Composite, method for producing composite, and terminal

Abstract

This composite comprises, on a material, a composite film composed of a silver layer containing carbon particles, wherein: the average value of the areas of the carbon particles on the surface of the composite film is at least 2.65 μm2; and the Vickers hardness HV of the composite film is at least 80.

Description

Composite material, method for manufacturing composite material, and terminal

[0001] The present invention relates to a composite material having a predetermined composite coating formed on a base material, and to a method for manufacturing the same, and more particularly to a composite material used as a material for sliding contact parts such as switches and connectors, and to a method for manufacturing the same.

[0002] Conventionally, silver (Ag) plated materials have been used as materials for sliding electrical contact components such as switches and connectors to prevent oxidation of conductive materials such as Cu (copper) and Cu alloys due to heating during the sliding process.

[0003] However, silver plating is soft and easily worn, and generally has a high coefficient of friction, making it prone to peeling due to sliding. To solve this problem, a method has been proposed to improve wear resistance by forming a composite material coating on a conductive material by electroplating, in which graphite particles are dispersed in a silver matrix, among carbon particles such as graphite and carbon black, which have excellent wear resistance and lubricity (see, for example, Patent Documents 1 and 2).

[0004] As a composite material with even better wear resistance than this one, Patent Document 3 discloses a composite material in which a composite coating consisting of a silver layer containing carbon particles is formed on a base material, wherein the crystallite size of the silver in the composite coating is 40 nm or less.

[0005] Japanese Patent Publication No. 9-7445, Japanese Patent Publication No. 2007-16250, International Publication No. 2021 / 261066

[0006] However, even with regard to the composite material disclosed in Patent Document 3, further improvements in wear resistance are still required to satisfy the latest market demands.

[0007] This invention was made under the circumstances described above, and the problem it aims to solve is to provide a composite material with even better wear resistance and a method for manufacturing the same.

[0008] The inventors diligently researched how to solve the above problems and, in creating composite materials, considered that if the carbon particles incorporated into the silver matrix (silver layer) during the formation of the composite film by electroplating or the like would be larger, the carbon particles present on the surface of the composite film would be larger, and its lubricity would be more strongly exhibited. After repeated studies to incorporate larger carbon particles, the inventors found that by performing electroplating using carbon particles exhibiting a specific particle size distribution, they were able to obtain a composite material in which large carbon particles are present on the surface of the composite film, and confirmed that this composite material exhibits even better wear resistance compared to conventional technologies such as those described in Patent Document 3. In this way, the inventors have completed the present invention.

[0009] In other words, the present invention is as follows. A first embodiment of the present invention is a composite material comprising a composite coating consisting of a silver layer containing carbon particles on a base material, wherein the average area of ​​the carbon particles on the surface of the composite coating is 2.65 μm ２ The above describes a composite material in which the Vickers hardness HV of the composite coating is 80 or higher.

[0010] A second embodiment of the present invention is the first embodiment, wherein the proportion of carbon particles on the surface of the composite coating is 8 to 60 area %.

[0011] A third embodiment of the present invention is the first or second embodiment, wherein the thickness of the composite coating is 0.5 to 30 μm.

[0012] A fourth embodiment of the present invention is that, in any of the first to third embodiments, the material is composed of Cu or a Cu alloy.

[0013] A fifth embodiment of the present invention is that, in any of the first to fourth embodiments, the average area of ​​carbon particles on the surface of the composite coating is 30 μm ２ The following conditions apply, and the Vickers hardness HV of the composite coating is 280 or less.

[0014] A sixth embodiment of the present invention is that, in any of the first to fifth embodiments, the thickness of the composite coating is 0.5 to 15 μm.

[0015] A seventh embodiment of the present invention is that, in any of the first to sixth embodiments, a base layer consisting of at least one selected from the group consisting of Cu, Ni, Sn, and Ag is formed on the material, and the composite coating is formed on this base layer.

[0016] An eighth embodiment of the present invention is an electrical contact terminal in which any of the composite materials of the first to seventh embodiments is used as a constituent material.

[0017] A ninth embodiment of the present invention is a method for producing a composite material in which a composite film consisting of a silver layer containing carbon particles and having a Vickers hardness HV of 80 or more is formed on a material by electroplating in a silver plating solution containing carbon particles, wherein when D10 is the volume-based cumulative 10% particle diameter (μm) of the carbon particles determined by a laser diffraction / scattering particle size distribution analyzer, D50 is the volume-based cumulative 50% particle diameter (μm) of the carbon particles determined by a laser diffraction / scattering particle size distribution analyzer, and D90 is the volume-based cumulative 90% particle diameter (μm) of the carbon particles determined by a laser diffraction / scattering particle size distribution analyzer, the following conditions are satisfied: D10 / D50 ≥ 0.320 and D10 / D90 ≥ 0.140, and the D50 of the carbon particles is 3 μm or more.

[0018] A tenth embodiment of the present invention is the ninth embodiment, wherein the carbon particles satisfy D10 / (D90-D10) ≥ 0.180.

[0019] An eleventh embodiment of the present invention is the ninth or tenth embodiment, wherein the material is composed of Cu or a Cu alloy.

[0020] The present invention provides a composite material with even greater wear resistance, a method for manufacturing the same, and related technologies.

[0021] Embodiments of the present invention will be described below.

[0022] [Composite Material] The embodiments of the composite material of the present invention will be described below. The composite material is a composite material in which a composite coating containing carbon particles in a silver layer is formed on a base material. This composite material can be manufactured, for example, by the embodiment of the manufacturing method of the composite material of the present invention described later. The various components of this composite material will be described below.

[0023] <<Materials>> Suitable materials for the constituent material are those that can be silver-plated and have the conductivity required for materials such as sliding contact parts like switches and connectors. Furthermore, from the viewpoint of cost, Cu (copper) and Cu alloys are preferred as constituent materials. As for the Cu alloy, from the viewpoint of achieving both conductivity and wear resistance, an alloy composed of Cu, at least one selected from the group consisting of Si (silicon), Fe (iron), Mg (magnesium), P (phosphorus), Ni (nickel), Sn (tin), Co (cobalt), Zn (zinc), Be (beryllium), Pb (lead), Te (tellurium), Ag (silver), Zr (zirconium), Cr (chromium), Al (aluminum), Ti (titanium), B (boron), Li (lithium), and Bi (bismuth), and unavoidable impurities is preferred. The amount of Cu in the Cu alloy is preferably 85% by mass or more, and more preferably 92% by mass or more. The amount of Cu is preferably 99.95% by mass or less.

[0024] As will be described later, the material is preferably used for terminal applications (as a composite material with a composite coating formed on it), but the material itself may have a shape suitable for such applications, or the material may be flat (such as a flat plate) and be molded into the desired shape after being made into a composite material.

[0025] <<Underlayment>> An underlayment may be formed between the material and the composite coating described below for various purposes. Examples of constituent metals of the underlayment include at least one metal or alloy selected from the group consisting of Cu, Ni, Sn, and Ag. For example, to prevent copper in the material from diffusing onto the composite coating surface and degrading conductivity, it is preferable to form an underlayment made of Ni. If the material is a copper alloy containing zinc, such as brass, and the purpose is to prevent zinc in the material from diffusing onto the composite coating surface, it is preferable to form an underlayment made of Cu. To improve the adhesion of the composite coating to the material, it is preferable to form an underlayment made of Ag. The thickness of the underlayment is not particularly limited, but from the viewpoint of its function and cost, it is preferably 0.1 to 2 μm, and more preferably 0.2 to 1.5 μm. Furthermore, terminals of electrical and electronic components often use materials that have been plated with Sn or reflow Sn, including a Cu or Ni underlayment (a laminated structure of Cu underlayment, Ni underlayment, and Sn underlayment from the material side), and in the present invention, such a laminated underlayment layer may also be formed. Therefore, in the present invention, the underlayment of the composite coating may consist of a single layer made of Cu, Ni, Sn, Ag, or an alloy thereof, or a layer made by combining them (a laminated structure), and different layers may be formed depending on the location, for example, by forming the composite coating defined in the present invention on the electrical contact part of the material (with or without an underlayment layer), and by forming a reflow Sn plated underlayment on the wire crimping part (without forming a composite coating).

[0026] <<Composite Coating>> Embodiments of the composite material of the present invention include a composite coating on the material described above (or on the underlayer if an underlayer is formed on the material). This composite coating is composed of a silver layer containing carbon particles. In this silver layer, carbon particles are dispersed (preferably substantially evenly) in a silver matrix. If the composite coating is formed by electroplating, and Ag strike plating is performed before forming the composite coating, an intermediate layer formed by this strike plating exists between the material (or underlayer) and the composite coating, but it is often very thin and indistinguishable from the composite coating. Furthermore, the composite coating may be formed on the entire surface layer of the material, or on a part of the surface layer.

[0027] The type of carbon particles contained in the composite coating is not particularly limited, but from the viewpoint of the wear resistance of the composite material, the carbon particles are preferably graphite particles. The shape of the carbon particles is not particularly limited, and may be substantially spherical, scaly, amorphous, or the like; however, a scaly shape is preferable because smoothing the surface of the composite coating improves the wear resistance of the composite material.

[0028] <Average Area of Carbon Particles on Composite Coating Surface> An embodiment of the composite material of the present invention is characterized in that the size of carbon particles present on the surface of the composite coating is larger than that of conventional composite materials. More specifically, the average area of carbon particles on the composite coating surface is 2.65 µm ２ or more. It is considered that such a large size of carbon particles present on the composite coating surface allows the lubricity of the carbon particles to be exerted more strongly, resulting in excellent wear resistance of the composite material. From the viewpoint of wear resistance, and since there is a certain limit to the size of carbon particles that can be incorporated into the composite coating, the average area of carbon particles on the composite coating surface is 2.70 to 30 µm ２ which is preferable. The average area of carbon particles on the composite coating surface may be 4.00 to 20 µm ２ or may be 5.80 to 15 µm ２ or. The area of carbon particles is obtained by binarization using image processing software from an electron micrograph of the composite coating surface, and a more detailed measurement method will be described in the Examples section.

[0029] Regarding the composite coating, there are two types of carbon particles: those that are incorporated (embedded) in the silver matrix and are less likely to fall off, and those that adhere to the surface rather than being incorporated and are more likely to fall off. In the present invention, when determining the average area of carbon particles on the composite coating surface, the latter easily detachable carbon particles shall be removed in advance. In the case where such a removal treatment for easily detachable carbon particles (for example, ultrasonic cleaning or electrolytic cleaning in the method for producing the composite material of the present invention described later) has already been performed in the production of the composite material, it is not necessary to perform the removal treatment again.

[0030] <Area Ratio of Carbon Particles on Composite Coating Surface> In the embodiment of the composite material of the present invention, the composite coating contains carbon particles of a predetermined size as described above, and the elemental composition of the composite coating in the embodiment of the composite material is typically substantially composed of silver and carbon.

[0031] In addition, the proportion (area ratio) occupied by carbon particles on the surface of the composite coating serves as an indicator of wear resistance, and it is desirable that the proportion is at or above a certain level from the viewpoint of wear resistance. On the other hand, if the proportion is too high, it may adversely affect conductivity. From the viewpoint of balancing these wear resistance and conductivity, the area ratio is preferably 8 to 60 area%, more preferably 12 to 50 area%, and still more preferably 15 to 40 area%. When carbon particles that are prone to falling off exist on the surface of the composite coating, such carbon particles shall be removed in advance by ultrasonic cleaning treatment before determining the area ratio of carbon particles on the surface of the composite coating. Details of the method for measuring the area ratio will be described in Examples.

[0032] <Vickers Hardness HV of Composite Coating> In the embodiment of the composite material of the present invention, the Vickers hardness HV of the composite coating is 80 or higher, and being such a hard coating contributes to the excellent wear resistance of the composite material. The Vickers hardness HV is preferably 100 or higher, and more preferably 120 to 280. Details of the method for measuring Vickers hardness HV will be described in Examples.

[0033] <Thickness of Composite Coating> The thickness of the composite coating is not particularly limited, but from the viewpoints of wear resistance and conductivity, it is preferable to have a minimum thickness. In addition, even if the thickness is too large, the effect of the composite coating will be saturated, and the raw material cost will increase. From the above viewpoints, the thickness of the composite coating is preferably 0.5 to 30 µm, more preferably 0.5 to 25 µm, and still more preferably 0.5 to 15 µm. Details of the method for measuring the thickness of the composite coating will be described in Examples.

[0034] Generally, in plating using a silver plating solution containing carbon particles (AgC plating), if the resulting plating film is thin, it is difficult for large carbon particles to be incorporated into the film. However, for example, by the composite material manufacturing method of the present invention described later, even if the composite film is thin, such as 15 μm or less in thickness, or even 0.5 to 10 μm, it is possible to incorporate large-sized carbon particles and provide a composite material that achieves both high wear resistance and cost competitiveness (of silver). In particular, from the viewpoint of achieving excellent wear resistance, it is preferable that the thickness of the composite film be 4 μm or more.

[0035] <<Abrasion Resistance of Composite Material>> As described above, the embodiment of the composite material of the present invention has a composite coating (especially the surface) equipped with large carbon particles, and exhibits excellent abrasion resistance. Specifically, when abrasion tests are performed in the examples described later, the number of sliding cycles required for 1 μm of the composite coating to wear away is 5,000 or more, preferably 6,000 or more, and more preferably 7,200 or more. The number of sliding cycles required for 1 μm of the composite coating to wear away is usually 15,000 or less.

[0036] [Method for Manufacturing Composite Materials] Next, embodiments of the method for manufacturing composite materials of the present invention will be described. This manufacturing method is a method for manufacturing composite materials in which a composite coating consisting of a silver layer containing carbon particles and having a Vickers hardness HV of 80 or higher is formed on a material by electroplating in a silver plating solution containing carbon particles, wherein the carbon particles exhibit a predetermined particle size distribution. The various components of the embodiments of the method for manufacturing composite materials of the present invention will be described below.

[0037] <<Material>> The material on which the composite coating is formed is the same as the material described in the embodiment of the composite material of the present invention. In other words, the constituent material of the material is preferably one that can be silver plated and has the conductivity required for materials such as sliding contact parts such as switches and connectors, and furthermore, from the viewpoint of cost, Cu (copper) and Cu alloy are preferred as constituent materials. The material may also be in a shape that suits its application, such as a terminal, or it may be in a flat shape (such as a flat plate shape).

[0038] <<Formation of the Underlayer>> In the method for manufacturing the composite material of the present invention, an underlayer may be formed on the material, and the underlayer may be subjected to electroplating as described later. The underlayer is formed for the purpose of preventing the copper of the material from diffusing and oxidizing on the plated surface, which would degrade the conductivity of the composite material, and for the purpose of improving the adhesion of the composite coating. The constituent metal of the underlayer may be at least one metal or alloy selected from the group consisting of Cu, Ni, Sn, and Ag. The underlayer may be a single layer made of Cu, Ni, Sn, Ag, or their alloys, or a layer made by combining them (a laminated structure), and the underlayer may be formed on the entire surface of the material or on a part thereof, depending on the application of the composite material to be manufactured.

[0039] The method for forming the underlayer is not particularly limited. For example, it can be formed by electroplating using a known method with a plating solution containing ions of the constituent metals, or by sequentially laminating layers made of each metal constituting the target alloy layer and then reflowing (heat treating).

[0040] <<Ag Strike Plating>> Before forming a composite film on the material, it is preferable to form a very thin intermediate layer by Ag strike plating to improve the adhesion between the material and the composite film. If a base layer is formed on the material, Ag strike plating is performed on the base layer. As for the method of performing Ag strike plating, conventionally known methods can be used without particular limitation as long as they do not impair the effects of the present invention.

[0041] <<Electroplating>> In the method for manufacturing the composite material of the present invention, electroplating is performed on the material described above in a silver plating solution containing carbon particles of a predetermined particle size distribution, thereby forming a composite coating on the material containing carbon particles in a silver layer.

[0042] <Silver Plating Solution> The silver plating solution contains silver and carbon particles.

[0043] {Silver Concentration} The silver plating solution contains silver. The concentration of silver in this silver plating solution is preferably 5 to 150 g / L, more preferably 10 to 120 g / L, and most preferably 20 to 100 g / L, from the viewpoint of the rate of formation of the composite film and the suppression of unevenness in the appearance of the composite film.

[0044] {Carbon particles} The carbon particles are the same as those described in the embodiments of the composite material of the present invention. That is, the type of carbon particles used is not particularly limited, but from the viewpoint of the wear resistance of the manufactured composite material, the carbon particles are preferably graphite particles. The shape of the carbon particles is not particularly limited, such as approximately spherical, flaky, or irregular, but a flaky shape is preferred because it can improve the wear resistance of the composite material by making the surface of the composite coating smooth.

[0045] (Particle size distribution of carbon particles) In the present invention, when the cumulative 10% particle diameter (μm) on a volume basis determined by a laser diffraction / scattering particle size distribution measuring device for the carbon particles is defined as D10, the cumulative 50% particle diameter (μm) on a volume basis determined in the same manner is defined as D50, and the cumulative 90% particle diameter (μm) on a volume basis determined in the same manner is defined as D90, the conditions D10 / D50 ≥ 0.320 and D10 / D90 ≥ 0.140 are satisfied.

[0046] Thus, when silver plating is performed using carbon particles with a particle size distribution in which D10 is larger than a predetermined proportion compared to D50 and D90, larger carbon particles can be incorporated into the silver matrix (silver layer), as described in the embodiment of the composite material of the present invention. More specifically, the silver matrix grows from a thickness of 0 due to silver plating, and it is thought that particles closer to the D10 side, which have a small cumulative proportion of the particle size distribution, are more likely to be incorporated into the growing silver matrix. Therefore, by using large D10 / D50 carbon particles, it is thought that larger carbon particles will be incorporated into the silver matrix. Also, if the particles on the D90 side, which have a large cumulative proportion in the particle size distribution, are large, the particle size is thought to be excessively large and less likely to be incorporated into the silver matrix. Therefore, by using large D10 / D90 carbon particles, it is thought that the carbon particles will be more easily incorporated into the silver matrix.

[0047] In particular, from the viewpoint of silver cost, the thickness of the composite coating is required to be as thin as possible. However, even when forming such a thin composite coating (for example, 0.5 to 15 μm thick, more preferably 0.5 to 10 μm thick), if carbon particles exhibiting the above-mentioned specific particle size distribution are used, larger carbon particles will be present on the surface of the composite coating, resulting in excellent wear resistance. From the viewpoint of achieving excellent wear resistance, D10 / D50 is preferably 0.380 or higher, and usually 0.900 or lower. From a similar viewpoint, D10 / D90 is preferably 0.170 or higher, and usually 0.600 or lower.

[0048] Furthermore, similar to the above, it is preferable that the carbon particles satisfy D10 / (D90-D10) ≥ 0.180 so that larger carbon particles are more easily incorporated into the silver matrix. The aforementioned D10 / (D90-D10) is usually 0.700 or less.

[0049] The D50 of the carbon particles is required to be larger than a certain size from the viewpoint of incorporating larger carbon particles into the silver matrix. Specifically, the D50 of the carbon particles used in this invention is 3 μm or larger. Furthermore, since carbon particles are less likely to be incorporated into the silver matrix if the D50 is too large, the D50 of the carbon particles is preferably 3 to 30 μm, and more preferably 3 to 15 μm.

[0050] (Method for obtaining carbon particles used in the present invention) The carbon particles described above can be obtained, for example, by subjecting commercially available carbon particles to a process that increases the relative size of D10.

[0051] One example of such a process is to heat-dry commercially available carbon particles of about 3 to 30 μm in size (D50) to agglomerate them. More specifically, after subjecting wet carbon particles to a wet oxidation treatment or wet basing treatment described later, and then separating the solid-liquid, the wet carbon particles are subjected to heat treatment at 90 to 250°C for 0.5 to 36 hours to agglomerate them. This increases the particle size of the carbon particles, especially in the parts with a small cumulative proportion. The heating may be carried out under reduced pressure, or the carbon particles may be heated while being stirred. The obtained agglomerated carbon particles may be crushed to adjust the D50. The means of crushing are not particularly limited, but for example, crushing using a mortar and pestle can be used. In such crushing, the particles in the parts with a large cumulative proportion of carbon particles are easily crushed, and the size of D50 (and D90) can be reduced without significantly changing the size of D10. As a result, carbon particles with the desired particle size distribution for use in the present invention can be obtained.

[0052] Another example of a process to increase the relative size of the D10 of carbon particles is sedimentation separation. Commercially available carbon particles with a D50 of approximately 3 to 30 μm are mixed with water and stirred to a carbon particle concentration of, for example, 50 to 200 g / L, and dispersed in the water. When this is left to stand for 1 to 4 hours, larger carbon particles will settle preferentially, and smaller particles will make up the majority of the carbon particles that have not settled. When these unsettled carbon particles are removed along with the water by suction, the particle size distribution of the remaining carbon particles changes so that the particle size on the side with the smallest cumulative proportion becomes larger. Water may be added to the residue, the carbon particles may be dispersed again, and the particles may be left to settle for the same amount of time as above, and the portion of the water in which the unsettled carbon particles are suspended may be suctioned. By repeating the above operations of dispersing carbon particles in water, letting it stand, and suctioning water an appropriate number of times (for example, 1 to 6 times in total), carbon particles with the desired particle size distribution used in the present invention can be obtained.

[0053] Another example of a process to increase the relative size of the D10 of carbon particles is classification. For example, by performing appropriate classification, such as wind classification, on commercially available carbon particles to obtain a particle size distribution that satisfies the above-mentioned D10 / D50 and D10 / D90, carbon particles with the desired particle size distribution for use in the present invention can be obtained.

[0054] (Oxidation treatment of carbon particles) It is preferable to remove lipophilic organic matter adsorbed on the surface of carbon particles by oxidizing them. This oxidation treatment may be performed before or after the above-mentioned treatment to increase the relative size of D10 of the carbon particles. The lipophilic organic matter includes aliphatic hydrocarbons such as alkanes and alkenes, and aromatic hydrocarbons such as alkylbenzenes. In addition to wet oxidation treatment, O ２Dry oxidation treatment using gas or other methods can be used, but from the viewpoint of mass production, wet oxidation treatment is preferable, as wet oxidation treatment can uniformly treat carbon particles with a large surface area. Methods for wet oxidation treatment include suspending carbon particles in water and then adding an appropriate amount of oxidizing agent. Suitable oxidizing agents include nitric acid, hydrogen peroxide, potassium permanganate, potassium persulfate, and sodium perchlorate. Lipophilic organic matter adhering to the carbon particles is oxidized by the added oxidizing agent, becoming water-soluble and effectively removed from the surface of the carbon particles. Furthermore, after this wet oxidation treatment, filtration and subsequent washing of the carbon particles with water can further enhance the effect of removing lipophilic organic matter from the surface of the carbon particles. Oxidation treatment of carbon particles removes lipophilic organic substances such as aliphatic hydrocarbons and aromatic hydrocarbons from the surface of the carbon particles. Analysis using gas heated at 300°C shows that the gas generated when the oxidized carbon particles are heated at 300°C contains almost no lipophilic aliphatic hydrocarbons such as alkanes and alkenes, or lipophilic aromatic hydrocarbons such as alkylbenzenes. Even if the oxidized carbon particles contain small amounts of aliphatic hydrocarbons or aromatic hydrocarbons, the carbon particles can be uniformly dispersed in the silver plating solution used in this invention. However, it is preferable that the carbon particles do not contain hydrocarbons with a molecular weight of 160 or more, and that the gas intensity (purge-and-trap gas chromatography-mass spectrometry intensity) of hydrocarbons with a molecular weight of less than 160 in the carbon particles when heated at 300°C is 5,000,000 or less.

[0055] (Basification treatment of carbon particles) The lipophilic organic substances adsorbed on the surface of the carbon particles can also be removed by subjecting the carbon particles to a basification treatment. This basification treatment may be performed after or before the above-described treatment for increasing the relative size of D10 of the carbon particles. Examples of the method for the basification treatment include a method of bringing carbon particles into contact with an alkaline aqueous solution, and as a specific method thereof, a method of suspending carbon particles in water and then adding an appropriate amount of an alkaline substance can be used. Examples of the alkaline substance include potassium hydroxide, sodium hydroxide, calcium hydroxide and lithium hydroxide.

[0056] (Amount of carbon particles in silver plating solution) The amount of carbon particles in the silver plating solution is from the viewpoint of the wear resistance of a composite material obtained by forming a composite coating on a base material using the silver plating solution, and there is a limit to the amount of particles that can be incorporated into the composite coating. Therefore, it is preferably 10 to 200 g / L, more preferably 25 to 150 g / L, and most preferably 50 to 120 g / L.

[0057] {Compound A} In an embodiment of the method for producing a composite material of the present invention, a composite coating having a Vickers hardness HV of 80 or more is formed on a base material. There is no particular limitation on the method for forming such a high-hardness composite coating, and for example, a method of including compound A represented by the following general formula (I) in a silver plating solution used in the production of the composite material can be mentioned.

[0058] In the above general formula (I), m is an integer of 1 to 5, and R １ is a carboxyl group, and R ２ is an aldehyde group, a carboxyl group, an amino group, a hydroxyl group or a sulfonic acid group, R ３ is hydrogen or any substituent, and R １ and R ２ each independently may be bonded to a benzene ring via a divalent group constituted by at least one selected from the group consisting of -O- and -CH ２ -. Examples of the divalent group include -CH ２ -CH ２ -O-, -CH ２ -CH２ -CH ２ -O-, (-CH ２ -CH ２ -O-) ｎ (where n is an integer greater than or equal to 2) are some examples.

[0059] Compound A is thought to reduce the size of silver crystallites in the composite film formed by electroplating by adsorbing onto the surface of the deposited silver and suppressing the growth of silver crystals. As a result, a composite material with high hardness and therefore excellent wear resistance can be obtained.

[0060] Furthermore, in the above general formula (I), if m is 2 or greater, there are multiple R ２ The elements may be the same or different from each other, and if m is 3 or less, there may be multiple R elements. ３ They may be the same or different from each other. ３ Examples of the "optional substituents" include alkyl groups, alkylaryl groups, acetyl groups, nitro groups, halogen groups, and alkoxyl groups having 1 to 10 carbon atoms.

[0061] The concentration of compound A in the silver plating solution is preferably 2 to 250 g / L, and more preferably 3 to 200 g / L, from the viewpoint of suppressing unevenness in the appearance of the composite film and appropriately controlling the size of the silver crystallites in the formed composite film.

[0062] {Complexing Agent} The silver plating solution used in this invention preferably contains a complexing agent. The complexing agent complexes the silver ions in the silver plating solution, thereby increasing their ionic stability. This action increases the solubility of silver in the solvent constituting the plating solution.

[0063] While conventionally known complexing agents can be used without particular limitation, compounds having a sulfonic acid group are preferred from the viewpoint of the stability of the formed complex. Examples of compounds having a sulfonic acid group include alkyl sulfonic acids having 1 to 12 carbon atoms, alkanol sulfonic acids having 1 to 12 carbon atoms, and hydroxyaryl sulfonic acids. Specific examples of these compounds include methanesulfonic acid, 2-propanolsulfonic acid, and phenolsulfonic acid.

[0064] From the viewpoint of stabilizing silver ions, the amount of complexing agent in the silver plating solution is preferably 30 to 200 g / L, and more preferably 50 to 120 g / L.

[0065] {Other additives} As other additives, for example, the silver plating solution used in the present invention may contain a brightener, a hardener, and a conductivity salt.

[0066] {Solvent} The solvent that makes up the silver plating solution is mainly water. Water is preferred because of its solubility of (complexed) silver ions, its solubility of other components contained in the plating solution, and its low environmental impact. Alternatively, a mixed solvent of water and alcohol may be used as the solvent.

[0067] <Electroplating Conditions> Next, we will explain the conditions for electroplating using the silver plating solution described above. For example, in the electroplating described below, metallic silver is deposited on the material, and at the same time, the carbon particles mentioned above are incorporated into the silver matrix, forming a composite film. If a base layer is formed on the material, the composite film is formed on top of it, and if silver strike plating is performed, the composite film is formed on top of the strike plating layer.

[0068] {Cathode and Anode} The material to be electroplated is the cathode. The anode is, for example, a silver electrode plate that is dissolved to provide silver ions.

[0069] {Current Density} The cathode and anode are immersed in a silver plating solution (plating bath), and silver plating is performed by passing an electric current through them. The current density here is set to 0.3 to 10 A / dm² from the viewpoint of the formation rate of the composite film and the suppression of unevenness in the appearance of the composite film. ２ Preferably, 0.5 to 8 A / dm ２ More preferably, 0.8 to 6 A / dm ２ That is even more preferable.

[0070] {Temperature, Stirring, Plating Time, Plating Target Area} When performing electroplating, the temperature of the plating bath (silver plating solution) (plating temperature) is preferably 15 to 50°C, and more preferably 20 to 45°C, from the viewpoint of improving the production efficiency of the plating and preventing excessive evaporation of the solution. When stirring the plating bath using a stirrer, the stirring speed of the stirrer is preferably 200 to 550 rpm, and more preferably 350 to 500 rpm, from the viewpoint of performing uniform plating and increasing the area ratio of carbon particles on the surface of the resulting composite film. The silver plating time (time for applying current) can be adjusted as appropriate according to the desired thickness of the composite film, but is typically in the range of 25 to 4500 seconds. The area to be plated may be the entire surface of the material or a part of the surface of the material, depending on the application of the composite material being manufactured.

[0071] Furthermore, in order to form a composite coating that is excellent in terms of wear resistance and suppression of silver detachment from the composite coating during bending, it is preferable to set the silver plating time to 2000 seconds or less.

[0072] <<Partial Removal of Carbon Particles from the Surface of the Composite Coating>> As described above, a composite coating is formed on the material by electroplating. On the surface of this composite coating, there are carbon particles that are embedded in the silver matrix and are difficult to remove, and carbon particles that are attached to the surface rather than embedded and are easy to remove. The latter can contaminate equipment when bending the composite material. Therefore, it is preferable to wash and remove such carbon particles. One washing method is ultrasonic washing of the surface of the composite coating. Ultrasonic washing is preferably performed at 20 to 100 kHz for 1 to 300 seconds. Another washing method is electrolytic washing. In this case, electrolytic washing is performed at 1 to 30 A / dm ２ It is preferable that this is done for 10 to 300 seconds.

[0073] [Terminals] The embodiments of the composite material of the present invention possess excellent wear resistance, making them suitable as constituent materials for terminals, particularly for electrical contact components such as switches and connectors, which are subjected to sliding during use. Terminals can be manufactured by processing the composite material of the present invention, which is not in the shape of a terminal (such as a flat plate), into a terminal shape by shearing or bending processes such as punching. Alternatively, terminals can be manufactured by applying the manufacturing method of the composite material of the present invention to a material that is already in the shape of a terminal.

[0074] The following describes in detail examples of the composite material and its manufacturing method according to the present invention. However, the present invention is not limited thereto.

[0075] [Example 1] <Wet Oxidation Treatment of Carbon Particles> 80 g of flake-shaped graphite particles (PAG-3000, manufactured by Nippon Graphite Industries Co., Ltd.) with an average particle size of 4.8 μm were added to 1.4 L of pure water, and the mixture was heated to 50°C while stirring. The average particle size was measured using a laser diffraction / scattering particle size distribution analyzer (MT3300 (LOW-WETMT3000IIMode), manufactured by Microtrac-Bell Co., Ltd.) by dispersing the carbon particles in pure water, which was the dispersion solvent, to a concentration of 2 g / L, and the volume-based cumulative value was the particle size at 50% (D50). For the dispersion, an ultrasonic homogenizer (US-300T, manufactured by Nippon Seiki Seisakusho Co., Ltd.) was used, with a V-LEVEL 300 μA, φ20 tip. 40 mL of pure water and a predetermined amount of carbon particles were placed in a 100 mL beaker and dispersed for 2 minutes. Next, 5.2 g of potassium hydroxide was added to the mixture obtained by adding 80 g of the aforementioned graphite particles to 1.4 L of pure water. Then, 0.6 L of a 0.1 mol / L aqueous solution of potassium peroxodisulfate (270 g / mol) was gradually added dropwise as an oxidizing agent, and the mixture was stirred for 2 hours to carry out the oxidation treatment. After that, the mixture was filtered using filter paper, and the resulting solid was washed with water. The washing was repeated until the conductivity of the filtrate after washing was 10 μS / cm or less.

[0076] <Process to relatively increase D10> After the wet oxidation treatment described above, the carbon particles were placed in an oven at 180°C and dried for 18 hours to agglomerate. Then, 5 g of the dried and agglomerated carbon particles were placed in a magnetic mortar (outer dimensions × inner dimensions × height × depth: φ90 mm × φ70 mm × 45 mm × 35 mm) and ground using a pestle (length approximately 90 mm, diameter 20 mm) at a length of 1 min per gram of carbon particles to adjust the particle size. D10, D50, and D90 were determined for the obtained carbon particles with adjusted particle size distribution using the same method as described above.

[0077] <Ag Strike Plating> A plate material made of Cu-Ni-Sn-P alloy with dimensions of 5.0 cm in length, 5.0 cm in width, and 0.2 mm in thickness was prepared. This plate material is NB-109EH manufactured by DOWA Metaltech Co., Ltd., and is a copper alloy plate material containing 1.0 mass% Ni, 0.9 mass% Sn, and 0.05 mass% P, with the remainder being Cu and unavoidable impurities. Using this plate material as the base material, and with the said material as the cathode and an iridium oxide mesh electrode plate (a titanium mesh material coated with iridium oxide) as the anode, the plating was performed in a sulfonic acid-based silver strike plating solution containing methanesulfonic acid as a complexing agent (Dyne Silver GPE-ST manufactured by Yamato Kasei Co., Ltd., substantially free of cyanide compounds, silver concentration 3 g / L, methanesulfonic acid concentration 42 g / L), at a solution temperature of 25°C and a current density of 5 A / dm². ２ Electroplating (silver strike plating) was performed for 120 seconds. The silver strike plating was applied to the entire surface layer of the material.

[0078] <AgC Plating> A sulfonic acid-based silver plating solution containing methanesulfonic acid as a complexing agent was prepared by adding the above-mentioned particle size distribution-adjusted carbon particles (graphite particles) to a silver concentration of 30 g / L and a methanesulfonic acid concentration of 60 g / L (Dyne Silver GPE-HB manufactured by Yamato Kasei Co., Ltd. (containing compound A corresponding to general formula (I) at a concentration of 4.2 g / L, with water as the main solvent)). This solution contained carbon particles at a concentration of 50 g / L, silver at a concentration of 30 g / L, and methanesulfonic acid at a concentration of 60 g / L. This silver plating solution is substantially free of Sb and cyanide compounds.

[0079] Next, using the Ag strike plated material as the cathode and the silver electrode plate as the anode, the above carbon particle-containing sulfonic acid-based silver plating solution is stirred at 400 rpm with a stirrer at a temperature of 25°C and a current density of 3 A / dm². ２ Electroplating was performed for 270 seconds to obtain a composite material in which a composite film (AgC plating film) containing carbon particles in a silver layer was formed on the material. The composite film was formed on the entire surface of the material.

[0080] <Ultrasonic Cleaning Treatment> The composite coating surface of the obtained composite material was subjected to ultrasonic cleaning treatment for 4 minutes at 28 kHz using an ultrasonic cleaner (ASONE VS-100III, output 100W, tank dimensions: 140 mm (length) x 240 mm (width) x 100 mm (depth)) with water as the liquid medium, to obtain the composite material according to Example 1.

[0081] <Measurement of the average area of ​​carbon particles on the composite coating surface> The surface of the composite coating was observed using a desktop microscope (TM4000 Plus, manufactured by Hitachi High-Tech Corporation) at an acceleration voltage of 5 kV and magnified 1000 times. The area of ​​carbon particles was evaluated using imagej (National Institutes of Health (NIH), Version 1.52a) in the following manner. For the analysis conditions using the software, the number of pixels of the scale bar length of the captured backscattered electron composition image was measured on the "Set Scale" screen, which is displayed by sequentially selecting Analyze and Set Scale, and entered into Distance in pixels. Pixel aspect ratio was set to 1.0 and Unit of length to μm. Next, the scale bar length (μm) was entered into Known distance to enable the software to recognize the size of the precipitates. Then, in the "Resize Image Canvas" screen, Width was set to 1280 pixels, Height to 850 pixels, and Position to Top-Center, displaying an image of the backscattered electron composition image portion excluding the scale bar. After setting the scale and removing the scale bar display portion, the "Threshold" screen, displayed by sequentially selecting Image, Adjust, and Threhold, was set to Auto to binarize and identify the graphite portion. Subsequently, in the "Analyze Particles" screen of the same software, Size was set to "0-Infinity". Furthermore, particle analysis was performed with the Circulation set to 0.00-1.00 and the "Fit Ellipse" option checked in the "Set Measurements" screen. The average area of ​​carbon particles was calculated by dividing the sum of the areas of all particles detected in the field of view (displayed under the item name "area") by the number of detected particles.

[0082] <Thickness of Composite Coating> The thickness of the composite coating of the composite material (a circular area with a diameter of 0.2 mm in the central part of a 5.0 cm x 5.0 cm surface) was measured using an X-ray fluorescence film thickness gauge (FT9450 manufactured by Hitachi High-Tech Science Co., Ltd.) and was found to be 6.0 μm. Note that it is difficult to detect C atoms (of carbon particles) with an X-ray fluorescence film thickness gauge, so the thickness is determined by detecting Ag atoms, but in this invention, the thickness determined in this way is approximated as the thickness of the composite coating.

[0083] <Carbon Area Ratio on Composite Coating Surface> The surface of the composite coating was observed using a desktop microscope (TM4000 Plus, manufactured by Hitachi High-Tech Corporation) at an acceleration voltage of 5 kV and magnified 1000 times. The backscattered electron composition (COMPO) image (1 field of view) was binarized using GIMP 2.10.10 (image analysis software), and the area ratio occupied by carbon on the composite coating surface was calculated. Specifically, assuming the highest brightness of all pixels was 255 and the lowest brightness was 0, the gradation was binarized so that pixels with a brightness of 127 or less were black and pixels with a brightness greater than 127 were white. The image was then separated into silver parts (white parts) and carbon particle parts (black parts), and the ratio Y / X of the number of pixels in the carbon particle part to the total number of pixels X in the image was calculated as the carbon area ratio (%) of the surface. The carbon area ratio was 27%.

[0084] <Vickers Hardness HV of Composite Coating Surface> The Vickers hardness HV of the composite coating surface was measured using a microhardness tester (HM221 manufactured by Mitutoyo Corporation) by applying a load of 0.1 N to a flat portion of the composite material for 15 seconds, according to JIS Z 2244, and the average value of three measurements was adopted. As a result, the Vickers hardness HV was 160. The composite material of Example 1 has a thin composite coating, but for Vickers hardness measurement, the composite material was prepared by changing only the plating time (the plating time was set to 1200 seconds). The Vickers hardness of the obtained composite material with a composite coating thickness of approximately 20 μm was measured using the above method (Vickers hardness measurements were similarly performed for Examples 2, 3, and 5, and Comparative Examples 1 to 3 and 6 described later).

[0085] Furthermore, our own research has shown that even when the composite coating is thin (for example, 0.5 μm or more and less than 15 μm), the Vickers hardness can be measured using a microhardness tester (HM221 manufactured by Mitutoyo Corporation) by employing the measurement load calculated by the following formula: Measurement load (N) = (80 × thickness of composite coating × thickness of composite coating) / 0.42547

[0086] In the above formula, the "thickness of the composite coating" should be replaced with the numerical value of the thickness of the composite coating in millimeters. The Vickers hardness value should be calculated by making 10 indentations on a single sample, determining the Vickers hardness for each, and then using the average of the 8 values ​​obtained, excluding the maximum and minimum values. If the indentations are small, they may be observed using an electron microscope at an appropriate magnification.

[0087] <Evaluation of wear resistance (wear test)> A flat test piece measuring 2.0 cm wide x 3.0 cm long was cut from the composite material obtained in Example 1. Meanwhile, the following convex-shaped indenter was prepared to slide against this flat test piece (plate).

[0088] The copper alloy sheet material used as the base material in Example 1 was press-formed (so-called indentation) to an inner radius of 1.0 mm. Using this processed product as the base material, silver strike plating was performed in the same manner as in Example 1. The silver strike plating was performed on the entire surface layer of the base material. Next, using the Ag strike plated material as the cathode and the silver electrode plate as the anode, electroplating was performed at a temperature of 15°C (current density 1.2 A / dm²) in an Ag-Sb alloy plating solution (cyanide bath) containing 10% by mass of silver sodium cyanide, 30% by mass of sodium cyanide, and 50 mL / L of Nissin Bright N (brightener, containing 6% by mass of antimony trioxide) (manufactured by Nisshin Kasei Co., Ltd.) while stirring with a stirrer at 400 rpm. ２ The test was conducted for 37.5 minutes. As a result, an indented specimen was obtained in which an AgSb plating layer containing 2% by mass of Sb was formed, with a Vickers hardness (HV) of 180 and a thickness of 30 μm. This indented specimen was used as a convex indenter in the following sliding wear test.

[0089] Abrasion resistance was evaluated by performing an abrasion test using a sliding abrasion tester (CRS-G2050-DWA, manufactured by Yamazaki Seiki Kenkyusho Co., Ltd.). The indented test piece was pressed against the flat test piece with a constant load (5N) and a reciprocating sliding motion was performed (sliding distance 10 mm (i.e., 20 mm per reciprocating motion), sliding speed 10 mm / s) to check the abrasion state of both the indented test piece and the flat test piece. The thickness of the composite coating on the flat test piece was x μm, and the reciprocating sliding motion was continued for x × 5,000 cycles.

[0090] As a result, in this Example 1, after 30,000 reciprocating sliding operations, the center of the sliding marks on the indented test piece (indenter) and the flat test piece (plate) was observed at a magnification of 200x using a microscope (VHX-1000 manufactured by Keyence Corporation). It was confirmed that the (brown) material (copper alloy plate) was not exposed in either case, indicating that the composite material of Example 1 has excellent wear resistance. Furthermore, the thickness of the composite coating remaining without wear in the center of the sliding mark on the flat test piece was measured using the same method as the thickness of the composite coating described above, and the number of durability cycles was calculated from (number of sliding operations) / ((thickness of composite coating before sliding) - (thickness of remaining composite coating in the center of the sliding mark)). The number of durability cycles is the number of reciprocating sliding operations required for 1 μm of the composite coating to wear away in the wear test. In this Example 1, the thickness of the remaining composite coating in the center of the sliding mark was 2.25 μm, so the number of durability cycles was calculated to be 8,000.

[0091] [Example 2] After the same wet oxidation treatment as in Example 1, carbon particles were dispersed in pure water at a concentration of 100 g / L and allowed to stand for 2 hours. Then, 80% of the total volume of slurry was removed as the supernatant by applying a suction tube to the water surface and the residue was collected. The same amount of pure water as the supernatant removed by suction was added to the residue and it was redispersed and allowed to stand for 2 hours. Then, 80% of the total volume of slurry was removed as the supernatant by suction and the residue was collected, and this process was repeated three more times (a total of four suction removals were performed). The resulting residue was filtered to recover the carbon particles, and D10, D50, and D90 were determined. A composite material was prepared in the same manner as in Example 1, except for the use of these carbon particles, and various evaluations were performed in the same manner as in Example 1.

[0092] [Example 3] A composite material was prepared in the same manner as in Example 1, except that the electroplating time for AgC plating was 180 seconds, and various evaluations were performed in the same manner as in Example 1.

[0093] [Example 4] A composite material was prepared in the same manner as in Example 1, except that the electroplating time for AgC plating was set to 1080 seconds, and various evaluations were performed in the same manner as in Example 1.

[0094] [Example 5] <Airflow Classification and Wet Oxidation Treatment of Carbon Particles> Airflow classification was performed on PAG-1500, a flake-shaped graphite particle manufactured by Nippon Graphite Industries Co., Ltd. (average particle size (D50): 3 μm, total volume percentage of particles with a particle size of 2.121 μm or less: 4.45 vol%, total volume percentage of particles with a particle size of 20.17 μm or more: 8.26 vol%), which was used as the carbon particle to remove coarse powder and most of the fine powder. The resulting carbon particles had a total volume percentage of particles with a particle size of 2.121 μm or less of 0.7 vol%, and a total volume percentage of particles with a particle size of 20.17 μm or more of 8.79 vol%. The carbon particles were subjected to wet oxidation treatment in the same manner as in Example 1 to obtain oxidized carbon particles.

[0095] <Ni Undercoat Plating> Using a Ni electrode plate as the anode, the nickel plating bath (aqueous solution) consisting of nickel sulfamate at a concentration of 342 g / L (80 g / L Ni concentration) and boric acid at a concentration of 45 g / L was performed at a liquid temperature of 55°C and a current density of 4 A / dm². ２Electroplating (Ni plating) was performed for 140 seconds while stirring to form a 1 μm thick Ni coating (Ni underlayer) on the same material as used in Example 1, thereby obtaining a Ni-underlayered material. The thickness of the Ni underlayer was measured using the same method as for determining the thickness of the composite coating.

[0096] <Ag strike plating> Ag strike plating was performed in the same manner as in Example 1, except that the Ni undercoat material described above was used.

[0097] <AgC Plating and Evaluation> The oxidized carbon particles obtained above were added to Dainsilver GPE-HB, a sulfonic acid-based silver plating solution manufactured by Yamato Kasei Co., Ltd. The resulting carbon particle-containing sulfonic acid-based silver plating solution (concentration of oxidized carbon particles: 50 g / L, concentration of silver: 30 g / L, concentration of methanesulfonic acid: 60 g / L) and the above Ag strike-plated Ni undercoat material were used to perform AgC plating in the same manner as in Example 1 to create a composite material. Various evaluations were performed on this composite material in the same manner as in Example 1.

[0098] [Comparative Example 1] A composite material was prepared in the same manner as in Example 1, except that the carbon particles obtained in the <wet oxidation treatment of carbon particles> in Example 1 were added to a sulfonic acid-based silver plating solution in AgC plating, and various evaluations were performed in the same manner as in Example 1.

[0099] [Comparative Example 2] The carbon particles obtained in the <wet oxidation treatment of carbon particles> in Example 1 were dispersed in pure water to a concentration of 100 g / L and allowed to stand for 2 hours. Then, a suction tube was applied to the surface of the slurry and 20% of the total volume of the slurry was aspirated to obtain the supernatant. The same amount of pure water as the amount aspirated was added to the remaining residue to redisperse the carbon particles, and it was allowed to stand for 2 hours. Then, 20% of the total volume of the slurry was aspirated in the same manner as above and the supernatant was collected, and this process was repeated twice (a total of suction was performed).

[0100] The supernatant, which amounted to 60% of the total volume of the original slurry, was combined with the slurry and filtered to recover the carbon particles contained in the supernatant.

[0101] A composite material was prepared in the same manner as in Example 1, except that the obtained carbon particles were added to a sulfonic acid-based silver plating solution in AgC plating, and various evaluations were performed in the same manner as in Example 1.

[0102] [Comparative Example 3] A composite material was prepared in the same manner as in Example 1, except that PAG-3000, manufactured by Nippon Graphite Industries Co., Ltd. (from a different manufacturing lot than that used in Example 1), which is a flake-shaped graphite particle, was used as the carbon particle; it was subjected to the same wet oxidation treatment and D10 relatively increasing treatment as in Example 1; the resulting carbon particles with adjusted particle size distribution were added to Dainsilver GPE-PL, a sulfonic acid-based silver plating solution manufactured by Yamato Kasei Co., Ltd. (silver concentration 30 g / L, methanesulfonic acid concentration 60 g / L, does not contain compound A corresponding to general formula (I)); and the carbon particle-containing sulfonic acid-based silver plating solution obtained as described above was used in AgC plating. Various evaluations were then performed in the same manner as in Example 1.

[0103] [Comparative Example 4] Water, potassium cyanide, silver cyanide, potassium carbonate, and a brightener (AgO-56, manufactured by Atotec) were mixed and dissolved in a reaction vessel. Next, the mixture obtained above was treated with activated carbon (the amount of activated carbon used was such that the concentration of activated carbon in the mixture after activation carbon was 2.5 g / L). Subsequently, the mixture treated with activated carbon was filtered, the liquid component was recovered, and a surfactant (Silver Glow TY, manufactured by Meltex) was added to it. Then, carbon nanofibers (VGCF, manufactured by Showa Denko K.K.) were added to the mixture with the surfactant, stirred with a stirrer for 15 minutes, and then ultrasonically dispersed for 15 minutes. This stirrer stirring and ultrasonic dispersion treatment was repeated five times to prepare a silver plating solution. The components were used so that the resulting silver plating solution had a potassium cyanide concentration of 140 g / L, a silver cyanide concentration of 40 g / L, a potassium carbonate concentration of 15 g / L, a brightener concentration of 4 mL / L, a surfactant concentration of 5 mL / L, and a carbon nanofiber concentration of 10 g / L.

[0104] A composite material was prepared in the same manner as in Example 1, except that a silver plating solution containing carbon nanofibers obtained as described above was used instead of the carbon particle-containing sulfonic acid-based silver plating solution used in Example 1, and the electroplating time was set to 900 seconds. Various evaluations were then performed in the same manner as in Example 1.

[0105] [Comparative Example 5] A composite material was prepared in the same manner as in Example 1, except that a silver plating solution containing 40 g / L of silver ions (silver 5,5-dimethylhydantoin), 70 g / L of 5,5-dimethylhydantoin, 35 g / L of sulfamic acid, 50 g / L of potassium hydroxide, and 20 g / L of graphite (graphite nanoparticles with an average diameter of 400 nm, supplied by Nanostructured and Amorphous Materials Incorporated) was used instead of the carbon particle-containing sulfonic acid-based silver plating solution used in Example 1, and the electroplating time was set to 1500 seconds. Various evaluations were performed in the same manner as in Example 1.

[0106] [Comparative Example 6] 40 parts by mass of PAG-1500 and 60 parts by mass of PAG-4500 (flaky graphite particles manufactured by Nippon Graphite Industries Co., Ltd., average particle size (D50): 10 μm) were mixed together as carbon particles, and the resulting mixed carbon particles were subjected to wet oxidation treatment in the same manner as in Example 1.

[0107] The obtained oxidized carbon particles were added to Dainsilver GPE-HB, a sulfonic acid-based silver plating solution manufactured by Yamato Kasei Co., Ltd. A composite material was prepared in the same manner as in Example 1, except that the obtained carbon particle-containing sulfonic acid-based silver plating solution (concentration of mixed carbon particles: 50 g / L, concentration of silver: 30 g / L, concentration of methanesulfonic acid: 60 g / L) was used in AgC plating, and various evaluations were performed in the same manner as in Example 1.

[0108] The evaluation results are summarized in Table 1 below.

[0109]

Claims

1. A composite material comprising a composite coating consisting of a silver layer containing carbon particles on a base material, wherein the average area of ​​the carbon particles on the surface of the composite coating is 2.65 μm. ２ The composite material wherein the composite coating has a Vickers hardness HV of 80 or higher.

2. The composite material according to claim 1, wherein the proportion of carbon particles on the surface of the composite coating is 8 to 60 area %.

3. The composite material according to claim 1, wherein the thickness of the composite coating is 0.5 to 30 μm.

4. The composite material according to claim 1, wherein the material is composed of Cu or a Cu alloy.

5. The average area of ​​carbon particles on the surface of the composite coating is 30 μm². ２ The composite material according to claim 1, wherein the Vickers hardness HV of the composite coating is 280 or less.

6. The composite material according to claim 1, wherein the thickness of the composite coating is 0.5 to 15 μm.

7. The composite material according to claim 1, wherein a base layer consisting of at least one selected from the group consisting of Cu, Ni, Sn, and Ag is formed on the material, and the composite coating is formed on this base layer.

8. A terminal for electrical contacts, in which the composite material described in any one of claims 1 to 7 is used as a constituent material.

9. A method for manufacturing a composite material, wherein electroplating is performed in a silver plating solution containing carbon particles to form a composite coating on a material, the composite coating consisting of a silver layer containing carbon particles and having a Vickers hardness HV of 80 or higher, wherein when D10 is the volume-based cumulative 10% particle diameter (μm) of the carbon particles determined by a laser diffraction / scattering particle size distribution analyzer, D50 is the volume-based cumulative 50% particle diameter (μm) of the carbon particles determined by a laser diffraction / scattering particle size distribution analyzer, and D90 is the volume-based cumulative 90% particle diameter (μm) of the carbon particles determined by a laser diffraction / scattering particle size distribution analyzer, the following conditions are satisfied: D10 / D50 ≥ 0.320 and D10 / D90 ≥ 0.140, and the D50 of the carbon particles is 3 μm or larger.

10. The method for producing a composite material according to claim 9, wherein the carbon particles satisfy D10 / (D90-D10) ≥ 0.

180.

11. The method for manufacturing a composite material according to claim 9 or 10, wherein the material is composed of Cu or a Cu alloy.

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