Coated terminal material and manufacturing method of the same

Abstract

To provide a coated terminal material having excellent wear resistance even when a base material has low strength.SOLUTION: A coated terminal material comprises: a base material made of copper or a copper alloy; a nickel layer made of nickel or a nickel alloy, which is formed on the base material with a thickness of 0.2 μm or more and 5.0 μm or less; and a silver alloy layer formed on at least a part of the outermost surface of the nickel layer, wherein the silver alloy layer contains 3 mass% or more and 25 mass% or less of N, and further contains C, S, and K in the remainder in a total amount not exceeding the content of N, the content ratio S / N of S to N being 0.05 or more and 0.1 or less, and the thickness of the silver alloy layer being 0.1 μm or more and 5.0 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a coated terminal material that is suitably applied to on-board terminals and the like, and has low friction and excellent wear resistance. [Background technology]

[0002] Conventionally, connector terminals that connect to electrical components in automotive signal and power systems have generally been made of a copper or copper alloy substrate with tin plating and a reflow process applied to the terminal material with a tin layer. However, with the recent increase in the electrification rate of automobiles, there has been an increase in the use of terminals with precious metal plating that can carry a larger current.

[0003] As a method for plating a noble metal on an in-vehicle terminal, there has been a method for plating a substrate with silver using a cyanide bath, as disclosed in Patent Document 1. However, silver plating is soft and has poor abrasion resistance, which requires the silver plating film to be thick, which creates a cost problem.Furthermore, as in Patent Document 2, there is a method of forming a silver alloy layer with a Vickers hardness of HV140 or more as the outermost layer on a silver or silver alloy layer, but the abrasion resistance is still insufficient.

[0004] Furthermore, the base material of high-voltage terminals, which often require a film of precious metal plating, is often pure copper material C10200 as specified by the Copper Development Association (CDA). This copper material has a hardness of HV100 or less, and even if a plating process is applied to it, the base material is still soft, so even if an attempt is made to harden the plating film and improve wear resistance, not much effect can be obtained. Therefore, as in Patent Document 3, there is a method of increasing abrasion resistance by plating the substrate with a very hard silver-tin alloy using an alkaline cyanide bath, but this is too hard and therefore difficult to process. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-169408 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-79250 [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-183216 Summary of the Invention [Problem to be solved by the invention]

[0006] Even if the entire plating film is made very hard in order to increase the wear resistance of silver plating films, which have poor wear resistance, cracking still occurs. Furthermore, when pure copper material (C10200) is used as the base material, the effect of improving wear resistance is significantly lost even if the plating film is made hard.

[0007] The present invention has been made in view of the above circumstances, and has as its object to provide a coated terminal material that has low friction and excellent wear resistance even when the strength of the substrate is low. [Means for solving the problem]

[0008] The coated terminal material of the present invention comprises a substrate made of copper or a copper alloy, a nickel layer made of nickel or a nickel alloy formed on the substrate to a thickness of 0.2 μm or more and 5.0 μm or less, and a silver alloy layer formed on the outermost surface of at least a part of the nickel layer, The silver alloy layer contains 3% by mass or more and 25% by mass or less of N, with the remainder being C, S, and K, the total amount of which does not exceed the content of N, and the content ratio of S to N, S / N, is 0.05 or more and 0.1 or less, The thickness of the silver alloy layer is 0.1 μm or more and 5.0 μm or less.

[0009] The silver alloy layer formed on the surface of the coated terminal material of the present invention is not as hard as hard silver, but it has excellent lubricity and a low coefficient of friction. Therefore, the wear resistance of the terminal material is significantly improved. Furthermore, although it contains N, the contact resistance is as low as that of a pure silver plating layer, and low contact resistance can be maintained even in high-temperature environments. In this case, if the N content is less than 3 mass%, lubricity is lost, the friction coefficient increases, and wear resistance decreases. If the N content exceeds 25 mass%, the silver alloy layer becomes brittle and prone to cracking during processing. Furthermore, if the total content of C, S, and K exceeds the N content, lubricity is lost, the friction coefficient increases, and wear resistance decreases.

[0010] The S / N is set to 0.05 or more and 0.1 or less because if the S / N is less than 0.05, the coefficient of friction increases and the wear resistance decreases, and if it exceeds 0.1, the silver alloy layer becomes more susceptible to cracking.

[0011] Furthermore, if the thickness of the silver alloy layer is less than 0.1 μm, the wear resistance cannot be maintained, and if the thickness exceeds 5.0 μm, the film formation during plating processing becomes poor, and cracks occur in the silver alloy layer when a terminal material having a thick silver alloy layer is processed.

[0012] The nickel layer functions as a barrier to prevent copper diffusion from the substrate in high-temperature environments, and if its thickness is less than 0.2 μm, the barrier properties in high-temperature environments are not obtained, resulting in high contact resistance. If the nickel layer thickness exceeds 5.0 μm, cracks will occur in the nickel layer or in the nickel layer and the layer above it during bending, etc.

[0013] The film-coated terminal material of the present invention may further have a base silver layer having a silver purity of 98.5% by mass or more and 99.5% by mass or less and a thickness of 0.2 μm or more and 5.0 μm or less, and the silver alloy layer may be formed on the base silver layer.

[0014] Since the silver base layer of the above purity is harder than the silver alloy layer, by forming it under the silver alloy layer, it can support the silver alloy layer from below and improve its wear resistance. In this case, if the thickness of the silver base layer is less than 0.2 μm, it will not be effective in supporting the silver alloy layer, and the effect of improving wear resistance due to the multilayer structure may not be achieved. If the thickness of the silver base layer is more than 5.0 μm, the wear resistance will be good, but the coefficient of friction may be high.

[0015] The method for producing a coated terminal material of the present invention is a method for producing the terminal material, and includes a nickel layer forming step of forming a nickel layer made of nickel or a nickel alloy having a thickness of 0.2 μm or more and 5.0 μm or less on a substrate made of copper or a copper alloy, and a silver alloy layer forming step of forming the silver alloy layer having a thickness of 0.1 μm or more and 5.0 μm or less on the nickel layer by plating, wherein the silver alloy forming step is carried out by plating a silver alloy containing silver cyanide (AgCN) of 45 g / L or more and 55 g / L or less, potassium cyanide The plating solution contains 110g / L to 130g / L of potassium carbonate (KCN), 10g / L to 20g / L of potassium carbonate (K2CO3), 0.2g / L to 10g / L of an additive containing an organic compound or its derivatives containing one or more thiol groups, thiolate groups, or sulfide groups in the triazine ring (hereinafter referred to as X agent), and 0.08g / L to 5g / L of bismuthiol (hereinafter referred to as Y agent), with the ratio of these two additives being 0.1 to 50. The current density is 2A / dm 2 More than 8A / dm 2 Electroplating is performed at the following current density:

[0016] As mentioned above, the ratio of N to N in the silver alloy layer is set to S / N, which is between 0.05 and 0.1. The S / N ratio can be adjusted by simultaneously adding bismuth thiol (agent Y) and agent X to the plating solution. Using agent X alone results in excessive S precipitation in the resulting silver alloy layer 5, but adding agent Y simultaneously can suppress this excessive S precipitation. In this case, if the ratio X / Y is less than 0.1, the friction coefficient is high and wear resistance is reduced. On the other hand, if the ratio X / Y is more than 50, excessive S is precipitated, resulting in an S / N ratio exceeding 0.1, making the silver alloy layer 5 brittle and potentially causing cracking during processing.

[0017] Even when both agents are added simultaneously, if the X agent exceeds 10 g / L, the S content in the silver alloy layer increases, causing the S / N ratio to exceed 0.1, making the silver alloy layer brittle and potentially causing cracking during processing. Conversely, if the Y agent is added in excess of 5 g / L, the precipitation of S in the silver alloy layer is suppressed, causing the S / N ratio to fall below 0.05, increasing the coefficient of friction and potentially reducing wear resistance. If the X agent is less than 0.2 g / L, the amount of N in the silver alloy layer is insufficient, the friction coefficient increases, and the wear resistance decreases. If the Y agent is less than 0.08 g / L, the co-deposition of S is not suppressed, If the S / N content exceeds 0.1, the silver alloy layer may crack. [Effects of the Invention]

[0018] According to the present invention, since the friction coefficient of the silver alloy layer formed on the surface is low, the wear resistance of the terminal material is significantly improved, and even if the strength of the base material is low, a coated terminal material with excellent wear resistance can be provided. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view schematically showing a film-coated terminal material according to a first embodiment of the present invention. [Figure 2] FIG. 4 is a cross-sectional view schematically showing a film-coated terminal material according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] [First embodiment] As shown in the cross section of Figure 1, the first embodiment of the coated terminal material 1 has a coating 3 formed on a plate-shaped substrate 2 made of copper or a copper alloy, and this coating 3 has a nickel layer 4 formed on the substrate 2 and a silver alloy layer 5 formed on the nickel layer 4.

[0022] The composition of the substrate 2 is not particularly limited as long as the surface is made of copper or a copper alloy, but in the present invention, a plate material made of pure copper with a purity of 99.90% or more, such as oxygen-free copper (C10200), tough pitch copper (C11000), or phosphorus-deoxidized copper (C12200), can be suitably used.

[0023] The nickel layer 4, which forms the lower layer of the coating 3, has a thickness of 0.2 μm to 5.0 μm. This nickel layer 4 functions as a barrier to prevent copper diffusion from the substrate in high-temperature environments. If copper diffuses and reaches the surface of the coating 3, the copper may oxidize, increasing contact resistance and reducing heat resistance. However, this nickel layer 4 prevents copper diffusion, allowing the wear resistance and heat resistance of the surface of the terminal material 1 to be maintained for a long period of time. If the thickness of the nickel layer 4 is less than 0.2 μm, the barrier properties in high-temperature environments will not be obtained, and contact resistance will increase. If the thickness of the nickel layer 4 exceeds 5.0 μm, cracks will occur in the nickel layer or in the nickel layer and the layer above it during bending, etc.

[0024] The silver alloy layer 5 contains 3% by mass or more and 25% by mass or less of N, with the remainder being C, S, and K, the total of which does not exceed the content of N. The thickness of this silver alloy layer 5 is 0.1 μm or more and 5.0 μm or less. Although this silver alloy layer 5 is not as hard as hard silver, it has lubricity and a low coefficient of friction. Therefore, the wear resistance of the terminal material is significantly improved. Furthermore, although the silver alloy layer 5 contains elements other than Ag, such as N, the contact resistance is as low as that of a pure silver plating layer, and low contact resistance can be maintained even in high-temperature environments. However, if the N content is less than 3% by mass, the lubricity decreases, the friction coefficient increases, and the wear resistance decreases. If the N content exceeds 25% by mass, the silver alloy layer becomes brittle and prone to cracking during processing. Furthermore, if the total content of C, S, and K exceeds the N content, the lubricity is lost, the friction coefficient increases, and the wear resistance decreases. Other than silver, it is preferable that the N content be the highest.

[0025] Furthermore, if the thickness of the silver alloy layer 5 is less than 0.1 μm, the wear resistance cannot be maintained. If the thickness exceeds 5.0 μm, the film formation property during plating processing deteriorates, and cracks occur when the terminal material 1 having the thick silver alloy layer 5 is processed.

[0026] The content ratio S / N of N to N in the silver alloy layer 5 is set to be in the range of 0.05 to 0.1. If the S / N ratio is less than 0.05, the coefficient of friction increases and the wear resistance may decrease, while if the S / N ratio exceeds 0.1, the silver alloy layer becomes more susceptible to cracking.

[0027] Next, we will explain the manufacturing method of this coated terminal material 1. The manufacturing method of the coated terminal material 1 includes a pretreatment step of cleaning a plate material made of copper or a copper alloy that will become the base material 2, a nickel layer forming step of applying nickel plating to the base material 2 to form a nickel layer 4, a silver strike plating step of applying silver strike plating to the nickel layer 4, and a silver alloy layer forming step of applying silver alloy plating after the silver strike plating to form a silver alloy layer 5.

[0028] [Pretreatment process] First, a plate made of copper or a copper alloy is prepared as the substrate 2, and the plate is subjected to pretreatment such as degreasing and pickling to clean the surface.

[0029] [Nickel layer formation process] At least a portion of the surface of the pretreated substrate is plated to form a nickel layer 4 made of nickel or a nickel alloy on the substrate 2. Specifically, for example, a nickel plating bath containing 350 g / L of nickel sulfamate, 10 g / L of nickel chloride hexahydrate, and 30 g / L of boric acid is used, and the plating is carried out at a bath temperature of 45°C and a current density of 5 A / dm 2 The nickel plating treatment for forming the nickel layer is not particularly limited as long as it can produce a dense nickel-based film, and may be an electroplating treatment using a known Watts bath.

[0030] [Silver strike plating process] After activation treatment is performed on the nickel layer 4 on the surface of the substrate 2 using a potassium cyanide aqueous solution containing 5% by mass to 10% by mass, a thin silver plating layer is formed by silver plating for a short period of time on the nickel layer 4. In this case, silver strike plating is preferred as the silver plating treatment.

[0031] The composition of the silver plating bath for this silver strike plating treatment is, for example, 1 g / L to 5 g / L of silver cyanide (AgCN) and 80 g / L to 120 g / L of potassium cyanide (KCN). A stainless steel (SUS316) anode was used in this silver plating bath at a bath temperature of 25°C and a current density of 1.5 A / dm 2 By carrying out silver plating treatment under the above conditions for about 30 seconds, a silver strike plating layer is formed. This silver strike plating layer becomes difficult to distinguish as a layer due to the subsequent formation of the silver alloy layer 5.

[0032] [Silver alloy layer formation process] After the silver strike plating, a silver alloy plating process is performed to form the silver alloy layer 5. The plating bath used to form the silver alloy layer 5 contains 45 g / L to 55 g / L of silver cyanide (AgCN), 110 g / L to 130 g / L of potassium cyanide (KCN), 10 g / L to 20 g / L of potassium carbonate (K2CO3), 0.2 g / L to 10 g / L of an additive containing an organic compound or its derivative containing one or more thiol groups, thiolate groups, or sulfide groups in a triazine ring (hereinafter referred to as X agent), and 0.08 g / L to 5 g / L of bismuthiol (hereinafter referred to as Y agent).

[0033] In this case, if the additive containing an organic compound or its derivative containing one or more thiol, thiolate, or sulfide groups on the triazine ring is agent X, and bismuthiol is agent Y, the ratio of these two additives, X / Y, is 0.1 or more and 50 or less. It is more preferable that the ratio of these additives, X / Y, is in the range of 0.5 or more and 20 or less.

[0034] As mentioned above, the content ratio of N and S in the silver alloy layer 5, S / N, is set to a range of 0.05 to 0.1. The S / N ratio can be adjusted by adding bismuthiol (agent Y) to agent X in the plating solution at the same time. Using agent X alone results in excessive precipitation of S in the resulting silver alloy layer 5, but adding agent Y at the same time can suppress excessive precipitation of S. If the additive is bismuthiol (agent Y) alone, or if X / Y is less than 0.1, the S to N content ratio S / N will not satisfy the range of 0.05 to 0.1, resulting in a high friction coefficient and reduced wear resistance. On the other hand, if the additive is agent X alone, or if X / Y exceeds 50, excessive S will precipitate, resulting in an S / N ratio exceeding 0.1, making the silver alloy layer 5 brittle and potentially causing cracking during processing.

[0035] Furthermore, even when they are added simultaneously, if the X agent is added in excess of 10 g / L, the S content in the silver alloy layer 5 increases, causing the S / N ratio to exceed 0.1, making the silver alloy layer 5 brittle and potentially causing cracking during processing. Conversely, if the Y agent is added in excess of 5 g / L, the precipitation of S in the silver alloy layer 5 is suppressed, causing the S / N ratio to become less than 0.05, increasing the coefficient of friction and potentially reducing wear resistance. If the X agent is less than 0.2 g / L, the amount of N in the silver alloy layer is insufficient, further increasing the coefficient of friction and reducing wear resistance. If the Y agent is less than 0.08 g / L, the co-deposition of S is not suppressed, and the S / N content ratio exceeds 0.1, which may cause cracking of the silver alloy layer 5. If both the X agent and the Y agent are insufficient (if the X agent is less than 0.2 g / L and the Y agent is less than 0.08 g / L), the amount of N in the silver alloy layer 5 is insufficient, further increasing the coefficient of friction and reducing wear resistance.

[0036] Specific examples of this additive X are listed below. Trithiocyanuric acid 6-(Dibutylamino)-1,3,5-triazine-2,4-dithiol 1,3,5-triazine-2,4,6-trithiol 2-(Dibutylamino)-1,3,5-triazine-4,6-dithiol 2,4-Bis(isopropylamino)-6-(methylthio)-s-triazine 2-(tert-butylamino)-4-(cyclopropylamino)-6-(methylthio)-1,3,5-triazine 6-Diallylamino-1,3,5-triazine-2,4-dithiol 6-(4-vinylbenzyl-n-propyl)amino-1,3,5-triazine-2,4-dithiol 6-(Diisopropylamino)-1,3,5-triazine-2,4-dithiol 6-Di(2-ethylhexyl)amino-1,3,5-triazine-2,4-dithiol 6-(allylamino)-1,3,5-triazine-2,4-dithiol 6-(butylamino)-1,3,5-triazine-2,4-dithiol 3-((4-nitrobenzyl)thio)-5,6-diphenyl-1,2,4-triazine 2,4,6-tris(methylsulfanyl)-1,3,5-triazine In this case, the additive has a smoothing effect and does not contain antimony or the like, which is a hardening agent.

[0037] A pure silver plate was used as the anode for this plating bath, and the current density was 2A / dm 2 More than 8A / dm 2 By plating silver alloy at a current density of 2 A / dm or less, a silver alloy layer 5 having a thickness of 0.1 μm or more and 5.0 μm or less is formed. 2 If the current density is less than 8 A / dm, the S content in the silver alloy layer 5 increases, the content ratio S / N increases, and the silver alloy layer 5 becomes more susceptible to cracking. 2 If the content of C in the silver alloy layer 5 exceeds this value, the total amount of S·K·C increases, which makes the silver alloy layer 5 more susceptible to cracking. The temperature of the plating bath is preferably in the range of 20°C or higher and 35°C or lower.

[0038] In this way, a coated terminal material 1 is formed having a nickel layer 4 and a silver alloy layer 5 on the surface of the substrate 2. Then, by subjecting this coated terminal material 1 to press working or the like, a connector terminal is formed having a coating 3 with a nickel layer 4 and a silver alloy layer 5 on its surface.

[0039] The coated terminal material 1 has a silver alloy layer 5 on the surface that is excellent in lubricity and has a low coefficient of friction, so that the wear resistance of the terminal material 1 is significantly improved. In this coated terminal material 1, if the N content of the silver alloy layer 5 is less than 3 mass %, lubricity is lost, the friction coefficient increases, and wear resistance decreases. If the N content exceeds 25 mass %, the silver alloy layer 5 becomes brittle and hard, and wear resistance decreases. Furthermore, if the total content of C, S, and K exceeds the N content, lubricity is lost, the friction coefficient increases, and wear resistance decreases.

[0040] Furthermore, if the thickness of the silver alloy layer 5 is less than 0.1 μm, the wear resistance cannot be maintained. If the thickness exceeds 5.0 μm, the film formation during plating processing deteriorates, and cracks occur when the terminal material 1 having the thick silver alloy layer 5 is processed.

[0041] In this embodiment, the thickness of the silver alloy layer 5 is set to 0.1 μm or more and 5.0 μm or less, the N content is set to 3 mass% or more and 25 mass% or less, and the total amount of C, S, and K is set to a range not exceeding the N content, so that the coefficient of friction is reduced and the terminal material 1 has excellent wear resistance.

[0042] The nickel layer 4 functions as a barrier to prevent copper diffusion from the substrate 2 in a high-temperature environment, and if the thickness is less than 0.2 μm, the barrier properties in a high-temperature environment cannot be obtained, resulting in high contact resistance. If the thickness of the nickel layer 4 exceeds 5.0 μm, cracks will occur in the nickel layer 4 during bending or the like, or cracks will occur in both the nickel layer 4 and the silver alloy layer 5 thereon. In this embodiment, the nickel layer 4 has a thickness of 0.2 μm or more and 5.0 μm or less, has excellent barrier properties, prevents copper diffusion, and can maintain low surface contact resistance even in high temperature environments.

[0043] [Second embodiment] 2, the film-coated terminal material 11 of the second embodiment has a film 12 formed on a plate-shaped substrate 2 made of copper or a copper alloy, and this film 12 has a nickel layer 4 formed on the substrate 2, a silver base layer 13 on the nickel layer 4, and a silver alloy layer 5 formed on the silver base layer 13. In other words, the film-coated terminal material 11 differs from the first embodiment in that it has the silver base layer 13. The substrate 2, nickel layer 4, and silver alloy layer 5 are the same as those in the first embodiment, and therefore a description thereof will be omitted.

[0044] This silver base layer 13 is formed to have a silver purity of 98.5% by mass or more and 99.5% by mass or less and a thickness of 0.2 μm or more and 5.0 μm or less. Since the base silver layer 13 of the above purity is harder than the silver alloy layer 5, by forming it below the silver alloy layer 5, it can support the silver alloy layer 5 from below and improve its wear resistance. In this case, if the thickness of the base silver layer 13 is less than 0.2 μm, it is not effective in supporting the silver alloy layer 5, and the effect of improving wear resistance due to the multilayer structure is not observed. If the thickness of the base silver layer 13 exceeds 5.0 μm, the wear resistance is good, but the coefficient of friction may become high.

[0045] Manufacturing the film-coated terminal material 11 of the second embodiment includes a pretreatment step of cleaning a copper or copper alloy plate material to serve as the substrate 2, a nickel layer formation step of applying nickel plating to the substrate 2 to form the nickel layer 4, a silver strike plating step of applying silver strike plating to the nickel layer 4, a base silver layer formation step of applying silver plating to form the base silver layer 13 after the silver strike plating, and a silver alloy layer formation step of applying silver alloy plating to the base silver layer 13 to form the silver alloy layer 5. Unlike the film-coated terminal material 1 of the first embodiment, the film-coated terminal material 11 includes the base silver layer formation step, and the other steps are the same as those of the first embodiment.

[0046] [Underlying silver layer formation process] The composition of the silver plating bath for forming the silver base layer 13 is, for example, a composition containing 45 g / L or more and 55 g / L or less of silver cyanide (AgCN), 110 g / L or more and 130 g / L or less of potassium cyanide (KCN), 10 g / L or more and 20 g / L or less of potassium carbonate (K2CO3), and general additives.

[0047] For example, if antimony is to be added to form a hard base silver layer 13, an antimony-containing additive may be used. A pure silver plate was used as the anode in this silver plating bath at a bath temperature of 25°C and a current density of 3 A / dm 2 More than 5A / dm 2 The silver base layer is formed by plating under the following conditions:

[0048] In addition, the detailed configuration is not limited to that of the embodiment, and various modifications can be made within the scope that does not deviate from the spirit of the present invention.

[0049] For example, in the above embodiment, the nickel layer 4 is formed on the entire upper surface of the base material 2, and the silver alloy layer 5 is formed thereon, but this is not limiting, and for example, the nickel layer 4 may be formed on a part of the upper surface of the base material 2, and the silver alloy layer 5 may be formed on the nickel layer 4. It is sufficient that at least the surface of the part that will become a contact point when formed into a terminal is made of the silver alloy layer 5. Even when the silver alloy layer 5 is formed only on a part of the surface of the substrate 2 , the nickel layer 4 may be formed on the entire surface of the substrate 2 .

[0050] In addition, when forming the base silver layer 23, in any of these forms, it may be formed in the area where the silver alloy layer 5 is to be provided. [Example]

[0051] A substrate made of a C10200 copper plate with a thickness of 0.25 mm was prepared, and this substrate was subjected to pretreatment to clean the surface by degreasing, pickling, etc. (pretreatment process), and then nickel plating was applied to the surface of the substrate to form a nickel layer with a film thickness of 0.8 μm (nickel layer formation process).

[0052] Then, the surface of the nickel layer was activated using a 10 mass % aqueous potassium cyanide solution, and then the base material coated with the nickel layer was subjected to a silver strike plating process (silver strike plating step). A silver plating process was performed on the silver substrate to form a silver base layer (silver base layer formation process), and a silver alloy plating process was performed on the silver substrate to form a silver alloy layer (silver alloy layer formation process). The content of N and other elements in the silver alloy layer was adjusted by adjusting the amount and ratio of additives (X / Y) and the current density during the plating process.

[0053] The conditions for each plating are as follows: <Nickel plating conditions> Plating bath composition Nickel sulfamate: 350g / L Nickel chloride hexahydrate: 10g / L Boric acid: 30g / L ·Bath temperature: 45℃ ·Current density: 5A / dm 2 Anode: S-containing nickel plate pH: 4

[0054] <Silver strike plating conditions> Plating bath composition Silver cyanide: 2g / L Potassium cyanide: 100g / L Anode: SUS316 ·Bath temperature: 25℃ ·Current density: 1.5A / dm 2

[0055] <Base silver plating conditions 1> Plating bath composition Silver cyanide: 45g / L Potassium cyanide: 115g / L Potassium carbonate: 15g / L Brightener: DDP Specialty Products Japan Co., Ltd. SILVER GLO 3K: 15ml / L SILVER GLORY: 5ml / L ·Bath temperature: 25℃ ·Current density: 4A / dm 2 Anode: Pure silver plate

[0056] <Base silver plating conditions 2> Plating bath composition Silver cyanide: 45g / L Potassium cyanide: 140g / L Potassium carbonate: 15g / L Additives: Nisshin Seiki Co., Ltd. Nissin Bright K: 20mL / L ·Bath temperature: 25℃ ·Current density: 2A / dm 2 Anode: Pure silver plate

[0057] <Silver alloy plating conditions> Plating bath composition Additives ·Bath temperature: 25℃ Anode: Pure silver plate

[0058] Among the additives in the silver plating conditions, the following A to E were used as the X agent. A: 6-(dibutylamino)-1,3,5-triazine-2,4-dithiol B: Trithiocyanuric acid C: Melamine D: 6-(diisopropylamino)-1,3,5-triazine-2,4-dithiol E: 6-(butylamino)-1,3,5-triazine-2,4-dithiol The amounts of these additives X added were as shown in Table 1. Table 1 also shows the amount of Bismuthiol (agent Y) added.

[0059] The plating conditions for each sample (terminal material) obtained in this manner are shown in Table 1. Sample 4 was also prepared without a base silver layer. Sample No. 22 did not form a nickel layer. For sample No. 25, bismuthiol (Y agent) was not added as an additive to the plating bath during the silver alloy layer formation process.

[0060] [Table 1]

[0061] The physical properties of the obtained terminal material were measured as follows. [Measurement of thickness of each layer] The thickness of each layer formed by nickel plating, silver underplating, and silver alloy plating was measured as follows. Each sample was cross-sectionally processed using a Seiko Instruments Inc. focused ion beam (FIB) (model number: SMI3050TB). The cross-sections were then observed with a scanning ion microscope (SIM). The film thicknesses were measured at three random locations in the cross-sectional SIM image taken at a tilt angle of 60°, and the average was calculated and then converted to the actual length. The measurement results are shown in Table 1.

[0062] [Measurement of N, S, K, and C content in silver alloy layer] For each sample, the contents (mass %) of N, K, C, and S in the silver alloy plating layer were measured by GD-MS (Glow Discharge-Mass Spectrometry). Measurements were performed using an Astrum manufactured by Nu Instruments, with the main components detected using a Faraday cup and impurities detected using an IC multiplier. The detection conditions were as follows: Glow discharge: constant current mode ·Discharge current: 0.7mA Discharge voltage: 0.5kV Discharge gas: Ar (>99.9999%) Depth resolution: 0.1 μm / scan

[0063] [Measuring the purity of the underlying silver layer] For each sample, the amount of impurities in the underlying silver layer, excluding gas components (H, O), was measured by GD-MS (Glow Discharge-Mass Spectrometry). Measurements were performed using an Astrum manufactured by Nu Instruments, with the main components detected using a Faraday cup and impurities detected using an IC multiplier. The detection conditions were as follows: Glow discharge: constant current mode ·Discharge current: 0.7mA Discharge voltage: 0.5kV Discharge gas: Ar (>99.9999%) Depth resolution: 0.1 μm / scan The purity of Ag was calculated by subtracting the amount of impurities obtained.

[0064] The thickness and composition of the coating of each sample obtained as described above are shown in Table 2.

[0065] [Table 2]

[0066] Next, the friction coefficient and contact resistance of each sample were measured and the wear resistance and other properties were evaluated by the following methods.

[0067] [Friction coefficient measurement] Each sample was cut into two test pieces, 60mm x 10mm and 60mm x 30mm. The former test piece had a 5mm radius of curvature embossed in the center to serve as a female terminal (female terminal test piece), while the latter, in its flat form, served as a male terminal (male terminal test piece). The friction coefficient was measured using a Bruker AXS friction and wear tester (UMT-Tribolab). The convex surface of the female terminal test piece was placed in contact with the horizontally placed male terminal test piece. A load of 5N was applied to the male terminal test piece, and the test piece was moved 10mm at a sliding speed of 1.33mm / sec. The change in the friction coefficient was measured. The average friction coefficient obtained between 5mm and 10mm was recorded as the friction coefficient.

[0068] [Contact resistance] Each sample was cut into two test pieces, measuring 60 mm x 10 mm and 60 mm x 30 mm. The former test piece had a central embossing with a 5 mm radius of curvature, which served as a substitute for a female terminal (female terminal test piece), while the latter, in its flat form, served as a substitute for a male terminal (male terminal test piece). The contact resistance (mΩ) of these test pieces was measured, both after heating at 150°C for 120 hours and after not heating. A Bruker AXS friction and wear tester (UMT-Tribolab) was used to measure the contact resistance by the four-terminal method, with the convex surface of the female terminal test piece in contact with the horizontally placed male terminal test piece and a 10 N load applied to the male terminal test piece.

[0069] [Presence or absence of cracks after indentation] After indenting the sample to create a spherical depression with a curvature radius of 3 mm, the apex of the convex surface opposite the depression was observed with an optical microscope to check for cracks. When observed at 50x magnification, cracks were judged as "present" if there were any cracks on the surface of the plated material, and those where no cracks were found were judged as "absent." For those where cracks were found, the cracks were observed from the surface using an SEM-ESD (scanning electron microscope) to determine in which layer the cracks had occurred.

[0070] [Wear resistance test] The same sample was prepared with two specimens: one with an indentation to form a spherical depression with a radius of curvature of 3 mm, and the other as a flat plate. The convex surface opposite the depression was pressed against the flat plate with a load of 5 N, and the plate was repeatedly slid over a distance of 5 mm 50 times. After this, it was observed using a SEM-EDS (scanning electron microscope) to see if any of the substrate was exposed. Both the flat plate side and the indented side were observed, and those in which more than half of the sliding area was exposed were rated "C," those in which only a small portion (less than half) was exposed were rated "B," and those in which no exposure was observed at all were rated "A."

[0071] The measurement results and evaluation results are shown in Table 3. For samples in which cracks were observed after indentation, the contact resistance and friction coefficient were not measured, and the wear resistance was not evaluated. [Table 3]

[0072] As shown in Table 3, samples 1 to 14, which had a nickel layer thickness of 0.2 μm to 5.0 μm, a silver alloy layer thickness of 0.1 μm to 5.0 μm, an N content of 3% by mass to 25% by mass, a total C, S, and K content within a range not exceeding the N content, and an S / N ratio of 0.05 to 0.1, maintained low contact resistance even after heating, had a low friction coefficient, excellent wear resistance, and no cracks were observed during indentation. Among these, sample 4, which did not have a silver base layer, and samples 3 and 7, which had a thin silver base layer, had slightly lower wear resistance than the other samples. Samples 1 and 14, which had a thick silver base layer, had slightly higher friction coefficients than the other samples. It can be said that a silver base layer thickness of 0.2 μm to 5.00 μm is preferable.

[0073] In contrast, the nickel layer of Sample 15 was too thick, and cracks were observed in the nickel layer during the indentation test. The nickel layer of Sample 16 was too thin, and therefore copper diffusion could not be suppressed, resulting in high contact resistance after heating. In Sample 17, the silver alloy layer was too thick, so cracks were observed in the silver alloy layer during the indentation test, and in Sample 18, the silver alloy layer was too thin, so the wear resistance was poor. In sample 19, the amount of additive X in the plating bath in the silver alloy layer formation process was too high, resulting in a high S content in the silver alloy layer, with the S / N ratio exceeding 0.1, making it brittle and resulting in cracks in the silver alloy layer in an indentation test. In sample 20, the additive X / Y ratio in the plating bath in the silver alloy layer formation process was too low, resulting in a low S / N ratio in the silver alloy layer, a high coefficient of friction, and poor wear resistance. In sample 21, melamine was used as additive X in the plating bath in the silver alloy layer formation process, resulting in the total amount of S, K, and C in the silver alloy layer being greater than the N content, resulting in a very high coefficient of friction and poor wear resistance.

[0074] In sample 22, the nickel layer was not formed, so the copper diffusion could not be suppressed, and the contact resistance after heating was high. In sample 23, the amount of additive X in the plating bath in the silver alloy layer formation process was too small, so the N content in the silver alloy layer was low, resulting in a high friction coefficient and poor wear resistance.

[0075] In sample 24, the amount of additive Y in the plating bath in the silver alloy layer formation process was too large, resulting in a small S / N ratio in the silver alloy layer, a large friction coefficient, and poor wear resistance.In sample 25, the amount of additive Y in the plating bath in the silver alloy layer formation process was too large, resulting in an S / N ratio in the silver alloy layer exceeding 0.1, making the silver alloy layer brittle and causing cracks in the silver alloy layer during the indentation processing test.

[0076] In sample 26, the amount of additive Y in the silver alloy layer formation process was small, causing the S / N ratio in the silver alloy layer to exceed 0.1, making the silver alloy layer brittle and resulting in cracks.In sample 27, the current density in the alloy layer formation process was too high, causing the total amount of S, K, and C in the silver alloy layer to exceed the N content, resulting in a high friction coefficient and poor wear resistance.In sample 28, the current density in the silver alloy layer formation process was too low, causing an increase in S in the silver alloy layer, increasing the S / N ratio, and resulting in cracks in the silver alloy layer during the indentation processing test.

[0077] In sample 29, the ratio X / Y of additives in the plating bath in the silver alloy layer formation step was too large, so the S / N in the silver alloy layer increased, and cracks occurred in the silver alloy layer during the indentation test. [Explanation of symbols]

[0078] 1,11 Film-coated terminal material 2 Base material 3,12 Membrane 4 nickel layers 5 Silver alloy layer 13 Undercoat silver layer

Claims

1. The electrode comprises a substrate made of copper or a copper alloy, a nickel layer made of nickel or a nickel alloy formed on the substrate to a thickness of 0.2 μm or more and 5.0 μm or less, and a silver alloy layer formed on the outermost surface of at least a part of the nickel layer, the silver alloy layer contains 3% by mass or more and 25% by mass or less of N, with the remainder being C, S, and K, the total amount of which does not exceed the content of N, and the content ratio of S to N, S / N, is 0.05 or more and 0.1 or less; A coated terminal material characterized in that the thickness of the silver alloy layer is 0.1 μm or more and 5.0 μm or less.

2. The coated terminal material according to claim 1, further comprising an underlying silver layer having a silver purity of 98.5% by mass or more and 99.5% by mass or less and a thickness of 0.2 μm or more and 5.0 μm or less, and the silver alloy layer is formed on the underlying silver layer.

3. A method for producing a coated terminal material, comprising: a nickel layer forming step of forming a nickel layer made of nickel or a nickel alloy having a thickness of 0.2 μm or more and 5.0 μm or less on a substrate made of copper or a copper alloy; and a silver alloy layer forming step of forming a silver alloy layer having a thickness of 0.1 μm or more and 5.0 μm or less on the nickel layer by plating; The silver alloy forming step is carried out by using silver cyanide (AgCN) in an amount of 45 g / L or more and 55 g / L or less, potassium cyanide (KCN) in an amount of 110 g / L or more and 130 g / L or less, and potassium carbonate (K ２ CO ３ ) at 10 g / L or more and 20 g / L or less, an additive containing an organic compound or a derivative thereof containing one or more thiol groups, thiolate groups, or sulfide groups on a triazine ring is designated as agent X, and agent Y is agent bismuthiol, the content of agent X is 0.2 g / L or more and 10 g / L or less, and the content of agent Y is 0.08 g / L or more and 5 g / L or less, and the content ratio of agent X to agent Y is designated as X / Y, and a plating bath in which X / Y is 0.1 or more and 50 or less is used, and the current density is 2 A / dm ２ 8A / dm or more ２ A method for producing a coated terminal material, characterized by electroplating at the following current density.

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