JP2022182670A - Conductive member and method for manufacturing conductive member - Google Patents

Abstract

To provide a conductive member having small contact resistance and excellent insertability and capable of suppressing abrasion of a plating layer.SOLUTION: A conductive member comprises a base material, and a plating layer covering a surface of the base material. The plating layer has a first layer serving as the outermost layer, and a second layer laminated inside the first layer. The first layer includes an I-th phase containing Sn, and an II-th phase dispersed in the I-th phase. The II-th phase contains Sn and Ag. The second layer contains Sn and a metal element other than Ag.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a conductive member and a method for manufacturing a conductive member.

A conductive member (for example, a connector terminal fitting) used for connection of an electric circuit includes, for example, a base material having conductivity and a plating layer covering the surface of the base material. The plating layer is applied for the purpose of suppressing corrosion of the conductive member, improving connection reliability, improving solderability, and the like. As such a plated layer, for example, a Sn plated layer is generally used because of its low contact resistance and excellent solderability and corrosion resistance.

On the other hand, the Sn plating layer is a relatively soft plating layer. Therefore, when a connector using a conductive member having a Sn-plated layer as a terminal is inserted into a mating member, the Sn-plated layer is deformed and worn, which tends to hinder smooth insertion. Therefore, the conductive member provided with the Sn plating layer is required to have excellent performance (insertability) for smooth insertion. In addition, a conductive member having a Sn plating layer is required to be able to suppress wear of the plating layer so that connection reliability does not deteriorate even when the connector is repeatedly inserted and pulled out.

In response to such demands, for example, a Sn plating layer has been proposed which includes a mother phase containing Sn, which has excellent electrical conductivity, as a main component, and a Sn-based intermetallic compound phase dispersed in the mother phase. Sn-based intermetallic compounds (eg, Sn—Cu-based intermetallic compounds and Sn—Pd-based intermetallic compounds) are relatively hard. Since the hard Sn-based intermetallic compound phase is dispersed in the parent phase, the Sn plating layer described above has relatively high strength and can suppress deformation and wear to some extent. Moreover, since the above-mentioned Sn plating layer has a parent phase containing Sn as a main component, the contact resistance is low. As a conductive member provided with such a Sn plating layer, for example, it has a substrate made of a metal material and a plating film covering the surface of the substrate, and the plating film is dispersed in the Sn matrix and the Sn matrix. A terminal fitting has been proposed which contains Sn—Pd particles and has an outermost layer in which the Sn mother phase and the Sn—Pd particles are present on the outer surface (Patent Document 1).

JP 2016-91990 A

However, even with the Sn plating layer described above, it is difficult to provide a conductive member that satisfies all of the contact resistance, insertability, and suppression of abrasion of the plating layer.

The present invention has been made in view of the above problems, and an object thereof is to provide a conductive member that has low contact resistance, excellent insertability, and can suppress abrasion of the plating layer. Another object of the present invention is to provide a method for manufacturing a conductive member that has excellent conductivity, low insertion resistance, and is capable of suppressing abrasion of the plating layer.

A conductive member of the present invention includes a substrate and a plating layer covering the surface of the substrate. The plating layer has a first layer, which is the outermost layer, and a second layer laminated inside the first layer. The first layer includes a Sn-containing phase I and a phase II dispersed in the first phase. The Phase II contains Sn and Ag. The second layer contains a metal element other than Ag and Sn.

The method for producing a conductive member of the present invention is a method for producing a conductive member comprising a base material and a plating layer covering the surface of the base material, and directly or via another layer on the base material. , Sn and Ag-containing coating layer forming step of forming a coating layer by plating, and a heating step of heating the substrate and the coating layer. The heating temperature in the heating step is 220° C. or higher and 450° C. or lower.

ADVANTAGE OF THE INVENTION The electrically-conductive member and the manufacturing method of an electrically-conductive member of this invention can provide the electrically-conductive member which is excellent in electroconductivity, has a small insertion resistance, and can suppress abrasion of a plating layer.

1 is a cross-sectional view of an example of a conductive member according to a first embodiment of the present invention; FIG. 2 is a cross-sectional view of a modification of the conductive member of FIG. 1; FIG. FIG. 7 is a cross-sectional view showing one step of an example of a method for manufacturing a conductive member according to a second embodiment of the present invention; FIG. 4 is a diagram showing the next step of FIG. 3; 5 is a diagram showing the next step of FIG. 4; FIG. 4 is a cross-sectional image of a conductive member of Comparative Example 1. FIG. 4 is a cross-sectional image of the conductive member of Example 1. FIG. 4 is a surface image of the plating layer of the conductive member of Example 1. FIG. 10 is a surface image of the plating layer of the conductive member of Example 6. FIG.

Embodiments of the present invention will be described below. However, the present invention is by no means limited to the embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present invention. Each material described in the embodiments of the present invention may be used singly or in combination of two or more unless otherwise specified.

As used herein, the term “main component” refers to a component with the highest content ratio on a mass basis (for example, a component containing more than 50% by mass). The “thickness” of the plated layer indicates the length in the direction orthogonal to the interface between the substrate and the plated layer. A fluorescent X-ray film thickness meter (for example, "SII SFT9200" manufactured by Hitachi High-Tech Science Co., Ltd.) can be used to measure the thickness of the plating layer. The "outermost layer" of the plating layer indicates the layer farthest from the substrate. The terms “inner side” and “outer side” of the plated layer indicate the direction of the plated layer closer to the base material and the direction of the side farther from the base material, respectively.

<First embodiment: conductive member>
A conductive member according to a first embodiment of the present invention will be described. A conductive member of the present invention includes a substrate and a plating layer covering the surface of the substrate. The plating layer has a first layer, which is the outermost layer, and a second layer laminated inside the first layer. The first layer includes a phase I containing Sn (hereinafter sometimes referred to as the Sn mother phase) and a phase II dispersed in the I phase (hereinafter sometimes referred to as the Sn—Ag phase ) and The Sn--Ag phase contains Sn and Ag. The second layer contains metal elements other than Ag and Sn.

The conductive member of the present invention can be used, for example, as a material for various electronic components (eg, connectors, relays, slide switches, resistors, capacitors, coils and circuit boards, flexible substrates, flat cables and electric wires). Electronic parts using the conductive member of the present invention can be used, for example, in semiconductor products, electrical products, solar cells, automobiles, and the like.

The conductive member of the present invention is particularly suitable as a terminal fitting used in a connector (especially a wire harness connector). A connector using the conductive member of the present invention includes, for example, the conductive member and a housing that holds the conductive member. The connector can be either a pin insert or a socket insert, preferably a pin insert.

The conductive member of the present invention has a low contact resistance, excellent insertability, and can suppress abrasion of the plating layer by having the above-described configuration. The reason is presumed as follows. The plating layer provided in the conductive member of the present invention has a multilayer structure. The first layer, which is the outermost layer of the plating layer, contains a Sn matrix and a Sn—Ag phase dispersed in the Sn matrix. The conductive member of the present invention has a small contact resistance because the Sn matrix containing Sn, which is excellent in conductivity, exists in the outermost layer (first layer) of the plating layer. In the Sn—Ag phase, Sn and Ag form, for example, an intermetallic compound (hereinafter sometimes referred to as a Sn—Ag intermetallic compound). Sn-based intermetallic compounds tend to have a higher hardness than simple Sn. Among them, the Sn—Ag intermetallic compound has a better balance of hardness and elasticity than other Sn-based intermetallic compounds (for example, Sn—Cu intermetallic compounds and Sn—Pd intermetallic compounds). judged to be excellent. In the conductive member of the present invention, the plating layer has a Sn—Ag phase present in the outermost layer (first layer) to reinforce the structure, and is judged to have higher strength than known Sn plating layers. be. Therefore, the conductive member of the present invention is excellent in insertability and can suppress abrasion of the plating layer.

Hereinafter, the details of the conductive member of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a conductive member 1 that is an example of the conductive member of the present invention. A conductive member 1 of FIG. 1 includes a base material 2 and a plating layer 3 covering the surface of the base material 2 . The plated layer 3 has a multi-layered structure and has a first layer 4, a second layer 5 and a third layer 6 in order from the outermost layer.

[Base material]
The shape and material of the base material 2 are not particularly limited as long as the shape and material can be used as the conductive member 1 . Examples of the shape of the substrate 2 include plate-like, prismatic, columnar, conical, and ring-like shapes. Examples of materials for the base material 2 include copper-based materials, iron-based materials, and Ni-based materials. Copper-based materials include, for example, copper, phosphor bronze, brass, beryllium copper, titanium copper, and nickel silver (an alloy of Cu, Ni, and zinc). Examples of iron-based materials include iron, Fe—Ni alloys, and stainless steel. The base material 2 may be a member in which a conductive layer is formed on the surface of an insulating member (for example, resin film). That is, the base material 2 may be, for example, a member including various insulating substrates and conductive patterns (for example, copper patterns) formed on the insulating substrates.

[Plating layer]
The plating layer 3 has a three-layer structure having a first layer 4 , a second layer 5 and a third layer 6 . In the plating layer 3, the total thickness of the first layer 4 and the second layer 5 is preferably 0.1 μm to 100.0 μm, more preferably 0.3 μm to 10.0 μm, and 0.7 μm to 10.0 μm. 0 μm or less is more preferable. By setting the total thickness of the first layer 4 and the second layer 5 to 0.1 μm or more, it is possible to suppress the exposure of the third layer 6 even when the plating layer 3 is worn. By setting the total thickness of the first layer 4 and the second layer 5 to 100.0 μm or less, it is possible to prevent the plating layer 3 from becoming unnecessarily thick.

In elemental analysis using energy dispersive X-ray fluorescence spectroscopy, when the acceleration voltage is 15 kV, the content of Ag relative to all metal elements contained in the plating layer 3 is preferably 3% by mass or more and 20% by mass or less. , 6% by mass or more and 17% by mass or less, more preferably 10% by mass or more and 17% by mass or less. By setting the content of Ag to 3% by mass or more and 20% by mass or less, the area ratio of the Sn—Ag phase 4b in the first layer 4 can be adjusted to an appropriate range. As a result, the conductive member 1 can exhibit excellent conductivity, low insertion resistance, and suppression of abrasion of the plating layer 3 in a well-balanced manner.

(first layer)
The first layer 4, which is the outermost layer of the plating layer 3, includes an Sn matrix 4a containing Sn and a Sn--Ag phase 4b dispersed in the Sn matrix 4a. When observing the first layer 4 from the surface, in the first layer 4, the Sn mother phase 4a and the Sn—Ag phase 4b form, for example, a sea-island structure. A natural oxide film may be formed on the outer surface of the first layer 4 .

In the first layer 4, the area ratio of the Sn—Ag phase 4b is preferably 2.0% or more and 50.0% or less, more preferably 5.0% or more and 25.0% or less, and 15.0% or more and 25%. 0% or less is more preferable. By setting the area ratio of the Sn—Ag phase 4b to 1% or more, the insertability of the conductive member 1 can be further improved, and the abrasion of the plating layer 3 can be more effectively suppressed. By setting the area ratio of the Sn—Ag phase 4b to 50.0% or less, the contact resistance of the conductive member 1 can be further reduced. The area ratio of the Sn—Ag phase 4b can be measured, for example, by observing the surface of the first layer 4 with an FE-SEM equipped with an energy dispersive X-ray fluorescence spectrometer.

(Sn mother phase)
The Sn mother phase 4a contains Sn. The Sn mother phase 4 a is the mother phase of the first layer 4 . The Sn mother phase 4a contains Sn as a main component, but may further contain elements other than Sn as long as they are in small amounts. Elements other than Sn include, for example, Cu and oxygen. In the Sn mother phase 4a, the Sn content is preferably 80% by mass or more, more preferably 97% by mass or more.

(Sn—Ag phase)
The Sn—Ag phase 4b contains Sn and Ag. Sn and Ag preferably form an intermetallic compound in the Sn—Ag phase 4b. However, in the Sn—Ag phase 4b, at least part of Sn and Ag may form, for example, an alloy or multiple oxides. In FIG. 1, the shape of the Sn—Ag phase 4b is particulate.

The Sn—Ag phase 4b may further contain elements other than Sn and Ag. Elements other than Sn and Ag include, for example, Cu and oxygen. In the Sn—Ag phase 4b, the total content of Sn and Ag is preferably 80% by mass or more, more preferably 97% by mass or more.

At least part of the Sn—Ag phase 4 b is preferably exposed on the surface of the plating layer 3 . As a result, when the conductive member 1 contacts the counterpart material, the hard Sn—Ag phase 4b rather than the soft Sn mother phase 4a contacts the counterpart material, so that the abrasion of the plating layer 3 can be further effectively suppressed. . Specifically, in cross-sectional observation with an electron microscope, the ratio of the number of Sn-Ag phases 4b exposed on the surface of the plating layer 3 to the total number of Sn-Ag phases 4b in the field of view was 10. % or more is preferable, 40 number % or more is more preferable, and 70 number % or more is still more preferable.

(Second layer)
The second layer 5 is laminated inside the first layer 4 on the plating layer 3 . Specifically, the second layer 5 is laminated between the first layer 4 and the third layer 6 . The second layer 5 contains metal elements other than Ag and Sn. The outer surface of the second layer 5 has an uneven shape.

In the second layer 5, metal elements other than Ag and Sn preferably form an intermetallic compound. However, in the second layer 5, at least part of the metal elements other than Ag and Sn may form, for example, an alloy or multiple oxides.

In the plated layer 3, the second layer 5 has a function of improving adhesion between the first layer 4 and the third layer 6, for example. In the second layer 5, metal elements other than Ag include, for example, Cu and Ni.

As will be described later, the second layer 5 is formed by reacting Sn in the coating layer containing Sn and Ag with the metal element contained in the third layer 6 . Therefore, the second layer 5 normally contains Sn and the metal element contained in the third layer 6 . For example, when the third layer 6 is a Ni layer, the second layer 5 contains Sn and Ni. When the third layer 6 is a Cu layer, the second layer 5 contains Sn and Cu.

In addition, the second layer 5 may further contain an element (for example, oxygen) other than the metal element and Sn contained in the third layer 6 . The content of other elements in the second layer 5 is preferably 20% by mass or less, more preferably 3% by mass or less.

Preferably, the first layer 4 and the second layer 5 further contain Cu. Since the first layer 4 and the second layer 5 further contain Cu, the plating layer 3 can be easily and reliably formed. In the first layer 4 and the second layer 5, Cu may be contained in any of the Sn mother phase 4a, the Sn—Ag phase 4b and the second layer 5. In the first layer 4 and the second layer 5, the content of Cu is preferably 0.1% by mass and 5.0% by mass or less, and more preferably 0.3% by mass or more and 2.0% by mass or less.

(third layer)
The third layer 6 improves adhesion between the second layer 5 and the substrate 2 . In addition, the third layer 6 suppresses the components contained in the base material 2 from diffusing into the plating layer 3 . The third layer 6 contains Ni or Cu.

The third layer 6 is particularly effective when the material of the base material 2 is a material that is difficult to adhere to the second layer 5 (for example, stainless steel (SUS) and iron). In addition, when the material of the base material 2 is brass, the third layer 6 is particularly effective because it can prevent zinc contained in brass from diffusing into the first layer 4 and lowering the solderability.

The thickness of the third layer 6 is preferably 0.1 μm or more and 100.0 μm or less, more preferably 0.1 μm or more and 5.0 μm or less, and still more preferably 0.5 μm or more and 3.0 μm or less. By setting the thickness of the third layer 6 to 0.1 μm or more, the above functions can be sufficiently exhibited. By setting the thickness of the third layer 6 to 100.0 μm or less, it is possible to prevent the plated layer 3 from becoming unnecessarily thick.

The conductive member 1, which is an example of the conductive member of the present invention, has been described above with reference to FIG. Next, a conductive member 11, which is a modification of the conductive member 1 of FIG. 1, will be described with reference to FIG.

[Modification]
The conductive member 11 of FIG. 2 has a base material 12 and a plated layer 13 covering the surface of the base material 12 . The plating layer 13 has a first layer 14 and a second layer 15 in order from the outermost layer. The first layer 14, which is the outermost layer of the plating layer 13, includes a Sn matrix 14a containing Sn and a Sn--Ag phase 14b dispersed in the Sn matrix 14a. The conductive member 11 in FIG. 2 differs from the conductive member 1 in FIG. 1 in that it does not have a layer corresponding to the third layer 6 . That is, in the conductive member 11 of FIG. 2, the second layer 15 covers the surface of the base material 12 . Also, the conductive member 11 of FIG. 2 differs from the conductive member 1 of FIG. 1 in the composition of the second layer 15 . Hereinafter, the composition of the second layer 15 will be described while omitting redundant description with the conductive member 1 of FIG.

(Second layer)
The second layer 15 is laminated inside the first layer 14 on the plating layer 13 . Specifically, second layer 15 is laminated between first layer 14 and substrate 12 . The second layer 15 contains metal elements other than Ag and Sn. The outer surface of the second layer 15 has an uneven shape.

In the second layer 15, metal elements other than Ag and Sn preferably form an intermetallic compound. However, in the second layer 15, at least part of the metal elements other than Ag and Sn may form, for example, an alloy or multiple oxides.

In the plating layer 13 , the second layer 15 has a function of improving adhesion between the first layer 14 and the substrate 12 , for example. In the second layer 15, metal elements other than Ag include, for example, Cu and Ni.

As will be described later, the second layer 15 is formed by reacting Sn in the coating layer containing Sn and Ag with metal elements contained in the substrate 12 . Therefore, the second layer 15 usually contains Sn and the metal element contained in the base material 12 . For example, when the base material 12 is a Cu layer, the second layer 15 contains Sn and Cu.

The conductive member of the present invention has been described above based on the conductive member 1 shown in FIG. 1 and the conductive member 11 shown in FIG. However, the conductive member 1 in FIG. 1 and the conductive member 11 in FIG. 2 are merely examples of the conductive member of the present invention. Various modifications can be made to the conductive member of the present invention without departing from the gist of the present invention.

For example, the shape of the Sn—Ag phase does not necessarily have to be particulate. The shape of the Sn—Ag phase is, for example, particulate or plate-like (more specifically, for example, strip-like plate). Here, "particulate" means that the aspect ratio (major axis/minor axis) is 5 or less, for example. "Plate-like" means that the aspect ratio is more than 5, for example. The major axis and minor axis of the Sn—Ag phase can be measured by observing the surface of the first layer with an FE-SEM equipped with an energy dispersive X-ray fluorescence spectrometer. Specifically, the maximum width of two imaginary parallel lines contacting the outer edge of the Sn—Ag phase to be measured is taken as the measurement value of the major axis. In addition, a third virtual parallel line is set at the center of the two virtual parallel lines set when measuring the major axis, and the length where the third virtual parallel line and the Sn—Ag phase to be measured overlap The width is taken as the measured value of the minor axis.

When the Sn—Ag phase is particulate, the particle diameter (length) is preferably 0.5 μm or more and 10.0 μm or less, more preferably 1.0 μm or more and 3.0 μm or less. When the Sn—Ag phase is plate-like, the major axis thereof is preferably 3.0 μm or more and 130.0 μm or less, more preferably 50.0 μm or more and 120.0 μm or less.

The first layer may further contain phases other than the Sn matrix phase and the Sn—Ag phase. Other phases include, for example, phases formed by unavoidable impurities. Also, the plated layer may further have layers other than the first layer, the second layer, and the third layer. Also, the outer surface of the second layer may be flat.

<Second Embodiment: Method for Manufacturing Conductive Member>
A method for manufacturing a conductive member according to a second embodiment of the present invention is a method for manufacturing a conductive member including a base material and a plating layer that coats the surface of the base material. It comprises a coating layer forming step of forming a coating layer containing Sn and Ag via a plating method, and a heating step of heating the substrate and the coating layer. The heating temperature in the heating step is 220° C. or higher and 450° C. or lower.

ADVANTAGE OF THE INVENTION The manufacturing method of the electrically-conductive member of this invention can provide the electrically-conductive member which is excellent in electroconductivity, has a small insertion resistance, and can suppress abrasion of a plating layer. The method for manufacturing a conductive member according to the present invention is suitable as the method for manufacturing a conductive member according to the first embodiment.

Hereinafter, the details of the method for manufacturing the conductive member of the present invention will be described with reference to the drawings. 3 to 5 are diagrams showing each step of an example of the method for manufacturing the conductive member of the present invention. 3 to 5 can manufacture a conductive member similar to the conductive member 1 of FIG. 1, for example. The details of the base material 21 and the third layer 22 appearing in FIGS. 3 to 5 have already been described in the first embodiment, so redundant description will be omitted.

[Coating layer forming step]
The coating layer forming step includes a first step of forming the third layer 22 on the base material 21 by plating, and a second step of forming the coating layer 23 containing Sn and Ag on the third layer 22 by plating. and That is, in this step, the coating layer 23 containing Sn and Ag is formed on the substrate 21 via the third layer 22 by plating. This step preferably further includes a pretreatment step for pretreating the substrate 21 . Details of each step will be described below.

(Pretreatment step)
The pretreatment process is performed for the purpose of improving the adhesion of the coating layer 23 to the substrate 21 and suppressing the occurrence of pinholes. The pretreatment process is particularly effective when the base material 21 is a member obtained by rolling a metal such as phosphor bronze.

In the pretreatment step, it is preferable to perform an acid treatment in which an acid having a pH of 5 or less is applied to the base material 21 . The acid treatment may be performed on the entire surface of the base material 21, or may be performed only on the area of the base material 21 where the coating layer 23 is to be formed. In the pretreatment process, the substrate 21 is subjected to a first cleaning treatment of immersing the substrate 21 in the aqueous cleaning solution, a second cleaning treatment of electrolyzing the substrate 21 in the electrolytic aqueous solution, and an acid of pH 5 or less acting on the substrate 21. It is more preferable to carry out the acid treatment in this order.

In the first cleaning process, the substrate 21 is immersed in a cleaning bath filled with a cleaning aqueous solution. After that, the substrate 21 is washed with water several times.

The pH of the aqueous cleaning solution is preferably 0.01 or higher, more preferably 9.0 or higher (alkaline), still more preferably 9.5 or higher, and particularly preferably 10.0 or higher. The pH of the aqueous cleaning solution is preferably 13.8 or less, more preferably 13.5 or less. Excessive roughening or deterioration of the surface of the substrate 21 can be suppressed by setting the pH of the aqueous cleaning solution to 0.01 or more and 13.8 or less.

The active ingredient (eg, alkaline ingredient) of the aqueous cleaning solution is not particularly limited, but examples thereof include sodium hydroxide, potassium hydroxide, calcium hydroxide, chelating agents, and surfactants. The temperature of the aqueous cleaning solution in the first cleaning process is preferably 20° C. or higher and 90° C. or lower, more preferably 40° C. or higher and 60° C. or lower.

In the second cleaning treatment, electrolysis is performed using the substrate 21 as an electrode in an electrolytic bath filled with an electrolytic aqueous solution. After that, the substrate 21 is washed with water several times. As a result, gas is generated on the surface of the base material 21, and contamination on the surface of the base material 21 is efficiently removed by the redox action of this gas and the physical action of gas bubbles.

The pH of the electrolytic aqueous solution in the second cleaning treatment is preferably 0.01 or higher, more preferably 9.0 or higher (alkaline), still more preferably 9.5 or higher, and particularly preferably 10.0 or higher. The pH of the aqueous electrolytic solution is preferably 13.8 or less, more preferably 13.5 or less. Excessive roughening or deterioration of the surface of the substrate 21 can be suppressed by setting the pH of the aqueous electrolytic solution to 0.01 or more and 13.8 or less.

The active ingredient (eg, alkaline ingredient) of the electrolytic aqueous solution is not particularly limited, but examples thereof include sodium hydroxide, potassium hydroxide, calcium hydroxide, chelating agents, and surfactants.

The liquid temperature during electrolysis is preferably 20° C. or higher and 90° C. or lower, more preferably 30° C. or higher and 60° C. or lower. The current density during electrolysis is preferably 0.1 A/dm ² or more and 20 A/dm ² or less, more preferably 2 A/dm ² or more and 8 A/dm ² or less. The electrolysis time is preferably 0.1 minute or more and 5 minutes or less, more preferably 0.5 minute or more and 2 minutes or less. In addition, in electrolysis, the substrate 21 may be used as an anode or a cathode. Also, the substrate 21 may be switched from the anode to the cathode (or from the anode to the cathode) as appropriate during electrolysis.

In the acid treatment, the base material 21 is immersed in an acid aqueous solution tank filled with an acid aqueous solution (eg, sulfuric acid, hydrochloric acid, ammonium persulfate solution, and hydrogen peroxide solution), and the acid acts on the surface of the base material 21 . Thus, an acid treatment (activation treatment) is performed.

Here, the pH of the acid aqueous solution is preferably from 0.001 to 6.0, more preferably from 0.1 to 4.5, and even more preferably from 0.1 to 3.0. By setting the pH of the acid aqueous solution to 0.01 or more, excessive roughening or deterioration of the surface of the base material 21 can be suppressed. By setting the pH of the acid aqueous solution to 6.0 or less, the surface of the substrate 21 can be sufficiently acid-treated.

The immersion time in the acid treatment is preferably from 0.1 minutes to 10 minutes, more preferably from 0.5 minutes to 5 minutes, and even more preferably from 1 minute to 3 minutes. By setting the immersion time to 0.1 minute or more, the surface of the substrate 21 can be sufficiently acid-treated. By setting the immersion time to 10 minutes or less, excessive roughening or deterioration of the surface of the substrate 21 can be suppressed.

(First step)
As shown in FIG. 3, in this step, the third layer 22 is formed on the base material 21 by plating. As a method for forming the third layer 22, for example, a known electroplating method can be adopted.

The plating solution used for electroplating in this step contains, for example, Ni compounds (eg, Ni chloride and Ni sulfate) or Cu compounds. Preferably, the plating solution further contains at least one of inorganic chelating agents, organic chelating agents, and other additives (eg, boric acid).

The concentration of the Ni compound or Cu compound in the plating solution in this step is preferably 50 g/L or more and 450 g/L or less, more preferably 150 g/L or more and 350 g/L or less.

The temperature of the plating solution during electroplating in this step is preferably 10° C. or higher and 80° C. or lower, more preferably 40° C. or higher and 60° C. or lower. In electroplating, the current density is preferably 0.1 A/dm ² or more and 30 A/dm ² or less, more preferably 2 A/dm ² or more and 25 A/dm ² or less.

(Second step)
As shown in FIG. 4, in this step, a coating layer 23 containing Sn and Ag is formed on a substrate 21 via a third layer 22 by plating. As a method for forming the coating layer 23, for example, a known electroplating method can be adopted.

The plating solution used for electroplating in this step contains a Sn compound and an Ag compound. Preferably, the plating solution further contains at least one of Cu compounds, inorganic chelating agents, organic chelating agents, and other additives.

Here, the Sn compound is a compound containing at least Sn, and examples thereof include stannous oxide, stannous sulfate, and tin salts of various organic acids. The Ag compound is a compound containing at least Ag, and examples thereof include silver oxide and Ag salts of various organic acids. A Cu compound is a compound containing at least Cu, and examples thereof include copper sulfate, copper chloride, and Cu salts of various organic acids.

The plating solution in this step preferably contains a Sn compound, an Ag compound, a Cu compound, an inorganic chelating agent, and an organic chelating agent. In this case, the Sn compound, Ag compound and Cu compound are each particularly preferably soluble salts containing a common anion as a counterion. This makes it possible to extremely effectively suppress separation and deposition of Ag and Cu from the plating solution. In addition, by using both an inorganic chelating agent and an organic chelating agent, separation and deposition of Ag and Cu from the plating solution can be extremely effectively suppressed.

Specific anions include, for example, anions derived from inorganic acids and anions derived from organic acids. Inorganic acids include, for example, sulfuric acid, nitric acid, phosphoric acid, hydrochloric acid, and hydrofluoric acid. Examples of organic acids include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, benzenesulfonic acid, phenolsulfonic acid, alkylarylsulfonic acid, alkanolsulfonic acid, formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, and phthalic acid. , oxalic acid, adipic acid, lactic acid, citric acid, malonic acid, succinic acid, tartaric acid, and malic acid.

As the inorganic chelating agent, a polyphosphoric acid chelating agent or a metal fluorocomplex chelating agent is preferred. Polyphosphate chelating agents include salts of polyphosphate with sodium, potassium, magnesium, aluminum or manganese. Metal fluoro complex chelating agents include, for example, TiF ₆ ^2- , SiF ₆ ^2- , and clustered compounds thereof. The plating solution containing the metal-fluoro complex chelating agent preferably further contains a fluoride ion scavenger (eg, boric acid) as an additive in order to convert free fluoride ions into stable complex ions.

Porphyrin compounds are preferred as organic chelating agents. Here, the porphyrin compound is a compound having a porphyrin skeleton in its molecule, and includes various derivatives.

In the plating solution of this step, the content of the inorganic chelating agent with respect to 1 part by mass of the Ag compound is preferably 1 part by mass or more and 300 parts by mass or less, more preferably 3 parts by mass or more and 200 parts by mass or less, and 4 parts by mass or more and 150 parts by mass. Part by mass or less is more preferable.

In the plating solution of this step, the content of the organic chelating agent with respect to 1 part by mass of the Cu compound is preferably 1 part by mass or more and 200 parts by mass or less, more preferably 2 parts by mass or more and 150 parts by mass or less, and 3 parts by mass or more and 130 parts by mass. Part by mass or less is more preferable.

In the plating solution of this step, the concentration of the Sn compound is preferably 50 g/L or more and 450 g/L or less, more preferably 150 g/L or more and 350 g/L or less. Moreover, in the plating solution, the concentration of the Ag compound is preferably 0.1 g/L or more and 100 g/L or less, more preferably 1 g/L or more and 50 g/L or less. In the plating solution, the concentration of the Cu compound is preferably 0.1 g/L or more and 100 g/L or less, more preferably 1 g/L or more and 50 g/L or less. In the plating solution, the concentration of the inorganic chelating agent is preferably 10 g/L or more and 500 g/L or less, more preferably 100 g/L or more and 300 g/L or less. In the plating solution, the concentration of the organic chelating agent is preferably 10 g/L or more and 500 g/L or less, more preferably 100 g/L or more and 300 g/L or less.

In the electroplating of this step, the temperature of the plating solution is preferably 10° C. or higher and 80° C. or lower, more preferably 20° C. or higher and 40° C. or lower. In electroplating, the current density is preferably 0.1 A/dm ² or more and 30 A/dm ² or less, more preferably 2 A/dm ² or more and 25 A/dm ² or less. In electroplating, it is preferable to use Sn, a Sn alloy, or an insoluble electrode plate as the anode, and it is more preferable to use an insoluble electrode plate.

The thickness of the coating layer 23 is preferably 0.1 μm or more and 100.0 μm or less, more preferably 0.3 μm or more and 10.0 μm or less, and still more preferably 0.7 μm or more and 3.0 μm or less. In addition, the thickness of the coating layer 23 substantially matches the total thickness of the first layer and the second layer formed in the heating process described later.

The Sn content in the coating layer 23 is preferably 70% by mass or more and 99.8% by mass or less, more preferably 80% by mass or more and 97% by mass or less, and even more preferably 90% by mass or more and 95% by mass or less.

The content of Ag in the coating layer 23 is preferably 0.1% by mass or more and 50% by mass or less, more preferably 1% by mass or more and 20% by mass or less, and even more preferably 6% by mass or more and 16% by mass or less.

The content of Cu in the coating layer 23 is preferably 0.1% by mass or more and 15% by mass or less, more preferably 0.5% by mass or more and 12% by mass or less, and even more preferably 1% by mass or more and 8% by mass or less.

[Heating process]
In this step, the laminate including the substrate 21, the third layer 22 and the coating layer 23 is heated. A heating method is not particularly limited, and a heating furnace or the like can be used.

By heating, the metal elements (for example, Cu and Ni) contained in the third layer 22 and Sn contained in the coating layer 23 react at the interface S between the third layer 22 and the coating layer 23, resulting in a first reaction. Crystals 24 of the product (eg intermetallic compound) are formed. Crystals 24 of the first reaction product grow gradually with heating. In addition, the grown first reaction product crystal 24 is integrated with another adjacent first reaction product crystal 24 . As a result, the crystals 24 of the first reaction product gradually form a layer under the coating layer 23 . As a result, a layer corresponding to the second layer 5 shown in FIG. 1 is formed. Also, in a region of the coating layer 23 away from the interface S, Sn and Ag contained in the coating layer 23 react to form crystals 25 of a second reaction product (for example, an intermetallic compound). Crystals 25 of the second reaction product grow gradually with heating. As the crystals 25 of the second reaction product grow, Ag contained in the coating layer 23 is incorporated into the crystals 25 of the second reaction product. As a result, the upper portion of coating layer 23 is separated into a phase consisting of crystals 25 of the second reaction product and a mother phase containing Sn. As a result, a layer corresponding to the first layer 4 shown in FIG. 1 is formed. That is, in the first layer 4, the Sn matrix 4a originates from the matrix described above. The Sn—Ag phase 4b originates from the phase consisting of crystals 25 of the second reaction product described above.

The heating temperature in this step is preferably 220° C. or higher and 450° C. or lower, more preferably 250° C. or higher and 350° C. or lower. By setting the heating temperature to 220° C. or higher, the first reaction product and the second reaction product can be sufficiently formed. By setting the heating temperature to 450° C. or lower, it is possible to suppress the melting of the coating layer 23 .

The heating time in this step is preferably 1 second or longer and 10 minutes or shorter, more preferably 10 seconds or longer and 1 minute or shorter. By setting the heating time to 1 second or more, the first reaction product and the second reaction product can be sufficiently formed. By setting the heating time to 10 minutes or less, melting of the coating layer 23 can be suppressed.

In this process, the heating temperature indicates the temperature of the laminate described above, not the ambient temperature. Moreover, the heating temperature indicates the peak temperature in this step. Furthermore, the heating time indicates the time during which the above peak temperature is maintained. For example, in this step, the temperature of the laminate is gradually increased until it reaches 250° C., then the temperature of the laminate is maintained at 250° C. for 30 seconds, and then cooled to room temperature. °C and the heating time is 30 seconds.

The method for manufacturing the conductive member of the present invention has been described above with reference to FIGS. However, the manufacturing method of the conductive member of the present invention is not limited to the manufacturing method shown in FIGS. For example, in the coating layer forming process, the pretreatment process and the first process can be omitted.

If the first step is omitted in the coating layer forming step, the metal element contained in the base material reacts with Sn contained in the coating layer in the heating step to form crystals of the first reaction product. be done. As a result, a conductive member similar to the conductive member 11 shown in FIG. 2 is manufactured.

EXAMPLES The present invention will be further described below with reference to Examples. However, the present invention is not limited to the examples.

In the examples, the imaging with an electron microscope was performed using an electron microscope (manufactured by JEOL Ltd., "focused ion beam processing and observation device JIB-4000") at a magnification of 10,000 times and 30 kV.

In the examples, elemental analysis of the plating layer was performed using a scanning electron microscope (“SU5000” manufactured by Hitachi High-Tech Co., Ltd.) equipped with an energy dispersive X-ray fluorescence spectrometer (“X-MaxN50” manufactured by Horiba, Ltd.). (magnification of 500 times, acceleration voltage of 15 kV). In the energy dispersive X-ray fluorescence spectroscopy, if the accelerating voltage is weakened, elemental analysis can be performed in a narrow range near the surface of the sample, and if the accelerating voltage is increased, elemental analysis can be performed in a wide range from the surface to the deep part of the sample. be able to. At the acceleration voltage described above, elemental analysis could be performed in a region from the surface of the plating layer to a depth of about 2 μm (generally the entirety of the first and second layers). In the elemental analysis, peak intensities derived from metals (Ag, Cu, Sn and Ni) were detected, and the peak intensity ratio of each element was calculated. Then, based on the peak intensity ratio, the mass ratio of each element in the plating layer was calculated.

[Example 1]
A conductive member of Example 1 was manufactured by the following method. First, a copper plate (thickness: 0.4 mm) was prepared as a base material. A cleaning agent containing sodium hydroxide (“S-CLEAN 30” manufactured by Okuno Chemical Industry Co., Ltd.) was diluted with water to prepare an aqueous cleaning solution (concentration of cleaning agent: 50 g/L, pH 12.5). The substrate was immersed for 1 minute in an immersion bath (liquid temperature 48° C.) filled with a washing aqueous solution. Thus, the first cleaning treatment was performed on the base material. Next, the substrate after the first cleaning treatment was washed with water several times until the aqueous cleaning solution was sufficiently removed from the surface of the substrate.

Next, an electrolytic degreasing agent (“NC Rustol” manufactured by Okuno Chemical Industry Co., Ltd.), which is an aqueous sodium hydroxide solution, was diluted with water to prepare an electrolytic aqueous solution (concentration of electrolytic degreasing agent: 100 g/L, pH 13.2). In an electrolytic bath (liquid temperature: 50°C) filled with an electrolytic aqueous solution, electrolytic treatment was performed for 1 minute using the base material after the first cleaning treatment as a cathode. In the electrolytic treatment, the current density was adjusted to 5 A/dm ² . Thus, the substrate was subjected to the second cleaning treatment. Next, the substrate after the second washing treatment was washed with water five times.

The base material after the second cleaning treatment was immersed for 1 minute in an activation tank (liquid temperature 30° C.) filled with sulfuric acid (pH 0.5). Thus, the substrate was subjected to acid treatment. After the acid treatment, the substrate was washed with water three times.

Next, the acid-treated substrate was immersed in a plating bath (liquid temperature: 55°C) filled with a Ni plating solution containing 240 g/L of nickel sulfate, 45 g/L of nickel chloride, 40 g/L of boric acid, and water. , electroplating treatment for 5 minutes. In the electroplating treatment, the pH was adjusted to 3.8 and the current density to 4 A/dm ² . As a result, a Ni layer (third layer) was formed on the surface of the base material after the acid treatment. After that, it was washed with water three times.

Next, the substrate covered with the Ni layer was electroplated to form a coating layer containing Sn—Ag and Cu (Sn—Ag—Cu ternary alloy thin film) on the Ni layer. Specifically, in electroplating, a substrate coated with a Ni layer was used as a cathode, and a titanium electrode coated with platinum was used as an anode. Sn compound (p-toluenesulfonic acid Sn salt) 250 g/L, Ag compound (p-toluenesulfonic acid Ag salt) 25 g/L, Cu compound (p-toluenesulfonic acid Cu salt) 8 g/L, inorganic chelating agent (metal 240 g/L of SiF ₆ ^2- , which is a fluoro complex chelating agent, 25 g/L of organic chelating agent (3,8,13,18-tetramethylporphyrin-2,7,12,17-tetrapropanoic acid), additive ( A substrate coated with a Ni layer is immersed in a plating bath (liquid temperature 31 ° C.) filled with a plating solution containing polyethylene glycol 30 mL / L and methanesulfonic acid 100 g / L) and water, and electroplating is performed for 2 minutes. processed. After that, the laminate including the base material, the Ni layer and the coating layer was washed with water four times, dried with air, and then dried with hot air at 70° C. for 2 minutes.

Next, the above laminate was heated using a heating furnace. In the heating, the temperature in the furnace was raised until the temperature of the laminate reached 280°C. Next, after the temperature of the above laminate reached 280° C., the temperature in the furnace was maintained for 20 seconds. Next, the temperature inside the furnace was gradually lowered to room temperature (heating at a peak temperature of 280° C. for 20 seconds). As a result, Ni contained in the Ni layer and Sn contained in the coating layer reacted to form a second layer containing a Ni—Sn intermetallic compound. Further, Sn contained in the coating layer was separated to form a Sn mother phase. Furthermore, Sn and Ag contained in the coating layer reacted to form a Sn--Ag phase containing a Sn--Ag intermetallic compound. As a result, a conductive member of Example 1 was obtained.

In forming the coating layer, the higher the current density during electroplating, the lower the Ag content in the coating layer. In Example 1, the current density during electroplating is increased or decreased in the range of 0.1 A/dm ² or more and 30.0 A/dm ² or less to manufacture a conductive member, and the content of Ag in the plating layer is measured. The work was repeated several times. As a result, the current density at which a laminate having a desired Ag content in the plating layer (7% by mass) can be formed was obtained.

[Cross-section observation]
Cross-sectional observation of the conductive members of Example 1 and Comparative Example 1 was performed using an electron microscope. FIG. 6 shows a cross-sectional image of the conductive member of Comparative Example 1. As shown in FIG. The conductive member of Comparative Example 1 includes a substrate (Cu in FIG. 6), a third layer (Ni in FIG. 6) covering the substrate, and a coating layer (Sn—Ag in FIG. 6) covering the third layer. I was prepared. The substrate contained Cu. The third layer contained Ni. The coating layer contained Sn and Ag.

FIG. 7 shows a cross-sectional image of the conductive member of Example 1. As shown in FIG. The conductive member of Example 1 includes a substrate (Cu in FIG. 7), a third layer (Ni in FIG. 7) covering the substrate, and a second layer (Ni—Sn in FIG. 7) covering the third layer. , and a first layer covering the second layer. The first layer contained a Sn matrix containing Sn (Sn) and a Sn--Ag phase (Sn--Ag) dispersed in the Sn matrix. The substrate contained Cu. The third layer contained Ni. The second layer contained a Sn—Ni intermetallic compound. The Sn matrix contained Sn. The Sn--Ag phase contained a Sn--Ag intermetallic compound.

As is clear from the comparison of FIGS. 6 and 7, by heating the conductive member of Comparative Example 1, a second layer is newly formed between the coating layer and the third layer, and the upper part of the coating layer is A first layer was formed by separating into a Sn matrix phase and a Sn—Ag phase.

[Examples 2 to 3 and Comparative Example 1]
Conductive members of Examples 2 and 3 and Comparative Example 1 were manufactured in the same manner as the method of manufacturing the conductive member of Example 1, except that the following points were changed. The peak temperature was changed to 300°C or 320°C in the production of the conductive members of Examples 2-3. In the production of the conductive member of Comparative Example 1, heat treatment was not performed. That is, the laminate including the base material, the Ni layer and the coating layer obtained during the production of the conductive member of Example 1 was used as the conductive member of Comparative Example 1 as it was.

[Comparative Example 2]
As the conductive member of Comparative Example 2, a low insertion force plating conductive member for connector terminals (commercially available) manufactured by another company was used. The conductive member of Comparative Example 2 had a substrate containing Cu, a Ni layer (0.3 μm thick) covering the surface of the substrate, and an outermost layer covering the surface of the Ni layer. The outermost layer contained a Sn matrix containing Sn and a Sn--Cu phase dispersed in the Sn matrix. The Sn--Cu phase contained a Sn--Cu based intermetallic compound.

[Comparative Example 3]
As the conductive member of Comparative Example 3, a reflow Sn-plated conductive member for connector terminals manufactured by another company was used. The conductive member of Comparative Example 3 includes a substrate containing Cu, a Ni layer (0.6 μm thick) covering the surface of the substrate, and a Sn plating layer (1.5 μm thick) covering the Ni layer. was equipped with The Sn plating layer was subjected to reflow treatment.

[Example 4]
A conductive member of Example 4 was manufactured in the same manner as the conductive member of Example 1, except that the following points were changed. In the conductive member of Example 4, the current density of electroplating was changed in the formation of the coating layer, and the content of Ag in the plating layer was adjusted to 7.0% by mass.

[Examples 5 to 6 and Comparative Example 4]
Conductive members of Examples 5 to 6 and Comparative Example 4 were produced in the same manner as in the production of the conductive member of Example 4, except that the following points were changed. The peak temperature was changed to 300°C or 320°C in the production of the conductive members of Examples 5-6. In the production of the conductive member of Comparative Example 4, no heat treatment was performed. That is, the laminate including the base material, the Ni layer and the coating layer obtained during the production of the conductive member of Example 4 was used as the conductive member of Comparative Example 4 as it was.

[Ag Content Ratio]
Using a scanning electron microscope equipped with the energy dispersive X-ray fluorescence spectrometer described above, the content of Ag relative to all metal elements contained in the plating layers of the conductive members of Examples 1 to 6 and Comparative Examples 1 to 4 was measured. did. The measurement results are shown in Table 1 below.

[Sn—Ag phase size and area ratio]
The plating layers of the conductive members of Examples 1 to 6 and Comparative Example 2 were subjected to surface observation (elemental mapping) using a scanning electron microscope equipped with the above energy dispersive X-ray fluorescence spectrometer. In the surface observation, the region where Sn and Ag were detected on the surface of the plating layer (the region containing Sn and Cu in Comparative Example 2) was defined as the Sn—Ag phase (Sn—Cu phase in Comparative Example 2).

8 and 9 show surface images of the plating layers of the conductive members of Examples 1 and 6. FIG. As shown in FIGS. 8 and 9, on the surfaces of the plating layers of the conductive members of Examples 1 and 6, the Sn--Ag phase (Sn--Ag) was dispersed in the Sn mother phase (Sn). In the conductive member of Example 1, the Sn—Ag phase was particulate. In the conductive member of Example 6, the Sn—Ag phase was tabular.

The conductive members of Examples 1 and 6 were significantly different in shape of the Sn—Ag phase. This is because the conductive member of Example 6 does not contain much Ag, which has a higher melting point than Sn, in the plating layer, and the heating temperature in the heating process is high, so that the Sn—Ag phase softens in the heating process. It is judged that it was because

Regarding the plating layers of the conductive members of Examples 1 to 6 and Comparative Example 2, the shape of the Sn—Ag phase (Sn—Cu phase in Comparative Example 2) and its size (when the shape is particulate, the particle diameter, shape If it is plate-shaped, the major axis) was measured. The results are shown in Table 1 below. In the size measurement, 20 randomly selected measurement objects were measured, and the arithmetic mean value of the obtained 20 measured values was obtained. The obtained value was defined as the size (particle diameter or length) of the object to be measured.

Further, by processing the above-described surface images with image analysis software, the area ratio of the Sn—Ag phase (Sn—Cu phase in Comparative Example 2) in the surface region of the plating layer of each conductive member was calculated. Specifically, the area ratio occupied by the Sn—Ag phase is measured in four measurement areas (field of view: 300 μm × 300 μm) randomly selected from the surface of the plating layer, and the arithmetic of the measured values measured at the four locations An average value was obtained. The obtained value was used as an evaluation value of the area ratio occupied by the Sn—Ag phase.

<Evaluation>
The contact resistance of the conductive members of Examples 1 to 6 and Comparative Examples 1 to 4, the wear resistance of the plating layer and the insertability were evaluated by the following methods. Also, for reference, the arithmetic mean roughness Ra of the surface of the plating layer of the conductive members of Examples 1 to 6 and Comparative Examples 1 to 4 was measured. The evaluation results are shown in Table 2 below. The evaluation was performed under an environment of temperature 25.0° C. (±0.2° C.) and humidity (50.0%±1.0%) RH.

[Arithmetic mean roughness]
The arithmetic mean roughness Ra of the surface of the plating layer of each conductive member was measured using a laser microscope ("VK-X210" manufactured by Keyence Corporation). Ra was measured at 10 points on the surface of each conductive member, and the arithmetic average value was used as the evaluation value. As shown in Table 2 below, the conductive members of Examples 1 to 6 had larger Ra values of the plating layers than the conductive members of Comparative Examples 1 and 4. It is believed that this is because the Sn—Ag phase was formed in the first layer, which is the outermost layer of the plating layer, to form bumps.

[Contact resistance]
The contact resistance of each conductive member was measured using a contact resistance measuring device ("Electrical Contact Simulator CRS-1" manufactured by Yamazaki Seiki Laboratory Co., Ltd.). The measurement was performed near the center of the plating layer of each conductive member under the conditions of a measurement current of 10 mA, a load variation method, a sliding distance of 0.5 mm, and a sliding speed of 1 mm/min. For the load in the measurement, a cycle of gradually increasing the load from 0.0N to 0.5N and a cycle of gradually decreasing the load from 0.5N to 0.0N were repeated.

The contact resistance of each conductive member was determined according to the following criteria.
A (accepted): evaluation value of 3.000 mΩ or less B (failed): evaluation value of more than 3.000 mΩ

[Insertability]
The insertability of each conductive member was evaluated based on the surface friction coefficient. Specifically, using a surface property measuring machine (“TYPE: 14FW” manufactured by Shinto Kagaku Co., Ltd.), slide the mating material (SUJ2 (high carbon chromium bearing steel)) near the center of the plating layer of each conductive member. The dynamic friction coefficient was measured by The measurement conditions were sliding distance: 30 mm, sliding speed: 10 mm/sec, number of sliding: 10 reciprocations, and load of 1000 gf. In the measurement, the dynamic friction coefficient was measured each time the mating material was reciprocated once. In the measurement, 10 measured values were obtained because the mating member was slid back and forth 10 times. The arithmetic mean value (dynamic friction coefficient) of the obtained 10 measured values was used as the insertability evaluation value.

The insertability of each conductive member was determined according to the following criteria.
A (accepted): evaluation value of 0.2800 or less B (failed): evaluation value of more than 0.2800

[Abrasion resistance]
In the measurement of the dynamic friction coefficient described above, the dynamic friction coefficient tended to increase gradually each time the mating member was slid one reciprocating motion. It is considered that this is because the surface of each conductive member is worn and deformed due to sliding with the mating member. That is, in the measurement of the dynamic friction coefficient, the more excellent the wear resistance of the conductive member, the more the measured value is suppressed from increasing due to the sliding of the mating member. Therefore, the difference between the minimum value and the maximum value among the 10 measured values obtained in the measurement of the dynamic friction coefficient was used as the evaluation value of the wear resistance of each conductive member.

The wear resistance of each conductive member was determined according to the following criteria.
A (accepted): evaluation value of 0.080 or less B (failed): evaluation value of more than 0.080

As described above, the conductive members of Examples 1 to 6 were provided with a substrate and a plated layer covering the surface of the substrate. The plating layer had a first layer as the outermost layer and a second layer laminated inside the first layer. The first layer contained a Sn matrix containing Sn and a Sn—Ag phase dispersed in the Sn matrix. The Sn--Ag phase contained Sn and Ag. The second layer contained nickel and Sn. As shown in Table 2, the conductive members of Examples 1 to 6 had small contact resistance, excellent insertability, and could suppress abrasion of the plating layer.

On the other hand, the plating layers of the conductive members of Comparative Examples 1, 3 and 4 had layer structures different from the plating layers of the conductive members of Examples 1-6. Specifically, in the plating layers of the conductive members of Comparative Examples 1, 3 and 4, the outermost layer did not contain the Sn mother phase and the Sn—Ag phase. As a result, the conductive members of Comparative Examples 1, 3 and 4 failed in wear resistance and insertability.

In the plating layer of the conductive member of Comparative Example 2, the outermost layer contained the Sn mother phase and the Sn—Cu phase. The Sn--Cu phase containing Sn and Cu is judged to have a poorer balance of hardness and flexibility than the Sn--Ag phase containing Sn and Ag. Therefore, the conductive member of Comparative Example 2 failed in wear resistance.

The conductive member and the method for manufacturing the conductive member of the present invention can provide a conductive member that can be used as a connector terminal fitting or the like.

1, 11 conductive member 2, 12, 21 base material 3, 13 plating layer 4, 14 first layer 4a, 14a Sn mother phase 4b, 14b Sn—Ag phase 5, 15 second layer 6, 22 third layer 23 coating Layer 24 Crystals of the first reaction product 25 Crystals of the second reaction product

Claims (8)

A base material and a plating layer covering the surface of the base material,
The plating layer has a first layer that is the outermost layer and a second layer that is laminated inside the first layer,
The first layer includes a phase I containing Sn and a phase II dispersed in the first phase,
The phase II contains Sn and Ag,
The conductive member, wherein the second layer contains a metal element other than Ag and Sn. The plating layer further comprises a third layer laminated inside the second layer,
The conductive member according to claim 1, wherein the third layer contains Ni or Cu. In elemental analysis using energy dispersive X-ray fluorescence spectroscopy, when the acceleration voltage is 15 kV, the content of Ag with respect to all metal elements contained in the plating layer is 1% by mass or more and 50% by mass or less. , The conductive member according to claim 1 or 2. 4. The conductive member according to claim 1, wherein said first layer and said second layer further contain Cu. Said Phase II comprises:
It is particulate and has a particle diameter of 0.5 μm or more and 10.0 μm or less, or is plate-shaped and has a major axis of 3.0 μm or more and 130.0 μm or less. The conductive member according to claim 1. The conductive member according to any one of claims 1 to 5, wherein the total thickness of the first layer and the second layer is 0.1 µm or more and 100.0 µm or less. The conductive member according to any one of claims 1 to 6, wherein the area ratio of the phase II in the first layer is 2.0% or more and 50.0% or less. A method for manufacturing a conductive member comprising a base material and a plating layer covering the surface of the base material,
A coating layer forming step of forming a coating layer containing Sn and Ag on the base material directly or via another layer by plating;
A heating step of heating the base material and the coating layer,
The method for manufacturing a conductive member, wherein the heating temperature in the heating step is 220°C or higher and 450°C or lower.

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