Conductive paste, its preparation method and electronic devices

Abstract

This invention relates to a conductive paste, its preparation method, and electronic devices, belonging to the technical field of conductive pastes. A conductive paste, by weight, comprises the following components: 30-80 parts of silver-coated copper powder, 0-40 parts of silver powder, 4-12 parts of resin, 8-55 parts of solvent, 0.1-5 parts of functional components, and 0-6 parts of additives; wherein the functional components include at least one of a dispersant, a fluorinated wax powder, or an antioxidant. This invention can improve the antioxidant capacity of silver-coated copper powder, maximally suppress its high-temperature oxidation problem, and improve the conductivity of the conductive paste, showing good application prospects.

Description

Technical Field

[0001] This invention belongs to the field of conductive paste technology, and particularly relates to a conductive paste, its preparation method and electronic device. Background Technology

[0002] In recent years, with the rapid development of electronic information technology, the market's functional requirements for conductive pastes have become increasingly stringent. Currently, the conductive particles used in conductive pastes (conductive coatings) and conductive inks are mainly micron-sized highly conductive metals, such as silver, copper, nickel, and aluminum powders, or graphite and carbon black powders. Among all metals, silver has the best conductivity, and pure silver powder currently dominates the market as a conductive particle. This is because silver has excellent oxidation resistance, and silver oxides are also conductive. However, the high price of silver limits the use of this type of conductive material to some extent. To reduce costs, conductive particles can also be made from copper powder, nickel powder, and aluminum powder. However, compared to silver, these materials have lower conductivity, and copper and aluminum are more prone to oxidation, forming an insulating oxide layer. Although nickel is not easily oxidized, its high hardness makes it difficult to process. In air, aluminum easily oxidizes to form aluminum oxide. The insulating aluminum oxide layer limits the use of aluminum powder in low-temperature processes. To balance cost and material conductivity, silver-coated copper powder can be used as a conductive particle.

[0003] Currently, the silver-coated copper powder prepared using commonly used methods in the industry has a low silver content, and the silver coating on the surface is dendritic, resulting in an uneven and incomplete coating layer. Furthermore, the copper is exposed to air and is easily oxidized, leading to poor conductivity and low heat resistance. Therefore, when existing silver-coated copper powder is used in conductive pastes, the conductivity of the paste containing it is reduced due to the powder's susceptibility to oxidation and low heat resistance, thus limiting its application. Summary of the Invention

[0004] In view of the aforementioned problems, the present invention aims to at least partially solve one of the technical problems in the related art. To this end, the present invention provides a conductive paste, its preparation method, and an electronic device, which can improve the oxidation resistance of silver-coated copper powder and enhance the conductivity of the conductive paste.

[0005] As one aspect of the present invention, a conductive paste is disclosed, comprising, by weight, the following components:

[0006] The mixture contains 30-80 parts of silver-coated copper powder, 0-40 parts of silver powder, 4-12 parts of resin, 8-55 parts of solvent, 0.1-5 parts of functional components, and 0-6 parts of additives.

[0007] The functional components include at least one of a dispersant, a fluorinated wax powder, or an antioxidant.

[0008] In some of these embodiments, the functional components include dispersants, fluorinated wax powders, and antioxidants;

[0009] Preferably, the conductive paste comprises, by weight, the following components: 30-70 parts of silver-coated copper powder, 0-30 parts of silver powder, 5-10 parts of resin, 10-50 parts of solvent, 0.05-0.5 parts of dispersant, 0.05-0.5 parts of fluorinated wax powder, 0.05-0.5 parts of antioxidant, and 0.01-5 parts of additives;

[0010] Preferably, the conductive paste comprises the following components by weight: 40-60 parts of silver-coated copper powder, 1-20 parts of silver powder, 6-8 parts of resin, 20-40 parts of solvent, 0.05-0.35 parts of dispersant, 0.1-0.5 parts of fluorinated wax powder, 0.1-0.5 parts of antioxidant, and 0.1-3 parts of additives.

[0011] In some embodiments, the morphology of the silver-coated copper powder and the silver powder includes at least one of flake, spherical, linear, or dendritic shapes;

[0012] And / or, the silver content in the silver-coated copper powder is 10% to 50% by mass percentage.

[0013] In some embodiments, the silver-coated copper powder has a particle size distribution of D50 of 6.0–10.0 μm and a bulk density of 0.5–1.5 g / cm³. 3 The tap density is 1.0–3.5 g / cm³. 3 ;

[0014] And / or, the silver powder has a particle size distribution of D50 of 6.0–10.0 μm and a bulk density of 0.5–1.5 g / cm³. 3 The tap density is 1.0–3.5 g / cm³. 3 .

[0015] In some of these embodiments, the resin is a thermoplastic resin;

[0016] Preferably, the thermoplastic resin includes at least one of polyurethane resin, vinyl chloride resin, polyacrylate, EVA resin, PVB resin, polybutadiene resin, or polyester resin.

[0017] In some embodiments, the solvent includes at least one selected from cyclohexanone, isophorone, ethylene glycol methyl ether, dipropylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol butyl ether, propylene glycol methyl ether acetate, diethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, dimethyl adipate, diethyl adipate, DBE, diester, diol ester, N-methylpyrrolidone, or terpineol;

[0018] And / or, the additives include at least one of leveling agents, thickeners, or rheology modifiers.

[0019] In some embodiments, the dispersant is an acidic dispersant;

[0020] And / or, the acid value of the acidic dispersant is (100-200) mg KOH / g;

[0021] And / or, the fluorinated wax powder includes one or more of polytetrafluoroethylene wax powder or polytetrafluoroethylene modified polyethylene wax powder;

[0022] And / or, the antioxidant includes one or more of hindered phenolic antioxidants, phosphite antioxidants, or sulfur-containing antioxidants.

[0023] As another aspect of the present invention, a method for preparing the above-mentioned conductive paste is provided, the method comprising the following steps:

[0024] The formula-formulated amounts of silver-coated copper powder, silver powder, resin, solvent, functional components, and additives are stirred, mixed, and ground to obtain a conductive paste.

[0025] In some of these embodiments, the method includes the following steps:

[0026] After the silver powder, a portion of the resin and the solvent are mixed evenly, they are ground using a three-roll mill to obtain the first conductive slurry.

[0027] The silver-coated copper powder, dispersant, fluorinated wax powder, antioxidant, remaining resin and remaining solvent are mixed evenly and then ground using a three-roll mill to obtain a second conductive slurry; the second conductive slurry is then mixed evenly with the first conductive slurry to obtain the conductive slurry.

[0028] Preferably, after the silver powder, a portion of the resin and the solvent are mixed evenly, the mixture is ground using a three-roll mill until the fineness is less than or equal to 10 μm to obtain the first conductive slurry;

[0029] Preferably, during the preparation of the second conductive slurry, the spacing between the rollers in the three-roll mill is 2 to 4 times the particle size of the silver-coated copper powder.

[0030] As another aspect of the present invention, there is a device comprising a substrate and a conductive structure located on the substrate, the conductive structure being made of a conductive paste comprising, or a conductive paste obtained by the aforementioned preparation method.

[0031] Compared with the prior art, the technical solution of this application has at least the following beneficial effects:

[0032] The conductive paste provided in this application includes silver-coated copper powder, resin, solvent, functional components, optional silver powder, and optional additives. "Optional" means that it may or may not be added. The functional components include one or more of dispersants, fluorinated wax powder, or antioxidants. Therefore, by adding functional additives, the antioxidant capacity of the silver-coated copper powder can be improved, alleviating the problem of increased resistivity caused by copper oxidation during use, and maximizing the suppression of oxidation.

[0033] The method of this invention is simple, easy to operate, and easy to scale up for production. Furthermore, the conductive paste prepared has good conductivity, which helps to improve the conductivity, service life, and reliability of electronic devices containing the conductive paste, and has good application prospects.

[0034] Additional aspects and advantages of the embodiments of this application will be described, shown, or illustrated in part by way of implementation of the embodiments of this application in the following description. Attached Figure Description

[0035] The accompanying drawings are provided for illustrative purposes only, and the proportions of the parts in the drawings may not be consistent with the actual product.

[0036] Figure 1 This is a comparative schematic diagram showing the oxidation and corrosion resistance of electronic devices containing conductive paste provided in the embodiments and comparative examples of the present invention. Detailed Implementation

[0037] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0038] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0039] In this document, unless otherwise stated, percentages, proportions, or parts are all expressed by mass. "Parts by mass" refers to the basic unit of measurement for the mass ratio of multiple components; one part can represent any unit mass. Unless otherwise specified, percentages (%) refer to percentages by mass relative to the composition.

[0040] As mentioned in the background section, the silver-coated copper powder prepared in related technologies is easily oxidized, resulting in poor conductivity and low heat resistance. The industry primarily focuses on modifying and optimizing the preparation of silver-coated copper powder, neglecting optimization and improvement from the perspective of its application. Based at least on the above insights into existing technologies, and considering the crucial impact of silver-coated copper powder on the performance of conductive pastes, this application optimizes the formulation and preparation method of conductive pastes containing silver-coated copper powder from the perspective of its application, aiming to minimize its high-temperature oxidation problem. A detailed description of the technical solution follows.

[0041] In some embodiments, a conductive paste is provided, comprising, by weight, the following components: 30-80 parts of silver-coated copper powder, 0-40 parts of silver powder, 4-12 parts of resin, 8-55 parts of solvent, 0.1-5 parts of functional component, and 0-6 parts of additive;

[0042] The functional component includes, but is not limited to, at least one of a dispersant, a fluorinated wax powder, or an antioxidant. For example, the functional component can be a dispersant, a fluorinated wax powder, an antioxidant, a dispersant and a fluorinated wax powder, a dispersant and an antioxidant, or a fluorinated wax powder and an antioxidant, or a dispersant, a fluorinated wax powder, and an antioxidant, or other functional components with the same or similar functions.

[0043] The conductive paste of this embodiment, after being mixed according to the above formula ratio, can form a uniform composite conductive silver-copper paste through processes such as high-speed dispersion and three-roll milling. Furthermore, the preparation method of this silver-coated copper conductive paste includes a step of dispersing silver-coated copper powder in organic components. Specific functional components are added during the dispersion step. The prepared silver-coated copper conductive paste exhibits good conductivity and excellent oxidation resistance, and can be widely used in fields such as RFID, membrane switches, and electrode wires.

[0044] The conductive paste of this application addresses the technical problem of increased resistivity in existing silver-coated copper powder due to copper oxidation during use. Specifically, on one hand, functional components are added to the formulation. These functional components, such as fluorinated wax powder (fluorinated additives), work synergistically with antioxidants to improve the oxidation resistance of the silver-coated copper powder. In particular, the fluorinated wax powder and antioxidants can respectively enhance the oxidation resistance of the surface and interior of the silver-coated copper powder. Furthermore, using specific dispersants, such as acidic dispersants, for the silver-coated copper powder can improve grinding efficiency and reduce damage to the silver-coated copper plating. On the other hand, employing differentiated preparation processes during the preparation of the silver-coated copper powder or the conductive paste can further improve its conductivity.

[0045] It should be noted that the present invention does not restrict the source of the components in the conductive paste, such as silver-coated copper powder, silver powder, resin, solvent, functional components, etc., which can be prepared by themselves or obtained by commercial purchase.

[0046] To achieve better coordination among the components of the conductive paste and to better suppress the oxidation of the silver-coated copper powder, thereby improving the conductivity of the conductive paste, the conductive paste comprises 30 to 80 parts of silver-coated copper powder by weight. Typical but non-limiting examples include 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, and 80 parts, as well as any value within any range of these values. The silver-coated copper powder, as the core component for conductivity, generally accounts for approximately 30% to 80% or 30% to 70% of the paste. If the content of silver-coated copper powder is too low, the conductivity function will be difficult to achieve; if the content is too high, it may affect other properties of the conductive paste and increase raw material costs. Therefore, by adding 30 to 80 parts of silver-coated copper powder, the overall performance of the conductive paste can be satisfied while ensuring conductivity and reducing costs.

[0047] The conductive paste comprises 0 to 40 parts by weight of silver powder. Typical, but not limiting, values ​​can be 0, 2, 5, 8, 10, 15, 20, 25, 30, 35, 40 parts, or any value within any range of two of these values. In this embodiment, the silver powder content is 0 to 40 parts, meaning that silver powder may or may not be added to the conductive paste. When silver powder is added, its content should be controlled to be within 40 parts (or within 40%). The combination of a small amount of silver powder with silver-coated copper powder helps to improve the conductivity of the conductive paste while reducing costs.

[0048] The conductive paste comprises 4 to 12 parts by weight of resin, typically but not limitingly, for example, 4, 5, 6, 7, 8, 9, 10, 11, 12 parts, and any value within the range formed by any two of these points. Adding an appropriate amount of resin to the conductive paste helps improve its flexibility or tensile properties, while adding too much resin may result in excessive resistance, making it difficult to apply. Therefore, it is necessary to control the resin content within the aforementioned range.

[0049] The conductive paste contains 8 to 55 parts solvent by weight. Typical, but not limiting, values ​​can be 8, 10, 12, 14, 15, 18, 20, 25, 30, 35, 40, 45, 50, 55, or any value within any range of two of these values. In the conductive paste, the solvent is generally used to adjust viscosity and printability. The amount added is typically 10% to 50% or 8% to 55%. If the amount of solvent added is too small, printability cannot be guaranteed; if the amount of solvent added is too large, the effective component content will be too low, and conductivity and other functions will be difficult to achieve.

[0050] The conductive paste comprises 0.1 to 5 parts by weight of functional components, typically but not limitingly, such as 0.1, 0.2, 0.5, 1, 1.2, 1.5, 2, 3, 4, 4.5, 5 parts, and any value within any range of any two of these values. The addition of functional components to this conductive paste can alleviate the problem of increased resistivity of silver-coated copper powder due to copper oxidation during use. If the content of the functional component is too low, the function of improving the oxidation resistance of the silver-coated copper powder cannot be guaranteed; if the content of the functional component is too high, the main effective component is reduced, and the cost increases.

[0051] The conductive paste contains 0 to 6 parts by weight of additives. Typical, but not limiting, amounts can be 0, 0.1, 0.2, 0.5, 1, 1.2, 1.5, 2, 3, 4, 5, 6 parts, or any value within any range of two of these values. The additive content in the conductive paste is 0 to 6 parts; that is, additives may or may not be added to the conductive paste. When additives are added, their content should be controlled within 6 parts (or 6%). The additives are mainly used to improve printing performance and other overall properties, and the amount of additives added is relatively small in the conductive paste.

[0052] The conductive paste formulation of this embodiment mainly consists of five parts: conductive silver-coated copper powder and optional silver powder, resin, solvent, functional components, and additives. The amount and type of each component vary depending on the specific objectives and applications. By adjusting the types and proportions of each raw material component and ensuring their synergistic effect with other components, the conductive paste, within the aforementioned ranges, exhibits good conductivity and stable performance, effectively suppressing the oxidation of the silver-coated copper powder during use.

[0053] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0054] In some embodiments, the functional components include dispersants, fluorinated wax powders, and antioxidants.

[0055] The synergistic effect of dispersants, fluorinated wax powder, and antioxidants enhances the oxidation resistance of silver-coated copper powder and improves the conductivity of the conductive paste. Specifically, the synergistic effect of fluorinated wax powder (surface layer) and antioxidants (internal layer) improves the oxidation resistance of silver-coated copper powder. For example, silver-coated copper powder is prone to forming non-conductive copper oxide in humid and high-temperature environments. The polytetrafluoroethylene wax powder floats during the paste curing process, inhibiting moisture corrosion and working with the antioxidant to suppress copper oxidation. Furthermore, using specific dispersants (such as acidic dispersants) for silver-coated copper powder can improve grinding efficiency and reduce damage to the silver-coated copper plating layer.

[0056] In some embodiments, the conductive paste comprises, by weight, the following components: 30-70 parts of silver-coated copper powder, 0-30 parts of silver powder, 5-10 parts of resin, 10-50 parts of solvent, 0.05-0.5 parts of dispersant, 0.05-0.5 parts of fluorinated wax powder, 0.05-0.5 parts of antioxidant, and 0.01-5 parts of additives.

[0057] In some embodiments, the conductive paste comprises, by weight, the following components: 40-60 parts of silver-coated copper powder, 1-20 parts of silver powder, 6-8 parts of resin, 20-40 parts of solvent, 0.05-0.35 parts of dispersant, 0.1-0.5 parts of fluorinated wax powder, 0.1-0.5 parts of antioxidant, and 0.1-3 parts of additives.

[0058] By rationally adjusting and optimizing the content of each component in the conductive paste, the synergistic effect between the components can be fully utilized to further improve the conductivity or overall performance of the conductive paste, while reducing the production cost of the conductive paste.

[0059] In some embodiments, the morphology of the silver-coated copper powder and the silver powder includes, but is not limited to, at least one of the following: flake-shaped, spherical, linear, or dendritic. For example, the silver-coated copper powder can be spherical, flake-shaped, linear, or dendritic; the silver powder can be spherical, flake-shaped, linear, or dendritic. The morphology of the silver-coated copper powder and the silver powder can be a single type, or a combination of two or more of the above selections, and when combined, any combination is permissible. Additionally, the morphology of the silver-coated copper powder and the silver powder can also include other morphologies such as rod-shaped.

[0060] Preferably, the silver-coated copper powder and the silver powder are in flake form, that is, flake-shaped silver-coated copper powder or flake-shaped silver powder are used.

[0061] Optionally, the silver powder can be micron-sized or nano-sized. Optionally, the silver-coated copper powder can be micron-sized or nano-sized.

[0062] In some embodiments, the silver content in the silver-coated copper powder is 10% to 50% by mass. In some embodiments, the silver content in the silver-coated copper powder is 15% to 45% by mass. Preferably, in some embodiments, the silver content in the silver-coated copper powder is 20% to 40% by mass. Typically, but not limitingly, the silver content in the silver-coated copper powder can be, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50% by mass, and any value within the range formed by any two of these points. Generally, when the silver content in the silver-coated copper powder is below 50% by mass, the probability of exposed copper particles increases, and the surface coverage incompleteness of the silver-coated copper powder becomes more pronounced. By maintaining the silver content in the silver-coated copper powder between 10% and 50%, especially between 20% and 40%, it helps to reduce the oxidation of the silver-coated copper powder and improve the conductivity of the conductive paste.

[0063] In some embodiments, the silver-coated copper powder has a particle size distribution of D50 of 6.0–10.0 μm and a bulk density of 0.5–1.5 g / cm³. 3 The tap density is 1.0–3.5 g / cm³. 3 .

[0064] In some embodiments, the silver powder has a particle size distribution of D50 of 6.0–10.0 μm and a bulk density of 0.5–1.5 g / cm³. 3 The tap density is 1.0–3.5 g / cm³. 3 .

[0065] In some embodiments, the resin is a thermoplastic resin. Preferably, in some embodiments, the thermoplastic resin includes, but is not limited to, at least one of polyurethane resin, vinyl chloride resin, polyacrylate, EVA (ethylene-vinyl acetate copolymer) resin, PVB (polyvinyl butyral) resin, polybutadiene resin, or polyester resin. For example, the resin can be polyurethane resin, vinyl chloride resin, polyacrylate, EVA resin, PVB resin, polybutadiene resin, polyester resin, or any combination of two or more of the above substances.

[0066] In some embodiments, the solvent includes, but is not limited to, at least one of cyclohexanone, isophorone, ethylene glycol methyl ether, dipropylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol butyl ether, propylene glycol methyl ether acetate, diethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, dimethyl adipate, diethyl adipate, DBE (divalent ester), dicarboxylic acid ester, diol ester, N-methylpyrrolidone, or terpineol. In this embodiment, the solvent can be any one of the above substances, or a combination of any two or more of the above substances; further details are not listed here.

[0067] According to this embodiment, the solvent's main function is to facilitate printing. The solvent's boiling point should not be lower than 100°C, otherwise it may affect printing. For solvent selection, commonly used high-boiling-point solvents are generally preferred, including but not limited to cyclohexanone, isophorone, ethylene glycol methyl ether, dipropylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol butyl ether, propylene glycol methyl ether acetate, diethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, dimethyl adipate, diethyl adipate, DBE, diesters, diol esters, N-methylpyrrolidone, terpineol, etc. The range of solvent choices is quite large; in practical applications, optimal selection can be made based on different formulations.

[0068] In addition, in other embodiments, the resin and solvent are not limited to the types listed above. Other types of resin and solvent can be used to meet the requirements of good conductivity, which will not be described in detail here.

[0069] In some embodiments, the additives include, but are not limited to, at least one of leveling agents, thickeners, or rheology modifiers. For example, the additive can be a leveling agent, a thickener, a rheology modifier, or a combination of any two or more of the above substances. The additives can be various conventional additives applicable to conductive pastes, utilizing different types of additives to achieve their corresponding functional roles. Furthermore, in other embodiments, other types of additives such as defoamers, accelerators, and molding modifiers can also be used; this embodiment does not limit this. The selection and range of additives are relatively large, and they can generally be preferred based on the performance of the conductive paste.

[0070] In some embodiments, the dispersant is an acidic dispersant. Preferably, in some embodiments, the acid value of the acidic dispersant is (100-200) mg KOH / g. Further, the acid value of the acidic dispersant can be (120-180) mg KOH / g. For example, the acid value of the acidic dispersant can be 100 mg KOH / g, 120 mg KOH / g, 140 mg KOH / g, 150 mg KOH / g, 160 mg KOH / g, 180 mg KOH / g, 200 mg KOH / g, etc.

[0071] It should be noted that the present invention does not limit the specific type of acidic dispersant, as long as the acid value of the acidic dispersant is in the range of (100-200) mg KOH / g.

[0072] The use of the aforementioned specific acidic dispersant in this conductive paste can improve grinding efficiency, reduce damage to the silver-coated copper plating layer, and help improve the conductivity of the conductive paste.

[0073] In some embodiments, the fluorinated wax powder comprises one or more of polytetrafluoroethylene (PTFE) wax powder or PTFE-modified polyethylene (PTFE) wax powder. For example, the fluorinated wax powder can be PTFE wax powder, PTFE-modified polyethylene (PTFE) wax powder, or a mixture of the two. Preferably, the fluorinated wax powder is selected from PTFE wax powder, which is widely available, has low cost, and can effectively improve the oxidation resistance of silver-coated copper powder.

[0074] In some embodiments, the antioxidant includes one or more of hindered phenolic antioxidants, phosphite antioxidants, or sulfur-containing antioxidants. For example, the antioxidant can be a hindered phenolic antioxidant, a phosphite antioxidant, a sulfur-containing antioxidant, or a combination of any two or more of the above substances. Preferably, the antioxidant is selected from hindered phenolic antioxidants, which have superior antioxidant effects.

[0075] In some embodiments, a method for preparing the above-mentioned conductive paste is also provided, the method comprising the following steps:

[0076] The formula-formulated amounts of silver-coated copper powder, silver powder, resin, solvent, functional components, and additives are stirred, mixed, and ground to obtain a conductive paste.

[0077] It should be understood that the specific selection and optimized dosage of the silver-coated copper powder, silver powder, resin, solvent, functional components and additives used in the preparation method of the conductive paste of this application are the same as those specified in the conductive paste described in the first aspect of this application, and can be referred to the description in the first aspect above, and will not be repeated here.

[0078] In some embodiments, the method for preparing conductive paste includes the following steps:

[0079] After the silver powder, a portion of the resin and the solvent are mixed evenly, they are ground using a three-roll mill to obtain the first conductive slurry.

[0080] After the silver-coated copper powder, dispersant, fluorinated wax powder, antioxidant, the remaining resin and the remaining solvent are mixed evenly, the mixture is then ground using a three-roll mill to obtain the second conductive slurry.

[0081] The second conductive paste and the first conductive paste are mixed evenly to obtain the conductive paste.

[0082] This embodiment employs a differentiated preparation process to improve the conductivity of the conductive paste. The preparation method involves mixing silver powder and silver-coated copper powder separately with organic components such as solvents and resins. During the step of dispersing the silver-coated copper powder in the organic components, functional components such as dispersants are added. The resulting premixes are then ground separately. This process allows the wetting, adsorption, and lubrication functions of the organic components to be fully utilized, enhancing the lubrication effect of the organic components on the surfaces of the silver powder and silver-coated copper powder, improving the grinding quality, and ultimately increasing the conductivity of the prepared conductive paste.

[0083] The addition of dispersants, especially acidic dispersants, can enhance the wetting effect of organic components on the silver-coated copper powder, reduce the oxidation of the silver-coated copper powder, and help ensure the conductivity of the silver-coated copper powder. Acidic dispersants can also improve grinding efficiency and reduce damage to the silver-coated copper plating.

[0084] In this embodiment, the ratio of a portion of the resin in the first conductive slurry to the remaining portion of the resin in the second conductive slurry, and the ratio of a portion of the solvent in the first conductive slurry to the remaining portion of the solvent in the second conductive slurry, can be selected and set according to actual conditions, as long as the sum of the mass of a portion of the resin and the remaining portion of the resin, and the sum of the mass of a portion of the solvent and the remaining portion of the solvent are within the specified range. That is, as long as the total resin content and the total solvent content contained in the conductive slurry are within the range defined in this application, this embodiment does not impose any limitations on this.

[0085] In some embodiments, the preparation of the first conductive slurry includes: mixing the silver powder, a portion of the resin and the solvent evenly in a high-speed disperser, and then grinding them with a three-roll mill until the fineness is less than or equal to 10 μm to obtain the first conductive slurry.

[0086] In some embodiments, the preparation of the second conductive paste includes: during the preparation of the second conductive paste, the spacing between the rollers in the three-roll mill is 2 to 4 times the particle size of the silver-coated copper powder. For example, the spacing between the rollers in the three-roll mill can be 2, 2.5, 3, 3.5, or 4 times the particle size of the silver-coated copper powder (powder).

[0087] By setting the mill roller spacing to between 2 and 4 times the powder particle size, damage to the powder surface coating can be prevented. Optimizing the grinding process of the conductive slurry helps improve grinding quality and the slurry's conductivity.

[0088] In some specific embodiments, the method for preparing the conductive paste includes the following steps:

[0089] According to the formula, silver powder, part of the resin and solvent are mixed evenly in a high-speed disperser, and then ground in a three-roll mill using a standard three-roll milling process until the fineness is less than or equal to 10μm to obtain the first conductive slurry.

[0090] According to the formula, the silver-coated copper powder, dispersant, fluorinated wax powder, antioxidant, the remaining resin and the remaining solvent are mixed evenly and then ground with a three-roll mill. The distance between the rollers in the three-roll mill is 2 to 4 times the particle size of the silver-coated copper powder (powder) to obtain the second conductive slurry.

[0091] The second conductive paste and the first conductive paste are mixed evenly to obtain the conductive paste.

[0092] In some specific embodiments, the preparation method of conductive paste may also include the following steps: according to the ratio, add silver-coated copper powder, silver powder, resin, solvent, dispersant, fluorinated wax powder and antioxidant to the paste tank, stir with a high-speed disperser for about 30 minutes to make the silver-coated copper powder fully wetted to uniformity, and then use a three-roll mill to grind the silver-coated copper conductive paste about 4 times to obtain the conductive paste.

[0093] Based on the same inventive concept, in some embodiments, an electronic device is also provided, including a substrate and a conductive structure located on the substrate, the conductive structure being made of a conductive paste as described above, or a conductive paste obtained by the aforementioned preparation method.

[0094] It should be understood that the electronic device includes the conductive paste provided in this embodiment, and therefore has at least all the features and advantages of the conductive paste, which will not be repeated here.

[0095] The electronic device described in this invention can be any type of electronic device well-known in the art. Considering the function of the conductive paste of this invention, in a preferred embodiment, the electronic device can be an RFID device, a membrane switch, an electrode wire, etc. That is, the conductive paste and its preparation method of this application can be widely used in fields such as RFID, membrane switches, and electrode wires, and have good application effects.

[0096] The conductive paste and its preparation method of this application are further illustrated below with specific embodiments. Those skilled in the art will understand that the examples described herein are merely some examples, and any other suitable specific examples are within the scope of this invention.

[0097] Example 1

[0098] 1. A conductive paste, comprising the following components in parts by weight:

[0099] The mixture contains 50 parts of silver-coated copper powder, 1 part of silver powder, 8 parts of thermoplastic polyurethane, 39 parts of solvent isophorone, 0.05 parts of acidic dispersant, 0.5 parts of fluorinated wax powder, and 0.2 parts of antioxidant.

[0100] Among them, both the silver-coated copper powder and the silver powder are in flake form, and the silver content in the silver-coated copper powder is 20%; the acid value of the acidic dispersant is 150 mg KOH / g; the fluorinated wax powder is polytetrafluoroethylene wax powder; and the antioxidant is a hindered phenolic antioxidant.

[0101] 2. A method for preparing a conductive paste, comprising:

[0102] According to the formula, add silver-coated copper powder, silver powder, resin, solvent, dispersant, fluorinated wax powder and antioxidant to the slurry tank, stir for 30 minutes with a high-speed disperser to fully impregnate the silver-coated copper powder until uniform, and then grind the silver-coated copper conductive slurry 4 times with a three-roll mill to obtain the conductive slurry.

[0103] Example 2

[0104] Example 2 is basically the same as Example 1, and the similarities will not be repeated. The difference is that the conductive paste in this example includes the following components in parts by weight:

[0105] The composition includes 70 parts of silver-coated copper powder, 5 parts of thermoplastic polyurethane, 24 parts of isophorone solvent, 0.1 parts of acidic dispersant, 0.5 parts of fluorinated wax powder, and 0.4 parts of antioxidant.

[0106] Everything else is the same as in Example 1.

[0107] Example 3

[0108] Example 3 is basically the same as Example 1, and the similarities will not be repeated. The difference is that the conductive paste in this example includes the following components in parts by weight:

[0109] The mixture contains 30 parts of silver-coated copper powder, 12 parts of silver powder, 10 parts of thermoplastic polyurethane, 47.6 parts of solvent isophorone, 0.5 parts of acidic dispersant, 0.4 parts of fluorinated wax powder, and 0.5 parts of antioxidant.

[0110] Everything else is the same as in Example 1.

[0111] Example 4

[0112] Example 4 is basically the same as Example 1, and the similarities will not be repeated. The difference is that the conductive paste in this example includes the following components in parts by weight:

[0113] The composition includes 45 parts silver-coated copper powder, 6 parts silver powder, 4 parts polyester resin, 4 parts EVA resin, 39 parts terpineol solvent, 0.05 parts acidic dispersant, 0.5 parts fluorinated wax powder, 0.2 parts antioxidant, and 0.3 parts leveling agent and thickener. The silver content in the silver-coated copper powder is 30%; the acidic dispersant has an acid value of 200 mg KOH / g; the fluorinated wax powder is polytetrafluoroethylene modified polyethylene wax powder; and the antioxidant is a phosphite antioxidant.

[0114] Everything else is the same as in Example 1.

[0115] Example 5

[0116] Example 5 is basically the same as Example 1, and the similarities will not be repeated. The difference is that the conductive paste in this example includes the following components in parts by weight:

[0117] The composition includes 55 parts silver-coated copper powder, 1.5 parts silver powder, 3 parts polyacrylate resin, 4 parts PVB resin, 20 parts solvent N-methylpyrrolidone, 20 parts dimethyl adipate, 0.1 parts acidic dispersant, 0.3 parts fluorinated wax powder, 0.3 parts antioxidant, and 0.5 parts leveling agent. The silver content in the silver-coated copper powder is 40%; the acid value of the acidic dispersant is 100 mg KOH / g; the fluorinated wax powder is polytetrafluoroethylene wax powder; and the antioxidant is a sulfur-containing antioxidant.

[0118] Everything else is the same as in Example 1.

[0119] Comparative Example 1

[0120] A conductive paste comprising the following components in parts by weight:

[0121] The composition includes 50 parts silver-coated copper powder, 1 part silver powder, 8 parts thermoplastic polyurethane, and 39 parts isophorone solvent. Both the silver-coated copper powder and the silver powder are in flake form, and the silver content in the silver-coated copper powder is 20%.

[0122] The method for preparing the conductive paste includes: adding silver-coated copper powder, silver powder, resin, and solvent to a slurry tank according to the specified ratio, stirring with a high-speed disperser for 30 minutes to ensure that the silver-coated copper powder is fully impregnated and homogeneous, and then grinding the silver-coated copper conductive paste four times with a three-roll mill to obtain the conductive paste.

[0123] The main difference between Comparative Example 1 and Example 1 is that the dispersant, fluorinated wax powder and antioxidant were omitted.

[0124] Comparative Example 2

[0125] A conductive paste comprising the following components in parts by weight:

[0126] The mixture contains 20 parts silver-coated copper powder, 0.5 parts silver powder, 3 parts thermoplastic polyurethane, 75 parts isophorone solvent, 0.01 parts acidic dispersant, 0.01 parts fluorinated wax powder, and 0.01 parts antioxidant.

[0127] The main difference between Comparative Example 2 and Example 1 is that the content of each component is not within the range defined by the present invention.

[0128] Performance testing

[0129] In this invention, the electronic devices containing the conductive paste of this application in Examples 1 to 5 and the electronic devices containing the conductive paste in Comparative Examples 1 to 2 are subjected to performance tests.

[0130] The testing methods included: using a resistivity meter to test the resistivity of the conductive pastes provided in each embodiment and comparative example, and the resistivity after aging at 85°C / 85%RH for 240 hours. The performance test results are shown in Table 1 below.

[0131] Table 1

[0132]

[0133] As can be seen from the data in Table 1, compared with the conductive pastes provided in Comparative Examples 1 and 2, the conductive pastes provided in Examples 1 to 5 of the present invention effectively suppress the high-temperature oxidation problem of silver-coated copper powder, improve the oxidation resistance of silver-coated copper powder, and thus effectively improve the conductivity of the conductive paste.

[0134] In addition, such as Figure 1 As shown, the water resistance of the silver paste (conductive paste) surface after adding fluorine-containing additives (left) is significantly enhanced compared to that without additives (right).

[0135] Figure 1 In the image, the silver paste on the left is the one with added fluorine-containing additives. Its surface has a larger water droplet angle, making it less prone to water droplet spread, indicating stronger water resistance and superior aging performance under the same conditions. Since it doesn't contain encapsulated copper powder, it won't oxidize and fail due to excessive moisture penetration. The silver paste on the right, however, is the one without added fluorine-containing additives. Its water droplet angle is smaller, and water droplets spread more easily, resulting in poorer moisture barrier properties. This makes it more susceptible to copper powder failure, leading to a significant loss in the overall conductivity of the silver paste.

[0136] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0137] It should be noted that the terms "and / or" or " / " used herein are merely descriptions of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The singular forms "a," "described," and "the" used in the embodiments of the invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0138] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrically conductive paste, characterized by, The conductive paste comprises The silver-coated copper powder, silver powder, resin, solvent, functional component and auxiliary agent; The functional component comprises acidic dispersant, fluorine-containing wax powder and antioxidant, and the silver-coated copper powder is 30-70 parts by mass, the silver powder is 0-30 parts by mass, the resin is 5-10 parts by mass, the solvent is 10-50 parts by mass, the acidic dispersant is 0.05-0.5 parts by mass, the fluorine-containing wax powder is 0.05-0.5 parts by mass, the antioxidant is 0.05-0.5 parts by mass and the auxiliary agent is 0.01-5 parts by mass.

2. The conductive paste according to claim 1, wherein The conductive paste comprises the following components by mass: silver-coated copper powder 40-60 parts, silver powder 1-20 parts, resin 6-8 parts, solvent 20-40 parts, acidic dispersant 0.05-0.35 parts, fluorine-containing wax powder 0.1-0.5 parts, antioxidant 0.1-0.5 parts and auxiliary agent 0.1-3 parts.

3. The conductive paste of claim 1, wherein The morphology of the silver-coated copper powder and the silver powder respectively comprises at least one of flaky, spherical, linear or dendritic shape. The silver content in the silver-coated copper powder is 10-50% by mass.

4. The conductive paste of claim 1, wherein The silver-coated copper powder has a particle size distribution of D50: 6.0-10.0 μm, a loose bulk density of 0.5-1.5 g / cm 3 , and a tap density of 1.0-3.5 g / cm 3 . And / or, the particle size distribution of the silver powder is D50: 6.0-10.0 μm, the loose bulk density is 0.5-1.5 g / cm 3 , the tap density is 1.0-3.5 g / cm 3 .

5. The electrically conductive paste of claim 1, wherein The resin is a thermoplastic resin.

6. The electroconductive paste according to claim 5, wherein The thermoplastic resin comprises at least one of polyurethane resin, chlorovinyl resin, polyacrylate, EVA resin, PVB resin, polybutadiene resin or polyester resin.

7. The electrically conductive paste of claim 1, wherein The solvent comprises at least one of cyclohexanone, isophorone, ethylene glycol methyl ether, dipropylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol butyl ether, propylene glycol methyl ether acetate, diethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, dimethyl adipate, diethyl adipate, DBE, dibasic acid ester, dibasic alcohol ester, N-methyl pyrrolidone or terpineol. The auxiliary agent comprises at least one of leveling agent, thickening agent or rheological auxiliary agent.

8. The electroconductive paste according to any one of claims 1 to 7, wherein The acid value of the acidic dispersant is (100-200) mg KOH / g. The fluorine-containing wax powder comprises one or more of polytetrafluoroethylene wax powder or polytetrafluoroethylene modified polyethylene wax powder. The antioxidant comprises one or more of hindered phenolic antioxidant, phosphite antioxidant or sulfur-containing antioxidant.

9. A method of preparing the electroconductive paste as claimed in any one of claims 1 to 8, characterized by, The method comprises the following steps: The formula amount of silver-coated copper powder, silver powder, resin, solvent, functional component and auxiliary agent are stirred and mixed, and grinded to obtain the conductive paste.

10. The method of claim 9, wherein the conductive paste is prepared by mixing the conductive filler, the organic vehicle, and the dispersant. The method comprises the following steps: The silver powder, part of the resin and the solvent are mixed uniformly, and then grinded by a three-roll grinder to obtain a first conductive paste. The silver-coated copper powder, acidic dispersant, fluorine-containing wax powder, antioxidant, the remaining part of the resin and the remaining part of the solvent are mixed uniformly, and then grinded by a three-roll grinder to obtain a second conductive paste; the second conductive paste and the first conductive paste are mixed uniformly to obtain the conductive paste.

11. The method of claim 10, wherein the conductive paste is prepared by mixing the conductive filler, the organic vehicle, and the dispersant. The silver powder, part of the resin and the solvent are mixed uniformly, and then grinded by a three-roll grinder to a fineness of less than or equal to 10 μm to obtain a first conductive paste.

12. The method of claim 10, wherein the conductive paste is prepared by mixing the conductive filler, the organic vehicle, and the dispersant. In the process of preparing the second conductive paste, the distance between the rollers in the three-roll grinder is 2-4 times the particle size of the silver-coated copper powder.

13. An electronic device comprising a substrate and an electrically conductive structure on the substrate, characterized in that The electrically conductive structure is made from an electrically conductive paste comprising any one of claims 1 to 8, or made from an electrically conductive paste prepared by any one of claims 9 to 12.

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