Materials for electrical contacts and electrical and electronic components

Abstract

By optimizing the grain size of the crystal grains contained in the Ag-Sn-containing layer formed in layers on a substrate, we provide an electrical contact material that has high bending properties when used in the electrical contacts of electrical and electronic components, and 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 comprises a Ni-containing layer containing Ni and an Ag-Sn-containing layer on the Ni-containing layer, the Ag-Sn-containing layer containing Ag and Sn and specific crystal grains having a hexagonal close-packed (hcp) structure, and the specific crystal grains have an average crystal grain size of 1.0 μm or more.

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 project] [Problems that the invention aims to solve]

[0007] However, in recent years, electronic devices have become smaller, and when considering the coatings that make up electrical contacts, such as those used in connectors and switches, the materials for electronic contacts are formed by minute bending processes, thus requiring materials for electronic contacts with excellent processability. Therefore, when electronic contact materials are used in electrical contacts, there is a need for materials that have high bending characteristics, especially when bending forces are applied to them. In this regard, the metal material for electronic components described in Patent Document 1 did not focus on the bending characteristics when bending forces are applied, and there was room for improvement.

[0008] This invention has been made in view of the above circumstances, and aims to provide an electrical contact material that has high bending characteristics when used in the electrical contacts of electrical and electronic components, and electrical and electronic components using the same, by optimizing the grain size of the crystal grains contained in the Ag-Sn-containing layer laminated on a substrate. [Means for solving the problem]

[0009] The inventors of the present invention have discovered that the bending properties of an electrical contact material can be improved by setting the average grain size of specific crystal grains having a hexagonal close-packed (hcp) structure to 1.0 μm or more, in an Ag-Sn-containing layer laminated on a substrate of an electrical contact material, and have 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 comprises a Ni-containing layer containing Ni and an Ag-Sn-containing layer on the Ni-containing layer, comprising specific crystal grains containing Ag and Sn and having a hexagonal close-packed (hcp) structure, and the specific crystal grains having an average crystal grain size of 1.0 μm or more. (2) The Ag-Sn containing layer, when viewed in a cross-section including the thickness direction of the electrical contact material, is parallel to the direction normal to the surface of the substrate. <0001> The electrical contact material according to (1) above, wherein the area ratio of directional crystal grains to the total area of ​​the specified crystal grains is 20% or less. (3) The electrical contact material according to (2) above, wherein the surface coating further comprises a Cu-containing layer between the Ni-containing layer and the Ag-Sn-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 grain size 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 has high bending characteristics when used in the electrical contacts of electrical and electronic components, 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 is a material for an electrical contact having a substrate made of a conductive material and a surface film formed on at least a part of the substrate. The surface film has a Ni-containing layer containing Ni, and an Ag-Sn-containing layer containing Ag and Sn and including specific crystal grains having a hexagonal close-packed (hcp) structure on the Ni-containing layer. The average crystal grain size of the specific crystal grains is 1.0 μm or more.

[0014] In the material for an electrical contact of the present invention, regarding the grain size of the crystal grains contained in the Ag-Sn-containing layer laminated on the substrate, by making the average crystal grain size of the specific crystal grains having a hexagonal close-packed (hcp) structure 1.0 μm or more, the grain boundaries contained in the material for an electrical contact are reduced, and even when the material for an electrical contact is bent, breakage of the Ag-Sn-containing layer due to cracking at the grain boundaries is less likely to occur. Therefore, it is possible to provide a material for an electrical contact having high bending characteristics when used for an electrical contact of an electric and electronic component, 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 film 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-Sn-Zn-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, in order from the one closest to the substrate, a Ni-containing layer, a Cu-containing layer, an Ag-Sn-containing layer, and an Ag-containing layer. The material for electrical contacts of the present invention has at least a Ni-containing layer and an Ag-Sn-containing layer as the surface coating.

[0020] (Ni-containing layer) Among these, the Ni-containing layer is a layer containing nickel (Ni), and is provided between the substrate and the Ag-Sn-containing layer. This Ni-containing layer serves as an underlayer for the Ag-Sn-containing layer, and reduces the deterioration of the conductivity of the material for electrical contacts caused by the diffusion of copper (Cu) atoms contained in the substrate into adjacent layers such as the Ag-Sn-containing layer and the Cu-containing layer in an alloying treatment process or the like. At the same time, it can reduce the increase in contact resistance when the material for electrical contacts is affected by heat, and enhance the heat resistance of the material for electrical contacts during reflow or the like.

[0021] This Ni-containing layer is composed of a nickel-based material of metallic nickel or a nickel alloy. The nickel alloy is not particularly limited, and examples thereof include Ni-P-based, Ni-Fe-based, and the like. Also, at least a part of the Ni-containing layer may form a NiSn-based compound at the interface with the Ag-Sn-containing layer or the like with Sn atoms diffused during the formation of the Ag-Sn-containing layer, and the layer composed of this NiSn-based compound is also included in the Ni-containing layer.

[0022] The thickness of the Ni-containing layer is not particularly limited, but for example, it may be set to a minimum of 0.05 μm. In particular, from the viewpoint of further reducing the increase in contact resistance when the electrical contact material is affected by heat, it is preferable that the thickness of the Ni-containing layer be set to a minimum of 0.10 μm. On the other hand, from the viewpoint of moldability and cost, the upper limit of the thickness of the Ni-containing layer may be 2.0 μm.

[0023] (Ag-Sn containing layer) The Ag-Sn-containing layer is a layer containing specific crystal grains that contain silver (Ag) and tin (Sn) and have a hexagonal close-packed (hcp) structure, and is located on top of the Ni-containing layer.

[0024] The Ag-Sn-containing layer has a specific crystal grain size of 1.0 μm or larger, which is the average grain size of grains having a hexagonal close-packed (hcp) structure. Here, the specific crystal grains having a hexagonal close-packed structure are the zeta phase crystal phase, and {0001} basal slip is the main slip system responsible for deformation. However, it is generally known that hexagonal close-packed structures have inferior workability compared to face-centered cubic (FCC) structures represented by silver (Ag) and copper (Cu). In particular, if the crystal grain size of the alloyed Ag-Sn-containing layer is fine, there is a risk of cracking at the grain boundaries when the electrical contact material is bent. In contrast, by making the average grain size of the specific crystal grains having a hexagonal close-packed (hcp) structure contained in the Ag-Sn-containing layer 1.0 μm or larger, damage to the Ag-Sn-containing layer becomes less likely when the electrical contact material is bent, thereby improving the bending properties of the electrical contact material.

[0025] The average grain size of specific crystal grains with a hexagonal close-packed structure 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) on a cross-section including the thickness direction of the electrical contact material. "EBSD" stands for Electron Backscatter Diffraction, a crystal orientation analysis technique that utilizes backscattered electron Kikuchi line diffraction that occurs when an electron beam is irradiated onto a copper alloy plate sample in a scanning electron microscope (SEM). "OIM Analysis" is software for analyzing data measured by EBSD. Measurements can be performed on a cross-section including the thickness direction of the electrical contact material, which has been finished using a cross-section polisher or the like. The measurement area in the cross-section is approximately 10 μm × 50 μm, and measurements can be performed with a step size of 0.02 μm. If the above field of view size cannot be obtained due to the sample size during cross-sectional measurement, the average value obtained by measuring multiple fields of view may be used.

[0026] 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 specific crystal phases having a hexagonal close-packed structure, and the average grain size of specific crystal grains having a hexagonal close-packed structure can be determined by drawing line segments parallel to the surface of the Ag-Sn-containing layer and determining the average length of the line segments overlapping with the specific crystal grains, which are demarcated by both ends of the specific crystal grains, using a sectioning method.

[0027] The Ag-Sn-containing layer, when viewed in a cross-section including the thickness direction of the electrical contact material, is parallel to the direction normal to the surface of the substrate. <0001> It is preferable that the area ratio of directional crystal grains to the total area of ​​the specific crystal grain is 20% or less. In specific crystal grains having a hexagonal close-packed structure, {0001} basal plane slip is the main slip system responsible for deformation, but since this slip system is smaller than in face-centered cubic (FCC) structures represented by silver (Ag) and copper (Cu), the anisotropy of plastic deformation is large. Therefore, the {0001} plane of the specific crystal grain is perpendicular to the {0001} plane. <0001> When the direction is parallel to the normal to the substrate surface, the {0001} plane of a specific crystal grain becomes approximately parallel to the surface of the electrical contact material, making the Ag-Sn-containing layer more susceptible to wear due to micro-sliding or repeated operation. Therefore, from the viewpoint of reducing wear on the surface of the electrical contact material and improving wear resistance, the direction should be 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 preferably 20% or less, and more preferably 15% or less.

[0028] The thickness of the Ag-Sn-containing layer can be, for example, 0.2 μm or more from the viewpoint of obtaining even better conductivity, but from the viewpoint of making the surface of the electrical contact material less prone to wear and further improving wear resistance, it is preferable to have a thickness of 1.2 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 of the electrical contact material, it is preferable to have a thickness of 5.0 μm or less.

[0029] 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.

[0030] The crystal structure of the crystal grains contained in the Ag-Sn-containing layer can be analyzed using the crystal orientation data obtained by the EBSD method described above, specifically focusing on measurement points with a reliability index (CI) of 0.1 or higher, and using the profile of a hexagonal close-packed crystal phase such as magnesium. In this case, only crystal phases with a hexagonal close-packed structure are extracted as the crystal orientation data to be analyzed, and within that, the orientation is determined in a direction parallel to the normal direction of the substrate surface. <0001> The proportion of the area occupied by directional crystal grains can be calculated.

[0031] (Cu-containing layer) The Cu-containing layer is a layer containing copper (Cu), and it is preferable that it be located between the Ni-containing layer and the Ag-Sn-containing layer in the surface coating. In the Ag-Sn-containing layer, there may be a layer made of NiSn-based compounds 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 its adhesion to the Ni-containing layer is weak, so the areas where these are adjacent can become the starting point for delamination. However, even in such cases, by having a Cu-containing layer between the Ni-containing layer and the Ag-Sn-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.

[0032] 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-Zn 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.

[0033] 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.

[0034] 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.

[0035] (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.

[0036] 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.

[0037] 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.

[0038] <Applications of materials for electrical contacts> The electrical contact material configured as described above has high bending properties when used in electrical contacts, especially when bending force is applied to the electronic contact material. Therefore, when used in electrical contacts such as connectors and switches, it has excellent processability even when formed by minute bending processes, making it less likely for the coating constituting the electrical contact to be damaged, thereby contributing to the extended lifespan of the electrical contact. 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 contact, and thus contributes to the extended lifespan of the electrical and electronic component having at least one electrical contact.

[0039] <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, then performing a Ni-containing layer formation step and, if necessary, a Cu-containing layer formation step, followed by an Ag-film formation step and a Sn-film formation step, and then performing a strain introduction step and an alloying treatment step on these films to form an Ag-Sn-containing layer, followed by an Ag-containing layer formation step if necessary.

[0040] (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

[0041] (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

[0042] (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 high pressures. An example of the liquid composition and processing conditions used in the Ni-containing layer formation process is shown below.

[0043] [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: 0.05 μm to 2.0 μm Processing time: Time adjusted according to the plating thickness

[0044] (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.

[0045] [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

[0046] (v)Ag film formation process The Ag coating formation process involves, if necessary, enhancing the adhesion of the Ag coating to the substrate surface 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.

[0047] [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

[0048] [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: 0.50 μm to 4.4 μm Processing time: Time adjusted according to the plating thickness

[0049] (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.

[0050] 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.

[0051] [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

[0052] (vii) Process of introducing strain into the surface coating The strain introduction process for the surface coating is a process that can be performed as needed on the Ag coating and Sn coating formed by the Ag coating formation process and the Sn coating formation process, and involves applying strain to the plating layer by compression processing such as rolling. By performing the strain introduction process, the crystal orientation of the Ag-Sn containing layer can be controlled.

[0053] The processing rate in this strain introduction process is preferably 5% or less, and more preferably in the range of 2% to 5%. In particular, by setting the processing rate in the strain introduction process to 2% or more, the specific crystal grains contained in the Ag-Sn-containing layer are distributed in a direction parallel to the normal direction of the substrate surface. <0001> The area ratio of directional crystal grains can be reduced. On the other hand, if the processing rate in the strain introduction process is too high, non-uniform deformation may occur inside the surface coating, so it is preferable that the processing rate in the strain introduction process be 5% or less.

[0054] Furthermore, the strain introduction process into the surface coating is not required, and in this specification, the processing rate of the strain introduction process into the surface coating in this case may be set to 0% for convenience.

[0055] (viii) Alloying process After the strain introduction process is performed as needed, the Ag and Sn coatings are subjected to an alloying process involving heat treatment to form an Ag-Sn containing layer. At this time, unreacted Ag may remain in the Ag-Sn containing layer.

[0056] In the alloying process, the heating temperature for the heat treatment is preferably in the range of 250°C to 350°C. By heat-treating the Ag film and Sn film within this temperature range, the Ag film and Sn film are alloyed, and specific crystal grains having a hexagonal close-packed (hcp) structure grow, thereby forming an Ag-Sn containing layer with a large average crystal grain size for the specific crystal grains.

[0057] The heating time for the heat treatment in the alloying process is preferably in the range of 1 hour to 10 hours. By performing heat treatment at the above heating temperature for 1 hour or more in the alloying process, specific crystal grains having a hexagonal close-packed (hcp) structure grow, making it possible to make the average crystal grain size of the specific crystal grains 1 μm or more. On the other hand, if heat treatment is performed at the above heating temperature for more than 10 hours, there is a risk that the performance will be impaired because copper (Cu) atoms contained in the substrate will diffuse in large quantities to the surface layer of the electrical contact material. Therefore, it is preferable to set the heating time for the heat treatment at the above heating temperature to 10 hours or less.

[0058] Furthermore, in the heat treatment of the alloying process, it is preferable to vary the heating time within the above range according to the heating temperature.

[0059] 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.

[0060] (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.

[0061] [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: 2 A / dm 2 Treatment time: 10 seconds

[0062] [An example of the liquid composition and treatment conditions of the electroplating solution in the step of forming an Ag-containing layer] Treatment solution: An aqueous solution containing 50 g / L of silver(I) cyanide, 10 g / L of potassium carbonate, and 90 g / L of free potassium cyanide Treatment temperature: 30°C Current density: 1 A / dm 2 Plating thickness: 0.05 μm to 4.4 μm Treatment time: Time adjusted according to the plating thickness

[0063] In this way, it is possible to form a material for an electrical contact including an Ag-Sn-containing layer having specific crystal grains with a hexagonal close-packed (hcp) structure and having a large average crystal grain diameter of the specific crystal grains.

Examples

[0064] Next, in order to further clarify the effects of the present invention, the present invention examples and comparative examples will be described, but the present invention is not limited to these invention examples.

[0065] [Examples 1 to 10 of the present invention, 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 press working. This substrate was subjected to cathodic electrolytic degreasing and activation treatment as pre-treatment.

[0066] Here, for cathodic electrolytic 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, the substrate was immersed in the heated degreasing solution at 60°C and connected to the anode of the electrolytic cell, and electrolysis was carried out by applying an electric current at a current density of 2.5 A / dm 2 for 30 seconds.

[0067] Furthermore, the activation treatment was performed by immersing the substrate, which had undergone cathode electrolytic degreasing, in a 100g / L sulfuric acid aqueous solution at 23°C for 30 seconds.

[0068] Subsequently, a Ni-containing layer was formed on the front surface of the conductive substrate by electroplating under the conditions shown below. On the other hand, in Comparative Example 3, no Ni-containing layer was formed on the substrate.

[0069] Here, when forming the Ni-containing layer by electroplating, an aqueous solution was prepared containing 400 g / L of nickel sulfamate (Ni(SO3NH2)2·5H2O, 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.

[0070] Next, for Examples 3 to 9 of the present invention and Comparative Example 1, a Cu-containing layer was formed on the front surface of the substrate by electroplating under the conditions shown below. On the other hand, for Examples 1, 2, and 10 of the present invention and Comparative Examples 2 and 3, no Cu-containing layer was formed on the substrate.

[0071] Here, when forming the Cu-containing layer by electroplating, an aqueous solution was prepared containing 60 g / L of copper(I) cyanide (CuCN, molecular 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.

[0072] Next, an Ag coating was formed on the front surface of the substrate by strike plating and electroplating under the conditions shown below.

[0073] 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.

[0074] 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 this current density, an Ag coating was formed on the surface side of the substrate by electroplating.

[0075] In this case, the Ag coating was formed such that the ratio of the Ag coating thickness to the total thickness of the Ag and Sn coatings was 75%, according to the thickness of the Ag-Sn containing layer described in Table 1.

[0076] Next, a Sn coating was formed on the front surface of the substrate by electroplating under the following conditions.

[0077] 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 this current density, a Sn coating was formed on the Ag coating by electroplating.

[0078] At this time, the Sn coating was formed such that the ratio of the thickness of the Sn coating to the total thickness of the Ag coating and Sn coating was 25%, according to the thickness of the Ag-Sn containing layer described in Table 1.

[0079] Subsequently, for Inventions 2-5, 7-10, and Comparative Examples 2 and 3, a strain introduction process was performed on the formed Ag and Sn coatings by rolling to introduce strain into the surface coating. The processing rate in the strain introduction process was as shown in Table 1. In Invention Examples 1 and 6 and Comparative Example 1, the strain introduction process was not performed, so the processing rate was 0%.

[0080] An alloying treatment was performed on the Ag and Sn coatings after the strain introduction process (for Examples 1 and 6 of the present invention and Comparative Example 1, the Ag and Sn coatings without the strain introduction process) using the heating temperatures and heating times listed in Table 1 to form an Ag-Sn containing layer.

[0081] 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 front surface of the substrate by strike plating and electroplating under the conditions shown below. On the other hand, for Examples 1 to 3, 6, 7, 9, and 10 of the present invention, and Comparative Example 1, no Ag-containing layer was formed on the substrate.

[0082] 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.

[0083] 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.

[0084] [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.

[0085] (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. As a result, the thicknesses of each layer were as shown in Table 1.

[0086] (Measurement of the average crystal grain size of specific crystal grains in the Ag-Sn-containing layer) The crystal structure of specific crystal grains with a hexagonal close-packed structure 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 including the thickness direction of the electrical contact material, which was 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.

[0087] 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. For this analysis, only specific crystal phases with hexagonal close-packed structures were extracted as the crystal orientation data to be analyzed. A 50 μm line segment parallel to the surface of the Ag-Sn-containing layer was drawn, and the average grain size of specific crystal grains with hexagonal close-packed structures was calculated using a sectioning method, determining the average length of the line segment overlapping the specific crystal grain, which is demarcated by both ends of the specific crystal grain. The results are shown in Table 1.

[0088] (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 analyzed using the crystal orientation data obtained by the EBSD method described above, with measurement points having a reliability index CI value of 0.1 or higher as the target of analysis. Orientation analysis was performed using the profile of a hexagonal close-packed crystal phase such as magnesium. In this case, only specific crystal phases with a hexagonal close-packed structure were extracted as the crystal orientation data to be analyzed, and the total area of ​​the specific crystal phase 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.

[0089] (Evaluation of bending properties) The obtained electrical contact materials were subjected to bending tests based on the Japan Copper Association Technical Standard T307:2007 (Method for Evaluating the Bendability of Copper and Copper Alloy Sheets and Strips). The bent areas were observed using a SEM at a magnification of 500x, and the bending properties were evaluated based on the following criteria, with reference to the Japan Copper Association Technical Standard T307:2007. More specifically, the bending properties of the electrical contact materials were evaluated by taking two test pieces, each 30 mm long and 10 mm wide, from the electrical contact material with the rolling direction of the base material being the longitudinal direction. Each test piece was bent in the Goodway direction using a jig with a bending angle of 90 degrees and a bending radius of 0.3 mm, and the presence or absence of cracks on the surface of the electrical contact material was evaluated. If no cracks occurred in either test piece, it was evaluated as having excellent bending properties, and was marked with a "○". On the other hand, if cracks occurred in at least one test piece, it was evaluated as having poor bending properties, and was marked with a "×". The results are shown in Table 1.

[0090] (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 6 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 6 mΩ and 10 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 10 mΩ, it was evaluated as "△" indicating that the wear resistance of the electrical contact material is not necessarily excellent. The results are shown in Table 2.

[0091] (Evaluation of heat resistance) The obtained electrical contact material was heated at 260°C for 1 minute in an atmospheric environment, simulating reflow conditions. The contact resistance values ​​before and after heating were measured using an electrical contact simulator. Measurements were taken using a test kit (manufactured by Yamazaki Seiki Kenkyusho Co., Ltd.). The load applied when bringing the contact area into contact with the electrical contact material was 1N. A test where the increase in contact resistance before and after heating was less than 5mΩ was evaluated as "○" because it indicated a small change in electrical properties before and after heating and high heat resistance. A test where the increase in contact resistance before and after heating was 5mΩ or more was evaluated as "△" because it indicated that the heat resistance was not necessarily superior. The results are shown in Table 2.

[0092] (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.

[0093] (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.

[0094] [Table 1]

[0095] [Table 2]

[0096] From the results in Table 1, the electrical contact materials of Examples 1 to 10 of the present invention had at least an Ag-Sn-containing layer formed on the surface of the substrate, and the Ag-Sn-containing layer contained specific crystal grains having a hexagonal close-packed (hcp) structure, and the average crystal grain size of these specific crystal grains was within the appropriate range for the present invention. At this time, the electrical contact materials of Examples 1 to 10 of the present invention all received a "○" evaluation result regarding bending properties.

[0097] In contrast, the electrical contact materials in Comparative Examples 1 to 3, in which the heating time during the alloying process was less than one hour, had an average grain size of specific crystal grains smaller than the appropriate range for the present invention, and the evaluation result for bending properties was rated as "×".

[0098] Therefore, the electrical contact materials of Examples 1 to 10 of the present invention have been optimized in terms of the average grain size of specific crystal grains having a hexagonal close-packed (hcp) structure in the Ag-Sn-containing layer, and as a result, it has become clear that they have high bending properties 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 aforementioned surface coating comprises a Ni-containing layer containing Ni, An Ag-Sn-containing layer is provided on the Ni-containing layer, which contains Ag and Sn and includes specific crystal grains having a hexagonal close-packed (hcp) structure. It has, The aforementioned specific crystal grains are electrical contact material having an average crystal grain size of 1.0 μm or more.

2. The electrical contact material according to claim 1, wherein, 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.

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