Multifunctional composite layer and aluminum terminal

Abstract

Provided in the present disclosure are a multifunctional composite layer and an aluminum terminal. The multifunctional composite layer comprises a surface layer and a bottom layer, the material of the surface layer being gold, silver, palladium, nickel, platinum, tin, zinc or alloy thereof; the bottom layer comprises at least two layers of a copper layer prepared by alkaline copper electroplating, a copper layer prepared by copper pyrophosphate electroplating, an electroless copper plated layer, an electroless nickel plated layer and a nickel aminosulfonate layer, preferably, the thickness of the copper layer prepared by alkaline copper electroplating being 0.5-15 μm, the thickness of the copper layer prepared by copper pyrophosphate electroplating being 2-20 μm, the thickness of the electroless copper plated layer being 2-30 μm, the thickness of the electroless nickel plated layer being 2-30 μm, the thickness of the nickel aminosulfonate layer being 0.5-30 μm, and the thickness of the surface layer being 0.2-35 μm. Further provided in the present disclosure are an aluminum terminal provided with the multifunctional composite layer. The bottom layer of the multifunctional composite layer has excellent resistance to salt-spray corrosion, and the surface layer thereof has excellent conductivity, wear resistance, brightness, weldability, etc. on the basis of the properties of its metal layers.

Description

A multifunctional composite layer and aluminum terminal

[0001] Related applications

[0002] This application claims priority to the Chinese invention patent application with application number 202310934938.X filed on July 27, 2023, and cites the entire contents disclosed in the above patent application as part of this application. Technical Field

[0003] The present disclosure relates to a multifunctional composite layer and an aluminum terminal, belonging to the technical field of conductive materials. Background Art

[0004] Aluminum and its alloys are widely used in power transmission systems in the military, automotive, aerospace and other industries due to their low density, high conductivity and good formability.

[0005] Aluminum and its alloys have the following chemical properties: 1. They readily oxidize in air, forming an oxide film that significantly increases terminal resistance and affects power transmission. 2. Aluminum's standard electrode potential is -1.662V, making it susceptible to potential corrosion when connected to other metals with higher standard electrode potentials (such as copper), resulting in connection failure and, in severe cases, short circuits. The limited corrosion resistance of aluminum and its alloys in corrosive environments has limited their further application.

[0006] Current electroplating, chemical plating, spraying, laser surface treatment and other processes can protect the substrate by coating a film layer on the surface of aluminum and its alloys. However, the results of salt spray resistance tests are not ideal. The salt spray time of common aluminum workpieces can only last for 48 hours before corrosion occurs, which greatly limits the service life of the aluminum workpiece in the assembly.

[0007] Current electroplating manufacturers have done little research and development on aluminum electroplating processes. They only perform secondary zinc deposition followed by nickel plating to proceed to the next electroplating step. The choice of plating solutions varies and the effects are average, making it difficult to meet the requirements for electroplating of highly corrosion-resistant aluminum workpieces, especially for aluminum workpieces used in harsh environments in military, aerospace, automotive and other fields.

[0008] Summary of the Invention

[0009] In order to solve the above technical problems, the purpose of the present disclosure is to provide a multifunctional composite layer that can obtain excellent corrosion resistance through a corrosion-resistant base layer to meet the corrosion resistance requirements of the workpiece in various situations.

[0010] To achieve the above-mentioned object, the present disclosure first provides a multifunctional composite layer, wherein the multifunctional composite layer comprises a surface layer and a bottom layer;

[0011] The surface layer is made of gold, silver, palladium, nickel, platinum, tin, zinc or their alloys;

[0012] The bottom layer comprises at least two layers of an alkaline copper layer, a burnt copper layer, an electroless copper plating layer, an electroless nickel plating layer, and a nickel sulfamate layer;

[0013] in:

[0014] The thickness of the alkaline copper layer is 0.5-15 μm;

[0015] The thickness of the charred copper layer is 2-20 μm;

[0016] The thickness of the chemical copper plating layer is 2-30 μm;

[0017] The thickness of the chemical nickel plating layer is 2-30 μm;

[0018] The thickness of the nickel sulfamate layer is 0.5-30 μm;

[0019] The thickness of the surface layer is 0.2-35 μm.

[0020] In the above-mentioned multifunctional composite layer, the bottom layer is arranged between the substrate and the surface layer. The bottom layer can be at least two layers of an alkali copper layer, a calcined copper layer, an electroless copper layer, an electroless nickel layer, and a nickel sulfamate layer, and the order of each layer can be arbitrarily set. The combination of two layers is, for example, an alkali copper layer + calcined copper layer, an alkali copper layer + an electroless copper layer, an alkali copper layer + an electroless nickel layer, an alkali copper layer + an electroless nickel layer, a calcined copper layer + an electroless copper layer, a calcined copper layer + an electroless nickel layer, a calcined copper layer + an electroless nickel layer, an electroless copper layer + an electroless nickel layer, an electroless copper layer + an electroless nickel layer, and an electroless nickel layer + an electroless nickel layer. The upper and lower order of the two layers in each combination can be arbitrary.

[0021] In the above-mentioned multifunctional composite layer, the bottom layer illustratively includes at least three layers of an alkaline copper layer, a burnt copper layer, an electroless copper layer, an electroless nickel layer, and a nickel sulfamate layer. The bottom layer can be a combination of three layers, a combination of four layers, or even a combination of five layers, wherein:

[0022] Combinations of three layers include, for example, alkaline copper layer + charred copper layer + chemically plated copper layer, alkaline copper layer + charred copper layer + chemically plated nickel layer, alkaline copper layer + charred copper layer + nickel sulfamate layer, alkaline copper layer + chemically plated copper layer + chemically plated nickel layer, alkaline copper layer + chemically plated copper layer + nickel sulfamate layer, charred copper layer + chemically plated copper layer + chemically plated nickel layer, charred copper layer + chemically plated copper layer + nickel sulfamate layer, charred copper layer + chemically plated nickel layer + nickel sulfamate layer, and chemically plated copper layer + chemically plated nickel layer + nickel sulfamate layer. The order of the three layers in each combination can be arbitrary.

[0023] Combinations of four layers include: alkaline copper layer + charred copper layer + chemical copper layer + chemical nickel layer, alkaline copper layer + charred copper layer + chemical copper layer + nickel sulfamate layer, alkaline copper layer + charred copper layer + chemical nickel layer + nickel sulfamate layer, alkaline copper layer + chemical copper layer + chemical nickel layer + nickel sulfamate layer, charred copper layer + chemical copper layer + chemical nickel layer + nickel sulfamate layer, and the order of the four layers in each combination can be arbitrary.

[0024] The combination of the five layers is an alkaline copper layer, a burnt copper layer, an electroless copper layer, an electroless nickel layer, and an aminosulfonic acid nickel layer. The order of the five layers can be arbitrary.

[0025] In the multifunctional composite layer, the thickness of the alkaline copper layer is illustratively 1-10 μm, further illustratively 1-6 μm, and further illustratively 2-4 μm. As an excellent base coating, the alkaline copper layer has good adhesion to a substrate (e.g., an aluminum substrate) and can be produced using cyanide electroplating. This coating has good density and can effectively increase its corrosion resistance. It is particularly suitable for base coatings in electronic devices, such as Damascus copper interconnects in PCBs and chips.

[0026] In the above multifunctional composite layer, the thickness of the pyrophosphate layer is 2-18 μm, 5-15 μm, and 8-10 μm, respectively. The pyrophosphate layer is generally obtained by electroplating copper pyrophosphate. Pyrophosphate has a stronger complexing ability in water than cyanide, and the cathodic polarization effect in the pyrophosphate system is also stronger. This is because [Cu(P2O7)2] 6- The more negative charges it carries, the greater the impact on the cathode process. At the same time, [Cu(P2O7)2] 6- Difficult to discharge, needs to be hydrolyzed into [CuP2O7] 2- To discharge and deposit the copper layer, [CuP2O7] 2- The hydrolysis of copper is slow, thus increasing the cathodic polarization again. The copper electroplated film is denser and less porous, which can effectively prevent the penetration of chloride ions in salt spray tests. As a bottom coating, it can greatly enhance the corrosion resistance of the workpiece.

[0027] In the above-mentioned multifunctional composite layer, illustratively, the thickness of the chemical copper plating layer is 3-28 μm, more illustratively 5-15 μm, further illustratively 8-15 μm, and further illustratively 9-13 μm. The chemical copper plating layer is obtained by chemical plating, specifically relying on its spontaneous chemical reaction to deposit copper ions, without involving interference from factors such as current, that is, the chemical copper plating layer has almost no internal stress generated by electroplating, has good bonding strength and the coating thickness is very uniform. The chemical copper plating layer in a high-phosphorus environment has an amorphous structure, the coating is fine and has low porosity, and has excellent corrosion resistance. Adding this layer in the present disclosure can enhance the corrosion resistance of the overall coating.

[0028] In the above-mentioned multifunctional composite layer, illustratively, the thickness of the chemical nickel plating layer is 3-28 μm, more illustratively 4-18 μm, further illustratively 4-15 μm, and further illustratively 10-15 μm. The chemical nickel plating layer is obtained by chemical nickel plating. Under the action of the catalyst iron ion, the hypophosphite in the solution catalyzes dehydrogenation to form an active hydride, which undergoes a reduction reaction with the nickel ions in the solution, thereby chemically depositing nickel onto the surface of the workpiece to form a chemical nickel plating layer. The thickness of the nickel layer deposited by the chemical reaction is very uniform, and because there is no additional current, it is not affected by the current size and the tip discharge effect. There is no internal stress generated by electroplating between the chemical nickel plating layer and the workpiece, and stress-free is truly achieved. In general, the electroplating layer will cause the release of internal stress between the coating and the substrate during temperature changes, making the coating under electroplating more easily torn and losing its protective effect on the workpiece. Electroless nickel is a chemically deposited layer. Since it has no internal stress, it only experiences tensile stress during temperature shock tests. Compared to other electroplated coatings, it is subjected to less stress and is less likely to tear due to stress. It can withstand the effects of temperature shock and effectively block chloride ion penetration and prevent corrosion in salt spray tests. Meanwhile, during the deposition process of conventional electroplated films, hydrogen evolution occurs as a side reaction. The generation and overflow of hydrogen leaves microscopic pores in the nickel layer, so the amount of hydrogen evolution directly affects the density of the film. Since electroless nickel plating is a simple chemical reaction, it does not involve the effects of current density and hydrogen atom overpotential on its reaction. The hydrogen produced by the side reaction is far less than that of electroplated nickel layers. Therefore, the porosity of the electroless nickel layer is lower, its density is better, and it can more effectively block chloride ion penetration, greatly improving the corrosion resistance of the workpiece.

[0029] In the multifunctional composite layer, the thickness of the nickel sulfamate layer is illustratively 3-28 μm, more illustratively 4-15 μm, and further illustratively 6-9 μm. The nickel sulfamate layer is generally obtained by electroplating, with nickel sulfamate as the main salt and nickel chloride as the anode depolarizer. The nickel layer electroplated in this solution system has good ductility. Compared with other electroplated nickel layers, the film layer electroplated with nickel sulfamate is more resilient and has lower internal stress. It can withstand tensile stress in an environment with rapid temperature changes without being torn, and still maintains its original density. It can effectively protect the workpiece from corrosion in salt spray tests.

[0030] In the above-mentioned multifunctional composite layer, for example, the zinc layer, the secondary zinc deposition layer, the alkaline copper layer, the char copper layer, the aminosulfonic acid nickel layer, the chemical nickel plating layer, and the chemical copper plating layer are respectively the bottom plating layers; and, in the multifunctional composite layer composed of several layers of the above-mentioned various layers, the thickness of each layer can be combined as needed.

[0031] For the multifunctional composite layer provided by the present invention, other functional layers are added on the basis of the corrosion-resistant material to meet the various performance requirements of the workpiece under different use environments, and other properties can be extended to obtain a corrosion-resistant multifunctional composite layer.

[0032] In the above-mentioned multifunctional composite layer, the surface layer is a functional coating located on the surface of the bottom layer, and the material of the surface layer is gold, silver, palladium, nickel, platinum, tin, zinc or their alloys, that is, the surface layer can be a pure metal coating of gold, silver, palladium, nickel, platinum, tin, zinc, or an alloy coating made of alloys of these metals, as well as a composite coating made of composite materials composed of these metals and non-metallic materials, etc. Moreover, the surface layer can be a combination of two or more of the above-mentioned various pure metal coatings, alloy coatings, and composite coatings, and is not limited thereto.

[0033] According to specific embodiments of the present disclosure, different metal plating layers can bring different functionalities, such as:

[0034] 1. Gold layer: As a precious metal, gold has good conductivity, corrosion resistance, weldability, brightness, and its alloys have good wear resistance. It can be used for exterior decoration parts, conductive connectors, welding connectors, corrosion-resistant protective parts, etc.

[0035] 2. Silver layer: Silver has better conductivity than gold and copper. At the same time, silver almost only reacts with sulfur in the air, that is, the silver layer has excellent corrosion resistance and can be used for exterior decoration, conductive connectors, corrosion-resistant protective parts, etc.

[0036] 3. Palladium layer: The electroplated palladium layer has good weldability, conductivity, and brightness, and can be used for exterior decorative parts, conductive connectors, welding connectors, corrosion-resistant protective parts, etc.

[0037] 4. Nickel layer: Nickel layer is widely used as an intermediate layer and surface layer because it can easily produce a dense oxide film with good corrosion resistance. At the same time, the nickel layer has good brightness. When it forms an alloy with other metal or non-metallic materials, it has extremely high hardness and wear resistance. It can be used for exterior decoration parts, conductive connectors, corrosion-resistant protective parts and friction contact parts.

[0038] 5. Platinum layer: Due to its inherent metallic inertness, electroplated platinum layer is often used as a protective coating and decorative coating on decorations, medical devices, etc.

[0039] 6. Tin layer: Tin is very soft and has good conductivity. It is often used for the male and female terminals of electronic connectors. The melting point of metallic tin is very low, at 231°C, and it is often used as a soldering layer after electroplating. At the same time, tin easily forms a dense oxide film in the air, which can prevent further corrosion and has strong corrosion resistance. It can be used in conductive connectors, corrosion-resistant protective parts, welding parts, etc.

[0040] 7. Zinc layer: As an anodic metal, the electroplated zinc layer is extremely susceptible to corrosion in a humid environment. It is often used as a sacrificial coating to protect the substrate. It is often used in fasteners such as steel and screws. When combined with other metals, it can form an alloy coating with better corrosion resistance.

[0041] In the above-mentioned multifunctional composite layer, the surface layer can have different thicknesses depending on the different corrosion resistance requirements of the applicable location. For example, in the contact area or welding area of ​​the male and female aluminum terminals, these areas have a small contact area with the environment and are semi-exposed areas. The requirements for corrosion resistance are low, and a thinner surface layer can be set; in the fully exposed area where the aluminum terminal has a large contact area with the environment, the requirements for corrosion resistance are high, and a thicker surface layer needs to be set. Exemplarily, the thickness of the surface layer is 3-30μm, and further exemplary is 0.2-10μm or 8-25μm. Wherein:

[0042] When the surface layer is a silver layer, the thickness of the silver layer (thin silver layer) applicable to the semi-exposed area is 0.2-3 μm, and further exemplary is 0.5-2 μm; the thickness of the silver layer (thick silver layer) applicable to the fully exposed area is 8-15 μm, and further exemplary is 10-15 μm;

[0043] When the surface layer is a tin layer, the thickness of the tin layer (thin tin layer) suitable for the semi-exposed area is 3-10 μm, and further exemplary is 3-6 μm; the thickness of the tin layer (thick tin layer) suitable for the fully exposed area is 10-25 μm, and further exemplary is 14-18 μm.

[0044] In the multifunctional composite layer described above, the bottom layer illustratively includes a transition layer. The transition layer is disposed on the side of the bottom layer that is not in contact with the surface layer, that is, on the side of the bottom layer that is in direct contact with the substrate. This transition layer is disposed between the bottom coating and the substrate requiring corrosion resistance treatment to serve as a transition. Suitable surface treatment methods can be used, including but not limited to vacuum plating, vapor deposition, sandblasting, powder spraying, and other aluminum surface modification processes.

[0045] In the above-mentioned multifunctional composite layer, illustratively, the transition layer includes a zinc layer, or a combination of a zinc layer and a secondary zinc deposition layer; the zinc layer (or zinc layer, secondary zinc deposition layer), alkali copper layer, char copper layer, and silver layer are arranged in sequence. The zinc layer and the secondary zinc deposition layer serve as transition layers for subsequent electroplating layers, which can ensure their adhesion. According to the specific embodiment of the present disclosure, the combination of the zinc layer and the secondary zinc deposition layer includes a method in which the zinc layer and the secondary zinc deposition layer are superimposed (superimposed up and down, the secondary zinc deposition layer covers the zinc layer); and a method in which the zinc layer and the secondary zinc deposition layer are located in different areas of the same layer, and in this method, a part of the two can be superimposed on each other. The transition layer disclosed in the present disclosure is not limited to the zinc layer and the secondary zinc deposition layer, and other metal or alloy materials can also be used, as long as it can be beneficial to improve the adhesion of the multifunctional composite layer. For example, other metal transition layers or alloy transition layers can be formed on the surface of the aluminum terminal through surface treatment processes such as spraying and vacuum plating.

[0046] In the above-mentioned multifunctional composite layer, the thickness of the zinc layer is 0.1-8.0 μm (for example, 0.1-5.0 μm, exemplarily 0.3-1.5 μm, further exemplarily 0.5-1 μm), and the thickness of the secondary zinc deposition layer is 0.1-9.0 μm (for example, 0.5-6 μm, exemplarily 1.0-4.0 μm).

[0047] The present disclosure also provides an aluminum terminal, wherein a partial area or the entire area of ​​the surface of the aluminum terminal is provided with the multifunctional composite layer.

[0048] The method for preparing the aluminum terminal provided in the present disclosure may include the following steps:

[0049] The front surface of the aluminum terminal is rolled and polished;

[0050] Stamping the sides of the aluminum terminals;

[0051] The various layers of the multifunctional composite layer are sequentially formed on the front and side surfaces of the processed aluminum terminal (by electroplating, chemical plating, etc.) to obtain an aluminum terminal provided with the multifunctional composite layer.

[0052] In the above-mentioned aluminum terminal manufacturing method, rolling, polishing, and stamping processes can be performed only on the areas requiring corrosion resistance, not the entire surface of the aluminum terminal. This localized treatment facilitates welding and can be combined with various joining processes, such as friction welding, friction stir welding, ultrasonic welding, molecular diffusion welding, and resistance welding, to produce highly reliable, corrosion-resistant terminals that can be used in a variety of connection processes.

[0053] In the above-mentioned method for preparing the aluminum terminal, illustratively, by performing a roller-pressing process on the terminal material, the density of the terminal surface can be enhanced, and the corrosion resistance of the subsequent electroplating process can be enhanced.

[0054] In the above-mentioned method for preparing the aluminum terminal, for example, by polishing the terminal material, the smoothness of the terminal surface can be enhanced, and the corrosion resistance of the subsequent electroplating treatment can be enhanced. The polishing treatment can be performed by chemical polishing, mechanical polishing, etc.

[0055] In the above-mentioned method for preparing the aluminum terminal, exemplarily, the front roughness of the aluminum terminal after rolling and polishing is less than Ra 3.6, further exemplarily less than Ra 0.8, that is, the front roughness of the aluminum substrate for preparing the aluminum terminal is less than Ra 3.6, more exemplarily less than Ra 0.8.

[0056] In the above-mentioned method for preparing the aluminum terminal, exemplarily, the side roughness of the aluminum terminal after rolling treatment is less than Ra 3.6 (further exemplarily less than Ra 0.8), and the bright band is greater than 50% (further exemplarily greater than 98%), that is, the side roughness of the aluminum substrate used to prepare the aluminum terminal is less than Ra 3.6 (further exemplarily less than Ra 0.8), and the bright band is greater than 50% (exemplarily greater than 98%).

[0057] In the above-mentioned method for preparing the aluminum terminal, illustratively, when a transition layer is provided, the transition layer is first formed on the front and side surfaces of the processed aluminum terminal before the alkaline copper layer is formed by electroplating.

[0058] The bottom layer of the multifunctional composite layer provided by the present invention has excellent salt spray corrosion resistance and can still provide good protection in environments with rapid temperature changes or continuous high temperature / low temperature / high humidity. At the same time, the surface layer achieves excellent conductivity, wear resistance, brightness, weldability, etc. based on the characteristics of its various metal layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] FIG1 is a schematic diagram of a typical structure of an aluminum terminal with a multifunctional composite layer provided by the present disclosure. DETAILED DESCRIPTION

[0060] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present disclosure, the technical solution of the present disclosure is now described in detail below, but it should not be understood as limiting the scope of implementation of the present disclosure.

[0061] A typical structure of an aluminum terminal with a multifunctional composite layer provided by the present disclosure is shown in FIG1 . The aluminum terminal comprises a substrate 1 and a multifunctional composite layer provided on one side of the substrate 1;

[0062] The multifunctional composite layer comprises a transition layer 2, a bottom layer and a surface layer 4, wherein:

[0063] The transition layer 2 can be a zinc layer or a combination of a zinc layer and a secondary zinc deposition layer;

[0064] The bottom layer includes a first bottom layer 31, a second bottom layer 32, and a third bottom layer 33, and the first bottom layer 31, the second bottom layer 32, and the third bottom layer 33 are respectively selected from an alkaline copper layer, a charred copper layer, an electroless copper plating layer, an electroless nickel plating layer, and an aminosulfonic acid nickel layer;

[0065] The surface layer 4 is selected from pure metal platings of gold, silver, palladium, nickel, platinum, tin, and zinc. It can also be an alloy plating made of alloys of these metals, a composite plating made of composite materials composed of these metals and non-metallic materials, and a combination of two or more of the above-mentioned pure metal platings, alloy platings, and composite platings, and is not limited to these.

[0066] The electroplating process of the aluminum terminal disclosed herein may include the following steps: ultrasonic degreasing, alkali cleaning, pickling, activation, electroplating or chemical plating, surface electroplating, post-treatment, pure water washing, and drying;

[0067] Wherein, when a transition layer is provided, chemical zinc deposition, chemical zinc stripping, and secondary zinc deposition can be performed after activation, and the secondary zinc deposition step can be selected as needed. For example, the secondary zinc deposition step can be included or not based on demand.

[0068] The technical solution disclosed in this disclosure is designed to prevent chloride ions from contacting the substrate. The front of the raw terminal is rolled and polished, resulting in a roughness of less than Ra 3.6, and in an exemplary embodiment, less than Ra 0.8. The side of the raw terminal is processed using a precision stamping process, resulting in a bright band greater than 50%, and in an exemplary embodiment greater than 98%, and a roughness less than Ra 3.6, and in an exemplary embodiment, less than Ra 0.8. In this disclosure, raw terminals are defined as terminals processed from a substrate without a plating layer.

[0069] The roller-pressing process involves repeatedly rolling the aluminum sheet between two rollers. Rolling mechanically applies pressure to increase the surface density of the aluminum, thereby reducing the porosity of the aluminum terminal material and improving its density, preparing it for the next electroplating layer. Less porosity in the material also results in a less porous electroplated film, providing greater protection. Rolling reduces surface roughness and significantly improves flatness.

[0070] The polishing process involves placing the terminal material in a polishing tank containing a polishing solution and magnetic needles. Magnetic polishing uses electricity to generate a magnetic field, which drives the stainless steel needles (i.e., magnetic needles) into motion. During this motion, the magnetic needles rub against the surface of the terminal material, achieving a mechanical polishing effect and improving the surface finish and flatness of the terminal material.

[0071] Polishing and precision stamping processes are all used to improve the smoothness and flatness of the front and side surfaces of the terminal material.

[0072] By improving the flatness and smoothness of the terminal material, it can be greatly beneficial to the electroplating film layer. Because of the influence of the current, the electroplating process will accumulate more electroplating film layers at the electron-rich positions of the workpiece, which will cause the thickness of the electroplating film layer on the terminal surface to be uneven, and even a large number of pits to appear, causing the chloride ions in the salt mist to gather and penetrate. When the flatness of the terminal material is insufficient, due to the principle of tip discharge, the more curved the conductor surface is, the more charges will be accumulated in places with smaller relative surface areas. The uneven protrusions on the surface of the material will gather a large number of electrons, making the protruding positions on the surface of the workpiece after electroplating more convex and the concave positions more concave, thus forming small holes that easily gather salt mist solution, causing the penetration of chloride ions, and then causing corrosion. After being processed by the process disclosed in the present invention, the terminal material can effectively cover the electroplating film layer, effectively improving its corrosion resistance.

[0073] Electroplating of alkaline copper: The plating parameters are as follows: cuprous cyanide: 40-50g / L, total sodium cyanide: 40-60g / L, free sodium cyanide: 8-14g / L, potassium sodium tartrate: 30-45g / L, sodium hydroxide: 1-3g / L, additives (one or a mixture of two or more of polyethylene glycol, fatty amine polyoxyethylene ether (AEO) and OP series octylphenol polyoxyethylene ether): 3-5mL / L, temperature: 40-50℃, anode and cathode area ratio of 1:1.5, current density: 0.7-1.2A / dm2, electroplating time: 5-15min, and the coating thickness is selected according to needs.

[0074] In order to enhance the density of the coating, the present invention has carried out process optimization: Generally, in order to meet the requirements of electroplating efficiency and faster production, the current density of electroplating alkali copper in electroplating plants is 4-10A / dm2, which is much higher than that of the present invention. The current density directly affects the density of the coating. A high current density will weaken the cathode polarization and make it easier to reach the precipitation overpotential of hydrogen ions in the solution, causing the occurrence of hydrogen evolution side reaction during electroplating. The evolved hydrogen will leave pores in the coating, reducing the density of the coating. The electroplating alkali copper process used in the present invention increases the concentration of the main salt cuprous cyanide and free sodium cyanide while reducing the current density, thereby obtaining an alkali copper coating with excellent electroplating efficiency and density.

[0075] Copper plating: The plating parameters are as follows: copper pyrophosphate: 50-70g / L, potassium pyrophosphate: 300-450g / L, ammonium citrate: 15-30g / L, ammonia: 2-5mL / L, current density 0.7-1.2A / dm 2 , temperature 40-50℃, anode and cathode area ratio of 1:1.5, electroplating time 50-90min, and coating thickness can be controlled by controlling electroplating parameters as needed.

[0076] Chemical copper plating layer: Chemical copper plating parameters are as follows: composition of chemical plating solution: copper sulfate: 5-20g / L, sodium hypophosphite: 20-50g / L, sodium citrate: 5-30g / L, nickel sulfate: 0.1-5g / L, potassium ferrocyanide: 0.5-7mg / L, boric acid: 15-50g / L; temperature 60-90°C, pH 7.8-10.2, electroplating time 40-100min, general plating speed is 1μm / 6min, i.e.: 6min-1μm, i.e. 24min-4μm, 48min-8μm; the coating thickness can be controlled as needed by controlling the parameters of chemical copper plating.

[0077] Electroless nickel plating: The parameters for the electroless nickel plating are as follows: Based on the total volume of the electroless nickel plating solution, the electroless nickel plating solution contains 15-25 g / L nickel sulfate, 15-25 g / L sodium hypophosphite, 20-30 g / L sodium acetate, 5-10 g / L succinic acid, and 10-20 g / L lactic acid. The remainder of the plating solution is water. The electroless nickel plating temperature is 85-95°C, and the plating time is 20-40 minutes. The electroless nickel plating reaction rate is stable. According to the disclosed method, the typical nickel plating rate is 1 μm / 5 minutes, i.e., 5 minutes to 1 μm, 20 minutes to 4 μm, and 40 minutes to 8 μm.

[0078] Nickel sulfamate layer: Electroplating parameters are as follows: Electroplating solution composition: nickel sulfamate: 300-500 g / L, nickel chloride: 10-25 g / L, boric acid: 30-40 g / L, sulfamate: 100-150 g / L, additives: 5-10 ml / L, current density: 0.8-1.2 A / dm2, temperature: 50-60°C, cathode and anode area ratio: 1:1.5, electroplating time: 1-80 min (exemplarily 40-60 min), and coating thickness is controlled by controlling the electroplating parameters as needed. Exemplary additives include one or a mixture of two or more of pyridine derivatives, propargyl alcohol derivatives, and saccharin.

[0079] The electroplating of the surface layer can be carried out in a conventional manner in the art, for example:

[0080] The silver electroplating parameters are as follows: electroplating solution composition: silver cyanide: 30-50 g / L, potassium cyanide: 130-150 g / L, free potassium cyanide: 45-60 g / L, potassium carbonate: 15-25 g / L, potassium hydroxide: 4-10 g / L, additives (one or a mixture of two or more of thiocarbamate, sodium dodecyl sulfonate, OP series octylphenol polyoxyethylene ether): 20-30 g / L, temperature: 20-25 ° C, anode and cathode area ratio of 1:1.5, current density: 0.2-0.5 A / dm2, electroplating time: 1-90 min (exemplarily 30-60 min), the coating thickness is controlled by controlling the electroplating parameters as needed.

[0081] The electroplating parameters of tin are as follows: electroplating solution composition: stannous sulfate: 10-50g / L, sulfuric acid: 60-190ml / L, gelatin: 1-10g / L, formaldehyde: 5-10ml / L, benzyl acetone: 5-30g / L; temperature: 10-40℃, anode and cathode area ratio: 1:1.5, current density: 0.7-1.2A / dm2, electroplating time: 15-120min, and the coating thickness is controlled by controlling the electroplating parameters as needed.

[0082] The relevant test methods in the embodiment are as follows:

[0083] Salt spray corrosion resistance: Conducted in accordance with the national standard GB / T 2423.17-2008. Qualified standard: No corrosion occurs on the coating, no surface pitting, peeling, blistering, etc., and no spots or color changes on the coating.

[0084] The temperature shock test was conducted in accordance with the national standard GB / T 2423.22-2012. Specifically, the sample was first held at -40°C for 30 minutes, then transferred to 140°C within 30 seconds and held for 30 minutes. After 100 cycles of "holding at -40°C for 30 minutes" and "holding at 140°C for 30 minutes," the salt spray corrosion resistance test was conducted in accordance with the national standard GB / T 2423.17-2008. Acceptance criteria: The coating showed no corrosion, no surface pitting, peeling, blistering, etc., and no spots or color changes.

[0085] Example 1

[0086] This embodiment provides an aluminum terminal with a multifunctional composite layer, wherein:

[0087] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0088] The fully exposed area of ​​the aluminum terminal material is provided with a multifunctional composite layer;

[0089] The multifunctional composite layer includes a transition layer, a bottom layer and a surface layer, wherein the transition layer includes a primary zinc deposition layer (thickness 1μm) and a secondary zinc deposition layer (thickness 2μm), the bottom layer includes a charred copper layer (thickness 10μm) and a chemically plated copper layer (thickness 10μm), and the surface layer is a silver layer (thickness 10μm).

[0090] The contact resistance of the aluminum terminal is 25μΩ, which was measured before the salt spray test and shows that the aluminum terminal has good electrical conductivity;

[0091] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 264 hours;

[0092] The aluminum terminal was subjected to a temperature shock test and then a salt spray corrosion resistance test. According to the experimental results, after enduring 100 temperature shocks, the salt spray resistance time of the aluminum terminal of this embodiment can still reach 144 hours.

[0093] According to the above test results, it can be seen that the multifunctional composite layer provided in this embodiment has excellent salt spray corrosion resistance.

[0094] Example 2

[0095] This embodiment provides an aluminum terminal with a multifunctional composite layer, wherein:

[0096] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0097] The fully exposed area of ​​the aluminum terminal material is provided with a multifunctional composite layer;

[0098] The multifunctional composite layer includes a transition layer, a bottom layer and a surface layer, wherein the transition layer includes a primary zinc plating layer (thickness 1μm) and a secondary zinc plating layer (thickness 2μm), the bottom layer includes a chemical nickel plating layer (thickness 15μm) and a charred copper layer (thickness 10μm), and the surface layer is a gold layer (thickness 3μm).

[0099] The contact resistance of the aluminum terminal is 55μΩ, which was measured before the salt spray test and shows that the aluminum terminal has good electrical conductivity;

[0100] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 228 hours;

[0101] The aluminum terminal was subjected to a temperature shock test and then a salt spray corrosion resistance test. According to the experimental results, after enduring 100 temperature shocks, the salt spray resistance time of the aluminum terminal of this embodiment can still reach 120 hours.

[0102] According to the above test results, it can be seen that the multifunctional composite layer provided in this embodiment has excellent salt spray corrosion resistance.

[0103] Example 3

[0104] This embodiment provides an aluminum terminal with a multifunctional composite layer, wherein:

[0105] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0106] The fully exposed area of ​​the aluminum terminal material is provided with a multifunctional composite layer;

[0107] The multifunctional composite layer includes a transition layer, a bottom layer and a surface layer, wherein the transition layer includes a primary zinc deposition layer (thickness 1 μm) and a secondary zinc deposition layer (thickness 2 μm), the bottom layer includes an electroless copper plating layer (thickness 20 μm) and an electroless nickel plating layer (thickness 20 μm), and the surface layer is a zinc-nickel alloy layer (thickness 10 μm; in the zinc-nickel alloy, the mass proportion of zinc is 89% and the mass proportion of nickel is 11%).

[0108] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 432 hours.

[0109] According to the above test results, it can be seen that the multifunctional composite layer provided in this embodiment has excellent salt spray corrosion resistance.

[0110] Example 4

[0111] This embodiment provides an aluminum terminal with a multifunctional composite layer, wherein:

[0112] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0113] The fully exposed area of ​​the aluminum terminal material is provided with a multifunctional composite layer;

[0114] The multifunctional composite layer includes a transition layer, a bottom layer and a surface layer, wherein the transition layer includes a primary zinc plating layer (thickness 1μm) and a secondary zinc plating layer (thickness 2μm), the bottom layer includes an alkaline copper layer (thickness 5μm) and a chemical copper plating layer (thickness 15μm), and the surface layer is a chemical nickel plating layer (thickness 20μm).

[0115] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 240 hours; the hardness after the salt spray resistance test was 800HV, and the aluminum terminal had good mechanical properties.

[0116] According to the above test results, it can be seen that the multifunctional composite layer provided in this embodiment has excellent salt spray corrosion resistance.

[0117] Example 5

[0118] This embodiment provides an aluminum terminal with a multifunctional composite layer, wherein:

[0119] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0120] The fully exposed area of ​​the aluminum terminal material is provided with a multifunctional composite layer;

[0121] The multifunctional composite layer includes a transition layer, a bottom layer and a surface layer, wherein the transition layer includes a primary zinc deposition layer (thickness 1μm) and a secondary zinc deposition layer (thickness 2μm), the bottom layer includes a nickel sulfamate layer (thickness 12μm) and a charred copper layer (thickness 15μm), and the surface layer is a platinum layer (thickness 5μm).

[0122] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 288 hours.

[0123] According to the above test results, it can be seen that the multifunctional composite layer provided in this embodiment has excellent salt spray corrosion resistance.

[0124] Example 6

[0125] This embodiment provides an aluminum terminal with a multifunctional composite layer, wherein:

[0126] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0127] The fully exposed area of ​​the aluminum terminal material is provided with a multifunctional composite layer;

[0128] The multifunctional composite layer includes a transition layer, a bottom layer and a surface layer, wherein the transition layer includes a primary zinc plating layer (thickness 1μm) and a secondary zinc plating layer (thickness 2μm), the bottom layer includes a chemical nickel plating layer (thickness 10μm), an alkaline copper layer (thickness 5μm) and a charred copper layer (thickness 15μm), and the surface layer is a palladium layer (thickness 10μm).

[0129] The contact resistance of the aluminum terminal is 67μΩ, which was measured before the salt spray test and shows that the aluminum terminal has good electrical conductivity.

[0130] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 252 hours.

[0131] According to the above test results, it can be seen that the multifunctional composite layer provided in this embodiment has excellent salt spray corrosion resistance.

[0132] Example 7

[0133] This embodiment provides an aluminum terminal with a multifunctional composite layer, wherein:

[0134] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0135] The fully exposed area of ​​the aluminum terminal material is provided with a multifunctional composite layer;

[0136] The multifunctional composite layer includes a transition layer, a bottom layer and a surface layer, wherein the transition layer includes a primary zinc deposition layer (thickness 1μm) and a secondary zinc deposition layer (thickness 2μm), the bottom layer includes a charred copper layer (thickness 10μm), an alkaline copper layer (thickness 4μm) and an aminosulfonic acid nickel layer (thickness 10μm), and the surface layer is a tin layer (thickness 15μm).

[0137] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 384 hours;

[0138] The aluminum terminal was subjected to a temperature shock test and then a salt spray corrosion resistance test. According to the experimental results, after enduring 100 temperature shocks, the salt spray resistance time of the aluminum terminal of this embodiment can still reach 252 hours.

[0139] According to the above test results, it can be seen that the multifunctional composite layer provided in this embodiment has excellent salt spray corrosion resistance.

[0140] Example 8

[0141] This embodiment provides an aluminum terminal with a multifunctional composite layer, wherein:

[0142] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0143] The fully exposed area of ​​the aluminum terminal material is provided with a multifunctional composite layer;

[0144] The multifunctional composite layer includes a transition layer, a bottom layer and a surface layer, wherein the transition layer includes a primary zinc plating layer (thickness 1μm) and a secondary zinc plating layer (thickness 2μm), the bottom layer includes a chemical copper plating layer (thickness 10μm) and a charred copper layer (thickness 10μm), and the surface layer is a silver layer (thickness 10μm).

[0145] The contact resistance of the aluminum terminal is 27μΩ, which was measured before the salt spray test and shows that the aluminum terminal has good electrical conductivity;

[0146] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 264 hours.

[0147] According to the above test results, it can be seen that the multifunctional composite layer provided in this embodiment has excellent salt spray corrosion resistance.

[0148] This embodiment corresponds to Example 1. The difference between the two is that the chemical copper plating layer and the char copper layer included in the bottom layer are in different upper and lower positions. According to the salt spray resistance test results, it can be seen that the order of the plating layers included in the bottom layer has no effect on the salt spray resistance test results, and the plating order can be adjusted.

[0149] Example 9

[0150] This embodiment provides an aluminum terminal with a multifunctional composite layer, wherein:

[0151] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0152] The fully exposed area of ​​the aluminum terminal material is provided with a multifunctional composite layer;

[0153] The multifunctional composite layer includes a transition layer, a bottom layer and a surface layer, wherein the transition layer includes a primary zinc deposition layer (thickness 1μm) and a secondary zinc deposition layer (thickness 2μm), the bottom layer includes a charred copper layer (thickness 10μm) and a chemical nickel plating layer (thickness 15μm), and the surface layer is a gold layer (thickness 3μm).

[0154] The contact resistance of the aluminum terminal is 51μΩ, which was measured before the salt spray test and shows that the aluminum terminal has good electrical conductivity.

[0155] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 228 hours;

[0156] The aluminum terminal was subjected to a temperature shock test and then a salt spray corrosion resistance test. According to the experimental results, after enduring 100 temperature shocks, the salt spray resistance time of the aluminum terminal of this embodiment can still reach 120 hours.

[0157] According to the above test results, it can be seen that the multifunctional composite layer provided in this embodiment has excellent salt spray corrosion resistance.

[0158] This embodiment corresponds to Example 2. The difference between the two is that the upper and lower positions of the char copper layer and the chemical nickel plating layer included in the bottom layer are different. According to the salt spray resistance test results, it can be seen that the order of the plating layers included in the bottom layer has no effect on the salt spray resistance test results, and the plating order can be adjusted.

[0159] Example 10

[0160] This embodiment provides an aluminum terminal with a multifunctional composite layer, wherein:

[0161] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0162] The fully exposed area of ​​the aluminum terminal material is provided with a multifunctional composite layer;

[0163] The multifunctional composite layer includes a transition layer, a bottom layer and a surface layer, wherein the transition layer includes a primary zinc deposition layer (thickness 1μm) and a secondary zinc deposition layer (thickness 2μm), the bottom layer includes a nickel sulfamate layer (thickness 10μm), a charred copper layer (thickness 10μm) and an alkaline copper layer (thickness 4μm), and the surface layer is a tin layer (thickness 15μm).

[0164] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 384 hours;

[0165] The aluminum terminal was subjected to a temperature shock test and then a salt spray corrosion resistance test. According to the experimental results, after enduring 100 temperature shocks, the salt spray resistance time of the aluminum terminal of this embodiment can still reach 252 hours.

[0166] According to the above test results, it can be seen that the multifunctional composite layer provided in this embodiment has excellent salt spray corrosion resistance.

[0167] This embodiment corresponds to Example 7. The difference between the two is that the upper and lower positions of the nickel sulfamate layer, the char copper layer, and the alkaline copper layer included in the bottom layer are different. According to the salt spray resistance test results, it can be seen that the order of the coatings included in the bottom layer has no effect on the salt spray resistance test results, and the coating order can be adjusted.

[0168] Example 11

[0169] This embodiment provides an aluminum terminal with a multifunctional composite layer, wherein:

[0170] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0171] The semi-exposed area of ​​the aluminum terminal material is provided with a multifunctional composite layer;

[0172] The multifunctional composite layer includes a transition layer, a bottom layer and a surface layer, wherein the transition layer includes a primary zinc deposition layer (thickness 1 μm) and a secondary zinc deposition layer (thickness 2 μm), the bottom layer includes a charred copper layer (thickness 1 μm) and a chemically plated copper layer (thickness 1 μm), and the surface layer is a silver layer (thickness 10 μm).

[0173] The contact resistance of the aluminum terminal is 28μΩ, measured before the salt spray test;

[0174] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 48 hours.

[0175] According to the above test results, it can be seen that the bottom layer thickness of the multifunctional composite layer of this embodiment is relatively low, and the salt spray corrosion resistance is not as good as the multifunctional composite layer with a thicker bottom layer. However, compared with conventional coatings, the corrosion resistance of this embodiment is still very good and can be applied to the welding area and semi-exposed area of ​​the aluminum terminal.

[0176] Example 12

[0177] This embodiment provides an aluminum terminal with a multifunctional composite layer, wherein:

[0178] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0179] The semi-exposed area of ​​the aluminum terminal material is provided with a multifunctional composite layer;

[0180] The multifunctional composite layer includes a transition layer, a bottom layer and a surface layer, wherein the transition layer includes a primary zinc plating layer (thickness 1μm) and a secondary zinc plating layer (thickness 2μm), the bottom layer includes a chemical nickel plating layer (thickness 1μm) and a charred copper layer (thickness 1μm), and the surface layer is a gold layer (thickness 3μm).

[0181] The contact resistance of the aluminum terminal is 50μΩ, measured before the salt spray test;

[0182] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 72 hours;

[0183] The aluminum terminal was subjected to a temperature shock test and then a salt spray corrosion resistance test. According to the experimental results, after enduring 100 temperature shocks, the salt spray resistance time of the aluminum terminal of this embodiment can still reach 36 hours.

[0184] According to the above test results, it can be seen that the bottom layer thickness of the multifunctional composite layer of this embodiment is relatively low, and the salt spray corrosion resistance is not as good as the multifunctional composite layer with a thicker bottom layer. However, compared with conventional coatings, the corrosion resistance of this embodiment is still very good and can be applied to the welding area and semi-exposed area of ​​the aluminum terminal.

[0185] Example 13

[0186] This embodiment provides an aluminum terminal with a multifunctional composite layer, wherein:

[0187] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0188] The semi-exposed area of ​​the aluminum terminal material is provided with a multifunctional composite layer;

[0189] The multifunctional composite layer includes a transition layer, a bottom layer and a surface layer, wherein the transition layer includes a primary zinc plating layer (thickness 1μm) and a secondary zinc plating layer (thickness 2μm), the bottom layer includes a chemical nickel plating layer (thickness 15μm) and a charred copper layer (thickness 10μm), and the surface layer is a gold layer (thickness 0.5μm).

[0190] The contact resistance of the aluminum terminal is 81 μΩ, measured before the salt spray test;

[0191] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 96 hours;

[0192] The aluminum terminal was subjected to a temperature shock test and then a salt spray corrosion resistance test. According to the experimental results, after enduring 100 temperature shocks, the salt spray resistance time of the aluminum terminal of this embodiment can still reach 48 hours.

[0193] According to the above test results, it can be seen that the surface thickness of the multifunctional composite layer of this embodiment is relatively low, and its salt spray corrosion resistance is not as good as that of the multifunctional composite layer with a thicker bottom layer. However, compared with conventional coatings, the corrosion resistance of this embodiment is still very good and can be applied to the welding area and semi-exposed area of ​​the aluminum terminal.

[0194] Example 14

[0195] This embodiment provides an aluminum terminal with a multifunctional composite layer, wherein:

[0196] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0197] The semi-exposed area of ​​the aluminum terminal material is provided with a multifunctional composite layer;

[0198] The multifunctional composite layer includes a transition layer, a bottom layer and a surface layer, wherein the transition layer includes a primary zinc deposition layer (thickness 1μm) and a secondary zinc deposition layer (thickness 2μm), the bottom layer includes a charred copper layer (thickness 1μm), an alkaline copper layer (thickness 0.5μm) and an aminosulfonic acid nickel layer (thickness 1μm), and the surface layer is a tin layer (thickness 0.5μm).

[0199] The aluminum terminal was subjected to a salt spray resistance test and the salt spray resistance time was measured to be 60 hours;

[0200] The aluminum terminal was subjected to a temperature shock test and then a salt spray corrosion resistance test. According to the experimental results, after withstanding 100 temperature shocks, the salt spray resistance time of the aluminum terminal of this embodiment can still reach 24 hours, which is suitable for the welding area and semi-exposed area of ​​the aluminum terminal.

[0201] The multifunctional composite layer based on a thin surface layer provided in Examples 11-14 of the present disclosure may not be as good as the multifunctional composite layer based on a thick surface layer in Examples 1-10 in terms of corrosion resistance time. However, the test is carried out in a fully exposed salt spray environment, and in the actual use of the aluminum terminal, the semi-exposed area of ​​the aluminum terminal is not fully exposed to the environment. Therefore, the corrosion resistance time of the multifunctional composite layer based on a thin surface layer is lower than that of the multifunctional composite layer based on a thick surface layer, which does not affect the service life of the aluminum terminal. This part of the multifunctional composite layer based on a thin surface layer will still exert a good corrosion resistance effect. If the semi-exposed area of ​​the aluminum terminal is set with a multifunctional composite layer based on a thin surface layer and the fully exposed area is set with a multifunctional composite layer based on a thick surface layer, the overall corrosion resistance of the aluminum terminal is also guaranteed.

[0202] Based on this, the present disclosure can set different corrosion-resistant composite layers at different positions of the aluminum terminal according to regional characteristics (whether exposed to the environment, the level of corrosion resistance requirements) and usage requirements, thereby reducing costs while ensuring corrosion resistance and service life.

Claims

1. A multifunctional composite layer, characterized in that: The multifunctional composite layer comprises a surface layer and a bottom layer; The material of the surface layer is gold, silver, palladium, nickel, platinum, tin, zinc or their alloys; The bottom layer comprises at least two layers of an alkali copper layer, a charred copper layer, a chemically plated copper layer, a chemically plated nickel layer, and a sulfamate nickel layer; in: The thickness of the alkaline copper layer is 0.5-15 μm; The thickness of the charred copper layer is 2-20 μm; The thickness of the chemical copper plating layer is 2-30 μm; The thickness of the chemical nickel plating layer is 2-30 μm; The thickness of the nickel sulfamate layer is 0.5-30 μm; The thickness of the surface layer is 0.2-35 μm.

2. The multifunctional composite layer according to claim 1, characterized in that: The bottom layer comprises at least three layers of an alkali copper layer, a charred copper layer, a chemically plated copper layer, a chemically plated nickel layer, and an aminosulfonate nickel layer.

3. The multifunctional composite layer according to claim 1 or 2, characterized in that: The thickness of the alkaline copper layer is 1-10 μm, more preferably 1-6 μm, and further preferably 2-4 μm.

4. The multifunctional composite layer according to claim 1 or 2, characterized in that: The thickness of the charred copper layer is 2-18 μm, more preferably 5-15 μm, and further preferably 8-10 μm.

5. The multifunctional composite layer according to claim 1 or 2, characterized in that: The thickness of the chemical copper plating layer is 3-28 μm, more preferably 5-15 μm, more preferably 8-15 μm, and further preferably 9-13 μm.

6. The multifunctional composite layer according to claim 1 or 2, characterized in that: The thickness of the chemical nickel plating layer is 3-28 μm, more preferably 4-18 μm, more preferably 4-15 μm, and further preferably 10-15 μm.

7. The multifunctional composite layer according to claim 1 or 2, characterized in that: The thickness of the nickel sulfamate layer is 3-28 μm, more preferably 4-15 μm, and further preferably 6-9 μm.

8. The multifunctional composite layer according to claim 1 or 2, characterized in that: The thickness of the surface layer is 3-30 μm, preferably 0.2-10 μm or 8-25 μm.

9. The multifunctional composite layer according to claim 1 or 2, characterized in that: The multifunctional composite layer also includes a transition layer, which is arranged on the side of the bottom layer that is not in contact with the surface layer.

10. The multifunctional composite layer according to claim 9, characterized in that: The transition layer comprises a zinc layer, or a combination of a zinc layer and a secondary zinc deposition layer. The thickness of the zinc layer is 0.1-8.0 μm, and the thickness of the secondary zinc deposition layer is 0.1-9.0 μm.

11. The multifunctional composite layer according to claim 10, characterized in that: The thickness of the zinc layer is 0.3-1.5 μm, and the thickness of the secondary zinc deposition layer is 1.0-4.0 μm.

12. An aluminum terminal, characterized in that: A partial area or the entire area of ​​the surface of the aluminum terminal is provided with the multifunctional composite layer according to any one of claims 1 to 11.

13. The aluminum terminal according to claim 12, characterized in that: The front surface roughness of the aluminum substrate for preparing the aluminum terminal is less than Ra 3.6, preferably less than Ra 0.

8.

14. The aluminum terminal according to claim 13, characterized in that: The side roughness of the aluminum substrate used to prepare the aluminum terminal is less than Ra 3.6, preferably less than Ra 0.8, and the bright band is greater than 50%, preferably greater than 98%.

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