JP2022068422A - Composite material, method of producing composite material, terminal, and method of producing terminal - Google Patents

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

The present invention relates to a composite material in which a predetermined composite coating is formed on a material and a method for manufacturing the same, and in particular, a composite material used as a material for sliding contact parts such as switches and connectors, and a method for manufacturing the same. Regarding.

Conventionally, as a material for sliding electrical contact parts such as switches and connectors, the conductor material is gold-plated in order to prevent oxidation (corrosion) of the conductor material such as copper (Cu) and copper alloy due to heating during the sliding process. And tin-plated plating materials are used.

However, with the progress of electrification and automatic driving of automobiles, for example, switches and connectors for automobiles are required to have higher reliability such as wear resistance than ever before. Since tin plating is easily worn and oxidizes, sufficient reliability cannot be obtained. Gold plating meets the required characteristics, but has the disadvantage of being extremely expensive.

Therefore, the application of silver plating, which is hard to oxidize and is cheaper than gold, has begun.
However, in general, silver plating has a problem that it is soft and easily worn by sliding, and silver plating has a high coefficient of friction because silver adheres to each other.

In order to solve this problem, a composite material in which carbon particles such as graphite and carbon black, which have excellent heat resistance, wear resistance and lubricity, are dispersed in a silver matrix is formed on the material by electroplating. Have been proposed (eg, Patent Documents 1 and 2).

As another solution to the above problem, a silver-plated material in which a first silver-plated layer having a specific crystal orientation is formed on the material and a second silver-plated layer containing antimony is formed on the silver-plated layer is also available. It has been proposed (Patent Document 3).

Japanese Unexamined Patent Publication No. 2007-16250 Japanese Unexamined Patent Publication No. 9-7445 Japanese Unexamined Patent Publication No. 2013-189680

Considering sliding, for example, when a protrusion slides on a plate, each part of the plate receives a force due to the sliding only when the protrusion is in contact, but the protrusion Is always under the force of sliding. Therefore, the plating material used as a protrusion (for example, a female terminal) is required to have extremely high wear resistance, and the composite material of Patent Documents 1 and 2 cannot satisfy this requirement. The silver-plated material of Patent Document 3 is very hard and has particularly excellent wear resistance, and can satisfy the above-mentioned requirements.

Here, as the plating process, "pre-plating", in which a plate-shaped material is plated and then bent into the shape of various products (for example, terminals), and "post-plating", in which the plate-shaped material is bent and then plated. There are two possibilities. From the viewpoint of product productivity, pre-plating has been attracting attention in recent years.

When the pre-plating process is adopted, the silver-plated material of Patent Document 3 exhibits excellent wear resistance as described above, but the plating layer is very hard, so that the plating layer is locally divided when bent. It will occur. Such local division applies strong stress to the portion of the material immediately below the divided portion of the plating layer, causing cracks in the material. When a crack occurs in the material, for example, when stress is applied to the terminal due to vibration during driving of a car, the stress tends to concentrate on the cracked part (of the material), and the risk of the terminal breaking at that part greatly increases. .. There is a demand for a material with excellent bending workability, in which such a situation is extremely unlikely to occur.

Therefore, an object of the present invention is to provide a composite material having excellent wear resistance and bending workability.

As a result of diligent studies to solve the above problems, the present inventors have made a hard composite film composed of a silver layer containing carbon particles, and the composite film in which carbon particles are uniformly dispersed in the composite film is formed on the material. We have found that the formed composite material is excellent in both wear resistance and bending workability, and have completed the present invention.
That is, the present invention is as follows.

[1] A composite material in which a composite film composed of a silver layer containing carbon particles is formed on the material.
The Vickers hardness of the composite film is 100 or more, and the composite film 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 micrograph was taken.
In the obtained captured image, a rectangular area having a size of 75% or more of the area of the image and a vertical: horizontal length ratio of 2: 3 is taken, and this area is vertically 2 with a square of the same size. Divide into a total of 6 pieces, 3 pieces on the side and 3 pieces on the side.
Within each square, the distance from the left vertical side of the square draws two vertical lines, one-third and two-thirds of the length of the horizontal side of the square, and the distance from the upper horizontal side of the square is Draw two horizontal lines, one-third and two-thirds of the length of the vertical side of the square, determine the number of carbon particles existing on each vertical line and horizontal line, and calculate the number of carbon particles existing on each line for each square. When calculating the average value of the number of
The CV values of the average values A1 to A6 for each of the six squares are 0.6 or less.
In each of the squares, out of a total of four lines of the vertical line and the horizontal line, one or less is a line in which the number of carbon particles existing on the line is 0.
Composite material.

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

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

[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.

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

[6] For the six squares, when the CV values (CV1 to CV6) for the number of carbon particles existing on each line in each square are obtained, the average value of CV1 to CV6 is 0.5 or less. , [1] to any one of [5].

[7] An SEM photograph of the surface of the composite coating was taken with a field of view of 80 to 100 μm in length × 120 to 140 μm in width at a magnification of 1000 times, and a rectangular area of 78 μm in length × 117 μm in width was taken in the obtained SEM image. , The composite material according to any one of [1] to [6], which divides this region into six sections of 39 μm × 39 μm.

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

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

[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% by mass.

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

[12] The composite material according to any one of [1] to [11], wherein the composite material has a flat plate shape.

[13] A terminal in which the composite material according to any one of [1] to [12] is used as a constituent material thereof.

[14] A method for manufacturing a terminal, comprising a step of bending the composite material according to [12] into a terminal shape.

[15] A method for producing a composite material, which forms a composite film composed of a silver layer containing carbon particles on a material by performing 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, and the content is 15 g / L or more.
A method for producing a composite material, wherein the composite film is formed so that the Vickers hardness of the composite film to be formed is 100 or more.

（式（Ｉ）において、ｍは１～５の整数であり、Ｒａは、カルボキシル基であり、Ｒｂは、アルデヒド基、カルボキシル基、アミノ基、水酸基又はスルホン酸基であり、Ｒｃは、水素又は任意の置換基であり、ｍが２以上の場合、複数存在するＲｂは互いに同一であっても異なっていてもよく、ｍが３以下の場合、複数存在するＲｃは互いに同一であっても異なっていてもよく、Ｒａ及びＲｂはそれぞれ独立に、－Ｏ－及び－ＣＨ_２－からなる群より選ばれる少なくとも一種で構成される２価の基を介してベンゼン環と結合していてもよい。）。 [16] The method for producing a composite material according to [15], wherein the silver plating solution contains the compound X represented by the following general formula (I).

(In the 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 a sulfonic acid group. It is an arbitrary substituent, and when m is 2 or more, a plurality of Rbs existing may be the same or different from each other, and when m is 3 or less, a plurality of Rc existing may be the same or different from each other. Ra and Rb may 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- . ).

[17] The carbon particles are graphite particles having a cumulative 50% particle diameter (D50) of 0.5 to 15 μm on a volume basis measured by a laser diffraction / scattering particle size distribution measuring device [15] or [16]. The method for producing a composite material according to.

INDUSTRIAL APPLICABILITY According to the present invention, a composite material having excellent wear resistance and bending workability, a method for producing the same, and the like are provided.

FIG. 1 is an image used for counting the number of carbon particles on the surface of the composite coating of the composite material obtained in Example 1. FIG. 2 is a schematic diagram illustrating the occurrence of cracks. FIG. 3 is an image of a test piece obtained by bending the composite material obtained in Example 1 in a bending test, in which the cross section of the apex of the bending portion is observed with a laser microscope at a magnification of 200 times. FIG. 4 is an image of a test piece obtained by bending the composite material obtained in Comparative Example 1 in a bending test, in which the cross section of the apex of the bending portion is observed with a laser microscope at a magnification of 200 times.

Hereinafter, embodiments of the present invention will be described.
[Composite material]
The composite material of the present invention has a composite film composed of a silver layer containing carbon particles formed on the material, has a Vickers hardness of 100 or more, and has specific conditions regarding the dispersed state of the carbon particles in the composite film. It is filled. Hereinafter, various configurations of such a composite material will be described.

<< Material >>
As the constituent material of the material for forming the composite film on it, a material that can be silver-plated and has the conductivity required for materials such as sliding contact parts such as switches and connectors is preferable, and further from the viewpoint of cost. Therefore, Cu (copper) and Cu alloy are suitable as constituent materials. The Cu alloy includes Cu, Si (silicon), Fe (iron), Mg (magnesium), P (phosphorus), Ni (nickel), and Sn (tin) from the viewpoint of achieving both conductivity and wear resistance. ), Co (cobalt), Zn (zinc), Be (berylium), Pb (lead), Te (tellu), Ag (silver), Zr (zirconium), Cr (chromium), Al (aluminum) and Ti (titanium). ), And an alloy composed of at least one selected from the group consisting of unavoidable impurities is preferable. 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).

The material is preferably used for terminal applications (as a composite material on which a composite film is formed) as described below, but the material itself may have a shape for that purpose, and the material may have a flat shape (flat plate shape). Etc.), it may be molded into the desired shape after being made into a composite material. The latter is the pre-plating manufacturing process described in the section [Problems to be Solved by the Invention], and is suitable from the viewpoint of the productivity of the final product.

<< Composite film >>
The composite film formed on the material is composed of a silver layer containing carbon particles. In this silver layer, carbon particles are dispersed in a matrix made of silver. When silver strike plating is performed before forming a composite film on the material in the production of the composite material, an intermediate layer by this strike plating exists between the material (or the base layer described later) and the composite film. , Very thin and often indistinguishable from composite coatings. Further, the composite film may be formed on the entire surface layer of the material, or may be formed on a part of the surface layer.

<Carbon particles>
The carbon particles are particles substantially composed of only carbon, and enhance the wear resistance and heat resistance of the composite material. From the viewpoint of exhibiting such a function, the carbon particles are preferably graphite particles.

The average primary particle diameter of the carbon particles is preferably 0.5 to 15 μm, more preferably 1 to 12 μm, and more preferably 2.5 to 10 μm from the viewpoint of wear resistance of the composite material. More preferred. The average primary particle diameter is the average value of the major axis of the particles, and the major axis is the amount of the carbon particles in the composite coating of the composite material drawn into the particles in the image (plane) observed at an appropriate observation magnification. The length of the longest possible line segment (the line segment has no part existing outside the particle). The major axis is determined for 50 or more particles. In the image, two or more carbon particles adhere to each other may appear as one, and it is difficult to accurately discriminate one carbon particle. Therefore, one lump framed by the silver matrix is regarded as one carbon particle.

The shape of the carbon particles is not particularly limited, such as substantially spherical, scaly, and amorphous, but the scaly shape is preferable because the wear resistance of the composite material can be enhanced by smoothing the surface of the composite coating.

<Vickers hardness>
The Vickers hardness of the composite coating in the embodiment of the composite material of the present invention is 100 or more. Due to the hardness of the composite coating, the composite material has excellent wear resistance. From the viewpoint of wear resistance, the Vickers hardness of the composite film is preferably 120 to 250, more preferably 140 to 230.

<Dispersion state of carbon particles>
An embodiment of the composite material of the present invention is obtained by, for example, an embodiment of the method for producing a composite material of the present invention described later, and carbon particles are uniformly dispersed in the composite coating film.

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 (the liquid used is pure water and the temperature is 20 ° C.). As a result, carbon particles that are simply attached to the surface of the composite coating are removed. Since it is considered that these do not function in terms of wear resistance and bending workability, they are first removed, and then the dispersed state of carbon particles in the composite coating is evaluated.

After ultrasonic cleaning, take a photomicrograph at an appropriate magnification according to the size of the carbon particles. It is desirable that the size of the field to be photographed is a rectangle having a side length of about 12 to 50 times the average primary particle diameter of the carbon particles when observing the dispersed state of the carbon particles. In the obtained captured image, a rectangular area having a size of 75% or more of the area of the image and a vertical: horizontal length ratio of 2: 3 is taken, and this area is vertically 2 with a square of the same size. Divide into a total of 6 pieces, 3 pieces on the side and 3 pieces on the side. As an example, when the average primary particle diameter of the carbon particles is about 0.5 to 15 μm, an SEM photograph was taken with a magnification of 1000 times and a field of 80 to 100 μm in length × 120 to 140 μm in width, and obtained. When a rectangular region of 78 μm × 117 μm in length is taken in the SEM image and this region is divided into six squares of 39 μm × 39 μm, it is easy to observe the dispersed state of carbon particles.

Then, the amount (number) of carbon particles present in each of these six squares is calculated. Specifically, the distance from the left vertical side of the square draws two vertical lines, one-third and two-thirds of the length of the horizontal side of the square, and the distance from the upper horizontal side of the square is Draw two horizontal lines, one-third and two-thirds of the length of the vertical side of the square, and determine the number of carbon particles present on each vertical line and horizontal line (for reference, FIG. 1 will be described later). This is an image used to determine the number of carbon particles in order to evaluate the dispersed state of carbon particles on the surface of the composite coating of the composite material obtained in Example 1), and the number of carbon particles present on each line for each square. The average value of A1 to A6 is obtained. The number of carbon particles on each line in each square and their average values A1 to A6 are indicators of the number (amount) of carbon particles existing in each square.

Here, when the composite film is observed by SEM, the portion where silver is present is a white color, and the portion where carbon is present is a blackish color. In this way, the state where there are shades of white and black is binarized into black and white to facilitate distinction. And, one black group in the SEM image may be one carbon particle, or two or more overlapping or adhering ones may be seen as one, and how many are actually It is difficult to accurately determine the presence. Therefore, as long as the black pixels continue on the vertical and horizontal lines in the square, the group is counted as one carbon particle. Even one pixel of black is counted as one. The number of pixels of the thickness of one line is one pixel. Also, adjust the size of one pixel so that the length of one line is about 350 to 450 pixels.

As described above, the number of carbon particles on each line is obtained, the average value per line is obtained for the above six squares, and the CV values of the average values A1 to A6 (CV _A1-A6 = (mean value A1 to)). (Standard deviation of A6) / (mean value B of mean values A1 to A6)) is obtained. The smaller the CV _A1-A6 , the more uniformly the carbon particles are dispersed in the composite film, and in the embodiment of the composite material of the present invention, the CV _A1-A6 is 0.6 or less.

Even if the number of carbon particles on all the lines is 0 in the 6 squares, the CV _A1-A6 becomes small, but in the present invention, in each square, a total of 4 lines of the vertical line and the horizontal line are formed. Among them, the number of carbon particles existing on the wire is 0 or less, and the number of carbon particles is appropriate in the composite coating, and CV _A1-A6 is small.

When the embodiment of the composite material of the present invention is bent, the composite coating of the composite material is hard, but if it is hard, stress due to bending is generally likely to be locally concentrated. Then, a large composite film can be divided where the stress is concentrated. As a result, stress is concentrated on the portion of the material immediately below the divided composite film, causing cracks in the material. With respect to the stressed portion, in the composite coating according to the embodiment of the composite material of the present invention, stress is likely to be applied to the interface between the carbon particles and the silver matrix. Since the carbon particles are uniformly dispersed in the composite film, the interface exists over the entire composite film, and the stress due to bending is easily dispersed in the entire composite film. As a result, the stressed part of the material is also dispersed and cracking of the material is very unlikely to occur. As a result, the embodiment of the composite material of the present invention achieves excellent bending workability.

From the viewpoint of excellent bending workability of the composite material, CV _A1-A6 is preferably 0.5 or less, more preferably 0.4 or less, and further preferably 0.3 or less. It is practically difficult to set CV _A1-A6 to 0, and CV _A1-A6 is usually 0.01 or more, preferably 0.03 or more.

(About average values A1 to A6)
As described above, the average value A1 to A6 of the number of carbon particles on each line in each square is an index of the number (amount) of carbon particles existing in each square. From the viewpoint of exhibiting the effects of the present invention (excellent wear resistance and bending workability), it is preferable that the carbon particles are present in the composite coating to some extent or more. The average primary particle diameter of the carbon particles is preferably in the above range, and the number of carbon particles that can exist on each line is limited to some extent. From these points, the average value B of the average values A1 to A6 is preferably 1.2 to 25, and more preferably 1.5 to 12.

(About the average of the 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, carbon particles are present in a reasonable amount in the composite coating, and CV _A1-A6 is small. From the viewpoint that carbon particles are uniformly dispersed and excellent in bending workability, it is preferable that the CV value (CV1 to CV6) of the number of carbon particles on each line in each square when obtaining CV _A1-A6 is also small. .. In this respect and since it is practically difficult to set the CV value to 0, the average value of CV1 to CV6 is preferably 1.2 or less, more preferably 0.5 or less, and 0. It is particularly preferably 0.05 to 0.35.

<Area ratio of carbon>
The composite coating in the embodiment of the composite material of the present invention contains carbon particles as described above. The area ratio (area ratio) occupied by the carbon particles on the surface of the composite film is an index of the wear resistance of the composite material, and is preferably 1 to 80% from the viewpoint of the balance between the wear resistance and the conductivity. It is more preferably 1.5 to 80%, still more preferably 4 to 50%. The area ratio is measured in the composite film obtained by subjecting the composite film to the above-mentioned ultrasonic treatment in advance. The details of the method for measuring the area ratio will be described in Examples.

<Total silver and carbon content>
The elemental composition of the composite coating in embodiments of the composite of the present invention typically comprises substantially silver and carbon. Specifically, the total content of these elements in the composite film is preferably 99% by mass or more, more preferably 99.5% by mass or more. When the antimony described below is contained, the total amount of silver, carbon and antimony in the composite film is preferably 99% by mass or more, more preferably 99.5% by mass or more.

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

In addition, antimony may adversely affect the heat resistance of the composite material, and when the composite material is used for applications in which heat resistance is important, the content of antimony in the composite coating is preferably less than 0.5% by mass. It is more preferably 0.1% by mass or less, still more preferably 500 ppm or less. When a composite material is produced using a silver plating solution containing the compound X represented by the general formula (I) described later, a composite film having a low antimony content and a Vickers hardness of 100 or more is formed. Will be done.

<Thickness of composite film>
The thickness of the composite coating is not particularly limited, but it is preferable that the composite coating has a minimum thickness in terms of wear resistance and conductivity. Moreover, even if the thickness is too large, the effect of the composite film is saturated and the raw material cost increases. From the above viewpoint, 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 described in Examples.

<< Underlayer >>
An underlayer may be formed between the material and the composite coating for various purposes. Examples of the constituent metals of the base layer include Cu, Ni, Sn and Ag. For example, for the purpose of preventing copper in the material from diffusing onto the surface of the composite film and deteriorating the heat resistance, it is preferable to form a base layer made of Ni. The material is a copper alloy containing zinc such as brass, and it is preferable to form a base layer made of Cu for the purpose of preventing zinc in the material from diffusing on the surface of the composite film. For the purpose of improving the adhesion of the composite film to the material, it is preferable to form a base layer made of Ag. The thickness of the base layer is not particularly limited, but is preferably 0.1 to 8 μm, more preferably 0.2 to 5 μm, from the viewpoint of exerting its function and cost. In addition, the terminals of electrical and electronic parts are often made of Sn-plated or reflow Sn-plated materials including Cu base and Ni base (laminated structure of Cu base, Ni base, and Sn base from the material side). Also in the present invention, an underlayer having such a laminated structure may be formed. Therefore, in the present invention, there may be a layer composed of Cu, Ni, Sn, and Ag, or a layer (in a laminated structure) in which they are combined, as the base of the composite coating, and for example, the electric contact portion of the material is defined in the present invention. A different layer is formed depending on the location, such as forming a composite coating (the base layer may or may not be formed) and forming a reflow Sn plating base layer on the wire crimping portion (the composite coating is not formed). It is also good.

[Terminal]
Since the embodiment of the composite material of the present invention is excellent in wear resistance and bending workability, it is suitable as a constituent material of terminals in electrical contact parts such as switches and connectors that are slidable in their use. ..

In particular, due to the excellent bending workability of the composite material, an embodiment of the long flat composite material of the present invention is manufactured in advance, punched out with a press, and molded (bending) into a terminal shape. It is preferable to manufacture the terminals from the viewpoint of terminal productivity.

[Manufacturing method of composite material]
The composite material of the present invention described above can be manufactured, for example, by the method for manufacturing the composite material of the present invention. Hereinafter, embodiments of the manufacturing method will be described.

The manufacturing method is a method for manufacturing a composite material, which forms a composite film composed of a silver layer containing carbon particles on a material by performing electroplating in a silver plating solution containing carbon particles. The composite film is formed so that the content of carbon particles in the liquid is 15 g / L or more and the Vickers hardness of the composite film to be formed is 100 or more. Hereinafter, each configuration of the embodiment of this manufacturing method will be described.

<< Material >>
The material is the same as the material described for embodiments of the composite material of the present invention. That is, Cu (copper) and Cu alloy are suitable as the constituent materials of the material. The Cu alloy includes Cu, Si (silicon), Fe (iron), Mg (magnesium), P (phosphorus), Ni (nickel), and Sn (tin) from the viewpoint of achieving both conductivity and wear resistance. ), Co (cobalt), Zn (zinc), Be (berylium), Pb (lead), Te (tellu), Ag (silver), Zr (zirconium), Cr (chromium), Al (aluminum) and Ti (titanium). ), And an alloy composed of at least one selected from the group consisting of unavoidable impurities is preferable. 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).

<< Electroplating >>
In the embodiment of the method for producing a composite material of the present invention, a composite material containing carbon particles in a silver layer is formed by electroplating the material described above in a specific silver plating solution. Form a film.

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

(Carbon particles)
The carbon particles are the same as described in the embodiments of the composite material of the present invention. When the silver plating solution contains carbon particles, the carbon particles are involved in the silver matrix when a composite film (AgC plating film) is formed on the material by electroplating. This enhances the wear resistance of the composite material. From the viewpoint of exhibiting such a function, the carbon particles are preferably graphite particles. The shape of the carbon particles is not particularly limited, such as substantially spherical, scaly, and amorphous, but the scaly shape is preferable because the wear resistance of the composite material can be enhanced by smoothing the surface of the composite coating.

Further, the cumulative 50% particle size (D50) of the carbon particles measured by the laser diffraction / scattering type particle size distribution measuring device should be 0.5 to 15 μm from the viewpoint of ease of entrainment in the AgC plating film. It is preferably 1 to 12 μm, more preferably 2.5 to 10 μm, and even more preferably 2.5 to 10 μm.

By using a silver plating solution containing carbon particles in a content of 15 g / L or more and forming a composite film so as to have a Vickers hardness of 100 or more, the carbon particles were uniformly dispersed (CV _A1- described above). A composite film ( _A6 of 0.6 or less) is formed. Since there is a limit to the amount of carbon particles that can be introduced into the composite film from the viewpoint of forming a composite film in which carbon particles are uniformly dispersed, the wear resistance of the obtained composite material, and the amount of carbon particles that can be introduced into the composite film, there is a limit to the amount of carbon particles in the silver plating solution. The content of the carbon particles is preferably 18 to 100 g / L, more preferably 30 to 90 g / L.

Further, it is preferable to remove the lipophilic organic matter adsorbed on the surface of the carbon particles by oxidizing the carbon particles. Such lipophilic organic substances include aliphatic hydrocarbons such as alkanes and alkenes, and aromatic hydrocarbons such as alkylbenzenes. As the oxidation treatment of carbon particles, in addition to the wet oxidation treatment, a dry oxidation treatment using O ₂ gas or the like can be used, but from the viewpoint of mass productivity, it is preferable to use the wet oxidation treatment, and the surface area is increased by the wet oxidation treatment. Large carbon particles can be treated uniformly. As a method of the wet oxidation treatment, a method of suspending carbon particles in water and then adding an appropriate amount of an oxidizing agent can be used. As the oxidizing agent, an oxidizing agent such as nitric acid, hydrogen peroxide, potassium permanganate, potassium persulfate, and sodium perchlorate can be used. It is considered that the lipophilic organic matter adhering to the carbon particles is oxidized by the added oxidizing agent to become easily soluble in water, and is appropriately removed from the surface of the carbon particles. Further, by performing this wet oxidation treatment, filtering, and further washing the carbon particles with water, the effect of removing lipophilic organic substances from the surface of the carbon particles can be further enhanced. By the oxidation treatment of carbon particles, lipophilic organic substances such as aliphatic hydrocarbons and aromatic hydrocarbons can be removed from the surface of the carbon particles, and according to the analysis with a heating gas at 300 ° C., the carbon particles after the oxidation treatment can be obtained. The gas generated by heating at 300 ° C. contains almost no lipophilic aliphatic hydrocarbons such as alkanes and alkanes and lipophilic aromatic hydrocarbons such as alkylbenzene. Even if some aliphatic hydrocarbons and aromatic hydrocarbons are contained in the carbon particles after the oxidation treatment, the carbon particles can be uniformly dispersed in the silver plating solution used in the present invention, but in the carbon particles. Does not contain hydrocarbons having a molecular weight of 160 or more and has a hydrocarbon having a molecular weight of less than 160 in carbon particles. Is preferable. The D50 of the carbon particles does not substantially change before and after the oxidation treatment.

(Silver ion)
The silver plating solution contains silver ions. The concentration of silver in this silver plating solution is preferably 5 to 150 g / L, more preferably 10 to 120 g / L, from the viewpoint of the formation speed of the composite film and the suppression of uneven appearance of the composite film. It is preferably 20 to 100 g / L, and more preferably 20 to 100 g / L.

(Compound X)
In forming a composite film having a Vickers hardness of 100 or more, a silver plating solution containing the compound X represented by the following general formula (I) is effective.

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 group. Ra and Rb may be independently bonded to the benzene ring via a divalent group composed of at least one selected from the group consisting of -O- and -CH _2- . .. Examples of the divalent group include -CH ₂ -CH ₂ -O-, -CH ₂ -CH _{2-CH 2-O-, and (-CH 2 - CH 2} -O-) _n (n). Is an integer greater than or equal to 2).

Compound X reduces the size of silver crystals in the composite film formed by electroplating by adsorbing it on the surface of the precipitated silver and suppressing the growth of silver crystals, thereby forming a hard composite film. it is conceivable that.

Further, in the above general formula (I), when m is 2 or more, a plurality of Rbs existing may be the same or different from each other, and when m is 3 or less, a plurality of Rc existing may be the same as each other. May be different. Regarding Rc, examples of the "arbitrary substituent" 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.

The concentration of compound X in the silver plating solution is preferably 3 to 250 ml / L from the viewpoint of suppressing uneven appearance of the composite film and appropriately controlling the hardness (Vickers hardness) of the formed composite film. More preferably, it is ~ 200 ml / L.

When the silver plating solution contains the compound X, the silver plating solution does not contain the antimony described below (specifically, the antimony content is less than 0.5 g / L, preferably 0.1 g / L or less). , More preferably 0.05 g / L or less), and a composite film having a Vickers hardness of 100 or more can be formed. The composite material thus produced is suitable for applications in which heat resistance is important.

(Antimony)
A silver plating solution containing antimony is also effective in forming a composite film having a Vickers hardness of 100 or more. When the silver plating solution contains antimony, a silver-antimony alloy is formed as a matrix (a portion other than carbon particles) of the composite film, and this alloy has a high Vickers hardness.

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 film.

(Coordinating 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 and enhances the stability as the ions. Due to this action, the solubility in the solvent constituting the silver plating solution is increased.

As the complexing agent, those having the above-mentioned functions can be widely used, but a compound having a sulfonic acid group is preferable from the viewpoint of the stability of the complex to be formed. Examples of the compound having a sulfonic acid group include an alkyl sulfonic acid having 1 to 12 carbon atoms, an alkanol sulfonic acid having 1 to 12 carbon atoms and a hydroxyaryl sulfonic acid. Specific examples of these compounds include methanesulfonic acid, 2-propanolsulfonic acid and phenolsulfonic acid.

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.

(Other additives)
As other additives, for example, the silver plating solution used in the present invention may contain a brightener, a curing agent, and a conductive salt. Examples of the curing agent include carbon sulfide compounds (for example, carbon disulfide), inorganic sulfur compounds (for example, sodium thiosulfate), organic compounds (sulfonates), selenium compounds, tellurium compounds, periodic table 4B or group 5B metals and the like. Can be mentioned. Examples of the conductivity salt include potassium hydroxide and the like.

(solvent)
The solvent constituting the silver plating solution is mainly water. Water is preferable because of the solubility of (complexed) silver ions, the solubility of other components contained in the plating solution, and the small burden on the environment. Moreover, you may use a mixed solvent of water and alcohol as a solvent.

(Cyanide)
Cyanide is widely used as an additive in plating solutions, but it is a target substance under the Water Pollution Control Law (Wastewater Standards) and PRTR (Pollutant Release and Transfer Register) system, and wastewater treatment costs are high. When the silver plating solution used in the present invention contains the above-mentioned compound X, the content of the cyanide compound in the silver plating solution is 1 mg / mg even if the silver plating solution does not substantially contain the cyanide compound (specifically, the content of the cyanide compound in the silver plating solution is 1 mg / L or less), the composite material of the present invention can be produced. This silver plating solution has an advantage that the wastewater treatment cost is low. The cyanide is a compound containing a cyano group (-CN), and the cyanide can be quantified according to JISK0102: 2019.

<Electroplating conditions>
Next, various conditions of electroplating using the silver plating solution described above will be described. For example, by electroplating described below, metallic silver (or silver-antimony alloy) is deposited on the material, and at that time, carbon particles are involved in the silver matrix to form a composite film.

(Cathode and anode)
The material to be electroplated is the cathode. For example, a silver electrode plate that dissolves and provides silver ions is an anode.

(Current density)
Immerse the cathode and anode in a silver plating solution (plating bath) and apply an electric current to perform silver plating. The current density here is preferably 0.5 to 10 A / dm ² , more preferably 1 to 8 A / dm ² , and 1.5 to 1.5 A / dm 2 from the viewpoint of the formation speed of the composite film and the suppression of unevenness in the appearance of the composite film. ~ 6A / dm ² is more preferable.

(Temperature, stirring, plating time, plating target part)
The temperature (plating temperature) of the plating bath (silver plating solution) during electroplating is preferably 15 to 50 ° C., preferably 20 to 45 ° C., from the viewpoint of plating production efficiency and prevention of excessive evaporation of the silver plating solution. More preferably, it is ° C. The stirring of the plating bath at this time is preferably 200 to 550 rpm, more preferably 350 to 500 rpm, from the viewpoint of performing uniform plating. The silver plating time (time for applying an electric current) can be appropriately adjusted according to the thickness of the target composite coating, but is typically in the range of 25 to 1800 seconds. Further, the target portion to be plated may be the entire surface layer of the material or a part of the surface layer of the material, depending on the use of the composite material to be manufactured.

(Silver strike plating)
Before forming the composite film on the material, it is preferable to form a very thin intermediate layer by silver strike plating to improve the adhesion between the material and the composite film. When the base layer described below is formed on the material, silver strike plating is performed on the base layer. As a method for carrying out silver strike plating, a conventionally known method can be adopted without particular limitation as long as the effect of the present invention is not impaired. The plating solution used for silver strike plating preferably contains substantially no cyanide from the viewpoint of wastewater treatment cost.

<< Formation of base layer >>
In the embodiment of the method for producing a composite material of the present invention, a base layer may be formed on the material, and the base layer may be electroplated for forming the composite film described above. The underlayer is formed for the purpose of preventing the copper of the material from diffusing and oxidizing on the plating surface and deteriorating the heat resistance of the composite material, and for the purpose of improving the adhesion of the composite film. Examples of the 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 in which they are combined (in a laminated structure), and the base layer may be formed depending on the use of the composite material to be manufactured. It may be the entire surface layer of the material or a part thereof.

The method for forming the base layer is not particularly limited, and the base layer can be formed by electroplating by a known method using a plating solution containing ions of the constituent metals. It is preferable that the plating solution does not substantially contain a cyanide compound from the viewpoint of wastewater treatment cost.

Hereinafter, examples of the composite material and the method for producing the composite material according to the present invention will be described in detail.

<Preparation of carbon particles>
As carbon particles, 80 g of scale-shaped graphite particles (PAG-3000 manufactured by Nippon Graphite Industry Co., Ltd.) having an average particle size of 5 μm is added to 1.4 L of pure water, and the temperature of this mixed solution is raised to 50 ° C. while stirring. rice field. The average particle size is measured using a laser diffraction / scattering type particle size distribution measuring device (MT3300 (LOW-WET MT3000II Mode) manufactured by Microtrac Bell Co., Ltd.), and the cumulative value based on the volume is 50%. The diameter. Next, 0.6 L of 0.1 mol / L potassium persulfate aqueous solution as an oxidizing agent was gradually added dropwise to this mixed solution, followed by stirring for 2 hours for oxidation treatment, and then filtering with filter paper. , The obtained solid matter was washed with water.

For carbon particles before and after this oxidation treatment, a purge-and-trap gas chromatograph mass spectrometer (JHS-100 manufactured by Nippon Analytical Industry Co., Ltd. as a heat desorption device and GCMS manufactured by Shimadzu Corporation as a gas chromatograph mass spectrometer). When the gas generated by heating at 300 ° C. was analyzed using a device combined with QP-5050A, it was attached to the carbon particles by the above oxidation treatment (nonan, decane, 3-methyl-2-heptene). It was found that lipophilic aliphatic hydrocarbons (such as xylene) and lipophilic aromatic hydrocarbons (such as xylene) were removed.

[Example 1]
<Silver strike plating>
Plate material made of Cu—Ni—Sn—P alloy with a length of 5.0 cm, a width of 5.0 cm, and a thickness of 0.2 mm (1.0% by mass of Ni, 0.9% by mass of Sn, and 0.05% by mass). A copper alloy plate containing P, the balance of which is Cu and an unavoidable impurity) (NB-109EH manufactured by DOWA Metaltech Co., Ltd.) was prepared. Using this plate as a material, the material as a cathode, and an iridium oxide mesh electrode plate (a titanium mesh material coated with iridium oxide) as an anode, sulfonic acid-based silver at 25 ° C. containing methanesulfonic acid as a complexing agent. In a strike plating solution (Dyne Silver GPE-ST manufactured by Daiwa Kasei Co., Ltd., substantially free of cyanide, silver concentration 3 g / L, methanesulfonic acid concentration 42 g / L, antimony concentration 0.05 g / L or less) , Electroplating (silver strike plating) was performed for 60 seconds at a current density of 5 A / dm ² . The silver strike plating was performed on the entire surface layer of the material.

<AgC plating>
A sulfonic acid-based silver plating solution containing methanesulfonic acid as a complexing agent and having a silver concentration of 30 g / L and a methanesulfonic acid concentration of 60 g / L (Dyne Silver GPE-HB manufactured by Daiwa Kasei Co., Ltd. (corresponding to the general formula (I)). The solvent is mainly water, and the antimony content is 0.05 g / L or less)), and the carbon particles (graphite particles) subjected to the above oxidation treatment are added to a concentration of 50 g. A carbon particle-containing sulfonic acid-based silver plating solution containing carbon particles of / L, silver having a concentration of 30 g / L, and methanesulfonic acid having a concentration of 60 g / L was prepared. This silver plating solution is substantially free of cyanide compounds.

Next, using the above-mentioned silver strike-plated material as a cathode and the silver electrode plate as an anode, the temperature is 25 ° C. and the current is in the above-mentioned carbon particle-containing sulfonic acid-based silver plating solution while stirring at 400 rpm with a stirrer. Electroplating was performed at a density of 3 A / dm ² for 500 seconds to obtain a composite material in which a composite film (AgC plating film) containing carbon particles in the silver layer was formed on the material. The composite film was formed on the entire surface layer of the material.

The production conditions and the like of the above composite materials are summarized in Table 2 below together with the production conditions and the like of Examples 2 to 9 and Comparative Examples 1 to 4 described later.

The composite material obtained in Example 1 was evaluated as follows.
<Thickness of composite film>
Measure the thickness of the composite coating of the composite material (a circular range with a diameter of 0.2 mm at the center of a 5.0 cm x 5.0 cm surface) with a fluorescent X-ray film thickness meter (FT110A manufactured by Hitachi High-Tech Science Corporation). As a result, it was 10 μm. It is difficult to detect C atoms (of carbon particles) with a fluorescent X-ray film thickness meter, and Ag atoms are detected to determine the thickness. However, in the present invention, the thickness obtained by this is approximated to the thickness of the composite film. ..

<Vickers hardness Hv on the surface of the composite film>
The Vickers hardness Hv on the surface of the composite film was measured 3 times according to JIS Z2244 by applying a load of 0.01 N to the flat part of the composite material for 15 seconds using a micro-hardness meter (HM221 manufactured by Mitutoyo Co., Ltd.). The average value of the measurement of was adopted. As a result, the Vickers hardness Hv was 180.

<Carbon area ratio on the surface of the composite film after ultrasonic cleaning treatment>
For the surface of the composite coating of the obtained composite material, an ultrasonic cleaner (VS-100III manufactured by AS ONE, output 100 W, internal dimensions: length 140 mm x width 240 mm x depth 100 mm, liquid used is pure water, water temperature 20 ° C.) was used to perform ultrasonic cleaning treatment at 28 kHz for 4 minutes.

The carbon area ratio on the surface of the composite coating after the ultrasonic cleaning treatment was measured as follows.
GIMP 2.10. GIMP 2.10. GIMP 2.10. The area ratio of carbon on the surface of the composite coating was calculated by binarizing with 10 (image analysis software). Specifically, assuming that the highest brightness of all the pixels is 255 and the lowest brightness is 0, the gradation is binarized so that the pixels with a brightness of 127 or less are black and the pixels with a brightness of more than 127 are white. , The ratio Q / P of the number of pixels Q of the carbon particle part to the number of pixels P of the entire image is divided into the silver part (white part) and the carbon particle part (black part), and the carbon area ratio of the surface ( %). As a result, the carbon area ratio after the ultrasonic cleaning treatment was 30%.

<Dispersion state of carbon particles after ultrasonic cleaning treatment on the surface of the composite film>
The dispersed state of the carbon particles in the composite film in the composite material was evaluated as follows.
Using a tabletop microscope (TM4000 Plus manufactured by Hitachi High-Technologies Corporation), the surface of the composite coating of the composite material after ultrasonic cleaning was observed in a field of view of 90 μm in length × 130 μm in width at an acceleration voltage of 5 kV at a magnification of 1000 times. The backscattered electron composition (COMPO) image (1 field of view) was binarized with GIMP 2.10.10. (Image analysis software). Specifically, when the highest brightness of all the pixels is 255 and the lowest brightness is 0, the gradation is binarized so that the pixels with a brightness of 127 or less are black and the pixels with a brightness of more than 127 are white. bottom.

A rectangular area of 78 μm in length × 117 μm in width is taken in the central part of the obtained binarized image (the ratio of the size of the area to the entire field of view is 78%), and this area is a square of 39 μm × 39 μm. In each square, draw two vertical lines with distances of 13 μm and 26 μm from the left vertical side of the square, and draw two horizontal lines with distances of 13 μm and 26 μm from the upper horizontal side of the square. , The number of carbon particles present on each vertical line and horizontal line was determined. Here, the portion where the pixels on each vertical line and the horizontal line continue in black is counted as one carbon particle, and even one pixel of black is counted as one carbon particle. The image used for counting the number of carbon particles is shown in FIG. The thickness of the vertical line and the horizontal line is 1 pixel, and the length of the vertical line and the horizontal line is 390 pixels. Further, in FIG. 1, the line of the outline of the square is shown thick for convenience, but when the actual carbon particles are counted, the thickness is the same as the vertical line.

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

From the result of counting the number of carbon particles, the average value (A1 to A6) of the number of carbon particles existing on each vertical line and the horizontal line was obtained for each square. The CV value (standard deviation of the average value (A1 to A6) / average value B of the average value (A1 to A6)) was calculated for the average value (A1 to A6) and found to be 0.19.

<Evaluation of wear resistance>
The same Cu—Ni—Sn—P alloy plate material used in Example 1 was subjected to the same plating treatment (AgSb plating) as in Comparative Example 2 described later, and was 2.0 cm wide × 3.0 cm long. A flat plate-shaped test piece of the size of 1 was cut out.

On the other hand, a test piece having a width of 1.0 cm and a length of 4.0 cm was cut out from the composite material obtained in Example 1 and indented (extruded into a hemispherical shape) having an inner diameter of 1.0 mm. A test piece (indent) was obtained.

Using a sliding wear tester (CRS-G2050-DWA manufactured by Yamasaki Seiki Laboratory Co., Ltd.), the indented test piece is indented so that the convex portion of the indented test piece hits the flat plate-shaped test piece. Is pressed against the flat plate-shaped test piece with a constant load (2N), and the reciprocating sliding motion (sliding distance 10 mm (that is, 20 mm for one reciprocation), sliding speed 3 mm / s) is continued, and the indented test piece is indented. The wear resistance was evaluated by conducting a wear test to confirm the wear state of the flat plate-shaped test piece. As a result, after 100 reciprocating sliding operations, the central part of the sliding marks of the indented test piece and the flat plate-shaped test piece was observed with a microscope (VHX-1000 manufactured by KEYENCE CORPORATION) at a magnification of 200 times. It was confirmed that the (brown) material (alloy plate material) was not exposed from either of the sliding marks, and it was found that the composite material of Example 1 was excellent in wear resistance.

<Evaluation of bending workability>
(Evaluation of maximum exposure width)
The maximum exposed width of the obtained composite material when the composite film was bent was evaluated as follows.

A bending test piece having a width of 10 mm is cut out from the obtained composite material so that the longitudinal direction is TD (direction perpendicular to the rolling direction) and the width direction is LD (rolling direction), and the LD is formed on the bending test piece. A 90 ° W bending test conforming to JIS H3130 with a bending axis (Bad Way bending (BW bending)) was performed with a bending radius R = 0.2 mm. For the test piece after this test, the surface of the apex of the bent portion was observed with a laser microscope (VK-X160 manufactured by KEYENCE) at a magnification of 200 times, and the composite film was divided by the bending process to expose the material. Among them, the length in the TD direction of the exposed portion having the maximum length in the TD (direction perpendicular to the rolling direction) direction was obtained as the maximum exposure width.

As a result of the evaluation, the maximum exposed width of the composite material of Example 1 was 22 μm. When the maximum exposure width was 30 μm or less, it was evaluated that the bending workability of the composite material was excellent. The reason is as follows.

Since tensile stress acts on the material portion immediately below the portion where the composite coating is stretched and divided by the bending process, a shearing force is likely to be applied to the portion of the material. Since the composite film is in close contact with the original material, the composite film is always divided when the material is plastically deformed by bending. The more the composite film is divided, the smaller the shearing force applied to the part of the material directly under it per division, so the material is wrinkled (the material is slipped and sheared (broken). (Not done)), but cracks in the material (material slips greatly and shear deformation progresses and breaks) are unlikely to occur (see Fig. 2 for wrinkles and cracks). As a result, the maximum exposure width observed is small. On the other hand, when the number of divisions generated in the composite coating is small, a large stress is applied to a specific portion of the material (the portion directly under the division), and the material is liable to crack. As a result, the maximum exposure width observed is large. If the material is cracked, there is a problem that the shape of the product such as a terminal becomes abnormal or the material is broken, and the function cannot be fulfilled.

(Evaluation of bending cross section)
For the composite material of Example 1, the cross section of the apex of the bending portion of the test piece in the bent state obtained in the bending test was subjected to a magnification of 200 times by a laser microscope (VK-X160 manufactured by KEYENCE). I made an observation at.

The obtained cross-sectional photograph is shown in FIG. It can be seen that the composite film has many divisions, but no cracks have occurred in the material.

The above evaluation results (excluding the evaluation results of the bending cross section) are summarized in Table 2 below together with the evaluation results of Examples 2 to 9 and Comparative Examples 1 to 4 described later.

[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 performed.

[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 performed.

[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 performed.

[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 performed.

[Example 6]
A nickel plating bath containing nickel sulfamate at a Ni concentration of 80 g / L and boric acid at a concentration of 45 g / L using the same material as in Example 1 as a cathode and a Ni electrode plate as an anode. In (aqueous solution), electroplating (Ni plating) was performed for 40 seconds while stirring at a liquid temperature of 55 ° C. and a current density of 4 A / dm ² , and a 0.2 μm-thick Ni film (Ni base layer) was formed on the material. Formed. The Ni base layer was formed on the entire surface layer of the material. The thickness of the base layer was measured by the same method as the method for determining the thickness of the composite film.

A composite material was prepared in the same manner as in Example 1 except that the material on which the Ni base layer was formed was subjected to silver strike plating, and various evaluations were performed.

[Example 7]
A composite material was prepared in the same manner as in Example 6 except that the electroplating time for forming the Ni base layer was changed to 600 seconds, and various evaluations were performed. The thickness of the Ni base layer was 3.4 μm.

[Example 8]
Dine Silver GPE-SB manufactured by Daiwa Kasei Co., Ltd. is used as a sulfonic acid-based silver plating solution, and carbon particles (graphite particles) subjected to the above oxidation treatment are added to the carbon particles-containing sulfonic acid-based silver plating. A composite material was prepared in the same manner as in Example 1 except that it was made into a liquid, and various evaluations were performed.

[Example 9]
Various composite materials were 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 oxidized in the same manner as above as carbon particles. Evaluation was performed.

[Comparative Example 1]
The same as in Example 1 except that electroplating was performed using a sulfonic acid-based silver plating solution (Dyne Silver GPE-HB manufactured by Daiwa Kasei Co., Ltd.) instead of the carbon particle-containing sulfonic acid-based silver plating solution. , A silver-plated material having a silver layer (Ag-plated film) formed on the material was obtained. Various evaluations were performed on this silver-plated material in the same manner as in Example 1.

The silver-plated material of Comparative Example 1 was not evaluated for carbon particles. In addition, since the evaluation result of bending workability of this silver-plated material was poor, the wear resistance of indenting (= bending) was not evaluated. Further, FIG. 4 shows the results (cross-sectional photograph) of observing the cross section of the test piece in the bent state obtained in the evaluation of the bending workability of the present plating material in the same manner as in Example 1. It is a photograph with a magnifying magnification of 200 times. The silver-plated layer is divided, and the number of the divisions is smaller and wider than that of the composite coating of Example 1, and small cracks (arrow portions) which are considered to have cracks are observed in the material.

[Comparative Example 2]
<Silver strike plating>
A material similar to that of Example 1 is prepared, and this material is used as a cathode and a titanium platinum mesh electrode plate (plated with a titanium mesh material) as an anode, and a cyanide-based silver strike containing a cyanide as a complexing agent is used. Electroplating (silver strike plating) in a plating solution (general reagent, standing bath, silver cyanide concentration 3 g / L, potassium cyanide concentration 90 g / L, solvent is water) at a liquid temperature of 25 ° C. and a current density of 5 A / dm ² for 30 seconds. ) Was performed.

<AgSb plating>
As a complexing agent, a cyanide Ag—Sb alloy plating solution (solvent is water) containing a cyanide compound and having a silver concentration of 60 g / L and an antimony (Sb) concentration of 2.5 g / L was prepared. The cyanide Ag-Sb alloy plating solution contains 10% by mass of silver cyanide, 30% by mass of sodium cyanide and Nissin Bright N (manufactured by Nikkei Seisei Co., Ltd.), and contains Nissin Bright N in the plating solution. The concentration is 50 mL / L. Nissin Bright N contains a brightener and diantimony trioxide, and the concentration of diantimony trioxide in Nissin Bright N is 6% by mass.

Next, using the silver strike-plated material as the cathode and the silver electrode plate as the anode, the temperature is 25 ° C. and the current density is set in the cyan-based Ag-Sb alloy plating solution while stirring with a stirrer at 400 rpm. Electroplating was performed at 3 A / dm ² for 1000 seconds to obtain a composite material in which a composite film (silver-antimony film) was formed on the material.

Various evaluations were performed on the obtained composite material in the same manner as in Example 1. The composite material of Comparative Example 2 was not evaluated for carbon particles. In addition, since the evaluation result of bending workability of this composite material was poor, the wear resistance of indenting (= bending) was not evaluated.

[Comparative Example 3]
A sulfonic acid-based silver plating solution having a silver concentration of 30 g / L containing methanesulfonic acid as a complexing agent at a concentration of 60 g / L instead of the sulfonic acid-based silver plating solution of Example 1 (Dyne Silver manufactured by Daiwa Kasei Co., Ltd.) GPE-PL (does not contain the compound corresponding to the general formula (I) and the solvent is water)) is used, and carbon particles (graphite particles) subjected to the same oxidation treatment as in Example 1 are added thereto. A composite material was prepared in the same manner as in Example 1 except that the obtained carbon particle-containing sulfonic acid-based silver plating solution was used, and various evaluations were performed.

[Comparative Example 4]
The composite material was the same 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. Was created and various evaluations were performed. Since the evaluation result of the bending workability of the composite material of Comparative Example 4 was poor, the wear resistance to be indented (= bending) was not evaluated.

Table 2 below summarizes the production conditions and evaluation results of the composite materials and silver-plated materials of Examples 1 to 9 and Comparative Examples 1 to 4 above. Further, the count results of the number of carbon particles for each composite material are shown in Table 3 below.

Claims (17)

A composite material in which a composite film consisting of a silver layer containing carbon particles is formed on the material.
The Vickers hardness of the composite film is 100 or more, and the composite film 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 micrograph was taken.
In the obtained captured image, a rectangular area having a size of 75% or more of the area of the image and a vertical: horizontal length ratio of 2: 3 is taken, and this area is vertically 2 with a square of the same size. Divide into a total of 6 pieces, 3 pieces on the side and 3 pieces on the side.
Within each square, the distance from the left vertical side of the square draws two vertical lines, one-third and two-thirds of the length of the horizontal side of the square, and the distance from the upper horizontal side of the square is Draw two horizontal lines, one-third and two-thirds of the length of the vertical side of the square, determine the number of carbon particles existing on each vertical line and horizontal line, and calculate the number of carbon particles existing on each line for each square. When calculating the average value of the number of
The CV values of the average values A1 to A6 for each of the six squares are 0.6 or less.
In each of the squares, out of a total of four lines of the vertical line and the horizontal line, one or less is a line in which the number of carbon particles existing on the line is 0.
Composite material. The composite material according to claim 1, wherein the composite film has a Vickers hardness of 120 to 250. The composite material according to claim 1 or 2, wherein the CV values of the average values A1 to A6 are 0.01 to 0.5. 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. The composite material according to any one of claims 1 to 4, wherein the ratio of the area of carbon particles to the surface of the composite film after ultrasonic cleaning on the surface of the composite film is 4 to 50%. Claimed that the average value of CV1 to CV6 is 0.5 or less when the CV value (CV1 to CV6) for the number of carbon particles existing on each line in each square is obtained for the six squares. The composite material according to any one of 1 to 5. An SEM photograph of the surface of the composite coating was taken with a field of view of 80 to 100 μm in length × 120 to 140 μm in width at a magnification of 1000 times, and a rectangular region of 78 μm in length × 117 μm in width was taken in the obtained SEM image, and this region was taken. The composite material according to any one of claims 1 to 6, wherein the composite material is divided into six pieces of 39 μm × 39 μm square. The composite material according to any one of claims 1 to 7, wherein the composite coating has a thickness of 0.5 to 40 μm. The composite material according to any one of claims 1 to 8, wherein the carbon particles are scale-shaped graphite particles. The composite material according to any one of claims 1 to 9, wherein the content of antimony in the composite coating is less than 0.5% by mass. The composite material according to any one of claims 1 to 10, wherein the material is made of copper or a copper alloy. The composite material according to any one of claims 1 to 11, wherein the composite material has a flat plate shape. A terminal in which the composite material according to any one of claims 1 to 12 is used as a constituent material thereof. A method for manufacturing a terminal, comprising a step of bending the composite material according to claim 12 into a terminal shape. A method for producing a composite material, which forms a composite film composed of a silver layer containing carbon particles on a material by performing 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, and the content is 15 g / L or more.
The composite film is formed so that the Vickers hardness of the composite film to be formed is 100 or more.
Method of manufacturing composite material. The method for producing a composite material according to claim 15, wherein the silver plating solution contains the compound X represented by the following general formula (I).

(In the 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 a sulfonic acid group. Any substituent,
When m is 2 or more, a plurality of Rbs may be the same or different from each other.
When m is 3 or less, a plurality of Rc may be the same or different from each other.
Ra and Rb may be independently bonded to the benzene ring via a divalent group composed of at least one selected from the group consisting of -O- and -CH _2- , respectively. ). The composite material according to claim 15 or 16, wherein the carbon particles are graphite particles having a cumulative 50% particle diameter (D50) of 0.5 to 15 μm on a volume basis measured by a laser diffraction / scattering particle size distribution measuring device. Manufacturing method.

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