Terminal

Abstract

To provide a terminal that suppresses increases in material cost and manufacturing process cost, prevents cracking during bending by making a lower layer thin, and suppresses a rate of increase in resistance due to temperature changes caused by long-term use.SOLUTION: A terminal 1 of the present invention comprises a copper-based substrate 11 made of copper or a copper alloy, and a surface coating 14 having a two-layer structure composed of a lower layer 12 formed on the copper-based substrate 11 and having a thickness in the range of 0.1 μm or more and 0.5 μm or less, and an upper layer 13 formed on the lower layer 12 and made of silver or a silver alloy, wherein the material constituting the lower layer 12 is a nickel alloy containing nickel and an alloy component X, and the alloy component X is one or more selected from the group consisting of gallium, bismuth, and indium.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a terminal. [Background technology]

[0002] Conventionally, the widely used high-voltage connector terminals for automotive applications are components used for connecting electrical wiring and circuits, and can be easily connected electrically by inserting them. However, as the voltage of these electrical wirings increases, low contact resistance is required for connections between terminals. To reduce this contact resistance, the contact portions of the terminals are generally made by providing a silver-plated layer on a copper-based substrate. The copper atoms in the copper-based substrate of this high-voltage connector terminal tend to diffuse toward the silver-plated layer located above, resulting in an increase in contact resistance due to alloying with the silver atoms in the silver-plated layer. To address this problem, an intermediate layer (lower layer) made of nickel or a nickel alloy is provided between the copper-based substrate and the silver-plated layer (upper layer), preventing the copper atoms from diffusing from the copper-based substrate to the silver-plated layer.

[0003] If the thickness of this lower layer made of nickel or a nickel alloy is too thin, the diffusion prevention effect is weak, and conventionally, a thickness of about 0.8 to 1.5 μm is required. However, if the lower layer is too thick, not only does the cost increase, but the resistance also increases and cracks and other breakages are more likely to occur during bending. From these viewpoints, it is desirable to make the thickness of the lower layer as thin as possible.

[0004] For example, Patent Document 1 discloses a silver-coated terminal material in which a nickel layer of 0.05 μm or more and 5.0 μm or less, an intermediate layer, and a silver layer are laminated in this order on a substrate made of copper or a copper alloy, and the intermediate layer has a thickness of 0.02 μm or more and 1.0 μm or less and is a silver alloy containing silver (Ag) and X, where the X contains one or more of tin, bismuth, gallium, indium, and germanium. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-031732 Summary of the Invention [Problem to be solved by the invention]

[0006] The silver-coated terminal material described in Patent Document 1 has a single-layer or double-layer intermediate layer made of a nickel (Ni) layer and a silver alloy containing X such as tin on the copper-based substrate to prevent diffusion of copper atoms that make up the copper-based substrate. Therefore, in contrast to conventional high-voltage connector terminals that have a two-layer surface coating consisting of a nickel layer (lower layer) and a silver (Ag) layer (upper layer) on a copper-based substrate, the silver-coated terminal material described in Patent Document 1 has a three-layer or four-layer surface coating formed on a copper-based substrate, consisting of a nickel layer (lower layer), a single or two-layer middle layer made of a silver alloy, and a silver layer (upper layer).As a result of the increased number of layers making up the surface coating, there are problems such as increased costs for materials, etc., and a deterioration in workability due to the increased number of manufacturing processes.

[0007] Therefore, the present invention aims to provide a terminal in which the surface coating formed on a copper-based substrate made of copper or a copper alloy has a two-layer structure consisting of a lower layer of a nickel alloy containing a specific alloy component X and an upper layer made of silver or a silver alloy, thereby suppressing increases in costs such as material costs and deterioration of workability in the manufacturing process, and by making the lower layer thin, preventing cracks during bending and suppressing the rate of increase in resistance due to temperature rise over time in use. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention is as follows. (1) a copper-based substrate made of copper or a copper alloy; a surface coating having a two-layer structure including a lower layer formed on the copper-based substrate and having a thickness in the range of 0.1 μm to 0.5 μm, and an upper layer formed on the lower layer and made of silver or a silver alloy; the material constituting the lower layer is a nickel alloy containing nickel and an alloy component X, The terminal, wherein the alloy component X is one or more of gallium, bismuth, and indium. (2) The terminal according to (1), wherein the content of X in the nickel alloy is in the range of 0.2 mass % to 7.0 mass %. (3) The terminal according to claim (1) or (2), wherein the thickness of the copper-based base material is in the range of 0.1 mm or more and 0.4 mm or less. [Effects of the Invention]

[0009] The present invention can reduce the number of layers that make up the surface coating, and by reducing the number of layers, it is possible to prevent increases in costs such as material costs, and by reducing the number of manufacturing steps, it is possible to improve workability.In addition, by making the lower layer thin, it is possible to provide a terminal that prevents cracks during bending and suppresses the rate of increase in resistance due to temperature rise over time during use. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing the structure of a terminal according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes embodiments of the present invention. Note that the following description is merely an example of an embodiment of the present invention and does not limit the scope of the claims.

[0012] A terminal according to one embodiment of the present invention will be described. A terminal according to one embodiment of the present invention is composed of a copper-based substrate made of copper or a copper alloy, and a two-layer surface coating comprising a lower layer formed on the copper-based substrate and having a thickness in the range of 0.1 μm to 0.5 μm, and an upper layer formed on the lower layer and made of silver or a silver alloy, wherein the material constituting the lower layer is a nickel alloy containing nickel and an alloy component X, and the alloy component X is one or more components selected from the group consisting of gallium, bismuth, and indium.

[0013] (Terminal) FIG. 1 is a schematic diagram showing the structure of a terminal according to one embodiment of the present invention. The terminal 1 shown in Fig. 1 is composed of a conductive copper-based substrate 11 containing copper or a copper alloy as a main component, a lower layer 12 formed on the surface of the substrate from a nickel alloy containing nickel and an alloy component X as a main component, and a two-layer surface coating 14 formed on the surface of the substrate from an upper layer 13 containing silver or a silver alloy as a main component. Each part of the terminal 1 of the present invention will be described in detail below. Note that reference numerals in the drawings are used only here.

[0014] (Copper base material) The copper-based substrate is a conductive member formed mainly of copper or a copper alloy. The shape of the copper-based substrate is not particularly limited and may be appropriately selected depending on the application, but is preferably a strip or plate material, and may also be a rod or wire material.

[0015] (copper or copper alloy) The copper-based substrate in the terminal of the present invention is electrically conductive and is made of copper or a copper alloy. Among these, copper (pure copper, for example, OFC (oxygen-free copper)) and Cu-Zn, Cu-Sn-P, Cu-Ni-Si, Cu-Sn-Ni, Cu-Cr-Mg, or Cu-Ni-Si-Zn-Sn-Mg copper alloys (hereinafter simply referred to as "copper alloys") are preferred. The thickness of the copper-based substrate is preferably in the range of 0.1 mm to 0.4 mm. If the thickness of the copper-based substrate is thinner than 0.1 mm, a large amount of heat may be generated when a large current and a high voltage are applied, and if the thickness of the substrate exceeds 0.4 mm, cracks may easily occur and bending workability may deteriorate. However, since it is expected that the evaluation of bending workability of a copper-based substrate may differ depending on the type of copper alloy, the usable thickness of the copper-based substrate can be appropriately set for each copper alloy used in the copper-based substrate.

[0016] (Surface coating) The surface coating in the terminal of the present invention has a two-layer structure consisting of a lower layer formed on a copper-based substrate and having a thickness in the range of 0.1 μm to 0.5 μm, and an upper layer formed on the lower layer and made of silver or a silver alloy.

[0017] (upper layer) The upper layer of the terminal of the present invention is the part that forms the surface of the surface coating that comes into contact with the conductive part of the mating terminal when mated, and is required to be smooth and conductive with low contact resistance, so the upper layer of the terminal is made of silver or a silver alloy.

[0018] (silver or silver alloy) The silver or silver alloy may be silver (Ag) or a silver alloy containing one or more metal elements (hereinafter also referred to as the second element) selected from the group consisting of zinc (Zn), copper (Cu), nickel (Ni), selenium (Se), antimony (Sb) and cobalt (Co). The presence of a second element in a silver alloy can reduce the contact resistance between terminals. Furthermore, the addition of a second element can increase the tensile strength and hardness of the silver alloy, thereby improving its wear resistance. The second element in the silver alloy preferably contains one or more elements selected from the group consisting of zinc (Zn), copper (Cu), nickel (Ni), selenium (Se), antimony (Sb), and cobalt (Co) in a total content of 0.1% by mass or more. Furthermore, from the viewpoints of improving the electrical connectivity of the contact metal material and reducing material costs, the silver alloy preferably contains less than 15.0% by mass of the second element in total. The thickness of the silver alloy upper layer is preferably 0.5 μm or more, more preferably 2.0 μm or more, and even more preferably 3.0 μm or more. The upper limit of the average thickness of the silver alloy upper layer is preferably 5.0 μm or less. If the lower limit of the upper layer is 0.5 μm or more, the excellent wear resistance of the contact metal material can be maintained for a long period of time. Furthermore, if the upper limit of the upper layer is 5.0 μm or less, increases in material costs and manufacturing costs can be suppressed.

[0019] (lower layer) The terminal of the present invention is composed of a copper-based substrate and a two-layer surface coating including a lower layer formed on the copper-based substrate and an upper layer formed on the lower layer. The lower layer in the terminal of the present invention can suppress the diffusion of copper atoms of the copper alloy from the copper-based substrate to the upper layer. This reduces the electrical resistance of the upper layer of the terminal, and also reduces the contact resistance with the opposing terminal, making it possible to prevent the generation of a large amount of heat.

[0020] (nickel alloy) The lower layer of the terminal of the present invention is formed of a nickel alloy. The nickel alloy is a nickel alloy containing nickel and alloy component X, where alloy component X contains one or more of gallium, bismuth, and indium. In this case, multiple gallium, bismuth, and indium may be contained. In addition to alloy component X, the lower layer of the present invention may also contain other metals such as phosphorus, boron, copper, chromium, molybdenum, tungsten, and sulfur, as long as the properties of the lower layer are not impaired.

[0021] (Alloy component X) The alloy component X in the nickel alloy includes one or more of gallium, bismuth, and indium, and the total content of the alloy component X is in the range of 0.2% by mass to 7.0% by mass. If the total content of the alloy component X is less than 0.2% by mass, the effect of suppressing the diffusion of copper atoms is small. If the total content exceeds 7.0% by mass, the effect of suppressing the diffusion of copper atoms saturates and a significant suppression effect cannot be obtained. In addition, this leads to an increase in material costs and causes problems such as the alloy component X precipitating in the nickel alloy and forming an abnormal phase. Preferably, the total content of the alloy component X is in the range of 0.3% by mass to 7.0% by mass.

[0022] (thickness of the lower layer) To prevent this diffusion of copper atoms, the thickness of the lower layer is set to a range of 0.1 μm to 0.5 μm. If the thickness is less than 0.1 μm, the effect of preventing the diffusion of copper atoms is small even if alloy elements are added, and if the thickness exceeds 0.5 μm, the strength is increased, but cracks are more likely to occur during bending.

[0023] The thickness of each layer was measured by a fluorescent X-ray testing method in accordance with JIS H 8501: 1999. The content of the metal added to each layer was measured using high-frequency inductively coupled plasma (ICP) emission spectroscopy.

[0024] As described above, the terminal of the present invention has a surface coating with a two-layer structure consisting of a copper-based substrate made of copper or a copper alloy, an upper layer made of silver or a silver alloy, and a lower layer made of a nickel alloy. By reducing the number of layers and simplifying the layer structure, increases in costs due to increased material costs and manufacturing processes can be suppressed, and by making the lower layer thin, cracks during bending can be prevented and the rate of increase in resistance due to temperature changes over time during use can be suppressed.

[0025] (Manufacturing method) Next, a method for manufacturing a terminal according to the present invention will be described.

[0026] (Pretreatment of copper-based substrates) The copper or copper alloy that forms the copper-based substrate in the terminal of the present invention is preferably subjected to electrolytic degreasing and pickling as pretreatment. For example, electrolytic degreasing is performed using the copper-based substrate as the cathode and a separately prepared SUS plate as the anode to remove organic matter from the copper-based substrate. The copper-based substrate is then pickled in an aqueous solution containing an acid such as sulfuric acid.

[0027] (Formation of the lower layer) Next, a lower layer is formed by plating containing a nickel alloy. There are no particular limitations on the formulation of the plating bath and the plating conditions when forming the nickel alloy lower layer. The plating can be carried out by either electrolytic plating or electroless plating. The following mainly describes electrolytic plating. Examples of plating bath formulations include a sulfamic acid bath containing nickel sulfamate, citric acid, boric acid, nickel chloride, etc. The nickel plating bath used in the manufacture of the terminal of the present invention preferably contains citric acid. Citric acid acts as a complexing agent, lowering the deposition potential and allowing alloys with different deposition potentials to codeposit. This action allows the content of alloy component X to be increased. Other plating baths include a Watts bath containing nickel sulfate, nickel chloride, boric acid, etc., and an all-chloride bath containing nickel chloride, boric acid, etc. The nickel concentration in the plating bath is preferably in the range of 5 g / L or more and 200 g / L or less, more preferably in the range of 10 g / L or more and 180 g / L or less, and most preferably in the range of 20 g / L or more and 150 g / L or less, and it is preferable to perform electroplating using such a plating solution. Here, alloy component X is dissolved in accordance with the content, and nickel is precipitated and alloy component X is precipitated at the same time to form a nickel alloy.

[0028] As plating conditions, the temperature of the plating solution is in the range of 10°C to 70°C, preferably in the range of 25°C to 55°C. The current density is 15 A / dm 2 less than 10 A / dm 2 Less than or equal to 0.5 A / dm 2 More than 7A / dm 2 The range is as follows:

[0029] (Upper layer formation) The terminal of the present invention has an upper layer formed by plating containing silver or a silver alloy directly on a lower layer of nickel alloy. There are no particular limitations on the formulation of the plating bath or plating conditions used to form the upper layer. The plating process can be carried out by either electrolytic plating or electroless plating. The following mainly describes electrolytic plating. The plating bath may be, for example, a silver cyanide plating bath containing potassium cyanide, sodium cyanide, or the like. The silver concentration in this plating bath is preferably in the range of 5 g / L to 200 g / L, more preferably in the range of 20 g / L to 180 g / L, and most preferably in the range of 50 g / L to 150 g / L. The alloying elements are dissolved in the mixture in accordance with the content, and the alloying elements are precipitated simultaneously with the precipitation of silver to form a silver alloy.

[0030] The plating solution temperature is in the range of 10°C to 60°C, preferably 15°C to 55°C. The plating current density is 15 A / dm 2less than 10 A / dm 2 Less than or equal to 0.5 A / dm 2 More than ~7A / dm 2 The range is as follows: [Example]

[0031] The present invention will be described in detail based on the following examples, but the present invention is not limited to the examples shown below.

[0032] (Preparation of Examples 1-1 to 1-18, Examples 2-1 to 2-20, and Comparative Examples 1-1 to 1-8) Various copper-based sheet materials were rolled and heat-treated, and then the surface processing-affected layer was removed with acid. After electrolytic degreasing and acid cleaning, the copper-based base material was formed into a predetermined shape. A Ni-Ga alloy plating layer (lower layer) with a thickness of 0.3 μm was then formed on the copper-based base material by electrolytic plating under the formation conditions shown below. Then, an Ag plating layer (upper layer) with a thickness of 3 μm was formed.

[0033] (Evaluation of Examples 1-1 to 1-18) The bending workability of the terminal of the present invention varies depending on the type of copper alloy used in the copper-based substrate, and the thickness that can be used varies for each copper alloy. Therefore, examples of bending workability tests were conducted on test plates measuring 50 mm x 50 mm, using copper-based substrates of various copper alloys with three different thicknesses (0.1 mm, 0.2 mm, and 0.4 mm). The results are shown in Table 1 below.

[0034] (Conditions for forming Ni-Ga alloy plating layer (lower layer)) Nickel sulfamate 500g / L Nickel chloride 30g / L Boric acid 30g / L Citric acid (complexing agent) 0 or 50g / L Gallium oxide (Ga metal equivalent) 10-2000mg / L Liquid temperature: 50℃ pH 4.0 Current density 12A / dm 2

[0035] (Conditions for forming Ag plating layer (upper layer)) Silver cyanide 50g / L Potassium cyanide 100g / L Antimony trichloride 12g / L Liquid temperature: 30℃ pH 13 Current density 15A / dm 2

[0036] (Layer thickness measurement) The thickness of each layer was measured using a fluorescent X-ray testing method in accordance with JIS H 8501: 1999. Specifically, a fluorescent X-ray film thickness meter (manufactured by SII NanoTechnology, model number: SFT9400) was used to measure the thickness of each layer at 10 random locations with a collimator diameter of 0.5 mm, and the thickness of each layer was obtained by calculating the average of these measurements.

[0037] (Content) The content of the added metal was measured using ICP (inductively coupled plasma) alone or a combination of ICP and X-ray fluorescence analysis (XRF). XRF (energy dispersive X-ray fluorescence analyzer: SSI NanoTechnology, model number: SEA1200VX) was used in a vacuum atmosphere at an accelerating voltage of 15 kV (using a Cr filter) or 50 kV (using a Pb filter). XRF calculates the amount of metal present based on fluorescence intensity, and XRF alone cannot calculate a quantitative value (in mass percent). Therefore, the content of the added metal element (M) and the main metal, where main metal / added metal = 100, was quantified using ICP analysis.

[0038] (Bending workability test) The bending workability test was carried out in accordance with JIS standard JIS H 8504 / 1999. The specimen was firmly clamped and fixed using a metal plate with a bending radius of 410 mm, and the outside of the bend was observed after bending it once by 90°. Evaluation "A": No cracks occurred during bending. It can be determined that there will be no practical problems. Rating "B": No cracks occurred during bending, but wrinkles occurred. It can be determined that this will not cause any problems in practical use. Rating "C": Cracks occurred during bending. It can be judged that there is a problem in practical use.

[0039] [Table 1]

[0040] As shown in Table 1, copper (pure copper (OFC): JIS symbol: C1020) and Cu-Cr-Mg (C18142), Cu-Ni-Si (C64770), Cu-Zn (C2700), Cu-Sn-P (C5210) or Cu-Ni-Si-Zn-Sn-Mg (C64775) copper or copper alloys are classified as "A" or "B" within the range of 0.1 mm or more and 0.4 mm or less, and are judged to pose no practical problems.

[0041] (Evaluation of Examples 2-1 to 2-20 and Comparative Examples 1-1 to 1-8) Surface coatings for various terminals were prepared on copper-based substrates, with different thicknesses of the underlayer and different types and contents of alloy component X. The prepared test plates were evaluated for bending workability, and the rate of increase in resistance after heating was measured, and a comprehensive evaluation of their practicality was conducted. The copper-based substrates used for the test plates of Examples 2-1 to 2-20 and Comparative Examples 1-1 to 1-8 were all made of copper (pure copper (OFC)) plates containing no additive elements and had a constant thickness of 0.3 mm. The upper layer constituting the test plates of Examples 2-1 to 2-20 and Comparative Examples 1-1 to 1-8 was a silver-plated layer containing antimony, and the Vickers hardness of the silver-plated layer was 130 Hv. The plating thickness was fixed at 3 μm for evaluation.

[0042] (Resistance increase rate after heating) The resistance rise rate was measured using an electrical contact simulator (Yamazaki Seiki Kenkyusho Co., Ltd., model number: CRS-1) at 0 N / cm 2 More than 10N / cm 2 The F (pressure)-R (electrical resistance) test was carried out and evaluated under the following loads. The resistance increase rate was measured before heating and after heating at a temperature of 150°C for 1000 hours, and expressed by the formula (1): resistance increase rate = (resistance after heating - before heating) / resistance before heating × 100 (%).

[0043] [Table 2]

[0044] Here, the resistance increase rate and overall evaluation were carried out. The results are shown in Table 3 below. [Table 3]

[0045] (Evaluation of resistance increase rate) The resistance increase rate after heating was evaluated according to the following criteria. Evaluation "A": The resistance increase rate after heating is less than 30%. It is judged that there will be no practical problems. Rating "B": The resistance increase rate after heating is 30% or more and less than 60%. It is judged that there will be no practical problems. Rating "C": The resistance increase rate after heating is 60% or more. It is judged to be problematic for practical use. In addition, if a crack occurred during the bending test, it was rated "C" regardless of the resistance increase rate after heating.

[0046] (comprehensive evaluation) The overall evaluation was made according to the following criteria. <Criteria for overall evaluation> Evaluation "A": This is the case where the evaluation of the resistance increase rate and the evaluation of the bending workability are both "A". It can be determined that there will be no problems in practical use. Rating "B": When either the resistance increase rate rating or the bending workability rating is "A" and the other rating is "B", or when both ratings are "B". It is judged that there will be no practical problems. Rating "C": At least one of the ratings of the resistance increase rate and the bending workability is rated "C." It can be determined that there is a problem in practical use.

[0047] As described above, Examples 1-1 to 1-18 show that, if a specified copper or copper alloy is used, the copper-based substrate can be practically used with a bending workability evaluation of "A" or "B" when the thickness is in the range of 0.1 mm or more and 0.4 mm or less. Examples 2-1 to 2-13 were both rated "A" for the resistance increase rate and bending workability, and the overall rating was also "A," indicating that they were suitable for practical use. In Examples 2-14 to 2-20, the bending workability was evaluated as "A", but the resistance increase rate was evaluated as "B" because the plating bath did not contain a complexing agent, and the overall evaluation was also "B", indicating that they are suitable for practical use. In Comparative Examples 1-1 and 1-2, the lower layer is a nickel layer that does not contain the alloy element X, so the resistance increase rate is evaluated as "C" and the overall evaluation is also "C", indicating that there is a problem in practical use. In Comparative Example 1-3, the lower layer was a nickel layer that did not contain the alloy element X and was thick at 1.0 μm. Therefore, although the resistance increase rate was evaluated as "A," the bending workability was evaluated as "C," and the overall evaluation was also "C," indicating that there are problems in practical use. In Comparative Examples 1-4 to 1-6, the lower layer is a nickel alloy containing alloy element X, but the thickness is 0.7 μm or more. Therefore, although the resistance increase rate is evaluated as "A", the bending workability is evaluated as "C", and the overall evaluation is also "C", indicating that there are problems in practical use. In Comparative Examples 1-7 to 1-8, the lower layer is a nickel alloy containing alloy element X, but the thickness is less than 0.05 μm and 0.1 μm in each case, so the resistance increase rate is rated "C" and the overall rating is also "C," indicating that there are problems in practical use. [Explanation of symbols]

[0048] 1 terminal 11 Copper base material 12 Lower layer 13 Upper layer 14 Surface coating

Claims

1. a copper-based substrate made of copper or a copper alloy; a surface coating having a two-layer structure including a lower layer formed on the copper-based substrate and having a thickness in the range of 0.1 μm to 0.5 μm, and an upper layer formed on the lower layer and made of silver or a silver alloy; the material constituting the lower layer is a nickel alloy containing nickel and an alloy component X, The terminal, wherein the alloy component X is one or more of gallium, bismuth, and indium.

2. 2. The terminal according to claim 1, wherein the content of said X in said nickel alloy is in the range of 0.2 mass % to 7.0 mass %.

3. The terminal according to claim 1 or 2, wherein the copper-based substrate has a thickness in the range of 0.1 mm or more and 0.4 mm or less.

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