Preparation method and application of high-purity spherical silver powder

Abstract

The invention relates to the technical field of silver powder preparation, and discloses a preparation method of high-purity spherical silver powder, which comprises the following specific steps: a) under a high-temperature condition, carrying out chemical reaction for a period of time, respectively preparing a first dispersing agent and a second dispersing agent, preparing an oxidation solution through the first dispersing agent, and preparing a reduction solution through the second dispersing agent; b) in a stirring state, adding the reduction solution into the oxidation solution, and forming spherical silver powder by reducing and depositing silver particles; and c) the formed silver powder is sequentially subjected to centrifugal cleaning, drying and mechanical polishing, so that the high-purity spherical silver powder is prepared, and the invention further discloses application of the high-purity spherical silver powder. Self-made oxidation liquid and reduction liquid are used as raw materials, then the oxidation liquid and the reduction liquid are stirred, mixed and reacted to obtain silver-containing paste, and finally the silver-containing paste is centrifugally cleaned, dried and polished to prepare the high-purity spherical silver powder with the low burning loss rate, so that the electrical property of the silver powder is improved, and the use of a dispersing agent is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of silver powder preparation, and in particular to a preparation method of high-purity spherical silver powder and application thereof. Background Art

[0002] Metallic silver has excellent electrical and thermal conductivity and is widely used in electronic pastes such as conductive pastes (photovoltaics, 5G), high and low temperature conductive adhesives, electromagnetic shielding, and semiconductor packaging. Silver powder is the main conductive filler with a content of up to 60-98%, making it the most widely used and largest-volume metal powder material.

[0003] The rapid iterative development of new electronic and microelectronic devices has also put forward more stringent requirements on the physical parameters of conductive pastes and their main conductive raw material silver powder. As a metal powder, in addition to controlling the basic powder characteristics of silver powder such as particle size, specific surface area, tap density, ablation rate, thermal expansion rate, etc., the microstructure of silver powder particles and the organic components remaining on their surface largely affect the application scenarios of silver powder and the efficacy of its ancillary products. The particle size unit of silver powder particles is usually expressed as D50, which refers to the particle size value corresponding to the cumulative distribution percentage reaching 50%, also known as the median diameter or median particle size. In the evaluation of powder particle size, D50 is an important indicator , indicating that particles with a particle size larger than it and particles with a particle size smaller than it each account for 50%. In most cases, silver powder is synthesized into micron- or nano-scale spherical or quasi-spherical silver powder by a certain preparation process using a reducing agent (vitamin C, glucose, hydrazine hydrate, formaldehyde, acetaldehyde, hydrogen peroxide, hydroquinone, etc.), an oxidizing silver source (silver nitrate, silver carbonate, silver chloride, etc.) and a dispersant (PVP, gum arabic, polyvinyl alcohol, gelatin and other macromolecular organic matter). Due to the addition of a large amount of dispersant, the silver powder has a good dispersibility, but the large-scale use of dispersion not only increases the cost of raw materials and sewage treatment costs, but also the organic matter remaining on the surface of the silver powder affects the purity and application range of the silver powder.

[0004] Some silver powder manufacturers have also conducted relevant research. For example, in patent CN112264629A, the inventor quickly added VC solution into silver ammonia solution to synthesize silver powder without using a dispersant. The silver powder has a small particle size (less than 1 micron) and a low tap density. The silver powder synthesized according to the patent has a burn loss rate of more than 0.3%; patent CN116967461A discloses a highly dispersed, low-burn loss ultrafine silver powder and a preparation method thereof, and the silver powder has a burn loss rate of more than 0.3%; patent CN111432965A discloses a method for preparing silver powder, in which formaldehyde aqueous solution is added to silver ammonia solution, and the silver powder has a burn loss rate of more than 0.5%.

[0005] At present, the silver powder prepared by the existing technology not only has the problem of high burn-out rate, which affects the use effect of the silver powder, but also the use of a large amount of dispersant easily causes waste and pollution; therefore, it does not meet the existing needs. In this regard, we propose a preparation method of high-purity spherical silver powder and its application. Summary of the invention

[0006] The present invention provides a preparation method of high-purity spherical silver powder and application thereof, which has the beneficial effects of reducing the use of dispersants and reducing the silver powder burn-off rate, thereby improving the use effect of the silver powder, and solves the problem that the silver powder prepared by the prior art mentioned in the above background technology not only has a high burn-off rate, which affects the use effect of the silver powder, but also the use of a large amount of dispersants easily causes waste and pollution.

[0007] The present invention provides the following technical solution: a method for preparing high-purity spherical silver powder, comprising the following specific steps: a) Under high temperature conditions, a chemical reaction is carried out for a period of time to prepare a first dispersant, and an oxidizing liquid is prepared by the first dispersant; Under high temperature conditions, a chemical reaction is carried out for a period of time to prepare a second dispersant, and a reducing liquid is prepared by the second dispersant; b). Add the reducing solution to the oxidizing solution under stirring to form spherical silver powder by reducing and depositing silver particles; c) The silver powder formed in step b) is centrifugally cleaned, dried and mechanically polished in sequence to prepare high-purity spherical silver powder.

[0008] As an optional scheme for the preparation method of a high-purity spherical silver powder described in the present invention, wherein: in step a), the preparation of the oxidizing solution is as follows: preparing a silver-containing aqueous solution, adding an amino compound to the silver-containing aqueous solution to form a silver complex solution, adding the prepared alkaline compound under stirring, stirring for a certain period of time, adding the first dispersant S11 solution, and continuing to stir for a period of time until the first dispersant S11 molecules are fully free in the solution; Preparation of the reducing solution in step a): After the reducing agent is dissolved and diluted with water, the second dispersant S12 solution is added under stirring, and after sufficient stirring, the second dispersant S12 molecules are fully free in the solution; The preparation method of the first dispersant S11 is as follows: 1 mol of boric acid and 5 mol of ethylenediamine, a small amount of azobenzene are added, and the mixture is reacted at 120° C. for 2 hours to obtain the first dispersant S11; The preparation method of the second dispersant S12 is as follows: 1 mol of 12-hydroxystearic acid and 3 mol of ethanolamine, a small amount of tetrabutyl titanate are added, and the mixture is reacted at 200° C. for 2 hours to obtain the second dispersant S12; In the above preparation method, other reagents are also required to participate in the reaction.

[0009] As an optional solution of the method for preparing high-purity spherical silver powder according to the present invention, the first dispersant S11 and the second dispersant S12 are formed by a small molecule acid and a small molecule amine under the action of catalytic emulsification, and the small molecule acid includes one or more unit acids or polyacids composed of C1-C20, including inorganic acids: phosphoric acid, boric acid or silicic acid; Small molecule amines include one or more of the following: alcohol amines, fatty amines, monoamines or polyamines; Other reagents: phosphate ester, silicate ester, silane coupling agent, p-methoxybenzoic acid, di(benzaldehyde)ethylenediamine, isopropyl-α, a'-bis(4-sulfonatophenyl)-p-dimethylaminodiphenylmethane, and azobenzene.

[0010] As an optional scheme for the preparation method of a high-purity spherical silver powder described in the present invention, the silver-containing body includes one or more of the following substances: silver nitrate, silver acetate and silver carbonate.

[0011] As an optional solution of the method for preparing high-purity spherical silver powder of the present invention, the reducing agent comprises one or more of the following substances: ascorbic acid, formaldehyde, acetaldehyde, propionaldehyde, hydrazine hydrate, sodium borohydride or p-diphenol; The alkaline compound includes one or more of the following: sodium hydroxide, sodium carbonate, sodium bicarbonate, calcium hydroxide, calcium oxide, potassium hydroxide, potassium carbonate, sodium peroxide or lithium hydroxide; The amine compound includes one or more of the following: aqueous ammonia solution, ammonium salt, ethanolamine, triethanolamine or triethylenetetramine.

[0012] As an optional scheme for the preparation method of high-purity spherical silver powder described in the present invention, the molar ratio of the amino compound to the silver-containing body is 8:1-2:1, the molar ratio of the alkaline compound to the silver-containing body is 3:1-1:3, and the molar ratio of the reducing agent to the silver-containing body is 5:1-1:1.

[0013] As an optional scheme of the method for preparing high-purity spherical silver powder described in the present invention, the adding time of the reducing agent is controlled within 1 to 120 seconds.

[0014] As an optional scheme for the preparation method of a high-purity spherical silver powder described in the present invention, wherein: based on the dosage of sodium hydroxide and the type of reducing agent, the particle size of the prepared silver powder is different, and the particle size D50 is 1-3.0 μm.

[0015] As an optional method for preparing a high-purity spherical silver powder according to the present invention, wherein: the silver powder burnout rate is less than 0.2%, and the tap density of the silver powder is 5.8 to 6.5 g / cm 3 , and the specific surface area is 0.1 to 2.0m 2 / g.

[0016] The present invention also proposes an application of high-purity spherical silver powder. The prepared high-purity spherical silver powder is applied in the field of solar cell paste and various thick film pastes.

[0017] The present invention has the following beneficial effects: 1. The preparation method and application of the high-purity spherical silver powder are as follows: self-made oxidizing liquid and reducing liquid are used as raw materials, the oxidizing liquid and reducing liquid are stirred and mixed, a silver-containing slurry is obtained by reaction, and finally the silver-containing slurry is centrifugally cleaned, dried and polished to prepare high-purity spherical silver powder with a low burning loss rate, thereby solving the problem of high burning loss rate of silver powder prepared by the prior art as much as possible, which easily affects the use effect of the silver powder.

[0018] 2. The preparation method of the high-purity spherical silver powder and its application. The preparation method greatly reduces the use of dispersants, thereby achieving the effect of saving raw materials and effectively reducing the environmental pollution caused by the large-scale use of dispersants.

[0019] 3. The preparation method of the high-purity spherical silver powder and its application. The high-purity spherical silver powder prepared by this method has universal applicability and is widely used in the field of solar cell paste and various thick film pastes, showing obvious electrical performance advantages. DETAILED DESCRIPTION

[0020] 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0021] Embodiment 1: This embodiment aims to promote the solution of the problem that the silver powder prepared by the prior art has a high burning rate, which affects the use effect of the silver powder, and the use of a large amount of dispersant easily causes waste and pollution. A method for preparing high-purity spherical silver powder includes the following specific steps: Preparation of oxidation solution: add 1 kg of silver nitrate to 10 kg of pure water, then add 2.5 kg of industrial ammonia water (28%) to prepare a silver complex; under stirring, add 7.5 kg of 2% sodium hydroxide solution, stir for 5 minutes, then add 1 kg of 1% S11, stir for 15 minutes, control the temperature at 30°C, and set aside; Preparation of reducing solution: add 1 kg of formaldehyde solution (37%) to 8 kg of pure water, add 1 kg of 1% S12 under stirring, stir for 15 minutes, control the temperature at 30°C, and set aside; The reducing solution was quickly injected into the oxidizing solution within 60 seconds, and stirring was continued for 20 minutes to obtain a silver-containing slurry. The slurry was centrifugally washed and then dried in an oven at 80°C for 10 hours. The powder was mechanically ball-milled to obtain silver powder with an average particle size of 1.57 microns and a burn-loss rate of 0.18%.

[0022] In this embodiment: homemade oxidizing solution and reducing solution are used as raw materials, the oxidizing solution and the reducing solution are stirred and mixed, and a silver-containing slurry is obtained by reaction. Finally, the silver-containing slurry is centrifugally cleaned, dried and polished to prepare a high-purity spherical silver powder with a low burn-out rate, thereby solving the problem of high burn-out rate of silver powder prepared by the prior art as much as possible, which affects the use effect of the silver powder and the use of a large amount of dispersant easily causes waste and pollution.

[0023] Example 2: This example prepares silver powders with different particle sizes and burning loss rates based on Example 1: Preparation of oxidation solution: add 1 kg of silver nitrate to 10 kg of pure water, then add 2.5 kg of industrial ammonia water (28%) to prepare a silver complex; under stirring, add 7.5 kg of 2% sodium hydroxide solution, stir for 5 minutes, then add 1 kg of 1% S11, stir for 15 minutes, control the temperature at 30°C, and set aside; Preparation of reducing solution: add 1 kg of formaldehyde solution (37%) to 8 kg of pure water, add 1 kg of 1% S12 under stirring, stir for 15 minutes, control the temperature at 30°C, and set aside; The reducing solution was quickly injected into the oxidizing solution within 60 seconds, and stirring was continued for 20 minutes to obtain a silver-containing slurry. The slurry was centrifugally washed and then dried in an oven at 80°C for 10 hours. The powder was mechanically ball-milled to obtain silver powder with an average particle size of 1.35 microns and a burn-loss rate of 0.2%.

[0024] In this embodiment: compared with the first embodiment, a silver powder with a smaller particle size and a slightly higher burning rate is prepared.

[0025] Embodiment 3: This embodiment is based on Embodiment 1, and uses different chemical components to prepare the oxidizing liquid and the reducing liquid: Preparation of oxidation solution: add 1 kg of silver nitrate to 10 kg of pure water, then add 2 kg of industrial ammonia (28%) and 0.6 kg of triethylenetetramine to prepare a silver complex; under stirring, add 7.5 kg of 3% sodium hydroxide solution, stir for 5 minutes, then add 1 kg of 1% S11, stir for 15 minutes, control the temperature at 30°C and set aside; Preparation of reducing solution: add 0.8 kg of formaldehyde solution (37%) and 0.2 kg of acetaldehyde solution (40%) to 8 kg of pure water, add 1 kg of 1% S12 under stirring, stir for 15 minutes, control the temperature at 30°C, and set aside; The reducing solution was quickly injected into the oxidizing solution within 60 seconds, and stirring was continued for 20 minutes to obtain a silver-containing slurry. The slurry was centrifugally washed and then dried in an oven at 80°C for 10 hours. The powder was mechanically ball-milled to obtain silver powder with an average particle size of 1.72 microns and a burn-loss rate of 0.17%.

[0026] Embodiment 4: This embodiment is based on Embodiment 1, and uses different chemical components to prepare the oxidizing liquid and the reducing liquid: Preparation of oxidation solution: add 1 kg of silver nitrate to 10 kg of pure water, then add 2.5 kg of industrial ammonia water (28%) to prepare a silver complex; under stirring, add 7.5 kg of 3% sodium hydroxide solution, stir for 5 minutes, then add 1 kg of 1% substance S11, stir for 15 minutes, control the temperature at 30°C, and set aside; Preparation of reducing solution: add 0.5 kg of formaldehyde solution (37%) and 0.8 kg of acetaldehyde solution (40%) to 8 kg of pure water, add 1 kg of 1% S12 under stirring, stir for 15 minutes, control the temperature at 30°C, and set aside; The reducing solution was quickly injected into the oxidizing solution within 60 seconds, and stirring was continued for 20 minutes to obtain a silver-containing slurry. The slurry was centrifugally washed and then dried in an oven at 80°C for 10 hours. The powder was mechanically ball-milled to obtain silver powder with an average particle size of 1.91 microns and a burn-loss rate of 0.18%.

[0027] Comparative Example 1: Preparation of oxidation solution: add 1 kg of silver nitrate to 10 kg of pure water, then add 2.5 kg of industrial ammonia water (28%) to prepare a silver complex; add 7.5 kg of 2% sodium hydroxide solution under stirring, stir for 5 minutes, control the temperature at 30°C, and set aside; Preparation of reducing solution: Add 1 kg of formaldehyde solution (37%) to 9 kg of pure water, stir for 15 minutes, control the temperature at 30°C, and set aside; The reducing solution was quickly injected into the oxidizing solution within 60 seconds, and then 50 g of stearic acid alcohol solution with a silver powder content of 0.3% was added, and stirring was continued for 20 minutes to obtain a silver-containing slurry. The slurry was centrifuged and washed, and then dried in an oven at 80°C for 10 hours; the powder was mechanically ball-milled to obtain silver powder with an average particle size of 1.63 microns and a burn loss rate of 0.45%.

[0028] Comparative Example 2: Preparation of oxidation solution: Add 1 kg of silver nitrate to 17.5 kg of pure water, then add 2.5 kg of industrial ammonia (28%) to prepare a silver complex; the temperature is controlled at 20°C. Preparation of reducing solution: Add 0.54 kg of ascorbic acid to 10 kg of pure water, stir for 15 min, control the temperature at 20°C, and set aside; The reducing solution was quickly injected into the oxidizing solution within 60 seconds, and then 50 g of stearic acid alcohol solution with a silver powder content of 0.3% was added and stirred for 20 minutes to obtain a silver-containing slurry. The slurry was centrifuged and washed, and then dried in an oven at 80°C for 10 hours. The powder was mechanically ball-milled to obtain a silver powder with an average particle size of 1.51 microns and a burn loss rate of 0.65%. Example 4: Application of high-purity spherical silver powder. The prepared high-purity spherical silver powder is applied in the field of solar cell paste and various thick film pastes, showing obvious electrical performance advantages.

[0029] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0030] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing high-purity spherical silver powder, characterized in that: The specific steps include: a) Under high temperature conditions, chemical reaction for a period of time to prepare a first dispersant S11, and the oxidation liquid is prepared by the first dispersant S11; Under high temperature conditions, chemical reaction for a period of time to prepare a second dispersant S12, and the reducing liquid is prepared by the second dispersant S12; b). Add the reducing solution to the oxidizing solution under stirring to form spherical silver powder by reducing and depositing silver particles; c) The silver powder formed in step b) is centrifugally cleaned, dried and mechanically polished in sequence to prepare high-purity spherical silver powder.

2. The method for preparing high-purity spherical silver powder according to claim 1, characterized in that: Preparation of the oxidizing solution in step a): preparing a silver-containing aqueous solution, adding an amino compound to the silver-containing aqueous solution to form a silver complex solution, adding the prepared alkaline compound under stirring, stirring for a certain period of time, adding the first dispersant S11 solution, and continuing to stir for a period of time until the first dispersant S11 molecules are fully free in the solution; Preparation of the reducing solution in step a): After the reducing agent is dissolved and diluted with water, the second dispersant S12 solution is added under stirring, and after sufficient stirring, the second dispersant S12 molecules are fully free in the solution; The preparation method of the first dispersant S11 is as follows: 1 mol of boric acid and 5 mol of ethylenediamine, a small amount of azobenzene are added, and the mixture is reacted at 120° C. for 2 hours to obtain the first dispersant S11; The preparation method of the second dispersant S12 is as follows: 1 mol of 12-hydroxystearic acid and 3 mol of ethanolamine, a small amount of tetrabutyl titanate are added, and the mixture is reacted at 200° C. for 2 hours to obtain the second dispersant S12; In the above preparation method, other reagents are also required to participate in the reaction.

3. The method for preparing high-purity spherical silver powder according to claim 2, characterized in that: The first dispersant S11 and the second dispersant S12 are formed by a small molecule acid and a small molecule amine under the action of catalytic emulsification, and the small molecule acid includes one or more unit acids or polyacids composed of C1-C20, including inorganic acids: phosphoric acid, boric acid or silicic acid; Small molecule amines include one or more of the following: alcohol amines, fatty amines, monoamines or polyamines; Other reagents: phosphate ester, silicate ester, silane coupling agent, p-methoxybenzoic acid, di(benzaldehyde)ethylenediamine, isopropyl-α, a'-bis(4-sulfonatophenyl)-p-dimethylaminodiphenylmethane, and azobenzene.

4. The method for preparing high-purity spherical silver powder according to claim 2, characterized in that: The silver-containing body includes one or more of the following substances: silver nitrate, silver acetate and silver carbonate.

5. The method for preparing high-purity spherical silver powder according to claim 2, characterized in that: The reducing agent includes one or more of the following substances: ascorbic acid, formaldehyde, acetaldehyde, propionaldehyde, hydrazine hydrate, sodium borohydride or p-diphenol; The alkaline compound includes one or more of the following: sodium hydroxide, sodium carbonate, sodium bicarbonate, calcium hydroxide, calcium oxide, potassium hydroxide, potassium carbonate, sodium peroxide or lithium hydroxide; The amine compound includes one or more of the following: aqueous ammonia solution, ammonium salt, ethanolamine, triethanolamine or triethylenetetramine.

6. The method for preparing high-purity spherical silver powder according to claim 5, characterized in that: The molar ratio of the amino compound to the silver-containing body is 8:1-2:1, the molar ratio of the alkaline compound to the silver-containing body is 3:1-1:3, and the molar ratio of the reducing agent to the silver-containing body is 5:1-1:

1.

7. The method for preparing high-purity spherical silver powder according to claim 2, characterized in that: The adding time of the reducing agent is controlled within 1 to 120 seconds.

8. The method for preparing high-purity spherical silver powder according to claim 1, characterized in that: Based on the dosage of sodium hydroxide and the type of reducing agent, the prepared silver powder has different particle sizes, and its particle size D50 is 1-3.0 μm.

9. The method for preparing high-purity spherical silver powder according to claim 1, characterized in that: The silver powder burning loss rate is less than 0.2%, and the tap density of the silver powder is 5.8 to 6.5 g / cm 3 , and the specific surface area is 0.1 to 2.0m 2 / g.

10. Application of high-purity spherical silver powder, according to the method for preparing high-purity spherical silver powder according to any one of claims 1 to 9, characterized in that: The prepared high-purity spherical silver powder is used in the field of solar cell paste and various thick film pastes.