Silver-plated material and its manufacturing method

Abstract

To provide a silver-plated material having better wear resistance than ever before while keeping high rigidity and a method for manufacturing the same.SOLUTION: In a method for manufacturing a silver-plated material by forming a surface layer made of silver on a material by performing electroplating in a silver plating solution made of an aqueous solution containing silver potassium cyanide, potassium cyanide, and mercapto thiazole, electroplating is performed under the conditions that a concentration of mercapto thiazole in the silver plating solution is greater than or equal to 5 g / L and a liquid temperature in the silver plating solution is higher than or equal to 30°C, and a current density is 1 to 15A / dm2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a silver-plated product and a method for manufacturing the same, and more particularly to a silver-plated product used as a material for contacts and terminal parts such as connectors, switches, and relays used in electrical wiring for automobiles and consumer use, and a method for manufacturing the same. [Background technology]

[0002] Conventionally, materials used for contacts and terminal parts of connectors and switches are relatively inexpensive materials such as copper, copper alloys, and stainless steel, which have excellent corrosion resistance and mechanical properties, and are plated with tin, silver, gold, etc. depending on the required properties such as electrical properties and solderability.

[0003] Tin-plated materials, which are made by plating copper or copper alloys or stainless steel with tin, are inexpensive but have poor corrosion resistance in high-temperature environments. Gold-plated materials, which are made by plating these materials with gold, have excellent corrosion resistance and high reliability, but are expensive. On the other hand, silver-plated materials, which are made by plating these materials with silver, are cheaper than gold-plated materials and have better corrosion resistance than tin-plated materials.

[0004] Furthermore, materials for contacts and terminal parts of connectors and switches are required to be resistant to wear caused by insertion and removal of connectors and sliding of switches.

[0005] However, because silver-plated materials are soft and prone to wear, when used as materials for connection terminals and the like, they are prone to adhesion and wear due to insertion, removal, and sliding.Furthermore, when the connection terminal is inserted, the surface is scraped off, increasing the coefficient of friction and resulting in a high insertion force.

[0006] To solve this problem, a method is known in which the hardness of a silver-plated product is improved by incorporating elements such as antimony into the silver plating (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2009-79250 A (paragraphs 0003-0004) Summary of the Invention [Problem to be solved by the invention]

[0008] However, when elements such as antimony are added to the silver plating, as in the method of Patent Document 1, the silver is alloyed and the hardness is improved, but the improvement in wear resistance is not sufficient, and there is a demand for silver-plated materials with even better wear resistance.

[0009] In view of the above-mentioned problems of the prior art, it is therefore an object of the present invention to provide a silver-plated product that maintains high hardness while exhibiting superior wear resistance compared to the prior art, and a method for producing the same. [Means for solving the problem]

[0010] As a result of intensive research by the present inventors to solve the above problems, the present inventors have discovered a method for producing a silver-plated material by electroplating a material with a silver surface layer by electroplating in a silver plating solution comprising an aqueous solution containing potassium silver cyanide, potassium cyanide, and mercaptothiazole, in which the concentration of mercaptothiazole in the silver plating solution is 5 g / L or more, the solution temperature is 30°C or more, and the current density is 1 to 15 A / dm 2 The present inventors have found that by electroplating at a temperature of 1000 K or less, it is possible to provide a silver-plated product that is superior in wear resistance to conventional products while maintaining high hardness, and a method for producing the same, and have completed the present invention.

[0011] That is, the method for producing a silver-plated product according to the present invention is a method for producing a silver-plated product by electroplating a material in a silver plating solution comprising an aqueous solution containing potassium silver cyanide, potassium cyanide, and mercaptothiazole, wherein the concentration of mercaptothiazole in the silver plating solution is 5 g / L or more, the solution temperature is 30°C or more, and the current density is 1 to 15 A / dm 2 The electroplating is carried out by

[0012] In this method for producing a silver-plated product, the concentration of mercaptothiazole in the silver plating solution is preferably 10 g / L or more, more preferably 30 g / L or less, and even more preferably 25 g / L or less. Also, the current density of electroplating is 2 to 10 A / dm 2 Preferably, the silver plating solution contains potassium silver cyanide at a concentration of 50 to 200 g / L, and preferably contains potassium cyanide at a concentration of 20 to 120 g / L. Preferably, the silver plating solution contains silver at a concentration of 20 to 120 g / L, and preferably contains free cyanide at a concentration of 5 to 50 g / L. Preferably, electroplating is performed at a solution temperature of 50°C or less. Preferably, the base material is made of copper or a copper alloy, and a nickel underlayer is formed between the base material and the surface layer.

[0013] The silver-plated product according to the present invention is characterized in that a surface layer made of silver is formed on a base material, and the surface layer has an average crystallite diameter of 23 nm or less and a Vickers hardness HV of 100 to 160, and the surface layer contains 0.3 mass % or more of carbon, 0.4 mass % or more of sulfur, and 0.1 mass % or more of nitrogen.

[0014] In this silver-plated product, the silver content in the surface layer is preferably 90 to 99% by mass, the carbon content in the surface layer is preferably 2% by mass or less, and the sulfur content in the surface layer is preferably 2% by mass or less.Furthermore, the base material is preferably made of copper or a copper alloy, and a base layer made of nickel is preferably formed between the base material and the surface layer. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a silver-plated product that is superior in wear resistance to conventional products while maintaining high hardness, and a method for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0016] In an embodiment of the method for producing a silver-plated product according to the present invention, a silver-plated product is produced by electroplating a material in a silver plating solution comprising an aqueous solution containing potassium silver cyanide, potassium cyanide, and mercaptothiazole, wherein the concentration of mercaptothiazole in the silver plating solution is 5 g / L or more, the solution temperature is 30°C or more, and the current density is 1 to 15 A / dm 2 Electroplating is performed.

[0017] When mercaptothiazole is added to a silver plating solution as an organic additive, it is incorporated into the silver plating film (the silver surface layer) by electroplating, suppressing the movement of dislocations in the silver plating film, thereby increasing the hardness and improving the wear resistance of the silver-plated product. Furthermore, the lubricating effect of the organic additive is thought to reduce the coefficient of friction of the silver-plated product. Mercaptothiazole, in particular, has a dithioiminocarbonate structure and is prone to proton dissociation, making it highly soluble in aqueous solutions and easily incorporated into the silver plating film. This improves the silver plating film formation rate. Furthermore, unlike N-allylthiourea and 2-mercaptobenzimidazole, it can improve wear resistance even at high film formation rates.

[0018] In this method for producing a silver-plated product, the concentration of mercaptothiazole in the silver plating solution is preferably 10 g / L or more, and more preferably 30 g / L or less, and more preferably 25 g / L or less. The current density of electroplating is 2 to 10 A / dm 2Preferably, the concentration of potassium silver cyanide in the silver plating solution is 50 to 200 g / L, more preferably 70 to 180 g / L. Preferably, the concentration of potassium cyanide in the silver plating solution is 20 to 120 g / L, more preferably 30 to 100 g / L. Preferably, the silver concentration in the silver plating solution is 20 to 120 g / L, more preferably 30 to 110 g / L, and most preferably 40 to 100 g / L. Preferably, the concentration of free cyanide in the silver plating solution is 5 to 50 g / L, more preferably 10 to 45 g / L, and most preferably 15 to 40 g / L. Electroplating is preferably performed at a solution temperature of 50°C or less, more preferably 45°C or less, and most preferably 40°C or less. The base material is preferably copper or a copper alloy, and a nickel underlayer is preferably formed between the base material and the surface layer. This nickel underlayer can be formed by electroplating using a known nickel plating bath such as a Watts bath or a sulfamic acid bath (preferably a sulfamic acid bath).

[0019] In addition, an embodiment of the silver-plated product according to the present invention is a silver-plated product in which a surface layer made of silver is formed on a base material, and the average crystallite size of the surface layer is 23 nm or less, and the Vickers hardness HV is 100 to 160, and the carbon content in the surface layer is 0.3 mass % or more, the sulfur content is 0.4 mass % or more, and the nitrogen content is 0.1 mass % or more.

[0020] In this silver-plated product, the silver content in the surface layer is preferably 90 to 99% by mass, more preferably 92 to 99% by mass, and most preferably 95 to 99% by mass. The carbon content in the surface layer is preferably 0.5% by mass or more and 2% by mass or less, and more preferably 1% by mass or less. The sulfur content in the surface layer is preferably 0.6% by mass or more and 2% by mass or less, and more preferably 1.5% by mass or less. The nitrogen content in the surface layer is preferably 0.2% by mass or more and 2% by mass or less, and preferably 1% by mass or less, and preferably 0.5% by mass or less. The potassium content in the surface layer is preferably 0.1 to 2% by mass, and more preferably 0.2 to 1% by mass. The ratio (C / S) of the carbon content (atomic concentration at%) to the sulfur content (atomic concentration at%) in the surface layer is preferably 1.5 to 2.5, the ratio (S / N) of the sulfur content (atomic concentration at%) to the nitrogen content (atomic concentration at%) is preferably 1.0 to 2.5, and the ratio (C / N) of the carbon content (atomic concentration at%) to the nitrogen content (atomic concentration at%) is preferably 2.5 to 4.0. The material is preferably made of copper or a copper alloy, and a base layer made of nickel is preferably formed between the material and the surface layer. [Example]

[0021] Examples of the silver-plated product and the method for producing the same according to the present invention will be described in detail below.

[0022] [Example 1] First, a rolled plate made of oxygen-free copper (C1020 1 / 2H) measuring 67 mm x 50 mm x 0.3 mm was prepared as the substrate (material to be plated). As a pretreatment for this material to be plated, the material to be plated and the SUS plate were placed in an alkaline degreasing solution, and electrolytic degreasing was performed for 30 seconds at a voltage of 5 V, with the material to be plated as the cathode and the SUS plate as the anode. After rinsing with water, the material was pickled in 3% sulfuric acid for 15 seconds and then rinsed with water.

[0023] Next, in a matte nickel plating solution consisting of an aqueous solution containing 540 g / L of nickel sulfamate tetrahydrate, 25 g / L of nickel chloride, and 35 g / L of boric acid, the pretreated workpiece was used as the cathode and the nickel electrode plate was used as the anode, and the solution was stirred at 500 rpm with a stirrer at a liquid temperature of 55°C and a current density of 5 A / dm 2 The thickness of the matte nickel plating film at the approximate center was measured using a fluorescent X-ray film thickness meter (SFT-110A, manufactured by Hitachi High-Tech Science Corporation) and found to be 1 μm.

[0024] Next, in a silver strike plating solution consisting of an aqueous solution containing 3 g / L of potassium silver cyanide (KAg(CN)2) and 90 g / L of potassium cyanide (KCN), the workpiece on which the undercoat plating film was formed was used as the cathode, and a platinum-coated titanium electrode plate was used as the anode, and the plating was conducted at a current density of 2.0 A / dm at room temperature (25°C) while stirring at 500 rpm with a stirrer. 2 for 10 seconds to form a silver strike plating film, and then the silver strike plating solution was thoroughly washed away by rinsing with water.

[0025] Next, in a silver plating solution consisting of an aqueous solution containing 80 g / L of potassium silver cyanide (KAg(CN)2), 39 g / L of potassium cyanide (KCN), and 12.4 g / L of mercaptothiazole (MT) (Ag concentration 43.4 g / L, free cyanide concentration 16 g / L), the workpiece on which the silver strike plating film had been formed was used as the cathode, and the silver electrode plate was used as the anode. The solution was stirred at 500 rpm with a stirrer, and the current density was 3 A / dm 2 After electroplating (silver plating) for 200 seconds to form a silver plating film, the material was rinsed with water and dried with air pressure from an air gun to obtain a silver-plated material.

[0026] The thickness of the silver plating film at the approximate center of the silver-plated product thus obtained was measured using the fluorescent X-ray film thickness meter and was found to be 5 μm.

[0027] In addition, the Vickers hardness HV of the surface of this silver-plated material was measured in accordance with JIS Z2244 using a microhardness tester (HM-221 manufactured by Mitutoyo Corporation) by applying a measurement load of 10 gf for 10 seconds, and was found to be 151.

[0028] Two pieces of the above silver-plated material were prepared, one of which was indented (with an inner radius of 1.5 mm) and used as an indenter, while the other was used as a flat evaluation specimen. Using a precision sliding tester (CRS-G2050-DWA manufactured by Yamazaki Seiki Kenkyusho Co., Ltd.), the indenter was pressed against the evaluation specimen with a constant load (5 N) while undergoing a reciprocating sliding motion (sliding distance 5 mm, sliding speed 1.67 mm / s) until the material was exposed. The center of the sliding marks on the silver-plated material was observed at 100x magnification using a microscope (VHX-1000 manufactured by Keyence Corporation) to evaluate the wear state of the silver-plated material. The results confirmed that the material was not exposed even after 1,000 reciprocating sliding motions, demonstrating its excellent wear resistance.

[0029] The crystallite diameters perpendicular to the (111), (200), (220), and (311) crystal planes of the silver-plated film of this silver-plated material were calculated using the Scherrer equation from the half-widths of the peaks of the crystal planes (the (111) peak at approximately 38°, the (200) peak at approximately 44°, the (220) peak at approximately 64°, and the (311) peak at approximately 77°) in the X-ray diffraction pattern (XRD pattern) obtained with an XRD analyzer (Rigaku Corporation, fully automated multipurpose horizontal X-ray diffractometer Smart Lab). The average crystallite diameter was calculated as a weighted average of the crystallite diameters of each crystal plane, weighted by the orientation ratio of each crystal plane. The average crystallite diameter of the silver-plated film was found to be 61.0 Å (6.10 nm). The orientation ratio was determined by using an X-ray diffraction (XRD) analyzer (Rigaku Corporation's fully automated multipurpose horizontal X-ray diffractometer, Smart Lab) with a Cu tube and a Kβ filter method to scan the scanning range 2θ / θ. The X-ray diffraction pattern was then corrected by dividing the X-ray diffraction peak intensities (X-ray diffraction peak intensities) of the (111), (200), (220), and (311) planes of the silver plating film by the relative intensity ratios (relative intensity ratios in powder measurement) listed in JCPDS Card No. 40783 ((111):(200):(220):(311)=100:40:25:26).

[0030] [Example 2] When forming the silver plating film, the current density is 5A / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out at 1000 kJ / min for 120 seconds.

[0031] The thickness of the silver plating film at the approximate center of the silver-plated product thus obtained was measured in the same manner as in Example 1, and was found to be 5 μm.

[0032] In addition, after dissolving the silver in the silver-plated product with nitric acid, hydrochloric acid was added until no white precipitate (AgCl) formed. The white precipitate was filtered and washed with water, and the weight of the AgCl was measured to calculate the weight of the silver in the silver-plated product. Furthermore, using a carbon-sulfur analyzer (Horiba, Ltd. EMIA-810), the silver-plated product was heated to 1350°C in an oxygen stream and melted. The CO and CO2 generated were qualitatively and quantitatively analyzed with an infrared detector to calculate the carbon content of the silver-plated product. The sulfur content of the silver-plated product was calculated as the sulfur content of the silver plating film by qualitatively and quantitatively analyzing with an infrared detector the SO2 generated when the silver-plated product was heated to 1350°C in an oxygen stream and melted. Furthermore, the silver-plated materials were melted in a helium stream at 5000 W using an oxygen, nitrogen, and hydrogen analyzer (LECO Japan, LLC). The nitrogen content in the silver-plated materials was calculated as the nitrogen content in the silver-plated film by quantifying the N2 generated using a thermal conductivity detector (TCD). The resulting silver-plated materials were dissolved in nitric acid (a precision analytical reagent) and diluted to a potassium concentration of 2 mg / L or less. The potassium content in the silver-plated materials was measured using an atomic absorption spectrophotometer (a ZA3300 biased Zeeman atomic absorption spectrophotometer, Hitachi High-Tech Science Corporation). The silver, carbon, sulfur, nitrogen, and potassium contents in the base material before the silver-plated film were determined using the same method as above. Since all values ​​were below the detection limit, the silver, carbon, sulfur, nitrogen, and potassium contents in the silver-plated materials were reported as the respective contents in the silver-plated film. As a result, the silver plating film was found to contain 0.7% by mass of carbon, 1.1% by mass of sulfur, 0.2% by mass of nitrogen, and 0.2% by mass of potassium, with the remainder being silver (Ag purity 97.8% by mass), where the total content of silver, carbon, sulfur, nitrogen, and potassium was taken as 100% by mass. Analysis of the silver plating film using a carbon / sulfur analyzer (EMIA-810, manufactured by Horiba, Ltd.) and an oxygen / nitrogen / hydrogen analyzer (manufactured by LECO Japan, LLC) revealed that the atomic concentration (at%) ratios in the silver plating film were C / S = 1.7, S / N = 2.2, and C / N = 3.8.

[0033] For this silver-plated material, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 129. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver-plated film was found to be 148.7 angstroms (14.87 nm).

[0034] [Example 3] The silver plating solution used was an aqueous solution containing 175 g / L of potassium silver cyanide (KAg(CN)2), 95 g / L of potassium cyanide (KCN), and 18.5 g / L of mercaptothiazole (MT) (Ag concentration: 94.9 g / L, free cyanide concentration: 38 g / L). The current density was 5 A / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out at 1000 kJ / min for 120 seconds.

[0035] The thickness of the silver plating film of the silver-plated product thus obtained at approximately the center was measured to be 5 μm by the same method as in Example 1. Furthermore, the silver plating film of this silver-plated product was subjected to surface analysis by the same method as in Example 2, and it was found to be a film containing 0.7 mass% carbon, 0.8 mass% sulfur, 0.3 mass% nitrogen, 0.5 mass% potassium, and the remainder silver (Ag purity 97.7 mass%) (C / S=2.2, S / N=1.3, C / N=2.9).

[0036] For this silver-plated material, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite size was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 129. Furthermore, it was confirmed that the material was not exposed even after 1,000 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite size of the silver-plated film was 109.1 angstroms (10.91 nm).

[0037] [Example 4] When forming the silver plating film, the current density is 7A / dm 2 A silver-plated product was produced in the same manner as in Example 3, except that electroplating (silver plating) was carried out at 1000 kJ / min for 86 seconds.

[0038] The thickness of the silver plating film of the silver-plated product thus obtained at approximately the center was measured to be 5 μm by the same method as in Example 1. Furthermore, the silver plating film of this silver-plated product was subjected to surface analysis by the same method as in Example 2, and it was found to be a film containing 0.3 mass% carbon, 0.4 mass% sulfur, 0.1 mass% nitrogen, 0.3 mass% potassium, and the remainder silver (Ag purity 98.9 mass%) (C / S=2.2, S / N=1.3, C / N=2.9).

[0039] For this silver-plated material, the Vickers hardness HV of the silver-plated film was measured using the same method as in Example 1, the wear resistance was evaluated, and the crystallite diameter was calculated. The Vickers hardness HV was found to be 147. It was also confirmed that the material was not exposed even after 200 reciprocating sliding operations, demonstrating excellent wear resistance. Furthermore, the average crystallite diameter of the silver-plated film was found to be 175.7 angstroms (17.57 nm).

[0040] [Comparative Example 1] The silver plating solution used was an aqueous solution containing 175 g / L of potassium silver cyanide (KAg(CN)2), 95 g / L of potassium cyanide (KCN), and 70 mg / L of selenium (Ag concentration 94.9 g / L, free cyanide concentration 38 g / L). The solution temperature was 18 (±0.5) °C, and the current density was 5 A / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out at 1000 kJ / min for 120 seconds.

[0041] The thickness of the silver plating film of the silver-plated product thus obtained at approximately the center was measured to be 5 μm by the same method as in Example 1. Furthermore, the silver plating film of this silver-plated product was subjected to surface analysis by the same method as in Example 2, and it was found to be a film containing 0.1 mass % or less of carbon, with the remainder being silver (Ag purity 99.9 mass % or more).

[0042] For this silver-plated material, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 134. Furthermore, it was confirmed that the material was exposed after 80 reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was 278.0 angstroms (27.80 nm).

[0043] Comparative Example 2 The silver plating solution used was an aqueous solution containing 148 g / L of potassium silver cyanide (KAg(CN)2), 140 g / L of potassium cyanide (KCN), and 8 mg / L of selenium (Ag concentration: 80.2 g / L, free cyanide concentration: 56 g / L). The solution temperature was 16 (±0.5) °C, and the current density was 8 A / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out at 1000 kJ / min for 75 seconds.

[0044] The thickness of the silver plating film at the approximate center of the silver-plated product thus obtained was measured in the same manner as in Example 1, and was found to be 5 μm.

[0045] For this silver-plated material, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 82. Furthermore, it was confirmed that the material was exposed after 50 reciprocating sliding operations, indicating that the wear resistance was not good. Furthermore, the average crystallite diameter of the silver-plated film was found to be 750.0 angstroms (75.00 nm).

[0046] Comparative Example 3 The silver plating solution used was an aqueous solution containing 115 g / L of potassium silver cyanide (KAg(CN)2), 60 g / L of potassium cyanide (KCN), and 40 mg / L of selenium (Ag concentration 62.3 g / L, free cyanide concentration 24 g / L). The solution temperature was 25 (±0.5) °C, and the current density was 2 A / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out at 1000 kJ / min for 300 seconds.

[0047] The thickness of the silver plating film at the approximate center of the silver-plated product thus obtained was measured in the same manner as in Example 1, and was found to be 5 μm.

[0048] For this silver-plated material, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 119. Furthermore, it was confirmed that the material was exposed after 100 reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was 636.0 angstroms (63.60 nm).

[0049] Comparative Example 4 The silver plating solution used was an aqueous solution containing 40 g / L of potassium silver cyanide (KAg(CN)2), 39 g / L of potassium cyanide (KCN), and 1 g / L of N-allylthiourea (Ag concentration: 21.7 g / L, free cyanide concentration: 16 g / L). The solution temperature was 25 (±0.5) °C, and the current density was 0.7 / dm 2 A silver-plated product was produced in the same manner as in Example 1, except that electroplating (silver plating) was carried out at 1000 kJ / min for 857 seconds.

[0050] The thickness of the silver plating film at the approximate center of the silver-plated product thus obtained was measured in the same manner as in Example 1, and was found to be 5 μm.

[0051] For this silver-plated material, the Vickers hardness HV of the silver-plated film was measured, the wear resistance was evaluated, and the crystallite diameter was calculated using the same method as in Example 1. The Vickers hardness HV was found to be 61. Furthermore, it was confirmed that the material was exposed after 30 reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was 455.6 angstroms (45.56 nm).

[0052] Comparative Example 5 When forming the silver plating film, the solution temperature is 25 (±0.5) °C, and the current density is 5 A / dm 2 A silver-plated product was produced in the same manner as in Example 3, except that electroplating (silver plating) was carried out at 1000 kJ / min for 120 seconds.

[0053] The thickness of the silver plating film of the silver-plated product thus obtained at approximately the center was measured to be 5 μm by the same method as in Example 1. Furthermore, the silver plating film of this silver-plated product was subjected to surface analysis by the same method as in Example 2, and it was found to be a film containing 0.2 mass% carbon, 0.3 mass% sulfur, 0.1 mass% nitrogen, 0.3 mass% potassium, and the remainder silver (Ag purity 99.2 mass%) (C / S=2.0, S / N=1.8, C / N=3.5).

[0054] For this silver-plated material, the Vickers hardness HV of the silver-plated film was measured using the same method as in Example 1, the wear resistance was evaluated, and the crystallite diameter was calculated. The Vickers hardness HV was found to be 131. Furthermore, it was confirmed that the material was exposed after 60 or fewer reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was 257.4 angstroms (25.74 nm).

[0055] Comparative Example 6 When forming the silver plating film, the solution temperature is 25 (±0.5) °C, and the current density is 7 A / dm 2 A silver-plated product was produced in the same manner as in Example 3, except that electroplating (silver plating) was carried out at 1000 kJ / min for 86 seconds.

[0056] The thickness of the silver plating film on the silver-plated product thus obtained at approximately the center was measured to be 5 μm by the same method as in Example 1. Furthermore, the silver plating film on this silver-plated product was subjected to surface analysis by the same method as in Example 2, and it was found to be a film (C / S=2.7) containing 0.1 mass% carbon, 0.1 mass% sulfur, less than 0.1 mass% nitrogen, 0.1 mass% potassium, and the remainder silver (Ag purity 99.5% or more).

[0057] For this silver-plated material, the Vickers hardness HV of the silver-plated film was measured using the same method as in Example 1, the wear resistance was evaluated, and the crystallite diameter was calculated. The Vickers hardness HV was found to be 145. Furthermore, it was confirmed that the material was exposed after 60 or fewer reciprocating sliding operations, indicating that the wear resistance was poor. Furthermore, the average crystallite diameter of the silver-plated film was 269.8 angstroms (26.98 nm).

[0058] Tables 1 to 9 show the manufacturing conditions and properties of the silver-plated products obtained in these Examples and Comparative Examples.

[0059] [Table 1]

[0060] [Table 2]

[0061] [Table 3]

[0062] [Table 4]

Claims

1. In a method for producing a silver-plated product by electroplating a material in a silver plating solution containing an aqueous solution containing potassium silver cyanide, potassium cyanide, and mercaptothiazole, the concentration of mercaptothiazole in the silver plating solution is 5 g / L or more, the solution temperature is 35°C or more, and the current density is 1 to 15 A / dm ２ A method for producing a silver-plated product, characterized in that electroplating is performed using a

2. 2. The method for producing a silver-plated product according to claim 1, wherein the concentration of mercaptothiazole in the silver plating solution is 10 g / L or more.

3. 3. The method for producing a silver-plated product according to claim 1, wherein the concentration of mercaptothiazole in the silver plating solution is 30 g / L or less.

4. 4. The method for producing a silver-plated product according to claim 1, wherein the concentration of mercaptothiazole in the silver plating solution is 25 g / L or less.

5. The current density of the electroplating is 2 to 10 A / dm ２ 5. The method for producing a silver-plated product according to claim 1, wherein

6. 6. The method for producing a silver-plated product according to claim 1, wherein the concentration of potassium silver cyanide in the silver plating solution is 50 to 200 g / L.

7. 7. The method for producing a silver-plated product according to claim 1, wherein the concentration of potassium cyanide in the silver plating solution is 20 to 120 g / L.

8. 8. The method for producing a silver-plated product according to claim 1, wherein the silver concentration in the silver plating solution is 20 to 120 g / L.

9. 9. The method for producing a silver-plated product according to claim 1, wherein the concentration of freshan in the silver plating solution is 5 to 50 g / L.

10. 10. The method for producing a silver-plated product according to claim 1, wherein the electroplating is carried out at a solution temperature of 50°C or less.

11. 11. The method for manufacturing a silver-plated product according to claim 1, wherein the material is made of copper or a copper alloy.

12. 12. The method for manufacturing a silver-plated product according to claim 1, wherein an underlayer made of nickel is formed between said base material and said surface layer.

13. A silver-plated product having a surface layer made of silver formed on a base material, characterized in that the surface layer has an average crystallite diameter of 17.57 nm or less, a Vickers hardness HV of 100 to 160, and a carbon content of 0.3 mass % or more, a sulfur content of 0.4 mass % or more, and a nitrogen content of 0.1 mass % or more in the surface layer.

14. 14. The silver-plated product according to claim 13, wherein the silver content in the surface layer is 90 to 99 mass %.

15. 15. The silver-plated product according to claim 13, wherein the carbon content in the surface layer is 2% by mass or less.

16. 16. The silver-plated product according to claim 13, wherein the sulfur content in the surface layer is 2% by mass or less.

17. 17. The silver-plated product according to claim 13, wherein the material is made of copper or a copper alloy.

18. 18. The silver-plated product according to claim 13, wherein an underlayer made of nickel is formed between the base material and the surface layer.

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