Material for electrical contacts and electrical and electronic components

Abstract

By optimizing the crystal orientation of crystal grains contained in an Ag-Sn-containing layer laminated on a substrate, there is provided an electrical contact material that is less likely to wear when used for an electrical contact of an electric and electronic component, thereby enabling a longer service life, and an electric and electronic component using the same. 【Solution means】The electrical contact material 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 electrical contact material, 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.

Description

Technical Field

[0001] The present invention relates to a material for electrical contacts and electrical and electronic components.

Background Art

[0002] For electrical connectors that make up the electrical contact parts of consumer and in-vehicle electronic components, such as connectors, on the surface of a conductive substrate mainly containing copper (Cu) such as brass, phosphor bronze, or Corson alloy, a nickel (Ni) or Cu undercoat is applied, and then a tin (Sn) or Sn alloy coating is further applied on top. Such materials for electrical contacts are used. In addition, for the current-carrying members of open / close switches and slide switches, as the conductive substrate, in addition to copper alloys such as brass, phosphor bronze, and Corson alloy mainly containing copper (Cu), pure copper, and stainless steel mainly containing iron, chromium, or nickel are used, and materials for electrical contacts with a silver coating applied to the surface of such a conductive substrate are used.

[0003] In recent years, against the backdrop of the high efficiency, energy saving, and long life of electrical and electronic devices, electrical contact materials are required to have resistance to high currents and high voltages and high reliability. Not only are the examples of using silver (Ag) plating, which is a plating of Ag or an Ag alloy, increasing in place of Sn or Sn alloy plating, but higher reliability is also being demanded for conventional silver plating materials.

[0004] On the other hand, Ag plating has the characteristics of being soft and difficult to oxidize, having good compatibility with metals, and being prone to adhesion, so the amount of wear tends to increase.

[0005] Regarding this, Patent Document 1 discloses a metal material for electronic components that includes, in this order, a lower layer made of Ni and an upper layer containing at least one of a ζ (zeta) phase, which is an SnAg alloy containing 11.8 to 22.9 at% of Sn, and an ε (epsilon) phase, which is Ag3Sn, and has low whisker properties, low adhesive wear properties, and high durability.

Prior Art Documents

Patent Document

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in recent years, miniaturization and long life of electronic devices have been progressing, and as a film constituting an electrical contact, a film that is less likely to wear is required. Regarding this, when the metal material for electronic parts described in Patent Document 1 is assumed to be used for electrical contacts such as connectors and switches, wear is not focused on even due to micro-sliding of the connector or repeated operation of the switch, and there is room for improvement.

[0008] The present invention has been made in view of the above circumstances, and by optimizing the crystal orientation of crystal grains contained in the Ag-Sn-containing layer laminated on the substrate, wear hardly occurs when used for electrical contacts of electrical and electronic parts, and an object of the present invention is to provide an electrical contact material capable of achieving a long life and an electrical and electronic part using the same.

Means for Solving the Problems

[0009] The present inventors have found that by making the area ratio of crystal grains having the <0001> direction in the direction parallel to the normal direction of the surface of the substrate with respect to the crystal orientation of crystal grains contained in the Ag-Sn-containing layer laminated on the substrate for an electrical contact material 20% or less of the entire specific crystal grains having a hexagonal close-packed (hcp) structure, wear of the electrical contact material hardly occurs, and the present invention has been completed.

[0010] To achieve the above object, the gist configuration of the present invention is as follows. (1) An electrical contact material having a substrate made of a conductive material and a surface coating formed on at least a part of the substrate, wherein 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, and in a cross-section including the thickness direction of the electrical contact material, 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 entire specific crystal grains is 20% or less. (2) The electrical contact material according to (1) above, wherein the surface coating further has 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 has 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 has an Ag-containing layer having a higher Ag content and a thinner thickness than the Ag-Sn-containing layer on the Ag-Sn-containing layer. (5) An electric and electronic component having at least an electrical contact formed using the electrical contact material according to any one of (1) to (4) above.

Advantages 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 laminated on the substrate, wear hardly occurs when used for the electrical contacts of electric and electronic components, and thus an electrical contact material capable of achieving a long service life and an electric and electronic component using the same can be provided.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, preferred embodiments of the electrical contact material and the electric and electronic component of the present invention will be described in detail.

[0013] <Regarding the electrical contact material> The material for an electrical contact according to the present invention has a substrate made of a conductive material and a surface film formed on at least a part of the substrate. The surface film 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 the 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 contained 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 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 easily plastically deformed 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 contained 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 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-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 electrical contact material 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 electrical contact material 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 electrical contact material 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 that of the fcc structure typified by copper and 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 electrical contact material, so that wear is likely to occur in the Ag-Sn-containing layer due to micro-sliding, repeated operation, etc.

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

[0022] From the viewpoint of providing even better electrical conductivity, the thickness of the Ag-Sn-containing layer can be, for example, 0.2 μm or more. However, from the viewpoint of further improving wear resistance, it is preferably 1.2 μm or more, and more preferably 2.0 μm or more. On the other hand, the upper limit of the thickness of the Ag-Sn-containing layer is not particularly limited, but from the viewpoint of the material cost of the electrical contact material, it is preferably 5.0 μm or less.

[0023] The Ag-Sn-containing layer contains silver (Ag) and tin (Sn) as main components, and may also contain impurities such as copper (Cu) and nickel (Ni). In the present invention, "containing M as a main component" (when M is a single metal element) means that the total content of the metal element M in all the metal 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 an 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 the crystal orientation analysis data calculated using analysis software (OIM Analysis, manufactured by TSL) from the crystal orientation data continuously measured using an EBSD detector attached to a high-resolution scanning transmission electron microscope (JSM-7001FA, manufactured by JEOL Ltd.). Also, "EBSD" is an abbreviation for Electron BackScatter Diffraction, which is a crystal orientation analysis technique that utilizes the reflection 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 analysis software for the data measured by EBSD. The measurement can be performed on a cross-section including the thickness direction of the material for electrical contacts, which has been finished using a cross-section polisher or the like. The measurement area in the cross-section can be set to approximately 10 μm × 50 μm, and the measurement can be performed with a step size of 0.02 μm. When the above-mentioned field of view size cannot be obtained depending on the sample size in the measurement of the cross-section, an average value obtained by measuring in a plurality of fields of view may be used.

[0025] Here, among the crystal orientation data obtained by the EBSD method, using the profile of the crystal phase of the hexagonal close-packed structure such as magnesium, orientation analysis can be performed on the measurement points where the reliability index CI value is 0.1 or more as the object of analysis. At this time, as the crystal orientation data to be the object of orientation analysis, only the crystal phase having a hexagonal close-packed structure is extracted, and among them, the area ratio occupied by the crystal grains having the <0001> direction in the direction parallel to the normal direction of the surface of the substrate can be calculated.

[0026] (Ni containing layer) The Ni containing layer is a layer containing nickel (Ni), and it is preferably provided 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, 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, and reduces the increase in contact resistance when the material for electrical contacts is affected by heat, thereby enhancing the heat resistance of the material for electrical contacts.

[0027] 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. Further, at least a part of the Ni-containing layer may form a NiSn-based compound at the interface with the Ag-Sn-containing layer and 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.

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

[0029] Note that the material for the electrical contact may not have a Ni-containing layer. When there is no Ni-containing layer, the Ag-Sn-containing layer is disposed adjacent to the substrate. At this time, the portion of the Ag-Sn-containing layer adjacent to the substrate may contain Ag that did not react during the formation of the Ag-Sn-containing layer by alloying.

[0030] (Cu-containing layer) The Cu-containing layer is a layer containing copper (Cu), and it is preferably provided between the Ag-Sn-containing layer and the Ni-containing layer in the surface coating. Here, in the portion of the Ag-Sn-containing layer adjacent to the Ni-containing layer, there may be a layer composed of a NiSn-based compound, or Ag that did not react may remain during the formation of the Ag-Sn-containing layer by alloying. Among these, in particular, the unreacted and remaining Ag has a face-centered cubic lattice (FCC) structure mainly composed of Ag, and since the adhesion between it and the Ni-containing layer is weak, the portion where they are adjacent can be a starting point for peeling. However, even in such a case, by having a Cu-containing layer between the Ag-Sn-containing layer and the Ni-containing layer, constituent atoms diffuse mutually between both the Ag-Sn-containing layer and the Ni-containing layer, so that the adhesion between the Ni-containing layer and the Ag-Sn-containing layer can be further improved.

[0031] This Cu-containing layer is composed of a copper-based material of metallic copper or a copper alloy. The copper alloy is not particularly limited, and examples thereof include a Cu-P system. Further, at least a part of the Cu-containing layer may form a CuSn-based compound at the interface with the Sn atoms diffused during the formation of the Ag-Sn-containing layer, and the layer composed of this CuSn-based compound is also included in the Cu-containing layer.

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

[0033] Note that the material for the electrical contact may not have a Cu-containing layer. In this case, the Ag-Sn-containing layer is disposed adjacent to the substrate or the Ni-containing layer. Here, when the Ag-Sn-containing layer is disposed adjacent to the Ni-containing layer, unreacted Ag during the formation of the Ag-Sn-containing layer by alloying may be present at a location adjacent to the Ni-containing layer in the Ag-Sn-containing layer.

[0034] (Ag-containing layer) The Ag-containing layer is a layer on the Ag-Sn-containing layer among the surface coatings, and has a higher Ag content and a thinner thickness than the Ag-Sn-containing layer. The Ag-containing layer is located on the outermost surface of the material for the electrical contact, and by having a higher Ag content than the Ag-Sn-containing layer, the time for the solder to wet can be shortened. The Ag-containing layer can be formed on the Ag-Sn-containing layer by a wet method such as strike plating or electroplating.

[0035] The thickness of the Ag-containing layer is not particularly limited, and for example, from the viewpoint of shortening the time for the solder to wet, it is preferably 0.05 μm or more as the lower limit. On the other hand, from the viewpoints of making it difficult for the Ag-containing layer to cause wear of the material for the electrical contact due to wear and cost, the upper limit of the thickness of the Ag-containing layer may be 0.5 μm.

[0036] Incidentally, the material for electrical contacts may not have an Ag-containing layer. Here, when there is no Ag-containing layer, the Ag-Sn-containing layer constitutes a part of the surface of the material for electrical contacts.

[0037] <Use of the material for electrical contacts> When the material for electrical contacts configured as described above is used for electrical contacts such as connectors and switches, for example, it is difficult to cause wear even by the micro-sliding of the connector or the repeated operation of the switch, etc., and thereby it can contribute to the long life of the electrical contacts. Further, it is preferable to configure an electric and electronic component having at least an electrical contact formed using such a material for electrical contacts. Thereby, since the long life of the electrical contacts is achieved, it can also contribute to the long life of the electric and electronic component having at least the electrical contacts.

[0038] <Manufacturing method of the material for electrical contacts> The manufacturing method of the above-described material for electrical contacts is not particularly limited, but a substrate having its size and thickness adjusted in advance is prepared, a degreasing process and an activation process are performed as pre-treatment, and after performing a Ni-containing layer formation process and a Cu-containing layer formation process as necessary, an Ag film formation process and a Sn film formation process are performed, and a strain introduction process and an alloying treatment process are performed on these films to form an Ag-Sn-containing layer, and then an Ag-containing layer formation process is performed as necessary.

[0039] (i) Degreasing process The degreasing process and the activation process described later are preferably performed from the viewpoint of enhancing the adhesion between the substrate and the surface film. Among these, as the degreasing process, for example, cathode electrolytic degreasing can be performed. An example of the liquid composition and treatment conditions used in cathode electrolytic degreasing is shown below. [Example of liquid composition and treatment conditions for electrolytic degreasing treatment] Treatment liquid: 60 g / L aqueous sodium hydroxide solution Treatment temperature: 60 °C Cathode current density: 2.5 A / dm 2 Treatment time: 30 seconds

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

[0041] (iii) Ni-containing layer formation process In the Ni-containing layer formation process, a Ni-containing layer is formed on at least one side of both sides of the substrate by electroplating. As a result, the Ni-containing layer can be formed by a cold process without requiring processing at high temperature and high pressure. An example of the liquid composition and treatment conditions used in the Ni-containing layer formation process is shown below.

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

[0043] (iv) Cu-containing layer formation process In the Cu-containing layer formation process, a Cu-containing layer is formed on the surface of the Ni-containing layer by electroplating. That is, the Cu-containing layer can also be constituted by an electroplated layer. As a result, the Cu-containing layer can also be formed by a cold process without requiring processing at high temperature and high pressure, similar to the Ni-containing layer. An example of the liquid composition and treatment conditions used in the Cu-containing layer formation process is shown below.

[0044] [Example of liquid composition and treatment conditions in the Cu-containing layer formation process] Treatment solution: An aqueous solution containing 60 g / L of cuprous cyanide, 70 g / L of sodium cyanide, and 5 g / L of free sodium cyanide Treatment temperature: 50 °C Current density: 1 A / dm 2 Plating thickness: 0.05 μm to 1.0 μm Treatment time: Time adjusted according to the plating thickness

[0045] (v) Ag film formation step In the Ag film formation step, on the surface of a substrate on which a Ni-containing layer and a Cu-containing layer are formed as necessary, after enhancing the adhesion of the Ag-containing layer by strike plating, an Ag film is formed by electroplating. An example of the liquid composition and treatment conditions used in the Ag film formation step is shown below.

[0046] [An example of the liquid composition and treatment conditions of the strike plating solution in the Ag film formation step] Treatment solution: An aqueous solution containing 4 g / L of silver(I) cyanide and 80 g / L of free potassium cyanide Treatment temperature: 30 °C Current density: 2 A / dm 2 Treatment time: 10 seconds

[0047] [An example of the liquid composition and treatment conditions of the electroplating solution in the Ag film formation step] 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: 0.85 μm to 4.4 μm Treatment time: Time adjusted according to the plating thickness

[0048] (vi) Sn film formation step The Sn film forming process forms an Sn film on the surface of a substrate on which a Ni-containing layer and a Cu-containing layer are formed as necessary. Here, the Ag film and the Sn film can be laminated in any order. That is, the Sn film may be formed after the Ag film is formed, or the Ag film may be formed after the Sn film is formed. In particular, from the viewpoint of forming a thick Ag-Sn-containing layer, the Ag film forming process and the Sn film forming process may be repeated.

[0049] The Ag film and the Sn film are preferably laminated such 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, the ratio of the thickness of the Sn film to the total thickness of the Ag film and the Sn film is preferably in the range of 0.125 or more and 0.375 or less. By forming the Ag film and the Sn film at such a ratio, specific crystal grains having a hexagonal close-packed (hcp) structure can be formed in the Ag-Sn-containing layer. An example of the liquid composition and treatment conditions used in the Sn film forming process is shown below.

[0050] [Example of the liquid composition and treatment conditions of the plating solution in the Sn film forming 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 Treatment temperature: 23 °C Current density: 2 A / dm 2 Plating thickness: 0.15 μm to 1.6 μm Treatment time: Time adjusted according to the plating thickness

[0051] (vii) Strain introduction process to the surface film The strain introduction process to the surface film is a process of applying strain to the plating layer by compression processing such as rolling to the Ag film and the Sn film formed by the Ag film forming process and the Sn film forming process. 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 step is preferably in the range of 2% or more and 5% or less. As the strain introduction step, by performing compression processing at a processing rate within this range, when the alloying treatment step described later is performed, an Ag-Sn-containing layer can be formed that contains specific crystal grains having a hexagonal close-packed (hcp) structure and has a small 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 entire specific crystal grains. In particular, from the viewpoint of forming 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 in the entire specific crystal grains is even smaller, the processing rate in the strain introduction step is more preferably 3% or more. On the other hand, if the processing rate in the strain introduction step is too large, non-uniform deformation occurs inside the surface film, so the processing rate in the strain introduction step is preferably 5% or less.

[0053] (viii) Alloying treatment step After performing the strain introduction step, the Ag film and the Sn film are formed into an Ag-Sn-containing layer by an alloying treatment step of performing heat treatment. At this time, unreacted Ag may remain in the Ag-Sn-containing layer.

[0054] The heating temperature of the heat treatment in the alloying treatment step is preferably in the temperature range of 300°C or more and 500°C or less. By heat-treating the Ag film and the Sn film after performing the strain introduction step within this temperature range, an Ag-Sn-containing layer can be formed that contains specific crystal grains having a hexagonal close-packed (hcp) structure and has a small 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 entire specific crystal grains. [[ID=eleven]]

[0055] The heating time of the heat treatment in the alloying treatment step is not particularly limited, but is preferably in the range of 30 seconds or more and 600 seconds or less. In the heat treatment of the alloying treatment step, it is preferable to change the heating time within the above range according to the heating temperature.

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

[0057] (ix) Ag-containing layer forming step In the Ag-containing layer forming step, after enhancing the adhesion of the Ag-containing layer by strike plating on the surface of the Ag-Sn-containing layer formed by the alloying process, the Ag-containing layer is formed by electroplating. An example of the liquid composition and treatment conditions used in the Ag-containing layer forming step is shown below.

[0058] [Example of liquid composition and treatment conditions of strike plating solution in Ag-containing layer forming step] Treatment solution: Aqueous solution containing 4 g / L of silver(I) cyanide and 80 g / L of free potassium cyanide Treatment temperature: 30°C Current density: 2 A / dm 2 Treatment time: 10 seconds

[0059] [Example of liquid composition and treatment conditions of electroplating solution in Ag-containing layer forming step] Treatment solution: 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

[0060] In this way, an electrical contact material can be formed 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 illustrate 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 the substrate and formed into a plate shape with a length of 20 cm and a width of 10 cm by pressing. The substrate was subjected to cathode electrolytic degreasing and activation treatment as pretreatment.

[0063] Here, for cathode 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 the treatment was performed by passing an electric current at a current density of 2.5 A / dm 2 for 30 seconds.

[0064] Also, the activation treatment was performed by immersing the substrate after cathode electrolytic 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 Example 1, 8, and Comparative Example 3 of the present invention, the Ni-containing layer was not formed on the substrate.

[0066] Here, when forming the Ni-containing layer by electroplating, an aqueous solution 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 was prepared, and at this time, the concentration of nickel (Ni) metal (atomic weight: 58.69) was about 107 g / L. Next, in the electroplating cell, the substrate as the cathode electrode was placed, and a pure Ni plate with a length of 20 cm and a width of 10 cm as the anode electrode was placed facing the front plate surface of the cathode electrode. 2 L of the electroplating solution was put into the cell, and at a temperature of 55 °C, electricity was passed at a current density of 10 A / dm 2 to form a Ni-containing layer with the thickness described in Table 1 by electroplating.

[0067] Next, for Examples 3 to 9 and Comparative Example 1 of the present invention, 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 and Comparative Examples 2 and 3 of the present invention, a Cu-containing layer was not formed on the substrate.

[0068] Here, when forming the Cu-containing layer by electroplating, an aqueous solution 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 was prepared, and at this time, the concentration of copper (Cu) metal (atomic weight: 63.55) was about 43 g / L. Next, in the electroplating cell, the substrate as the cathode electrode was placed, and a phosphorus-depleted copper plate with a length of 20 cm and a width of 10 cm as the anode electrode was placed facing the front plate surface of the cathode electrode. 2 L of the electroplating solution was put into the cell, and at a temperature of 50 °C, electricity was passed at a current density of 1 A / dm 2 to form a Cu-containing layer with the thickness described in Table 1 by electroplating.

[0069] Next, an Ag film 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 containing 4 g / L of silver(I) cyanide (AgCN, formula weight: 133.89 g / mol), 80 g / L of free potassium cyanide, and having a concentration of silver (Ag) metal (atomic weight: 107.87) of about 3 g / L at this time was prepared as the strike plating solution. Next, in the plating electrolytic cell, the substrate serving as the cathode electrode was placed, and an insoluble plate with a length of 20 cm and a width of 10 cm serving as the anode electrode was placed facing the plate surface on the front side of the cathode electrode. 2 L of the strike plating solution was put into the cell, and strike plating was performed by applying an electric current at a current density of 2 A / dm 2 for 10 seconds at a temperature of 30°C.

[0071] After performing strike plating, when forming an Ag film by electroplating, an aqueous solution containing 50 g / L of silver(I) cyanide (AgCN, formula weight: 133.89 g / mol), 10 g / L of potassium carbonate, 90 g / L of free potassium cyanide, and having a concentration of silver (Ag) metal (atomic weight: 107.87) of about 40 g / L at this time was prepared as the electroplating solution. Next, in the plating electrolytic cell, the substrate serving as the cathode electrode was placed, and a silver plate with a length of 20 cm and a width of 10 cm serving as the anode electrode was placed facing the plate surface on the front side (the side where strike plating was performed) of the cathode electrode. 2 L of the electroplating solution was put into the cell, and an Ag film with the plating thickness described in Table 1 was formed on the surface side of the substrate by electroplating by applying an electric current at a current density of 1 A / dm 2 at a temperature of 30°C.

[0072] Next, an Sn film was formed on the surface side of the substrate by electroplating under the conditions shown below.

[0073] Here, when forming the Sn film by electroplating, an aqueous solution containing stannous sulfate (SnSO4, formula weight: 214.77 g / mol) at 40 g / L, sulfuric acid at 60 g / L, cresolsulfonic acid at 40 g / L, and gelatin at 2 g / L was prepared, and the concentration of tin (Sn) metal (atomic weight: 118.71) at this time was about 22 g / L. Next, in the electroplating bath, the substrate as the cathode electrode was placed, and a tin plate with a length of 20 cm and a width of 10 cm as the anode electrode was placed facing the front plate surface of the cathode electrode. 2 L of the electroplating solution was put into the bath, and at a temperature of 23 °C, an Sn film with the plating thickness described in Table 1 was formed on the Ag film by electroplating by energizing at a current density of 2 A / dm 2 Thereby, the Sn film was formed on the Ag film by electroplating at a current density of 2 .

[0074] Thereafter, for Examples 1 to 9 and Comparative Example 3 of the present invention, a strain introduction step of applying strain to the surface film by rolling was performed on the formed Ag film and Sn film. Here, the processing rate in the strain introduction step was the ratio described in Table 1. On the other hand, for Comparative Examples 1 and 2, the strain introduction step was not performed.

[0075] An alloying treatment step of performing heat treatment on the Ag film and Sn film after the strain introduction step at the heating temperature and heating time described in Table 1 was performed to form an Ag-Sn containing layer.

[0076] Next, for Examples 4, 5, 8 and Comparative Examples 2, 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, 9 and Comparative Example 1, the Ag-containing layer was not formed on the substrate.

[0077] Here, when performing strike plating, an aqueous solution containing 4 g / L of silver(I) cyanide (AgCN, formula weight: 133.89 g / mol), 80 g / L of free potassium cyanide, and having a concentration of silver (Ag) metal (atomic weight: 107.87) of about 3 g / L at this time was prepared. Next, in the plating electrolytic cell, the substrate serving as the cathode electrode was placed, and an insoluble plate with a length of 20 cm and a width of 10 cm serving as the anode electrode was placed facing the surface plate on the front side of the cathode electrode. 2 L of the strike plating solution was put into the cell, and at a temperature of 30 °C, 2 strike plating was performed by applying an electric current at a current density of 2 A / dm

[0078] for 10 seconds. After performing strike plating, when forming an Ag film by electroplating, as the electroplating solution, an aqueous solution containing 50 g / L of silver(I) cyanide (AgCN, formula weight: 133.89 g / mol), 10 g / L of potassium carbonate, 90 g / L of free potassium cyanide, and having a concentration of silver (Ag) metal (atomic weight: 107.87) of about 40 g / L at this time was prepared. Next, in the plating electrolytic cell, the substrate serving as the cathode electrode was placed, and a silver plate with a length of 20 cm and a width of 10 cm serving as the anode electrode was placed facing the surface plate on the front side (the side where strike plating was performed) of the cathode electrode. 2 L of the electroplating solution was put into the cell, and at a temperature of 30 °C, 2 an Ag film with the thickness described in Table 1 was formed on the surface side of the substrate by electroplating by applying an electric current at a current density of 1 A / dm

[0079] [Various Measurement and Evaluation Methods] Regarding the materials for electrical contacts obtained in the above-described inventive examples and comparative examples, the following characteristic evaluations were performed. The evaluation conditions for each characteristic are as follows.

[0080] (Measurement of the Thickness of Each Layer Constituting the Surface Film) The thicknesses of the Ni-containing layer, Cu-containing layer, Ag-Sn-containing layer, and Ag-containing layer that constitute the surface film were measured by performing fluorescence X-ray analysis from the surface of each prepared sample in accordance with the fluorescence X-ray test method of JIS H8501:1999. Also, for confirmation of the thickness of each layer, the thickness was also measured by an image analysis method for a cross-section including the thickness direction. The image analysis method was carried out in accordance with the scanning electron microscope test method of JIS H8501:1999.

[0081] (Measurement of the area ratio of crystal grains having the <0001> direction in the direction parallel to the normal direction of the surface of the substrate in the entire specific crystal grains of the Ag-Sn-containing layer) The crystal structure of the crystal grains contained in the Ag-Sn-containing layer was determined from the crystal orientation analysis data calculated using analysis software (OIM Analysis manufactured by TSL) from the crystal orientation data continuously measured using an EBSD detector attached to a high-resolution scanning analytical electron microscope (JSM-7001FA manufactured by JEOL Ltd.). The measurement was performed on a cross-section including the thickness direction of the material for electrical contacts finished using a cross-section polisher. The measurement region in the cross-section was about 10 μm × 50 μm, and the step size was 0.02 μm.

[0082] Here, among the crystal orientation data obtained by the EBSD method, the measurement points with a reliability index CI value of 0.1 or more were used as the objects of analysis, and orientation analysis was performed using the profile of the crystal phase of the hexagonal close-packed structure such as magnesium. At this time, as the crystal orientation data to be the object of orientation analysis, only the specific crystal phase having the hexagonal close-packed structure was extracted, and the ratio (area ratio) occupied by the area of the crystal grains having the <0001> direction in the direction parallel to the normal direction of the surface of the substrate in the total area of the specific crystal phase was calculated. The results are shown in Table 1.

[0083] (Evaluation of wear resistance) The wear resistance of the electrical contact material was evaluated by performing a sliding test using a multi-functional tribology evaluation machine (friction and wear tester) UMT TriboLab (manufactured by Bruker) to slide the same material on the surface of the obtained electrical contact material. The resistance values of the surface before sliding the same material on the surface of the electrical contact material and after sliding the same material 2,000 times were measured respectively. When the increase in the resistance value before and after sliding the same material on the surface of the electrical contact material was 3 mΩ or less, it was evaluated as "◎", indicating that the wear resistance of the electrical contact material was particularly excellent in terms of high wear resistance. In addition, when the increase in the resistance value before and after sliding the same material on 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 that the wear resistance of the electrical contact material was good in terms of high wear resistance. On the other hand, when the increase in the resistance value before and after sliding the same material on the surface of the electrical contact material was more than 5 mΩ, it was evaluated as "×", indicating that the wear resistance of the electrical contact material was poor in terms of low wear resistance. 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 air atmosphere. The values of the contact resistance before and after heating were measured using an electrical contact simulator (manufactured by Yamazaki Seiki Kenkyusho Co., Ltd.). At this time, the load when bringing the contact part into contact with the electrical contact material was set to 1 N. When the increase in the contact resistance before and after heating was less than 5 mΩ, it was evaluated as "○", indicating that the change in the electrical characteristics before and after heating was small and it was excellent in terms of high heat resistance. In addition, when the increase in the contact resistance before and after heating was 5 mΩ or more, it was evaluated as "△", indicating that it was not necessarily excellent from the viewpoint of heat resistance. The results are shown in Table 2.

[0085] (Evaluation of adhesion of surface coating) For the obtained electrical contact material, the tape peeling test specified in JIS H 8504 was conducted to evaluate the presence or absence of peeling of the surface coating from the electrical contact material. More specifically, for the surface coating of the electrical contact material on which streaks reaching the conductive substrate were formed so as to make a square with a side of 2 mm using a sharp blade, the tape peeling test was conducted. When no peeling of the surface coating was observed, it was evaluated as "○", indicating excellent adhesion of the surface coating. In addition, when partial peeling was observed in the surface coating, it was evaluated as "△", indicating that it is not necessarily excellent from the viewpoint of the adhesion of the surface coating. The results are shown in Table 2.

[0086] (Evaluation of solder wettability) For the obtained electrical contact material, the solder wettability was evaluated by the wetting balance method specified in JIS Z3198-4, Test methods for lead-free solders - Part 4: Test methods for wettability by the wetting balance method and the contact angle method. Here, the bath temperature was 245°C, and Sn-3Ag-0.1Cu solder was used for the bath. Also, an RMA type flux was used. When the measured zero-crossing time (the time t0 when wetting starts) was 2 seconds or less, it was evaluated as "○", indicating excellent solder wettability. In addition, when the measured zero-crossing time (the time t0 when wetting starts) exceeded 2 seconds, it was evaluated as "△", indicating that it is not necessarily excellent from the viewpoint of solder wettability. The results are shown in Table 2.

[0087]

Table 1

[0088]

Table 2

[0089] From the results in Table 1, for the materials for electrical contacts of Invention Examples 1 to 9, at least an Ag-Sn containing layer is formed on the surface of the substrate, and the Ag-Sn containing layer contains specific crystal grains having a hexagonal close-packed (hcp) structure. The area ratio of the crystal grains having the <0001> direction in the direction parallel to the normal direction of the surface of the substrate, which accounts for the whole of these specific crystal grains, was within the appropriate range of the present invention. At this time, the evaluation results regarding the wear resistance of the materials for electrical contacts of Invention Examples 1 to 9 were all evaluated as "◎" or "〇".

[0090] On the other hand, for the materials for electrical contacts of Comparative Examples 1 and 2 in which the strain introduction process was not performed, the area ratio of the crystal grains having the <0001> direction in the direction parallel to the normal direction of the surface of the substrate, which accounts for the whole of the specific crystal grains, was larger than the appropriate range of the present invention, and the evaluation results regarding the wear resistance were evaluated as "×".

[0091] Also, for the material for an electrical contact of Comparative Example 3 in which the processing rate in the strain introduction process was 1%, the area ratio of the crystal grains having the <0001> direction in the direction parallel to the normal direction of the surface of the substrate, which accounts for the whole of the specific crystal grains, was larger than the appropriate range of the present invention, and the evaluation result regarding the wear resistance was evaluated as "×".

[0092] Therefore, for the materials for electrical contacts of Invention Examples 1 to 9, the area ratio of the crystal grains having the <0001> direction in the direction parallel to the normal direction of the surface of the substrate, which accounts for the whole of the specific crystal grains having a hexagonal close-packed (hcp) structure in the Ag-Sn containing layer, has been optimized. As a result, it has been clarified that wear hardly occurs when used for the 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 part of the substrate, wherein 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, and in a cross section including the thickness direction of the electrical contact material, 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 entire specific crystal grains is 20% or less. The electrical contact material.

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

3. The electrical contact material according to claim 2, wherein the surface coating further has 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 has an Ag-containing layer having a higher Ag content and a thinner thickness than the Ag—Sn-containing layer on the Ag—Sn-containing layer.

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

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