Spherical and flake doped silver powder and preparation method and application thereof

Abstract

The present invention provides a spherical and flaky doped silver powder, a preparation method and an application thereof. In the spherical and flaky doped silver powder: the particle size of the spherical silver powder is 0.8-2.0 μm, accounting for 70-95%; the flake diameter of the flaky silver powder is 2.5-6.5 μm, accounting for 5-30%; in the spherical and flaky doped silver powder provided by the present invention, the ratio between the spherical silver powder and the flaky silver powder is controllable, and the overlap is dense, so that the conductive paste prepared by the spherical and flaky doped silver powder has low resistance and excellent conductive performance.

Description

Technical Field

[0001] The present invention relates to the technical field of precious metal powder materials, and in particular to spherical and flaky doped silver powder, a preparation method thereof, and applications thereof. Background Art

[0002] Flake silver powder is a key functional material in conductive pastes. The proper blending of flake silver powder with spherical silver powder helps reduce resistance and silver usage. Therefore, it is typically mixed with spherical silver powder in a specific ratio for use in low-temperature silver pastes, such as conductive adhesives for light-emitting diode (LED) and chip packaging, and heterojunction (HJT) photovoltaic silver pastes. With the rapid development of the downstream industry chain, component integration and fine-line printing have become the current mainstream trends. Paste manufacturers are placing increasingly stringent demands on silver powder performance, raw material costs, and production efficiency.

[0003] Silver powder produced by the liquid-phase reduction method is mostly spherical, while flake silver powder is generally produced using mechanical ball milling. Under current research conditions, single spherical or flake silver powders are insufficient to meet customer needs. The technical difficulty of synthesizing both flake and spherical silver powders simultaneously is high. Slurry customers need to purchase both spherical and flake silver powders separately and determine the appropriate mixing ratio, resulting in high investment costs and low production efficiency.

[0004] Therefore, there is an urgent need for a spherical and flake doped silver powder and its preparation method and application to meet client application needs. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problem that the preparation method of silver powder is difficult to prepare spherical and flake doped silver powder.

[0006] In order to solve the above technical problems, the present invention first provides a spherical and flake doped silver powder, wherein, in the spherical and flake doped silver powder: the particle size of the spherical silver powder is 0.8~2.0μm, accounting for 70~95%; the flake diameter of the flake silver powder is 2.5~6.5μm, accounting for 5~30%.

[0007] Accordingly, the present invention also provides a method for preparing spherical and flake doped silver powder, comprising:

[0008] S1, mixing a silver nitrate solution, an activator, a nucleation inhibitor and a reducing solution to obtain a primary product;

[0009] S2, mixing the initial product with the coating agent and stirring to obtain a reaction mother solution;

[0010] S3, sequentially precipitating, washing, drying and screening the reaction mother liquid to obtain spherical and flake doped silver powder.

[0011] Preferably, step S1 specifically includes:

[0012] S11, mixing the silver nitrate solution and the activator and placing the mixture in a reaction kettle with stirring to obtain a first mixed solution;

[0013] S12, mixing the nucleation inhibitor and the reducing liquid to obtain a second mixed liquid, and then adding the second mixed liquid to the first mixed liquid and stirring to obtain a primary product;

[0014] In step S12, the second mixed liquid is added to the first mixed liquid for 5 to 15 seconds, and the stirring speed is 200 to 400 r / min.

[0015] Preferably, in step S11, the activator includes one or more of methanol, ethanol, formic acid, acetic acid, n-propanol, n-butanol, ethylene glycol and glycerol; the mass ratio of the activator to the silver nitrate in the silver nitrate solution is (0.05~0.3):1.

[0016] Preferably, in step S12, the nucleation inhibitor includes one or more of sodium phosphate, potassium phosphate, sodium sulfate, potassium sulfate, sodium carbonate, potassium carbonate, sodium chloride and potassium chloride; the mass ratio of the nucleation inhibitor to the silver nitrate in the silver nitrate solution is (0.01~0.1):1.

[0017] Preferably, in step S12, the reducing solution comprises one or more of ascorbic acid, hydrogen peroxide, glucose and hydrazine hydrate; the mass ratio of the reducing solution to the silver nitrate in the silver nitrate solution is (0.5-1.0): 1

[0018] Preferably, in step S2, the coating agent includes one or more of stearic acid, lauric acid and oleic acid.

[0019] Preferably, step S3 specifically includes:

[0020] S31, allowing the reaction mother liquor to stand and then performing solid-liquid separation to obtain a filter residue;

[0021] S32, washing the filter residue with deionized water until the conductivity is less than or equal to 20 μs / cm to obtain a wet powder;

[0022] S33, drying the wet powder and passing it through a 200-mesh sieve to obtain spherical and flake-shaped doped silver powder.

[0023] Correspondingly, the present invention further provides a use of the above-mentioned spherical and flake doped silver powder in the preparation of a conductive paste.

[0024] The beneficial effects of the present invention are as follows: different from the prior art, the present invention provides a spherical and flake doped silver powder, a preparation method and application thereof, in which: the particle size of the spherical silver powder is 0.8-2.0 μm, accounting for 70-95%; the flake diameter of the flake silver powder is 2.5-6.5 μm, accounting for 5-30%; in the spherical and flake doped silver powder provided by the present invention, the ratio between the spherical silver powder and the flake silver powder is controllable, and the overlap is dense, thereby making the conductive paste prepared by the spherical and flake doped silver powder have low resistance and excellent conductive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flow chart of a method for preparing spherical and flake doped silver powders according to an embodiment of the present invention;

[0026] Figure 2 Electron microscope images of spherical and flake-shaped doped silver powders provided in Example 1 of the present invention;

[0027] Figure 3 Electron microscope images of spherical and flake-shaped doped silver powders provided in Example 2 of the present invention;

[0028] Figure 4 This is an electron microscope image of the spherical and flake-shaped doped silver powder provided in Example 3 of the present invention;

[0029] Figure 5 The electron microscope images of the spherical and flake-shaped doped silver powder provided for Comparative Example 1. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] In response to the technical problem that existing silver powder preparation methods are difficult to prepare spherical and flake-shaped doped silver powder, the present invention provides a spherical and flake-shaped doped silver powder and a preparation method and application thereof. The spherical and flake-shaped doped silver powder prepared by this method has the characteristics of good dispersibility and controllable proportion of spherical and flake shapes. The entire process is prepared in one step, the operation method is fast and simple, green and harmless, and suitable for large-scale production.

[0032] In order to achieve the above technical objectives, this application adopts the following technical solutions:

[0033] In the first aspect, the present invention first provides a spherical and flake doped silver powder, wherein in the spherical and flake doped silver powder: the particle size of the spherical silver powder is 0.8~2.0μm, accounting for 70~95%; the flake diameter of the flake silver powder is 2.5~6.5μm, accounting for 5~30%.

[0034] In a second aspect, the present invention also provides a method for preparing the above-mentioned spherical and flake doped silver powder.

[0035] See also Figure 1 , Figure 1 Flowchart of a method for preparing spherical and flake-shaped doped silver powder according to an embodiment of the present invention; wherein the above-mentioned preparation method specifically includes:

[0036] S1, mixing a silver nitrate solution, an activator, a nucleation inhibitor and a reducing solution to obtain a primary product.

[0037] Specifically, step S1 further includes:

[0038] S11, mixing the silver nitrate solution and the activator and placing the mixture in a reaction kettle with stirring to obtain a first mixed solution;

[0039] S12, mixing the nucleation inhibitor and the reducing liquid to obtain a second mixed liquid, and then adding the second mixed liquid to the first mixed liquid and stirring to obtain a primary product;

[0040] In step S12, the second mixed liquid is added to the first mixed liquid for 5 to 15 seconds, and the stirring speed is 200 to 400 r / min.

[0041] Specifically, the silver nitrate solution and the reducing solution undergo an oxidation-reduction reaction, so that the silver ions in the silver nitrate solution are reduced to silver powder.

[0042] Specifically, an activator refers to a solution that increases the rate of a chemical reaction or improves reaction performance. Activators are typically substances that interact with reactants, thereby altering the reaction pathway or reducing the activation energy of the reaction. In this embodiment, the introduction of an activator controls the release of silver ions and improves the dispersion of silver particles.

[0043] In step S11, the activator includes one or more of methanol, ethanol, formic acid, acetic acid, n-propanol, n-butanol, ethylene glycol and glycerol; the mass ratio of the activator to the silver nitrate in the silver nitrate solution is (0.05~0.3):1.

[0044] Specifically, when the mass ratio of the activator to the silver nitrate in the silver nitrate solution is less than 0.05:1, the release rate of silver ions is too low, which increases the reaction time; when the mass ratio of the activator to the silver nitrate in the silver nitrate solution is greater than 0.3:1, the release rate of silver ions is too fast, which deteriorates the dispersion of silver particles.

[0045] Specifically, a nucleation inhibitor refers to a substance that can inhibit or prevent the formation of crystal nuclei during crystal growth. Nucleation is a key step in crystal growth, and the role of the nucleation inhibitor is to inhibit the formation and growth of crystal nuclei by binding to active sites on the crystal surface. In this embodiment, the present invention controls the anisotropic growth of silver crystal nuclei in the reaction system by introducing a nucleation inhibitor, causing some silver powder to tend to grow in a flaky form, thereby achieving a controllable ratio of spherical and flaky silver powders. The dense overlap between the flaky and spherical silver powders makes the resulting conductive paste low in resistance and excellent in conductivity.

[0046] In step S12, the nucleation inhibitor includes one or more of sodium phosphate, potassium phosphate, sodium sulfate, potassium sulfate, sodium carbonate, potassium carbonate, sodium chloride and potassium chloride; the mass ratio of the nucleation inhibitor to the silver nitrate in the silver nitrate solution is (0.01~0.1):1.

[0047] Specifically, when the mass ratio of the nucleation inhibitor to the silver nitrate in the silver nitrate solution is less than 0.01:1, the amount of flaky silver powder generated after the reaction will be too small, making it difficult to meet customer needs; when the mass ratio of the nucleation inhibitor to the silver nitrate in the silver nitrate solution is greater than 0.1:1, the amount of powdered silver powder generated after the reaction will be too small, making it difficult to meet customer needs.

[0048] In step S12, the reducing solution includes one or more of ascorbic acid, hydrogen peroxide, glucose and hydrazine hydrate; the mass ratio of the reducing solution to the silver nitrate in the silver nitrate solution is (0.5~1.0):1.

[0049] Specifically, when the mass ratio of the reducing solution to the silver nitrate in the silver nitrate solution is less than 0.5:1, the degree of oxidation of the silver ions in the silver nitrate solution will be reduced, thereby reducing the amount of oxidation products generated accordingly; when the mass ratio of the reducing solution to the silver nitrate in the silver nitrate solution is greater than 1.0:1, the excessive reducing solution does not fully participate in the reaction, resulting in waste of reagents and increased experimental costs.

[0050] S2, mixing the initial product with the coating agent and stirring to obtain a reaction mother solution.

[0051] Specifically, step S2 further includes:

[0052] After the second mixed solution and the first mixed solution are completely oxidized and reduced, the primary product generated after the reaction is mixed with a coating agent and stirred to obtain a reaction mother solution; wherein the coating agent includes one or more of stearic acid, lauric acid and oleic acid.

[0053] Specifically, the coating agent is used to coat the primary product, which can form a protective film on the surface of the silver powder, reducing the contact between the silver powder and the air, thereby reducing the degree of oxidation of the silver powder.

[0054] S3, sequentially precipitating, washing, drying and screening the reaction mother liquid to obtain spherical and flake doped silver powder.

[0055] Specifically, step S3 includes:

[0056] S31, allowing the reaction mother liquor to stand for 10 minutes and then performing solid-liquid separation to obtain a filter residue;

[0057] S32, washing the filter residue with deionized water until the conductivity is less than or equal to 20 μs / cm to obtain a wet powder; wherein, the residual impurity ions are removed by repeatedly washing with deionized water so that the conductivity meets the requirement of less than or equal to 20 μs / cm, thereby ensuring the quality and performance of the product.

[0058] S33, drying the wet powder and passing it through a 200-mesh sieve to obtain spherical and flake-shaped doped silver powder.

[0059] Correspondingly, the present invention further provides a use of the above-mentioned spherical and flake doped silver powder in the preparation of a conductive paste.

[0060] The technical solution of the present invention will now be further described with reference to specific embodiments.

[0061] Example 1:

[0062] Example 1 of the present invention provides a method for preparing spherical and flake doped silver powder, comprising the following steps:

[0063] S1, raw material preparation: weigh 200g analytical grade silver nitrate and dissolve it in 2L deionized water to obtain a silver nitrate solution, then add 20g ethanol and mix well for later use; weigh 6g potassium sulfate and dissolve it in 100mL deionized water to obtain a nucleation inhibitor; weigh 95g ascorbic acid and dissolve it in 1.5L deionized water to obtain a reducing agent solution for later use; weigh 5g oleic acid and dissolve it in 20mL anhydrous ethanol to obtain a coating agent for later use.

[0064] S2, transfer the mixture of silver nitrate solution and activator to the reactor, start stirring, and pour the mixture of nuclear inhibitor and reducing solution into the reactor under stirring at 300r / min, controlling the feeding time to be 10s. After the feeding is completed, pour the coating agent into the reactor and continue stirring for 10min until the reaction is complete to obtain the reaction mother liquor;

[0065] S3: The reaction mother liquor is allowed to stand for 10 minutes before being discharged into a solid-liquid separator, filtered, and washed with deionized water until the conductivity is below 20 μs / cm. The wet powder is then placed in a forced air drying oven and dried at 70°C for 10 hours. The dried silver powder is sieved through a 200-mesh screen to obtain spherical and flake-shaped doped silver powder.

[0066] Specifically, the spherical and flake doped silver powders obtained in Example 1 have a D50 of 2.1 μm, and the electron microscope photos thereof are as follows: Figure 2 As shown, spherical silver powder accounts for about 85% and flake silver powder accounts for about 15%. The silver powder prepared in Example 1 was mixed with an organic resin, a binder, and the like to prepare a low-temperature conductive silver paste. Standard lines were printed using a screen printer. After baking at 150°C for 1 hour, the paste was tested using an ohmmeter to obtain a resistance value of 0.13Ω.

[0067] Example 2:

[0068] Example 2 of the present invention provides a method for preparing spherical and flake doped silver powder, comprising the following steps:

[0069] S1, raw material preparation: weigh 200g analytical grade silver nitrate and dissolve it in 2L deionized water to obtain a silver nitrate solution, then add 20g ethylene glycol and mix well for later use; weigh 8g potassium chloride and dissolve it in 100mL deionized water to obtain a nucleation inhibitor; weigh 95g ascorbic acid and dissolve it in 1.5L deionized water to obtain a reducing agent solution for later use; weigh 5g lauric acid and dissolve it in 20mL anhydrous ethanol to obtain a coating agent for later use.

[0070] S2, transfer the mixture of silver nitrate solution and activator to the reactor, start stirring, and pour the mixture of nuclear inhibitor and reducing solution into the reactor under stirring at 300r / min, controlling the feeding time to be 10s. After the feeding is completed, pour the coating agent into the reactor and continue stirring for 10min until the reaction is complete to obtain the reaction mother liquor;

[0071] S3: The reaction mother liquor is allowed to stand for 10 minutes before being discharged into a solid-liquid separator, filtered, and washed with deionized water until the conductivity is below 20 μs / cm. The wet powder is then placed in a forced air drying oven and dried at 70°C for 10 hours. The dried silver powder is sieved through a 200-mesh screen to obtain spherical and flake-shaped doped silver powder.

[0072] Specifically, the spherical and flake doped silver powders obtained in Example 2 have a D50 of 2.2 μm, and the electron microscope photos thereof are as follows: Figure 3 As shown, spherical silver powder accounts for about 95% and flake silver powder accounts for about 5%. The silver powder prepared in Example 2 was mixed with an organic resin, a binder, and the like to prepare a low-temperature conductive silver paste. Standard lines were printed using a screen printer. After baking at 150°C for 1 hour, the paste was tested using an ohmmeter to obtain a resistance value of 0.22Ω.

[0073] This embodiment 3:

[0074] This embodiment 3 provides a method for preparing spherical and flake doped silver powder, comprising the following steps:

[0075] S1, raw material preparation: weigh 200g analytical grade silver nitrate and dissolve it in 2L deionized water to obtain a silver nitrate solution, then add 10g ethanol and mix well for later use; weigh 5g sodium sulfate and dissolve it in 100mL deionized water to obtain a nucleation inhibitor; weigh 95g ascorbic acid and dissolve it in 1.5L deionized water to obtain a reducing agent solution for later use; weigh 5g oleic acid and dissolve it in 20mL anhydrous ethanol to obtain a coating agent for later use.

[0076] S2, transfer the mixture of silver nitrate solution and activator to the reactor, start stirring, and pour the mixture of nuclear inhibitor and reducing solution into the reactor under stirring at 200 r / min, controlling the feeding time to be 10 s. After the feeding is completed, pour the coating agent into the reactor and continue stirring for 10 min until the reaction is complete to obtain the reaction mother liquor;

[0077] S3: The reaction mother liquor is allowed to stand for 10 minutes before being discharged into a solid-liquid separator, filtered, and washed with deionized water until the conductivity is below 20 μs / cm. The wet powder is then placed in a forced air drying oven and dried at 70°C for 10 hours. The dried silver powder is sieved through a 200-mesh screen to obtain spherical and flake-shaped doped silver powder.

[0078] Specifically, the spherical and flake doped silver powders obtained in Example 3 have a D50 of 2.0 μm, and the electron microscope photos thereof are as follows: Figure 4 As shown, spherical silver powder accounts for about 90% and flake silver powder accounts for about 10%. The silver powder prepared in Example 3 was mixed with an organic resin, a binder, and the like to prepare a low-temperature conductive silver paste. Standard lines were printed using a screen printer. After baking at 150°C for 1 hour, the paste was tested using an ohmmeter to obtain a resistance value of 0.17Ω.

[0079] Comparative Example 1:

[0080] Comparative Example 1 provides a method for preparing micro-nano silver powder, except that no activator and nucleation inhibitor are added, and other contents are the same as those of Example 1 of the present invention.

[0081] Specifically, the silver powder prepared in Comparative Example 1 is substantially spherical in shape and poorly dispersed, as shown in the electron microscope photograph. Figure 5 As shown, after the low-temperature conductive silver paste is printed and baked, the resistance value is tested to be 0.37Ω, which is poor in conductivity.

[0082] Specifically, by comparing the spherical and flake doped silver powder prepared in Example 1 of the present invention with the silver powder prepared in Comparative Example 1, it can be seen that the resistance value of the low-temperature conductive silver paste prepared by the spherical and flake doped silver powder prepared in Example 1 of the present invention and organic resin, binder, etc. is much lower than that of the low-temperature conductive silver paste prepared in Comparative Example 1.

[0083] The spherical and flake doped silver powders prepared by the present invention through a process with rapid reaction, simple operation, and green and harmless properties have good dispersibility, and the proportion of flakes is controllable at 5-30%. The powders can be applied in the field of low-temperature conductive silver paste and are suitable for mass production.

[0084] In the process of generating spherical and flaky doped silver powders through oxidation-reduction of a silver nitrate solution and a reducing solution, the present invention controls the release of silver ions and improves the dispersibility of silver particles by introducing an activator, and controls the anisotropy of the growth of silver crystal nuclei in the reaction system by introducing a nucleation inhibitor, so that part of the silver powder tends to grow in a flaky form, thereby achieving a controllable ratio between the spherical silver powder and the flaky silver powder, and making the overlap between the flaky silver powder and the spherical silver powder dense, thereby making the prepared conductive paste low in resistance and excellent in conductive performance; at the same time, the synthesis process of the present invention has the characteristics of rapid reaction, simple operation, and being green and harmless, and is suitable for mass production.

[0085] In summary, different from the prior art, the present invention provides a spherical and flake doped silver powder, a preparation method and application thereof, in which: the particle size of the spherical silver powder is 0.8~2.0μm, accounting for 70~95%; the flake diameter of the flake silver powder is 2.5~6.5μm, accounting for 5~30%; in the spherical and flake doped silver powder provided by the present invention, the ratio between the spherical silver powder and the flake silver powder is controllable, and the overlap is dense, thereby making the conductive paste prepared by the above-mentioned spherical and flake doped silver powder low in resistance and excellent in conductive performance.

[0086] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0087] The above embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing spherical and flake doped silver powder, characterized in that: include: S1, mixing a silver nitrate solution, an activator, a nucleation inhibitor and a reducing solution to obtain a primary product; The reducing solution comprises one or more of ascorbic acid, hydrogen peroxide, glucose and hydrazine hydrate, and the mass ratio of the reducing solution to the silver nitrate in the silver nitrate solution is (0.5-1.0):1; the nucleation inhibitor comprises one or more of sodium phosphate, potassium phosphate, sodium sulfate, potassium sulfate, sodium carbonate, potassium carbonate, sodium chloride and potassium chloride, and the mass ratio of the nucleation inhibitor to the silver nitrate in the silver nitrate solution is (0.01-0.1):1; S2, mixing the primary product with a coating agent and stirring to obtain a reaction mother solution; the coating agent includes one or more of stearic acid, lauric acid and oleic acid; S3, sequentially precipitating, washing, drying and screening the reaction mother solution to obtain spherical and flaky doped silver powder; Among them, among the spherical and flake doped silver powders: the particle size of the spherical silver powder is 0.8~2.0μm, accounting for 70~95%; the flake diameter of the flake silver powder is 2.5~6.5μm, accounting for 5~30%; The S1 step specifically includes: S11, mixing the silver nitrate solution and the activator and placing them in a reaction kettle and stirring to obtain a first mixed solution, wherein the activator includes one or more of methanol, ethanol, formic acid, acetic acid, n-propanol, n-butanol, ethylene glycol and glycerol, and the mass ratio of the activator to the silver nitrate in the silver nitrate solution is (0.05-0.3): 1; S12, mixing the nucleation inhibitor and the reducing liquid to obtain a second mixed liquid, and then adding the second mixed liquid to the first mixed liquid for stirring to obtain the primary product; Wherein, in the step S12, the adding time of the second mixed liquid to the first mixed liquid is 5-15s, and the stirring speed of the stirring treatment is 200-400r / min.

2. The method for preparing spherical and flake doped silver powder according to claim 1, characterized in that: The S3 step specifically includes: S31, allowing the reaction mother liquor to stand for solid-liquid separation to obtain a filter residue; S32, washing the filter residue with deionized water until the conductivity is less than or equal to 20 μs / cm to obtain wet powder; S33, drying the wet powder and passing it through a 200-mesh sieve to obtain the spherical and flaky doped silver powder.

3. Use of the spherical and flake doped silver powder prepared by the method for preparing spherical and flake doped silver powder according to any one of claims 1 to 2 in preparing conductive paste.

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