Electrical contact materials and electrical and electronic components

Abstract

The present invention provides an electrical contact material that has high bending properties when used in 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 an Ag-Sn-containing layer formed on a substrate. [Solution] The electrical contact material has a substrate made of a conductive material and a surface coating formed on at least a portion of the substrate, the surface coating having 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 including specific crystal grains with a hexagonal close-packed (hcp) structure, the specific crystal grains having an average crystal grain size of 1.0 μm or more.

Description

[Technical Field]

[0001] The present invention relates to an electrical contact material and an electric / electronic component. [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 in which the surface of a conductive substrate containing copper (Cu) as its main component, such as brass, phosphor bronze, or Corson alloy, is underplated with nickel (Ni) or Cu, and then plated with tin (Sn) or an Sn alloy. For current-carrying members of open / close switches and slide switches, conductive substrates are used, such as brass, phosphor bronze, or copper alloys containing copper (Cu) as its main component, or pure copper, or stainless steel containing iron, chromium, and nickel as its main components, and electrical contact materials are used in which the surface of such conductive substrates is silver-plated.

[0003] In recent years, with the trend toward higher efficiency, energy conservation, and longer lifespans in electrical and electronic equipment, electrical contact materials are being required to be able to withstand large currents and high voltages, as well as to have high reliability. Not only are there increasing examples of using Ag plating, which is made of silver (Ag) and Ag alloys, instead of Sn and Sn alloy plating, but there is also a growing demand for higher reliability in conventional silver-plated materials.

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

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

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-206094 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in recent years, electronic devices have become increasingly miniaturized, and when coatings constituting electrical contacts are used in electrical contacts such as connectors and switches, electronic contact materials are formed by minute bending processes, so there is a demand for electronic contact materials with excellent processability. Therefore, when used in electrical contacts, electronic contact materials are required to have high bending properties, particularly when a bending force is applied to the electronic contact materials. In this regard, the metal material for electronic components described in Patent Document 1 does not focus on bending properties when a bending force is applied, and there is room for improvement.

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

[0009] The present inventors discovered that the bending properties of an electrical contact material can be improved by setting the average grain size of specific grains having a hexagonal close-packed (hcp) structure to 1.0 μm or more, regarding the grain size of the crystal grains contained in the Ag—Sn-containing layer formed on the substrate of the electrical contact material, and thus completed the present invention.

[0010] In order to achieve the above object, the gist of the present invention is as follows. (1) A material for electrical contacts having a substrate made of an electrically conductive material and a surface coating formed on at least a portion of the substrate, wherein the surface coating has 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 including specific crystal grains with a hexagonal close-packed (hcp) structure, and the specific crystal grains have an average crystal grain size of 1.0 μm or more. (2) The Ag—Sn-containing layer has a thickness in a direction parallel to the normal to the surface of the substrate when viewed from a cross section including the thickness direction of the electrical contact material. <0001> The electrical contact material according to (1) above, wherein the area ratio of the oriented crystal grains to the entire area of ​​the specific crystal grains is 20% or less. (3) The material for electrical contacts 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 material for electrical contacts 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 a thinner thickness than the Ag—Sn-containing layer. (5) An electric / electronic component having at least an electric contact formed using the material for electric contacts according to any one of (1) to (4) above. [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 on the substrate, it is possible to provide an electrical contact material that has high bending properties when used in electrical contacts of electrical and electronic components, and electrical and electronic components using the same. DETAILED DESCRIPTION OF THE INVENTION

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

[0013] <About electrical contact materials> The material for electrical contacts according to the present invention has a substrate made of an electrically conductive material and a surface coating formed on at least a portion of the substrate, the surface coating having 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 including specific crystal grains with a hexagonal close-packed (hcp) structure, the specific crystal grains having an average crystal grain size of 1.0 μm or more.

[0014] In the electrical contact material of the present invention, the grain size of the crystal grains contained in the Ag-Sn-containing layer formed on the substrate is set to 1.0 μm or more, which is a specific crystal grain having a hexagonal close-packed (hcp) structure. This reduces the number of grain boundaries contained in the electrical contact material, making it less likely that the Ag-Sn-containing layer will break due to cracks at the grain boundaries when the electrical contact material is bent. This makes it possible to provide an electrical contact material that has high bending properties when used in electrical contacts for electrical and electronic components, and electrical and electronic components using the same.

[0015] [About the base] The electrical contact material of the present invention has a substrate made of a conductive material, and a surface coating, which will be described later, is formed on at least a portion of the surface of this substrate.

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

[0017] The shape of the substrate is not particularly limited and may be appropriately selected depending on the application, but is preferably a strip or plate material, and may also be a rod or wire material.

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

[0019] [About the surface coating] The electrical contact material has a surface coating formed on at least a portion of the substrate. Examples of the surface coating include, in order from closest to the substrate, a Ni-containing layer, a Cu-containing layer, an Ag—Sn-containing layer, and an Ag-containing layer. The electrical contact material of the present invention has at least a Ni-containing layer and an Ag—Sn-containing layer as surface coatings.

[0020] (Ni-containing layer) 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, reducing the deterioration of the electrical conductivity of the electrical contact material that occurs when copper (Cu) atoms contained in the substrate diffuse into adjacent layers, such as the Ag-Sn-containing layer or the Cu-containing layer, during an alloying treatment process described below. It also reduces the increase in contact resistance when the electrical contact material is subjected to heat, thereby improving the heat resistance of the electrical contact material during reflow and other processes.

[0021] This Ni-containing layer is made of a nickel-based material such as metallic nickel or a nickel alloy. Examples of nickel alloys include, but are not limited to, Ni-P and Ni-Fe alloys. Furthermore, at least a portion of the Ni-containing layer may form a NiSn-based compound at the interface with the Ag-Sn-containing layer, due to Sn atoms diffused during the formation of the Ag-Sn-containing layer. This layer made of the NiSn-based compound is also included in the Ni-containing layer.

[0022] The thickness of the Ni-containing layer is not particularly limited, but may be, for example, 0.05 μm as the lower limit. In particular, from the viewpoint of further reducing the increase in contact resistance when the electrical contact material is subjected to thermal effects, it is preferable that the thickness of the Ni-containing layer be set to 0.10 μm as the lower limit. On the other hand, from the viewpoints of formability and cost, the upper limit of the thickness of the Ni-containing layer may be set to 2.0 μm.

[0023] (Ag-Sn containing layer) The Ag—Sn-containing layer is a layer containing silver (Ag) and tin (Sn) and including specific crystal grains with a hexagonal close-packed (hcp) structure, and is provided on the Ni-containing layer.

[0024] The Ag-Sn-containing layer has a specific crystal grain having a hexagonal close-packed (hcp) structure with an average crystal grain size of 1.0 μm or more. The specific crystal grains having a hexagonal close-packed (hcp) structure are a zeta (ζ) phase, and {0001} basal slip is the primary slip system responsible for deformation. However, a hexagonal close-packed structure is generally known to be less workable than a face-centered cubic (FCC) structure, such as that found in silver (Ag) or copper (Cu). In particular, if the alloyed Ag-Sn-containing layer has a fine crystal grain size, the electrical contact material may crack at the grain boundaries when bent. By increasing the average crystal grain size of the specific crystal grains having a hexagonal close-packed (hcp) structure in the Ag-Sn-containing layer to 1.0 μm or more, the Ag-Sn-containing layer is less likely to break when bent, thereby improving the bending properties of the electrical contact material.

[0025] The average crystal 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 (OIM Analysis, manufactured by TSL) from crystal orientation data continuously measured on a cross-section of the electrical contact material in the thickness direction using an EBSD detector attached to a high-resolution scanning analytical electron microscope (JEOL Ltd., JSM-7001FA). "EBSD" stands for Electron Backscatter Diffraction, a crystal orientation analysis technique that utilizes backscattered electron Kikuchi diffraction generated when a copper alloy sample is irradiated with an electron beam inside a scanning electron microscope (SEM). "OIM Analysis" is software for analyzing data measured by EBSD. Measurements can be performed on a cross-section of the electrical contact material in the thickness direction, which has been polished using a cross-section polisher or similar tool. The measurement area on the cross-section is approximately 10 μm x 50 μm, with a step size of 0.02 μm. When the above field of view size cannot be obtained due to the sample size in cross-sectional measurement, measurements may be taken in multiple fields of view and the average value may be used.

[0026] Here, among the crystal orientation data obtained by the EBSD method, measurement points with a reliability index (CI) value of 0.1 or more can be analyzed, and orientation analysis can be performed using the profile of a hexagonal close-packed crystalline phase of magnesium, etc. In this case, as the crystal orientation data to be analyzed, only a specific crystalline phase with a hexagonal close-packed structure is extracted, and the average grain size of the specific crystal grains with a hexagonal close-packed structure can be determined using a cutting method in which line segments are drawn parallel to the surface of the Ag-Sn-containing layer and the average length of the line segments that overlap the specific crystal grains, bounded by both ends of the specific crystal grains, is determined.

[0027] The Ag-Sn containing layer is formed in a direction parallel to the normal to the surface of the substrate when viewed in a cross section including the thickness direction of the electrical contact material. <0001> It is preferable that the area ratio of the crystal grains with a specific orientation to the entire specific crystal grains is 20% or less. The specific crystal grains with a hexagonal close-packed structure are deformed by {0001} basal slip as the main slip system, but since this slip system is less than that of the face-centered cubic lattice (FCC) structure represented by silver (Ag) and copper (Cu), the anisotropy of plastic deformation is large. Therefore, the specific crystal grains are deformed by {0001} basal slip as the main slip system. <0001> When the direction is parallel to the normal to the surface of the substrate, the {0001} plane of the specific crystal grains becomes approximately parallel to the surface of the material for electrical contacts, and therefore the Ag-Sn-containing layer becomes more likely to wear due to slight sliding or repeated operation. Therefore, from the viewpoint of making the surface of the material for electrical contacts less prone to wear and improving the wear resistance, it is preferable to set the direction parallel to the normal to the surface of the substrate. <0001> The area ratio of the oriented crystal grains to the entire 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 providing even better electrical conductivity, but is preferably 1.2 μm or more from the viewpoint of making the surface of the electrical contact material less susceptible to wear and further improving wear resistance. On the other hand, the upper limit of the thickness of the Ag-Sn-containing layer is not particularly limited, but is preferably 5.0 μm or less from the viewpoint of material cost for the electrical contact material.

[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 the present invention, "containing M as its main component" (where M is one type of metal element) means that the total content of the metal element M in all 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.

[0030] The crystal structure of the crystal grains contained in the Ag-Sn-containing layer can be analyzed by analyzing measurement points with a reliability index (CI) value of 0.1 or more among the crystal orientation data obtained by the EBSD method described above, using the profile of a crystalline phase with a hexagonal close-packed structure such as magnesium. In this case, the crystal orientation data to be analyzed is extracted only from the crystalline phase with a hexagonal close-packed structure, and the data that is the target of the orientation analysis is the data that is the direction parallel to the normal direction of the substrate surface. <0001> The percentage of the area occupied by oriented grains can be calculated.

[0031] (Cu-containing layer) The Cu-containing layer is a layer containing copper (Cu) and is preferably present between the Ni-containing layer and the Ag—Sn-containing layer of the surface coating. The Ag—Sn-containing layer may have a layer of NiSn-based compounds adjacent to the Ni-containing layer, or may contain unreacted Ag that remained when the Ag—Sn-containing layer was formed by alloying. The unreacted Ag, in particular, has a face-centered cubic (FCC) structure primarily composed of Ag, which weakens the adhesion between the Ni-containing layer and the Cu-containing layer. However, even in such cases, the presence of a Cu-containing layer between the Ni-containing layer and the Ag—Sn-containing layer allows for mutual diffusion of constituent atoms 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] The Cu-containing layer is made of a copper-based material such as metallic copper or a copper alloy. The copper alloy is not particularly limited, but examples thereof 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, due to Sn atoms diffused during the formation of the Ag-Sn-containing layer. The layer made of this CuSn-based compound is also included in the Cu-containing layer.

[0033] The thickness of the Cu-containing layer is not particularly limited, but may be, for example, 0.05 μm as the lower limit, and 1.0 μm as the upper limit from the viewpoints of heat resistance and cost.

[0034] The electrical contact material 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. When the Ag—Sn-containing layer is disposed adjacent to the Ni-containing layer, the Ag—Sn-containing layer may contain unreacted Ag that remains in the Ag—Sn-containing layer when the Ag—Sn-containing layer is formed by alloying, in a portion adjacent to the Ni-containing layer.

[0035] (Ag-containing layer) The Ag-containing layer is a surface coating layer that is present on the Ag-Sn-containing layer 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 electrical contact material, and because it has a higher Ag content than the Ag-Sn-containing layer, it can shorten the time it takes for the solder to wet out. The Ag-containing layer can be formed on the Ag-Sn-containing layer by a wet method 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 time it takes for the solder to wet out, it is preferable to set the lower limit to 0.05 μm. On the other hand, the upper limit of the thickness of the Ag-containing layer may be set to 0.5 μm from the viewpoint of reducing the abrasion of the electrical contact material due to the abrasion of the Ag-containing layer and from the viewpoint of cost.

[0037] The material for electrical contacts does not necessarily have to have an Ag-containing layer. When the material for electrical contacts does not have an Ag-containing layer, the Ag—Sn-containing layer forms part of the surface of the material for electrical contacts.

[0038] <Applications of electrical contact materials> The electrical contact material configured as described above exhibits high bending properties when used in electrical contacts, particularly when a bending force is applied to the electronic contact material. Therefore, when used in electrical contacts, such as connectors and switches, the material exhibits excellent workability even when formed by minute bending, making it difficult for the coating that constitutes the electrical contact to be damaged, thereby contributing to a longer service life of the electrical contact. It is also preferable to construct electrical and electronic components that have at least electrical contacts formed using such an electrical contact material. This extends the service life of the electrical contacts, thereby contributing to a longer service life of the electrical and electronic components that have at least the electrical contacts.

[0039] <Method of manufacturing electrical contact materials> The method for producing the electrical contact material described above is not particularly limited, but includes preparing a substrate whose size and thickness have been adjusted in advance, carrying out a degreasing process and an activation process as pretreatment, carrying out a Ni-containing layer forming process and, if necessary, a Cu-containing layer forming process, followed by an Ag coating process and an Sn coating process, carrying out a strain introduction process and an alloying process on these coatings to form an Ag-Sn-containing layer, and then, if necessary, carrying out the Ag-containing layer forming process.

[0040] (i) Degreasing process The degreasing step and the activation step described below are preferably carried out from the viewpoint of increasing the adhesion between the substrate and the surface coating. Among these, the degreasing step may be, for example, cathodic electrolytic degreasing. An example of the solution composition and processing conditions used in cathodic electrolytic degreasing is shown below. [Example of electrolytic degreasing solution composition and processing conditions] Treatment liquid: 60g / 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 treatment conditions used in the activation step is shown below. [Example of liquid composition and processing conditions in the activation process] Treatment liquid: 100g / L sulfuric acid aqueous solution Processing temperature: 23℃ Immersion time: 30 seconds

[0042] (iii) Ni-containing layer formation step In the Ni-containing layer forming step, the Ni-containing layer is formed on at least one of the two surfaces of the substrate by electroplating, which allows the Ni-containing layer to be formed by a cold process without requiring processing at high temperature and high pressure. An example of the liquid composition and processing conditions used in the Ni-containing layer forming step is shown below.

[0043] [Example of liquid composition and processing conditions in the Ni-containing layer formation process] Treatment solution: Aqueous solution containing 400 g / L of nickel sulfamate, 30 g / L of nickel (II) chloride, and 30 g / L of boric acid Processing temperature: 55℃ Current density: 10A / dm 2 Plating thickness: 0.05μm~2.0μm Processing time: Adjusted according to plating thickness

[0044] (iv)Cu-containing layer formation process In the Cu-containing layer forming step, 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 formed by an electroplated layer. As a result, like the Ni-containing layer, the Cu-containing layer can also be formed by a cold process without requiring processing at high temperature and high pressure. An example of the liquid composition and processing conditions used in the Cu-containing layer forming step is shown below.

[0045] [Example of liquid composition and processing conditions in the Cu-containing layer formation process] Treatment solution: Aqueous solution containing 60 g / L copper cyanide (I), 70 g / L sodium cyanide, and 5 g / L free sodium cyanide Processing temperature: 50℃ Current density: 1A / dm 2 Plating thickness: 0.05μm~1.0μm Processing time: Adjusted according to plating thickness

[0046] (v)Ag film formation process In the Ag coating formation step, the adhesion of the Ag coating is increased by strike plating on the surface of the substrate on which the Ni-containing layer and Cu-containing layer have been formed as needed, and then the Ag coating is formed by electroplating. An example of the liquid composition and processing conditions used in the Ag coating formation process is shown below.

[0047] [Example of strike plating solution composition and processing conditions in the Ag film formation process] Processing solution: Aqueous solution containing 4 g / L of silver cyanide (I) and 80 g / L of free potassium cyanide Processing temperature: 30℃ Current density: 2A / dm 2 Processing time: 10 seconds

[0048] [Example of electroplating solution composition and processing conditions in the Ag coating formation process] Processing solution: Aqueous solution containing 50 g / L of silver cyanide (I), 10 g / L of potassium carbonate, and 90 g / L of free potassium cyanide Processing temperature: 30℃ Current density: 1A / dm 2 Plating thickness: 0.50μm~4.4μm Processing time: Adjusted according to plating thickness

[0049] (vi) Sn film formation process In the Sn coating formation step, an Sn coating is formed on the surface of the substrate on which the Ni-containing layer and the Cu-containing layer have been formed as needed. Here, the Ag coating and the Sn coating can be formed in any order. That is, the Sn coating may be formed after the Ag coating, or the Ag coating may be formed after the Sn 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] The Ag coating and the Sn coating are preferably laminated so that the ratio of the Ag coating thickness to the Sn coating thickness is in the range of 5:3 to 7:1. That is, the ratio of the Sn coating thickness to the total thickness of the Ag coating and the Sn coating is preferably in the range of 0.125 to 0.375. By forming the Ag coating and the Sn coating 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 processing conditions used in the Sn film formation process is shown below.

[0051] [Example of plating solution composition and processing conditions in the Sn film formation process] Processing 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: 0.15μm~1.6μm Processing time: Adjusted according to plating thickness

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

[0053] The strain-introducing step is preferably performed at a processing rate of 5% or less, more preferably at a processing rate of 2% or more and 5% or less. In particular, by setting the processing rate at a processing rate of 2% or more in the strain-introducing step, the strain-introducing step can be performed at a processing rate of 2% or more, so that the strain-introducing step can be performed at a processing rate of 2% or more. <0001> On the other hand, if the processing rate in the strain-introducing step is too large, non-uniform deformation may occur inside the surface coating, so the processing rate in the strain-introducing step is preferably 5% or less.

[0054] It should be noted that the step of introducing strain into the surface coating may not be performed, and in this case, the processing rate of the step of introducing strain into the surface coating may be set to 0% for the sake of convenience in this specification.

[0055] (viii) Alloying treatment process After the strain-introducing step is performed as necessary, the Ag coating and the Sn coating are subjected to an alloying step of heat treatment to form an Ag—Sn-containing layer, in which unreacted Ag may remain in the Ag—Sn-containing layer.

[0056] The heating temperature for the heat treatment in the alloying treatment step is preferably in the range of 250° C. to 350° C. By heat treating the Ag coating and the Sn coating within this temperature range, the Ag coating and the Sn coating are alloyed and specific crystal grains having a hexagonal close-packed (hcp) structure grow, making it possible to form an Ag—Sn-containing layer in which the average crystal grain size of the specific crystal grains is large.

[0057] The heating time of the heat treatment in the alloying treatment step is preferably in the range of 1 hour to 10 hours. By performing the heat treatment at the above heating temperature for 1 hour or more in the alloying treatment step, specific crystal grains having a hexagonal close-packed (hcp) structure grow, and the average crystal grain size of the specific crystal grains can be made 1 μm or more. On the other hand, if the heat treatment is performed at the above heating temperature for more than 10 hours, copper (Cu) atoms contained in the base may diffuse to the surface layer of the electrical contact material, thereby impairing performance, so the heating time of the heat treatment at the above heating temperature is preferably 10 hours or less.

[0058] In the heat treatment of the alloying treatment step, it is preferable to change the heating time within the above range depending on the heating temperature.

[0059] The heat treatment in the alloying process is preferably carried out in a non-oxidizing atmosphere, more specifically, in an inert gas atmosphere or a reducing gas atmosphere. Here, inert gases such as N2, Ar, He, etc., or a mixed gas of two or more of these can be used. Furthermore, reducing gases such as H2, CO, CH4, etc., or a mixed gas of two or more of these, such as a mixed gas of H2 and CO, can be used. By carrying out the heat treatment in an inert gas atmosphere or a reducing gas atmosphere, oxidation of the metals constituting the substrate and each layer of the electrical contact material can be prevented.

[0060] (ix)Ag-containing layer formation process In the Ag-containing layer forming step, the adhesion of the Ag-containing layer is increased by strike plating on the surface of the Ag—Sn-containing layer formed in the alloying treatment step, and then the Ag-containing layer is formed by electroplating. An example of the liquid composition and processing conditions used in the Ag-containing layer forming step is shown below.

[0061] [Example of strike plating solution composition and processing conditions in the Ag-containing layer formation process] Processing solution: Aqueous solution containing 4 g / L of silver cyanide (I) and 80 g / L of free potassium cyanide Processing temperature: 30℃ Current density: 2A / dm 2 Processing time: 10 seconds

[0062] [Example of electroplating solution composition and processing conditions in the Ag-containing layer formation process] Processing solution: Aqueous solution containing 50 g / L of silver cyanide (I), 10 g / L of potassium carbonate, and 90 g / L of free potassium cyanide Processing temperature: 30℃ Current density: 1A / dm 2 Plating thickness: 0.05μm~4.4μm Processing time: Adjusted according to plating thickness

[0063] In this manner, an electrical contact material can be formed that includes specific crystal grains having a hexagonal close-packed (hcp) structure and that has an Ag—Sn-containing layer in which the average crystal grain size of the specific crystal grains is large. [Example]

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

[0065] [Invention Examples 1 to 10, Comparative Examples 1 to 3] A 0.15 mm thick H-type substrate made of C5210, a Cu-Sn-P based copper alloy, was prepared and pressed into a 20 cm x 10 cm plate. This substrate was then subjected to cathodic electrolytic degreasing and activation treatment as pretreatment.

[0066] Here, cathodic electrolytic degreasing is carried out by heating an aqueous solution of sodium hydroxide with a concentration of 60 g / L in an electrolytic cell as a degreasing solution, immersing the substrate in the degreasing solution heated to 60°C, connecting it to the anode of the electrolytic cell, and applying a current of 2.5 A / dm 2 The treatment was carried out by passing a current at a current density of 0.05 for 30 seconds.

[0067] The activation treatment was carried out by immersing the substrate after cathodic electrolytic degreasing in a 100 g / L aqueous sulfuric acid solution at 23° C. for 30 seconds.

[0068] Thereafter, a Ni-containing layer was formed on the front surface of the conductive substrate by electroplating under the following conditions: 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 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 was prepared as the electroplating solution, with a concentration of nickel (Ni) metal (atomic weight: 58.69) of approximately 107 g / L. Next, a substrate serving as a cathode electrode was placed in a plating electrolytic cell, and a pure Ni plate measuring 20 cm long and 10 cm wide serving as an anode electrode was placed opposite the front surface of the cathode electrode. 2 L of electroplating solution was poured into the cell, and the plating was conducted at a temperature of 55°C and a current of 10 A / dm 2 A Ni-containing layer having a thickness shown in Table 1 was formed by electroplating by passing a current through the electrode at a current density of 1000 kJ / cm2.

[0070] Next, for Invention Examples 3 to 9 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 Invention Examples 1, 2, and 10 and Comparative Examples 2 and 3, a Cu-containing layer was not formed on the substrate.

[0071] 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, with a copper (Cu) metal (atomic weight: 63.55) concentration of approximately 43 g / L, was prepared as the electroplating solution. Next, a substrate serving as a cathode electrode was placed in a plating electrolytic bath, and a phosphorus-deoxidized copper plate measuring 20 cm long and 10 cm wide was placed as an anode electrode facing the front surface of the cathode electrode. 2 L of the electroplating solution was poured into the bath, and the plating was conducted at a temperature of 50°C and a current of 1 A / dm 2 A Cu-containing layer having a thickness shown in Table 1 was formed by electroplating by passing a current through the electrode at a current density of 1000 kJ / cm2.

[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 containing 4 g / L of silver cyanide (I) (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, was prepared as the strike plating solution. Next, a substrate serving as a cathode electrode was placed in a plating electrolytic bath, and an insoluble plate measuring 20 cm in length and 10 cm in width serving as an anode electrode was placed opposite the front surface of the cathode electrode. 2 L of strike plating solution was then poured into the bath, and the temperature was 30°C and the current was 2 A / dm. 2 Strike plating was carried out by passing a current at a current density of 1000 kJ / min for 10 seconds.

[0074] After the strike plating, an Ag coating was formed by electroplating. An aqueous solution containing 50 g / L of silver cyanide (I) (AgCN, formula weight: 133.89 g / mol), 10 g / L of potassium carbonate, and 90 g / L of free potassium cyanide, with a silver (Ag) metal (atomic weight: 107.87) concentration of approximately 40 g / L, was prepared as the electroplating solution. Next, a substrate serving as a cathode electrode was placed in the electroplating bath, and a silver plate measuring 20 cm long and 10 cm wide was placed as an anode electrode facing the front surface of the cathode electrode (the side where the strike plating was performed). 2 L of electroplating solution was poured into the bath, and the plating was conducted at a temperature of 30°C and a current of 1 A / dm 2 An Ag coating was formed on the surface of the substrate by electroplating by passing a current through the substrate at a current density of 1000 kJ / cm2.

[0075] At this time, the Ag coating was formed in accordance with the thickness of the Ag-Sn containing layer listed in Table 1 so that the ratio of the thickness of the Ag coating to the total thickness of the Ag coating and the Sn coating was 75%.

[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 sulfate containing 40 g / L of tin(II) sulfate (SnSO4, formula weight: 214.77 g / mol), 60 g / L of sulfuric acid, 40 g / L of cresol sulfonic acid, and 2 g / L of gelatin was prepared as an electroplating solution, with a tin (Sn) metal (atomic weight: 118.71) concentration of approximately 22 g / L. Next, a substrate serving as a cathode electrode was placed in a plating electrolytic cell, and a tin plate measuring 20 cm long and 10 cm wide serving as an anode electrode was placed opposite the front surface of the cathode electrode. 2 L of electroplating solution was poured into the cell, and the plating was conducted at a temperature of 23°C and a current of 2 A / dm 2 A Sn film was formed on the Ag film by electroplating by passing a current through the electrode at a current density of 1000 kJ / cm2.

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

[0079] Thereafter, for Invention Examples 2 to 5, 7 to 10 and Comparative Examples 2 and 3, a strain-introducing step was carried out in which the formed Ag coating and Sn coating were subjected to rolling to impart strain to the surface coating. The working ratio in the strain-introducing step was set to the ratio shown in Table 1. Note that for Invention Examples 1 and 6 and Comparative Example 1, the strain-introducing step was not carried out, and therefore the working ratio was set to 0%.

[0080] The Ag coating and Sn coating after the strain-introducing process (for Invention Examples 1 and 6 and Comparative Example 1, the Ag coating and Sn coating without the strain-introducing process) were subjected to an alloying process in which heat treatment was performed at the heating temperature and for the heating time shown in Table 1, thereby forming an Ag-Sn-containing layer.

[0081] Next, for Inventive Examples 4, 5, and 8 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 Inventive Examples 1 to 3, 6, 7, 9, and 10 and Comparative Example 1, an Ag-containing layer was not formed on the substrate.

[0082] Here, when performing strike plating, an aqueous solution containing 4 g / L of silver cyanide (I) (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, was prepared as the strike plating solution. Next, a substrate serving as a cathode electrode was placed in a plating electrolytic bath, and an insoluble plate measuring 20 cm in length and 10 cm in width serving as an anode electrode was placed opposite the front surface of the cathode electrode. 2 L of strike plating solution was then poured into the bath, and the temperature was 30°C and the current was 2 A / dm. 2 Strike plating was carried out by passing a current at a current density of 1000 kJ / min for 10 seconds.

[0083] After the strike plating, an Ag coating was formed by electroplating. An aqueous solution containing 50 g / L of silver cyanide (I) (AgCN, formula weight: 133.89 g / mol), 10 g / L of potassium carbonate, and 90 g / L of free potassium cyanide, with a silver (Ag) metal (atomic weight: 107.87) concentration of approximately 40 g / L, was prepared as the electroplating solution. Next, a substrate serving as a cathode electrode was placed in the electroplating bath, and a silver plate measuring 20 cm long and 10 cm wide was placed as an anode electrode facing the front surface of the cathode electrode (the side where the strike plating was performed). 2 L of electroplating solution was poured into the bath, and the plating was conducted at a temperature of 30°C and a current of 1 A / dm 2 By passing a current at a current density of 1000 kJ / cm2, an Ag coating having a 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-mentioned examples and comparative examples were evaluated for the following characteristics. The evaluation conditions for each characteristic are as follows.

[0085] (Measurement of the thickness of each layer that makes up the surface coating) The thicknesses of the Ni-containing layer, Cu-containing layer, Ag-Sn-containing layer, and Ag-containing layer that make up the surface coating were measured by fluorescent X-ray analysis of the surface of each prepared sample in accordance with the fluorescent X-ray testing method of JIS H8501:1999. To confirm the thickness of each layer, the thickness was also measured by image analysis of a cross section including the thickness direction. The image analysis was performed in accordance with the scanning electron microscope testing method of JIS H8501:1999. The resulting thicknesses of each layer were as shown in Table 1.

[0086] (Measurement of the average grain size of specific 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 (OIM Analysis, manufactured by TSL) 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 had been polished using a cross-section polisher. The measurement area on the cross section was approximately 10 μm × 50 μm, with a step size of 0.02 μm.

[0087] Here, we performed orientation analysis using profiles of hexagonal close-packed crystalline phases, such as magnesium, from the crystal orientation data obtained by EBSD analysis, focusing on measurement points with a reliability index (CI) value of 0.1 or greater. For this analysis, we extracted only specific crystalline phases with hexagonal close-packed structures from the crystal orientation data to be analyzed. We then used a cutting method to calculate the average grain size of specific hexagonal close-packed crystalline phases, drawing a 50 μm line parallel to the surface of the Ag-Sn-containing layer and determining the average length of the line segment that overlaps the specific crystalline grain, bounded by both ends of the specific crystalline grain. The results are shown in Table 1.

[0088] (The specific grains in the Ag-Sn containing layer are in the direction parallel to the normal to the surface of the substrate. <0001> Measurement of the area ratio of oriented grains The crystal structure of the crystal grains contained in the Ag-Sn-containing layer was analyzed using the profile of a hexagonal close-packed crystalline phase such as magnesium, with the crystal orientation data obtained by the EBSD method described above being the measurement points where the reliability index CI value was 0.1 or more. At this time, only specific crystalline phases with a hexagonal close-packed structure were extracted as the crystal orientation data to be analyzed, and the area of ​​the specific crystalline phase that was the target of the orientation analysis was determined by dividing the area of ​​the specific crystalline phase that was parallel to the normal direction of the substrate surface. <0001> The area ratio of the oriented crystal grains was calculated, and the results are shown in Table 1.

[0089] (Evaluation of bending properties) The resulting electrical contact materials were subjected to a bending test in accordance with the Japan Copper and Brass Association's Technical Standard T307:2007 (Method for Evaluating the Bending Workability of Copper and Copper Alloy Thin Sheet Strips). The bent sections were observed using an SEM at 500x magnification. The bending properties of the observation results were evaluated based on the following criteria, with reference to the Japan Copper and Brass Association's Technical Standard T307:2007. More specifically, the bending properties of the electrical contact materials were evaluated by cutting two test pieces, each 30 mm long and 10 mm wide, with the rolling direction of the substrate aligned longitudinally. Each test piece was bent in the Goodway direction using a jig with a bending angle of 90° and a bending radius of 0.3 mm. When no cracks were observed in either test piece, the bending properties were evaluated as excellent and marked with a "Good." On the other hand, when cracks were observed in at least one test piece, the bending properties were evaluated as poor and marked with a "Poor." The results are shown in Table 1.

[0090] (Evaluation of abrasion resistance) The wear resistance of electrical contact materials was evaluated using a multi-function tribology evaluation machine (friction and wear tester) UMT TriboLab (manufactured by Bruker) in a sliding test in which the same material was slid over the surface of the resulting electrical contact material. The surface resistance was measured before and after 2000 sliding cycles. If the increase in resistance between before and after sliding the same material over the surface of the electrical contact material was 6 mΩ or less, the electrical contact material was evaluated as being particularly excellent in terms of high wear resistance, with a rating of "Excellent." If the increase in resistance between before and after sliding the same material over the surface of the electrical contact material was in the range of more than 6 mΩ and 10 mΩ or less, the electrical contact material was evaluated as being good in terms of high wear resistance, with a rating of "Good." On the other hand, if the increase in resistance between before and after sliding the same material over the surface of the electrical contact material was more than 10 mΩ, the electrical contact material was evaluated as not necessarily excellent in terms of wear resistance, with a rating of "Average." 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 air atmosphere under conditions simulating reflow. The contact resistance values ​​before and after heating were measured using an electrical contact simulator. Measurements were made using a contact resistance tester (manufactured by Yamazaki Seiki Kenkyusho Co., Ltd.). The load used when bringing the contact part into contact with the electrical contact material was 1 N. When the increase in contact resistance before and after heating was less than 5 mΩ, the change in electrical properties before and after heating was small and the material was evaluated as excellent in terms of high heat resistance, with a rating of "Good." When the increase in contact resistance before and after heating was 5 mΩ or more, the material was evaluated as not necessarily excellent in terms of heat resistance, with a rating of "Good." The results are shown in Table 2.

[0092] (Evaluation of surface coating adhesion) The resulting electrical contact materials were subjected to a tape peeling test according to JIS H 8504 to evaluate whether the surface coating had peeled off from the electrical contact material. More specifically, the tape peeling test was performed on samples in which a sharp blade was used to create a 2 mm square on the surface coating of the electrical contact material, reaching all the way to the conductive substrate. When no peeling of the surface coating was observed, the adhesion of the surface coating was evaluated as "Good." Furthermore, when partial peeling of the surface coating was observed, the adhesion of the surface coating was evaluated as not necessarily excellent, and was evaluated as "Poor." The results are shown in Table 2.

[0093] (Evaluation of solder wettability) The solder wettability of the resulting electrical contact materials was evaluated using the wetting balance method specified in JIS Z3198-4, Part 4: Testing Methods for Lead-Free Solder - Wetting Balance and Contact Angle Methods. The bath temperature was 245°C, and Sn-3Ag-0.1Cu solder was used. RMA-type flux was used. Materials with a measured zero-cross time (t0) of 2 seconds or less were evaluated as excellent in terms of solder wettability, with a rating of "Good." Materials with a measured zero-cross time (t0) of more than 2 seconds were evaluated as not necessarily excellent in terms of solder wettability, with a rating of "Fair." 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 have at least an Ag—Sn-containing layer formed on the surface of the substrate, and the Ag—Sn-containing layer contains specific crystal grains with a hexagonal close-packed (hcp) structure, and the average crystal grain size of these specific crystal grains is within the appropriate range of the present invention. In this case, the electrical contact materials of Examples 1 to 10 of the present invention were all evaluated as "good" in terms of bending properties.

[0097] In contrast, the electrical contact materials of Comparative Examples 1 to 3, in which the heating time for the heat treatment in the alloying process was less than 1 hour, had average crystal grain sizes of specific crystal grains that were smaller than the appropriate range of the present invention, and the evaluation results for bending properties were rated as ``X.''

[0098] Therefore, it was revealed that the electrical contact materials of Examples 1 to 10 of the present invention have an optimized average crystal grain size of specific crystal grains having a hexagonal close-packed (hcp) structure in the Ag-Sn-containing layer, and as a result, have high bending properties when used as electrical contacts for electrical and electronic components.

Claims

1. A material for electrical contacts having a substrate made of a conductive material and a surface coating formed on at least a portion of the substrate, The surface coating includes a Ni-containing layer containing Ni, an Ag—Sn-containing layer on the Ni-containing layer, the Ag—Sn-containing layer containing 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, and In the Ag-Sn-containing layer, when viewed in a cross section including the thickness direction of the material for electrical contacts, crystal grains having a <0001> orientation in a direction parallel to the normal direction of the surface of the base account for an area ratio of 20% or less of the total area of ​​the specific crystal grains.

2. 2. 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.

3. 2. 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 a thinner thickness than the Ag—Sn-containing layer.

4. An electric / electronic component having at least an electric contact formed using the material for electric contacts according to any one of claims 1 to 3.

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