Plating material for terminal, terminal using them, and electric wire with terminal

Abstract

To provide a plating material for a terminal, using silver plating and having an excellent corrosion resistance, a terminal used for them, and an electric wire with the terminal.SOLUTION: A plating material 1 for a terminal, comprises a metal base material 2 containing a copper or a copper alloy; and a silver plating layer 4 containing a silver or a silver alloy arranged onto the metal base material 2. A front surface roughness Sa of the silver plating layer 4 is 0.17 μm or more and 0.50 μm or less, and a Vickers hardness of a front surface of the silver plating layer 4 is 70Hv or more and 130Hv or less.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a plating material for a terminal, and a terminal and an electric wire with a terminal using the same. [Background technology]

[0002] In recent years, the demand for hybrid and electric vehicles has been increasing, but these vehicles use high-power motors, which cause large currents to flow through their wiring and terminals, resulting in large amounts of heat. For this reason, silver plating, which has a low heat generation rate (low electrical resistivity), is used for the terminals used in these vehicles.

[0003] The silver constituting the silver plating layer reacts with sulfur in the air to become silver sulfide, which easily discolors, and furthermore, the silver sulfide forms an insulating coating that increases the contact resistance between the terminal fittings. Therefore, Patent Document 1 discloses an electrical contact material in which a precious metal plating layer made of an alloy of palladium, ruthenium, etc. is provided instead of a silver plating layer on a metal base material containing copper or a copper alloy, thereby adjusting the surface hardness and preventing corrosion due to sulfidation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5676053 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in Patent Document 1, since the additive element is a precious metal, there is a problem in that the production costs are higher than in silver plating.

[0006] The present invention has been made in view of the problems inherent in the conventional techniques, and an object of the present invention is to provide a plating material for terminals using silver plating and having excellent corrosion resistance, as well as a terminal and an electric wire with a terminal using the same. [Means for solving the problem]

[0007] A plating material for a terminal according to an embodiment of the present invention comprises a metal base material containing copper or a copper alloy, and a silver plating layer containing silver or a silver alloy arranged on the metal base material, in which the surface roughness Sa of the silver plating layer is 0.17 μm or more and 0.50 μm or less, and the Vickers hardness of the surface of the silver plating layer is 70 Hv or more and 130 Hv or less.

[0008] A terminal according to another aspect of the present invention is formed from the terminal plating material.

[0009] A terminal-attached electric wire according to another aspect of the present invention includes a terminal. Effect of the Invention

[0010] According to the present invention, it is possible to provide a plating material for terminals using silver plating and having excellent corrosion resistance, as well as a terminal and an electric wire with a terminal using the same. [Brief description of the drawings]

[0011] [Figure 1] 2 is a cross-sectional view showing a schematic state of the terminal plating material according to the present embodiment before a corrosive gas test. FIG. [Diagram 2] 4 is a cross-sectional view showing a schematic state of the terminal plating material according to the present embodiment after a corrosive gas test. FIG. [Diagram 3] FIG. 1 is a cross-sectional view showing a schematic state of a conventional terminal plating material before a corrosive gas test. [Figure 4] FIG. 1 is a cross-sectional view showing a schematic state of a conventional terminal plating material after a corrosive gas test. [Diagram 5] FIG. 2 is a perspective view showing an example of an electric wire with a terminal according to the present embodiment before the electric wire is crimped with the terminal. [Figure 6] FIG. 2 is a perspective view showing an example of an electric wire with a terminal according to the present embodiment after the electric wire is crimped with the terminal. [Figure 7A]4 is an electron microscope photograph showing an enlarged view of the surface state of the silver plating layer of the terminal plating material according to the present embodiment before a corrosive gas test. [Figure 7B] 1 is an electron microscope photograph showing an enlarged view of the surface state of a silver plating layer of a conventional terminal plating material before a corrosive gas test. [Figure 8A] 4 is an electron microscope photograph showing an enlarged view of the surface state of the silver plating layer of the terminal plating material according to the present embodiment after a corrosive gas test. [Figure 8B] 1 is an electron microscope photograph showing an enlarged view of the surface state of a silver plating layer of a conventional terminal plating material after a corrosive gas test. [Figure 9A] 4 is an electron microscope photograph of an enlarged cross section of a silver plating layer of the terminal plating material according to the present embodiment after a corrosive gas test. [Figure 9B] 1 is an electron microscope photograph showing an enlarged cross section of a silver plating layer of a conventional terminal plating material after a corrosive gas test. [Figure 10A] FIG. 1 is a schematic diagram of an experiment for measuring contact resistance. [Figure 10B] FIG. 1 is a schematic diagram of an experiment for measuring contact resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the plating material for a terminal according to the present embodiment, and the terminal and the electric wire with terminal using the same will be described in detail with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for the convenience of explanation and may differ from the actual ratios.

[0013] [Terminal plating materials 1] 1, the plating material for terminal 1 of this embodiment has a metal base material 2 containing copper or a copper alloy, and a silver plating layer 4 disposed on the metal base material 2. Hereinafter, each component of this embodiment will be described in detail.

[0014] [Metal base material 2] The metal base material 2 is a material to be plated on the silver plating layer 4 or the undercoat layer 3 described below. The metal base material 2 includes copper or a copper alloy. As the copper or copper alloy used for the metal base material 2, for example, those specified in the Japanese Industrial Standard JIS H3100 (copper and copper alloy plate and strip) can be used. Specifically, oxygen-free copper (C1020), tough pitch copper (C1100), phosphorus-deoxidized copper (C1201), tin-containing copper (C1441), zirconium-containing copper (C1510), iron-containing copper (C1921), etc. can be used.

[0015] Furthermore, the material of the metal base material 2 may include metals and compounds other than copper and copper alloys. Examples of metals and compounds other than copper and copper alloys include one or more elements selected from the group consisting of Ni, Co, Fe, Pt, Au, Al, Si, Cr, Mg, Mn, Mo, Rh, Ta, Ti, W, U, V, and Zr, or compounds containing the one or more elements. The specific shape of the metal base material 2 is not particularly limited, and may be a shape according to the application.

[0016] [Silver plating layer 4] The silver plating layer 4 is disposed on the metal base material 2 or the underlayer 3 described later. The silver plating layer 4 contains silver or a silver alloy. The silver plating layer 4 has a role of leaving copper diffused from the metal base material 2 and suppressing the surface precipitation of copper. Therefore, the terminal plating material 1 of this embodiment can improve the heat resistance of the silver plating by suppressing the surface precipitation of copper on the metal base material 2 after heat generation. From the viewpoint of suppressing the surface precipitation of copper, it is preferable that the silver plating layer 4 covers the entire metal base material 2. Also, as shown in FIG. 1, the silver plating layer 4 may indirectly cover the metal base material 2 via the underlayer 3 described later.

[0017] The silver plating layer 4 may be an alloy containing silver and at least one metal selected from the group consisting of tin (Sn), copper (Cu), nickel (Ni), cobalt (Co), palladium (Pd), bismuth (Bi), indium (In), antimony (Sb), selenium (Se) and tellurium (Te). The silver alloy may be a binary alloy containing two metal components, a ternary alloy containing three metal components, or an alloy containing four or more metal components. The silver plating layer 4 may be a single layer or a multi-layer.

[0018] The silver plating bath used to form the silver plating layer 4 may contain, for example, silver salt, salts of the above-mentioned metals, electrical conductivity salts, and brighteners. Materials used for the silver salt include, for example, at least one salt selected from the group consisting of silver cyanide, silver iodide, silver oxide, silver sulfate, silver nitrate, silver methanesulfonate, and silver chloride. The electrical conductivity salt includes, for example, at least one salt selected from the group consisting of potassium cyanide, sodium cyanide, potassium pyrophosphate, silver methanesulfonate, potassium iodide, and sodium thiosulfate. Brighteners include, for example, metal brighteners such as antimony, selenium, and tellurium, and organic brighteners such as benzenesulfonic acid and mercaptan. The silver ion concentration of the silver plating bath is preferably, for example, 30 g / L to 50 g / L.

[0019] The plating process for forming the silver plating layer 4 is preferably constant current electrolysis, since the film thickness can be easily controlled. The conditions for electrolytic plating are not particularly limited, and plating can be performed by a known plating method. The current density may be set in consideration of various factors such as productivity, plating bath composition, ion concentration, and the shape of the object to be plated. In addition, there is no particular limitation on the plating bath temperature.

[0020] From the viewpoint of suppressing the diffusion of copper in the metal base material after heating and suppressing surface precipitation of copper, the thickness of the silver plating layer 4 is preferably 3 μm or more and 10 μm or less, and more preferably 5 μm or more and 10 μm or less.

[0021] The surface roughness Sa of the silver plating layer 4 is 0.17 μm or more and 0.50 μm or less. By setting the surface roughness Sa of the silver plating layer 4 in this range, as described later, it is possible to reduce the effects of corrosion and discoloration on the surface of the terminal plating material 1 and to minimize the increase in contact resistance. The surface roughness Sa is the arithmetic mean roughness, and can be measured in accordance with Japanese Industrial Standard JIS B0601:2013 (Geometrical Product Specifications (GPS)-Surface Quality: Profile Curve Method-Terminology, Definitions, and Surface Quality Parameters).

[0022] The Vickers hardness of the surface of the silver plating layer 4 is 70 Hv or more and 130 Hv or less. By setting the Vickers hardness of the surface of the silver plating layer 4 in this range, as described later, it is possible to easily destroy the sulfide film formed by corrosion of the surface of the plating material for terminal 1. The Vickers hardness can be measured in accordance with Japanese Industrial Standard JIS Z2244:2009 (Vickers hardness test - Test method).

[0023] FIG. 2 shows a cross-sectional view of the terminal plating material 1 of this embodiment after the corrosion gas test. In general, silver constituting the silver plating layer reacts with sulfur in the air to become silver sulfide and discolor, and the silver sulfide forms an insulating coating, which increases the contact resistance of the surface of the silver plating layer 4. However, due to the unevenness and low surface hardness of the surface of the terminal plating material 1 of this embodiment, i.e., the silver plating layer 4, the corrosion film (sulfide film) formed by corrosion of the surface of the silver plating layer 4 is easily destroyed, and the corrosion film 5 is generated intensively in the valleys of the silver plating layer 4. On the other hand, the corrosion of the peaks of the silver plating layer 4 is small, so the discolored area on the entire surface of the silver plating layer 4 is small. Furthermore, it is possible to minimize the increase in contact resistance on the surface of the silver plating layer 4.

[0024] Meanwhile, a cross-sectional view of a conventional terminal plating material 51 is shown in FIG. 3. The silver plating layer 54 is disposed on a metal base material 52 containing copper or a copper alloy or on a base layer 53 described later. The silver plating layer 54 contains silver or a silver alloy. In the conventional terminal plating material 51, the surface roughness Sa of the silver plating layer 54 is less than 0.17 μm, or the Vickers hardness of the surface of the silver plating layer 54 exceeds 130 Hv. A cross-sectional view of the conventional terminal plating material 51 after a corrosion gas test is shown in FIG. 4. In the conventional terminal plating material 51, a corrosion film 55 is generated uniformly on the entire surface of the silver plating layer 54, so that the entire surface of the silver plating layer 54 is discolored, and it is difficult to suppress an increase in the contact resistance of the surface of the silver plating layer 54.

[0025] [Base layer 3] 1, the plating material for terminal 1 of this embodiment may further include an underlayer 3 in order to impart various functions. In this embodiment, the underlayer 3 is disposed between the metal base material 2 and the silver plating layer 4.

[0026] The underlayer 3 preferably contains at least one metal selected from the group consisting of nickel, copper, and silver. Specifically, the underlayer 3 preferably contains at least one metal selected from the group consisting of nickel, a nickel alloy, copper, a copper alloy, silver, and a silver alloy.

[0027] It is more preferable that the underlayer 3 contains nickel or a nickel alloy. When the underlayer 3 contains nickel or a nickel alloy, for example, the underlayer 3 can suppress the diffusion of copper of the metal base material 2 into the silver plating layer 4, and improve the contact reliability and heat resistance. That is, the underlayer 3 functions as a barrier layer. When the underlayer 3 contains either nickel or a nickel alloy, the layer thickness is not particularly limited as long as it functions as a barrier layer, but is preferably more than 0.5 μm and 1 μm or less.

[0028] When the underlayer 3 contains at least one metal selected from the group consisting of copper, a copper alloy, silver, and a silver alloy, it can improve the adhesion between the metal base material 2 and the silver plating layer 4, for example. That is, the underlayer 3 functions as a strike plating layer. When the underlayer 3 contains at least one metal selected from the group consisting of copper, a copper alloy, silver, and a silver alloy, the layer thickness is not particularly limited as long as the adhesion is improved, and even a very thin layer thickness may improve the adhesion in some cases.

[0029] The underlayer 3 may be a single layer or multiple layers. For example, the underlayer 3 may include a lower layer and an upper layer disposed on the lower layer. For example, the lower layer of the underlayer 3 may include either nickel or a nickel alloy, and the upper layer of the underlayer 3 may include at least one metal selected from the group consisting of copper, a copper alloy, silver, and a silver alloy. Thus, for example, a nickel plating layer may be formed on the lower layer of the underlayer 3, and a silver strike plating layer may be formed on the upper layer of the underlayer 3. The combination of these layers may be appropriately changed depending on the purpose.

[0030] The method for forming the underlayer 3 is not particularly limited, but for example, the material to be plated, that is, the metal base material 2, can be placed in a plating bath and plated by a known plating method.

[0031] The surface of the plating material 1 for terminals preferably has a contact resistance of 0 mΩ to 0.9 mΩ, more preferably 0 mΩ to 0.7 mΩ, when a contact load of 2 N is applied using a contact having a hemispherical protrusion with a radius of 1 mm as the contact portion. By setting the contact resistance of the plating material 1 for terminals in this range, heat generation and power consumption can be reduced when the material is used as a terminal.

[0032] Thus, the terminal plating material 1 of this embodiment includes the metal base material 2 containing copper or a copper alloy, and the silver plating layer 4 containing silver or a silver alloy disposed on the metal base material 2. The silver plating layer has a surface roughness Sa of 0.17 μm or more and 0.50 μm or less, and a Vickers hardness of the surface of the silver plating layer of 70 Hv or more and 130 Hv or less. Therefore, the terminal plating material 1 has excellent corrosion resistance.

[0033] [Terminal 10] The terminal 10 of the present embodiment is formed from the terminal plating material 1. Therefore, the terminal 10 of the present embodiment has high corrosion resistance while minimizing the increase in contact resistance, compared to terminals plated with conventional silver or silver alloys.

[0034] [Terminal Wire 20] As shown in Fig. 5 and Fig. 6, the electric wire with terminal 20 of this embodiment includes a terminal 10. Specifically, the electric wire with terminal 20 of this embodiment includes an electric wire 30 having a conductor 31 and a wire coating material 32 that covers the conductor 31, and a terminal 10 that is connected to the conductor 31 of the electric wire 30 and is formed from a plating material. Note that Fig. 5 shows a state before the electric wire is crimped with the terminal, and Fig. 6 shows a state after the electric wire is crimped with the terminal.

[0035] The terminal 10 shown in FIG. 5 is a female crimp terminal. The terminal 10 has an electrical connection portion 11 that is connected to a mating terminal (not shown). The electrical connection portion 11 has a box-like shape and incorporates a spring piece that engages with the mating terminal. Furthermore, on the opposite side of the terminal 10 to the electrical connection portion 11, an electric wire connection portion 12 is provided that is connected to an end portion of the electric wire 30 by crimping. The electrical connection portion 11 and the electric wire connection portion 12 are connected via a connecting portion 13. Note that the electrical connection portion 11, the electric wire connection portion 12, and the connecting portion 13 are made of the same material and integrally constitute the terminal 10, but for convenience, names are given to each portion.

[0036] The electric wire connection portion 12 includes a conductor crimping portion 14 that crimps a conductor 31 of the electric wire 30 , and a covering material crimping portion 15 that crimps a wire covering material 32 of the electric wire 30 .

[0037] The conductor crimping portion 14 comes into direct contact with the conductor 31 exposed by removing the wire coating material 32 at the end portion of the electric wire 30, and has a bottom plate portion 16 and a pair of conductor clamping pieces 17. The pair of conductor clamping pieces 17 extend upward from both side edges of the bottom plate portion 16. The pair of conductor clamping pieces 17 are bent inward so as to wrap around the conductor 31 of the electric wire 30, thereby enabling the conductor 31 to be clamped so as to be in close contact with the upper surface of the bottom plate portion 16. The conductor crimping portion 14 is formed into a generally U-shaped cross section by the bottom plate portion 16 and the pair of conductor clamping pieces 17.

[0038] The covering material clamping portion 15 is in direct contact with the wire covering material 32 at the end portion of the electric wire 30, and has a bottom plate portion 18 and a pair of covering material clamping pieces 19. The pair of covering material clamping pieces 19 extend upward from both side edges of the bottom plate portion 18. The pair of covering material clamping pieces 19 are bent inward to wrap around the portion to which the wire covering material 32 is attached, so that the wire covering material 32 can be clamped in a state in which it is in close contact with the upper surface of the bottom plate portion 18. The covering material clamping portion 15 is formed into a generally U-shaped cross section by the bottom plate portion 18 and the pair of covering material clamping pieces 19. The bottom plate portion 16 of the conductor crimping portion 14 to the bottom plate portion 18 of the covering material clamping portion 15 are continuously formed as a common bottom plate portion.

[0039] The electric wire 30 has a conductor 31 and an electric wire covering material 32 that covers the conductor 31. The material of the conductor 31 may be a metal having high electrical conductivity. For example, copper, a copper alloy, aluminum, an aluminum alloy, or the like may be used. Note that in recent years, there has been a demand for lighter electric wires. For this reason, the conductor 31 is preferably made of lightweight aluminum or an aluminum alloy.

[0040] The material of the wire coating material 32 that covers the conductor 31 can be a resin that can ensure electrical insulation. For example, an olefin-based resin can be used as the material of the wire coating material 32. Specifically, the material of the wire coating material 32 can be mainly composed of at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), an ethylene copolymer, and a propylene copolymer. Also, the material of the wire coating material 32 can be mainly composed of polyvinyl chloride (PVC). Among these, it is preferable that the material of the wire coating material 32 contains polypropylene or polyvinyl chloride as the main component because of its high flexibility and durability. Here, the main component refers to a component that accounts for 50% by mass or more of the entire wire coating material 32.

[0041] The terminal 10 can be manufactured, for example, as follows. First, as shown in FIG. 5, the end portion of the electric wire 30 is inserted into the electric wire connection portion 12 of the terminal 10. As a result, the conductor 31 of the electric wire 30 is placed on the upper surface of the bottom plate portion 16 of the conductor crimping portion 14, and the portion of the electric wire 30 to which the electric wire coating material 32 is attached is placed on the upper surface of the bottom plate portion 18 of the coating material crimping portion 15. Next, the electric wire connection portion 12 and the end portion of the electric wire 30 are pressed to deform the conductor crimping portion 14 and the coating material crimping portion 15. Specifically, the pair of conductor crimping pieces 17 of the conductor crimping portion 14 are bent inward to encase the conductor 31, thereby crimping the conductor 31 so as to be in close contact with the upper surface of the bottom plate portion 16. Furthermore, the pair of coating material clamping pieces 19 of the coating material clamping portion 15 are bent inward to enclose the portion with the wire coating material 32 attached, thereby clamping the wire coating material 32 so that it is in close contact with the upper surface of the bottom plate portion 18. In this manner, the terminal 10 and the wire 30 can be crimped and connected, as shown in FIG.

[0042] The electric wire with terminal 20 of this embodiment includes a terminal 10. Therefore, the electric wire with terminal 20 of this embodiment has high corrosion resistance at the terminal 10, and can minimize an increase in contact resistance, compared to conventional terminals plated with silver or a silver alloy. Therefore, the electric wire with terminal 20 of this embodiment can be suitably used in places such as hybrid cars and electric cars.

[0043] The above describes the terminal 10 and the electric wire 20 with terminal according to this embodiment, but this embodiment is not limited to the above embodiment and can be suitably used, for example, as a high-voltage connector terminal that is repeatedly inserted and removed in an electric vehicle or the like. EXAMPLES

[0044] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0045] First, the metal base material to be plated was pretreated. Specifically, the metal base material was washed with an alkaline degrease, pickled by immersing in 10% sulfuric acid for 1 minute, and then washed with water. The metal base material used was NB-109EH (manufactured by DOWA Metaltech Co., Ltd.), a copper alloy.

[0046] Next, a nickel plating layer was formed on the metal base material. The nickel plating layer was an undercoat layer. Specifically, the metal base material pretreated as described above was immersed in a plating bath for the nickel plating layer, and constant current electrolysis was performed using a DC stabilized power source. After electrolysis was completed, the metal base material was removed from the silver plating bath and washed with water. As a result, a metal base material was obtained in which a nickel plating layer was formed on the entire surface of the metal base material. The thickness of the nickel plating layer was 1.0 μm.

[0047] Furthermore, a silver plating layer was formed on the nickel plating layer. The metal base material on which the nickel plating layer was formed was immersed in a silver plating bath and electrolyzed at a constant current using a DC stabilized power source. After electrolysis, the metal base material was removed from the plating bath and washed with water. As a result, a metal base material was obtained in which a nickel plating layer and a silver plating layer were formed on the entire surface of the metal base material. The target thickness of the silver plating layer was set to 5 to 10 μm. Test samples of Example 1 (terminal plating material 1 according to this embodiment) and Comparative Example 1 (conventional terminal plating material 51) were produced by the above-mentioned production method.

[0048] [evaluation] The terminal plating materials prepared as described above were used as test samples and were evaluated by the following methods.

[0049] (Surface roughness) The surface roughness was measured by measuring the arithmetic average roughness of the test sample surface using a contact surface roughness measuring device (Alpha-Step D500, manufactured by KLA Tencor Corporation) in accordance with JIS B0601: 2013. The measurement results for Example 1 and Comparative Example 1 are shown in Table 1.

[0050] (Vickers hardness) The Vickers hardness was evaluated by measuring the surface of the test sample using a microhardness tester (DUH-211, manufactured by Shimadzu Corporation) in accordance with JIS Z2244:2009. The test temperature was 25°C and the test force was 3 gf. The measurement results of Example 1 and Comparative Example 1 are shown in Table 1.

[0051] (Corrosive gas test) Using a gas corrosion tester, a corrosion gas test was performed on the test sample under the conditions of corrosive gas type H2S (hydrogen sulfide), concentration 1 ppm, temperature 25°C, humidity 75% RH, and exposure time 504 hours.

[0052] (Microscopic Observation) The cross sections of the test samples before and after the corrosive gas test were observed by a transmission electron microscope (TEM-EDX). For the terminal plating material 1 according to this embodiment, FIG. 7A is a photograph showing an enlarged view of the surface state of the silver plating layer before the corrosive gas test, and FIG. 8A is a photograph showing an enlarged view of the surface state of the silver plating layer after the corrosive gas test. Also, FIG. 9A is a photograph showing an enlarged view of the cross section of the silver plating layer after the corrosive gas test for the terminal plating material 1. In FIG. 7A, the streaks visible on the surface of the silver plating layer are rolling marks on the copper base material before plating. In FIG. 8A, rolling marks on the copper base material could be confirmed as in FIG. 7A. And, in FIG. 9A, it was observed that the corrosion film shown as sulfide was generated intensively in the valleys of the silver plating layer on the surface of the silver plating layer. Therefore, it was confirmed that the terminal plating material 1 according to this embodiment was in the state shown in FIG. 2.

[0053] On the other hand, for the conventional terminal plating material 51, FIG. 7B is a photograph showing an enlarged view of the surface state of the silver plating layer before the corrosive gas test, and FIG. 8B is a photograph showing an enlarged view of the surface state of the silver plating layer after the corrosive gas test. FIG. 9B is a photograph showing an enlarged view of the cross section of the silver plating layer after the corrosive gas test for the conventional terminal plating material. In FIG. 7B, the streaks visible on the surface of the silver plating layer are rolling marks on the copper base material before plating. In FIG. 8B, rolling marks on the copper base material could be confirmed as in FIG. 7B. And, in FIG. 9B, it was observed that a corrosion film was uniformly generated on the entire surface of the silver plating layer. Therefore, it was confirmed that the conventional terminal plating material 51 was in the state shown in FIG. 4.

[0054] (contact resistance) The contact resistance was measured by a four-terminal method (N=3) using an electric contact simulator (manufactured by Yamazaki Seiki Kenkyusho Co., Ltd.). Specifically, as shown in Figs. 10A and 10B, a plate 60 with a film thickness of 5 μm, which is a test sample, was fixed on a stage, and a contactor 61 was brought into contact with the plate 60. The contactor 61 had a hemispherical convex portion with a radius of 1 mm as a contact portion, and the projection height of the contactor 61 was set to 0.5 mm. Then, the contact resistance (mΩ) was measured when a contact load of 2 N was applied to the surface of the silver plating layer before and after the corrosive gas test. The measurement results of Example 1 and Comparative Example 1 are shown in Table 1.

[0055] (Whether or not discoloration occurs) The surfaces of the test samples after the corrosive gas test were visually observed to check for discoloration. The results of Example 1 and Comparative Example 1 are shown in Table 1.

[0056] [Table 1]

[0057] From the results in Table 1, in Example 1, the surface roughness Sa of the silver plating layer was 0.17 μm or more and 0.50 μm or less, and the Vickers hardness of the surface of the silver plating layer was 70 Hv or more and 130 Hv or less. Therefore, on the surface of the silver plating layer after the corrosive gas test, the corrosion film was generated intensively in the valleys of the silver plating layer, and no discoloration of the surface of the silver plating layer was observed. In addition, the contact resistance of the silver plating layer before and after the corrosive gas test was both 0.7 mΩ or less, which was a good result.

[0058] On the other hand, in Comparative Example 1, the surface roughness Sa of the silver plating layer was less than 0.17 μm, and the Vickers hardness of the silver plating layer exceeded 130 Hv. Therefore, on the surface of the silver plating layer after the corrosive gas test, a corrosion film was uniformly formed on the entire surface of the silver plating layer, and discoloration of the surface of the silver plating layer was observed. In addition, the contact resistance of the silver plating layer before and after the corrosive gas test was 1.0 mΩ or more, and it was found that the increase in contact resistance was more difficult to suppress than in Example 1.

[0059] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment. [Explanation of symbols]

[0060] 1. Terminal plating materials 2. Metallic Base Material 3 Base layer 4 Silver plating layer 10 Terminals 20 Wire with terminal

Claims

1. A metal base material including copper or a copper alloy; a silver plating layer including silver or a silver alloy disposed on the metal base material; Equipped with The silver plating layer has a surface roughness Sa of 0.17 μm or more and 0.50 μm or less, and a Vickers hardness of the surface of the silver plating layer is 70 Hv or more and 130 Hv or less.

2. 2. The plating material for a terminal according to claim 1, further comprising a base layer disposed between the metal base material and the silver plating layer and containing at least one metal selected from the group consisting of nickel, copper, and silver.

3. A terminal formed from the plating material for terminals according to claim 1 or 2.

4. A terminal-attached electric wire comprising the terminal according to claim 3 .

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