WO2021180029A1 - 银包铜粉及其制备方法、电子浆料 - Google Patents

银包铜粉及其制备方法、电子浆料 Download PDF

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WO2021180029A1
WO2021180029A1 PCT/CN2021/079529 CN2021079529W WO2021180029A1 WO 2021180029 A1 WO2021180029 A1 WO 2021180029A1 CN 2021079529 W CN2021079529 W CN 2021079529W WO 2021180029 A1 WO2021180029 A1 WO 2021180029A1
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Prior art keywords
silver
copper powder
reducing agent
coated copper
ammonia solution
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PCT/CN2021/079529
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English (en)
French (fr)
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赵维巍
傅振邦
李康
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哈尔滨工业大学(深圳)(哈尔滨工业大学深圳科技创新研究院)
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Publication of WO2021180029A1 publication Critical patent/WO2021180029A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • C23C18/42—Coating with noble metals
    • C23C18/44—Coating with noble metals using reducing agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/17—Metallic particles coated with metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/02—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of metals or alloys
    • H01B1/026—Alloys based on copper
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables

Definitions

  • the invention relates to the technical field of electronic pastes, in particular to silver-coated copper powder, a preparation method thereof, and electronic pastes.
  • silver paste has a high price and is prone to electromigration failure. Therefore, people have turned their attention to copper, which has a conductivity similar to that of silver. However, copper is easily oxidized in the air, which reduces the conductivity of copper paste.
  • the silver-clad copper paste combines the advantages of the two, which can not only solve the electromigration problem of silver, but also reduce the cost and improve the oxidation problem of copper. Therefore, silver-coated copper powder is an ideal substitute for silver powder.
  • replacement electroless plating uses the reducibility of copper to directly replace silver ions to obtain silver-coated copper particles, but the silver layer obtained by replacement electroless plating is usually loose; reduction electroless plating uses silver ions and a complexing agent to mix to obtain silver The ionic solution reacts with the reducing agent to replace the silver particles coated on the surface of the micron copper, but this method usually obtains an island-shaped silver coating layer, and a higher proportion of silver is required to obtain a better coating.
  • Silver-coated copper powder and if the reducing agent is too strong, it is silver mixed copper powder; the replacement and chemical deposition compound method is to first use the reducing property of copper to coat a part of the silver particles on the surface, and then add the reducing agent.
  • copper ions will generate copper oxide or copper hydroxide precipitates. These precipitates will adhere to the surface of the copper powder, increase the surface resistance of the copper powder, and hinder the continued deposition of the silver coating.
  • the copper powder will be partially oxidized during the pretreatment process of the copper powder, which hinders the subsequent coating process.
  • the purpose of the present invention is to provide a method for preparing silver-coated copper powder, which aims to solve the problem that oxides adhere to the surface of copper powder in the existing preparation method of silver-coated copper powder, which leads to loose silver coating in the silver-coated copper powder and reduces the cost of silver-coated copper powder.
  • Technical issues such as resistivity.
  • Another object of the present invention is to provide a silver-coated copper powder.
  • Another object of the present invention is to provide an electronic paste.
  • a preparation method of silver-coated copper powder includes the following steps:
  • the intermediate product is mixed with the second silver ammonia solution and the second reducing agent and reacted to obtain silver-coated copper powder; wherein the molar ratio of the copper powder to the second silver ammonia solution and the second reducing agent is 1.26: (0.06 ⁇ 0.20): (0.02 ⁇ 0.15).
  • the first reducing agent and the second reducing agent are independently selected from at least one of glucose, hydrazine hydrate, sodium borohydride, and acetaldehyde.
  • the concentration of the first silver ammonia solution is 0.10-0.75 mol/L; and/or,
  • the concentration of the first reducing agent is 0.02-0.2 mol/L.
  • the volume fraction of the ammonia water is 10-40%, and the volume ratio of the ammonia water to the first silver ammonia solution and the first reducing agent is 1: (1.5 to 2.5): (4 to 6) .
  • the concentration of the second silver ammonia solution is 0.05-0.20 mol/L; and/or,
  • the concentration of the second reducing agent is 0.025-0.075 mol/L.
  • the time of the mixing treatment is 1-60 minutes; and/or,
  • the step of mixing the intermediate product with the second silver ammonia solution and the second reducing agent and reacting includes: adding the intermediate product to the dispersant for mixing treatment, and then dripping separately at a temperature of 25-60°C The second silver ammonia solution and the second reducing agent are reacted for 1 to 4 hours after the dripping, and the silver-coated copper powder is obtained by separation.
  • the dispersant is selected from: at least one of octylphenol polyoxyethylene ether-10 and polyvinylpyrrolidone; and/or,
  • the rate of dripping the second silver ammonia solution and the second reducing agent is 10 to 80 drops/minute, respectively.
  • the copper powder further includes the pretreatment of the copper powder, including the step of sequentially using octylphenol polyoxyethylene ether-10, deionized water, and sulfuric acid with a concentration of 5-20% for the copper powder. Wash with deionized water to obtain pretreated copper powder.
  • a silver-coated copper powder the particle size of the silver-coated copper powder is 500 nanometers to 20 microns, and the mass percentage of silver in the silver-coated copper powder is 10-30%.
  • an electronic paste which contains the silver-coated copper powder prepared by the above-mentioned method or contains the above-mentioned silver-coated copper powder.
  • the preparation method of silver-coated copper powder provided by the present invention first, according to the molar ratio of the copper powder to the first silver ammonia solution and the first reducing agent is 1.26: (0.06 to 0.30): (0.05 to 0.25),
  • the copper powder is mixed with the first silver ammonia solution with a lower molar ratio and the first reducing agent for the first coating, and copper oxide or copper hydroxide precipitation will be generated during the replacement reaction of copper and silver;
  • the addition of ammonia water can not only reduce the oxides or hydroxides of copper powder and inhibit the oxidation of copper powder, but also inhibit the formation of large particles of silver ions on the surface of copper, making the silver coating layer formed by replacement denser and improving silver
  • the coating rate of copper powder reduces the amount of silver source used, and obtains an intermediate product with a smooth surface after the first coating.
  • the intermediate product and the second silver ammonia solution are combined with each other.
  • the second reducing agent After the second reducing agent is mixed, it reacts, and the intermediate product is coated with silver for the second time using a lower molar ratio of the second silver ammonia solution and the second reducing agent to further ensure that the silver is completely coated on the surface of the copper powder, which improves the silver
  • the conductivity and oxidation resistance of the copper-coated powder make the prepared silver-coated copper powder have high conductivity, and the resistivity is as low as 1.1 ⁇ 10 -5 ⁇ cm, which prevents the second silver ammonia solution and the second reducing agent from being too high. Lead to separate generation of silver impurity particles.
  • the preparation method of silver-coated copper powder provided by the invention has simple operation and is suitable for industrialized large-scale production and application.
  • the silver-coated copper powder provided by the present invention has a particle size of 500 nanometers to 20 microns, and the particle size is uniform, which not only prevents the unevenness of the silver layer from reducing the conductivity and oxidation resistance of the silver-coated copper powder, but also ensures the silver-coated copper powder The applicability of it is suitable for screen printing and other processes to prevent problems such as blockage caused by excessive particles.
  • the silver-coated copper powder provided by the invention has a mass percentage of 10-30%.
  • the silver layer is densely coated, has high coating efficiency and good stability, thereby reducing the amount of silver source used and ensuring that the silver-coated copper
  • the electrical conductivity of the powder achieves low silver coating, high electrical conductivity, and resistivity as low as 1.1 ⁇ 10 -5 ⁇ cm.
  • the electronic paste provided by the present invention contains the silver-coated copper powder with good stability, low conductivity and high conductivity, the electronic paste has good conductivity, good stability, and a wide range of applications.
  • FIG. 1 is a scanning electron micrograph of the intermediate product after the first silver plating provided in Example 1 of the present invention
  • Example 2 is a scanning diagram of the silver-coated copper powder finally obtained in Example 1 of the present invention.
  • Fig. 3 is a scanning diagram of silver-coated copper powder provided by Comparative Example 1 of the present invention.
  • Fig. 4 is a scanning diagram of pure copper powder after only pretreatment of the present invention.
  • Example 5 is an EDS characterization diagram of silver-coated copper powder provided in Example 1 of the present invention.
  • Fig. 6 is an X-ray diffraction diagram of the silver-coated copper powder provided in Example 1 of the present invention.
  • Figure 7 is a thermogravimetric analysis diagram of the intermediate product, silver-coated copper powder, comparative example 1 silver-coated copper powder and pure copper powder of Example 1 of the present invention.
  • first and second are only used for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with “first” and “second” may explicitly or implicitly include one or more of these features.
  • “plurality” means two or more than two, unless otherwise specifically defined.
  • the weight of the relevant components mentioned in the description of the embodiments of the present invention can not only refer to the specific content of each component, but also can indicate the proportion of weight between the components. Therefore, as long as the relevant group is in accordance with the description of the embodiment of the present invention Enlargement or reduction in proportion to the content of the fennel is within the scope disclosed in the specification of the embodiments of the present invention.
  • the weight described in the specification of the embodiment of the present invention may be a mass unit known in the chemical industry, such as ⁇ g, mg, g, kg, etc.
  • the embodiment of the present invention provides a method for preparing silver-coated copper powder, which includes the following steps:
  • the silver-coated copper powder is separated and obtained; wherein the moles of the copper powder, the second silver ammonia solution and the second reducing agent The ratio is 1.26:(0.06 ⁇ 0.20):(0.02 ⁇ 0.15).
  • the preparation method of the silver-coated copper powder provided by the embodiment of the present invention first, according to the molar ratio of the copper powder to the first silver ammonia solution and the first reducing agent is 1.26: (0.06 ⁇ 0.20): (0.05 ⁇ 0.25 ), mixing the copper powder with the first silver ammonia solution with a lower molar ratio and the first reducing agent for the first coating, and copper oxide or copper hydroxide precipitation will be generated during the replacement reaction of copper and silver; Then by adding ammonia water, not only the ammonia water can reduce the oxides or hydroxides of the copper powder and inhibit the oxidation of the copper powder, but also the ammonia water can inhibit the formation of large particles of silver ions on the copper surface, making the silver coating layer formed by replacement denser and improve The coverage rate of silver to copper powder reduces the amount of silver source used, and obtains an intermediate product with a smooth surface after the first coating.
  • the intermediate product and the second silver ammonia solution are combined with each other.
  • the second reducing agent After the second reducing agent is mixed, it reacts, and the intermediate product is coated with silver for the second time using a lower molar ratio of the second silver ammonia solution and the second reducing agent to further ensure that the silver is completely coated on the surface of the copper powder, which improves the silver
  • the conductivity and oxidation resistance of the copper-coated powder make the prepared silver-coated copper powder have high conductivity, and the resistivity is as low as 1.1 ⁇ 10 -5 ⁇ cm, which prevents the second silver ammonia solution and the second reducing agent from being too high. Lead to separate generation of silver impurity particles.
  • the preparation method of silver-coated copper powder provided by the embodiment of the present invention has simple operation and is suitable for industrialized large-scale production and application.
  • step S10 copper powder is obtained, the copper powder is mixed with the first silver ammonia solution and the first reducing agent, and then ammonia water is added, mixed treatment, and separated to obtain an intermediate product; wherein, the copper powder and the first reducing agent
  • the molar ratio of the silver ammonia solution to the first reducing agent is 1.26: (0.06 to 0.30): (0.05 to 0.25).
  • the molar ratio of the copper powder to the first silver ammonia solution and the first reducing agent is 1.26:(0.06 ⁇ 0.30):(0.05 ⁇ 0.25), and the copper powder has a lower molar ratio
  • the first silver ammonia solution and the first reducing agent are mixed for the first coating.
  • the molar ratio of the copper powder to the first silver ammonia solution and the first reducing agent is 1.26:0.06:0.05, 1.26:(0.06 ⁇ 0.1):(0.05 ⁇ 0.1) or 1.26: (0.1 ⁇ 0.3): (0.1 ⁇ 0.25) etc.
  • the first reducing agent is selected from at least one of glucose, hydrazine hydrate, sodium borohydride, and acetaldehyde.
  • the first reducing agent can undergo a reduction reaction with the silver ions in the silver ammonia solution, and the silver ions are coated on the surface of the copper powder to form a silver coating layer.
  • the concentration of the first silver ammonia solution is 0.1-0.75 mol/L. In some embodiments, the concentration of the first reducing agent is 0.02-0.2 mol/L. In the embodiment of the present invention, a first silver ammonia solution with a higher concentration and a first reducing agent are first used to coat the copper powder.
  • the high-concentration silver source can improve the coating efficiency of the silver source on the copper powder.
  • the concentration of the ammonia solution is higher than 0.75 mol/L, or the concentration of the first reducing agent is higher than 0.2 mol/L, which will cause the generated silver particles to be suspended in the solution and increase the consumption of the silver source.
  • the concentration of the first silver ammonia solution may be 0.1 mol/L, 0.2 mol/L, 0.3 mol/L, 0.4 mol/L, 0.5 mol/L, 0.6 mol/L, or 0.75 mol. /L, etc.
  • the concentration of the first reducing agent is 0.02 mol/L, 0.05 mol/L, 0.1 mol/L, 0.15 mol/L, or 0.2 mol/L, etc.
  • the volume fraction of the ammonia water is 10-40%, and the volume ratio of the ammonia water to the first silver ammonia solution and the first reducing agent is 1: (1.5 to 2.5): (4 ⁇ 6).
  • the ammonia water added after mixing the copper powder with the first silver ammonia solution and the first reducing agent.
  • the ammonia water can reduce the oxide or hydroxide of the copper powder, inhibit the oxidation of the copper powder, and make the copper
  • the surface of the powder is cleaner, which is conducive to the coating of silver ions;
  • ammonia water can inhibit the formation of large particles of silver ions on the copper surface, making the silver coating layer formed by replacement denser, and improving the coating rate of silver to copper powder.
  • the volume fraction of the ammonia water may be 10%, 15%, 20%, 30%, or 40%, etc.
  • the ammonia water is combined with the first silver ammonia solution and the first reducing agent.
  • the volume ratio is 1:(1.5 ⁇ 2.5):(4 ⁇ 6).
  • the copper powder is mixed with the first silver ammonia solution and the first reducing agent, and then ammonia water is added, and the mixing treatment is carried out for 1 to 60 minutes, and then the intermediate product can be separated and obtained.
  • the solid and liquid are separated with a Buchner funnel, and the solid is washed repeatedly with deionized water for 3 to 5 times to obtain an intermediate product.
  • pretreatment of the copper powder is further included, including the step of sequentially using octylphenol polyoxyethylene ether-10, deionized water, and a concentration of 5-20 for the copper powder. % Sulfuric acid and deionized water to obtain pretreated copper powder. Because the surface of commercial copper powder is usually covered with impurities such as oil, the embodiment of the present invention first uses octylphenol polyoxyethylene ether-10 to ultrasonically clean the micron copper. Specifically, it can be cleaned for 5-30 minutes and repeated with deionized water.
  • the copper powder is washed sequentially with octylphenol polyoxyethylene ether-10, deionized water, sulfuric acid with a concentration of 5-20%, and deionized water to obtain the pretreated copper powder ; Then according to the molar ratio of the copper powder to the first silver ammonia solution and the first reducing agent is 1.26: (0.06 ⁇ 0.30): (0.05 ⁇ 0.25), the copper powder and the concentration of 0.1 ⁇ 0.75mol /L of the first silver ammonia solution and at least one first reducing agent selected from the group consisting of glucose, hydrazine hydrate, sodium borohydride, and acetaldehyde with a concentration of 0.02 ⁇ 0.2mol/L.
  • the volume fraction is 10 ⁇ 40% after mixing
  • the volume ratio of the ammonia water to the first silver ammonia solution and the first reducing agent is 1: (1.5 ⁇ 2.5): (4 ⁇ 6), mixed treatment, and separated to obtain an intermediate product.
  • the intermediate product is mixed with the second silver ammonia solution and the second reducing agent and then reacted to separate the silver-coated copper powder; wherein, the copper powder is combined with the second silver ammonia solution and the second reducing agent.
  • the molar ratio of the two reducing agents is 1.26: (0.06-0.20): (0.02-0.15).
  • the molar ratio of the copper powder to the second silver ammonia solution and the second reducing agent is 1.26: (0.06 ⁇ 0.20): (0.02 ⁇ 0.15), and the intermediate product and the second silver ammonia The solution and the second reducing agent are mixed and reacted.
  • the intermediate product is coated with the second silver-ammonia solution and the second reducing agent with a lower molar ratio to further ensure that the silver is completely coated on the surface of the copper powder.
  • Improve the conductivity and oxidation resistance of the silver-coated copper powder so that the prepared silver-coated copper powder has high conductivity and the resistivity is as low as 1.1 ⁇ 10 -5 ⁇ cm, and prevents the concentration of the second silver ammonia solution and the second reducing agent Too high results in the generation of silver impurity particles alone.
  • the molar ratio of the copper powder to the second silver ammonia solution and the second reducing agent may be 1.26: (0.06 ⁇ 0.1): (0.02 ⁇ 0.08), 1.26: (0.1 ⁇ 0.15): (0.08 ⁇ 0.12) or 1.26: (0.15 ⁇ 0.20): (0.12 ⁇ 0.15), etc.
  • the second reducing agent is selected from at least one of glucose, hydrazine hydrate, sodium borohydride, and acetaldehyde.
  • the second reducing agent can undergo a reduction reaction with the silver ions in the silver ammonia solution, and the generated silver ions can be coated on the outer surface of the intermediate product to further ensure that the silver is completely coated on the surface of the copper powder to form a silver layer coating Dense, high-conductivity silver-coated copper powder.
  • the concentration of the second silver ammonia solution is 0.05 to 0.20 mol/L. In some embodiments, the concentration of the second reducing agent is 0.025-0.075 mol/L. In the embodiment of the present invention, a low-concentration second silver ammonia solution and a second reducing agent are used for the second silver coating of the intermediate product, which further ensures that the silver is completely coated on the surface of the copper powder, and improves the conductivity of the silver-coated copper powder.
  • the concentration of the second silver ammonia solution may be 0.05 mol/L, 0.1 mol/L, 0.15 mol/L or 0.20 mol/L, and the concentration of the second reducing agent is 0.025 mol/L , 0.035mol/L, 0.05mol/L, 0.06mol/L or 0.075mol/L.
  • the step of mixing the intermediate product with the second silver ammonia solution and the second reducing agent and reacting includes: adding the intermediate product to the dispersant for mixing treatment, and then at a temperature of 25-60°C.
  • the second silver ammonia solution and the second reducing agent were respectively added dropwise under the conditions of, and reacted for 1 to 4 hours after the dropwise addition, and the silver-coated copper powder was separated and obtained.
  • the embodiment of the present invention first disperses the intermediate product in the dispersant to prevent the agglomeration between the intermediate products and cause the particles to be too large, which is not conducive to the re-coating of silver ions to form a silver-coated copper powder with uniform particles and a smaller particle size.
  • the second silver ammonia solution and the second reducing agent were respectively added dropwise at a temperature of 25-60°C, and reacted for 1 to 4 hours after the dropwise addition.
  • the silver was effectively controlled by controlling the reaction temperature and the addition rate.
  • the coating effect of the ion on the intermediate product ensures that the silver layer in the silver-coated copper powder obtained is densely covered and has good stability.
  • the temperature is too high, it will cause the silver ion to be oxidized, making the prepared silver-coated copper powder black and poor conductivity; if the second silver ammonia solution and the second reducing agent are added too fast, too much silver ions will be replaced , The coated silver ion is easy to be oxidized before it is too late, which also leads to the blackening of the silver-coated copper powder and the deterioration of conductivity.
  • the dispersant is selected from at least one of octylphenol polyoxyethylene ether-10 and polyvinylpyrrolidone.
  • at least one dispersant of octylphenol polyoxyethylene ether-10 and polyvinylpyrrolidone is used to disperse the intermediate product to prevent agglomeration of the intermediate product, and to ensure that the prepared silver-coated copper powder is micron-sized
  • the particle size not only ensures the conductivity of silver-coated copper powder, but is also beneficial to industrial applications, preventing the excessively large particle size from causing network blocking.
  • the rate of dripping the second silver ammonia solution and the second reducing agent is 10 to 10 respectively. 80 drops/minute.
  • the addition rate of the second silver ammonia solution and the second reducing agent in the embodiment of the present invention enables the replaced silver ions to have the best coating effect and rate on the surface of the intermediate product. If the second silver ammonia solution and the second reducing agent are added too fast, the replaced silver ions will be too much, and the coated silver ions will be easily oxidized before it is too late, which will also cause the prepared silver-coated copper powder to turn black and deteriorate the conductivity.
  • the embodiment of the present invention also provides a silver-coated copper powder, which can be prepared by the method in each of the above embodiments.
  • the particle size of the silver-coated copper powder is 500 nanometers to 20 microns.
  • silver The mass percentage content is 10-30%.
  • the particle size of the silver-coated copper powder provided by the embodiment of the present invention is 500 nanometers to 20 microns, which not only prevents the unevenness of the silver layer from reducing the conductivity and oxidation resistance of the silver-coated copper powder, but also ensures the application of the silver-coated copper powder It is suitable for screen printing and other processes to prevent problems such as blocking the network caused by excessive particles.
  • the silver-coated copper powder provided by the embodiments of the present invention has a mass percentage of silver of 10-30%.
  • the silver layer is densely coated, has high coating efficiency and good stability, thereby reducing the amount of silver source used and ensuring silver
  • the electrical conductivity of the copper-clad powder achieves low silver coating, high electrical conductivity, and resistivity as low as 1.1 ⁇ 10 -5 ⁇ cm.
  • an embodiment of the present invention also provides an electronic paste, which contains the silver-coated copper powder prepared by the above-mentioned method or contains the above-mentioned silver-coated copper powder.
  • the electronic paste provided by the embodiments of the present invention contains the above-mentioned silver-coated copper powder with good stability, low conductivity, and high conductivity, so the electronic paste has good conductivity, good stability, and a wide range of applications.
  • a silver-coated copper powder, which preparation includes the steps:
  • 1Copper powder pretreatment First, the purchased copper powder is ultrasonically cleaned with octylphenol polyoxyethylene ether-10 for 5-10 minutes, and then repeated ultrasonic cleaning with deionized water three times to remove octylphenol polyoxyethylene ether-10 ; Then use 5% dilute sulfuric acid to ultrasonically clean the micron copper powder for 5-10min to remove the oxide film on the surface, and then repeatedly ultrasonically clean three times with deionized water until the lotion is neutral, and the obtained copper powder is ready for use.
  • 1Copper powder pretreatment First, the purchased copper powder is ultrasonically cleaned with octylphenol polyoxyethylene ether-10 for 5-10 minutes, and then repeated ultrasonic cleaning with deionized water three times to remove octylphenol polyoxyethylene ether-10 ; Then use 5% dilute sulfuric acid to ultrasonically clean the micron copper powder for 5-10min to remove the oxide film on the surface, and then repeatedly ultrasonically clean three times with deionized water until the lotion is neutral, and the obtained copper powder is ready for use.
  • the embodiment of the present invention has been subjected to a performance test.
  • Figure 1 is the morphology of the intermediate product of the first silver plating in Example 1
  • Figure 2 is the silver-coated copper powder prepared in Example 1.
  • Fig. 3 is the morphology of the silver-coated copper powder prepared in Comparative Example 1
  • Fig. 4 is the morphology of the uncoated copper powder.
  • the silver-coated copper powder prepared in Example 1 of the present invention can be seen from the microscopic morphological characterization that the silver layer evenly and smoothly covers the entire surface of the copper powder.
  • the silver layer on the surface is rough, the silver coating is not uniform, and the compactness is poor.
  • the present invention can be used in pre-treatment with a lower molar ratio of silver-ammonia solution and reducing agent.
  • the surface of the treated copper powder is densely covered with a silver layer, which improves the oxidation resistance of the silver-coated copper powder and improves its stability.
  • the silver-coated copper powder prepared in Example 1 is characterized by element analysis (EDS) as shown in the area within the frame in Figure 2, as shown in Figure 5 (the abscissa is the X-ray energy, the ordinate is the X-ray count ), combined with the inductively coupled plasma ICP test, it is known that the silver content in the silver-coated copper powder is 10-30%.
  • EDS element analysis
  • thermogravimetric analysis was performed on the silver-coated copper powder prepared in Example 1 and Comparative Example 1, and the pretreated copper powder, as shown in Figure 7 (the abscissa is temperature, and the ordinate is weight) ,
  • the pure copper powder begins to oxidize at about 175°C, and the final weight gain is 2.88wt.%; the comparative example 1 silver-coated copper powder is oxidized at about 220°C, and the final weight gain is 1.59wt.%.
  • the intermediate product silver-coated copper powder is oxidized at about 220°C and the final weight gain is 0.74wt.%.
  • the silver-coated copper powder prepared in Example 1 is oxidized at about 250°C, and the final weight gain is only 0.50wt.%, indicating The silver-coated copper powder prepared in Example 1 of the present invention has the best thermal stability, its anti-oxidation performance is improved, and the coating effect is better.
  • the conductivity of the silver-coated copper powder prepared in Example 1 and the silver-coated copper powder prepared in Comparative Example 1 was tested. As shown in the following table 1, the silver-coated copper powder prepared in Example 1 of the present invention The resistivity of the powder is much lower than that of the silver-coated copper powder prepared in Comparative Example 1, indicating that the silver-coated copper powder prepared in Example 1 of the present invention has better conductivity.

Abstract

本发明属于电子浆料技术领域，尤其涉及一种银包铜粉的制备方法，包括步骤：获取铜粉，将所述铜粉与第一银氨溶液和第一还原剂混合后添加氨水，混合处理，分离得到中间产物；其中，所述铜粉与所述第一银氨溶液和第一还原剂的摩尔比为1.26：(0.06～0.30)：(0.05～0.25)；将所述中间产物与第二银氨溶液和第二还原剂混合后反应，分离得到银包铜粉；其中，所述铜粉与所述第二银氨溶液和第二还原剂的摩尔比为1.26：(0.06～0.20)：(0.02～0.15)。本发明提供的银包铜粉的制备方法，操作简单，适用于工业化大规模生产和应用，制备的银包铜粉电导率高，电阻率低至1.1×10 -5Ω·cm。

Description

银包铜粉及其制备方法、电子浆料
本申请要求于2020年03月10日提交中国专利局、申请号为CN202010160828.9、发明名称为“银包铜粉及其制备方法、电子浆料”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及电子浆料技术领域，特别涉及银包铜粉及其制备方法、电子浆料。
背景技术
随着印刷电子行业的发展，电子浆料的市场也日益受到人们的关注。因为银的电导率极高且不易氧化，市面上的电子浆料多为银浆。但是银浆存在着价格高，并且容易发生电迁移失效的问题，因此人们把目光转移到了和银电导率差不多的铜。但是铜在空气中极易氧化，降低了铜浆的导电率。而银包铜浆则结合了两者的优点，既能解决银的电迁移问题，又能降低成本，改善铜的氧化问题。因此银包铜粉是银粉的理想替代材料。
目前，银包铜粉的主要制备方法有三种，包括：混合球磨法、熔融雾化法及化学镀法。其中，混合球磨法和熔融雾化法工艺复杂，成本较高，因此目前市面上的银包铜多是采用化学镀法，也是目前被认为最适合制备银包铜粉的方法之一。
化学镀法包括三种：置换化学镀法、还原化学镀法以及置换与化学沉积复合法。其中，置换化学镀是利用铜的还原性直接置换银离子，从而得到银包铜颗粒，但置换化学镀得到的银层通常较疏松；还原化学镀法则是利用银离子与配位剂混合得到银配离子溶液，与还原剂发生反应置换出银颗粒包覆在微米铜表面，但这种方法得到的通常是呈岛状的银包覆层，需要较高的银比例才能得到包覆较好的银包铜粉，并且如果还原剂还原性过强得到的则是银混铜粉；置换与化学沉积复合法则是先利用铜的还原性先在表面包覆一部分的银颗粒，再加入还原剂，然而铜银发生置换反应过程中，铜离子会生成氧化铜或氢氧化铜沉淀，这些沉淀物会附着在铜粉表面，增大铜粉表面电阻，并且阻碍银镀层继续沉积。并且无论采用前三种的任 意方法，在铜粉的前处理过程中铜粉都会发生部分氧化而阻碍后续包覆过程。
发明内容
本发明的目的在于提供一种银包铜粉的制备方法，旨在解决现有银包铜粉制备方法中铜粉表面附着氧化物，导致银包铜粉中银镀层疏松，降低银包铜粉的电阻率等技术问题。
本发明的另一目的在于提供一种银包铜粉。
本发明的再一目的在于提供一种电子浆料。
为了实现上述发明目的，本发明采用的技术方案如下：
一种银包铜粉的制备方法，包括以下步骤：
获取铜粉，将所述铜粉与第一银氨溶液和第一还原剂混合后添加氨水，混合处理，分离得到中间产物；其中，所述铜粉与所述第一银氨溶液和第一还原剂的摩尔比为1.26：(0.06～0.30)：(0.05～0.25)；
将所述中间产物与第二银氨溶液和第二还原剂混合后反应，分离得到银包铜粉；其中，所述铜粉与所述第二银氨溶液和第二还原剂的摩尔比为1.26：(0.06～0.20)：(0.02～0.15)。
优选地，所述第一还原剂和所述第二还原剂分别独立地选自：葡萄糖、水合肼、硼氢化钠、乙醛中的至少一种。
优选地，所述第一银氨溶液的浓度为0.10～0.75mol/L；和/或，
所述第一还原剂的浓度为0.02～0.2mol/L。
优选地，所述氨水的体积分数为10～40％，所述氨水与所述第一银氨溶液和所述第一还原剂的体积比为1：(1.5～2.5)：(4～6)。
优选地，所述第二银氨溶液的浓度为0.05～0.20mol/L；和/或，
所述第二还原剂的浓度为0.025～0.075mol/L。
优选地，所述混合处理的时间为1～60分钟；和/或，
将所述中间产物与第二银氨溶液和第二还原剂混合后反应的步骤包括：将所述中间产物添加到分散剂中混合处理，然后在温度为25～60℃的条件下分别滴加所述第二银氨溶液和所述第二还原剂，滴加完后反应1～4小时，分离得到银包铜粉。
优选地，所述分散剂选自：辛基酚聚氧乙烯醚-10、聚乙烯吡咯烷酮 中的至少一种；和/或，
以体积为200毫升的所述中间产物和所述分散剂形成的反应体系为基准，滴加所述第二银氨溶液和所述第二还原剂的速率分别为10～80滴/分钟。
优选地，获取铜粉后还包括对所述铜粉进行预处理，包括步骤：将所述铜粉依次采用辛基酚聚氧乙烯醚-10、去离子水、浓度为5～20％的硫酸和去离子水进行清洗，得到预处理后的铜粉。
相应地，一种银包铜粉，所述银包铜粉的粒径为500纳米～20微米，所述银包铜粉中，银的质量百分含量为10～30％。
相应地，一种电子浆料，所述电子浆料中包含有上述的方法制备的银包铜粉，或者包含有上述的银包铜粉。
本发明提供的银包铜粉的制备方法，首先，按所述铜粉与所述第一银氨溶液和第一还原剂的摩尔比为1.26：(0.06～0.30)：(0.05～0.25)，将所述铜粉与较低摩尔比的第一银氨溶液和第一还原剂混合进行第一次包覆，在铜和银的置换反应过程中会生成氧化铜或氢氧化铜沉淀；然后通过添加氨水，不但氨水可还原铜粉的氧化物或氢氧化物，抑制铜粉被氧化，而且氨水能够抑制银离子在铜表面形成大颗粒，使置换形成的银包覆层更致密，提高银对铜粉的包覆率，减少银源的使用量，得到表面平滑的经第一次包覆后的中间产物。然后，按所述铜粉与所述第二银氨溶液和第二还原剂的摩尔比为1.26：(0.06～0.20)：(0.02～0.15)，将所述中间产物与第二银氨溶液和第二还原剂混合后反应，采用较低摩尔比的第二银氨溶液和第二还原剂对中间产物进行第二次银包覆，进一步确保银完全包覆在铜粉的表面，既提高银包铜粉的电导率、抗氧化性能，使制备的银包铜粉电导率高，电阻率低至1.1×10 -5Ω·cm，又防止第二银氨溶液和第二还原剂浓度过高导致单独生成银杂质颗粒。本发明提供的银包铜粉的制备方法，操作简单，适用于工业化大规模生产和应用。
本发明提供的银包铜粉的粒径为500纳米～20微米，粒径均匀，既防止了银层包裹不均匀降低银包铜粉的导电性以及抗氧化能力，又确保了银包铜粉的应用性，适用于丝网印刷等工艺，防止颗粒过大导致堵网等问题。本发明提供的银包铜粉中银的质量百分含量为10～30％，银层包覆致密严 实，包覆效率高，稳定性好，从而降低了银源的使用量，确保了银包铜粉的导电率，实现低银包覆量，高电导率，电阻率低至1.1×10 -5Ω·cm。
本发明提供的电子浆料，由于包含有上述稳定性好、电导率低、导电效率高的上述银包铜粉，因而电子浆料的导电性能好，稳定性好，应用范围广泛。
说明书附图
图1是本发明实施例1提供的进行第一次镀银后的中间产物的扫描电镜图；
图2是本发明实施例1最终制得得到银包铜粉的扫描图；
图3是本发明对比例1提供的银包铜粉的扫描图；
图4是本发明仅经过预处理后的纯铜粉的扫描图；
图5是本发明实施例1提供的银包铜粉的EDS表征图；
图6是本发明实施例1提供的银包铜粉的X射线衍射图；
图7是本发明实施例1中间产物、银包铜粉、对比例1银包铜粉以及纯铜粉的热重分析图。
具体实施方式
为使本发明实施例的目的、技术方案和技术效果更加清楚，对本发明实施例中的技术方案进行清楚、完整的描述，显然，所描述的实施例是本发明一部分实施例，而不是全部的实施例。结合本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
在本发明的描述中，需要理解的是，术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括一个或者多个该特征。在本发明的描述中，“多个”的含义是两个或两个以上，除非另有明确具体的限定。
本发明实施例说明书中所提到的相关成分的重量不仅仅可以指代各组分的具体含量，也可以表示各组分间重量的比例关系，因此，只要是按照本发明实施例说明书相关组分的含量按比例放大或缩小均在本发明实施例说明书公开的范围之内。具体地，本发明实施例说明书中所述的重量 可以是μg、mg、g、kg等化工领域公知的质量单位。
本发明实施例提供了一种银包铜粉的制备方法，包括以下步骤：
S10.获取铜粉，将所述铜粉与第一银氨溶液和第一还原剂混合处理后添加氨水，混合处理，分离得到中间产物；其中，所述铜粉与所述第一银氨溶液和第一还原剂的摩尔比为1.26：(0.06～0.30)：(0.05～0.25)；
S20.将所述中间产物与第二银氨溶液和第二还原剂混合反应后，分离得到银包铜粉；其中，所述铜粉与所述第二银氨溶液和第二还原剂的摩尔比为1.26：(0.06～0.20)：(0.02～0.15)。
本发明实施例提供的银包铜粉的制备方法，首先，按所述铜粉与所述第一银氨溶液和第一还原剂的摩尔比为1.26：(0.06～0.20)：(0.05～0.25)，将所述铜粉与较低摩尔比的第一银氨溶液和第一还原剂混合进行第一次包覆，在铜和银的置换反应过程中会生成氧化铜或氢氧化铜沉淀；然后通过添加氨水，不但氨水可还原铜粉的氧化物或氢氧化物，抑制铜粉被氧化，而且氨水能够抑制银离子在铜表面形成大颗粒，使置换形成的银包覆层更致密，提高银对铜粉的包覆率，减少银源的使用量，得到表面平滑的经第一次包覆后的中间产物。然后，按所述铜粉与所述第二银氨溶液和第二还原剂的摩尔比为1.26：(0.06～0.20)：(0.02～0.15)，将所述中间产物与第二银氨溶液和第二还原剂混合后反应，采用较低摩尔比的第二银氨溶液和第二还原剂对中间产物进行第二次银包覆，进一步确保银完全包覆在铜粉的表面，既提高银包铜粉的电导率、抗氧化性能，使制备的银包铜粉电导率高，电阻率低至1.1×10 -5Ω·cm，又防止第二银氨溶液和第二还原剂浓度过高导致单独生成银杂质颗粒。本发明实施例提供的银包铜粉的制备方法，操作简单，适用于工业化大规模生产和应用。
具体地，上述步骤S10，获取铜粉，将所述铜粉与第一银氨溶液和第一还原剂混合后添加氨水，混合处理，分离得到中间产物；其中，所述铜粉与所述第一银氨溶液和第一还原剂的摩尔比为1.26：(0.06～0.30)：(0.05～0.25)。本发明实施例按所述铜粉与所述第一银氨溶液和第一还原剂的摩尔比为1.26：(0.06～0.30)：(0.05～0.25)，将所述铜粉与较低摩尔比的第一银氨溶液和第一还原剂混合进行第一次包覆，在铜和银的置换反应过程中会生成氧化铜或氢氧化铜沉淀；然后通过添加氨水，不但 氨水可还原铜粉的氧化物或氢氧化物，抑制铜粉被氧化，而且氨水能够抑制银离子在铜表面形成大颗粒，使置换形成的银包覆层更致密，提高银对铜粉的包覆率，减少银源的使用量，得到表面平滑的经第一次包覆后的中间产物，该产物中银包覆层平滑致密，中间产物电阻率低至2×10 -5Ω·cm。在一些具体实施例中，所述铜粉与所述第一银氨溶液和第一还原剂的摩尔比为1.26:0.06:0.05、1.26:(0.06～0.1):(0.05～0.1)或者1.26:(0.1～0.3):(0.1～0.25)等。
在一些实施例中，所述第一还原剂选自：葡萄糖、水合肼、硼氢化钠、乙醛中的至少一种。本发明实施例第一还原剂能够与银氨溶液中的银离子发生还原反应，银离子包覆在铜粉表面形成银包覆层。
在一些实施例中，所述第一银氨溶液的浓度为0.1～0.75mol/L。在一些实施例中，所述第一还原剂的浓度为0.02～0.2mol/L。本发明实施例首先采用较高浓度的第一银氨溶液和第一还原剂对铜粉进行包覆，高浓度的银源能够提高银源对铜粉的包覆效率，若所述第一银氨溶液的浓度高于0.75mol/L，或者所述第一还原剂的浓度高于0.2mol/L，则会导致生成银颗粒悬浮在溶液中，提高了银源的消耗。在一些具体实施例中，所述第一银氨溶液的浓度可以是0.1mol/L、0.2mol/L、0.3mol/L、0.4mol/L、0.5mol/L、0.6mol/L或者0.75mol/L等，所述第一还原剂的浓度为0.02mol/L、0.05mol/L、0.1mol/L、0.15mol/L或者0.2mol/L等。
在一些实施例中，所述氨水的体积分数为10～40％，所述氨水与所述第一银氨溶液和所述第一还原剂的体积比为1：(1.5～2.5)：(4～6)。本发明实施例将所述铜粉与第一银氨溶液和第一还原剂混合后添加的氨水，一方面，氨水可还原铜粉的氧化物或氢氧化物，抑制铜粉被氧化，使铜粉表面更洁净，有利于银离子的包覆；另一方面，氨水能够抑制银离子在铜表面形成大颗粒，使置换形成的银包覆层更致密，提高银对铜粉的包覆率，减少银源的使用量，得到表面平滑的经第一次包覆后的中间产物。在一直具体实施例中，所述氨水的体积分数可以是10％、15％、20％、30％或者40％等，所述氨水与所述第一银氨溶液和所述第一还原剂的体积比为1：(1.5～2.5)：(4～6)。
在一些实施例中，将所述铜粉与第一银氨溶液和第一还原剂混合后添 加氨水，混合处理1～60分钟，即可分离得到中间产物。在一些具体实施例中混合处理1分钟、10分钟、30分钟或60分钟后，用布氏漏斗分离固液，并用去离子水反复清洗固体3～5次，即得到中间产物。
在一些实施例中，获取铜粉后还包括对所述铜粉进行预处理，包括步骤：将所述铜粉依次采用辛基酚聚氧乙烯醚-10、去离子水、浓度为5～20％的硫酸和去离子水进行清洗，得到预处理后的铜粉。由于商业铜粉表面通常覆有油之类的杂质，因此，本发明实施例首先采用辛基酚聚氧乙烯醚-10对微米铜进行超声清洗，具体可清洗5-30min，并用去离子水反复超声清洗三次去除辛基酚聚氧乙烯醚-10；之后用5％的稀硫酸超声清洗铜粉，具体可清洗5-30min，去除其表面的氧化膜，随后用去离子水反复超声清洗三次，直至洗液呈中性，得到的预处理后的铜粉待用。
在一些具体实施例中，将所述铜粉依次采用辛基酚聚氧乙烯醚-10、去离子水、浓度为5～20％的硫酸和去离子水进行清洗，得到预处理后的铜粉；然后按所述铜粉与所述第一银氨溶液和第一还原剂的摩尔比为1.26：(0.06～0.30)：(0.05～0.25)，将所述铜粉与浓度为0.1～0.75mol/L的第一银氨溶液和浓度为0.02～0.2mol/L的选自葡萄糖、水合肼、硼氢化钠、乙醛中的至少一种第一还原剂混合后添加体积分数为10～40％的氨水，所述氨水与所述第一银氨溶液和所述第一还原剂的体积比为1：(1.5～2.5)：(4～6)，混合处理，分离得到中间产物。
具体的，上述步骤S20，将所述中间产物与第二银氨溶液和第二还原剂混合后反应，分离得到银包铜粉；其中，所述铜粉与所述第二银氨溶液和第二还原剂的摩尔比为1.26：(0.06～0.20)：(0.02～0.15)。本发明实施例按所述铜粉与所述第二银氨溶液和第二还原剂的摩尔比为1.26：(0.06～0.20)：(0.02～0.15)，将所述中间产物与第二银氨溶液和第二还原剂混合后反应，采用较低摩尔比的第二银氨溶液和第二还原剂对中间产物进行第二次银包覆，进一步确保银完全包覆在铜粉的表面，既提高银包铜粉的电导率、抗氧化性能，使制备的银包铜粉电导率高，电阻率低至1.1×10 -5Ω·cm，又防止第二银氨溶液和第二还原剂浓度过高导致单独生成银杂质颗粒。在一些具体实施中，所述铜粉与所述第二银氨溶液和第二还原剂的摩尔比可以是1.26：(0.06～0.1)：(0.02～0.08)、1.26：(0.1～0.15)： (0.08～0.12)或者1.26：(0.15～0.20)：(0.12～0.15)等。
在一些实施例中，所述第二还原剂选自：葡萄糖、水合肼、硼氢化钠、乙醛中的至少一种。本发明实施例第二还原剂能够与银氨溶液中的银离子发生还原反应，生成的银离子能够包覆在中间产物外表面，进一步确保银完全包覆在铜粉表面，形成银层包覆致密，导电率高的银包铜粉。
在一些实施例中，所述第二银氨溶液的浓度为0.05～0.20mol/L。在一些实施例中，所述第二还原剂的浓度为0.025～0.075mol/L。本发明实施例采用低浓度的第二银氨溶液和第二还原剂对中间产物进行第二次银包覆，进一步确保银完全包覆在铜粉的表面，既提高银包铜粉的电导率、抗氧化性能，使制备的银包铜粉电导率高，电阻率低至1.1×10 -5Ω·cm，又防止第二银氨溶液和第二还原剂浓度过高导致单独生成银杂质颗粒。在一些具体实施中，所述第二银氨溶液的浓度可以是0.05mol/L、0.1mol/L、0.15mol/L或者0.20mol/L，所述第二还原剂的浓度为0.025mol/L、0.035mol/L、0.05mol/L、0.06mol/L或者0.075mol/L。
在一些实施例中，将所述中间产物与第二银氨溶液和第二还原剂混合后反应的步骤包括：将所述中间产物添加到分散剂中混合处理，然后在温度为25～60℃的条件下分别滴加所述第二银氨溶液和所述第二还原剂，滴加完后反应1～4小时，分离得到银包铜粉。本发明实施例首先将中间产物分散在分散剂中，防止中间产物之间聚集团聚导致颗粒过大，不利于银离子的再次包覆形成颗粒均匀，粒径较小的银包铜粉。然后，在温度为25～60℃的条件下分别滴加所述第二银氨溶液和所述第二还原剂，滴加完后反应1～4小时，通过控制反应温度和添加速率有效控制银离子对中间产物的包覆效果，确保得到的银包铜粉中银层包覆致密严实，稳定性好。若温度过高，则会导致银离子被氧化，使制得的银包铜粉变黑，导电性变差；若第二银氨溶液和第二还原剂添加过快，置换的银离子过多，来不及包覆的银离子容易被氧化，同样导致制得的银包铜粉变黑，导电性变差。
在一些实施例中，所述分散剂选自：辛基酚聚氧乙烯醚-10、聚乙烯吡咯烷酮中的至少一种。本发明实施例通过辛基酚聚氧乙烯醚-10、聚乙烯吡咯烷酮中的至少一种分散剂，将中间产物分散处理，防止中间产物聚集团聚，确保制得的银包铜粉为微米级小粒径颗粒，既确保银包铜粉的导 电性，又有利于工业应用，防止其粒径过大导致堵网等。
在一些实施例中，以体积为200毫升的所述中间产物和所述分散剂形成的反应体系为基准，滴加所述第二银氨溶液和所述第二还原剂的速率分别为10～80滴/分钟。本发明实施例第二银氨溶液和第二还原剂的添加速率，使置换出来的银离子在中间产物表面有最佳的包覆效果和速率。若第二银氨溶液和第二还原剂添加过快，置换的银离子过多，来不及包覆的银离子容易被氧化，同样导致制得的银包铜粉变黑，导电性变差。
本发明实施例还提供了一种银包铜粉，可通过上述各实施例方法制得，所述银包铜粉的粒径为500纳米～20微米，所述银包铜粉中，银的质量百分含量为10～30％。
本发明实施例提供的银包铜粉的粒径为500纳米～20微米，既防止了银层包裹不均匀降低银包铜粉的导电性以及抗氧化能力，又确保了银包铜粉的应用性，适用于丝网印刷等工艺，防止颗粒过大导致堵网等问题。本发明实施例提供的银包铜粉中银的质量百分含量为10～30％，银层包覆致密严实，包覆效率高，稳定性好，从而降低了银源的使用量，确保了银包铜粉的导电率，实现低银包覆量，高电导率，电阻率低至1.1×10 -5Ω·cm。
相应地，本发明实施例还提供了一种电子浆料，所述电子浆料中包含有上述的方法制备的银包铜粉，或者包含有上述的银包铜粉。
本发明实施例提供的电子浆料，由于包含有上述稳定性好，电导率低，导电效率高的上述银包铜粉，因而电子浆料的导电性能好，稳定性好，应用范围广泛。
为使本发明上述实施细节和操作能清楚地被本领域技术人员理解，以及本发明实施例银包铜粉及其制备方法的进步性能显著的体现，以下通过多个实施例来举例说明上述技术方案。
实施例1
一种银包铜粉，其制备包括步骤：
①铜粉预处理：购买来的铜粉首先用辛基酚聚氧乙烯醚-10对微米铜进行超声清洗5-10min，并用去离子水反复超声清洗三次去除辛基酚聚氧乙烯醚-10；之后用5％的稀硫酸超声清洗微米铜粉5-10min，去除其表面的氧化膜，随后用去离子水反复超声清洗三次，直至洗液呈中性，得到的 铜粉待用。
②银氨溶液的配置：取4.5g硝酸银溶于100ml水溶液中，边搅拌边将体积分数为20％的氨水滴入硝酸银溶液中，直至沉淀刚好消失，待用。
③取40ml配好的银氨溶液加入8g预处理后的铜粉，随后加入100ml浓度为0.05mol/L的葡萄糖溶液。充分搅拌后，加入20ml体积分数为20％的氨水，溶液迅速由透明转为蓝色，溶液中分散的铜粉由亮红棕色变为浅灰色。反应5min后用布氏漏斗将固液分离，并用去离子水反复清洗固体三次后，得到第一次镀银的中间产物。
④将得到第一次镀银的中间产物加入200ml浓度为0.5g/L的聚乙烯吡咯烷酮溶液中，在400r/min的机械搅拌作用下充分混合5min。随后在40℃的条件下，以60滴/min的速度分别加入剩下的银氨溶液稀释至120ml，以及150ml浓度为0.05mol/L的葡萄糖溶液。滴加完成后继续反应1h。反应结束后用去离子水以及无水乙醇反复清洗三次，60℃干燥4h，即得到核壳结构的银包铜粉。
对比例1
①铜粉预处理：购买来的铜粉首先用辛基酚聚氧乙烯醚-10对微米铜进行超声清洗5-10min，并用去离子水反复超声清洗三次去除辛基酚聚氧乙烯醚-10；之后用5％的稀硫酸超声清洗微米铜粉5-10min，去除其表面的氧化膜，随后用去离子水反复超声清洗三次，直至洗液呈中性，得到的铜粉待用。
②银氨溶液的配置：取4.5g硝酸银溶于100ml水溶液中，边搅拌边将体积分数为20％的氨水滴入硝酸银溶液中，直至沉淀刚好消失，待用。
③取8g预处理后的铜粉加入200ml浓度为0.5g/L的聚乙烯吡咯烷酮溶液中，在400r/min的机械搅拌作用下充分混合5min。随后在40℃的条件下，以60滴/min的速度分别加入100ml配置好的银氨溶液，以及150ml浓度为0.05mol/L的葡萄糖溶液。滴加完成后继续反应1h。反应过程中可以观察到溶液中漂浮着亮白色的银颗粒。反应结束后用去离子水以及无水乙醇反复清洗三次，60℃干燥4h，得到了黑色的银包铜粉。
进一步的，为了验证本发明实施例制备的产物银包铜粉的进步性，本发明实施例进行了性能测试。
测试例1
本发明测试例通过扫描电镜对实施例1进行第一次镀银的中间产物和最终得到的银包铜粉，对比例1制得银包铜粉，以及未经包覆的铜粉的形貌进行了观测，如附图1～4所示，其中，附图1为实施例1进行第一次镀银的中间产物的形貌图，附图2为实施例1制得的银包铜粉的形貌图，附图3为对比例1制得的银包铜粉的形貌图，附图4为未经包覆铜粉的形貌图。由附图1-4形貌图可知，本发明实施例1制得的银包铜粉从微观形貌表征可以看到银层均匀光滑地包裹了整个铜粉表面，而对比文件1铜粉外表面银层较粗糙、银包覆不均匀，致密性差，相对于对比例1制得的银包铜粉的微观形貌，本发明通过较低摩尔比的银氨溶液和还原剂就可以在预处理后的铜粉表面致密地覆盖一层银层，使银包铜粉的抗氧化能力提高，提高其稳定性。
测试例2
本发明测试例对实施例1制得的银包铜粉，如附图2中框内区域进行元素分析(EDS)表征，由附图5(横坐标为X射线能量，纵坐标为X射线计数)，并结合电感耦合等离子体ICP测试，可知银包铜粉中银含量在10～30％。
测试例3
本发明测试例对实施例1制得的银包铜粉进行X射线衍射测试，如附图6所示(纵坐标为强度)，图中各衍射峰均为铜和银的特征峰，而不存在其他氧化物峰，表明得到的银包铜粉末纯度较高，无其他氧化物的存在。
测试例4
本发明测试例对实施例1和对比例1制得的银包铜粉，以及预处理后的铜粉分别进行热重分析，如附图7所示(横坐标为温度，纵坐标为重量)，纯铜粉在175℃左右开始发生氧化，并且最终增重2.88wt.％；对比例1银包铜粉在220℃左右发生氧化，最终增重1.59wt.％，而实施例1制得的中间产物银包铜粉在220℃左右发生氧化，且最终增重0.74wt.％，实施例1制得的银包铜粉在250℃左右发生氧化，且最终仅增重0.50wt.％，说明本发明实施例1制得的银包铜粉有最佳的热稳定性，其抗氧化性能得到了提 高，包覆效果较好。
测试例5
本发明测试例对实施例1制得的银包铜粉和对比例1制得的银包铜粉的导电性进行了测试，如下表1所示，本发明实施例1制得的银包铜粉的电阻率远低于对比例1制得的银包铜粉，说明本发明实施例1制得的银包铜粉有更好的导电性。
表1实施例1制得的银包铜粉和对比例1制得的银包铜粉的导电性
Figure PCTCN2021079529-appb-000001
以上实施例的说明只是用于帮助理解本发明的方法及其核心思想。应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以对本发明进行若干改进和修饰，这些改进和修饰也落入本发明权利要求的保护范围内。对这些实施例的多种修改对本领域的专业技术人员来说是显而易见的，本文中所定义的一般原理可以在不脱离本发明的精神或范围的情况下在其它实施例中实现。因此，本发明将不会被限制于本文所示的这些实施例，而是要符合与本文所公开的原理和新颖特点相一致的最宽的范围。

Claims (13)

  1. 一种银包铜粉的制备方法，其特征在于，包括以下步骤：
    获取铜粉，将所述铜粉与第一银氨溶液和第一还原剂混合后添加氨水，混合处理，分离得到中间产物；其中，所述铜粉与所述第一银氨溶液和第一还原剂的摩尔比为1.26：(0.06～0.30)：(0.05～0.25)；
    将所述中间产物与第二银氨溶液和第二还原剂混合后反应，分离得到银包铜粉；其中，所述铜粉与所述第二银氨溶液和第二还原剂的摩尔比为1.26：(0.06～0.20)：(0.02～0.15)。
  2. 如权利要求1所述的银包铜粉的制备方法，其特征在于，所述第一还原剂和所述第二还原剂分别独立地选自：葡萄糖、水合肼、硼氢化钠和乙醛中的至少一种。
  3. 如权利要求2所述的银包铜粉的制备方法，其特征在于，所述第一银氨溶液的浓度为0.10mol/L～0.75mol/L；和/或，
    所述第一还原剂的浓度为0.02mol/L～0.2mol/L。
  4. 如权利要求1～3任一项所述的银包铜粉的制备方法，其特征在于，所述氨水的体积分数为10％～40％，所述氨水与所述第一银氨溶液和所述第一还原剂的体积比为1：(1.5～2.5)：(4～6)。
  5. 如权利要求1～3任一项所述的银包铜粉的制备方法，其特征在于，所述铜粉与所述第一银氨溶液和第一还原剂的摩尔比为1.26:0.06:0.05、1.26:(0.06～0.1):(0.05～0.1)或1.26:(0.1～0.3):(0.1～0.25)。
  6. 如权利要求4所述的银包铜粉的制备方法，其特征在于，所述第二银氨溶液的浓度为0.05mol/L～0.20mol/L；和/或，
    所述第二还原剂的浓度为0.025mol/L～0.075mol/L。
  7. 如权利要求1、2或6所述的银包铜粉的制备方法，其特征在于，铜粉与所述第二银氨溶液和第二还原剂的摩尔比为1.26：(0.06～0.1)：(0.02～0.08)、1.26：(0.1～0.15)：(0.08～0.12)或1.26：(0.15～0.20)：(0.12～0.15)。
  8. 如权利要求7所述的银包铜粉的制备方法，其特征在于，所述混合处理的时间为1分钟～60分钟；和/或，
    将所述中间产物与第二银氨溶液和第二还原剂混合后反应的步骤包 括：将所述中间产物添加到分散剂中混合处理，然后在温度为25℃～60℃的条件下分别滴加所述第二银氨溶液和所述第二还原剂，滴加完后反应1小时～4小时。
  9. 如权利要求8所述的银包铜粉的制备方法，其特征在于，所述分散剂选自：辛基酚聚氧乙烯醚-10和聚乙烯吡咯烷酮中的至少一种；和/或，
    以体积为200毫升的所述中间产物和所述分散剂形成的反应体系为基准，滴加所述第二银氨溶液和所述第二还原剂的速率分别为10～80滴/分钟。
  10. 如权利要求1或9所述的银包铜粉的制备方法，其特征在于，所述获取铜粉后还包括对所述铜粉进行预处理，所述预处理包括步骤：将所述铜粉依次采用辛基酚聚氧乙烯醚-10、去离子水、浓度为5％～20％的硫酸和去离子水进行清洗，得到预处理后的铜粉。
  11. 如权利要求10所述的银包铜粉的制备方法，其特征在于，所述清洗的方式为超声清洗；
    所述采用辛基酚聚氧乙烯醚-10和浓度为5％～20％的硫酸进行清洗的时间独立地为5～30min。
  12. 一种权利要求1～11任一项所述制备方法制备得到的银包铜粉，其特征在于，所述银包铜粉的粒径为500纳米～20微米，所述银包铜粉中，银的质量百分含量为10％～30％。
  13. 一种电子浆料，其特征在于，所述电子浆料中包含有包含有如权利要求12所述的银包铜粉。
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