Ultrahigh specific surface area microcrystalline silver powder and preparation method and application thereof
By adding hydrophilic surfactant and strong alkali to the silver salt solution to generate silver oxide, and adding dispersant and amine reducing agent on the basis of it, microcrystalline silver powder with high specific surface area and low tap density was prepared, which solved the problem of low specific surface area of silver powder in the prior art, and achieved high-performance silver powder preparation suitable for low silver conductive silver paste.
Patent Information
- Application Number
- CN202411979947.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-05-13
AI Technical Summary
In the prior art, the specific surface area of silver powder is relatively low, making it difficult to meet the application needs of low-silver conductive silver paste in electronic components.
Silver oxide is generated by adding hydrophilic surfactant and strong alkali solution to the silver salt solution, followed by adding dispersant and amine-based reducing agent. After solid-liquid separation, cleaning, and drying, microcrystalline silver powder with high specific surface area and low tap density is prepared.
The prepared microcrystalline silver powder has an ultra-high specific surface area, low tap density and high sintering activity. It is suitable for applications with low silver conductive silver paste and can show excellent performance in high-temperature sintering and low-temperature curing.
Smart Images
Figure CN119973127A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of preparation of metal powder for the electronic industry, and in particular to ultra-high specific surface area microcrystalline silver powder and a preparation method and application thereof. Background Art
[0002] Metallic silver powder has excellent electrical and thermal conductivity and antioxidant properties. Therefore, silver paste with it as the main conductive functional phase can have the advantages of excellent conductivity, adhesion, solderability, bending resistance, simple process, precise wiring, etc. It is widely used in photovoltaics, liquid crystal displays (LCDs), SMD light emitting diodes (LEDs), integrated circuit (IC) chips, printed circuit board assemblies (PCBAs), ceramic capacitors, membrane switches, smart cards, radio frequency identification and other electronic components.
[0003] In order to meet the ever-changing functional requirements of electronic and microelectronic devices, higher performance requirements are also placed on electronic pastes and their silver powders. As a precious metal powder material, in order to meet specific requirements, it is usually necessary to control the basic powder characteristics of the silver powder, such as morphology, particle size, and specific surface area. Under the premise of equivalent particle size and morphology, the higher the specific surface area, the better the sintering activity of the silver powder. At the same time, the specific surface area of the silver powder has a significant effect on the viscosity and printing performance of the paste. At the same time, in order to reduce device costs, reducing the amount of precious metal silver powder while ensuring the application performance of the silver paste is also one of the focuses of attention in this field. High specific surface area silver powder can help low-silver silver pastes have excellent printability and conductivity.
[0004] At present, high specific surface area silver powder is mainly prepared by liquid phase reduction method. For example, patent CN114682792B first adds a certain amount of coupling agent to silver nitrate solution to form silver ammonia solution, and then adds two reducing agents of different concentrations at different rates to reduce the specific surface area of 3-4m 2 / g spherical silver powder has relatively high sintering activity and can be sintered at a lower sintering temperature, but its tap density is not less than 4g / cm 3 , so that it is mainly used in high silver content paste, which does not meet the use requirements of low silver content conductive silver paste for electronic components. Summary of the invention
[0005] In order to solve the problems of low specific surface area of silver powder in the prior art, the present invention provides an ultra-high specific surface area microcrystalline silver powder which can be used in low silver content slurry and a preparation method thereof, which has a simple method, a short process and low energy consumption, and the specific scheme is as follows:
[0006] A method for preparing ultra-high specific surface area microcrystalline silver powder comprises the following steps:
[0007] Step 1: prepare a silver salt solution with a silver ion concentration of 50-500 g / L and maintain a constant temperature of 30-60°C;
[0008] Step 2: preparing a hydrophilic surfactant solution with a mass concentration of 3%-5%, adding the hydrophilic surfactant solution to the silver salt solution in step 1 and stirring evenly to obtain a silver-containing solution; the mass ratio of the hydrophilic surfactant to the silver salt is 0.002-0.005:1, and the HLB of the hydrophilic surfactant is 10-15;
[0009] Step 3: prepare a strong alkali solution with a concentration of 100-200 g / L, maintain a constant temperature of 30-60° C., and then slowly add it to the silver-containing solution obtained in step 2 under stirring to generate silver oxide, and maintain the temperature at 40-60° C. during the process; the mass ratio of the strong alkali to the silver salt is 0.2-0.5:1;
[0010] Step 4: prepare a dispersant solution with a concentration of 18-22 g / L, add the dispersant solution to the silver oxide obtained in step 3, stir evenly, and obtain a silver oxide reaction solution; the mass ratio of the dispersant to the silver salt is 0.02-0.2:1, and the HLB of the dispersant is 3-10;
[0011] Step 5: prepare 250g / L of an amine reducing agent, quickly add the reducing agent to the silver oxide reaction solution obtained in step 4, stir for 30-50min until the reaction is completed, separate the solid from the liquid, wash, dry, crush and sieve to obtain ultrafine microcrystalline silver powder; the mass ratio of the amine reducing agent to the silver salt is 0.12-0.13:1.
[0012] Furthermore, in step 1, the silver salt is silver nitrate, silver acetate, silver sulfate, or silver oxalate, among which silver nitrate is preferred.
[0013] Furthermore, the solvent of the hydrophilic surfactant solution in step 2 is water, and the hydrophilic surfactant is one or more combinations of polysorbate, fatty alcohol polyoxyethylene ether, sodium alkyl aryl sulfonate, and tragacanth.
[0014] Furthermore, the strong base in step 3 is one or more combinations of beaded sodium hydroxide, potassium hydroxide, and calcium hydroxide, among which beaded sodium hydroxide is preferred.
[0015] Furthermore, the solvent in the dispersant solution in step 4 is alcohol or water, and the dispersant is one or more combinations of gum arabic, gelatin, Span 80, palmitic acid, and rosin.
[0016] Furthermore, the amine reducing agent in step 5 is a combination of ethylenediamine, p-phenylenediamine, monoethanolamine, diethanolamine, and triethanolamine, among which a combination of ethylenediamine, p-phenylenediamine, and triethanolamine is preferred.
[0017] Furthermore, the drying temperature in step 5 is 60-80°C.
[0018] The microcrystalline silver powder prepared by the above method is a cluster of nano-scale silver powder with a specific surface area of not less than 5m 2 / g, tap density is not higher than 2g / cm 3 , can be used for low silver content conductive silver paste, and low silver content conductive silver paste can be further used in electronic components.
[0019] Compared with the prior art, the present invention has the following advantages: the present invention first prepares small-particle silver oxide by adding a hydrophilic surfactant solution to a silver salt solution and then adding a strong alkali solution. Since silver oxide is insoluble in water and the generation reaction is quite rapid, the addition of a hydrophilic surfactant can significantly enhance the dispersibility of fine particles in water in the initial stage of silver oxide generation, slow down the agglomeration and growth caused by sedimentation, so as to facilitate the formation of small-particle silver oxide; subsequently, a dispersant is added to the silver oxide solution so that the silver oxide in the silver oxide solution is evenly dispersed, and a weak reducing agent-amine mixed reducing agent is quickly added so that the silver oxide is quickly contacted with a large amount of weak reducing agent, so that the reduction process speed is appropriate, and finally a large amount of nanometer-level secondary particles softly agglomerated microcrystalline silver powder can be prepared, which has an ultra-high specific surface area, a low tap density, and a high sintering activity. In the pulping and printing process, the silver powder can be evenly distributed in the slurry system, reducing the square resistance, and can be used for high-temperature sintering and low-temperature curing of low-silver-containing slurry. The method of the present invention is simple and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The embodiments of the present invention are further described below with reference to the accompanying drawings, in which:
[0021] Figure 1 The process flow chart of the preparation method of the present invention is shown;
[0022] Figure 2 This is a scanning electron microscope image of the product prepared in Example 1 of the present invention;
[0023] Figure 3 This is a scanning electron microscope image of the product prepared in Example 2 of the present invention;
[0024] Figure 4 This is a scanning electron microscope image of the product prepared in Example 3 of the present invention;
[0025] Figure 5 This is a scanning electron microscope image of the product prepared in Example 4 of the present invention;
[0026] Figure 6 This is a scanning electron microscope image of the product prepared in Example 5 of the present invention;
[0027] Figure 7 This is a scanning electron microscope image of the product prepared in Comparative Example 1;
[0028] Figure 8This is a scanning electron microscope image of the product prepared in Comparative Example 2;
[0029] Fig. 9 This is a scanning electron microscope image of the product prepared in Comparative Example 3;
[0030] Fig.10 This is a scanning electron microscope image of the product prepared in Comparative Example 4. DETAILED DESCRIPTION
[0031] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.
[0032] A method for preparing ultra-high specific surface area microcrystalline silver powder comprises the following steps:
[0033] Step 1: prepare a silver salt solution with a silver ion concentration of 50-500 g / L and maintain a constant temperature of 30-60° C.; the silver salt is silver nitrate, silver acetate, silver sulfate, or silver oxalate, among which silver nitrate is preferred.
[0034] Step 2: prepare a hydrophilic surfactant solution with a mass concentration of 3%-5%, add the hydrophilic surfactant solution to the silver salt solution in step 1, stir evenly to obtain a silver-containing solution; the mass ratio of the hydrophilic surfactant to the silver salt is 0.002-0.005:1, and the HLB of the hydrophilic surfactant is 10-15; the solvent of the hydrophilic surfactant solution is water, and the hydrophilic surfactant is one or more combinations of polysorbate, fatty alcohol polyoxyethylene ether, sodium alkyl aryl sulfonate, and tragacanth gum.
[0035] Step 3: prepare a strong alkali solution with a concentration of 100-200 g / L, maintain a constant temperature of 30-60° C., and then slowly add it to the silver-containing solution obtained in step 2 under stirring to generate silver oxide. During the process, the temperature is maintained at 40-60° C.; the mass ratio of the strong alkali to the silver salt is 0.2-0.5:1; the strong alkali is one or more combinations of beaded sodium hydroxide, potassium hydroxide, and calcium hydroxide.
[0036] Step 4: prepare a dispersant solution with a concentration of 18-22 g / L, add the dispersant solution to the silver oxide obtained in step 3, stir evenly, and obtain a silver oxide reaction solution; the mass ratio of the dispersant to the silver salt is 0.02-0.2:1, and the HLB of the dispersant is 3-10; the dispersant is one or more combinations of gum arabic, gelatin, Span 80, palmitic acid, and rosin.
[0037] Step 5: prepare 250g / L of an amine reducing agent, which is a combination of ethylenediamine, p-phenylenediamine, monoethanolamine, diethanolamine, and triethanolamine; quickly add the reducing agent to the silver oxide reaction solution obtained in step 4; stir for 30-50 minutes until the reaction is completed; and separate the solid from the liquid, wash, dry, crush, and sieve at a drying temperature of 60-80°C to obtain ultrafine microcrystalline silver powder; the mass ratio of the amine reducing agent to the silver salt is 0.12-0.13:1.
[0038] Embodiment 1:
[0039] A method for preparing ultra-high specific surface area microcrystalline silver powder comprises the following steps:
[0040] (1) Prepare silver salt solution: weigh 200 g of silver nitrate into a 5 L beaker, then add 2 L of pure water, keep the temperature at 30 °C, and stir thoroughly.
[0041] (2) Weigh 0.4 g of sodium alkyl aryl sulfonate into a 20 mL beaker, add 10 mL of pure water, and then add the water into the above silver salt solution and stir evenly to obtain a silver-containing solution.
[0042] (3) Weigh 50 g of beaded sodium hydroxide into a 1 L beaker, add 500 mL of pure water and stir thoroughly until completely dissolved, keep the temperature at 30°C, then slowly add it to the silver-containing solution under stirring to generate silver oxide, and keep the temperature at 40°C.
[0043] (4) Add 400 mL of 20 g / L gum arabic solution into the silver oxide solution and stir thoroughly for 5 min.
[0044] (5) Quickly pour the reducing agent into the silver oxide solution obtained in step 4, stir for 30-50 minutes, and detect whether there is Ag in the reaction solution. + The reaction was judged to be over when the stirring was stopped, and the mixture was separated into solid and liquid, washed, dried at 80°C for 10 hours, crushed, and passed through a 200-mesh sieve to obtain ultrafine microcrystalline silver powder.
[0045] Wherein: Prepare the reducing agent: weigh 20g triethanolamine and 5g ethylenediamine in a 1L beaker, then add 100mL pure water, stir well and keep the temperature at 40°C.
[0046] Embodiment 2:
[0047] A method for preparing ultra-high specific surface area microcrystalline silver powder comprises the following steps:
[0048] (1) Prepare the silver salt solution in the same manner as in Example 1.
[0049] (2) Weigh 0.4 g of polysorbate 85 into a 20 mL beaker, add 10 mL of pure water, and then add the water into the above silver salt solution and stir evenly to obtain a silver-containing solution.
[0050] (3) Weigh 50 g of beaded sodium hydroxide into a 1 L beaker, add 500 mL of pure water and stir thoroughly until completely dissolved, keep the temperature at 30°C, then slowly add it to the silver-containing solution under stirring to generate silver oxide, and keep the temperature at 40°C.
[0051] (4) Add 400 mL of 20 g / L gum arabic solution into the silver oxide solution and stir thoroughly for 5 min.
[0052] (5) Quickly pour the reducing agent into the silver oxide solution obtained in step 4, stir for 30-50 minutes, and detect whether there is Ag in the reaction solution. + The reaction was judged to be over when the stirring was stopped, and the mixture was separated into solid and liquid, washed, dried at 80°C for 10 hours, crushed, and passed through a 200-mesh sieve to obtain ultrafine microcrystalline silver powder.
[0053] Wherein: Prepare the reducing agent: weigh 15g triethanolamine and 10g ethylenediamine in a 1L beaker, then add 100mL pure water, stir well and keep the temperature at 40°C.
[0054] Embodiment 3:
[0055] A method for preparing ultra-high specific surface area microcrystalline silver powder comprises the following steps:
[0056] (1) Prepare the silver salt solution in the same manner as in Example 1.
[0057] (2) Weigh 0.4 g of polysorbate 85 into a 20 mL beaker, add 10 mL of pure water, and then add the water into the above silver salt solution and stir evenly to obtain a silver-containing solution.
[0058] (3) Weigh 50 g of beaded sodium hydroxide into a 1 L beaker, add 500 mL of pure water and stir thoroughly until completely dissolved, keep the temperature at 30°C, then slowly add it to the silver-containing solution under stirring to generate silver oxide, and keep the temperature at 40°C.
[0059] (4) Add 500 mL of 20 g / L gelatin solution into the silver oxide solution and stir thoroughly for 5 min.
[0060] (5) Quickly pour the reducing agent into the silver oxide solution obtained in step 4, stir for 30-50 minutes, and detect whether there is Ag in the reaction solution. + The reaction was judged to be over when the stirring was stopped, and the mixture was separated into solid and liquid, washed, dried at 80°C for 10 hours, crushed, and passed through a 200-mesh sieve to obtain ultrafine microcrystalline silver powder.
[0061] Wherein: Prepare the reducing agent: weigh 20g triethanolamine and 5g ethylenediamine in a 1L beaker, then add 100mL pure water, stir well and keep the temperature at 40°C.
[0062] Embodiment 4:
[0063] A method for preparing ultra-high specific surface area microcrystalline silver powder comprises the following steps:
[0064] (1) Prepare silver salt solution: weigh 100 g of silver nitrate into a 5 L beaker, then add 2 L of pure water, keep the temperature at 40 °C, and stir thoroughly.
[0065] (2) Weigh 0.5 g of sodium alkyl aryl sulfonate into a 20 mL beaker, add 10 mL of pure water, and then add the water into the above silver salt solution and stir evenly to obtain a silver-containing solution.
[0066] (3) Weigh 50 g of beaded sodium hydroxide into a 1 L beaker, add 500 mL of pure water and stir thoroughly until completely dissolved, keep the temperature at 40°C, then slowly add it to the silver-containing solution under stirring to generate silver oxide, and keep the temperature at 50°C.
[0067] (4) Add 800 mL of 20 g / L gum arabic solution into the silver oxide solution and stir thoroughly for 5 min.
[0068] (5) Quickly pour the reducing agent into the silver oxide solution obtained in step 4, stir for 30-50 minutes, and detect whether there is Ag in the reaction solution. + The reaction was judged to be over when the stirring was stopped, and the mixture was separated into solid and liquid, washed, dried at 80°C for 10 hours, crushed, and passed through a 200-mesh sieve to obtain ultrafine microcrystalline silver powder.
[0069] Wherein: Prepare the reducing agent: weigh 10g triethanolamine and 2.5g ethylenediamine in a 1L beaker, then add 50mL pure water, stir well and keep the temperature at 40°C.
[0070] Embodiment 5:
[0071] A method for preparing ultra-high specific surface area microcrystalline silver powder comprises the following steps:
[0072] (1) Prepare silver salt solution: weigh 400 g of silver nitrate into a 5 L beaker, then add 2 L of pure water, keep the temperature at 30 °C, and stir thoroughly.
[0073] (2) Weigh 1 g of sodium alkyl aryl sulfonate into a 50 mL beaker, add 20 mL of pure water, and then add the water into the above silver salt solution and stir evenly to obtain a silver-containing solution.
[0074] (3) Weigh 100 g of beaded sodium hydroxide into a 1 L beaker, add 500 mL of pure water and stir thoroughly until completely dissolved, keep the temperature constant at 30° C., then slowly add it to the silver-containing solution under stirring to generate silver oxide, and keep the temperature constant at 40° C.
[0075] (4) Add 500 mL of 20 g / L gum arabic solution to the silver oxide solution and stir thoroughly for 5 min.
[0076] (5) Quickly pour the reducing agent into the silver oxide solution obtained in step 4, stir for 30-50 minutes, and detect whether there is Ag in the reaction solution. + The reaction was judged to be over when the stirring was stopped, and the mixture was separated into solid and liquid, washed, dried at 80°C for 10 hours, crushed, and passed through a 200-mesh sieve to obtain ultrafine microcrystalline silver powder.
[0077] Wherein: Prepare the reducing agent: weigh 40g triethanolamine and 10g ethylenediamine in a 1L beaker, then add 200mL pure water, stir well and keep the temperature at 40°C.
[0078] Comparative Example 1:
[0079] (1) Prepare the silver salt solution in the same manner as in Example 1.
[0080] (2) Weigh 0.4 g of polysorbate 85 into a 20 mL beaker, add 10 mL of pure water, and then add the water into the above silver salt solution and stir evenly to obtain a silver-containing solution.
[0081] (3) Weigh 50 g of beaded sodium hydroxide into a 1 L beaker, add 500 mL of pure water and stir thoroughly until completely dissolved, keep the temperature at 30°C, then slowly add it to the silver-containing solution under stirring to generate silver oxide, and keep the temperature at 40°C.
[0082] (4) Quickly pour the reducing agent into the silver oxide solution obtained in step 3, stir for 30-50 minutes, and detect whether there is Ag in the reaction solution. + The reaction was judged to be over when the stirring was stopped, and the mixture was separated into solid and liquid, washed, dried at 80°C for 10 hours, crushed, and passed through a 200-mesh sieve to obtain ultrafine microcrystalline silver powder.
[0083] Wherein: Prepare the reducing agent: weigh 20g triethanolamine and 5g ethylenediamine in a 1L beaker, then add 100mL pure water, stir well and keep the temperature at 40°C.
[0084] Comparative Example 2:
[0085] (1) Prepare the silver salt solution in the same manner as in Example 1.
[0086] (2) Weigh 50 g of sodium hydroxide beads into a 1 L beaker, add 500 mL of pure water and stir thoroughly until completely dissolved, keep the temperature at 30°C, then slowly add it to the silver salt solution under stirring to generate silver oxide, and keep the temperature at 40°C.
[0087] (3) Add 50 mL of 20 g / L gelatin solution into the silver oxide solution and stir thoroughly for 5 min.
[0088] (4) Quickly pour the reducing agent into the silver oxide solution obtained in step 3, stir for 30-50 minutes, and detect whether there is Ag in the reaction solution. + The reaction was judged to be over when the stirring was stopped, and the mixture was separated into solid and liquid, washed, dried at 80°C for 10 hours, crushed, and passed through a 200-mesh sieve to obtain ultrafine microcrystalline silver powder.
[0089] Wherein: Prepare the reducing agent: weigh 20g triethanolamine and 5g ethylenediamine in a 1L beaker, then add 100mL pure water, stir well and keep the temperature at 40°C.
[0090] Comparative Example 3:
[0091] A method for preparing ultra-high specific surface area microcrystalline silver powder comprises the following steps:
[0092] (1) Prepare silver salt solution: weigh 200 g of silver nitrate into a 5 L beaker, then add 2 L of pure water, keep the temperature at 30 °C, and stir thoroughly.
[0093] (2) Add 400 mL of 20 g / L gum arabic solution to the silver salt solution to obtain a silver-containing solution, and stir thoroughly for 5 minutes.
[0094] (3) Weigh 50 g of beaded sodium hydroxide into a 1 L beaker, add 500 mL of pure water and stir thoroughly until completely dissolved, keep the temperature at 30°C, then slowly add it to the silver-containing solution under stirring to generate silver oxide, and keep the temperature at 40°C.
[0095] (4) Quickly pour the reducing agent into the silver oxide solution obtained in step 3, stir for 30-50 minutes, and detect whether there is Ag in the reaction solution. + The reaction is judged to be complete when the temperature is high, and a silver powder solution is obtained.
[0096] (5) Weigh 0.4 g of sodium alkyl aryl sulfonate in a 20 mL beaker, add 10 mL of pure water, then add it to the silver powder solution in step 4 above and stir evenly. Check if there is any Ag in the reaction solution. + The reaction was judged to be over when the stirring was stopped, and the mixture was separated into solid and liquid, washed, dried at 80°C for 10 hours, crushed, and passed through a 200-mesh sieve to obtain silver powder.
[0097] Wherein: Prepare the reducing agent: weigh 25g of triethanolamine in a 1L beaker, then add 100mL of pure water, stir well and keep the temperature at 40℃.
[0098] Comparative Example 4:
[0099] A method for preparing ultra-high specific surface area microcrystalline silver powder comprises the following steps:
[0100] (1) Prepare silver salt solution: weigh 200 g of silver nitrate into a 5 L beaker, then add 2 L of pure water, keep the temperature at 30 °C, and stir thoroughly.
[0101] (2) Preparation of reducing agent: weigh 20 g of triethanolamine and 5 g of ethylenediamine in a 1 L beaker, then add 100 mL of pure water, stir thoroughly and keep the temperature at 40°C.
[0102] (3) Weigh 50 g of sodium hydroxide beads into a 1 L beaker, add 500 mL of pure water and stir thoroughly until completely dissolved, and keep the temperature at 30 °C.
[0103] (4) Prepare 400 mL of 20 g / L gum arabic solution.
[0104] (5) Add sodium hydroxide solution, silver salt solution and reducing agent solution to the gum arabic solution in parallel, stir slowly for 30-50 minutes, keep the temperature at 40°C, and check if there is any Ag in the reaction solution. + The reaction was judged to be complete and stirring was stopped.
[0105] (6) Weigh 0.4 g of sodium alkyl aryl sulfonate into a 20 mL beaker, add 10 mL of pure water, then add it to the solution in step 5 and stir evenly, separate the solid and liquid, wash, dry at 80° C. for 10 hours, crush, and pass through a 200 mesh sieve to obtain ultrafine microcrystalline silver powder.
[0106] The silver powders obtained in Examples 1-5 and Comparative Examples 1-4 were photographed by SEM, and the results are as follows: Figure 2-9 As shown in the figure, it can be found that compared with the comparative example, the silver powder prepared in Examples 1-5 is composed of a large number of nano-scale particles (several to tens of nanometers) clusters, while the silver powder in the comparative example is composed of larger particles (about hundreds of nanometers) clusters, so the silver powder in the examples has a higher specific surface area and higher sintering activity.
[0107] The silver powder obtained in Examples 1-5 and Comparative Examples 1-4 was tested for specific surface area, tap density and square resistance using a dynamic nitrogen adsorption specific surface tester, a tap density tester and a four-probe tester. The results are shown in Table 1. It can be found from Table 1 that the specific surface areas (BET determination) of the products obtained in Examples 1-5 are all over 5 m 2 / g, and the tap density (TD measurement) is less than 2g / cm 3 , and the square resistance is lower than 230mΩ / □.
[0108] Table 1 Performance test
[0109]
[0110] Some exemplary embodiments of the present invention are described above. It can be understood that the above embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention. The features in these embodiments can be recombined in a suitable manner, and the scheme obtained thereby is still within the protection scope required by the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without making creative work, that is, all modifications, equivalent substitutions and improvements made within the spirit and principles of this application, fall within the protection scope required by the present invention.
Claims
1. A method for preparing ultra-high specific surface area microcrystalline silver powder, characterized in that: The following steps are involved: Step 1: prepare a silver salt solution with a silver ion concentration of 50-500 g / L and maintain a constant temperature of 30-60°C; Step 2: preparing a hydrophilic surfactant solution with a mass concentration of 3%-5%, adding the hydrophilic surfactant solution to the silver salt solution in step 1 and stirring evenly to obtain a silver-containing solution; the mass ratio of the hydrophilic surfactant to the silver salt is 0.002-0.005:1, and the HLB of the hydrophilic surfactant is 10-15; Step 3: prepare a strong alkali solution with a concentration of 100-200 g / L, maintain a constant temperature of 30-60° C., and then slowly add it to the silver-containing solution obtained in step 2 under stirring to generate silver oxide, and maintain the temperature at 40-60° C. during the process; the mass ratio of the strong alkali to the silver salt is 0.2-0.5:1; Step 4: prepare a dispersant solution with a concentration of 18-22 g / L, add the dispersant solution to the silver oxide obtained in step 3, stir evenly, and obtain a silver oxide reaction solution; the mass ratio of the dispersant to the silver salt is 0.02-0.2:1, and the HLB of the dispersant is 3-10; Step 5: prepare 250g / L of an amine reducing agent, quickly add the reducing agent to the silver oxide reaction solution obtained in step 4, stir for 30-50min until the reaction is completed, separate the solid from the liquid, wash, dry, crush and sieve to obtain ultrafine microcrystalline silver powder; the mass ratio of the amine reducing agent to the silver salt is 0.12-0.13:
1.
2. The method for preparing ultra-high specific surface area microcrystalline silver powder according to claim 1, characterized in that: In step 1, the silver salt is silver nitrate, silver acetate, silver sulfate or silver oxalate.
3. The method for preparing ultra-high specific surface area microcrystalline silver powder according to claim 1, characterized in that: The solvent of the hydrophilic surfactant solution in step 2 is water, and the hydrophilic surfactant is one or more combinations of polysorbate, fatty alcohol polyoxyethylene ether, sodium alkyl aryl sulfonate, and tragacanth gum.
4. The method for preparing ultra-high specific surface area microcrystalline silver powder according to claim 1, characterized in that: The strong base in step 3 is one or more combinations of beaded sodium hydroxide, potassium hydroxide, and calcium hydroxide.
5. The method for preparing ultra-high specific surface area microcrystalline silver powder according to claim 1, characterized in that: The solvent in the dispersant solution in step 4 is alcohol or water, and the dispersant is one or more combinations of gum arabic, gelatin, Span 80, palmitic acid, and rosin.
6. The method for preparing ultra-high specific surface area microcrystalline silver powder according to claim 1, characterized in that: The amine reducing agent in step 5 is a combination of ethylenediamine, p-phenylenediamine, monoethanolamine, diethanolamine and triethanolamine.
7. The method for preparing ultra-high specific surface area microcrystalline silver powder according to claim 1, characterized in that: The drying temperature in step 5 is 60-80°C.
8. A microcrystalline silver powder prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The microcrystalline silver powder is a cluster of nano-scale silver powder with a specific surface area of not less than 5m 2 / g, tap density is not higher than 2g / cm 3 .
9. Use of the microcrystalline silver powder according to claim 8 in low-silver-containing conductive silver paste for electronic components.