Connector terminal with coating film and preparation method thereof

Abstract

The invention discloses a connector terminal with a coating film and a preparation method thereof. The terminal comprises a contact part, an extension part and a welding part which are connected in sequence; a coating film on the surface of the contact part comprises metal silver and graphene; and the coating film has a peak at 500 + / -30 cm <-1 > in a Raman spectrum detected by Raman spectroscopy.

Description

Technical Field

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

[0002] With the rapid development of the automotive industry, the requirements for the electrical performance of automotive wiring harnesses are becoming higher and higher. The terminal connector is a separable interface between two parts of the electronic system. It serves as a connecting bridge between different components and plays the role of transmitting data or current. It is one of the important components in electronic equipment and must be able to conduct and be reliable. Based on the requirements of conduction reliability, the base material of the connector terminal is usually selected from a copper alloy material with high mechanical strength and good conductivity. In addition, the surface of the base material is usually treated to form a coating, in order to further improve the electrical connection stability of the terminal and shield the mechanical and environmental attacks of the external environment on the copper alloy base material during use. In recent years, with the rapid development of electric vehicles and various electronic appliances, connectors need to operate at unprecedented high currents, so it is necessary to improve the conductivity and heat resistance of the terminal material to reduce heat generation and the power loss caused by it. Therefore, it is generally believed that the pure silver (Ag) coating material with the highest conductivity among all metals can be used as the preferred terminal electrode material in terms of improving conductivity and is being widely promoted and used. However, since pure silver is very soft and easy to adhere when joined, the wear resistance of the silver coating is low. Therefore, in order to ensure the service life of the product, most materials are now super-thick silver-plated materials that are several times or even dozens of times thicker than conventional coatings, which inevitably increases the production cost. Moreover, if the coating of all terminal materials is made of pure silver materials of precious metals, it is impossible in terms of cost and resources. The traditional method is to increase the hardness / wear resistance of the silver-plated material by adding toxic alloy elements including antimony, selenium, nickel, cobalt, tellurium or bismuth to the silver plating, or to increase the lubricity of the coating by adding solid lubricants including molybdenum disulfide, Teflon particles and other non-metallic parts to 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 hardness improvement is also limited.

[0003] Based on this, patent document 1 (JP2021072185A) discloses a method for obtaining a silver-graphene composite coating by using stacked graphene peeled from graphite as an additive to the plating solution. The method provides a silver-graphene composite coating that increases the coating hardness from 80HV to 120HV while maintaining the conductivity unchanged, thereby improving the wear resistance to a certain extent, but compared with the pure silver coating, the conductivity and wear resistance of the silver-graphene composite coating still have room for further improvement. Based on this, patent document 2 (JP2022170877A) further provides a substrate with a silver-graphene composite coating, which studies the size (0.05-6μm), content (3.0-30at%), and arrangement direction (vertical, parallel or inclined) of graphene dispersed in the silver-graphene composite coating, and realizes effective control and substantial improvement of the conductivity and wear resistance (lubricity) of the silver-graphene composite coating. However, there is no solution for how to ensure the stability of the contact resistance of the silver-graphene composite coating when a large current is applied or when the coating is used under a continuous high temperature. Therefore, the contact resistance and stability of the silver-graphene composite coating need to be improved, thereby effectively improving the heat resistance of the metal terminal. In addition, from the perspective of improving wear resistance and service life, it is hoped that the hardness of the coating can be further improved.

[0004] In addition, due to the rising and unstable price of copper materials, materials with conductivity second only to copper materials have gradually attracted people's attention. The typical representative of such materials is aluminum materials. In particular, various electrical parts have recently been required to be lightweight and low-cost, and there is a great demand for the technology of coating on aluminum materials. However, because the surface of aluminum materials will also form an oxide film in aqueous solution, it is particularly important to study how to achieve electroplating and obtain coating materials with good bonding strength. Summary of the invention

[0005] 1. Problem to be solved

[0006] In view of the problem of unsatisfactory connection reliability of existing coated connector terminals, one of the objectives of the present invention is to provide a connector terminal with a coating; at the same time, the present invention also provides a method for preparing the connector terminal with a coating.

[0007] 2. Technical solution

[0008] A first aspect of the present invention provides a connector terminal with a coating, the terminal comprising a contact portion, an extension portion and a welding portion connected in sequence;

[0009] The substrate surface of the contact portion has a coating 1;

[0010] The extension portion has a bending structure, and the surface of the extension portion has a second coating;

[0011] The base surface of the welding part has a coating three;

[0012] The type of the coating three is the same as or different from the type of the coating one;

[0013] The coating film 1 includes graphene;

[0014] Taking the atoms of the coating film 1 as the total number and calculated as carbon atoms, the content of the graphene is not less than 1 at%;

[0015] Wherein, the graphene includes stacked graphene sheets and silver located between the graphene sheets;

[0016] The silver includes silver ions and nano-sized silver particles.

[0017] According to any embodiment of the first aspect of the present invention, the coating one on the substrate surface of the contact portion (when the coating one is detected or when the coating one and the intermediate coating one 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.

[0018] Furthermore, taking the atoms of the coating film 1 as the total number and calculating by carbon atoms, the content of graphene in the coating film 1 can be arbitrarily selected from any numerical range of 1 to 50 at%, 1 to 30 at%, 1 to 20 at%, and 1 to 15 at%.

[0019] According to any embodiment of the first aspect of the present invention, taking the atoms of the coating film 1 as the total number and calculated as carbon atoms, the content of graphene in the coating film 1 is not less than 3 at %.

[0020] Furthermore, taking the atoms of the coating one as the total number and calculating by carbon atoms, the content of graphene in the coating one can be arbitrarily selected from any numerical range of 3-50at%, 5-30at%, 5-20at%, 10-20at%, and 5-15at%.

[0021] 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.

[0022] Furthermore, taking the atoms of the graphene as the total number, 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%.

[0023] According to any embodiment of the first aspect of the present invention, in addition to the silver contained in the graphene, the coating also includes other metals.

[0024] According to any embodiment of the first aspect of the present invention, based on the total number of atoms of the coating film 1, the content of the other metal is not less than 40 at %, and the sum of the content of the other metal and the graphene is 95-100 at %.

[0025] According to any embodiment of the first aspect of the present invention, taking the atoms of the coating film 1 as the total number, the other metals include any one or a combination of two or more of the following: silver, copper, iron, aluminum, tin, nickel, zinc, cobalt;

[0026] Preferably, the other metals include any one or a combination of two or more of the following: silver, tin, copper;

[0027] Further preferably, the other metal is selected from any one or a combination of two or more of the following: silver, tin, and copper.

[0028] Most preferably, the other metal is selected from silver and tin.

[0029] It should be noted that the “other metals” described herein do not include the “silver located between the graphene sheets” as mentioned above.

[0030] According to any embodiment of the first aspect of the present invention, the coating including other metals can be selected from any one of the following: a coating including silver; a coating including copper; a coating including iron; a coating including aluminum; a coating including tin; a coating including nickel; a coating including zinc; a coating including cobalt; a coating including silver and copper; a coating including silver and iron; a coating including silver and aluminum; a coating including silver and tin; a coating including silver and nickel; a coating including silver and zinc; a coating including silver and cobalt; a coating including copper and iron; a coating including copper , aluminum plating; including copper, tin plating; including copper, nickel plating; including copper, zinc plating; including copper, cobalt plating; including iron, aluminum plating; including iron, tin plating; including iron, nickel plating; including iron, zinc plating; including iron, cobalt plating; including aluminum, tin plating; including aluminum, nickel plating; including aluminum, zinc plating; including aluminum, cobalt plating; including tin, nickel plating; including tin, zinc plating; including tin, cobalt plating; including nickel, zinc plating; including nickel, cobalt plating; including zinc, cobalt plating.

[0031] According to any embodiment of the first aspect of the present invention, the thickness of the coating film 1 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, 0.3-30 μm, 0.3-10 μm, 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, 2.2~100μm, 2.2~90μm, 2.2~30μm, 2.2~10μm, 2.2~8μm, 2.5~100μ m, 2.5-90μm, 2.5-30μm, 2.5-10μm, 2.5-8μm, 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; preferably, the thickness of the coating one is not less than 3μm, and preferably is 3-100μm, 3-90μm, 3-30μm, 3-10μm, 3-8μm in sequence.

[0032] According to any embodiment of the first aspect of the present invention, the 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.

[0033] According to any embodiment of the first aspect of the present invention, the type of coating 2 is the same as the type of coating 1; the type described here only includes the material composition of the coating; or, the type includes both the material composition and the dimensional characteristics of the coating.

[0034] According to any embodiment of the first aspect of the present invention, the type of the coating 2 is different from the type of the coating 1;

[0035] For example, the second coating is a metal coating with a content of not less than 95 wt %, and the metal includes any one of copper, iron, aluminum, tin, nickel, zinc, and cobalt, or a combination of two or more thereof.

[0036] According to any embodiment of the first aspect of the present invention, the thickness of the second 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, 0.1-50 μm, 0.1-30 μm, 0.1-15 μm, 0.1-10 μm, 0.1-8 μm, 0.3-100 μm, 0.3-90 μm, 0.3-30 μm, 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, 1.5~10 0μm, 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, 2~9 0μm, 2~30μm, 2~10μm, 2~8μm, 2.2~100μm, 2.2~90μm, 2.2~30μm, 2.2~10μm, 2.2~8μm, 2.5~100μm, 2.5~90μm, 2.5~30μm m, 2.5-10μm, 2.5-8μm, 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; preferably, the thickness of the second coating is not less than 0.1μm, and is preferably 0.1-100μm, 0.1-90μm, 0.1-50μm, 0.1-30μm, 0.1-15μm, 0.1-10μm, 0.1-8μm in sequence.

[0037] According to any embodiment of the first aspect of the present invention, the type of coating three is the same as the type of coating one; the type described here only includes the material composition of the coating; or, the type includes both the material composition and the dimensional characteristics of the coating.

[0038] According to any embodiment of the first aspect of the present invention, the type of coating three is different from the type of coating one; for example, coating three 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.

[0039] According to any embodiment of the first aspect of the present invention, the thickness of the coating three 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, 0.1-50 μm, 0.1-30 μm, 0.1-15 μm, 0.1-10 μm, 0.1-8 μm, 0.3-100 μm, 0.3-90 μm, 0.3-30 μm, 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, 1.5~10 0μm, 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, 2~9 0μm, 2~30μm, 2~10μm, 2~8μm, 2.2~100μm, 2.2~90μm, 2.2~30μm, 2.2~10μm, 2.2~8μm, 2.5~100μm, 2.5~90μm, 2.5~30μm m, 2.5-10μm, 2.5-8μm, 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; preferably, the thickness of the coating three is not less than 0.1μm, and is preferably 0.1-100μm, 0.1-90μm, 0.1-50μm, 0.1-30μm, 0.1-15μm, 0.1-10μm, 0.1-8μm in sequence.

[0040] According to any embodiment of the first aspect of the present invention, there is an intermediate coating film 1 between the substrate surface of the contact portion and the coating film 1.

[0041] According to any embodiment of the first aspect of the present invention, the type of the intermediate coating film one is different from the type of the coating film one.

[0042] According to any embodiment of the first aspect of the present invention, 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.

[0043] According to any embodiment of the first aspect of the present invention, the intermediate coating can be selected from any one of the following: a coating comprising a copper metal content of not less than 95wt%; a coating comprising an iron metal content of not less than 95wt%; a coating comprising an aluminum metal content of not less than 95wt%; a coating comprising a tin metal content of not less than 95wt%; a coating comprising a zinc metal content of not less than 95wt%; a coating comprising a cobalt metal content of not less than 95wt%; a coating comprising copper and iron metal content of not less than 95wt%; a coating comprising copper and aluminum metal content of not less than 95wt%; a coating comprising copper and tin metal content of not less than 95wt%; a coating comprising copper and nickel metal content of not less than 95wt%; a coating comprising copper and zinc metal content of not less than 95wt%; a coating comprising copper and cobalt metal content of not less than 95wt%; a coating comprising iron and aluminum metal content of not less than 95wt%; Film; including iron and tin metal plating with a content of not less than 95wt%; including iron and nickel metal plating with a content of not less than 95wt%; including iron and zinc metal plating with a content of not less than 95wt%; including iron and cobalt metal plating with a content of not less than 95wt%; including aluminum and tin metal plating with a content of not less than 95wt%; including aluminum and nickel metal plating with a content of not less than 95wt%; including aluminum and zinc metal plating with a content of not less than 95wt%; including aluminum and cobalt metal plating with a content of not less than 95wt%; including tin and nickel metal plating with a content of not less than 95wt%; including tin and zinc metal plating with a content of not less than 95wt%; including tin and cobalt metal plating with a content of not less than 95wt%; including nickel and zinc metal plating with a content of not less than 95wt%; including nickel and cobalt metal plating with a content of not less than 95wt%.

[0044] According to any embodiment of the first aspect of the present invention, the thickness of the intermediate coating film 1 does not exceed the thickness of the coating film 1.

[0045] According to any embodiment of the first aspect of the present invention, the thickness of the intermediate coating film 1 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, 0.01-5 μm, 0.01-2 μm, 0.1-100 μm, 0.1-90 μm, 0.1-30 μm, 0.1-10 μm, 0.1-8 μm, 0.1-5 μm, 0.3-100 μm, 0.3-90 μm, 0.3- 30μm, 0.3~10μm, 0.3~8μm, 0.3~5μm, 0.5~100μm, 0.5~90μm, 0.5~30μm, 0.5~10μm, 0.5~8μm, 0.5~5μm, 0.7~100μm, 0.7 ~90μm, 0.7~30μm, 0.7~10μm, 0.7~8μm, 0.7~5μm, 1~100μm, 1~90μm, 1~30μm, 1~10μm, 1~8μm, 1~5μm, 1.2~100μm, 1.2~9 0μm, 1.2~30μm, 1.2~10μm, 1.2~8μm, 1.2~5μm, 1.5~100μm, 1.5~90μm, 1.5~30μm, 1.5~10μm, 1.5~8μm, 1.5~5μm, 1.7~1 00μm, 1.7~90μm, 1.7~30μm, 1.7~10μm, 1.7~8μm, 1.7~5μm, 2~100μm, 2~90μm, 2~30μm, 2~10μm, 2~8μm, 2~5μm, 2.2~100 μm, 2.2~90μm, 2.2~30μm, 2.2~10μm, 2.2~8μm, 2.2~5μm, 2.5~100μm, 2.5~90μm, 2.5~30μm, 2.5~10μm, 2.5~8μm, 2.5~5 μm, 2.7~100μm, 2.7~90μm, 2.7~30μm, 2.7~10μm, 2.7~8μm, 2.7~5μm, 3~100μm, 3~90μm, 3~30μm, 3~10μm, 3~8μm, 3~5μm.

[0046] According to any embodiment of the first aspect of the present invention, there is an intermediate coating film 2 between the base surface of the extension portion and the coating film 2.

[0047] According to any embodiment of the first aspect of the present invention, the type of the intermediate coating film 2 is different from the type of the coating film 2.

[0048] According to any embodiment of the first aspect of the present invention, the second 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.

[0049] According to any embodiment of the first aspect of the present invention, the intermediate coating film 2 can be selected from any one of the following: a coating film including a copper metal content of not less than 95wt%; a coating film including an iron metal content of not less than 95wt%; a coating film including an aluminum metal content of not less than 95wt%; a coating film including a tin metal content of not less than 95wt%; a coating film including a zinc metal content of not less than 95wt%; a coating film including a cobalt metal content of not less than 95wt%; a coating film including copper and iron metal content of not less than 95wt%; a coating film including copper and aluminum metal content of not less than 95wt%; a coating film including copper and tin metal content of not less than 95wt%; a coating film including copper and nickel metal content of not less than 95wt%; a coating film including copper and zinc metal content of not less than 95wt%; a coating film including copper and cobalt metal content of not less than 95wt%; a coating film including iron and aluminum metal content of not less than 95wt%; Film; including iron and tin metal plating with a content of not less than 95wt%; including iron and nickel metal plating with a content of not less than 95wt%; including iron and zinc metal plating with a content of not less than 95wt%; including iron and cobalt metal plating with a content of not less than 95wt%; including aluminum and tin metal plating with a content of not less than 95wt%; including aluminum and nickel metal plating with a content of not less than 95wt%; including aluminum and zinc metal plating with a content of not less than 95wt%; including aluminum and cobalt metal plating with a content of not less than 95wt%; including tin and nickel metal plating with a content of not less than 95wt%; including tin and zinc metal plating with a content of not less than 95wt%; including tin and cobalt metal plating with a content of not less than 95wt%; including nickel and zinc metal plating with a content of not less than 95wt%; including nickel and cobalt metal plating with a content of not less than 95wt%.

[0050] According to any embodiment of the first aspect of the present invention, the thickness of the intermediate coating film 2 does not exceed the thickness of the coating film 2.

[0051] According to any embodiment of the first aspect of the present invention, the thickness of the intermediate coating film 2 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, 0.01-5 μm, 0.01-2 μm, 0.1-100 μm, 0.1-90 μm, 0.1-30 μm, 0.1-10 μm, 0.1-8 μm, 0.1-5 μm, 0.3-100 μm, 0.3-90 μm, 0.3- 30μm, 0.3~10μm, 0.3~8μm, 0.3~5μm, 0.5~100μm, 0.5~90μm, 0.5~30μm, 0.5~10μm, 0.5~8μm, 0.5~5μm, 0.7~100μm, 0.7 ~90μm, 0.7~30μm, 0.7~10μm, 0.7~8μm, 0.7~5μm, 1~100μm, 1~90μm, 1~30μm, 1~10μm, 1~8μm, 1~5μm, 1.2~100μm, 1.2~9 0μm, 1.2~30μm, 1.2~10μm, 1.2~8μm, 1.2~5μm, 1.5~100μm, 1.5~90μm, 1.5~30μm, 1.5~10μm, 1.5~8μm, 1.5~5μm, 1.7~1 00μm, 1.7~90μm, 1.7~30μm, 1.7~10μm, 1.7~8μm, 1.7~5μm, 2~100μm, 2~90μm, 2~30μm, 2~10μm, 2~8μm, 2~5μm, 2.2~100 μm, 2.2~90μm, 2.2~30μm, 2.2~10μm, 2.2~8μm, 2.2~5μm, 2.5~100μm, 2.5~90μm, 2.5~30μm, 2.5~10μm, 2.5~8μm, 2.5~5 μm, 2.7~100μm, 2.7~90μm, 2.7~30μm, 2.7~10μm, 2.7~8μm, 2.7~5μm, 3~100μm, 3~90μm, 3~30μm, 3~10μm, 3~8μm, 3~5μm.

[0052] According to any embodiment of the first aspect of the present invention, according to any embodiment of the first aspect of the present invention, there is an intermediate coating film three between the surface of the welding portion and the coating film three.

[0053] According to any embodiment of the first aspect of the present invention, the type of the intermediate coating three is different from the type of the coating three;

[0054] The third 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.

[0055] According to any embodiment of the first aspect of the present invention, the intermediate coating three can be selected from any one of the following: a coating including a copper metal content of not less than 95wt%; a coating including an iron metal content of not less than 95wt%; a coating including an aluminum metal content of not less than 95wt%; a coating including a tin metal content of not less than 95wt%; a coating including a zinc metal content of not less than 95wt%; a coating including a cobalt metal content of not less than 95wt%; a coating including a copper and iron metal content of not less than 95wt%; a coating including a copper and aluminum metal content of not less than 95wt%; a coating including a copper and tin metal content of not less than 95wt%; a coating including a copper and nickel metal content of not less than 95wt%; a coating including a copper and zinc metal content of not less than 95wt%; a coating including a copper and cobalt metal content of not less than 95wt%; a coating including an iron and aluminum metal content of not less than 95wt%; Film; including iron and tin metal plating with a content of not less than 95wt%; including iron and nickel metal plating with a content of not less than 95wt%; including iron and zinc metal plating with a content of not less than 95wt%; including iron and cobalt metal plating with a content of not less than 95wt%; including aluminum and tin metal plating with a content of not less than 95wt%; including aluminum and nickel metal plating with a content of not less than 95wt%; including aluminum and zinc metal plating with a content of not less than 95wt%; including aluminum and cobalt metal plating with a content of not less than 95wt%; including tin and nickel metal plating with a content of not less than 95wt%; including tin and zinc metal plating with a content of not less than 95wt%; including tin and cobalt metal plating with a content of not less than 95wt%; including nickel and zinc metal plating with a content of not less than 95wt%; including nickel and cobalt metal plating with a content of not less than 95wt%.

[0056] According to any embodiment of the first aspect of the present invention, the thickness of the intermediate coating film three does not exceed the thickness of the coating film three.

[0057] According to any embodiment of the first aspect of the present invention, the thickness of the intermediate coating film three 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, 0.01-5 μm, 0.01-2 μm, 0.1-100 μm, 0.1-90 μm, 0.1-30 μm, 0.1-10 μm, 0.1-8 μm, 0.3-10 0μm, 0.3~90μm, 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 m, 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. 2~100μm, 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, 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] According to any embodiment of the first aspect of the present invention, the base surface of the extension portion has a coating, and the coating is the same as the "intermediate coating one" possessed by the contact portion of the connector terminal described in any embodiment of the first aspect of the present invention.

[0059] According to any embodiment of the first aspect of the present invention, the base surface of the extension portion has a coating, and the coating is the same as the "coating one" possessed by the contact portion of the connector terminal described in any embodiment of the first aspect of the present invention.

[0060] According to any embodiment of the first aspect of the purpose of the present invention, the base surface of the extension portion has a coating, and the coating is the same as the "coating one" and "intermediate coating one" possessed by the contact portion of the connector terminal described in any embodiment of the first aspect of the purpose of the present invention.

[0061] According to any embodiment of the first aspect of the present invention, the base surface of the extension portion has a coating, and the coating is the same as the "intermediate coating three" possessed by the welding portion of the connector terminal described in any embodiment of the first aspect of the present invention.

[0062] According to any embodiment of the first aspect of the present invention, the base surface of the extension portion has a coating, and the coating is the same as the "coating three" possessed by the welding portion of the connector terminal described in any embodiment of the first aspect of the present invention.

[0063] According to any embodiment of the first aspect of the purpose of the present invention, the base surface of the extension portion has a coating, and the coating is the same as the "coating three" and "intermediate coating three" possessed by the welding portion of the connector terminal described in any embodiment of the first aspect of the purpose of the present invention.

[0064] A second aspect of the present invention provides a method for preparing a connector terminal with a coating, wherein the connector terminal comprises a contact portion, an extension portion and a welding portion connected in sequence, and specifically comprises the steps of:

[0065] 1) Prepare the plating solution and the substrate to be plated of the connector terminal

[0066] The plated substrate of the terminal has a metal surface; or

[0067] The plated substrate of the terminal has a metal surface and an intermediate plating film covering the metal surface;

[0068] The plating solution contains graphene;

[0069] The graphene includes stacked graphene sheets and silver located between the graphene sheets;

[0070] The silver includes silver ions and nano-sized silver particles;

[0071] Calculated based on the carbon content, the concentration of graphene in the plating solution is 0.1 to 100 g / L;

[0072] Wherein, 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 %.

[0073] 2) Electroplating the substrate using the plating solution.

[0074] The "intermediate coating" as described herein is the same as the "intermediate coating one" and / or "intermediate coating two" and / or "intermediate coating three" possessed by the connector terminal as described in any embodiment of the first aspect of the present invention.

[0075] According to any embodiment of the second aspect of the present invention, 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.

[0076] According to any embodiment of the second aspect of the present invention, the content of graphene in the coating one is not less than 3 at % calculated by carbon content based on the total number of atoms in the coating one.

[0077] Furthermore, according to the total number of atoms in the coating and calculated by carbon content, the content of graphene in the coating 1 can be arbitrarily selected from any group of numerical ranges including 3-50at%, 5-30at%, 5-20at%, 10-20at%, and 5-15at%.

[0078] 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.

[0079] 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%.

[0080] According to any embodiment of the second aspect of the present invention, the plating solution further comprises other metals, and the other metals comprise any one or a combination of two or more of the following metals: silver, copper, iron, aluminum, tin, nickel, zinc, and cobalt;

[0081] Preferably, the other metal includes any one or a combination of two or three of the following metals: silver, tin, copper; more preferably, the other metal includes the following silver and / or tin.

[0082] According to any embodiment of the second aspect of the present invention, the plating solution can be selected from any one of the following: a plating solution including silver; a plating solution including copper; a plating solution including iron; a plating solution including aluminum; a plating solution including tin; a plating solution including nickel; a plating solution including zinc; a plating solution including cobalt; a plating solution including silver and copper; a plating solution including silver and iron; a plating solution including silver and aluminum; a plating solution including silver and tin; a plating solution including silver and nickel; a plating solution including silver and zinc; a plating solution including silver and cobalt; a plating solution including copper and iron; a plating solution including copper and aluminum. ; including plating solutions of copper and tin; including plating solutions of copper and nickel; including plating solutions of copper and zinc; including plating solutions of copper and cobalt; including plating solutions of iron and aluminum; including plating solutions of iron and tin; including plating solutions of iron and nickel; including plating solutions of iron and zinc; including plating solutions of iron and cobalt; including plating solutions of aluminum and tin; including plating solutions of aluminum and nickel; including plating solutions of aluminum and zinc; including plating solutions of aluminum and cobalt; including plating solutions of tin and nickel; including plating solutions of tin and zinc; including plating solutions of tin and cobalt; including plating solutions of nickel and zinc; including plating solutions of nickel and cobalt; including plating solutions of zinc and cobalt.

[0083] Furthermore, the concentration of metal ions 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, 70-1 00g / L, 80~100g / L, 90~100g / L, 0.1~80g / L, 0.25~80g / L, 1~80g / L, 5~80g / L, 10 ~80g / L, 20~80g / L, 30~80g / L, 40~80g / 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, 40~60 g / L, 0.25~50g / L, 1~50g / L, 5~50g / L, 10~50g / L, 20~50g / L, 30~50g / L, 40~50g / Any one of the numerical intervals among 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, and 10-20g / L.

[0084] It should be noted that the “other metals included in the plating solution” described herein does not include the “silver located between the graphene sheets” as mentioned above.

[0085] According to any embodiment of the second aspect of the present invention, the current density during electroplating is 0.1A / dm 2 ~100A / dm 2 .

[0086] Preferably, the current density during electroplating is 0.1A / dm 2 ~40A / dm 2 .

[0087] According to any embodiment of the second aspect of the present invention, a connector terminal with a plated film as described in any embodiment of the first aspect of the present invention can be prepared.

[0088] According to any embodiment of the second aspect of the present invention, the plated substrate of the connector terminal has a metal surface; the metal includes but is not limited to any one or two or more of copper, copper alloy, aluminum, aluminum alloy, iron, iron alloy, nickel, nickel alloy, and stainless steel.

[0089] According to any embodiment of the second aspect of the present invention, the plated substrate of the connector terminal can be selected from any one of the following: a substrate having a copper metal surface, a substrate having a copper alloy metal surface, a substrate having a brass metal surface, a substrate having a phosphor bronze metal surface, a substrate having an aluminum metal surface, a substrate having an aluminum alloy metal surface, a substrate having an iron metal surface, a substrate having an iron alloy metal surface, a substrate having a nickel metal surface, and a substrate having a nickel alloy metal surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Figure 1 (a) is a SEM image of a coating film with ordinary graphene (abbreviated as Ag-Gr film) of a terminal provided in comparative example 1-1; (b) is a SEM image of a coating film with silver-infiltrated graphene (abbreviated as Ag-Gr (Ag) film) of a terminal provided in specific embodiment 1-1 of the present invention;

[0091] Figure 2 (a) Raman spectrum of the Ag-Gr (Ag) film (thickness 5 μm) of the terminal provided in the specific embodiment 1-1 of the present invention; Raman spectrum of the Ag-Gr film (thickness 5 μm) provided in the comparative example 1-1; (b) Raman spectrum of the Ag-Gr (Ag) film (thickness 0.3 μm) of the terminal provided in the specific embodiment 1-5 of the present invention;

[0092] Figure 3 XRD patterns of Ag-Gr (Ag) films of different thicknesses (thicknesses of 5 μm, 3 μm, and 1 μm, respectively) provided for the terminals of the specific embodiments 1-1, 1-2, and 1-3 of the present invention; and XRD pattern of the Ag-Gr film (thickness of 5 μm) of the terminal provided in the comparative example 1-1 of the present invention;

[0093] Figure 4 The hardness measurement results of the Ag-Gr (Ag) film of the terminal provided in the specific embodiment 1-1 of the present invention, the Ag-Gr film of the terminal provided in the comparative example 1-1, and the pure silver-plated film (abbreviated as Pure-Ag film) of the terminal provided in the comparative example 1-7 are respectively shown;

[0094] Figure 5 The contact resistance measurement results of the connecting component (abbreviated as Cu-TC, Ag-Gr (Ag)) provided in the specific embodiments 1-5 of the present invention with pure copper as the base material of the terminal, and a 0.3 μm thick Ag-Gr (Ag) film on the base;

[0095] The contact resistance measurement result of the connection component (abbreviated as Cu-Ni-Si, Ag-Gr(Ag)) provided in the specific embodiment 1-1 of the present invention, which uses the copper alloy Cu-Ni-Si as the base material of the terminal and has a 5 μm thick Ag-Gr(Ag) film on the base;

[0096] The contact resistance measurement results of the connecting parts (abbreviated as Cu-Sn-P, Cyan-Ag-Gr(Ag)) provided in the specific embodiments 1-9 of the present invention, which use the copper alloy Cu-Sn-P as the base material of the terminal, and the base has a 5 μm-thick coating (abbreviated as Cyan-Ag-Gr(Ag) film) using silver-containing graphene obtained by electroplating with a cyanide-containing silver plating solution;

[0097] The contact resistance measurement results of the connecting component (abbreviated as Cu-TC, Ag-Gr (Ag)) provided in the specific embodiments 1-10 of the present invention with pure copper Cu-TC as the base material of the terminal, and a 5 μm thick Ag-Gr (Ag) film on the base;

[0098] The copper alloy Cu-Ni-Si provided in Comparative Example 1-1 of the present invention is used as the base material of the terminal, and the contact resistance measurement result of the connecting component (abbreviated as Cu-Ni-Si, Ag-Gr) having a 5 μm thick Ag-Gr film on the base;

[0099] The contact resistance measurement results of the base material with copper alloy Cu-Sn-P as the terminal provided in Comparative Examples 1-6 of the present invention, wherein the base has a connecting component (abbreviated as Cu-Sn-P, Cyan-Ag-Gr) having a 5 μm-thick plated film (abbreviated as Cyan-Ag-Gr film) using graphene without silver obtained by electroplating with a cyanide-containing silver plating solution;

[0100] The contact resistance measurement results of the connection parts provided in Comparative Examples 1-7 of the present invention using copper alloy Cu-Ni-Si as the base material of the terminal, and having a Pure-Ag film with a thickness of 5 μm on the base;

[0101] Figure 6 The contact resistance changes of various 5μm-thick coatings (specific examples 1-1, comparative examples 1-1, comparative examples 1-7) obtained under the same electroplating conditions in a cyanide-free plating solution before heating (heating time is 0h) and after heating at 200°C for different time periods are shown in Table 1. The contact resistance changes of various 5μm-thick coatings (specific examples 1-9, comparative examples 1-6) obtained under the same electroplating conditions in a cyanide-containing plating solution before heating (heating time is 0h) and after heating at 200°C for different time periods are shown in Table 1.

[0102] Figure 7 The contact resistance measurement results of the connection parts of the Ag-Gr film (thickness 5μm) with pure copper Cu-TC, copper alloy Cu-Be-Ni, brass Cu-Zn, copper alloy Cu-Ni-Si, and copper film (Pure-Cu, Cu>99%, film thickness 50μm) as the base material of the terminal; The contact resistance measurement results of the connection parts of the Ag-Gr (Ag) film (thickness 5μm) with pure copper Cu-TC, copper alloy Cu-Be-Ni, brass Cu-Zn, copper alloy Cu-Ni-Si, and copper film (Pure-Cu, Cu>99%) as the base material of the terminal;

[0103] Figure 8 The contact resistance measurement results of the connection parts of the Ag-Gr (Ag) film (thickness 5 μm) with copper alloy Cu-Be-Ni, brass Cu-Zn, and copper alloy Cu-Ni-Si as the base material of the terminal; and the contact resistance measurement results of the terminals of the Ag-Gr (Ag) film (thickness 5 μm) with copper alloy Cu-Ni-Si as the base material of the terminal and pre-plated with nickel intermediate film (Cu / Ni) and tin intermediate film (Cu / Sn) on the base (corresponding to Cu-Ni-1 and Cu-Sn-1 in the figure);

[0104] Fig. 9 The SEM images are as follows: (a) is a SEM image of a 30 nm thick Ni intermediate coating formed on a pure aluminum A1100 substrate; (b) is a SEM image of a 3 μm thick Ni intermediate coating formed on a pure aluminum A1100 substrate; (c) is a SEM image of a 3 μm thick Ni intermediate coating formed on a pure aluminum A1100 substrate. Fig. 9 (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; Fig. 9 (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;

[0105] Fig.10 is the element distribution diagram, (a) is for Fig. 9 (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 Fig. 9 (d) element distribution diagram in the depth (also called thickness) direction of the coating formed on the pure aluminum A1100 substrate material;

[0106] Fig.11 The contact resistance measurement results of the terminals of the Ag-Gr (Ag) film (thickness 5 μm) with A1100, A1050, A2017, A2024, and 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)), and 3 μm (Ni-3 / Ag-Gr (Ag))) on the substrate materials;

[0107] Fig.12 : are Raman spectra, (a) is a Raman spectrum of a coating film (abbreviated as Sn-Gr film) without silver-infiltrated graphene provided in comparative example 3-1; (b) is a Raman spectrum of a coating film (abbreviated as Sn-Gr(Ag)-L film) using silver-infiltrated graphene (L-5%) provided in specific example 3-1 of the present invention;

[0108] Fig.13 : are XRD patterns, (a) is the XRD pattern of the coating film (abbreviated as Pure-Sn film) without silver-infiltrated graphene of the terminal provided in Comparative Example 3-2 of the present invention; (b) is the XRD pattern of the Sn-Gr film of the terminal provided in Comparative Example 3-1; (c) is the XRD pattern of the Sn-Gr(Ag)-L film using silver-infiltrated graphene (silver content L-5%) of the terminal provided in Specific Example 3-1 of the present invention; (d) is the XRD pattern of the Sn-Gr(Ag)-H film using silver-infiltrated graphene (silver content H-10%) of the terminal provided in Specific Example 3-2 of the present invention;

[0109] Fig.14 The contact resistance measurement results of the terminals with Pure-Sn film, Sn-Gr film, Sn-Gr(Ag)-L film, and Sn-Gr(Ag)-H film;

[0110] Fig.15The figures are contact resistance correlation diagrams, (a) are terminal contact resistance and load curves provided in the specific embodiments 3-1 and 3-2 of the present invention and the comparative example 3-2; (b) are contact resistance measurement results of terminals with copper alloy Cu-Ni-Si as the base material and Pure-Sn film, Sn-Gr film, Sn-Gr(Ag)-L film, and Sn-Gr(Ag)-H film;

[0111] Fig.16 Schematic diagram of the structure of silver-infiltrated graphene used in an embodiment of the present invention;

[0112] Fig.17 Schematic diagrams of terminal-related structures: (a) a schematic diagram of a terminal structure provided by the present invention; (b) a schematic diagram of a mating terminal structure used in conjunction with the terminal provided by the present invention; (c) a schematic diagram of a terminal pair formed by combining the terminal provided by the present invention and the mating terminal;

[0113] Fig.18 are schematic diagrams of terminal-related structures, (a) to (c) are schematic diagrams of another terminal structure provided by the present invention;

[0114] Fig.19 Schematic diagrams of terminal-related structures: (a) a schematic diagram of another terminal structure provided by the present invention; (b) a schematic diagram of a structure in which a terminal provided by the present invention is connected to a printed circuit substrate P;

[0115] Fig. 20 Schematic diagram of the layer structure of the welding portion 130, (a) Schematic diagram of the layer structure of the welding portion 130 of another terminal provided by the present invention Figure 1 (b) schematic diagram of the layer structure of the welding portion 130 of the terminal provided by the present invention Figure 2 ;

[0116] Fig.21 Schematic diagram of the layer structure of the extension portion 120, (a) Schematic diagram of the layer structure of the extension portion 120 of another terminal provided by the present invention Figure 1 (b) schematic diagram of the layer structure of the extension portion 120 of the terminal provided by the present invention Figure 2 ;

[0117] Fig. 22 Schematic diagram of the layer structure of the contact portion 110, (a) Schematic diagram of the layer structure of the contact portion 110 of another terminal provided by the present invention Figure 1 (b) schematic diagram of the layer structure of the contact portion 110 of the terminal provided by the present invention Figure 2 . DETAILED DESCRIPTION

[0118] 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.

[0119] 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.

[0120] 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".

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126]

Connector terminal

[0127] The "connector terminal" provided by the present invention is also called a "plug terminal", Figures 20-22 As shown, in terms of structural composition, the terminal 100 includes a base material and a surface coating located on the base material.

[0128] Reference again Fig.17 As shown in (a), in terms of specific structure, the terminal 100 includes a contact portion 110, an extension portion 120 and a welding portion 130 connected in sequence; the contact portion 110 has an insertion / extraction end 111; the extension portion 120 has at least one bending structure 121, but there may be multiple bending structures in actual application; the welding portion 130 has a welding end 131, and the welding end 131 here refers to a portion connected by crimping, bonding, or welding, but welding is preferred for connection stability;

[0129] The welding part 130 mainly realizes the electrical connection between the terminal 100 and the circuit board or the crimping wire through the welding end 131.

[0130] The contact portion 110 actually acts as a plug-in component to achieve a stable connection with its matching mating terminal;

[0131] The extension portion 120 is used to match various connectors to achieve a transition between the contact portion and the welding portion and a stable connection between the mating terminals.

[0132] Actually Fig.17 (a) is only a schematic diagram of a terminal structure and is not limited to this structure. Fig.18(a) to 18 (c) and 19 (a) are also shown within the structural scope of the terminal 100 provided by the present invention.

[0133] The "connector terminal" provided by the present invention usually works with the terminals it matches to form a complete set of terminal pairs. Fig.17 (b) shows a typical mating terminal 200, which includes a tubular portion 210 having an insertion port 211 opened at the front end for the contact portion 110 of the terminal 100 to be inserted; an elastic contact piece 220 is provided inside the tubular portion 210, and the elastic contact piece 220 is used to apply an upward force to a surface of the inserted contact portion 110. The contact portion 110 is pressed against the inner surface of the top plate of the tubular portion 210 by the elastic contact piece 220. As a result, the contact portion 110 is clamped between the elastic contact piece 220 and the inner surface of the top plate. A protrusion 221 is formed on the elastic contact piece 220. The protrusion 221 is formed by making the elastic contact piece 220 protrude hemispherically from the back side toward the surface. For another example, as Fig.19 As shown, the connector housing 300 has a rear wall 310 for holding the terminal 100 and a cover 320 erected from the outer peripheral edge of the rear wall 310. The contact portion 110 of the terminal 100 extends into the interior of the cover 320, and the interior of the cover 320 can accommodate the mating terminal 200 (not shown, see Fig.17 (c)). In addition, the soldering portion 130 of the terminal 100 disposed outside the cover portion 320 constitutes a pin electrically connected to the printed circuit board P.

[0134] In summary, from the different functions and requirements of each part, it is not difficult to see that the contact portion 110, the extension portion 120 and the welding portion 130 in the terminal 100 need to be designed through coating in order to meet various specific requirements. Figures 17 to 22 The terminal 100 includes a contact portion 110, an extension portion 120 and a welding portion 130 which are connected in sequence, the contact portion 110 includes a coating a3 and an intermediate coating a2, the extension portion 120 includes a coating b3 and an intermediate coating b2, and the welding portion 130 includes a coating c3 and an intermediate coating c2.

[0135] The types of coating one a3, coating three c3, and coating two b3 can be the same, especially when considering the requirements of high temperature resistance, conductivity and other performance requirements, it is preferred that coating one, two, and three (a3, b3, c3) are of the same type (as described in the [coating one a3] section below). Of course, the types of coating one, two, and three (a3, b3, c3) can also be different, such cases include: coating one and three (a3, c3) are of the same type, coating two b3 is different from the type of coating one and three (a3, c3); coating one and two (a3, b3) are of the same type, coating three c3 is different from the type of coating one and two (a3, b3); coating three and two (c3, b3) are of the same type, coating one a3 is different from the type of coating three and two (c3, b3); the types of coating one, two, and three (a3, b3, c3) are all different.

[0136] Similarly, the types of the intermediate coatings one, two, and three (a2, b2, and c2) may be the same or different, and the different situations include: the intermediate coatings one and three (a2 and c2) are the same type, and the intermediate coating two b2 is different from the type of the intermediate coatings one and three (a2 and c2); the intermediate coatings one and two (a2 and b2) are the same type, and the intermediate coating three c2 is different from the type of the intermediate coatings one and two (a2 and b2); the intermediate coatings three and two (c2 and b2) are the same type, and the intermediate coating one a2 is different from the type of the intermediate coatings three and two (c2 and b2); the types of the intermediate coatings one, two, and three (a2, b2 and c2) are all different. More specifically:

[0137]

Contact part 110

[0138] For the contact portion 110, its conductivity, stability, heat resistance and surface hardness are required to be higher than other parts. Fig. 22 (a) The surface of the base material a1 of the contact portion 110 includes a coating a3.

[0139] Specifically, the “plating film a3” of the contact portion 110 of the present invention has the following characteristics:

[0140] The coating provided by the present invention mainly comprises "silver-infiltrated graphene" as the main or characteristic component, and 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 -1Peak at. In some embodiments of the present invention, according to the total number of atoms of the coating one, calculated by carbon content, the content of "graphene infiltrated with silver" contained in the coating one is not less than 1at%, preferably not less than 3at%, further preferably 3-50at%, and more preferably 5-20at%. It is further explained that the content of "graphene infiltrated with silver" in the "coating one" is in the value range of 3-50at%, and the influence on the conductivity and heat resistance of the coating one can be basically ignored. The wear resistance trend line of the coating one is obtained by fitting the experimental data, and the trend line changes basically linearly. In the following embodiments, the coating one with a "graphene infiltrated with silver" content of 8at% and 12at% is used to schematically illustrate the technical solution of the present invention.

[0141] On this basis, in some embodiments of the present invention, the "coating film one" also includes another main or characteristic component other than "graphene infiltrated with silver", which is a metal. As described herein, the "other metals" do not include the "silver infiltrated in graphene", and the other metals 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 coating film one, the content of other metals contained in the coating film one is not less than 40at%, and in theory, the sum of the content of other metals contained in the coating film one as described herein and the content of "graphene infiltrated with silver" contained in the coating film one described above should be infinitely close to 100at%, but in actual situations, it is impossible to exclude the existence of some inevitable impurities, so the sum of the content of metals contained in the coating film one and the content of "graphene infiltrated with silver" contained in the coating film one described above is in the range of 95-100at%.

[0142] 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” 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 coating one has 500±30cm -1 One of the key reasons for the peak.

[0143] In fact, the silver between the graphene sheets will affect the conductivity of the coating 1. As far as the "body composed of stacked graphene sheets" is concerned, the bonding force between the layers of the graphene sheets is the 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 coating 1 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.

[0144] 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 content 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 content 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 within the value range of 0.1-50at%, and the conductivity trend line of "coating one" 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.

[0145] In summary, the "coating film 1" 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 coating film 1 contains metallic silver and silver-infiltrated graphene, the "coating film 1" 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.

[0146] Furthermore, the thickness of the "coating film one" can be selected from any numerical range within the range of 0.01 to 100 μm, or any numerical value.

[0147] In addition, from the perspective of further optimizing performance, refer to Fig. 22(b) The surface of the base material a1 of the contact portion 110 of the "connector terminal" provided by the present invention includes a coating a3 and an intermediate coating a2 located between the coating a3 and the base material a1 of the contact portion.

[0148] Specifically, the “intermediate coating a2” of the contact portion 110 of the present invention has the following characteristics:

[0149] The "intermediate coating a2" described in the present invention is mainly a "metal intermediate coating", one of the main functions of which is diffusion prevention; the second main function is to improve the bonding force between the "coating a3" and the "substrate a1"; 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 a2" can prevent the elements (such as copper, iron, aluminum, etc.) on the metal surface of the "substrate a1" 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.

[0150] Based on this, the elements forming the "intermediate coating-a2" 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.

[0151] Furthermore, 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.

[0152] [Extension portion 120]

[0153] Similar to the contact portion 110, in fact, the extension portion 120 also has at least a portion exposed to the plug surface of the plug terminal, so the corrosion resistance requirements of the contact portion 110 and the extension portion 120 are higher than those of the welding portion 130. Fig.21 (a) The surface of the base material b1 of the extension portion 120 includes a coating b3.

[0154] Specifically, the “plating film b3” of the contact portion 120 of the present invention has the following characteristics:

[0155] Regarding the "coating two b3", one option is that it can be the same as the "coating one a3" described in the present invention.

[0156] Another option is different from "Coating-a3", but can optionally meet any one or more of the following conditions Ⅰ) to Ⅷ):

[0157] Ⅰ) the "coating 2" comprises a metal content of not less than 95wt%;

[0158] II) the “coating 2” comprises an alloy having a content of not less than 95wt%;

[0159] III) the “coating 2” comprises a combination of metals and alloys with a content of not less than 95wt%;

[0160] 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;

[0161] 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;

[0162] In order to match the specifications of various connectors, metal terminals are bent by stamping. However, it has been observed for a long time that the bending parts, corners, or parts with arc transitions of the terminals will have uneven coating. At the same time, due to the effect of stress, the coatings in these parts are prone to cracks, damage, or even peeling at the bending parts. In this way, it is very likely that the local coating will fall off, causing accelerated oxidation and corrosion at the bending parts, thereby greatly affecting the conductive properties of the terminals. Generally speaking, when the coating exceeds 2μm, cracks, damage, and even peeling of the coating can be observed at the bending parts. Based on this, it is worth mentioning that if the "coating b3" is of the same type as the "coating a3", its thickness is recommended not to exceed 20μm, and preferably not to exceed 10μm. The reason is that generally speaking, for ordinary metal coatings, when the thickness exceeds 2μm, cracks, breakages, and even coating shedding can be observed at the bending parts of the components. When the type of coating b3 on the surface of the extension portion 120 in multiple bending areas of the terminal 100 of the present invention is the same as the "coating a3", its advantage is that it can break through the limitation of 2μm of ordinary coatings in the past and provide the extension portion 120 with a thicker coating for protection. However, at the same time, it is also hoped to avoid cracks, breakages, and even coating shedding as much as possible. Therefore, the thickness of the "coating b3" is limited to no more than 15μm. The main reason is that the plating solution used to prepare "coating b3" 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 final coating, but also actually affects the coating formation behavior of the electroplating process, so that the surface of the base material can grow the coating more uniformly and stably, especially avoiding the occurrence of cracks and detachment of the bending structure 121 of the extension part 120 and the insertion / extraction end 111 of the contact part 110. In addition, the thickness of the "coating b3" is required to be not less than 0.05μm, preferably not less than 0.1μm.

[0163] In addition, from the perspective of further optimizing performance, refer to Fig.21(b) The surface of the base material b1 of the extension portion 120 includes a second coating b3 and a second intermediate coating b2 located between the second coating b3 and the base material b1 of the extension portion 120. The features of the "second intermediate coating b2" of the contact portion 110 of the present invention are basically the same as those of the "first intermediate coating a2" described above, except that on the basis of the above, it is preferred that the maximum thickness of the "second intermediate coating b2" does not exceed 2 μm, and the value range can be selected from any numerical range within the range of 0.01 to 2 μm, or any numerical value, for example, the thickness of the "second intermediate coating" can be 0.5 μm, 1 μm, 1.5 μm or 2 μm.

[0164] In addition, regarding the plating on the surface of the extension portion 120 , the plating of “plating film 2 b3 ” may be performed first, and then the plating of “intermediate plating film 2 b2 ” may be performed.

[0165] [Welding section 130]

[0166] The welding portion 130 in the terminal 100 is required to have weldability and corrosion resistance. Based on this, a coating film may be provided on the surface of the welding portion 130. Fig. 20 (a) The surface of the base material c1 of the welding portion 130 includes a coating c3.

[0167] Specifically, the “coating three c3” of the welding portion 130 of the present invention has the following characteristics:

[0168] One option is to use the same film type as the "coating a3" described in the present invention;

[0169] Another option is to use the same film type as the "coating three c3" described in the present invention;

[0170] In addition, from the perspective of improving the weldability of the welding portion 130, reference Fig. 20 (b) The surface of the base material c1 of the welding portion 130 includes a coating three c3 and an intermediate coating three c2 located between the coating three c3 and the base material c1. The characteristics of the "intermediate coating three c2" of the welding portion 130 are basically the same as those of the "intermediate coating one a2" described above, but on the basis of the above, it is recommended that the maximum thickness of the "intermediate coating three c2" does not exceed 10 μm, and the value range can be selected from any numerical range within the range of 0.01 to 5 μm, or any numerical value, for example, the thickness of the "intermediate coating" can be 0.5 μm, 1 μm, 1.5 μm, 2 μm or 5 μm.

[0171] In addition, in order to further avoid the reduction of solderability, reduction of bonding strength and increase of contact resistance of the welding part 130 due to exposure to air and other factors, the present invention preferably includes the welding part 130 at the same time, including the coating three c3 and the intermediate coating three c2 located between the coating three c3 and the base material c1. It is preferred that the "intermediate coating three c2" has a tin content as high as possible, such as a tin content of not less than 90wt%, while at the same time, the tin content in the coating three c3 is lower than that in the intermediate coating three c2. On this basis, the maximum thickness of the "intermediate coating three c2" is recommended not to exceed 10μm, and the value range can be selected from any numerical interval within the range of 0.01 to 5μm, or any numerical value, for example, the thickness of the "intermediate coating three c2" can be 0.5μm, 1μm, 1.5μm, 2μm or 5μm. The reason is that based on the above-mentioned limited tin content and thickness, the "intermediate coating three c2" can form a relatively suitable alloy phase of the interface diffusion layer between the Sn coating and the metal substrate with the base material, thereby improving the solderability.

[0172] Meanwhile, the thickness of the coating film c3 is greater than the thickness of the intermediate coating film c2, but the maximum thickness of the coating film c3 is not recommended to exceed 50 μm. Based on this, the coating film c3 can prevent the oxidation of the intermediate coating film c2 containing tin, while maintaining the weldability of the welding portion 130, and can also ensure the performance such as the fixing strength and contact resistance after welding, so it is preferred.

[0173] Finally, regarding the base material of the "connector terminal" (including a1, b1, c1), first consider that it has a metal surface (therefore, the connecting part can also be called a metal part), and on this basis, it can be further considered that it has excellent thermal conductivity, electrical conductivity and machinability, and there are no special restrictions. Based on this, for example, copper, aluminum, iron, nickel, etc. can be cited. In addition, copper alloys, aluminum alloys, iron alloys, nickel alloys, stainless steel materials, etc. can also be used. In addition, in the case of electronic equipment mounted on a vehicle, it can also be copper foil, aluminum foil, or copper film, aluminum film, nickel film, zinc film, etc. vacuum-deposited or chemically plated metal film on organic materials and inorganic non-metallic materials. It is preferably copper or copper alloy, because copper or copper alloy has high conductivity and high strength. Copper and copper alloys that can be cited include: pure copper series such as oxygen-free copper and oxygen-containing copper, copper alloys such as Cu-Ni-Si (Cu content is about 96wt%), Cu-Mg-P (Cu content is about 97wt%), Cu-Fe-P (Cu content is about 97.6wt%), Cu-Be (Cu content is about 98wt%), Cu-Be-Ni (Cu content is about 97.6wt%), Cu-Te, Cu-Sn (Cu content is about 90wt%) alloys, brass Cu-Zn (Cu content is about 62wt%), phosphor bronze Cu-Sn-P (Cu content is about 91.6wt%), and pure copper Cu-TC (C11000 copper content>99wt%).

[0174]

Connector terminal preparation method

[0175] Pretreatment of the "base material" of the connector terminal: As a pretreatment, the metal surface of the "base material" is mainly degreased to remove the oil on the surface, and pickled to remove the oxide film on the surface. This step can be performed depending on the actual situation of the metal surface of the base. For example, in the case of a "base" or "metal surface of the base" made of Al or Al alloy, it is recommended to perform the "pretreatment".

[0176] Preparation of "intermediate coatings a2, b2, c2 (hereinafter collectively referred to as intermediate coatings)": prepare "intermediate coatings" on the surface of the "metal substrate". There is no special restriction on the method of forming the "intermediate coating". According to the properties 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 is necessary to perform catalytic treatment in advance before forming the intermediate coating.

[0177] Make "coatings a3, b3, c3 (hereinafter collectively referred to as coatings)": make coatings on the surfaces of the "substrates a1, b1, c1" respectively, or make coatings on the surface of the "intermediate coating"; the "coatings" are mainly formed by the "electroplating" method.

[0178] The “electroplating” comprises the following steps 1) and 2) :

[0179] 1) Prepare the plating solution and substrate

[0180] The plating solution includes components for forming a coating; for example, if the coating is "coating one", the "components for forming a coating" at least include "graphene infiltrated with silver", and on this basis, may also contain other metals; for example, if the coating is a "metal coating" different from "coating one", the "components for forming a coating" mainly refer to at least including the corresponding metal;

[0181] The substrate has a metal surface; or

[0182] The substrate has a metal surface and an intermediate coating covering the metal surface;

[0183] 2) Electroplating the substrate using the plating solution. The detailed operation of the electroplating for reference is as follows:

[0184] 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.

[0185] On the basis of the aforementioned "electroplating" steps 1) and 2), the preparation of the "plating film 1" is further used as a schematic and detailed description:

[0186] During the electroplating process, the plating solution (i.e., plating solution 1) contains "silver-infiltrated graphene", or contains 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 also). Fig.16). 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.

[0187] 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;

[0188] 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.

[0189] 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.

[0190] The orientation of the "laminated graphene sheets" in the "coating one" provided by the present invention is not specially set, and can be arranged perpendicularly, parallel, inclined or randomly oriented to the substrate according to the required characteristics of the component.

[0191] Finally, the "connector terminal with coating" provided by the present invention is mainly used in electrical connection, such as vehicle-mounted terminals and electrical contacts, and has excellent conductivity, wear resistance and heat resistance.

[0192] The detection instruments (or models) and conditions used in the following specific embodiments are:

[0193] Surface morphology: The surface states of various target objects were investigated by field effect scanning electron microscopy (FE-SEM) (JEOL-JSM_7800F, 5 kV,).

[0194] 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).

[0195] 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).

[0196] 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).

[0197] 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).

[0198] 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).

[0199] 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.

[0200] 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).

[0201] Welding quality observation: The outer surface of the welding part was observed by field effect scanning electron microscope (FE-SEM), where the connector terminal and the printed circuit board P were welded by reflow soldering process, and the parameters were set as follows: the convection heat transfer coefficient between the components and the air was set to 20w / mz·K, the PCB was selected to use FR4 epoxy glass fiber as the substrate, which was a multilayer board with 4 layers of copper foil, the solder material was solder paste SAC305 (thickness 0.15mm), the ambient temperature was 25°C, and the temperature zone setting conditions were as follows:

[0202] Preheating zone: heating rate 2℃ / s, temperature range from room temperature to 150℃, residence time 63s.

[0203] Constant temperature zone: the temperature zone is 150℃~200℃, and the residence time is 100s;

[0204] Reflow zone: temperature 190℃, residence time 60s; temperature 200℃, residence time 30s; temperature 220℃~250℃, residence time 60s;

[0205] Cooling zone: cooling rate 3℃ / s, cooling to 75℃.

[0206] 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.

[0207] 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.

[0208] Example series one

[0209] The coating a3 includes metallic silver and graphene infiltrated with silver, and more detailed information is as follows:

[0210] 1) About the plating solution used

[0211] Basic electroplating solution-1: A commercially available cyanide-free silver plating solution (model PRECIOUSFAB Ag4730, Ag concentration 30 g / L, available at https: / / www.tanaka.com.cn / products / detail / plating-processes / ) from Tanaka Precious Metals Co., Ltd. is used as the basic electroplating solution; 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. Based on the "comparative electroplating solution-2", a Pure-Ag plating film can be formed on the plated substrate;

[0212] 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%).

[0213] Based on the "electroplating solution containing silver-infiltrated graphene-1", an Ag-Gr (Ag) plating film can be formed on the plated substrate;

[0214] 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.

[0215] Based on the "Comparative plating solution-1", an Ag-Gr film can be formed on the plated substrate;

[0216] 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;

[0217] Based on the "basic electroplating solution-2", a Cyan-Pure-Ag coating can be formed on the substrate to be plated;

[0218] 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%).

[0219] 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;

[0220] 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.

[0221] Based on the "Comparative electroplating solution-3", a Cyan-Ag-Gr coating can be formed on the substrate to be plated;

[0222] 2) Regarding the conditions for electroplating

[0223] The current density is controlled at 0.1A / dm 2 ~10A / dm 2 ; The plating solution temperature was fixed at 50°C; the electroplating process adopted a magnetic stirring method of 500 rpm.

[0224] 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 plating materials used in different parts of the current vehicle terminals, in this embodiment, coatings with thicknesses of 0.3 μm, 1 μm, 3 μm, and 5 μm are prepared respectively by adjusting the electroplating time;

[0225] 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.

[0226] Based on the above, the connection terminal 100 provided in this series of embodiments adopts Fig.17(a) The base material of the terminal 100 is selected from copper-containing metals (including copper alloy Cu-Ni-Si (CDA No. C64725, copper content of about 96wt%), Cu-Be-Ni (CDA No. C1720, copper content of about 97.6wt%), Cu-Te (B10, copper content of about 97wt%), brass Cu-Zn (C3602, copper content of about 62wt%), phosphor bronze Cu-Sn-P (C5191, copper content of about 91.6wt%), and pure copper Cu-TC (C11000 copper content> 99wt%)).

[0227] As shown in Table 1-1, the contact portion 110 of the terminal 100 prepared in the specific embodiments 1-1 to 1-12 and 1-16 of the first embodiment series has only the coating film a3, the extension portion 120 has only the coating film b3, the welding portion 130 has only the coating film c3, and the coating film a3, the coating film b3 and the coating film c3 are the same;

[0228] The contact portion 110 of the terminal 100 prepared in the specific embodiments 1-14 and 1-15 of the first embodiment series has a coating a3 and an intermediate coating a2 at the same time, the extension portion 120 has a coating b3 and an intermediate coating b2, the welding portion 130 has a coating c3 and an intermediate coating c2, and the coating a3 and the coating b3 are the same as the coating c3, ​​and the intermediate coating a2, the intermediate coating b2 and the intermediate coating c2 are the same. Specific embodiment 1-14 uses electroplating to produce 1μm thick intermediate coatings one, two and three (a2, b2 and c2) mainly composed of metal Sn on the surface of the metal substrate. Specific embodiment 1-15 uses electroplating to produce 1μm thick intermediate coatings one, two and three (a2, b2 and c2) mainly composed of metal Ni on the surface of the metal substrate.

[0229] Table 1-1. Basic description of specific embodiments of this embodiment series 1

[0230]

[0231] Note that the total number of atoms in the coating is calculated based on the carbon content:

[0232] Coating type Ag-Gr (Ag), current density 0.5A / dm 2 When the content of silver-infiltrated graphene in the coating a3 obtained in Example 1 is 12 at %;

[0233] Coating type Ag-Gr (Ag), current density 1A / dm 2 When the silver-infiltrated graphene content in the coating film a3 obtained in Example 1 is 11 at %;

[0234] Coating type Ag-Gr (Ag), current density 2A / dm 2 When the content of silver-infiltrated graphene in the coating a3 obtained in Example 1 is 10 at %;

[0235] Coating type Ag-Gr (Ag), current density 4~8A / dm 2 When the content of silver-infiltrated graphene in the coating a3 obtained in Example 1 is 8at%;

[0236] Coating type Cyan-Ag-Gr-Ag, current density 1A / dm 2 At this time, the content of silver-infiltrated graphene in the coating a3 obtained in Example 1 is 12 at %.

[0237] As shown in Table 1-2, the contact portion 110 of the terminal 100 prepared in Comparative Examples 1-1 to 1-12 of the first embodiment series has only the first coating, the extension portion 120 has only the second coating, and the welding portion 130 has only the third coating, and the first coating, the second coating and the third coating are the same;

[0238] The contact portion 110 of the terminal 100 prepared in the comparative examples 1-13 and 1-14 of the first series of the present embodiment has both a coating 1 and an intermediate coating 1 a2, the extension portion 120 has a coating 2 and an intermediate coating 2 b2, the welding portion 130 has a coating 3 and an intermediate coating 3 c2, and the coating 1 and coating 2 are the same as the coating 3, and the intermediate coating 1 a2, the intermediate coating 2 b2, and the intermediate coating 3 c2 are the same. Comparative example 1-13 uses electroplating to produce 1μm thick intermediate coatings 1, 2, and 3 (a2, b2, and c2) mainly composed of metal Sn on the surface of the metal substrate. Comparative example 1-14 uses electroplating to produce 1μm thick intermediate coatings 1, 2, and 3 (a2, b2, and c2) mainly composed of metal Ni on the surface of the metal substrate.

[0239] In addition, comparative examples 1-15 to 1-18 are provided:

[0240] The contact portion 110 of the terminal 100 of the comparative example 1-15 is configured the same as that of the comparative example 1-13, and the welding portion 130 of the terminal 100 of the comparative example 1-15 is configured the same as that of the comparative example 1-13, except that the thickness of the coating film b3 of the extension portion 120 is 15 μm;

[0241] The contact portion 110 of the terminal 100 of the comparative example 1-16 is configured the same as that of the comparative example 1-13, and the welding portion 130 of the terminal 100 of the comparative example 1-16 is configured the same as that of the comparative example 1-13, except that the coating film b3 of the extension portion 120 has a thickness of 15 μm, and the film type is the same as that of the specific embodiment 1-14;

[0242] The contact portion 110 of the terminal 100 of the comparative example 1-17 is configured the same as that of the comparative example 1-13, and the welding portion 130 of the terminal 100 of the comparative example 1-16 is configured the same as that of the comparative example 1-13, except that the thickness of the intermediate coating b2 of the extension portion 120 is 5 μm;

[0243] The contact portion 110 of the terminal 100 of the comparative example 1-18 is configured the same as that of the comparative example 1-13, and the welding portion 130 of the terminal 100 of the comparative example 1-16 is configured the same as that of the comparative example 1-13, except that the thickness of the intermediate coating b2 of the extension portion 120 is 5 μm, the thickness of the coating b3 of the extension portion 120 is 15 μm, and the film type is the same as that of the specific embodiment 1-14;

[0244] And comparative examples 1-19 to 1-20 are provided:

[0245] The contact portion 110 of the terminal 100 of the comparative example 1-19 is arranged in the same manner as in the specific embodiment 1-14, and the extension portion 120 of the terminal 100 of the comparative example 1-19 is arranged in the same manner as in the specific embodiment 1-14, except that the thickness of the coating b3 of the welding portion 130 is 70 μm;

[0246] The contact portion 110 of the terminal 100 of the comparative example 1-20 is configured the same as that of the specific embodiment 1-14, and the extension portion 120 of the terminal 100 of the comparative example 1-20 is configured the same as that of the specific embodiment 1-14, except that the thickness of the intermediate coating film b2 of the welding portion 130 is 15 μm, and the film type is the same as that of the specific embodiment 1-14;

[0247] Table 1-2. Basic information of the comparative examples of the first embodiment

[0248]

[0249] Note that the total number of atoms in the coating is calculated based on the carbon content:

[0250] Coating type Ag-Gr, current density 0.5A / dm 2 When the graphene content in the comparative coating 1 is 12 at%;

[0251] Coating type Ag-Gr, current density 1A / dm 2 When the graphene content in the comparative coating 1 is 11 at%;

[0252] Coating type Ag-Gr, current density 2A / dm 2 When the graphene content in the comparative coating 1 is 10at%;

[0253] Coating type Ag-Gr, current density 4~8A / dm 2When the graphene content in the comparative coating 1 is 8at%;

[0254] Coating type Cyan-Ag-Gr, current density 1A / dm 2 When the graphene content in the comparative coating film 1 is 12 at %.

[0255] 2) Performance test of the terminal 100

[0256] Surface FE-SEM observation: Figure 1 As shown, the Ag-Gr (Ag) film ( Figure 1 (b)), and the surface Ag-Gr film ( Figure 1 (a) SEM image of the sample.

[0257] like Figure 1 As shown by the arrow in the figure, in the Ag-Gr film ( Figure 1 (a)) and Ag-Gr(Ag) film ( Figure 1 Translucent and opaque flakes were observed in both (b) and were identified as carbon substances derived from graphene by EDS analysis.

[0258] In such Figure 1 (b) Tiny silver particles (3-10 nm in size) were also observed on the Ag-Gr (Ag) film, and the graphene sheets were also relatively large. It can be inferred that the silver ions that penetrated into the graphene sheets were reduced and then fixed.

[0259] Raman detection: Figure 2 (a) shows the Raman spectrum of the Ag-Gr (Ag) film with a thickness of 5 μm formed on the surface of the terminal 100 by electroplating (the matrix material is Cu-Ni-Si copper alloy) provided in the specific embodiment 1-1; the Raman spectrum of the Ag-Gr film with a thickness of 5 μm formed on the surface of the terminal 100 by electroplating (the matrix material is Cu-Ni-Si copper alloy) provided in the comparative example 1-1.

[0260] like Figure 2 (b) shows the Raman spectrum of a 0.3 μm thick Ag—Gr (Ag) film (the base material is Cu—Ni—Si copper alloy) formed on the surface of the terminal 100 by electroplating provided in Specific Embodiments 1-5.

[0261] It can be seen from the figure that the Ag-Gr (Ag) film provided in the specific embodiment 1-1, the Ag-Gr film provided in the comparative example 1-1, and the Ag-Gr (Ag) film provided in the specific embodiment 1-5 are respectively at 1350cm -1 (D peak), 1580cm -1 (G peak) and 2800cm -1 A characteristic peak attributed to graphene was detected near (2D peak).

[0262] In addition, in the Ag-Gr (Ag) film provided in Specific Example 1-1 and the Ag-Gr (Ag) film provided in Specific Example 1-5, a wavelength of 500 cm -1 The peak is near the surface of the graphene sheet, and the thinner the coating is, the more obvious it is. The analysis shows that the peak is formed by the combination of Ag and graphene sheets, which can prove that the graphene in the coatings of Specific Embodiment 1-1 and Specific Embodiment 1-5 contains a silver-carbon bonding structure. That is to say, the silver-infiltrated graphene used in the electroplating solution 1 contains silver ions and nano-sized silver particles. These silver ions and nano-sized silver particles added between the graphene sheets can effectively promote the combination of graphene sheets and Ag (including in the plating solution) during the formation of the coating.

[0263] like Figure 2 (b) shows the Raman spectrum of the Ag-Gr (Ag) film with a thickness of 0.3 μm formed on the surface of the terminal 100 by electroplating (the matrix material is Cu-Ni-Si copper alloy) provided in specific embodiments 1-5; it shows that even in a thin coating with a thickness of 0.3 μm, the graphene sheet still forms a good combination with Ag, and further illustrates that the graphene used in the electroplating solution 1 has been pre-dispersed with a solution containing silver ions to achieve the addition of silver ions, and these silver ions and nano-sized silver particles added between the graphene sheets can effectively promote the combination of the graphene sheet and Ag (including in the plating solution) during the formation of the coating.

[0264] XRD detection: Figure 3 As shown, there are shown the XRD graph of the Ag-Gr (Ag) film (thickness 5 μm) formed on the surface of the terminal 100 (the matrix material is Cu-Ni-Si copper alloy) prepared by electroplating using the electroplating solution-1 containing "silver-infiltrated graphene" provided in specific embodiment 1-1, the XRD graph of the Ag-Gr (Ag) film (thickness 3 μm) on the surface of the terminal 100 of specific embodiment 1-2, the XRD graph of the Ag-Gr (Ag) film (thickness 1 μm) on the surface of the terminal 100 of specific embodiment 1-3, and the XRD graph of the Ag-Gr film (thickness 5 μm) on the surface of the terminal 100 in comparative example 1-1.

[0265] from Figure 3It can be seen from (a) that the silver crystals in the Ag-Gr film on the surface of the terminal 100 provided in the comparative example 1-1 have a preferential orientation of the (111) plane, while the silver crystals in the Ag-Gr (Ag) film on the surface of the terminal 100 of the specific embodiment 1-1 have a preferential orientation of the (220) plane. In the heat resistance test of the coating, it was found that the preferential orientation of the crystal structure of the silver-containing coating gradually shifted from the (111) plane to the (220) plane. Therefore, compared with the Ag-Gr film provided in the comparative example 1-1, the Ag-Gr (Ag) film provided in the specific embodiment 1-1 in which the Ag is preferentially oriented toward the (220) plane has better crystal structure stability, that is, better heat resistance, and thus the corresponding terminal 100 has better heat resistance.

[0266] from Figure 3 (a) Combination Figure 3 (b) It can be seen that when the thickness of the Ag-Gr (Ag) film is 1 μm (Specific Example 1-3), the preferred orientation of Ag in the coating is in the (111) plane direction. This is because when the coating is thin, it is affected by the copper substrate. When the thickness of the Ag-Gr (Ag) film is 3 μm (Specific Example 1-2), the preferred orientation of Ag in the coating is shifted toward the (220) plane direction. Therefore, from the perspective of crystal structure stability, the coating thickness is preferably 3 μm or more.

[0267] Hardness test: Figure 4 As shown, the hardness measurement results of the terminal 100 with Ag-Gr (Ag) film in the specific embodiment 1-1, the terminal 100 with Ag-Gr film in the comparative example 1-1, and the terminal 100 with Pure-Ag film in the comparative example 1-7 are shown.

[0268] It can be seen from the results that the hardness values ​​of the terminals 100 are, in descending order, the terminals 100 having the Ag-Gr (Ag) film, the Ag-Gr film, and the Pure-Ag film.

[0269] The reason is that the graphene sheets in the coating containing graphene effectively prevent the movement of grains, thereby increasing the hardness of the coating. The coating provided in the present invention contains silver-infiltrated graphene, and silver is filled in the middle of the graphene sheets to further increase the hardness of the coating, and ultimately can improve the hardness of the terminal 100.

[0270] Conductivity (contact resistance) detection: According to the comparison of the terminal 100 with Ag-Gr (Ag) film provided by Specific Examples 1-6, Specific Examples 1-7, and Specific Examples 1-8 in Table 1 and the terminal 100 with Ag-Gr film provided by Comparative Examples 1-1, Comparative Examples 1-2, Comparative Examples 1-4, and Comparative Examples 1-5, it can be seen that the contact resistance value of the terminal 100 with Ag-Gr (Ag) film prepared under different current densities is smaller than that of the terminal 100 with Ag-Gr film. This shows that the silver-infiltrated graphene contained in the plating film can effectively improve the conductivity of the terminal 100.

[0271] from Figure 5 It can be seen that, in general, compared with the terminal 100 with the Pure-Ag film, the terminal 100 with the Ag-Gr (Ag) film or the Ag-Gr film has a significantly smaller contact resistance, indicating that the presence of graphene in the coating can effectively improve the conductivity and reduce the contact resistance.

[0272] Secondly, compared with the terminal 100 with the Ag-Gr film, the terminal 100 with the Ag-Gr (Ag) film has a significantly smaller contact resistance, indicating that the plating contains silver-infiltrated graphene sheets, which realizes the "penetration" of silver particles and silver ions in the graphene sheets. These silver (silver particles, silver ions) added between the graphene sheets through "penetration" ultimately transform the two-dimensional conductivity between the stacked graphene sheets into three-dimensional conductivity, which can further reduce the contact resistance of the terminal 100 and improve the conductivity.

[0273] In addition, from Figure 5 It can also be seen that the contact resistance value of the terminal 100 of the Cyan-Ag-Gr (Ag) film formed by the electroplating solution-2 containing silver-infiltrated graphene is lower than the contact resistance value of the terminal 100 of the Cyan-Ag-Gr film formed by the comparative electroplating solution-3, which shows that the addition effect of silver-infiltrated graphene is applicable to various silver electroplating solution systems.

[0274] in addition, Figure 5The contact resistance of the terminal 100 samples with different base materials is also given. The contact resistance of the terminal 100 with pure copper Cu-TC as the base material is smaller than the contact resistance of the terminal 100 with copper alloy Cu-Ni-Si as the base material. This is because when a coating is formed on the terminal 100 with pure copper Cu-TC as the base material, the surface of the base material can grow the coating more uniformly and stably, which is an important factor in making the coating have a lower contact resistance. In addition, the electrical conductivity of the terminal 100 with copper alloy Cu-Ni-Si as the base material is 48% IACS, while the terminal 100 with pure copper Cu-TC as the base material has the highest electrical conductivity (101% IACS). In summary, affected by the base material, the contact resistance value of the terminal 100 with pure copper Cu-TC as the base material is the smallest.

[0275] Finally, on the terminal 100 which also uses pure copper Cu-TC as the base material, coatings with thicknesses of 0.3μm and 5μm are formed respectively. The contact resistance of the terminal 100 with a coating thickness of 0.3μm is slightly greater than the contact resistance of the terminal 100 with a coating thickness of 5μm. This is because the electrical conductivity of copper is lower than that of silver. When the thickness of the coating becomes thinner, the influence of the conductivity of the metal base becomes greater, resulting in an increase in the contact resistance.

[0276] Heat resistance evaluation-contact resistance: Figure 6 It can be seen that the contact resistance value of the terminal 100 with the ordinary pure silver coating Pure-Ag film provided in Comparative Examples 1-7 increases significantly after more than 1000 hours. This is because the copper in the copper matrix of the coating on the general copper alloy will diffuse to the surface of the coating to form an oxide film under a long-term high temperature environment, thereby increasing the contact resistance. In sharp contrast, the terminal 100 with the coating added with graphene (whether obtained by using a cyanide plating solution or a cyanide-free plating solution) can maintain a relatively stable contact resistance or conductivity in a long-term high temperature environment of 1500 hours.

[0277] In addition, from Figure 6 It can also be seen that the terminal 100 containing the silver-infiltrated graphene coating (whether it is the Cyan-Ag-Gr (Ag) film of specific embodiment 1-9 obtained using a cyanide plating solution, or the Ag-Gr (Ag) film of specific embodiment 1-1 obtained using a cyanide-free plating solution) has lower contact resistance and higher thermal stability than the terminal 100 containing ordinary graphene coating (Ag-Gr film of comparative example 1-1, Cyan-Ag-Gr film of comparative example 1-6). This indicates that the silver-infiltrated graphene in the coating a3 provided by the present invention will form a barrier layer in the coating, thereby inhibiting the thermal diffusion of copper, thereby maintaining the stability of the contact resistance of the coating a3.

[0278] (2) Influence of copper substrate and intermediate coating:

[0279] As shown in Table 1, this series of embodiments not only uses representative copper alloys Cu-Ni-Si, Cu-Sn-P, and pure copper Cu-TC for large current conduction as the base material of the terminal, but also uses Cu-Be-Ni, Cu-Te, and brass Cu-Zn as the base material of the terminal for high-speed charging components that require both conductivity and machinability.

[0280] In addition, the effect of adding an intermediate coating (also called a pre-coating) between the base material and the coating is also discussed, where the intermediate coating can also be regarded as a different base. For example, the surface of the terminal 100 provided in Specific Embodiment 1-14 has a 1 μm thick intermediate coating (including a2, b2, c2) mainly composed of metal Sn, and then a 3 μm thick Ag-Gr (Ag) film (respectively a3, b3, c3) is prepared on the intermediate coating, which is recorded as Sn-1 / Ag-Gr (Ag) film. The surface of the terminal 100 provided in Specific Embodiment 1-15 has a 1 μm thick intermediate coating (including a2, b2, c2) mainly composed of metal Ni, and then a 5 μm thick Ag-Gr (Ag) film (respectively a3, b3, c3) is prepared on the intermediate coating, which is recorded as Ni-1 / Ag-Gr (Ag) film.

[0281] Hardness test: From the comparison of the hardness of the specific examples 1-9 to 1-15 and the comparative examples 1-6 to 1-11 in Table 1, it can be seen that the hardness values ​​of the terminals 100 with various Ag-Gr (Ag) films are higher than those of the terminals 100 with Pure-Ag films. This shows that the coating containing silver-infiltrated graphene is suitable for terminals 100 of various base materials.

[0282] Among them, the brass Cu-Zn which is easy to cut has a lower hardness than other terminals 100 because the base material itself is relatively soft.

[0283] In addition, the hardness of the terminal 100 generally decreases slightly after heating at 200° C. for 500 hours, which is a result of silver recrystallization at high temperature.

[0284] The hardness variation of the terminal 100 in the specific embodiments 1-15 using the Ni intermediate plating film is the same as that of the copper alloy base material.

[0285] However, the hardness of the terminal 100 of the specific embodiment 1-14 using the Sn intermediate coating is significantly increased to 190HV (close to the terminal with the ordinary silver alloy electroplating layer). This is because tin and copper will form a harder Cu-Sn alloy layer at the substrate interface, and will also form a harder Ag-Sn alloy layer, so that the coating becomes a multi-layer composite coating of Cu-Sn / Ag-Sn / Ag-Gr (Ag). Here, the Cu-Sn alloy and the Ag-Sn alloy are respectively the intermetallic compounds Cu 6 Sn 5 and Ag 3 Sn is located between the substrate and the Ag-Gr (Ag) coating, which improves the hardness and wear resistance of the coating while maintaining stable conductivity.

[0286] Contact resistance detection: such as Figure 7 As shown in the figure, the contact resistance of the terminal 100 (having a 5μm thick Ag-Gr (Ag) film and a Pure-Ag film) of various base materials is compared, and it can be seen that the contact resistance of the terminal 100 having the Ag-Gr (Ag) film is lower than that of the terminal 100 having the Pure-Ag film. This shows that a highly conductive Ag-Gr (Ag) composite plating film can be obtained on various copper alloy base materials.

[0287] like Figure 8 As shown, the contact resistance changes of the terminals 100 (having a 5 μm thick Ag-Gr (Ag) plating) with various base materials before heating and after heating at 200°C for 500 hours. The contact resistance of the terminal 100 with the copper alloy Cu-Ni-Si as the base material and the terminal 100 with the copper alloy Cu-Be-Ni as the base material (Specific Example 1-1, Specific Example 1-11) is slightly lower than the contact resistance of the terminal 100 with the brass plate Cu-Zn as the base material and the terminal 100 with the Sn intermediate plating (Specific Example 1-12, Specific Example 1-14), mainly because of the influence of tin and zinc elements.

[0288] After heating at 200°C for 500 hours, the contact resistance of the terminals 100 of various base materials is slightly reduced or remains unchanged, because the silver in the coating will increase the grain size and reduce the grain boundary due to recrystallization under long-term high temperature environment, so that the contact resistance becomes smaller or the conductivity increases. Here, the use of Sn intermediate coating as in specific embodiment 1-14 or the use of Ni intermediate coating as in specific embodiment 1-15 can prevent the thermal diffusion of copper in the base material under high temperature environment, and can also reduce the gap defects caused by copper diffusion on the interface, thereby improving the adhesion between the coating (including coatings 1, 2, and 3) of the terminal 100 and the base material.

[0289] Comparison of other performances: Tables 1-3 below show the experimental results of observing the bending structure 121 of the extension portion 120 of the terminal 100 with an optical microscope. Here, A+ means that there is no visual damage or cracks, and the surface of the coating is not obviously damaged when observed with an optical microscope. A means that there is no visual damage or cracks, 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 portion. C means that cracks can be observed on the surface of the coating by visual observation.

[0290] Table 1-3. Basic information of the embodiment series 1 and comparative examples 1-13 to 1-18

[0291] Coating surface condition Specific Examples 1-14 A+ Comparative Examples 1-13 B Comparative Examples 1-14 B Comparative Examples 1-15 C Comparative Examples 1-16 A Comparative Examples 1-17 B Comparative Examples 1-18 A

[0292] In fact, the bonding force between the coating and the substrate affects not only the electrical contact performance and its stability, but also the stability (weldability) of the terminal during crimping or welding, because copper and aluminum are both easy to oxidize, and oxidation often occurs during welding to generate high-melting-point oxides, resulting in the weld failing to completely fuse. The welding problem will cause the weld joint to be prone to breakage, corrosion, heat generation and other problems during service. Moreover, compared with copper, aluminum is more easily oxidized to form aluminum oxide, making welding difficult; in addition, aluminum is relatively soft, and the mechanical and electrical properties after crimping are relatively low. Galvanic corrosion and gap corrosion are prone to occur in the crimping area, affecting the conduction reliability of the connector. The following Tables 1-4 show the observation results of the welding interface formed by friction welding between the welding portion 130 of the terminal 100 and the printed circuit substrate P. If the welding interface surface is flat and smooth, and there are no microcracks or unfused weld surface, it indicates that the welding quality is good and the weldability is excellent; if there are tiny textures on the welding interface surface, or only microcracks on the weld surface, it indicates that the weldability is good; if there are obvious processing textures on the welding interface surface, it indicates that the weldability is average; if there are obvious processing textures on the welding interface surface, and slag inclusions and holes can be observed in the weld, it indicates that the weldability is poor.

[0293] Table 1-4. Basic information of the first embodiment and comparative examples 1-19 to 1-20

[0294] Solderability Specific Examples 1-14 excellent Comparative Examples 1-13 good Comparative Examples 1-14 generally Comparative Examples 1-19 Difference Comparative Examples 1-20 generally

[0295] Example series 2

[0296] The terminal 100 prepared in the second series of the present embodiment includes plating films one, two, and three (a3, b3, and c3), and optionally includes an intermediate plating film (a2, b2, and c2).

[0297] 1) About the substrate used

[0298] As shown in Table 2 below, various aluminum and aluminum alloy materials are used as the metal matrix:

[0299] Table 2. Basic information of each aluminum matrix

[0300]

[0301]

[0302] Pure aluminum as described in Table 1, wherein the aluminum content exceeds 99wt% or 99.5wt%;

[0303] 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;

[0304] 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.

[0305] 2) Regarding the intermediate coating

[0306] 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, Ni intermediate coatings with a thickness of 30nm and 3μm are mainly prepared, and then Ag-Gr (Ag) coatings with a thickness of 5μm are prepared on the Ni intermediate coatings, 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.

[0307] 3) About the plating solution used

[0308] Basic electroplating solution-1 is the same as the basic electroplating solution-1 of Example Series 1;

[0309] The electroplating solution-1 containing “graphene infiltrated with silver” is the same as the electroplating solution-1 containing “graphene infiltrated with silver” in the first embodiment.

[0310] Comparative plating solution-1 is the same as the comparative plating solution-1 of Example series 1;

[0311] 4) Regarding the conditions for electroplating

[0312] The current density is controlled at 1A / dm 2; The plating solution temperature was fixed at 50°C; an Ag-Gr (Ag) coating with a thickness of 5 μm was prepared by adjusting the electroplating time (the content of silver-infiltrated graphene in the coating was 12 at% in terms of carbon atomic percentage); the rest of the electroplating conditions were the same as those in Example Series 1.

[0313] Based on the above, the specific embodiments of electroplating Ag-Gr (Ag) film on aluminum alloy substrate provided in this series of embodiments are listed in Table 3:

[0314] Specific embodiments 2-1 to 2-3 are terminals 100 whose base material is pure aluminum A1100, whose surface is pre-plated with a Ni intermediate coating (intermediate coating three and coating three are the same as intermediate coating one) of different thicknesses (0 μm, 0.03 μm, 3 μm), and then an Ag-Gr (Ag) coating (coating three and coating two are the same as coating one) with a thickness of 5 μm is formed by electroplating;

[0315] Specific embodiment 2-4 is a terminal 100 whose base material is A1050 aluminum alloy with high purity, the surface is pre-plated with a 0.03 μm thick Ni intermediate coating 1 (intermediate coating 3 and 3 are the same as intermediate coating 1), and then an Ag-Gr (Ag) coating 1 with a thickness of 5 μm is formed by electroplating (coating 3 and coating 2 are the same as coating 1);

[0316] Specific embodiments 2-5 to 2-10 are terminals 100 respectively pre-plated with Ni intermediate coating one (intermediate coating three, coating three is the same as intermediate coating one) of different thicknesses (0μm, 0.03μm) on the surface of base materials of Al-Cu alloys A2017 and A2024 and Al-Si alloy A6061, and then electroplated with Ag-Gr (Ag) coating one (coating three, coating two is the same as coating one) with a thickness of 5μm; as shown in Table 3.

[0317] Table 3. Basic description of the specific embodiments of the second embodiment

[0318]

[0319] 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;

[0320] "Ni-03" means a 0.03μm thick intermediate coating mainly composed of metallic Ni (including a2, b2, and c2);

[0321] "Ni-3" means a 3μm thick intermediate coating mainly composed of metallic Ni (including a2, b2, and c2);

[0322] 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;

[0323] 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.

[0324] 5) About performance testing

[0325] Surface morphology: Fig. 9 (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 pure aluminum A1100 substrate material, respectively. It can be seen from the figure that the 30nm thick Ni intermediate coating obtained by electroplating using alternating current has a smoother surface state. In comparison, the surface of the 3μm thick Ni intermediate coating obtained by electroplating using direct current is relatively rough.

[0326] Fig. 9 (c, d) are respectively Fig. 9 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). Fig. 9 (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.

[0327] 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.

[0328] Elemental analysis in the coating thickness direction - GD-OES: Fig.10 (a) and (b) are element distribution diagrams in the depth direction of the coating films (labeled as Ni-03 / Ag-Gr(Ag) and Ni-3 / Ag-Gr(Ag) in the figures) of the terminal 100 provided in the specific embodiments 2-1 and 2-2, respectively; Fig.10It 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.

[0329] Conductivity (contact resistance) detection: As shown in Table 3, by comparing the contact resistance of the terminal 100 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 terminal 100 with a copper alloy as the base material. This is mainly because the electrical conductivity of aluminum is lower than that of copper metal.

[0330] By comparing Specific Example 2-1 and Specific Example 2-2, it is found that the thicker the nickel (Ni) intermediate coating of the terminal 100, the higher the contact resistance, because the electrical conductivity of Ni is lower than that of aluminum. The terminal 100 provided in Specific Example 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 resistance of the terminal 100 with the Ni-3 / Ag-Gr (Ag) film provided in Specific Example 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 strength of the coating but also improve the conductivity.

[0331] like Fig.11As 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 terminal 100 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 terminal 100 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 terminal 100 is 0. The contact resistance of the terminal 100 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 terminal 100 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 terminal 100 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 terminal 100 using A1100 as the metal matrix material is generally higher than the contact resistance value of the terminal 100 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 terminal 100.

[0332] Moreover, the contact resistance of the terminal 1000, which uses pure copper as the metal base material and has an Ag-Gr (Ag) coating (5μm) of the same thickness on the surface of the metal base material, is 0.400mΩ; based on this result, it can be seen that the terminal 100 with a coating, which is provided by the present invention and uses Al-Cu alloy (A2017) as the metal base material and combines the design of the intermediate coating, has the advantage of lightweight and excellent conductivity.

[0333] Comparison of other properties: The welding interface formed by friction welding of the welding portion 130 of the terminal 100 and the printed circuit board P in specific embodiments 2-5 and 2-6 was observed. It was found that the welding interface surface of specific embodiment 2-5 was flat and smooth, and there were no microcracks or unfused weld surface, indicating good welding quality and excellent weldability; the welding interface surface of specific embodiment 2-6 had obvious processing textures and average weldability.

[0334] Embodiment series three

[0335] 1) About the substrate used

[0336] In order to verify that the terminal 100 with the silver-infiltrated graphene coating has better conductivity and heat resistance than the terminal 10 with the ordinary graphene coating, as shown in Table 4, in the specific embodiment 3-1 and the specific embodiment 3-2 of this series of embodiments and the comparative example 3-1 and the comparative example 3-2, the same copper alloy Cu-Ni-Si is used as the metal matrix material (same as the embodiment series 1);

[0337] The contact portion 110 of the terminal 100 prepared in the specific embodiments 3-1 and 3-2 has only the first coating a3, the extension portion 120 has only the second coating b3, the welding portion 130 has only the third coating c3, ​​and the first coating a3, the second coating b3 and the third coating c3 are the same;

[0338] The contact portion 110 of the terminal 100 prepared in comparative examples 3-1 and 3-2 has only the first plating film, the extension portion 120 has only the second plating film, the welding portion 130 has only the third plating film, and the first plating film, the second plating film and the third plating film are the same.

[0339] 2) About the plating solution used

[0340] Basic electroplating solution: A bright sulfate Sn plating solution is used as the basic liquid, with a Sn concentration of 30 g / L; based on the "basic electroplating solution", a Pure-Sn plating film can be formed on the substrate to be plated.

[0341] Electroplating solution L containing "silver-infiltrated graphene": On the basis of the basic electroplating solution, silver-infiltrated graphene which is basically the same as that in Example Series 1 is added thereto, the only difference being that the Ag content of the silver-infiltrated graphene is 5at%. Finally, the concentration of the silver-infiltrated graphene in this electroplating solution is 1wt%.

[0342] Based on the "electroplating solution L containing silver-doped graphene", a Sn-Gr(Ag)-L film can be formed on the plated substrate.

[0343] Electroplating solution H containing "silver-infiltrated graphene": On the basis of the basic electroplating solution, silver-infiltrated graphene which is basically the same as that in Example Series 1 is added thereto, the only difference being that the Ag content of the silver-infiltrated graphene is 10at%. Finally, the concentration of the silver-infiltrated graphene in this electroplating solution is 1wt%.

[0344] Based on the "electroplating solution H containing silver-doped graphene", a Sn-Gr(Ag)-H film can be formed on the plated substrate.

[0345] Comparative electroplating solution: On the basis of the basic electroplating solution, ordinary graphene that is not permeated with silver (i.e., a body consisting of only stacked graphene sheets, excluding silver) is added thereto. The final electroplating solution is formed, and the rest is the same as the basic electroplating solution. Finally, the concentration of graphene in this electroplating solution is 1wt%. Based on the "comparative electroplating solution", a Sn-Gr film can be formed on the plated substrate;

[0346] 3) The conditions for electroplating are the same as those in Example 2

[0347] In addition, by adjusting the current density and the electroplating time, Sn-Gr (Ag) film, Sn-Gr film and Pure-Sn film with a thickness of 5 μm were obtained, as shown in Table 4.

[0348] Table 4. Basic information of specific examples and comparative examples of this embodiment series 3

[0349]

[0350] Note: The "carbon content at %" of specific embodiments 3-1 and 3-2 in the table represents the content of the silver-infiltrated graphene calculated based on the carbon content, taking the total number of atoms in the coating as the total number.

[0351] The "carbon content at %" of Comparative Example 3-1 in the table represents the content of the ordinary graphene (graphene without silver) calculated by carbon content based on the total number of atoms of the coating.

[0352] 4) About performance testing

[0353] Raman determination: Fig.12 As shown, the Sn-Gr(Ag)-L film ( Fig.12 (b)), the Sn-Gr film of the terminal 100 of Comparative Example 3-1 ( Fig.12 (a)) are both at 1350cm -1 (D peak), 1580cm -1 (G peak) and 2800cm -1 A characteristic peak attributed to graphene was detected near (2D peak).

[0354] In addition, the Sn-Gr(Ag)-L film sample of the terminal 100 of the specific embodiment 3-1 detected a -1 Nearby peaks.

[0355] XRD determination: Fig.13As shown, the preferred orientation of the crystal structure of Sn is gradually transferred from the (101) plane to the (220) plane. Therefore, compared with the Pure-Sn film of the terminal 100 of Comparative Examples 3-1 and 3-2, the Sn-Gr(Ag)-L film of the terminal 100 of the specific embodiment 3-1 and the Sn-Gr(Ag)-H film of the terminal 100 of the specific embodiment 3-2 have better crystal structure stability, that is, better heat resistance.

[0356] Conductivity (contact resistance) detection: combined Fig.14 It can be seen that, in general, compared with the terminal 100 with the Pure-Sn film, the terminal 100 with the Sn-Gr (Ag) film or the Sn-Gr film has a significantly smaller contact resistance, indicating that the graphene sheet contained in the coating can effectively improve the conductivity and reduce the contact resistance;

[0357] Secondly, compared with the terminal 100 with the Sn-Gr film, the terminal 100 with the Sn-Gr (Ag) film has a significantly smaller contact resistance, indicating that the coating 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, which can further reduce the contact resistance of the terminal 100 and improve the conductivity. However, in general, compared with the terminal 100 with the Sn-Gr (Ag) coating, the terminal 100 with the Ag-Gr (Ag) coating has a significantly smaller contact resistance.

[0358] Heat resistance (contact resistance stability) test: In recent years, the heat resistance requirements for terminal and connector materials have increased from the previous 100°C (USCAR: Class-I) - 120°C (Class-II) to 150°C (Class-III). In addition, depending on the installation location, it may sometimes rise to 175°C (Class-IV) and 200°C (Class-V). Based on this, combined with Fig.15 It can be seen that in this study, taking into account practical conditions, the change in contact resistance value was measured after the accelerated heat resistance test was carried out at 200°C for 150 hours.

[0359] Fig.15 (a) It can be seen that the Pure-Sn film is unstable in the low load region and the contact resistance value also increases, but the Sn-Gr (Ag) film has a significant decrease in resistance value from the moment of contact, and the stable contact resistance value range is wider.

[0360] Fig.15(b) is a graph showing the contact resistance of various coatings at a maximum load of 0.5 N after the heat resistance test. The contact resistance value of the Pure-Sn film is 2.11 mΩ, which is 114% higher than that immediately after the coating. On the other hand, the Sn-Gr (Ag) coating remains at a platform of 0.6 mΩ regardless of the Ag concentration, and the contact resistance value increases by only about 30% compared to that immediately after the coating. That is, it can be considered that the terminal 100 with the Sn-Gr (Ag) coating has significantly higher heat resistance than the terminal 100 with the pure Sn coating.

[0361] In addition, referring to the existing heat resistance test research of Sn-Gr coating, the heat resistance of Sn-Gr (Ag) composite coating is higher than that of Sn-Gr composite coating. Based on this, it is believed that the presence of graphene in the coating effectively inhibits the formation and alloying of Sn oxide film, and the heat resistance can be further improved through the synergistic effect of graphene and Ag.

Claims

1. A connector terminal with a coating, the terminal comprising a substrate and a coating located on the surface of the substrate, It is characterized in that The terminal comprises a contact portion, an extension portion and a welding portion connected in sequence; The substrate surface of the contact portion has a coating 1; The extension portion has a bending structure, and the surface of the extension portion has a second coating; The base surface of the welding part has a coating three; The type of the coating three is the same as or different from the type of the coating one; The coating film 1 includes graphene; Taking the atoms of the coating film 1 as the total number and calculated as carbon atoms, the content of the graphene is 1 to 30 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 connector terminal with a plated film according to claim 1, It is characterized in that Taking the atoms of the coating film 1 as the total number and calculating by carbon atoms, the content of graphene in the coating film 1 is 5 to 20 at %, preferably 5 to 15 at %.

3. The connector terminal with a plated film according to claim 1, It is characterized in that In addition to the silver contained in the graphene, the coating 1 also includes other metals; Furthermore, taking the atoms of the coating film 1 as the total number, the content of the other metal is not less than 40 at %, and the sum of the content of the other metal and the graphene is 95 to 100 at %; Among them, the other metals include any one or a combination of two or more of the following: silver, copper, iron, aluminum, tin, nickel, zinc, and cobalt. Preferably, the other metals include any one or a combination of two or more of the following: silver, tin, and copper.

4. The connector terminal with a coating according to any one of claims 1 to 3, 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 %.

5. The connector terminal with a plated film according to claim 4, It is characterized in that There is also an intermediate coating film 1 between the substrate surface of the contact portion and the coating film 1; An intermediate coating film three is provided between the base surface of the welding portion and the coating film three.

6. The connector terminal with a plated film according to claim 5, It is characterized in that The type of the coating 2 and / or the coating 3 is the same as the type of the coating 1; Alternatively, the type of coating two and / or coating three is different from the type of coating one; and the type of coating two and / or coating three 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.

7. The connector terminal with a plated film according to claim 6, It is characterized in that The thickness of the coating film 1 is 0.01 to 100 μm, preferably 0.1 to 30 μm; The thickness of the second coating is 0.1 to 50 μm, preferably 0.1 to 15 μm; The thickness of the coating three is 0.1-50 μm, preferably 0.1-10 μm.

8. The connector terminal with a plated film according to claim 7, It is characterized in that There is also an intermediate coating film 2 between the base surface of the extension portion and the coating film 2.

9. The connector terminal with a coating according to any one of claims 6 to 8, It is characterized in that The type of the intermediate coating 1 is different from the type of the coating 1; The type of the intermediate coating 2 is different from the type of the coating 2; The type of the intermediate coating three is different from the type of the coating three; The intermediate coating film 1, the intermediate coating film 2, and the intermediate coating film 3 are each independently a metal coating film including a metal content of not less than 95wt%, and the metal includes any one or a combination of two or more of copper, iron, aluminum, tin, nickel, zinc, and cobalt. Preferably, the metal includes any one or a combination of two or more of the following: tin and nickel.

10. The connector terminal with a plated film according to claim 9, It is characterized in that The thickness of the intermediate coating film 1 does not exceed the thickness of the coating film 1; preferably, the thickness of the intermediate coating film 1 is 0.01-5 μm.

11. The connector terminal with a plated film according to claim 9, It is characterized in that The thickness of the intermediate coating film 2 does not exceed the thickness of the coating film 2; preferably, the thickness of the intermediate coating film 2 is 0.01-2 μm.

12. The connector terminal with a plated film according to claim 9, It is characterized in that The thickness of the intermediate coating film three does not exceed the thickness of the coating film three; preferably, the thickness of the intermediate coating film three is 0.01-10 μm.

13. A method for preparing a connector terminal with a coating, wherein the connector terminal comprises a contact portion, an extension portion and a welding portion connected in sequence, It is characterized in that Includes steps: 1) Prepare the plating solution and the substrate to be plated of the connector terminal The plated substrate of the terminal has a metal surface; or The plated substrate of the terminal has a metal surface and an intermediate plating film covering the metal surface; The plating solution contains graphene; The graphene includes stacked graphene sheets and silver located between the graphene sheets; The silver includes silver ions and nano-sized silver particles; Calculated based on the carbon content, the concentration of graphene in the plating solution is 0.1 to 100 g / L; Wherein, 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 %. 2) Electroplating the substrate using the plating solution.

14. The method for preparing a connector terminal with a coating according to claim 13, It is characterized in that The plating solution also includes other metals, and the other metals include any one of silver, copper, iron, aluminum, tin, nickel, zinc, and cobalt, or a combination of two or more thereof; The concentration of other metal ions in the plating solution is 0.25-100 g / L, and preferably the concentration of other metal ions in the plating solution is 0.25-50 g / L.

15. The method for preparing a connector terminal with a coating according to any one of claims 13 to 14, 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 .

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