Copper terminal with silver-containing coating film and tin-containing coating film and preparation method thereof

Abstract

The invention discloses a copper terminal with a silver-containing coating film and a tin-containing coating film and a preparation method of the copper terminal. The terminal comprises a metal matrix with the copper content exceeding 90% and a coating film, and the coating film at the contact part comprises metal silver and graphene; the coating film has a peak of 500 + / -30 cm <-1 > in a Raman spectrum detected by Raman spectroscopy; the coating film of the welding part comprises metal tin.

Description

Technical Field

[0001] The invention belongs to the technical field of conductive materials, and more specifically, relates to a copper terminal with a silver-containing plating film and a tin-containing plating film and a preparation method thereof. Background Art

[0002] A connector (i.e. CONNECTOR), also called a plug-in connector, is a small component used to achieve electrical connection between two parts of an electronic system. Although the connector is small, it is a very important and indispensable electronic component in electronic products. It is related to the reliability of the product and personal safety. Based on this, the basic requirement for the connector is that it can be conductive and reliable.

[0003] Connectors are mainly used to connect two active device circuits to achieve the transmission of current, signals or data. They are the core basic components necessary for the electrical connection of circuit systems. Their common application areas include smart homes, automobiles, communications, computers and peripherals, industry, military and aerospace, etc., and their application scope will become wider and wider with development.

[0004] Taking the common plug-in connector as an example, its normal working state is divided into male end and female end. The female end is directly soldered to the printed circuit board, and the male end is used to connect the external circuit of the box and is inserted into the female end, so it is called a jack terminal block. 。 The most widely used terminals are PCB board (printed circuit board) terminals. In addition, there are hardware terminals, nut terminals, spring terminals, etc. There are many types of connectors, including circular connectors, rectangular connectors, and stepped connectors. Terminal blocks generally belong to rectangular connectors. The application range of terminal blocks is relatively single, and they are generally used in the electronic and electrical fields for internal and external connections of PCB circuit boards, printed boards, and distribution cabinets.

[0005] Based on the above, in order to achieve reliable electrical connection, the first requirement is that the terminals of electronic connectors have good electrical conductivity, so that their energy consumption is low and power consumption is low, and the heat generation is low and the temperature rise is small. Therefore, the substrate of the connector terminal is generally made of copper alloy materials with good electrical conductivity and heat transfer. The second requirement is that the terminal has excellent mechanical strength and service life. Although copper alloy has sufficient strength to ensure the connection strength of small terminals, copper alloy is very susceptible to corrosion in an environment containing sulfur and oxygen. Sulfides and oxides as corrosion products will accumulate on the contact interface to produce an insulating layer, making it difficult to maintain its conductive stability. In severe cases, it will destroy the electrical stability of electronic equipment and even cause accidents. Therefore, in order to maintain conductivity and mechanical properties such as wear resistance and fatigue resistance to meet the life requirements of electronic equipment, the terminals of modern electrical connectors must be subjected to conductive and wear-resistant surface treatment to form a metal coating, thereby shielding the mechanical and environmental attacks on the copper alloy matrix material. Generally speaking, the metal coating is divided into two categories: precious metal coating including gold, silver, palladium and its alloys and general metal coating. By selecting the appropriate electroplating material and coating thickness, the mechanical properties, chemical properties and electrical properties of the contact interface can be managed. The choice of electroplating for electrical connectors depends on many factors, the most important of which are performance parameters including conductivity and durability, followed by cost, application environment and reliability requirements. In recent years, with the rapid development of electric vehicles and various electronic appliances, the conductivity and heat resistance of connector terminals are used to reduce heat generation and power loss caused by it. Because silver has excellent conductivity, silver (Ag) coatings are being widely promoted and applied to terminals. Pure silver coating has the problem of low wear resistance. The way to extend the service life by simply increasing the coating thickness is limited, and it is impossible in terms of cost and resources. In addition, the hardness / wear resistance / lubricity of the silver-containing coating can be improved by adding alloy elements such as antimony, selenium, nickel, cobalt, tellurium or bismuth, or molybdenum disulfide, Teflon particles, etc., but the actual hardness improvement is limited, and the accompanying problem is a significant increase in resistance. Based on this, Patent Document 1 (JP2021072185A) discloses a silver-graphene composite coating containing stacked graphene. Compared with pure silver coating, the hardness of the coating is increased from 80HV to 120HV, but the wear resistance is still not ideal, and the conductivity also has room for further improvement. Based on this, Patent Document 2 (JP2022170877A) further provides a substrate with a silver-graphene composite coating, which studies the size (0.05-6μm), content, and arrangement direction of the graphene dispersed in the silver-graphene composite coating relative to the substrate, and achieves the improvement of the conductivity and wear resistance of the silver-graphene composite coating. However, there is no solution for how to ensure the contact resistance stability of the silver-graphene composite coating when a large current is energized or in a continuous high temperature environment.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.

[0006] From the above, it can be seen that in order to ensure the conduction and reliability of the aforementioned electrical connection, the research focus on the terminal substrate and coating is basically centered around the aforementioned "first and second" requirements, in order to achieve the ideal conductivity and wear resistance. But in fact, in recent years, in the electronic and electrical industry, the requirements for product integration and lightweight are getting higher and higher. This requirement also affects the development direction of automotive electronic and electrical products, so that more PCB designs are applied to automotive electronic and electrical products. However, compared with 3C industry electronic products, automotive electronic and electrical products need to transmit larger currents and voltages. Therefore, the board-end connection terminals used in the automotive electronic and electrical industry will be applied to larger specifications of welding terminals. The larger the specifications of the welding terminals, the higher the requirements for the welding process. In other words, if the welding process cannot be broken through, the larger the specifications of the welding terminals, if the corresponding welding performance cannot be guaranteed, then the reliability of the terminal will be sacrificed. Summary of the invention

[0007] 1. Problem to be solved

[0008] In view of the problem that the existing PCB-based soldered copper terminals are used in automotive electronic and electrical products and have unstable usage (heat resistance, conductivity, etc.), one of the objects of the present invention is to provide a copper terminal with a silver-containing coating and a tin-containing coating; at the same time, the present invention also provides a preparation method of the copper terminal with a silver-containing coating and a tin-containing coating.

[0009] 2. Technical solution

[0010] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] A first aspect of the present invention provides a copper terminal having a silver-containing plating film and a tin-containing plating film, wherein the copper terminal comprises a substrate and a plating film located on the surface of the substrate, and is characterized in that:

[0012] The copper content of the base of the copper terminal is not less than 60wt%;

[0013] The terminal comprises a connected contact portion and a welding portion;

[0014] The surface of the substrate of the contact portion has a silver-containing coating;

[0015] The surface of the substrate of the welding part has a coating film three, and a tin-containing coating film located between the surface of the substrate and the coating film three;

[0016] Wherein, the thickness of the tin-containing coating is 0.01 to 10 μm, and the tin content is not less than 80 wt%;

[0017] The silver-containing coating includes graphene and other metals, and the other metals include silver;

[0018] Taking the atoms of the silver-containing coating as the total number and calculating by carbon content, the content of graphene included in the silver-containing coating is not less than 1at%, the content of other metallic silver included is not less than 40at%, and the sum of the content of the metal and the graphene is 95-100at%; wherein the graphene includes stacked graphene sheets and silver located between the graphene sheets, and the silver includes silver ions and nano-sized silver particles.

[0019] It should be noted that the “other metallic silver” as described herein is different from the “silver located between the graphene sheets” as described above.

[0020] According to any embodiment of the first aspect of the present invention, the copper content of the base of the copper terminal is not less than 80 wt %, preferably not less than 90 wt %.

[0021] According to any embodiment of the first aspect of the present invention, the terminal further comprises an extending portion, and the extending portion is used to connect the contact portion and the welding portion.

[0022] According to any embodiment of the first aspect of the present invention, the extension portion has a bent structure.

[0023] According to any embodiment of the first aspect of the present invention, the base surface of the extension portion has a second coating.

[0024] According to any embodiment of the first aspect of the present invention, the terminal further comprises an extension portion, the extension portion being used to connect the contact portion and the welding portion;

[0025] The welding portion includes a welding pin area and an area close to the printed circuit substrate;

[0026] Calculated by the weight of the base body, the area close to the printed circuit substrate is reduced in weight compared to the extension portion.

[0027] According to any embodiment of the first aspect of the present invention, the reduction includes: compared with the base of the extension portion, the base of the area close to the printed circuit substrate has a hollow structure;

[0028] Alternatively, compared with the base of the extension portion, the base in the area close to the printed circuit substrate has a reduced thickness and / or reduced width design.

[0029] According to any embodiment of the first aspect of the present invention, the coating on the surface of the contact portion (when the silver coating is detected or when the silver coating and the intermediate coating are detected together) has a Raman spectrum detected by Raman spectroscopy at 500±30cm -1 Peak, 1330±30cm -1 Peak, 1550±30cm -1 The peak and 2800±30cm -1 The peak.

[0030] Furthermore, taking the atoms of the coating as the total number and calculating the carbon content, the content of graphene included in the coating can be arbitrarily selected from any numerical range of 1-50at%, 1-30at%, 1-20at%, and 1-15at%.

[0031] According to any embodiment of the first aspect of the present invention, taking the atoms of the silver-containing coating as the total number and calculated by carbon content, the content of graphene included in the silver-containing coating is not less than 3 at %.

[0032] Furthermore, according to the total number of atoms of the silver-containing coating and calculated by carbon content, the content of graphene included in the coating can be arbitrarily selected from any group of numerical ranges including 3-50at%, 5-30at%, 5-20at%, 10-20at%, and 5-15at%.

[0033] 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.

[0034] 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%.

[0035] According to any embodiment of the first aspect of the present invention, the silver-containing plating film including other metallic silver further includes another metal, and the other metal includes any one or a combination of two or more of the following: copper, iron, aluminum, tin, nickel, zinc, and cobalt; these other metals may be unavoidable impurities, or the content is controlled to be below 5at%.

[0036] According to any embodiment of the first aspect of the present invention, the thickness of the silver-containing coating can be selected from any value within the following ranges: 0.01-100 μm, 0.01-90 μm, 0.01-30 μm, 0.01-10 μm, 0.01-8 μm, 0.1-100 μm, 0.1-90 μm, 0.1-50 μm, 0.1-30 μm, 0.1-10 μm, 0.1-8 μm, 0.3-100 μm, 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, 0.7~10 0μm, 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, 2.5~100μm, 2.5~90μm, 2.5~30μm, 2.5~10μm, 2.5~8 μm, 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;

[0037] Preferably, the thickness of the silver-containing plating film is not less than 3 μm, and preferably is 3 to 100 μm, 3 to 90 μm, 3 to 30 μm, 3 to 10 μm, and 3 to 8 μm, respectively.

[0038] Based on any embodiment of the first aspect of the above-mentioned object of the present invention, the silver-containing 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.

[0039] According to any embodiment of the first aspect of the present invention, the type of the coating three is the same as the type of the silver-containing coating;

[0040] The types described here include only the material composition of the coating;

[0041] Alternatively, the type includes both the material composition and the dimensional characteristics of the coating.

[0042] According to any embodiment of the first aspect of the present invention, the type of the coating three is different from the type of the silver-containing coating;

[0043] For example, the third 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.

[0044] According to any embodiment of the first aspect of the present invention, the coating three 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% ; 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%; Including zinc and cobalt metal plating with a content of not less than 95wt%.

[0045] 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, 0.1-10 μm, 0.1-8 μm, 0.3-100 μm, 0.3-9 0μm, 0.3~30μm, 0.3~10μm, 0.3~8μm, 0.5~100μm, 0.5~90μm, 0.5~30μm, 0.5~10μm, 0.5~8μm, 0.7~100 μm, 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, 2.2~1 00μm, 2.2~90μm, 2.2~30μm, 2.2~10μm, 2.2~8μm, 2.5~100μm, 2.5~90μm, 2.5~30μm, 2.5~10μm, 2.5~8 μm, 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;

[0046] Preferably, the thickness of the coating three is not less than 0.1 μm, and preferably is 0.1-100 μm, 0.1-90 μm, 0.1-50 μm, 0.1-30 μm, 0.1-10 μm, 0.1-8 μm, and 0.1-5 μm, respectively.

[0047] According to any embodiment of the first aspect of the present invention, the thickness of the tin-containing coating does not exceed the thickness of the coating three.

[0048] According to any embodiment of the first aspect of the present invention, the thickness of the tin-containing coating can be selected from any value within the following ranges: 0.01-100 μm, 0.01-90 μm, 0.01-30 μm, 0.01-10 μm, 0.01-8 μm, 0.01-5 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- 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, 0.7~10 0μm, 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, 2.5~100μm, 2.5~90μm, 2.5~30μm, 2.5~10μm, 2.5~8 μm, 2.7~100μm, 2.7~90μm, 2.7~30μm, 2.7~10μm, 2.7~8μm, 3~100μm, 3~90μm, 3~30μm, 3~10μm, 3~8μm.

[0049] Preferably, the thickness of the tin-containing coating is not less than 0.1 μm, and is preferably 0.1-100 μm, 0.1-90 μm, 0.1-30 μm, 0.1-10 μm, 0.1-8 μm, 0.1-5 μm, 0.1-3 μm, 0.1-2 μm, and 0.1-1 μm, respectively.

[0050] According to any embodiment of the first aspect of the present invention, an intermediate coating film 1 is provided between the surface of the contact portion and the silver-containing coating film.

[0051] 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.

[0052] 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%.

[0053] 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, 0.1-100 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, 0.3-30 μm, 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, 1.2~90μm, 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, 1.7~100μm , 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, 2.2~100μm, 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, 2.5~5μm , 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.

[0054] According to any embodiment of the first aspect of the present invention, the surface of the substrate 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 copper terminal described in any embodiment of the first aspect of the present invention.

[0055] According to any embodiment of the first aspect of the present invention, the surface of the base of the extension portion has a plating film, and the plating film is the same as the "silver-containing plating film" of the contact portion of the copper terminal described in any embodiment of the first aspect of the present invention.

[0056] According to any embodiment of the first aspect of the present invention, the surface of the substrate of the extension portion has a coating, and the coating includes a second coating and an intermediate second coating located between the second coating and the surface of the substrate, and the second coating and the intermediate second coating are respectively the same as the "silver-containing coating" and "intermediate coating one" possessed by the contact portion of the copper terminal described in any embodiment of the first aspect of the present invention.

[0057] According to any embodiment of the first aspect of the present invention, the surface of the base of the extension portion has a coating, and the coating is the same as the "tin-containing coating" of the welding portion of the copper terminal described in any embodiment of the first aspect of the present invention.

[0058] According to any embodiment of the first aspect of the present invention, the surface of the base of the extension portion has a coating, and the coating is the same as the "coating three" possessed by the welding portion of the copper 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 surface of the substrate of the extension portion has a coating, and the coating includes a coating two and an intermediate coating two located between the coating two and the surface of the substrate, and the coating two and the intermediate coating two are respectively the same as the "coating three" and the "tin-containing coating" possessed by the welding part of the copper terminal described in any embodiment of the first aspect of the present invention.

[0060] A second aspect of the present invention provides a method for preparing a copper terminal having a silver-containing plating film and a tin-containing plating film, wherein the copper terminal comprises a contact portion, an extension portion and a welding portion connected in sequence, and is characterized in that the method comprises the steps of:

[0061] 1) Prepare the plating solution and the substrate to be plated of the copper terminal

[0062] The plated substrate has a metal surface; or

[0063] The plated substrate has a metal surface and an intermediate plated film covering the metal surface;

[0064] Wherein, the intermediate coating includes a tin-containing coating;

[0065] The plating solution contains graphene and other metallic silver;

[0066] The concentration of graphene in the plating solution is 0.1 to 100 g / L, calculated based on the weight of carbon;

[0067] The concentration of other metallic silver ions is 0.25 to 100 g / L;

[0068] The graphene includes stacked graphene sheets and silver located between the graphene sheets, and the silver includes silver ions and nano-sized silver particles;

[0069] 2) Electroplating the substrate using the plating solution.

[0070] Further, calculated by the weight of carbon, the concentration of graphene in the plating solution can be arbitrarily selected from any group of numerical ranges among 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.

[0071] According to any embodiment of the second aspect of the present invention, the content of graphene in the silver-containing film is not less than 3 at % calculated by carbon content based on the total number of atoms of the silver-containing film.

[0072] Furthermore, according to the total number of atoms of the silver-containing coating and calculated by carbon content, the content of graphene in the silver-containing coating can be arbitrarily selected from any numerical range of 3-50at%, 5-30at%, 5-20at%, 10-20at%, and 5-15at%.

[0073] 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.

[0074] 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%.

[0075] According to any embodiment of the second aspect of the present invention, the concentration of other metal ions silver in the plating solution can be arbitrarily selected from 0.1-100g / L, 0.25-100g / L, 1-100g / L, 5-100g / L, 10-100g / L, 20-100g / L, 30-100g / L, 40-100g / L, 50-100g / L, 60-100g / L, 70-100g / 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, Any one of the numerical ranges of 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, 40-60g / L, 50-60g / L, 0.1-40g / L, 0.25-40g / L, 1-40g / L, 5-40g / L, 10-40g / L, 20-40g / L, 30-40g / L, 0.1-20g / L, 0.25-20g / L, 1-20g / L, 5-20g / L, 10-20g / L.

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

[0077] 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 .

[0078] Preferably, the current density during electroplating is 0.1A / dm 2 ~40A / dm 2 .

[0079] According to any embodiment of the second aspect of the present invention, a copper terminal having a silver-containing plating film and a tin-containing plating film as described in any embodiment of the first aspect of the present invention can be prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] 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;

[0081] 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;

[0082] 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;

[0083] 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;

[0084] Figure 5 They are: the contact resistance measurement results of the connecting component (abbreviated as Cu-TC, Ag-Gr (Ag)) with a 0.3 μm thick Ag-Gr (Ag) film on the base material provided by specific embodiment 1-5 of the present invention, which has pure copper as the terminal; the contact resistance measurement results of the connecting component (abbreviated as Cu-Ni-Si, Ag-Gr (Ag)) with a 5 μm thick Ag-Gr (Ag) film on the base material provided by specific embodiment 1-1 of the present invention, which has a 5 μm thick Ag-Gr (Ag) film on the base material provided by specific embodiment 1-9 of the present invention, which has a 5 μm thick plating film (abbreviated as Cyan-Ag-Gr (Ag) film) using silver-containing graphene obtained by electroplating with a cyanide-containing silver plating solution on the base material (abbreviated as Cu-Sn-P, Cyan-Ag-Gr (Ag));

[0085] 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;

[0086] 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;

[0087] 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;

[0088] The contact resistance measurement results of the connection parts provided in Comparative Examples 1-7 of the present invention using the 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;

[0089] 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.

[0090] 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;

[0091] Figure 8The 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);

[0092] Fig. 9 : (a) is the Raman spectrum of the coating film (abbreviated as Sn-Gr film) without silver-infiltrated graphene provided in comparative example 2-1; (b) is the Raman spectrum of the coating film (abbreviated as Sn-Gr(Ag)-L film) using silver-infiltrated graphene (L-5%) provided in specific embodiment 2-1 of the present invention for the terminal;

[0093] Fig.10 : (a) XRD spectrum of the coating film (abbreviated as Pure-Sn film) without silver-infiltrated graphene provided for the terminal of comparative example 2-2 of the present invention; (b) XRD spectrum of the Sn-Gr film of the terminal provided for comparative example 2-1; (c) XRD spectrum of the Sn-Gr(Ag)-L film using silver-infiltrated graphene (silver content L-5%) of the terminal provided for specific embodiment 2-1 of the present invention; (d) XRD spectrum of the Sn-Gr(Ag)-H film using silver-infiltrated graphene (silver content H-10%) of the terminal provided for specific embodiment 2-2 of the present invention;

[0094] Fig.11 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;

[0095] Fig.12 :(a) is a terminal contact resistance and load curve provided in specific embodiments 2-1, 2-2 and comparative example 2-2 of the present invention; (b) is the 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;

[0096] Fig.13 Schematic diagram of the structure of silver-infiltrated graphene used in an embodiment of the present invention;

[0097] Fig.14 A schematic diagram of the main structure of a terminal provided by the present invention;

[0098] Fig.15A schematic diagram of a structure in which another terminal provided by the invention is combined with the matching terminal to form a terminal pair;

[0099] Fig.16 A schematic diagram of another structure of connecting a terminal to a printed circuit substrate P provided by the present invention;

[0100] Fig.17 A schematic diagram of the layer structure of another welding portion 130 of a terminal provided by the present invention;

[0101] Fig.18 : (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 ;

[0102] Fig.19 : (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

[0103] 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.

[0104] 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.

[0105] 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".

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111]

Copper terminal

[0112] The "copper terminal" provided by the present invention is also called a "plug terminal", refer to Figures 14 to 19 As shown, in terms of structural composition, the terminal 100 includes a base material and a surface coating located on the base material.

[0113] Reference again Fig.14As shown, in terms of specific structure, 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 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 applications; the welding portion 130 has a welding pin area 132, and the welding pin area 132 mentioned here refers to the part where the connection is achieved by welding, and the area 131 close to the printed circuit board. The welding portion 130 mainly realizes the electrical connection between the terminal 100 and the circuit board or the crimping wire through the welding pin area 132. The contact portion 110 actually serves as a plug-in component to achieve a stable connection with its matching matching terminal. The extension portion 120 is to cooperate with various different connectors to achieve the transition between the contact portion and the welding portion and the stable connection between the matching terminals. In fact Fig.14 This is only a schematic diagram of a terminal structure and is not limited to this structure.

[0114] The "copper terminal" provided by the present invention usually forms a complete set of terminal pairs with its matching terminals in practical applications. Fig.15 As shown, a typical matching terminal 200 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.16 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 a matching terminal 200 (not shown, see Fig.16 In addition, the soldering portion 130 of the terminal 100 disposed outside the cover portion 320 constitutes a soldering pin area 132 electrically connected to the printed circuit board P.

[0115] 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 14 to 19The terminal 100 includes a contact portion 110, an extension portion 120 and a welding portion 130 connected in sequence, the contact portion 110 includes a silver-containing plating a3, or includes a silver-containing plating a3 and an intermediate plating a2, the extension portion 120 includes a plating b3, or includes a plating b3 and an intermediate plating b2, and the welding portion 130 includes a plating c3 and a tin-containing plating c2.

[0116] The types of silver-containing coating a3, coating three c3, and coating two b3 can be the same, especially when considering the performance requirements such as high temperature resistance and conductivity, it is preferred that the silver-containing coatings a3, b3, and c3 are of the same type (as described in the [Silver-containing coating a3] section below). Of course, the types of silver-containing coatings a3, b3, and c3 may also be different. Such situations include: the silver-containing coating and coating two (a3 and b3) are of the same type, but coating three c3 is different from the type of silver-containing coating and coating two (a3 and b3); the silver-containing coating and coating three (a3 and c3) are of the same type, but coating two b3 is different from the type of silver-containing coating and coating three (a3 and c3); coating three and coating two (c3 and b3) are of the same type, but the type of silver-containing coating a3 is different from the type of coating three and coating two (c3 and b3); and the types of coating two and coating three (a3, b3, and c3) are all different.

[0117] Similarly, the types of intermediate coatings one, two, and tin-containing coatings (a2, b2, c2) may be the same or different, and the different situations include: intermediate coatings one and two (a2, b2) are of the same type, and the type of tin-containing coating c2 is different from that of intermediate coatings one and two (a2, b2); intermediate coating one and tin-containing coating (a2, c2) are of the same type, and intermediate coating two b2 is different from that of intermediate coating one and tin-containing coating (a2, c2); tin-containing coatings two (c2, b2) are of the same type, and intermediate coating one a2 is different from that of tin-containing coating two (c2, b2); the types of intermediate coatings one, two, and tin-containing coatings (a2, c2, b2) are all different. More specifically:

[0118]

Contact part 110

[0119] For the contact portion 110, its conductivity, stability, heat resistance and surface hardness are required to be higher than other parts. Fig.19 (a) The surface of the base material a1 of the contact portion 110 includes a silver-containing coating a3. Specifically, the silver-containing coating a3 of the contact portion 110 of the present invention has the following characteristics:

[0120] The main or characteristic component is "graphene infiltrated with silver", and the silver-containing coating provided by the present invention has a Raman spectrum at 500±30cm -1 Peak at 1330±30cm -1 Peak at 1550±30cm -1 The peak at 2800±30cm -1 In some embodiments of the present invention, according to the total number of atoms of the silver-containing film, calculated by carbon content, the content of "graphene infiltrated with silver" contained in the silver-containing film is not less than 1at%, preferably not less than 3at%, further preferably 3-50at%, and more preferably 5-30at%. It is further explained that the content of "graphene infiltrated with silver" in the "silver-containing film" is in the range of 3-50at%, and the influence on the conductivity and heat resistance of the silver-containing film can be basically ignored. The wear resistance trend line of the silver-containing film is obtained by fitting the experimental data, and the trend line changes basically linearly. In the following embodiments, silver-containing films with "graphene infiltrated with silver" contents of 8at% and 12at% are used to schematically illustrate the technical solution of the present invention.

[0121] On this basis, in some embodiments of the present invention, the "silver-containing coating" also includes another main or characteristic component other than "graphene infiltrated with silver", which is metal. As described herein, the "metal" does not include the "silver infiltrated in graphene", and the metal can be any one or a combination of two or more of silver, copper, iron, aluminum, tin, nickel, zinc, and cobalt. In some embodiments of the present invention, according to the total number of atoms of the silver-containing coating, the content of the metal contained in the silver-containing coating is not less than 40at%, and in theory, the sum of the content of the metal contained in the silver-containing coating as described herein and the content of the "graphene infiltrated with silver" contained in the aforementioned silver-containing coating should be infinitely close to 100at%, but in actual situations, the presence of some inevitable impurities cannot be ruled out, so the sum of the content of the metal contained in the silver-containing coating and the content of the "graphene infiltrated with silver" contained in the aforementioned silver-containing coating is in the range of 95at% to 100at%.

[0122] Regarding the “silver-infiltrated graphene”, it has a layered structure formed by stacked graphene sheets, with gaps between the layers, and the gaps form an effective space inside the graphene. The “silver between the graphene sheets” can be understood as the silver ions and nano-sized silver particles filled / dispersed in the effective space. Generally, silver ions and nano-silver particles (also called particles) exist at the same time. The “filling / dispersion” can be a small amount of local filling, or a large part of the filling, or all of the filling. Based on this, the “silver-infiltrated graphene” in the silver-containing coating provided by the present invention includes a body composed of stacked graphene sheets, and silver ions and nano-sized silver particles located between the graphene sheets. This is also the reason why the Raman spectrum of the silver-containing coating has 500±30cm -1 One of the key reasons for the peak.

[0123] In fact, the silver between the graphene sheets will affect the conductivity of the silver-containing coating. As for the "body composed of stacked graphene sheets", the bonding force between the layers of the graphene sheets is van der Waals force, and the carbon atoms in the layers are bonded by covalent bonds. Therefore, compared with the conductivity within the layer, the conductivity between the layers is poor, that is, it generally only has two-dimensional conductivity. The "silver-infiltrated graphene" in the silver-containing coating provided by the present invention, the silver ions and nano-sized silver particles "infiltrated" or "inserted" between the stacked graphene sheet structures, can effectively reduce the contact resistance between the layers of the graphene sheets, improve the conductivity between the layers of the graphene sheets, and then convert the two-dimensional conductivity between the stacked graphene sheets into three-dimensional conductivity. In particular, a silver-carbon bonding structure can be formed in the middle of the graphene sheet to realize silver-carbon interface-free conductivity or high conductivity path, thereby improving the heat generation of the connecting parts under high current operation and the high power loss caused by it.

[0124] In addition, the silver between the graphene sheets will increase the interlayer bonding force of the graphene sheets, and the interlayer bonding force of the graphene sheets will be further increased as the silver content increases, but it should be noted that too much silver will cause serious agglomeration of the graphene and make it unusable; therefore, in some embodiments of the present invention, according to the atoms of the "graphene infiltrated with silver" as the total number, the amount of silver between the graphene sheets is 0.1-50at%, and in some preferred embodiments of the present invention, according to the atomic percentage of the "graphene", the amount of silver between the graphene sheets is 0.1-45at%. It is further explained that the silver content in the "graphene infiltrated with silver" is in the range of 0.1-50at%, and the conductivity trend line of the "silver-containing coating" is obtained by fitting the experimental data, and the trend line changes basically linearly. In the following embodiments, the "graphene infiltrated with silver" with a silver content of 5at% is used to schematically illustrate the technical solution of the present invention.

[0125] In summary, the "silver-containing coating" provided by the present invention has a contact resistance of no more than 4 mΩ, a friction coefficient of no more than 0.4, and a Vickers hardness of no less than 130 HV. For example, if the silver-containing coating contains metallic silver and silver-infiltrated graphene, the "silver-containing coating" provided by the present invention can optimally have a contact resistance of no more than 0.7 mΩ, a friction coefficient of 0.1 to 0.4, and a Vickers hardness of more than 130 HV.

[0126] Furthermore, the thickness of the "silver-containing coating" can be selected from any numerical range within the range of 0.01 to 100 μm, or any numerical value.

[0127] In addition, from the perspective of further optimizing performance, refer to Fig.19 (b) The surface of the base material a1 of the contact portion 110 of the "copper terminal" provided by the present invention includes both a silver-containing coating a3 and an intermediate coating a2 located between the silver-containing coating a3 and the base material a1 of the contact portion. Specifically, the intermediate coating a2 of the contact portion 110 of the present invention has the following characteristics:

[0128] 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 "silver-containing coating" and the "substrate"; the third main function is to reduce the induced influence of the "substrate" on the crystal structure of the "surface coating" and improve the coating's all-plating ability. 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" in contact with it from entering the "surface coating" or diffusing to the surface of the "surface coating" under high temperature conditions to form an oxide film, resulting in an increase in contact resistance or a decrease in conductivity, that is, to improve 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.

[0129] 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, and an anti-diffusion layer. Based on this, the "intermediate coating-a2" can optionally meet any one or more of the following conditions Ⅰ) to Ⅷ):

[0130] Ⅰ) the “intermediate coating a2” comprises a metal content of not less than 95wt%;

[0131] II) the “intermediate coating a2” comprises an alloy having a content of not less than 95wt%;

[0132] III) the “intermediate coating a2” comprises a combination of metals and alloys with a content of not less than 95 wt %;

[0133] 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;

[0134] 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;

[0135] 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.

[0136] [Extension portion 120]

[0137] 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.18 (a) The surface of the base material b1 of the extension portion 120 includes a second coating b3. Specifically, the second coating b3 of the contact portion 120 of the present invention has the following characteristics:

[0138] Regarding the "film coating b3", one option is that it can be the same as the "silver-containing film coating a3" described in the present invention.

[0139] Another option is different from the "silver-containing coating a3", but can optionally meet any one or more of the following conditions Ⅰ) to Ⅷ): Ⅰ) the "coating b3" includes a metal content of not less than 95wt%;

[0140] II) the “coating b3” comprises an alloy having a content of not less than 95wt%;

[0141] III) the “coating b3” comprises a combination of metals and alloys with a content of not less than 95wt%;

[0142] 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;

[0143] 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;

[0144] It is worth mentioning that if the "film coating b3" is of the same type as the "silver-containing film 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 film shedding can be observed at the bending parts of the components. When the type of film 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 "silver-containing film 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 film shedding as much as possible. Therefore, the thickness of the "film 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.

[0145] In addition, from the perspective of further optimizing performance, refer to Fig.18(b) The surface of the base material b1 of the extension part 120 includes a second coating b3 and an intermediate coating b2 located between the second coating b3 and the base material b1 of the extension part 120. The features of the intermediate coating b2 of the extension part 120 described in the present invention are basically the same as those of the above-mentioned "intermediate coating a2", except that on the basis of the above, it is preferred that the maximum thickness of the "intermediate coating b2" is not more than 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 "intermediate coating" can be 0.5 μm, 1 μm, 1.5 μm or 2 μm.

[0146] 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.

[0147] [Welding section 130]

[0148] 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.17 The surface of the base material c1 of the welding part 130 includes a tin-containing coating c2 and a coating c3. Specifically, the coating c3 of the welding part 130 of the present invention has the following characteristics: one option is the same film type as the "silver-containing coating a3" of the present invention; another option is the same film type as the "coating c3" of the present invention;

[0149] 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 as the coating three c3 and the tin-containing coating c2 located between the coating three c3 and the base material c1, and the "tin-containing coating c2" preferably has as high a tin content as possible, such as a tin content of not less than 80wt% or 90wt%, while at the same time the tin content of the coating three c3 is lower than that of the tin-containing coating c2. On this basis, the maximum thickness of the "tin-containing coating c2" is recommended not to exceed 10μm, and the value range can be selected from any numerical range within the range of 0.01 to 5μm, or any numerical value, for example, the thickness of the "tin-containing coating c2" can be 0.5μm, 1μm, 1.5μm, 2μm or 5μm. The reason is that based on the above-defined tin content and thickness, the "tin-containing coating 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 solderability.

[0150] Meanwhile, the thickness of the coating c3 is greater than the thickness of the tin-containing coating c2, but the maximum thickness of the coating c3 is not recommended to exceed 50 μm. Based on this, the coating c3 can prevent the oxidation of the tin-containing coating c2, 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.

[0151] In addition, it is worth mentioning that during the welding process of the terminal 100 and the printed circuit substrate P, wave soldering or reflow soldering can generally be used. Taking the wave soldering process as an example, it includes four modules: flux spraying, preheating, welding, and cooling. The flux spraying process is mainly for spraying flux to improve the wettability of the pad, and there is no heat transfer process that affects the welding of the PCB and the terminal. Among them, the preheating temperature should reach 100-130°C (the preheating temperature is set to 110°C in the following specific embodiment), and its main function is to activate the flux. The assembly that reaches the preheating temperature enters the welding module with the conveyor belt; during welding, the temperature of the tin material in the tin tank (the tin material is SAC305 in the following specific embodiment) is 250-290°C (the solder temperature in the tin tank in the following specific embodiment is 280°C), and the wave peak height should reach 1 / 3-2 / 3 of the PCB thickness. Generally speaking, the wave soldering time is 3-10s (the welding time is set to 8s in the following specific embodiment). In actual research, it was found that the combined influence of various factors led to a higher soldering temperature of the tin or an increase in the terminal temperature difference, causing the lag time to increase to greater than the soldering time, especially for larger terminals. Based on this, it was found that the time lag problem of the soldering temperature can be solved by changing the terminal design. Based on this, reference Fig.14 or Fig.16 The welding portion 130 of the terminal 100 provided by the present invention further includes a welding pin area 132 and an area 131 close to the printed circuit substrate. Calculated by the weight of the base, the area 131 close to the printed circuit substrate is reduced compared to the extension portion 120. The "reduction" mentioned herein means that the volume and weight of the area 131 close to the printed circuit substrate are reduced, the heat transfer and temperature rise rate of the welding pin area 132 are increased, and the time lag problem of reaching the welding temperature is shortened. Based on this, the reduction can be achieved as follows Fig.14 As shown, compared with the base of the extension portion 120 , the base of the region 131 close to the printed circuit substrate has a hollow structure 133 , or, compared with the base of the extension portion, the base of the region close to the printed circuit substrate has a reduced thickness and / or reduced width design.

[0152]

Base of copper terminal

[0153] Regarding the base material of the "copper terminal" (including a1, c1, b1), copper and copper alloys that can be listed 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%).

[0154]

Method for preparing copper terminals

[0155] Pretreatment of the "base material" of the copper 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".

[0156] 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.

[0157] Making "silver-containing coatings a1, b1, c1 (hereinafter collectively referred to as coatings)": making coatings on the surface of the "substrate" or making coatings on the surface of the "intermediate coating"; the "coatings" are mainly formed by the "electroplating" method.

[0158] The "electroplating" includes the following steps 1) and 2) :

[0159] 1) Prepare the plating solution and substrate

[0160] The plating solution includes components for forming a coating; for example, if the coating is a "silver-containing coating", the "components for forming a coating" at least include "graphene infiltrated with silver", and may also contain other metals on this basis; for example, if the coating is a "metal coating" different from a "silver-containing coating", the "components for forming a coating" mainly refer to at least including the corresponding metal;

[0161] The substrate has a metal surface; or the substrate has a metal surface and an intermediate coating covering the metal surface;

[0162] 2) Electroplating the substrate using the plating solution. The detailed operation of the electroplating for reference is as follows:

[0163] 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.

[0164] On the basis of the aforementioned “electroplating” steps 1) and 2), the preparation of the “silver-containing coating” is further described in detail as an illustrative example: during the electroplating process, the plating solution (i.e., plating solution one) contains “graphene infiltrated with silver”, or contains other metals besides silver at the same time. Among them, the “graphene infiltrated with silver” also has a layered structure formed by stacked graphene sheets, and there are gaps between the 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) will 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.13 ). 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.

[0165] 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;

[0166] 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.

[0167] 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.

[0168] The orientation of the "laminated graphene sheets" in the "silver-containing coating" provided by the present invention is not specially set, and can be arranged perpendicularly, parallel, tilted or randomly oriented to the substrate according to the required characteristics of the component.

[0169] Finally, the "copper terminal with silver-containing plating and tin-containing plating" provided by the present invention is mainly used in electrical connections, such as vehicle-mounted terminals and electrical contacts, and has excellent conductivity, wear resistance and heat resistance.

[0170] The detection instruments (or models) and conditions used in the following specific embodiments are:

[0171] Surface morphology: The surface states of various target objects were investigated by field effect scanning electron microscopy (FE-SEM) (JEOL-JSM_7800F, 5 kV,).

[0172] 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).

[0173] 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).

[0174] 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).

[0175] Elemental analysis: The elemental analysis in the depth direction was studied by glow discharge luminescence GD-OES measurement. (Equipment name: glow discharge luminescence surface analyzer (HORIBA-GD-profiler 2-MN), measurement area: diameter 8mm, flowing gas: nitrogen).

[0176] 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).

[0177] 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.

[0178] 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).

[0179] 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:

[0180] Preheating zone: heating rate 2℃ / s, temperature range from room temperature to 150℃, residence time 63s;

[0181] Constant temperature zone: the temperature zone is 150℃~200℃, and the residence time is 100s;

[0182] Reflow zone: temperature 190℃, residence time 60s; temperature 200℃, residence time 30s; temperature 220℃~250℃, residence time 60s;

[0183] Cooling zone: cooling rate 3℃ / s, cooling to 75℃.

[0184] 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.

[0185] 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.

[0186] Example series one

[0187] The silver-containing coating a3 includes metallic silver and graphene infiltrated with silver, and more detailed information is as follows:

[0188] 1) About the plating solution used

[0189] Basic electroplating solution-1: A commercially available cyanide-free silver plating solution (model PRECIOUSFAB Ag4730, Ag concentration 30 g / L, reference website https: / / www.tanaka.com.cn / products / detail / plating-processes / ) from Tanaka Precious Metals Co., Ltd. was used as the basic electroplating solution;

[0190] 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 coating can be formed on the substrate to be plated;

[0191] 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. Considering 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 based on 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 about 9.6wt%). Based on the "electroplating solution-1 containing silver-infiltrated graphene", an Ag-Gr (Ag) plating film can be formed on the plated substrate;

[0192] 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. The final plating solution is formed, 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 the aqueous solution. Based on the "Comparative plating solution-1", an Ag-Gr film can be formed on the plated substrate;

[0193] 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 / ) of Tanaka Precious Metals Co., Ltd. is used as a basic solution; based on the “basic electroplating solution-2”, a Cyan-Pure-Ag plating film can be formed on the plated substrate;

[0194] 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%).

[0195] 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;

[0196] 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 according to the aqueous solution, the concentration of silver-infiltrated graphene in this plating solution is 100g / L (equivalent to a concentration of about 9.6wt%). Based on the "Comparative plating solution-3", a Cyan-Ag-Gr coating can be formed on the plated substrate;

[0197] 2) Regarding the conditions for electroplating

[0198] The current density is controlled at 0.1~10A / dm 2 ; Plating solution temperature 50℃; 500rpm magnetic stirring method is used during electroplating.

[0199] 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;

[0200] 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.

[0201] Based on the above, the connection terminal 100 provided in this series of embodiments adopts Fig.14 In the structure described above, the base material of the terminal 100 is selected from 6 kinds of 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%).

[0202] 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 a silver-containing plating a3, the extension portion 120 has only a second plating b3, the welding portion 130 has only a third plating c3, ​​and the silver-containing plating a3, the second plating b3 and the third plating c3 are the same;

[0203] 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 silver-containing 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 a tin-containing coating c2, and the coating b3 and the coating c3 are of the same type as the silver-containing coating a3, and the intermediate coating a2 and the intermediate coating b2 are of the same type as the tin-containing coating c2. Specific embodiment 1-14 uses electroplating to produce intermediate coatings one and two, and tin-containing coatings (a2, b2, c2) with a thickness of 1 μm mainly composed of metal Sn on the surface of the metal substrate. Specific embodiment 1-15 uses electroplating to produce intermediate coatings one and two, and tin-containing coatings (a2, b2, c2) with a thickness of 1 μm mainly composed of metal Ni on the surface of the metal substrate.

[0204] Table 1-1. Basic description of specific embodiments of this embodiment series 1

[0205]

[0206] Note that the total number of atoms in the coating is calculated based on the carbon content:

[0207] Coating type Ag-Gr (Ag), current density 0.5A / dm 2 When, the content of silver-infiltrated graphene in the silver-containing coating a3 obtained in Example is 12at%;

[0208] Coating type Ag-Gr (Ag), current density 1A / dm 2 When, the content of silver-infiltrated graphene in the silver-containing coating a3 obtained in Example is 11 at %;

[0209] Coating type Ag-Gr (Ag), current density 2A / dm 2 When, the content of silver-infiltrated graphene in the silver-containing coating a3 obtained in Example is 10at%;

[0210] Coating type Ag-Gr (Ag), current density 4~8A / dm 2 When, the content of silver-infiltrated graphene in the silver-containing coating a3 obtained in Example is 8at%;

[0211] Coating type Cyan-Ag-Gr-Ag, current density 1A / dm 2 When the content of silver-infiltrated graphene in the silver-containing coating a3 obtained in Example 1 is 12 at %.

[0212] 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 of the present invention only has a silver-containing coating a3, the extension portion 120 only has a second coating b3, and the welding portion 130 only has a third coating c3, ​​and the second coating b3 and the third coating c3 are both the same as the silver-containing coating a3.

[0213] 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 a silver-containing 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 a tin-containing coating c2, and the coating b3 and the coating c3 are the same as the silver-containing coating a3, and the intermediate coating a2 and the intermediate coating b2 are the same as the tin-containing coating c2. Comparative example 1-13 uses electroplating to produce intermediate coatings one and two, and tin-containing coatings (a2, b2, c2) with a thickness of 1 μm mainly composed of metal Sn on the surface of the metal substrate. Comparative example 1-14 uses electroplating to produce intermediate coatings one and two, and tin-containing coatings (a2, b2, c2) with a thickness of 1 μm mainly composed of metal Ni on the surface of the metal substrate.

[0214] In addition, comparative examples 1-15 to 1-18 are provided:

[0215] 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, with the only difference being that the thickness of the coating film b3 of the extension portion 120 is 15 μm.

[0216] 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: (1) the coating b3 thickness of the extension portion 120 is 15 μm, and (2) the film type is the same as that of the specific embodiment 1-14.

[0217] 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, with the only difference being that the thickness of the intermediate coating film b2 of the extension portion 120 is 5 μm.

[0218] 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: (1) the thickness of the intermediate coating b2 of the extension portion 120 is 5 μm, (2) the thickness of the coating b3 of the extension portion 120 is 15 μm, and (3) the film type is the same as that of the specific embodiment 1-14.

[0219] And comparative examples 1-19 to 1-22 are provided:

[0220] 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 film c3 of the welding portion 130 is 70 μm;

[0221] 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 tin-containing plating film c2 of the welding portion 130 has a thickness of 15 μm, and the film type is the same as that of the specific embodiment 1-14;

[0222] The contact portion 110 of the terminal 100 of the comparative example 1-21 is arranged the same as that of the specific embodiment 1-14, and the extension portion 120 of the terminal 100 of the comparative example 1-21 is arranged the same as that of the specific embodiment 1-14, with the only difference being that the welding portion 130 is no longer reduced in size, i.e. the hollow structure 133 is replaced by the substrate, i.e. the coating.

[0223] The contact portion 110 of the terminal 100 of the comparative example 1-22 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 1-22 is configured the same as that of the specific embodiment 1-14, with the only difference being that the type of the coating c3 of the welding portion 130 is the same as that of the comparative example 1-1.

[0224] Table 1-2. Basic information of the comparative examples of the first embodiment

[0225]

[0226] Note that the total number of atoms in the coating is calculated based on the carbon content:

[0227] Coating type Ag-Gr, current density 0.5A / dm 2 When , the graphene content in the silver-containing coating of the comparative example is 12at%;

[0228] Coating type Ag-Gr, current density 1A / dm 2 When , the graphene content in the silver-containing coating of the comparative example is 11 at %;

[0229] Coating type Ag-Gr, current density 2A / dm 2 When the graphene content in the silver-containing coating of the comparative example is 10at%;

[0230] Coating type Ag-Gr, current density 4~8A / dm 2 When , the graphene content in the silver-containing coating of the comparative example is 8at%;

[0231] Coating type Cyan-Ag-Gr, current density 1A / dm 2 When the graphene content in the silver-containing coating of the comparative example is 12 at %.

[0232] 2) Performance test of the terminal 100

[0233] 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.

[0234] 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 1Translucent and opaque flakes were observed in both (b) and were identified as carbon substances derived from graphene by EDS analysis.

[0235] 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.

[0236] 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.

[0237] 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.

[0238] 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).

[0239] 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.

[0240] 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.

[0241] 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.

[0242] from Figure 3 It 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.

[0243] 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.

[0244] 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.

[0245] 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.

[0246] 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.

[0247] 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.

[0248] 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.

[0249] 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 film 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.

[0250] In addition, from Figure 5It 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.

[0251] in addition, Figure 5 The 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.

[0252] 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.

[0253] 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.

[0254] In addition, from Figure 6It can also be seen that the terminal 100 of the coating containing silver-infiltrated graphene (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 of the coating containing ordinary graphene (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 silver-containing 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 silver-containing coating a3.

[0255] (2) Influence of copper substrate and intermediate plating: 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 substrate terminals, which are automotive terminal materials, but also uses Cu-Be-Ni, Cu-Te, and brass Cu-Zn as substrate terminals for high-speed charging components that require both electrical conductivity and machinability.

[0256] 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.

[0257] 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.

[0258] 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.

[0259] 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.

[0260] The hardness variation of the terminal 100 in the specific embodiment 1-15 using the Ni intermediate coating is the same as that of the copper alloy substrate material. However, the hardness of the terminal 100 in the specific embodiment 1-14 using the Sn intermediate coating is significantly increased to 190HV (close to the terminal with an ordinary silver alloy electroplating film). 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.

[0261] 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.

[0262] like Figure 8 As shown, the change in contact resistance of the terminal 100 (having a 5μm thick Ag-Gr (Ag) silver-containing plating) of 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.

[0263] 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 generally recrystallize to increase the grain size and reduce the grain boundary 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 silver-containing coating, second and third) of the terminal 100 and the base material.

[0264] 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.

[0265] Table 1-3. Basic information of the embodiment series 1 and comparative examples 1-13 to 1-18

[0266] 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

[0267] Tables 1-4 below 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 board 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 good weldability; 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 at the weld, it indicates that the weldability is poor.

[0268] Table 1-4. Basic information of the first embodiment and comparative examples 1-19 to 1-20

[0269] 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

[0270] In addition, the temperature of the terminal 100 at the area 131 (0.7 mm from the upper surface of the printed circuit substrate P) close to the printed circuit substrate provided in the specific embodiments 1-14, the temperature at the same position in the comparative examples 1-21, and the temperature at the same position in the comparative examples 1-22 were tested and found to be:

[0271] (1) The time for the terminal of comparative example 1-21 to reach 250°C lags by 1.13s relative to the terminal of specific embodiment 1-14. This indicates that the terminal of specific embodiment 1-14 has a better solder creeping effect during soldering. The addition of the hollow structure 133 of the area 131 of the terminal 100 close to the printed circuit substrate ensures that the heat of the soldering part 130 is concentrated during soldering, making it easier to achieve good soldering of terminals of different sizes at the same time.

[0272] (2) The time for the terminal of comparative example 1-22 to reach 250°C lags by 0.8s relative to the terminal of specific embodiment 1-14. This indicates that the terminal of specific embodiment 1-14 has a better creeping tin effect when being welded, because compared with the Ag-Gr film, the Ag-Gr (Ag) film contains silver-infiltrated graphene sheets, which realizes the "penetration" of silver particles and silver ions in the graphene sheets. The silver (silver particles, silver ions) added between the graphene sheets by "penetration" eventually transforms the two-dimensional heat conduction between the stacked graphene sheets into three-dimensional heat conduction, which can improve the creeping tin effect of the terminal when being welded.

[0273] Example series 2

[0274] 1) About the substrate used

[0275] 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 2-1 and the specific embodiment 2-2 of this series of embodiments and the comparative example 2-1 and the comparative example 2-2, the same copper alloy Cu-Ni-Si is used as the metal matrix material (same as the embodiment series 1);

[0276] The contact portion 110 of the terminal 100 prepared in the specific embodiments 2-1 and 2-2 has only the silver-containing plating a3, the extending portion 120 has only the plating b3, the welding portion 130 has only the plating c3, ​​and the silver-containing plating a3, the plating b3 and the plating c3 are the same;

[0277] The contact portion 110 of the terminal 100 prepared in comparative examples 2-1 and 2-2 has only a silver-containing plating film, the extension portion 120 has only a second plating film, and the welding portion 130 has only a third plating film, and the silver-containing plating film, the second plating film and the third plating film are the same.

[0278] 2) About the plating solution used

[0279] Basic electroplating solution: Bright sulfate Sn plating solution is used as the basic liquid, with a Sn concentration of 30g / L;

[0280] Based on the “basic electroplating solution”, a Pure-Sn plating film can be formed on a substrate to be plated.

[0281] 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%.

[0282] Based on the "electroplating solution L containing silver-doped graphene", a Sn-Gr(Ag)-L film can be formed on the plated substrate.

[0283] 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%.

[0284] Based on the "electroplating solution H containing silver-doped graphene", a Sn-Gr(Ag)-H film can be formed on the plated substrate.

[0285] 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;

[0286] 3) The conditions for electroplating are the same as those in Example 2

[0287] In addition, by adjusting the current density and the electroplating time, a Sn-Gr (Ag) film, a Sn-Gr film, and a Pure-Sn film with a thickness of 5 μm were obtained, as shown in Table 4.

[0288] Table 4. Basic information of specific examples and comparative examples of this embodiment series 3

[0289]

[0290] Note: The "carbon content at %" of specific embodiments 2-1 and 2-2 in the table represents the content of the silver-infiltrated graphene calculated based on the total number of atoms of the coating film and the carbon content.

[0291] The "carbon content at %" of Comparative Example 2-1 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.

[0292] 4) About performance testing

[0293] Raman determination: Fig. 9 As shown, the Sn-Gr(Ag)-L film ( Fig. 9 (b)), the Sn-Gr film of the terminal 100 of Comparative Example 2-1 ( Fig. 9 (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).

[0294] In addition, a 500 cm -1 Nearby peaks.

[0295] XRD determination: Fig.10 As 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 2-1 and 2-2, the Sn-Gr(Ag)-L film of the terminal 100 of the specific embodiment 2-1 and the Sn-Gr(Ag)-H film of the terminal 100 of the specific embodiment 2-2 have better crystal structure stability, that is, better heat resistance.

[0296] Conductivity (contact resistance) detection: combined Fig.11 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;

[0297] 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 through "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.

[0298] However, in general, the terminal 100 having the Ag—Gr (Ag) plating film has a significantly lower contact resistance than the terminal 100 having the Sn—Gr (Ag) plating film.

[0299] 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.12 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.

[0300] Fig.12 (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.

[0301] Fig.12 (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.

[0302] 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 copper terminal having a silver-containing plating film and a tin-containing plating film, wherein the copper terminal comprises a substrate and a plating film located on the surface of the substrate, It is characterized in that The copper content of the copper terminal is not less than 60wt% The terminal comprises a connected contact portion and a welding portion; The surface of the substrate of the contact portion has a silver-containing coating; The surface of the substrate of the welding part has a coating film three, and a tin-containing coating film located between the surface of the substrate and the coating film three; Wherein, the thickness of the tin-containing coating is 0.01 to 10 μm, and the tin content is not less than 80 wt%; The silver-containing coating includes graphene and other metals, and the other metals include silver; Taking the atoms of the silver-containing coating as the total number and calculating the carbon content, the content of graphene included in the silver-containing coating is 1 to 30 at%, the content of other metallic silver included is not less than 40 at%, and the sum of the content of other metallic silver and the graphene is 95 to 100 at%; The graphene includes stacked graphene sheets and silver located between the graphene sheets, and the silver includes silver ions and nano-sized silver particles.

2. The copper terminal having a silver-containing plating film and a tin-containing plating film according to claim 1, It is characterized in that The terminal further comprises an extension portion, and the extension portion is used to connect the contact portion and the welding portion; The welding portion includes a welding pin area and an area close to the printed circuit substrate; Calculated by the weight of the base body, the area close to the printed circuit substrate is reduced in weight compared to the extension portion.

3. The copper terminal having a silver-containing plating film and a tin-containing plating film according to claim 2, It is characterized in that The reduction includes: compared with the base of the extension portion, the base of the area close to the printed circuit substrate has a hollow structure; Alternatively, compared with the base of the extension portion, the base in the area close to the printed circuit substrate has a reduced thickness and / or reduced width design.

4. The copper terminal having a silver-containing plating film and a tin-containing plating film according to any one of claims 1 to 3, It is characterized in that Taking the atoms of the silver-containing film as the total number and calculating the carbon content, the content of graphene in the silver-containing film is 5 to 20 at %, preferably 5 to 15 at %.

5. The copper terminal having a silver-containing plating film and a tin-containing plating film according to claim 4, 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 %.

6. The copper terminal having a silver-containing plating film and a tin-containing plating film according to claim 4, It is characterized in that The type of the coating three is the same as the type of the silver-containing coating.

7. The copper terminal having a silver-containing plating film and a tin-containing plating film according to claim 4, It is characterized in that The type of the coating three is different from the type of the silver-containing coating; The third 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.

8. The copper terminal having a silver-containing plating film and a tin-containing plating film according to claim 6 or 7, It is characterized in that The thickness of the silver-containing coating is 0.01-100 μm, preferably 0.1-30 μm.

9. The copper terminal having a silver-containing plating film and a tin-containing plating film according to claim 6 or 7, It is characterized in that The thickness of the coating three is 0.1-50 μm, preferably 0.1-10 μm.

10. The copper terminal having a silver-containing plating film and a tin-containing plating film according to claim 9, It is characterized in that The thickness of the tin-containing coating does not exceed the thickness of the coating three.

11. The copper terminal having a silver-containing plating film and a tin-containing plating film according to claim 10, It is characterized in that The thickness of the tin-containing plating film is 0.01-5 μm.

12. A method for preparing a copper terminal having a silver-containing plating film and a tin-containing plating film, wherein the copper terminal comprises a contact portion and a welding portion. It is characterized in that Includes steps: 1) Prepare the plating solution and the substrate to be plated of the copper terminal; The plated substrate has a metal surface; or The plated substrate has a metal surface and an intermediate plated film covering the metal surface; Wherein, the intermediate coating includes a tin-containing coating; The plating solution contains graphene and other metallic silver; The concentration of graphene in the plating solution is 0.1 to 100 g / L, calculated based on the weight of carbon; The concentration of other metallic silver ions is 0.25 to 100 g / L; The graphene includes stacked graphene sheets and silver located between the graphene sheets, and the silver includes silver ions and nano-sized silver particles; 2) Electroplating the substrate using the plating solution.

13. The method for preparing a copper terminal having a silver-containing plating film and a tin-containing plating film according to claim 112, It is characterized in that In step 2), the current density during electroplating is 0.1A / dm 2 ~100A / dm 2 Preferably, the current density is 0.1A / dm 2 ~40A / dm 2 .

Images