Silver-coated copper powder particles with ultra-large particle size and preparation process thereof

Abstract

The invention discloses ultra-large-particle-size silver-coated copper powder particles and a preparation process thereof, and relates to the technical field of electronic metal materials. The process comprises the steps of atomization preparation of copper powder particles, acid washing, alkali washing, silver coating plating, cleaning and drying and the like. According to the method, the copper powder particles are prepared through the atomization technology, the atomization pressure and the medium flow speed are accurately controlled to crush molten copper into liquid drops with the proper granularity, then the liquid drops are rapidly condensed into the copper powder particles, the particle size of the prepared copper powder particles is stabilized between 7.5 micrometers and 8 micrometers, the particle size is uniform, the yield is high, and the production rate is extremely high; in addition, the silver layer on the particle surface of the silver-coated copper powder prepared by the method is densely and uniformly covered, the average thickness is controlled below 100nm, and the particle performance is ensured on the basis of reducing the cost.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic metal materials, in particular to ultra-large-diameter silver-coated copper powder particles and a preparation process thereof. Background Art

[0002] Silver-coated copper powder is a very good highly conductive filler. It is often added to coatings (paints), glues (adhesives), inks, polymer slurries, plastics, rubber, etc. It can be made into various conductive and electromagnetic shielding products. It is widely used in the fields of conductivity, electromagnetic shielding, etc. in various industrial sectors such as electronics, electromechanics, communications, printing, aerospace, and weapons.

[0003] Such as computers, mobile phones, electronic medical equipment, electronic instruments and other electronic, electrical, and communication products, and electromagnetic shielding.

[0004] The particle size of most silver-coated copper powders is usually between 100 nanometers and 5 microns. Ultra-large particle size silver-coated copper powders generally refer to those with a particle size of 7.5 microns or above.

[0005] Ultra-large particle size silver-coated copper powder can be used as the core component of conductive paste, which can replace part of pure silver powder and be used in the preparation of N-type battery silver paste. It can reduce the silver usage by more than 50%, greatly reducing production costs; at the same time, by optimizing the particle size distribution, the conductivity and anti-break performance of the printed electrode can be improved.

[0006] It can also be used in conductive adhesives, conductive inks, and plastic / rubber-based composites. The ultra-large particle size of silver-coated copper powder provides thermal conductivity, while the silver layer ensures electrical conductivity, reducing the material cost of electronic packaging and circuit board wiring. Alternatively, it can be added to paints or plastics to form a conductive coating for mobile phone and computer casings and integrated circuit packaging, shielding electromagnetic radiation and reducing signal interference. Furthermore, ultra-large particle size silver-coated copper powder is also being used in specialized military applications, high-temperature ceramics, catalytic energy, and other related fields.

[0007] At present, there are few patents and papers related to ultra-large particle size silver-coated copper powder particles. For example, Chinese patent publication number CN119870451A discloses a spherical copper powder and a preparation method thereof, the preparation method comprising: preparing a copper salt dispersion comprising a copper salt and a dispersant, as well as a first reducing liquid and a second reducing liquid; adding the first reducing liquid to the copper salt dispersion, reacting at a first preset temperature and for a first preset time to obtain a reaction liquid, wherein the first preset time is 0.5 to 1 hour; adding the second reducing liquid to the reaction liquid, reacting at a second preset temperature and for a second preset time to obtain a copper powder slurry, wherein the second preset time is 1 to 2 hours; separating spherical copper powder from the copper powder slurry, wherein the spherical copper powder has a large particle size and high sphericity. In this way, by adopting a liquid phase reduction method, using copper salt as a raw material, adding a dispersant and mixing, and undergoing two-step reduction, a copper powder with good dispersibility and high sphericity can be prepared.

[0008] The invention has a simple preparation process, and the high-sphericity copper powder has the characteristics of large particle size, wide distribution and high sphericity, which is conducive to the overlapping of conductive networks.

[0009] However, this invention uses a reduction method to prepare copper powder particles. This method has significant advantages when preparing small-sized copper powder particles. By controlling the reaction time and concentration, large quantities of small-sized copper powder particles can be quickly obtained. However, when preparing ultra-large-sized copper powder particles, the reaction time is difficult to control, resulting in uneven copper powder particle size and a long production process, which significantly affects the yield and production rate. Summary of the Invention

[0010] The present invention aims to solve the above technical problems, overcome the shortcomings of the prior art, and provide ultra-large-size silver-coated copper powder particles and a preparation process thereof.

[0011] Technical effect: Copper powder particles are prepared through atomization technology, and the atomization pressure and medium flow rate are precisely controlled to break the molten copper liquid into droplets of suitable particle size, and then quickly condense into copper powder particles. The copper powder particles prepared in this way have a stable particle size between 7.5 and 8 microns, uniform particle size, high yield rate, and excellent production rate; in addition, the silver layer on the surface of the silver-coated copper powder particles prepared by the invention is densely and evenly covered, and the average thickness is controlled below 100nm, which reduces costs while ensuring particle performance.

[0012] The technical solution further defined in the present invention is:

[0013] A process for preparing ultra-large-size silver-coated copper powder particles comprises the following steps:

[0014] S1, molten copper liquid is sprayed into an atomizing chamber through an atomizing device, and the medium airflow in the atomizing chamber breaks the copper liquid into droplets of suitable size. The droplets fall into the cooling medium in the atomizing chamber and are cooled to form copper powder particles, and the copper powder particles with a particle size of D50 = 7.5-8 are filtered out;

[0015] S2, taking a 7% sodium hydroxide solution, placing the screened copper powder particles in the sodium hydroxide solution, ultrasonically washing for 3 to 5 minutes, and then taking them out and repeatedly washing them with water until they are neutral;

[0016] S3, taking a 7% dilute sulfuric acid solution, placing the copper powder particles after alkali washing in the dilute sulfuric acid solution, ultrasonically pickling for 10 minutes to remove the surface oxide layer, repeatedly washing with water until neutral, obtaining activated copper powder and storing it under argon protection;

[0017] S4, taking a certain amount of silver nitrate, a complexing agent and nano-silver particles and mixing them, adding 5% ammonia water until the pH is 9-11, and ultrasonically dispersing them to prevent agglomeration; heating the mixture in a 60°C water bath with ultrasonic stirring, adding activated copper powder to the mixture, adding a reducing agent, stirring and immersion plating for 4 minutes, and then filtering to remove the particles to complete the zinc plating;

[0018] S5, washing the particles with deionized water until they are neutral, and vacuum drying them at 70° C. for 2 h to obtain finished silver-coated copper powder particles.

[0019] Furthermore, in step S1, the temperature of the copper liquid is stabilized between 1170 and 1190° C., and the nozzle pressure is 0.7 MPa.

[0020] In the aforementioned process for preparing ultra-large-size silver-coated copper powder particles, in step S1 , the flow rate of the medium airflow is 10-11 m / s, the impact angle is 40°, and the cooling medium is water.

[0021] In the aforementioned process for preparing ultra-large-size silver-coated copper powder particles, in step S1, the atomization chamber is in a nitrogen protective atmosphere, the medium gas flow is nitrogen, a 3.5 mm conical nozzle is used, and the cooling water depth is 30 cm.

[0022] In the aforementioned process for preparing ultra-large-size silver-coated copper powder particles, in step S1, the bottom surface of the atomizing chamber is a conical barrel structure, and the bottom is a detachable straight cylinder structure. A filter screen is provided in the straight cylinder structure, and the filter screen is 1500 mesh.

[0023] In the aforementioned process for preparing ultra-large-size silver-coated copper powder particles, in step S4, the complexing agent is a phosphate, an alcoholamine complexing agent, a hydroxycarboxylate, an aminocarboxylate, or ethylenediaminetetraacetic acid.

[0024] In the aforementioned process for preparing ultra-large-size silver-coated copper powder particles, in step S4, the reducing agent is glucose or formaldehyde.

[0025] In the aforementioned process for preparing ultra-large-size silver-coated copper powder particles, in step S4, the thickness of the silver plating layer is 50-100 nm.

[0026] In the aforementioned process for preparing ultra-large-size silver-coated copper powder particles, in step S4, the speed of ultrasonic stirring is 200-300 rpm.

[0027] The present invention also provides ultra-large-size silver-coated copper powder particles, which are prepared by any one of the above-mentioned preparation processes for ultra-large-size silver-coated copper powder particles.

[0028] The beneficial effects of the present invention are:

[0029] (1) In the present invention, the nozzle pressure is reduced to 0.7 MPa, the medium flow rate is controlled at 10-11 m / s, and the impact angle is fixed at 40°. The particle size of the copper liquid formed by the impact can be controlled to be above 8 microns. After removing the influence of thermal expansion and contraction, copper powder particles with a particle size of above 7.5 microns are formed;

[0030] (2) In the present invention, nitrogen protection is used in the atomizing chamber to prevent the copper liquid and the generated copper powder particles from being oxidized to form copper oxide. The conical nozzle can increase the spraying range of the copper liquid. The cooling water depth is above 20 cm for complete cooling, which can form copper powder particles with uniform particle size. The bottom surface of the atomizing chamber is a conical barrel structure, and the bottom is a detachable straight cylinder structure. The formed copper powder particles fall along the conical structure and are screened in the straight cylinder structure.

[0031] (3) In the present invention, acid washing and alkali washing can remove organic matter and re-condensed oxide layer on the surface of copper powder, thereby ensuring the activity of copper powder and avoiding affecting the adhesion of silver layer during silver plating and causing uneven silver layer;

[0032] (4) In the present invention, the addition of the complexing agent can improve the dispersibility of the copper powder in the slurry, making the silver plating process more uniform. The addition is completed within 4 minutes, which can ensure that the thickness of the silver layer reaches 50-100nm. The present invention accurately controls the concentration of the plating solution and the reaction temperature to avoid local over-plating or under-plating, and adds an organic carrier to prevent particle sedimentation;

[0033] (5) In the present invention, copper powder particles are prepared by atomization technology, and the atomization pressure and medium flow rate are precisely controlled to break the molten copper liquid into droplets of suitable particle size, and then quickly condense into copper powder particles. The particle size of the copper powder particles prepared in this way is stable between 7.5 and 8 microns, the particle size is uniform, the yield rate is high, and the production rate is excellent; in addition, the silver layer on the surface of the silver-coated copper powder particles prepared by the invention is densely and uniformly covered, and the average thickness is controlled below 100 nm, thereby ensuring the particle performance on the basis of reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the schematic diagram of the atomization equipment;

[0035] Figure 2 This is a picture of the finished product of the silver-coated copper powder particles prepared in Example 1.

[0036] Among them: 1. Atomizing chamber; 2. Filter; 3. Conical nozzle; 4. Medium nozzle. DETAILED DESCRIPTION

[0037] To make the objectives, technical solutions, and advantages of the present invention more apparent, a detailed description is given below in conjunction with the accompanying drawings and specific embodiments. The following description sets forth many specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0038] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0040] This embodiment provides a process for preparing ultra-large-size silver-coated copper powder particles, comprising the following steps:

[0041] S1, molten copper liquid is sprayed into an atomizing chamber through an atomizing device, and the medium airflow in the atomizing chamber breaks the copper liquid into droplets of suitable size. The droplets fall into the cooling medium in the atomizing chamber and are cooled to form copper powder particles, and the copper powder particles with a particle size of D50 = 7.5 to 8 μm are filtered out.

[0042] In this step, the temperature of the copper liquid is stabilized between 1170 and 1190°C, the nozzle pressure is 0.7 MPa; the flow rate of the medium air flow is 10 to 11 m / s, the impact angle is 40°, and the cooling medium is water; Figure 1 As shown, the atomizing chamber is protected by nitrogen atmosphere, the medium gas flow is nitrogen, a 3.5mm conical nozzle is used, and the cooling water depth is 30cm; the bottom surface of the atomizing chamber is a cone barrel structure, and the bottom is a detachable straight cylinder structure. A filter screen is set in the straight cylinder structure, and the filter screen is 1500 mesh;

[0043] Increasing the pressure or flow rate of the gas or liquid atomizing medium can enhance the crushing effect of the metal stream column, thereby reducing the particle size. Therefore, in this step, the nozzle pressure is reduced to 0.7 MPa, the medium flow rate is controlled at 10-11 m / s, and the impact angle is fixed at 40°. The particle size of the copper liquid formed by the impact can be controlled to be above 7.5 microns. After removing the influence of thermal expansion and contraction, copper powder particles with a particle size of more than 45 microns are formed.

[0044] In addition, nitrogen protection is used in the atomization chamber to prevent the copper liquid and the generated copper powder particles from oxidizing to form copper oxide. The conical nozzle can increase the spraying range of the copper liquid. The cooling water depth of more than 20 cm can be completely cooled to form copper powder particles with uniform particle size.

[0045] The bottom surface of the atomization chamber is a conical barrel structure, and the bottom is a detachable straight cylinder structure. The formed copper powder particles fall along the conical structure and are screened in the straight cylinder structure.

[0046] S2, taking a sodium hydroxide solution with a concentration of 7%, placing the screened copper powder particles in the sodium hydroxide solution, ultrasonically washing them for 3 to 5 minutes, and then taking them out and repeatedly washing them with water until they are neutral.

[0047] S3, taking a 7% dilute sulfuric acid solution, placing the copper powder particles after alkali washing in the dilute sulfuric acid solution, ultrasonically pickling for 10 minutes to wash away the surface oxide layer, repeatedly washing with water until neutral, obtaining activated copper powder and storing it under argon protection.

[0048] Acid washing and alkaline washing can remove organic matter and re-condensed oxide layer on the surface of copper powder, ensure the activity of copper powder, and avoid affecting the adhesion of silver layer during silver plating and causing uneven silver layer.

[0049] S4, taking a certain amount of silver nitrate, a complexing agent and nano-silver particles and mixing them, adding 5% ammonia water until the pH is 9-11, and ultrasonically dispersing them to prevent agglomeration; heating the mixture in a 60°C water bath with ultrasonic stirring, adding activated copper powder to the mixture, adding a reducing agent, stirring and immersion plating for 4 minutes, and then filtering to remove the particles to complete the zinc plating;

[0050] In this step, the speed of ultrasonic stirring is 200-300 rpm, the complexing agent is phosphate, alcoholamine complexing agent, hydroxycarboxylate, aminocarboxylate or ethylenediaminetetraacetic acid, and the thickness of the silver plating layer is 50-100 nm.

[0051] The addition of a complexing agent improves the dispersion of copper powder in the slurry, making the silver plating process more uniform. Addition is completed within 4 minutes, ensuring a silver layer thickness of 50-100nm. This step precisely controls the plating solution concentration and reaction temperature to avoid localized over- or under-plating. An organic carrier is also added to prevent particle sedimentation.

[0052] S5, washing the particles with deionized water until they are neutral, and vacuum drying them at 70° C. for 2 h to obtain finished silver-coated copper powder particles.

[0053] The present invention verifies the performance of the ultra-large silver-coated copper powder particles obtained through several examples, while the comparative examples are prepared by a reduction method. The preparation conditions of each example are shown in Table 1.

[0054] Table 1 Preparation conditions of each embodiment

[0055] project Nozzle pressure MPa Medium flow rate m / s Impact angle complexing agent reducing agent Example 1 0.7 11 40 EDTA glucose Example 2 0.5 10 30 EDTA glucose Example 3 1.0 11 60 EDTA glucose Example 4 0.7 11 40 EDTA formaldehyde

[0056] After the preparation was completed, the silver-coated copper powder particles prepared in each embodiment and comparative example were tested, and the test results were shown in Table 2.

[0057] Table 2 Performance of silver-coated copper powder particles prepared in various embodiments and comparative examples

[0058]

[0059]

[0060] It can be seen from the data in Table 2 that the silver-coated copper powder prepared in Example 1 of the present invention has the best performance and can be used in various fields such as conductive slurry, conductive adhesive, 5G equipment, photovoltaic cells, high shielding scenarios, etc. In addition, the prepared particles have uniform particle size and excellent effect.

[0061] In addition to the above embodiments, the present invention may also have other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the scope of protection required by the present invention.

Claims

1. A process for preparing ultra-large-size silver-coated copper powder particles, characterized in that: The steps include: S1, molten copper liquid is sprayed into an atomizing chamber through an atomizing device, and the medium airflow in the atomizing chamber breaks the copper liquid into droplets of suitable size. The droplets fall into the cooling medium in the atomizing chamber and are cooled to form copper powder particles, and the copper powder particles with a particle size D50 = 7.5 to 8 μm are filtered out; S2, taking a 7% sodium hydroxide solution, placing the screened copper powder particles in the sodium hydroxide solution, ultrasonically washing for 3 to 5 minutes, and then taking them out and repeatedly washing them with water until they are neutral; S3, taking a 7% dilute sulfuric acid solution, placing the copper powder particles after alkali washing in the dilute sulfuric acid solution, ultrasonically pickling for 10 minutes to remove the surface oxide layer, repeatedly washing with water until neutral, obtaining activated copper powder and storing it under argon protection; S4, taking a certain amount of silver nitrate, a complexing agent and nano-silver particles and mixing them, adding 5% ammonia water until the pH is 9-11, and ultrasonically dispersing them to prevent agglomeration; heating the mixture in a 60°C water bath with ultrasonic stirring, adding activated copper powder to the mixture, adding a reducing agent, stirring and immersion plating for 4 minutes, and then filtering to remove the particles to complete the zinc plating; S5, washing the particles with deionized water until they are neutral, and vacuum drying them at 70° C. for 2 h to obtain finished silver-coated copper powder particles.

2. The process for preparing ultra-large-size silver-coated copper powder particles according to claim 1, wherein: In step S1, the temperature of the copper liquid is stabilized between 1170 and 1190° C., and the nozzle pressure is 0.7 MPa.

3. The process for preparing ultra-large-size silver-coated copper powder particles according to claim 2, characterized in that: In step S1, the flow rate of the medium airflow is 10-11 m / s, the impact angle is 40°, and the cooling medium is water.

4. The process for preparing ultra-large-size silver-coated copper powder particles according to claim 1, wherein: In step S1, the atomization chamber is in a nitrogen protective atmosphere, the medium gas flow is nitrogen, a 3.5 mm conical nozzle is used, and the cooling water depth is 30 cm.

5. The process for preparing ultra-large-size silver-coated copper powder particles according to claim 1, wherein: In step S1, the bottom surface of the atomizing chamber is a conical barrel structure, and the bottom is a detachable straight cylinder structure. A filter screen is set in the straight cylinder structure, and the filter screen is 1500 mesh.

6. The process for preparing ultra-large-size silver-coated copper powder particles according to claim 1, wherein: In step S4, the complexing agent is a phosphate, an alcoholamine complexing agent, a hydroxycarboxylate, an aminocarboxylate, or ethylenediaminetetraacetic acid.

7. The process for preparing ultra-large-size silver-coated copper powder particles according to claim 1, characterized in that: In step S4, the reducing agent is glucose or formaldehyde.

8. The process for preparing ultra-large-size silver-coated copper powder particles according to claim 1, wherein: In step S4, the thickness of the silver plating layer is 50-100 nm.

9. The process for preparing ultra-large-size silver-coated copper powder particles according to claim 1, characterized in that: In step S4, the rotation speed of ultrasonic stirring is 200-300 rpm.

10. A super-large-size silver-coated copper powder particle, characterized in that: The super-large-size silver-coated copper powder is prepared by any one of the preparation processes of claims 1 to 9.

Images