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

Abstract

To provide a composite material excellent both in abrasion resistance and in bendability.SOLUTION: The composite material comprises a composite film constituted of a silver layer containing carbon particles and formed on a material, which composite film has Vickers hardness of not lower than 100, with the carbon particles being uniformly dispersed in the composite film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a composite material in which a predetermined composite coating 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 switches and connectors, and a manufacturing method thereof. [Background technology]

[0002] Conventionally, gold- or tin-plated conductive materials have been used for sliding electrical contact parts such as switches and connectors to prevent oxidation (corrosion) of conductive materials such as copper (Cu) and copper alloys caused by heating during the sliding process.

[0003] However, as automobiles become more electrified and autonomous, automotive switches and connectors are required to have higher reliability, such as higher wear resistance than ever before. Tin plating is prone to wear and oxidation, making it insufficient for reliability. While gold plating meets the required characteristics, it has the drawback of being very expensive.

[0004] Therefore, silver plating, which is less prone to oxidation and is cheaper than gold, is beginning to be used. However, silver plating is generally soft and easily wears away due to sliding, and silver particles adhere to each other, resulting in a high coefficient of friction.

[0005] To solve this problem, composite materials have been proposed in which a composite coating is formed on a base material by electroplating, with carbon particles such as graphite or carbon black, which have excellent heat resistance, wear resistance, and lubricity, dispersed in a silver matrix (see, for example, Patent Documents 1 and 2).

[0006] Another method for solving the above problem has been proposed: forming a first silver plating layer with a specific crystal orientation on a base material, and then forming a second silver plating layer containing antimony on the first silver plating layer (Patent Document 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-16250 [Patent Document 2] Japanese Patent Application Publication No. 9-7445 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-189680 Summary of the Invention [Problem to be solved by the invention]

[0008] Considering sliding, for example, when a protruding object slides on a plate, the various parts of the plate are subjected to a sliding force only when the protruding object is in contact with them, but the protruding object is constantly subjected to a sliding force. For this reason, plated materials used as protruding objects (e.g., female terminals) are required to have extremely high abrasion resistance, a requirement that cannot be met by the composite materials of Patent Documents 1 and 2. The silver-plated material of Patent Document 3 is very hard and has particularly excellent abrasion resistance, and can meet the above requirements.

[0009] There are two types of plating processes: "pre-plating," in which plated material is plated and then bent into the shape of various products (such as terminals), and "post-plating," in which plating is performed after bending. Pre-plating has been attracting attention in recent years from the perspective of product productivity.

[0010] When a pre-plating process is adopted, the silver-plated material of Patent Document 3 exhibits excellent abrasion resistance as described above, but because the plating layer is very hard, localized cracks occur in the plating layer when bending. Such localized cracks impose strong stress on the material directly below the broken portion of the plating layer, causing cracks in the material. If cracks occur in the material, when stress is applied to the terminal due to vibrations, for example, when a vehicle is running, stress tends to concentrate at the cracked portion (of the material), significantly increasing the risk of the terminal breaking at that portion. A material with excellent bending processability that is highly resistant to such situations is required.

[0011] Therefore, an object of the present invention is to provide a composite material that is excellent in both abrasion resistance and bending workability. [Means for solving the problem]

[0012] As a result of extensive research to solve the above problems, the inventors discovered that a composite material in which a hard composite coating made of a silver layer containing carbon particles, in which the carbon particles are uniformly dispersed, is formed on a base material, has excellent both wear resistance and bending workability, and have completed the present invention. That is, the present invention is as follows.

[0013] [1] A composite material in which a composite coating made of a silver layer containing carbon particles is formed on a base material, The composite coating has a Vickers hardness of 100 or more, The surface of the composite coating was ultrasonically cleaned at 28 kHz for 4 minutes, and then a microphotograph was taken. A rectangular area with a length to width ratio of 2:3 and a size of at least 75% of the area of ​​the image is taken from the obtained photographed image, and this area is divided into six squares of the same size, two vertically and three horizontally. Within each square, two vertical lines are drawn from the vertical side of the left side of the square at distances of one-third and two-thirds of the length of the horizontal side of the square, and two horizontal lines are drawn from the horizontal side of the top side of the square at distances of one-third and two-thirds of the length of the vertical side of the square, and the number of carbon particles present on each vertical and horizontal line is calculated, and the average number of carbon particles present on each line for each square is calculated. The CV value of the average values ​​A1 to A6 for each of the six squares is 0.6 or less, In each of the squares, of the total four lines, including the vertical and horizontal lines, there is one or less line on which the number of carbon particles present is zero. Composite material.

[0014] [2] The composite material according to [1], wherein the composite coating has a Vickers hardness of 120 to 250.

[0015] [3] The composite material according to [1] or [2], wherein the CV value of the average values ​​A1 to A6 is 0.01 to 0.5.

[0016] [4] The composite material according to any one of [1] to [3], wherein the average value B of the average values ​​A1 to A6 is 1.5 to 12.

[0017] [5] The composite material according to any one of [1] to [4], wherein the area ratio of carbon particles to the surface of the composite coating after the ultrasonic cleaning is 4 to 50%.

[0018] [6] A composite material according to any one of [1] to [5], wherein when the CV values ​​(CV1 to CV6) for the number of carbon particles present on each line in each of the six squares are calculated, the average value of CV1 to CV6 is 0.5 or less.

[0019] [7] A composite material according to any one of [1] to [6], wherein the surface of the composite coating is photographed by SEM at a magnification of 1000 times with a field of view of 80 to 100 μm in length and 120 to 140 μm in width, and a rectangular area of ​​78 μm in length and 117 μm in width is taken from the obtained SEM image, and this area is divided into six squares of 39 μm in length and 39 μm in width.

[0020] [8] The composite material according to any one of [1] to [7], wherein the thickness of the composite coating is 0.5 to 40 μm.

[0021] [9] The composite material according to any one of [1] to [8], wherein the carbon particles are flake-shaped graphite particles.

[0022]

[10] The composite material according to any one of [1] to [9], wherein the content of antimony in the composite coating is less than 0.5 mass %.

[0023]

[11] The composite material according to any one of [1] to

[10] , wherein the material is composed of copper or a copper alloy.

[0024]

[12] The composite material according to any one of [1] to

[11] , wherein the composite material has a flat plate shape.

[0025]

[13] A terminal using the composite material according to any one of [1] to

[12] as a constituent material.

[0026]

[14] A method for manufacturing a terminal, comprising a step of bending the composite material according to

[12] into a terminal shape.

[0027]

[15] A method for producing a composite material, comprising: forming a composite coating made of a silver layer containing carbon particles on a base material by electroplating in a silver plating solution containing carbon particles; the content of carbon particles in the silver plating solution is 15 g / L or more; A method for manufacturing a composite material, comprising forming a composite coating so that the composite coating has a Vickers hardness of 100 or more.

[0028]

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

[15] , wherein the silver plating solution contains a compound X represented by the following general formula (I): [ka] (In formula (I), m is an integer of 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, Rc is hydrogen or an arbitrary substituent, and when m is 2 or more, multiple Rb groups may be the same or different from each other, and when m is 3 or less, multiple Rc groups may be the same or different from each other, and Ra and Rb may each independently be bonded to a benzene ring via a divalent group consisting of at least one selected from the group consisting of -O- and -CH2-.)

[0029]

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

[15] or

[16] , wherein the carbon particles are graphite particles having a volume-based cumulative 50% particle diameter (D50) of 0.5 to 15 μm as measured by a laser diffraction / scattering particle size distribution analyzer. [Effects of the Invention]

[0030] According to the present invention, a composite material having excellent wear resistance and bending workability, and a method for producing the same are provided. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 is an image used to count the number of carbon particles on the surface of the composite coating of the composite material obtained in Example 1. [Figure 2] FIG. 2 is a schematic diagram illustrating the occurrence of cracks. [Figure 3] FIG. 3 is an image of the cross section of the apex of the bent portion of a test piece obtained by bending the composite material obtained in Example 1 in a bending test, observed with a laser microscope at a magnification of 200 times. [Figure 4] FIG. 4 is an image of the cross section of the apex of the bent portion of a test piece obtained by bending the composite material obtained in Comparative Example 1 in a bending test, observed with a laser microscope at a magnification of 200 times. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, an embodiment of the present invention will be described. [Composite material] The composite material of the present invention is formed by forming a composite coating made of a silver layer containing carbon particles on a base material, and has a Vickers hardness of 100 or more, and the dispersion state of the carbon particles within the composite coating satisfies specific conditions. Various configurations of such a composite material will be described below.

[0033] <<Material>> The constituent material of the substrate on which the composite coating is formed is preferably one that can be silver-plated and has the conductivity required for sliding contact parts such as switches and connectors. Furthermore, from a cost perspective, Cu (copper) and Cu alloys are preferred. From the viewpoint of achieving both electrical conductivity and wear resistance, the Cu alloy is preferably an alloy composed of Cu, at least one element 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 Cu content in the Cu alloy is preferably 85% by mass or more, more preferably 92% by mass or more (the Cu content is preferably 99.95% by mass or less).

[0034] As will be described later, the material is preferably used for terminals (as a composite material with a composite coating formed thereon), but the material itself may have a shape for such use, or the material may be in a flat shape (such as a flat plate) and formed into a composite material before being shaped into the shape for use. The latter is the pre-plating manufacturing process described in the section [Problem to be Solved by the Invention], and is preferable from the viewpoint of productivity of the final product.

[0035] <<Composite coating>> The composite coating formed on the substrate is composed of a silver layer containing carbon particles. In this silver layer, the carbon particles are dispersed in a silver matrix. When silver strike plating is performed before forming the composite coating on the substrate in the manufacture of a composite material, this strike plating layer exists between the substrate (or the base layer, described below) and the composite coating, but it is often so thin that it cannot be distinguished from the composite coating. The composite coating may be formed on the entire surface of the substrate, or on only a portion of the surface.

[0036] <Carbon particles> The carbon particles are particles consisting essentially of carbon and enhance the wear resistance and heat resistance of the composite material. From the viewpoint of exhibiting such functions, the carbon particles are preferably graphite particles.

[0037] From the viewpoint of the abrasion resistance of the composite material, the average primary particle diameter of the carbon particles is preferably 0.5 to 15 μm, more preferably 1 to 12 μm, and even more preferably 2.5 to 10 μm. The average primary particle diameter is the average value of the particle's major axis, and the major axis is the length of the longest line segment that can be drawn within a particle in an image (plane) of the carbon particles in the composite coating of the composite material observed at an appropriate magnification (this line segment does not have any portion that exists outside the particle). The major axis is determined for 50 or more particles. In the image, two or more carbon particles may adhere to each other and appear as one particle, making it difficult to accurately identify individual carbon particles. Therefore, a single mass surrounded by a silver matrix is ​​considered to be one carbon particle.

[0038] The shape of the carbon particles is not particularly limited and may be substantially spherical, flaky, or irregular, but flaky is preferred because it improves the abrasion resistance of the composite material by smoothing the surface of the composite coating.

[0039] <Vickers hardness> In an embodiment of the composite material of the present invention, the composite coating has a Vickers hardness of 100 or more. Because the composite coating is thus hard, the composite material has excellent abrasion resistance. From the viewpoint of abrasion resistance, the Vickers hardness of the composite coating is preferably 120 to 250, and more preferably 140 to 230.

[0040] <Dispersion state of carbon particles> The composite material according to the embodiment of the present invention can be obtained, for example, by the composite material manufacturing method according to the embodiment of the present invention described below, and the carbon particles are uniformly dispersed in the composite coating.

[0041] In the present invention, the degree of uniformity of dispersion of carbon particles is determined as follows. First, the surface of the composite coating is ultrasonically cleaned at 28 kHz for 4 minutes (using pure water at 20°C). This removes any carbon particles that are simply attached to the surface of the composite coating. These are thought to have no effect on wear resistance or bending workability, so these are first removed before evaluating the dispersion of the carbon particles in the composite coating.

[0042] After ultrasonic cleaning, a micrograph is taken at a magnification appropriate for the size of the carbon particles. For observing the dispersion state of carbon particles, it is desirable to photograph a rectangular field of view with a side length approximately 12 to 50 times the average primary particle diameter of the carbon particles. A rectangular area with a length:width ratio of 2:3 and a size of at least 75% of the area of ​​the image is taken from the obtained photograph. This area is then divided into six squares of the same size, two vertically and three horizontally. For example, if the average primary particle diameter of carbon particles is approximately 0.5 to 15 μm, an SEM photograph is taken at a magnification of 1000x with a field of view of 80 to 100 μm vertically and 120 to 140 μm horizontally. A rectangular area of ​​78 μm vertically x 117 μm vertically is taken from the obtained SEM image, and this area is then divided into six 39 μm x 39 μm squares, which makes it easy to observe the dispersion state of the carbon particles.

[0043] The number of carbon particles present in each of the six squares is then determined. Specifically, two vertical lines are drawn from the left vertical side of the square at distances of one-third and two-thirds of the horizontal length of the square, and two horizontal lines are drawn from the top horizontal side of the square at distances of one-third and two-thirds of the vertical length of the square. The number of carbon particles present on each vertical and horizontal line is determined (for reference, Figure 1 is an image used to determine the number of carbon particles to evaluate the dispersion state of carbon particles on the composite coating surface of the composite material obtained in Example 1, which will be described later). The average values ​​A1 to A6 of the number of carbon particles present on each line in each square are then calculated. The number of carbon particles on each line in each square and their average values ​​A1 to A6 serve as indicators of the number (quantity) of carbon particles present in each square.

[0044] When the composite coating is observed with an SEM, the areas where silver is present appear white, while the areas where carbon is present appear dark. This white and black shading is binarized to black and white to facilitate easy discrimination. A single black cluster in an SEM image may represent a single carbon particle, or it may represent two or more particles overlapping or adhering together, making it difficult to accurately determine how many particles there are. Therefore, as long as there are continuous black pixels on the vertical and horizontal lines within a square, the cluster is counted as one carbon particle. Even a single black pixel is counted as one particle. The number of pixels per line is one. The size of one pixel is adjusted so that the length of each line is approximately 350 to 450 pixels.

[0045] The number of carbon particles on each line was calculated as described above, and the average value per line was calculated for the six squares. The CV values ​​of the average values ​​A1 to A6 (CV A1-A6 = (standard deviation of average values ​​A1 to A6) / (average value B of average values ​​A1 to A6)). A1-A6 The smaller the value, the more uniformly the carbon particles are dispersed in the composite coating. A1-A6 is less than 0.6.

[0046] In addition, even if there are no carbon particles on any line in the six squares, CV A1-A6 However, in the present invention, in each square, among the total of four vertical and horizontal lines, there is one or less line on which the number of carbon particles present is zero, and a reasonable amount of carbon particles is present in the composite coating, and CV A1-A6 is small.

[0047] When bending an embodiment of the composite material of the present invention, the composite coating of the composite material is hard. However, when the composite material is hard, bending stress generally tends to concentrate locally. This can lead to large fractures in the composite coating where the stress is concentrated. As a result, stress also concentrates in the area of ​​the material directly below the fractured composite coating, causing cracks in the material. Regarding the location of stress, in the composite coating of the embodiment of the composite material of the present invention, stress is likely to be applied at the interface between the carbon particles and the silver matrix. Furthermore, because the carbon particles are uniformly dispersed in the composite coating, the interface exists throughout the entire composite coating, and bending stress is easily distributed throughout the entire composite coating. As a result, the areas where stress is applied in the material are also dispersed, making it very unlikely that cracks will occur. This allows the embodiment of the composite material of the present invention to achieve excellent bending workability.

[0048] From the viewpoint of excellent bending workability of composite materials, CV A1-A6 is preferably 0.5 or less, more preferably 0.4 or less, and even more preferably 0.3 or less. A1-A6 It is practically difficult to make CV zero. A1-A6 is usually 0.01 or more, preferably 0.03 or more.

[0049] (Average values ​​A1 to A6) As described above, the average values ​​A1 to A6 of the number of carbon particles on each line in each square are indicators of the number (quantity) of carbon particles present in each square. From the viewpoint of exerting the effects of the present invention (excellent wear resistance and bending workability), it is preferable that a certain number of carbon particles are present in the composite coating. Furthermore, the average primary particle diameter of the carbon particles is preferably within the above-mentioned range, and there is a certain limit to the number of carbon particles that can be present on each line. From these points of view, the average value B of the average values ​​A1 to A6 is preferably 1.2 to 25, and more preferably 1.5 to 12.

[0050] (Average of CV values ​​(CV1 to CV6) of the number of carbon particles on each line for each square) As described above, in the embodiment of the composite material of the present invention, the carbon particles are present in a certain amount in the composite coating, and then the CV A1-A6From the viewpoint of excellent bending workability due to uniformly dispersed carbon particles, CV A1-A6 It is also preferable that the CV values ​​(CV1 to CV6) of the number of carbon particles on each line in each square when calculating CV1 to CV6 are small. In this respect, and because it is practically difficult to achieve a CV value of 0, the average value of CV1 to CV6 is preferably 1.2 or less, more preferably 0.5 or less, and particularly preferably 0.05 to 0.35.

[0051] <Carbon area ratio> As described above, the composite coating in the embodiment of the composite material of the present invention contains carbon particles. The area ratio (area fraction) of the surface of this composite coating occupied by the carbon particles is an index of the abrasion resistance of the composite material, and from the viewpoint of the balance between abrasion resistance and electrical conductivity, it is preferably 1 to 80%, more preferably 1.5 to 80%, and even more preferably 4 to 50%. Note that this area fraction is measured on a composite coating that has been previously subjected to the above-mentioned ultrasonic treatment. Details of the method for measuring the area fraction will be explained in the examples.

[0052] <Total silver and carbon content> The elemental composition of the composite coating in the embodiment of the composite material of the present invention typically consists essentially of silver and carbon. Specifically, the total content of these elements in the composite coating is preferably 99% by mass or more, more preferably 99.5% by mass or more. When antimony, as described below, is contained, the total content of silver, carbon, and antimony in the composite coating is preferably 99% by mass or more, more preferably 99.5% by mass or more.

[0053] <Antimony> The composite coating in the embodiment of the composite material of the present invention may contain antimony. The inclusion of antimony makes it easier to increase the Vickers hardness of the composite coating, which contributes to excellent wear resistance of the composite material. When the composite coating contains antimony, the content of antimony in the composite coating is preferably 0.5 to 3 mass % from the viewpoint of the wear resistance of the composite material.

[0054] Since antimony can adversely affect the heat resistance of a composite material, when the composite material is used in applications where heat resistance is important, the antimony content in the composite coating is preferably less than 0.5 mass%, more preferably 0.1 mass% or less, and even more preferably 500 ppm or less. When a composite material is produced using a silver plating solution containing compound X represented by general formula (I) described below, a composite coating having a low antimony content and a Vickers hardness of 100 or more is formed.

[0055] <Thickness of composite coating> The thickness of the composite coating is not particularly limited, but it is preferable that there is a minimum thickness in terms of abrasion resistance and conductivity. Also, if the thickness is too large, the effect of the composite coating saturates and the raw material cost increases. From the above viewpoints, the thickness of the composite coating is preferably 0.5 to 40 μm, more preferably 0.5 to 35 μm, and even more preferably 3 to 20 μm. Details of the method for measuring the thickness of the composite coating will be explained in the examples.

[0056] <<Underlayer>> A base layer may be formed between the substrate and the composite coating for various purposes. Examples of constituent metals of the base layer include Cu, Ni, Sn, and Ag. For example, a base layer made of Ni is preferred to prevent copper from diffusing into the surface of the composite coating, thereby deteriorating heat resistance. When the substrate is a zinc-containing copper alloy such as brass, a base layer made of Cu is preferred to prevent zinc from diffusing into the surface of the composite coating. To improve adhesion of the composite coating to the substrate, a base layer made of Ag is preferred. The thickness of the base layer is not particularly limited, but from the standpoints of functionality and cost, a thickness of 0.1 to 8 μm is preferred, and a thickness of 0.2 to 5 μm is more preferred. Furthermore, terminals of electrical and electronic components often use materials that are Sn-plated or reflow-plated with a Cu or Ni base (a laminated structure of Cu, Ni, and Sn from the substrate side). Such a laminated base layer may also be formed in the present invention. Therefore, in the present invention, the composite coating may have a layer made of Cu, Ni, Sn, or Ag or a layer made of a combination of these (laminated structure) as the base. Also, different layers may be formed in different locations, for example, by forming the composite coating defined in the present invention on the electrical contact portion of the material (with or without forming a base layer) and forming a reflow Sn-plated base layer on the wire crimping portion (without forming a composite coating).

[0057] Terminal The composite material according to the embodiment of the present invention has excellent abrasion resistance and bending workability, and is therefore suitable as a constituent material for terminals, particularly terminals in electrical contact parts such as switches and connectors that are subjected to sliding during use.

[0058] In particular, due to the excellent bending workability of the composite material, it is preferable from the viewpoint of terminal productivity to manufacture a long, flat-plate-shaped embodiment of the composite material of the present invention in advance, punch it out with a press, and mold (bend) it into a terminal shape to manufacture a terminal.

[0059] [Manufacturing method for composite materials] The composite material of the present invention described above can be produced, for example, by the composite material production method of the present invention. An embodiment of the production method will be described below.

[0060] The manufacturing method is a method for manufacturing a composite material, in which a composite coating consisting of a silver layer containing carbon particles is formed on a base material by electroplating in a silver plating solution containing carbon particles, the carbon particle content in the silver plating solution being 15 g / L or more, and the composite coating is formed so that the Vickers hardness of the formed composite coating is 100 or more. Each configuration of an embodiment of this manufacturing method will be described below.

[0061] <<Material>> The material is the same as the material described in the embodiment of the composite material of the present invention. Specifically, Cu (copper) and Cu alloys are suitable as constituent materials of the material. From the viewpoint of achieving both electrical conductivity and wear resistance, the Cu alloy is preferably an alloy composed of Cu, at least one element 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 85% by mass or more, more preferably 92% by mass or more (the amount of Cu is preferably 99.95% by mass or less).

[0062] <<Electroplating>> In an embodiment of the method for manufacturing a composite material of the present invention, the above-described material is electroplated in a specific silver plating solution to form a composite coating containing carbon particles in a silver layer on the material.

[0063] <Silver plating solution> The silver plating solution contains silver ions and carbon particles, and the carbon particle content is 15 g / L or more.

[0064] (carbon particles) The carbon particles are the same as those described in the embodiment of the composite material of the present invention. If the silver plating solution contains carbon particles, the carbon particles are caught in the silver matrix when a composite coating (AgC plating film) is formed on a substrate by electroplating. This enhances the wear resistance of the composite material. From the viewpoint of exhibiting such functions, the carbon particles are preferably graphite particles. The shape of the carbon particles is not particularly limited, and may be substantially spherical, flaky, or irregular. However, flaky shapes are preferred because they can smooth the surface of the composite coating, thereby enhancing the wear resistance of the composite material.

[0065] Furthermore, the volume-based cumulative 50% particle size (D50) of the carbon particles, measured using a laser diffraction / scattering particle size distribution analyzer, is preferably 0.5 to 15 μm, more preferably 1 to 12 μm, and even more preferably 2.5 to 10 μm, from the viewpoint of ease of inclusion in the AgC plating film.

[0066] By using a silver plating solution containing carbon particles at a content of 15 g / L or more and forming a composite coating with a Vickers hardness of 100 or more, the carbon particles were uniformly dispersed (as in the above-mentioned CV A1-A6 From the viewpoint of forming a composite coating in which the carbon particles are uniformly dispersed, from the viewpoint of the abrasion resistance of the resulting composite material, and from the viewpoint of the fact that there is a limit to the amount of carbon particles that can be introduced into the composite coating, the content of carbon particles in the silver plating solution is preferably 18 to 100 g / L, and more preferably 30 to 90 g / L.

[0067] Furthermore, it is preferable to remove lipophilic organic substances adsorbed on the surface of the carbon particles by oxidizing the carbon particles. Examples of such lipophilic organic substances include aliphatic hydrocarbons such as alkanes and alkenes, and aromatic hydrocarbons such as alkylbenzenes. While wet oxidation and dry oxidation using O2 gas can be used for the oxidation of carbon particles, wet oxidation is preferred from the perspective of mass production, as wet oxidation allows for uniform treatment of carbon particles with large surface areas. Examples of wet oxidation methods include suspending carbon particles in water and then adding an appropriate amount of oxidizing agent. Examples of oxidizing agents that can be used include nitric acid, hydrogen peroxide, potassium permanganate, potassium persulfate, and sodium perchlorate. Lipophilic organic substances adhering to the carbon particles are oxidized by the added oxidizing agent to a water-soluble form, which is believed to be appropriately removed from the surface of the carbon particles. Furthermore, filtering and then washing the carbon particles after the wet oxidation can further enhance the effect of removing lipophilic organic substances from the surface of the carbon particles. Oxidation of carbon particles can remove lipophilic organic substances such as aliphatic and aromatic hydrocarbons from their surfaces. Analysis of heated gas at 300°C shows that the gas generated by heating the oxidized carbon particles at 300°C contains almost no lipophilic aliphatic hydrocarbons such as alkanes and alkenes, or lipophilic aromatic hydrocarbons such as alkylbenzenes. Even if the oxidized carbon particles contain a small amount of aliphatic or aromatic hydrocarbons, they can be uniformly dispersed in the silver plating solution used in this invention. However, it is preferable that the carbon particles contain no hydrocarbons with a molecular weight of 160 or more, and that the intensity of the gas generated by heating the carbon particles at 300°C (purge-and-trap gas chromatograph mass spectrometry intensity) of the hydrocarbons with a molecular weight of less than 160 is 5,000,000 or less. The D50 of the carbon particles remains essentially unchanged before and after oxidation.

[0068] (silver ions) The silver plating solution contains silver ions, and the silver concentration in the silver plating solution is preferably 5 to 150 g / L, more preferably 10 to 120 g / L, and even more preferably 20 to 100 g / L, from the viewpoints of the rate of formation of the composite coating and suppressing unevenness in the appearance of the composite coating.

[0069] (Compound X) In order to form a composite coating having a Vickers hardness of 100 or more, a silver plating solution containing a compound X represented by the following general formula (I) is effective. [ka]

[0070] In formula (I), m is an integer of 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, Rc is hydrogen or an arbitrary substituent, and Ra and Rb may each independently be bonded to the benzene ring via at least one divalent group selected from the group consisting of -O- and -CH2-. Examples of the divalent group include -CH2-CH2-O-, -CH2-CH2-CH2-O-, (-CH2-CH2-O-) n (n is an integer of 2 or more).

[0071] It is believed that Compound X adsorbs to the surface of deposited silver and inhibits the growth of silver crystals, thereby reducing the silver crystallite size in the composite coating formed by electroplating and forming a hard composite coating.

[0072] In the general formula (I), when m is 2 or greater, multiple Rb's may be the same or different from each other, and when m is 3 or less, multiple Rc's may be the same or different from each other. Examples of the "optional substituent" for Rc include an alkyl group having 1 to 10 carbon atoms, an alkylaryl group, an acetyl group, a nitro group, a halogen group, and an alkoxyl group having 1 to 10 carbon atoms.

[0073] The concentration of compound X in the silver plating solution is preferably 3 to 250 ml / L, more preferably 4 to 200 ml / L, from the viewpoints of suppressing uneven appearance of the composite coating and appropriately controlling the hardness (Vickers hardness) of the composite coating formed.

[0074] When the silver plating solution contains compound X, it is possible to form a composite coating having a Vickers hardness of 100 or more, even if the silver plating solution does not contain antimony (specifically, an antimony content of less than 0.5 g / L, preferably 0.1 g / L or less, more preferably 0.05 g / L or less), as described below. The composite material produced in this manner is suitable for applications where heat resistance is important.

[0075] (antimony) Silver plating solutions containing antimony are also effective in forming composite coatings with a Vickers hardness of 100 or more. When silver plating solutions contain antimony, a silver-antimony alloy is formed as the matrix of the composite coating (the part other than the carbon particles), and this alloy has a high Vickers hardness.

[0076] The concentration of antimony in the silver plating solution is preferably 0.5 to 5 g / L from the viewpoint of appropriately controlling the hardness of the composite coating.

[0077] (complexing agent) The silver plating solution used in the present invention preferably contains a complexing agent. The complexing agent complexes the silver ions in the silver plating solution, increasing their stability as ions. This action increases the solubility of silver in the solvent that constitutes the plating solution.

[0078] A wide variety of complexing agents having the above-mentioned functions can be used, but compounds having a sulfonic acid group are preferred from the viewpoint of the stability of the complex formed. Examples of compounds having a sulfonic acid group 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.

[0079] The amount of the complexing agent in the silver plating solution is preferably 30 to 200 g / L, more preferably 50 to 120 g / L, from the viewpoint of stabilizing silver ions.

[0080] (Other additives) The silver plating solution used in the present invention may contain other additives, such as brighteners, hardeners, and conductive 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 conductive salts include potassium hydroxide.

[0081] (solvent) The solvent constituting the silver plating solution is mainly water. Water is preferred because of its solubility in (complexed) silver ions and other components contained in the plating solution, and its low environmental impact. A mixed solvent of water and alcohol may also be used as the solvent.

[0082] (cyanide compounds) Cyanide compounds are widely used as additives in plating solutions, but they are subject to the Water Pollution Control Act (Effluent Standards) and the PRTR (Pollutant Release and Transfer Register) system, resulting in high wastewater treatment costs. When the silver plating solution used in the present invention contains the above-mentioned compound X, the composite material of the present invention can be produced even if the silver plating solution is substantially free of cyanide compounds (specifically, the content of cyanide compounds in the silver plating solution is 1 mg / L or less). This silver plating solution has the advantage of low wastewater treatment costs. Note that cyanide compounds are compounds containing a cyano group (-CN), and cyanide compounds can be quantified according to JIS K0102:2019.

[0083] <Electroplating conditions> Next, we will explain the conditions for electroplating using the silver plating solution described above. For example, by electroplating as described below, metallic silver (or a silver-antimony alloy) is deposited on a substrate, and carbon particles are caught in the silver matrix during this process, forming a composite coating.

[0084] (Cathode and Anode) The material to be electroplated is the cathode. The anode is the electrode that dissolves to provide silver ions, e.g., a silver electrode plate.

[0085] (current density) The cathode and anode are immersed in a silver plating solution (plating bath) and an electric current is passed through them to perform silver plating. The current density here is set to 0.5 to 10 A / dm from the viewpoints of the speed at which the composite coating is formed and the prevention of unevenness in the appearance of the composite coating. 2 is preferred, and 1 to 8 A / dm 2 is more preferable, 1.5 to 6 A / dm 2 is more preferred.

[0086] (Temperature, stirring, plating time, plating area) The temperature (plating temperature) of the plating bath (silver plating solution) during electroplating 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 silver plating solution. The stirring of the plating bath is preferably 200 to 550 rpm, more preferably 350 to 500 rpm, from the viewpoint of achieving uniform plating. The silver plating time (time during which current is applied) can be adjusted appropriately depending on the desired thickness of the composite coating, but is typically in the range of 25 to 1800 seconds. Furthermore, the area to be plated may be the entire surface of the material or only a portion of the surface, depending on the intended use of the composite material being manufactured.

[0087] (Silver strike plating) Before forming a composite coating on a base material, it is preferable to form a very thin intermediate layer by silver strike plating to improve adhesion between the base material and the composite coating. When a base layer, as described below, is formed on the base material, silver strike plating is performed on the base layer. As a method for performing silver strike plating, any conventionally known method can be used without particular limitation, as long as it does not impair the effects of the present invention. It is preferable that the plating solution used for silver strike plating be substantially free of cyanide compounds, in terms of wastewater treatment costs.

[0088] << Formation of base layer >> In an embodiment of the composite manufacturing method of the present invention, a base layer may be formed on the base material, and the base layer may then be electroplated to form the composite coating described above. The base layer is formed to prevent copper from the base material from diffusing to the plating surface and oxidizing, which could degrade 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 be a layer composed of Cu, Ni, Sn, or Ag, or a layer combining these (layer structure). The base layer may be formed on the entire surface of the base material, or only on a portion of it, depending on the application of the composite material to be manufactured.

[0089] The method for forming the underlayer is not particularly limited, and the underlayer can be formed by electroplating using a plating solution containing ions of the above-mentioned constituent metals by a known method. In view of wastewater treatment costs, the plating solution preferably does not substantially contain cyanide compounds. [Example]

[0090] Examples of the composite material and the method for producing the same according to the present invention will be described in detail below.

[0091] <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.

[0092] 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 by heating at 300°C. It was found that the oxidation treatment removed lipophilic aliphatic hydrocarbons (such as nonane, decane, and 3-methyl-2-heptene) and lipophilic aromatic hydrocarbons (such as xylene) that had adhered to the carbon particles.

[0093] [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. This plate was used as the cathode and an iridium oxide mesh electrode plate (a titanium mesh material coated with iridium oxide) was used as the anode. Plating was performed 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., substantially cyanide-free, with a silver concentration of 3 g / L, a methanesulfonic acid concentration of 42 g / L, and an antimony concentration of 0.05 g / L or less) containing methanesulfonic acid as a complexing agent at 25°C.2 The silver strike plating was performed on the entire surface of the material.

[0094] <AgCめっき> The carbon particles (graphite particles) that had been subjected to the oxidation treatment described above 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 (containing a compound corresponding to general formula (I), the solvent is mainly water, and the antimony content is 0.05 g / L or less) manufactured by Daiwa Kasei Co., Ltd.). This solution contained 50 g / L of carbon particles, 30 g / L of silver, and 60 g / L of methanesulfonic acid. This silver plating solution was substantially free of cyanide compounds.

[0095] 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 composite material was obtained by electroplating for 500 seconds with a silver layer containing carbon particles (AgC plating film). The composite film was formed on the entire surface of the material.

[0096] The manufacturing conditions for the above composite materials are summarized in Table 2 below, along with the manufacturing conditions for Examples 2 to 9 and Comparative Examples 1 to 4, which will be described later.

[0097] The composite material obtained in Example 1 was evaluated as follows. <Thickness of composite coating> The thickness of the composite coating (a circular area with a diameter of 0.2 mm in the center of a 5.0 cm × 5.0 cm surface) of the composite material was measured using a fluorescent X-ray thickness meter (FT110A manufactured by Hitachi High-Tech Science Corporation) and was found to be 10 μm. Note that it is difficult to detect C atoms (of carbon particles) with a fluorescent X-ray thickness meter, so the thickness was determined by detecting Ag atoms, but in the present invention, the thickness determined in this way is used as an approximation of the thickness of the composite coating.

[0098] <Vickers hardness Hv of composite coating surface> The Vickers hardness Hv of the composite coating surface was measured using a microhardness tester (Mitutoyo Corporation HM221) by applying a load of 0.01 N to a flat part of the composite for 15 seconds in accordance with JIS Z2244, and the average value of three measurements was used. The resulting Vickers hardness Hv was 180.

[0099] <Carbon area ratio of composite coating surface after ultrasonic cleaning treatment> The surface of the composite coating of the obtained composite material 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).

[0100] The carbon area ratio of the composite coating surface after ultrasonic cleaning treatment was measured as follows. The composite coating surface was observed using a tabletop microscope (Hitachi High-Tech TM4000 Plus) at an accelerating voltage of 5 kV and 1000x magnification. The backscattered electron composition (COMPO) image (one field of view) was binarized using GIMP 2.10.10 (image analysis software) to calculate the carbon area fraction of the composite coating surface. Specifically, the highest brightness of all pixels was set to 255, the lowest brightness to 0, and the gradation was binarized so that pixels with a brightness of 127 or less were black and pixels with a brightness of more than 127 were white. The image was separated into silver (white) and carbon particle (black) regions. The ratio Q / P, where Q is the number of carbon particle pixels in the image and P is the total number of pixels in the image, was calculated as the carbon area fraction (%) of the surface. The carbon area fraction after ultrasonic cleaning was 30%.

[0101] <Dispersion state of carbon particles on the composite coating surface after ultrasonic cleaning treatment> The dispersion state of the carbon particles in the composite coating in the composite material was evaluated as follows. A backscattered electron composition (COMPO) image (one field of view) of the surface of the composite coating of the composite material after ultrasonic cleaning was observed using a tabletop microscope (Hitachi High-Tech TM4000 Plus) at an accelerating voltage of 5 kV and a magnification of 1000 times, with a field of view of 90 μm vertical x 130 μm horizontal, and the image was binarized using GIMP 2.10.10 (image analysis software). Specifically, the highest brightness of all pixels was set to 255, and the lowest brightness was set to 0, so that pixels with a brightness of 127 or less were black and pixels with a brightness of more than 127 were white.

[0102] A rectangular area measuring 78 μm in height and 117 μm in width was taken in the center of the obtained binarized image (the size of this area was 78% of the entire field of view). This area was divided into six 39 μm by 39 μm squares. Within each square, two vertical lines were drawn at distances of 13 μm and 26 μm from the vertical side of the left side of the square, and two horizontal lines were drawn at distances of 13 μm and 26 μm from the horizontal side of the top side of the square. The number of carbon particles present on each vertical and horizontal line was calculated. A continuous black pixel on each vertical or horizontal line was counted as one carbon particle, and even a single black pixel was counted as one carbon particle. The image used to count the number of carbon particles is shown in Figure 1. Note that the vertical and horizontal lines are 1 pixel thick and 390 pixels long. Furthermore, although the outlines of the squares are shown thick in Figure 1 for convenience, the actual carbon particle count uses the same thickness as the vertical lines.

[0103] For reference, the count results of the number of carbon particles on each line in the square at the top left of FIG. 1 are shown in Table 1 below (all count results are shown in Table 3 below).

[0104] [Table 1]

[0105] From the results of counting the number of carbon particles, the average number of carbon particles present on each vertical and horizontal line for each square (A1 to A6) was calculated. The CV value (standard deviation of the average values ​​(A1 to A6) / average value B of the average values ​​(A1 to A6)) was calculated and found to be 0.19.

[0106] <Abrasion resistance evaluation> The same Cu-Ni-Sn-P alloy sheet material as used in Example 1 was subjected to a plating treatment (AgSb plating) similar to that described in Comparative Example 2 below, and flat test pieces measuring 2.0 cm wide x 3.0 cm long were cut out from the plated material.

[0107] On the other hand, a test piece measuring 1.0 cm wide x 4.0 cm long was cut out from the composite material obtained in Example 1 above, and an indentation process (extrusion into a hemispherical shape) with an inner diameter of 1.0 mm was performed on this piece to obtain an indented test piece (indenter).

[0108] Using a sliding wear tester (CRS-G2050-DWA manufactured by Yamazaki Seiki Kenkyusho Co., Ltd.), the indented specimen was pressed against the flat specimen with a constant load (2 N) while undergoing a reciprocating sliding motion (sliding distance 10 mm (i.e., 20 mm per reciprocating motion), sliding speed 3 mm / s). Wear resistance was evaluated by performing a wear test to confirm the wear state of the indented specimen and the flat specimen. After 100 reciprocating sliding motions, the center of the sliding marks on the indented specimen and the flat specimen was observed at 200x magnification using a microscope (VHX-1000 manufactured by Keyence Corporation). It was confirmed that the (brown) material (alloy plate material) was not exposed from either sliding mark. This indicated that the composite of Example 1 had excellent wear resistance.

[0109] <Evaluation of bending workability> (Maximum exposure width rating) The maximum exposed width when the composite coating of the obtained composite material was bent was evaluated as follows.

[0110] A 10 mm wide bending test piece was cut from the resulting composite material so that the longitudinal direction was TD (direction perpendicular to the rolling direction) and the width direction was LD (rolling direction), and a 90°W bending test was performed on the bending test piece in accordance with JIS H3130, with the LD as the bending axis (Bad Way bending (BW bending)) and a bending radius R of 0.2 mm. After this test, the surface of the apex of the bent part of the test piece was observed at 200x magnification using a laser microscope (Keyence VK-X160). Of the areas where the composite coating was divided by bending and the material was exposed, the length in the TD (direction perpendicular to the rolling direction) of the exposed part with the longest length in the TD direction was determined as the maximum exposed width.

[0111] As a result of the evaluation, the maximum exposed width of the composite material in Example 1 was 22 μm. If the maximum exposed width was 30 μm or less, the composite material was evaluated as having excellent bending workability. The reasons for this are as follows.

[0112] When the composite coating is stretched during bending, tensile stress acts on the material directly below the breaks, which makes it more likely that shear force will be applied to those parts of the material. Furthermore, because the composite coating adheres closely to the original material, the composite coating inevitably breaks when the material is plastically deformed by bending. The more breaks there are in the composite coating, the smaller the shear force acting on the material directly below each break. Therefore, while wrinkles (where the material has slipped and undergone shear deformation (but not fractured)) may occur in the material, cracks (where the material has slipped significantly and undergoes shear deformation to cause fractures) are unlikely to occur (see Figure 2 for details on wrinkles and cracks). As a result, the maximum exposed width observed is smaller. On the other hand, if the number of breaks in the composite coating is small, large stress is applied to specific parts of the material (the parts directly below the breaks), making the material more likely to crack. As a result, the maximum exposed width observed is larger. If cracks occur in the material, problems arise in that the shape of the product, such as a terminal, becomes abnormal or even breaks, causing the product to no longer function properly.

[0113] (Evaluation of bending cross section) For the composite material of this Example 1, the cross section of the apex of the bent portion of the bent test piece obtained in the bending test was observed at a magnification of 200 times using a laser microscope (VK-X160 manufactured by Keyence).

[0114] The cross-sectional photograph obtained is shown in Figure 3. It can be seen that many divisions have occurred in the composite coating, but no cracks have occurred in the material.

[0115] The above evaluation results (excluding the evaluation results of the bent cross section) are summarized in Table 2 below, along with the evaluation results of Examples 2 to 9 and Comparative Examples 1 to 4, which will be described later.

[0116] [Example 2] A composite material was prepared in the same manner as in Example 1, except that the carbon concentration in the carbon particle-containing sulfonic acid-based silver plating solution was changed to 20 g / L, and various evaluations were carried out.

[0117] [Example 3] A composite material was prepared in the same manner as in Example 1, except that the carbon concentration in the carbon particle-containing sulfonic acid-based silver plating solution was changed to 80 g / L, and various evaluations were carried out.

[0118] [Example 4] A composite material was prepared in the same manner as in Example 1, except that the AgC plating time was changed to 60 seconds, and various evaluations were carried out.

[0119] [Example 5] A composite material was prepared in the same manner as in Example 1, except that the AgC plating time was changed to 1500 seconds, and various evaluations were carried out.

[0120] [Example 6] Using the same material as in Example 1 as the cathode and a Ni electrode plate as the anode, plating was carried out in a nickel plating bath (aqueous solution) containing nickel sulfamate at a Ni concentration of 80 g / L and also containing boric acid at a concentration of 45 g / L, at a liquid temperature of 55°C and a current density of 4 A / dm 2Electroplating (Ni plating) was performed for 40 seconds while stirring at 50°C, forming a 0.2 μm thick Ni coating (Ni underlayer) on the material. The Ni underlayer was formed on the entire surface of the material. The thickness of the underlayer was measured using the same method as for determining the thickness of the composite coating.

[0121] A composite material was produced in the same manner as in Example 1, except that silver strike plating was performed on the material on which the Ni underlayer was formed, and various evaluations were carried out.

[0122] [Example 7] A composite material was prepared and evaluated in the same manner as in Example 6, except that the electroplating time for forming the Ni underlayer was changed to 600 seconds. The thickness of the Ni underlayer was 3.4 μm.

[0123] [Example 8] A composite material was prepared in the same manner as in Example 1, except that Dynesilver GPE-SB manufactured by Daiwa Kasei Co., Ltd. was used as the sulfonic acid-based silver plating solution, and the carbon particles (graphite particles) that had been subjected to the above-mentioned oxidation treatment were added to this to prepare a sulfonic acid-based silver plating solution containing carbon particles, and various evaluations were performed on the composite material.

[0124] [Example 9] A composite material was prepared in the same manner as in Example 4, except that UTC-48J (average particle size: 1.8 μm) manufactured by Nippon Graphite Co., Ltd. was used as the carbon particles and was oxidized in the same manner as above, and various evaluations were carried out.

[0125] [Comparative Example 1] A silver-plated product having a silver layer (Ag plating film) formed on a base material was obtained in the same manner as in Example 1, except that electroplating was performed using a sulfonic acid-based silver plating solution (Dynesilver GPE-HB manufactured by Daiwa Kasei Co., Ltd.) instead of the carbon particle-containing sulfonic acid-based silver plating solution. This silver-plated product was subjected to various evaluations in the same manner as in Example 1.

[0126] The silver-plated material of Comparative Example 1 was not evaluated for carbon particles. Because the evaluation of bending workability of this silver-plated material was poor, the abrasion resistance of the material was not evaluated by indenting (i.e., bending). The cross-section of a bent test piece obtained in the evaluation of bending workability of this plated material was observed in the same manner as in Example 1 (cross-sectional photograph), and the results are shown in Figure 4. The photograph is enlarged 200 times. The silver-plated layer was split, and these splits were fewer in number and wider than those in the composite coating of Example 1. Small cracks (indicated by arrows) that appear to be due to fractures were visible in the material.

[0127] Comparative Example 2 <Silver strike plating> A material similar to that in Example 1 was prepared, and this material was used as the cathode and a titanium platinum mesh electrode plate (platinized titanium mesh material) as the anode. The plating was carried out in a cyanide-based silver strike plating solution containing a cyanide compound as a complexing agent (prepared from a general reagent, silver cyanide concentration 3 g / L, potassium cyanide concentration 90 g / L, solvent water) at a solution temperature of 25°C and a current density of 5 A / dm 2 Electroplating (silver strike plating) was carried out at 1000 kJ / min for 30 seconds.

[0128] <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 a brightener and diantimony trioxide, with the concentration of diantimony trioxide in Nissin Bright N being 6% by mass.

[0129] Next, using the silver strike-plated material as the cathode and the silver electrode plate as the anode, the plating was carried out in the cyan-based Ag-Sb alloy plating solution at a temperature of 25°C and a current density of 3 A / dm while stirring at 400 rpm with a stirrer. 2The composite material was obtained by electroplating for 1000 seconds with a composite coating (silver-antimony coating) formed on the base material.

[0130] The obtained composite material was subjected to various evaluations in the same manner as in Example 1. Note that the carbon particles were not evaluated for the composite material of Comparative Example 2. Furthermore, since the evaluation result of the bending workability of this composite material was poor, the wear resistance of the composite material, which involves indentation (bending), was not evaluated.

[0131] Comparative Example 3 A composite material was prepared in the same manner as in Example 1, except that a sulfonic acid-based silver plating solution containing methanesulfonic acid at a concentration of 60 g / L as a complexing agent and having a silver concentration of 30 g / L (Dainsilver GPE-PL (containing no compound corresponding to general formula (I) and using water as the solvent) manufactured by Daiwa Kasei Co., Ltd.) was used instead of the sulfonic acid-based silver plating solution of Example 1, and carbon particles (graphite particles) that had been subjected to the same oxidation treatment as in Example 1 were added to the sulfonic acid-based silver plating solution containing the carbon particles. The composite material was then subjected to various evaluations in the same manner as in Example 1.

[0132] Comparative Example 4 A composite material was prepared in the same manner as in Example 1, except that the amount of carbon particles added to the sulfonic acid-based silver plating solution was changed so that the carbon concentration in the carbon particle-containing sulfonic acid-based silver plating solution was 10 g / L, and various evaluations were carried out. Note that the composite material of Comparative Example 4 showed poor evaluation results for bending workability, so the abrasion resistance of the composite material, which involves indentation (bending), was not evaluated.

[0133] The manufacturing conditions and evaluation results of the composite materials and silver-plated materials of Examples 1 to 9 and Comparative Examples 1 to 4 are summarized in Table 2. Furthermore, the count results of the number of carbon particles in each composite material are shown in Table 3.

[0134] [Table 2]

[0135] [Table 3]

Claims

1. A composite material in which a composite coating made of a silver layer containing carbon particles is formed on a base material, The composite coating has a Vickers hardness of 100 or more, The surface of the composite coating was ultrasonically cleaned at 28 kHz for 4 minutes, and then an SEM photograph was taken at a magnification of 1000 times with a field of view of 80 to 100 μm in length and 120 to 140 μm in width. A rectangular region of 78 μm in length and 117 μm in width was taken in the obtained SEM image, and this region was divided into six squares of 39 μm in length and 39 μm in width. Within each square, two vertical lines are drawn from the vertical side of the left side of the square at distances of one-third and two-thirds of the length of the horizontal side of the square, and two horizontal lines are drawn from the horizontal side of the top side of the square at distances of one-third and two-thirds of the length of the vertical side of the square, and the number of carbon particles present on each vertical line and horizontal line is calculated, and the average number of carbon particles present on each line for each square is calculated. The CV value of the average values ​​A1 to A6 for each of the six squares is 0.6 or less, A composite material in which, in each square, of the total four vertical and horizontal lines, there is one or less line on which the number of carbon particles present is zero.

2. The composite material of claim 1, wherein the composite coating has a Vickers hardness of 120 to 250.

3. The composite material according to claim 1 or 2, wherein the CV value of the average values ​​A1 to A6 is 0.01 to 0.

5.

4. The composite material according to any one of claims 1 to 3, wherein the average value B of the average values ​​A1 to A6 is 1.5 to 12.

5. 5. The composite material according to claim 1, wherein the area ratio of the carbon particles to the surface of the composite coating after the ultrasonic cleaning is 4 to 50%.

6. The composite material according to any one of claims 1 to 5, wherein when CV values ​​(CV1 to CV6) for the number of carbon particles present on each line in each of the six squares are calculated, the average value of CV1 to CV6 is 0.5 or less.

7. The composite material according to any one of claims 1 to 6, wherein the thickness of the composite coating is 0.5 to 40 µm.

8. 8. The composite material according to claim 1, wherein the carbon particles are flake-shaped graphite particles.

9. 9. The composite material according to claim 1, wherein the content of antimony in the composite coating is less than 0.5% by mass.

10. The composite material according to any one of claims 1 to 9, wherein the material is made of copper or a copper alloy.

11. The composite material according to any one of claims 1 to 10, wherein the composite material has a flat plate shape.

12. A terminal using the composite material according to any one of claims 1 to 11 as a constituent material thereof.

13. A method for manufacturing a terminal, comprising the step of bending the composite material according to claim 11 into a terminal shape.

14. A method for producing a composite material, comprising: forming a composite coating made of a silver layer containing carbon particles on a base material by electroplating in a silver plating solution containing carbon particles, The silver plating solution contains a compound X represented by the following general formula (I): the content of carbon particles in the silver plating solution is 15 g / L or more; A method for manufacturing a composite material, comprising forming a composite coating so that the composite coating has a Vickers hardness of 100 or more. 【Chemistry 1】 (In formula (I), m is an integer of 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 an arbitrary substituent, When m is 2 or more, a plurality of Rb's may be the same or different, When m is 3 or less, a plurality of Rc's may be the same or different from each other, Ra and Rb each independently represent —O— and —CH ２ - may be bonded to the benzene ring via a divalent group consisting of at least one selected from the group consisting of

15. The method for producing a composite material according to claim 14, wherein the carbon particles are graphite particles having a volume-based cumulative 50% particle diameter (D50) of 0.5 to 15 μm as measured with a laser diffraction / scattering particle size distribution analyzer.

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