Composite material, manufacturing method of composite material, terminal, and manufacturing method of terminal

Abstract

To provide a material for sliding contact parts with a coefficient of friction reduced more than conventional materials.SOLUTION: There is provided a composite in which an oxygen-containing silver-based coating layer containing silver with oxygen present near the surface is formed on a material composed of copper or a copper alloy.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a composite material in which a predetermined coating layer is formed on a base material, and a manufacturing method thereof, and in particular to a composite material used as a material for sliding contact parts such as connectors and switches, and a manufacturing method thereof. [Background technology]

[0002] In recent years, in the automotive industry, various functions have been increasingly electronically controlled in order to improve environmental performance, safety, comfort, etc. Controlled objects such as automatic transmissions and sensors are connected to electronic control units (ECUs) via wire harnesses, and the controlled objects and ECUs are connected to the wire harnesses via connectors provided on each.

[0003] As mentioned above, the electronic control of various functions is progressing, and the number of sensors connected to the ECU is increasing, which in turn is increasing the number of terminals that make up the connector (multipolarity). As connectors become more multipolar, the force (insertion force) required to mate the connectors (terminals) increases, making manual mating difficult. The terminal insertion force F is basically expressed as F = μN, where N is the vertical load when mating the male and female terminals and μ is the coefficient of friction during insertion.

[0004] As mentioned above, the insertion force increases when the number of poles in a connector increases, which requires the connector to be divided or to have a mating aid (lever), which results in an increase in the size and manufacturing costs of the connector.

[0005] To address this issue, since the number of terminals cannot be reduced, it is necessary to reduce the insertion force per set of terminals.

[0006] In addition to the low insertion force mentioned above, sliding contact parts such as terminals used in connectors are also required to have electrical conductivity. To meet these requirements, copper (Cu) and copper alloys, which have excellent electrical conductivity, are used as the conductor material for these parts.

[0007] Since copper is easily oxidized, tin (Sn)-plated materials, which have excellent oxidation resistance, are used as conductor materials.

[0008] However, tin plating is prone to frictive wear due to vehicle vibrations (such as those from the road surface while driving or the engine), which increases the electrical resistance between the contacts and causes problems with poor electrical conductivity, making it impossible to reduce the contact pressure (contact pressure) between the terminals. As a result, the insertion force increases. Note that frictive wear is a phenomenon in which repeated sliding of the contacts over several tens of micrometers accelerates the oxidation of tin between the terminal contacts, resulting in the formation and accumulation of thick tin oxide between the contacts. As mentioned above, Sn plating cannot reduce the contact pressure between the terminals, so in order to ensure low insertion force, it is necessary to reduce the friction coefficient of the Sn plating. Thinning the plating layer has been proposed as a way to reduce the friction coefficient of Sn plating, but this only reduces the friction coefficient by about 10 to 20%, which is insufficient.

[0009] On the other hand, silver (Ag) has excellent oxidation resistance and conductivity, and Ag-plated materials have low electrical resistance even when the contact pressure of the terminal is reduced. Silver also has excellent heat resistance, so Ag-plated materials have excellent contact reliability (characteristics such as conductivity do not deteriorate easily even when heated).

[0010] However, Ag-plated materials have a relatively high coefficient of friction because silver adhesion occurs during insertion and removal (sliding). Therefore, in order to reduce the coefficient of friction of Ag-plated materials, a method has been proposed in which a composite coating made of carbon particles such as graphite and carbon black, which have excellent wear resistance and lubricity, is dispersed in a silver matrix and formed on the conductor material by electroplating to improve wear resistance (see, for example, Patent Documents 1 and 2).

[0011] Specifically, Patent Documents 1 and 2 disclose composite materials in which a composite coating containing carbon particles in a silver layer is formed on a base material by electroplating using a silver plating solution to which carbon particles from which lipophilic organic matter has been removed by oxidation treatment and a silver matrix orientation adjuster (potassium selenocyanate) have been added.

[0012] Patent document 3 discloses a lead frame comprising a die pad for mounting an electronic circuit element, an inner lead wire-bonded to the bonding pad of the electronic circuit element, and an outer lead integrally formed with the inner lead, wherein at least the tip of the inner lead is plated with a metal such as silver or gold, and at least the metal-plated portion is subjected to a hydrophilic treatment (oxygen plasma treatment). [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-16250 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-074499 [Patent Document 3] Japanese Patent Application Publication No. 6-53380 Summary of the Invention [Problem to be solved by the invention]

[0014] Conventional silver (Ag) plated materials, which are conductor materials used in sliding contact parts, have the advantages of excellent conductivity, oxidation resistance, and contact reliability, but their relatively high coefficient of friction limits the applications in which they can be used. If this coefficient of friction could be reduced, and the insertion force could be reduced, it is expected that their applications would expand.

[0015] In addition, in the composite materials disclosed in Patent Documents 1 and 2, in which a composite coating in which graphite particles are dispersed in a silver matrix is ​​formed on a base material, the portions of the composite coating surface where the graphite particles are not exposed are silver. As with Ag plating, this silver adheres when the composite material slides against a mating material. Therefore, although this composite material also has a lower friction coefficient than silver plating that does not contain graphite particles, it does not fully meet the recent cutting-edge demand for low insertion force.

[0016] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a material for a sliding contact part having a reduced coefficient of friction compared to conventional materials. [Means for solving the problem]

[0017] As a result of intensive research to solve the above problems, the inventors discovered that the friction coefficient of materials for sliding contact components can be reduced by subjecting the surface of a silver plating layer or a composite coating (coating layer) containing carbon particles in a silver layer to plasma treatment in the presence of oxygen, thereby causing oxygen to be present near the surface, and thus completed the present invention.

[0018] That is, the present invention is as follows. [1] A composite material in which an oxygen-containing silver-based coating layer containing silver and having oxygen present near the surface is formed on a base material made of copper or a copper alloy.

[0019] [2] The composite material according to [1], which is used for terminal applications.

[0020] [3] The composite material according to [1] or [2], wherein the oxygen-containing silver-based coating layer contains carbon particles.

[0021] [4] The composite material according to any one of [1] to [3], wherein an underlayer made of nickel is formed between the material and the oxygen-containing silver-based coating layer.

[0022] [5] A composite material according to any one of [1] to [4], wherein when the surface of the oxygen-containing silver-based coating layer is subjected to EDS analysis, the amount of oxygen is 1 mass% or more relative to 100 mass% of the total amount of all detected elements.

[0023] [6] A composite material according to any one of [1] to [5], wherein, when the surface of the oxygen-containing silver-based coating layer is subjected to EDS analysis, the total amount of silver, oxygen, carbon, antimony, and tin is 99% by mass or more relative to 100% by mass of the total amount of all detected elements, and the amount of oxygen is 1 part by mass or more relative to 100 parts by mass of the total amount of silver, oxygen, carbon, antimony, and tin.

[0024] [7] The composite material according to [6], wherein the total amount of silver and carbon is 88 parts by mass or more when the total amount of silver, oxygen, carbon, antimony and tin is 100 parts by mass.

[0025] [8] The composite material according to [6] or [7], wherein the amount of oxygen is 1.1 to 12 parts by mass when the total amount of the silver, oxygen, carbon, antimony and tin is 100 parts by mass.

[0026] [9] A terminal made of a composite material in which an oxygen-containing silver-based coating layer containing silver and having oxygen present near the surface is formed on a material made of copper or a copper alloy.

[0027]

[10] The terminal according to [9], wherein the oxygen-containing silver-based coating layer contains carbon particles.

[0028]

[11] The terminal according to [9] or

[10] , wherein when the surface of the oxygen-containing silver-based coating layer is subjected to EDS analysis, the amount of oxygen is 1 mass% or more relative to 100 mass% of the total amount of all detected elements.

[0029]

[12] The terminal according to any one of [9] to

[11] , wherein, when the surface of the oxygen-containing silver-based coating layer is subjected to EDS analysis, the total amount of silver, oxygen, carbon, antimony, and tin is 99% by mass or more relative to 100% by mass of the total amount of all detected elements, and the amount of oxygen is 1 part by mass or more relative to 100 parts by mass of the total amount of silver, oxygen, carbon, antimony, and tin.

[0030]

[13] A method for producing a composite material, comprising: forming an oxygen-containing silver-based coating layer on the surface of a laminated material in which a coating layer containing silver is formed on a material made of copper or a copper alloy, and subjecting the surface of the coating layer to plasma treatment in the presence of oxygen.

[0031]

[14] The method for producing a composite material according to

[13] , wherein a gas containing oxygen is used as the plasma gas in the plasma treatment.

[0032]

[15] The method for producing a composite material according to

[14] , wherein the plasma gas contains 1 to 20 volume % of oxygen, the remainder being non-oxidizing elements.

[0033]

[16] A method for manufacturing a terminal, comprising molding the composite material according to any one of [1] to [8] into the shape of a terminal. [Effects of the Invention]

[0034] According to the present invention, a material for a sliding contact part is provided which has a reduced coefficient of friction compared to conventional materials. DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, an embodiment of the present invention will be described. [Composite material] Hereinafter, an embodiment of the composite material of the present invention will be described. The composite material is a material in which an oxygen-containing silver-based coating layer containing silver and having oxygen present near its surface is formed on a material made of copper or a copper alloy. This composite material can be produced, for example, by the method for producing a composite material of the present invention described below. Each component of this composite material will be described below.

[0036] <<Material>> The constituent material of the substrate on which the oxygen-containing silver-based coating layer is formed is preferably one that can be silver-plated and has the conductivity required for materials such as sliding contact parts in connectors and switches. Furthermore, from the viewpoint of cost, Cu (copper) and Cu alloys are used in the present invention. From the viewpoint of achieving both electrical conductivity and wear resistance, the Cu alloy is preferably 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), and Ti (titanium), and inevitable impurities.

[0037] The amount of Cu in the Cu alloy is preferably 50% by mass or more, more preferably 85% by mass or more, and even more preferably 92% by mass or more. The amount of Cu is preferably 99.95% by mass or less. When the copper alloy is a so-called brass containing 20% ​​by mass or more of Zn, the amount of Cu is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more. The amount of Cu is preferably 79% by mass or less.

[0038] As described below, the material is preferably used for terminals (as a composite material with an oxygen-containing silver-based coating layer formed thereon), but the material itself may have a shape for such use, or the material may be flat (such as a plate) and then molded into the desired shape after being made into a composite material. It may also be molded at the laminate stage in the manufacturing method for the composite material of the present invention, which will be described later. The plate shape is a low rectangular parallelepiped shape, more specifically, a shape with a height of 0.1 to 5 when the shorter of the length and width (short side, although the length and width may be the same) is 100. The two surfaces formed by the length and width are referred to as plate surfaces.

[0039] Regarding the long and short sides of the flat plate surface (however, both may be the same length), the short side length is, for example, 10 mm to 300 mm, the long side length is, for example, 15 mm or more, and the height is, for example, 3 mm or less, and usually 0.1 mm or more.

[0040] <<Oxygen-containing silver coating layer>> The oxygen-containing silver-based coating layer formed on the base material contains silver. If Ag strike plating is performed on the base material before forming the oxygen-containing silver-based coating layer, an intermediate layer formed by this strike plating exists between the base material (or the underlayer described below) and the oxygen-containing silver-based coating layer, but this intermediate layer is often so thin that it cannot be distinguished from the oxygen-containing silver-based coating layer. The oxygen-containing silver-based coating layer may be formed on the entire surface of the base material, or on only a part of the surface.

[0041] Examples of oxygen-containing silver-based coating layers include, from the viewpoints of electrical conductivity and a low coefficient of friction, Ag layers made of silver (Ag), AgSb alloy layers made of a silver-antimony alloy (AgSb alloy), AgSn alloy layers made of a silver-tin alloy (AgSn alloy), and AgC composite layers containing carbon particles, AgSbC composite layers, and AgSnC composite layers in which oxygen exists near the surface (hereinafter, these may also be referred to as "oxygen-containing Ag layers," "oxygen-containing AgSn alloy layers," or "oxygen-containing AgC composite layers"). Among these, oxygen-containing Ag layers and oxygen-containing AgC composite layers are preferred because of their excellent heat resistance and electrical conductivity, and oxygen-containing AgC composite layers are particularly preferred because of their particularly low coefficient of friction.

[0042] In the oxygen-containing AgC composite layer, oxygen-containing AgSbC composite layer, and oxygen-containing AgSnC composite layer, carbon particles are preferably uniformly dispersed in a matrix made of silver, AgSb alloy, or AgSn alloy. A typical method for forming these composite layers is electroplating, and when a plating film is formed on a substrate by electroplating, the carbon particles become entrapped in the silver, AgSb alloy, or AgSn alloy matrix. When the oxygen-containing silver-based coating layer contains carbon particles, the wear resistance of the composite material is enhanced. From the viewpoint of exhibiting this function, the carbon particles are preferably graphite particles. The shape of the carbon particles is not particularly limited, and may be substantially spherical, flaky, or amorphous. However, flake-shaped carbon particles are preferred because they are easily entrapped in the silver matrix. Furthermore, the average primary particle diameter of the carbon particles is preferably 0.5 to 15 μm, more preferably 1 to 10 μm, from the viewpoint of the wear resistance of the composite material (composite layer). The average primary particle size is the average value of the long diameter of the particles, and the long diameter is the length of the longest line that can be drawn within the particle without going outside the particle outline in an image (plane) of the carbon particles in the composite layer (oxygen-containing silver-based coating layer) of the composite material observed at an appropriate observation magnification. The long diameter is determined for 50 or more particles.

[0043] <Oxygen near the surface of the oxygen-containing silver-based coating layer> In the composite material of the present invention, oxygen is present near the surface of the oxygen-containing silver-based coating layer. The "near the surface" refers to the vicinity of the surface of the coating layer that is exposed to the outside and that faces the surface that is in contact with the base material (through the underlayer, if any, described below). The presence of oxygen near the surface is thought to contribute to the low friction coefficient of the composite material. The present inventors speculate that the mechanism behind this is as follows.

[0044] Oxygen chemically bonds with silver near the surface of the oxygen-containing silver-based coating layer to form silver oxide, and as a result, at least a portion of the surface of the oxygen-containing silver-based coating layer is made up of silver oxide, which is very unlikely to cause adhesion, a problem in friction between the composite and the mating material when silver is used. This is thought to be the reason for the lower coefficient of friction of the composite.

[0045] Oxygen near the surface of the oxygen-containing silver-based coating layer can be detected and quantified by EDS (energy dispersive X-ray spectroscopy). Specific EDS methods will be described in the Examples below. From the viewpoint of reducing the coefficient of friction, when the surface of the oxygen-containing silver-based coating layer is analyzed by EDS, the amount of oxygen is preferably 1% by mass or more relative to 100% by mass, which is the total amount of all detected elements. Furthermore, excessively high oxygen content may reduce the conductivity of the composite material. From the viewpoint of the coefficient of friction and conductivity, the amount of oxygen relative to 100% by mass is more preferably 1.1 to 12% by mass, even more preferably 1.6 to 10% by mass, and particularly preferably 5 to 8% by mass.

[0046] <Constituent elements of oxygen-containing silver-based coating layer> As mentioned above, examples of the oxygen-containing silver-based coating layer include an oxygen-containing Ag layer, an oxygen-containing AgSb alloy layer, an oxygen-containing AgSn alloy layer, an oxygen-containing AgC composite layer, an oxygen-containing AgSbC composite layer, and an oxygen-containing AgSnC composite layer.

[0047] When the oxygen-containing silver-based coating layer is any of these, when the surface of the oxygen-containing silver-based coating layer is subjected to EDS analysis, the total amount of silver, oxygen, carbon, antimony, and tin is 99% by mass or more relative to 100% by mass of the total amount of all detected elements, and the amount of oxygen (mass) is 1 part by mass or more relative to 100 parts by mass of the total amount of silver, oxygen, carbon, antimony, and tin. From the viewpoint of reducing the friction coefficient of the composite material and because excessive oxygen may reduce the conductivity of the composite material, the amount of oxygen is preferably 1.1 to 12 parts by mass, more preferably 1.6 to 10 parts by mass, and particularly preferably 5 to 8 parts by mass relative to 100 parts by mass of the total amount of silver, oxygen, carbon, antimony, and tin.

[0048] When the oxygen-containing silver-based coating layer is an oxygen-containing AgC composite layer, the total amount (mass) of silver, carbon, and oxygen is typically 99.5 parts by mass or more, relative to 100 parts by mass of the total amount (mass) of silver, oxygen, carbon, antimony, and tin. Furthermore, the total amount of silver and carbon is preferably 88 parts by mass or more, relative to 100 parts by mass of the total amount. From the viewpoints of conductivity and friction coefficient, the total amount of silver and carbon is more preferably 90 to 98.4 parts by mass. From the same viewpoint, the amount of carbon is preferably 3 to 30 parts by mass, more preferably 4 to 20 parts by mass, relative to 100 parts by mass of the total amount of silver, oxygen, carbon, antimony, and tin.

[0049] <Thickness of oxygen-containing silver-based coating layer> The thickness of the oxygen-containing silver-based coating layer is not particularly limited, but it is preferable that there is a minimum thickness in terms of the friction coefficient and conductivity. Also, if the thickness is too large, the effect of the oxygen-containing silver-based coating layer will be saturated and the raw material cost will increase. From the above viewpoints, the thickness of the oxygen-containing silver-based coating layer is preferably 0.5 to 45 μm, more preferably 0.5 to 35 μm, and even more preferably 1 to 20 μm.

[0050] <<Underlayer>> An underlayer may be formed between the base material and the oxygen-containing silver-based coating layer for various purposes. Examples of constituent metals of the underlayer include Cu, Ni, and Ag. For example, to prevent copper in the base material from diffusing to the surface of the oxygen-containing silver-based coating layer and thereby deteriorating heat resistance, it is preferable to form an underlayer made of Ni. When the base material is a zinc-containing copper alloy such as brass, it is preferable to form an underlayer made of Cu to prevent zinc in the base material from diffusing to the surface of the oxygen-containing silver-based coating layer. To improve the adhesion of the oxygen-containing silver-based coating layer to the base material, it is preferable to form an underlayer made of Ag. The thickness of the underlayer is not particularly limited, but from the viewpoints of its functionality and cost, it is preferably 0.1 to 2 μm, and more preferably 0.1 to 1.5 μm.

[0051] Furthermore, terminals of electric and electronic components often use materials that are Sn-plated or reflow Sn-plated with a Cu or Ni underlayer, and such an underlayer may also be formed in the present invention. That is, in the present invention, the underlayer for the oxygen-containing silver-based coating layer may include a layer made of Cu, Ni, or Ag, or a layer combining these (a laminate structure). Furthermore, when the composite material of the present invention is used for terminal applications, different layers may be formed in different locations, for example, by forming the oxygen-containing silver-based coating layer as defined in the present invention at the connection portion of the material that connects to a mating terminal (with or without forming an underlayer), and by forming reflow Sn plating without forming an oxygen-containing silver-based coating layer at the crimp portion that crimps to an electric wire.

[0052] <<Coefficient of friction>> The composite material of the present invention has a low friction coefficient because the oxygen-containing silver-based coating layer has oxygen near its surface. Specifically, the friction coefficient (average sliding load F / 5N) measured under the conditions described in the Examples below is preferably 0.25 or less, more preferably 0.05 to 0.17, and even more preferably 0.05 to 0.14.

[0053] <<Electrical resistance>> The composite material of the present invention has excellent conductivity equivalent to that of conventional silver-plated materials, and specifically, the contact resistance measured by the method in the examples described below is 10 mΩ or less, preferably 5 mΩ or less, and more preferably 0.05 to 2 mΩ.

[0054] Terminal The composite of the present invention has an extremely low coefficient of friction, making it suitable as a constituent material for terminals, particularly terminals in electrical contact parts that undergo sliding during use, such as connectors and switches.

[0055] Terminals can be formed into a predetermined shape, for example, by subjecting the composite material of the present invention to press-forming, such as punching, bending, or cutting. A terminal may be formed by subjecting a copper or copper alloy material to the press-forming process and then forming an oxygen-containing silver-based coating layer on the material. Furthermore, after the press-forming process is performed on the laminate in the manufacturing method for the composite material of the present invention described below, a terminal may be formed by subjecting the surface (or a portion of the surface) of the silver-containing coating layer to plasma treatment in the presence of oxygen. Alternatively, after the laminate is partially press-formed, the surface (or a portion of the surface) of the coating layer may be subjected to the plasma treatment, and then the remaining press-forming may be performed to form a terminal.

[0056] The terminals are typically a set of male and female terminals, each of which has a connection part 1 for physical and electrical connection to the mating terminal, and a connection part 2 for connection to an external electronic component, electric wire, etc. The connection parts 1 and 2 are typically formed by press molding from a single composite material, and are electrically connected.

[0057] The connection portion 1 of a male terminal is typically formed in a rod shape (e.g., a cylindrical or polygonal pillar shape) such as a pin or tab, or in a convex shape. The connection portion 1 of a female terminal has a housing formed to accommodate the connection portion 1 of the male terminal, and a fixing portion inside the housing for fixing the mated connection portion 1 of the male terminal within the connection portion 1 of the female terminal and conducting electricity. Examples of the shape of the housing include a cylindrical shape and a box-like (rectangular) shape. Specific examples of the fixing means for the fixing portion include a spring and a screw. The fixing means must have excellent conductivity because it contacts the male terminal to conduct electricity, and may be formed from the same material as the material used in the composite material of the present invention. Alternatively, the fixing portion of the connection portion 1 of a female terminal may be, for example, a separate spring separate from the housing, and this fixing portion may be placed within the housing when the terminal is connected.

[0058] Furthermore, when connecting the male and female terminals to external electronic components, the connection portions 2 are formed into a crimped shape for crimping and fixing the terminals to a conductor such as a copper wire from which the resin of the wire has been stripped, when the connection portions 2 are to be connected to an electric wire, for example. If the connection portions 2 are to be soldered to a printed circuit board (PCB), the connection portions 2 are formed into a rod shape such as a round or square rod. In this case, the connection portions 2 do not need to have an oxygen-containing silver-based coating layer formed thereon.

[0059] [Manufacturing method for composite materials] Next, an embodiment of a method for producing a composite material of the present invention will be described. This method involves forming an oxygen-containing silver-based coating layer by subjecting the surface of a laminated material in which a silver-containing coating layer is formed on a copper or copper alloy substrate, to plasma treatment in the presence of oxygen. Each component of this method for producing a composite material will be described below.

[0060] <<Material>> The material is the same as that described for the composite material of the present invention, and Cu (copper) and Cu alloys are used as its constituent materials. The Cu alloy is preferably 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), and Ti (titanium), and inevitable impurities. The amount of Cu in the Cu alloy is preferably 50% by mass, more preferably 85% by mass or more, and even more preferably 92% by mass or more. The amount of Cu is preferably 99.95% by mass or less. Furthermore, when the copper alloy is a so-called brass containing 20% ​​by mass or more of Zn, the amount of Cu is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more. The amount of Cu is preferably 79% by mass or less.

[0061] As described above, the composite material is preferably used for terminal applications. The material itself may have the shape required for the terminal, may have a flat shape such as a plate shape, or may be a flat plate that has been partially processed, such as by pressing, to form a terminal. Regarding the long and short sides of the plate surface of the flat plate (although they may be the same length), the length of the short side is, for example, 10 mm to 300 mm, and the length of the long side is, for example, 15 mm or more. Furthermore, the height of the flat plate, when the length of the short side is taken as 100, is 0.1 to 5, specifically, for example, 3 mm or less, and typically 0.1 mm or more.

[0062] <<Coating layer>> A coating layer containing silver can be formed on a material by any known method. For example, the coating layer can be formed on the material by electroplating, vapor deposition, or cladding (metal lamination). Electroplating can inexpensively form a coating layer made of a single metal plating or alloy plating, or a composite layer such as an AgC composite layer. The coating layer may be formed on the entire surface of the material, or on only a portion of the surface. The electroplating method will now be described.

[0063] <Electroplating> (Ag strike plating) Before forming a coating layer on a base material by electroplating, it is preferable to form a very thin intermediate layer by Ag strike plating to improve adhesion between the base material and the coating layer. When a base layer described below is formed on the base material, Ag strike plating is performed on the base layer. Conventional known methods can be used for Ag strike plating without any particular limitations, as long as they do not impair the effects of the present invention.

[0064] (Formation of base layer) A base layer may be formed on the base material, and a coating layer may be formed on the base layer. This base layer is the same as that described for the composite material of the present invention. That is, constituent metals of the base layer include Cu, Ni, and Ag. The base layer may include a layer made of each of Cu, Ni, and Ag, or a layer made of a combination of these (a laminate structure). The base layer may be formed on the entire surface of the base material, or only on a part of it, depending on the application of the composite material to be manufactured. The method for forming the base layer is not particularly limited, and it can be formed by electroplating the base material by a known method using a base plating solution containing ions of the above-mentioned constituent metals.

[0065] (Electroplating) The above-mentioned material is electroplated in a specific electroplating solution to form a coating layer containing silver on the material. The electroplating solution contains silver ions and may contain other metal ions depending on the composition of the coating layer to be formed. From the viewpoints of the coating layer formation rate and suppression of uneven appearance, the silver concentration in the electroplating solution is preferably 5 to 150 g / L, and more preferably 10 to 120 g / L.

[0066] Furthermore, when forming a composite layer such as an AgC composite layer, the electroplating solution also contains carbon particles. These carbon particles are similar to those described for the composite material of the present invention. Their volume-based cumulative 50% particle size (D50), measured using a laser diffraction / scattering particle size analyzer, is preferably 0.5 to 15 μm, more preferably 1 to 10 μm, from the viewpoint of ease of incorporation into the electroplating film. The shape of the carbon particles is not particularly limited, and may be substantially spherical, flaky, or amorphous, but flaky is preferred. The carbon particles are preferably graphite particles. Furthermore, it is preferable to remove lipophilic organic substances adsorbed on the surface of the carbon particles by oxidizing the carbon particles. The amount of the carbon particles described above in the electroplating solution is preferably 10 to 100 g / L, more preferably 15 to 90 g / L, from the viewpoint of the wear resistance and heat resistance of the composite material and the limited amount of carbon particles that can be introduced into the coating layer.

[0067] The electroplating solution preferably contains a complexing agent. The complexing agent complexes silver ions (and other metal ions, if included) in the electroplating solution, increasing their ionic stability. This action increases the solubility of silver and other metals in the solvent that constitutes the plating solution. Examples of complexing agents include alkylsulfonic acids having 1 to 12 carbon atoms, alkanolsulfonic acids having 1 to 12 carbon atoms, and hydroxyarylsulfonic acids. Specific examples of these compounds include methanesulfonic acid, 2-propanolsulfonic acid, and phenolsulfonic acid. From the viewpoint of stabilizing silver ions and other metal ions, the amount of complexing agent in the electroplating solution is preferably 30 to 200 g / L, more preferably 50 to 120 g / L.

[0068] The electroplating solution may contain other additives such as brighteners, hardeners, and conductivity salts. Examples of the hardeners include carbon sulfide compounds (e.g., carbon disulfide), inorganic sulfur compounds (e.g., sodium thiosulfate), organic compounds (sulfonates), selenium compounds, tellurium compounds, and metals from Group 4B or 5B of the periodic table. Examples of the conductivity salts include potassium hydroxide.

[0069] The solvent constituting the electroplating solution is mainly water. Water is preferred because of its solubility in complexed silver ions and other components contained in the electroplating solution, and its low environmental impact. A mixed solvent of water and alcohol may also be used as the solvent. In the mixed solvent, the proportion of water is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0070] In electroplating, the material to be electroplated is the cathode, and the anode is the electrode that dissolves to provide silver ions, for example, a silver electrode plate. Electroplating is performed by immersing the cathode and anode in an electroplating solution (plating bath) and passing an electric current through them. The current density here is set to 0.5 to 10 A / dm from the viewpoints of the speed at which the coating layer is formed and the prevention of uneven appearance. 2 is preferred, and 1 to 8 A / dm 2 is more preferable, 1.5 to 6 A / dm 2 is more preferable. The temperature of the plating bath (plating temperature) is preferably 15 to 50°C, more preferably 20 to 45°C, from the viewpoints of plating production efficiency and preventing excessive evaporation of the solution. The electroplating time (time for applying electric current) can be adjusted appropriately depending on the desired thickness of the coating layer, but is typically in the range of 25 to 1800 seconds. Furthermore, the target area to be plated may be the entire surface layer of the material or only a part of the surface layer of the material, depending on the application of the composite material to be manufactured.

[0071] <<Plasma treatment>> The surface of the coating layer formed on the base material as described above is subjected to plasma treatment in the presence of oxygen. The surface of the coating layer is the surface of the coating layer that is exposed to the outside and faces the surface of the coating layer that is in contact with the base material (through the above-mentioned underlayer, if present). By the plasma treatment, oxygen is introduced into the surface of the coating layer, resulting in the oxygen-containing silver-based coating layer in the composite material of the present invention.

[0072] If the coating layer is a composite layer, such as an AgC composite layer, the surface of the coating layer may be subjected to ultrasonic cleaning before the plasma treatment. This is to remove carbon particles that simply adhere to the surface and do not contribute to abrasion resistance or the like and that may inhibit the introduction of oxygen to the coating layer surface by the plasma treatment. The ultrasonic cleaning is preferably performed at 20 to 100 kHz for 1 to 300 seconds, and more preferably at 25 to 50 kHz for 2 to 270 seconds.

[0073] Next, an embodiment of the plasma treatment will be described. Plasma is generated by glow discharge or arc discharge. By injecting oxygen-containing plasma gas from the plasma gas injection unit and introducing it into the location where the plasma is generated (position A), highly reactive oxygen radicals and oxygen ions (hereinafter collectively referred to as active oxygen) are generated. These active oxygen also constitute the plasma. By arranging the coating layer in the following order along the direction of plasma gas injection: plasma gas injection unit - position A - coating layer, the active oxygen constituting the plasma is irradiated onto the surface of the coating layer. As a result, the active oxygen reacts with the silver on the surface of the coating layer to form silver oxide, resulting in the presence of oxygen near the surface of the coating layer, i.e., the oxygen-containing silver-based coating layer in the composite material of the present invention. Note that glow discharge is preferred as a plasma generation method, as it allows processing at room temperature and is safe and cost-effective.

[0074] For the plasma treatment in the method for producing a composite material of the present invention, any known plasma generator can be used without particular limitation. An example of a commercially available product is the plasma generator manufactured by Cresul Co., Ltd. (Model 618-920 SP power supply, Capplas2007A electrode).

[0075] As the plasma gas, from the viewpoint of generating sufficient active oxygen, a gas containing oxygen is preferred, and a mixed gas containing oxygen with the remainder being a non-oxidizing element is more preferred. Examples of non-oxidizing elements include argon, nitrogen, fluorine, and hydrogen. As the plasma gas, a mixed gas of argon gas and oxygen gas is particularly preferred from the viewpoint of generating sufficient active oxygen. The proportion of oxygen gas in the mixed gas is preferably 1 to 20% by volume, more preferably 2 to 10% by volume, from the viewpoint of efficiently introducing oxygen to the surface of the coating layer. When a mixed gas containing hydrogen is used, it should be used outside the concentration range of the explosion limit of hydrogen for safety reasons.

[0076] The flow rate of the plasma gas is, for example, 0.3 to 10 L / min, and preferably 0.5 to 5 L / min. Furthermore, the amount of active oxygen irradiated per unit area of ​​the material by plasma treatment is important for the introduction of oxygen to the surface of the coating layer, and the amount of oxygen gas in the plasma gas can be used as an indicator of this amount. In the present invention, from the viewpoint of the introduction of oxygen to the surface of the coating layer and costs, the amount of oxygen gas injected per unit area of ​​the material is 0.05 to 3 mL / cm. 2 is preferably 0.15 to 2.7 mL / cm 2 More preferably, the concentration is 0.8 to 2.5 mL / cm 2 It is more preferable that:

[0077] Regarding the generation of plasma, for example, in the case of glow discharge, the voltage of the plasma power supply in the plasma generator is preferably 3 to 20 kV, and the AC frequency is preferably 5 to 20 kHz.

[0078] Furthermore, the distance between the position A where plasma is generated and the coating layer is preferably small from the viewpoint of efficiently introducing oxygen to the surface of the coating layer. On the other hand, if the long side of the laminate is long, slight warping may occur, and in this case, it is preferable to ensure a certain distance so that the warped portion does not come into contact with the electrode. Specifically, the distance is preferably 0.5 to 30 mm, more preferably 0.8 to 10 mm, and even more preferably 0.8 to 5 mm. Note that position A is usually the tip of the electrode where plasma is generated, close to the coating layer.

[0079] When the composite material is used as a material for sliding contact parts such as terminals, the shape of the laminated material may be a flat plate shape, a terminal shape, or the like, as described above, and the coating layer may be formed on the entire surface of the material or on only a part of the surface. When the laminated material has the flat plate shape, the material is also flat, and as an example, the coating layer is formed on the entire plate surface of that shape (it may be one or both of the two plate surfaces). It is preferable to perform a uniform plasma treatment on such a coating layer from the viewpoint of reducing variations in the friction coefficient depending on the location of the coating layer.

[0080] For example, when the laminated material has a flat plate shape, it is preferable to carry out plasma treatment by using a plasma generating device having a plasma generating unit capable of generating plasma with a width equal to or greater than the short side of the flat plate surface, and irradiating plasma (active oxygen) from the plasma generating unit onto the coating layer while moving the plasma generating unit relatively in the long side direction of the plate surface of the laminated material and scanning it.

[0081] For example, if the short side is approximately 10 mm to 200 mm, the plasma generator (Model 618-920 SP power supply, Capplas 2007A electrode) manufactured by Cresul Co., Ltd. can generate plasma with a width equal to or greater than the short side and can be suitably used. In this embodiment, a mixture of argon gas and oxygen gas is preferred as the plasma gas, with the argon gas flow rate preferably being 1 to 10 L / min and the oxygen gas flow rate preferably being 0.01 to 1 L / min. Regarding the relative movement of the electrode relative to the laminate plate surface, the electrode may be fixed and the laminate moved, or vice versa, or both may be moved. The scanning speed of plasma irradiation accompanied by such relative movement is preferably 100 mm / s or less, more preferably 50 mm / s or less, even more preferably 12 mm / s or less, particularly preferably 7 mm / s or less, and most preferably 0.3 to 3 mm / s, from the viewpoints of productivity of the composite material and introducing a sufficient amount of oxygen into the surface of the coating layer to produce a composite material with a low friction coefficient. If a plurality of plasma generating devices are arranged so that each device irradiates the entire surface of the laminated material with plasma, the scanning speed of each device can be increased accordingly. [Example]

[0082] Examples of the composite material and the method for producing the same according to the present invention will be described in detail below.

[0083] <Preparation 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 5 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-WET MT3000II Mode) manufactured by Microtrac-Bell Corporation) and is the particle size at which the cumulative volumetric value reaches 50%. Next, 0.6 L of a 0.1 mol / L potassium persulfate aqueous solution was gradually added dropwise to the mixture as an oxidizing agent, and the mixture was then stirred for 2 hours to carry out an oxidation treatment. The mixture was then filtered through filter paper, and the resulting solid was washed with water.

[0084] The carbon particles were analyzed before and after this oxidation treatment using a purge-and-trap gas chromatograph mass spectrometer (a combination of a JHS-100 thermal desorption device manufactured by Japan Analytical Industry Co., Ltd. and a GCMS QP-5050A gas chromatograph mass spectrometer manufactured by Shimadzu Corporation) to analyze the gas generated when heated to 300°C. It was found that the oxidation treatment had removed lipophilic aliphatic hydrocarbons such as nonane, decane, and 3-methyl-2-heptene, as well as lipophilic aromatic hydrocarbons such as xylene, which had been attached to the carbon particles.

[0085] [Example 1] <Silver strike plating> A Cu-Ni-Sn-P alloy plate (NB-109EH manufactured by DOWA Metaltech Co., Ltd.) measuring 5.0 cm in length, 5.0 cm in width, and 0.2 mm in thickness was prepared. The plate was used as the cathode and an iridium oxide mesh electrode plate, which was a titanium mesh material coated with iridium oxide, was used as the anode. The plate was then plated at a current density of 5 A / dm in a sulfonic acid-based silver strike plating solution (Dainsilver GPE-ST manufactured by Daiwa Kasei Co., Ltd., silver concentration 3 g / L, methanesulfonic acid concentration 42 g / L) containing methanesulfonic acid as a complexing agent at 25°C. 2 Electroplating (silver strike plating) was performed for 150 seconds. The silver strike plating was performed on the entire surface of the material. The thickness of the strike plating film was measured with a fluorescent X-ray film thickness meter (FT110A, manufactured by Hitachi High-Tech Science Corporation) and was found to be 0.20 μm.

[0086] <AgCめっき> The carbon particles (graphite particles) that had been subjected to the above oxidation treatment were added to a sulfonic acid-based silver plating solution containing methanesulfonic acid as a complexing agent, with a silver concentration of 30 g / L and a methanesulfonic acid concentration of 60 g / L (Dainsilver GPE-HB, manufactured by Daiwa Kasei Co., Ltd., using water and isopropanol as the solvent), to prepare a carbon particle-containing sulfonic acid-based silver plating solution containing 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.

[0087] Next, the silver strike-plated material was used as the cathode and the silver electrode plate as the anode, and the plating solution was stirred at 400 rpm with a stirrer at a temperature of 25°C and a current density of 3 A / dm 2 The material was electroplated at 1000 kJ / min for 210 seconds to obtain a laminated material in which a coating layer containing carbon particles in a silver layer (AgC composite layer) was formed on the material. The coating layer was formed on the entire surface of the material.

[0088] <Ultrasonic cleaning treatment> The surface of the coating layer of the obtained laminate was subjected to ultrasonic cleaning treatment at 28 kHz for 4 minutes using an ultrasonic cleaner (VS-100III manufactured by AS ONE, output 100 W, tank dimensions: length 140 mm x width 240 mm x depth 100 mm, liquid used: pure water, water temperature: 20°C).

[0089] <Plasma treatment> A plasma generator (Cresul Co., Ltd. Model 618-920 SP power supply, Capplas2007A electrode, capable of generating plasma with a width of 5.0 cm or more) was used to apply a voltage of 11.8 kV to the electrode at a frequency of 10 kHz, and glow discharge plasma was generated using a plasma gas consisting of a mixture of Ar flow rate of 3.0 L / min and O2 flow rate of 0.1 L / min. Plasma treatment was performed with a distance of 1 mm between the coating layer surface of the laminate and the tip of the electrode (where plasma is generated) and a scanning speed of 1 mm / s, forming an oxygen-containing silver-based coating layer from the coating layer.

[0090] During this process, the electrode was fixed and the laminate was moved, scanning the electrode once from one end of the laminate to the other, completing the plasma treatment. The electrode began scanning from a position not above the laminate and completely passed over the laminate. The plasma gas was sprayed downward from above the glow discharge area, and the oxygen in the plasma gas became radicals at the glow discharge area and was irradiated onto the surface of the coating layer directly below. In this way, a composite material was obtained in which an oxygen-containing silver-based coating layer was formed on the base material.

[0091] The amount of oxygen gas injected per unit area of ​​the material was 1.1 mL / cm, based on the flow rate of the plasma gas, the size of the electrode of the plasma generator, the dimensions of the laminated material, and the scanning speed. 2 It was calculated that: The composite material obtained in Example 1 was evaluated as follows.

[0092] <Thickness of oxygen-containing silver-based coating layer> The thickness of the oxygen-containing silver-based coating layer of the composite (a circular area with a diameter of 0.2 mm at the center of a 5.0 cm × 5.0 cm surface) was measured using a fluorescent X-ray film thickness meter (FT110A manufactured by Hitachi High-Tech Science Corporation) and was found to be 3.0 μm. Note that it is difficult to detect the C and O elements of carbon particles with a fluorescent X-ray film thickness meter, so the thickness was determined by detecting the Ag element, but in this example, the thickness determined in this manner is considered to be the thickness of the oxygen-containing silver-based coating layer.

[0093] <Amount of elements constituting the oxygen-containing silver-based coating layer> The surface of the oxygen-containing silver-based coating layer was observed using a tabletop electron microscope (Hitachi High-Technologies Corporation TM4000 Plus) at an accelerating voltage of 15 kV and 1000x magnification. This observation area (one field of view) was subjected to EDS analysis using an energy dispersive X-ray analyzer (Oxford Instruments AztecOne, analysis software AZtecOne 3.3 SP2) attached to the tabletop microscope. As a result, the elements O, Ag, and C were detected. When the total amount of the detected elements was taken as 100% by mass, the O content was 6.6% by mass, the Ag content was 86.5% by mass, and the C content was 6.9% by mass.

[0094] <Measurement of friction coefficient> The same Cu-Ni-Sn-P alloy plate material as used in Example 1 was subjected to an indentation process by extruding it into a hemispherical shape with an inner diameter of 1.0 mm, and the protruding surface of this alloy plate material (the surface that will be pressed against the plate test piece described below) was subjected to a plating process (AgSb plating) similar to that described in Comparative Example 2 below, to obtain an indentation test piece.

[0095] On the other hand, the plate-shaped composite material obtained in Example 1 was used as a plate test piece, and a sliding wear tester (CRS-G2050-DWA, manufactured by Yamazaki Seiki Kenkyusho Co., Ltd.) was used to test the indent test piece so that the protrusion of the indent test piece contacted the surface of the oxygen-containing silver-based coating layer of the plate test piece. The indent test piece was pressed against the plate test piece with a constant load (5 N) while sliding at a sliding speed of 0.4 mm / sec, and the sliding load was measured from the start of sliding to a sliding distance of 5 mm. The sliding load data from a sliding distance of 2 mm to 3 mm was then averaged to determine the friction coefficient (average sliding load F / 5N). The resulting friction coefficient was 0.11.

[0096] <Contact resistance measurement> The plate test piece and the indent test piece were placed in the sliding wear tester used to measure the friction coefficient, and the contact resistance was measured using the four-terminal method when the protrusion of the indent test piece was pressed against the oxygen-containing silver-based coating layer of the plate test piece with a constant load (5 N). The contact resistance was found to be 0.7 mΩ.

[0097] [Example 2] Using the same material as in Example 1 as the cathode and a Ni electrode plate as the anode, the plating was carried out in a nickel plating bath (aqueous solution) containing nickel sulfamate at a concentration of 342 g / L (Ni concentration of 80 g / L) and boric acid at a concentration of 45 g / L, at a liquid temperature of 55°C and a current density of 4 A / dm 2 Electroplating (Ni plating) was carried out for 135 seconds while stirring at 400°C to form a 1.0 μm thick Ni coating (Ni underlayer) on the material. The Ni coating was formed on the entire surface of the material.

[0098] A composite material was produced in the same manner as in Example 1, except that Ag strike plating was applied to a material with a Ni underlayer and the scanning speed of the electrodes of the plasma generator during plasma treatment was set to 5 mm / s.

[0099] The thickness of the oxygen-containing silver-based coating layer, the amount of constituent elements, the friction coefficient, and the contact resistance of the obtained composite material were evaluated in the same manner as in Example 1. The evaluation results are summarized in Table 1 below.

[0100] [Example 3] A composite material was produced in the same manner as in Example 1, except that the scanning speed of the electrodes of the plasma generating device in the plasma treatment was set to 10 mm / s.

[0101] The thickness of the oxygen-containing silver-based coating layer, the amount of constituent elements, the friction coefficient, and the contact resistance of the obtained composite material were evaluated in the same manner as in Example 1. The evaluation results are summarized in Table 1 below.

[0102] [Example 4] <Agストライクめっき> A material similar to that used in Example 1 was prepared, and this material was used as the cathode, and a titanium-platinum mesh electrode plate, which was made by plating a titanium mesh material with platinum, was used as the anode. The plating was carried out in a cyanide-based Ag strike plating solution containing a cyanide compound as a complexing agent (bath made from individual general reagents, silver cyanide concentration 3 g / L, potassium cyanide concentration 90 g / L, solvent water) at a current density of 5 A / dm 2 Electroplating (Ag strike plating) was carried out for 30 seconds.

[0103] <AgSbめっき> A cyanide-based Ag-Sb alloy plating solution (water solvent) containing a cyanide compound as a complexing agent, with a silver concentration of 60 g / L and an antimony (Sb) concentration of 2.5 g / L, was prepared. The cyanide-based Ag-Sb alloy plating solution contained 10% by mass of silver cyanide, 30% by mass of sodium cyanide, and Nissin Bright N (manufactured by Nissin Shinko Co., Ltd.), with the concentration of Nissin Bright N in the plating solution being 50 mL / L. Nissin Bright N also contained selenium dioxide and diantimony trioxide, with the selenium dioxide concentration being 0.01% by mass and the diantimony trioxide concentration being 6% by mass.

[0104] Next, using the Ag strike-plated material as the cathode and the silver electrode plate as the anode, the material was placed in the cyan-based Ag-Sb alloy plating solution at a temperature of 18°C ​​and a current density of 3 A / dm while stirring at 400 rpm with a stirrer. 2 Electroplating was performed for 530 seconds at 1000 kJ / cm2 for 530 seconds to form an Ag-Sb alloy plating layer (AgSb alloy layer) on the material, and then a composite material was obtained by performing a plasma treatment similar to that in Example 1. The thickness of the coating layer, the amount of constituent elements, and the friction coefficient of the obtained composite material were evaluated in the same manner as in Example 1. The evaluation results are summarized in Table 1 below.

[0105] [Example 5] <Silver strike plating> As in Example 1, electroplating (silver strike plating) was carried out on the material.

[0106] <Agめっき> A sulfonic acid-based silver plating solution containing methanesulfonic acid as a complexing agent, with a silver concentration of 30 g / L and a methanesulfonic acid concentration of 60 g / L (Dainsilver GPE-HB manufactured by Daiwa Kasei Co., Ltd., solvents of water and isopropanol) was prepared.

[0107] Next, using the silver strike-plated material as the cathode and the silver electrode plate as the anode, the material was immersed in the sulfonic acid-based silver plating solution at a temperature of 25°C and a current density of 3 A / dm while stirring at 400 rpm with a stirrer. 2 Electroplating was performed at 4000 kJ / min for 210 seconds to form a coating layer (Ag layer) on the material, and then a composite material was obtained by performing plasma treatment in the same manner as in Example 1. The thickness of the coating layer, the amount of constituent elements, the friction coefficient, and the contact resistance of the obtained composite material were evaluated in the same manner as in Example 1. The evaluation results are summarized in Table 1 below.

[0108] [Comparative Example 1] A composite material was produced in the same manner as in Example 1, except that plasma treatment was not performed. The thickness of the coating layer, the amount of constituent elements, the friction coefficient, and the contact resistance of the obtained composite material were measured and evaluated in the same manner as in Example 1. The evaluation results are summarized in Table 1 below.

[0109] Comparative Example 2 A composite material was produced in the same manner as in Example 4, except that plasma treatment was not performed. The resulting composite material was evaluated for the thickness of the coating layer, the amount of constituent elements, the friction coefficient, and the contact resistance, in the same manner as in Example 1. The evaluation results are summarized in Table 1 below.

[0110] Comparative Example 3 A composite material was produced in the same manner as in Example 5, except that plasma treatment was not performed. The resulting composite material was evaluated for the thickness of the coating layer, the amount of constituent elements, the friction coefficient, and the contact resistance, in the same manner as in Example 1. The evaluation results are summarized in Table 1 below.

[0111] The evaluation results and plasma treatment conditions of the above examples and comparative examples are summarized in Table 1 below. [Table 1]

Claims

1. A composite material for terminals, which are sliding contact parts, in which an oxygen-containing silver-based coating layer containing silver and having oxygen present near the surface is formed on a base material made of copper or a copper alloy.

2. The composite of claim 1 , wherein the oxygen-containing silver-based coating layer comprises carbon particles.

3. A composite material in which an oxygen-containing silver-based coating layer containing silver and carbon particles and having oxygen present near the surface is formed on a material made of copper or a copper alloy.

4. 4. The composite material according to claim 1, wherein an underlayer made of nickel is formed between the material and the oxygen-containing silver-based coating layer.

5. The composite material according to any one of claims 1 to 4, wherein when the surface of the oxygen-containing silver-based coating layer is analyzed by EDS, the amount of oxygen is 1 mass% or more relative to 100 mass% of the total amount of all detected elements.

6. When the surface of the oxygen-containing silver-based coating layer is analyzed by EDS, the total amount of silver, oxygen, carbon, antimony, and tin is 99% by mass or more relative to 100% by mass of the total amount of all detected elements, 6. The composite material according to claim 1, wherein the amount of oxygen is 1 part by mass or more when the total amount of silver, oxygen, carbon, antimony, and tin is 100 parts by mass.

7. 7. The composite material according to claim 6, wherein the total amount of silver and carbon is 88 parts by mass or more when the total amount of silver, oxygen, carbon, antimony, and tin is 100 parts by mass.

8. 8. The composite material according to claim 6, wherein the amount of oxygen is 1.1 to 12 parts by mass when the total amount of silver, oxygen, carbon, antimony, and tin is 100 parts by mass.

9. A terminal, which is a sliding contact part, is made of a composite material in which an oxygen-containing silver-based coating layer containing silver and having oxygen present near the surface is formed on a base material made of copper or a copper alloy.

10. The terminal of claim 9 , wherein the oxygen-containing silver-based coating layer comprises carbon particles.

11. A terminal made of a composite material in which an oxygen-containing silver-based coating layer containing silver and carbon particles and having oxygen present near the surface is formed on a material made of copper or a copper alloy.

12. The terminal according to any one of claims 9 to 11, wherein when the surface of the oxygen-containing silver-based coating layer is analyzed by EDS, the amount of oxygen is 1 mass% or more relative to 100 mass% of the total amount of all detected elements.

13. When the surface of the oxygen-containing silver-based coating layer is analyzed by EDS, the total amount of silver, oxygen, carbon, antimony, and tin is 99% by mass or more relative to 100% by mass of the total amount of all detected elements, The terminal according to any one of claims 9 to 12, wherein the amount of oxygen is 1 part by mass or more when the total amount of silver, oxygen, carbon, antimony and tin is 100 parts by mass.

14. A method for producing a composite material for a terminal, which is a sliding contact part, comprising the steps of: forming a silver-containing coating layer on a surface of a laminated material made of copper or a copper alloy; and subjecting the surface of the coating layer to plasma treatment in the presence of oxygen to form an oxygen-containing silver-based coating layer; The plasma gas used in the plasma treatment is a gas containing 1 to 20 volume % of oxygen and the remainder being a non-oxidizing element; The method for producing a composite material, wherein the amount of gas injected per unit area of ​​the material is 0.05 to 3 mL / cm 2 .

15. A method for producing a composite material, comprising: forming a coating layer containing silver and carbon particles on a base material made of copper or a copper alloy; and subjecting the surface of the coating layer to plasma treatment in the presence of oxygen to form an oxygen-containing silver-based coating layer, The plasma gas used in the plasma treatment is a gas containing 1 to 20 volume % of oxygen and the remainder being a non-oxidizing element; The method for producing a composite material, wherein the amount of gas injected per unit area of ​​the material is 0.05 to 3 mL / cm 2 .

16. A method for manufacturing a terminal, comprising molding the composite material according to any one of claims 1 to 8 into the shape of a terminal.

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