JP2021025086A - Terminal material for connector, and connector terminal - Google Patents

Abstract

To provide a terminal material for a connector, capable of enhancing adhesion of a silver tin alloy-plating layer to improve abrasion resistance and heat resistance, and to provide a connector terminal.SOLUTION: A terminal material for a connector includes: a base material, at least a surface of which consists of copper or a copper alloy; a nickel plating layer formed on a surface of the base material; an intermediate plating layer formed on the nickel plating layer; and a silver tin alloy-plating layer formed on the intermediate plating layer, wherein the intermediate plating layer comprises 90 mass% or more of one of Cu, Pd, Co, and Mn, the film thickness of the intermediate plating layer is 0.02 μm or more, the silver tin alloy-plating layer contains Ag in a range of 70 at.% or more and 85 at.% or less and mainly comprises a silver tin-based intermetallic compound, and the film thickness of the silver tin-plating layer is 0.5 μm or more and 5 μm or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a connector terminal material and a connector terminal provided with a useful film used for connecting electrical wiring of automobiles, consumer devices, etc. in which fine sliding occurs.

Conventionally, connectors used for connecting electrical wiring of automobiles and the like are known. A contact piece provided on the female terminal is electrically connected to the vehicle-mounted connector (vehicle-mounted terminal) by contacting the male terminal inserted in the female terminal with a predetermined contact pressure. Those with a pair of terminals designed to be used are used. As such a connector (terminal), a tin-plated terminal in which a copper or copper alloy plate is tin-plated and reflowed is generally used. However, in recent years, with the increase in current and voltage of automobiles, the use of precious metal-plated terminals having excellent heat resistance and wear resistance, which can pass a larger current, is increasing.

As plating for in-vehicle terminals that are required to have such heat resistance and wear resistance, for example, there is a method of applying silver plating to the terminals as described in Patent Document 1. In this respect, the hardness of the silver-plated layer is lowered because the crystal grain size of silver is enlarged by heating. When this hardness decreases, the wear resistance also decreases, and the silver plating layer tends to wear. Therefore, it is conceivable to increase the film thickness of the silver plating layer as a countermeasure, but there is a problem in terms of cost. .. Further, when the nickel plating layer is used as the base of the silver plating layer, there is a problem that the silver plating layer is peeled off due to the oxidation of the nickel plating layer.
On the other hand, as in Patent Document 2, it is also conceivable to add antimony to the silver-plated layer to make the crystal grains in the silver-plated layer finer and increase the hardness of the silver-plated layer. However, although the initial hardness is high, the antimony in the silver plating layer is concentrated on the outermost surface of the plating layer by heating to reduce the hardness, and the antimony on the surface layer is oxidized to increase the contact resistance. Further, when the nickel plating layer is used as a base, nickel oxide is generated between the nickel plating layer and the silver plating layer by heating, and the nickel oxide may cause the plating layer to peel off.

Further, as in Patent Document 3, there is also a method of alloying the surface by laminating a silver plating layer and a tin plating layer in order and performing a reflow treatment, but since an oxide film is formed by the heat treatment, connection reliability Decreases.
Therefore, as in Patent Document 4, it is considered to directly apply silver-tin alloy plating to the base material to keep the composition of the entire plating layer uniform.

Japanese Unexamined Patent Publication No. 2008-169408 JP-A-2009-79250 JP-A-2017-79143 JP-A-2015-183216

The silver-tin plating layer of Patent Document 4 is preferably subjected to silver strike plating before the silver-tin alloy plating in order to form a uniform film directly on the nickel plating layer. However, nickel and silver are difficult to diffuse to each other, and the alloyed silver-tin plating layer is very hard, so that there is a risk of peeling from the interface between the nickel plating layer and the silver strike plating layer, which have weak adhesion, during sliding.

The present invention has been made in view of such circumstances, and provides a connector terminal material and a connector terminal capable of improving the adhesion of the silver-tin alloy plating layer to improve wear resistance and heat resistance. The purpose.

The terminal material for a connector of the present invention has at least an intermediate surface formed on a base material made of copper or a copper alloy, a nickel plating layer formed on the surface of the base material, and at least a part thereof on the nickel plating layer. The intermediate plating layer includes a plating layer and a silver-tin alloy plating layer formed on the intermediate plating layer, and the intermediate plating layer contains any one of Cu, Pd, Co, and Mn as a main component, and the intermediate plating. The thickness of the layer is 0.02 μm or more, the silver-tin alloy plating layer contains Ag in the range of 70 at% or more and 85 at% or less, and the thickness of the silver-tin alloy plating layer is 0.5 μm or more and 5 μm or less. is there.

This connector terminal material has excellent wear resistance due to the hard silver-tin alloy layer. In this case, since the nickel plating layer is formed on the surface of the base material, diffusion of the Cu component from the base material in a high temperature environment is prevented, and the performance deterioration of the silver-tin alloy plating layer is suppressed. The thickness of the nickel plating layer is preferably 0.5 μm or more and 2.0 μm or less.
Further, since an intermediate layer containing any one of Cu, Pd, Co, and Mn as a main component is formed on the nickel plating layer as an intermediate layer, the adhesion between them is improved, and silver tin is obtained. The wear resistance of the alloy plating layer can be effectively exhibited. If the film thickness of the intermediate plating layer is less than 0.02 μm, the film is not uniformly formed on the entire surface, so that the effect of improving the wear resistance is reduced and the silver-tin alloy plating layer is easily peeled off. From the viewpoint of workability, the film thickness of the intermediate plating layer is preferably 0.5 μm or less.
If the Ag in the silver-tin alloy plating layer is less than 70 at%, the contact resistance after heating increases, and if the Ag exceeds 85 at%, the ratio of soft silver to the hard silver-tin alloy increases, so that the wear resistance is improved. descend. In addition, it becomes difficult to form a uniform film on the entire surface.
Examples of the silver-tin-based intermetallic compound include Ag ₃ Sn and Ag ₄ Sn intermetallic compounds.
If the silver-tin alloy plating layer is less than 0.5 μm, the effect of improving the wear resistance when used as a connector becomes poor. There is no problem even if the film thickness exceeds 5 μm, but it is preferably 5 μm or less from the viewpoint of cost and workability.

As one aspect of the terminal material for a connector, it is preferable that a silver plating layer made of Ag having a purity of 99% by mass or more is formed on the silver-tin alloy plating layer with a film thickness of 0.1 μm or more and 2.0 μm or less. ..

Since the silver plating layer is formed on the silver-tin alloy plating layer of this connector terminal material, the surface is less likely to be oxidized even in a heating environment, and an increase in contact resistance can be suppressed. Further, since the silver plating layer softer than this silver tin alloy plating layer is formed on the relatively hard silver tin alloy plating layer, the slipperiness is improved and the attachment / detachment resistance when used as a connector is reduced. There is also an effect. If the film thickness of the silver-plated layer is less than 0.1 μm, it is too thin, so that the effect of suppressing the increase in contact resistance after heating is low, and the silver-plated layer is easily worn away at an early stage. If the thickness exceeds 2.0 μm, the friction coefficient increases because the soft silver-plated layer is thick.

In the connector terminal made of the connector terminal material of the present invention, the surface of the contact portion with the connector terminal of the other party may be made of the silver-tin alloy plating layer or the silver plating layer.

According to the present invention, the adhesion of the silver-tin alloy plating layer can be enhanced, and the wear resistance and heat resistance of the terminal material for the connector can be improved.

It is sectional drawing which shows typically the terminal material for a connector which concerns on one Embodiment of this invention. It is a scanning ion microscope (SIM) image of the cross section of the terminal material for a connector before heating in an Example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Structure of terminal material for connector]
FIG. 1 schematically shows a cross section of a terminal material for a connector according to an embodiment. The terminal material 1 for a connector has at least a plate-shaped base material 2 whose surface is made of copper or a copper alloy, a nickel plating layer 3 made of nickel or a nickel alloy coated on the surface of the base material 2, and a nickel plating layer. An intermediate plating layer 4 formed on a part of the surface of 3, a silver-tin alloy plating layer 5 formed on the intermediate plating layer 4, and a silver-tin alloy plating layer 5 formed on the silver-tin alloy plating layer 5. It is equipped with 6.

The composition of the base material 2 is not particularly limited as long as it is made of copper or a copper alloy. Further, it may be composed of a plating material having a copper plating layer made of copper or a copper alloy on the surface of the base material. In this case, the base material may be a metal material other than copper.

The nickel plating layer 3 is coated by applying nickel or nickel alloy plating on the base material 2. The nickel plating layer 3 has a function of suppressing diffusion of Cu and alloy components from the base material 2 into the silver-tin alloy plating layer 5 coated therein. The thickness of the nickel plating layer 3 is preferably 0.5 μm or more and 2.0 μm or less. When the thickness of the nickel plating layer 3 is less than 0.5 μm, the copper and alloy components diffuse from the base material 2 made of copper or a copper alloy to the upper plating layer under a high temperature environment, so that the terminal material 1 for the connector The contact resistance value of the surface may increase and the heat resistance may decrease, and if it exceeds 2.0 μm, cracks may occur during bending. The composition of the nickel plating layer 3 is not particularly limited as long as it is made of nickel or a nickel alloy.

The intermediate plating layer 4 contains any one of Cu, Pd, Co, and Mn as a main component. The intermediate plating layer 4 has good adhesion to both the nickel plating layer 3 and the silver-tin alloy plating layer 5, and the wear resistance is improved. The film thickness of the intermediate plating layer 4 is 0.02 μm or more, and if it is less than 0.02 μm, the film is not uniformly formed on the entire surface, so that the effect of improving the wear resistance is reduced and the silver-tin alloy plating layer is easily peeled off. Although not particularly limited, the film thickness of the intermediate plating layer 4 is preferably 0.5 μm or less from the viewpoint of cost and workability. The content of Cu, Pd, Co, and Mn in the intermediate plating layer 4 is not particularly limited, but is preferably 90% by mass or more.

The silver-tin alloy plating layer 5 is coated on the upper surface of the intermediate plating layer 4 after being subjected to silver strike plating described later. The silver-tin alloy plating layer 5 contains _{an intermetallic compound of Ag 3} Sn and Ag ₄ Sn as a main component, and contains Ag in the range of 70 at% or more and 85 at% or less. Since it contains such an intermetallic compound, wear resistance is improved.

Further, the silver-tin alloy plating layer 5 has an effect of supporting the soft silver plating layer 6 formed on the silver-tin alloy plating layer 5 and improving the wear resistance when used as a connector. The thickness of the silver-tin alloy plating layer 5 is preferably 0.5 μm or more and 5 μm or less. If the silver-tin alloy plating layer 5 is less than 0.5 μm, the effect of improving the wear resistance becomes poor. There is no problem even if the film thickness exceeds 5 μm, but it is preferably 5 μm or less from the viewpoint of workability.

The surface of the silver-plated layer 6 is less likely to be oxidized even in a heating environment, and an increase in contact resistance can be suppressed. The silver-plated layer 6 is made of pure silver having a purity of 99% by mass or more, preferably 99.9% by mass or more. The purity is set to 99% by mass or more because if the Ag concentration of the silver plating layer 6 is less than 99% by mass, a large amount of impurities are contained and the contact resistance becomes high.
The film thickness of the silver plating layer 6 is 0.1 μm or more and 2.0 μm or less. If the film thickness of the silver plating layer 6 is less than 0.1 μm, it is too thin, so that it easily wears and disappears at an early stage. If the film thickness exceeds 2.0 μm, the soft silver plating layer 6 becomes thick, so that the coefficient of friction increases.

Next, a method of manufacturing the terminal material 1 for the connector will be described. The method for manufacturing the terminal material 1 for a connector includes a pretreatment step for cleaning a plate material made of copper or a copper alloy as a base material 2, a nickel plating layer forming step for forming a nickel plating layer 3 on the base material 2, and nickel. An intermediate plating layer forming step of forming an intermediate plating layer 4 on the plating layer 3, a silver strike plating step of applying silver strike plating on the intermediate plating layer 4, and a silver-tin alloy plating layer 5 being formed after the silver strike plating. It includes a silver-tin alloy plating layer forming step and a silver plating layer forming step of forming the silver plating layer 6 on the silver-tin alloy plating layer 5.

[Pretreatment process]
First, as the base material 2, a plate material made of copper or a copper alloy is prepared, and the surface is cleaned by degreasing, pickling, or the like.

[Nickel plating layer forming process]
At least a part of the surface of the base material 2 is plated with nickel or a nickel alloy to form a nickel plating layer 3 on the base material 2. For example, it is formed by performing nickel plating under the conditions of ^{a bath temperature of 45 ° C. and a current density of 3 A / dm 2} using a nickel plating solution composed of nickel sulfamate 300 g / L, nickel chloride 30 g / L, and borate 30 g / L. Will be done. The nickel plating for forming the nickel layer 3 is not particularly limited as long as a dense nickel-based film can be obtained, and may be formed by electroplating using a known watt bath.

[Intermediate plating layer forming process]
The surface of the nickel plating layer 3 formed on the base material 2 is activated with a 5% by mass to 10% by mass sulfuric acid aqueous solution, and then the intermediate plating layer 4 is formed. The plating bath for forming the intermediate plating layer 4 may be of any type as long as it can form a uniform film. If the intermediate plating layer 4 is a copper plating layer, it may be a copper sulfate bath, if it is a palladium plating layer, it may be a plating bath containing a palladium compound such as palladium chloride, if it is a cobalt plating layer, it may be a plating bath containing cobalt sulfate, or a manganese plating layer. For example, a plating bath typical of the metal species, such as a plating bath containing manganese sulfate, may be used.

[Silver strike plating process]
The surface of the intermediate plating layer 4 is silver-plated for a short time to form a thin silver-plated layer. As the silver plating in this case, silver strike plating is preferable. The composition of the plating solution for performing this silver strike plating is not particularly limited as long as it is a no-cyanide bath (a plating bath containing no cyanide such as silver cyanide, silver potassium cyanide, sodium cyanide, potassium cyanide, etc.). It is desirable to use a silver cyanide bath as the main component. The silver strike plating layer formed by the silver strike plating becomes difficult to identify as a layer because the silver-tin alloy plating layer is formed thereafter.

[Silver-tin alloy plating layer forming process]
Then, after the silver strike plating is performed, the silver-tin alloy plating is performed to form the silver-tin alloy plating layer 5. The plating bath for this silver-tin alloy plating has, for example, a composition containing an organic additive containing methanesulfonic acid, tin methanesulfonic acid, silver methanesulfonic acid, and sulfur. Specifically, it is preferable to use a silver-tin alloy plating solution having a methanesulfonic acid concentration of 40 g / L, an Ag concentration of more than 40 g / L and 90 g / L or less, and a Sn concentration of 5 to 35 g / L. .. This silver-tin alloy plating solution does not contain cyanide such as silver cyanide, potassium silver cyanide, sodium cyanide, and potassium cyanide. Further, as the tin anode, both Ag and Pt / Ti (titanium plate coated with platinum) insoluble electrode are used, these areas are more than twice as large as the cathode, and the current distribution of Ag and Pt / Ti is Ag. : Pt / Ti = 4: 1 is preferable. Further, the bath temperature is 40 ° C. to 60 ° C., the current density is 1 to 15 A / dm ² , and the silver-tin alloy plating layer 5 is formed.

[Silver plating layer forming process]
Silver plating is applied on the silver-tin alloy plating layer 5 to form the silver plating layer 6. The composition of the plating bath for this silver plating is not particularly limited, but for example, silver potassium cyanide (K [Ag (CN) ₂ ] 30 g / L to 60 g / L, potassium cyanide (KCN) 120 g / L to 160 g / A plating bath consisting of L, potassium carbonate (K ₂ CO ₃ ) 10 g / L to 20 g / L, and an organic additive that is easily incorporated into the plating layer is preferable. As the organic additive, for example, 2,2 thioethanol Thioalcohols such as, benzothiazoles, azoles such as benzotriazole, and imidazoles such as imidazole can be used. The addition concentration of this organic additive should be 0.1 g / L or more and 10 g / L or less. Good. A nosian bath based on methanesulfonic acid or potassium iodide can also be used.
Then, using a pure silver plate as an anode for this silver plating bath, silver plating is performed for 1 second to 7 minutes under the conditions of a bath temperature of 10 ° C. or higher and 40 ° C. or lower and a current density of 1 A / dm ² or higher and 10 A / dm ^{2 or lower.} The silver plating layer 6 is formed by applying the degree.

In this way, the nickel plating layer 3 is formed on the surface of the base material 2, and the silver-tin alloy plating layer 5 and the silver plating layer 6 are sequentially formed on the intermediate plating layer 4 formed on at least a part of the surface thereof. The terminal material 1 for a connector is subjected to press processing or the like to form a terminal for a connector in which a silver plating layer 6 is arranged on the surface of a portion used as a contact.

In the present embodiment, since the silver plating layer 6 is formed on the surface, the surface is less likely to be oxidized even in a heating environment. Therefore, the contact resistance is as small as 1 mΩ or less even after heating at 150 ° C. for 250 hours, and the heat resistance can be improved.
Since the silver-tin alloy plating layer 5 is formed, oxygen does not permeate from the surface layer, and it is possible to suppress peeling from the nickel plating layer 3 in the heating test. If the Ag in the silver-tin alloy plating layer 5 is less than 70 at%, the contact resistance after heating decreases, and if the Ag exceeds 85 at%, the particle size of the silver-tin alloy plating layer increases and the wear resistance decreases. To do.

In the embodiment, the intermediate plating layer 4, the silver-tin alloy plating layer 5, and the silver plating layer 6 are formed on a part of the nickel plating layer 3 on the surface of the base material 2, but the terminal material of the present invention is used. Each plating layer may be laminated on the entire surface of the base material 2. The intermediate plating layer 4, the silver-tin alloy plating layer 5, and the silver plating layer 6 may be formed at least on a part of the surface of the terminal material, specifically, on a portion serving as a contact portion as a connector terminal.

Nickel plating is performed on a base material having a thickness of 0.25 mm made of a copper alloy to form a nickel plating layer having a thickness of 1.0 μm, and 5% by mass of sulfuric acid is used with respect to the sample on which the nickel plating layer is formed. An activation treatment was performed to clean the surface of the nickel plating layer using an aqueous solution. After this activation treatment, each sample (samples 1 to 10) in which an intermediate plating, a silver strike plating, a silver-tin alloy plating layer, and a silver plating layer were formed in this order on a base material coated with a nickel plating layer was prepared. .. At this time, the amount of Ag (g / L) and the amount of Sn (g / L) in the silver-tin alloy plating solution were the values shown in Table 1.

Further, for comparison, those in which the intermediate plating layer was not formed on the nickel plating layer were also prepared (Samples 19 to 21). In these samples, only the silver-tin alloy plating layer was formed with a thickness of 1 μm and no silver plating layer was formed (Sample 18), and the silver-tin alloy plating layer and the silver plating layer were laminated with a thickness of 0.5 μm, respectively. (Sample 19), only the silver plating layer formed with a thickness of 1 μm without forming the silver-tin alloy plating layer (Sample 20), and the silver alloy plating layer to which antimony was added formed with a thickness of 1 μm (Sample 20). It was used as sample 21).
The conditions for each plating were as follows.

<Nickel plating conditions>
-Plating bath composition Nickel sulfamate: 300 g / L
Nickel chloride: 30 g / L
Boric acid: 30 g / L
・ Bath temperature: 45 ° C
-Current density: 3A / dm ²

<Copper plating conditions>
-Plating bath composition Copper sulfate pentahydrate 250 g / L
Sulfuric acid 50g / L
・ Bath temperature: 50 ℃
-Current density: 3A / dm ²
・ Anode: Phosphorus-containing copper

<Palladium plating conditions>
・ Plating bath composition Palladium chloride 17 g / L
Ammonium phosphate 100 ml / L
Ammonium chloride 25 g / L
・ Bath temperature: 30 ℃
・ Current density: 1A / dm ²
-Anode: Pt / Ti (insoluble electrode made of titanium coated with platinum)

<Cobalt plating conditions>
-Plating bath composition Cobalt sulfate heptahydrate 140 g / L
Boric acid 40g / L
・ Bath temperature: 30 ℃
・ Current density: 1A / dm ²
・ Anode: Pt / Ti

<Manganese plating conditions>
・ Plating bath composition Manganese sulfate 200g / L
Ammonium sulfate 100 g / L
・ Bath temperature: 30 ℃
・ Current density: 8A / dm ²
・ Anode: Pt / Ti

<Silver strike plating conditions>
・ Plating bath composition Daiwa Kasei Co., Ltd. die silver used ・ Bath temperature: 25 ℃
・ Current density: 1A / dm ²
・ Anode: Ir / Ti
(Insoluble electrode in which a titanium plate is coated with iridium oxide (IrO ₂₎₎

<Silver-tin alloy plating conditions>
-Plating bath composition Methanesulfonic acid: 40 g / L
Tin methanesulfonate: 13-91 g / L
Silver methanesulfonate: 75-170 g / L
Organic additive: 5 mg / L
・ Bath temperature: 50 ℃
-Current density: 1 to 15 A / dm ²

<Silver plating conditions>
-Plating bath composition Silver cyanide potassium: 55 g / L
Potassium cyanide: 130 g / L
Potassium carbonate: 15 g / L
Nonionic surfactant: 1 g / L
2,2 thioethanol: 5 g / L
・ Bath temperature: 25 ℃
・ Current density: 5A / dm ²
・ Anode: Sterling silver plate

The antimony-containing silver alloy plating layer of Sample 21 was prepared by performing glossy silver plating using a Nissin Bright N bath to which antimony was added, which was manufactured by Nikkei Seisei Co., Ltd. The composition of the plating bath was a standard composition, a bath temperature of 25 ° C., a current density of 5 A / dm ^2, and a pure silver plate as an anode to form a silver alloy plating layer (AgSb alloy layer) having a thickness of 1 μm.

For the obtained sample, the Ag content in the silver-tin alloy plating layer, the film thickness of the silver-tin alloy plating layer, the film thickness of the silver plating layer were measured, the film thickness of the intermediate plating layer, and the contact resistance were measured. Abrasion resistance was evaluated.

[Ag content in silver-tin alloy plating]
A cross-sectional sample is prepared by processing the plating material with a focused ion beam device (FIB), and the Ag content (at%) in the silver-tin alloy plating is the electron probe microanalyzer manufactured by Nippon Denshi Co., Ltd .: EPMA (model number). Using JXA-8530F), the cross section of each sample was measured at an acceleration voltage of 10 kV.

[Film thickness of each plating layer]
A plated material is processed with a focused ion beam device (FIB) to prepare a cross-sectional sample, the cross-sectional surface is observed with a scanning ion microscope (SIM), and the film thickness (μm) is measured from the obtained SIM image. The obtained value was taken as the film thickness.

[Contact resistance]
Each sample before heating and each sample after heating at 150 ° C. for 250 hours were cut into test pieces of 60 mm × 10 mm, and a flat plate sample was used as a substitute for a male terminal, and this flat plate sample was subjected to convex processing with a radius of curvature of 3 mm. The sample was used as a substitute for the female terminal. The contact resistance (mΩ) was measured before heating and after heating at 150 ° C. for 250 hours. For the measurement, a friction and wear tester (UMT-Tribolab) manufactured by Bruker AXS Corporation was used to bring the convex surface of the female test piece into contact with the horizontally installed male terminal test piece, and the male terminal test piece was loaded with a load of 20 N. The contact resistance value at the time of applying was measured by the 4-terminal method.

[Abrasion resistance]
Each sample was cut into a test piece of 60 mm × 10 mm, and a flat plate sample was used as a substitute for a male terminal, and a sample obtained by subjecting this flat plate sample to a convex processing with a radius of curvature of 3 mm was used as a substitute for a female terminal. For the sliding test, a friction and wear tester (UMT-Tribolab) manufactured by Bruker AS Corporation was used, and the convex surface of the female test piece was brought into contact with the horizontally installed male terminal test piece, and a load of 2N was applied. Then, the male terminal test piece was slid horizontally at a moving distance of 5 mm and a sliding speed of 1 Hz. After the sliding test, the wear resistance was judged by whether or not the base (nickel layer) of the convex processed sample was exposed. At this time, the one in which the base was not exposed after the sliding test was rated as good "A", and the one in which the base was exposed after the sliding test was rated as "B".

These results are shown in Tables 1 and 2. "-" In the table indicates that the measurement or evaluation was not performed because the plating was not performed or the film could not be formed.

As is clear from Tables 1 and 2, the thickness of the intermediate plating layer is 0.02 μm or more, the silver-tin alloy plating layer contains Ag in the range of 70 at% or more and 85 at% or less, and the silver-tin alloy. Samples 1 to 4,7,8,10,11,13 to 17 having a plating layer thickness of 0.5 μm or more and 5 μm or less have good contact resistance after heating of 2 mΩ or less and good wear resistance. there were. Of these, samples 8, 10, 11, 13 to 17 in which a silver-plated layer was formed on the outermost surface with a film thickness of 0.1 μm or more and 2 μm or less were samples 1 to 4 in which a silver-plated layer was not formed, and silver-plated. It can be seen that the contact resistance value after heating is lower than that of sample 7 in which the film thickness of the layer is 0.1 μm, and that it is suitable for use in a heating environment.
FIG. 2 is a SIM image of sample 13, in which a layer composed of Cu (denoted as Cu) and a silver-tin alloy as an intermediate plating layer are placed on a nickel plating layer (denoted as Ni) on the surface of a base material (denoted as Base Material). A plating layer (denoted as AgSn) and a silver plating layer (denoted as Ag) are formed.
On the other hand, in Sample 5, the film thickness of the silver-tin alloy plating layer was as small as 0.4 μm, so that the wear resistance was inferior.
In Sample 6, since the Sn content in the silver-tin alloy plating layer is high (the Ag content is low), Sn diffused by heating forms an oxide film on the outermost layer, and the contact resistance is increased.
Since the Ag content in the silver-tin alloy plating layer of Sample 9 was 87 at%, the size of the crystal grains in the silver-tin alloy plating layer was extremely uneven, and a uniform film formation could not be performed.
Sample 12 was inferior in wear resistance because the film thickness of the intermediate plating layer was 0.01 μm.
Samples 18 to 21 that did not form an intermediate plating layer were inferior in wear resistance.

1 Terminal material for connector 2 Base material 3 Nickel plating layer 4 Intermediate plating layer 5 Silver-tin alloy plating layer 6 Silver plating layer

Claims (4)

A base material whose surface is at least made of copper or a copper alloy, a nickel plating layer formed on the surface of the base material, an intermediate plating layer formed on the nickel plating layer, and an intermediate plating layer formed on the intermediate plating layer. The intermediate plating layer contains any one of Cu, Pd, Co, and Mn as a main component, and the thickness of the intermediate plating layer is 0.02 μm or more. The terminal material for a connector, wherein the silver-tin alloy plating layer contains Ag in a range of 70 at% or more and 85 at% or less, and the thickness of the silver-tin alloy plating layer is 0.5 μm or more and 5 μm or less. The connector according to claim 1, wherein a silver plating layer made of Ag having a purity of 99% by mass or more is formed on the silver-tin alloy plating layer with a film thickness of 0.1 μm or more and 2.0 μm or less. Terminal material for. The connector terminal made of the connector terminal material according to claim 1, wherein the surface of the contact portion with the mating connector terminal is made of the silver-tin alloy plating layer. The connector terminal made of the connector terminal material according to claim 2, wherein the surface of the contact portion with the counterpart connector terminal is made of the silver-plated layer.