Monodisperse micron-sized spherical copper powder and preparation method thereof

Abstract

The invention discloses monodisperse micron-sized spherical copper powder and a preparation method thereof, and belongs to the technical field of material scientificity, the preparation method comprises the following steps: mixing a dispersing agent and a copper salt solution, and uniformly stirring to obtain a copper salt dispersion liquid; adding a first complexing agent into the copper salt dispersion liquid, and heating to 30-50 DEG C to obtain a reaction liquid; adding a second complexing agent into the reaction solution in batches, then adding a pH regulator until the pH is 3-8, then adding a reducing solution, then heating to 90-95 DEG C, reacting for 0.5-1.5 hours, and then aging to obtain copper powder slurry; and the copper powder slurry is subjected to solid-liquid separation, solids obtained through separation are sequentially cleaned and dried, and the spherical copper powder is obtained. The micron-sized spherical copper powder with controllable particle size, excellent monodispersity and excellent conductivity can be prepared, the preparation process is simple, lap joint of a conductive network is facilitated, and the application requirement of low-temperature sintering slurry is met.

Description

Technical Field

[0001] This invention belongs to the field of materials science and technology, and particularly relates to a monodisperse micron-sized spherical copper powder and its preparation method. Background Technology

[0002] Spherical copper powder, as a key functional powder material, is widely used in electronics, chemical engineering, and materials science, with significant differences in appearance, properties, and application scenarios among products of different sizes. Micron-sized spherical copper powder, in particular, has become a core raw material for heat-conducting materials and anti-corrosion coatings due to its excellent thermal conductivity and oxidation resistance. Especially with the rapid development of low-temperature sintering slurry technology, copper powder, as a base metal alternative, is gradually becoming an important development trend in the electronics and photovoltaic industries.

[0003] However, current chemical methods for preparing micron-sized spherical copper powder still face significant technical bottlenecks: mainstream processes mostly employ a "two-step reduction method," requiring the preparation of cuprous oxide intermediates before further reduction to copper powder. This lengthy process significantly limits production efficiency. Simultaneously, the process necessitates the addition of large amounts of alkaline regulators, and the highly alkaline environment makes it difficult to precisely control the nucleation and growth rates of the copper powder, resulting in poor dispersibility of the final product, directly impacting its suitability for subsequent processing and its performance.

[0004] On the one hand, the mainstream two-step reduction method requires the preparation of cuprous oxide intermediates before further reduction to copper powder. This not only results in a lengthy process but also increases the complexity of reaction control, severely limiting production efficiency. On the other hand, the preparation process relies on an alkaline environment, necessitating the addition of large amounts of alkaline reagents to adjust the solution pH. This strongly alkaline condition makes it difficult to precisely control the nucleation rate of copper ions and the crystal growth rate, ultimately resulting in copper powder with inconsistent sphericity and dispersibility. These problems directly affect the product's application performance: whether used as a raw material for silver-coated copper powder or directly in copper paste preparation, the final paste exhibits poor conductivity, failing to meet practical application requirements. Summary of the Invention

[0005] One of the objectives of this invention is to provide a method for preparing monodisperse micron-sized spherical copper powder. This method can produce micron-sized spherical copper powder with controllable particle size, excellent monodispersity, and excellent conductivity. Moreover, the preparation process is simple, which is conducive to the bonding of conductive networks and meets the application requirements of low-temperature sintering slurry.

[0006] The second objective of this invention is to provide a monodisperse micron-sized spherical copper powder.

[0007] To achieve one of the above objectives, the present invention employs the following technical solution: A method for preparing monodisperse micron-sized spherical copper powder, the method comprising the following steps: Step S1: Mix the dispersant and copper salt solution and stir until homogeneous to obtain a copper salt dispersion; Step S2: Add the first complexing agent to the copper salt dispersion at a mass ratio of 0.5 to 2:100, and then heat to 30 to 50°C to obtain the reaction solution; Step S3: After adding the second complexing agent to the reaction solution in batches, add the pH adjuster until the pH is 3-8, then add the reducing solution, then heat to 90-95℃, react for 0.5-1.5 hours, and then age for 2-8 minutes to obtain copper powder slurry. Step S4: Separate the copper powder slurry into solid and liquid phases, and wash and dry the separated solids in sequence to obtain spherical copper powder.

[0008] Further, in step S1, the mass-volume concentration of the copper salt solution is 0.1 to 1 kg / L.

[0009] Further, in step S1, the mass ratio of dispersant to copper salt solution in the copper salt dispersion is 0.5 to 2:100.

[0010] Further, in step S1, the copper salt solution is one of copper sulfate solution, copper nitrate solution, copper chloride solution, copper citrate solution, and copper tartrate solution; In step S1, the dispersant is one of polyethylene glycol 400, polyethylene glycol 1500, polyvinylpyrrolidone, sodium dodecyl sulfonate, and polyvinyl alcohol.

[0011] Further, in step S2, the first complexing agent is one of tartaric acid, citric acid, gluconic acid, malic acid, or lactic acid solution.

[0012] Further, in step S3, the mass ratio of the second complexing agent to the reaction solution is 2~10:100; The amount added in each batch is 25-35% of the total amount of the second complexing agent.

[0013] Furthermore, the second complexing agent is one of ammonia, ammonium bicarbonate, ethylenediamine, ethylenediaminetetraacetic acid, and triethylenetetraamine.

[0014] Further, in step S3, the mass ratio of reducing agent to copper salt in the reducing solution is 30-80:100; In step S3, 0.1 to 0.5 kg of reducing agent is dissolved in each liter of water in the reducing solution.

[0015] Further, in step S3, the pH adjuster is at least one of sodium hydroxide, ammonium bicarbonate, oxalic acid, phosphoric acid, nitric acid, hydrochloric acid, and sulfuric acid; In step S3, the reducing agent is at least one of glucose, ascorbic acid, hydrazine hydrate, hydrogen peroxide, formaldehyde, and acetaldehyde.

[0016] To achieve the second objective mentioned above, the present invention employs the following technical solution: A monodisperse micron-sized spherical copper powder, wherein the monodisperse micron-sized spherical copper powder is prepared by the preparation method described above.

[0017] In summary, the solution proposed in this invention has the following technical effects: This invention utilizes a pH adjuster to regulate the pH value, achieving a low-pH reaction and reducing the amount of alkaline reagents and reaction steps, resulting in significant economic benefits. Furthermore, it employs a dual complexing agent to control the chemical reaction rate, precisely controlling the copper nucleation and growth rates. This avoids the problems of excessive copper crystal formation, excessively small particle size, and copper powder agglomeration caused by an excessively fast reaction rate in the early stages. By regulating the particle size, the conductivity of the slurry is reduced, ultimately yielding micron-sized spherical copper powder with controllable particle size and excellent monodispersity. The simple preparation process and well-dispersed copper powder facilitate the bonding of conductive networks, making it suitable for applications in the electrical field. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 The image is a scanning electron microscope (SEM) image of monodisperse micron-sized spherical copper powder from Example 1 (magnification x2000). Figure 2 The image is a scanning electron microscope (SEM) image of monodisperse micron-sized spherical copper powder from Example 2 (magnification x2000). Figure 3 The image shows a scanning electron microscope (SEM) image (magnification x2000) of monodisperse micron-sized spherical copper powder from Example 3. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This embodiment provides a method for preparing monodisperse micron-sized spherical copper powder, referring to... Figure 1 The preparation method includes the following steps: Step S1: Mix the dispersant and copper salt solution and stir until homogeneous to obtain a copper salt dispersion.

[0022] To ensure the growth rate and uniformity of copper particles, in this embodiment, the mass-volume concentration of the copper salt solution is 0.1–1 kg / L.

[0023] In this embodiment, the mass ratio of dispersant to copper salt solution in the copper salt dispersion is 0.5 to 2:100.

[0024] The copper salt solution in this embodiment is one of copper sulfate solution, copper nitrate solution, copper chloride solution, copper citrate solution, and copper tartrate solution.

[0025] In this embodiment, the dispersant is one of polyethylene glycol 400, polyethylene glycol 1500, polyvinylpyrrolidone, sodium dodecyl sulfonate, and polyvinyl alcohol. After the reduction reaction begins, the steric hindrance effect of the dispersant causes the copper particles to grow in a directional and co-directional manner. Step S2: Add the first complexing agent to the copper salt dispersion at a mass ratio of 0.5 to 2:100 and then heat to 30 to 50°C to obtain the reaction solution.

[0026] This embodiment controls the initial reaction kinetics by controlling the first complexing agent, its dosage, and the temperature.

[0027] In this embodiment, the first complexing agent is one of tartaric acid, citric acid, gluconic acid, malic acid, or lactic acid solutions. Utilizing the synergistic effect of the carboxyl hydroxyl groups in the complexing agent, it can coordinate with metallic copper ions to form a stable structure.

[0028] Step S3: After adding the second complexing agent to the reaction solution in batches, add the pH adjuster until the pH is 3-8, then add the reducing solution, then heat to 90-95℃, react for 0.5-1.5 hours, and then age for 2-8 minutes to obtain copper powder slurry.

[0029] In this embodiment, the copper ions are locked in by the stabilizing effect of the complexation bond of the second complexing agent, and then gradually dissociated and released according to the system conditions (such as pH, temperature, and reaction progress), thus avoiding problems such as agglomeration and loss of activity caused by a large amount of copper ions precipitated at once.

[0030] In this embodiment, the mass ratio of the second complexing agent to the reaction solution is 2~10:100, and the amount added in each batch is 25~35% of the total amount of the second complexing agent. This embodiment uses multiple batches to add the second complexing agent to avoid the complexing reaction being too violent in one go.

[0031] In this embodiment, the second complexing agent is one of ammonia, ammonium bicarbonate, ethylenediamine, ethylenediaminetetraacetic acid, and triethylenetetraamine. This allows the formation of a stable copper-ammonia complex ion to regulate the form and reactivity of copper ions.

[0032] To adjust the initial reaction activity, the pH adjuster in this embodiment is at least one of sodium hydroxide, ammonium bicarbonate, oxalic acid, phosphoric acid, nitric acid, hydrochloric acid, and sulfuric acid.

[0033] To ensure complete reduction of the copper source and avoid waste or loss of raw materials, the mass ratio of reducing agent to copper salt in the reducing solution in this embodiment is 30-80:100. 0.1-0.5 kg of reducing agent is dissolved per liter of water in the reducing solution. The reducing agent is at least one of glucose, ascorbic acid, hydrazine hydrate, hydrogen peroxide, formaldehyde, and acetaldehyde.

[0034] Step S4: Separate the copper powder slurry into solid and liquid phases, and wash and dry the separated solids in sequence to obtain spherical copper powder.

[0035] This embodiment uses a pH adjuster to regulate the pH value, achieving a low-pH reaction, reducing the amount of alkaline reagents and reaction steps, resulting in significant economic benefits. This embodiment utilizes a dual complexing agent to control the chemical reaction rate, precisely controlling the copper nucleation and growth rates. This avoids the problems of excessive copper crystal formation, excessively small particle size, and copper powder agglomeration in the early stages of the reaction due to excessively fast reaction rates. Regulating the particle size reduces the conductivity of the slurry, ultimately obtaining micron-sized spherical copper powder with controllable particle size and excellent monodispersity. The preparation process of this embodiment is simple, and the well-dispersed copper powder is beneficial for the bonding of conductive networks, making it suitable for applications in the electrical field.

[0036] The technical solution of the present invention is illustrated below with specific embodiments: Example 1 Step S1: Mix polyethylene glycol 400 and copper sulfate solution with a mass concentration of 0.1 kg / L at a mass ratio of 1.3:100 and stir until homogeneous to obtain copper sulfate dispersion.

[0037] Step S2: Add tartaric acid to the copper sulfate dispersion at a mass ratio of 2:100 and heat to 35°C to obtain the reaction solution.

[0038] Step S3: Ammonia water is added to the reaction solution in batches at a mass ratio of 10:100, followed by sodium hydroxide until the pH reaches 6. Then, glucose with a mass-volume concentration of 0.2 kg / L is added. The mixture is then heated to 92°C and reacted for 1.0 hour, followed by aging for 6 minutes to obtain a copper powder slurry. The amount added in each batch is 25% of the total amount of the second complexing agent. The mass ratio of glucose to copper sulfate is 60:100.

[0039] Step S4: Separate the copper powder slurry into solid and liquid phases, and wash and dry the separated solids in sequence to obtain monodisperse micron-sized spherical copper powder.

[0040] The scanning electron microscope image (magnification x2000) of the monodisperse micron-sized spherical copper powder in this embodiment is as follows: Figure 1 As shown.

[0041] Example 2 Step S1: Mix polyethylene glycol 1500 and copper nitrate solution with a mass concentration of 1 kg / L at a mass ratio of 1:100 and stir until homogeneous to obtain copper nitrate dispersion.

[0042] Step S2: Add citric acid to the copper nitrate dispersion at a mass ratio of 0.5:100 and heat to 50°C to obtain the reaction solution.

[0043] Step S3: Add ammonium bicarbonate to the reaction solution in batches at a mass ratio of 2:100, followed by ammonium bicarbonate, until the pH reaches 3. Then add ascorbic acid at a mass-volume concentration of 0.1 kg / L. Heat to 95°C and react for 0.5 hours, then age for 2 minutes to obtain a copper powder slurry. The amount added in each batch is 33% of the total amount of the second complexing agent. The mass ratio of ascorbic acid to copper nitrate is 30:100.

[0044] Step S4: Separate the copper powder slurry into solid and liquid phases, and wash and dry the separated solids in sequence to obtain monodisperse micron-sized spherical copper powder.

[0045] The scanning electron microscope image (magnification x2000) of the monodisperse micron-sized spherical copper powder in this embodiment is as follows: Figure 2 As shown.

[0046] Example 3 Step S1: Mix polyvinylpyrrolidone and copper chloride solution with a mass-volume concentration of 0.1 kg / L at a mass ratio of 2:100 and stir until homogeneous to obtain copper chloride dispersion.

[0047] Step S2: Add gluconic acid to the copper chloride dispersion at a mass ratio of 1:100 and heat to 50°C to obtain the reaction solution.

[0048] Step S3: Ethylenediamine is added to the reaction solution in batches at a mass ratio of 6:100, followed by oxalic acid until the pH reaches 8. Then, 0.5 kg / L hydrazine hydrate is added, the temperature is raised to 90°C, and the reaction is carried out for 1.5 hours, followed by aging for 8 minutes to obtain a copper powder slurry. The amount added in each batch is 35% of the total amount of the second complexing agent. The mass ratio of hydrazine hydrate to copper chloride is 80:100.

[0049] Step S4: Separate the copper powder slurry into solid and liquid phases, and wash and dry the separated solids in sequence to obtain monodisperse micron-sized spherical copper powder.

[0050] The scanning electron microscope image (magnification x2000) of the monodisperse micron-sized spherical copper powder in this embodiment is as follows: Figure 3 As shown.

[0051] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing monodisperse micron-sized spherical copper powder, characterized in that, The preparation method includes the following steps: Step S1: Mix the dispersant and copper salt solution and stir until homogeneous to obtain a copper salt dispersion; Step S2: Add the first complexing agent to the copper salt dispersion at a mass ratio of 0.5 to 2:100, and then heat to 30 to 50°C to obtain the reaction solution; Step S3: After adding the second complexing agent to the reaction solution in batches, add the pH adjuster until the pH is 3-8, then add the reducing solution, then heat to 90-95℃, react for 0.5-1.5 hours, and then age for 2-8 minutes to obtain copper powder slurry. Step S4: Separate the copper powder slurry into solid and liquid phases, and wash and dry the separated solids in sequence to obtain spherical copper powder.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass-volume concentration of the copper salt solution is 0.1 to 1 kg / L.

3. The preparation method according to claim 2, characterized in that, In step S1, the mass ratio of dispersant to copper salt solution in the copper salt dispersion is 0.5 to 2:

100.

4. The preparation method according to claim 3, characterized in that, In step S1, the copper salt solution is one of copper sulfate solution, copper nitrate solution, copper chloride solution, copper citrate solution, and copper tartrate solution; In step S1, the dispersant is one of polyethylene glycol 400, polyethylene glycol 1500, polyvinylpyrrolidone, sodium dodecyl sulfonate, and polyvinyl alcohol.

5. The preparation method according to any one of claims 1 to 4, characterized in that, In step S2, the first complexing agent is one of tartaric acid, citric acid, gluconic acid, malic acid, or lactic acid solution.

6. The preparation method according to claim 5, characterized in that, In step S3, the mass ratio of the second complexing agent to the reaction solution is 2~10:100; The amount added in each batch is 25-35% of the total amount of the second complexing agent.

7. The preparation method according to claim 6, characterized in that, The second complexing agent is one of ammonia, ammonium bicarbonate, ethylenediamine, ethylenediaminetetraacetic acid, and triethylenetetraamine.

8. The preparation method according to claim 7, characterized in that, In step S3, the mass ratio of reducing agent to copper salt in the reducing solution is 30-80:100; In step S3, 0.1 to 0.5 kg of reducing agent is dissolved in each liter of water in the reducing solution.

9. The preparation method according to claim 8, characterized in that, In step S3, the pH adjuster is at least one of sodium hydroxide, ammonium bicarbonate, oxalic acid, phosphoric acid, nitric acid, hydrochloric acid, and sulfuric acid. In step S3, the reducing agent is at least one of glucose, ascorbic acid, hydrazine hydrate, hydrogen peroxide, formaldehyde, and acetaldehyde.

10. A monodisperse micron-sized spherical copper powder, characterized in that, The monodisperse micron-sized spherical copper powder is prepared using the preparation method described in any one of claims 1 to 9.

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