly drop it into mixed solution two. After fully reacting for 1 h, a black flocculent mixed solution is obtained; After washing, vacuum filtration and vacuum drying for many times, a composite functional material based on gallium-based liquid metal is obtained.

[0088] Preparation of silver nanowires: Through microwave-assisted heating technology, using 200 mg of silver nitrate as the silver source, 800 mg of polyvinylpyrrolidone as the stabilizer and protective agent, and 200 mg of sodium chloride as the controller, add them to an appropriate amount of ethylene glycol and carry out microwave reaction (temperature 140 °C, frequency 400 W, time 4 min) to prepare a high-purity silver nanowire dispersion. After the reaction is completed, cool the suspension in ice cubes, and add it to a centrifuge tube containing acetone and centrifuge at high speed (rotation speed: 2000 rpm) to retain the silver nanowires in the lower layer until the final high-concentration silver nanowire dispersion is obtained.

[0089] Preparation of organic carrier: Take 1 part of hydroxyl-terminated polyester resin, 3 parts of epoxy-modified acrylic resin and 5 parts of organic solvent (2 parts of butyl carbitol, 1 part of xylene and 2 parts of mixed binary ester) by weight parts and add them to the above high-concentration silver nanowire dispersion, and mix and stir at a rotation speed of 1000 revolutions per minute in a high-speed dispersion kettle at 80 °C until a homogeneous state is reached.

[0090] Preparation of Conductive Silver Paste: Add 25 parts of gallium-based liquid metal-based composite functional materials, 30 parts of flaky silver powder, and 15 parts of nano-spherical silver powder into a thermostatic high-speed dispersion kettle containing an organic carrier in small amounts and multiple times. After high-speed stirring for 20 minutes, transfer it to a planetary stirring and defoaming machine and continue stirring for 5 minutes. Then add 3 parts of modified urea, 5 parts of polysiloxane, and 2 parts of thixotropic agent. After defoaming and stirring for 10 minutes, roll the mixed slurry through a three-roll mill. The three rolls in the three-roll mill can be defined as the first roll body, the second roll body, and the third roll body. First, adjust the distance between the first roll body and the second roll body to 20 μm, and at the same time adjust the distance between the second roll body and the third roll body to 15 μm to conduct preliminary rolling on the mixed slurry. Then adjust the distance between the first roll body and the second roll body to 15 μm, and at the same time adjust the distance between the second roll body and the third roll body to 7 μm to conduct secondary rolling on the preliminarily rolled mixed slurry. Then adjust the distance between the first roll body and the second roll body to 7 μm, and at the same time adjust the distance between the second roll body and the third roll body to 3 μm to conduct tertiary rolling on the secondarily rolled mixed slurry to make the fineness of the slurry less than 5 μm. Finally, after passing through a double filtration system of 500 mesh - 300 mesh, the conductive silver paste is prepared.

[0091] The specific implementation processes of Example 2 - Example 5 and Comparative Example 1 are similar to that of Example 1, with the only difference being the components or the weight parts of the components used. Therefore, the specific implementation processes of Example 2 - Example 5 and Comparative Example 1 will not be elaborated here. The specific components and weight parts of Example 2 - Example 5 and Comparative Example 1 are shown in Table 1 below.

[0092] Table 1 Specific Components and Weight Parts of Example 2 - Example 5 and Comparative Example 1

[0093]

[0094] In this disclosure, the performance of the conductive silver paste prepared in each example and comparative example was also tested. Specifically, the prepared conductive silver paste in each example and comparative example can be screen-printed on a polyethylene terephthalate film through a 350-mesh screen (screen printing area: 1×1 cm). Place the printed sample in a constant-temperature drying oven at 90°C and dry it for 20 minutes, then take it out for performance testing. The performance test results of all examples and comparative examples are shown in Table 2.

[0095] Table 2 Performance Parameters of the Samples Prepared in Each Example and Comparative Example

[0096]

[0097] It should be noted that in the present disclosure, the bending resistance of the conductive silver paste is mainly affected by the weight parts of the conductive silver powder and the gallium-based liquid metal-based composite functional material, and the influence of other components on the bending resistance of the conductive silver paste is not obvious.

[0098] By comparing Examples 1-5 with Comparative Example 1, it can be seen that the bending resistance of the conductive silver paste using the gallium-based liquid metal-based composite functional material as the conductive functional phase is significantly better than that of the conductive silver paste not using the gallium-based liquid metal-based composite functional material as the conductive functional phase. This is because: the gallium-based liquid metal-based composite functional material in the present disclosure selects a graphene-like layered 2D material (Ti 3 C 2 T x ) as the framework material, which has the characteristics of high conductivity, high flexibility and large specific surface area. It can realize the effective adsorption and in-situ polymerization self-assembly of pyrrole monomers by virtue of its electronegativity and hydrogen bond action, so as to prepare a highly flexible "liquid metal-polypyrrole-Ti 3 C 2 T x " composite material, improve the printing pattern resolution of the conductive silver paste based on liquid metal, and at the same time give full play to its crack repair ability in the conductive silver paste, thereby greatly improving the bending resistance of the conductive silver paste.

[0099] At the same time, the conductive silver paste prepared in the present disclosure uses the gallium-based liquid metal-based composite functional material and the multi-dimensional micro-nano hybrid conductive silver powder as the conductive functional phase together, so that the highly flaked sheet metal silver powder, nano-spherical silver powder, silver nanowires and the liquid metal-based composite functional material are in direct contact to form a smooth three-dimensional conductive network, which can effectively reduce the resistivity of the conductive silver paste, and show a small resistance change rate after bending, with excellent bending resistance; by adjusting the ratio of the conductive functional phase, as the proportion of the gallium-based liquid metal-based composite functional material increases, the bending resistance of the conductive silver paste generally shows an increasing trend. At the same time, based on the formula analysis of the examples and comparative examples, the optimal ratios of the conductive silver powder, the gallium-based liquid metal-based composite functional material, the organic resin binder phase, the curing agent, the additives and the organic solvent can be obtained. In summary, the conductive silver paste prepared in the present disclosure has high reliability, good printing adaptability on flexible substrates, and after rapid curing under the low-temperature condition of 90°C, the conductive silver paste has excellent adhesion, low sheet resistance and high bending resistance.

[0100] Other embodiments of the present disclosure will be readily apparent to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include known common general knowledge or conventional technical means in the technical field not disclosed in the present disclosure. The specification and examples are only to be considered as exemplary, and the true scope and spirit of the present disclosure are pointed out by the appended claims.

Claims

1. A conductive silver paste, characterized in that: The conductive silver paste comprises the following components: conductive silver powder, gallium-based liquid metal-based composite functional material, organic resin bonding phase, curing agent, organic solvent and auxiliary agent, wherein: the weight portion of the conductive silver powder is 55-75 parts; the weight portion of the gallium-based liquid metal-based composite functional material is 5-25 parts; the weight portion of the organic resin bonding phase is 4-10 parts; the weight portion of the curing agent is 1-3 parts; the weight portion of the organic solvent is 2-10 parts; the weight portion of the auxiliary agent is 0.1-10 parts; The gallium-based liquid metal-based composite functional material includes gallium-based liquid metal, conductive polymer and few-layer two-dimensional material, wherein the gallium-based liquid metal includes one or more of gallium, gallium-tin alloy, gallium-indium alloy, gallium-indium-tin alloy or gallium-indium-tin-zinc alloy; the conductive polymer includes one or more of polypyrrole, polydopamine or polyaniline; the few-layer two-dimensional material includes graphene or transition metal carbide.

2. The conductive silver paste according to claim 1, characterized in that: The conductive silver powder comprises silver nanowires, flaky metal silver powder and nano-spherical silver powder, and the silver nanowires are synthesized by a polyol method.

3. The conductive silver paste according to claim 1, characterized in that: The organic resin bonding phase is one or more of a hydroxyl-terminated polyester resin, an epoxy-modified acrylic resin and a polyurethane resin.

4. The conductive silver paste according to claim 1, characterized in that: The curing agent is a blocked isocyanate curing agent.

5. The conductive silver paste according to claim 1, characterized in that: The organic solvent includes two or more of xylene, alkylbenzene, butyl carbitol, terpineol, N-methylpyrrolidone, butyl carbitol acetate and mixed dibasic esters.

6. The conductive silver paste according to claim 1, characterized in that: The auxiliary agent includes two or three of modified urea, polysiloxane and thixotropic agent.

7. A method for preparing a conductive silver paste, for preparing the conductive silver paste according to any one of claims 1 to 6, characterized in that: The preparation method comprises: Prepare a gallium-based liquid metal-based composite functional material, wherein the gallium-based liquid metal-based composite functional material comprises a gallium-based liquid metal, a conductive polymer and a few-layer two-dimensional material, wherein the gallium-based liquid metal comprises one or more of gallium, gallium-tin alloy, gallium-indium alloy, gallium-indium-tin alloy or gallium-indium-tin-zinc alloy; the conductive polymer comprises one or more of polypyrrole, polydopamine or polyaniline; the few-layer two-dimensional material comprises graphene or transition metal carbide; The silver nanowire dispersion was prepared by polyol synthesis method; Weighing an organic resin binder phase and an organic solvent by weight, adding them to the silver nanowire dispersion, and stirring until a homogeneous state to form an organic carrier; Adding the gallium-based liquid metal-based composite functional material, flaky metal silver powder and nano-spherical silver powder into the organic carrier in small amounts and repeatedly, and continuing to stir in a planetary mixer to prepare a uniform slurry; Adding an auxiliary agent and a curing agent to the uniform slurry, and continuing stirring to adjust the viscosity and thixotropic properties of the slurry to form an initial conductive silver slurry; The fineness of the initial conductive silver paste is adjusted by a three-roll mill, and the target conductive silver paste is obtained after double-layer filtration.

8. The preparation method according to claim 7, characterized in that: The method for preparing the gallium-based liquid metal-based composite functional material comprises: Weigh gallium-based liquid metal by weight and add it into a special ultrasonic crushing vessel containing 10 ml of sodium dodecylbenzene sulfonate aqueous solution, and crush it by ultrasonic at a constant temperature of 20° C. to form a suspension 1; Ti3AlC2 powder and lithium fluoride powder were weighed by weight and added into hydrochloric acid solution. The dark green few-layer Ti3C2T x A dispersed aqueous solution of nanosheets is used as suspension II; The suspension 1 and the suspension 2 were mixed by weight and ultrasonicated for 10 minutes. x The electrostatic repulsion between the liquid metal and the gallium-based liquid metal results in a uniform mixed solution of the two-dimensional material. Adding the reactant conductive polymer monomer-polypyrrole to the mixed solution, mixing and stirring, adding the oxidant ferric chloride hexahydrate, and fully reacting for 1 hour to obtain a black suspension; The black suspension is washed multiple times, vacuum filtered and vacuum dried to obtain a gallium-based liquid metal-based composite functional material.

9. The preparation method according to claim 7, characterized in that: The polyol synthesis method is used to prepare the silver nanowire dispersion, comprising: 0.3 parts of sodium chloride, 1.2 parts of silver nitrate and 1.2 parts of polyvinyl pyrrolidone were added into a reaction kettle containing ethylene glycol, and a silver nanowire dispersion was prepared by microwave reaction at 140°C.

10. The preparation method according to claim 7, characterized in that: The curing agent is a blocked isocyanate curing agent; the organic solvent includes two or more of xylene, alkylbenzene, butyl carbitol, terpineol, N-methylpyrrolidone, butyl carbitol acetate and mixed dibasic esters; the auxiliary agent includes two or three of modified urea, polysiloxane and thixotropic agent; the organic resin bonding phase is one or more of hydroxyl-terminated polyester resin, epoxy-modified acrylic resin and polyurethane resin.

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