JP2015130308A - Electric contact material, connector terminal, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric contact material that is low in costs, and that can be manufactured with ease, and that has an excellent performance.SOLUTION: An electric contact material 1 has: a base material 2; and a composite plating film 3 provided on the base material 2, and in which lubricant particles 32 are dispersed on a parent phase 31 consisting of Ni or an Ni alloy. In addition, both a conductive oxide film 33 obtained by oxidizing the parent phase 31, and the lubricant particles 32 are exposed on a surface of the composite plating film 3. The electric contact member 1 is fabricated by a manufacturing method including: a composite plating step of forming on the base material 2 the composite plating film 3 in which the lubricant particles 32 are dispersed on the parent phase 31 consisting of Ni or an Ni alloy, a part of the lubricant particles 32 being exposed on a surface; and an oxidation treatment step of oxidizing the parent phase 31 to form the conductive oxide film 33.

Description

  The present invention relates to an electrical contact material, a connector terminal using the electrical contact material, and a method for producing the electrical contact material.

  As an electrical contact material used for a connector terminal or the like, a material in which a Sn (tin) plating film is provided on the surface of a base material made of a Cu (copper) alloy is frequently used. However, in the above-mentioned electrical contact material, the relatively soft Sn plating film is worn at an early stage as the contact part slides, and there is a possibility that the contact resistance increases. Furthermore, the terminal using the above-mentioned electrical contact material also has a drawback that the insertion force is increased particularly in a multipolar connector due to the frictional force generated at the contact portion when the terminal is inserted. Therefore, there is a need for an electrical contact material that has a low contact resistance with the counterpart terminal and a low friction coefficient during sliding.

  On the other hand, in the field of sliding members, in order to reduce the friction coefficient, a composite plating film in which particles having a low friction coefficient such as PTFE (polytetrafluoroethylene) particles are dispersed in a metal plating film is used. There is known a method of providing in (Patent Documents 1 and 2). As the metal used for the composite plating film, Ni (nickel) or Ni alloy is often used. However, when Ni is left in the atmosphere, an insulating oxide film containing NiO as a main component is formed on the surface. Therefore, when using the material which has the conventional composite plating film for an electrical contact use, there existed a problem that contact resistance became high.

  In order to cope with this problem, a technique for forming a noble metal plating film on the surface of a composite plating film has been proposed (Patent Document 3). By providing a noble metal plating film that is not easily oxidized on the surface of the composite plating film, a low contact resistance can be maintained for a long period of time. On the other hand, when the thickness of the noble metal plating film is larger than the particle size of the lubricating particles, the friction reducing effect by the lubricating particles cannot be obtained. Therefore, it is necessary to make the thickness of the noble metal plating film thinner than the particle diameter of the lubricating particles (Patent Documents 4 and 5).

JP-A-4-285199 JP-A-6-308575 JP 2001-123292 A JP 2006-286574 A JP 2003-151707 A

  By the way, when using the composite plating film mentioned above, a friction coefficient can be made small, so that the particle size of lubricating particles is small. Therefore, generally, lubricating particles having a particle size of about 0.1 to 5 μm are used. However, if the film thickness of the noble metal plating film is made thinner than the particle size of the lubricating particles, the film thickness of the noble metal plating film is precisely controlled and the noble metal plating film is generated when the film thickness is 1 μm or less. It is difficult to reduce defects such as pinholes. Moreover, the electrical contact material using the noble metal plating film has a problem that the material cost is increased.

  The present invention has been made in view of such a background, and an object of the present invention is to provide an electrical contact material that is low in cost and easy to manufacture and has excellent performance, and a method for manufacturing the same.

One embodiment of the present invention is a substrate;
A composite plating film provided on the base material and having lubricating particles dispersed in a matrix made of Ni or Ni alloy;
An electrical contact material is characterized in that a conductive oxide film obtained by oxidizing the matrix and the lubricating particles are exposed on the surface of the composite plating film.

According to another aspect of the present invention, a lubricating plating particle is dispersed in a matrix composed of Ni or a Ni alloy, and a composite plating film in which a part of the lubricating particle is exposed on the surface is formed on a substrate. A composite plating process;
And an oxidation treatment step of oxidizing the matrix to form a conductive oxide film.

  The electric contact material has the composite plating film in which the lubricating particles are dispersed in the matrix made of Ni or Ni alloy on the base material. Therefore, the electrical contact material has a small friction coefficient and excellent lubricity.

  Further, the conductive oxide film formed by oxidizing the matrix and the lubricating particles are exposed on the surface of the composite plating film. Therefore, the electrical contact material has excellent lubricity due to the lubricious particles exposed on the surface, and the contact resistance can be reduced by the conductive oxide film. And since the said conductive oxide film interrupts | blocks between the said mother phase of the said composite plating layer and air | atmosphere, formation of insulating Ni oxide can be suppressed and low contact resistance can be maintained for a long period of time. Further, it is not necessary to use a noble metal for forming the conductive oxide film. Therefore, the electrical contact material is inexpensive.

  Moreover, the said electrical contact material which has said electroconductive oxide film can be easily manufactured with the said manufacturing method which has the said composite plating process and the said oxidation treatment process.

  As described above, according to the present invention, it is possible to obtain an electrical contact material which is low in cost and easy to manufacture and has excellent performance and a method for manufacturing the same.

  And the connector terminal formed from the said electrical contact material has small contact resistance, can obtain favorable electrical contact, and can make small insertion force required when fitting a terminal. Therefore, the connector terminal formed from the electrical contact material has excellent performance.

Sectional drawing of the electrical contact material in Example 1. FIG. The graph which shows the result of the high temperature durability test in Example 1. FIG. The graph which shows the result of the sliding test when sliding a hard Au plating copper plate on the electrical contact material in Example 1. FIG. The graph which shows the result of the sliding test (reference test) when sliding a Ni plating copper plate on the electrical contact material in Example 1. FIG. The graph which shows the result of the high temperature durability test in Example 2. FIG. The graph which shows the result of the sliding test when the hard Au plating copper plate is slid on the Ni plating copper plate which does not contain the lubricous particle in the comparative example 1. FIG. The graph which shows the result of the sliding test (reference test) when sliding the Ni plating copper plates which do not have lubricous particle | grains in the comparative example 1. FIG. The graph which shows the result of the sliding test when the hard Au plating copper plates in the comparative example 2 are made to slide.

  In the electrical contact material, as the base material, various metals having conductivity and capable of forming the composite plating film can be used. As the base material, it is common to use a metal mainly composed of Cu (copper) such as a copper alloy or brass, but Al (aluminum), Fe (iron) or an alloy containing these metals is used. You can also. These metal materials are excellent not only in electrical conductivity but also in formability and springiness, and can be applied to various types of electrical contacts.

  The film thickness of the composite plating film can be appropriately set according to the application. The film thickness of the composite plating film is usually selected from the range of 1 to 30 μm, and more preferably in the range of 1 to 10 μm.

  Moreover, the composite plating film may be directly formed on the surface of the base material, or an intermediate film may be provided between the base material and the composite plating film. The material that constitutes the intermediate film, for example, improves the adhesion between the base material and the composite plating film, suppresses the peeling of the composite plating film, and diffuses the metal constituting the base material into the composite plating film. The material is appropriately selected according to the material of the base material and the composite plating film so as to have an inhibiting action. By providing the intermediate film having these functions, the durability of the electrical contact material can be further improved. As the intermediate film, for example, pure Cu or pure Ni can be used. The film thickness of the intermediate film is preferably in the range of 0.1 to 1.0 μm.

  The composite plating film can reduce the friction coefficient as the total area of the lubricating particles exposed on the surface increases. Therefore, it is preferable that the lubricating particles have a projected area equivalent circle diameter (Heywood diameter), that is, a diameter of a circle having the same area as the projected area of the particle on the plane. From the viewpoint of reducing the friction coefficient, the average value of the projected area equivalent circle diameter of the lubricating particles is preferably in the range of 0.1 to 10 μm, and more preferably in the range of 0.1 to 1.0 μm. preferable.

  Further, the content of the lubricating particles in the composite plating film can be appropriately set according to the application so as to satisfy the required contact resistance and friction coefficient. When the content of the lubricating particles is small, the number of the lubricating particles exposed on the surface of the composite plating film is small, so that the contact resistance is low, but the friction coefficient tends to be large. On the other hand, when the content of the lubricating particles is large, the contact resistance increases, but the friction coefficient tends to decrease.

  The content of the lubricating particles in the composite plating film is preferably selected from the range of 2 to 50% by volume and may be selected from the range of 3 to 30% by volume with respect to the total volume of the composite plating film. More preferred. Thereby, the electrical contact material has a sufficiently low contact resistance and can reduce the friction coefficient.

As a material constituting the lubricating particles, for example, a material having self-lubricating properties such as fluorinated resin, DLC (diamond-like carbon), graphite, and MoS ₂ (molybdenum sulfide) can be used. Examples of the fluorinated resin include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-hexa. Fluorinated resin copolymers such as fluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE) and tetrafluoroethylene-ethylene copolymer (ETFE), and block copolymers and graft copolymers containing fluorinated resins, etc. Can be used.

  The lubricating particles are preferably made of a fluorinated resin. As will be described later, when the conductive oxide film is formed on the surface of the matrix phase, it is necessary to immerse the composite plating film in an acid. For this reason, the use of lubricating particles made of a material that is unlikely to be altered by acid, such as a fluorinated resin, can suppress the alteration of the lubricating particles, resulting in an increase in the coefficient of friction due to the alteration of the lubricating particles. Can be prevented. Further, from the viewpoint of suppressing deterioration of the lubricating particles and further reducing the friction coefficient, it is more preferable to use PTFE as the material of the lubricating particles.

  If the conductive oxide film formed on the surface of the mother phase usually has a thickness of about several nm, the contact resistance can be reduced and the effect of blocking the atmosphere can be sufficiently obtained. Note that an excessively thick conductive oxide film is not preferable because the contact resistance may increase.

The conductive oxide film preferably contains Ni ₃ O ₄ . The resistivity of Ni ₃ O ₄ is considered to be 10 ⁻⁴ to 10 ⁻² Ωm, which is comparable to other conductive spinel type oxides. Therefore, for example, when the thickness of the conductive oxide film is about several nanometers, the electrical resistance derived from the conductive oxide film can be sufficiently reduced, and the contact resistance can be further reduced. In addition, since the conductive oxide film containing Ni ₃ O ₄ becomes a dense film, oxygen or the like in the atmosphere can be prevented from passing through the conductive oxide film. Therefore, it is possible to suppress the parent phase from being oxidized by oxygen or the like that has passed through the conductive oxide film, and it is possible to stably maintain a low contact resistance state for a long period of time.

  As described above, the electrical contact material has a composite plating film on the surface, so that the contact resistance is low and the friction coefficient is small. Therefore, the connector terminal made of the above-described electrical contact material can obtain the effect of the composite plating film and has excellent performance. In addition, the above-mentioned effect can be acquired if the composite plating film is formed in the contact part which comprises the electrical contact with an other party terminal at least.

  Further, the effect of reducing the friction coefficient by the composite plating film becomes more remarkable as the number of connector terminals provided in the connector is larger. That is, a multipolar connector having a large number of connector terminals requires a larger insertion force when mating the connector because the area of the sliding portion when mating with the counterpart connector is larger than that of a single-polar connector. . On the other hand, the multipolar connector using the connector terminal can reduce the coefficient of friction at the contact portion of each connector terminal due to the presence of the composite plating film, and can reduce the frictional force accompanying the sliding of the connector terminal. Therefore, the connector terminal can effectively reduce the insertion force in the multipolar connector.

  Next, the manufacturing method of the said electrical contact material is demonstrated. The manufacturing method includes a composite plating step and an oxidation treatment step.

<Composite plating process>
In the composite plating step, the lubricant particles are dispersed in the matrix phase made of Ni or Ni alloy, and a composite plating film in which a part of the lubricant particles is exposed on the surface is formed on the substrate. Formation of the composite plating film can be performed by a method similar to normal Ni plating such as electroplating using a plating solution to which lubricating particles and a dispersant are added.

<Oxidation process>
As the oxidation treatment step, either a method of anodizing the composite plating film in a weakly acidic electrolyte solution or a method of performing a self-passivation treatment of immersing the composite plating film in a dilute acid having an oxidizing property Can be adopted. In any case, the surface of the parent phase is oxidized and a conductive oxide film is formed.

  In the anodizing process, a composite plating film is used as an anode, and a counter electrode made of a material such as platinum (Pt) that does not react with the electrolyte is used as a cathode, and a voltage is applied between both electrodes in a weakly acidic electrolyte. Is implemented. The voltage applied between the two electrodes is measured with reference to the reference electrode inserted in the electrolyte, and controlled so that the potential of the anode (Ni) is about 0.2 to 1.5 V in terms of standard hydrogen electrode potential. Is done. Note that the voltage applied between the two electrodes can be controlled based on the potential difference between the anode and the cathode without using the reference electrode. Also, the potentials of both electrodes can be appropriately controlled by controlling the concentration and current density of the electrolytic solution.

  Diluted sulfuric acid or the like can be used as the weak acid electrolyte. When dilute sulfuric acid is used, the concentration is preferably 0.01% by volume or less, and more preferably 0.001% by volume or less.

The current density in the anodic oxidation treatment varies depending on the concentration of the weak acidic electrolyte, the shape of the electrode, the liquid temperature, etc., but is usually 0.01 to 1 mA / cm ² .

  The self-passivation treatment is performed by immersing the composite plating film in an acid having a sufficiently low hydrogen ion concentration and an oxidizing property. As the diluted acid, for example, an aqueous solution obtained by diluting an oxidizing acid such as nitric acid with pure water can be used. Further, an aqueous solution imparted with oxidizing property by dissolving oxygen acting as an oxidizing agent in an acid having no oxidizing property such as diluted sulfuric acid can also be used. In addition, sulfuric acid diluted with water in which oxygen is dissolved in advance to 0.01% by volume or less, preferably 0.001% by volume or less may be used. The dissolution of oxygen in diluted sulfuric acid or water can be performed by, for example, a method of bubbling oxygen gas or air, a method of stirring water or the like in the atmosphere, and the like. Usually, about 7 to 30 ppm of oxygen is dissolved in the water in which oxygen is dissolved by these methods.

Example 1
Examples of the electrical contact material will be described with reference to FIGS. As shown in FIG. 1, the electrical contact material 1 includes a base material 2 and a composite plating film 3 provided on the base material 2 and having a lubricating particle 32 dispersed in a matrix 31 made of Ni or Ni alloy. Have. On the surface of the composite plating film 3, the conductive oxide film 33 formed by oxidizing the matrix 31 and the lubricating particles 32 are exposed.

  The electrical contact material 1 of this example was produced by a manufacturing method having a composite plating step and an oxidation treatment step by anodizing treatment. Below, the manufacturing method of the electrical contact material 1 is explained in full detail.

<Composite plating process>
A copper plate having a thickness of 0.3 mm was used as the substrate 2, and a composite plating film 3 having a thickness of 10 μm was formed on the substrate 2 by electroplating. The matrix phase 31 of the composite plating film 3 was Ni, and the lubricating particles 32 were PTFE particles having a diameter of 0.1 to 0.2 μm. The content of PTFE particles was 8 to 10% by volume with respect to the total volume of the composite plating film 3.

<Oxidation process>
One plate surface of the base material 2 after the composite plating step was protected with a polyimide tape, and only the other plate surface was subjected to anodization. Next, the base material 2 on which the composite plating film 3 was formed was immersed in sulfuric acid diluted to 20% by volume with pure water to remove the insulating natural oxide film generated on the surface of the composite plating film 3, and then washed with water. Subsequently, the composite plating film 3 was anodized in a weakly acidic electrolytic solution, and the surface of the mother phase 31 was oxidized to form a conductive oxide film 33. As the weak acid electrolyte, sulfuric acid diluted to 0.001% by volume with pure water was used. A Pt electrode was used as the counter electrode (cathode). The treatment time for the anodizing treatment was 2 minutes, and the current density immediately before the treatment was 0.12 mA / cm ² .

  After the anodizing treatment was completed, the electrical contact material 1 was taken out from the weakly acidic electrolyte and washed with pure water. Thereafter, nitrogen gas was blown and dried to obtain an electrical contact material 1.

  Using the electrical contact material 1 obtained as described above, a high temperature durability test and a sliding test were performed.

<High temperature durability test>
A hard Au plated copper plate having a hemispherical convex portion having a curvature radius of 1 mm was prepared as a contact, and the hemispherical convex portion of the contact was brought into contact with the plate surface having the conductive oxide film 33 of the electrical contact material 1. From this state, the contact resistance between the electrical contact material 1 and the contact was measured while gradually increasing the load applied to the contact. Moreover, after performing the high temperature leaving process which heats at 160 degreeC for 120 hours in air | atmosphere to the electrical contact material 1, the same contact resistance was measured using the electrical contact material 1 after the high temperature standing process.

  FIG. 2 shows the measurement results of the contact resistance before and after the high temperature storage treatment. In addition, the vertical axis | shaft of FIG. 2 is a contact resistance, and a horizontal axis is the load added to the contactor.

  As can be seen from FIG. 2, the electrical contact material 1 of this example had a contact resistance of about 5 mΩ when the load was 1 N before the high temperature standing treatment. Further, after the high temperature standing treatment, the contact resistance when the load was 1 N was about 10 mΩ. As described above, the electrical contact material 1 of this example exhibits sufficiently low contact resistance for a connector terminal, and does not excessively increase contact resistance even when left in a high temperature environment, and has excellent high temperature durability. showed that.

<Sliding test>
A hard Au-plated copper plate having a hemispherical convex portion with a radius of curvature of 3 mm was prepared as a slider, and the hemispherical convex portion of the slider was brought into contact with the plate surface having the conductive oxide film 33 of the electrical contact material 1. . In this state, the electric contact material 1 was reciprocated while applying a vertical load of 5N to the slider, and the frictional force applied to the slider was measured. Then, the friction coefficient was calculated by dividing the friction force by the vertical load. Simultaneously with the measurement of the friction coefficient, the contact resistance between the electrical contact material 1 and the slider was measured.

  FIG. 3 shows the measurement results of the coefficient of friction and the contact resistance. The vertical axis in FIG. 3 is the coefficient of friction or contact resistance, and the horizontal axis is the number of cycles of reciprocation.

  As shown in FIG. 3, the friction coefficient between the electrical contact material 1 and the hard Au plated copper plate was about 0.2 to 0.3 after 100 cycles. Moreover, the contact resistance between the electrical contact material 1 and the hard Au plated copper plate was about 0.5 to 0.6 mΩ after 100 cycles. Thus, even when the electrical contact material 1 is repeatedly slid, the friction coefficient and the contact resistance are sufficiently small and stable, and has excellent sliding durability. Therefore, the connector terminal using the electrical contact material 1 of the present example can reduce the insertion force, has little deterioration in performance even after repeated insertion and extraction, and has excellent insertion and extraction properties.

  In this example, as a reference experiment, a sliding test was performed when a slider made of a Ni-plated copper plate having a conductive oxide film 33 was used instead of a slider made of a hard gold-plated copper plate. . The slider in this reference experiment was manufactured by the same manufacturing method as the electrical contact material 1 except that the lubricating particles 32 were not dispersed. The sliding test conditions and procedures are the same as described above.

  FIG. 4 shows the results of the reference experiment. In addition, the vertical axis | shaft of FIG. 4 is a friction coefficient or contact resistance, and a horizontal axis is the cycle number of a reciprocating motion.

  As is known from FIG. 4, the coefficient of friction between the electrical contact material 1 and the Ni-plated copper plate having the conductive oxide film 33 was about 0.3 after 100 cycles. Moreover, the contact resistance between the electrical contact material 1 and the Ni-plated copper plate was about 1 to 2 mΩ after 100 cycles. These results sufficiently satisfy the electrical contact and sliding durability required for the connector terminals.

  In this reference test, the contact resistance was relatively high, about 4 to 8 mΩ, from the start of the test to 60 cycles, and rapidly decreased to about 2 mΩ after exceeding 60 cycles. The cause of this is unknown at present, but a contact resistance of about 4 to 8 mΩ is in an allowable range for a connector terminal.

(Example 2)
This example is an example of the electrical contact material 1 in which the conditions of the anodizing treatment in Example 1 are changed. The electrical contact material 1 of this example was produced under the same conditions as in Example 1 except that sulfuric acid diluted to 0.0001% by volume with pure water was used as the weakly acidic electrolyte.

  Using the electrical contact material 1 obtained as described above, a high temperature durability test was performed. As a result, as shown in FIG. 5, the electrical contact material 1 of this example had a contact resistance of about 5 mΩ when the load was 1 N before the high temperature standing treatment. Further, after the high temperature standing treatment, the contact resistance when the load was 1 N was about 8 mΩ. As described above, the electrical contact material 1 of this example exhibits sufficiently low contact resistance for a connector terminal, and does not excessively increase contact resistance even when left in a high temperature environment, and has excellent high temperature durability. showed that.

(Example 3)
This example is an example of the electrical contact material 1 in which the conductive oxide film 33 is formed by the self-passivation process in the oxidation process. Specifically, the oxidation treatment process of this example was performed according to the following procedure. In addition, it is the same as that of Example 1 except an oxidation treatment process.

<Oxidation process>
One plate surface of the substrate 2 after performing the composite plating step was protected with a polyimide tape, and only the other plate surface was subjected to a self-passivation treatment. Next, the base material 2 was immersed in sulfuric acid diluted to 20% by volume with pure water, the insulating natural oxide film generated on the surface of the composite plating film 3 was removed, and washed with water.

  Subsequently, the base material 2 on which the composite plating film 3 was formed was diluted for 2 minutes in a dilute acid having an oxidizing property prepared in advance, and the surface of the mother phase 31 was oxidized to form a conductive oxide film 33. As the dilute acid described above, sulfuric acid diluted to 0.0001% by volume with pure water in which oxygen was sufficiently dissolved by stirring in the atmosphere was used.

  After the self-passivation treatment was completed, the electrical contact material 1 was taken out from the diluted acid and washed with pure water. Thereafter, nitrogen gas was blown and dried to obtain an electrical contact material 1.

  In this example, the obtained electrical contact material 1 was allowed to stand in a normal temperature atmosphere for 2 days, and then a hard Au-plated copper plate having a hemispherical convex portion with a curvature radius of 1 mm was used as a contact, as in Example 1. The contact resistance between the contact material 1 and the contact was measured. As a result, the contact resistance when the load was 1 N was 4.1 mΩ, and the contact resistance was sufficiently low for connector terminals.

(Comparative Example 1)
As an electrical contact material of Comparative Example 1, an electrical contact material made of a Ni-plated copper plate not containing the lubricating particles 32 was prepared. In addition, the electrical contact material of this example was produced by the same manufacturing method as the electrical contact material 1 of Example 1 except that the lubricating particles 32 were not used. That is, the electrical contact material of this example has a structure in which a Ni plating film made of the same material as the parent phase 31 in Example 1 and a conductive oxide film 33 formed by oxidizing Ni are sequentially laminated on the substrate 2. doing.

  Using the electrical contact material obtained as described above, a sliding test was performed under the same conditions as in Example 1. The result is shown in FIG. In addition, the vertical axis | shaft of FIG. 6 is a friction coefficient or contact resistance, and a horizontal axis is the cycle number of a reciprocating motion.

  As is known from FIGS. 3 and 6, the electrical contact material of this example has a coefficient of friction of about 0.5 to 0.6 after 100 cycles with the hard Au-plated copper plate. The coefficient of friction was greater than that of material 1. The contact resistance between the electrical contact material and the hard Au-plated copper plate was about 0.2 to 0.3 mΩ after 100 cycles and was slightly lower than that of the electrical contact material 1 of Example 1.

  As described above, the electrical contact material of this example does not include the lubricating particles 32 that are non-conductors, and thus the contact resistance is lowered, while the coefficient of friction is increased. Therefore, the insertion force increases when used as a connector terminal.

  Similarly to Example 1, a sliding test was performed as a reference experiment when a Ni-plated copper plate having the conductive oxide film 33 was used as a slider.

  FIG. 7 shows the result of the reference experiment. In addition, the vertical axis | shaft of FIG. 7 is a friction coefficient or contact resistance, and a horizontal axis is the cycle number of a reciprocating motion.

  As is known from FIG. 7, the friction coefficient between the Ni-plated copper plates having the conductive oxide film 33 was about 0.9 to 1.1 after 100 cycles. Moreover, the contact resistance between the Ni plated copper plates was about 0.5 to 0.7 mΩ after 100 cycles. From comparison between FIG. 7 and FIG. 4, the electric contact material that does not contain the lubricating particles 32 has a coefficient of friction compared to the case where the lubricating particles 32 are included, as in the sliding test using the hard Au plated copper plate described above. Increases and the insertion force increases when used as a connector terminal.

(Comparative Example 2)
As an electrical contact material of Comparative Example 2, an electrical contact material made of a hard Au plated copper plate was prepared, and a sliding test was performed under the same conditions as in Example 1. The result is shown in FIG. In addition, the vertical axis | shaft of FIG. 8 is a friction coefficient or contact resistance, and a horizontal axis is the cycle number of a reciprocating motion.

  As is known from FIG. 8, the friction coefficient between the hard Au plated copper plates was about 0.8 to 1.0 after 100 cycles, and the friction coefficient was larger than that of the electrical contact material of Example 1. The contact resistance between the hard Au plated copper plates was about 0.2 to 0.3 mΩ after 100 cycles, and showed a stable low value.

  As described above, the electrical contact material made of the hard Au plated copper plate does not form an insulating oxide film on the surface, and thus stably exhibits a low contact resistance while increasing the friction coefficient. Therefore, the insertion force increases when used as a connector terminal. In addition, since Au plating uses a noble metal, it is difficult to reduce the cost.

DESCRIPTION OF SYMBOLS 1 Electric contact material 2 Base material 3 Composite plating film 31 Mother phase 32 Lubricity particle 33 Conductive oxide film

Claims (8)

A substrate;
A composite plating film provided on the base material and having lubricating particles dispersed in a matrix made of Ni or Ni alloy;
An electrical contact material characterized in that a conductive oxide film formed by oxidizing the matrix and the lubricating particles are exposed on the surface of the composite plating film. The electrical contact material according to claim 1, wherein the conductive oxide film contains Ni ₃ O ₄ .   The electrical contact material according to claim 1, wherein the lubricating particles are made of a fluorinated resin. It is a connector terminal comprised from the electrical contact material of any one of Claims 1-3,
A connector terminal, wherein the composite plating film is formed at least in a contact portion constituting an electrical contact with a counterpart terminal. A composite plating step of forming on the substrate a composite plating film in which the lubricating particles are dispersed in the matrix composed of Ni or Ni alloy, and a part of the lubricating particles are exposed on the surface;
And an oxidation treatment step of oxidizing the surface of the matrix to form a conductive oxide film.   6. The method for producing an electrical contact material according to claim 5, wherein in the oxidation treatment step, the composite plating film is anodized in a weakly acidic electrolytic solution.   6. The method for producing an electrical contact material according to claim 5, wherein in the oxidation treatment step, a self-passivation treatment is performed in which the composite plating film is immersed in a dilute acid having oxidizing properties.   The method for producing an electrical contact material according to claim 7, wherein oxygen as an oxidant is dissolved in the diluted acid.

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