Silver-containing films and terminal materials

Abstract

To provide a terminal material that can sufficiently suppress a short circuit of a contact caused by falling of conductive particles, and has sufficient resistance to micro-sliding wear and conductivity.SOLUTION: A terminal material has a base metal which consists of copper or copper alloy, a base layer which consists of any one kind or more of Ni, Co and Fe, and a silver-containing film in this order, the silver-containing film includes a silver plated layer which contains silver by 50 mass% or more, and particles made of non-conductive organic compound having a circle-equivalent diameter of 50 μm or less, where the contact resistance of a silver-containing film side surface when the following micro-sliding wear test is applied is 1 mΩ or less. Micro-sliding wear test: a terminal material to be tested and a counterpart material on which a hemispherical protrusion having a curvature radius R=1.8 mm is formed on the silver-containing film side surface of the terminal material are prepared, and a surface having the protrusion of the counterpart material is allowed to reciprocally slide against the silver-containing film side surface of the terminal material to be tested at a vertical load to be applied: 3 N, slide distance: 50 μm, and slide speed: 100 μm / sec., which is 1 cycle and the material is allowed to slide for 10000 cycles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to silver-containing films and termination materials. [Background technology]

[0002] With the trend toward lighter automobiles in recent years, there is a demand to reduce the amount of wire harnesses used in automobiles. For example, the amount of wire harnesses can be reduced by directly connecting devices such as engines and motors to the electronic components (called "ECUs") that control them.

[0003] Because engines, motors, and other equipment vibrate violently, the connectors used to connect them and the terminals that make them up are exposed to intense vibration. Vibration can cause fretting wear (i.e., repeated microscopic friction wears the plating on the contacts). The recent miniaturization of terminals has led to a decrease in contact pressure and a worsening vibration environment, further increasing the likelihood of fretting wear.

[0004] To address fretting wear, Patent Document 1 discloses a technique in which a copper alloy base material is roughened, and then Ni, Cu, and Sn plating is applied thereon, followed by a reflow treatment, exposing a predetermined Cu-Sn layer on the surface of the Sn layer. While this technique makes fretting wear less likely to occur, once fretting wear occurs, there is a risk that the material may easily become exposed.

[0005] The use of Ag plating film is also being considered to improve wear resistance. For a long time, the purpose of improving wear resistance by increasing the hardness of Ag plating film has been (1) High hardness of Ag plating film due to fine grain (2) High hardness achieved by alloying Ag with Se (selenium) or Sb (antimony) However, neither of the above methods (1) nor (2) is effective enough against fretting wear. In addition, Se and Sb are toxic elements, so they must be carefully controlled, and alloying them also causes the problem of reduced electrical conductivity.

[0006] In addition, various attempts have been made to improve the wear resistance of plating films by ideas other than increasing their hardness. As disclosed in Non-Patent Documents 1 and 2, the following have been mainly considered: (3) Improvement of wear resistance by codeposition (dispersion plating) of carbon particles into Ag plating film have also been investigated. These investigations have mainly used graphite, carbon black (CB), or carbon nanotubes (CNT), which act as solid lubricants. In fact, Non-Patent Document 1 shows that an Ag-graphite composite plating film, which is formed by suspending graphite particles in an Ag plating solution and performing plating, can achieve better wear resistance than not only Ag plating films but also hard Ag-Sb alloy plating films. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2014-208904 [Non-patent literature]

[0008] [Non-Patent Document 1] Materia, Vol. 58, No. 1 (2019), pp. 41-43 [Non-patent document 2] Surface Finishing Society of Japan, Abstracts of the 81st Lecture Meeting, 27A-1 Summary of the Invention [Problem to be solved by the invention]

[0009] In the prior art related to (3) above, as disclosed in Non-Patent Documents 1 and 2, when carbon particle-dispersed plating is applied to terminal materials and repeated sliding (insertion and removal) occurs, the carbon particles held in the plating film may fall off as the contact wears. Because carbon-based particles have good conductivity, if they fall off the terminal surface and accumulate around the contact, it may cause a short circuit of the contact. Furthermore, the prior art related to (3) above may not be able to sufficiently suppress fretting wear.

[0010] The present invention was made in consideration of these circumstances, and one of its purposes is to provide a terminal material and a terminal that can sufficiently suppress short circuits at the contacts due to the falling off of conductive particles, and that have sufficient fretting wear resistance and conductivity. [Means for solving the problem]

[0011] Aspect 1 of the present invention is A substrate including, in this order, a base material made of copper or a copper alloy, an underlayer which is one or more layers made of one or more selected from the group consisting of Ni, Co, and Fe, and a silver-containing film, the silver-containing film includes a silver plating layer containing 50% by mass or more of silver, and particles made of a non-conductive organic compound having an equivalent circle diameter of 50 μm or less and brought into contact with the silver plating layer; This terminal material has a contact resistance of 1 mΩ or less on the silver-containing film side surface when subjected to the following fretting wear test. Micro-sliding wear test: Prepare the terminal material to be tested and a mating material having a hemispherical protrusion with a curvature radius R = 1.8 mm formed on the silver-containing film side surface of the terminal material. The surface of the mating material having the protrusion is slid back and forth against the silver-containing film side surface of the terminal material to be tested with an applied normal load of 3 N, a sliding distance of 50 μm, and a sliding speed of 100 μm / sec, for 10,000 cycles.

[0012] Aspect 2 of the present invention is In the terminal material according to aspect 1, the silver plating layer contains 90% by mass or more of silver.

[0013] Aspect 3 of the present invention is In the terminal material according to aspect 1 or 2, the non-conductive organic compound contains a carbonyl group (—C(═O)—) in a unit molecular structure and does not have a ring structure.

[0014] A fourth aspect of the present invention is A terminal using the terminal material according to any one of the first to third aspects. [Effects of the Invention]

[0015] According to the embodiments of the present invention, it is possible to provide a terminal material and a terminal that can sufficiently suppress short circuits at contact points due to the falling off of conductive particles and that have sufficient fretting wear resistance and conductivity. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic cross-sectional view of an example of a terminal material according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view of another example of a terminal material according to an embodiment of the present invention. [Figure 3] FIG. 3 is a schematic cross-sectional view of another example of a terminal material according to an embodiment of the present invention. [Figure 4] Figure 4 shows the results of the fretting wear resistance evaluation of No. 1 terminal material. [Figure 5] Figure 5 shows the results of the fretting wear resistance evaluation of terminal material No. 2. [Figure 6] Figure 6 shows the results of the fretting wear resistance evaluation of terminal material No. 3. [Figure 7] Figure 7 shows the results of the fretting wear resistance evaluation of terminal material No. 4. [Figure 8] Figure 8 shows the results of the fretting wear resistance evaluation of terminal material No. 5. [Figure 9] Figure 9 shows the results of the fretting wear resistance evaluation of terminal material No. 6. DETAILED DESCRIPTION OF THE INVENTION

[0017] The inventors conducted extensive research to develop a terminal material that can adequately suppress contact shorts due to the shedding of conductive particles and has sufficient fretting wear resistance and conductivity. As a result, they discovered that sufficient fretting wear resistance and conductivity can be achieved by using a specific layer structure comprising a silver-containing film containing particles of a non-conductive organic compound with a circle-equivalent diameter of 50 μm or less in contact with (supported by) the silver-plated layer. This is believed to be due to, for example, fretting (and the resulting heat generation, etc.) causing some of the non-conductive organic compound to decompose and diffuse to the vicinity of the terminal material surface, and / or some of the non-conductive organic compound to react with the silver-plated layer near the terminal material surface, thereby reducing the coefficient of friction near the terminal material surface, thereby improving fretting wear resistance. The amount of decomposition and reaction products is small, and is therefore believed not to reduce the conductivity of the terminal material. Furthermore, because the non-conductive organic compound is in the form of particles rather than a film and in contact with the silver-plated layer, the silver-plated layer can be exposed on the terminal material surface, thereby maintaining the initial conductivity of the terminal material. As a result, it is possible to sufficiently suppress the risk of short-circuiting of the contacts due to the dropping off of conductive particles, and it is possible to realize a terminal material that has sufficient fretting wear resistance and conductivity. It should be noted that the above mechanism does not limit the technical scope of the embodiments of the present invention.

[0018] The following provides details of each requirement stipulated by the embodiment of the present invention.

[0019] A terminal material according to an embodiment of the present invention comprises, in this order, a base material made of copper or a copper alloy, one or more underlayers composed of at least one selected from the group consisting of Ni, Co, and Fe, and a silver-containing film, wherein the silver-containing film comprises a silver plating layer containing at least 50 mass% silver, and particles made of a non-conductive organic compound having an equivalent circle diameter of 50 μm or less that are in contact with the silver plating layer, and the contact resistance of the surface on the silver-containing film side when subjected to the fretting wear test described below is 1 mΩ or less. Micro-sliding wear test: Prepare the terminal material to be tested and a mating material having a hemispherical protrusion with a curvature radius R = 1.8 mm formed on the silver-containing film side surface of the terminal material. The surface of the mating material having the protrusion is slid back and forth against the silver-containing film side surface of the terminal material to be tested with an applied normal load of 3 N, a sliding distance of 50 μm, and a sliding speed of 100 μm / sec, for 10,000 cycles. As a result, short circuits at the contact points due to the dropping off of conductive particles can be sufficiently suppressed, and sufficient fretting wear resistance and conductivity can be exhibited.

[0020] FIG. 1 shows a schematic cross-sectional view of an example of a terminal material according to an embodiment of the present invention. In FIG. 1, terminal material 1 includes, in this order, a base material 2 (hereinafter simply referred to as "base material 2") made of copper or a copper alloy, one or more underlayers 3 composed of at least one element selected from the group consisting of Ni, Co, and Fe, and a silver-containing film 4. Silver-containing film 4 includes a silver plating layer 4a and particles 4b (hereinafter simply referred to as "particles 4b") made of a non-conductive organic compound and having an equivalent-circle diameter of 50 μm or less, which are in contact with (or adhere to) silver plating layer 4a. Terminal material 1 exhibits a contact resistance of 1 mΩ or less on the surface of silver-containing film 4 when subjected to the fretting wear test.

[0021] The base material 2 may be made of pure copper such as oxygen-free copper (OFC), or one or more of copper alloys such as CuFeP, CuNiSi, CuTiCr, CuSnP, and CuMg. The required properties (e.g., conductivity, springiness, strength) of the terminal material vary depending on the location of use. Therefore, the material of the base material 2 (and its tempering conditions) can be appropriately selected depending on the required properties.

[0022] The terminal material 1 (and a terminal using the same) including the base material 2 can be used in high-temperature environments, such as in the engine compartment of an internal combustion engine or in the connection part of a battery in an electric vehicle. In high-temperature environments, Cu in the base material 2 may diffuse toward the silver-containing film 4 and reach the surface of the silver-containing film 4, generating Cu oxides and possibly increasing the contact resistance of the terminal material 1. Therefore, one or more underlayers 3 composed of one or more elements selected from the group consisting of Ni, Co, and Fe are provided between the base material 2 and the silver-containing film 4. This makes it possible to suppress diffusion of Cu from the base material 2 into the silver-containing film 4. It is particularly preferable that the underlayer 3 contains Ni in terms of plating workability, etc. The underlayer 3 may be made up of multiple layers.

[0023] The average thickness of the underlayer 3 (for example, the average thickness of the underlayer 3 obtained from two or more cross sections of the terminal material) is preferably 0.1 μm or more, and more preferably 0.2 μm or more. This suppresses pinholes and effectively prevents copper diffusion. On the other hand, if the underlayer 3 becomes too thick, the effect of suppressing Cu diffusion may saturate. From the viewpoints of productivity, cost, and processability during terminal molding, the average thickness of the underlayer 3 is preferably 3.0 μm or less, and more preferably 2.0 μm or less.

[0024] The silver plating layer 4a is a layer containing 50% or more by mass of silver. As the silver plating layer 4a, in addition to soft Ag plating, hard Ag plating, bright Ag plating, semi-bright Ag plating, and the like, which are commonly used for terminal surface treatment, Ag alloy plating containing Sn and / or Ni, etc., can also be used for the purpose of improving the corrosion resistance (such as sulfurization resistance) and fretting wear resistance of the silver-containing film 4. However, since fretting wear resistance can be imparted mainly by particles 4b made of a non-conductive organic compound, if there is no other purpose such as improving corrosion resistance, it is preferable to use a pure Ag plating layer with excellent conductivity as the carrier. For example, it is preferable for the silver plating layer 4a to contain 90% or more by mass of silver, more preferably 95% or more by mass, and even more preferably 99% or more by mass.

[0025] The average thickness of the silver plating layer 4a (for example, the average thickness of the silver plating layer 4a obtained from any two or more cross sections of the terminal material) is not particularly limited and can be adjusted appropriately depending on the application, but may be, for example, 100 μm or less, or even 50 μm or less.

[0026] Regarding the particles 4b made of a non-conductive organic compound, "non-conductive" means that they do not exhibit conductivity, and for example, the volume resistivity measured based on ASTM D257 is approximately 10 3 This refers to a value of [Ω·cm] or more.

[0027] With respect to particles 4b made of a non-conductive organic compound, the term "organic compound" refers to compounds containing carbon, excluding compounds with simple structures such as carbon monoxide, carbon dioxide, carbonates, hydrocyanic acid, cyanates, thiocyanates, BC, and SiC. For example, a silicone resin having a siloxane bond (-Si-O-Si-) in the main chain and organic groups in the side chains is included in the term "organic compound" in this specification.

[0028] Non-conductive organic compounds contain a fluoro group (-F), a methyl group (-CH3), a carbonyl group (-C(=O)-), an amino group (-NR 1 R 2 and R 1 and R 2 is hydrogen or a hydrocarbon group, and R 1 and R 2 Preferably, the polymer contains at least one selected from the group consisting of a carbonyl group (-C(=O)-), which may be the same or different, and a hydroxy group (-OH). More preferably, the polymer contains a carbonyl group (-C(=O)-) and does not have a ring structure within the unit molecular structure. This further enhances fretting wear resistance. Here, the term "unit molecular structure" refers to one repeating unit in the case of a macromolecule (polymer), and to an individual molecule in the case of a non-polymer.

[0029] With respect to the particles 4b made of a non-conductive organic compound, the term "particles" refers to relatively small substances having a circle-equivalent diameter of 50 μm or less, and may have any shape. In one embodiment of the present invention, from the viewpoint of conductivity, the average particle size (average circle-equivalent diameter) of the particles 4b may be 10 μm or less. In another embodiment of the present invention, from the viewpoint of fretting wear resistance, the average particle size of the particles 4b may be 0.1 μm or more.

[0030] 2 shows a schematic cross-sectional view of another example of a terminal material according to an embodiment of the present invention, in which particles 4b are embedded in the silver plating layer 4a in terminal material 11. Here, "embedded" means that, for each particle 4b, either all of the particles are embedded in the silver plating layer 4a, or a portion of the particles is embedded in the silver plating layer 4a, with the remaining portion exposed on the surface of the silver plating layer 4a.

[0031] 3 shows a schematic cross-sectional view of another example of a terminal material according to an embodiment of the present invention, in which the particles 4b are completely embedded in the silver plating layer 4a in the terminal material 21. In the case of FIG. 3, the particles 4b may be of a size that allows them to be completely embedded in the silver plating layer 4a, that is, the average particle size of the particles 4b may be less than the thickness of the silver plating layer 4a.

[0032] In the terminal material according to the embodiment of the present invention, "particles are in contact" may mean, for example, that particles 4b are in contact with (adhered to) the surface of the silver plating layer 4a as shown in FIG. 1, or that particles 4b are co-deposited (embedded) in the silver plating layer 4a. In this case, each particle 4b may be completely embedded in the silver plating layer 4a as shown in FIG. 3, or a portion of each particle 4b may be exposed on the surface of the silver plating layer 4a as shown in FIG. 2. Whether or not "particles are in contact" can be determined, for example, by observing the cross section of the terminal material 1 (11, 21).

[0033] From the viewpoint of further increasing the electrical conductivity (further decreasing the contact resistance), a configuration in which the particles 4b are co-deposited (embedded) in the silver plating layer 4a as shown in Fig. 2, or a configuration in which the particles 4b are completely embedded in the silver plating layer 4a as shown in Fig. 3, is preferred. On the other hand, from the viewpoint of further increasing the fretting wear resistance, a configuration in which the particles 4b are in contact with (adhered to) the surface of the silver plating layer 4a as shown in Fig. 1, or a configuration in which the particles 4b are co-deposited (embedded) in the silver plating layer 4a as shown in Fig. 2, is preferred.

[0034] In the terminal materials 1, 11, and 21 according to the embodiments of the present invention, conductive particles may be in contact with the silver plating layer 4a in some cases. However, the fewer conductive particles there are, the more preferable it is, as it is possible to prevent short circuits at the contacts due to the conductive particles falling off. Therefore, of the particles in contact with the terminal materials 1, 11, and 21 according to the embodiments of the present invention, preferably 50% by volume or more of the particles 4b made of a non-conductive organic compound are particles, and more preferably 60% by volume or more, 70% by volume or more, 80% by volume or more, or 90% by volume or more, and even more preferably all (100% by volume) of the particles 4b made of a non-conductive organic compound are particles. In addition, the terminal materials 1, 11, and 21 according to the embodiments of the present invention may be in contact with inorganic particles in some cases.

[0035] The terminal materials 1, 11, and 21 according to the embodiments of the present invention may include other layers (for example, a strike plating layer, etc.) in order to achieve the object of the present invention.

[0036] In a method for manufacturing a terminal material 1 according to an embodiment of the present invention, for example, a base layer 3 is formed on a base material 2, such as a copper plate, by passing an electric current through a predetermined plating solution containing at least one material selected from the group consisting of Ni, Co, and Fe, which are materials that have a copper diffusion suppression effect under typical conditions. Then, a silver (or silver alloy) plating solution is passed through under typical conditions to form a silver plating layer 4a. A dispersion of particles 4b made of a non-conductive organic compound is then applied to the surface. This results in the terminal material 1. In some cases, a strike silver plating process may be performed before the silver plating process.

[0037] In the above manufacturing method, particles 4b made of a non-conductive organic compound are dispersed in a silver (or silver alloy) plating solution, and electroplating is performed while stirring, thereby obtaining a terminal material in which particles 4b made of a non-conductive organic compound are co-deposited in the silver plating layer 4a (terminal material 11 in which some of the particles 4b are exposed on the surface of the silver plating layer 4a, or terminal material 21 in which all of the particles 4b are buried in the silver plating layer 4a).

[0038] In the process of dispersing the particles 4b in a plating solution and conducting electroplating to codeposit the particles 4b into the silver plating layer 4a, the following reactions (A) and (B) proceed simultaneously. (A) A reaction in which particles dispersed in liquid are electrostatically or physically adsorbed (contacted) to the surface of a substrate. (B) A reaction in which a silver plating layer 4a is deposited (grown) on the surface of the substrate. The particles 4b adsorbed in (A) are incorporated into the silver plating layer 4a in (B), resulting in "co-deposition." Under conditions where the co-deposition plating proceeds steadily, the particles 4b adsorbed in the early stages of the reaction are incorporated into the silver plating layer 4a, while at the same time new particles 4b are adsorbed. For this reason, even when the plating process is stopped, in many cases the particles 4b are exposed on the outermost surface. In a typical co-deposition plating process, it is possible to easily produce a terminal material 11 in which some of the particles 4b are exposed on the surface of the silver plating layer 4a. Here, the amount of co-deposition of particles 4b into the silver plating layer 4a is determined by the balance between the adsorption frequency of (A) and the plating film growth rate of (B), and therefore, it is possible to change the amount of co-deposition by changing the plating conditions (and plating bath conditions). For example, by using a plating solution that does not contain particles 4b dispersed in the plating solution at the final stage of the plating process, or by changing the stirring speed of the plating solution to reduce the adsorption frequency of (A), a layer that does not co-deposit particles 4b can be formed on the outermost surface of the plating, thereby making it possible to manufacture a terminal material 21 in which all of the particles 4b are embedded in the silver plating layer 4a.

[0039] Terminal materials 1, 11, and 21 according to embodiments of the present invention have not only sufficient electrical conductivity but also sufficient fretting wear resistance. Specifically, terminal materials 1, 11, and 21 according to embodiments of the present invention can achieve an initial contact resistance of 1.0 mΩ or less, and can maintain the contact resistance at 1.0 mΩ or less even after 10,000 cycles of the fretting wear test described below. Terminal materials 1, 11, and 21 according to embodiments of the present invention preferably maintain the contact resistance at 1.0 mΩ or less even after 20,000 cycles of the fretting wear test described below. <Fretting wear test> A terminal material to be tested and a mating material, on the silver-containing film side surface of the terminal material, on which a hemispherical protrusion with a curvature radius R = 1.8 mm is formed, for example, by a hand press, are prepared. The surface of the mating material with the protrusion is slid back and forth against the silver-containing film side surface of the terminal material to be tested for a predetermined number of cycles, with a normal load of 3 N, a sliding distance of 50 μm, and a sliding speed of 100 μm / sec. The sliding tester can be, for example, a CRS-B1050CHO manufactured by Yamazaki Seiki Kenkyusho.

[0040] Terminals according to embodiments of the present invention include terminal materials 1, 11, and 21 according to embodiments of the present invention. Terminals according to embodiments of the present invention can be manufactured by forming terminal materials 1, 11, and 21 according to embodiments of the present invention into a terminal shape, or by first forming a base material 2 into a terminal shape, and then forming an underlayer 3, which is one or more layers composed of at least one type selected from the group consisting of Ni, Co, and Fe, and a silver-containing film 4 (silver plating layer 4a and particles 4b composed of a non-conductive organic compound) on the base material 2. Terminals according to embodiments of the present invention can be used to directly connect devices such as engines and motors to an ECU. [Example]

[0041] The following examples are provided to more specifically describe the embodiments of the present invention. The embodiments of the present invention are not limited to the following examples, and may be modified as appropriate within the scope of the above-described and below-described aims, and all such modifications are within the technical scope of the embodiments of the present invention.

[0042] A 0.3 mm thick pure copper (copper content 99% by mass or more) base material was used, and after degreasing the surface of the base material with acetone, a matte Ni Watt bath was used, and a Ni plate was used as the counter electrode, and the current was 5 A / dm 2 A current was applied for 2 minutes at a current density of 5 A / dm to form a 1 μm thick underlayer (Ni content of 99 mass % or more). 2A current was passed through the plating solution at a current density of 3 A / dm for 1 minute to form a strike Ag plating layer (silver content of 99% by mass or more) with a thickness of approximately 0.1 μm. Subsequently, a commercially available non-cyanide semi-bright Ag plating solution (Dainsilver GPE-SB manufactured by Daiwa Kasei Co., Ltd.) was used, and a predetermined amount of particles made of non-conductive organic compounds with a circle equivalent diameter of 50 μm or less and a surfactant (dispersant) shown in Table 1 was dispersed in the plating solution. While stirring, a pure Ag plate was used as the counter electrode and a current density of 3 A / dm was passed through the plating solution. 2 Electricity was applied for 5 minutes at a current density of 1000 kJ / s to obtain terminal materials Nos. 1 to 4, each of which contained a silver-containing film in which each particle was co-deposited (embedded) in a semi-bright Ag plating layer (silver content of 99% by mass or more) approximately 10 μm thick. Surflon S231 (manufactured by AGC Seimi Chemical) was used as the surfactant for Nos. 1 to 3, with an additive amount of 50 g / L. No. 4 used sodium naphthalene sulfonate as the surfactant and carboxymethyl cellulose (CMC) as the dispersant (stabilizer).

[0043] To compare terminal materials Nos. 1 to 4, terminal materials Nos. 5 and 6 were fabricated, which do not contain particles made of non-conductive organic compounds. Unlike Nos. 1 to 4, No. 5 was fabricated by forming a semi-bright Ag plating layer approximately 10 μm thick (silver content of 99% by mass or more) without dispersing particles made of various non-conductive organic compounds and surfactants (dispersants) in the semi-bright Ag plating solution. Unlike Nos. 1 to 4, No. 6 was fabricated by forming a strike Ag plating layer approximately 0.1 μm thick (silver content of 99% by mass or more) using a cyanide bath strike Ag plating solution, then changing the semi-bright Ag plating solution to a bright Ag plating solution (N-BRIGHT manufactured by Metalor Technologies). The bright Ag plating solution was not dispersed with particles made of various non-conductive organic compounds and surfactants (dispersants), and the plating was performed at 1.5 A / dm using a pure Ag plate as the counter electrode. 2 A current was passed through the wire for 15 minutes at a current density of 10 μm to form a bright Ag plating layer (silver content of 99% by mass or more) having a thickness of about 10 μm.

[0044] [Table 1]

[0045] Terminal materials No. 1 to No. 6 were evaluated for initial contact resistance and fretting wear resistance.

[0046] <Evaluation of initial contact resistance> The silver-containing film side surfaces of terminal materials Nos. 1 to 6 were measured five times using an electrical contact simulator (manufactured by Yamazaki Seiki Kenkyusho) by the four-terminal method under conditions of an open circuit voltage of 20 mV, a current of 10 mA, and a load of 3 N, and the average value was taken as the initial contact resistance value. Contact resistance exceeding 1.0 mΩ was rated as poor conductivity (×), and contact resistance of 1.0 mΩ or less was rated as sufficient conductivity (◯).

[0047] <Fretting wear resistance evaluation> Terminal materials Nos. 1 to 6 (10 cm × 10 cm) were prepared, along with mating materials (0.5 cm × 5 cm) on which hemispherical protrusions with a curvature radius of 1.8 mm were formed by hand pressing on the silver-containing film side surface of the terminal materials. The surface of the mating material with the protrusions was slid back and forth against the silver-containing film side surface of terminal materials Nos. 1 to 6 using a sliding tester, a Yamazaki Seiki Kenkyusho CRS-B1050CHO, with a normal load of 3 N, a sliding distance of 50 μm, and a sliding speed of 100 μm / sec., for a set number of cycles. The contact resistance after each cycle was measured in the same manner as above. The results are shown in Figures 4 to 9. Figures 4 to 9 show the results of fretting wear tests conducted on terminal materials Nos. 1 to 6, respectively, with N=2. The number of cycles at which the contact resistance exceeded 1.0 mΩ, and the shorter of the two cycles (N=2) was less than 10,000, was rated as poor (×), 10,000 or more but less than 20,000 was rated as good (◯), and 20,000 or more was rated as excellent (◎). After 20,000 cycles, the wear marks were observed to evaluate whether the base material (or the underlayer) was exposed.

[0048] The results are summarized in Table 2. In the "Short Circuit Prevention" column, if 50% or more by volume of the particles in contact with the silver plating layer are non-conductive, a rating of "Good" indicates that short circuits at the contact points due to particle shedding can be sufficiently prevented. If less than 50% by volume of the particles in contact with the silver plating layer are non-conductive (i.e., if more than 50% by volume of the particles in contact with the silver plating layer are conductive), a rating of "Possible" indicates that there is a risk of short circuits at the contact points due to particle shedding. In the "Overall Evaluation" column, if the "Short Circuit Prevention," "Conductivity," and "Freak Wear Resistance" columns were all rated "Good," the rating was recorded as "Good." If the "Freak Wear Resistance" column was rated "Good," the rating was recorded as "Good." If even one of the "Short Circuit Prevention," "Conductivity," and "Freak Wear Resistance" columns was rated "Possible," the rating was recorded as "Possible."

[0049] [Table 2]

[0050] The results in Table 2 can be considered as follows. All of the terminal materials Nos. 1 to 4 in Table 2 satisfied the requirements specified in the embodiment of the present invention, and were able to sufficiently suppress short circuits at the contacts due to the detachment of conductive particles, and had sufficient conductivity and fretting wear resistance. Of these, the silver-containing films Nos. 1 to 3 satisfied the preferable requirements that the non-conductive organic compound contain a carbonyl group (-C(=O)-) in the unit molecular structure and do not have a ring structure, and therefore the number of cycles at which the contact resistance exceeded 1.0 mΩ was 20,000 or more.

[0051] For terminal materials No. 5 and 6, the contact resistance exceeded 1.0 mΩ in less than 10,000 cycles of the fretting abrasion test. This is thought to be because, in terminal materials No. 5 and 6, the particles made of non-conductive organic compounds were not in contact with the silver plating layer, and the base material (or underlayer) was easily exposed by fretting abrasion, which then oxidized, increasing the contact resistance. Note that for No. 6, the silver plating layer had hardened due to the action of the brightener, and although the timing of the increase in contact resistance was slightly delayed compared to No. 5, no significant improvement was observed. [Explanation of symbols]

[0052] 1 Terminal material 2 Base material 3 Base layer 4 Silver-containing film 4a Silver plating layer 4b Particles made of non-conductive organic compounds 11 Terminal material 21 Terminal material

Claims

1. A terminal material including a silver-containing film, The silver-containing film includes a silver plating layer containing 50% by mass or more of silver, and particles made of a non-conductive organic compound having an equivalent circle diameter of 50 μm or less and embedded in the silver plating layer, wherein the non-conductive organic compound contains a carbonyl group (—C(═O)—) in a unit molecular structure and does not have a ring structure. terminal material.

2. The terminal material according to claim 1 , wherein the silver plating layer contains 90% by mass or more of silver.

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