JP2021075772A - Material for electric contact, its manufacturing method, connector terminal, connector, and electronic component - Google Patents

Abstract

To provide a material for an electric contact which has a low contact resistance value having a sufficient resistance level even when a high voltage and large current is applied, has a low dynamic friction coefficient, and is excellent in heat resistant adhesion after heating in heat treatment performed after laminating layers on a copper alloy base material, and to provide a method for manufacturing the same, a connector terminal, a connector and an electronic component.SOLUTION: A material for an electric contact of the present invention is characterized in that on at least one surface of a conductive base material comprising copper (Cu) as a main component, a base layer comprising at least a Ni-containing layer comprising nickel (Ni) as a main component and a surface layer comprising silver (Ag) and tin (Sn) as main components are provided, and the number of crystal grain boundaries (the number of interface grain boundaries) present at an interface formed between the surface layer and the base layer is in a range of 5 to 60 per 10 μm of an extension length of the interface, as seen in a cross section including a thickness direction of the material for an electric contact.SELECTED DRAWING: Figure 1

Description

The present invention relates to a material for electrical contacts, a method for manufacturing the same, a connector terminal, a connector, and an electronic component.

For consumer and automotive electronic components, for example, the connector terminals that make up the electrical contacts of the connector, on the surface of a conductive substrate containing copper (Cu) as the main component, such as brass, phosphorus bronze, and Corson alloy. Materials for electrical contacts are used, which are base-plated with nickel (Ni) or Cu, and further plated with tin (Sn) or Sn alloy.

In recent years, in order to achieve fuel saving, the electrification of vehicle drive systems has progressed, and for example, connection parts between a battery, an inverter, and a motor are required to withstand high voltage and large current, and Sn and Sn alloys have been required. There are an increasing number of cases where silver (Ag) or Ag alloy plating is used instead of the plating of.

On the other hand, in such an application, for the purpose of improving the assembleability of the vehicle, the connection portion, which has been conventionally bolted, is being replaced by the merging type connector. Therefore, the plating formed on the surface of the connector, particularly the connector terminal, is required to have a low contact resistance value and a low insertion force when the connector is fitted (connected). However, Ag plating has good compatibility with metal and easily causes agglomeration, so that the coefficient of kinetic friction tends to increase and the insertion force tends to increase.

For example, in Patent Document 1, a Ni layer (lower layer), an Ag layer (middle layer), an ε-AgSn layer (upper layer) and a Sn layer (outermost layer) are formed on a copper alloy base material, and have low whisker properties and low wear. Metallic materials for electronic components that have adhesive wear resistance and high durability are disclosed.

Japanese Unexamined Patent Publication No. 2014-29007

However, the metal material for electronic components described in Patent Document 1 has a Sn layer on the outermost layer and has a higher contact resistance value than the Ag layer, so that it is suitable for a connector that requires resistance to high voltage and large current. Is not applicable. Further, the metal material for electronic parts described in Patent Document 1 forms a Ni layer as a barrier layer (lower layer) between a copper alloy base material and an Ag layer (middle layer), and is a constituent metal of the copper alloy base material. Although measures have been taken to prevent (Cu) from diffusing into the upper layer, Ni, which is a constituent metal of the Ni layer, and Ag, which is a constituent metal of the Ag layer formed on the Ni layer, are composed of a compound. Since it is not formed, there is a problem that the adhesion strength after heating in the heat treatment applied after laminating and forming each layer on the copper alloy base material is low.

The present invention has been made in view of the above circumstances, and the composition of each layer including the base layer and the surface layer laminated on the conductive base material, and the grain boundaries existing at the interface between the base layer and the surface layer. By optimizing the number (number of interfacial grain boundaries), even when a high voltage and a large current are applied, it has a low contact resistance value with a sufficient resistance level, a low dynamic friction coefficient, and copper. An object of the present invention is to provide a material for electrical contacts having excellent heat-resistant adhesion after heating in a heat treatment performed after laminating and forming each layer on an alloy substrate, and a manufacturing method thereof, a connector terminal, a connector, and an electronic component. To do.

As a result of diligent studies to achieve the above-mentioned object, the present inventors have contained nickel (Ni) as a main component on at least one surface of a conductive base material containing copper (Cu) as a main component. A material for electrical contacts having a base layer containing at least a Ni-containing layer and a surface layer containing silver (Ag) and tin (Sn) as main components, in a cross section including the thickness direction of the material for electrical contacts. As seen, the number of crystal grain boundaries (number of interface grain boundaries) existing at the interface formed by the surface layer and the base layer is in the range of 5 to 60 per 10 μm of the extending length of the interface, so that the high voltage is obtained. Even when a large current is applied, it has a low contact resistance value with a sufficient resistance level, a low dynamic friction coefficient, and heating in the heat treatment performed after the lamination of each layer is formed on the copper alloy substrate. It is possible to provide a material for electrical contacts that is also excellent in heat resistance and adhesion later, and such an electrical contact material is a conductive base material containing Cu as a main component after being at least rolled. The surface of the material is dissolved and removed with an acid, and a Ni-containing layer containing Ni as a main component is formed on at least one surface of the conductive base material by plating so that the crystal particle size is 0.01 to 2.0 μm. Alternatively, a Ni-containing layer containing Ni as a main component is formed, and then a Cu-containing layer containing Cu as a main component is formed by plating so that the crystal particle size is 0.01 to 2.0 μm. After that, on the Ni-containing layer in the former case and on the Cu-containing layer in the latter case, a layer containing Ag as a main component and a layer containing Sn as a main component are laminated or formed in no particular order. , Ag and Sn as main components are laminated and formed, and then heat treatment is performed at a heating temperature of 231 to 900 ° C. to find that the product can be produced, and the present invention has been completed.

That is, the gist structure of the present invention is as follows.
(1) On at least one surface of a conductive base material containing copper (Cu) as a main component, a base layer containing at least a Ni-containing layer containing nickel (Ni) as a main component, and silver (Ag) and tin (Ag) and tin ( A material for electrical contacts having a surface layer containing Sn) as a main component, which exists at an interface formed by the surface layer and the base layer when viewed in a cross section including the thickness direction of the electrical contact material. A material for electrical contacts, wherein the number of crystal grain boundaries (the number of interfacial grain boundaries) is in the range of 5 to 60 per 10 μm of the extending length of the interface.
(2) The number of interfacial grain boundaries is larger than the number of crystal grain boundaries (number of surface grain boundaries) existing on the surface of the surface layer when viewed in a cross section including the thickness direction of the material for electrical contacts. The material for electrical contacts according to (1) above.
(3) In the above (2), the ratio of the number of interfacial grain boundaries to the number of surface grain boundaries (number of interfacial grain boundaries / number of surface grain boundaries) is in the range of 1.1 to 2.0. The material for electrical contacts described.
(4) The material for electrical contacts according to (1), (2) or (3) above, wherein the base layer is the Ni-containing layer.
(5) The base layer is composed of a two-layer laminate of the Ni-containing layer and a Cu-containing layer containing copper (Cu) as a main component formed on the Ni-containing layer. The material for electrical contacts according to (1), (2) or (3) above.
(6) When the surface layer is measured by the X-ray diffraction method, it is in the range of 2θ = 39.7 to 40.3 ° with respect to the total area of the X-ray intensities of all the peaks appearing in the range of 2θ = 38 to 41 °. The material for electrical contacts according to any one of (1) to (5) above, wherein the ratio of the area of the X-ray intensity of the appearing peak is 50% or more.
(7) A connector terminal using the material for electrical contacts according to any one of (1) to (6) above.
(8) A connector having the connector terminal according to (7) above.
(9) An electronic component having the connector according to (8) above.
(10) The method for producing an electrical contact material according to (4) above, wherein the conductive base material containing Cu as a main component is at least rolled, and then the surface of the conductive base material is coated. It is dissolved and removed with an acid, and a Ni-containing layer containing Ni as a main component is formed on at least one surface of the conductive base material by plating so that the crystal particle size is 0.01 to 2.0 μm. A layer containing Ag as a main component and a layer containing Sn as a main component are laminated in no particular order on the Ni-containing layer, or a layer containing Ag and Sn as a main component is laminated and then formed. A method for producing a material for electrical contacts, which comprises performing heat treatment at a heating temperature of 231 to 900 ° C.
(11) The method for producing an electrical contact material according to (5) above, wherein the conductive base material containing Cu as a main component is at least rolled, and then the surface of the conductive base material is subjected to at least rolling processing. It is dissolved and removed with an acid to form a Ni-containing layer containing Ni as a main component on at least one surface of the conductive substrate, and then a Cu-containing layer containing Cu as a main component is plated to have a crystal particle size of 0. It is formed to be 0.01 to 2.0 μm, and then a layer containing Ag as a main component and a layer containing Sn as a main component are laminated on the Cu layer in no particular order, or Ag and A method for producing a material for electrical contacts, which comprises laminating and forming a layer containing Sn as a main component, and then performing heat treatment at a heating temperature of 231 to 900 ° C.

According to the present invention, even when a high voltage and a large current are applied, it has a low contact resistance value having a sufficient resistance level, a low dynamic friction coefficient, and further, lamination of each layer on a copper alloy base material. It is possible to provide an electric contact material having excellent heat-resistant adhesion after heating in a heat treatment performed after formation, a method for manufacturing the same, a connector terminal, a connector, and an electronic component.

It is a schematic diagram of the cross section including the thickness direction of the material for electrical contacts of this invention. It is a schematic diagram for demonstrating the calculation method of the number of interfacial grain boundaries and the number of surface grain boundaries, and schematically shows the cross section including the thickness direction of the material 1 for electrical contact. This is an example of the X-ray diffraction pattern on the surface layer of the material for electrical contacts of the present invention. It is a schematic diagram of the cross section including the thickness direction of the modification of the material for electrical contacts of this invention.

Hereinafter, preferred embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

In the present invention, "containing M as a main component" (when M is one kind of metal element) means that the content of the metal element M in the total metal elements contained in the base material or each layer is 50 at% or more. It means that.

1. 1. Material for electrical contacts The material for electrical contacts of the present invention contains at least a Ni-containing layer containing nickel (Ni) as a main component on at least one surface of a conductive base material containing copper (Cu) as a main component. A material for electrical contacts having a stratum and a surface layer containing silver (Ag) and tin (Sn) as main components, and the surface layer and the base layer when viewed in a cross section including the thickness direction of the electrical contact material. The number of crystal grain boundaries (number of interfacial grain boundaries) existing at the interface formed by is in the range of 5 to 60 per 10 μm of the extending length of the interface.

(1) Material for Electrical Contact of One Embodiment FIG. 1 schematically shows a cross section including the thickness direction of the material for electrical contact of one embodiment. The material 1 for electrical contacts shown in FIG. 1 is a base layer 12 which is a Ni-containing layer containing nickel (Ni) as a main component on at least one surface of a conductive base material 11 containing copper (Cu) as a main component. , And a surface layer 13 containing silver (Ag) and tin (Sn) as main components. Then, when viewed in cross section (cross section as shown in FIG. 1) including the thickness direction of the electrical contact material 1, the interface formed by the surface layer 13 and the base layer 12 (Ni-containing layer in this embodiment). The number of crystal grain boundaries (number of interfacial grain boundaries) present in the interface is in the range of 5 to 60 per 10 μm of extending length of the interface.

Hereinafter, each part of the material for electrical contacts of the present invention will be described in detail.

(Conductive base material)
The conductive base material 11 contains copper as a main component.

Specifically, the conductive base material 11 is made of a copper-based material of (pure) copper or a copper alloy. The copper alloy is not particularly limited, but for example, Cu-Zn-based, Cu-Ni-Si-based, Cu-Sn-Ni-based, Cu-Cr-Mg-based, Cu-Ni-Si-Zn-Sn-Mg-based, etc. Can be mentioned.

The shape of the conductive base material 11 is not particularly limited and may be appropriately selected depending on the intended use, but is preferably a strip material or a plate material, and may be a bar material or a wire material.

The conductivity of the conductive base material 11 is not particularly limited, but is preferably 20% IACS or more, and more preferably 40% IACS or more. As a result, the conductive material as a whole can have excellent conductivity. Here, the conductivity (ICAS; International Annealed Copper Standard) can be determined by measuring in a constant temperature bath controlled at 20 ° C. (± 1 ° C.) using the four-terminal method.

(Underground layer)
In the electrical contact material 1 of the present embodiment, the base layer 12 is composed of a Ni-containing layer containing nickel (Ni) as a main component. The Ni-containing layer as the base layer 12 is an electricity generated by the diffusion of Cu in the conductive base material 11 into an adjacent layer (in the case of other embodiments described later, the Cu layer) such as the surface layer 13 described later. It is possible to prevent deterioration of the conductivity of the contact material 1.

Specifically, in the electrical contact material 1 of the present embodiment, the base layer 12 is made 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 type and Ni-Fe type.

The thickness of the base layer 12 is not particularly limited, but is preferably 0.1 to 3.0 μm, more preferably 0.3 to 2.0 μm, for example. The method of calculating the thickness of the base layer will be described later.

Even if a cobalt (Co) -containing layer or an iron (Fe) -containing layer is used as the base layer 12 instead of the Ni-containing layer made of a nickel-based material, the same effect as that of the Ni-containing layer can be obtained. ..

(surface)
The surface layer 13 contains silver (Ag) and tin (Sn) as main components. In addition, "containing silver (Ag) and tin (Sn) as main components" means that the content of silver in the total metal elements contained in the surface layer 13 is 40 at% or more and the content of tin is 10 at%. It means that the total content of silver and tin is 50 at% or more.

The surface layer 13 has a large number of granular precipitates. Then, in the surface layer 13, the number of crystal grain boundaries existing at the interface formed by the surface layer 13 and the base layer 12 (the number of interface grain boundaries) when viewed in cross section including the thickness direction of the electrical contact material 1. However, the range is 5 to 60 per 10 μm of the extending length of the interface. As a result, the material 1 for electrical contacts has a low coefficient of dynamic friction and exhibits excellent bending workability.

Further, in the surface layer 13, the number of interfacial grain boundaries is larger than the number of crystal grain boundaries (number of surface grain boundaries) existing on the surface of the surface layer 13 when viewed in a cross section including the thickness direction of the material for electrical contacts. That is, the ratio of the number of interfacial grain boundaries to the number of surface grain boundaries (number of interfacial grain boundaries / number of surface grain boundaries) is preferably more than 1, and more preferably 1.1 to 2.0.

Hereinafter, the calculation method of the number of interfacial grain boundaries and the number of surface grain boundaries will be described in detail with reference to the drawings. FIG. 2 is a schematic view for explaining a method of calculating the number of interfacial grain boundaries and the number of surface grain boundaries, and schematically shows a cross section including the thickness direction of the material 1 for electrical contacts. As shown in FIG. 2, a large number of grain boundaries 131 are present inside the surface layer 13. Of these, the portion indicated by “⊚” indicates the crystal grain boundary existing at the interface formed by the surface layer 13 and the base layer 12. Therefore, in the example of the schematic diagram of FIG. 2, the number of interfacial grain boundaries is 5 per 10 μm of the extending length of the interface. On the other hand, the portion indicated by "○" indicates the grain boundary existing on the surface of the surface layer. Therefore, in the example of the schematic diagram of FIG. 2, the number of surface grain boundaries is 6 per 10 μm of the extending length of the interface.

Further, the surface layer 13 is in the range of 2θ = 39.7 to 40.3 ° with respect to the total area of the X-ray intensities of all the peaks appearing in the range of 2θ = 38 to 41 ° when measured by the X-ray diffraction method. The ratio of the area of the X-ray intensity of the appearing peak is preferably 50% or more.

FIG. 3 is an example of an X-ray diffraction pattern of the surface layer (surface) of the material for electrical contacts of the present embodiment. Among the compounds containing silver (Ag) and tin (Sn) as main components, the compound showing a peak in the range of 2θ = 39.7 to 40.3 ° is ζ-AgSn. _{On the other hand, peaks of other compounds such as Ag 3} Sn (ε-AgSn) also appear in the range of 2θ = 38 to 41 °. Therefore, when the surface layer 13 is measured by the X-ray diffraction method, it appears in the range of 2θ = 39.7 to 40.3 ° with respect to the total area of the X-ray intensities of all the peaks appearing in the range of 2θ = 38 to 41 °. When the ratio of the area of the peak X-ray intensity is 50% or more, it means that the surface layer 13 has a specific amount or more of the ζ-AgSn phase. Here, ζ-AgSn is an intermetallic compound of Ag and Sn whose main component is _{Ag 4} Sn, in which the atomic number ratio (Sn / Ag) of Sn to Ag is in the range of 0.13 to 0.30. Means the phase of. Since ζ-AgSn has a high hardness, the coefficient of kinetic friction can be reduced by forming the surface of the surface layer 13 with ζ-AgSn. Further, since ζ-AgSn is excellent in conductivity, the contact resistance can be lowered. Further, in ζ-AgSn, since Cu existing in the base layer is hard to diffuse inside even when heated, the Cu diffuses to the surface of the surface layer, and the decrease in conductivity caused by contacting with the outside air and oxidizing is reduced. It can be suppressed.

The ratio of the area of the X-ray intensity of the peak appearing in the range of 2θ = 39.7 to 40.3 ° to the total area of the X-ray intensity of all the peaks appearing in the range of 2θ = 38 to 41 ° is 50%. The above is not particularly limited, but is preferably 60% or more, more preferably 70% or more, and further preferably 75% or more.

The atomic number ratio (Sn / Ag) of Sn to Ag of the compound showing a peak in the range of 2θ = 39.7 to 40.3 ° in the surface layer 13 is not particularly limited, but is 0.15 to 0. It is preferably 28, more preferably 0.20 to 0.27, further preferably 0.22 to 0.26, and particularly preferably 0.245 to 0.255.

In one embodiment, the compound showing a peak in the range of 2θ = 39.7 to 40.3 ° is preferably _{Ag 4 Sn.} The _{higher the content of Ag 4} Sn, the lower the contact resistance and the coefficient of dynamic friction, and it is useful as a material for electrical contacts.

The thickness of the surface layer 13 is not particularly limited, but is preferably 0.1 to 30.0 μm, more preferably 0.5 to 10.0 μm, and 1.0 to 5.0 μm, for example. Is even more preferable. When the surface layer 13 has such a thickness, it has more excellent conductivity and exhibits excellent bending workability. The method of calculating the thickness of the surface layer 13 will be described later.

(2) Material for Electrical Contact of Other Embodiments FIG. 4 schematically shows a cross section including the thickness direction of the material for electrical contact of another embodiment. The material 1A for electrical contacts shown in FIG. 4 is a base layer 12A which is a Ni layer containing nickel (Ni) as a main component on at least one surface of a conductive base material 11A containing copper (Cu) as a main component. It also has a surface layer 13A containing silver (Ag) and tin (Sn) as main components. Of these, the base layer 12A is different from the material 1 for electrical contacts shown in FIG. 1, and specifically, the base layer 12A is mainly composed of a Ni-containing layer 121A and copper (Cu) formed on the Ni-containing layer. It is composed of a two-layer laminate with a Cu-containing layer 122A contained as a component.

In the electrical contact material 1A of this embodiment, the conductive base material 11A and the surface layer 13A are the same as the conductive base material 11 and the surface layer 13 of the electrical contact material 1 described above, and thus the description thereof will be omitted below. However, only the base layer 12A will be described.

(Underground layer of other embodiments)
The base layer 12A is composed of a two-layer laminate of a Ni-containing layer 121A and a Cu-containing layer 122A formed on the Ni-containing layer and containing copper (Cu) as a main component. That is, the Cu-containing layer 122A exists between the Ni-containing layer 121A and the surface layer 13A, and further improves the adhesion between them.

Since it has such a configuration, the number of interfacial grain boundaries in the electrical contact material 1A of this embodiment means the number of crystal grain boundaries existing at the interface between the surface layer 13A and the Cu-containing layer 122A.

Specifically, the Cu-containing layer 122A is made of a copper-based material such as metallic copper or a copper alloy. The copper alloy is not particularly limited, and examples thereof include Cu—Zn type.

The thickness of the Cu-containing layer 122A is not particularly limited, but is preferably 0.01 to 1.0 μm, more preferably 0.03 to 0.5 μm, for example. The method of calculating the thickness of the Cu-containing layer 122A will be described later.

The electrical contact materials 1, 1A configured as described above have a low contact resistance value having a sufficient resistance level, a low dynamic friction coefficient, and copper even when a high voltage and a large current are applied. It also has excellent heat-resistant adhesion after heating in the heat treatment performed after laminating and forming each layer on the alloy base material. Then, such an electric contact material can be used for the connector terminal. Since such a connector terminal has a low coefficient of dynamic friction on the surface and a low insertion force, it can be used for a connector that improves assembleability of a vehicle or the like. Further, such a connector can be used for various electronic components. In the present invention, each layer laminated on the conductive base material may be formed on at least one surface of the conductive base material. For example, the formation of each layer laminated on the conductive base material may be provided at the electrical contact portion that is electrically connected by sliding contact with the terminal of the mating connector at the time of connecting (fitting) the connector. Often, it can be formed on one or both sides of a conductive substrate.

3. 3. Method for manufacturing electric contact material The method for manufacturing an electric contact material of the present invention is the above-mentioned method for manufacturing an electric contact material, in which at least a conductive base material containing Cu as a main component is rolled. After that, the surface of the conductive base material is dissolved and removed with an acid, and a Ni-containing layer containing Ni as a main component is plated on at least one surface of the conductive base material to have a crystal particle size of 0.01 to 2.0 μm. A Ni-containing layer containing Ni as a main component is formed, and then a Cu-containing layer containing Cu as a main component is plated to have a crystal grain size of 0.01 to 2.0 μm. After that, on the Ni-containing layer in the former case and on the Cu-containing layer in the latter case, a layer containing Ag as a main component and a layer containing Sn as a main component are formed in no particular order. It is characterized in that it is laminated or formed by laminating a layer containing Ag and Sn as main components, and then heat-treated at a heating temperature of 231 to 900 ° C. The heat treatment may be performed at, for example, 200 to 700 ° C. after the rolling process and before the dissolution and removal of the surface of the conductive substrate.

More specifically, a method for manufacturing a material for electrical contacts will be described. First, the conductive substrate is at least rolled. Rolling produces a work-altered layer on its surface. Since this processed altered layer has very fine crystal grains (processed altered layer), if it is present on the surface, the crystal grain size of each plating layer cannot be adjusted, and the adhesion between the layers is reduced. Sometimes. Therefore, in order to remove this processed altered layer, an acid treatment is performed to dissolve and remove the layer. Next, a Ni-containing layer containing Ni as a main component is laminated or formed on the conductive substrate thus obtained by plating, or a Ni-containing layer containing Ni as a main component and Cu are formed. The Cu-containing layer contained as the main component is laminated and formed in this order. In the following, the Ni-containing layer alone or the two layers of the Ni-containing layer and the Cu-containing layer may be referred to as a "base layer". At this time, these layers are formed so that the crystal grain size of the Ni-containing layer in the former case and the Cu-containing layer in the latter case is 0.01 to 2.0 μm. Specifically, as a control method of the crystal grain system, it is controlled by the temperature at the time of plating, the current density, and the like. By setting the crystal grain size of the Ni-containing layer or the Cu-containing layer to 0.01 to 2.0 μm, the crystal grain size at the interface of the surface layer formed immediately above the Ni-containing layer is similarly 0.01 to 2.0 μm, and Ni It is possible to obtain a material in which 5 to 60 crystal grain boundaries are present per 10 μm of the line segment formed by the containing layer or the interface between the Cu-containing layer and the surface layer.

After that, a layer containing Ag as a main component and a layer containing Sn as a main component are laminated in no particular order on a Ni-containing layer in the former case and on a Cu-containing layer in the latter case (that is,). , After forming a layer containing Ag as a main component, a layer containing Sn as a main component is formed, or a layer containing Sn as a main component is formed and then a layer containing Ag as a main component. , Or a layer containing Ag and Sn as main components (for example, Ag—Sn eutectoid layer) is laminated. Next, heat treatment is performed at 231 ° C. (melting point of Sn) to 900 ° C. After that, it is cooled to obtain a material for electrical contacts.

The plating method for forming each layer is not particularly limited, and for example, wet plating such as electrolytic plating and electroless plating, and dry plating such as vapor deposition and sputtering can be used. Among these, wet plating is preferably used, and electrolytic plating is more preferable. At this time, the plating conditions may be appropriately adjusted according to the plating method, the type and thickness of the plating layer, the temperature and holding time of the subsequent heat treatment, and the like.

When the layer containing Ag as the main component and the layer containing Sn as the main component are formed as different layers, the thickness of the layer containing Ag as the main component is relative to the thickness of the layer containing Sn as the main component. The ratio (Ag / Sn) of is preferably 2.1 to 7.0, and more preferably 2.8 to 5.0. When such a ratio is 2.1 to 7.0, it becomes easy to obtain a surface layer having 5 to 60 grain boundaries per 10 μm of the line segment formed by the interface with the adjacent layer. The material for electrical contacts has a low contact resistance and a coefficient of dynamic friction, and is excellent.

The heat treatment performed after laminating and forming each of the above layers on the conductive substrate may have a heating temperature of 231 ° C. (melting point of tin) to 900 ° C., particularly preferably 250 to 700 ° C.

The heat treatment preferably has a heating time of 5 seconds or more and 8 hours or less. In the heat treatment, it is preferable to change the heating time within the above range depending on the heating temperature. Specifically, for example, at 250 ° C., it is preferably 10 minutes or more and 3 hours or less, and at 700 ° C., it is preferably 5 seconds or more and 10 minutes or less.

The heat treatment is preferably carried out in an inert gas atmosphere or a reducing gas atmosphere. Specifically, as the inert gas, N ₂ , Ar, He or the like can be used. Further, as the reducing gas, H ₂ , CO, CH ₄ , H ₂ + CO and the like can be used. Oxidation of the metal in each layer can be prevented by performing the heat treatment in an atmosphere of an inert gas or an atmosphere of a reducing gas.

Next, in order to further clarify the effect of the present invention, Examples and Comparative Examples will be described, but the present invention is not limited to these Examples.

Samples of Examples 1 to 48 were prepared by any of the following production methods A to F. In addition, the samples of Comparative Examples 1 to 8 were prepared by any of the following production methods GM. The prepared samples were evaluated for their structure and characteristics, and are shown in Table 1 together with their production conditions.

(Measurement of thickness of Ag layer, Sn layer, Ni layer and Cu layer)
According to the fluorescent X-ray test method of JIS H8501: 1999, fluorescent X-ray analysis was performed from the surface of each prepared sample for measurement. In addition, in order to confirm the thickness of each layer, the thickness of the cross section was also measured by an image analysis method. The image analysis method was performed according to the scanning electron microscope test method of JIS H8501: 1999.

(Measurement of Ag-Sn eutectoid layer and surface layer thickness)
It was measured by the electrolytic test method of JIS H8501: 1999. Further, the thickness was measured by the image analysis method in the same manner as the measurement of the thickness of the Ag layer, Sn layer, Ni layer and Cu layer.

(Number of interfacial grain boundaries, number of surface grain boundaries)
The cross section of each of the prepared samples was observed with a scanning electron microscope, the number of interfacial grain boundaries and the number of surface grain boundaries at 10 locations were measured according to the method described above using FIG. 2, and the arithmetic mean was calculated. The average values of these 10 locations are referred to as "interfacial grain boundary number" and "surface grain boundary number", respectively. In addition, the number of interfacial grain boundaries / the number of surface grain boundaries was calculated based on the measured number of interfacial grain boundaries (average of 10 locations) and the number of surface grain boundaries.

(Measurement method of the ratio of peak X-ray intensity area)
The surface of the surface layer of each sample is analyzed by X-ray diffraction method, and 2θ = 39.7 to 40.3 ° with respect to the total area of X-ray intensities of all peaks appearing in the range of 2θ = 38 to 41 °. The ratio of the area of the X-ray intensity of the peak appearing in the range of was calculated. The X-ray diffraction measurement was performed under the following conditions.
Sample size: 15 mm x 15 mm
Measuring device: Rigaku Co., Ltd. Geigerflex RAD-A
Number of N: n = 10

(Measuring method of average particle size (crystal particle size) of granular precipitate)
The surface of the sample was observed with a scanning electron microscope, and the average particle size was determined by the section method. Specifically, it is set so that 20 or more (400 or more in total) granular precipitates are contained in each of the vertical and horizontal sides in the rectangular viewing range, and a diagonal line is drawn in this state, and the drawn diagonal line passes through the grain size. The number of precipitates was measured, and the average particle size (crystal grain size) of the granular precipitates was calculated by dividing the diagonal length by the number of the measured granular precipitates.

(Measurement of contact resistance value)
The contact resistance between the conductive material (each sample) and the Ag surface coating overhanging material (oxygen-free copper C1020 having an Ag layer with a film thickness of 3 μm on the surface layer, the radius of curvature of the overhanging portion is 5 mm) is controlled by the four-terminal method. It was obtained by measuring with. A 6220 type DC current source manufactured by TFF Caseley Instruments Co., Ltd. was used as the DC current source, and a current measuring device (2182A type nanovolt meter manufactured by the same company) was used to measure the electrical resistance. The contact resistance values at any five points were measured, the average value (n = 5) was calculated for each, and the evaluation was performed according to the following criteria.
⊚: less than 10 mΩ 〇: 10 mΩ or more and less than 20 mΩ ×: 20 mΩ or more

(Measurement of dynamic friction coefficient)
Using a surface measuring machine (manufactured by Shinto Kagaku Co., Ltd., TYPE: 14), the surface on which the surface layer of each sample was formed was subjected to an Ag surface coating overhanging material (an oxygen-free copper C1020 having an Ag layer having a film thickness of 3 μm on the surface layer). , The radius of curvature of the overhanging part is 5 mm), the moving speed is 100 mm / min, the sliding distance is 5 mm, the contact load is 5 N, the conductive material is slid back and forth 15 times, and the numerical value at the 15th sliding is dynamic friction. It was measured as a coefficient and evaluated according to the following criteria.
⊚: less than 0.5 〇: 0.5 or more and less than 0.8 ×: 0.8 or more

(Heat resistance test)
Each sample was heated at 150 ° C. for 1000 hours in an air atmosphere. After heating, the contact resistance value after heating was determined according to the method for measuring the contact resistance value. The evaluation criteria were the same. The heat-resistant adhesion measured after heating was evaluated according to the following criteria by performing a tape test method according to JIS H 8504: 1999.
⊚: When the tape peeling test was performed on each sample after heating at 150 ° C. for 1000 hours and the plating on the surface layer, etc. did not peel off. ×: When the tape peeling test was performed on each sample after heating at 150 ° C. for 1000 hours, the surface layer, etc. When the plating is peeled off

[Examples 1 to 8: Manufacturing method A]
After rolling and heat treatment, oxygen-free copper C1020 whose surface processing alteration layer has been removed with acid is electrolytically degreased and acid-cleaned, then nickel-plated in a sulfamic acid bath, copper-plated in a copper sulfate bath, and silver in an alkaline cyanide silver bath. Plating and tin plating in a tin sulfate bath were performed in this order so as to have a predetermined thickness. Then, in an atmosphere of an inert gas or a reducing gas, the silver plating and the tin plating are alloyed by heating in a heat treatment furnace at a set temperature of 250 to 300 ° C. for 10 minutes to 8 hours, and then cooled to form a surface layer. Ag—Sn alloy layer was formed.

[Examples 9 to 16: Manufacturing method B]
After rolling and heat treatment, copper alloy strips from which the surface processing alteration layer has been removed with acid are electrolytically degreased and acid-cleaned, then nickel-plated in a sulfamic acid bath, copper-plated in a copper sulfate bath, and silver-plated in an alkali cyan silver bath. , Tin plating was performed in this order in a tin sulfate bath so as to have a predetermined thickness. Then, in an atmosphere of an inert gas or a reducing gas, the silver plating and the tin plating are alloyed by heating in a heat treatment furnace at a set temperature of 300 to 700 ° C. for 5 to 600 seconds, and then cooled to form a surface layer. Ag—Sn alloy layer was formed.

[Examples 17 to 24: Manufacturing method C]
After rolling and heat treatment, oxygen-free copper C1020 whose surface processing alteration layer has been removed with acid is electrolytically degreased and acid-cleaned, then nickel-plated in a sulfamic acid bath, silver-plated in an alkali cyan-silver bath, and in a tin sulfate bath. Tin plating was applied in this order so as to have a predetermined thickness. Then, in an atmosphere of an inert gas or a reducing gas, the silver plating and the tin plating are alloyed by heating in a heat treatment furnace at a set temperature of 250 to 300 ° C. for 10 minutes to 8 hours, and then cooled to form a surface layer. Ag—Sn alloy layer was formed.

[Examples 25 to 32: Manufacturing method D]
After rolling and heat treatment, copper alloy strips from which the surface processing alteration layer has been removed with acid are electrolytically degreased and acid-cleaned, then nickel-plated in a sulfamic acid bath, silver-plated in an alkaline cyanide silver bath, and tin in a tin sulfate bath. Plating was performed in this order so as to have a predetermined thickness. Then, in an atmosphere of an inert gas or a reducing gas, the silver plating and the tin plating are alloyed by heating in a heat treatment furnace at a set temperature of 300 to 700 ° C. for 5 to 600 seconds, and then cooled to form a surface layer. Ag—Sn alloy layer was formed.

[Examples 33 to 40: Manufacturing method E]
After rolling and heat treatment, copper alloy strips from which the surface processing alteration layer has been removed with acid are electrolytically degreased and acid-cleaned, and then nickel-phosphorus alloy plating, copper-zinc alloy plating in a copper cyanide-zinc bath, and alkali cyan. Silver plating was performed in a silver bath and tin plating was performed in a tin sulfate bath in this order so as to have a predetermined thickness. Then, in an atmosphere of an inert gas or a reducing gas, the silver plating and the tin plating are alloyed by heating in a heat treatment furnace at a set temperature of 300 to 700 ° C. for 5 to 600 seconds, and then cooled to form a surface layer. Ag—Sn alloy layer was formed.

[Examples 41 to 48: Manufacturing method F]
Oxygen-free copper C1020, which has been rolled and heat-treated and has its surface processed and altered layer removed by acid, is electrolytically degreased and acid-cleaned, then nickel-plated in a sulfamic acid bath, copper-plated in a copper sulfate bath, and co-deposited with silver and tin. Plating was performed in this order so as to have a predetermined thickness. No heat treatment was performed.

[Comparative Example 1: Manufacturing Method G]
After electrolytic degreasing and acid cleaning of oxygen-free copper C1020, silver plating was performed in an alkaline cyanide silver bath and tin plating was performed in a tin sulfate bath in this order so as to have a predetermined thickness. Then, in a heat treatment furnace having a set temperature of 250 ° C. under a reducing gas atmosphere, the mixture was heated for 60 minutes and then cooled. Nickel plating and copper plating are not formed.

[Comparative Example 2: Manufacturing Method H]
After electrolytic degreasing and acid cleaning of oxygen-free copper C1020, nickel plating was performed in a sulfamic acid bath, silver plating in an alkaline cyanide silver bath, and tin plating in a tin sulfate bath in this order so as to have a predetermined thickness. Then, in a heat treatment furnace having a set temperature of 250 ° C. under a reducing gas atmosphere, the mixture was heated for 60 minutes and then cooled. No copper plating is formed.

[Comparative Example 3: Manufacturing Method I]
After electrolytic degreasing and acid cleaning of oxygen-free copper C1020, nickel plating is performed in a sulfamic acid bath and tin plating is performed in a tin sulfate bath in this order to a predetermined thickness, and then the set temperature is 400 under a reducing gas atmosphere. It was heated in a heat treatment furnace at ° C. for 20 seconds and then cooled. No copper plating or Ag plating is formed.

[Comparative Example 4: Manufacturing Method J]
After electrolytic degreasing and acid cleaning of oxygen-free copper C1020, nickel plating was performed in a sulfamic acid bath, copper plating in a copper sulfate bath, and silver plating in an alkali cyan silver bath in this order so as to have a predetermined thickness. Sn plating was not formed and no heat treatment was performed.

[Comparative Examples 5 to 6: Manufacturing Method K]
After electrolytic degreasing and acid cleaning of oxygen-free copper C1020, nickel plating is performed in a sulfamic acid bath, copper plating is performed in a copper sulfate bath, silver plating is performed in an alkali cyan silver bath, and tin plating is performed in a tin sulfate bath in this order. After that, the plating was carried out in an inert gas atmosphere in a heat treatment furnace in which the set temperature was set to a low temperature of 200 ° C. for 60 seconds and then cooled.

[Comparative Example 7: Manufacturing Method L]
After electrolytic degreasing and acid cleaning of oxygen-free copper C1020, nickel plating is performed in a sulfamic acid bath, copper plating is performed in a copper sulfate bath, silver plating is performed in an alkali cyan silver bath, and tin plating is performed in a tin sulfate bath in this order. After the plating, the plating was performed in an inert gas atmosphere in a heat treatment furnace in which the set temperature was set to a low temperature of 200 ° C. for 60 minutes and then cooled.

[Comparative Example 8: Manufacturing Method M]
After electrolytic degreasing and acid cleaning of oxygen-free copper C1020, nickel plating is performed in a sulfamic acid bath, copper plating is performed in a copper sulfate bath, silver plating is performed in an alkali cyan silver bath, and tin plating is performed in a tin sulfate bath in this order. After the plating was performed so as to be the same, the plating was cooled for 20 seconds in a heat treatment furnace in which the set temperature was set to a low temperature of 200 ° C. in an inert gas atmosphere.

As can be seen from Table 1 above, the samples of Examples 1 to 48 had a low contact resistance value and a dynamic friction coefficient, and also had excellent heat-resistant adhesion after heating in the heat treatment. In addition, in the samples of Examples 1 to 48, the contact resistance after heating was not different from the contact resistance before heating, and remained low.

On the other hand, the sample of Comparative Example 1 in which the surface of the conductive base material was not dissolved and removed by acid had a processed alteration layer remaining and did not have a Ni layer (base layer), and had contact resistance after heating. Was high, and the heat resistance and adhesion were inferior.

The sample of Comparative Example 2 in which the surface of the conductive substrate was not dissolved and removed by an acid had 97 interfacial grain boundaries, had high contact resistance after heat treatment, and was inferior in heat adhesion.

The sample of Comparative Example 3 in which the surface of the conductive base material was not dissolved and removed by acid and the surface layer was formed only by tin (Sn) had 68 interfacial grain boundaries, and any contact before or after heat treatment was performed. The resistance was high and the heat resistance was inferior.

The sample of Comparative Example 4 in which the surface of the conductive base material was not dissolved and removed by an acid, the surface layer was formed only of silver (Ag), and the heat treatment was not performed in the manufacturing process thereof, had a number of interfacial grain boundaries. It was 78, the coefficient of dynamic friction was high, and the contact resistance after heating was high.

The samples of Comparative Examples 5 to 8 in which the surface of the conductive substrate was not dissolved and removed by an acid had 73 interfacial grain boundaries per 10 μm of the line segment formed by the interface between the surface layer and the adjacent layer in the surface layer. The number was 97, 91, and 80, and it was found that the contact resistance was high before and after the heat treatment. In addition, the dynamic friction coefficient was also high in the samples of Comparative Examples 6 to 7.

1,1A Materials for electrical contacts 11, 11A Conductive base materials 12, 12A Base layer 121A Ni layer 122A Cu layer 13, 13A Surface layer 131 Grain boundaries

Claims (11)

On at least one side of a conductive substrate containing copper (Cu) as the main component,
A material for electrical contacts having a base layer containing at least a Ni-containing layer containing nickel (Ni) as a main component and a surface layer containing silver (Ag) and tin (Sn) as main components.
The number of crystal grain boundaries (the number of interface grain boundaries) existing at the interface formed by the surface layer and the base layer when viewed in a cross section including the thickness direction of the material for electrical contacts is the extending length of the interface. A material for electrical contacts, characterized in that the range is 5 to 60 per 10 μm. A claim characterized in that the number of interfacial grain boundaries is larger than the number of crystal grain boundaries (number of surface grain boundaries) existing on the surface of the surface layer when viewed in a cross section including the thickness direction of the material for electrical contacts. Item 2. The material for electrical contacts according to item 1. The electrical contact according to claim 2, wherein the ratio of the number of interfacial grain boundaries to the number of surface grain boundaries (number of interfacial grain boundaries / number of surface grain boundaries) is in the range of 1.1 to 2.0. Material for. The material for electrical contacts according to claim 1, 2 or 3, wherein the base layer is the Ni-containing layer. The base layer is characterized by being composed of a two-layer laminate of the Ni-containing layer and a Cu-containing layer containing copper (Cu) as a main component formed on the Ni-containing layer. The material for electrical contacts according to claim 1, 2 or 3. When the surface layer is measured by the X-ray diffraction method, the peaks appearing in the range of 2θ = 39.7 to 40.3 ° with respect to the total area of the X-ray intensities of all the peaks appearing in the range of 2θ = 38 to 41 °. The material for electrical contacts according to any one of claims 1 to 5, wherein the ratio of the area of the X-ray intensity is 50% or more. A connector terminal using the material for electrical contacts according to any one of claims 1 to 6. A connector having the connector terminal according to claim 7. An electronic component having the connector according to claim 8. The method for manufacturing the material for electrical contacts according to claim 4.
After at least rolling the conductive base material containing Cu as a main component, the surface of the conductive base material is dissolved and removed with an acid, and at least one surface of the conductive base material contains Ni as a main component. The Ni-containing layer to be rolled is formed by plating so that the crystal particle size is 0.01 to 2.0 μm, and then a layer containing Ag as a main component and Sn as a main component are contained on the Ni-containing layer. Manufacture of a material for electrical contacts, characterized in that the layers are laminated in no particular order, or layers containing Ag and Sn as main components are laminated and then heat-treated at a heating temperature of 231 to 900 ° C. Method. The method for manufacturing the material for electrical contacts according to claim 5.
After at least rolling the conductive base material containing Cu as a main component, the surface of the conductive base material is dissolved and removed with an acid, and at least one surface of the conductive base material contains Ni as a main component. Then, a Cu-containing layer containing Cu as a main component is formed by plating so that the crystal particle size is 0.01 to 2.0 μm, and then, on the Cu-containing layer, A layer containing Ag and Sn as a main component and a layer containing Sn as a main component are laminated in no particular order, or a layer containing Ag and Sn as a main component is laminated and then heated at 231 to 900 ° C. A method for producing a material for electrical contacts, which comprises performing heat treatment at a temperature.

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