Materials for electrical contacts and electrical and electronic components

Abstract

By optimizing the crystal orientation of the crystal grains contained in the Ag-Sn-containing layer formed in layers on a substrate, this material for electrical contacts in electrical and electronic components is less prone to wear when used in electrical contacts, thereby extending their lifespan. The present invention also provides electrical and electronic components using this material. [Solution] The electrical contact material comprises a substrate made of a conductive material and a surface coating formed on at least a portion of the substrate, wherein the surface coating contains Ag and Sn and has an Ag-Sn containing specific crystal grains having a hexagonal close-packed (hcp) structure, and the Ag-Sn containing layer, when viewed in a cross-section including the thickness direction of the electrical contact material, is parallel to the normal direction of the surface of the substrate. <0001> The area ratio of directional crystal grains to the total area of ​​the specified crystal grains is 20% or less.

Description

[Technical Field]

[0001] This invention relates to materials for electrical contacts and electrical and electronic components. [Background technology]

[0002] For consumer and automotive electronic components, such as connector terminals that make up the electrical contacts of connectors, electrical contact materials are used. These materials consist of a conductive substrate mainly composed of copper (Cu), such as brass, phosphor bronze, or Corson alloy, with a nickel (Ni) or Cu underplating on the surface, and then a tin (Sn) or Sn alloy plating on top. For the conductive components of on / off switches and slide switches, conductive substrates include copper alloys such as brass, phosphor bronze, and Corson alloy, which mainly contain copper (Cu), as well as pure copper and stainless steel mainly composed of iron, chromium, and nickel. Electrical contact materials are used in which the surface of such conductive substrates is silver-plated.

[0003] In recent years, driven by the increasing efficiency, energy conservation, and extended lifespan of electrical and electronic equipment, electrical contact materials are required to withstand high currents and voltages, as well as possess high reliability. As a result, there is a growing demand for silver (Ag) or Ag alloy plating to replace Sn or Sn alloy plating, and even conventional silver plating materials are now required to be more reliable.

[0004] On the other hand, Ag plating is soft and resistant to oxidation, and it has good affinity with metals, making it prone to adhesion, which tends to increase wear.

[0005] In this regard, Patent Document 1 discloses a metal material for electronic components comprising, in this order, a lower layer composed of Ni on a substrate, and an upper layer containing at least one of a zeta (ζ) phase which is a SnAg alloy containing 11.8 to 22.9 at% Sn, and an epsilon (ε) phase which is Ag3Sn, and having low whiskering, low adhesive wear, and high durability. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2015-206094 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, in recent years, electronic devices have become smaller and have longer lifespans, and there is a growing demand for coatings that are less prone to wear as they make up electrical contacts. In this regard, the metal material for electronic components described in Patent Document 1, when intended for use in electrical contacts such as connectors and switches, does not take into account wear caused by the slight sliding of connectors or the repeated operation of switches, and there is room for improvement.

[0008] This invention has been made in view of the above circumstances, and aims to provide an electrical contact material that is less prone to wear when used in electrical contacts of electrical and electronic components, thereby extending the lifespan, by optimizing the crystal orientation of the crystal grains contained in the Ag-Sn-containing layer laminated on a substrate, and an electrical and electronic component using the same. [Means for solving the problem]

[0009] The inventors have determined that the crystal orientation of the crystal grains contained in the Ag-Sn-containing layer laminated on a substrate of an electrical contact material is parallel to the normal direction of the substrate surface. <0001> We discovered that by reducing the area ratio of directional crystal grains to 20% or less of the total area of ​​specific crystal grains having a hexagonal close-packed (hcp) structure, wear of electrical contact materials becomes less likely, and thus completed the present invention.

[0010] To achieve the above objective, the gist of the present invention is as follows. (1) An electrical contact material comprising a substrate made of a conductive material and a surface coating formed on at least a portion of the substrate, wherein the surface coating has an Ag-Sn containing layer containing Ag and Sn and specific crystal grains having a hexagonal close-packed (hcp) structure, and the Ag-Sn containing layer, when viewed in a cross-section including the thickness direction of the electrical contact material, is parallel to the normal direction of the surface of the substrate. <0001> An electrical contact material in which directional crystal grains account for 20% or less of the total area of ​​the specified crystal grains. (2) The electrical contact material according to (1) above, wherein the surface coating further comprises a Ni-containing layer containing Ni between the substrate and the Ag-Sn-containing layer. (3) The electrical contact material according to (2) above, wherein the surface coating further comprises a Cu-containing layer between the Ag-Sn-containing layer and the Ni-containing layer. (4) The electrical contact material according to any one of (1) to (3) above, wherein the surface coating further comprises an Ag-containing layer on the Ag-Sn-containing layer, the Ag-containing layer having a higher Ag content and thinner thickness than the Ag-Sn-containing layer. (5) An electrical electronic component having at least an electrical contact formed using an electrical contact material described in any one of the above items (1) to (4). [Effects of the Invention]

[0011] According to the present invention, by optimizing the crystal orientation of the crystal grains contained in the Ag-Sn-containing layer formed in layers on a substrate, it is possible to provide an electrical contact material that is less prone to wear when used in the electrical contacts of electrical and electronic components, thereby extending their lifespan, and electrical and electronic components using the same. [Modes for carrying out the invention]

[0012] Preferred embodiments of the electrical contact material and electrical / electronic component of the present invention will be described in detail below.

[0013] <Regarding materials for electrical contacts> The material for an electrical contact according to the present invention has a substrate made of a conductive material and a surface coating formed on at least a part of the substrate. The surface coating has an Ag-Sn-containing layer containing Ag and Sn and including specific crystal grains having a hexagonal close-packed (hcp) structure. In a cross-section including the thickness direction of the material for an electrical contact, the area ratio of crystal grains having a <0001> direction in a direction parallel to the normal direction of the surface of the substrate in the total area of the specific crystal grains is 20% or less.

[0014] In the material for an electrical contact of the present invention, regarding the crystal orientation of the crystal grains included in the Ag-Sn-containing layer laminated on the substrate, by making the area ratio of the crystal grains having a <0001> direction in a direction parallel to the normal direction of the surface of the substrate to be 20% or less with respect to the total area of the specific crystal grains having a hexagonal close-packed (hcp) structure, the ratio of the {0001} plane of the crystal grains that are easy to plastically deform exposed on the surface of the Ag-Sn-containing layer becomes small. Therefore, when the material for an electrical contact is used for an electrical contact of an electric and electronic component, wear of the material for an electrical contact is less likely to occur even due to micro-sliding of a connector or repeated operation of a switch. At this time, since the crystal orientation of the crystal grains included in the Ag-Sn-containing layer laminated on the substrate is optimized, it is possible to provide a material for an electrical contact that is less likely to wear when used for an electrical contact of an electric and electronic component, thereby achieving a long service life, and an electric and electronic component using the same.

[0015] [Regarding the substrate] The material for an electrical contact of the present invention has a substrate made of a conductive material, and a surface coating described later is formed on at least a part of the surface of this substrate.

[0016] Here, the substrate is mainly composed of a copper-based material of (pure) copper or a copper alloy. Among these, the copper alloy is not particularly limited, and examples include Cu-Sn-P-based, Cu-Zn-based, Cu-Ni-Si-based, Cu-Sn-Ni-based, Cu-Cr-Mg-based, Cu-Cr-Zn-Sn-based, Cu-Ni-Si-Zn-Sn-Mg-based, and the like.

[0017] The shape of the substrate is not particularly limited and may be appropriately selected according to the application. Preferably, it is a strip or a plate, and it can also be a rod or a wire.

[0018] The conductivity of the substrate is not particularly limited, but it is preferably 10% IACS or more, and more preferably 30% IACS or more. Thereby, the material for electrical contacts can have excellent conductivity as a whole. Here, the conductivity (IACS; International Annealed Copper Standard) can be obtained by measuring in a thermostatic bath controlled at 20 °C (±1 °C) using the four-terminal method.

[0019] [Regarding the surface coating] The material for electrical contacts has a surface coating formed on at least a part of the substrate. Here, examples of the surface coating include an Ag-Sn-containing layer, a Ni-containing layer, a Cu-containing layer, and an Ag-containing layer. The material for electrical contacts of the present invention has at least an Ag-Sn-containing layer as the surface coating.

[0020] (Ag-Sn-containing layer) Among these, the Ag-Sn-containing layer is a layer containing silver (Ag) and tin (Sn) and including specific crystal grains having a hexagonal close-packed (hcp) structure. Here, the specific crystal grains having a hexagonal close-packed structure are the crystal phase of the ζ (zeta) phase, and the {0001} basal plane slip is responsible for deformation as the main slip system. Since this slip system is less than the fcc structure typified by copper or silver, the anisotropy of plastic deformation is large. Therefore, when the <0001> direction orthogonal to the {0001} plane of the specific crystal grains becomes parallel to the normal of the surface of the substrate, the {0001} plane of the specific crystal grains becomes substantially parallel to the surface of the material for electrical contacts, so that wear is likely to occur in the Ag-Sn-containing layer due to micro-sliding or repeated operation.

[0021] Therefore, in order to reduce surface wear of the electrical contact material and improve wear resistance, when viewing the Ag-Sn-containing layer in a cross-section including the thickness direction of the electrical contact material, in a direction parallel to the normal direction of the substrate surface, <0001> The area ratio of directional crystal grains to the total area of ​​specific crystal grains having a hexagonal close-packed structure is 20% or less, preferably 15% or less.

[0022] From the viewpoint of obtaining even better conductivity, the thickness of the Ag-Sn-containing layer can be, for example, 0.2 μm or more, but from the viewpoint of further improving wear resistance, it is preferable to be 1.2 μm or more, and more preferably 2.0 μm or more. On the other hand, there is no particular upper limit to the thickness of the Ag-Sn-containing layer, but from the viewpoint of material cost for electrical contact materials, it is preferable to be 5.0 μm or less.

[0023] The Ag-Sn-containing layer contains silver (Ag) and tin (Sn) as its main components, but may also contain impurities such as copper (Cu) and nickel (Ni). In this invention, "containing M as the main component" (where M is one type of metallic element) means that the total content of metallic element M in the total metallic elements contained in each layer is 50 at% or more. Here, the Ag-Sn-containing layer may have an Ag content of 78 at% or more and a Sn content of 10 at% or more.

[0024] The crystal structure of the crystal grains contained in the Ag-Sn-containing layer can be obtained from crystal orientation analysis data calculated using analysis software (TSL Corporation, OIM Analysis) from crystal orientation data continuously measured using an EBSD detector attached to a high-resolution scanning electron microscope (JEOL Ltd., JSM-7001FA). "EBSD" stands for Electron Backscatter Diffraction, a crystal orientation analysis technique that utilizes backscattered electron Kikuchi line diffraction generated when an electron beam is irradiated onto a copper alloy plate sample within a scanning electron microscope (SEM). "OIM Analysis" is software for analyzing data measured by EBSD. Measurements can be performed on a cross-section of the electrical contact material, including the thickness direction, which has been finished using a cross-section polisher or similar device. The measurement area in the cross-section should be approximately 10 μm × 50 μm, and measurements can be performed with a step size of 0.02 μm. If the above field size cannot be obtained due to the sample size during cross-sectional measurement, the average value obtained by measuring in multiple fields may be used.

[0025] Here, using the crystal orientation data obtained by the EBSD method, measurement points with a reliability index CI value of 0.1 or higher are selected for analysis, and orientation analysis can be performed using the profile of a hexagonal close-packed crystal phase such as magnesium. In this case, the crystal orientation data to be analyzed is extracted only from crystal phases having a hexagonal close-packed structure, and within that, the orientation is determined in a direction parallel to the normal direction of the substrate surface. <0001> The area percentage occupied by directional crystal grains can be calculated.

[0026] (Ni-containing layer) The Ni-containing layer is a layer containing nickel (Ni), and is preferably located between the substrate and the Ag-Sn-containing layer in the surface coating. This Ni-containing layer serves as an underlayer for the Ag-Sn-containing layer, reducing the degradation of the electrical contact material's conductivity caused by the diffusion of copper (Cu) atoms contained in the substrate to adjacent layers such as the Ag-Sn-containing layer and the Cu-containing layer. It also reduces the increase in contact resistance when the electrical contact material is affected by heat, thereby improving the heat resistance of the electrical contact material.

[0027] This Ni-containing layer is composed of a nickel-based material, such as metallic nickel or a nickel alloy. The nickel alloy is not particularly limited, but examples include Ni-P and Ni-Fe alloys. Furthermore, at least a portion of the Ni-containing layer may form NiSn-based compounds at the interface with the Ag-Sn-containing layer between the Ni-containing layer and Sn atoms diffused during the process of forming the Ag-Sn-containing layer, and this layer made of NiSn-based compounds is also included in the Ni-containing layer.

[0028] The thickness of the Ni-containing layer is not particularly limited, but for example, it may be set at a lower limit of 0.1 μm. On the other hand, the upper limit of the thickness of the Ni-containing layer may be set at 2.0 μm from the viewpoint of moldability and cost.

[0029] Furthermore, the electrical contact material does not necessarily have to have a Ni-containing layer. If there is no Ni-containing layer, the Ag-Sn-containing layer is arranged adjacent to the substrate. In this case, the portion of the Ag-Sn-containing layer adjacent to the substrate may contain unreacted Ag that was formed during the alloying process.

[0030] (Cu-containing layer) The Cu-containing layer is a layer containing copper (Cu), and it is preferable that it be located between the Ag-Sn-containing layer and the Ni-containing layer in the surface coating. In this case, in the Ag-Sn-containing layer, there may be a layer made of NiSn-based compounds in the area adjacent to the Ni-containing layer, or unreacted Ag may remain when the Ag-Sn-containing layer is formed by alloying. In particular, the unreacted remaining Ag has a face-centered cubic (FCC) lattice structure with Ag as the main component, and because the adhesion force between it and the Ni-containing layer is weak, the area where these are adjacent can become the starting point for delamination. However, even in such cases, by having a Cu-containing layer between the Ag-Sn-containing layer and the Ni-containing layer, the constituent atoms diffuse with each other between the Ag-Sn-containing layer and the Ni-containing layer, thereby further improving the adhesion between the Ni-containing layer and the Ag-Sn-containing layer.

[0031] This Cu-containing layer is composed of a copper-based material, such as metallic copper or a copper alloy. The copper alloy is not particularly limited, but examples include Cu-P alloys. Furthermore, at least a portion of the Cu-containing layer may form a CuSn-based compound at the interface with the Ag-Sn-containing layer between the Cu-containing layer and Sn atoms diffused during the process of forming the Ag-Sn-containing layer, and this layer made of the CuSn-based compound is also included in the Cu-containing layer.

[0032] The thickness of the Cu-containing layer is not particularly limited, but for example, it may be set at a lower limit of 0.05 μm. On the other hand, the upper limit of the thickness of the Cu-containing layer may be set at 1.0 μm from the viewpoint of heat resistance and cost.

[0033] Furthermore, the electrical contact material does not necessarily have to have a Cu-containing layer. In this case, the Ag-Sn-containing layer is arranged adjacent to the substrate or the Ni-containing layer. Here, when the Ag-Sn-containing layer is arranged adjacent to the Ni-containing layer, unreacted Ag from the alloying process to form the Ag-Sn-containing layer may be present in the portion of the Ag-Sn-containing layer adjacent to the Ni-containing layer.

[0034] (Ag-containing layer) The Ag-containing layer is a layer located on top of the Ag-Sn-containing layer in the surface coating. Compared to the Ag-Sn-containing layer, it has a higher Ag content and is thinner. The Ag-containing layer is located on the outermost surface of the electrical contact material, and its higher Ag content allows for a shorter solder wetting time. The Ag-containing layer can be formed on the Ag-Sn-containing layer by wet methods such as strike plating or electroplating.

[0035] The thickness of the Ag-containing layer is not particularly limited, but from the viewpoint of shortening the solder wetting time, for example, it is preferable to set the lower limit to 0.05 μm. On the other hand, the upper limit of the Ag-containing layer thickness may be 0.5 μm from the viewpoint of making wear of the electrical contact material due to wear of the Ag-containing layer less likely, and from the viewpoint of cost.

[0036] Furthermore, the electrical contact material does not necessarily have to have an Ag-containing layer. In this case, if there is no Ag-containing layer, the Ag-Sn-containing layer constitutes a part of the surface of the electrical contact material.

[0037] <Applications of materials for electrical contacts> The electrical contact material configured as described above, when used in electrical contacts such as connectors and switches, is less prone to wear due to micro-sliding of connectors or repeated operation of switches, thereby contributing to a longer lifespan for electrical contacts. Furthermore, it is preferable to construct an electrical and electronic component having at least one electrical contact formed using such an electrical contact material. This extends the lifespan of the electrical contacts and thus contributes to a longer lifespan for the electrical and electronic component having at least one electrical contact.

[0038] <Method for manufacturing materials for electrical contacts> The method for manufacturing the electrical contact material described above is not particularly limited, but involves preparing a substrate with adjusted size and thickness in advance, performing a degreasing step and an activation step as pretreatment, performing a Ni-containing layer formation step and a Cu-containing layer formation step as needed, then performing an Ag-film formation step and a Sn-film formation step, and then forming an Ag-Sn-containing layer by performing a strain introduction step and an alloying treatment step on these films, and then performing an Ag-containing layer formation step as needed.

[0039] (i) Degreasing process The degreasing step and the activation step described later are preferable to perform from the viewpoint of improving the adhesion between the substrate and the surface coating. Of these, the degreasing process can be performed, for example, by cathode electrolytic degreasing. An example of the liquid composition and processing conditions used in cathode electrolytic degreasing is shown below. [Example of liquid composition and treatment conditions for electrolytic degreasing] Treatment solution: 60 g / L sodium hydroxide aqueous solution Processing temperature: 60℃ Cathode current density: 2.5A / dm 2 Processing time: 30 seconds

[0040] (ii) Activation step An example of the liquid composition and processing conditions used in the activation process is shown below. [Example of liquid composition and processing conditions in the activation process] Treatment solution: 100 g / L sulfuric acid aqueous solution Processing temperature: 23℃ Immersion time: 30 seconds

[0041] (iii) Ni-containing layer formation step The Ni-containing layer formation process involves forming a Ni-containing layer on at least one of the two surfaces of the substrate by electroplating. This allows the Ni-containing layer to be formed by a cold process without requiring processing at high temperatures and pressures. An example of the liquid composition and processing conditions used in the Ni-containing layer formation process is shown below.

[0042] [An example of liquid composition and processing conditions in the Ni-containing layer formation process] Treatment solution: An aqueous solution containing 400 g / L nickel sulfamate, 30 g / L nickel(II) chloride, and 30 g / L boric acid. Processing temperature: 55℃ Current density: 10A / dm 2 Plating thickness: 0.1 μm to 2.0 μm Processing time: Time adjusted according to the plating thickness

[0043] (iv)Cu-containing layer formation process The Cu-containing layer formation process involves forming a Cu-containing layer on the surface of the Ni-containing layer by electroplating. In other words, the Cu-containing layer can also be formed by an electroplated layer. As a result, the Cu-containing layer, like the Ni-containing layer, can be formed by a cold process without requiring processing at high temperatures and pressures. An example of the liquid composition and processing conditions used in the Cu-containing layer formation process is shown below.

[0044] [An example of liquid composition and processing conditions in the Cu-containing layer formation process] Treatment solution: An aqueous solution containing 60 g / L of copper(I) cyanide, 70 g / L of sodium cyanide, and 5 g / L of free sodium cyanide. Processing temperature: 50℃ Current density: 1A / dm 2 Plating thickness: 0.05 μm to 1.0 μm Processing time: Time adjusted according to the plating thickness

[0045] (v)Ag film formation process The Ag coating formation process involves, if necessary, enhancing the adhesion of the Ag-containing layer to the surface of a substrate on which a Ni-containing layer and a Cu-containing layer have been formed by strike plating, and then forming the Ag coating by electroplating. An example of the liquid composition and processing conditions used in the Ag coating process is shown below.

[0046] [An example of the liquid composition and processing conditions of the strike plating solution in the Ag coating formation process] Treatment solution: An aqueous solution containing 4 g / L silver(I) cyanide and 80 g / L free potassium cyanide. Processing temperature: 30℃ Current density: 2A / dm 2 Processing time: 10 seconds

[0047] [An example of the solution composition and processing conditions of the electroplating solution used in the Ag coating formation process] Treatment solution: An aqueous solution containing 50 g / L silver(I) cyanide, 10 g / L potassium carbonate, and 90 g / L free potassium cyanide. Processing temperature: 30℃ Current density: 1A / dm 2 Plating thickness: 0.85 μm to 4.4 μm Processing time: Time adjusted according to the plating thickness

[0048] (vi) Sn film formation process The Sn coating formation step involves forming a Sn coating on the surface of a substrate on which Ni-containing layers and Cu-containing layers have been formed as needed. Here, the Ag coating and Sn coating can be formed in any order. That is, the Ag coating may be formed first and then the Sn coating, or the Sn coating may be formed first and then the Ag coating. In particular, from the viewpoint of forming a thick Ag-Sn-containing layer, the Ag coating formation step and the Sn coating formation step may be repeated.

[0049] It is preferable to laminate the Ag film and Sn film so that the ratio of the thickness of the Ag film to the thickness of the Sn film is in the range of 5:3 to 7:1. That is, it is preferable that the ratio of the thickness of the Sn film to the total thickness of the Ag film and Sn film be in the range of 0.125 to 0.375. By forming the Ag film and Sn film in such a ratio, it is possible to form specific crystal grains having a hexagonal close-packed (hcp) structure in the Ag-Sn containing layer. An example of the liquid composition and processing conditions used in the Sn coating process is shown below.

[0050] [An example of the composition of the plating solution and processing conditions in the Sn coating formation process] Treatment solution: An aqueous solution containing 40 g / L of tin(II) sulfate, 60 g / L of sulfuric acid, 40 g / L of cresol sulfonic acid, and 2 g / L of gelatin. Processing temperature: 23℃ Current density: 2A / dm 2 Plating thickness: 0.15 μm to 1.6 μm Processing time: Time adjusted according to the plating thickness

[0051] (vii) Process of introducing strain into the surface coating The strain introduction process for the surface coating involves applying strain to the Ag and Sn coatings formed by the Ag coating formation process and the Sn coating formation process, respectively, through compression processing such as rolling. By performing the strain introduction process, the crystal orientation of the Ag-Sn-containing layer can be controlled.

[0052] The processing rate in this strain introduction process is preferably in the range of 2% to 5%. By performing compression processing with a processing rate within this range as the strain introduction process, when the alloying process described later is performed, the material will contain specific crystal grains having a hexagonal close-packed (hcp) structure, and the entirety of the specific crystal grains will be in a direction parallel to the normal direction of the substrate surface. <0001> It is possible to form an Ag-Sn-containing layer in which the area proportion of directional crystal grains is small. In particular, the direction parallel to the normal direction of the substrate surface occupies a portion of the total area of ​​specific crystal grains. <0001> From the viewpoint of forming an Ag-Sn-containing layer in which the area ratio of directional crystal grains is even smaller, it is more preferable that the processing rate in the strain introduction process be 3% or more. On the other hand, if the processing rate in the strain introduction process is too large, non-uniform deformation occurs inside the surface film, so it is preferable that the processing rate in the strain introduction process be 5% or less.

[0053] (viii) Alloying process After the strain introduction process, the Ag and Sn coatings are subjected to an alloying process involving heat treatment to form an Ag-Sn containing layer. Unreacted Ag may remain in the Ag-Sn containing layer during this process.

[0054] The heating temperature for the heat treatment in the alloying process is preferably in the temperature range of 300°C to 500°C. By heat-treating the Ag and Sn coatings after the strain introduction process within this temperature range, specific crystal grains having a hexagonal close-packed (hcp) structure are produced, and the entirety of the specific crystal grains is in a direction parallel to the normal direction of the substrate surface. <0001> It is possible to form an Ag-Sn-containing layer in which the area ratio of directional crystal grains is small.

[0055] The heating time for the heat treatment in the alloying process is not particularly limited, but is preferably in the range of 30 seconds to 600 seconds. In the heat treatment of the alloying process, it is preferable to vary the heating time within the above range depending on the heating temperature.

[0056] The heat treatment in the alloying process is preferably carried out in a non-oxidizing atmosphere, and more specifically, in an inert gas atmosphere or a reducing gas atmosphere. Here, as the inert gas, in addition to N2, Ar, He, a mixture of two or more of these can be used. As the reducing gas, in addition to H2, CO, CH4, a mixture of two or more of these, such as a mixture of H2 and CO, can be used. By performing heat treatment in an inert gas atmosphere or a reducing gas atmosphere, oxidation of the substrate and the metals constituting each layer of the electrical contact material can be prevented.

[0057] (ix)Ag-containing layer formation process The Ag-containing layer formation process involves first improving the adhesion of the Ag-containing layer to the surface of the Ag-Sn-containing layer formed by the alloying process using strike plating, and then forming the Ag-containing layer by electroplating. An example of the liquid composition and processing conditions used in the Ag-containing layer formation process is shown below.

[0058] [An example of the liquid composition and processing conditions of the strike plating solution in the Ag-containing layer formation process] Treatment solution: An aqueous solution containing 4 g / L silver(I) cyanide and 80 g / L free potassium cyanide. Processing temperature: 30℃ Current density: 2A / dm 2 Processing time: 10 seconds

[0059] [An example of the solution composition and processing conditions of the electroplating solution used in the Ag-containing layer formation process] Treatment solution: An aqueous solution containing 50 g / L silver(I) cyanide, 10 g / L potassium carbonate, and 90 g / L free potassium cyanide. Processing temperature: 30℃ Current density: 1A / dm 2 Plating thickness: 0.05 μm to 4.4 μm Processing time: Time adjusted according to the plating thickness

[0060] In this way, it is possible to form a material for an electrical contact that includes specific crystal grains having a hexagonal close-packed (hcp) structure and has an Ag-Sn-containing layer in which the area ratio of crystal grains having a <0001> direction in a direction parallel to the normal direction of the surface of the substrate, which occupies the entire specific crystal grains, is small.

Examples

[0061] Next, in order to more clearly clarify the effects of the present invention, examples and comparative examples will be described, but the present invention is not limited to these examples.

[0062] [Examples 1 to 9, Comparative Examples 1 to 3] An H material of C5210, which is a Cu-Sn-P-based copper alloy with a thickness of 0.15 mm, was prepared as a substrate and formed into a plate shape with a length of 20 cm and a width of 10 cm by pressing. This substrate was subjected to cathodic degreasing and activation treatment as pretreatment.

[0063] Here, for cathodic degreasing, an aqueous sodium hydroxide solution with a concentration of 60 g / L was put into an electrolytic cell as a degreasing solution and heated, and the substrate was immersed in the heated degreasing solution at 60 °C and connected to the anode of the electrolytic cell, and electrolysis was performed by applying a current density of 2.5 A / dm 2 for 30 seconds.

[0064] Also, the activation treatment was performed by immersing the substrate after cathodic degreasing in a 100 g / L sulfuric acid aqueous solution at 23 °C for 30 seconds.

[0065] Thereafter, for Examples 2 to 7, 9, and Comparative Examples 1 and 2 of the present invention, a Ni-containing layer was formed on the surface of the conductive substrate by electroplating under the conditions shown below. On the other hand, for Examples 1 and 8 and Comparative Example 3 of the present invention, a Ni-containing layer was not formed on the substrate.

[0066] Here, when forming the Ni-containing layer by electroplating, an aqueous solution was prepared containing 400 g / L of nickel sulfamate (Ni(SO3NH2)2, formula weight: 250.93 g / mol), 30 g / L of nickel(II) chloride (NiCl2, formula weight: 129.59 g / mol), and 30 g / L of boric acid, with a nickel (Ni) metal (atomic weight: 58.69) concentration of approximately 107 g / L. Next, a substrate serving as the cathode electrode was placed in the electroplating cell, and a pure Ni plate measuring 20 cm x 10 cm, serving as the anode electrode, was placed opposite the front surface of the cathode electrode. 2 L of the electroplating solution was added to the cell, and the electroplating was performed at a temperature of 55°C at 10 A / dm². 2 By applying current at the specified current density, a Ni-containing layer of the thickness shown in Table 1 was formed by electroplating.

[0067] Next, for Examples 3 to 9 of the present invention and Comparative Example 1, a Cu-containing layer was formed on the surface side of the substrate by electroplating under the conditions shown below. On the other hand, for Examples 1 and 2 of the present invention and Comparative Examples 2 and 3, no Cu-containing layer was formed on the substrate.

[0068] Here, when forming the Cu-containing layer by electroplating, an aqueous solution was prepared containing 60 g / L of copper(I) cyanide (CuCN, formula weight: 89.56 g / mol), 70 g / L of sodium cyanide, and 5 g / L of free sodium cyanide, with a copper (Cu) metal (atomic weight: 63.55) concentration of approximately 43 g / L. Next, a substrate serving as the cathode electrode was placed in the electroplating cell, and a phosphorus-deoxidized copper plate measuring 20 cm x 10 cm, serving as the anode electrode, was placed opposite the front surface of the cathode electrode. 2 L of the electroplating solution was added to the cell, and the electroplating was performed at a temperature of 50°C at 1 A / dm². 2 By applying current at the specified current density, a Cu-containing layer of the thickness shown in Table 1 was formed by electroplating.

[0069] Next, an Ag coating was formed on the surface side of the substrate by strike plating and electroplating under the conditions shown below.

[0070] Here, when performing strike plating, an aqueous solution was prepared containing 4 g / L of silver(I) cyanide (AgCN, formula weight: 133.89 g / mol) and 80 g / L of free potassium cyanide, with a silver (Ag) metal (atomic weight: 107.87) concentration of approximately 3 g / L as the strike plating solution. Next, a substrate serving as the cathode electrode was placed in the plating electrolytic cell, and an insoluble plate measuring 20 cm x 10 cm, serving as the anode electrode, was placed opposite the front surface of the cathode electrode. 2 L of the strike plating solution was added to the cell, and the plating was performed at a temperature of 30°C at 2 A / dm². 2 Strike plating was performed by applying current at this current density for 10 seconds.

[0071] After strike plating, an Ag film was formed by electroplating. The electroplating solution prepared contained 50 g / L of silver(I) cyanide (AgCN, formula weight: 133.89 g / mol), 10 g / L of potassium carbonate, and 90 g / L of free potassium cyanide, resulting in an aqueous solution with a silver (Ag) metal concentration (atomic weight: 107.87) of approximately 40 g / L. Next, a substrate serving as the cathode electrode was placed in the electroplating cell, and a 20 cm x 10 cm silver plate serving as the anode electrode was placed opposite the front side (strike-plated side) of the cathode electrode. 2 L of the electroplating solution was added to the cell, and the electroplating was performed at a temperature of 30°C at 1 A / dm². 2 By applying current at the specified current density, an Ag coating with the plating thickness shown in Table 1 was formed on the surface side of the substrate by electroplating.

[0072] Next, a Sn coating was formed on the surface side of the substrate by electroplating under the following conditions.

[0073] Here, when forming a Sn coating by electroplating, an aqueous solution containing tin(II) sulfate (SnSO4, formula weight: 214.77 g / mol) at 40 g / L, sulfuric acid at 60 g / L, cresol sulfonic acid at 40 g / L, and gelatin at 2 g / L was prepared as the electroplating solution, with a concentration of tin (Sn) metal (atomic weight: 118.71) of approximately 22 g / L. Next, a substrate serving as the cathode electrode was placed in the electroplating cell, and a tin plate measuring 20 cm x 10 cm serving as the anode electrode was placed opposite the front surface of the cathode electrode. 2 L of the electroplating solution was added to the cell, and the electroplating was performed at a temperature of 23°C at 2 A / dm². 2 By applying current at the specified current density, a Sn coating with the plating thickness shown in Table 1 was formed on the Ag coating by electroplating.

[0074] Subsequently, for Examples 1 to 9 and Comparative Example 3 of the present invention, a strain introduction process was performed on the formed Ag and Sn coatings by rolling to introduce strain into the surface coating. Here, the processing rate in the strain introduction process was the ratio shown in Table 1. On the other hand, for Comparative Examples 1 and 2, the strain introduction process was not performed.

[0075] After the strain introduction process, the Ag and Sn coatings were subjected to an alloying process using the heating temperatures and times listed in Table 1 to form an Ag-Sn containing layer.

[0076] Next, for Examples 4, 5, and 8 of the present invention, and Comparative Examples 2 and 3, an Ag-containing layer was formed on the substrate by strike plating and electroplating under the conditions shown below. On the other hand, for Examples 1 to 3, 6, 7, and 9 of the present invention, and Comparative Example 1, no Ag-containing layer was formed on the substrate.

[0077] Here, for strike plating, an aqueous solution was prepared containing 4 g / L of silver(I) cyanide (AgCN, formula weight: 133.89 g / mol) and 80 g / L of free potassium cyanide, with a silver (Ag) metal (atomic weight: 107.87) concentration of approximately 3 g / L. Next, a substrate serving as the cathode electrode was placed in the plating electrolytic cell, and an insoluble plate measuring 20 cm x 10 cm, serving as the anode electrode, was placed opposite the front surface of the cathode electrode. 2 L of strike plating solution was added to the cell, and the plating was carried out at a temperature of 30°C at 2 A / dm². 2 Strike plating was performed by applying current at this current density for 10 seconds.

[0078] After strike plating, an Ag film was formed by electroplating. The electroplating solution prepared contained 50 g / L of silver(I) cyanide (AgCN, formula weight: 133.89 g / mol), 10 g / L of potassium carbonate, and 90 g / L of free potassium cyanide, resulting in an aqueous solution with a silver (Ag) metal concentration (atomic weight: 107.87) of approximately 40 g / L. Next, a substrate serving as the cathode electrode was placed in the electroplating cell, and a 20 cm x 10 cm silver plate serving as the anode electrode was placed opposite the front side (strike-plated side) of the cathode electrode. 2 L of the electroplating solution was added to the cell, and the electroplating was performed at a temperature of 30°C at 1 A / dm². 2 By applying current at the specified current density, an Ag coating of the thickness shown in Table 1 was formed on the surface side of the substrate by electroplating.

[0079] [Various measurement and evaluation methods] The electrical contact materials obtained in the above-described examples and comparative examples were subjected to the following characteristic evaluations. The evaluation conditions for each characteristic are as follows.

[0080] (Measurement of the thickness of each layer constituting the surface coating) The thicknesses of the Ni-containing layer, Cu-containing layer, Ag-Sn-containing layer, and Ag-containing layer constituting the surface coating were measured by performing X-ray fluorescence analysis on the surface of each prepared sample in accordance with the X-ray fluorescence testing method of JIS H8501:1999. In addition, to confirm the thickness of each layer, the thickness was also measured by image analysis of the cross-section including the thickness direction. The image analysis method was performed in accordance with the scanning electron microscopy testing method of JIS H8501:1999.

[0081] (In the direction parallel to the normal direction of the substrate surface, within the entire specific crystal grain of the Ag-Sn-containing layer) <0001> (Measurement of the area ratio of grains with directionality) The crystal structure of the crystal grains contained in the Ag-Sn-containing layer was determined from crystal orientation analysis data calculated using analysis software (TSL Corporation, OIM Analysis) from crystal orientation data continuously measured using an EBSD detector attached to a high-resolution scanning analytical electron microscope (JEOL Ltd., JSM-7001FA). Measurements were performed on a cross-section of the electrical contact material, including the thickness direction, which had been finished using a cross-section polisher. The measurement area in the cross-section was approximately 10 μm × 50 μm, with a step size of 0.02 μm.

[0082] Here, using crystal orientation data obtained by the EBSD method, measurement points with a reliability index (CI) of 0.1 or higher were selected for analysis, and orientation analysis was performed using profiles of hexagonal close-packed crystal phases such as magnesium. In this case, only specific crystal phases with hexagonal close-packed structures were extracted as the crystal orientation data to be analyzed, and the total area of ​​the specific crystal phases was analyzed in a direction parallel to the normal direction of the substrate surface. <0001> The proportion of the area occupied by directional crystal grains (area ratio) was calculated. The results are shown in Table 1.

[0083] (Evaluation of wear resistance) The wear resistance of electrical contact materials was evaluated using a multi-functional tribology evaluation machine (friction and wear tester) UMT TriboLab (manufactured by Bruker). A sliding test was conducted by sliding a similar material against the surface of the obtained electrical contact material. The surface resistance value was measured before sliding the similar material against the surface of the electrical contact material and after sliding the similar material 2000 times. If the increase in resistance value before and after sliding the similar material against the surface of the electrical contact material was 3 mΩ or less, it was evaluated as "◎" indicating particularly excellent wear resistance of the electrical contact material. If the increase in resistance value before and after sliding the similar material against the surface of the electrical contact material was in the range of more than 3 mΩ and 5 mΩ or less, it was evaluated as "○" indicating good wear resistance of the electrical contact material. On the other hand, if the increase in resistance value before and after sliding the similar material against the surface of the electrical contact material was more than 5 mΩ, it was evaluated as "×" indicating poor wear resistance of the electrical contact material. The results are shown in Table 1.

[0084] (Evaluation of heat resistance) The obtained electrical contact material was heated at 155°C for 1 hour in an atmospheric environment. The contact resistance before and after heating was measured using an electrical contact simulator (manufactured by Yamazaki Seiki Kenkyusho Co., Ltd.). The load applied when bringing the contact area into contact with the electrical contact material was 1N. If the increase in contact resistance before and after heating was less than 5mΩ, it was evaluated as "○" because the change in electrical properties before and after heating was small and it was excellent in terms of high heat resistance. If the increase in contact resistance before and after heating was 5mΩ or more, it was evaluated as "△" because it was not necessarily excellent in terms of heat resistance. The results are shown in Table 2.

[0085] (Evaluation of surface coating adhesion) The obtained electrical contact materials were subjected to a tape peel test as specified in JIS H 8504 to evaluate whether or not the surface coating peeled off from the electrical contact material. More specifically, the surface coating of the electrical contact material was marked with a sharp blade to create a 2 mm square, reaching the conductive substrate, and then subjected to the tape peel test. If no peeling of the surface coating was observed, it was evaluated as having excellent adhesion of the surface coating, and was rated "○". If partial peeling of the surface coating was observed, it was evaluated as not necessarily having excellent adhesion of the surface coating, and was rated "△". The results are shown in Table 2.

[0086] (Evaluation of solder wettability) The obtained electrical contact materials were evaluated for solder wettability using the wetting balance method, as specified in JIS Z3198-4, Lead-Free Solder Test Method - Part 4: Wetting Balance Method and Contact Angle Method. The bath temperature was set to 245°C, and Sn-3Ag-0.1Cu solder was used in the bath. RMA type flux was also used. A measured zero-crossing time (time t0, when wetting begins) of 2 seconds or less was evaluated as "○" indicating excellent solder wettability. A measured zero-crossing time (t0, when wetting begins) exceeding 2 seconds was evaluated as "△" indicating that the solder wettability was not necessarily excellent. The results are shown in Table 2.

[0087] [Table 1]

[0088] [Table 2]

[0089] From the results in Table 1, the electrical contact materials of Examples 1 to 9 of the present invention have at least an Ag-Sn-containing layer formed on the surface of the substrate, and the Ag-Sn-containing layer contains specific crystal grains having a hexagonal close-packed (hcp) structure, and these specific crystal grains are distributed in a direction parallel to the normal direction of the substrate surface. <0001> The area ratio of directional crystal grains was within the appropriate range for the present invention. In this case, the electrical contact materials of Examples 1 to 9 of the present invention all received an evaluation result of "◎" or "〇" regarding wear resistance.

[0090] In contrast, the electrical contact materials of Comparative Examples 1 and 2, which did not undergo a strain introduction process, show that the proportion of specific crystal grains in the direction parallel to the normal direction of the substrate surface is greater than the proportion of the entire grain. <0001> The area ratio of directional crystal grains was greater than the appropriate range for the present invention, resulting in a wear resistance evaluation result of "×".

[0091] Furthermore, in Comparative Example 3, the electrical contact material in which the processing rate in the strain introduction process was 1%, the proportion of specific crystal grains in the direction parallel to the normal direction of the substrate surface was <0001> The area ratio of directional crystal grains was greater than the appropriate range for the present invention, resulting in a wear resistance evaluation result of "×".

[0092] Therefore, in the electrical contact materials of Examples 1 to 9 of the present invention, in the Ag-Sn-containing layer, the specific crystal grains having a hexagonal close-packed (hcp) structure are distributed in a direction parallel to the normal direction of the substrate surface. <0001> The area ratio of directional crystal grains has been optimized, which has resulted in reduced wear when used in electrical contacts of electrical and electronic components.

Claims

1. An electrical contact material comprising a substrate made of a conductive material and a surface coating formed on at least a portion of the substrate, The surface coating has an Ag-Sn containing layer which includes specific crystal grains containing Ag and Sn and having a hexagonal close-packed (hcp) structure. The Ag-Sn-containing layer is an electrical contact material in which, when viewed in a cross-section including the thickness direction of the electrical contact material, the area ratio of crystal grains having a <0001> direction parallel to the normal direction of the surface of the substrate to the total area of ​​the specific crystal grains is 20% or less.

2. The electrical contact material according to claim 1, wherein the surface coating further comprises a Ni-containing layer between the substrate and the Ag-Sn-containing layer.

3. The electrical contact material according to claim 2, wherein the surface coating further comprises a Cu-containing layer between the Ag-Sn-containing layer and the Ni-containing layer.

4. The electrical contact material according to claim 1, wherein the surface coating further comprises an Ag-containing layer on the Ag-Sn-containing layer, the Ag-containing layer having a higher Ag content and thinner thickness compared to the Ag-Sn-containing layer.

5. An electrical electronic component having at least an electrical contact formed using the electrical contact material described in any one of claims 1 to 4.

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