JP6665387B2 - Silver plated member and method of manufacturing the same - Google Patents

Description

  The present invention relates to a method for producing a silver-plated member and a silver-plated member obtained by the method, and more specifically, has excellent wear resistance, electrical conductivity, slidability and low friction, and The present invention relates to a silver-plated member suitable for suppressing embrittlement of a plating layer and a method for manufacturing the same.

  Silver plating has excellent properties such as electrical conductivity, low contact resistance, and heat resistance, and is widely used for electric and electronic components such as various contacts, terminals, connectors, and switches (for example, see Patent Document 1 JP 2001-3194 A).

  In recent years, electric vehicles, plug-in hybrid vehicles, and the like have been widely used, and accordingly, charging devices such as home charging devices and quick charging devices have also been widely used. The terminals of the charging connector that connects the vehicle and the charging device must withstand tens of thousands of insertion / removal operations in addition to use under high voltage and high current.

  Here, for the terminals of the above-mentioned electric / electronic parts, a material obtained by applying tin plating or reflow tin plating on a copper substrate is often used, and if a good silver plating can be applied to the surface of the material. It seems that the terminal can be provided with excellent wear resistance and electrical conductivity.

  However, it is extremely difficult to plate silver, which is a noble metal, on tin, which is a base metal, and substitution of tin and silver occurs due to the potential difference between tin and silver (diffusing with each other). Peeling of silver plating or the like occurs. For these reasons, at present, there is no technique for laminating good silver plating on tin plating.

  In this regard, for example, in Patent Document 2 (Japanese Patent Application Laid-Open No. 8-176883), an Sn plating layer is provided on at least a part of the surface of a base material made of copper or a copper alloy, and Cu, In is provided on the Sn plating layer. , Ag, Zn, and Sb are disclosed.

  However, the production method described in Patent Document 2 is intended to produce a Sn alloy plated material, and heating the multilayer plating obtained in the above-described process in a non-oxidizing atmosphere to at least the surface of the base material. In part, a Sn alloy plating layer containing 80 to 99% of Sn (however, the total amount of Cu, Zn, and Sb in the plating layer is 10% or less) is formed. Although this method is to alloy tin and silver by heating, poor adhesion between tin plating and silver plating does not become a serious problem, but it is not a technique for forming a silver plating layer on the outermost surface of the member .

JP 2001-3194 A JP-A-8-176883

  In view of the above problems in the prior art, an object of the present invention is to have excellent wear resistance, electrical conductivity, slidability and low friction, and to suppress embrittlement of a silver plating layer. It is an object of the present invention to provide a silver-plated member and a method for manufacturing the same, which are suitable for the present invention.

  The present inventor has conducted intensive studies on a method of manufacturing a silver-plated member in order to achieve the above object, and as a result, has excellent wear resistance, electrical conductivity, slidability and low friction, and a silver-plated layer. In order to obtain a silver-plated member suitable for suppressing embrittlement of a metal substrate having a reflow tin plating layer, a reaction formed at the interface between the reflow tin plating layer and the reflow tin plating layer and the metal substrate. The present inventors have found that it is extremely effective to apply a silver plating treatment to a region where the layer has been completely peeled off, and have reached the present invention.

That is, the present invention
A metal substrate having a reflow tin plating layer at least in part, from a metal substrate having a reaction layer at an interface between the reflow tin plating layer and the metal substrate, the reflow tin plating layer and the reaction layer A first step of completely peeling off at least a part,
A second step of performing a silver plating process on at least a part of the region from which the reflow tin plating layer and the reaction layer have been completely peeled off,
And a method for producing a silver-plated member.

  In the method for manufacturing a silver-plated member of the present invention, at least a part of the region where the reflow tin plating layer and the reaction layer are completely peeled off is subjected to silver strike plating and copper strike plating as a preliminary treatment of the second step. , One or more strike plating selected from the group consisting of gold strike plating and nickel strike plating. The strike plating is more preferably silver strike plating in order to avoid unexpected adverse effects of intermetallic compounds generated by the reaction with silver plating.

  In the method for manufacturing a silver-plated member of the present invention, before the first step, a reflow treatment is performed on the tin-plated layer of the metal base material including at least a part thereof, and the tin-plated layer is formed. The method may include a pre-process of forming a reaction layer at an interface between the reflow tin plating layer and the metal base material while converting the reflow tin plating layer into a reflow tin plating layer.

  Here, the reflow treatment is a treatment in which the electrodeposited tin plating layer is heated, temporarily melted, and rapidly cooled. By melting the tin plating layer, stress (strain) during plating is removed, and a reaction layer is formed at the interface between the metal substrate and the tin plating layer, thereby reducing the change over time of the tin plating layer. be able to.

In addition, a reaction layer is formed at the interface between the tin plating layer and the metal substrate by the reflow treatment. The composition and shape of the reaction layer are not particularly limited as long as they are effective in suppressing atomic diffusion and / or reaction between the metal base material and each plating layer, but it is preferable that the reaction layer contains Cu ₃ Sn.

  As the conditions for the reflow treatment, various conventionally known reflow treatments can be used as long as the effects of the present invention are not impaired. In the reflow treatment, the tin plating layer applied to a part or the whole of the surface of the metal substrate may be melted by heating to a temperature equal to or higher than the melting point of tin. In order to alleviate the internal stress of the tin plating layer, a preferable treatment temperature is 250 to 600 ° C, more preferably 300 to 500 ° C, and further preferably 350 to 450 ° C. In order to improve the plating appearance, a preferable treatment time is 3 to 40 seconds, more preferably 5 to 30 seconds, and further preferably 5 to 20 seconds. In addition, the heat treatment is preferably performed in a reducing atmosphere or an inert atmosphere.

  In the method for producing a silver-plated member of the present invention, in the first step, at least a part of the reflow tin plating layer from the metal substrate and the reaction layer formed at the interface between the reflow tin plating layer and the metal substrate. Peel completely. As a method of completely peeling off the reflow tin plating layer and the reaction layer, various conventionally known peeling methods can be used as long as the effects of the present invention are not impaired. A method of immersion peeling or electrolytic peeling with a suitable peeling liquid can be used.

  As the stripping solution used in the first step, a general immersion stripping solution or non-electrolytic stripping solution for non-ferrous metals can be used. Immersion peeling, electrolytic peeling, or the like can be performed by using a material to which chromium is added. Note that the outermost surface of the metal substrate in the region where the reflow tin plating layer and the reaction layer are completely peeled off is the metal substrate itself.

  In the method for manufacturing a silver-plated member according to the present invention, it is preferable to perform a strike plating process on at least a part of the peeled portion obtained in the first step. Here, the strike plating layer formed by the strike plating process may have a continuous film shape or a granular or island-like discontinuous film shape as long as the effects of the present invention are not impaired. In the latter case, the granular and island-shaped portions may be partially continuous. The strike plating layer preferably has a thickness of 0.01 to 0.5 μm. The silver plating process in the second step forms a silver plating layer on an extremely thin strike plating layer, and a single silver plating layer is obtained roughly.

  In the method for producing a silver-plated member of the present invention, it is preferable that the thickness of the single silver plating layer obtained through the silver plating in the second step is 0.1 μm to 50 μm. The thickness is a value obtained by combining the strike plating layer and the silver plating layer.

  The single silver plating layer obtained through the silver plating process in the second step basically has a constant thickness, but is partially thinned or thickened as long as the effect of the present invention is not impaired. Or you may. The silver plating layer preferably has a Vickers hardness of 10 HV to 250 HV.

Further, the present invention also provides a silver-plated member obtained by the method for producing a silver-plated member, and the silver-plated member is
On the surface of the metal substrate, a region in which the reflow tin plating layer is formed, and a region in which the silver plating layer is formed, each having a plating material,
There is a reaction layer containing Cu ₃ Sn at the interface between the reflow tin plating layer and the metal base,
No reaction layer containing Cu ₃ Sn is present at the interface between the silver plating layer and the metal base,
It is characterized by.

  In the silver-plated member of the present invention, the silver-plated layer is metallurgically bonded to the metal substrate. Metallurgical bonding does not mean that the silver plating layer and the metal substrate are bonded together through mechanical bonding such as an anchor effect or a heterogeneous bonding layer such as an adhesive, but rather that the metals are directly bonded to each other. Means that. Metallurgical bonding is a concept that naturally includes bonding by crystallographic matching (epitaxy). In the present invention, the silver plating layer and the metal base material achieve bonding by crystallographic matching (epitaxy) to each other. Is preferred.

When the tin plating layer and the silver plating layer are in contact with each other, the tin plating layer and / or the silver plating layer are embrittled by the formation of an intermetallic compound (eg, Ag ₃ Sn) accompanying the diffusion and reaction of tin and silver. Would. On the other hand, in the plating material of the present invention, since the silver plating layer is formed directly on the metal base material, embrittlement of the tin plating layer and / or the silver plating layer can be extremely effectively suppressed. .

  The present invention also relates to a connection terminal including the silver-plated member of the present invention, wherein the male and / or female terminals of the connection terminal are formed of the silver-plated member of the present invention.

  In the connection terminal of the present invention described above, it is preferable that the outermost surface of the fitting portion requiring abrasion resistance be a tin plating layer, and the outermost surface of the contact portion requiring electrical conductivity be a silver plating layer. .

  According to the method for producing a silver-plated member of the present invention, silver plating having excellent wear resistance, electrical conductivity, slidability and low friction, and suitable for suppressing embrittlement of a silver-plated layer is provided. A member and a method for manufacturing the member can be provided. Further, the silver-plated member of the present invention can be suitably used as a material for a connection terminal requiring excellent wear resistance and electrical conductivity, and has excellent wear resistance, electrical conductivity, and fitting property. A combined connection terminal can be provided.

It is process drawing of the manufacturing method of the silver plating member of this invention. It is an outline sectional view showing an example of the silver plating member of the present invention. It is a schematic diagram showing an example of a connection terminal of the present invention.

  Hereinafter, typical embodiments of the method for manufacturing a silver-plated member, silver-plated members, and connection terminals of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto. In the following description, the same or corresponding parts are denoted by the same reference characters, and redundant description may be omitted. Further, since the drawings are for conceptually explaining the present invention, the dimensions of the components and their ratios may be different from the actual ones.

製造 Production method of plating material≪
FIG. 1 is a process chart of the method for producing a silver-plated member of the present invention. The method for producing a silver-plated member of the present invention is a method for producing a plating material having a metal substrate, a reflow tin plating layer, and a silver plating layer, wherein the reflow tin plating layer and the reaction layer are formed from the metal substrate. A first step (S01) of completely peeling off at least a part, and silver strike plating, copper strike plating, gold strike plating, and nickel strike plating on at least a part of a region where the reflow tin plating layer and the reaction layer are completely peeled. A strike plating step (S02 ') of performing one or more strike plating treatments selected from the group consisting of: a second step (S02) of subjecting at least a part of the region subjected to the strike plating treatment to a silver plating treatment; Contains. The strike plating step (S02 ') is an optional step, and can be omitted when the adhesion between the silver plating layer formed in the second step (S02) and the metal base material is good. Further, a pre-process (S00) of performing a reflow treatment on the tin plating layer to form a reaction layer at an interface between the metal base material and the tin plating layer may be included.

  The metal used for the metal substrate is not particularly limited as long as it has conductivity, and examples thereof include aluminum and aluminum alloys, iron and iron alloys, titanium and titanium alloys, stainless steel, copper and copper alloys, and the like. However, among them, it is preferable to use copper and a copper alloy because they are excellent in electrical conductivity, thermal conductivity, and spreadability.

  A reflow process is performed on the plating material having a tin plating layer on the surface of the metal base material in the previous step (S00), and a cleaning process is performed after the reflow process. The first step (S01) includes a strike plating process (S02). ') And the second step (S02), a silver-plated member can be obtained. Hereinafter, each process will be described in detail.

(1) Tin plating treatment Commercially available materials can be used for a material obtained by subjecting a metal substrate to tin plating and a material obtained by subjecting a metal substrate having a tin plating layer to a reflow treatment. For the tin plating, various conventionally known tin plating methods can be used as long as the effects of the present invention are not impaired.

  Examples of the tin plating bath include an acidic bath, a neutral bath, and an alkaline bath, and any bath can be used. Generally, a sulfuric acid bath or an organic sulfonic acid bath is used as an acidic bath, a pyrophosphoric acid bath or a gluconic acid bath is used as a neutral bath, and a potassium stannate bath or a sodium stannate bath is used as an alkaline bath.

(2) Reflow treatment (pre-process (S00))
Generally, reflow to tin plating is a process for suppressing the growth of whiskers (needle-shaped metal crystals) with the passage of time. The electrodeposited tin plating layer is heated, melted once, and rapidly cooled. A method is used. By melting the tin plating layer, stress (strain) at the time of plating is removed, and a change with time can be reduced by forming a reaction layer with the metal base material. In the method for producing a plated material of the present invention, the main purpose of the reflow treatment is to form a reaction layer at the interface between the tin plating layer and the metal substrate. The whisker is said to be caused by the formation of Cu ₆ Sn _{5 having} a large crystal lattice generated at the interface between the whiskers due to the diffusion of copper and tin plating. The reflow treatment is performed to suppress the whisker formation. By forming dense Cu ₃ Sn as a barrier layer, diffusion of copper is suppressed, and whisker generation is suppressed.

  In the reflow treatment, the tin plating layer applied to a part or the whole of the surface of the metal substrate may be melted by heating to a temperature equal to or higher than the melting point of tin. In order to alleviate the internal stress of the tin plating layer, a preferable treatment temperature is 250 to 600 ° C, more preferably 300 to 500 ° C, and further preferably 350 to 450 ° C. In order to improve the plating appearance, a preferable treatment time is 3 to 40 seconds, more preferably 5 to 30 seconds, and further preferably 5 to 20 seconds. In addition, the heat treatment is preferably performed in a reducing atmosphere or an inert atmosphere. In addition, you may purchase the plating material which performed the reflow process on the metal base material which has a tin plating layer, and may omit a front process (S00).

(3) Cleaning Treatment The cleaning step is an optional step, and although not shown in FIG. 1, is a step of cleaning at least the surface of the reflow tin plating layer of the metal base material having the reflow tin plating layer. Here, various conventionally known cleaning treatment liquids and treatment conditions can be used as long as the effects of the present invention are not impaired.

  A general immersion degreasing solution for non-ferrous metals or an electrolytic degreasing solution can be used as the cleaning solution. However, in order to prevent corrosion of tin, which is an amphoteric metal, a cleaning solution having a pH of more than 2 and less than 11 is used. It is preferable to use a strong acid bath having a pH of 2 or less or a strong alkaline bath having a pH of 11 or more.

Specifically, a bath in which 0.1 to 10 g / L of a surfactant is added to a weakly alkaline bath in which 10 to 50 g / L of tribasic sodium phosphate, sodium carbonate, sodium metasilicate or sodium orthosilicate is dissolved. Soak at a bath temperature of 20-70 ° C for 10-60 seconds. Alternatively, cathodic electrolytic degreasing may be performed at a cathode current density of ² to 5 A / dm ² using an insoluble anode such as stainless steel, a titanium platinum plate, and iridium oxide as the anode.

(4) Peeling treatment (first step (S01))
The stripping process is a process for completely stripping the reflow tin plating layer and the reaction layer from an arbitrary region of the plating material. For areas where peeling is not required, tape, sparger mask, resist, and masking are performed by various conventionally known methods such as an ink jet printing method, and peeling is performed only on the area where the silver plating layer is to be finally formed. Can be applied.

  As the method of peeling the reflow tin plating layer, various conventionally known peeling methods can be used as long as the effect of the present invention is not impaired. For example, a part to be peeled is immersed or electrolytically peeled with an appropriate peeling liquid. Can be used.

  Examples of the stripping solution used in the first step include a solution obtained by adding an oxidizing agent to a solution obtained by dissolving sulfuric acid, nitric acid, and sodium hydroxide. When an aqueous solution of sulfuric acid is used, it is more preferable to use an aqueous solution of nitric acid because S (sulfur) of sulfuric acid remains after peeling and may react with silver plating to cause discoloration or deterioration. In this step, since the reflow tin plating layer and the reaction layer are completely peeled off, the outermost surface of the peeled area is the metal substrate itself.

  Note that it is preferable to perform acid cleaning after the release treatment. For acid cleaning, a general acid cleaning solution in which an acid such as sulfuric acid or nitric acid is diluted to 3 to 50% can be used.

(5) Strike plating process (S02 ')
The strike plating process is a process performed to improve the adhesion between the metal base material and the silver plating layer. At least a part of the region where the reflow tin plating layer and the reaction layer are completely peeled off has a silver strike. One or more strike plating processes selected from the group of plating, copper strike plating, gold strike plating, and nickel strike plating are performed.

(A) Silver strike plating As the silver strike plating bath, for example, a bath containing a silver salt such as silver cyanide and silver potassium cyanide and a conductive salt such as potassium cyanide and potassium chloride can be used.

  In the silver strike plating treatment, various conventionally known silver plating techniques can be used as long as the effects of the present invention are not impaired, but the silver salt concentration in the plating bath is reduced as compared with ordinary silver plating. It is preferable to increase the concentration of the conductive salt.

  The silver strike plating bath that can be suitably used in the silver strike plating treatment is composed of a silver salt, an alkali cyanide salt, and a conductive salt, and may contain a brightener as needed. The preferred amounts of the respective components are: silver salt: 1 to 10 g / L, alkali cyanide: 80 to 200 g / L, conductive salt: 0 to 100 g / L, and brightener: to 1000 ppm.

  Examples of the silver salt include silver cyanide, silver iodide, silver oxide, silver sulfate, silver nitrate, and silver chloride.Examples of the conductive salt include potassium cyanide, sodium cyanide, potassium pyrophosphate, and potassium iodide. And sodium thiosulfate.

  As the brightener, a metallic brightener and / or an organic brightener can be used. Examples of the metallic brightener include antimony (Sb), selenium (Se), tellurium (Te), and the like, and examples of the organic brightener include aromatic sulfonic acid compounds such as benzenesulfonic acid and mercaptans. can do.

Silver strike plating conditions such as bath temperature, anode material, and current density of the silver strike plating bath can be appropriately set depending on the plating bath to be used, the required plating thickness, and the like. For example, as the anode material, it is preferable to use a soluble anode or an insoluble anode such as stainless steel, a titanium platinum plate, and iridium oxide. Suitable plating conditions include a bath temperature of 15 to 50 ° C., a current density of 0.5 to 5 A / dm ² , and a processing time of 5 to 60 seconds.

  The silver strike plating may be applied to the entire surface of the metal substrate, or may be applied only to a region where silver plating is to be formed in the second step (S02).

(B) Copper strike plating As the copper strike plating bath, either an acidic bath or an alkaline bath may be used.

  The acidic bath is composed of a copper salt and an acid, and may contain additives. As the copper salt, for example, copper sulfate, copper sulfamate and the like can be used. As the acid, for example, sulfuric acid, sulfamic acid and the like can be used. As the additive, for example, a sulfur compound (thiourea, disulfone salt, mercaptobenzothiazole, or the like), an organic compound (polyoxyethylene glycol ether, polyethylene glycol, or the like), a selenium compound, or the like can be used.

  The preferred amounts of the respective components of the acidic bath that can be suitably used for the copper strike plating treatment are copper salt: 60 to 200 g / L, acid: 30 to 200 g / L, and additives: 0 to 100 ppm.

  A cyanic bath can be used as the alkaline bath, and the cyanic bath is composed of a copper salt, an alkali cyanide salt, and a conductive salt, and an additive may be added. As the copper salt, for example, copper cyanide or the like can be used. As the alkali cyanide salt, for example, potassium cyanide, sodium cyanide and the like can be used. As the conductive salt, for example, potassium carbonate and sodium carbonate can be used. As the additive, for example, Rochelle salt, potassium selenite, sodium selenite, potassium thiocyanate, lead acetate, lead tartrate and the like can be used.

  Suitable amounts of each component of the cyanic bath that can be suitably used for the copper strike plating treatment are as follows: copper salt: 10 to 80 g / L, alkali cyanide: 20 to 50 g / L, and conductive salt: 10 to 10 g / L. 50 g / L, additive: 0 to 60 g / L.

The copper strike plating conditions such as the bath temperature, anode material, and current density of the copper strike plating bath can be appropriately set according to the plating bath to be used, the required plating thickness, and the like. For example, as the anode material, it is preferable to use a soluble anode such as electrolytic copper and / or an insoluble anode such as stainless steel, a titanium platinum plate, and iridium oxide. Examples of suitable plating conditions include a bath temperature of 25 to 70 ° C., a current density of 0.1 to 6.0 A / dm ² , and a processing time of 5 to 60 seconds.

  The copper strike plating may be applied to the entire surface of the metal substrate, or may be applied only to the region where silver plating is to be formed in the second step (S02).

(C) Gold strike plating As the gold strike plating bath, for example, a bath containing a gold salt, a conductive salt, a chelating agent and a crystal growth agent can be used. In addition, a brightener may be added to the gold strike plating bath.

  As the gold salt, for example, gold cyanide, potassium gold cyanide, potassium gold cyanide, sodium gold sulfite, sodium gold thiosulfate and the like can be used. As the conductive salt, for example, potassium citrate, potassium phosphate, potassium pyrophosphate, potassium thiosulfate and the like can be used. As the chelating agent, for example, ethylenediaminetetraacetic acid, methylenephosphonic acid and the like can be used. As the crystal growth agent, for example, cobalt, nickel, thallium, silver, palladium, tin, zinc, copper, bismuth, indium, arsenic, cadmium and the like can be used. In addition, you may add polyphosphoric acid, citric acid, tartaric acid, potassium hydroxide, hydrochloric acid, etc. as a pH adjuster, for example.

  Suitable amounts of each component of the gold strike plating bath that can be suitably used for the gold strike plating treatment are as follows: gold salt: 1 to 10 g / L, conductive salt: 0 to 200 g / L, chelating agent: 0 to 30 g. / L, crystal growth agent: 0 to 30 g / L.

The gold strike plating conditions such as the bath temperature, anode material, and current density of the gold strike plating bath can be appropriately set according to the plating bath to be used, the required plating thickness, and the like. For example, it is preferable to use an insoluble anode such as a titanium platinum plate and iridium oxide as the anode material. Examples of suitable plating conditions include a bath temperature of 20 to 40 ° C., a current density of 0.5 to 5.0 A / dm ² , a processing time of 5 to 60 seconds, and a pH of 0.5 to 7.0. can do.

  The gold strike plating may be applied to the entire surface of the metal substrate, or may be applied only to the region where silver plating is to be formed in the second step (S02).

(D) Nickel strike plating As the nickel strike plating bath, for example, a bath containing a nickel salt, an anode dissolution promoter and a pH buffer can be used. Further, an additive may be added to the nickel strike plating bath.

  As the nickel salt, for example, nickel sulfate, nickel sulfamate, nickel chloride and the like can be used. As the anode dissolution accelerator, for example, nickel chloride and hydrochloric acid can be used. As the pH buffer, for example, boric acid, nickel acetate, citric acid and the like can be used. Additives include, for example, primary brighteners (saccharin, benzene, naphthalene (di, tri), sodium sulfonate, sulfonamide, sulfinic acid, etc.), secondary brighteners (organic compounds: butynediol, coumarin, allylaldehyde) Sulfonic acid and the like, metal salts: cobalt, lead, zinc, etc.) and pit inhibitors (sodium lauryl sulfate, etc.) can be used.

  Suitable amounts of each component of the nickel strike plating bath that can be suitably used for the nickel strike plating treatment are: nickel salt: 200 to 600 g / L, anodic dissolution accelerator: 0 to 300 g / L, pH buffer: 0 to 50 g / L, additive: 0 to 20 g / L.

Nickel strike plating conditions such as a bath temperature, an anode material, and a current density of the nickel strike plating bath can be appropriately set according to a plating bath to be used, a required plating thickness, and the like. For example, it is preferable to use a soluble anode such as electrolytic nickel, carbonized nickel, deposited nickel, and sulfur nickel as the anode material. Examples of suitable plating conditions include a bath temperature of 20 to 70 ° C., a current density of 0.1 to 15.0 A / dm ² , a processing time of 5 to 60 seconds, and a pH of 0.5 to 4.5. can do.

  The nickel strike plating may be applied to the entire surface of the metal substrate, or may be applied only to the region where silver plating is to be formed in the second step (S02).

  Although only one type of the above strike plating may be applied or a plurality of strike platings may be laminated, it is preferable to apply only the silver strike plating. In addition, when the adhesion state of silver plating becomes good without the strike plating treatment depending on the surface state of the region where the reflow tin plating layer and the reaction layer are completely peeled off, the strike plating treatment can be omitted.

(6) Silver plating treatment (second step (S02))
The silver plating treatment is at least a part of the region where the reflow tin plating layer and the reaction layer are completely peeled off in the first step (S01), or at least the strike plating region in the strike plating treatment step (S02 ′). In part, this is a process to form a single, thicker silver plating layer.

  For the silver plating treatment, various conventionally known silver plating techniques can be used as long as the effects of the present invention are not impaired. However, compared to silver strike plating, the concentration of silver salt in the plating bath is increased, and the conductivity is increased. It is preferred to lower the salt concentration.

  The silver plating bath that can be suitably used for the silver plating treatment is composed of a silver salt, an alkali cyanide salt, and a conductive salt, and an additive may be added as necessary. Suitable amounts of the respective components are: silver salt: 40 to 150 g / L, alkali cyanide: 20 to 200 g / L, conductive salt: 10 to 300 g / L, and additive: 0 to 10 g / L.

  As the silver salt, for example, silver cyanide, potassium silver cyanide, silver iodide, silver oxide, silver sulfate, silver nitrate, silver chloride and the like can be used. As the alkali cyanide salt, for example, potassium cyanide, sodium cyanide and the like can be used. As the conductive salt, for example, potassium cyanide, sodium cyanide, potassium pyrophosphate, potassium iodide, sodium thiosulfate and the like can be used.

  As the additives, for example, metal additives (antimony, selenium, tellurium, etc.) and organic additives (benzenesulfonic acid, mercaptans, ethylenediaminetetraacetic acid, etc.) can be used.

Plating conditions such as bath temperature, anode material, and current density of the plating bath can be appropriately set according to the plating bath to be used, the required plating thickness, and the like. For example, as the anode material, it is preferable to use an insoluble anode such as silver, stainless steel, a titanium platinum plate, and iridium oxide. Suitable plating conditions include a bath temperature of 15 to 70 ° C., a current density of 0.5 to 20.0 A / dm ² , a processing time of 0.5 to 10000 seconds, and a pH of 7.0 to 10.0. Can be exemplified.

  The silver plating may be applied to the entire surface of the metal substrate and the tin plating layer. The silver plating may be applied to the entire area of the reflow tin plating layer and the reaction layer in the first step (S01), or the strike plating step (S02). ') May be applied only to the region where the strike plating is formed.

≪Plating material≫
FIG. 2 is a schematic sectional view of an example of the embodiment of the silver-plated member of the present invention. In the plating material 1, a reflow tin plating layer 4 and a silver plating layer 6 are formed on a surface of a metal substrate 2. A reaction layer 8 is formed at the interface between the reflow tin plating layer 4 and the metal substrate 2.

  The reaction layer 8 is formed by atomic diffusion and reaction between the metal base material 2 and the tin plating layer in the step of forming the reflow tin plating layer 4 by performing a reflow treatment on the tin plating layer. Since the silver plating layer 6 is formed in a region where the reflow tin plating layer 4 and the reaction layer 8 are completely peeled off, the reflow tin plating layer 4 and the reaction layer 8 are provided between the silver plating layer 6 and the metal substrate 2. 8 does not exist.

  The metal of the metal substrate 2 is not particularly limited as long as it has electrical conductivity, and examples thereof include aluminum and aluminum alloys, iron and iron alloys, titanium and titanium alloys, stainless steel, copper and copper alloys, and the like. However, among them, it is preferable to use copper and a copper alloy because they are excellent in electrical conductivity, thermal conductivity, and spreadability.

  When the adhesion between the silver plating layer 6 and the metal substrate 2 is not sufficient, a strike plating layer 10 is formed between the silver plating layer 6 and the metal substrate 2, but the strike plating layer 10 is a continuous film. The film may have a discontinuous film shape such as a granular or island shape as long as the effects of the present invention are not impaired. In the latter case, the granular and island-shaped portions may be partially continuous. In some cases, it is difficult to identify the strike plating layer 10 depending on the strike plating conditions. The thickness of strike plating layer 10 is preferably 0.01 to 0.5 μm.

  Silver plating layer 6 is formed on the surface of strike plating layer 10. The thickness of the silver plating layer 6 is preferably 0.1 μm to 50 μm, and the Vickers hardness is preferably 10 HV to 250 HV. When the thickness is less than 0.1 μm, the wear resistance of the silver plating layer 6 cannot be utilized, and when the thickness is more than 50 μm, the amount of silver used increases, which is not economical.

≪Connection terminal≫
The silver plated member of the present invention can be suitably used for various connection terminals. Specifically, the outermost surface of the fitting portion where abrasion resistance is required is the reflow tin plating layer 4 and the outermost surface of the contact portion where the conductivity is required is the silver plating layer 6. A high-performance connection terminal can be manufactured. The term “fitting portion” as used herein refers to a portion that is connected to another member by, for example, bending or caulking another member.

  FIG. 3 is a schematic view showing an example of the connection terminal of the present invention. Although the connection terminal 20 shown in FIG. 3 is a high-voltage terminal, the outermost surface of the contact portion 22 where electrical conductivity is required in the connection terminal 20 is the silver plating layer 6 and is required to have wear resistance. The outermost surface of the connection portion 24 with the harness is the reflow tin plating layer 4.

  Conventionally, reflow tin plating excellent in bearing properties and workability has been often used for connection terminals, but has problems such as poor wear resistance and high electric resistance. On the other hand, when the outermost surface is the silver plating layer 6, the excellent wear resistance, low electric resistance, and good heat resistance of the silver plating layer 6 can be used.

In the plating material 1, since the reflow tin plating layer 4 does not exist between the silver plating layer 6 and the metal base material 2, an intermetallic compound (eg, Ag ₃ Sn) accompanying the diffusion and reaction between tin and silver is formed. Embrittlement of the reflow tin plating layer 4 and / or the silver plating layer 6 due to the formation can be suppressed very effectively.

  Furthermore, by setting the outermost surface of the region where the sliding wear is remarkable to be the silver plating layer 6, serious accidents such as ignition and electric shock caused by fragments of the reflow tin plating layer 4 scattered due to the sliding wear can be prevented. can do.

  As described above, the representative embodiments of the present invention have been described, but the present invention is not limited thereto, and various design changes are possible, and all of these design changes are included in the technical scope of the present invention. It is.

<< Example 1 >>
A 0.1 μm silver plating layer was formed on a commercially available reflow tin-plated material (a copper alloy material having a thickness of 0.6 mm, which was subjected to tin plating and subjected to a reflow treatment (pre-process)) in the following steps. The surface of the tin plating layer was subjected to a cleaning treatment by immersing the tin plating material in a cleaning treatment solution at 50 ° C. containing 40 g / L of Mac Screen NG-30 manufactured by Kizai Co., Ltd. for 60 seconds.

  Next, the tin-plated material after the above-mentioned cleaning treatment was immersed for 360 seconds in a stripping solution at 25 ° C containing 450 ml / L and 100 ml / L of Ebastrip ST-40A and ST-401NC manufactured by JCU Corporation, respectively. A peeling treatment (first step) was performed. Note that masking is performed by attaching a masking tape (insulating tape) to a region where peeling is not required.

Next, using a silver plating bath containing 40 g / L of silver cyanide, 30 g / L of potassium cyanide, and 30 g / L of potassium carbonate, the anode material was used as a titanium platinum plate, and the cathode material was used as a tin plating material after peeling treatment. A treatment was performed for 3 seconds under the conditions of a bath temperature of 30 ° C. and a current density of 4 A / dm ² to form a single silver plating layer of 0.1 μm (second step).

[Evaluation]
(1) Evaluation of Adhesion Adhesion was evaluated for the plated material prepared as described above. A cellophane tape (# 405, made by Nichiban Co., Ltd.) is pressed against the silver plating layer by finger pressure, and when the silver plating layer does not peel or swell after peeling off the cellophane tape, x; Table 1 shows the obtained results.

(2) to confirm whether an intermetallic compound (Ag ₃ Sn) phase confirmed the above manner intermetallic compounds for plating material produced by (Ag ₃ Sn) phase is formed. Specifically, the presence or absence of a diffraction peak derived from the intermetallic compound (Ag ₃ Sn) phase was confirmed by the X-ray diffraction result of the plated material left at room temperature for 50 hours. The device used was Rigaku's Ultima IV (detector D / teX Ultra, using CuKα radiation), which was measured under the conditions of 40 kV-40 mA, step angle 0.1 °, scan angle range 20 ° -100 °. . When a diffraction peak derived from the intermetallic compound (Ag ₃ Sn) phase was confirmed, the result was ×, and when it was not confirmed, the result was ○. The obtained results are shown in Table 1.

<< Example 2 >>
Except that the silver plating time was set to 26 seconds and a silver plating layer having a thickness of 1 μm was formed, plating materials were prepared in the same manner as in Example 1, and various evaluations were made. Table 1 shows the obtained results.

Example 3
Except that the silver plating time was set to 130 seconds and a silver plating layer having a thickness of 5 μm was formed, plating materials were prepared in the same manner as in Example 1, and various evaluations were performed. Table 1 shows the obtained results.

Example 4
Plating materials were prepared and various evaluations were performed in the same manner as in Example 1, except that the silver plating time was 260 seconds and a silver plating layer having a thickness of 10 μm was formed. Table 1 shows the obtained results.

Example 5
After performing the peeling treatment of Example 1, using a silver strike plating bath containing 3 g / L of silver cyanide, 150 g / L of potassium cyanide, and 15 g / L of potassium carbonate, using a titanium platinum plate as an anode material and a cathode material Was subjected to silver strike plating for 10 seconds under conditions of bath temperature: room temperature and current density: 2 A / dm ² (strike plating step). Thereafter, the silver plating process was performed for 130 seconds, a silver plating layer having a thickness of 5 μm was formed, and various evaluations were performed. Table 1 shows the obtained results.

Example 6
After performing the peeling treatment of Example 1, using a copper strike plating bath containing 10 g / L of copper cyanide, 30 g / L of potassium cyanide, and 15 g / L of potassium carbonate, using a titanium platinum plate as an anode material and a cathode material Was subjected to a copper strike plating treatment for 10 seconds under the conditions of a bath temperature: room temperature and a current density: 2 A / dm ² (strike plating treatment step). Thereafter, under the same conditions as in Example 1, the silver plating time was 130 seconds, a silver plating layer having a thickness of 5 μm was formed, and various evaluations were made. Table 1 shows the obtained results.

Example 7
After being subjected to the release treatment of Example 1, gold strike plating containing 5 g / L potassium gold (I) cyanide, 150 g / L potassium citrate, 2 g / L cobalt sulfate, and 5 g / L EDTA-2K Using a bath, a gold strike plating treatment was performed for 10 seconds under the conditions of a bath temperature: room temperature and a current density: 2 A / dm ² using a titanium platinum plate as an anode material and a tin-plated material after peeling treatment as a cathode material (strike). Plating process). Thereafter, under the same conditions as in Example 1, the silver plating time was 130 seconds, a silver plating layer having a thickness of 5 μm was formed, and various evaluations were made. Table 1 shows the obtained results.

Example 8
After performing the peeling treatment of Example 1, a nickel strike plating bath containing 200 g / L nickel sulfate hexahydrate, 50 g / L nickel chloride hexahydrate, and 30 g / L boric acid was used. A nickel strike plating treatment was performed for 10 seconds at a bath temperature of room temperature and a current density of 2 A / dm ² , using an anode material as an electrolytic nickel plate and a cathode material as a tin plating material after peeling treatment (strike plating treatment step). ). Thereafter, under the same conditions as in Example 1, the silver plating time was 130 seconds, a silver plating layer having a thickness of 5 μm was formed, and various evaluations were made. Table 1 shows the obtained results.

<< Comparative Example 1 >>
A plating material having a silver plating layer having a thickness of 0.1 μm was prepared on the reflow tin plating layer in the same manner as in Example 1 without performing a peeling treatment, and various evaluations were made. Table 1 shows the obtained results.

<< Comparative Example 2 >>
A plating material having a silver plating layer having a thickness of 10 μm was prepared on the reflow tin plating layer in the same manner as in Example 4 without performing the peeling treatment, and various evaluations were made. Table 1 shows the obtained results.

  From the results shown in Table 1, it can be seen that the silver plating layer and the metal base material were satisfactorily bonded to the examples of the present invention regardless of the thickness of the silver plating layer. On the other hand, when the release treatment is not performed, regardless of the thickness of the silver plating layer, the silver plating layer is peeled off by the adhesion evaluation, and the silver plating layer and the metal base material are not bonded well. Is confirmed (Comparative Examples 1 and 2).

In the examples of the present invention, no intermetallic compound (Ag ₃ Sn) phase was formed. On the other hand, when the reflow tin plating layer was not peeled off (Comparative Examples 1 and 2), an intermetallic compound (Ag ₃ Sn) phase was formed, and embrittlement of the silver plating layer was progressing.

1 ... plating material,
2 ... metal substrate,
4 ... reflow tin plating layer
6 ... Silver plating layer,
8 ... reaction layer,
10 ... strike plating layer,
20 connection terminal,
22 ... contact part,
24 connection part.

Claims (4)

A metal substrate having a reflow tin plating layer at least in part, from a metal substrate having a reaction layer at an interface between the reflow tin plating layer and the metal substrate, the reflow tin plating layer and the reaction layer A first step of completely peeling off at least a part,
Include, a second step of forming a silver plating layer and facilities silver plating on at least a portion of the completely peeled reflow tin-plated layer and the reaction layer region,
A method for producing a silver-plated member. As a preliminary treatment of the second step, at least a part of the region where the reflow tin plating layer and the reaction layer are completely peeled off, from a group of silver strike plating, copper strike plating, gold strike plating, and nickel strike plating. Applying one or more selected strike platings,
The method for producing a silver-plated member according to claim 1, wherein: The strike plating is silver strike plating;
The method for producing a silver-plated member according to claim 2 , wherein: The thickness of the silver plating layer is 0.1 μm to 50 μm,
Vickers hardness of the silver plating layer is 10 HV to 250 HV,
The method for producing a silver-plated member according to claim 1, wherein:

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