Liquid-phase preparation method of non-pressure crystallized superfine copper powder

Abstract

The invention relates to the technical field of copper powder preparation, and provides a liquid-phase preparation method of non-pressure crystallized superfine copper powder, which adopts a water-phase reduction process, and realizes stable control of crystallization proportion and particle size distribution of superfine spheroidal copper powder by accurately regulating and controlling a reducing agent, a complexing agent, a crystallization modifier and reaction conditions. The problems of harsh reaction conditions, high energy consumption, high toxicity and the like of a traditional high-temperature method are solved; the obtained copper powder is uniform and stable, is suitable for the fields of precision electronics, specific catalysis and the like, flexibly adapts to downstream requirements by adjusting the sintering temperature within the range of 250-350 DEG C, and meets the application of flexible electronics, power chip interconnection and the like. The process is simplified in steps, environment-friendly and safe, the production cost is greatly reduced, the production efficiency is improved, and large-scale industrial production is facilitated.

Description

Technical Field

[0001] This invention relates to the field of copper powder preparation, and more specifically, to a method for preparing pressureless crystallized ultrafine copper powder in the liquid phase. Background Technology

[0002] In recent years, ultrafine copper powder has shown broad application prospects in fields such as integrated circuits, sterilization technology, photovoltaic cells and special catalysis due to its excellent electrical conductivity, thermal conductivity and strong catalytic performance. As an important functional material, ultrafine copper powder has great potential application value in many fields due to its unique physical and chemical properties, such as surface interface effect, small size effect and quantum size effect.

[0003] Especially in the fields of popularization and iteration of electronic information technology, advancement and implementation of the 5G communication era, and progress and development of intelligent and automated industrial manufacturing, slurries prepared from ultrafine copper powder play an important role in large-scale integrated circuits.

[0004] However, current industrial-grade copper powder is generally synthesized using high-temperature methods, a process that requires stringent reaction temperatures and consumes a large amount of energy. Furthermore, large-scale single-batch production of copper powder can lead to instability and inconsistent morphology. In addition, the resulting copper particles are large and of poor quality, making them unsuitable for applications in precision electronics and specific catalysis fields.

[0005] Although the liquid-phase reduction method for preparing ultrafine copper powder has advantages such as low cost, readily available raw materials, and simple operation, there are still some problems that need to be solved, such as low reduction efficiency, multiple preparation steps, high energy consumption, and poor dispersion effect.

[0006] For example, Chinese patent publication CN117620195A discloses a method for preparing spherical ultrafine copper powder in large quantities. This technology discloses that "by mixing a copper source solution with a complexing agent, adjusting the pH of the mixed solution to ≥7, adding a reducing agent, and then performing steps such as heating, stirring, and cold water bath, copper powder particles are finally obtained. This method aims to improve the morphology of copper powder and increase its yield." However, this method still has problems in terms of preparation efficiency and product quality that need to be improved during the preparation of ultrafine copper powder.

[0007] For example, Chinese patent publication CN111957986A discloses a spherical ultrafine copper powder, its preparation method, and its application. This technology discloses that "by adding specific copper salts and reacting them with a certain amount of dispersant and reducing agent under the action of a regulator, the amount and method of adding coating agent and hydrazine hydrate in subsequent processing are controlled, while simultaneously controlling the reaction conditions, to achieve effective control over the morphology and size of the copper powder. The prepared copper powder has a narrow particle size distribution and possesses high tap density, high dispersibility, high sintering activity, low carbon content, extremely low impurity content, and excellent oxidation resistance." However, this method still needs further optimization in terms of the preparation process to improve the tap density, dispersibility, sintering activity, and oxidation resistance of the copper powder.

[0008] The aforementioned existing technologies, represented by “CN117620195A” and “CN111957986A”, mostly employ high-temperature synthesis processes. This not only places stringent requirements on reaction temperature control and consumes a lot of energy, but also easily leads to problems such as uneven copper powder morphology and poor product quality stability during single large-scale production. As a result, these technologies are difficult to meet the stringent requirements for the consistency and reliability of copper powder in high-end fields such as precision electronics manufacturing and specific catalytic reactions.

[0009] Therefore, there is an urgent need to develop a method for preparing spherical ultrafine copper powder with mild reaction conditions, low energy consumption, uniform product morphology, and stable quality.

[0010] To address the aforementioned issues, this application proposes a method for preparing pressureless crystallized ultrafine copper powder in liquid phase. Summary of the Invention

[0011] The purpose of this invention is to provide a method for preparing ultrafine copper powder in liquid phase without pressure crystallization. By adjusting the reducing agent, complexing agent and crystallization modifier, and by coordinating parameters such as pH, temperature and time, and by precisely controlling the crystallization process, a stable control of the crystallization ratio of ultrafine spherical copper powder is achieved, thereby solving the problems in the prior art.

[0012] The objective of this invention can be achieved through the following technical solution: a method for preparing pressureless crystallized ultrafine copper powder in liquid phase, comprising the following steps:

[0013] S1. Mix the copper source and complexing agent at a molar ratio of 1:0.1 to 1.5, add deionized water, stir at 20 to 30°C for 5 to 30 minutes, mix the reducing agent at a molar ratio of 1:0.005 to 0.3 of the copper source, stir for 0.5 to 2 hours to obtain a copper salt solution;

[0014] S2. Mix the copper salt solution and the modifier at a mass ratio of 1:0.01 to 0.05, adjust the pH value to 3 to 12 with the regulator, raise the temperature to 40℃ to 70℃, add the reducing agent solution, wherein the molar ratio of the reducing agent to the copper source is 1:0.5 to 6, and control the reaction time to 1 to 8 hours to carry out the reduction reaction;

[0015] S3. Cool the reaction solution to room temperature, filter and wash until neutral, and dry for 2-8 hours to obtain ultrafine copper powder.

[0016] Preferably, in step 1, the copper salt and complexing agent are weighed in the specified proportions, deionized water is added, and under stirring conditions, the reaction temperature is controlled and the pH value is adjusted to 6-8. Then, a reducing agent is added, and the reaction temperature is controlled and the pH value is adjusted to 7-9.

[0017] Preferably, the pH value is adjusted to 5-12 in step 2.

[0018] Preferably, in step 2, the copper salt solution is mixed with the modifier, and after the reducing agent is added, the temperature is raised to 50℃~90℃. The pH value and temperature of the reaction solution are monitored. The purpose of raising the temperature is to improve the crystallinity of the product.

[0019] Preferably, in step 3, a vacuum filtration device is used for filtration, and the solid is washed with deionized water and ethanol 3 to 5 times in sequence. The obtained solid is then dried at 60°C to 80°C for 4 to 8 hours to obtain ultrafine copper powder.

[0020] Preferably, the copper source in step 1 is one or more of copper oxide, copper sulfate, copper chloride, and copper nitrate.

[0021] Preferably, the complexing agent in step 1 is one or more of EDTA salt (ethylenediaminetetraacetic acid), citrate, amino acids, etc.

[0022] Preferably, the reducing agent in step 2 is one or more of hydrazine hydrate, sodium hypophosphite, ascorbic acid, glucose, etc.

[0023] Preferably, the modifier in step 2 is one or more of CTAB (hexadecyltrimethylammonium bromide), PVP (polyvinylpyrrolidone), PEG (polyethylene glycol), sodium hexametaphosphate, and organic amine salts.

[0024] Preferably, the pH adjuster in step 2 is 3% to 10% dilute acid and 0.5 to 6 mol / L NaOH (sodium hydroxide per mole per liter).

[0025] The beneficial effects of this invention are:

[0026] 1. By adopting an aqueous phase reduction process and adjusting the reducing agent, complexing agent, and crystallization modifier, along with parameters such as pH, temperature, and time, stable control of the crystallization ratio of ultrafine spherical copper powder was achieved. This solved the problems of the traditional high-temperature synthesis method, which requires harsh reaction temperatures and has high energy consumption, greatly reducing production costs and improving production efficiency.

[0027] 2. By precisely controlling the crystallization process, copper powder with uniform particle size distribution was obtained, exhibiting excellent uniformity and stability, meeting the needs of different application fields, and is particularly suitable for precision electronics and specific catalysis fields;

[0028] 3. By adjusting the sintering temperature, a wide temperature range of 250℃~350℃ was achieved, providing downstream paste manufacturers with a wider range of choices and meeting the application needs of flexible electronics and power chip interconnection, etc.

[0029] 4. The aqueous phase reduction method avoids the problems of high toxicity of reducing agents and low reduction efficiency in traditional methods, improves the environmental friendliness and safety of the preparation process, and reduces energy consumption.

[0030] 5. By optimizing the preparation process, the number of preparation steps has been reduced, the production process has been simplified, and it is conducive to achieving large-scale industrial production. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the copper powder distribution in Example 1;

[0033] Figure 2 This is a thermogravimetric analysis curve from Example 1;

[0034] Figure 3 This is a schematic diagram of the copper powder distribution in Example 2;

[0035] Figure 4 This is a thermogravimetric analysis curve from Example 2;

[0036] Figure 5 This is a schematic diagram of the copper powder distribution in Example 3;

[0037] Figure 6 This is a thermogravimetric analysis curve from Example 3. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0039] Example 1

[0040] like Figure 1 - Figure 2 As shown, Figure 2 In the figure, TG & DTG analysis refers to thermogravimetric analysis, Temperature (°C) refers to temperature (°C), Weight Loss (%) refers to weight loss (%) or percentage of weight loss (%), and Derivative Weight Loss (% / °C) refers to differential weight loss (% / °C) or rate of weight loss (% / °C). In addition, the upper curve in the figure is Weight Loss (%), and the lower curve is Derivative Weight Loss (% / °C).

[0041] A method for preparing pressureless crystallization ultrafine copper powder in liquid phase includes the following steps:

[0042] S1. Copper oxide was selected as the copper source, hydrazine hydrate as the reducing agent, EDTA salt as the complexing agent, and CTAB as the modifier.

[0043] S2. Mix 0.1 mol of copper oxide with 0.05 mol of EDTA salt, add 500 mL of deionized water, stir at 25 °C for 20 min, add 0.005 mol of hydrazine hydrate, stir for 1 h, and obtain a copper salt solution;

[0044] S3. Mix copper salt solution and CTAB at a mass ratio of 1:0.02, adjust the pH value to 7, raise the temperature to 70℃, add 0.25mol hydrazine hydrate solution, and control the reaction time to 3 hours to carry out the reduction reaction;

[0045] S4. Cool the reaction solution to room temperature, filter it, wash it with deionized water until neutral, and dry it at 70°C for 6 hours to obtain ultrafine copper powder.

[0046] The prepared copper powder has a particle size of 700-1200 nm and a sintering temperature of about 250-310℃.

[0047] Example 2

[0048] like Figure 3 - Figure 4 As shown:

[0049] A method for preparing pressureless crystallization ultrafine copper powder in liquid phase includes the following steps:

[0050] S1. Copper sulfate was selected as the copper source, ascorbic acid as the reducing agent, citrate as the complexing agent, and PEG as the modifier;

[0051] S2. Mix 0.15 mol copper sulfate with 0.075 mol citrate, add 600 mL deionized water, stir at 30 °C for 10 min, add 0.01 mol ascorbic acid, stir for 0.5 h to obtain the copper salt solution.

[0052] S3. Mix copper salt solution with PEG at a mass ratio of 1:0.03, adjust the pH value to 8, heat to 80℃, add 0.2 mol ascorbic acid, and control the reaction time to 6 hours to carry out the reduction reaction;

[0053] S4. Cool the reaction solution to room temperature, filter it, and wash it three times with deionized water and ethanol in sequence. Dry it at 75°C for 5 hours to obtain ultrafine copper powder.

[0054] The average particle size of the sintered copper powder is 800-1000 nm, and the sintering temperature is around 350℃.

[0055] Example 3

[0056] like Figure 5 - Figure 6 As shown:

[0057] A method for preparing pressureless crystallization ultrafine copper powder in liquid phase includes the following steps:

[0058] S1. Copper sulfate was selected as the copper source, hydrazine hydrate as the reducing agent, amino acids as the complexing agent, and ethylenediamine as the modifier;

[0059] S2. Mix 0.12 mol copper sulfate with 0.06 mol amino acids, add 550 mL deionized water, stir at 22 °C for 1 h, add 0.02 mol hydrazine hydrate, stir for 0.5 h to obtain a copper salt solution;

[0060] S3. Mix copper salt solution with ethylenediamine at a mass ratio of 1:0.04, adjust the pH value to 6, raise the temperature to 60℃, add 0.6 mol hydrazine hydrate, and control the reaction time to 2 hours to carry out the reduction reaction;

[0061] S4. Cool the reaction solution to room temperature, filter it, and wash it four times with deionized water and ethanol in sequence. Dry it at 65°C for 7 hours to obtain ultrafine copper powder.

[0062] The copper powder has a particle size of 800–1200 nm and a sintering temperature of around 320 °C.

[0063] In all the above embodiments, under the condition of basically the same particle size, the sintering temperature of copper powder can be effectively adjusted by adjusting the degree of crystallinity of copper powder.

[0064] Understandably, this invention employs an aqueous reduction process, achieving stable control over the crystallization ratio and particle size distribution of ultrafine spherical copper powder through precise regulation of the reducing agent, complexing agent, crystallization modifier, and reaction conditions. This overcomes the problems of harsh reaction conditions, high energy consumption, and high toxicity associated with traditional high-temperature methods. The resulting copper powder is uniform and stable, suitable for applications such as precision electronics and specific catalysis. Furthermore, by adjusting the sintering temperature within the range of 250℃ to 350℃, it can flexibly adapt to downstream demands, meeting the needs of applications such as flexible electronics and power chip interconnects. This process is simplified, environmentally friendly, and safe, significantly reducing production costs and improving production efficiency, thus facilitating large-scale industrial production.

[0065] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; it should be understood that the terms "opening", "upper", "lower", "thickness", "top", "middle", "length", "inner", "around", etc., which indicate orientation or positional relationship, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting this invention.

[0066] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing pressureless crystallized ultrafine copper powder in liquid phase, characterized in that, Includes the following steps: S1. Mix the copper source and complexing agent at a molar ratio of 1:0.1 to 1.5, add deionized water, stir at 20 to 30°C for 5 to 30 minutes, mix the reducing agent at a molar ratio of 1:0.005 to 0.3 of the copper source, stir for 0.5 to 2 hours to obtain a copper salt solution; S2. Mix the copper salt solution and the modifier at a mass ratio of 1:0.01 to 0.05, adjust the pH value to 3 to 12 with the regulator, raise the temperature to 40℃ to 70℃, add the reducing agent solution, wherein the molar ratio of the reducing agent to the copper source is 1:0.5 to 6, and control the reaction time to 1 to 8 hours to carry out the reduction reaction; S3. Cool the reaction solution to room temperature, filter and wash until neutral, and dry for 2-8 hours to obtain ultrafine copper powder.

2. The method for preparing pressureless crystallization ultrafine copper powder in liquid phase according to claim 1, characterized in that: In step 1, weigh out the copper salt and complexing agent in the specified ratio, add deionized water, and under stirring conditions, control the reaction temperature and adjust the pH value to 6-8. Then add the reducing agent, control the reaction temperature and adjust the pH value to 7-9.

3. The method for preparing pressureless crystallization ultrafine copper powder in liquid phase according to claim 1, characterized in that: In step 2, adjust the pH value to 5-12.

4. The method for preparing pressureless crystallization ultrafine copper powder in liquid phase according to claim 1, characterized in that: In step 2, the copper salt solution is mixed with the modifier, and after the reducing agent is added, the temperature is raised to 50℃~90℃, and the pH and temperature of the reaction solution are monitored.

5. The method for preparing pressureless crystallization ultrafine copper powder in liquid phase according to claim 2, characterized in that: In step 3, a vacuum filtration device is used for filtration, and the solid is washed with deionized water and ethanol 3 to 5 times in sequence. The obtained solid is dried at 60℃ to 80℃ for 4 to 8 hours to obtain ultrafine copper powder.

6. The method for preparing pressureless crystallization ultrafine copper powder in liquid phase according to claim 1, characterized in that: The copper source in step 1 is one or more of copper oxide, copper sulfate, copper chloride, and copper nitrate.

7. The method for preparing pressureless crystallization ultrafine copper powder in liquid phase according to claim 6, characterized in that: The complexing agent in step 1 is one or more of EDTA salt, citrate, amino acid, etc.

8. The method for preparing pressureless crystallization ultrafine copper powder in liquid phase according to claim 1, characterized in that: The reducing agent in step 2 is one or more of the following: hydrazine hydrate, sodium hypophosphite, ascorbic acid, glucose, etc.

9. The method for preparing pressureless crystallization ultrafine copper powder in liquid phase according to claim 8, characterized in that: The modifier in step 2 is one or more of CTAB, PVP, PEG, sodium hexametaphosphate, and organic amine salts.

10. The method for preparing pressureless crystallization ultrafine copper powder in liquid phase according to claim 1, characterized in that: The pH adjuster in step 2 is 3%–10% dilute acid and 0.5–6 mol / L NaOH.

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