Thin film silver powder and its preparation method and application

Abstract

The present invention provides a thin-film silver powder, a preparation method, and applications thereof. The preparation method comprises: mixing organic silver, a reducing agent, an alcohol, an acid, and water, heating the mixture, and then maintaining the temperature to obtain the thin-film silver powder. This method is simple, easy to operate, environmentally friendly, and suitable for mass production. The silver powder produced by this method has high purity, a high aspect ratio, a large aspect ratio, is resistant to fracture, and is easily stretchable and foldable. It is suitable for various fields of flexible printed electronics, has a wide range of applications, and exhibits excellent conductivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic pastes, and in particular relates to a thin film silver powder and a preparation method and application thereof. Background Art

[0002] With the rapid development of the electronics industry, metallic silver has become an indispensable key material in the fields of printed electronics, integrated circuits, surface assembly, and sensing due to its excellent electrical and thermal conductivity. The performance of metallic silver depends largely on the morphology and size structure of the silver particles. According to the morphology of silver powder, it can be divided into spherical, flaky, dendritic, and mixed silver powders. Spherical silver powder particles are in point contact with each other, and the resistance is relatively high. It is mainly used in low-end, fixed conductive silver pastes. Flake silver powder has a relatively large surface area. During sintering, the film layer shrinks, resulting in contact between silver sheets. The particles are in surface contact or line contact, so the resistance is relatively low and the conductivity is good. It is mainly used in high-end electronics or special flexible electronics.

[0003] Currently, the most widely used silver paste for printed electronics is flaky silver powder. The technical route for preparing flaky silver powder mostly uses silver nitrate reduction technology. First, under certain conditions, a reducing agent is added to a silver nitrate solution to prepare spherical or quasi-spherical silver particles. Then, the spherical silver is ground into a flake-like morphology through mechanical ball milling. This two-step process is complex and costly. The mechanical ball milling process is time-consuming and cannot be performed in large quantities to ensure the ball milling effect. The ball milling process is full of variables, making it difficult to uniformly obtain results under the same technical conditions. Batch stability is poor, and impurities are easily introduced during ball milling, reducing the purity of the silver powder and affecting performance.

[0004] Thin-film silver powder is a type of flaky silver powder that has a higher aspect ratio than flaky silver, that is, the length-to-thickness ratio of the silver powder can reach more than 50. In silver paste applications, the silver particles form the same line / surface contact as flaky silver, with low resistance and good conductivity. In addition to forming surface-to-surface contact in conductive pastes, thin-film silver powder can also form a tight conductive pattern of overlapping upper and lower silver sheets. Under this structure, the contact area between the conductive layers in the silver paste application is larger, making it easier to stretch, fold, and bend, and the conductivity is better. At the same time, the thin-film silver powder has a high aspect ratio, a large surface area, strong fracture resistance and excellent stretchability, and the electronic components prepared therefrom also have very strong reliability. Compared with silver powders with other morphologies, thin-film silver powder shows a wider range of applicability in the fields of flexible printed electronics, flexible stretchable electronics, etc. Therefore, it is of great significance to find a suitable, simple and large-scale method for preparing thin-film silver powder. Summary of the Invention

[0005] The present invention aims to at least partially address one of the technical problems in the related art. To this end, one object of the present invention is to provide a thin film of silver powder, a method for its preparation, and its use. This method is simple, easy to operate, environmentally friendly, and suitable for mass production. The silver powder produced by this method has high purity, a high aspect ratio, a large diameter-to-thickness ratio, is fracture-resistant, and is easily stretchable and foldable. It is suitable for various applications in flexible printed electronics and exhibits excellent conductivity.

[0006] In one aspect, the present invention provides a method for preparing a thin film of silver powder. According to an embodiment of the present invention, the method includes: mixing organic silver, a reducing agent, an alcohol, an acid, and water, heating the mixture, and then maintaining the temperature to obtain the thin film of silver powder.

[0007] The method comprises mixing organic silver, a reducing agent, an alcohol, an acid, and water, heating the mixture, and then keeping the mixture warm. The organic silver and the reducing agent are dissolved in an alcohol-water solution and heated and kept warm under acidic conditions to cause a reduction reaction. Due to the presence of a conjugated eight-membered ring structure in the crystal structure of the organic silver, the organic silver and the reducing agent undergo an oxidation-reduction reaction to generate silver atoms. The silver atoms accumulate along the eight-membered ring structure to form silver atom clusters. The silver atom clusters further grow and mature to obtain silver in the shape of a thin sheet, thereby obtaining a thin film of silver powder. Compared with the existing process, the present application adopts a one-step reduction direct template method to prepare a thin film of silver powder. The entire reaction process is carried out in an aqueous solution and can be mass-produced. Therefore, the method is simple and easy to operate, environmentally friendly, and suitable for mass production. The silver powder prepared by this method has high purity, high aspect ratio, large diameter-to-thickness ratio, fracture resistance, and is easy to stretch and fold. It is suitable for various fields of flexible printed electronics, has a wide range of applications, and has excellent conductivity.

[0008] In addition, the method for preparing thin film silver powder according to the above embodiment of the present invention may also have the following technical features:

[0009] In some embodiments of the present invention, the method for preparing a thin film of silver powder further comprises: (1) mixing organic silver, alcohol, and water to obtain an organic silver solution; (2) mixing a reducing agent and water to obtain a reducing agent solution; (3) mixing water and an acid to obtain a reaction mother liquor; and (4) adding the organic silver solution and the reducing agent solution to the reaction mother liquor, heating and stirring, and then keeping the temperature. Thus, a thin film of silver powder with high purity, high aspect ratio, large diameter-to-thickness ratio, resistance to fracture, and easy stretching and folding can be obtained.

[0010] In some embodiments of the present invention, in step (1), the organic silver, alcohol, water, and dispersant are mixed to obtain an organic silver solution, thereby making the organic silver more uniformly dispersed.

[0011] In some embodiments of the present invention, in step (3), water, acid, and an emulsifier are mixed to obtain a reaction mother liquor, thereby facilitating the reaction between the organic silver and the reducing agent.

[0012] In some embodiments of the present invention, the organic silver comprises an organic silver carboxylate having a carbon number between 18 and 22. Thus, a thin film-shaped silver powder with high purity, high aspect ratio, large diameter-to-thickness ratio, fracture resistance, and easy stretching and folding can be obtained.

[0013] In some embodiments of the present invention, the organic silver carboxylate includes at least one of silver stearate and silver behenate.

[0014] In some embodiments of the present invention, the reducing agent includes at least one of citric acid, ascorbic acid, ethylene glycol, glucose and hydroquinone.

[0015] In some embodiments of the present invention, the alcohol includes at least one of ethanol and propanol.

[0016] In some embodiments of the present invention, the acid includes at least one of acetic acid, dilute sulfuric acid, and dilute nitric acid.

[0017] In some embodiments of the present invention, the dispersant includes tetradecyldimethylamine n-propyl sulfonate.

[0018] In some embodiments of the present invention, the emulsifier includes sodium triisopropylnaphthalenesulfonate.

[0019] In some embodiments of the present invention, the molar ratio of the reducing agent to the organic silver is 1 to 5. Thus, a thin film-like silver powder with high purity, high aspect ratio, large diameter-to-thickness ratio, fracture resistance, and easy stretching and folding can be obtained.

[0020] In some embodiments of the present invention, the mass ratio of the organic silver, the alcohol, the water, and the dispersant in the organic silver solution is (5-10):(10-20):(67-84):(1-3). Thus, a thin film of silver can be prepared.

[0021] In some embodiments of the present invention, the concentration of the reducing agent solution is 5-10 wt %, which is conducive to the reaction between the organic silver and the reducing agent.

[0022] In some embodiments of the present invention, the mass ratio of the water, the acid, and the emulsifier in the reaction mother liquor is (75-88):(10-20):(2-5). This facilitates the reaction between the organic silver and the reducing agent to prepare a thin film of silver powder.

[0023] In some embodiments of the present invention, the mass ratio of the organic silver solution to the reaction mother solution is (45-75): (15-25). Thus, a thin film of silver powder can be prepared.

[0024] In some embodiments of the present invention, in step (4), the organic silver solution and the reducing agent solution are added to the reaction mother solution at a rate of 8-12 mL / min and 10-15 mL / min, respectively. Thus, a thin film of silver powder can be prepared.

[0025] In some embodiments of the present invention, in step (4), the temperature of the heat preservation reaction is 50 to 80 degrees Celsius, and the heat preservation reaction time is 0.5 to 2 hours, thereby facilitating the reaction between the organic silver and the reducing agent.

[0026] In another aspect, the present invention provides a thin film of silver powder. According to an embodiment of the present invention, the thin film of silver powder is prepared using the above-described method. As a result, the thin film of silver powder has high purity, a high aspect ratio, a large diameter-to-thickness ratio, is resistant to fracture, and is easily stretched and folded. It is suitable for use in various fields of flexible printed electronics, has a wide range of applications, and exhibits excellent conductivity.

[0027] In addition, the thin film silver powder according to the above embodiment of the present invention may also have the following technical features:

[0028] In some embodiments of the present invention, the particle size of the thin film silver powder is 5 to 15 μm, and the aspect ratio is greater than 50.

[0029] In a third aspect, the present invention provides an electronic component. According to an embodiment of the present invention, the electronic component includes an electronic component substrate and a silver paste coating, wherein the silver paste coating is formed on at least one side of the electronic component substrate and includes the thin film silver powder described above.

[0030] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments with reference to the following drawings, in which:

[0032] Figure 1 This is a diagram of the double-injection emulsification process used in Example 1 of the present invention;

[0033] Figure 2 is a SEM image of the thin film silver powder of Example 1 of the present invention;

[0034] Figure 3 is a SEM image of the thin film silver powder of Example 2 of the present invention;

[0035] Figure 4 This is a SEM image of the thin film silver powder of Example 3 of the present invention. DETAILED DESCRIPTION

[0036] The embodiments of the present invention are described in detail below, which are intended to explain the present invention but are not to be construed as limiting the present invention.

[0037] In one aspect, the present invention provides a method for preparing a thin film of silver powder. According to an embodiment of the present invention, the method includes: mixing organic silver, a reducing agent, an alcohol, an acid, and water, heating the mixture, and then maintaining the temperature to obtain the thin film of silver powder.

[0038] The inventors discovered that by mixing organic silver, a reducing agent, an alcohol, an acid, and water, heating and then keeping the mixture warm, wherein the organic silver and the reducing agent are dissolved in an alcohol-water solution and heated and kept warm under acidic conditions to produce a reduction reaction, the organic silver and the reducing agent undergo an oxidation-reduction reaction due to the presence of a conjugated eight-membered ring structure in the crystal structure of the organic silver, generating silver atoms. The silver atoms accumulate along the eight-membered ring structure to form silver atom clusters. The silver atom clusters further grow and mature to obtain thin-sheet-shaped silver, thereby obtaining a thin-film silver powder. Compared with existing processes, the present application adopts a one-step reduction direct template method to prepare thin-film silver powder. The entire reaction process is carried out in an aqueous solution and can be mass-produced. Therefore, the method is simple and easy to operate, environmentally friendly, and suitable for mass production. The silver powder prepared by this method has high purity, high aspect ratio, large diameter-to-thickness ratio, fracture resistance, easy stretching and folding, and is suitable for various fields of flexible printed electronics. It has a wide range of applications and excellent conductivity.

[0039] According to an embodiment of the present invention, organic silver includes organic carboxylate silver with a carbon number between 18 and 22. Since there is a natural template in the crystal structure of organic carboxylate silver with a carbon number between 18 and 22, there is no need to introduce an additional template, and a thin film of silver powder can be directly prepared by a one-step reaction. Furthermore, organic carboxylate silver includes but is not limited to at least one of silver stearate and silver behenate. Therefore, the present application uses organic carboxylate silver with a carbon number between 18 and 22 to obtain a thin film of silver powder with high purity, high aspect ratio, large diameter-to-thickness ratio, fracture resistance, and easy stretching and folding. It should be noted that the above-mentioned alcohol, acid and reducing agent are conventional reagents in the field, and those skilled in the art can select them according to actual conditions. For example, alcohol includes but is not limited to at least one of ethanol and propanol; acid includes but is not limited to at least one of acetic acid, dilute sulfuric acid and dilute nitric acid; reducing agent includes but is not limited to at least one of citric acid, ascorbic acid, ethylene glycol, glucose and hydroquinone.

[0040] According to an embodiment of the present invention, the method for preparing thin film silver powder further comprises:

[0041] S100: Mixing organic silver, alcohol and water

[0042] In this step, the organosilver is insoluble in water but soluble in alcohol. The organosilver, alcohol, and water are mixed and stirred to obtain an organosilver solution. Furthermore, to improve the dispersibility of the organosilver in the solution, the organosilver, alcohol, water, and a dispersant can be mixed and stirred to prepare the organosilver solution. It should be noted that dispersants are conventional reagents in the art, and those skilled in the art can select dispersants based on practical needs. For example, dispersants include, but are not limited to, tetradecyldimethylamine n-propyl sulfonate. Those skilled in the art will appreciate that, to achieve a more uniform dispersion of the organosilver solution, the present application employs stirring to thoroughly mix the various materials.

[0043] According to an embodiment of the present invention, the mass ratio of organic silver, alcohol, water and dispersant in the organic silver solution is (5-10): (10-20): (67-84): (1-3). The inventors found that if the amount of organic silver added is too large, because the long-chain organic carboxylate itself is an emulsifier, excessive addition will easily cause increased foaming in the system, which is difficult to eliminate, and the uniformity of the system will deteriorate, affecting the degree of reaction; if the amount of organic silver added is too small, the actual amount of silver produced by the reaction under the same device conditions will be too small due to the low concentration of the silver source, resulting in low efficiency and insufficient for mass production. If the amount of dispersant added is too much, it will affect the accumulation and growth of silver atoms in the silver source during the reduction reaction, hindering the formation of thin film silver; if the amount of dispersant added is too little, it will affect the uniformity and stability of the silver source system, affect the uniformity of the injection rate during the injection process, and thus affect the morphology of the silver powder. Therefore, the present application adopts an organic silver solution with a mass ratio of organic silver, alcohol, water and dispersant of (5-10): (10-20): (67-84): (1-3) to prepare a thin film of silver.

[0044] S200: Mix reducing agent and water

[0045] In this step, a reducing agent and water are mixed to prepare a reducing agent solution. According to an embodiment of the present invention, the concentration of the reducing agent solution is 5-10wt%. The inventors have discovered that if the reducing agent solution concentration is too high, the reaction rate will be accelerated. Because the growth and maturation of thin-film silver is a slow process, excessively high reducing agent concentrations will rapidly react to generate a large number of silver nuclei, which will further accumulate and eventually form agglomerated silver, preventing the formation of thin-film silver. If the reducing agent solution concentration is too low, the reaction will not be complete, and the small amount of thin-film silver produced will be wrapped in the organic carboxylate silver, making it difficult to separate. Therefore, the present application uses a reducing agent solution with a concentration of 5-10wt%, which is conducive to the reaction between the organic silver and the reducing agent.

[0046] S300: Water and acid mixture

[0047] In this step, water and acid are mixed to obtain a reaction mother liquor. Furthermore, water, acid, and an emulsifier are mixed to obtain a reaction mother liquor, thereby facilitating the reduction reaction between the organosilver and the reducing agent. It should be noted that emulsifiers are conventional reagents in the art and can be selected by those skilled in the art based on practical needs. For example, emulsifiers include, but are not limited to, sodium triisopropylnaphthalenesulfonate.

[0048] According to an embodiment of the present invention, the mass ratio of water, acid and emulsifier in the reaction mother liquor is (75-88): (10-20): (2-5). The inventors found that if the acidity of the reaction mother liquor is too strong, it will inhibit the ionization of organic silver, thereby reducing the reaction rate and changing the morphology of the final prepared silver; if the acidity is too weak, it will promote the ionization of organic silver, increase the reaction rate, increase the number of silver nuclei, and ultimately increase the number of granular silver, and the proportion of thin-film silver powder will decrease accordingly; if the amount of emulsifier added is too much, it will affect the accumulation and growth of silver atoms in the silver source during the reduction reaction, hindering the formation of thin-film silver; if the amount of emulsifier added is too little, it will affect the uniformity and stability of the reaction system, affect the reaction rate during the reaction, and thus affect the morphology of the silver powder. Therefore, the present application uses a reaction mother liquor with a mass ratio of water, acid and emulsifier of (75-88): (10-20): (2-5), which is conducive to the reaction between organic silver and reducing agent to prepare thin-film silver.

[0049] S400: Add the organic silver solution and reducing agent solution to the reaction mother liquor, heat and stir, and then keep warm

[0050] In this step, the organic silver solution and reducing agent solution are added to the reaction mother liquor, heated and stirred, and then kept warm. The organic silver and reducing agent react in the reaction mother liquor to produce silver. The resulting silver powder is then filtered, washed, and dried to obtain a thin film. Because the organic silver crystal structure contains a conjugated eight-membered ring structure, the silver generated by the reduction of the organic silver by the reducing agent can grow on the conjugated eight-membered ring structure, forming a thin sheet of silver, thus obtaining a thin film of silver powder. It should be noted that the heating and stirring methods can be selected by those skilled in the art based on practical needs and will not be further elaborated here.

[0051] According to an embodiment of the present invention, the molar ratio of the reducing agent to the organic silver is 1 to 5. The inventors have found that when the molar ratio of the reducing agent to the organic silver is less than 1, the reaction will not be complete, and the small amount of thin film silver produced will be wrapped in the organic carboxylate silver, making it difficult to separate. When the molar ratio of the reducing agent to the organic silver is greater than 5, the reducing agent concentration is too high, which will accelerate the reaction rate, rapidly react to generate a large number of silver nuclei, and the silver nuclei further accumulate and eventually become agglomerated silver, and no thin film silver can be obtained. Therefore, the present application adopts a molar ratio of the reducing agent to the organic silver of 1 to 5, which can obtain a thin film silver powder with high purity, high aspect ratio, large diameter-to-thickness ratio, fracture resistance, and easy stretching and folding.

[0052] According to an embodiment of the present invention, the mass ratio of the organic silver solution and the reaction mother liquor is (45-75): (15-25). The inventors found that if the mass ratio of the reaction mother liquor is too large, the silver source concentration in the reaction system will be low, which will affect the reaction rate, result in less nucleation, and it will not be easy to grow into the desired thin film silver powder when it finally grows and matures; if the mass ratio of the reaction mother liquor is too small, the silver source concentration in the reaction system will increase, which will affect the reaction rate, result in more nucleation, and it will be easy to grow into agglomerated silver when it finally grows and matures. Therefore, the present application adopts a mass ratio of the organic silver solution and the reaction mother liquor of (45-75): (15-25), which is conducive to the preparation of thin film silver powder.

[0053] According to an embodiment of the present invention, the rates at which the organic silver solution and the reducing agent solution are added to the reaction mother liquor are independently 8-12 mL / min and 10-15 mL / min, respectively. The inventors have found that if the rates at which the organic silver solution and the reducing agent solution are added to the reaction mother liquor are too high, the reaction rate will be increased, resulting in a large number of silver nuclei being generated in the system in a short period of time. The silver nuclei aggregate and grow and easily accumulate together to form agglomerated spherical or plate-like silver; if the rates at which the organic silver solution and the reducing agent solution are added to the reaction mother liquor are too low, the reaction rate will be reduced, the nucleation speed will be slow, and the thickness of the silver powder finally obtained will be thick, affecting the performance. Therefore, the present application adopts the rates at which the organic silver solution and the reducing agent solution are added to the reaction mother liquor independently of 8-12 mL / min and 10-15 mL / min, respectively, which is conducive to the preparation of thin film silver powder.

[0054] According to an embodiment of the present invention, the temperature of the insulation reaction is 50 to 80 degrees Celsius, and the insulation reaction time is 0.5 to 2 hours. The inventors have found that if the insulation reaction temperature is too low or the time is too short, the reduction reaction is insufficient, and the silver obtained by the reaction is easily wrapped by unreacted organic carboxylic acid silver, making it difficult to separate. If the insulation reaction temperature is too high or the time is too long, the reactivity of the silver source is increased, the reaction produces more silver nuclei, and they are easily aggregated into agglomerated and plate-like silver. Therefore, the insulation reaction conditions of 50 to 80 degrees Celsius and 0.5 to 2 hours adopted in the present application are conducive to the reaction between organic silver and the reducing agent to prepare thin film silver powder.

[0055] According to an embodiment of the present invention, the organic silver solution obtained in S100 and the reaction mother liquor obtained in S300 are first mixed, and then the reducing agent solution obtained in S200 is added to the mixed solution, and the mixture is heated and kept warm to allow the organic silver and reducing agent to react. Alternatively, the reducing agent solution obtained in S200 and the reaction mother liquor obtained in S300 are first mixed, and then the organic silver solution obtained in S100 is added to the mixed solution, and the mixture is heated and kept warm to allow the organic silver and reducing agent to react. It will be understood by those skilled in the art that the thin film-shaped silver powder of the present application can be obtained regardless of whether the organic silver solution and the reaction mother liquor are first mixed and then the reducing agent solution is added, or whether the reducing agent solution and the reaction mother liquor are first mixed and then the organic silver solution is added.

[0056] In another aspect, the present invention provides a thin film of silver powder. According to an embodiment of the present invention, the thin film of silver powder is prepared using the above-described method. As a result, the thin film of silver powder has high purity, a high aspect ratio, a large diameter-to-thickness ratio, is resistant to fracture, and is easily stretchable and foldable. It is suitable for use in various fields of flexible printed electronics, enjoys a wide range of applications, and exhibits excellent conductivity. It should be noted that the features and advantages described above for the method for preparing the thin film of silver powder also apply to the thin film of silver powder and will not be further elaborated here.

[0057] According to an embodiment of the present invention, the particle size of the thin film silver powder is 5 to 15 μm, and the aspect ratio is greater than 50. Those skilled in the art will understand that the aspect ratio in this application refers to the ratio of the particle size of the thin film silver powder to the thickness of the thin film silver powder, which will not be further described here.

[0058] In its third aspect, the present invention provides an electronic component. According to an embodiment of the present invention, the electronic component comprises an electronic component substrate and a silver paste coating, the silver paste coating being formed on at least one side of the electronic component substrate and comprising the aforementioned thin-film silver powder. As a result, the electronic component exhibits a compact size and excellent conductivity. It should be noted that the features and advantages described above for the thin-film silver powder and its preparation method also apply to this electronic component and will not be further elaborated here.

[0059] The present invention is described below with reference to specific examples. It should be noted that these examples are merely illustrative and do not limit the present invention in any way.

[0060] Example 1

[0061] (1) 75 g of silver behenate powder, 150 g of ethanol, and 20 g of tetradecyldimethylamine n-propyl sulfonate (dispersant) were mixed, and after being fully soaked, 750 g of water was added. The mixture was stirred for 2 hours at 500 rpm to obtain a silver behenate dispersion having a concentration of 7.5 wt %.

[0062] (2) 55.3 g of the reducing agent hydroquinone was added to water and dissolved to obtain 745 kg of the reducing agent solution. The molar ratio of the reducing agent to silver behenate was 3:1.

[0063] (3) 10 g of sodium triisopropylnaphthalenesulfonate (an emulsifier), 37.5 g of acetic acid, and 200 g of water were mixed to obtain a reaction mother solution.

[0064] (4) Using double injection emulsification process, refer to Figure 1 The reaction mother liquor 100 is added to an emulsifying tank 400. Under an emulsification temperature of 70° C. and paddle stirring conditions, the silver behenate dispersion 200 and the reducing agent solution 300 are injected into the reaction mother liquor 100 at a rate of 10 mL / min and 12 mL / min, respectively. After the injection is completed, the reaction is continued under the same control conditions for 1 hour. The film-like silver powder is then obtained by filtration, washing with water, and drying.

[0065] The SEM image of the thin film silver powder prepared in Example 1 is shown in Figure 2 The specific particle size and diameter-to-thickness ratio of the thin film silver powder are shown in Table 1.

[0066] Example 2

[0067] (1) 50 g of silver behenate powder, 100 g of ethanol, and 15 g of tetradecyldimethylamine n-propyl sulfonate (a dispersant) were mixed, and after being fully soaked, 750 g of water was added. The mixture was stirred for 2 hours at 500 rpm to obtain a silver behenate dispersion with a concentration of 5.5 wt %.

[0068] (2) 12.3 g of reducing agent hydroquinone was added to water and dissolved to obtain 237.5 g of reducing agent solution, wherein the molar ratio of reducing agent to silver behenate was 1:1.

[0069] (3) 6 g of sodium triisopropylnaphthalenesulfonate (an emulsifier), 20 g of acetic acid, and 170 g of water were mixed to obtain a reaction mother solution.

[0070] (4) Using a double-injection emulsification process, the reaction mother liquor is added to an emulsification tank. At an emulsification temperature of 50° C. and under paddle stirring conditions, the silver behenate dispersion and the reducing agent solution are injected into the reaction mother liquor at a rate of 10 mL / min and 15 mL / min, respectively. After the injection is completed, the control conditions remain unchanged and the reaction is continued for 0.5 h. Then, the silver powder is filtered, washed with water, and dried to obtain a thin film.

[0071] The SEM image of the thin film silver powder prepared in Example 2 is shown in FIG. Figure 3 The specific particle size and diameter-to-thickness ratio of the thin film silver powder are shown in Table 1.

[0072] Example 3

[0073] (1) 100 g of silver behenate powder, 200 g of ethanol, and 30 g of tetradecyldimethylamine n-propyl sulfonate (a dispersant) were mixed, and after being fully soaked, 670 g of water was added. The mixture was stirred for 2 hours at 500 rpm to obtain a 10 wt % silver behenate dispersion.

[0074] (2) 123 g of reducing agent hydroquinone was added to water and dissolved to obtain 1107 g of reducing agent solution, wherein the molar ratio of reducing agent to silver behenate was 5:1.

[0075] (3) 15 g of sodium triisopropylnaphthalenesulfonate (an emulsifier), 40 g of acetic acid, and 300 g of water were mixed to obtain a reaction mother solution.

[0076] (4) Using a double-injection emulsification process, the reaction mother liquor is added to an emulsification tank. Under an emulsification temperature of 80° C. and paddle stirring conditions, the silver behenate dispersion and the reducing agent solution are injected into the reaction mother liquor at a rate of 10 mL / min and 10 mL / min, respectively. After the injection is completed, the control conditions remain unchanged and the reaction is continued for 2 hours. Then, the film-like silver powder is obtained by filtering, washing with water, and drying.

[0077] The SEM image of the thin film silver powder prepared in Example 3 is shown in FIG. Figure 4 The specific particle size and diameter-to-thickness ratio of the thin film silver powder are shown in Table 1.

[0078] Comparative Example 1

[0079] (1) 100 g of silver behenate powder, 100 g of ethanol, and 10 g of tetradecyldimethylamine n-propyl sulfonate (a dispersant) were mixed, and after being fully soaked, 457 g of water was added. The mixture was stirred for 2 hours at 500 rpm to obtain a silver behenate dispersion having a concentration of 15 wt %.

[0080] (2) 12.3 g of reducing agent hydroquinone was added to water and dissolved to obtain 487.7 g of reducing agent solution. The molar ratio of reducing agent to silver behenate was 1:2.

[0081] (3) 5 g of sodium triisopropylnaphthalenesulfonate (an emulsifier), 80 g of acetic acid, and 300 g of water were mixed to obtain a reaction mother solution.

[0082] (4) Using a double-injection emulsification process, the reaction mother liquor is added to an emulsification tank. At an emulsification temperature of 40° C. and under paddle stirring conditions, the silver behenate dispersion and the reducing agent solution are injected into the reaction mother liquor at a rate of 10 mL / min and 8 mL / min, respectively. After the injection is completed, the control conditions remain unchanged and the reaction is continued for 0.3 h. Then, the thin film silver powder is obtained by filtration, washing with water, and drying.

[0083] The specific particle size and diameter-to-thickness ratio of the thin film silver powder of Comparative Example 1 are shown in Table 1.

[0084] Comparative Example 2

[0085] Commercially available ground silver powder.

[0086] The specific particle size and diameter-to-thickness ratio of the ground silver powder of Comparative Example 2 are shown in Table 1.

[0087] Table 1

[0088]

[0089] It can be seen from the data in Table 1 that the aspect ratios of the thin-film silver powders of Examples 1-3 are all greater than 50, which is much larger than the aspect ratio of the currently commercially available ground silver powder. This indicates that the method of the present application can be used to prepare thin-film silver powders with a relatively large aspect ratio.

[0090] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0091] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing thin film silver powder, characterized in that: include: (1) mixing organic silver, alcohol and water to obtain an organic silver solution; (2) mixing a reducing agent and water to obtain a reducing agent solution; (3) mixing water and acid to obtain a reaction mother liquor; (4) adding the organic silver solution and the reducing agent solution to the reaction mother liquor, heating and stirring, and then keeping warm; The organic silver comprises an organic carboxylate silver having a carbon number between 18 and 22; The molar ratio of the reducing agent to the organic silver is 1 to 5; The organic silver has a conjugated eight-membered ring structure in its crystal structure; mixing the organosilver, alcohol, water and a dispersant to obtain an organosilver solution; In step (3), water, acid and emulsifier are mixed to obtain a reaction mother liquor; The mass ratio of the organic silver, the alcohol, the water and the dispersant in the organic silver solution is (5-10): (10-20): (67-84): (1-3); The mass ratio of the water, the acid and the emulsifier in the reaction mother liquor is (75-88): (10-20): (2-5).

2. The method according to claim 1, characterized in that The organic silver carboxylate includes at least one of silver stearate and silver behenate.

3. The method according to claim 1, characterized in that The reducing agent includes at least one of citric acid, ascorbic acid, ethylene glycol, glucose and hydroquinone.

4. The method according to claim 1, wherein The alcohol includes at least one of ethanol and propanol.

5. The method according to claim 1, characterized in that The acid includes at least one of acetic acid, dilute sulfuric acid and dilute nitric acid.

6. The method according to claim 1, wherein The dispersant includes tetradecyldimethylamine n-propyl sulfonate.

7. The method according to claim 1, characterized in that The emulsifier includes sodium triisopropylnaphthalene sulfonate.

8. The method according to claim 1, characterized in that The concentration of the reducing agent solution is 5-10 wt %.

9. The method according to claim 1, characterized in that The mass ratio of the organic silver solution to the reaction mother liquor is (45-75): (15-25).

10. The method according to claim 1, characterized in that In step (4), the organic silver solution and the reducing agent solution are added to the reaction mother liquor at a rate of 8-12 mL / min and 10-15 mL / min, respectively.

11. The method according to claim 1, wherein In step (4), the temperature of the insulation reaction is 50 to 80 degrees Celsius, and the time of the insulation reaction is 0.5 to 2 hours.

12. A thin film silver powder, characterized in that: The method according to any one of claims 1 to 11 is used to prepare the present invention.

13. The thin film silver powder according to claim 12, characterized in that The particle size of the thin film silver powder is 5-15 μm, and the aspect ratio is greater than 50.

14. An electronic component, characterized in that: The invention comprises an electronic component substrate and a silver paste coating, wherein the silver paste coating is formed on at least one side of the electronic component substrate, and the silver paste coating comprises the thin film silver powder according to claim 12 or 13.

Images