Aluminum-containing metal terminal with coating film and preparation method of aluminum-containing metal terminal

Abstract

The invention discloses an aluminum-containing metal terminal with a coating film and a preparation method of the aluminum-containing metal terminal. The terminal comprises an aluminum-containing metal matrix and a coating film, wherein the coating film comprises metal silver and graphene; the graphene comprises laminated graphene sheets and silver located between the graphene sheets.

Description

Technical Field

[0001] The present invention belongs to the technical field of conductive materials, and more specifically, relates to an aluminum-containing metal terminal with a coating and a preparation method thereof. Background Art

[0002] Terminal connectors are detachable interfaces between two parts of an electronic system. They serve as a bridge between different components to transmit data or current. They are extremely critical and indispensable in electronic devices. The more functions and complexity of electronic devices, the more electronic connectors there are, and the smaller the contact force dispersed to each contact point. Therefore, the requirements for the connection reliability of terminal materials are higher. The detachable interface of electronic connectors is different from the plug-in interface between larger electrical appliances that most people understand. In the electronics industry, it is a more extensive connector from micro to macro.

[0003] Copper wires are usually used for wiring harnesses distributed to vehicles such as cars. Then, when the wiring harnesses are connected to each other or between the wiring harness and the vehicle-mounted device, the terminal is attached to the wiring harness formed by the copper wire; and such a terminal is usually attached to the copper wire by crimping. The terminal usually crimped to the copper wire is formed by punching a conductive plate material such as a copper alloy into a predetermined shape and bending it, because the copper alloy material has certain advantages in electrical conductivity, heat transfer, mechanical strength and service life. However, the shortage of copper and its alloy resources, coupled with the rising and unstable prices of copper alloy materials, in addition to considering the lightweight and easy recycling of vehicles, various energized parts have been proposed for lightweight and low-cost requirements, resulting in aluminum materials, which are second only to copper in electrical conductivity, also attracting attention. However, the surface of aluminum is prone to form an oxide film, and the thickness of the oxide film formed on the surface of the aluminum material is much greater than the thickness of the oxide film formed on the surface of the copper material. Therefore, the contact resistance between the conductor part and the aluminum and its alloy terminals is relatively high.

[0004] On this basis, in recent years, the market has also generated a strong demand for the miniaturization of terminals, and has required a reduction in the thickness of aluminum and its alloy materials used as materials. However, when the thickness of the plate is reduced, stress relaxation will be further promoted, so that conventional aluminum alloy materials cannot fully suppress the reduction of contact load during use, and cannot maintain a high contact load for a long time. Not only that, if the temperature of the terminal remains high for a long time, a thick oxide film will still be easily formed on its surface, resulting in an increase in contact resistance with the matching (mating) terminal. In order to reduce the contact resistance, one of the effective ways is to increase the contact load with the matching terminal to break the oxide film and form a good electrical contact. However, as mentioned above, it is difficult for terminals using traditional aluminum alloy materials to maintain a high contact load for a long time, and therefore it is difficult to maintain good conductivity in a practical environment.

[0005] As a countermeasure to the above problems, it is possible to consider processing the aluminum alloy material so that a metal coating, such as Au coating, is formed on the surface of the terminal of the aluminum alloy material. This coating is difficult to be oxidized, thereby shielding the mechanical and environmental attacks on the copper alloy base material. Metal coatings are divided into two categories: precious metal electroplating and general metal electroplating. This classification is based on the corrosion resistance of the metal. Precious metals are difficult to corrode. The available precious metal coatings include gold, silver, palladium and their alloys. However, in actual situations, the practical use of precious metal coatings will greatly increase the cost of the entire terminal, limiting the application. Non-precious metal electroplating materials include tin, nickel, zinc, copper and tin. At present, ordinary terminal materials generally use tin plating on copper alloys, which is low in cost but insufficient in heat resistance, conductivity and wear resistance. Based on this, tin plating on the surface of the terminal of the aluminum alloy material can no longer meet the requirements of conductivity and wear resistance. In addition, important components generally use special terminal materials, that is, nickel, palladium and gold plating on copper alloys for multiple electroplating, which can obtain sufficient heat resistance and wear resistance. Although the conductivity is lower than that of tin-plated materials, the cost is high. In recent years, with the rapid development of electric vehicles and various electronic appliances, it is theoretically believed that silver (Ag) plating is suitable for improving the conductivity of terminal materials to reduce power loss. However, in actual use, it is found that due to the softness of pure silver, the silver plating is easy to stick during the joint use process and has low wear resistance. Therefore, in order to ensure the service life of the product, it can only be increased by several times or even dozens of times. Ultra-thick silver plating will inevitably increase the cost. Moreover, if the plating of all terminal materials is made of pure silver material of precious metal, it is impossible in terms of cost and resources.

[0006] To solve the above problems, toxic alloy elements including antimony, selenium, nickel, cobalt, tellurium or bismuth are generally added to silver plating to improve the hardness / wear resistance of the silver-plated material, or solid lubricants including molybdenum disulfide, Teflon particles, etc. are added to non-metallic parts to improve the lubricity of the coating and reduce the wear of the coating. However, the problem with this method is that it will cause a significant increase in the resistance of the silver-plated material, and the degree of improvement in hardness is also limited.

[0007] Based on this, patent document 1 (JP2021072185A) discloses a method for obtaining a silver-graphene composite coating using stacked graphene peeled from graphite as an additive to a plating solution. Compared with pure silver plating, the silver-graphene composite coating prepared by this method increases the hardness of the coating from 80HV to 120HV, thereby improving the wear resistance to a certain extent, but its conductivity still has room for further improvement. Based on this, patent document 2 (JP2022170877A) further provides a substrate with a silver-graphene composite coating, which studies the arrangement direction (vertical, parallel or inclined) of graphene dispersed in the silver-graphene composite coating relative to the substrate, and achieves the improvement of the conductivity and wear resistance (lubricity) of the silver-graphene composite coating. However, there is no solution for how to ensure the contact resistance stability of the silver-graphene composite coating when a large current is energized or in a continuous high-temperature use environment.

[0008] In addition to being affected by the above-mentioned properties of the coating itself, for terminals with aluminum alloy as the base material, since an oxide film is easily formed on the surface of aluminum and its aluminum alloy materials, how to achieve electroplating and obtain a coating with good bonding strength is also an important factor affecting the conductivity of the terminal and the size and stability of the contact resistance. Summary of the invention

[0009] 1. Problem to be solved

[0010] Aiming at the problem that the electrical conductivity and contact resistance of the terminal with aluminum alloy as the base material are insufficient in use stability, the main purpose of the present invention is to provide an aluminum-containing metal terminal with a coating;

[0011] At the same time, a method for preparing an aluminum-containing metal terminal with a coating is provided;

[0012] The aluminum-containing metal terminal with coating can solve the problems of unstable usage (coating shedding, breakage, etc.) and lightweight of existing coated connector terminals.

[0013] 2. Technical solution

[0014] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0015] A first aspect of the present invention provides an aluminum-containing metal terminal with a coating, the terminal comprising a first barrel portion, and a second barrel portion connected to the first barrel portion;

[0016] The first barrel is tubular, and has an elastic contact member inside.

[0017] The first barrel cooperates with the elastic contact piece to form a space for inserting the matching terminal, and the elastic contact piece contacts the matching terminal;

[0018] The elastic contact element includes a substrate, and an intermediate coating and a surface coating located on the surface of the substrate;

[0019] The substrate is a material with an aluminum content not exceeding 99wt% and not less than 90wt%;

[0020] The surface coating includes graphene and other metals, and the other metals include silver;

[0021] Calculated based on the total number of atoms in the surface coating:

[0022] The content of other metals in the surface coating is not less than 40at%.

[0023] The content of graphene in the surface coating is 1 to 30 at%.

[0024] The sum of the contents of the other metals and the graphene satisfies 95 at% to 100 at%;

[0025] Wherein, the graphene includes stacked graphene sheets and silver located between the graphene sheets;

[0026] The silver includes silver ions and nano-sized silver particles;

[0027] As described herein, the "content of graphene in the surface coating" herein is calculated based on the carbon atom content.

[0028] The "other metals in the surface coating" as described herein are different from the "silver located between the graphene sheets" as described above.

[0029] According to any embodiment of the first aspect of the present invention, the base material contains copper, and the content of copper is not less than 3 wt %.

[0030] According to any embodiment of the first aspect of the present invention, the base material contains copper, and the content of copper is 3-5 wt %.

[0031] According to any embodiment of the first aspect of the present invention, the base material is an aluminum-copper alloy, and the copper content of the aluminum-copper alloy is 3-5wt%.

[0032] According to any embodiment of the first aspect of the present invention, the base of the elastic contact piece is in a plate shape, and the thickness of the base is 0.01 mm to 0.6 mm.

[0033] According to any embodiment of the first aspect of the present invention, the thickness of the substrate can be selected from any value within the following ranges: 0.01-0.6 mm, 0.01-0.5 mm, 0.01-0.4 mm, 0.01-0.3 mm, 0.01-0.2 mm, 0.01-0.1 mm, 0.05-0.6 mm, 0.05-0.5 mm, 0.05-0.4 mm, 0.05-0.3 mm, 0.05-0.2 mm, 0.05-0.1 mm, 0.1-0.6 mm, 0.1-0.5 mm, 0.01-0.6 mm, 0.01-0.5 mm, 0.01-0.2 mm, 0.01-0.1 mm, 0.05-0.6 mm, 0.05-0.5 mm, 0.05-0.4 mm, 0.05-0.3 mm, 0.05-0.2 mm, 0.05-0.1 mm, 0.1-0.6 mm, 0.1-0.5 mm, 0 .1~0.4mm, 0.1~0.3mm, 0.1~0.2mm, 0.15~0.6mm, 0.15~0.5mm, 0.15~0.4mm, 0.15~0.3mm, 0.15~0.2mm, 0.2~0.6mm, 0.2~0 .5mm, 0.2~0.4mm, 0.2~0.3mm, 0.25~0.6mm, 0.25~0.5mm, 0.25~0.4mm, 0.25~0.3mm, 0.3~0.6mm, 0.3~0.5mm, 0.3~0.4mm.

[0034] According to any embodiment of the first aspect of the present invention, the coating on the surface of the elastic contact member (when the surface coating is detected or when the surface coating and the intermediate coating are detected together) has a Raman spectrum detected by Raman spectroscopy at 500±30cm -1 Peak, 1330±30cm -1 Peak, 1550±30cm -1 The peak and 2800±30cm -1 The peak.

[0035] Furthermore, according to the total number of atoms contained in the surface coating, (calculated by carbon content) the content of graphene in the coating can be arbitrarily selected from any numerical range of 1-50at%, 1-30at%, 1-20at%, and 1-15at%.

[0036] According to any embodiment of the first aspect of the present invention, the content of graphene in the surface coating is not less than 3 at % calculated based on the total number of atoms contained in the surface coating.

[0037] Furthermore, according to the total number of atoms in the surface coating and calculated by carbon content, the content of graphene in the surface coating can be arbitrarily selected from any group of numerical ranges including 3-50at%, 5-30at%, 5-20at%, 10-20at%, and 5-15at%.

[0038] According to any embodiment of the first aspect of the present invention, the amount of silver located between the graphene sheets is 0.1 to 50 at % based on the total number of atoms of the graphene.

[0039] Furthermore, calculated based on the total number of atoms of the graphene, the amount of silver located between the graphene sheets can be arbitrarily selected from any numerical range of 1-50at%, 1-45at%, 1-40at%, 1-30at%, 1-20at%, and 1-10at%.

[0040] According to any embodiment of the first aspect of the present invention, the surface coating may also include any one or a combination of two or more of the following: copper, iron, aluminum, tin, nickel, zinc, cobalt;

[0041] According to any embodiment of the first aspect of the present invention, the thickness of the surface coating can be selected from any value within the following ranges: 0.01-100 μm, 0.01-90 μm, 0.01-30 μm, 0.01-10 μm, 0.01-8 μm, 0.1-100 μm, 0.1-90 μm, 0.1-30 μm, 0.1-10 μm, 0.1-8 μm, 0.3-100 μm, 0.3-90 μm, 0. 3~30μm, 0.3~10μm, 0.3~8μm, 0.5~100μm, 0.5~90μm, 0.5~30μm, 0.5~10μm, 0.5~8μm, 0.7~100μm, 0. 7~90μm, 0.7~30μm, 0.7~10μm, 0.7~8μm, 1~100μm, 1~90μm, 1~30μm, 1~10μm, 1~8μm, 1.2~100μm, 1.2~ 90μm, 1.2~30μm, 1.2~10μm, 1.2~8μm, 1.5~100μm, 1.5~90μm, 1.5~30μm, 1.5~10μm, 1.5~8μm, 1.7~1 00μm, 1.7~90μm, 1.7~30μm, 1.7~10μm, 1.7~8μm, 2~100μm, 2~90μm, 2~30μm, 2~10μm, 2~8μm, 2.2~100 μm, 2.2~90μm, 2.2~30μm, 2.2~10μm, 2.2~8μm, 2.5~100μm, 2.5~90μm, 2.5~30μm, 2.5~10μm, 2.5~8μm m, 2.7~100μm, 2.7~90μm, 2.7~30μm, 2.7~10μm, 2.7~8μm, 3~100μm, 3~90μm, 3~30μm, 3~10μm, 3~8μm;

[0042] Preferably, the thickness of the surface coating is not less than 3 μm.

[0043] More preferably, the thickness of the surface coating is not less than 3-10 μm.

[0044] According to any embodiment of the first aspect of the present invention, the surface coating has a contact resistance of no more than 4 mΩ; or, the coating has a contact resistance of 0.1 to 4 mΩ; or, the coating has a contact resistance of no more than 2 mΩ; or, the coating has a contact resistance of 0.1 to 2 mΩ; or, the coating has a contact resistance of no more than 1 mΩ; or, the coating has a contact resistance of 0.1 to 1 mΩ; or, the coating has a contact resistance of no more than 0.7 mΩ; or, the coating has a contact resistance of 0.1 to 0.7 mΩ.

[0045] According to any embodiment of the first aspect of the present invention, the type of the intermediate coating is the same as the type of the surface coating, and the type described here only includes the material composition of the coating.

[0046] According to any embodiment of the first aspect of the present invention, the type of the intermediate coating is the same as the type of the surface coating, and the type described herein also includes the material composition and size characteristics of the coating.

[0047] According to any embodiment of the first aspect of the present invention, the type of the intermediate coating is different from the type of the surface coating, and the intermediate coating is a metal coating including a metal content of not less than 95wt%, and the metal includes any one of copper, iron, aluminum, tin, nickel, zinc, and cobalt, or a combination of two or more thereof.

[0048] According to any embodiment of the first aspect of the present invention, the thickness of the intermediate coating film can be selected from any value within the following value ranges: 0.01-100 μm, 0.01-90 μm, 0.01-30 μm, 0.01-10 μm, 0.01-8 μm, 0.1-100 μm, 0.1-90 μm, 0.1-30 μm, 0.1-10 μm, 0.1-8 μm, 0.3-100 μm, 0.3-90 μm, 0. 3~30μm, 0.3~10μm, 0.3~8μm, 0.5~100μm, 0.5~90μm, 0.5~30μm, 0.5~10μm, 0.5~8μm, 0.7~100μm, 0. 7~90μm, 0.7~30μm, 0.7~10μm, 0.7~8μm, 1~100μm, 1~90μm, 1~30μm, 1~10μm, 1~8μm, 1.2~100μm, 1.2~ 90μm, 1.2~30μm, 1.2~10μm, 1.2~8μm, 1.5~100μm, 1.5~90μm, 1.5~30μm, 1.5~10μm, 1.5~8μm, 1.7~1 00μm, 1.7~90μm, 1.7~30μm, 1.7~10μm, 1.7~8μm, 2~100μm, 2~90μm, 2~30μm, 2~10μm, 2~8μm, 2.2~100 μm, 2.2~90μm, 2.2~30μm, 2.2~10μm, 2.2~8μm, 2.5~100μm, 2.5~90μm, 2.5~30μm, 2.5~10μm, 2.5~8μm m, 2.7~100μm, 2.7~90μm, 2.7~30μm, 2.7~10μm, 2.7~8μm, 3~100μm, 3~90μm, 3~30μm, 3~10μm, 3~8μm;

[0049] Preferably, the thickness of the intermediate coating is not less than 0.1 μm.

[0050] More preferably, the thickness of the intermediate coating film is preferably: 0.1-2.5 μm, 0.1-2 μm, 0.1-1 μm, respectively.

[0051] According to any embodiment of the first aspect of the present invention, the intermediate coating is independently selected from any one of the following: an intermediate coating including a copper metal content of not less than 95wt%; an intermediate coating including an iron metal content of not less than 95wt%; an intermediate coating including an aluminum metal content of not less than 95wt%; a surface coating including a tin metal content of not less than 95wt%; a surface coating including a zinc metal content of not less than 95wt%; an intermediate coating including a cobalt metal content of not less than 95wt%; a surface coating including copper and iron metals with a content of not less than 95wt%; an intermediate coating including copper and aluminum metals with a content of not less than 95wt%; an intermediate coating including copper and tin metals with a content of not less than 95wt%; an intermediate coating including copper and nickel metals with a content of not less than 95wt%; an intermediate coating including copper and zinc metals with a content of not less than 95wt%; an intermediate coating including copper and cobalt metals with a content of not less than 95wt%; an intermediate coating including iron and aluminum metals with a content of not less than 95wt%; Including an intermediate coating of iron and tin metals with a content of not less than 95wt%; Including an intermediate coating of iron and nickel metals with a content of not less than 95wt%; Including an intermediate coating of iron and zinc metals with a content of not less than 95wt%; Including an intermediate coating of iron and cobalt metals with a content of not less than 95wt%; Including an intermediate coating of aluminum and tin metals with a content of not less than 95wt%; Including an intermediate coating of aluminum and nickel metals with a content of not less than 95wt%; Including an intermediate coating of aluminum and zinc metals with a content of not less than 95wt%; Including an intermediate coating containing not less than 95wt% of aluminum and cobalt metals; including an intermediate coating containing not less than 95wt% of tin and nickel metals; including an intermediate coating containing not less than 95wt% of tin and zinc metals; including an intermediate coating containing not less than 95wt% of tin and cobalt metals; including an intermediate coating containing not less than 95wt% of nickel and zinc metals; including an intermediate coating containing not less than 95wt% of nickel and cobalt metals; including an intermediate coating containing not less than 95wt% of zinc and cobalt metals.

[0052] According to any embodiment of the first aspect of the present invention, the thickness of the intermediate surface coating does not exceed the thickness of the surface coating.

[0053] According to any embodiment of the first aspect of the present invention, the elastic contact member includes a protruding area and a bending area.

[0054] According to any embodiment of the first aspect of the present invention, the thickness of the surface coating of the protrusion area can be selected from any value within the following value ranges: 0.01-100 μm, 0.01-90 μm, 0.01-30 μm, 0.01-10 μm, 0.01-8 μm, 0.1-100 μm, 0.1-90 μm, 0.1-30 μm, 0.1-10 μm, 0.1-8 μm, 0.3-100 μm, 0.3-90 μm , 0.3~30μm, 0.3~10μm, 0.3~8μm, 0.5~100μm, 0.5~90μm, 0.5~30μm, 0.5~10μm, 0.5~8μm, 0.7~100μm, 0.7~90μm, 0.7~30μm, 0.7~10μm, 0.7~8μm, 1~100μm, 1~90μm, 1~30μm, 1~10μm, 1~8μm, 1.2~100μm, 1. 2~90μm, 1.2~30μm, 1.2~10μm, 1.2~8μm, 1.5~100μm, 1.5~90μm, 1.5~30μm, 1.5~10μm, 1.5~8μm, 1.7~ 100μm, 1.7~90μm, 1.7~30μm, 1.7~10μm, 1.7~8μm, 2~100μm, 2~90μm, 2~30μm, 2~10μm, 2~8μm, 2.2~10 0μm, 2.2~90μm, 2.2~30μm, 2.2~10μm, 2.2~8μm, 2.5~100μm, 2.5~90μm, 2.5~30μm, 2.5~10μm, 2.5~8μm m, 2.7~100μm, 2.7~90μm, 2.7~30μm, 2.7~10μm, 2.7~8μm, 3~100μm, 3~90μm, 3~30μm, 3~10μm, 3~8μm;

[0055] Preferably, the thickness of the surface coating of the protruding area is not less than 3 μm.

[0056] More preferably, the thickness of the surface coating of the protruding area is not less than 3-10 μm.

[0057] According to any embodiment of the first aspect of the present invention, the thickness of the surface coating of the bending zone can be selected from any value within the following value ranges: 0.01-100 μm, 0.01-90 μm, 0.01-30 μm, 0.01-10 μm, 0.01-8 μm, 0.1-100 μm, 0.1-90 μm, 0.1-30 μm, 0.1-10 μm, 0.1-8 μm, 0.3-100 μm, 0.3-90 μm , 0.3~30μm, 0.3~10μm, 0.3~8μm, 0.5~100μm, 0.5~90μm, 0.5~30μm, 0.5~10μm, 0.5~8μm, 0.7~100μm, 0.7~90μm, 0.7~30μm, 0.7~10μm, 0.7~8μm, 1~100μm, 1~90μm, 1~30μm, 1~10μm, 1~8μm, 1.2~100μm, 1. 2~90μm, 1.2~30μm, 1.2~10μm, 1.2~8μm, 1.5~100μm, 1.5~90μm, 1.5~30μm, 1.5~10μm, 1.5~8μm, 1.7~ 100μm, 1.7~90μm, 1.7~30μm, 1.7~10μm, 1.7~8μm, 2~100μm, 2~90μm, 2~30μm, 2~10μm, 2~8μm, 2.2~10 0μm, 2.2~90μm, 2.2~30μm, 2.2~10μm, 2.2~8μm, 2.5~100μm, 2.5~90μm, 2.5~30μm, 2.5~10μm, 2.5~8μm m, 2.7~100μm, 2.7~90μm, 2.7~30μm, 2.7~10μm, 2.7~8μm, 3~100μm, 3~90μm, 3~30μm, 3~10μm, 3~8μm;

[0058] Preferably, the thickness of the surface coating of the bending area does not exceed 10 μm.

[0059] More preferably, the thickness of the surface coating of the bending area is 0.01-10 μm.

[0060] A second aspect of the present invention provides a method for preparing an aluminum-containing metal terminal with a coating, wherein the metal terminal comprises an elastic contact piece, and the preparation method comprises the following specific steps:

[0061] 1) Prepare the plating solution and the substrate containing aluminum metal terminals

[0062] The plating solution contains graphene and other metallic silver; in the plating solution:

[0063] The concentration of graphene is 0.1 to 100 g / L.

[0064] The concentration of other metallic silver ions is 0.25 to 100 g / L;

[0065] Wherein, the graphene includes stacked graphene sheets and silver located between the graphene sheets;

[0066] The silver includes silver ions and nano-sized silver particles.

[0067] 2) Electroplating the substrate using the plating solution.

[0068] The "intermediate plating film" as described herein is the same as the "intermediate plating film" possessed by the resilient contact member of the terminal according to any embodiment of the first aspect of the present invention.

[0069] As described herein, the "concentration of graphene" in the plating solution herein is calculated based on the carbon atom content.

[0070] As described herein, the "other metal silver ions" in the plating solution herein are different from the "silver located between the graphene sheets" as described above.

[0071] Furthermore, the concentration of graphene in the plating solution can be arbitrarily selected from any group of numerical ranges of 0.1-100 g / L, 1-100 g / L, 5-100 g / L, 10-100 g / L, 20-100 g / L, 30-100 g / L, 40-100 g / L, 50-100 g / L, 60-100 g / L, 70-100 g / L, 80-100 g / L, and 90-100 g / L.

[0072] According to any embodiment of the second aspect of the present invention, the content of graphene in the surface coating is not less than 3 at % calculated by carbon content based on the total number of atoms in the surface coating.

[0073] Furthermore, according to the total number of atoms in the surface coating and calculated by carbon content, the content of graphene in the surface coating can be arbitrarily selected from any group of numerical ranges including 3-50at%, 5-30at%, 5-20at%, 10-20at%, and 5-15at%.

[0074] According to any embodiment of the second aspect of the present invention, the amount of silver located between the graphene sheets is 0.1 to 50 at % based on the total number of atoms of the graphene.

[0075] Furthermore, based on the total number of graphene atoms, the amount of silver located between the graphene sheets can be arbitrarily selected from any group of numerical ranges including 1-50at%, 1-45at%, 1-40at%, 1-30at%, 1-20at%, and 1-10at%.

[0076] According to any embodiment of the second aspect of the present invention, the plating solution further comprises silver, or any one or a combination of two or three of the following metals other than silver: copper, iron, aluminum, tin, nickel, zinc, cobalt;

[0077] Further, the concentration of the metallic silver ion in the above plating solution can be arbitrarily selected from 0.1-100 g / L, 0.25-100 g / L, 1-100 g / L, 5-100 g / L, 10-100 g / L, 20-100 g / L, 30-100 g / L, 40-100 g / L, 50-100 g / L, 60-100 g / L, 70-100 g / L, 80-100 g / L, 90-100 g / L, 0.1-80 g / L, 0.25-80 g / L, 1-80 g / L, 5-80 g / L, 10-80 g / L, 20-80 g / L, 30-80 g / L, 40-80 g / L , 50-80g / L, 60-80g / L, 70-80g / L, 0.1-60g / L, 0.25-60g / L, 1-60g / L, 5-60g / L, 10-60g / L, 20-60g / L, 30-60g / L, 40-60g / L, 50-60g / L, 0.1-40g / L, 0.25-40g / L, 1-40g / L, 5-40g / L, 10-40g / L, 20-40g / L, 30-40g / L, 0.1-20g / L, 0.25-20g / L, 1-20g / L, 5-20g / L, 10-20g / L.

[0078] According to any embodiment of the second aspect of the present invention, in step 2), the current density during electroplating is 0.1A / dm 2 ~100A / dm 2 .

[0079] Preferably, in step 2), the current density during electroplating is 0.1A / dm 2 ~40A / dm 2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 :(a) is a SEM image of a 30nm thick Ni intermediate coating formed on a pure aluminum A1100 substrate; (b) is a SEM image of a 3μm thick Ni intermediate coating formed on a pure aluminum A1100 substrate; (c) is a SEM image of a 3μm thick Ni intermediate coating formed on a pure aluminum A1100 substrate Figure 1 (a) shows a SEM image of a uniform and smooth 5 μm thick Ag-Gr (Ag) film formed on a 30 nm thick Ni intermediate coating; (d) shows a SEM image of a uniform and smooth 5 μm thick Ag-Gr (Ag) film formed on a 30 nm thick Ni intermediate coating; Figure 1(b) SEM image of a uniform and smooth 5 μm thick Ag-Gr (Ag) film formed on a 3 μm thick Ni intermediate plating film;

[0081] Figure 2 :(a) For example Figure 1 (c) is an element distribution diagram in the depth (also called thickness) direction of the coating formed on the pure aluminum A1100 substrate material; (b) is an element distribution diagram for Figure 1 (d) element distribution diagram in the depth (also called thickness) direction of the coating formed on the pure aluminum A1100 substrate material;

[0082] Figure 3 The contact resistance measurement results of the elastic contact of the terminal with Ag-Gr (Ag) film (thickness 5 μm) respectively using A1100, A1050, A2017, A2024, A6061 as aluminum substrate materials, and pre-plated with nickel intermediate films of different thicknesses (0 μm (Ag-Gr (Ag)), 0.03 μm (Ni-03 / Ag-Gr (Ag)), 3 μm (Ni-3 / Ag-Gr (Ag))) on the substrate materials;

[0083] Figure 4 Schematic diagram of the structure of silver-infiltrated graphene used in an embodiment of the present invention;

[0084] Figure 5 A schematic structural diagram of a metal terminal containing aluminum and having a coating provided by the present invention;

[0085] Figure 6 A schematic diagram of the structure of another aluminum-containing metal terminal with a coating provided by the present invention combined with the matching terminal to form a terminal pair;

[0086] Figure 7 A schematic diagram of the layer structure of the elastic contact piece of the terminal provided by the present invention. DETAILED DESCRIPTION

[0087] The present disclosure may be more easily understood by reference to the following description in conjunction with the accompanying drawings and examples, all of which constitute a part of the present disclosure. It should be understood that the present disclosure is not limited to the specific products, methods, conditions or parameters described and / or shown herein. Further, the terms used herein are only used for the purpose of describing specific embodiments by way of example and are not intended to be limiting unless otherwise stated.

[0088] It should also be understood that, for the sake of clarity, certain features of the present disclosure may be described herein in the context of separate embodiments, but may also be provided in combination with each other in a single embodiment. That is, unless clearly incompatible or specifically not included, each separate embodiment is considered to be combinable with any other embodiment, and the combination is considered to represent another different embodiment. Conversely, for the sake of simplicity, the various features of the present disclosure described in the context of a single embodiment may also be provided individually or in any sub-combination. Finally, although a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or substructure itself may also be considered to be an independent embodiment.

[0089] Unless otherwise indicated, it should be understood that each individual element in a list and each combination of individual elements in the list will be interpreted as a different embodiment. For example, a list of embodiments represented as "A, B, or C" should be interpreted to include embodiments "A", "B", "C", "A or B", "A or C", "B or C", or "A, B, or C".

[0090] In the present disclosure, the singular forms of the articles "a," "an," and "the" also include the corresponding plural references, and a reference to a specific value includes at least that specific value unless the context clearly indicates otherwise. Thus, for example, a reference to "a substance" is a reference to at least one of that substance and equivalents thereof.

[0091] The terms including ordinal numbers such as "first" and "second" can be used to explain various components or fluids, but these components and fluids are not limited by these terms. Therefore, without departing from the teachings of the present disclosure, these terms are only used to distinguish the component / fluid from another component / fluid.

[0092] When items are described by using the conjunction terms "... and / or...," etc., the description should be understood to include any one of the associated listed items and all combinations of one or more thereof.

[0093] In general, the use of the term "about" indicates an approximate value that may vary depending on the desired properties obtained by the disclosed subject matter, and will be interpreted in a context-dependent manner based on function. Therefore, one of ordinary skill in the art will be able to interpret a certain degree of difference on a case-by-case basis. In some cases, the number of significant figures used when expressing a particular value can be a representative technique for determining the difference allowed by the term "about". In other cases, a gradient in a range of values ​​can be used to determine the range of differences allowed by the term "about". Further, all ranges in this disclosure are inclusive and combinable, and reference to the values ​​stated in the range includes each value within the range.

[0094] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs; the terms used herein and / or include any and all combinations of one or more of the associated listed items.

[0095] The detection instruments (or models) and conditions used in the following specific embodiments are:

[0096] Surface morphology: The surface states of various target objects were investigated by field effect scanning electron microscopy (FE-SEM) (JEOL-JSM_7800F, 5 kV,).

[0097] Chemical composition analysis: The chemical composition of various target objects was measured by energy dispersive spectroscopy (EDS) installed on FE-SEM (measurement range 1000 times, measurement voltage 20 kV).

[0098] Raman Detection: The binding state of various target objects was studied by Raman spectroscopy (machine name: laser Raman spectrophotometer (NRS-3300), the measurement light wave range is 254.896cm -1 ~3899.87cm -1 , center wave number: 2301.01cm -1 , excitation wavelength: 532.08nm, laser intensity: 7.9mW).

[0099] XRD measurement: The crystal state and crystal plane orientation state of various target objects were studied by XRD measurement (machine name: powder X-ray diffraction measurement device, RINT-2000, 40kV / 30mA, Cu / Ka).

[0100] Elemental analysis: Elemental analysis in the depth direction was studied by glow discharge luminescence GD-OES measurement (machine name: glow discharge luminescence surface analyzer (HORIBA-GD-profiler 2-MN), measurement area: diameter 8mm, flowing gas: nitrogen).

[0101] Conductivity (contact resistance) test: By using a precision metal terminal electrical contact resistance tester (Yamazaki Seiki Laboratory: CRS-1 type, sliding load Reciprocating sliding distance 0.5mm, measuring current 10mA, measuring terminal 24K pure gold U-shaped contact) was used to investigate the conductivity of the coating; each sample was tested at 5 points and the average value was taken).

[0102] Heat resistance (electrical contact resistance stability under high temperature environment) test: Referring to the most stringent Class-V standard in the standards of the United States Automobile Association (USCAR), the contact resistance value of the samples before and after the heat resistance test is measured by heating at 200°C for 150 to 1500 hours.

[0103] Hardness test: The Vickers hardness of the coating was measured by using a micro hardness measuring instrument (Shimadzu HMV-G31ST; load 490.3 mN; holding time: 20 sec, 5 points for each sample were tested and the average value was taken).

[0104] Observation of terminal coating: Referring to the standard published by the American Materials Association, the use and coordination of connector terminals includes two stages: insertion stage and sliding stage. Therefore, according to the standard, the positive pressure of 200g and 400g was applied to the terminals for friction test, and then the wiping contact effectiveness was measured. The wiping contact effectiveness test results of Examples 1-14 were relatively stable, while the wiping contact effectiveness test results of Comparative Examples 1-13 to 1-18 decreased and were unstable. Then, an optical microscope was used for observation.

[0105] The present invention is further described below in conjunction with specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. The essential characteristics and remarkable effects of the present invention can be reflected from the following examples, and the described embodiments are part of the embodiments of the present invention, rather than all the embodiments, and therefore, they do not limit the present invention in any way, and those skilled in the art make some non-essential improvements and adjustments based on the content of the present invention, which all belong to the protection scope of the present invention.

[0106] Specific embodiment 1: Aluminum-containing metal terminal with coating

[0107] like Figure 6 As shown, the aluminum-containing metal terminal 1 provided by the present invention has a matching terminal 8 used in conjunction with it as a mating terminal to form a terminal pair when in use.

[0108] like Figure 5 As shown Figure 7As shown, the aluminum-containing metal terminal 100 of this example includes a substrate and a surface coating located on the substrate in terms of material composition, and the material of the substrate is an aluminum-containing material. Structurally, the aluminum-containing metal terminal 100 of this example has: a first barrel 110 and a second barrel 120. The first barrel 110 and the second barrel 120 are arranged in parallel. In this example, the side of the second barrel 120 in the longitudinal direction of the aluminum-containing metal terminal 100 can be called the rear part, and the side of the first barrel 110 is called the front part. The description of the front and rear directions is for convenience and has nothing to do with the actual direction of the aluminum-containing metal terminal 100 when it is used. In addition, in this example, the first barrel 110, the second barrel 120 and the elastic contact member 130 are preferably formed integrally.

[0109] The first barrel 110 is tubular. Figure 5 As shown, the first barrel portion 110 provided in this example has a substantially square tube shape extending in the length direction of the aluminum-containing metal terminal 100. Figure 5 and Figure 6 As shown, the first barrel 110 has an open end 111 in front, so that the insertion portion 210 of the matching terminal 200 used in conjunction with it can be inserted. Figure 5 As shown, the first barrel portion 110 has a rear open end 112 at its rear, and the second barrel portion 120 is connected to the rear open end 112 of the first barrel portion 110 .

[0110] The second barrel 120 is connected to the first barrel 110 and is used to connect the wires / conductors. In terms of shape, the second barrel 120 can be tubular or semi-open. Figure 5 As shown, the second barrel portion 120 provided in this example is semi-open and includes a wire barrel portion 121, an insulating barrel portion 122, and a protruding portion 123; the wire barrel portion 121 is used to crimp the conductor exposed from the end of the wire in order to form an electrical connection with the conductor. The insulating barrel portion 122 is connected to the rear of the wire barrel portion 121, and the two have a cross-section that is perpendicular to the aluminum-containing metal terminal 100 and is longer than the extension direction, and the cross-section is roughly U-shaped; the insulating barrel portion 122 is an insulating covering portion for crimping an insulator. The protruding portion 123 is arranged on the bottom surface 133 of the wire barrel portion 121, and the protruding portion 123 has the function of concentrating the pressure on the contact portion between the protruding portion 123 and the conductor when crimping the conductor. Thereby, the quality of the electrical connection between the two can be guaranteed.

[0111] The aluminum-containing metal terminal 100 also has an elastic contact piece 130, which is present inside the tubular first barrel 110 and cooperates with the top plate 113 of the first barrel 110 to form contact with and compress the insertion portion 210 of the matching terminal 200 inserted into the first barrel 110. At the same time, the elastic contact piece 130 can effectively cooperate with the first barrel 110, and after thousands of plug-in and pull-out tests, it still has a low insertion force or even zero insertion force, meeting the use requirements.

[0112] It can be seen from the above that the elastic contact member 130 is the main component that affects the stability of the electrical connection of the terminal. Figure 7 As shown, the elastic contact member includes a substrate 1303 and a coating located on the substrate 1303. The substrate 1303 is a plate with a thickness of 0.01 mm to 0.6 mm. The coating includes a surface coating 1305 and an intermediate coating 1304. The types of the surface coating and the intermediate coating can be the same, especially when considering the performance requirements such as high temperature resistance and conductivity, the surface coating 1305 and the intermediate coating 1304 are preferably of the same type (as described in the [Surface Coating 1305] section below). Of course, the types of the surface coating 1305 and the intermediate coating 1304 can also be different. More specifically:

[0113] The "surface coating 1305" has the following characteristics:

[0114] The main or characteristic component is "graphene infiltrated with silver", and the surface coating provided by the present invention has a Raman spectrum detected by Raman spectroscopy at 500±30cm -1 Peak at 1330±30cm -1 Peak at 1550±30cm -1 The peak at 2800±30cm -1 Peak at. In some embodiments of the present invention, according to the total number of atoms of the surface coating, calculated by carbon content, the content of "graphene infiltrated with silver" contained in the surface coating is not less than 1at%, preferably not less than 3at%, further preferably 3-50at%, and more preferably 5-30at%. It is further explained that the content of "graphene infiltrated with silver" in the "surface coating" is in the range of 3-50at%, and the influence on the conductivity and heat resistance of the surface coating is basically negligible. The wear resistance trend line of the surface coating is obtained by fitting the experimental data, and the trend line changes basically linearly. In the following embodiments, surface coatings with "graphene infiltrated with silver" contents of 8at% and 12at% are used to schematically illustrate the technical solution of the present invention.

[0115] On this basis, in some embodiments of the present invention, the "surface coating" also includes another main or characteristic component other than "graphene infiltrated with silver", which is metal. As described herein, the "metal" does not include the "silver infiltrated in graphene", and the metal can be any one or a combination of two or more of silver, copper, iron, aluminum, tin, nickel, zinc, and cobalt. In some embodiments of the present invention, according to the total number of atoms of the surface coating, the content of the metal contained in the surface coating is not less than 40at%, and in theory, the sum of the content of the metal contained in the surface coating as described herein and the content of the "graphene infiltrated with silver" contained in the surface coating described above should be infinitely close to 100at%, but in actual situations, the presence of some inevitable impurities cannot be ruled out, so the sum of the content of the metal contained in the surface coating and the content of the "graphene infiltrated with silver" contained in the surface coating described above is in the range of 95at% to 100at%.

[0116] Regarding the “silver-infiltrated graphene”, it has a layered structure formed by stacked graphene sheets, with gaps between the layers, and the gaps form an effective space inside the graphene. The “silver between the graphene sheets” can be understood as the silver ions and nano-sized silver particles filled / dispersed in the effective space. Generally, silver ions and nano-silver particles (also called particles) exist at the same time. The “filling / dispersion” can be a small amount of local filling, or a large part of the filling, or all of the filling. Based on this, the “silver-infiltrated graphene” in the surface coating provided by the present invention includes a body composed of stacked graphene sheets, and silver ions and nano-sized silver particles located between the graphene sheets. This is also the reason why the Raman spectrum of the surface coating has 500±30cm -1 One of the key reasons for the peak.

[0117] In fact, the silver between the graphene sheets will affect the conductivity of the surface coating. As far as the "body composed of stacked graphene sheets" is concerned, the bonding force between the layers of the graphene sheets is van der Waals force, and the carbon atoms in the layers are bonded by covalent bonds. Therefore, compared with the conductivity within the layer, the conductivity between the layers is poor, that is, it generally has only two-dimensional conductivity. The "silver-infiltrated graphene" in the surface coating provided by the present invention, the silver ions and nano-sized silver particles "infiltrated" or "inserted" between the stacked graphene sheet structures, can effectively reduce the contact resistance between the layers of the graphene sheets, improve the conductivity between the layers of the graphene sheets, and then convert the two-dimensional conductivity between the stacked graphene sheets into three-dimensional conductivity. In particular, a silver-carbon bonding structure can be formed in the middle of the graphene sheet to realize silver-carbon interface-free conductivity or a high conductive path, thereby improving the heat generation of the connecting components when running under large currents and the high power loss caused by it.

[0118] In addition, the silver between the graphene sheets will increase the interlayer bonding force of the graphene sheets, and the interlayer bonding force of the graphene sheets will be further increased as the silver content increases, but it should be noted that too much silver will cause serious agglomeration of the graphene and make it unusable; therefore, in some embodiments of the present invention, according to the atoms of the "graphene infiltrated with silver" as the total number, the amount of silver between the graphene sheets is 0.1-50at%, and in some preferred embodiments of the present invention, according to the atomic percentage of the "graphene", the amount of silver between the graphene sheets is 0.1-45at%. It is further explained that the silver content in the "graphene infiltrated with silver" is in the range of 0.1-50at%, and the conductivity trend line of the "surface coating" is obtained by fitting the experimental data, and the trend line changes basically linearly. In the following embodiments, the "graphene infiltrated with silver" with a silver content of 5at% is used to schematically illustrate the technical solution of the present invention.

[0119] In summary, the "surface coating" provided by the present invention has a contact resistance of no more than 4 mΩ, a friction coefficient of no more than 0.4, and a Vickers hardness of no less than 130 HV. For example, if the surface coating contains metallic silver and silver-infiltrated graphene, the "surface coating" provided by the present invention can optimally have a contact resistance of no more than 0.7 mΩ, a friction coefficient of 0.1 to 0.4, and a Vickers hardness of more than 130 HV.

[0120] Furthermore, the thickness of the "surface coating" can be selected from any numerical range within the range of 0.01 to 100 μm, or any numerical value.

[0121] The "intermediate coating 1304" has the following characteristics:

[0122] In terms of material composition, the "intermediate coating" described in the present invention may be the same as the "surface coating", which will not be elaborated at this time; in addition, when the "intermediate coating" is different from the "surface coating", it is mainly a "metal intermediate coating".

[0123] One of the main functions of the "intermediate coating" described in the present invention is diffusion prevention; the second main function is to improve the bonding force between the "surface coating" and the "substrate"; the third main function is to reduce the induced influence of the "substrate" on the crystal structure of the "surface coating" and improve the all-plating ability of the coating. Therefore, in this case, the "intermediate coating" can prevent the elements (such as copper, iron, aluminum, etc.) on the metal surface of the "substrate" in contact with it from entering the "surface coating" or diffusing to the surface of the "surface coating" under high temperature environment to form an oxide film, resulting in an increase in contact resistance or a decrease in conductivity, that is, improving the heat resistance of the "surface coating". At the same time, it can enhance the bonding strength between the "substrate" and the "surface coating" and improve the uniformity of the "surface coating". Especially when it comes to the situation where the metal surface of the "substrate" is prone to produce a stable metal oxide film, such as the connecting part serving as the "substrate" whose surface is an easily passivated metal surface such as aluminum alloy, stainless steel, titanium alloy, and copper alloys containing special alloy elements such as tellurium copper and beryllium copper, as well as difficult-to-plate metals such as tungsten, molybdenum, chromium, and metal surfaces containing tungsten, molybdenum, chromium, etc. as the "substrate", the "second function" of the aforementioned "intermediate coating" is particularly important for ensuring that the electroplated "surface coating" and the "substrate" have good bonding.

[0124] Based on this, the elements that form the "intermediate coating" are mainly considered to be any elements that are not easy to react with the elements in the metal surface of the "substrate" or are not easy to form a thick oxide film at high temperature. For example, in the case of a "substrate" or "metal surface of the substrate" made of Cu or Cu alloy, Ni, Cr, Mo, W, Al, Ti, Zr, V, Ta, Nb, etc. or their alloys can be used as the "intermediate coating"; for another example, in the case of a "substrate" or "metal surface of the substrate" made of Al or Al alloy, Ni, Cr, Mo, W, Cu, Ti, Zr, V, Ta, Nb, etc. or their alloys can be used as the "intermediate coating". The "intermediate coating" can also be called an intermediate film, a transition layer, a transition film, or an anti-diffusion layer. On this basis, the "intermediate coating" can optionally meet any one or more of the following conditions Ⅰ) to Ⅷ):

[0125] Ⅰ) includes a metal content of not less than 95wt%;

[0126] II) alloys containing not less than 95 wt%;

[0127] III) Combinations of metals and alloys containing not less than 95 wt%;

[0128] The metals described in Ⅰ) or Ⅲ) include any one of copper, iron, aluminum, tin, nickel, zinc and cobalt, or a combination of two or more thereof;

[0129] The alloy as described in II) or III) includes any one of copper, iron, aluminum, tin, nickel, zinc and cobalt alloys or a combination of two or more thereof.

[0130] In terms of size, the thickness of the "intermediate coating" can be selected from any numerical range within the range of 0.01 to 10 μm, or any numerical value. For example, the thickness of the "intermediate coating" can be 0.5 μm, 1 μm, 3 μm or 5 μm.

[0131] Furthermore, if Figure 6 As shown, the elastic contact piece 130 in this example is formed by folding the bottom plate 123 of the first barrel portion 110, based on which the elastic contact piece 130 has a bending area 1302. In addition, the elastic contact piece 130 is also provided with a protruding area 1301 protruding toward the top plate 113 of the first barrel portion 110, and the protruding area 1301 is in direct contact with the insertion part 210 of the matching terminal 200 to form compression to achieve electrical connection.

[0132] The properties of the "surface coating" and "intermediate coating" of the protruding area 1301 are as described above.

[0133] The properties of the "intermediate coating" of the bending area 1302 are further described based on the above description. Figure 6 As shown, in order to match the specifications of various connectors, metal terminals are generally plated first, using the principle of the Galvanic effect to prevent the internal metal terminals from contacting the external environment and causing oxidation or corrosion, and then bent by stamping. However, it has been observed for a long time that there will be problems with uneven coating at the bends, corners, or areas where the arc transitions of the terminals; at the same time, due to the effect of stress, the coatings at these locations are prone to poor bonding (cracks, breakage, shedding, etc.) at the bends. In this way, it is very likely that due to the partial shedding of the coating, accelerated oxidation and corrosion will occur at the bends, which will greatly affect the conductive properties of the terminals. Generally speaking, problems will occur when the coating exceeds 2μm. In this regard, regarding the bending zone 1302 described in the present invention, by adding an "intermediate coating", the bonding strength between the "surface coating" provided by the present invention and the substrate can be effectively improved. Based on this, on the basis of the above, it is preferred that the maximum thickness of the "intermediate coating" of the bending zone 1302 is not more than 2.5μm, and the value range can be selected from any numerical interval in the range of 0.01 to 2.5μm, or any numerical value. For example, the thickness of the "intermediate coating" can be 0.5μm, 1μm, 1.5μm, 2μm or 2.5μm.

[0134] The properties of the "surface coating" of the bending zone 1302 are further described on the basis of what has been described above. The thickness of the "surface coating" of the bending zone 1302 is recommended to be no more than 20 μm, and preferably no more than 10 μm. The reason is that in general, when the thickness of ordinary metal coatings exceeds 2 μm, cracks, breakages, and even shedding of the coating can be observed at the bending part of the component. When the "surface coating" of the bending zone 1302 of the present invention is a coating provided by the present invention as described above, which mainly uses "silver-infiltrated graphene" as the main or characteristic component, its advantage is that it can break through the limitation of 2 μm of ordinary coatings in the past and provide the bending zone 1302 with a coating of greater thickness for protection. However, at the same time, it is also hoped to avoid cracks, breakages, and even shedding of the coating as much as possible, so the thickness of the "surface coating" of the bending zone 1302 is limited to no more than 15 μm. The main reason is that the plating solution used to prepare the "surface coating" provided by the present invention contains silver-infiltrated graphene sheets. The silver added between the graphene sheets by "infiltration" can change the two-dimensional conductivity between the graphene sheets into three-dimensional conductivity. This change from two-dimensional conductivity to three-dimensional conductivity not only affects the low contact resistance and high conductivity of the coating formed in the end, but also actually affects the coating formation behavior of the electroplating process, so that the surface of the substrate can grow the coating more uniformly and stably, especially avoiding the occurrence of rupture and shedding of the coating in the bending area 1302 and the protruding area 1301 of the elastic contact 130. In addition, it is required that the thickness of the "surface coating" of the bending area 1302 is not less than 0.05μm, preferably not less than 0.1μm.

[0135] Finally, regarding the substrate of the "aluminum-containing metal terminal", its material can be pure aluminum or aluminum-copper alloy. The "pure aluminum" contains more than 99.00wt% aluminum. From the perspective of low contact resistance, "pure aluminum" containing no more than 99.50wt% aluminum is preferred. Typical grades of "pure aluminum" that can be listed include: 1100, 1050, etc.

[0136] Further from the perspective of lightweight and low contact resistance, the material of the "aluminum-containing metal terminal", especially the base of the elastic contact 130, is preferably an aluminum-copper alloy. The "aluminum-copper alloy" is an aluminum-containing alloy with copper as the main alloying element. Manganese, magnesium, lead and bismuth may also be added. Typical grades of "aluminum-copper alloy" that can be listed include: 2017, 2014, 2011, 2618, 2219, 2024, etc. The best preference is that the copper content of the aluminum-copper alloy is not less than 3wt%.

[0137] Specific embodiment 2: Preparation method of aluminum-containing metal terminal with coating

[0138] Pretreatment of aluminum-containing "matrix material": As a pretreatment, the metal surface of the "matrix material" is mainly degreased to remove surface oil stains, and pickled to remove surface oxide film.

[0139] Making an "intermediate coating": Making an "intermediate coating" on the surface of the "metal substrate". There is no particular limitation on the method of forming the "intermediate coating". Depending on the nature of the substrate, it can be electroplating, chemical plating or displacement plating to achieve the required thickness. However, it should be noted that if the intermediate coating is formed on a non-metallic substrate, it needs to be catalytically treated in advance before forming the intermediate coating.

[0140] Making a "surface coating": making a surface coating on the surface of the "intermediate coating"; the "surface coating" is mainly formed by an "electroplating" method.

[0141] The “electroplating” comprises the following steps 1) and 2) :

[0142] 1) Prepare the plating solution and substrate

[0143] The plating solution includes components for forming a "surface coating"; the "components for forming the coating" at least include "graphene infiltrated with silver", and may also contain other metals on this basis; for example, if the coating is a "metal coating" different from the "surface coating", then the "components for forming the coating" mainly refer to at least including the corresponding metal;

[0144] 2) Electroplating the substrate with the "intermediate coating" using the electroplating solution. The detailed operation of the electroplating for reference is as follows:

[0145] The plating solution is supplied approximately perpendicularly to the surface to be plated of the substrate, and convects approximately horizontally on the surface to be plated, or flows approximately horizontally on the surface to be plated; the process includes electroplating the metal substrate with the plating solution, wherein the plating solution is an industrial plating solution containing or not containing cyanide, preferably a plating solution not containing cyanide. The current density during electroplating can be between 0.1A / dm 2 ~100A / dm 2 The thickness of the "plating film" can be adjusted within a range of , and the thickness of the "plating film" can be adjusted by adjusting the current density and time. For example, when the current density is constant, the thickness of the obtained "plating film" can be increased by extending the electroplating time.

[0146] On the basis of the aforementioned "electroplating" steps 1) and 2), the preparation of the "surface coating" is further described as an illustrative and detailed description:

[0147] During the electroplating process, the plating solution contains "silver-infiltrated graphene" or other metals besides silver. The "silver-infiltrated graphene" also has a layered structure formed by stacked graphene sheets, with gaps between layers. The gaps form an effective space inside the graphene. The "silver between the graphene sheets" can be understood as silver ions and / or nanosilver particles filled / dispersed in the effective space. Generally, silver ions and nanosilver particles (also called particles) exist at the same time. The "filling / dispersion" can be a small amount of local filling, a large part of the filling, or all of the filling (see Figure 4 ). Based on this, the "silver-infiltrated graphene" includes a body composed of stacked graphene sheets, and silver ions and / or nanosilver particles located between the graphene sheets. The silver ions and nanosilver particles between the graphene sheets can accelerate the movement speed of the "silver-infiltrated graphene" under the electric field, thereby facilitating the rapid formation of the coating, and is particularly suitable for local small-scale electroplating and high-speed electroplating of the substrate.

[0148] Regarding the main body of the "laminated graphene sheet" constituting the "silver-infiltrated graphene" used in the electroplating process, it is preferably a sheet-shaped or laminated graphene with a size of 6 μm or less; in some preferred embodiments of the present invention, it mainly refers to a sheet-shaped or laminated graphene with a size of 0.01 to 6 μm or less; in further preferred embodiments of the present invention, it mainly refers to a sheet-shaped or laminated graphene with a size of 0.01 to 5 μm or less;

[0149] Regarding the preparation method of the body of the "laminated graphene sheet" of the "silver-infiltrated graphene" used in the electroplating process, it can be carried out by electrolytic stripping as shown below, and the specific electrolytic stripping conditions that can be referred to are as follows: immersing graphite in an aqueous solution and decomposing the graphite into layers through a strong electric field and an electrochemical reaction. The decomposed layered graphene is classified into the following graphene sizes. The graphene size is a mixture of 1 μm or less, 1 to 3 μm, 3 to 5 μm, and 6 μm or less. In addition, the size of the graphene is classified according to the mesh size of the filter paper used for filtration.

[0150] Regarding the "graphene infiltrated with silver" used in the electroplating process, it can be obtained by commercial means, or by methods such as self-assembly, chemical reduction, hydrothermal, electrochemical deposition, and thermal evaporation. For example, the self-assembly method is to mix the graphene dispersion with pre-prepared or commercially available silver nanopowder or silver ion solution, and combine it through covalent bonds or non-covalent bonds (van der Waals forces, electrostatic forces, intermolecular forces, and hydrogen bonds, etc.) to obtain "graphene infiltrated with silver". Based on, the self-assembly method can prepare a graphene nanocomposite material with a simple and controllable silver loading and a highly uniform distribution. Therefore, in the actual preparation process, functionalized graphene can be first used as a raw material, modified with n-octadecyl mercaptan, then added to an ethanol solution, ultrasonically dispersed, silver chloride is added, and a composite material is prepared by photochemical reduction. The interaction between n-octadecyl mercaptan molecules and silver can effectively control the arrangement and orientation of silver on the graphene surface, so that it generates specific nano-Ag particles, thereby controlling the preparation of graphene / silver nanocomposite materials, which can be used as "graphene infiltrated with silver" in the electroplating process of the present invention. Alternatively, it can be obtained by "chemical reduction method", which is the most common method for preparing graphene / silver nanocomposite materials. The process is to configure graphene and silver into graphene solution and silver chloride solution, mix the two, add corresponding reducing agent, and prepare graphene / metal silver nanocomposite materials by oxidation-reduction method. The obtained graphene / metal silver nanocomposite materials can be used as "graphene infiltrated with silver" in the electroplating process of the present invention. Alternatively, it can be obtained through "electrochemical deposition method", which is a highly efficient preparation method. By electrochemical deposition method, graphene sheets are directly dispersed into a silver-containing electroplating solution, and a surfactant is added and stirred to obtain a graphene / silver nanocomposite material. The graphene / silver nanocomposite material can be used as "silver-infiltrated graphene" in the electroplating process of the present invention.

[0151] The orientation of the "laminated graphene sheets" in the coating provided by the present invention is not specially set, and can be arranged perpendicularly, parallel, tilted or randomly oriented to the substrate according to the required characteristics of the component. Specific embodiment three

[0153] like Figure 6 As shown, the structure of the aluminum-containing metal terminal with a coating prepared in this example is the same as that of the specific embodiment 1. In addition, in this example:

[0154] The base materials of the elastic contact members 130 of the specific embodiments 2-1 to 2-3 are respectively pure aluminum A1100, the surface is pre-plated with a Ni intermediate coating of different thicknesses (0 μm, 0.03 μm, 3 μm), and then a Ag-Gr (Ag) surface coating with a thickness of 5 μm is formed by electroplating;

[0155] The base materials of the elastic contact member 130 of the specific embodiments 2-4 are respectively A1050 aluminum alloy with high purity, a Ni intermediate coating with a thickness of 0.03 μm pre-plated on the surface, and a Ag-Gr (Ag) surface coating with a thickness of 5 μm formed by electroplating;

[0156] The base materials of the elastic contact members 130 of the specific embodiments 2-5 to 2-10 are respectively Al-Cu alloys A2017 and A2024, and the surface of the Al-Si alloy A6061 is pre-plated with Ni intermediate films of different thicknesses (0 μm, 0.03 μm), and then an Ag-Gr (Ag) surface film with a thickness of 5 μm is formed by electroplating;

[0157] Comparative Example D2-1: The elastic contact member 130 of D2-1 is substantially the same as that of Specific Example 2-1, except that the surface coating of D2-1 is a pure Ag surface coating with a thickness of 5 μm formed by electroplating;

[0158] Comparative Example D2-2: The elastic contact member 130 of D2-2 is substantially the same as that of Specific Example 2-1, except that the surface coating of D2-2 is a Ag-Gr (Ag) surface coating with a thickness of 30 μm formed by electroplating;

[0159] Comparative Example D2-3, the elastic contact member 130 of D2-3 is substantially the same as that of Specific Example 2-1, except that the thickness of the intermediate coating of D2-3 is a 5 μm Ag-Gr surface coating;

[0160] In the above, the "surface coating" of the protruding area 1301, the bending area 1302 and the remaining areas of the same elastic contact member 130 is completely the same; the "intermediate coating" of the protruding area 1301, the bending area 1302 and the remaining areas of the same elastic contact member 130 is completely the same. Among them:

[0161] 1. The surface coating includes metallic silver and graphene infiltrated with silver. More detailed information is as follows:

[0162] 1) About the plating solution used

[0163] Basic electroplating solution-1: A commercially available cyanide-free silver plating solution (model PRECIOUSFAB Ag4730, Ag concentration 30 g / L, reference website https: / / www.tanaka.com.cn / products / detail / plating-processes / ) from Tanaka Precious Metals Co., Ltd. was used as the basic electroplating solution;

[0164] The "basic electroplating solution-1" described herein is also used as the subsequent "comparative electroplating solution-2", that is, the final electroplating solution does not contain any graphene components.

[0165] Based on the "Comparative Plating Solution-2", a Pure-Ag coating can be formed on the plated substrate;

[0166] Electroplating solution-1 containing "silver-infiltrated graphene": On the basis of basic electroplating solution-1, "silver-infiltrated graphene (hereinafter referred to as silver-infiltrated graphene)" with a silver content of 5at% is added thereto. The size of the graphene sheets of the silver-infiltrated graphene used here is 0.05-6μm. In view of the need to reduce costs as much as possible in practical applications, the present invention uses mixed-size graphene sheets without graded separation, wherein the particle size distribution of graphene sheets below 5μm, 3μm and 1μm accounts for approximately 30%, 35% and 30% respectively). Finally, the silver-infiltrated graphene is calculated by the weight of carbon. According to the aqueous solution, the concentration of the silver-infiltrated graphene in this electroplating solution is 100g / L (equivalent to a concentration of approximately 9.6wt%).

[0167] Based on the "electroplating solution containing silver-infiltrated graphene-1", an Ag-Gr (Ag) plating film can be formed on the plated substrate;

[0168] Comparative plating solution-1: On the basis of basic plating solution-1, ordinary graphene that is not permeated with silver (i.e., a body consisting of only stacked graphene sheets, excluding silver) is added thereto to form a final plating solution, and the rest is the same as basic plating solution 1. Finally, the concentration of graphene in this plating solution is 100g / L (equivalent to a concentration of about 9.6wt%), calculated based on the weight of carbon and according to the aqueous solution.

[0169] Based on the "Comparative plating solution-1", an Ag-Gr film can be formed on the plated substrate;

[0170] Basic electroplating solution-2: A commercially available general-purpose cyanide silver plating solution (model Ag-10, Ag 30 g / L, reference website https: / / www.tanaka.com.cn / products / detail / plating-processes / ) from Tanaka Precious Metals Co., Ltd. was used as the basic solution;

[0171] Based on the "basic electroplating solution-2", a Cyan-Pure-Ag coating can be formed on the substrate to be plated;

[0172] Electroplating solution containing silver-infiltrated graphene-2: On the basis of basic electroplating solution-2, silver-infiltrated graphene is added thereto (the silver-infiltrated graphene is the same as that of electroplating solution containing "silver-infiltrated graphene"-1). Finally, the silver-infiltrated graphene is calculated based on the weight of carbon. According to the aqueous solution, the concentration of graphene in this electroplating solution is 100g / L (equivalent to a concentration of about 9.6wt%).

[0173] Based on the "electroplating solution containing silver-infiltrated graphene-2", a Cyan-Ag-Gr (Ag) coating can be formed on the substrate to be plated;

[0174] Comparative plating solution-3: On the basis of basic plating solution-2, ordinary graphene without silver infiltration is added thereto (the ordinary graphene is the same as described in comparative plating solution-1). The final plating solution is formed, and the rest is the same as basic plating solution-2. Finally, the graphene is calculated by the weight of carbon, and the concentration of silver-infiltrated graphene in this plating solution is 100g / L (equivalent to a concentration of about 9.6wt%) according to the aqueous solution.

[0175] Based on the "Comparative electroplating solution-3", a Cyan-Ag-Gr coating can be formed on the substrate to be plated;

[0176] 2) Regarding the conditions for electroplating

[0177] The current density is controlled at 1A / dm 2 ;

[0178] The bath temperature was fixed at 50°C;

[0179] The thickness of the coating can be adjusted by combining the electroplating time and the current density to ensure that the coating of the target thickness is finally obtained. Referring to the silver-plated materials used in different parts of the current vehicle terminals, in this embodiment, the electroplating time is adjusted to prepare a 5 μm thick Ag-Gr (Ag) coating (calculated according to the carbon atomic percentage, the content of silver-infiltrated graphene in the coating is 12 at%).

[0180] In addition, before electroplating, the surface of the base material needs to be alkaline electrolytically degreased to remove oil stains and the anti-discoloration film on the copper, and then pickled to remove the oxide film on the surface.

[0181] 2. About the intermediate coating

[0182] In this embodiment, an intermediate coating mainly composed of metal Ni is prepared on the surface of the aluminum metal substrate by electroplating. There is no special requirement for its thickness, which can be tens of nanometers and several microns. Here, a Ni intermediate coating with a thickness of 30nm and 3μm is mainly prepared, and then a Ag-Gr (Ag) coating with a thickness of 5μm is prepared on the Ni intermediate coating as a surface coating, which are respectively recorded as Ni-03 / Ag-Gr (Ag) and Ni-3 / Ag-Gr (Ag) coatings. For comparison, an Ag-Gr (Ag) coating directly electroplated on an aluminum substrate without a pre-plating layer is also prepared as a surface coating.

[0183] 3. As shown in Table 1 below, various aluminum and aluminum alloy materials used as metal substrates are described:

[0184] Table 1. Basic information of each aluminum matrix

[0185]

[0186] Pure aluminum as described in Table 1, wherein the aluminum content exceeds 99wt% or 99.5wt%;

[0187] As described in Table 1, the copper content of the main alloying element of the Al-Cu alloy may be between 3 and 5 wt%, such as 3.5 to 4.5 wt%, and the aluminum content is about 90 wt%, excluding other inevitable impurities;

[0188] As described in Table 1, the Al-Si alloy has a silicon content of 0.3-0.7 wt % and a magnesium content of 0.45-0.9 wt % as the main alloying element, and an aluminum content of 97 wt %; other inevitable impurities are not counted.

[0189] Based on the above, the specific examples of the surface coating (Ag-Gr (Ag) film) formed by electroplating on the aluminum alloy substrate provided in this series of embodiments are listed in Tables 2-1 and 2-2:

[0190] Table 2-1. Basic description of the specific implementation example of this example

[0191]

[0192]

[0193] In the table: "Carbon content at%" means the content of the silver-infiltrated graphene / graphene calculated by the carbon content according to the total number of atoms in the coating; "--" means there is no corresponding film structure;

[0194] Hereinafter, "Ni-03" indicates an intermediate coating with a thickness of 0.03 μm and mainly composed of metallic Ni;

[0195] Hereinafter, "Ni-3" indicates a 3 μm thick intermediate coating mainly composed of metallic Ni;

[0196] Hereinafter, “Ni-3 / Ag-Gr(Ag) film” means the superposition of a 3 μm thick intermediate coating film mainly composed of metal Ni and an Ag-Gr(Ag) film;

[0197] Hereinafter, "Ni-03 / Ag-Gr(Ag) film" means the superposition of a 0.03 μm thick intermediate plating film mainly composed of metal Ni and an Ag-Gr(Ag) film.

[0198] Table 2-2. Basic description of the specific implementation example of this example

[0199]

[0200] 5) About performance testing surface morphology: Figure 1 (a, b) are the surface states of a 30nm thick Ni intermediate coating (marked as Ni: 30nm in the figure) and a 3μm thick Ni intermediate coating (marked as Ni: 3μm in the figure) formed on the surface of the elastic contact member 130 of the pure aluminum A1100 substrate, respectively. It can be seen from the figure that the 30nm thick Ni intermediate coating obtained by electroplating with alternating current has a smoother surface state. In comparison, the surface of the 3μm thick Ni intermediate coating obtained by electroplating with direct current is relatively rough.

[0201] Figure 1 (c, d) are respectively Figure 1 A uniform and smooth 5 μm thick Ag-Gr(Ag) film (denoted as Ag-Graphene(Ag) in the figure) formed on a 30 nm thick Ni intermediate plated film as shown in (a) is formed on a 30 nm thick Ni intermediate plated film as shown in (b). Figure 1 (b) shows the surface state of a uniformly smooth 5 μm thick Ag-Gr (Ag) film (labeled Ag-Graphene (Ag) in the figure) formed on a 3 μm thick Ni intermediate coating. It can be seen from the figure that the surface state of the Ni intermediate coating will affect the surface state of the Ag-Gr (Ag) film finally formed.

[0202] In addition, semi-transparent film flakes were also found on the surface of the two Ag-Gr (Ag) coatings. A large amount of carbon was detected in the material through EDS analysis, confirming that it was derived from graphene. At the same time, the results of Raman spectroscopy further confirmed that the carbon detected in the EDS analysis was graphene. In addition, crystal grains were also observed near the graphene sheet, which was determined to be Ag through EDS analysis, indicating that it was a silver-infiltrated graphene sheet.

[0203] Elemental analysis in the coating thickness direction - GD-OES: Figure 2(a) is an element distribution diagram in the depth direction of the coating (labeled as Ni-03 / Ag-Gr(Ag) in the figure) of the elastic contact member 130 provided in the specific embodiment 2-1;

[0204] Figure 2 (b) is an element distribution diagram in the depth direction of the coating (labeled as Ni-3 / Ag-Gr(Ag)) of the elastic contact member 130 provided in the specific embodiment 2-2;

[0205] pass Figure 2 It can be seen that Ag and C were detected on both surfaces, Ni was detected at the coating interface, and then the aluminum component of the substrate was detected. The results show that a Ni intermediate coating and Ag-Gr (Ag) film with good bonding strength were successfully formed on the pure aluminum metal A1100 substrate material.

[0206] Conductivity (contact resistance) detection: As shown in Table 2, by comparing the contact resistance of the elastic contact member 130 with a coating provided by Specific Embodiment 2-1 and Specific Embodiment 2-2, it is found that the contact resistance of both is actually higher than the contact resistance of the elastic contact member 130 with a copper alloy as the base material. This is mainly because the electrical conductivity of aluminum is lower than that of copper metal.

[0207] By comparing the specific embodiments 2-1 and 2-2, it is found that the thicker the nickel (Ni) intermediate coating of the elastic contact 130, the higher the contact resistance, because the conductivity of Ni is lower than that of aluminum. The elastic contact 130 provided in the specific embodiment 2-3 has no intermediate coating, and the Ag-Gr (Ag) film directly formed on the surface of the A1100 base material has a contact resistance higher than the elastic contact 130 with the Ni-3 / Ag-Gr (Ag) film provided in the specific embodiment 2-2. This is mainly because even after the pre-treatment to remove the oxide film, aluminum will still form an oxide film in the aqueous solution, resulting in an increase in contact resistance. This shows that the Ni intermediate coating can not only improve the bonding force of the coating but also improve the conductivity.

[0208] like Figure 3As shown, A1100 is used as the metal base material, and the surface of the base material has a Ni intermediate coating with a thickness of 30nm and an Ag-Gr (Ag) film in sequence, and the contact resistance of the elastic contact member 130 is 0.77mΩ; A2017 is used as the metal base material, and the surface of the base material has a Ni intermediate coating with a thickness of 30nm and an Ag-Gr (Ag) film in sequence, and the contact resistance of the elastic contact member 130 is 0.54mΩ; A1050 is used as the metal base material, and the surface of the base material has a Ni intermediate coating with a thickness of 30nm and an Ag-Gr (Ag) film in sequence, and the contact resistance of the elastic contact member 130 is 0. The contact resistance of the elastic contact piece 130 with a Ni intermediate coating of 30 nm and an Ag-Gr (Ag) film on the surface of the base material is 2 mΩ; the contact resistance of the elastic contact piece 130 with A2024 as the metal material and a Ni intermediate coating of 30 nm and an Ag-Gr (Ag) film on the surface of the base material is 1.18 mΩ, because the excessive copper and other elements in the A2024 alloy will affect the formation and uniformity of the coating, thereby reducing the conductivity. The contact resistance of the elastic contact piece 130 with A6061 as the metal base material and a Ni intermediate coating of 30 nm and an Ag-Gr (Ag) film on the surface of the base material is 2.4 mΩ, because the low-conductivity elements such as silicon and magnesium in the A6061 alloy will affect the formation and uniformity of the coating, thereby reducing the conductivity. In summary, it can be seen that the contact resistance value of the elastic contact piece 130 using A1100 as the metal matrix material is generally higher than the contact resistance value of the elastic contact piece 130 using A2017 as the metal matrix material, indicating that the addition of copper in the aluminum matrix is ​​beneficial to improving the conductivity of the elastic contact piece 130.

[0209] As shown in Table 2-2, the changes in contact resistance of the elastic contact members 130 of specific embodiments 2-1, 2-2, 2-3, 2-5, and 2-6 before heating and after heating at 200° C. for 500 to 1500 hours can be seen:

[0210] 1) Compared with the contact resistance before heating, the contact resistance of the elastic contact member 130 of the specific embodiment 2-2 with a Ni intermediate coating having a thickness of 3 μm after heating has increased significantly, and the change rate of the contact resistance becomes more obvious as the heating time increases. In sharp contrast, the contact resistance of the elastic contact member 130 with a Ni intermediate coating having a thickness of 30 nm provided in the specific embodiment 2-1 remains below 5% even after heating for 1500 hours.

[0211] 2) From the changes in contact resistance of the elastic contact piece 130 provided in specific embodiments 2-2 and 2-3, or the elastic contact piece 130 provided in specific embodiments 2-5 and 2-6 before heating and after heating at 200°C for 500 hours to 1500 hours, it can be seen that the contact resistance of the elastic contact piece 130 with a Ni intermediate coating has better thermal stability.

[0212] 3) In addition, the change in contact resistance of the elastic contact member 130 provided in comparative examples D2-1 and D2-3 after heating at 200° C. for 500 to 1500 hours was also tested, and the surface level thereof was also significantly higher than that of specific example 2-1.

[0213] Here, as in specific embodiments 2-1 and 2-5, the use of Ni intermediate coating can improve the bonding strength between the surface coating and the substrate, prevent the thermal diffusion of aluminum in the substrate material under high temperature environment, and further ensure the adhesion between the surface coating and the substrate material.

[0214] Moreover, the contact resistance of the elastic contact 130 with pure copper as the metal base material and the Ag-Gr (Ag) coating (5 μm) of the same thickness combined on the surface of the metal base material is 0.400 mΩ; according to this result, it can be seen that the elastic contact 130 with coating obtained by the present invention using Al-Cu alloy (A2017) as the metal base material and combining the design of the intermediate coating has the advantage of lightweight and excellent conductivity. Comparison of other performances:

[0215] Table 3 below shows the experimental results of observing the bending area 141 of the elastic contact member 130 with an optical microscope. Here, A+ means that there is no damage or cracks visible to the eye, and the surface of the coating is not obviously damaged when observed with an optical microscope; A means that there is no damage or cracks visible to the eye, but only a small amount of damage or cracks can be observed in some areas with larger bending angles when observed with an optical microscope; B means that obvious cracks can be seen visually; but the overall extension area of ​​the crack does not exceed 5% of the area of ​​the bending part; C means that cracks can be observed on the surface of the coating by visual observation.

[0216] Table 3. Basic information

[0217] Specific examples / comparative examples Observation of terminal coating condition: coating integrity level 2-1 A+ 2-2 B 2-3 C D2-1 B D2-2 C D2-3 A

[0218] The main reason is that the 30nm thick Ni intermediate coating obtained by electroplating using alternating current has a smoother surface state. On this basis, the plating solution used to prepare the surface coating of specific embodiment 2-1 contains silver-infiltrated graphene sheets. These silver added between the graphene sheets by "infiltration" can transform the two-dimensional conductivity between the graphene sheets into three-dimensional conductivity. The change from two-dimensional conductivity to three-dimensional conductivity not only affects the low contact resistance and high conductivity of the coating finally formed, but also actually affects the coating formation behavior of the electroplating process, so that a relatively complete coating grows on the surface of the substrate material.

Claims

1. Aluminum-containing metal terminals with coating, It is characterized in that The terminal comprises a first barrel portion and a second barrel portion connected to the first barrel portion; The first barrel is tubular, and has an elastic contact member inside. The first barrel cooperates with the elastic contact piece to form a space for inserting the matching terminal, and the elastic contact piece contacts the matching terminal; The elastic contact element includes a substrate, and an intermediate coating and a surface coating located on the surface of the substrate; The substrate is a material with an aluminum content not exceeding 99wt% and not less than 90wt%; The surface coating includes graphene and other metals, and the other metals include silver; Calculated based on the total number of atoms in the surface coating: The content of other metals in the surface coating is not less than 40at%. The content of graphene in the surface coating is 1 to 30 at%. The sum of the contents of the other metals and the graphene satisfies 95 at% to 100 at%; Wherein, the graphene includes stacked graphene sheets and silver located between the graphene sheets; The silver includes silver ions and nano-sized silver particles.

2. The aluminum-containing metal terminal with a coating according to claim 1, It is characterized in that The substrate contains copper, and the content of the copper is not less than 3wt%.

3. The aluminum-containing metal terminal with a plated film according to claim 2, It is characterized in that The base of the elastic contact piece is in a plate shape, and the thickness of the base is 0.01 mm to 0.6 mm.

4. The aluminum-containing metal terminal with a plated film according to claim 1, It is characterized in that The material of the substrate is an aluminum-copper alloy, and the copper content of the aluminum-copper alloy is 3-5wt%.

5. The aluminum-containing metal terminal with a plated film according to claim 1, It is characterized in that The type of the intermediate coating is the same as the type of the surface coating; or, The type of the intermediate coating is different from the type of the surface coating. The intermediate coating is a metal coating including a metal content of not less than 95wt%, and the metal includes any one of copper, iron, aluminum, tin, nickel, zinc, and cobalt, or a combination of two or more thereof.

6. The aluminum-containing metal terminal with a plated film according to claims 1 to 5, It is characterized in that The content of graphene in the surface coating is 5 to 20 at %, preferably 5 to 15 at %.

7. The aluminum-containing metal terminal with a plated film according to claim 6, It is characterized in that Taking the atoms of the graphene as the total number, the amount of silver located between the graphene sheets is 0.1 to 50 at %, preferably 1 to 10 at %.

8. The aluminum-containing metal terminal with a plated film according to claim 7, It is characterized in that The thickness of the surface coating is 0.01 to 100 μm; The thickness of the intermediate coating does not exceed the thickness of the surface coating.

9. The aluminum-containing metal terminal with a plated film according to claim 8, It is characterized in that The thickness of the surface coating is 0.1-10 μm.

10. The aluminum-containing metal terminal with a plated film according to claim 8, It is characterized in that The thickness of the intermediate coating is 0.1-2.5 μm.

11. The aluminum-containing metal terminal with a coating according to any one of claims 8 to 10, It is characterized in that The elastic contact element includes a protruding area and a bending area, The thickness of the surface coating of the protrusion area is 0.01 to 100 μm, preferably 0.1 to 10 μm; The thickness of the surface coating of the bending area is 0.01-10 μm.

12. A method for preparing a metal terminal containing aluminum having a coating, wherein the terminal comprises an elastic contact member, It is characterized in that Includes steps: 1) Prepare the plating solution and the substrate to be plated containing aluminum metal terminals; The plating solution contains graphene and other metallic silver; in the plating solution: The concentration of graphene is 0.1 to 100 g / L. The concentration of other metallic silver ions is 0.25 to 100 g / L; Wherein, the graphene includes stacked graphene sheets and silver located between the graphene sheets; The silver includes silver ions and nano-sized silver particles; 2) Electroplating the substrate using the plating solution.

13. The method for preparing the aluminum-containing metal terminal with a coating according to claim 12, It is characterized in that In step 2), the current density during electroplating is 0.1A / dm 2 ~100A / dm 2 The preferred current density is 0.1A / dm 2 ~40A / dm 2 .

14. The method for preparing the aluminum-containing metal terminal with a coating according to claim 12 or 13, It is characterized in that The surface of the plated substrate has an intermediate plating film.

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