Electrical contact pair and terminal pair

Abstract

Provided are: an electrical contact pair comprising a group of electrical contacts having a coating layer containing Ag on the surface thereof, the electrical contact pair and the terminal pair being capable of improving abrasion resistance and suppressing damage to the coating layer due to processing; an electrical contact pair (1) is provided with: a protruding electrical contact (2) protruding toward the front surface side; the present invention relates to an electrical contact (1) comprising a protruding electrical contact (2), and a flat-plate-shaped electrical contact (3) having a curvature smaller than that of the protruding electrical contact (2) and capable of electrically contacting the protruding electrical contact (2) on the surface, the protruding electrical contact (2) having a high-purity Ag coating layer (24) on the surface, the high-purity Ag coating layer (24) containing Ag and having an Ag content of 99.9% by mass or more, and the flat-plate-shaped electrical contact (3) having a curvature smaller than that of the protruding electrical contact (2) and being capable of electrically contacting the protruding electrical contact (2) on the surface. The surface of the flat electrical contact (3) is provided with a low-purity Ag coating layer (34), the low-purity Ag coating layer (34) contains Ag and a sulfur-containing organic compound, and the Ag content is 97.0% by mass or more and 99.5% by mass or less.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrical contact pair and a terminal pair. BACKGROUND

[0002] In automobiles, a terminal provided with an Ag coating layer on the surface is sometimes used as an electrical connection terminal for large current. The terminal provided with the Ag coating layer on the surface is excellent in heat resistance, corrosion resistance, and electrical conductivity, on the one hand, but, on the other hand, since Ag has the properties of being soft and easily causing adhesion, surface abrasion is easily caused when sliding. Therefore, as one of the means for utilizing the excellent properties of Ag such as heat resistance and electrical conductivity and suppressing abrasion, a method of making a hard silver layer by containing an additive element such as Se in the Ag coating layer to increase the hardness of the Ag coating layer is sometimes adopted.

[0003] However, the method of making a hard silver layer by containing an additive element such as Se in the Ag coating layer of the terminal surface sometimes fails to sufficiently improve the abrasion resistance. For example, as the terminal is made to carry a large current, a high contact load needs to be applied to the electrical contact, but in the case where the high contact load is thus applied and the electrical contact is caused to slide, the conventional hard silver layer sometimes fails to sufficiently satisfy the required abrasion resistance. In this case, as the Ag coating layer provided on the surface of the electrical contact of the terminal, an Ag coating layer having superior abrasion resistance to the conventional hard silver layer is considered to be applied. For example, Patent Literature 1 discloses a technique of manufacturing a silver-plated material by forming a silver-containing surface layer on a raw material using a silver-plating solution containing a benzothiazole or a derivative thereof. Thereby, a silver-plated material having superior abrasion resistance to the conventional silver-plated material can be obtained. PRIOR ART DOCUMENTS PATENT LITERATURE

[0004] Patent Literature 1: Japanese Patent Application Publication No. 2022-048977 SUMMARY PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] As in the manner disclosed in Patent Literature 1, by adding an additive containing an organic compound such as a benzothiazole to the Ag coating layer provided on the electrical contact, the Ag concentration in the Ag coating layer is suppressed to be low, and thus an effect of greatly improving the abrasion resistance can be expected. It is considered that since the Ag concentration is low, the adhesion of Ag is suppressed, and the friction coefficient of the surface of the Ag coating layer is suppressed to be low.

[0006] On the other hand, in the case where an additive containing an organic compound is added, if the additive is added to the Ag-coated layer in an amount only sufficient to obtain an effect of improving wear resistance, the Ag-coated layer is likely to be brittle compared to a conventional hard silver layer. Thus, when a metal material having the Ag-coated layer is processed into a prescribed shape by mechanical processing such as press working, damage such as cracking is likely to occur on the surface of the Ag-coated layer. Once such damage occurs, denaturation such as oxidation is likely to occur in the metal material in which a base layer, a substrate, or the like is present under the Ag-coated layer, which becomes a cause of deterioration of the durability of the terminal. In particular, in the case where an electrical contact in a relief shape is formed, cracking is likely to occur on the surface of the protruding portion of the electrical contact. In this way, if cracking occurs in the Ag-coated layer at the electrical contact and the progress of oxidation accompanying the cracking proceeds, it is difficult to maintain the desired electrical connection characteristics for a long period of time.

[0007] In view of the above, an object of the present application is to provide an electrical contact pair composed of a group of electrical contacts each having a coated layer containing Ag on a surface, and a terminal pair having such an electrical contact pair, which can improve wear resistance and suppress damage to the coated layer accompanying processing. Means for solving the problem

[0008] The electrical contact pair of the present application includes: a protruding electrical contact protruding toward a surface side; and a flat plate-shaped electrical contact having a smaller curvature than the protruding electrical contact and capable of being in electrical contact with the protruding electrical contact on a surface, wherein the protruding electrical contact has a high-purity Ag-coated layer on a surface, the high-purity Ag-coated layer contains Ag, and the content of Ag in the high-purity Ag-coated layer is 99.9 mass% or more, and the flat plate-shaped electrical contact has a low-purity Ag-coated layer on a surface, the low-purity Ag-coated layer contains Ag and a sulfur-containing organic compound, and the content of Ag in the low-purity Ag-coated layer is 97.0 mass% or more and 99.5 mass% or less.

[0009] The terminal pair of the present application includes a first terminal having a first contact portion and a second terminal having a second contact portion, the group of the first contact portion and the second contact portion is composed of the electrical contact pair, and the first contact portion and the second contact portion can be in electrical contact with each other. Effects of the Invention

[0010] The electrical contact pair and the terminal pair of the present application can improve wear resistance and suppress damage to a coated layer accompanying processing in an electrical contact pair composed of a group of electrical contacts each having a coated layer containing Ag on a surface and a terminal pair having such an electrical contact pair. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a cross-sectional view schematically showing an electrical contact pair of an embodiment of the present application. Figure 2is a cross-sectional view showing an example of a structure of a terminal pair of an embodiment of the present application. Figure 3 is a STEM image of a cross section of a low-purity Ag coating layer (organic matter-containing Ag layer 1) observed. Figure 4 is a table showing results obtained by measuring a friction coefficient while sliding two electric contacts for a plurality of samples in which Ag coating layers of different kinds are provided on surfaces of convex electric contacts and flat electric contacts. Figure 5A 、 5B is an SEM image of a surface of a convex electric contact observed. Figure 5A shows a case where a metal material provided with a high-purity Ag coating layer (hard Ag layer) is used, Figure 5B shows a case where a metal material provided with a low-purity Ag coating layer (organic matter-containing Ag layer 1) is used. The upper side is a view of the entire region of the surface of a convex electric contact observed, and the lower side is a view of the vicinity of the top of the convex electric contact observed at a higher magnification. DETAILED DESCRIPTION

[0012] [Explanation of Embodiments of the Present Invention] An embodiment of the present application will be described first.

[0013] [1] An electric contact pair of the present application includes: a convex electric contact protruding toward a surface side; and a flat electric contact having a smaller curvature than the convex electric contact and capable of electrically contacting the surface and the convex electric contact, wherein the convex electric contact has a high-purity Ag coating layer on a surface, the high-purity Ag coating layer contains Ag, and the content of Ag in the high-purity Ag coating layer is 99.9 mass% or more, and on the other hand, the flat electric contact has a low-purity Ag coating layer on a surface, the low-purity Ag coating layer contains Ag and a sulfur-containing organic compound, and the content of Ag in the low-purity Ag coating layer is 97.0 mass% or more and 99.5 mass% or less.

[0014] The above-mentioned pair of electrical contacts has a good electrical contact characteristic and durability by having a coating layer containing Ag on the surface of the convex electrical contact and the surface of the flat plate-shaped electrical contact, thereby utilizing the characteristics of Ag such as heat resistance, corrosion resistance, high electrical conductivity, and the like. The convex electrical contact is processed into a shape protruding toward the surface side, and thus, as compared with the case where the flat plate-shaped electrical contact has a shape with a small curvature, the Ag coating layer on the surface is likely to be damaged by cracking and the like due to processing. However, the Ag coating layer of the high-purity Ag on the surface of the convex electrical contact has an Ag content of 99.9% by mass or more and does not contain an additive or contains only a small amount of an additive, and thus, does not cause embrittlement due to the addition of the additive. Therefore, even if the convex shape is processed, the surface of the high-purity Ag coating layer is not likely to be damaged by cracking and the like due to processing, and is not likely to cause a decrease in durability due to damage such as oxidation of the underlying metal from the cracked portion.

[0015] On the other hand, the low-purity Ag coating layer formed on the surface of the flat plate-shaped electrical contact contains a sulfur-containing organic compound and has an Ag content of 97.0% by mass or more and 99.5% by mass or less, and is thus suppressed to a low-purity range, thereby obtaining high wear resistance on the surface and suppressing the coefficient of friction between the electrical contacts to be low. By the flat plate-shaped electrical contact having the low-purity Ag coating layer on the surface, as shown in the following examples, even if the metal layer formed on the surface of the convex electrical contact which is the mating electrical contact is single, high wear resistance is obtained to the same degree as that of the high-purity Ag coating layer which does not show high wear resistance. The flat plate-shaped electrical contact is different from the convex electrical contact in that it is not processed into a shape with a large curvature, and thus, even if the low-purity Ag coating layer has a property of being likely to be damaged due to processing, damage occurring at the electrical contact and a decrease in durability due to the same are suppressed to be small.

[0016] Thus, by forming the Ag coating layer having a predetermined composition on the surface of each of the convex electrical contact and the flat plate-shaped electrical contact, it is possible to improve wear resistance in the pair of electrical contacts and suppress damage of the coating layer due to processing. In addition, the sulfur-containing organic compound contained in the low-purity Ag coating layer not only shows an effect of improving wear resistance but also shows an effect of preventing discoloration of the Ag coating layer, and thus, it is not necessary to additionally apply a discoloration preventing agent to the surfaces of the electrical contacts.

[0017] [2] In the mode of the above-mentioned [1], the content of the sulfur-containing organic compound in the low-purity Ag coating layer can be 0.5% by mass or more and 3.0% by mass or less. Thus, in the pair of electrical contacts, an effect of improving wear resistance due to the sulfur-containing organic compound is obtained to a higher degree, and it is possible to suppress the contact resistance between the electrical contacts to be low.

[0018] [3] In the above-mentioned [1] or [2], the high-purity Ag coating layer can be configured as a hard silver layer. Thus, when the metal material is processed into a convex shape to form a convex-shaped electrical contact, the formation of cracks on the surface of the high-purity Ag coating layer can be effectively suppressed. As a result, high durability is obtained in the electrical contact pair.

[0019] [4] In any of the above-mentioned [1] to [3], in the convex-shaped electrical contact and the flat-plate-shaped electrical contact, a base layer composed of Ni or Ni alloy can be formed to coat the surface of a base material composed of Cu or Cu alloy, and the high-purity Ag coating layer and the low-purity Ag coating layer can be formed to coat the surface of the base layer, respectively. The base layer composed of Ni or Ni alloy functions to improve the adhesion of the Ag coating layer to the base material composed of Cu or Cu alloy and to suppress the diffusion of the base material metal into the Ag coating layer. If a crack is generated in the Ag coating layer, the base layer composed of Ni or Ni alloy is oxidized from the crack site, which can cause an increase in contact resistance and the like in the electrical contact pair, but the high-purity Ag coating layer is formed on the surface of the convex-shaped electrical contact, and thus a crack or the like is not easily formed even by processing into a convex shape. Thus, the oxidation of the base layer and the increase in contact resistance due to a crack in the Ag coating layer are less likely to occur, and high durability can be obtained in the electrical contact pair.

[0020] [5] The terminal pair of the present application includes a first terminal having a first contact portion and a second terminal having a second contact portion, and the group of the first contact portion and the second contact portion is composed of the electrical contact pair of any one of the above-mentioned [1] to [4], and can be electrically contacted with each other. The terminal pair can improve the wear resistance and suppress the damage to the coating layer caused by processing by having the above-mentioned electrical contact pair as the group of the contact portions that can be electrically contacted with each other.

[0021] [6] In the above-mentioned [5], the first terminal can be configured as a female terminal having the convex-shaped electrical contact, and the second terminal can be configured as a male terminal that can be fitted with the first terminal and has the flat-plate-shaped electrical contact. In a fitted terminal pair composed of a group of a female terminal and a male terminal, the contact portion of the female terminal is generally provided with a convex-shaped electrical contact that is embossed, and the contact portion of the male terminal is generally provided with a flat-plate-shaped electrical contact that is tab-shaped, but by providing the convex-shaped electrical contact and the flat-plate-shaped electrical contact that constitute the above-mentioned electrical contact pair as the contact portions, respectively, high wear resistance and suppression of damage caused by processing can be obtained in the electrical contact portion between the two contact portions.

[0022] [Details of Embodiments of the Present Invention] Hereinafter, the pair of electrical contacts and the pair of terminals of the embodiment of the present application will be described in detail using the drawings. Hereinafter, the values indicating various characteristics are values obtained in a room temperature and in the atmosphere, unless otherwise specifically noted.

[0023] Figure 1 A pair of electrical contacts 1 of an embodiment of the present application is schematically shown in a sectional view. The pair of electrical contacts 1 of an embodiment of the present application includes a convex electrical contact 2 and a flat plate electrical contact 3. The convex electrical contact 2 and the flat plate electrical contact 3 are capable of electrically contacting each other on respective surfaces.

[0024] The convex electrical contact 2 has a shape protruding toward the surface side (embossed shape). The specific protruding shape of the convex electrical contact 2 is not particularly limited, and can have a shape that can be approximated to a partial ellipsoid (ellipsoidal cap; a shape obtained by cutting a part of an ellipsoid with a plane; an ellipsoid also includes a sphere) represented by a semi-ellipsoid. Further preferably, it can have a partial sphere (spherical cap; a shape obtained by cutting a part of a sphere with a plane) represented by a semi-sphere. Note that in the present specification, the shape that can be approximated to a certain shape means a shape having a dimensional deviation of about 10% or less from the certain shape.

[0025] The flat plate electrical contact 3 has a planar structure having a smaller curvature (a larger curvature radius) than the convex electrical contact 2. The specific shape of the flat plate electrical contact 3 is not particularly limited, and can have a curved surface shape that is flatter than the protruding shape of the convex electrical contact 2, but preferably has a flat shape that is planar or can be approximated to be planar. By the convex electrical contact 2 and the flat plate electrical contact 3 electrically contacting each other on respective surfaces, an electrical connection is formed between the metal material 20 constituting the convex electrical contact 2 and the metal material 30 constituting the flat plate electrical contact 3. When the electrical contact is formed between the two electrical contacts 2, 3, as shown in the drawing, the convex electrical contact 2 contacts the surface of the flat plate electrical contact 3 at the top.

[0026] The combination of the convex electrical contact 2 having a partial ellipsoid shape and the flat plate electrical contact 3 having a planar shape is often used in the pair of terminals of the male-female fitting type described later. Figure 2 By the movement of plugging the terminal having the flat plate electrical contact 3 (the male terminal 6) with respect to the terminal having the convex electrical contact 2 (the female terminal 5) and the like, the convex electrical contact 2 and the flat plate electrical contact 3 relatively slide with respect to each other in the plane of the flat plate electrical contact 3 (for example, in the lateral direction of the drawing), whereby the electrical contact between the two electrical contacts 2, 3 can be reversibly formed or released.

[0027] As Figure 1 ​As shown, the protrusion-shaped electric contact 2 is composed of a metal material 20 having a high-purity Ag coating layer 24 on the surface. Also, the flat-plate-shaped electric contact 3 is composed of a metal material 30 having a low-purity Ag coating layer 34 on the surface. The protrusion-shaped electric contact 2 and the flat-plate-shaped electric contact 3 are in contact with each other on the surface of the high-purity Ag coating layer 24 and the surface of the low-purity Ag coating layer 34. The high-purity Ag coating layer 24 and the low-purity Ag coating layer 34 are each composed of a metal layer having Ag as a main component, but the component compositions are different from each other. Details of the structure of the protrusion-shaped electric contact 2 and the flat-plate-shaped electric contact 3 will be described below in order.

[0028] (Structure of protrusion-shaped electric contact) As shown, the protrusion-shaped electric contact 2 is composed of a metal material 20 having a high-purity Ag coating layer 24 on the surface. Also, the flat-plate-shaped electric contact 3 is composed of a metal material 30 having a low-purity Ag coating layer 34 on the surface. The protrusion-shaped electric contact 2 and the flat-plate-shaped electric contact 3 are in contact with each other on the surface of the high-purity Ag coating layer 24 and the surface of the low-purity Ag coating layer 34. The high-purity Ag coating layer 24 and the low-purity Ag coating layer 34 are each composed of a metal layer having Ag as a main component, but the component compositions are different from each other. Details of the structure of the protrusion-shaped electric contact 2 and the flat-plate-shaped electric contact 3 will be described below in order. Figure 1 As shown, the protrusion-shaped electric contact 2 is composed of a metal material 20 having a high-purity Ag coating layer 24 on the surface. Also, the flat-plate-shaped electric contact 3 is composed of a metal material 30 having a low-purity Ag coating layer 34 on the surface. The protrusion-shaped electric contact 2 and the flat-plate-shaped electric contact 3 are in contact with each other on the surface of the high-purity Ag coating layer 24 and the surface of the low-purity Ag coating layer 34. The high-purity Ag coating layer 24 and the low-purity Ag coating layer 34 are each composed of a metal layer having Ag as a main component, but the component compositions are different from each other. Details of the structure of the protrusion-shaped electric contact 2 and the flat-plate-shaped electric contact 3 will be described below in order.

[0029] The high-purity Ag coating layer 24 is a layer exposed on the outermost surface of the metal material 20. The high-purity Ag coating layer 24 contains Ag, and the Ag content is 99.9 mass% or more. Preferably, the high-purity Ag coating layer 24 can be composed of a hard silver layer. Here, the hard silver layer refers to a layer of Ag or Ag alloy having a surface hardness of about 90 HV or more, preferably 110 HV or more, in terms of Vickers hardness. Also, the surface hardness of the high-purity Ag coating layer 24 is preferably higher than the surface hardness of the low-purity Ag coating layer 34 of the flat-plate-shaped electric contact 3.

[0030] The high-purity Ag coating layer 24 can contain only Ag and inevitable impurities, and preferably contains, in addition to Ag and inevitable impurities, an additive element having a hardening effect on the Ag layer. As such an additive element, Se, Sb, C, N, S, and the like can be listed. It is particularly preferable to use Se as the additive element. The additive amount of these additive elements is suppressed to 0.1 mass% or less of the entire high-purity Ag coating layer 24.

[0031] By making the high-purity Ag coating layer 24 have an Ag purity of up to 99.9 mass% or more, the properties of Ag, such as heat resistance, corrosion resistance, and electrical conductivity, can be effectively utilized as the properties of the high-purity Ag coating layer 24. In addition, by making the high-purity Ag coating layer 24 have a high purity, as will be described later, unlike the low-purity Ag coating layer 34 that contains an additive composed of an organic compound and has a low Ag purity, the high-purity Ag coating layer 24 is less likely to be subject to a phenomenon in which the metal structure becomes brittle due to the additive. Therefore, even if the metal material 20 provided with the high-purity Ag coating layer 24 is subjected to mechanical processing such as press working and is shaped into a protruding shape, the high-purity Ag coating layer 24 is less likely to be damaged by cracking and the like due to a load accompanying the processing. Therefore, even if the protruding electrical contact 2 is used for a long period of time and in an environment in which corrosion is likely to occur, the metal material present in the lower layer of the high-purity Ag coating layer 24, represented by the base layer 22, is not denatured by oxidation and the like due to the damage such as cracking in the high-purity Ag coating layer 24, and the electrical properties of the protruding electrical contact 2 are less likely to be degraded due to an increase in contact resistance and the like. That is, the protruding electrical contact 2 has high durability. The upper limit of the Ag concentration of the high-purity Ag coating layer 24 is not particularly specified, and it is preferable to suppress the concentration to that of an additive element such as Se that hardens the Ag layer.

[0032] The thickness of the high-purity Ag coating layer 24 is not particularly limited, and for example, from the viewpoint of sufficiently exerting the properties possessed by the high-purity Ag coating layer 24 such as the effect of suppressing damage during processing, it is preferable to be 1 μm or more, and further preferable to be 3 μm or more. On the other hand, from the viewpoint of ensuring the processability of the metal material 20 and the like, it is preferable to be 10 μm or less. In addition, the thickness of the high-purity Ag coating layer 24 is preferably greater than the thickness of the low-purity Ag coating layer 34 of the flat plate-shaped electrical contact 3.

[0033] In the metal material 20 that constitutes the protruding electrical contact 2, the above-described high-purity Ag coating layer 24 can be formed directly on the surface of the base material 21. Alternatively, another type of metal layer can be formed between the base material 21 and the high-purity Ag coating layer 24. As such another metal layer, a base layer 22 formed of Ni or a Ni alloy can be cited. The base layer 22 formed of Ni or a Ni alloy exerts the effects of suppressing the diffusion of the constituent elements of the base material 21 such as Cu to the high-purity Ag coating layer 24 and improving the adhesion of the high-purity Ag coating layer 24 to the base material 21. As the thickness of the base layer 22, a range of 0.5 μm or more and 10 μm or less can be exemplified.

[0034] Additionally, an intermediate layer can be provided immediately below the high-purity Ag coating layer 24, i.e., between the base layer 22 and the high-purity Ag coating layer 24. This intermediate layer is composed of a layer with a higher Ag purity and a thinner thickness than the high-purity Ag coating layer 24. The intermediate layer 23 serves to improve the adhesion between the high-purity Ag coating layer 24 and the base layer 22. Furthermore, the intermediate layer 23 suppresses the diffusion of elements such as C and S contained in the high-purity Ag coating layer 24 from the high-purity Ag coating layer 24 to the base layer 22. In the metal material 20, at the interfaces of adjacent layers, a portion of the metal atoms constituting the two sides of the layers can form an alloy. Furthermore, the high-purity Ag coating layer 24 is preferably exposed on the outermost surface of the metal material 20, but as long as it does not significantly impair the properties of the high-purity Ag coating layer 24, a coating made of organic materials or the like can also be formed on the surface of the high-purity Ag coating layer 24. As will be described later, the sulfur-containing organic compounds contained in the low-purity Ag coating layer 34 of the flat electrical contact 3 can act as a discoloration inhibitor, so there is no need to provide a separate layer of discoloration inhibitor on the surface of the high-purity Ag coating layer 24.

[0035] The high-purity Ag coating layer 24 can be formed by any method, such as plating or vapor deposition. From the viewpoint of simplicity, plating is particularly preferred. For example, electroplating can be performed using an Ag plating solution containing additive elements such as Se that have the effect of hardening the Ag layer. A metal layer such as a base layer 22 is appropriately formed on the surface of the substrate 21, and a high-purity Ag coating layer 24 is formed on this basis to form a flat metal material 20. The metal material 20 is then stamped to form a protruding shape, thereby creating a protruding electrical contact 2.

[0036] (Structure of a flat electrical contact) like Figure 1 As shown, the flat electrical contact 3 is made of a metal material 30, which has a substrate 31 and a low-purity Ag coating layer 34 covering the surface of the substrate 31. Similar to the substrate 21 of the metal material 20 constituting the protruding electrical contact 2, the type of metal of the substrate 31 of the metal material 30 constituting the flat electrical contact 3 is not particularly limited, and can be made of Cu or Cu alloy.

[0037] The low-purity Ag coating layer 34 contains Ag and sulfur-containing organic compounds. Furthermore, in the low-purity Ag coating layer 34, the Ag content is in the range of 97.0% by mass or more and 99.5% by mass or less.

[0038] The kind of the sulfur-containing organic compound contained in the low-purity Ag coating layer 34 is not particularly limited, and as preferable examples, benzothiazoles, mercaptans, sulfides, disulfides, sulfur-containing polymers represented by sulfonated anion polymers, and derivatives of these can be cited. The sulfur-containing organic compound can be used alone or in combination with two or more. Particularly preferably, mercaptobenzothiazole and derivatives thereof, and thio-bis-ethanol are used. The kind of the derivative is not particularly limited, and metal salts such as sodium salts can be cited.

[0039] In the low-purity Ag coating layer 34, the sulfur-containing organic compound functions to improve the wear resistance. That is, when the flat plate-shaped electrical contact 3 is brought into contact with and slides on the convex-shaped electrical contact 2, it is helpful to suppress adhesion between the low-purity Ag coating layer 34 and the high-purity Ag coating layer 24, and to keep the friction coefficient between the two electrical contacts 2, 3 low. In particular, the benzothiazoles or derivatives thereof cited above show a high effect in improving the hardness of the low-purity Ag coating layer 34 and the wear resistance resulting therefrom due to the fine crystallization of Ag. In the present specification, the sulfur-containing organic compound contained in the low-purity Ag coating layer 34 includes all components derived from the organic molecule containing a sulfur atom, and in addition to a state in which the shape of the organic molecule containing a sulfur atom is maintained, a state in which at least a part of the molecule causes a breakage and / or recombination of the intramolecular bond, a state in which at least a part of the constituent atoms represented by the sulfur atom forms a bond with an external atom such as Ag, and the like. The content of the sulfur-containing organic compound also refers to the total amount of these all components.

[0040] By the low-purity Ag coating layer 34 containing Ag at a concentration of 97.0 mass% or more, the properties of Ag, such as heat resistance, corrosion resistance, and electrical conductivity, can be sufficiently utilized as the properties of the low-purity Ag coating layer 34. In particular, by securing high electrical conductivity in the low-purity Ag coating layer 34, the contact resistance of the surface of the flat plate-shaped electrical contact 3 is reduced, and a good electrical connection can be formed with the convex-shaped electrical contact 2 of the counterpart. In addition, by the low-purity Ag coating layer 34 having high electrical conductivity, the heat generation when a large current flows through the metal material 30 can be suppressed to be small, and the flat plate-shaped electrical contact 3 can be easily applied to applications that apply a large current, represented by a large-current terminal. Further, in the manufacture of an electrical connection member such as a terminal having the flat plate-shaped electrical contact 3, although the electrical connection member including the convex-shaped electrical contact 2 is slightly lighter, by being formed into a terminal shape by machining such as press forming, a certain degree of load is applied to the metal material 30, but by the low-purity Ag coating layer 34 containing Ag at a purity of 97.0 mass% or more, the ductility of Ag can be utilized to suppress the damage of the low-purity Ag coating layer 34 accompanying the machining of the metal material 30. From the viewpoint of further improving these effects, it is more preferable that the Ag concentration of the low-purity Ag coating layer 34 be 98.0 mass% or more, and further 99.0 mass% or more.

[0041] On the other hand, by suppressing the Ag concentration of the low-purity Ag coating layer 34 to be 99.5 mass% or less, the wear resistance of the low-purity Ag coating layer 34 can be effectively improved. This is because, by suppressing the concentration of Ag in the low-purity Ag coating layer 34 to be low, and including components other than Ag, represented by sulfur-containing organic molecules, at a certain degree of concentration, the hardness of the low-purity Ag coating layer 34 is increased and the probability of contact between Ag atoms is reduced, and thus Ag adhesion is less likely to occur, and the friction coefficient of the surface of the low-purity Ag coating layer 34 is reduced. From the viewpoint of further improving these effects, it is more preferable that the Ag concentration of the low-purity Ag coating layer 34 be 99.4 mass% or less.

[0042] In the low-purity Ag coating layer 34, if the Ag content is in the range of 97.0 mass% or more and 99.5 mass% or less, the low-purity Ag coating layer 34 can contain other components in addition to Ag and the sulfur-containing organic compound, but from the viewpoint of suppressing the influence on the characteristics imparted by the sulfur-containing organic compound, it is preferable that the low-purity Ag coating layer 34 be composed only of Ag and the sulfur-containing organic compound, except for inevitable impurities. In particular, it is preferable that the low-purity Ag coating layer 34 contain, in addition to the C, S, N, and the like atoms derived from the added sulfur-containing organic compound, no added elements such as Se and the like that have the effect of hardening the Ag layer, which are appropriately added to the high-purity Ag coating layer 24, except for inevitable impurities. In addition, the content of the sulfur-containing organic compound in the low-purity Ag coating layer 34 is preferably 0.5 mass% or more and 3.0 mass% or less. Thus, the improvement effect on the wear resistance due to the addition of the sulfur-containing organic compound can be obtained at a higher level, and the decrease in the conductivity of the low-purity Ag coating layer 34 due to the addition of a large amount of the sulfur-containing organic compound is suppressed to a smaller extent.

[0043] As described above, in the low-purity Ag coating layer 34, the sulfur-containing organic compound typified by benzothiazoles has the effect of refining the Ag crystals. For example, the particle diameter of the Ag crystal grains in the low-purity Ag coating layer 34 can be 5 nm or more and 20 nm or less. The refinement of the Ag crystal grains contributes to the improvement in the hardness of the low-purity Ag coating layer 34, and the hardness of the low-purity Ag coating layer 34 is preferably 90 HV or more and 150 HV or less in terms of Vickers hardness.

[0044] The thickness of the low-purity Ag coating layer 34 is not particularly limited. For example, a thickness of 0.5 μm or more and 5 μm or less can be exemplified. The low-purity Ag coating layer 34 can sufficiently exhibit the improvement effect on the wear resistance even if it is formed to be thin, and thus can be formed thinner than the high-purity Ag coating layer 24 of the protrusion-shaped electrical contact 2. In addition, the thickness can be set to 2 μm or less.

[0045] The metal material 30 constituting the flat-shaped electrical contact 3 can also have, like the metal material 20 having the protrusion-shaped electrical contact 2, other kinds of metal layers such as a base layer 32 and / or an intermediate layer 33 between the low-purity Ag coating layer 34 and the base material 31. In addition, a coating film composed of an organic material or the like can be provided on the surface of the low-purity Ag coating layer 34. The structures that can be used as these base layer 32, intermediate layer 33, and coating film are the same as those described above with respect to the metal material 20 constituting the protrusion-shaped electrical contact 2. The same also applies to the point that it is not necessary to provide a discoloration-preventing agent layer on the surface.

[0046] The preferred structure of the low-purity Ag coating layer 34 is as described above, and for example, the Ag plating layer disclosed in Patent Document 1 can be preferably appropriately applied as the low-purity Ag coating layer 34. The low-purity Ag coating layer 34 can be formed by any method such as plating, vapor deposition, or the like. From the viewpoint of convenience and the like, plating is particularly preferable. For example, electroplating can be performed using an Ag plating solution containing a sulfur-containing organic compound. A metal layer such as a base layer 32 can be appropriately formed on the surface of the substrate 31, and the low-purity Ag coating layer 34 can be formed thereon to produce a metal material 30, and the flat plate-shaped electrical contact 3 can be formed from the metal material 30.

[0047] (Characteristics of the electrical contact pair) As described above, the electrical contact pair 1 of the present embodiment includes the protrusion-shaped electrical contact 2 having the high-purity Ag coating layer 24 on the surface and the flat plate-shaped electrical contact 3 having the low-purity Ag coating layer 34 on the surface, and the two electrical contacts 2, 3 can be electrically contacted with each other at the surfaces of the two Ag coating layers 24, 34. The high-purity Ag coating layer 24 contains Ag at a concentration of 99.0 mass% or more. The low-purity Ag coating layer 34 contains a sulfur-containing organic compound in addition to Ag, and the concentration of Ag is 97.0 mass% or more and 99.5 mass% or less.

[0048] The surfaces of the protrusion-shaped electrical contact 2 and the flat plate-shaped electrical contact 3 are both coated with a metal layer that mainly contains Ag, which is a metal excellent in characteristics such as heat resistance, corrosion resistance, and electrical conductivity, and thus the electrical contact pair 1 is excellent in electrical contact characteristics and durability. Further, by providing the low-purity Ag coating layer 34 containing a sulfur-containing organic compound and having a concentration of Ag suppressed to a prescribed range on the surface of the flat plate-shaped electrical contact 3, the occurrence of adhesion between the flat plate-shaped electrical contact 3 and the protrusion-shaped electrical contact 2 can be suppressed, and the coefficient of friction at the time of sliding can be suppressed to be low. Thus, the electrical contact pair 1 has high wear resistance. The low-purity Ag coating layer 34 is sometimes brittle in material characteristics due to the low purity of Ag, but the flat plate-shaped electrical contact 3 is different from the protrusion-shaped electrical contact 2 in that the curvature is small, and thus a large load is not applied at the time of processing, and the brittleness of the low-purity Ag coating layer 34 does not easily cause damage due to the load at the time of processing.

[0049] On the other hand, the high-purity Ag coating layer 24 having high purity of Ag is formed on the surface of the convex-shaped electrical contact 2. The convex-shaped electrical contact 2 is subjected to a large load when it is shaped into a convex shape by mechanical processing such as punching. However, since the metal layer formed on the surface is the high-purity Ag coating layer 24, the high-purity Ag coating layer 24 is less likely to be damaged by such a load. Therefore, the deterioration of the metal material 20 due to damage, such as oxidation of the lower layer metal from the crack site and a change in electrical characteristics accompanying the oxidation, can be suppressed, and the convex-shaped electrical contact 2 can be made highly durable. If the metal layer formed on the surface of the convex-shaped electrical contact 2 is a brittle metal layer such as the low-purity Ag coating layer 34, the metal layer can be cracked by the load accompanying the shaping into a convex shape. Then, with the passage of time, the metal existing in the lower layer such as the base layer 22 is oxidized from the crack site, the surface contact resistance rises, and the like, which can affect the electrical characteristics.

[0050] As described above, in the electrical contact pair 1 of the present embodiment, the high-purity Ag coating layer 24 which is less likely to be damaged at the time of processing is formed on the surface of the convex-shaped electrical contact 2 to which a large load is applied accompanying the processing, and on the other hand, the low-purity Ag coating layer 34 which shows a high effect in improving the wear resistance is formed on the surface of the flat-shaped electrical contact 3 to which the application of the load accompanying the processing is not applied or to which a small load is applied, whereby the entire electrical contact pair 1 including the convex-shaped electrical contact 2 and the flat-shaped electrical contact 3 can be made highly resistant to wear and can suppress the damage of the surface coating layer accompanying the processing, and can be made highly durable. Thus, while the influence of wear is suppressed and a low coefficient of friction between the two electrical contacts 2, 3 is obtained, the state showing good electrical characteristics such as the low coefficient of friction can be maintained for a long time and durably. By forming the low-purity Ag coating layer 34 having a high effect in improving the wear resistance on the surface of the flat-shaped electrical contact 3, although the high-purity Ag coating layer 24 which does not show such a high wear resistance when formed alone on the surface of the convex-shaped electrical contact 2, as shown in the following embodiment, a wear resistance of a high level equivalent to that when the low-purity Ag coating layer 34 is formed on the convex-shaped electrical contact 2 as well is obtained between the two electrical contacts 2, 3.

[0051] The electrical contact pair 1 of the present embodiment can be applied as an electrical contact pair constituting an electrical contact portion of various electrical connection members. The kind of the electrical connection member is not particularly limited, and a kind in which sliding between the electrical contacts 2, 3 is accompanied when the electrical connection is formed or released is preferable. Next, as a contact pair of an electrical connection terminal, the electrical contact pair 1 of the present embodiment can be applied as described below.

[0052] < Terminal Pair > The terminal pair of the embodiment of the present application includes the pair of electrical contacts 1 of the embodiment of the present application described above. That is, in the terminal pair including a first terminal having a first contact portion and a second terminal having a second contact portion, as long as the group of the first contact portion and the second contact portion is constituted by the pair of electrical contacts 1 of the embodiment of the present application and is allowed to be in electrical contact with each other.

[0053] The kind and shape of the specific terminal pair are not particularly limited, and it is preferable to constitute the terminal pair in the manner of the terminal pair 4 as shown in FIG. 1, for example. The terminal pair 4 is constituted as a group of a female terminal 5 and a male terminal 6 which is fitted into the female terminal 5. The female terminal 5 becomes a first terminal having a convex-shaped electrical contact 2 as a first contact portion, and the male terminal 6 becomes a second terminal having a flat plate-shaped electrical contact 3 as a second contact portion. Further, a high-purity Ag coating layer 24 is provided on the surface of the contact portion of the female terminal 5, and a low-purity Ag coating layer 34 is provided on the surface of the contact portion of the male terminal 6. Figure 2

[0054] The female terminal 5 and the male terminal 6 have the same shape as the publicly known female terminal and the male terminal of the fitting type. The female terminal 5 has a clamping portion 53. The clamping portion 53 is formed in a square tube shape with an opening in the front, and has an elastic contact piece 51 with a shape folded back inwardly at the inner side of the bottom surface of the clamping portion 53. On the other hand, the male terminal 6 has a tab portion 61 formed in a flat plate shape in the front. When the tab portion 61 of the male terminal 6 is inserted into the clamping portion 53 of the female terminal 5, the elastic contact piece 51 of the female terminal 5 comes into contact with the tab portion 61 of the male terminal 6 at a relief portion 51a protruding inwardly of the clamping portion 53, and exerts an upward force on the tab portion 61. The surface of the top portion of the clamping portion 53 opposite to the elastic contact piece 51 is formed as an inner opposing contact surface 52, and the tab portion 61 of the male terminal 6 is pressed by the elastic contact piece 51 to the inner opposing contact surface 52, so that the tab portion 61 is clamped and held in the clamping portion 53. Thus, electrical contact is formed between the relief portion 51a of the female terminal 5 as the convex-shaped electrical contact 2 and the surface of the tab portion 61 of the male terminal 6 as the flat plate-shaped electrical contact 3, and is maintained.

[0055] Here, the surface of at least the relief portion 51a of the elastic contact piece 51 in the metal material 20 forming the female terminal 5 is appropriately formed with the high-purity Ag coating layer 24 together with the base layer 22 and / or the intermediate layer 23 (not shown). Further, the surface of at least the tab portion 61 in the metal material 30 forming the male terminal 6 is appropriately formed with the low-purity Ag coating layer 34 together with the base layer 32 and / or the intermediate layer 33 (not shown). From the viewpoint of ease of manufacture and the like, it is sufficient that the high-purity Ag coating layer 24 is formed on the entire surface of the female terminal 5 and the low-purity Ag coating layer 34 is formed on the entire surface of the male terminal 6.

[0056] ​Thus, by forming the high-purity Ag coating layer 24 on the surface of the embossed portion 51a of the elastic contact piece 51 of the female terminal 5 that becomes the convex-shaped electrical contact 2, and forming the low-purity Ag coating layer 34 on the surface of the tab portion 61 of the male terminal 6 that becomes the flat-plate-shaped electrical contact 3, high wear resistance can be obtained in the electrical contact portion between the female terminal 5 and the male terminal 6, and damage to the surface coating layer accompanying processing can be suppressed, and high durability can be ensured. By making the electrical contact portion have high wear resistance, even if the male terminal 6 is inserted and pulled with respect to the female terminal 5 with sliding, a state with a low coefficient of friction can be stably maintained. In addition, by the surface coating layer of the electrical contact portion not being easily damaged accompanying processing, high durability is obtained. For example, even if the terminal pair 4 is used in an environment in which oxidation of metal is easily caused, such as a high-temperature environment, changes in electrical characteristics caused by oxidation can be suppressed to be small. In addition, in the female terminal 5, compared to the male terminal 6, there are portions other than the embossed portion 51a, such as the cylindrical portion of the clamping portion 53, that are easily subjected to a large load during processing, but by coating the metal layer that constitutes the surface of the metal material 20 of the female terminal 5 with the high-purity Ag coating layer 24 that is not easily brittle, damage accompanying processing is not easily caused in their processed portions. Example

[0057] An example is shown below. Note that the present application is not limited by these examples. Here, the relationship between the composition of the Ag coating layer of the convex-shaped electrical contact and the flat-plate-shaped electrical contact that constitute an electrical contact pair and the characteristics of the electrical contact pair was verified. Unless otherwise specified, the production and evaluation of the test samples were performed at room temperature in the atmosphere.

[0058] <Production of Test Samples> First, a plurality of metal materials were prepared. Specifically, a Ni layer with a thickness of 1 μm was formed on the surface of a clean Cu alloy substrate with a thickness of 0.25 mm by an electroplating method as a base layer. Then, an intermediate layer composed of pure Ag with a thickness of 0.2 μm was formed on the surface of the Ni layer by an electroplating method. Further, a plurality of Ag coating layers shown below were formed on the surface of the intermediate layer by an electroplating method. Note that the Ag concentration of each Ag coating layer was evaluated by X-ray photoelectron spectroscopy (XPS). Hard Ag layer - Ag concentration: 99.9 mass%, with Se added, thickness: 5 μm Organic-containing Ag layer 1 - Ag concentration: 99.4 mass%, with 2-mercaptobenzothiazole sodium added, thickness: 1 μm Organic-containing Ag layer 2 - Ag concentration: 98.6 mass%, with thio-bis-ethanol added, thickness: 1 μm Organic-containing Ag layer 3 - Ag concentration: 97.0 mass%, with 2-mercaptobenzothiazole sodium added, thickness: 1 μm Organic Ag layer containing 4-Ag concentration: 96.0% by mass, with added 2-mercaptobenzothiazole sodium, thickness: 1 μm Ni-containing Ag layer - Ag concentration: 99.8% by mass, Ni added, thickness: 1 μm

[0059] Using fabricated metal materials as models for electrical contact pairs, such as Figure 1 As shown, groups of protruding and flat test pieces are prepared. For the protruding test pieces, a hemispherical protrusion with an radius of 3 mm is formed by stamping a metal material. For the flat test pieces, a flat metal material is used directly as the flat electrical contact. In each sample, a metal material with an Ag coating layer having the combinations shown in Table 1 is used as the metal material constituting the protruding and flat test pieces.

[0060] <Evaluation Methods> The state of Ag coating containing sulfur-containing organic compounds Regarding a metallic material containing an organic Ag layer 1, which is representative of a low-purity Ag coating layer containing sulfur-containing organic compounds, a cross-sectional sample cut along the thickness direction was prepared and observed using a scanning transmission electron microscope (STEM). This confirmed the state of the low-purity Ag coating layer.

[0061] Initial contact resistance For electrical contact pairs in their initial state before sliding between electrical contacts, the contact resistance was measured. Specifically, for each sample's electrical contact pair, the protruding electrical contact of the protruding test piece was brought into contact with the flat electrical contact of the flat test piece at its top, and the contact resistance was measured while applying a contact load of 30 N. The measurement was performed using the four-terminal method. The open-circuit voltage was set to 20 mV, and the current was set to 10 mA. A contact resistance less than 0.2 mΩ was considered sufficiently low (A). Conversely, a contact resistance greater than 0.2 mΩ was considered high (B).

[0062] abrasion resistance For each pair of protruding and flat test pieces, the coefficient of friction was measured while the test piece was sliding to evaluate its wear resistance. For each pair of electrical contacts, the protruding electrical contact of the protruding test piece was slid across the surface of the flat test piece with its top in contact with the flat electrical contact of the flat test piece. A contact load of 5 N was applied, and the sliding was repeated over a distance of 2 mm. During the sliding, the dynamic friction force acting between the electrical contacts was measured using a load cell. The coefficient of friction was obtained by dividing the dynamic friction force by the load.

[0063] In the obtained friction coefficient measurement results, when the friction coefficient falls to less than 0.3 during 30 sliding cycles, it is evaluated as high wear resistance (A). On the other hand, when the friction coefficient is greater than 0.3 during the same sliding, it is evaluated as low wear resistance (B). Furthermore, when the friction coefficient is greater than 1.0 during the sliding, it is evaluated as very low wear resistance (B-).

[0064] Damage to protruding electrical contacts The surface of the protruding test piece in the electrical contact pair of each sample was observed using scanning electron microscopy (SEM). In the obtained SEM images, when no cracks with a width exceeding 0.5 μm appeared on the surface of the protruding electrical contact, it was evaluated as having minimal processing damage (A). On the other hand, when cracks with a width exceeding 0.5 μm appeared, it was evaluated as having significant processing damage (B).

[0065] <Experimental Results> Figure 3 The image shows a STEM image (1,000,000x magnification) of a cross-section of the Ag layer 1 containing organic matter. In the image, the gray areas represent the Ag coating layer, indicating the presence of multiple grains aggregated within it. The grain size is as small as approximately 10 nm.

[0066] Figure 4 The results of measuring the coefficient of friction while sliding samples A1 and B1-B3 are shown as representative examples. The evaluation results of the type of Ag coating and wear resistance of the two electrical contacts are also presented in tabular form, along with the figures. Figure 4 In all the samples shown, although the initial coefficient of friction was suppressed to a low level, in sample B1, the coefficient of friction fluctuated violently with sliding, and a tendency to increase with the number of sliding cycles was observed. In sample B3, although not as pronounced as in sample B1, a tendency for the coefficient of friction to increase with the number of sliding cycles was also observed. In contrast, in samples A1 and B2, the change and increase in the coefficient of friction with sliding was suppressed to a small extent, and even after 50 sliding cycles, the coefficient of friction remained essentially unchanged.

[0067] Furthermore, in Figure 5A , 5B This shows a representative example of a SEM image obtained to evaluate damage to a protruding electrical contact. Figure 5A A diagram showing the protruding electrical contacts, made of a metallic material with a hard Ag layer, constituting sample A1, etc. On the other hand, Figure 5B Images are shown for observation of the protruding electrical contacts, etc., made of a metallic material containing an organic Ag layer 1, constituting sample B2. The upper images are all observed at 50x magnification, and the lower images are all observed at 500x magnification, focusing on the area near the top of the protruding electrical contacts.Figure 5B The use of a metal material provided with an organic matter-containing Ag layer 1 resulted in the occurrence of many dark stripe-shaped cracks observed over a large area of the surface of the convex-shaped electrical contact. In contrast, the use of a metal material provided with a hard Ag layer resulted in no clear cracks identifiable by SEM images in the entire area of the convex-shaped electrical contact. Figure 5A

[0068] The evaluation results for each of the test samples Al to A3 and the test samples Bl to B5 are summarized in Table 1 below, together with the combination of the Ag coating layers.

[0069] [Table 1]

[0070] The following conclusions can be drawn from Table 1. The test samples Al to A3 are each provided with a hard Ag layer on the surface of the convex-shaped electrical contact, i.e., a high-purity Ag coating layer containing Ag at a concentration of 99.9 mass% or more, and an organic matter-containing Ag layer 1, 2, or 3 on the surface of the flat-shaped electrical contact, i.e., a low-purity Ag coating layer containing Ag and a sulfur-containing organic compound and having an Ag concentration of 97.0 mass% or more and 99.5 mass% or less. In each of these test samples Al to A3, the initial contact resistance is sufficiently low and high wear resistance is obtained. Damage to the convex-shaped electrical contact is also suppressed to be small. As to the test sample Al, these results are also shown in Figure 4 and Figure 5A .

[0071] On the other hand, in the test samples Bl to B5, the Ag coating layer provided on the surface of the convex-shaped electrical contact is not a high-purity Ag coating layer containing Ag at a concentration of 99.9 mass% or more, or the Ag coating layer provided on the surface of the flat-shaped electrical contact is not a low-purity Ag coating layer containing Ag and a sulfur-containing organic compound and having an Ag concentration of 97.0 mass% or more and 99.5 mass% or less. Or both. In each of these test samples Bl to B5, at least one of the initial contact resistance being low, the wear resistance being high, and the damage to the convex-shaped electrical contact being small is not achieved at a sufficiently high level.

[0072] In the test sample Bl, both electrical contacts have a hard Ag layer on the surface. In this test sample Bl, as shown in Figure 4 , the wear resistance is reduced. In the test samples B2 and B3, at least the surface of the convex-shaped electrical contact is provided with an organic matter-containing Ag layer 1. In each of these test samples B2 and B3, as shown in Figure 5B ​As shown, the damage to the surface of the convex-shaped electrical contact is large. From the above comparison of the samples Al to A3 and the samples Bl to B3, in order to improve the wear resistance and suppress the damage to the surface of the convex-shaped electrical contact accompanying the processing, it is necessary to form a cladding layer that is not easily damaged, such as a hard Ag layer, on the surface of the convex-shaped electrical contact, and to form a cladding layer that has a high wear resistance improvement effect, such as a low-purity Ag cladding layer containing a sulfur-containing organic compound, on the surface of the flat-shaped electrical contact. Note that, as shown in the results of the friction coefficient measurement, in the sample B3 in which the combination of the surface cladding layers of the convex-shaped electrical contact and the flat-shaped electrical contact is opposite to that of the sample Al, the wear resistance is lower than that of the sample Al, but it is considered that this is the influence of the damage generated on the surface of the convex-shaped electrical contact. Figure 4

[0073] In the samples B4 and B5, as in the samples Al to A3, a hard Ag layer is provided on the surface of the convex-shaped electrical contact, and an Ag cladding layer having a lower Ag concentration than the hard Ag layer is provided on the surface of the flat-shaped electrical contact. However, in the sample B4, unlike the samples Al to A3, the Ag concentration in the Ag cladding layer provided on the surface of the flat-shaped electrical contact is lower than 97.0 mass%. In this sample B4, the initial contact resistance is high. It is considered that this is because the Ag concentration in the Ag cladding layer is too low, and thus the electrical conductivity is low. In the sample B5, unlike the samples Al to A3, a sulfur-containing organic compound is not added to the Ag cladding layer on the surface of the flat-shaped electrical contact. In addition, the Ag concentration exceeds 99.5 mass%. In this sample B5, the wear resistance is low. It is considered that this is because the Ag concentration of the Ag cladding layer is too high, and thus the increase in the friction coefficient due to Ag adhesion cannot be sufficiently suppressed. From the comparison of the samples Al to A3 and the samples B4 and B5, in order to sufficiently suppress the contact resistance and obtain the effects of improving the wear resistance of the electrical contact pair and suppressing the damage to the convex-shaped electrical contact accompanying the processing, it is effective to provide the Ag cladding layer on the surface of the flat-shaped electrical contact as a low-purity Ag cladding layer containing a sulfur-containing organic compound and having an Ag concentration of 97.0 mass% or more and 99.5 mass% or less.

[0074] The embodiments of the present application have been described in detail above, but the present application is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present application. Explanation of Reference Signs

[0075] 1 Electrical contact pair 2 Convex-shaped electrical contact 3 Flat-shaped electrical contact 20, 30 Metal material 21, 31 Base material 22, 32 Base layer 23, 33 Intermediate layer​ 24 high purity Ag cladding layer 34 low purity Ag cladding layer 4 terminal pair 5 female terminal 51 elastic contact piece 51a embossed portion 52 inner opposing contact surface 53 clamping portion 6 male terminal 61 tab portion

Claims

1. An electrical contact pair comprising: a convex electrical contact projecting toward a surface side; and a flat plate-shaped electrical contact having a smaller curvature than the convex electrical contact and capable of being in electrical contact with the surface and the convex electrical contact, wherein the convex electrical contact has a high-purity Ag coating layer containing Ag on a surface, the content of Ag in the high-purity Ag coating layer being 99.9 mass% or more, and on the other hand the flat plate-shaped electrical contact has a low-purity Ag coating layer containing Ag and a sulfur-containing organic compound on a surface, the content of Ag in the low-purity Ag coating layer being 97.0 mass% or more and 99.5 mass% or less.

2. The electrical contact pair according to claim 1, wherein the content of the sulfur-containing organic compound in the low-purity Ag coating layer is 0.5 mass% or more and 3.0 mass% or less.

3. The electrical contact pair according to claim 1, wherein the high-purity Ag coating layer is configured as a hard silver layer.

4. The electrical contact pair according to claim 1, wherein in the convex electrical contact and the flat plate-shaped electrical contact, a base layer composed of Ni or a Ni alloy is formed so as to coat a surface of a base material composed of Cu or a Cu alloy, the high-purity Ag coating layer and the low-purity Ag coating layer are respectively formed so as to coat surfaces of the base layer.

5. A terminal pair comprising: a first terminal having a first contact portion and a second terminal having a second contact portion, a group of the first contact portion and the second contact portion is configured by the electrical contact pair according to any one of claims 1 to 4 and capable of being in electrical contact with each other.

6. The terminal pair according to claim 5, wherein the first terminal is configured as a female terminal having the convex electrical contact, the second terminal is configured as a male terminal having the flat plate-shaped electrical contact and capable of being fitted with the first terminal.

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