High-thermal-conductivity silver-coated copper powder particles and preparation method thereof

Abstract

The invention relates to the technical field of silver-coated copper powder, in particular to high-thermal-conductivity silver-coated copper powder particles and a preparation method thereof. Comprising the steps of pretreatment, plating solution preparation, copper powder plating, nanowire growth, surface modification, proportioning and mixing and the like, macroscopic gaps are reduced through grading, the contact probability is increased, point contact among particles is changed into surface contact and body contact by adding nanowire microstructures on the surface of a silver layer, the contact area and mechanical interlocking are improved, and the contact efficiency is improved. In addition, the heat transfer efficiency from a polymer matrix to the surface of the filler is improved through chemical bonding by means of surface modification, and interface phonon scattering is reduced.

Description

Technical Field

[0001] This invention relates to the field of silver-coated copper powder technology, specifically to a high thermal conductivity silver-coated copper powder particle and its preparation method. Background Technology

[0002] Silver-coated copper powder, as an excellent highly conductive filler, can be added to coatings (paints), adhesives, inks, polymer slurries, plastics, rubber, etc., to produce various conductive and electromagnetic shielding products. These products are widely used in conductive and electromagnetic shielding applications across various industrial sectors, including electronics, electromechanical engineering, communications, printing, aerospace, and weaponry. Examples include conductive and electromagnetic shielding in electronic, electrical, and communication products such as computers, mobile phones, electronic medical equipment, and electronic instruments.

[0003] High thermal conductivity silver-coated copper powder is a composite metal powder consisting of copper particles coated with a silver layer. It combines the high electrical conductivity of silver with the high thermal conductivity of copper. Its volume resistivity is as low as 2×10⁻³Ω·cm, its oxidation resistance temperature exceeds 220℃, its thermal conductivity is better than that of pure silver powder, and its cost is reduced by 30%-50% compared to pure silver powder. Furthermore, the silver layer prevents the oxidation of copper.

[0004] High thermal conductivity silver-coated copper powder is used in conductive adhesives, electrode materials, and flexible circuits, such as electromagnetic shielding layers for mobile phones. It can also be used as a low-temperature slurry for HJT heterojunction batteries, with a market size of 2 billion yuan in 2024. It can also be used in heat dissipation coatings for 5G equipment, utilizing the high thermal conductivity of copper to quickly dissipate heat.

[0005] For example, Chinese patent CN104829987A discloses a heat dissipation material for LED light sources made of polytetrafluoroethylene doped with spherical silver-coated copper powder and its preparation method. The material is made from the following raw materials in parts by weight: 0.1-0.2 parts of 200-300 mesh strontium zirconate micro powder, 5-8 parts of silica sol with a solid content of 15-20%, 4-6 parts of quartz fiber, 3-5 parts of nano iron oxide, 3-5 parts of polyethylene wax, 1-2 parts of room temperature non-foaming surfactant, 1-3 parts of 200-300 mesh spherical silver-coated copper powder, 3-5 parts of sodium silicate, 30-40 parts of water, 20-25 parts of 400-600 mesh aluminum nitride micro powder, 40-50 parts of 200-300 mesh polytetrafluoroethylene micro powder, and 2-3 parts of additives. The heat dissipation material of this invention has high efficiency, uniformity, and stable thermal conductivity, is resistant to environmental corrosion, does not deform due to heat, has a clean and dirt-resistant surface, is safe and insulating, and is easy to process and cut. It is an environmentally friendly and efficient heat dissipation material for LED lamps.

[0006] However, including this patented technology, most commercially available silver-coated copper powders currently have relatively high contact thermal resistance. Even if the powder itself has high thermal conductivity, if heat cannot be efficiently transferred between particles, the overall performance will be significantly reduced.

[0007] To address the above problems, this invention provides highly thermally conductive silver-coated copper powder particles and a method for preparing the same. Summary of the Invention

[0008] The purpose of this invention is to provide a high thermal conductivity silver-coated copper powder particle and its preparation method, so as to solve the problems mentioned in the background art.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing highly thermally conductive silver-coated copper powder particles, comprising the following steps:

[0010] S1, Pretreatment: Take various copper powders with different particle sizes and shapes, soak them in 5% dilute sulfuric acid solution for 15 minutes, and wash them with deionized water until neutral to remove the surface oxide layer. Then wash them twice with anhydrous ethanol and finally vacuum dry them for later use.

[0011] S2, prepare the plating solution: take a certain amount of silver nitrate, add deionized water, and add ammonia dropwise until the precipitate is completely dissolved to form solution A; take a certain amount of glucose, potassium sodium tartrate, and PVP, add them to deionized water to obtain solution B;

[0012] S3, copper plating powder: Pretreated copper powder of a certain particle size is dispersed in solution B and stirred at a constant temperature of 40°C in a water bath. At the same time, solution A is slowly added dropwise to the mixed solution. After the addition is complete, the temperature is raised to 45°C and kept at that temperature for 1.5 hours. After filtration, it is washed 4-5 times alternately with deionized water and ethanol, and then vacuum dried. Repeating this process multiple times will yield silver-plated copper powder of various particle sizes.

[0013] S4, Nanowire growth: A dilute silver nitrate growth solution was prepared, PVP solution was added as a crystal orientation inducer, and the pH was adjusted to 11 with dilute ammonia. Silver-plated copper powders of various particle sizes were placed in the growth solution and subjected to low-power intermittent ultrasonic disruption for 25-30 minutes using an ultrasonic cell disruptor to form nanowires. The nanowires were then washed alternately with deionized water and ethanol and vacuum dried to obtain silver-coated copper powders modified with nanowires of various particle sizes.

[0014] S5, surface modification: A quantitative amount of mercaptopropyltriethoxysilane and 95% ethanol aqueous solution were taken and magnetically stirred for 30 min to allow for complete hydrolysis. Various nanowire-modified silver-coated copper powders with different particle sizes were placed in the hydrolysate, ultrasonically dispersed for 30 min, and then transferred to a 60℃ water bath and mechanically stirred for 2.5 h. After vacuum filtration, the powders were vacuum dried at 80℃ for 2 h to obtain modified silver-coated copper powders with different particle sizes.

[0015] S6, Proportional Mixing: Mix various modified silver-coated copper powders of different particle sizes in a low-speed three-dimensional mixer for 2 hours to ensure uniform mixing and obtain high thermal conductivity silver-coated copper powder granules.

[0016] Ideally, three types of modified silver-coated copper powder should be selected when mixing different types of powder.

[0017] The optimal volume ratio of the three different types of modified copper powder is 69:20.5:10.5.

[0018] In a more optimized manner, the particle size and shape of the three different types of modified copper powder are 4.8 μm granular powder, 3.5 μm spherical powder, and 2.1 μm granular powder, respectively.

[0019] In a more optimized manner, in step S2, the concentration of silver nitrate is 20 g / L, the concentration of glucose is 30 g / L, the concentration of potassium sodium tartrate is 15 g / L, and the concentration of PVP is 2 g / L.

[0020] Ideally, in step S3, the dropping rate of liquid A is 2.5 mL / min.

[0021] In a more optimized manner, in step S4, the concentration of the silver nitrate solution is 0.02 mol / L and the concentration of the PVP solution is 5 mg / mL.

[0022] In a more optimized manner, in step S4, when the silver-plated copper powder is dispersed into the growth solution, the solid-liquid ratio is 1:55.

[0023] In a more optimized manner, in step S4, the ultrasonic cell disruptor has a power of 280W, the intermittent ultrasound detection time is 3s, and the ultrasound time is 2s.

[0024] In a more optimized manner, in step S5, mercaptopropyltriethoxysilane accounts for 1.0% of the total mass of the powder.

[0025] The present invention also provides a high thermal conductivity silver-coated copper powder particle, which is prepared by any of the above-mentioned methods for preparing high thermal conductivity silver-coated copper powder particles.

[0026] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0027] (1) The present invention can construct a multi-scale heat conduction network, with 4.8μm silver-coated copper powder forming the main channel to ensure rapid long-distance heat flow, and 3.5μm and 2.1μm silver-coated copper powder forming the capillary network to ensure that heat can be transferred from the main channel to every corner without obstruction, thus realizing three-dimensional full interconnection.

[0028] (2) The present invention reduces macroscopic voids by gradation, increases the contact probability, increases nanowire microstructure, and transforms the “point contact” between particles into “surface contact” and “volume contact”, thereby improving the contact area and mechanical interlocking. It can also pierce interfacial contaminants and thin oxide layers. In addition, surface modification improves the heat transfer efficiency from the polymer matrix to the filler surface through chemical bonding, and reduces interfacial phonon scattering.

[0029] (3) If the present invention does not have gradation, there will be a large number of voids between the nanowire powders, making it impossible to form an efficient backbone network. If there is only gradation but no nanowires, the contact thermal resistance between particles will still be a bottleneck. Therefore, the present invention achieves systematic and comprehensive suppression of contact thermal resistance through the combined action of multiple scales and multiple mechanisms. Attached Figure Description

[0030] Figure 1 The image shown is an electron microscope image of the highly thermally conductive silver-coated copper powder particles obtained in the example. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0032] This invention provides a preferred embodiment, the preparation of which includes the following steps:

[0033] S1, Pretreatment: Take three types of copper powder, namely 4.8μm granular, 3.5μm spherical, and 2.1μm granular, soak them in 5% dilute sulfuric acid solution for 15 minutes, and wash them with deionized water until neutral to remove the surface oxide layer. Then wash them twice with anhydrous ethanol and finally vacuum dry them for later use.

[0034] S2, Prepare the plating solution: Take a measured amount of silver nitrate, add deionized water, and add ammonia dropwise until the precipitate is completely dissolved to form solution A; Take a measured amount of glucose, potassium sodium tartrate, and PVP, and add them to deionized water to obtain solution B; In this step, the concentration of silver nitrate is 20 g / L, the concentration of glucose is 30 g / L, the concentration of potassium sodium tartrate is 15 g / L, and the concentration of PVP is 2 g / L.

[0035] S3, Copper plating powder: Pretreated copper powder of one particle size is dispersed in solution B and stirred at a constant temperature of 40°C in a water bath. At the same time, solution A is slowly added dropwise to the mixed solution. After the addition is complete, the temperature is raised to 45°C and kept at this temperature for 1.5 hours. After filtration, it is washed 4-5 times alternately with deionized water and ethanol, and then vacuum dried. Repeating this process three times yields three different silver-plated copper powders with different particle sizes. In this step, the dropping rate of solution A is 2.5 mL / min.

[0036] S4, Nanowire Growth: A dilute silver nitrate growth solution was prepared, and PVP solution was added as a crystal orientation inducer. The pH was adjusted to 11 with dilute ammonia. Three different sizes of silver-plated copper powder were placed in the growth solution and intermittently ultrasonically disrupted for 25-30 minutes using an ultrasonic cell disruptor to form nanowires. The nanowires were then washed alternately with deionized water and ethanol, and vacuum dried to obtain the three different sizes of nanowire-modified silver-plated copper powder. The solid-liquid ratio of the silver-plated copper powder in the growth solution was 1:55. The ultrasonic cell disruptor power was 280W, the intermittent ultrasonic detection time was 3 seconds, and the ultrasonic time was 2 seconds. In this step, the ultrasonic power and time are crucial; excessive power or time can lead to excessively long nanowires, entanglement, agglomeration, or even detachment from the substrate.

[0037] S5, Surface Modification: A quantitative amount of mercaptopropyltriethoxysilane was mixed with a 95% ethanol aqueous solution and magnetically stirred for 30 minutes to ensure complete hydrolysis. Three nanowire-modified silver-coated copper powders of different particle sizes were placed in the hydrolysate and ultrasonically dispersed for 30 minutes. The mixture was then transferred to a 60°C water bath and mechanically stirred for 2.5 hours. After vacuum filtration, the powders were vacuum dried at 80°C for 2 hours to obtain three modified silver-coated copper powders of different particle sizes. Mercaptopropyltriethoxysilane accounted for 1.0% of the total powder mass. This step ensures that the silane coupling agent forms a monolayer on the powder surface, rather than self-polymerizing into a film.

[0038] S6, Mixing: Three modified copper powders of different particle sizes are mixed in a low-speed three-dimensional mixer for 2 hours in a specified ratio to ensure uniform mixing and obtain high thermal conductivity silver-coated copper powder particles. The volume ratio of the three modified copper powders of different particle sizes is 69:20.5:10.5, which yields the optimal packing model.

[0039] This invention verifies the improved thermal conductivity of the silver-coated copper powder obtained through examples and several comparative examples. Furthermore, five different types of modified copper powder were added as comparative examples, including 4.8μm granular, 3.5μm spherical, 3.5μm granular, 2.1μm spherical, and 2.1μm granular particles, with a particle size distribution ratio of 30:25:20:15:10. The designs of each example and comparative example are shown in Table 1, and the experimental results are shown in Table 2.

[0040] Table 1 Design Considerations for Each Embodiment and Comparative Example

[0041] The prepared silver-coated copper powder was placed in a polymer-based composite thermally conductive silicone, and measured at the same temperature using the same Hot Disk thermal conductivity analyzer or laser scintillation method at a 60% filling rate.

[0042] Table 2. Test results of thermal conductivity of silver-coated copper powder prepared in each embodiment and comparative example.

[0043] A comparison of Tables 1 and 2 shows that both simple particle size distribution (Comparative Example 2) and simple micro / nano structures (Comparative Example 3) can effectively improve the thermal conductivity of the composite material, proving that these two methods are feasible in reducing contact thermal resistance and optimizing the thermal conductivity network. Constructing nanowires to increase mechanical interlocking and contact area has a remarkably significant effect on reducing interparticle contact thermal resistance.

[0044] The integrated solution in this invention produces a powerful synergistic effect of "1+1>2":

[0045] The gradation provides a more ideal working environment for micro and nanostructures, enabling nanowires not only to connect particles of the same size, but also to efficiently bridge particles of different sizes and fill voids of different scales. Surface modification ensures that heat can be efficiently transferred from the polymer matrix to this optimized three-dimensional thermally conductive network.

[0046] Compared to the comparative embodiments, the embodiments exhibit superior composite thermal conductivity and thermal resistance, thus the embodiments represent the optimal gradation combination in this invention.

[0047] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing highly thermally conductive silver-coated copper powder particles, characterized in that, Includes the following steps: S1, Pretreatment: Take various copper powders with different particle sizes and shapes, soak them in 5% dilute sulfuric acid solution for 15 minutes, and wash them with deionized water until neutral to remove the surface oxide layer. Then wash them twice with anhydrous ethanol and finally vacuum dry them for later use. S2, prepare the plating solution: take a certain amount of silver nitrate, add deionized water, and add ammonia dropwise until the precipitate is completely dissolved to form solution A; take a certain amount of glucose, potassium sodium tartrate, and PVP, add them to deionized water to obtain solution B; S3, copper plating powder: Pretreated copper powder of a certain particle size is dispersed in solution B and stirred at a constant temperature of 40°C in a water bath. At the same time, solution A is slowly added dropwise to the mixed solution. After the addition is complete, the temperature is raised to 45°C and kept at that temperature for 1.5 hours. After filtration, it is washed 4-5 times alternately with deionized water and ethanol, and then vacuum dried. Repeating this process multiple times will yield silver-plated copper powder of various particle sizes. S4, Nanowire growth: A dilute silver nitrate growth solution was prepared, PVP solution was added as a crystal orientation inducer, and the pH was adjusted to 11 with dilute ammonia. Silver-plated copper powders of various particle sizes were placed in the growth solution and subjected to low-power intermittent ultrasonic disruption for 25-30 minutes using an ultrasonic cell disruptor to form nanowires. The nanowires were then washed alternately with deionized water and ethanol and vacuum dried to obtain silver-coated copper powders modified with nanowires of various particle sizes. S5, surface modification: A quantitative amount of mercaptopropyltriethoxysilane and 95% ethanol aqueous solution were taken and magnetically stirred for 30 min to allow for complete hydrolysis. Various nanowire-modified silver-coated copper powders with different particle sizes were placed in the hydrolysate, ultrasonically dispersed for 30 min, and then transferred to a 60℃ water bath and mechanically stirred for 2.5 h. After vacuum filtration, the powders were vacuum dried at 80℃ for 2 h to obtain modified silver-coated copper powders with different particle sizes. S6, Proportional Mixing: Mix various modified silver-coated copper powders of different particle sizes in a low-speed three-dimensional mixer for 2 hours to ensure uniform mixing and obtain high thermal conductivity silver-coated copper powder granules.

2. The method for preparing high thermal conductivity silver-coated copper powder particles according to claim 1, characterized in that: The modified copper powder has at least three of the following particle sizes: 4.8 μm granular powder, 3.5 μm spherical powder, 3.5 μm granular powder, 2.1 μm spherical powder, and 2.1 μm granular powder.

3. The method for preparing high thermal conductivity silver-coated copper powder particles according to claim 1, characterized in that: In step S2, the concentration of silver nitrate is 20 g / L, the concentration of glucose is 30 g / L, the concentration of potassium sodium tartrate is 15 g / L, and the concentration of PVP is 2 g / L.

4. The method for preparing high thermal conductivity silver-coated copper powder particles according to claim 3, characterized in that: In step S3, the dropping rate of liquid A is 2.5 mL / min.

5. The method for preparing high thermal conductivity silver-coated copper powder particles according to claim 1, characterized in that: In step S4, the concentration of the silver nitrate solution is 0.02 mol / L, and the concentration of the PVP solution is 5 mg / mL.

6. The method for preparing high thermal conductivity silver-coated copper powder particles according to claim 5, characterized in that: In step S4, when the silver-plated copper powder is dispersed into the growth solution, the solid-liquid ratio is 1:

55.

7. The method for preparing high thermal conductivity silver-coated copper powder particles according to claim 1, characterized in that: In step S4, the ultrasonic cell disruptor has a power of 280W, the intermittent ultrasound detection time is 3s, and the ultrasound time is 2s.

8. The method for preparing high thermal conductivity silver-coated copper powder particles according to claim 1, characterized in that: In step S5, mercaptopropyltriethoxysilane accounts for 1.0% of the total mass of the powder.

9. The method for preparing high thermal conductivity silver-coated copper powder particles according to claim 2, characterized in that: Three types of modified copper powder are selected, and the volume ratio of the three different modified copper powders when mixed is 69:20.5:10.

5.

10. A type of silver-coated copper powder with high thermal conductivity, characterized in that: It is prepared by any one of the preparation methods of high thermal conductivity silver-coated copper powder particles as described in claims 1 to 9.

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