Terminal connection structure

Abstract

A terminal connection structure is provided in which the contact resistance of a terminal whose surface is formed of a graphene oxide film is reduced. [Solution] A terminal connection structure (1) includes a terminal (200) and a mating terminal (100) that mates with the terminal (200). The terminal (200) includes a first connecting portion (110) and a first terminal contact (120) that is provided on at least a portion of the surface of the first connecting portion (110) and is formed of a graphene oxide film (122). The mating terminal (100) includes a second connecting portion (10) and a second terminal contact (20) that is provided on at least a portion of the surface of the second connecting portion (10) and has a protrusion (21). The protrusion (21) of the second terminal contact (20) is embedded inside the first terminal contact (120) and is electrically connected thereto.

Description

[Technical Field]

[0001] The present invention relates to a terminal connection structure. [Background technology]

[0002] Electrical connection components such as connectors require high contact reliability with mating terminals and high wear resistance at the connection with the mating terminal. Therefore, connector contacts are typically plated with precious metals such as gold, silver, and tin. However, the use of expensive precious metal plating tends to increase the production costs of connectors. Therefore, forming a graphene film on the contacts (terminal contacts) of connectors instead of the precious metal plating layer has been proposed. Graphene film is a monoatomic film composed of carbon atoms and has excellent electrical conductivity and chemical stability, making it a promising new terminal contact material with high reliability. Various methods have been proposed for forming graphene films on the surfaces of various components.

[0003] Graphene oxide, which is obtained by oxidizing graphene, is synthesized by chemically oxidizing graphite, which is inexpensive and readily available in large quantities. Graphene oxide contains polar groups, such as carboxyl groups and hydroxyl groups, and is therefore dispersible in polar solvents such as water. Therefore, when a substrate is placed in the polar solvent and a voltage is applied to the substrate, graphene oxide can be deposited on the substrate, which has an opposite charge to that of graphene oxide. Therefore, a method has been proposed for forming a graphene oxide film on the surface of a copper substrate or the like using electrophoretic deposition (EPD) (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2011 / 116369 Summary of the Invention [Problem to be solved by the invention]

[0005] When a graphene oxide film is formed on a terminal surface by the electrophoretic deposition method described in Patent Document 1, the graphene oxide film is formed in a direction parallel to the substrate surface of the terminal. When a terminal with a graphene oxide film formed on its surface is connected to a counterpart terminal and a current is applied, current flows mainly in the c-axis direction of the graphene oxide film (the direction perpendicular to the surface on which the graphene oxide film is formed). It is known that the resistivity of a graphene oxide film is lower when the current flows in the ab-plane direction (the surface on which the graphene oxide is formed) than when the current flows in the c-axis direction. Therefore, there is a problem of reducing the contact resistance on the terminal surface by passing a current in the ab-plane direction of the graphene oxide film.

[0006] The present invention has been made in view of the problems inherent in the conventional techniques, and an object of the present invention is to provide a terminal connection structure in which the contact resistance of a terminal having a surface formed of a graphene oxide film is reduced. [Means for solving the problem]

[0007] A terminal connection structure according to an aspect of the present invention is a terminal connection structure including a terminal and a mating terminal to be fitted with the terminal. The terminal includes a first connection portion and a first terminal contact formed of a graphene oxide film and provided on at least a portion of the surface of the first connection portion. The mating terminal includes a second connection portion and a second terminal contact provided on at least a portion of the surface of the second connection portion and having a protrusion. In the terminal connection structure, the protrusion of the second terminal contact is embedded inside the first terminal contact and is electrically connected thereto. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a terminal connection structure in which the contact resistance of a terminal having a surface formed of a graphene oxide film is reduced. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing an example of a terminal connection structure according to the present embodiment, in which a female terminal and a male terminal are fitted together. [Figure 2] 2 is a perspective view showing an example of a terminal-attached electric wire in which an electric wire is crimped onto the female terminal shown in FIG. 1. FIG. [Figure 3] FIG. 4 is a cross-sectional view showing the surface state of the female terminal. [Figure 4] FIG. 10 is a schematic diagram showing the state of a graphene oxide film at a first terminal contact point of a female terminal. [Figure 5] FIG. 10 is a cross-sectional view showing the state of the second terminal contact surface of the male terminal. [Figure 6] FIG. 2 is an enlarged cross-sectional view of a portion D1 in FIG. [Figure 7] FIG. 7 is an enlarged view of part D2 in FIG. 6, and is a schematic diagram showing the state of electrical conduction in a graphene oxide film. [Figure 8] FIG. 1 is a schematic diagram showing how a graphene oxide film is formed by electrophoretic deposition. [Figure 9] 1 is a graph showing the relationship between the pH of a dispersion and the zeta potential of graphene oxide. DETAILED DESCRIPTION OF THE INVENTION

[0010] The terminal connection structure according to the present embodiment will be described in detail below with reference to the drawings. Note that the dimensional proportions in the drawings are exaggerated for the sake of explanation and may differ from the actual proportions.

[0011] [Terminal connection structure] The terminal connection structure of this embodiment is a terminal connection structure 1 including a terminal 200 and a mating terminal 100 that is fitted with the terminal 200. The terminal 200 includes a first connection portion 110 and a first terminal contact 120 that is provided on at least a portion of the surface of the first connection portion 110 and is formed of a graphene oxide film 122. The mating terminal 100 also includes a second connection portion 10 and a second terminal contact 20 that is provided on at least a portion of the surface of the second connection portion 10 and has a protrusion 21. The protrusion 21 of the second terminal contact 20 is embedded inside the first terminal contact 120 and is electrically connected thereto.

[0012] The terminal connection structure 1 may include a female terminal and a male terminal that mates with the female terminal. That is, as shown in Fig. 1, the terminal 200 may be a female terminal and the mating terminal 100 may be a male terminal. As an example of the terminal connection structure of this embodiment, a case will be described in which the terminal 200 is a female terminal and the mating terminal 100 is a male terminal.

[0013] When the second connection portion 10 of the male terminal 100 is inserted into the first connection portion 110 of the female terminal 200 and the male terminal 100 is mated with the female terminal 200, the second connection portion 10 of the male terminal 100 and the first connection portion 110 of the female terminal 200 are physically and electrically connected. As will be described later, since the first connection portion 110 and the second connection portion 10 are conductive, contact between the first terminal contact 120 and the second terminal contact 20 establishes electrical continuity between the electric wire 210 connected to the male terminal 100 and the electric wire 220 connected to the female terminal 200.

[0014] (female terminal) First, the female terminal 200 will be described. As shown in Figures 1, 3, and 4, the female terminal 200 includes a first connecting portion 110 and a first terminal contact 120 that is provided on at least a portion of the surface of the first connecting portion 110 and is formed of a graphene oxide film 122. Furthermore, as shown in Figure 2, the female terminal 200 may further include a first crimping portion 130.

[0015] The female terminal 200 is formed from a conductive material. The conductive material is preferably a conductive metal such as copper, aluminum, iron, magnesium, or an alloy containing these metals. The first connecting portion 110 and the first crimping portion 130 of the female terminal 200 are formed from a single sheet of conductive material, and the first connecting portion 110 and the first crimping portion 130 are conductive. However, the female terminal 200 may also be formed from a plurality of separate members of different types.

[0016] The first connecting portion 110 of the female terminal 200 is conductive and is provided to mate with the second connecting portion 10 of the male terminal 100. The first connecting portion 110 has a box body into which the second connecting portion 10 of the male terminal 100 is inserted, and a plate-like body that extends from a part of the box body into the box body and uses elastic force to press the second connecting portion 10 of the male terminal 100 inserted into the box body.

[0017] The box body of the first connection portion 110 of the female terminal 200 is a box-shaped body that includes a first wall portion 111, a second wall portion 112, a third wall portion 113, a fourth wall portion 114, and a fifth wall portion 115, with the fifth wall portion 115 overlapping the outside of the first wall portion 111. These walls are bent and processed so as to form a substantially square shape in a direction perpendicular to the connection direction of the female terminal 200 and the male terminal 100. The first wall portion 111 and the third wall portion 113, as well as the second wall portion 112 and the fourth wall portion 114, are arranged substantially parallel to each other with a space between them.

[0018] The plate-like body of first connecting portion 110 of female terminal 200 has elastic portion 116 that is continuous with the longitudinal end of third wall portion 113 and is provided so as to be strongly bent, and sliding portion 117 that is continuous with the end of elastic portion 116 and is provided so as to be weakly bent. In other words, elastic portion 116 is provided so as to have a smaller interior angle than sliding portion 117.

[0019] The elastic portion 116 is formed from the same material as the other portions of the first connecting portion 110, such as the third wall portion 113, but its bent shape imparts a strong elastic force to it. The sliding portion 117 is formed from the same material as the other portions of the first connecting portion 110, such as the third wall portion 113, but its bent shape imparts a weak elastic force to it. When the male terminal 100 is mated with the female terminal 200, the sliding portion 117 of the first connecting portion 110 of the female terminal 200 is pressed against the second terminal contact 20 of the male terminal 100 by the strong elastic force of the elastic portion 116 and the weak elastic force of the sliding portion 117. Then, the second terminal contact 20 of the male terminal 100 is physically and electrically connected to the first terminal contact 120 of the female terminal 200 by the pressing force (pressing force) exerted by the second terminal contact 20 of the male terminal 100.

[0020] As shown in FIGS. 1 and 3 , the first terminal contact 120 is provided on at least a portion of the surface of the first connecting portion 110. At least a portion of the surface of the first connecting portion 110 may be the surface of the first connecting portion 110 that comes into contact with the male terminal 100 via the first terminal contact 120 of the female terminal 200 when mated with the male terminal 100. The first terminal contact 120 may be provided on a portion of the outer corner surface of one of the two surfaces with larger areas that form the surface of the weakly bent sliding portion 117. The first terminal contact 120 may be provided on the surface of the sliding portion 117 that faces the first wall portion 111. The first terminal contact 120 of the female terminal 200 is provided so as to be physically and electrically connected to the second terminal contact 20 of the male terminal 100 when mated with the male terminal 100.

[0021] The first terminal contact 120 is formed of a graphene oxide film 122. The graphene oxide film 122 may be graphene oxide or a stack of graphene oxides. FIG. 4 shows the state of the graphene oxide film 122 at the first terminal contact 120, in which the graphene oxide film 122 is a stack of graphene oxides. Specifically, the graphene oxide film 122 is formed in a direction parallel to the ab-plane formed by the a-axis and b-axis. The graphene oxide film 122 is then stacked in the direction of the c-axis, which is perpendicular to the surface on which the graphene oxide film 122 is formed.

[0022] Like graphene, graphene oxide has high chemical stability and mechanical strength, and therefore, forming the first terminal contact 120 from the graphene oxide film 122 can improve the contact reliability of the female terminal 200. Graphene oxide can be synthesized by chemically oxidizing graphite, which is inexpensive and available in large quantities.

[0023] Graphene is obtained by reducing graphene oxide. Graphene is a compound in which carbon atoms are connected in the sp 2Graphene is a film-like material with a thickness of one atom that has a planar hexagonal lattice structure formed by bonding graphene oxide and graphene oxide films. Graphene has higher electrical conductivity than insulating graphene oxide, so graphene obtained by reducing graphene oxide is usually used in areas where electrical conductivity is required. Graphene has better electrical conductivity than graphene oxide, but requires a process for reducing the graphene oxide. However, in this embodiment, the thickness of the graphene oxide film 122 is within a predetermined range, so the electrical resistance of the terminal contact is low even though graphene oxide is used.

[0024] The thickness of the graphene oxide film 122 is preferably 1 nm or more and 10 nm or less. The size of one carbon atom is approximately 0.335 nm, and the thickness of a single graphene oxide layer is approximately 1 nm. The graphene oxide film 122 also includes a single layer of graphene oxide, so the lower limit of the thickness of the graphene oxide film 122 is set to 1 nm. Furthermore, by setting the thickness of the graphene oxide film 122 to 10 nm or less, the distance from the first connecting portion 110 of the female terminal 200 to the second connecting portion 10 of the male terminal 100 is shortened, thereby reducing the electrical resistance of the graphene oxide film 122. The thickness of the graphene oxide film 122 can be measured by observing a cross section of the graphene oxide film 122 using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0025] The number of stacked graphene oxide layers contained in the graphene oxide film 122 is preferably 1 to 30. When the number of stacked graphene oxide layers is in this range, a female terminal 200 with excellent conductivity can be provided.

[0026] When the number of stacked graphene oxide layers included in the graphene oxide film 122 is two or more, a conductive metal may be inserted (intercalated) between the graphene oxide layers. Intercalation of the conductive metal can reduce the electrical resistance between the graphene oxide layers. The conductive metal is not particularly limited as long as it is a metal having conductivity, and may be gold, silver, copper, tin, nickel, iron, aluminum, a mixture thereof, or the like.

[0027] The first crimping portion 130 is connected to the first connecting portion 110 and is provided so as to be able to crimp the electric wire 220. The first crimping portion 130 includes a conductor crimping portion 131 that crimps the conductor 221 of the electric wire 220, and a coating crimping portion 132 that crimps the coating 222 of the electric wire 220. Of the first crimping portion 130, at least the conductor crimping portion 131 is formed from a conductive material. As the conductive material, for example, a material similar to that used for the first connecting portion 110 is used.

[0028] The electric wire 220 includes a conductor 221 and a covering material 222 that covers the conductor 221. The material of the conductor 221 may be, for example, copper, aluminum, or an alloy containing these metals, and is preferably lightweight aluminum or an aluminum alloy.

[0029] The material of the covering material 222 that covers the conductor 221 may be a resin, preferably an olefin-based resin or a resin whose main component is polyvinyl chloride (PVC). Here, the main component refers to a component that accounts for 50% by mass or more of the entire covering material 222. The olefin-based resin may be, for example, one or more resins selected from the group consisting of polyethylene (PE), polypropylene (PP), ethylene copolymers, and propylene copolymers. Of these, resins whose main component is polypropylene (PP) or polyvinyl chloride (PVC) are preferred because of their high flexibility and durability.

[0030] The female terminal 200 is connected to the electric wire 220 by being crimped at the first crimping portion 130, but the electric wire 220 may also be connected by soldering. That is, the conductor 221 of the electric wire 220 may be electrically connected by soldering, which involves heating a solder paste applied to a substrate connected to the first connection portion 110.

[0031] (Male terminal) Next, the male terminal 100 will be described. As shown in Figures 1 and 5, the male terminal 100 includes a second connecting portion 10 and a second terminal contact 20 provided on at least a portion of the surface of the second connecting portion 10 and having a protrusion 21. The male terminal 100 may further include a second crimping portion 30.

[0032] The male terminal 100 is formed of a conductive material. The second connection portion 10 and the second crimping portion 30 of the male terminal 100 are formed from a single sheet of conductive material, and the second connection portion 10 and the second crimping portion 30 are conductive. However, the male terminal 100 may be formed from multiple separate members of different types. The conductive member constituting the male terminal 100 may be made of the same material as that of the female terminal 200. From the viewpoint of electrical conductivity of the terminal connection structure, it is preferable that the hardness of the conductive member of the male terminal 100 be higher than that of the female terminal 200. For example, it is preferable to use pure copper such as C1020 for the female terminal 200 and a copper alloy such as NB109 for the male terminal 100, thereby making the hardness of the male terminal 100 higher than that of the female terminal 200.

[0033] The second connection portion 10 of the male terminal 100 is conductive and is provided to mate with the first connection portion 110 of the female terminal 200. The second connection portion 10 is plate-like and is formed into a substantially rectangular parallelepiped shape by laminating metal plates.

[0034] 1 , the second terminal contacts 20 are provided on at least a portion of the surface of the second connecting portion 10. At least a portion of the surface of the second connecting portion 10 may be the outer surface of the second connecting portion 10 that comes into contact with the female terminal 200 via the second terminal contacts 20 of the male terminal 100 when mated with the female terminal 200. The second terminal contacts 20 may be provided on a portion of one of the two surfaces with the larger area that form the surface of the plate-like second connecting portion 10. The second terminal contacts 20 of the male terminal 100 are provided so as to be physically and electrically connected to the first terminal contacts 120 of the female terminal 200 when mated with the female terminal 200.

[0035] As shown in Fig. 5, the second terminal contact 20 has a protrusion 21. By providing the fine protrusion 21 on the surface of the second terminal contact 20, when the male terminal 100 is mated with the female terminal 200, the protrusion 21 is embedded inside the first terminal contact 120 and electrically connected. Furthermore, as shown in Fig. 6, when the male terminal 100 is mated with the female terminal 200, at least a portion of the protrusion 21 may penetrate the first terminal contact 120, and a portion of the first connecting portion 110 of the female terminal 200 may be depressed by being pressed by the protrusion 21.

[0036] When the male terminal 100 is mated with the female terminal 200, the protrusion 21 of the second terminal contact 20 is embedded in the first terminal contact 120 as described above. Therefore, as shown in FIG. 7 , the shear force of the protrusion 21 partially cuts the carbon-carbon bonds in the graphene oxide film 122, causing the end 124 of the cut graphene oxide film 122 to come into contact with the side of the protrusion 21. Therefore, when electricity is applied between the male terminal 100 and the female terminal 200, current flows from the protrusion 21 in a direction E along the a-axis of the graphene oxide film 122. The a-axis of the graphene oxide film 122 is the longitudinal direction of the female terminal 200 (first terminal contact 120). It is known that the resistivity of the graphene oxide film 122 is lower when current flows in the a-plane direction than when current flows in the c-axis direction. Therefore, by utilizing the high electrical conductivity of the graphene oxide film 122 in the a-plane, especially in the a-axis direction, the contact resistance of the terminal surface can be reduced. Furthermore, the graphene oxide film 122 has high gas barrier properties, which also helps prevent corrosion of the metal terminals.

[0037] As described above, the second terminal contact 20 of the male terminal 100 is physically and electrically connected to the first terminal contact 120 of the female terminal 200 by the pressing force (pressing force) applied by the second terminal contact 20 of the male terminal 100. In order to generate a shear force of the protrusion 21 necessary to cut a part of the carbon-carbon bond of the graphene oxide film 122, the pressing force is preferably 1 N or more and 10 N or less, and more preferably 2 N or more and 5 N or less, assuming the contact pressure of the terminal.

[0038] The shape of the protrusions 21 is not particularly limited, and may be, for example, a rectangular pillar or a cylinder. The shapes of the protrusions 21 may be the same or different. The number of protrusions 21 is also not particularly limited. Furthermore, the width of the protrusions 21 in the longitudinal direction of the male terminal 100 (second terminal contact 20) is not particularly limited, and may be, for example, 0.1 mm or more and 1 mm or less.

[0039] There are no particular limitations on the manufacturing method (molding method) of the protrusion 21. For example, the protrusion 21 may be formed when the second terminal contact 20 of the male terminal 100 is subjected to press processing (punching, bending, etc.) using a mold.

[0040] The second crimping portion 30 is connected to the second connection portion 10 and is provided so as to be able to crimp the electric wire 210. The second crimping portion 30 includes a conductor crimping portion 31 that crimps the conductor 211 of the electric wire 210, and a coating material crimping portion 32 that crimps the coating material 212 of the electric wire 210. Of the second crimping portion 30, at least the conductor crimping portion 31 is formed from a conductive material. As the conductive material, for example, a material similar to that used for the second connection portion 10 is used.

[0041] The electric wire 210 includes a conductor 211 and a covering material 212 that covers the conductor 211 . The conductive material used for the conductor 211 of the electric wire 210 may be, for example, the same as the conductive material used for the conductor 221 of the electric wire 220. In addition, the material used for the covering material 212 of the electric wire 210 may be, for example, the same as the material used for the covering material 222 of the electric wire 220.

[0042] The male terminal 100 is connected to the electric wire 210 by being crimped at the second crimping portion 30, but the electric wire 210 may also be connected by soldering. That is, the conductor 211 of the electric wire 210 may be electrically connected by soldering, which heats a solder paste applied to a substrate connected to the second connection portion 10.

[0043] As described above, the terminal connection structure of this embodiment is a terminal connection structure 1 including a terminal (female terminal) 200 and a mating terminal (male terminal) 100 that mates with the terminal 200. The terminal 200 includes a first connecting portion 110 and a first terminal contact 120 that is provided on at least a portion of the surface of the first connecting portion 110 and is formed of a graphene oxide film 122. The mating terminal 100 also includes a second connecting portion 10 and a second terminal contact 20 that is provided on at least a portion of the surface of the second connecting portion 10 and has a protrusion 21. The protrusion 21 of the second terminal contact 20 is embedded inside the first terminal contact 120 and is electrically connected thereto. By providing the protrusions 21 on the surface of the second terminal contact 20, when the male terminal 100 is mated with the female terminal 200, the graphene oxide film 122 is cut by the shear force of the protrusions 21, and the end portions 124 of the cut graphene oxide film 122 come into contact with the side surfaces of the protrusions 21. Therefore, by utilizing the high electrical conductivity of the ab-plane of the graphene oxide film, particularly in the a-axis direction, it is possible to provide a terminal connection structure in which the contact resistance of the terminals whose surfaces are formed of the graphene oxide film is reduced.

[0044] The above describes an example of the terminal connection structure of this embodiment in which the terminal 200 is a female terminal and the mating terminal 100 is a male terminal. However, the terminal 200 may also be a male terminal and the mating terminal 100 may also be a female terminal. Furthermore, an electrical connection component using the terminal connection structure of this embodiment is, for example, an electrical component that can be electrically connected to a mating electrical component. The electrical connection component is not particularly limited as long as it exhibits the effects of this embodiment. Examples of electrical connection components include terminals such as the male or female terminals described above, terminals of card edge connectors, ring terminals, or U-shaped terminals. The electrical connection component may also be a connector terminal.

[0045] [Manufacturing method of terminal connection structure] Next, a method for manufacturing the terminal connection structure according to the present embodiment will be described. In the method for manufacturing the terminal connection structure, the graphene oxide film may be formed by electrophoretic deposition. The manufacturing method may include a step of forming the graphene oxide film on the surface of the metal base material by electrophoretic deposition.

[0046] Electrophoretic deposition is a technique used to form a film on an electrode. Electrophoretic deposition is a film formation method in which, for example, a voltage is applied between an anode and a cathode inserted in a dispersion liquid to migrate charged particles in the dispersion liquid and deposit them on the electrode. Because electrophoretic deposition does not require heat treatment and can be performed without vacuum and at room temperature, it is possible to easily form a graphene oxide film at low cost.

[0047] FIG. 8 shows an electrophoresis apparatus 400 used in electrophoretic deposition. The electrophoresis apparatus 400 includes an electrophoresis tank 410, a cathode 430 connected to the negative electrode of a DC power supply 420, and a metal base material 440 connected to the positive electrode of the DC power supply 420. In this embodiment, the metal base material 440 is an anode. The electrophoresis tank 410 contains a dispersion liquid 450 in which graphene oxide 460 is dispersed in water. When a voltage is applied between the cathode 430 and the metal base material 440 (anode) by the DC power supply 420, the graphene oxide 460, which has a negative zeta potential, migrates toward the metal base material 440. As a result, the graphene oxide 460 is deposited on the surface of the metal base material 440, as indicated by the open circle.

[0048] The metal base material 440 is a component from which the first connection portion 110 in the terminal connection structure 1 is derived, and the terminal (female terminal) 200 can be produced by forming a graphene oxide film on the surface of the metal base material 440. There are no particular limitations on the metal base material 440, and the components used in the first connection portion 110 described above can be used. The metal base material 440 is preferably made of a conductive metal such as copper, aluminum, iron, magnesium, or an alloy containing these metals. The metal base material 440 may have various shapes such as a plate shape, a rod shape, or a combination thereof, and the dimensions such as thickness can be selected from a variety of shapes depending on the application.

[0049] Before forming a graphene oxide film on the surface of the metal base material 440, it is preferable to remove the oxide film from the surface of the metal base material 440. The method for removing the oxide film is not particularly limited, and the oxide film may be removed physically by polishing or chemically by using a chemical solution. The chemical solution can be appropriately selected depending on the characteristics of the oxide film. The chemical solution may be, for example, an acid solution such as sulfuric acid, hydrochloric acid, or nitric acid.

[0050] It is also preferable to smooth the surface of the metal base material 440 before forming a graphene oxide film on the surface of the metal base material 440. The method for smoothing the surface of the metal base material 440 is not particularly limited, and for example, the surface of the metal base material 440 may be smoothed by polishing or the like. Among polishing methods, it is preferable to smooth the surface of the metal base material 440 by chemical mechanical polishing. Chemical mechanical polishing (CMP) is a method in which a chemical solution such as an acid or base is applied to the surface of the metal base material 440, and the surface of the metal base material 440 is mechanically polished with abrasive particles or the like to smooth the surface of the metal base material 440. According to CMP, the chemical solution can modify the surface of the metal base material 440 so that it is easier to polish, making mechanical polishing easier and resulting in a smooth and excellent surface.

[0051] The cathode is not particularly limited and may be a soluble or insoluble cathode. The soluble cathode may be a copper-containing metal such as phosphorus-containing copper, electrolytic copper, or oxygen-free copper, or a nickel-containing metal such as nickel or a nickel alloy. The insoluble cathode may be carbon, platinum, platinum-coated titanium, or the like.

[0052] The dispersion contains graphene oxide. The dispersion may be prepared by dispersing graphene oxide in water, or may be a commercially available graphene oxide dispersion. Graphene oxide can be prepared by a known method, but commercially available graphene oxide may also be used.

[0053] In this embodiment, the graphene oxide film is preferably a single layer having a size of 1 μm to 10 μm, where the size of the graphene oxide film refers to the average of the maximum and minimum lengths of the surface on which the graphene oxide film is formed.

[0054] Graphene oxide may have a structure in which a functional group having oxygen, such as a carboxyl group, a hydroxyl group, an epoxy group, or a carbonyl group, is bonded to graphene. In a polar solution, different graphene oxides are unlikely to aggregate together because the oxygen in the functional group is negatively charged. Therefore, graphene oxide is easily dispersed uniformly in a polar solvent.

[0055] As described above, when a conductive metal is intercalated between layers of graphene oxide, the dispersion may contain, for example, a salt of the conductive metal. Examples of the conductive metal salt include sulfates and nitrates. From the viewpoint of reducing the electrical resistance of the graphene oxide film, the concentration of the conductive metal salt in the aqueous dispersion is preferably 0.0005% by mass to 0.01% by mass, and more preferably 0.001% by mass to 0.002% by mass. From the viewpoint of forming a graphene oxide film in which the conductive metal is appropriately intercalated, the mass ratio of the conductive metal salt to the graphene oxide in the aqueous dispersion is preferably 0.01 to 0.1, and more preferably 0.02 to 0.04.

[0056] When a conductive metal is intercalated between layers of graphene oxide, the dispersion may be adjusted so that the zeta potential of graphene oxide is positive. This adjustment can be achieved by adjusting the pH of the dispersion. Here, the relationship between the pH of the dispersion and the zeta potential of graphene oxide will be described. FIG. 9 is a graph showing the relationship between the pH of the dispersion and the zeta potential of graphene oxide. From FIG. 9, it can be seen that the zeta potential of graphene oxide can be made positive by reducing the pH of the dispersion. Specifically, the pH of the dispersion is preferably set to 1 to 7, and more preferably 1 to 3. The pH of the dispersion can be reduced by adding an acid, and examples of the acid include sulfuric acid, hydrochloric acid, and nitric acid. In this embodiment, the pH is preferably adjusted by adding 0.1 M sulfuric acid.

[0057] The dispersion may contain various additives in addition to graphene oxide, such as a pH buffer solution or a preservative.

[0058] The thickness of the graphene oxide film can be controlled by adjusting the concentration of graphene oxide in the dispersion, the voltage between the anode and cathode electrodes, the current density, the voltage application time, or the distance between the electrodes.

[0059] In this embodiment, the concentration of graphene oxide in the dispersion is preferably 0.001 mg / L to 100 mg / L, and more preferably 0.005 mg / L to 50 mg / L, from the viewpoint of forming a graphene oxide film with an appropriate thickness.

[0060] The voltage applied between the anode and cathode electrodes is preferably 1 V or more and 5 V or less. By setting the voltage in this range, the graphene oxide film can be formed to an appropriate thickness. From the viewpoint of reducing the thickness of the graphene oxide film, the voltage applied between the anode and cathode electrodes is more preferably 4 V or less, and even more preferably 3 V or less.

[0061] The voltage application time varies depending on the voltage, but is preferably 0.1 to 4 minutes. By setting the application time to 0.1 minutes or more, a good graphene oxide film can be formed on the metal base material. Furthermore, by setting the application time to 4 minutes or less, the thickness of the graphene oxide film can be reduced. The voltage application time is more preferably 1 minute or more. Furthermore, the voltage application time is more preferably 3 minutes or less.

[0062] The distance between the anode and cathode electrodes is preferably 5 mm or more and 20 mm or less. By setting the distance between the electrodes to 5 mm or more, the thickness of the graphene oxide film can be reduced. Furthermore, by setting the distance between the electrodes to 20 mm or less, a good graphene oxide film can be formed on the metal base material. The distance between the electrodes is more preferably 8 mm or more, and even more preferably 10 mm or more. Furthermore, the distance between the electrodes is more preferably 15 mm or less.

[0063] In the electrophoretic deposition method, graphene oxide migrates due to Coulomb force generated by an external electric field and is firmly deposited on the surface of the metal base material 440. Therefore, the adhesion between the graphene oxide film obtained in this embodiment and the metal base material 440 is higher than that formed by a film formation method such as spin coating, in which van der Waals forces are the main factor in adhesion. The adhesion of graphene oxide can be adjusted by the Coulomb force. Here, when the external electric field is E (N / C) and the charge is q (C), the Coulomb force F (N) is given by F = qE. That is, the Coulomb force acting on graphene oxide in the dispersion can be controlled by the charge of graphene oxide or the external electric field. The external electric field depends on the applied voltage, so it can be adjusted by the applied voltage. Furthermore, as described above, the charge of graphene oxide can be adjusted by the zeta potential, i.e., the pH of the dispersion. Therefore, by increasing the applied voltage and / or decreasing the pH of the dispersion, the Coulomb force can be increased and the adhesion between the graphene oxide film and the metal base material can be improved.

[0064] As shown in FIGS. 1 and 2, the terminal (female terminal) 200 includes a first connecting portion 110 and a first terminal contact 120 formed on at least a portion of the surface of the first connecting portion 110 and made of a graphene oxide film 122. That is, the first connecting portion 110 may have a region where the graphene oxide film is not formed. Such a region can be formed by placing a mask on the metal base material during the electrophoretic deposition process. Specifically, a mask is placed on the region where the graphene oxide film is not to be formed, and the mask is removed after the electrophoretic deposition process is performed.

[0065] After the graphene oxide film is formed as described above, the metal base material is pulled out of the dispersion liquid and then dried. The drying temperature when drying the graphene oxide film is preferably 80°C to 120°C. The drying time is preferably 5 minutes to 30 minutes. The drying atmosphere is preferably an inert gas atmosphere such as nitrogen to prevent oxidation of the metal base material.

[0066] As described above, in the manufacturing method of the terminal connection structure according to this embodiment, the graphene oxide film may be formed by electrophoretic deposition. That is, by electrophoretic deposition, the first terminal contact 120 formed of the graphene oxide film 122 is provided on at least a portion of the surface of the first connection portion 110, which is a metal base material. Because the graphene oxide film is thin, it has low electrical resistance and excellent adhesion. Therefore, it is useful as an electrical contact for electrical connection components. Furthermore, as described above, by utilizing the high electrical conductivity of the graphene oxide film in the ab-plane, particularly in the a-axis direction, it is possible to provide a manufacturing method of a terminal connection structure in which the contact resistance of a terminal whose surface is formed of the graphene oxide film is reduced.

[0067] The graphene oxide film may be used as an electrical contact as it is, but to further reduce the electrical resistance, the graphene oxide may be reduced by known methods such as chemical reduction, thermal reduction, or photoreduction.

[0068] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment. [Explanation of symbols]

[0069] 1 terminal connection structure 10 Second connection part 20 Second terminal contact 21 Protrusion 100 Mating terminal (male terminal) 110 First connection part 120 First terminal contact 122 Graphene oxide film 200 terminal (female terminal)

Claims

1. A terminal connection structure including a terminal and a mating terminal to be fitted with the terminal, the terminal includes a first connection portion and a first terminal contact provided on at least a portion of a surface of the first connection portion and formed of a graphene oxide film; the mating terminal includes a second connection portion and a second terminal contact provided on at least a portion of a surface of the second connection portion and having a protrusion, A terminal connection structure in which the protrusion of the second terminal contact is embedded in and electrically connected to the first terminal contact.

2. The terminal connection structure according to claim 1 , wherein at least a portion of the protrusion of the second terminal contact penetrates the first terminal contact.

3. 3. The terminal connection structure according to claim 1, wherein the terminal is a female terminal and the mating terminal is a male terminal.

Images