Conductive carbon particles with excellent corrosion resistance

Abstract

The present invention aims to provide conductive carbon-based particles having a metal layer formed on the surface thereof, which has excellent electrical conductivity, corrosion resistance, and bonding strength with carbon-based particles. In order to achieve the above-mentioned object, the present invention can provide conductive carbon-based particles including a first layer containing silver oxide formed on the surface of the carbon-based particle, a second layer containing copper formed on the first layer, and a third layer containing nickel or silver formed on the second layer.

Description

[Technical Field]

[0001] The present invention relates to conductive carbon-based particles having a conductive metal coating layer, and more particularly to conductive carbon-based particles having a multilayer structure and excellent corrosion resistance, in which a copper metal layer is formed on the surface without an expensive palladium catalyst layer, and a nickel or silver coating layer is further formed to protect the copper metal layer, and a method for producing the same. [Background technology]

[0002] Conductive particles are widely used in electronic materials. Among them, metal particles such as copper or nickel have high conductivity and are highly cost-competitive, so they are widely used in a variety of electronic components, including films, adhesives, and coating slurries, which require electrical conductivity.

[0003] However, these metal particles are difficult to produce in various sizes during the synthesis process, and it is difficult to maintain uniform particle size and spherical shape among the particles. This makes it difficult to produce a film or adhesive layer of uniform thickness and maintain uniform contact characteristics when manufacturing a conductive film or adhesive. Furthermore, to compensate for poor contact characteristics, metal particles are added in large volumes to the film or adhesive, but the high volume ratio of these metal particles can make the film or adhesive layer heavy and weaken the adhesive strength.

[0004] On the other hand, carbon-based particles, which have low density, excellent chemical resistance, and a certain level of conductivity, are also widely used as conductive materials, including graphite particles, graphene particles, and CNT particles. However, films or adhesive layers made from these carbon-based particles still have the problem of lower conductivity than metal particles.

[0005] To overcome this problem, it is necessary to apply conductive carbon-based particles in which a conductive metal layer such as copper, nickel, silver, or gold is formed on the surface of carbon-based particles such as graphite, graphene, or CNT, which have low density and excellent chemical resistance.

[0006] However, the carbon-based particles as the base material and the metal layer are different materials, and it is difficult to maintain a bonding force between them. Generally, to form a metal coating layer on the surface of a different material such as a carbon-based material or a ceramic, a method of forming a catalyst layer using palladium and then forming a metal layer is often used, but palladium is expensive, which increases the process cost.

[0007] Meanwhile, the metal layer coated on the surface of carbon-based particles can be made of various metals, but copper has excellent conductivity close to that of silver but has the problem of being easily oxidized, nickel has excellent corrosion resistance and is advantageous in terms of long-term reliability but has the problem of low electrical conductivity, and silver (Ag), another metal, has excellent conductivity and corrosion resistance but has the problem of being too expensive.

[0008] Thus, it is difficult for the metal layer formed on the surface of the carbon-based particles to satisfy all of the desired qualities. Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide conductive carbon-based particles having a metal layer formed on the surface thereof, which has excellent electrical conductivity, corrosion resistance, and bonding strength with carbon-based particles.

[0010] Yet another object of the present invention is to provide a method for producing conductive carbon-based particles, which can inexpensively form a metal layer on the surface of the conductive carbon-based particles, the metal layer having excellent electrical conductivity, corrosion resistance, and bonding strength with the carbon-based particles. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention can provide conductive carbon-based particles including a first layer containing silver oxide formed on the surface of carbon-based particles, a second layer formed on the first layer and containing copper, and a third layer formed on the second layer and containing nickel or silver.

[0012] Further, the carbon-based particles may be one or more selected from the group consisting of graphite, graphene, and CNT.

[0013] Further, the first layer further contains metallic silver, and the molar ratio of silver element in the silver oxide to silver element in the metallic silver (Ag x+ / Ag 0 (0 < x ≤ 3)) may be in the range of 1 to 20.

[0014] Further, the first layer may further contain tin.

[0015] Further, the content of silver contained in the first layer may be 10 to 1,000 ppm of the total weight of the conductive carbon-based particles.

[0016] Further, the third layer may further contain phosphorus together with the nickel.

[0017] Further, the third layer may contain 0.1 to 13.0% by weight of phosphorus.

[0018] The method for manufacturing conductive carbon-based particles according to the present invention may include: (a) a hydrophilization step of hydrophilizing the surface of carbon-based particles; (b) a first layer formation step of coating silver oxide on the hydrophilized carbon-based particles; (c) a second layer formation step of electroless plating copper on the first layer; and (d) a third layer formation step of electroless plating nickel or silver on the second layer.

[0019] Further, between the steps (a) and (b), a step of forming a tin layer may be further included.

[0020] Furthermore, after step (b) and before step (c), a post-treatment step of stirring the carbon-based particles on which the first layer has been formed in an aqueous solution having a pH of 8 to 14 and a temperature of 20 to 80°C to adjust the amount of silver oxide may be further included. [Effects of the Invention]

[0021] The conductive carbon-based particles according to the present invention are inexpensive, have excellent electrical conductivity and corrosion resistance, and can be applied to various electronic components that require electrical conductivity. They also have excellent bonding strength to the surface metal layer, making it possible to achieve weight reduction and improved electrical conductivity and reliability for the components to which they are applied.

[0022] Furthermore, the method for producing conductive carbon-based particles provided by the present invention enables mass production of conductive carbon-based particles with excellent conductivity and reliability through an inexpensive process. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a scanning electron microscope image of conductive carbon-based particles according to an example and a comparative example of the present invention. [Figure 2] FIG. 1 is a diagram showing the results of analysis by X-ray Photoelectron Spectroscopy (XPS) of conductive carbon-based particles in one example according to the present invention.

[0024] BEST MODE FOR CARRYING OUT THE INVENTION The following describes the configuration and operation of an embodiment of the present invention with reference to the accompanying drawings. In the following description of the present invention, if a detailed description of a related known function or configuration is deemed to obscure the gist of the present invention, the detailed description will be omitted. Furthermore, when a part "includes" a certain element, this does not mean that it excludes other elements, but that it may further include other elements, unless otherwise specified.

[0025] Although carbon-based particles have the advantages of excellent chemical resistance and low density, their use as conductive particles is limited due to their low electrical conductivity. To overcome this, forming a conductive metal layer on the surface of carbon-based particles of various shapes and sizes can impart conductivity.

[0026] However, because carbon and metal are dissimilar materials and have very low adhesive strength, it is very difficult to form a metal layer on the surface of carbon-based particles. To overcome this, a conventional method has been to form an intermediate layer between the metal layer that provides conductivity and the carbon-based particles to facilitate adhesion. These intermediate layers include a catalyst layer containing palladium. These palladium catalyst layers facilitate the formation of metal layers such as copper, nickel, and silver. However, as is well known, palladium is an expensive precious metal, and in recent years, its price has become even higher than that of gold, making the process cost too high for fabricating such materials.

[0027] To solve this problem, the inventors of the present invention investigated an intermediate layer that is less expensive than palladium and yet can provide sufficient bonding strength with the surface of carbon-based particles. Silver oxide is an oxide that can smoothly adhere to the surface of carbon-based particles and is known to have excellent bonding strength with metals, so they developed a technology in which silver oxide is formed as an intermediate layer and then a metal coating layer is formed.

[0028] As a result, it was found that when an intermediate layer of silver oxide alone or a composite of silver oxide and metallic silver is formed, the metal layer formed thereafter can be strongly bonded to the carbon-based particles, exhibiting a bonding strength equal to or greater than that when a conventional layer containing palladium is used.

[0029] Meanwhile, the characteristics of conductive carbon-based particles are determined by the type of metal layer formed on the surface of the carbon-based particles. Copper has excellent electrical conductivity but is easily oxidized, which makes reliability a problem. Nickel, on the other hand, has excellent corrosion resistance but lower electrical conductivity than copper. Silver has both excellent corrosion resistance and electrical conductivity but is expensive. As such, it is difficult for any one type of metal to satisfy all of the properties required in industry.

[0030] In order to overcome such problems, the inventors of the present invention have invented conductive carbon-based particles having a multilayer metal layer formed on the surface thereof by first forming a copper metal layer and then forming a nickel or silver metal layer on the copper metal layer to protect the copper metal layer.

[0031] As a result, the present invention can provide conductive carbon-based particles comprising: a first layer containing silver oxide formed on the surface of a carbon-based particle; a second layer containing copper formed on the first layer; and a third layer containing nickel or silver formed on the second layer.

[0032] The carbon-based particles constituting the core of the conductive carbon-based particles may be one or more types selected from the group consisting of graphite, graphene, and CNT.

[0033] Conductive carbon-based particles have low density, excellent chemical resistance, and can be produced in various particle sizes, making them advantageous for use in various electronic components. To this end, the carbon-based particles constituting the core are preferably graphite, graphene, or CNTs, all of which are commercially available in products with a variety of properties, allowing for the production of a variety of conductive carbon-based particle products. In particular, graphite is commercially available in various particle sizes and shapes depending on the type, such as artificial graphite and natural graphite, and its diverse properties and unit prices allow for the production of a variety of products and applications.

[0034] As described above, due to the characteristics of the material, the surface of the carbon-based particles is difficult to easily bond with the metal layer. In order to modify the characteristics of these surfaces, it is necessary to form a catalyst layer. In the present invention, instead of the conventional catalyst layer containing palladium, a first layer which is a catalyst layer containing silver oxide is formed first. Since silver oxide is excellent not only in bonding with carbon but also in bonding with metals, the bond between the carbon-based particles constituting the core and the surface metal layer can be strongly maintained.

[0035] In the present invention, the first layer containing silver oxide may further contain tin. Tin is an element used to guide silver oxide to smoothly adhere to the surface of the carbon-based particles. When performing the coating operation with an aqueous solution, it gives hydrophilicity to the surface of the carbon-based particles and helps the silver element to adhere to the surface of the carbon-based particles. These tins can also form the first layer together with silver oxide, or may be formed between the first layer containing silver oxide and the surface of the carbon-based particles.

[0036] In the present invention, the first layer containing silver oxide may further contain metallic silver together with silver oxide. When metallic silver is further contained, the bond with copper, which is the metal contained in the second layer, can be further strengthened. Silver oxide strengthens the bond with the carbon-based particles, and metallic silver strongly bonds with these silver oxides and provides a strong bond with copper, which is the same metal. As a result, the bonding force between the second layer containing copper and the carbon-based particles is further strengthened.

[0037] At this time, the molar ratio of silver element in silver oxide to silver element in metallic silver in the first layer (Ag x+ / Ag 0 (0 < x ≤ 3)) is preferably in the range of 1 to 20.

[0038] As mentioned above, the inclusion of metallic silver strengthens the bond between the first layer containing silver oxide and the second layer containing copper. However, if the proportion of elemental silver in metallic silver is too high compared to that of elemental silver in silver oxide, the bonding strength of the silver oxide to the surface of the carbon-based particles in the first layer decreases accordingly, which is undesirable. Therefore, the molar ratio of elemental silver in metallic silver to elemental silver in silver oxide is preferably 1 to 20, more preferably 1 to 10, so that the proportion of elemental silver in silver oxide is even higher. These molar ratios can be measured by X-ray photoelectron spectroscopy (XPS).

[0039] Here, the oxidation number of silver in silver oxide can range from +1 to +3, and since the oxidation number does not have to be a constant in the amorphous phase, the oxidation number of silver in silver oxide can be greater than 0 and less than or equal to 3.

[0040] The first layer may further contain palladium, which can further strengthen the bond between the surface of the carbon-based particle and the silver oxide and the bond between the second layer and the silver oxide. The amount of palladium contained in this case may be even less than that contained in conventional conductive carbon-based particles without silver oxide. For example, the amount of palladium used in the manufacturing process of conventional conductive carbon-based particles is generally in the range of 100 to 1,000 ppm based on the conductive carbon-based particles, but the amount of palladium used in the conductive carbon-based particles of the present invention can be greater than 0 and less than 50 ppm.

[0041] The content of silver in the first layer may be 10 to 1,000 ppm based on the total weight of the conductive carbon-based particles.

[0042] The metallic silver or silver oxide formed in the first layer must have a certain content or more in order to provide a satisfactory level of bonding strength to the second layer, and if the content is too high, the process cost increases, which is undesirable. More preferably, it may be 10 to 500 ppm.

[0043] The first layer in the present invention may be discontinuous islands formed on the surface of the carbon-based particle. The first layer is a layer that strengthens the bonding force between the carbon-based particle and the second layer that imparts electrical conductivity, and even if it is discontinuous islands, it can provide sufficient bonding force to the second layer.

[0044] Meanwhile, the first layer may be in the form of a continuous film, in which case the first layer occupies at least 50% or more of the surface area of ​​the carbon-based particle, because even if it is in the form of a continuous film, it must occupy at least 50% or more of the surface area of ​​the particle in order to provide sufficient bonding strength to the second layer.

[0045] A second layer containing copper, a metal with excellent electrical conductivity, is formed on the first layer containing silver oxide. Copper, which has particularly excellent electrical conductivity among metals, provides excellent electrical conductivity to the conductive carbon particles.

[0046] The copper-containing second layer may account for 5 to 40 wt% of the total conductive carbon-based particle, but if it is less than 5 wt%, electrical conductivity may decrease, and if it exceeds 40 wt%, the density of the entire conductive carbon-based particle increases, increasing the risk of the second layer falling off, which is undesirable. Therefore, the content of the second layer in the conductive carbon-based particle is preferably 5 to 30 wt%, more preferably 8 to 20 wt%.

[0047] On the other hand, in the present invention, the copper content in the second layer containing copper is 90% by weight or more, because if it is less than 90% by weight, the electrical conductivity of the second layer decreases.

[0048] In the present invention, a third layer containing nickel or silver may be further formed on the second layer containing copper.

[0049] The third layer containing nickel or silver prevents the metallic copper formed in the second layer from oxidizing and also has excellent electrical conductivity, ultimately enabling the conductive carbon-based particles to ensure both electrical conductivity and reliability.

[0050] When a metal layer containing nickel, which has excellent corrosion resistance, is formed as the third layer, it protects the second layer while the formation of metallic nickel ensures a certain level of electrical conductivity.

[0051] These third layers may contain not only nickel but also phosphorus. However, the inclusion of phosphorus slightly reduces electrical conductivity, but improves chemical resistance and oxidation resistance. Therefore, when used in components where reliability is important, it is preferable for the third layer to contain phosphorus in addition to nickel. If phosphorus is included, the phosphorus content in the third layer is preferably 0.1 to 13.0 wt. %. If it is too low, the desired improvement in chemical resistance and oxidation resistance will not be achieved, and if the phosphorus content exceeds 13 wt. %, sufficient electrical conductivity will not be obtained. More preferably, the phosphorus content is 0.5 to 6 wt. %.

[0052] Meanwhile, the third layer may contain metallic silver instead of nickel, but silver is an ideal metal in terms of properties, as it has excellent corrosion resistance and electrical conductivity, but has the disadvantage of being expensive. Therefore, by forming a third layer of silver, which has excellent electrical conductivity and protects the copper on the second layer made of copper, which has the same level of electrical conductivity as silver, it is possible to minimize the amount of silver used while ensuring reliability and maximizing the conductivity of the conductive carbon-based particles.

[0053] The present invention can also provide a method for producing conductive carbon-based particles, including: (a) a hydrophilization step of hydrophilizing the surfaces of carbon-based particles; (b) a first layer formation step of coating the hydrophilized surface carbon-based particles with silver oxide; (c) a second layer formation step of electrolessly plating copper onto the first layer; and (d) a third layer formation step of electrolessly plating nickel or silver onto the second layer.

[0054] To produce conductive carbon-based particles, a hydrophilization step is first required, in which chemical functional groups are introduced onto the surface of the carbon-based particles to make them hydrophilic. This hydrophilization step may involve a strong acid solution of pH 3 or less. This is because the strong acid solution partially cleaves the carbon bonds on the surface of the carbon-based particles, facilitating the attachment of chemical functional groups to the surface of the carbon-based particles. Therefore, to treat the surface of stable carbon-based particles, a strong acid atmosphere of pH 3 or less created with an inorganic acid such as sulfuric acid, nitric acid, or hydrochloric acid is preferred.

[0055] On the other hand, the hydrophilization treatment of carbon-based particles can be carried out in a strong acid aqueous solution as described above, but the hydrophilization can also be carried out in a dry manner by modifying the surface of the carbon-based particles by plasma treatment.

[0056] After the hydrophilization treatment, a first layer containing silver oxide is formed, and tin can be coated along with the silver oxide. Tin can increase the bonding strength of the silver oxide on the surface of the hydrophilized carbon-based particles.

[0057] For more precise control, a tin layer can be formed first on the surface of the hydrophilized carbon-based particles, and then the first layer containing silver oxide can be formed.

[0058] The first layer containing silver oxide can be formed in an alkaline aqueous solution with a pH of 8 or higher. This is because silver oxide is well formed in an alkaline atmosphere with a pH of 8 or higher. More preferably, the first layer can be formed in an aqueous solution with a pH in the range of 9 to 11.

[0059] In addition, the method for producing conductive carbon-based particles may further include, after step (b) and before step (c), a post-treatment step of stirring the carbon-based particles on which the first layer has been formed in an aqueous solution having a pH of 8 to 14 and a temperature of 20 to 80°C to adjust the amount of silver oxide.

[0060] When the first layer is formed in an aqueous solution, silver ions in the aqueous solution may be reduced and adhere to the surface of the carbon-based particles as metallic silver rather than silver oxide. If the proportion of metallic silver becomes too high, the bonding strength between the carbon-based particles and the first layer may be weakened, which is undesirable. Therefore, to increase the silver oxide content to a desired level, the amount of silver oxide can be adjusted by treating the carbon-based particles with an alkaline aqueous solution at an appropriate temperature.

[0061] In this way, by adjusting the amount of silver oxide and then forming a second layer containing conductive copper, it is possible to provide conductive carbon-based particles that have excellent bonding strength between the metal coating layer that imparts conductivity and the carbon-based particles. DETAILED DESCRIPTION OF THE INVENTION

[0062] In order that the present invention may be fully understood, preferred embodiments of the present invention will now be described with reference to the accompanying drawings.

[0063] The examples of the present invention are provided to more completely explain the present invention to those skilled in the art, and the following examples may be modified in various different forms, and the scope of the present invention is not limited to the following examples. Rather, these examples are provided to make the present disclosure more complete and thorough, and to fully convey the concept of the present invention to those skilled in the art.

[0064] [Example 1] 3 g of hydrochloric acid (35% solution) was added to 100 g of deionized water, and the temperature was raised to 60°C. 50 10 g of graphite with a particle size of 20 μm was added and stirred for 10 hours to hydrophilize the surface of the graphite powder. The hydrophilized graphite powder was then collected, stirred with 100 g of deionized water, washed three times, and then collected.

[0065] The recovered graphite particles were added to a solution of 1.5 g of stannous chloride (SnCl2·2H2O) and 6 ml of hydrochloric acid (35% solution) in 100 g of deionized water, and stirred for 30 minutes to form a tin layer. The temperature of the solution was maintained at 35°C.

[0066] The graphite particles with the tin layer formed were collected by filtering and then added to a silver nitrate solution prepared by dissolving 0.15 g of silver nitrate (AgNO3) in 100 g of deionized water and stirred. At this time, 28% ammonia water was added dropwise to adjust the pH to 9.3.

[0067] The temperature was maintained at 40°C and the mixture was stirred for 1 hour to form a silver oxide layer. After 1 hour, the mixture was collected by filtration and then washed three times with 200 g of deionized water. A portion of the powder on which the silver oxide layer had formed was sampled and subjected to surface analysis by X-ray photoelectron spectroscopy (XPS).

[0068] The powder with the silver oxide layer formed was collected and a copper coating layer was formed using electroless plating. A copper sulfate complex solution was prepared by adding 40 g of EDTA (Ethylene-diamine-tetraacetic acid), 30 g of NaOH, and 20 g of copper sulfate to 300 g of deionized water, and the graphite powder with the silver oxide layer formed was added. While stirring, a formaldehyde solution was dripped in as a reducing agent to form a copper coating layer.

[0069] A nickel coating layer was further formed on the graphite powder with the copper coating layer. To this end, 20 g of nickel chloride (NiCl2·6H2O), 10 g of sodium acetate, 5 g of maleic acid, 30 g of sodium hypophosphite (a reducing agent), and 3 ml of lead acetate were added to 300 g of deionized water. The powder with the copper coating layer was then added to a nickel plating solution, which was then stirred and maintained at 70-90°C for 2 hours to perform electroless plating.

[0070] [Example 2] The process up to the formation of the copper coating layer was carried out in the same manner as in Example 1, and then a silver-containing coating layer was formed by electroless plating. To this end, a silver coating solution was prepared by adding 2 g of EDTA (Ethylene-diamine-tetraacetic acid), 2.5 ml of 28% ammonia water, and 3 g of silver nitrate (AgNO3) to 300 g of deionized water. The graphite particles with the copper coating layer formed thereon were then added to the solution, and a reducing solution prepared by dissolving 10 g of glucose and 2 g of sodium hydroxide in 50 g of deionized water was dripped in for 1 hour while stirring to form a third silver-containing layer.

[0071] [Example 3] As in Example 1, after the first layer containing silver oxide was formed on the surface of the graphite particles, post-treatment was carried out with an alkaline aqueous solution. For the post-treatment, 28% ammonia water was added to 100 g of deionized water and maintained at 60°C, after which the graphite particles with the first layer formed were added and stirred. Before adding the graphite particles, the pH of the aqueous solution was 10.1.

[0072] Thereafter, the second layer containing copper and the third layer containing nickel were formed in the same manner as in Example 1.

[0073] [Comparative Example 1] As in Example 1, a hydrophilic treatment and a tin layer were formed. Then, without forming a silver oxide layer, electroless plating was immediately performed to sequentially form a second layer containing copper and a third layer containing nickel. The electroless plating of copper and nickel was performed in the same manner as in Example 1.

[0074] Comparative Example 2 As in Example 1, a first layer containing silver oxide was formed on the surface of the graphite particles. Then, ascorbic acid was added to the aqueous solution to convert part of the silver oxide on the surface into metallic silver, and then electroless plating was performed to sequentially form a second layer containing copper and a third layer containing nickel. The electroless plating of copper and nickel was performed in the same manner as in Example 1.

[0075] Comparative Example 3 As in Example 1, the copper coating layer was formed, but no subsequent steps were carried out.

[0076] After forming a first layer on the conductive graphite particles, the silver ratio between silver oxide and metallic silver, the silver content, nickel content, and phosphorus content were analyzed, and the coating condition was observed using a scanning electron microscope (SEM). The silver ratio was determined by analyzing samples taken after forming the first layer using XPS. The silver content, nickel content, and phosphorus content were analyzed using an inductively coupled plasma mass spectrometer (ICP).

[0077] The reliability was evaluated by a reflow test in which a certain amount of conductive graphite particles prepared in Examples 1 to 3 and Comparative Examples 1 and 2 was mixed with an acrylic binder, coated on a polyimide film, dried, and then left on molten lead for 30 seconds, after which the conductivity was measured.

[0078] The results are shown in Table 1 below. Here, the Cu content indicates the weight percentage of copper element based on the total conductive graphite particles.

[0079] [Table 1]

[0080] Figure 1 shows scanning electron microscope images of conductive graphite particles according to the examples. Figure 1(a) is a scanning electron microscope image of a sample from Example 1, Figure 1(b) is a scanning electron microscope image of a sample from Example 2, Figure 1(c) is a scanning electron microscope image of a sample from Comparative Example 1, and Figure 1(d) is a scanning electron microscope image of a sample from Comparative Example 2.

[0081] Both the samples of Examples 1 and 2 showed that a dense coating layer was formed, but in Comparative Example 1, which did not have a first layer containing silver oxide, the coating layer was not formed properly, and in Comparative Example 2, which had a high content of metallic silver in the first layer, the coating layer was not dense and the bonding was not strong.

[0082] FIG. 2 shows the results of measuring the ratio of silver element between silver oxide and metallic silver in the first layer of the sample of Example 3. As a result of XPS, it can be measured by the ratio of the peaks of the ratio of silver in the reduced state and the ratio of silver in the oxidized state. These molar ratios (Ag x+ / Ag 0 ) was 7.83.

[0083] On the other hand, as shown in Table 1, corrosion resistance was evaluated by a reflow test. In Examples 1 to 3, the resistance of the film using conductive graphite particles was good, at 50 mΩ or less, even after the reflow test. However, in Comparative Example 2, in which the formation of the coating layer was unstable, the resistance increased significantly, and in the sample of Comparative Example 3, in which the third protective layer was not formed, the resistance was too high and was not measured.

Claims

1. a first layer including silver oxide formed on the surface of the carbon-based particle; a second layer formed on the first layer and comprising copper; a third layer formed on the second layer and including nickel or silver; Including, Conductive carbon-based particles.

2. The carbon-based particles are one or more selected from the group consisting of graphite, graphene, and CNT. The conductive carbon-based particles according to claim 1 .

3. The first layer further contains metallic silver, and the molar ratio of the silver element in the silver oxide to the silver element in the metallic silver (Ag ｘ＋ / Ag ０ (0<x≦3)) is in the range of 1 to 20; The conductive carbon-based particles according to claim 1 .

4. the first layer further comprises tin; The conductive carbon-based particles according to claim 1 .

5. The content of silver in the first layer is 10 to 1,000 ppm based on the total weight of the conductive carbon-based particles. The conductive carbon-based particles according to claim 1 .

6. the third layer further contains phosphorus together with the nickel; The conductive carbon-based particles according to claim 1 .

7. the third layer contains 0.1 to 13.0 wt % phosphorus; The conductive carbon-based particles according to claim 6 .

8. (a) a hydrophilization step of hydrophilizing the surface of carbon-based particles; (b) forming a first layer by coating silver oxide on the carbon-based particles whose surfaces have been hydrophilized; (c) forming a second layer by electrolessly plating copper on the first layer; (d) forming a third layer by electrolessly plating nickel or silver on the second layer; Including, A method for producing conductive carbon-based particles.

9. The method further comprises forming a tin layer between steps (a) and (b). The method for producing conductive carbon-based particles according to claim 8 .

10. After step (b) and before step (c), the method may further include a post-treatment step of stirring the carbon-based particles on which the first layer has been formed in an aqueous solution having a pH of 8 to 14 and a temperature of 20 to 80° C. to adjust the amount of silver oxide. The method for producing conductive carbon-based particles according to claim 8 .

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