Method for manufacturing an oxide composite material, method for manufacturing a terminal, and terminal

Abstract

The material for sliding contact parts reduces the coefficient of friction while maintaining low contact resistance regardless of shape. [Solution] A method for producing an oxidized composite material, wherein a composite coating consisting of a silver layer containing carbon particles is formed on a base material, and the composite material is oxidized by contacting it with a nonmetallic oxidizing agent in a wet manner.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing an oxidized composite material, a method for manufacturing a terminal, and a terminal. [Background technology]

[0002] For example, terminals are used in sliding contact components such as switches and connectors. These terminals require conductivity, and copper (Cu) or copper alloys are used as the conductor material. Since copper is easily oxidized, silver (Ag) plating is applied to the conductor material to prevent oxidation (corrosion).

[0003] By applying silver plating to this conductor material, it is possible to manufacture terminals with excellent conductivity, oxidation resistance, and contact reliability (meaning that properties such as conductivity do not deteriorate easily even when heat is applied).

[0004] However, silver plating has a high coefficient of friction and is prone to peeling due to sliding. In particular, in recent years, the number of terminals has increased due to the multi-polarization of connectors, and with the increase in the number of terminals, the insertion force when mating terminals tends to increase. Therefore, silver plating materials are required to reduce the coefficient of friction and suppress the insertion force of terminals while maintaining low contact resistance.

[0005] In this regard, in order to further reduce the coefficient of friction of silver plating, a technique has been proposed in which carbon particles such as graphite or carbon black, which have excellent wear resistance and lubricity, are added to the silver plating solution (see, for example, Patent Documents 1 and 2). With this silver plating solution, a composite material can be formed in which carbon particles are dispersed in the silver matrix, thereby improving wear resistance. Furthermore, the plating method using the silver plating solution to which the carbon particles have been added is also called silver-carbon plating, and the plated material obtained by this plating method is also called silver-carbon plated material.

[0006] Another proposed technique involves adding a benzoic acid-based compound having a predetermined chemical structure to the silver plating solution along with carbon particles (see, for example, Patent Document 3). This compound can reduce the crystallite size of silver in the silver plating film containing carbon particles of the composite material, thereby increasing the hardness of the composite material.

[0007] Another proposed technique involves applying plasma treatment to silver-plated materials or silver-carbon-plated materials to oxidize their surfaces and reduce the coefficient of friction (see, for example, Patent Document 4).

[0008] Another proposed technique to improve the reflectivity of the silver film on the reflective surface of an LED involves oxidizing the silver film by heating it in an oxidizing gas atmosphere or by oxidizing it in an aqueous solution containing manganese peroxide or sodium hydroxide (see, for example, Patent Document 5). [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 9-7445 [Patent Document 2] Japanese Patent Publication No. 2007-16250 [Patent Document 3] International Publication No. 2021 / 261066 [Patent Document 4] Japanese Patent Publication No. 2023-7553 [Patent Document 5] International Publication No. 2011 / 145647 [Overview of the project] [Problems that the invention aims to solve]

[0010] As mentioned above, conventional silver-plated materials, which are conductive materials used in sliding contact parts and are silver-plated, have advantages such as excellent conductivity, but their coefficient of friction is relatively high, limiting their applications. If this coefficient of friction can be reduced and the insertion force reduced, it is expected that the range of applications will expand.

[0011] On the other hand, regarding composite materials that are silver-carbon plated, although the composite materials produced using the technologies described in Patent Documents 1 to 3 have a lower coefficient of friction than silver-plated materials, the reduction in the coefficient of friction is not sufficient.

[0012] Furthermore, while Patent Document 4 describes a method for reducing the coefficient of friction through plasma treatment compared to Patent Document 2, etc., it sometimes limits the shapes that can be treated. That is, in the case of plasma treatment, it is necessary to bring the electrode that emits the plasma and the material to be treated to within a certain distance. Therefore, if the material to be treated is flat, its surface can be treated uniformly, but if it has a complex shape such as a cylinder or pin, uneven treatment may occur.

[0013] Furthermore, while the wet oxidation treatment described in Patent Document 5 is inexpensive, easy to handle, and allows for uniform treatment of the plated film surface, it uses a metal-based oxidizing agent, which has strong oxidizing power. Therefore, applying the method described in Patent Document 5 for achieving the desired reflectivity in a silver film to a composite material would result in excessive oxidation, making it impossible to achieve the contact resistance required for the composite material.

[0014] Therefore, the present invention aims to provide a technology for materials used in sliding contact parts that reduces the coefficient of friction compared to conventional materials while maintaining low contact resistance, regardless of the shape of the material. [Means for solving the problem]

[0015] The inventors of the present invention have conducted intensive research to solve the above problems. In the plasma treatment disclosed in Patent Document 4, the shape of the material to be treated that can be uniformly oxidized is limited. Therefore, as an alternative method, attention was paid to wet treatment. According to wet treatment, regardless of the shape of the material to be treated, oxidation treatment can be uniformly applied to its surface, and treatment unevenness can be suppressed. And, it has been found that by using a non-metallic oxidant in the wet oxidation treatment, the silver carbon plating layer / silver plating layer of the material to be treated can be oxidized, and while maintaining a low contact resistance, its friction coefficient can be reduced.

[0016] That is, the present invention is as follows.

[0017] The first aspect of the present invention is A method for producing an oxidized composite material, comprising oxidizing a composite material formed by forming a composite film composed of a silver layer containing carbon particles on a material by bringing it into contact with a non-metallic oxidant in a wet state.

[0018] The second aspect of the present invention is, in the first aspect, The oxidation is carried out by immersing the composite material in water containing the non-metallic oxidant.

[0019] The third aspect of the present invention is, in the first or second aspect, The non-metallic oxidant is at least one selected from the group consisting of hydrogen peroxide and sulfuric acid.

[0020] The fourth aspect of the present invention is, in any one of the first to third aspects, The concentration of the non-metallic oxidant in the water is 3 to 40% by mass.

[0021] The fifth aspect of the present invention is, in any one of the first to fourth aspects, The oxidation is carried out at 20 to 60°C.

[0022] The sixth aspect of the present invention is, in any one of the first to fifth aspects, The material is made of copper or a copper alloy.

[0023] A seventh aspect of the present invention is, in any one of the first to sixth aspects, A base layer is formed between the material and the composite coating, consisting of at least one metal selected from the group consisting of copper, nickel, tin, and silver.

[0024] An eighth aspect of the present invention is, in any one of the first to seventh aspects, In the region of the composite film in the aforementioned oxidized composite material from the surface to a depth of 100 nm, the oxygen atom content was measured by X-ray photoelectron spectroscopy (XPS), and in the obtained oxygen content profile, the depth at which the amount of oxygen, when viewed from the surface side, first becomes half of the maximum value in the profile is 0.5 to 30 nm.

[0025] A ninth aspect of the present invention is, in any one of the first to eighth aspects, The composite material has at least one portion selected from the group consisting of bent portions, curved portions, convex portions, concave portions, and pore portions in the portion where the composite coating is formed.

[0026] A tenth aspect of the present invention is, in any one of the first to ninth aspects, The shape of the composite material is terminal-shaped.

[0027] An eleventh aspect of the present invention is, in the tenth aspect, A method for producing an oxidized composite material according to claim 9, wherein the composite material is obtained by either (1) or (2) below: (1) A laminated material having a composite coating consisting of a silver layer containing carbon particles formed on a base material is processed into a terminal shape. (2) The material is processed into a terminal shape, and the material is electroplated in a silver plating solution containing carbon particles to form a composite coating consisting of a silver layer containing carbon particles on the material.

[0028] A twelfth aspect of the present invention is, in the eleventh aspect, The aforementioned processing is at least one selected from the group consisting of bending, punching, extrusion, and cutting.

[0029] A thirteenth aspect of the present invention is, in the twelfth aspect, The shape of the laminated material in (1) and the raw material before processing in (2) is either a flat plate or a cylindrical shape.

[0030] A fourteenth aspect of the present invention is: This is a method for manufacturing terminals, which involves processing a silver-coated material, in which a silver layer is formed on a base material, into a terminal shape, and then oxidizing the processed silver-coated material by bringing it into contact with a non-metallic oxidizing agent in a wet manner.

[0031] A fifteenth aspect of the present invention is: A terminal made of a material in which at least the contact portion is covered with a composite coating consisting of a silver layer or a silver layer containing carbon particles, The terminal has at least one portion selected from the group consisting of a bent portion, a curved portion, a convex portion, a concave portion, and a hole portion in the portion where the silver layer or composite coating is formed. Oxygen is present near the surface of the silver layer or composite coating. A terminal is defined as one in which, when multiple points on the surface are analyzed using EDS, the value obtained by dividing the standard deviation of the amount of oxygen relative to 100 mass% of the total amount of all detected elements at each analysis point by the mean value is 0.5 or less.

[0032] A sixteenth aspect of the present invention is, in the fifteenth aspect, These are pin terminals, tab terminals, terminals with louvers, faston terminals, or bullet connectors.

[0033] A 17th aspect of the present invention is, in the 15th or 16th aspect, The oxygen atom content is measured by X-ray photoelectron spectroscopy (XPS) in the region from the surface of the silver layer or composite coating to a depth of 100 nm. In the obtained oxygen content profile, the depth at which the amount of oxygen, when viewed from the surface, first becomes half of the maximum value in the profile is 0.5 to 30 nm.

[0034] The 18th aspect of the present invention is, in any one of the 15th to 17th aspects, the entire surface of the material is coated with the silver layer or the composite coating.

Advantages of the Invention

[0035] According to the present invention, with respect to the material for sliding contact parts, regardless of its shape, it is possible to reduce the friction coefficient more than before while maintaining a low contact resistance.

Brief Description of the Drawings

[0036] [Figure 1] FIG. 1 is a diagram for explaining a sample for evaluating the uniformity of oxidation. (a) is a perspective view of the sample, (b) is a schematic view when the sample is viewed in plan, and (c) is a schematic view showing a cross section of the sample.

Modes for Carrying Out the Invention

[0037] Hereinafter, an embodiment of the present invention will be described. In this specification, the notation "n_{1}~n_{2}" indicating a numerical range means "n_{1} or more and n_{2} or less". Here, n_{1} and n_{2} are numerical values satisfying n_{1}<n_{2}.

[0038] [One Embodiment] Hereinafter, an embodiment of the present invention will be described.

[0039] [Method for Producing Oxidation Composite Material] The method for producing the oxidation composite material of this embodiment is to perform an oxidation treatment on a composite material formed by forming a composite coating composed of a silver layer containing carbon particles on a material by using a specific oxidant by a wet method. The oxidation composite material is configured to have a terminal shape that can be used for terminals in electrical contact parts that slide during use, particularly terminals such as connectors and switches. Hereinafter, the composite material, its manufacturing method, and the method for manufacturing the oxidation composite material from the composite material will be specifically described.

[0040] <<Composite material>> <Materials> The materials constituting the composite material are preferably those that can be silver-plated and possess 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), and Ti (titanium), and unavoidable impurities is preferred. The amount of Cu in the Cu alloy is preferably 85% by mass or more, more preferably 92% by mass or more (the amount of Cu is preferably 99.95% by mass or less).

[0041] In the case of so-called brass, which is a copper alloy 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.

[0042] <Composite coating> The composite coating is applied to the material. As described later, the composite coating can be formed by electroplating the material in a silver plating solution containing carbon particles. Specifically, the composite coating is composed of a silver layer containing carbon particles. The composite coating may be applied to a part of the material or to the entire surface.

[0043] The composite coating is formed, for example, using a silver plating solution containing carbon particles, so that the carbon particles are embedded in the silver matrix. Preferably, the carbon particles are dispersed substantially evenly in the composite coating. Due to the inclusion of carbon particles, the composite coating has a low coefficient of friction, excellent wear resistance, and excellent electrostatic properties.

[0044] While the amounts of silver and carbon in the composite coating are not particularly limited, from the viewpoint of friction coefficient and conductivity, it is preferable that the amount of silver be 75% to 95% and the amount of carbon be 3% to 20% relative to 100% of the total amount of all elements detected. More preferably, the amount of silver be 80% to 90% and the amount of carbon be 5% to 16%.

[0045] Furthermore, it is preferable that the composite coating substantially does not contain antimony (Sb) or cyanide compounds. As will be described later, by using a predetermined silver plating solution, the desired wear resistance and heat resistance can be obtained even without containing Sb or cyanide compounds in the composite coating. The respective contents are not particularly limited, but the Sb content in the composite coating is 1% by mass or less, and from the viewpoint of the heat resistance of the oxidized composite material, it is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and even more preferably 500 ppm or less. Also, the cyanide compound content in the composite coating is 1% by mass or less, preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and even more preferably 500 ppm or less.

[0046] The thickness of the composite coating is not particularly limited, but it is preferable to have a minimum thickness in terms of friction coefficient and conductivity. If the thickness is too large, the effect of the composite coating will saturate, and raw material costs will increase. From these viewpoints, the thickness of the composite coating is preferably 0.5 to 45 μm, more preferably 0.5 to 35 μm, and even more preferably 1 to 20 μm.

[0047] <Underlayer> Composite materials may have a base layer between the base material and the composite coating for various purposes. The base layer is formed to prevent the copper of the base material from diffusing and oxidizing on the plating surface, thereby degrading the heat resistance of the composite material, and to improve the adhesion of the composite coating. Examples of constituent metals of the base layer include Cu, Ni, Sn, and Ag. The base layer may consist of layers made of Cu, Ni, Sn, and Ag individually, or layers combining them (a laminated structure). The formation of the base layer may cover the entire surface of the base material or only a part of it, depending on the intended use of the composite material being manufactured.

[0048] <Ag strike plating layer> The composite material may include an Ag strike plating layer between the material and the composite coating for the purpose of enhancing the adhesion between the material and the composite coating. When forming the underlayer on the material, it is preferable to form the Ag strike plating layer on the underlayer. The Ag strike plating layer is formed as a very thin intermediate layer and may not be distinguishable from the composite coating. Note that the Ag strike plating layer may cover the entire surface layer of the material or a part thereof depending on the application of the produced oxidized composite material.

[0049] <Shape of the composite material> The composite material is subjected to the specific oxidation treatment defined in the present invention. Before that, it may be processed into a shape that can be used as a terminal for the final application, or it may be processed after the oxidation treatment (in this case, the shape of the composite material is, for example, a flat plate shape). Since the effects of the present invention can be preferably achieved and a large number of oxidized composite materials as terminals can be obtained in a batch form, it is preferable that the composite material is processed into the shape of the terminal before the oxidation treatment. Note that the composite material is obtained by forming a composite coating on the material as described later, but the material may be processed into the shape of the terminal. Preferably, the composite material is configured to have at least one processed portion such as a bent portion, a curved surface portion, a convex portion, a concave portion, or a hole portion at a location where the composite coating is formed on the material. This shape is not particularly limited, but the terminal shape may be, for example, a pin terminal, a tab terminal, a terminal with a louver, a fastener terminal, or a giboshi terminal.

[0050] <<Manufacturing method of the composite material>> Subsequently, the manufacturing method of the composite material described above will be explained. The composite material can be manufactured by any known method. For example, it can be manufactured by plating a material with a silver plating solution containing carbon particles. In the present embodiment, an example of manufacturing the composite material by performing a plating process on the material using a specific silver plating solution containing carbon particles will be described. Note that after plating, it is preferable to process it into the shape of the terminal, or the plating may be performed on the material processed into the shape of the terminal.

[0051] <Preparation process> First, prepare the materials.

[0052] The material is as described above for composite materials, and is silver-platable and electrically conductive. The shape of the material is not particularly limited, but a flat plate or cylindrical shape is preferred. The material may be processed into the desired terminal shape by the processing steps described later, or it may be processed after the composite coating has been formed.

[0053] <Plating Process> The silver plating solution used for silver-carbon plating should contain at least silver ions, compound A represented by the following general formula (1), and carbon particles. The silver plating solution may also contain complexing agents and other additives as needed. Each component will be described in detail below.

[0054] (Silver ions) The concentration of silver ions in the silver plating solution is not particularly limited, but from the viewpoint of the formation rate of the composite film and suppression of unevenness in the appearance of the composite film, it is preferably 5 to 150 g / L, more preferably 10 to 120 g / L, and most preferably 20 to 100 g / L.

[0055] (Compound A) Compound A is represented by the following general formula (I).

[0056] [ka] In formula (I), m is an integer from 1 to 5, Ra is a carboxyl group, Rb is an aldehyde group, a carboxyl group, an amino group, a hydroxyl group, or a sulfonic acid group, and Rc is hydrogen or any substituent. Ra and Rb may each be independently bonded to the benzene ring via a divalent group composed of at least one selected from the group consisting of -O- and -CH2-. Examples of the divalent group include -CH2-CH2-O-, -CH2-CH2-CH2-O-, and (-CH2-CH2-O-). nThese are some examples (where n is an integer greater than or equal to 2).

[0057] Compound A adsorbs onto the surface of precipitated silver, inhibiting silver crystal growth, thereby reducing the size of silver crystallites in the composite coating and improving the hardness of the silver layer. At the same time, it can maintain high heat resistance.

[0058] Furthermore, in the above general formula (I), when m is 2 or more, the multiple Rb groups may be the same or different from each other, and when m is 3 or less, the multiple Rc groups may be the same or different from each other. As for Rc, the "any substituent" mentioned above includes alkyl groups, alkylaryl groups, acetyl groups, nitro groups, halogen groups, and alkoxyl groups having 1 to 10 carbon atoms.

[0059] When the silver plating solution contains compound A, 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.

[0060] In addition to compound A, other compounds that can reduce the crystallite size of silver in the composite film formed by electroplating by adsorbing onto the surface of deposited silver and suppressing the growth of silver crystals, i.e., crystallite size growth inhibiting compounds, may also be used.

[0061] (Carbon particles) Carbon particles are incorporated into the silver matrix when a composite coating (silver plating film) is formed on the material by electroplating. The carbon particles can reduce the coefficient of friction of the composite coating and improve its wear resistance. From the viewpoint of further improving the wear resistance of the composite coating, graphite particles are preferable as the carbon particles.

[0062] While the particle size of the carbon particles is not particularly limited, from the viewpoint of making it easier to incorporate the carbon particles into the silver layer in the composite coating, the volume-based cumulative 50% particle size (D50) measured by a laser diffraction / scattering particle size distribution analyzer is preferably 0.5 to 15 μm, and more preferably 1 to 10 μm. Furthermore, while the shape of the carbon particles is not particularly limited, such as approximately spherical, flaky, or irregular, a flaky shape is preferred because it improves the wear resistance of the composite material by smoothing the surface of the composite coating.

[0063] From the viewpoint of suppressing aggregation and compounding of carbon particles in the silver plating solution, it is preferable that carbon particles be subjected to oxidation or basicization treatment. The surface of the carbon particles may be coated with lipophilic organic substances such as aliphatic hydrocarbons or aromatic hydrocarbons. Lipophilic organic substances can cause carbon particles to aggregate in the water-soluble silver plating solution and compound together. As a result, uniform dispersion of carbon particles in the composite film may be hindered. In this regard, by subjecting the carbon particles to oxidation treatment or the like, the carbon particles can be uniformly dispersed in the silver plating solution and uniformly dispersed in the composite film.

[0064] Furthermore, the amount of carbon particles in the silver plating solution is preferably 10 to 100 g / L, more preferably 15 to 90 g / L, and most preferably 20 to 70 g / L, considering the wear resistance of the composite material obtained by forming a composite film on a material using the silver plating solution, and the fact that there is a limit to the amount of carbon particles that can be introduced into the composite film.

[0065] (Complexing agent) The silver plating solution preferably contains a complexing agent. The complexing agent complexes the silver ions in the silver plating solution, increasing their ionic stability. This action increases the solubility of silver in the solvent that makes up the plating solution.

[0066] While complexing agents with the above-mentioned functions can be widely used, 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.

[0067] 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.

[0068] (Other additives) The silver plating solution may contain other additives as needed. Other additives may include, for example, brighteners, hardeners, and conductivity salts. Examples of 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 of group 4B or 5B of the periodic table (excluding antimony). Examples of conductivity salts include potassium hydroxide.

[0069] (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 in the silver plating solution, and its low environmental impact. Alternatively, a mixed solvent of water and alcohol may be used as the solvent.

[0070] (Antimony and cyanide compounds) Furthermore, it is preferable that the silver plating solution of this embodiment is substantially free of antimony (Sb). Specifically, the Sb content in the silver plating solution is 1 g / L or less, preferably 0.5 g / L or less, more preferably 0.1 g / L or less, and even more preferably 0.05 g / L or less. As described above, by including compound A and carbon particles in the silver plating solution, it is possible to reduce the crystallite size and improve wear resistance even without including Sb.

[0071] Furthermore, it is preferable that the silver plating solution mainly contains the above-mentioned components and substantially does not contain cyanide compounds. Specifically, the cyanide compound content in the silver plating solution is 1 mg / L or less. Cyanide compounds are compounds containing a cyano group (-CN), and cyanide compounds can be quantified according to JIS K0102:2019. Cyanide compounds are substances subject to the Water Pollution Control Law (wastewater standards) and the PRTR (Pollutant Release and Transfer Registration) system, resulting in high wastewater treatment costs. As described above, the silver plating solution used in this invention typically substantially does not contain cyanide compounds, so its wastewater treatment costs are low.

[0072] <Plating process> Next, the material is plated using the silver plating solution described above. This results in a composite material having a composite coating containing carbon particles on the material. The composite coating may be formed on a part of the material or on the entire surface of the material.

[0073] During the plating process, metallic silver is deposited on the material, and carbon particles are incorporated into the silver matrix, forming a composite film. Furthermore, if the silver plating solution contains compound A, its function keeps the size of the silver crystallites in the composite film small. Moreover, since the silver plating solution preferably contains substantially no Sb (content is 1 g / L or less), the resulting composite film also contains substantially no Sb (content is 1 mass% or less).

[0074] Here, we will explain the various conditions for electroplating in the plating process.

[0075] In the plating process, the material to be plated is used as the cathode, and a silver electrode plate, for example, which is dissolved to provide silver ions, is used as the anode.

[0076] 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 0.5 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, 1 to 8 A / dm 2 More preferably, 1.5~6A / dm 2 That is even more preferable.

[0077] The temperature of the plating bath (silver plating solution) when performing electroplating (plating temperature) is preferably 15 to 50°C, and more preferably 20 to 45°C, from the viewpoint of plating production efficiency and preventing excessive evaporation of the solution. The stirring speed of the plating bath at this time is preferably 200 to 550 rpm, and more preferably 350 to 500 rpm, from the viewpoint of performing uniform plating. The silver plating time (time for applying current) can be appropriately adjusted according to the desired thickness of the composite film, but is typically in the range of 25 to 1800 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.

[0078] The composite coating may be formed directly on the material, or it may be formed on the substrate by first forming a base layer on the material and then performing the electroplating described above. The method for forming the base layer is not particularly limited and can be formed by electroplating using a known method with a plating solution containing ions of the constituent metals. It is preferable that the plating solution substantially does not contain cyanide compounds from the viewpoint of wastewater treatment costs.

[0079] Furthermore, it is preferable to form a very thin intermediate layer by Ag strike plating before forming the composite film on the material to improve adhesion between the material and the composite film. If a base layer is formed on the material, it is preferable to perform Ag strike plating 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. The plating solution used for Ag strike plating is preferably substantially free of cyanide compounds from the viewpoint of wastewater treatment costs.

[0080] <<Processing process>> Next, the resulting composite material (a composite coating consisting of a silver layer containing carbon particles formed on the base material) is processed into a terminal shape. Through processing, the composite material is configured to have at least one processed portion, such as a bent portion, a curved portion, a convex portion, a concave portion, or a hole, where the composite coating is present. The processing method here can be appropriately selected according to the terminal shape, and conventionally known methods can be used. For example, it is preferable to use at least one of bending, punching, extrusion, and cutting. These processes may also be performed on the base material before the composite coating is formed.

[0081] <<Wet oxidation treatment process>> Next, the processed composite material is subjected to a wet oxidation treatment to obtain an oxidized composite material. Specifically, the processed composite material is brought into contact with water containing a specific oxidizing agent (hereinafter also referred to as the treatment solution) to oxidize the surface of the composite coating of the composite material. As a result, the composite coating is configured so that oxygen is present near its surface.

[0082] The treatment solution contains a non-metallic oxidizing agent and water. The non-metallic oxidizing agent is an oxidizing agent that does not contain metal as a constituent element. However, it may contain trace amounts of metal that are inevitably introduced during the manufacturing process. As the non-metallic oxidizing agent, it is preferable to use at least one of hydrogen peroxide and sulfuric acid. Metallic oxidizing agents have strong oxidizing power and can excessively oxidize the composite film, resulting in high contact resistance. Furthermore, when using a metallic oxidizing agent, there is a possibility that metal derived from the oxidizing agent may remain in the resulting oxidized composite material, causing adverse effects. On the other hand, with a non-metallic oxidizing agent, the composite film can be oxidized moderately, so the coefficient of friction can be reduced while maintaining low contact resistance. Moreover, non-metallic oxidizing agents do not leave metal residues in the oxidized composite material like metallic oxidizing agents do. Among non-metallic oxidizing agents, hydrogen peroxide is preferred from the viewpoint of wastewater treatment.

[0083] Conditions for wet oxidation treatment include the concentration of the oxidizing agent in the treatment solution, the temperature of the treatment solution, and the contact time (treatment time) between the composite material and the treatment solution. If the oxidizing power of the oxidizing agent in wet oxidation treatment is excessively high, it may become difficult to control the degree of oxidation of the composite material. If the surface of the composite material is excessively oxidized, the coefficient of friction can be reduced and wear resistance can be improved, but the amount of oxygen on the surface of the composite film may become excessively high, or the oxide layer may become excessively thick, which may increase contact resistance. On the other hand, if the oxidation of the surface of the composite film is insufficient, the coefficient of friction may not be sufficiently reduced. Therefore, from the viewpoint of improving wear resistance while maintaining low contact resistance, it is advisable to adjust the concentration of the non-metallic oxidizing agent, the temperature of the treatment solution, and the contact time in order to perform an appropriate amount of oxidation on the composite material. Preferably, each condition should be adjusted so that the amount of oxygen on the surface of the composite film or the thickness of the oxide layer falls within the range described later.

[0084] From the viewpoint of productivity and uniform treatment when oxidizing multiple composite materials simultaneously, specifically, the concentration of the oxidizing agent is preferably 3% to 40% by mass, and more preferably 5% to 35% by mass. The temperature of the treatment solution is preferably 20°C to 60°C, and more preferably 25°C to 50°C. The contact time can be appropriately adjusted according to the concentration of the oxidizing agent and the temperature of the treatment solution, for example, preferably 2 seconds to 300 seconds, and more preferably 2 seconds to 240 seconds.

[0085] The method of contact with the treatment solution is not particularly limited, but conventionally known methods such as spraying the treatment solution onto the composite material or immersing the composite material in the treatment solution can be employed. Among these, the immersion method is preferred from the viewpoint of oxidizing the surface of the composite material more uniformly.

[0086] As a result, an oxide composite material that can be used as a terminal can be obtained.

[0087] <Physical properties and characteristics of oxide composite materials> In the oxide composite material of the present invention manufactured as described above, oxygen is present near the surface of the composite film. In other words, an oxide layer is present. It is thought that oxygen chemically combines with silver on the surface of the composite film to form silver oxide, and that at least a portion of the surface of the composite film is composed of silver oxide. Generally, silver tends to adhere easily during sliding and has a high coefficient of friction, but it is presumed that silver oxide is less likely to adhere compared to silver and can reduce the coefficient of friction. Furthermore, because it is a wet oxidation treatment using a non-metallic oxidizing agent, excessive oxidation does not occur, and the contact resistance is kept low.

[0088] (Oxidized composite coating) In the oxide composite material of the present invention, as described above, an oxide layer containing silver oxide is formed on the surface of the composite film. The thickness of the oxide layer varies depending on the oxidation treatment conditions, but from the viewpoint of reducing the coefficient of friction, it is preferably 0.5 nm or more, more preferably 1 nm or more, and even more preferably 1.5 nm or more. On the other hand, if the oxide layer is excessively thick, not only will the surface of the oxide composite material become brittle, but the contact resistance may increase and the conductivity may decrease. From the viewpoint of friction coefficient, conductivity, and suppression of brittleness, the thickness of the oxide layer is preferably 30 nm or less. The thickness of the oxide layer can be determined by measuring the composite film by X-ray photoelectron spectroscopy (XPS), as shown in the examples described later. Specifically, the oxygen atom content up to 100 nm in the depth direction of the composite film is measured by the XPS method. With respect to the maximum value of oxygen content in the obtained profile, the region where the amount of oxygen becomes half of the maximum value in the profile when viewed from the surface side is considered to be the oxide layer.

[0089] Furthermore, oxygen near the surface of the composite coating (oxygen constituting the oxide layer) can also be detected and quantified using EDS (Energy Dispersive X-ray Spectrometer). The specific method of EDS will be explained in the examples below. From the viewpoint of reducing the coefficient of friction, when the surface of the composite coating is analyzed by EDS, the amount of oxygen is preferably 0.8 mass% or more relative to 100 mass% of the total amount of all detected elements. Also, if there is too much oxygen, the conductivity of the oxidized composite material may decrease. From the viewpoint of the coefficient of friction and conductivity, the amount of oxygen relative to the above 100 mass% is more preferably 1 mass% to 10.0 mass%, even more preferably 1.0 mass% to 7.5 mass%, and particularly preferably 2.8 mass% to 7.2 mass%. Also, when the surface of the composite coating is analyzed by EDS, the amount of silver is preferably 75 to 91 mass%, and the amount of carbon is preferably 7 to 20 mass%, relative to 100 mass% of the total amount of all detected elements.

[0090] (Coefficient of friction) The oxide composite material of this embodiment is configured such that the composite film contains carbon particles and oxygen near its surface, resulting in a low coefficient of friction and excellent wear resistance. Specifically, the coefficient of friction measured under the conditions described in the examples below is preferably 0.20 or less, more preferably 0.03 to 0.15, and even more preferably 0.05 to 0.10.

[0091] (Electrical resistance) The oxide composite material of this embodiment has excellent conductivity equivalent to that of conventional silver-carbon plated materials, and specifically, the contact resistance value measured by the method of the example described later is 7 mΩ or less, preferably 6 mΩ or less, and more preferably 0.05 to 2.8 mΩ.

[0092] [Terminals] The oxide composite material has a shape that can be used as a terminal. Preferably, the oxide composite material (terminal) is configured to have at least one processed part, such as a bent part, a curved part, a convex part, a concave part, or a hole, in the part where the composite coating is formed. Examples of terminals having such processed parts (shapes) are pin terminals, tab terminals, terminals with louvers, faston terminals, and bullet terminals. In the case of terminals with louvers, at least one of the louvers or the other part is made of oxide composite material.

[0093] Regarding the terminals, they typically consist of a set of male and female terminals (the louvers are usually components set inside the female terminal), and each has a connection part 1 (contact part) for physically and electrically connecting to the mating terminal and a connection part 2 (contact part) for connecting to external electronic components or wires. Connection parts 1 and 2 are typically made of a single oxide composite material. Note that at the location of connection part 2, a composite coating may not be formed, or a type of plating other than a composite coating may be applied, or the material may be exposed.

[0094] The male terminal connector 1 is typically formed in a rod shape (such as a pin or tab, or a cylindrical or polygonal prism shape) or a convex shape. The female terminal connector 1 has a housing part formed in a shape that accommodates the male terminal connector 1, and inside the housing part is a fixing part for fixing the mated male terminal connector 1 within the female terminal connector 1 and conducting electricity. Examples of the shape of the housing part include a cylindrical shape and a box-shaped (rectangular parallelepiped) shape. In this embodiment, by constructing both the male terminal and the female terminal from an oxidized composite material, high conductivity can be obtained while suppressing wear due to sliding.

[0095] The oxidized composite material preferably has a predetermined terminal shape, but by wet oxidizing the surface of the composite coating, even if the terminal has a complex shape with bends and other features, its surface can be uniformly oxidized. Therefore, the terminal of this embodiment has little variation in the amount of oxygen at multiple locations on the surface of the composite coating. Specifically, when multiple locations on the surface of the composite coating of the terminal are analyzed with EDS (energy dispersive X-ray spectrometer), the value obtained by dividing the standard deviation of the amount of oxygen relative to 100% by mass of the total amount of all detected elements at each analysis point by the mean value (so-called coefficient of variation) is 0.5 or less. This value is preferably 0.4 or less, more preferably 0.3 or less (usually it is 0.05 or more).

[0096] More specifically, the locations to be analyzed using EDS are as follows (see also Figure 1): The terminals are arranged horizontally, with the horizontal dimension being longer than the vertical dimension. Nine vertical lines are drawn on the plan view of the terminals, dividing them into 10 equal blocks of equal horizontal length. Two more lines are drawn parallel to these lines, passing through one end and the other end of the terminal, respectively. EDS analysis is performed on one or more arbitrary points on the terminal corresponding to each of the 11 lines mentioned above. In other words, EDS analysis is performed on a total of 11 or more points. If the amount of oxygen determined at an analysis point is less than 0.1 mass%, that point is considered untreated and EDS analysis is performed on other points.

[0097] Furthermore, when using plasma as an oxidation treatment for terminal-shaped composite materials, uniform oxidation can be achieved on surfaces perpendicular to the plasma irradiation direction, but not on areas perpendicular to the irradiation direction. In other words, variations occur in the amount of oxygen produced by oxidation in the composite coating, making it difficult to achieve low contact resistance and a low coefficient of friction.

[0098] Furthermore, the oxide layer, friction coefficient, and electrical resistance in the composite coating of the terminals are the same as those described above for oxide composite materials.

[0099] <Other Embodiments> Although embodiments of the present invention have been described above, the present invention is not limited in any way to the embodiments described above, and can be modified in various ways without departing from the spirit of the invention.

[0100] Furthermore, although the above-described embodiment described the case in which a composite film is formed using a silver plating solution containing carbon particles, instead of a composite film, a silver layer may be formed using a silver plating solution that does not contain carbon particles and used as a silver coating material. Conventional known silver plating solutions can be used without particular restriction, and in the case of the silver plating solution described in the manufacturing of the composite material, a plating solution without added carbon particles can also be used. In addition, the plating process, processing process and wet oxidation process may be performed on the material in that order, or the processing process may be performed on the material first, followed by the plating process and wet oxidation process.

[0101] In this way, a silver-plated terminal material (terminal) in the shape of a terminal made of a material coated with a silver layer is obtained, and a silver oxide plated material is obtained in which oxygen exists near the surface of the silver layer. The amount of oxygen near the surface of the silver layer is preferably 1% by mass or more relative to 100% by mass of the total amount of all elements detected when the surface of the silver layer is analyzed by EDS. If there is too much oxygen, the conductivity of the silver oxide plated material (terminal) may decrease. From the viewpoint of friction coefficient and conductivity, the amount of oxygen relative to the total 100% by mass is more preferably 1.1% by mass to 10% by mass, and even more preferably 1.2% by mass to 8% by mass. Furthermore, the amount of silver is preferably 90% by mass to 99% by mass, and more preferably 92% by mass to 98.9% by mass, relative to 100% by mass of the total amount of all elements detected.

[0102] Furthermore, while a silver layer in a silver oxide plating material that does not contain carbon particles tends to have a higher coefficient of friction compared to a composite coating containing carbon particles, in this embodiment, the coefficient of friction can be kept low by applying an oxidation treatment to the silver layer. The coefficient of friction of the silver layer that does not contain carbon particles is not particularly limited, but it is preferably 0.20 or more and 0.32 or less. In addition, the contact resistance value of the silver layer is low, similar to that of a composite coating containing carbon particles, for example, 7 mΩ or less, preferably 6 mΩ or less, and more preferably 0.05 to 2.8 mΩ.

[0103] Other physical properties and characteristics of the silver oxide plated material are the same as those of the oxide composite material described above. [Examples]

[0104] In this example, after fabricating the oxidized composite material, the evaluation described later was performed.

[0105] (1) Manufacturing of oxidized composite materials (Examples 1-12) First, the materials were prepared. In this example, a 0.2 mm thick Cu-Ni-Sn-P alloy plate was prepared (a copper alloy plate containing 1.0 mass% Ni, 0.9 mass% Sn, and 0.05 mass% P, with the remainder being Cu and unavoidable impurities) (NB109EH manufactured by DOWA Metaltech Co., Ltd.).

[0106] Next, the aforementioned material was subjected to Ag strike plating. Specifically, using this plate material as the base material, 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, plating was performed in a sulfonic acid-based silver strike plating solution containing methanesulfonic acid as a complexing agent at 25°C (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, antimony concentration 0.05 g / L or less) at a current density of 5 A / dm². 2 Electroplating (silver strike plating) was performed for 90 seconds. The silver strike plating was applied to the entire surface layer of the material.

[0107] Next, a plating solution was prepared. Specifically, a sulfonic acid-based silver plating solution (Dyne Silver GPE-HB manufactured by Yamato Kasei Co., Ltd., containing compound A corresponding to general formula (I), with a silver concentration of 30 g / L and a methanesulfonic acid concentration of 60 g / L) containing methanesulfonic acid as a complexing agent was prepared by adding carbon particles (graphite particles) that had undergone the following oxidation treatment. This resulted in 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. This silver plating solution is substantially free of Sb and cyanide compounds.

[0108] The oxidation treatment of the carbon particles was carried out as follows. First, 80 g of flake-shaped graphite particles (PAG-3000 manufactured by Nippon Graphite Industry 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-WET MT3000II Mode) manufactured by Microtrac-Bell Co., Ltd.), and the particle size at which the cumulative value based on volume reached 50% was measured. 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 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.

[0109] Analysis of the gas generated by heating carbon particles at 300°C using a purge-and-trap gas chromatograph-mass spectrometer (a system combining a JHS-100 thermal desorption unit manufactured by Nippon Analytical Industries Co., Ltd. and a GCMS QP-5050A gas chromatograph-mass spectrometer manufactured by Shimadzu Corporation) revealed that the above oxidation treatment removed lipophilic aliphatic hydrocarbons (such as nonane, decane, and 3-methyl-2-heptene) and lipophilic aromatic hydrocarbons (such as xylene) that were attached to the carbon particles.

[0110] Next, using the material with the Ag strike plating described above as the cathode and the silver electrode plate as the anode, the carbon particle-containing sulfonic acid-based silver plating solution was stirred at 400 rpm with a stirrer at a temperature of 25°C and a current density of 3 A / dm². 2 Electroplating (AgC plating) was performed for 300 seconds to obtain a composite material in which a composite film (AgC plated film) containing carbon particles in a silver layer was formed on the material. The composite film was formed on the entire surface layer of the material.

[0111] Next, the AgC plating film was ultrasonically cleaned in pure water at 28kHz for 240 seconds using an ultrasonic cleaner (USK-5 manufactured by AS ONE Corporation) to remove some of the carbon from the surface. After that, it was rinsed with pure water and dried with air blow.

[0112] Next, the composite material was subjected to wet oxidation treatment using a treatment solution containing an oxidizing agent. Specifically, the composite material was immersed (without stirring) in a treatment solution (aqueous solution) containing hydrogen peroxide as an oxidizing agent at a predetermined concentration to perform wet oxidation treatment. In Examples 1 to 12, the concentration of the oxidizing agent in the treatment solution, the temperature of the treatment solution, and the treatment time were appropriately changed, as shown in Table 1 below.

[0113] [Table 1]

[0114] Then, after wet oxidation treatment, the oxidized composite materials of Examples 1 to 12 were prepared by pure washing and drying with air blowing.

[0115] (Examples 13 and 14) In Examples 13 and 14, a silver-coated material was prepared in the same manner as in Example 1, except that a silver layer without carbon particles was formed instead of a composite coating containing carbon particles, and the wet oxidation treatment was appropriately modified. Specifically, a sulfonic acid-based silver plating solution (Dyne Silver GPE-HB, manufactured by Yamato Kasei Co., Ltd., with water and isopropanol as solvents) was prepared, containing methanesulfonic acid as a complexing agent, with a silver concentration of 30 g / L and a methanesulfonic acid concentration of 60 g / L. Subsequently, using a silver strike-plated material as the cathode and a silver electrode plate as the anode, the above sulfonic acid-based silver plating solution was prepared while stirring 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 300 seconds to form a coating layer (Ag layer) on the material. Then, the conditions for the wet oxidation treatment were appropriately changed as shown in Table 1 above to produce the silver-coated materials of Examples 13 and 14.

[0116] (Comparative Examples 1 and 2) In Comparative Examples 1 and 2, the composite materials were prepared using the same procedure as in Examples 1 and 13, except that a wet oxidation treatment was not performed.

[0117] (Comparative Example 3) In Comparative Example 3, an oxidized composite material was prepared using the same procedure as in Example 1, except that the treatment solution (aqueous solution) containing 50 g / L (5 mass%) of potassium permanganate and 40 g / L (4 mass%) of sodium hydroxide was used during the wet oxidation treatment, and the temperature of the treatment solution and the treatment time were appropriately changed as shown in Table 1.

[0118] (2) Evaluation For each of the fabricated oxide composites and composites, the thickness of the composite coating, the amount of elements constituting the composite coating, the thickness of the oxide layer, the coefficient of friction, the contact resistance, and the uniformity of oxidation were evaluated using the following methods.

[0119] (Thickness of composite coating) The thickness of the composite coating of the oxide 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 (FT110A manufactured by Hitachi High-Tech Science Co., Ltd.). Since detection of C and O elements is difficult with the X-ray fluorescence film thickness gauge, the Ag element was detected, and the thickness determined by this detection was defined as the thickness of the composite coating.

[0120] (element content) Using a desktop electron microscope (TM4000 Plus manufactured by Hitachi High-Technologies Corporation), the surface of the composite coating was observed at an acceleration voltage of 15kV and magnified 1000 times. EDS analysis was then performed on this observation area (1 field of view) using an energy-dispersive X-ray analyzer (AztecOne manufactured by Oxford Instruments Ltd., with analysis software AZtecOne 3.3 SP2) attached to the desktop microscope. This detected elements O, Ag, and C, and the content of each element was determined when the total amount of detected elements was set to 100 mass%.

[0121] (Thickness of the oxide layer) To determine the thickness of the oxide layer on the composite coating surface, the amount of oxygen (at%) relative to the total of all elements detected in the analysis area was measured using XPS (Versa Probe III, manufactured by ULVAC-PHI, Inc.) under the following conditions. • XPS measurement conditions X-ray source: Monochromatic AlKα X-ray output: 50 W Analysis area: 200 μmΦ Photoelectron extraction angle: 45° Pass energy: 140,000 eV · Sputtering conditions Inert gas species: Ar + Sputtering voltage: 1 kV Sputtering range: 2.5 × 2.5 (mm) Sputtering rate: 1 nm / min (SiO2 equivalent) In addition, the measurement of the oxygen amount by XPS was performed every time sputtering that could remove 0.1 nm in terms of SiO2 was carried out.

[0122] (Coefficient of friction) An indentation (extruded into a hemispherical shape) with an inner diameter of 1.0 mm was formed on the same Cu-Ni-Sn-P alloy plate material (raw material) used in Example 1 by extrusion processing into a hemispherical shape. After performing Ag strike plating on the protruding surface (the surface that is pressed against the following plate test piece) side of this alloy plate material in the same manner as above, using a cyanide-based Ag-Sb alloy plating solution (solvent is water) with a silver concentration of 60 g / L containing a cyanide compound as a complexing agent and an antimony (Sb) concentration of 2.5 g / L, using the Ag strike-plated material as the cathode and a silver electrode plate as the anode, in the above cyanide-based Ag-Sb alloy plating solution, while stirring at 400 rpm with a stirrer, at a temperature of 18 °C and a current density of 1.2 A / dm 2 Electroplating was carried out for 35 minutes to obtain a composite material (indentation test piece) on which a composite film (silver-antimony film) was formed on the raw material. The cyanide-based Ag-Sb alloy plating solution contains 10 mass% silver cyanide, 30 mass% sodium cyanide, and Nisshin Bright N (manufactured by Nisshin Kasei Co., Ltd.), and the concentration of Nisshin Bright N in the plating solution is 50 mL / L. And Nisshin Bright N contains a brightening agent and antimony trioxide, and the concentration of antimony trioxide in Nisshin Bright N is 6 mass%.

[0123] Using a plate-shaped oxide composite material as a plate test specimen, a sliding abrasion tester (CRS-G2050-DWA, manufactured by Yamazaki Seiki Kenkyusho Co., Ltd.) was used. The indent test specimen was pressed against the plate test specimen with a constant load (6N) while sliding at a sliding speed of 0.3 mm / second, with the convex portion of the indent test specimen in contact with the surface of the composite coating of the plate test specimen. The sliding load was measured from the start of sliding up to a sliding distance of 5 mm. The friction coefficient (average sliding load F / 6N) was then calculated by averaging the sliding load data between a sliding distance of 2 mm and 3 mm.

[0124] (contact resistance) Simultaneously with the measurement of the friction coefficient described above, the resistance value was measured from the start of sliding up to a sliding distance of 5 mm. Then, the sliding load data between a sliding distance of 2 mm and 3 mm was averaged to determine the resistance value.

[0125] (Homogeneity of oxidation) The uniformity of oxidation was assessed by measuring the oxygen content at multiple locations on the oxidized composite material processed into a terminal shape, and determining the coefficient of variation of the oxygen content from the average value and standard deviation. In this example, in order to evaluate the uniformity of oxidation, a round bar-shaped material with the same alloy composition as used in Example 1 was machined, and then silver strike plating, AgC plating, ultrasonic cleaning of the AgC plating film, and wet oxidation treatment were performed under the same conditions as in Example 7 to produce an evaluation sample 10 with the shape shown in Figure 1(a). The shape of the evaluation sample 10 is such that a rod-shaped projection 11 is formed on one end, and a cylindrical part 12 with a hollow section is formed on the other end opposite to the projection 11.

[0126] For the evaluation sample, multiple locations were selected from its external and internal surfaces, and the oxygen content at each location was measured. Specifically, the evaluation sample shown in Figure 1(a) was first placed horizontally, and a two-dimensional photograph of it was taken. Nine vertical lines (1) to (9) were drawn across the evaluation sample, dividing it into 10 equal blocks of the same horizontal length (Figure 1(b)). Furthermore, two lines (a) and (b) were drawn parallel to these lines, passing through one end and the other end of the evaluation sample. Then, EDS analysis was performed on one or more arbitrary points on the evaluation sample shown in Figure 1(b), corresponding to each of the 11 lines (1) to (9), (a), and (b), under the same conditions as when the "(elemental amount)" was determined. As a result, the oxygen content at 20 locations on the external surface of the evaluation sample was measured.

[0127] In addition, similar to the external surface of the evaluation sample, the oxygen content was measured at multiple locations on the internal surface of the hollow section. Specifically, as shown in Figure 1(c), a cross-sectional view of the evaluation sample along the axial direction was obtained, and a total of 11 straight lines (1) to (9), (a), and (b) were drawn in the same manner as above. Of these, EDS analysis was performed at any two points corresponding to the positions of each of the straight lines (1), (2), and (a) that correspond to the internal surface of the cylindrical section, under the same conditions as when the "(elemental amount)" was determined above. As a result, the oxygen content at six locations on the internal surface was measured.

[0128] As a result, the oxygen content was measured at a total of 26 points: 20 points on the outer surface of the evaluation sample and 6 points on the inner surface of the hollow section. Based on these oxygen content measurements, the coefficient of variation was calculated as shown in equation (1). In this example, a coefficient of variation of 0.5 or less was considered to indicate that the terminal surface had been uniformly oxidized. (Coefficient of variation) = (Standard deviation) / (Mean) ... (1)

[0129] (3) Evaluation results The evaluation results are shown in Table 1 above.

[0130] In Examples 1-14 and Comparative Examples 1-3, the thickness of the composite film and silver layer was confirmed to be 5.0 μm. Furthermore, in Examples 1-14 and Comparative Example 3, where oxidation treatment was performed, it was confirmed that the composite film and silver layer were oxidized near the surface and contained a predetermined amount of oxygen. On the other hand, in Comparative Examples 1 and 2, where no oxidation treatment was performed, it was confirmed that no oxygen was present on the surface of the composite film.

[0131] As shown in Table 1, it was observed that increasing the concentration of hydrogen peroxide in the treatment solution used for oxidation, increasing the temperature of the treatment solution, and extending the treatment time led to further oxidation of the surface of composite coatings, and consequently, a tendency for the oxygen content to increase. In Examples 1 to 14, the wet oxidation treatment was performed using a non-metallic oxidizing agent to prevent excessive oxidation, and it was confirmed that the friction coefficient could be kept low while also keeping the contact resistance low. Specifically, in Examples 1 to 12, in which carbon particles were contained in the composite coating, the friction coefficient was 0.25 or less and the contact resistance was 10 mΩ or less. In Examples 13 and 14, in which carbon particles were not contained in the composite coating, the friction coefficient was 0.32 or less and the contact resistance was 5 mΩ or less. On the other hand, in Comparative Examples 1 and 2, since no oxidation treatment was performed, the contact resistance could be kept low, but it was confirmed that the friction coefficient was higher compared to Examples 1 and 14.

[0132] Furthermore, when the thickness of the oxide layer formed on the surface of the composite film of the oxidized composite material of Example 7 was measured, it was confirmed to be 1.8 nm. Similarly, when the thickness of the oxide layer was measured for the other examples, it was confirmed to be within the range of 0.5 nm to 30 nm. On the other hand, in the oxidized composite material of Comparative Example 3, it was confirmed that the thickness of the oxide layer was 100 nm or more. This is thought to be because, in Comparative Example 3, the oxidation process was excessively advanced because potassium permanganate, a metal-based oxidizing agent, was used in the wet oxidation treatment. In both Example 7 and Comparative Example 3, the coefficient of friction was lowered by oxidizing the surface of the composite film, but in Comparative Example 3, the contact resistance value was significantly higher than in Example 7 because the oxide layer was excessively thick.

[0133] Furthermore, in Example 7, which involved wet oxidation treatment, it was confirmed that even terminals with complex shapes could be uniformly oxidized, demonstrating high oxidation uniformity. Specifically, in the terminals composed of the oxidized composite material in Example 7, the average oxygen content at all 26 locations was 2.1% by mass, with a standard deviation of 0.5. The coefficient of variation calculated from these values ​​was 0.2, which is lower than 0.5. In addition, in other examples where wet treatment was performed, the coefficient of variation was confirmed to be 0.5 or less, similar to Example 7.

[0134] In contrast, when plasma treatment is applied to the terminal, as in the technology described in Patent Document 4, the surface of the terminal cannot be uniformly oxidized, resulting in low oxidation uniformity. This is because, in the case of plasma treatment, oxidation can be uniformly applied to surfaces perpendicular to the direction of plasma irradiation, but not to surfaces or areas that are not in such a relationship. As a result, variations occur in the oxygen content on the surface of the formed composite coating, and the coefficient of variation calculated by equation (1) becomes high. Therefore, it is not possible to achieve the low coefficient of friction and contact resistance values ​​shown in the examples for complex-shaped terminals equipped with a composite coating using plasma treatment.

[0135] As described above, by applying a wet oxidation treatment to the composite material, the surface can be uniformly treated regardless of its shape. As a result, it was found that when used as a terminal, the coefficient of friction can be lowered while simultaneously lowering the contact resistance.

Claims

1. A method for producing an oxidized composite material, comprising oxidizing a composite material in which a composite film consisting of a silver layer containing carbon particles is formed on a base material by contacting it with a non-metallic oxidizing agent in a wet manner.

2. The oxidation is carried out by immersing the composite material in water containing the nonmetallic oxidizing agent. A method for producing an oxidized composite material according to claim 1.

3. The nonmetallic oxidizing agent is at least one selected from the group consisting of hydrogen peroxide and sulfuric acid. A method for producing an oxidized composite material according to claim 1 or 2.

4. The concentration of the nonmetallic oxidizing agent in the water is 3 to 40% by mass. A method for producing an oxidized composite material according to claim 2.

5. The oxidation is carried out at 20 to 60°C. A method for producing an oxidized composite material according to claim 1 or 2.

6. A method for producing an oxide composite material according to claim 1 or 2, wherein the material is made of copper or a copper alloy.

7. Between the material and the composite coating, a base layer is formed which is composed of at least one metal selected from the group consisting of copper, nickel, tin, and silver. A method for producing an oxidized composite material according to claim 1 or 2.

8. In the region of the composite film of the aforementioned oxidized composite material from the surface to a depth of 100 nm, the oxygen atom content is measured by X-ray photoelectron spectroscopy (XPS), and in the obtained oxygen content profile, the depth at which the amount of oxygen, when viewed from the surface side, first becomes half of the maximum value in the profile is 0.5 to 30 nm. A method for producing an oxidized composite material according to claim 1 or 2.

9. The method for manufacturing an oxidized composite material according to claim 1 or 2, wherein the composite material has at least one portion selected from the group consisting of a bent portion, a curved portion, a convex portion, a concave portion, and a pore portion in the portion where the composite coating is formed.

10. The method for manufacturing an oxide composite material according to claim 1 or 2, wherein the shape of the composite material is terminal-shaped.

11. The method for producing an oxidized composite material according to claim 10, wherein the composite material is obtained by either (1) or (2) below: (1) A laminated material, in which a composite coating consisting of a silver layer containing carbon particles is formed on a base material, is processed into a terminal shape. (2) The material is processed into a terminal shape, and the material is electroplated in a silver plating solution containing carbon particles to form a composite coating consisting of a silver layer containing carbon particles on the material.

12. The aforementioned processing is at least one selected from the group consisting of bending, punching, extrusion, and cutting. A method for producing an oxidized composite material according to claim 11.

13. The shape of the laminated material in (1) and the raw material before processing in (2) is a flat plate shape or a cylindrical shape. A method for producing an oxidized composite material according to claim 12.

14. A method for manufacturing terminals, comprising processing a silver-coated material, which has a silver layer formed on a base material, into a terminal shape, and then oxidizing the processed silver-coated material by contacting it with a non-metallic oxidizing agent in a wet manner.

15. A terminal made of a material in which at least the contact portion is covered with a composite coating consisting of a silver layer or a silver layer containing carbon particles, The terminal has at least one portion selected from the group consisting of a bent portion, a curved portion, a convex portion, a concave portion, and a hole portion in the portion where the silver layer or composite coating is formed. Oxygen is present near the surface of the silver layer or composite coating. A terminal in which, when multiple points on the surface are analyzed by EDS, the value obtained by dividing the standard deviation of the amount of oxygen relative to 100 mass% of the total amount of all elements detected at each analysis point by the mean value is 0.5 or less.

16. These are pin terminals, tab terminals, terminals with louvers, faston terminals, or bullet connectors. The terminal according to claim 15.

17. The oxygen atom content is measured by X-ray photoelectron spectroscopy (XPS) in the region from the surface of the silver layer or composite coating to a depth of 100 nm, and in the obtained oxygen content profile, the depth at which the amount of oxygen, when viewed from the surface side, first becomes half of the maximum value in the profile is 0.5 to 30 nm. The terminal according to claim 15.

18. The entire surface of the aforementioned material is covered with the silver layer or composite coating. A terminal according to any one of claims 15 to 17.

Images