Corrosion and temperature shock resistant composite layer, method of treating an aluminum substrate for corrosion and temperature shock resistance, and corrosion and temperature shock resistant aluminum terminal

Abstract

The application provides a corrosion-resistant and temperature-shock-resistant composite layer, an aluminum base material corrosion-resistant and temperature-shock-resistant processing method and a corrosion-resistant and temperature-shock-resistant aluminum terminal. The corrosion-resistant and temperature-shock-resistant composite layer comprises an alkaline copper layer, a cupric pyrolysis layer, a nickel sulfamate layer and a silver layer. The thickness of the alkaline copper layer is 1-10 microns, the thickness of the cupric pyrolysis layer is 2-18 microns, the thickness of the nickel sulfamate layer is 0.5-28 microns, and the thickness of the silver layer is 0.2-25 microns. The aluminum base material corrosion-resistant processing method comprises the step of arranging the corrosion-resistant and temperature-shock-resistant composite layer on the surface of the aluminum base material. The surface of the corrosion-resistant and temperature-shock-resistant aluminum terminal is provided with the corrosion-resistant and temperature-shock-resistant composite layer. The corrosion-resistant and temperature-shock-resistant composite layer has good salt spray corrosion resistance, and the salt spray corrosion resistance time can reach 120 hours after temperature shock, and the mechanical life is long in the harsh environment with rapid temperature change and high corrosion.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of corrosion-resistant temperature shock composite layer, aluminum base material corrosion-resistant temperature shock processing method and corrosion-resistant aluminum terminal, belong to corrosion-resistant technical field. BACKGROUND

[0002] Current electroplating and chemical plating, spraying, laser surface treatment process, can be coated on the surface of aluminum and its alloy film to protect the substrate, but the effect of salt spray test is not ideal, the salt spray time of common aluminum workpiece can only maintain 48 hours to appear corrosion, greatly limit the service life of aluminum workpiece in assembly.Meanwhile, the expansion coefficient of metal aluminum is very large, 23.21x10 -6 / K, will certainly produce stress on the surface film in temperature shock, tear the film.In subsequent salt spray test, the protective effect of damaged film is greatly reduced, so that the salt spray of aluminum workpiece after temperature shock can not even reach 12 hours.

[0003] Current electroplating manufacturers have less research on aluminum electroplating process, only through secondary zinc deposition and nickel plating to make it proceed to the next step of electroplating, the selection of plating scheme is different and the effect is general, it is difficult to solve the electroplating requirements of aluminum workpiece with high corrosion resistance after temperature shock, especially the aluminum workpiece used in harsh environments with rapid temperature changes in military, aerospace, automobile and other fields cannot meet the use requirements.

[0004] The terminals or workpieces applied to connectors, vehicle bodies, controllers, battery packs and other assemblies on the market will be tested by temperature shock test, kept at-40℃ for 30min, transferred to 140℃ within 30s and kept for 30min, tested for 100 cycles without contact resistance overrun, appearance defects, voltage overrun, etc.The surface of the terminal tested in this way looks good, but under the microscope and cracks appear, and the aluminum terminal is more serious.

[0005] However, the existing technology does not pay attention to the corrosion resistance after temperature shock cycle, and the plating layer has been damaged at this time, losing the corrosion resistance of the plating layer, which has a great influence on the use performance of the terminal or workpiece.If the corrosion resistance of the terminal or workpiece after temperature shock cycle cannot meet the actual use requirements, it will cause serious consequences. SUMMARY

[0006] To solve the above technical problems, the purpose of the present application is to provide a kind of corrosion-resistant temperature shock composite layer, the corrosion-resistant temperature shock composite layer has excellent salt spray corrosion resistance, especially the corrosion resistance after temperature shock, which can be used for corrosion-resistant temperature shock treatment of aluminum base material.

[0007] To achieve the above object, the present application first provides a corrosion and temperature shock resistant composite layer, which comprises: an alkaline copper layer, a cupric pyrolytic layer, a nickel aminosulfonate layer, and a silver layer.

[0008] In the above corrosion and temperature shock resistant composite layer, preferably, the alkaline copper layer, the cupric pyrolytic layer, the nickel aminosulfonate layer, and the silver layer are sequentially arranged.

[0009] In the above corrosion and temperature shock resistant composite layer, preferably, the thickness of the alkaline copper layer is 1-10 μm, more preferably 1-6 μm, and further preferably 2-4 μm.

[0010] In the above corrosion and temperature shock resistant composite layer, preferably, the thickness of the cupric pyrolytic layer is 2-18 μm, more preferably 5-15 μm, and further preferably 8-10 μm.

[0011] In the above corrosion and temperature shock resistant composite layer, preferably, the thickness of the nickel aminosulfonate layer is 0.5-28 μm, more preferably 0.5-18 μm, and further preferably 6-9 μm. In some cases, the thickness of the nickel aminosulfonate layer can be controlled to be 3-28 μm, more preferably 4-15 μm.

[0012] In the above corrosion and temperature shock resistant composite layer, preferably, the thickness of the silver layer is 0.2-25 μm. According to different requirements for corrosion resistance in different applicable positions, the thickness of the silver layer can be different. For example, in the contact area or welding area of a male or female aluminum terminal, the contact area with the environment is small, which belongs to a semi-exposed area, and the requirement for corrosion resistance is low, so a thinner silver layer can be provided, preferably, the thickness of the silver layer (thin silver layer) is 0.2-3 μm, and more preferably 0.5-2 μm; in the completely exposed area of the aluminum terminal, the contact area with the environment is large, and the requirement for corrosion resistance is high, so a thicker silver layer needs to be provided, preferably, the thickness of the silver layer (thick silver layer) is 8-15 μm, and more preferably 10-15 μm. In some cases, the thickness of the silver layer can be further controlled to be 10-13 μm.

[0013] In the above corrosion and temperature shock resistant composite layer, preferably, the composite layer further comprises a transition layer, which is arranged on the side of the alkaline copper layer that is not in contact with the cupric pyrolytic layer. The transition layer is arranged between the alkaline copper layer and the substrate that needs to be treated for corrosion resistance, and serves as a transition. The transition layer can be achieved by using appropriate surface treatment methods.

[0014] In the above corrosion-resistant and temperature-shock-resistant composite layer, preferably, the transition layer comprises a zinc layer or a combination of a zinc layer and a secondary zinc layer; the zinc layer (or the zinc layer and the secondary zinc layer), the alkaline copper layer, the pyrophoric copper layer, and the silver layer are sequentially arranged. The zinc layer and the secondary zinc layer as the transition layer of the subsequent electroplated layer can ensure the adhesion. According to a specific embodiment of the present application, the combination of the zinc layer and the secondary zinc layer comprises a mode in which the zinc layer and the secondary zinc layer are stacked (up and down) or the secondary zinc layer covers the zinc layer; and a mode in which the zinc layer and the secondary zinc layer are located in different regions of the same layer, and in this mode, a part of the zinc layer and the secondary zinc layer can be stacked. The transition layer of the present application is not limited to the zinc layer and the secondary zinc layer, and other metal or alloy materials can also be used as long as they can improve the adhesion of the corrosion-resistant and temperature-shock-resistant composite layer, for example, other metal transition layers or alloy transition layers can be formed on the surface of the aluminum terminal by surface treatment processes such as spraying and vacuum electroplating.

[0015] In the above corrosion-resistant and temperature-shock-resistant composite layer, preferably, the thickness of the zinc layer is 0.1-10.0 μm, and more preferably 0.5-1 μm.

[0016] In the above corrosion-resistant and temperature-shock-resistant composite layer, preferably, the thickness of the secondary zinc layer is 0.1-10 μm, and more preferably 1.5-2.5 μm.

[0017] In the above corrosion-resistant and temperature-shock-resistant composite layer, preferably, the zinc layer, the secondary zinc layer, the alkaline copper layer, the pyrophoric copper layer, the nickel sulfamate layer, and the silver layer are respectively electroplated layers.

[0018] In the above corrosion-resistant and temperature-shock-resistant composite layer, preferably, the corrosion-resistant and temperature-shock-resistant composite layer further comprises a chemical copper layer (or a chemical plating copper layer).

[0019] In the above corrosion-resistant and temperature-shock-resistant composite layer, preferably, the chemical copper layer is arranged on the surface of the alkaline copper layer or the surface of the pyrophoric copper layer, that is, the chemical copper layer can have the following arrangement modes: (1) arranged on the side surface of the alkaline copper layer which does not contact the pyrophoric copper layer; (2) arranged between the alkaline copper layer and the pyrophoric copper layer; and (3) arranged on the side surface of the pyrophoric copper layer which does not contact the alkaline copper layer.

[0020] In the above corrosion-resistant and temperature-shock-resistant composite layer, preferably, the thickness of the chemical copper layer is 3-25 μm, and more preferably 5-15 μm.

[0021] In the above corrosion-resistant and temperature-shock-resistant composite layer, preferably, the corrosion-resistant and temperature-shock-resistant composite layer further comprises an acid copper layer.

[0022] In the above corrosion-resistant and temperature shock-resistant composite layer, preferably, the acid copper layer is arranged on the surface of the alkaline copper layer or the surface of the cupric oxide layer, i.e., the chemical copper layer can be arranged in the following manners: (1) on the surface of the alkaline copper layer which is not in contact with the cupric oxide layer; (2) between the alkaline copper layer and the cupric oxide layer; (3) on the surface of the cupric oxide layer which is not in contact with the alkaline copper layer.

[0023] In the above corrosion-resistant and temperature shock-resistant composite layer, preferably, the thickness of the acid copper layer is 1-20 μm, more preferably 3-10 μm.

[0024] In the above corrosion-resistant and temperature shock-resistant composite layer, preferably, the corrosion-resistant and temperature shock-resistant composite layer further comprises a watt nickel layer.

[0025] In the above corrosion-resistant and temperature shock-resistant composite layer, preferably, the watt nickel layer is arranged on the surface of the nickel sulfamate layer, i.e., the watt nickel layer can be arranged in the following manners: (1) between the nickel sulfamate layer and the cupric oxide layer; (2) between the nickel sulfamate layer and the silver layer.

[0026] In the above corrosion-resistant and temperature shock-resistant composite layer, preferably, the thickness of the watt nickel layer is 1-20 μm, more preferably 3-9 μm.

[0027] In the above corrosion-resistant and temperature shock-resistant composite layer, preferably, the corrosion-resistant and temperature shock-resistant composite layer can simultaneously comprise a chemical copper layer and an acid copper layer, and as for the specific positions of the two, they can be arranged in any one or two of the following three positions: the surface of the alkaline copper layer which is not in contact with the cupric oxide layer, between the alkaline copper layer and the cupric oxide layer, and the surface of the cupric oxide layer which is not in contact with the alkaline copper layer, and when the two are arranged in the same position, their order can be arbitrary, for example, when the chemical copper layer and the acid copper layer are both arranged between the alkaline copper layer and the cupric oxide layer, they can be arranged in the order of alkaline copper layer, chemical copper layer, acid copper layer, cupric oxide layer, or in the order of alkaline copper layer, acid copper layer, chemical copper layer, cupric oxide layer. On this basis, a watt nickel layer can also be arranged.

[0028] Due to the difference in expansion coefficient between the aluminum base material (e.g., aluminum terminal, workpiece) and the electroplated film layer, and the difference in expansion coefficient between the electroplated film layer and the electroplated film layer, when the temperature shock test is performed, the expansion coefficient of the aluminum base material is generally 23.21 x 10 -6 / K, and the expansion coefficient of nickel is 13 x 10 -6 / K, the thermal expansion volume of the aluminum base material is much larger than that of the nickel layer, and the volume difference between the two causes great tensile stress between the workpiece and the electroplated film layer. This stress causes the electroplated film layer to tear and even break, and the surface film layer of the workpiece torn in the salt spray test is easily penetrated by chloride ions in the salt spray solution, and contacts the aluminum base material, causing electrochemical corrosion of the aluminum base material.

[0029] The alkali copper layer, the cupric pyrophosphate layer, the silver layer and the aluminum expansion coefficient of the corrosion-resistant and temperature shock-resistant composite layer provided by the present application are similar (copper 17x10 -6 / K, silver 19.5x10 -6 / K), which greatly reduces the tensile stress caused by volume expansion in temperature shock, and the high ductility and high toughness of the nickel sulfamate layer can withstand the tensile stress without being torn, still maintaining the original compactness, and can effectively protect the workpiece in the salt spray test to avoid corrosion.

[0030] The present application also provides a preparation method of the above-mentioned corrosion-resistant and temperature shock-resistant composite layer, which comprises the following steps: forming an alkali copper layer, a cupric pyrophosphate layer, a nickel sulfamate layer and a silver layer on the surface of the base material in sequence by electroplating to obtain the corrosion-resistant and temperature shock-resistant composite layer.

[0031] In the preparation method of the above-mentioned corrosion-resistant and temperature shock-resistant composite layer, preferably, the electroplating solution for the alkali copper layer contains cuprous cyanide 40-50 g / L, total sodium cyanide 40-60 g / L, free sodium cyanide 8-14 g / L, potassium sodium tartrate 30-45 g / L, sodium hydroxide 1-3 g / L, and additives (one or more than two kinds of mixture of polyethylene glycol, fatty amine polyoxyethylene ether (AEO) and OP series octylphenol polyoxyethylene ether) 3-5 mL / L, based on the total volume of the electroplating solution. The remaining components in the electroplating solution are water.

[0032] In the preparation method of the above-mentioned corrosion-resistant and temperature shock-resistant composite layer, preferably, the temperature for electroplating the alkali copper layer is 40-50℃, the area ratio of anode to cathode is 1:1-2 (preferably 1:1.5), the current density is 0.7-1.2 A / dm 2 , and the electroplating time is 5-15 min.

[0033] In the preparation method of the above-mentioned corrosion-resistant and temperature shock-resistant composite layer, preferably, the electroplating solution for the cupric pyrophosphate layer contains cupric pyrophosphate 50-70 g / L, potassium pyrophosphate 300-450 g / L, ammonium citrate 15-30 g / L, and ammonia water 2-5 mL / L, based on the total volume of the electroplating solution. The remaining components in the electroplating solution are water.

[0034] In the preparation method of the above-mentioned corrosion-resistant and temperature shock-resistant composite layer, preferably, the temperature for electroplating the cupric pyrophosphate layer is 40-50℃, and the current density is 0.7-1.2 A / dm2 The temperature of plating the silver layer is 20-25°C, the area ratio of cathode to anode is 1:1-2 (preferably 1:1.5), the current density is 0.2-0.5 A / dm

[0035] In the method for preparing the corrosion-resistant and temperature-impact-resistant composite layer, preferably, the plating solution for the silver layer contains 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, and additives 20-30 g / L, with the rest being water.

[0036] In the method for preparing the corrosion-resistant and temperature-impact-resistant composite layer, preferably, the temperature of plating the silver layer is 20-25°C, the area ratio of cathode to anode is 1:1-2 (preferably 1:1.5), the current density is 0.2-0.5 A / dm 2 The temperature of plating the silver layer is 20-25°C, the area ratio of cathode to anode is 1:1-2 (preferably 1:1.5), the current density is 0.2-0.5 A / dm

[0037] In the method for preparing the corrosion-resistant and temperature-impact-resistant composite layer, preferably, the plating solution for the silver layer contains 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, and additives 20-30 g / L, with the rest being water.

[0038] In the method for preparing the corrosion-resistant and temperature-impact-resistant composite layer, preferably, the temperature of plating the silver layer is 20-25°C, the area ratio of cathode to anode is 1:1-2 (preferably 1:1.5), the current density is 0.2-0.5 A / dm 2 The temperature of plating the silver layer is 20-25°C, the area ratio of cathode to anode is 1:1-2 (preferably 1:1.5), the current density is 0.2-0.5 A / dm

[0039] In the method for preparing the corrosion-resistant and temperature-impact-resistant composite layer, preferably, the plating of the alkaline copper layer, the pyrolytic copper layer, the silver layer, etc. can adopt the pulse plating process, which can further improve the compactness of the original compact layer, so that the plating layer is more compact, has fewer pores, and has stronger salt spray resistance.

[0040] In the method for preparing the corrosion-resistant and temperature-impact-resistant composite layer, preferably, when the chemical copper layer, the acid copper layer, and the watt nickel layer are present, these layers can be obtained by corresponding methods at appropriate times.

[0041] In the preparation method of the corrosion-resistant and temperature impact-resistant composite layer, preferably, the zinc layer and the secondary zinc deposition layer are prepared by a conventional electroplating method.

[0042] In the preparation method of the corrosion-resistant and temperature impact-resistant composite layer, in order to ensure the electroplating adhesion, other processes can be added to the electroplating process, such as acid activation treatment before each process and pure water cleaning before each process.

[0043] The application also provides a corrosion-resistant and temperature impact-resistant treatment method for an aluminum base material, which comprises the step of arranging the corrosion-resistant and temperature impact-resistant composite layer provided by the application on the surface of the aluminum base material. The aluminum base material of the application comprises a pure aluminum base material and an aluminum alloy base material.

[0044] In the corrosion-resistant and temperature impact-resistant treatment method for the aluminum base material, preferably, the corrosion resistance refers to salt spray corrosion resistance.

[0045] In the corrosion-resistant and temperature impact-resistant treatment method for the aluminum base material, preferably, the temperature impact resistance refers to temperature cycle impact resistance, i.e. resistance to alternating cold and hot cycle impact.

[0046] In the corrosion-resistant and temperature impact-resistant treatment method for the aluminum base material, preferably, the surface roughness of the aluminum base material is less than Ra 3.6, and more preferably less than Ra 0.8.

[0047] The application also provides a corrosion-resistant and temperature impact-resistant aluminum terminal, wherein part of the surface of the corrosion-resistant and temperature impact-resistant aluminum terminal or the entire surface thereof is provided with the corrosion-resistant and temperature impact-resistant composite layer provided by the application.

[0048] In the corrosion-resistant and temperature impact-resistant aluminum terminal, the corrosion-resistant and temperature impact-resistant composite layer can cover the entire surface of the aluminum terminal, or can only cover the surface area that needs to be treated for corrosion resistance and temperature impact resistance.

[0049] The application also provides a preparation method of the corrosion-resistant and temperature impact-resistant aluminum terminal, which comprises the following steps:

[0050] The front surface of the aluminum terminal is subjected to roll pressing treatment and polishing treatment;

[0051] The side surface of the aluminum terminal is subjected to stamping treatment;

[0052] The front surface and the side surface of the treated aluminum terminal are sequentially subjected to electroplating to form a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a pyrolytic copper layer and a silver layer, thereby obtaining the corrosion-resistant and temperature impact-resistant aluminum terminal.

[0053] In the above preparation method, the roll processing, polishing processing, stamping processing, etc. can be performed only on the region requiring corrosion-resistant and temperature-impact-resistant treatment, and is not limited to the entire region of the surface of the aluminum terminal. By adopting the local region processing mode, the welding can be facilitated, and various connection processes such as friction welding, friction stir welding, ultrasonic welding, molecular diffusion welding, resistance welding, etc. can be combined, so as to obtain a corrosion-resistant terminal with high reliability and various connection processes.

[0054] In the above preparation method of the corrosion-resistant and temperature-impact-resistant aluminum terminal, preferably, the compactness of the terminal surface of the terminal material is enhanced by the roll processing, and the corrosion-resistant and temperature-impact-resistant property of the subsequent electroplating processing is enhanced.

[0055] In the above preparation method of the corrosion-resistant and temperature-impact-resistant aluminum terminal, preferably, the smoothness of the terminal surface of the terminal material is enhanced by the polishing processing, and the corrosion-resistant and temperature-impact-resistant property of the subsequent electroplating processing is enhanced. The polishing processing can be performed by chemical polishing, mechanical polishing, etc.

[0056] In the above preparation method of the corrosion-resistant aluminum terminal, preferably, the roughness of the front surface of the aluminum terminal after the roll processing and the polishing processing is less than Ra 3.6, and more preferably less than Ra 0.8.

[0057] In the above preparation method of the corrosion-resistant aluminum terminal, preferably, the roughness of the side surface of the aluminum terminal after the roll processing is less than Ra 3.6 (more preferably less than Ra 0.8), and the bright band is greater than 50% (more preferably greater than 98%).

[0058] In the above preparation method of the corrosion-resistant aluminum terminal, preferably, when the transition layer is provided, the transition layer is formed on the front surface and the side surface of the processed aluminum terminal before the alkali copper layer is formed by electroplating.

[0059] The technical scheme of the present application is from the practical application point of view (in practical application, the terminal is more easily corroded after the temperature changes sharply, and corrosion exists all the time), and the corrosion resistance of the aluminum terminal after the temperature impact cycle is optimized, which can still have good corrosion resistance after 100 cycles of 30 minutes at -40℃ to 140℃, the salt spray time of the full exposed region of the aluminum terminal provided with the corrosion-resistant and temperature-impact-resistant composite layer can reach 120H, and the half exposed region of the aluminum terminal provided with the corrosion-resistant and temperature-impact-resistant composite layer can realize salt spray resistance for 28 hours, and still has a long mechanical life in a harsh environment with rapid temperature change and high corrosion. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 The overall structure schematic diagram of one embodiment of the aluminum terminal provided by the present application.

[0061] Figure 2 An exemplary electroplating process diagram of the aluminum terminal provided by the present application.

[0062] Figure 3 SEM images of the conventional aluminum plate and the rolled aluminum plate.

[0063] Figure 4 Morphology images of the side surface of the aluminum terminal obtained by the ordinary stamping and the precision stamping.

[0064] Figure 5 Picture of the corrosion points appearing on the side surface of Comparative Example 9.

[0065] Figure 6 Morphology images of the sample before and after the temperature shock experiment.

[0066] Figure 7 Picture of the sample in which the adhesion problem appeared in the case of directly electroplating the copper layer and the silver layer.

[0067] Figure 8 Surface SEM images and side cross-section metallographic images of the conventional plating layer (plating nickel) before and after the temperature shock.

[0068] Figure 9 Side cross-section metallographic images of the conventional plating layer (plating nickel) and the plating layer of Example 1 of the present application after the temperature shock. DETAILED DESCRIPTION

[0069] In order to have a clearer understanding of the technical features, objects and beneficial effects of the present application, the technical solutions of the present application are described in detail as follows, but cannot be understood as limiting the implementable scope of the present application.

[0070] The aluminum terminal provided by the present application is an aluminum terminal with an electroplated film layer, comprising an aluminum terminal material and an electroplated film layer, wherein the aluminum terminal material has a terminal surface and a terminal side surface; the electroplated film layer (corrosion-resistant and temperature-shock-resistant composite layer) comprises a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a pyrophoric copper layer, a nickel sulfamate layer and a silver layer. An exemplary overall structure of the aluminum terminal with the corrosion-resistant and temperature-shock-resistant composite layer is shown in Figure 1 wherein the zinc layer 2, the alkaline copper layer 3, the pyrophoric copper layer 4, the nickel sulfamate layer 5 and the silver layer 6 are sequentially arranged on the surface of the aluminum base material 1; if necessary, a secondary zinc deposition layer can be further arranged between the zinc layer 2 and the alkaline copper layer 3.

[0071] An exemplary electroplating process of the aluminum terminal is shown in Figure 2As shown: the electroplating process includes the following steps: ultrasonic degreasing, alkaline cleaning, pickling, chemical zinc deposition, chemical zinc removal, secondary zinc deposition, activation, electroplating of alkaline copper, electroplating of pyrolytic copper, electroplating of nickel sulfamate, pre-plating of silver, electroplating of silver, post-treatment, pure water washing, drying; wherein the step of secondary zinc deposition can be selected as needed.

[0072] The technical scheme of the present application starts from the design of avoiding the contact of chloride ions with the substrate, the front surface of the substrate terminal is subjected to roller pressing treatment and polishing treatment, the roughness after treatment is less than Ra 3.6, preferably less than Ra 0.8; the side surface of the substrate terminal is processed using a precision stamping process, the lightness after treatment is greater than 50%, preferably greater than 98%, the roughness is less than Ra 3.6, preferably less than Ra 0.8.

[0073] The roller pressing treatment increases the surface density of the aluminum material by applying pressure through mechanical means, thereby reducing the porosity of the surface of the aluminum terminal substrate and improving its density, preparing for the coverage of the electroplated film layer in the next step. The fewer the pores of the substrate, the fewer the pores of the electroplated film layer, and the higher the protection. The SEM images of the conventional aluminum plate and the roller-pressed aluminum plate are shown in Figure 3 Figure 3 In Figure 3 , figure a shows a conventional aluminum plate, and figure b shows a roller-pressed aluminum plate. As can be seen from , through roller pressing treatment, the roughness of the surface of the aluminum plate is reduced, and the flatness is greatly improved.

[0074] The polishing treatment is carried out in a magnetic polishing manner, specifically by generating a magnetic field through electrification, the magnetic field drives the stainless steel needle to move, and in the process of movement, the stainless steel needle rubs the surface of the terminal substrate, thereby achieving the effect of mechanical polishing and improving the smoothness and flatness of the surface of the terminal substrate.

[0075] The polishing treatment, precision stamping process, etc. all serve to improve the smoothness and flatness of the surface and side surface of the terminal substrate.

[0076] By improving the flatness and smoothness of the terminal substrate, the electroplated film layer can be greatly improved. Due to the influence of electric current, the electroplating process will accumulate more electroplated film layer at the position of electron enrichment of the workpiece, which will cause the thickness of the electroplated film layer on the surface of the terminal to be uneven, and even a large number of pits will appear, causing the accumulation and penetration of chloride ions in the salt mist. When the flatness of the terminal substrate is insufficient, due to the principle of tip discharge, the more curved the surface of the conductor, the smaller the relative surface area, and the more charge will be accumulated in the place. The protrusions on the uneven surface of the substrate will gather a large amount of electrons, making the surface of the workpiece after electroplating more convex at the protruding position and more concave at the recessed position, which forms small holes that are easy to gather salt mist, causing the penetration of chloride ions and further causing corrosion. After the process of the present application, the terminal substrate can effectively cover the electroplated film layer, effectively improving its corrosion resistance.

[0077] Alkaline copper electroplating: Alkaline copper electroplating is a cyanide copper plating process. Cyanide has a very strong complexing ability in water, which can greatly increase the cathode polarization of electroplating, causing copper ions to accumulate in large quantities at the cathode and deposit together, increasing the density of the electroplated film. The coating produced by cyanide system electroplating is dense and the reaction is fast and efficient, which can cover the zinc layer with a dense and smooth copper layer. Moreover, copper is chemically inert and has low electroplating internal stress, making it an excellent intermediate coating that is easy to electroplat with subsequent metal coatings.

[0078] The electroplating parameters are as follows: cuprous cyanide: 40-50 g / L, total sodium cyanide: 40-60 g / L, free sodium cyanide: 8-14 g / L, potassium sodium tartrate: 30-45 g / L, sodium hydroxide: 1-3 g / L, additives: 3-5 mL / L; temperature: 40-50℃, anode-cathode area ratio: 1:1.5, current density: 0.7-1.2 A / dm² 2 Electroplating time: 5-15 min, coating thickness: preferably 1-6 μm.

[0079] To enhance the density of the coating, the present invention has optimized the process: generally, to meet the requirements of electroplating efficiency and achieve faster production, the current density for electroplating alkaline copper is 4-10 A / dm³. 2 The current density directly affects the density of the coating. A high current density weakens cathodic polarization and makes it easier to reach the hydrogen ion evolution overpotential in the solution, causing hydrogen evolution side reactions during electroplating. The evolved hydrogen gas leaves pores in the coating, reducing its density. The alkaline copper electroplating process used in this invention increases the concentration of the main salt cuprous cyanide and free sodium cyanide while reducing the current density, thereby obtaining an alkaline copper coating with excellent electroplating efficiency and density.

[0080] Electroplated copper pyrophosphate: The electroplated copper pyrophosphate layer is made of copper pyrophosphate. Pyrophosphate has a stronger complexing ability in water than cyanide, and its cathodic polarization in the pyrophosphate system is also stronger. This is because [Cu(P₂O₇)₂] in the solution... 6- It carries a greater number of negative charges and has a greater impact on the cathode process, while [Cu(P2O7)2] 6- It is difficult to discharge and requires hydrolysis to form [CuP2O7]. 2- Only then can a copper layer, [CuP2O7], be deposited via electrical discharge. 2- The hydrolysis is relatively slow, thus further increasing cathodic polarization. The charred copper electroplated film is denser with fewer pores, effectively preventing chloride ion penetration in salt spray tests and enhancing the workpiece's corrosion resistance and temperature shock resistance.

[0081] The electroplating parameters are as follows: copper pyrophosphate: 50-70 g / L, potassium pyrophosphate: 300-450 g / L, ammonium citrate: 15-30 g / L, ammonia: 2-5 mL / L; current density: 0.7-1.2 A / dm³2 temperature 40-50℃, anode / cathode area ratio: 1:1.5, plating time 50-90min, plating thickness: preferably 5-15μm. Also, to improve the compactness of the plating layer, the process used in the present application is optimized, reducing the current density.

[0082] The nickel sulfamate plating layer has good ductility, and compared with other nickel plating layers, the nickel sulfamate plating layer is more flexible and has lower internal stress, can withstand temperature impact to generate tensile stress without being torn, still maintains the original compactness, can effectively protect the workpiece in the salt spray test, and avoid corrosion.

[0083] The plating parameters are as follows: nickel sulfamate: 300-500g / L, nickel chloride: 10-25g / L, boric acid: 30-40g / L, sulfamic acid: 100-150g / L, additive: 5-10ml / L; current density: 0.8-1.2A / dm 2 temperature 40-50℃, anode / cathode area ratio: 1:1.5, plating time 50-90min, plating thickness: preferably 5-15μm. Also, to improve the compactness of the plating layer, the process used in the present application is optimized, reducing the current density.

[0084] The chemical copper layer is formed by self-catalytic plating through chemical reaction, and good bonding force can be obtained by adding the chemical copper layer between each layer. The chemical copper layer is a good intermediate plating layer, which can enhance the bonding force of the overall plating layer. At the same time, since the preparation process of the chemical copper layer is a pure chemical reaction, the thickness and porosity of the plating layer will not be affected by the current distribution, so the thickness of the chemical copper layer is more uniform, the porosity is lower, and the corrosion resistance is good. In the present application, the addition of this layer can enhance the corrosion resistance of the overall plating layer.

[0085] The chemical copper plating parameters are as follows: composition of the 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℃, pH 7.8-10.2, plating time 40-100min, general plating rate 1μm / 6min, i.e. 6min-1μm, 24min-4μm, 48min-8μm; the plating thickness can be controlled by controlling the parameters of the chemical copper plating.

[0086] The acid copper layer (i.e. acid copper plating layer) is copper sulfate electroplating, which has good adhesion with other plating layers and can be used as an excellent intermediate plating layer. The copper sulfate plating solution used in preparing the acid copper layer is stable and low in cost. Adding the acid copper layer between or on both sides of the base copper layer and the pyrophoric copper layer can enhance the brightness and corrosion resistance of the overall plating layer.

[0087] The parameters for electroplating the acid copper layer are as follows: composition of the electroplating solution: copper sulfate pentahydrate 160-250 g / L, sulfuric acid 25-50 mL / L, chloride ion 40-120 ppm, additives (one or a mixture of two or more of polydithiopropanesulfonic acid sodium, 2-mercaptobenzimidazole, 1,2-ethylene thiourea, and polyamine compound) 4-15 mL / L, current density 0.8-2.0 A / dm 2 , temperature 20-30℃, anode to cathode area ratio 1:1.5, electroplating time 20-80 min, and plating layer thickness controlled by adjusting the electroplating parameters as needed.

[0088] The watt nickel layer (i.e. watt nickel plating layer, bright nickel plating layer) is a nickel sulfate electroplating layer, which has good adhesion with other plating layers and can be used as an excellent intermediate plating layer. Adding the watt nickel layer between or on both sides of the base copper layer and the pyrophoric copper layer can enhance the brightness and corrosion resistance of the overall plating layer.

[0089] The parameters for electroplating the watt nickel layer are as follows: composition of the electroplating solution: nickel sulfate hexahydrate 250-350 g / L, nickel chloride hexahydrate 60-95 g / L, boric acid 40-60 g / L, additives (one or a mixture of two or more of dodecyl sodium sulfate, saccharin, and butynediol ethoxy ether) 6-12 mL / L, pH 3-5, current density 0.8-2.0 A / dm 2 , temperature 50-60℃, anode to cathode area ratio 1:1.5, electroplating time 30-70 min, and plating layer thickness controlled by adjusting the electroplating parameters as needed.

[0090] The pre-plated silver layer serves to pre-plate a silver layer under high current density and low solution concentration, thereby enhancing the adhesion between the electroplated layers and preparing for the next process.

[0091] The electroplating parameters are as follows:

[0092] Cyanide silver 30-120 g / L, potassium cyanide 80-200 g / L, free potassium cyanide 30-80 g / L, potassium carbonate 5-30 g / L, potassium hydroxide 2-20 g / L, temperature 20-25℃, anode to cathode area ratio 1:1.5, current density 0.5-2 A / dm 2 , electroplating time about 1 min.

[0093] Electroplated silver: electroplated silver is cyanide silver plating, which also has strong cathode polarization to make the plating layer more dense, and can effectively hinder the penetration of chloride ions in the salt spray test, and enhance the corrosion resistance and temperature impact resistance of the workpiece. The standard electrode potential of silver is +0.799V, and the chemical inertness of silver is extremely high. Silver only reacts with sulfur in the air and hardly reacts with other substances, so it has strong corrosion resistance and temperature impact resistance. The electroplated silver layer on the surface of the workpiece can effectively improve the corrosion resistance and temperature impact resistance.

[0094] The electroplating parameters are as follows:

[0095] Silver cyanide: 30-50g / L, potassium cyanide: 130-150g / L, free potassium cyanide: 45-60g / L, potassium carbonate: 15-25g / L, potassium hydroxide: 4-10g / L, additives: 20-30g / L, temperature: 20-25℃, anode / cathode area ratio: 1:1.5, current density: 0.2-0.5A / dm 2 , electroplating time: 1-90min, and the thickness of the plating layer is controlled by controlling the electroplating parameters as needed. Similarly, to improve the density of the plating layer, the process used in the present application is optimized, and the current density is reduced.

[0096] The aluminum terminal provided by the present application can still achieve 120H in salt spray resistance after impact test. The expansion coefficients of the alkaline copper layer, the cupric pyrite layer and the silver layer are close to that of aluminum. In temperature impact cycles, the expansion volumes of these plating layers and the aluminum material are similar, and the tensile stress they suffer is smaller, and the volume change has less effect on the plating layer. At the same time, the ductility of the alkaline copper, cupric pyrite and silver layers is also excellent, and they can effectively withstand the tensile stress (on the one hand, the tensile stress is reduced, and on the other hand, the tensile stress can be withstood) without damage.

[0097] The nickel sulfamate layer used in the present application has good ductility and toughness, and can easily withstand the stress caused by volume change without damage at the microscopic level of the plating layer, and can continue to maintain its good density and still have good protection effect.

[0098] The alkaline copper layer, cupric pyrite layer, nickel sulfamate layer and silver layer used in the present application can bring the following technical effects:

[0099] 1. In temperature cycles, the increase of temperature will cause the release of internal stress in the electroplating layer, resulting in the failure of the bonding force between the plating layers. The alkaline copper layer as the lowermost layer has good bonding force, which can ensure the bonding force of the terminal in temperature impact and prevent problems such as blistering and peeling. At the same time, the nickel sulfamate is also a low-stress nickel plating species, which has relatively low internal stress itself, and cooperates with the alkaline copper layer to effectively increase the plating layer bonding force of the terminal.

[0100] 2, enhance the salt spray effect: because the surface state of the substrate has a great influence on the electroplated layer, it is not possible to directly electroplate a very dense plating layer on the porous surface of aluminum material, the present application preferably adopts a scheme of gradually improving the density, the density of the zinc layer is lower than that of the alkaline copper, the density of the alkaline copper is slightly lower than that of the pyro-copper, and the density of the three layers is gradually improved, so that the density of the final pyro-copper layer is optimal, therefore, the present application preferably adopts 1-6 μm alkaline copper + 5-15 μm pyro-copper for combination, which can effectively improve the corrosion resistance of the workpiece.

[0101] When the electroplated alkaline copper layer is thick, rough plating layer is prone to occur, therefore, the present application selects electroplating of 1-10 μm (preferably 1-6 μm), under this plating layer thickness, the bonding force and the density can meet the requirements. The pyro-copper layer is preferably selected between 5-15 μm, the thicker the plating layer, the more it can cover its own pores, but considering the influence of electroplating time, 5-15 μm is preferably selected. The thickness range of the nickel sulfamate layer is 4-15 μm, and the preferred thickness is 4-15 μm, and the plating layer is still prone to cause the increase of internal stress and the decrease of ductility, therefore, 4-15 μm is preferably selected in combination.

[0102] The corrosion-resistant composite layer provided by the present application has strong density of the alkaline copper layer, the pyro-copper layer, the nickel sulfamate layer, the silver layer and other electroplated film layers, which can effectively hinder the penetration of chloride ions in the salt spray test, and the interaction between the metal / alloy layers, and the mutual superposition, so that the pores originally existing in the single plating layer are covered by other electroplated film layers, even if the chloride ions penetrate one electroplated film layer in the salt spray test, other dense plating layers can still effectively hinder the further penetration of chloride ions, greatly improving the corrosion resistance of the aluminum base material. By increasing the zinc layer, the secondary zinc deposition layer, and the chemical copper layer, the acid copper layer, the watt nickel layer, etc., the corrosion resistance can be further improved.

[0103] The aluminum terminals of the examples and the comparative examples of the present application can be prepared by the above-mentioned method.

[0104] Example 1

[0105] The present embodiment provides an aluminum terminal with a corrosion-resistant and temperature-shock-resistant composite layer, wherein:

[0106] The front surface of the aluminum terminal material has been subjected to roll pressing and polishing treatment, and the roughness is less than Ra 0.8, and the side surface has been processed by precise stamping process, and the bright band is greater than 98% and the roughness is less than Ra 0.8; Figure 4 The first picture in the above is a picture of the side surface of ordinary stamping, and the second picture is a picture of the side surface of precise stamping, and the difference between the two is Figure 4It can be seen that the rough band of the aluminum terminal obtained by ordinary stamping accounts for a high proportion, while the side surface of the aluminum terminal obtained by precise stamping is basically bright band, accounting for more than 98%. The condition of the bright band is determined by a projector detection, and the proportion of the bright band is determined by calculating the length or area. The roughness of the surface and side surface of the aluminum terminal material before and after polishing is 0.315 μm and 0.282 μm respectively, so it can be seen that the surface roughness can be greatly reduced and the smoothness can be improved by polishing. In the roughness test, the sampling cutoff wavelength of the filter is λc=0.8 mm×5.

[0107] The composite corrosion-resistant and temperature-impact-resistant layer includes a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a pyrolytic copper layer, a nickel sulfamate layer, and a silver layer arranged on the fully exposed area of the surface of the aluminum terminal material, and the thicknesses are 0.5 μm, 2 μm, 2 μm, 8 μm, 8 μm, and 10 μm respectively.

[0108] Embodiment 2

[0109] The embodiment provides an aluminum terminal with a composite corrosion-resistant and temperature-impact-resistant layer, wherein:

[0110] The front surface of the aluminum terminal material is subjected to rolling and polishing treatment, and the roughness is less than Ra 0.8; the side surface is subjected to precise stamping process, and the bright band is greater than 98% and the roughness is less than Ra 0.8.

[0111] The composite corrosion-resistant and temperature-impact-resistant layer includes a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a pyrolytic copper layer, a nickel sulfamate layer, and a silver layer arranged on the fully exposed area of the surface of the aluminum terminal material, and the thicknesses are about 0.5 μm, about 2.0 μm, about 2.0 μm, about 10 μm, about 10 μm, and about 15 μm respectively. After the composite corrosion-resistant layer is formed, the roughness of the surface of the aluminum terminal is also improved and reduced to 0.203 μm.

[0112] Embodiment 3

[0113] The embodiment provides an aluminum terminal with a composite corrosion-resistant and temperature-impact-resistant layer, wherein:

[0114] The front surface of the aluminum terminal material is subjected to rolling and polishing treatment, and the roughness is less than Ra 0.8; the side surface is subjected to precise stamping process, and the bright band is greater than 98% and the roughness is less than Ra 0.8.

[0115] The composite corrosion-resistant and temperature-impact-resistant layer includes a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a pyrolytic copper layer, a nickel sulfamate layer, and a silver layer arranged on the fully exposed area of the surface of the aluminum terminal material, and the thicknesses are about 0.5 μm, about 2.0 μm, about 2.0 μm, about 10 μm, about 10 μm, and about 15 μm respectively. After the composite corrosion-resistant layer is formed, the roughness of the surface of the aluminum terminal is also improved and reduced to 0.203 μm.

[0116] Embodiment 4

[0117] The embodiment provides an aluminum terminal with a corrosion-resistant and temperature-impact-resistant composite layer, and the aluminum terminal comprises the following components in sequence:

[0118] The front surface of the aluminum terminal material is subjected to rolling and polishing treatment, and the roughness is less than Ra 0.8; the side surface is subjected to precise stamping process, and the bright band is greater than 98% and the roughness is less than Ra 0.8.

[0119] The composite corrosion-resistant and temperature-impact-resistant layer comprises a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a pyrolytic copper layer, a nickel sulfamate layer and a silver layer arranged on the full exposed area of the surface of the aluminum terminal material, and the thicknesses of the zinc layer, the secondary zinc deposition layer, the alkaline copper layer, the pyrolytic copper layer, the nickel sulfamate layer and the silver layer are 0.5 μm, 2 μm, 3 μm, 5 μm, 5 μm and 5 μm respectively.

[0120] Embodiment 5

[0121] The embodiment provides an aluminum terminal with a corrosion-resistant and temperature-impact-resistant composite layer, and the aluminum terminal comprises the following components in sequence:

[0122] The front surface of the aluminum terminal material is subjected to rolling and polishing treatment, and the roughness is less than Ra 0.8; the side surface is subjected to precise stamping process, and the bright band is greater than 98% and the roughness is less than Ra 0.8.

[0123] The composite corrosion-resistant and temperature-impact-resistant layer comprises a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a pyrolytic copper layer, a nickel sulfamate layer and a silver layer arranged on the full exposed area of the surface of the aluminum terminal material, and the thicknesses of the zinc layer, the secondary zinc deposition layer, the alkaline copper layer, the pyrolytic copper layer, the nickel sulfamate layer and the silver layer are 0.5 μm, 2 μm, 3 μm, 5 μm, 5 μm and 20 μm respectively.

[0124] Embodiment 6

[0125] The embodiment provides an aluminum terminal with a corrosion-resistant and temperature-impact-resistant composite layer, and the aluminum terminal comprises the following components in sequence:

[0126] The front surface of the aluminum terminal material is subjected to rolling and polishing treatment, and the roughness is less than Ra 0.8; the side surface is subjected to precise stamping process, and the bright band is greater than 98% and the roughness is less than Ra 0.8.

[0127] The composite corrosion-resistant and temperature-impact-resistant layer comprises a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a pyrolytic copper layer, a nickel sulfamate layer and a silver layer arranged on the full exposed area of the surface of the aluminum terminal material, and the thicknesses of the zinc layer, the secondary zinc deposition layer, the alkaline copper layer, the pyrolytic copper layer, the nickel sulfamate layer and the silver layer are 0.5 μm, 2 μm, 3 μm, 5 μm, 18 μm and 5 μm respectively.

[0128] Comparative example 1

[0129] The comparative example provides an aluminum terminal with a corrosion-resistant and temperature-impact-resistant composite layer, and the difference between the aluminum terminal and the aluminum terminal in the embodiment 1 is that the corrosion-resistant and temperature-impact-resistant composite layer only comprises a zinc layer, a secondary zinc deposition layer and an alkaline copper layer, and the thicknesses of the zinc layer, the secondary zinc deposition layer and the alkaline copper layer are 0.5 μm, 2 μm and 28 μm respectively.

[0130] The thickness of each comparative example was kept constant with Example 1, and the total thickness of each layer was unchanged.

[0131] Comparative Example 2

[0132] This comparative example provides an aluminum terminal having a corrosion-resistant temperature shock-resistant composite layer, which differs from Example 1 in that the corrosion-resistant temperature shock-resistant composite layer has only a zinc layer, a secondary zinc deposition layer, a silver layer, and a thickness of 0.5 μm, 2 μm, and 28 μm.

[0133] Comparative Example 3

[0134] This comparative example provides an aluminum terminal having a corrosion-resistant temperature shock-resistant composite layer, which differs from Example 1 in that the corrosion-resistant temperature shock-resistant composite layer has only a zinc layer, a secondary zinc deposition layer, a silver layer, and a thickness of 0.5 μm, 2 μm, and 28 μm.

[0135] Comparative Example 4

[0136] This comparative example provides an aluminum terminal having a corrosion-resistant temperature shock-resistant composite layer, which differs from Example 1 in that the corrosion-resistant temperature shock-resistant composite layer has only a zinc layer, a secondary zinc deposition layer, a silver layer, and a thickness of 0.5 μm, 2 μm, and 28 μm. The aluminum terminal obtained in this Comparative Example 4 exhibited large-area peeling, indicating that the composite layer (plating layer) formed did not have adhesion to the surface of the aluminum terminal, as shown in FIG. 2. Figure 7

[0137] Comparative Example 5

[0138] This comparative example provides an aluminum terminal having a corrosion-resistant temperature shock-resistant composite layer, which differs from Example 1 in that the corrosion-resistant temperature shock-resistant composite layer omits the alkaline copper layer and has only a zinc layer, a secondary zinc deposition layer, a silver layer, and a thickness of 0.5 μm, 2 μm, and 10 μm.

[0139] Comparative Example 6

[0140] This comparative example provides an aluminum terminal having a corrosion-resistant temperature shock-resistant composite layer, which differs from Example 1 in that the corrosion-resistant temperature shock-resistant composite layer omits the alkaline copper layer and has only a zinc layer, a secondary zinc deposition layer, a silver layer, and a thickness of 0.5 μm, 2 μm, and 10 μm.

[0141] Comparative Example 7

[0142] ​This comparative example provides an aluminum terminal having a corrosion-resistant and temperature-impact-resistant composite layer, which differs from Example 1 in that the corrosion-resistant and temperature-impact-resistant composite layer omits the silver layer and only has a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a pyrophoric copper layer, and a nickel sulfamate layer, with thicknesses of 0.5 μm, 2 μm, 2 μm, 8 μm, and 18 μm.

[0143] Comparative Example 8

[0144] This comparative example provides an aluminum terminal having a corrosion-resistant and temperature-impact-resistant composite layer, which differs from Example 1 in that the corrosion-resistant and temperature-impact-resistant composite layer omits the silver layer and only has a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a pyrophoric copper layer, and a nickel sulfamate layer, with thicknesses of 0.5 μm, 2 μm, 2 μm, 8 μm, and 18 μm.

[0145] Comparative Example 9

[0146] This comparative example provides a wire-cut aluminum material: the plating layer is the same as in Example 1, and the material has not been subjected to precision stamping and polishing treatment.

[0147] Comparative Example 10

[0148] This comparative example provides an aluminum terminal having a corrosion-resistant and temperature-impact-resistant composite layer, which differs from Example 1 in that the plating layer is the same as in Example 1, and the material has not been subjected to rolling treatment.

[0149] Comparative Examples 11-14

[0150] These comparative examples each provide an aluminum terminal having a corrosion-resistant composite layer, which differs from Example 3 in that the thickness of the plating layer is different from that of Example 3, as shown in Table 1.

[0151] Comparative Example 15

[0152] This comparative example provides an aluminum terminal having a corrosion-resistant composite layer, which differs from Example 1 in that the thickness of the plating layer is different from that of Example 1, as shown in Table 1.

[0153] Comparative Example 16

[0154] This comparative example provides an aluminum terminal having a transition layer and a conventional chemical nickel layer on the surface.

[0155] The results of the salt spray corrosion test after the temperature impact cycle test of the aluminum terminals of the examples and comparative examples and the wire-cut aluminum material of Comparative Example 9 are shown in Table 1.

[0156] The temperature shock experiment is carried out in the following manner: first, the sample is kept at -40 DEG C for 30 min, then transferred to 140 DEG C within 30 s for 30 min, after 100 cycles of "keeping at -40 DEG C for 30 min" and "keeping at 140 DEG C for 30 min", the salt spray corrosion resistance experiment is carried out according to the national standard GB / T 2423.17-2008. The qualified standard is: no corrosion occurs on the plating layer, no surface pitting, peeling, bubbling, etc., and no spots and color changes on the plating layer.

[0157] Table 1

[0158]

[0159]

[0160] Test results:

[0161] It is found through experiments that the aluminum terminal of the application has no problems such as over-limit contact resistance, poor appearance, over-limit voltage resistance, etc.

[0162] The four plating layers of alkaline copper, cupric pyrite, ammonia nickel and silver are stacked, and the corrosion prevention effect is better than that of a single plating layer.

[0163] Compared with the conventional electroplating method (Comparative Example 16, a 3 μm thick chemical nickel layer is plated on the transition layer by chemical plating), the corrosion resistant layer obtained by the conventional electroplating method appears corrosion after temperature cycling and salt spray experiment for 12H (as shown in Table 1), while the corrosion resistance of the scheme provided by the application is more excellent.

[0164] Comparative Example 9 is based on wire cutting substrate processing, and in the corrosion resistance experiment, the side of the sample first appears corrosion points at 48H, and the corrosion point condition is as shown in Figure 5 .

[0165] The conventional electroplated terminal is compared in terms of the following performances: 1. SEM after temperature cycling (to see the damage of the plating layer); 2. Salt spray after temperature cycling (to see the corrosion resistance). The test results are as shown in Figure 6 , wherein, Figure 6 a figure in the table is a conventional plating layer (only 1 μm of copper plating + 4 μm of silver plating) after 100 times of temperature shock, b figure is the corrosion resistant layer of Example 1 of the application after 100 times of temperature shock, c figure is a conventional plating layer without temperature shock, and d figure is the plating layer of Example 1 of the application without temperature shock.

[0166] As can be seen from Figure 6 , the corrosion resistance of the aluminum terminal after temperature shock decreases more, and the corrosion points are obviously more than those of the sample without temperature shock; the corrosion resistance of the conventional plating layer (only 1 μm of copper plating + 4 μm of silver plating) is poorer than that of the corrosion resistant layer of the application, and serious corrosion occurs whether or not the temperature shock experiment is carried out.

[0167] Figure 8 The surface SEM image and the side section metallographic image of the conventional coating (nickel plating) before and after temperature impact.

[0168] From Figure 8 It can be seen that the conventional nickel coating after temperature impact can be seen obvious cracks under SEM, and obvious cracks can be observed on the side after section metallographic test, which shows that the temperature impact has a great influence on the coating, leading to the failure of the coating and losing the protection of the terminal.

[0169] Figure 9 The side section metallographic images of the conventional coating (nickel plating) after temperature impact and the corrosion-resistant layer of the embodiment 1 of the present application, wherein the left image is the conventional coating, and the right image is the corrosion-resistant layer of the embodiment 1 of the present application.

[0170] From Figure 9 It can be seen that the corrosion-resistant layer of the embodiment 1 of the present application can effectively withstand temperature impact without cracks, and has good ductility in the environment with sharp temperature change, maintaining the integrity of the coating.

[0171] The salt spray corrosion resistance of the aluminum terminal with the semi-exposed area provided by the embodiment 3 of the present application can reach 28H, although it is not as good as the embodiment 1 in terms of corrosion resistance time, but the test is carried out in the completely exposed salt spray environment, and in the actual use process of the aluminum terminal, the area is not completely exposed to the environment, therefore, the lower corrosion resistance time of the embodiment 3 test than the embodiment 1 does not affect the service life of the aluminum terminal, and the corrosion-resistant composite layer in the semi-exposed area still has good corrosion resistance effect, that is, if the semi-exposed area of the aluminum terminal of the embodiment 1 is provided with the corrosion-resistant composite layer in the embodiment 3, the service life of the corrosion-resistant composite layer in the semi-exposed area will not be lower than that of the corrosion-resistant composite layer in the exposed area, and the corrosion resistance of the whole aluminum terminal is also guaranteed.

[0172] Based on this, the present application can set different corrosion-resistant composite layers in different positions of the aluminum terminal according to the area characteristics (whether exposed to the environment, the high and low of the corrosion resistance requirement) and the use demand, so as to reduce the cost while guaranteeing the corrosion resistance and service life.

[0173] Other performances of the coating obtained by the embodiment 1 of the present application:

[0174] 1. Roughness Ra < 0.4;

[0175] 2. Keep for half an hour at 500℃ and quench in water, no bubble appears (national standard 220℃), which shows that the adhesion of the coating is good, and the electroplated layers are closely connected.

[0176] Effect of surface roughness and bright band on corrosion resistance experiments:

[0177] Example 7, Comparative Example 9 and Comparative Examples 17-19 form the same corrosion-resistant layer (i.e. the corrosion-resistant layer in Example 1) on the surface of the terminal (including wire-cut material) with different surface roughness (surface roughness before preparing the corrosion-resistant layer) and different proportion of bright band, and conduct a salt spray test (according to GB / T 2423.17-2008), to evaluate the influence of surface roughness and proportion of bright band on the salt spray corrosion resistance, and the qualified standard is: no corrosion occurs on the plating layer, no pitting, peeling, blistering, etc. on the surface, and no spots and color changes on the plating layer. The experimental results are shown in Table 2.

[0178] Table 2

[0179]

[0180] According to the experimental data of Example 7, Comparative Example 17 and Comparative Example 18 given in Table 2, it can be seen that under the same conditions, the smaller the surface roughness of the substrate surface, the longer the time of the aluminum terminal with the corrosion-resistant composite layer on the surface to resist salt spray, and the better the salt spray corrosion resistance;

[0181] According to the experimental data of Example 7, Comparative Example 19 and Comparative Example 9 given in Table 2, it can be seen that under the same conditions and similar surface roughness, the higher the proportion of bright band on the substrate surface, the longer the time of the aluminum terminal with the corrosion-resistant composite layer on the surface to resist salt spray, and the better the salt spray corrosion resistance.

[0182] The technical solution of the present application has the following advantages:

[0183] 1. Low cost and simple process; 2. The performance of the composite layer is excellent, and when a thicker silver layer is used, it can meet the 120H salt spray corrosion resistance requirement, and when a thinner silver layer is used, it can meet the 28H salt spray corrosion resistance requirement, which can be applied to different situations and meet different corrosion resistance requirements; 3. The adhesion of each layer is excellent; 4. Although the aluminum terminal surface is provided with a corrosion-resistant and temperature-impact-resistant composite layer, the conductivity is still very good.

Claims

1. A corrosion and temperature shock resistant composite layer comprising: A basic copper layer, a pyrolytic copper layer, a nickel aminosulfonate layer, and a silver layer; The thickness of the basic copper layer is 1-10 μm, the thickness of the pyrolytic copper layer is 2-18 μm, the thickness of the nickel aminosulfonate layer is 0.5-28 μm, and the thickness of the silver layer is 0.2-25 μm. The basic copper layer, the pyrolytic copper layer, the nickel aminosulfonate layer, and the silver layer are sequentially arranged.

2. The corrosion resistant temperature shock resistant composite layer of claim 1, wherein, The thickness of the basic copper layer is 1-6 μm.

3. The corrosion and temperature shock resistant composite layer of claim 1, wherein, The thickness of the pyrolytic copper layer is 5-15 μm.

4. The corrosion and temperature shock resistant composite layer of claim 1, wherein, The thickness of the nickel aminosulfonate layer is 0.5-18 μm.

5. The corrosion and temperature shock resistant composite layer of claim 1, wherein, The thickness of the silver layer is 0.2-3 μm or 8-15 μm.

6. The corrosion and temperature shock resistant composite layer of claim 1, wherein, The corrosion-resistant and temperature-shock-resistant composite layer further comprises a transition layer arranged on the side of the basic copper layer not in contact with the pyrolytic copper layer.

7. The corrosion and temperature shock resistant composite layer of claim 6, wherein, The transition layer comprises a zinc layer or a combination of a zinc layer and a secondary zinc layer.

8. The corrosion and temperature shock resistant composite layer of claim 7, wherein, The thickness of the zinc layer is 0.1-10.0 μm.

9. The corrosion and temperature shock resistant composite layer of claim 8, wherein, The thickness of the zinc layer is 0.5-1 μm.

10. The corrosion and temperature shock resistant composite layer of claim 7, wherein, The thickness of the secondary zinc layer is 0.1-10 μm.

11. The corrosion and temperature shock resistant composite layer of claim 10, wherein, The thickness of the secondary zinc layer is 1.5-2.5 μm.

12. The corrosion and temperature shock resistant composite layer of any of claims 1-11, wherein, The basic copper layer, the pyrolytic copper layer, the nickel aminosulfonate layer, and the silver layer are respectively electroplated layers.

13. The corrosion and temperature shock resistant composite layer of any of claims 1-11, wherein, The corrosion-resistant and temperature-shock-resistant composite layer further comprises a chemical copper layer arranged on the surface of the basic copper layer or the surface of the pyrolytic copper layer.

14. The corrosion resistant temperature shock resistant composite layer of claim 13, wherein, The thickness of the chemical copper layer is 3-25 μm.

15. The corrosion resistant temperature shock resistant composite layer of claim 14, wherein, The thickness of the chemical copper layer is 5-15 μm.

16. The corrosion resistant temperature shock resistant composite layer of claim 12, wherein, The corrosion-resistant and temperature-shock-resistant composite layer further comprises a chemical copper layer arranged on the surface of the basic copper layer or the surface of the pyrolytic copper layer.

17. The corrosion resistant temperature shock resistant composite layer of claim 16, wherein, The thickness of the chemical copper layer is 3-25 μm.

18. The corrosion resistant temperature shock resistant composite layer of claim 17, wherein, The thickness of the chemical copper layer is 5-15 μm.

19. The corrosion and temperature shock resistant composite layer of any of claims 1-11, 14-18, wherein, The corrosion-resistant and temperature-shock-resistant composite layer further comprises an acid copper layer arranged on the surface of the basic copper layer or the surface of the pyrolytic copper layer.

20. The corrosion resistant temperature shock resistant composite layer of claim 19, wherein, The thickness of the acid copper layer is 1-20 μm.

21. The corrosion resistant temperature shock resistant composite layer of claim 20, wherein, The thickness of the acid copper layer is 3-10 μm.

22. The corrosion resistant temperature shock resistant composite layer of claim 12, wherein, The corrosion-resistant and temperature-shock-resistant composite layer further comprises an acid copper layer arranged on the surface of the basic copper layer or the surface of the pyrolytic copper layer.

23. The corrosion resistant temperature shock resistant composite layer of claim 22, wherein, The thickness of the acid copper layer is 1-20 μm.

24. The corrosion resistant temperature shock resistant composite layer of claim 23, wherein, The thickness of the acid copper layer is 3-10 μm.

25. The corrosion resistant temperature shock resistant composite layer of claim 13, wherein, The corrosion-resistant and temperature-shock-resistant composite layer further comprises an acid copper layer arranged on the surface of the basic copper layer or the surface of the pyrolytic copper layer.

26. The corrosion resistant temperature shock resistant composite layer of claim 25, wherein, The thickness of the acid copper layer is 1-20 μm.

27. The corrosion resistant temperature shock resistant composite layer of claim 26, wherein, The thickness of the acid copper layer is 3-10 μm.

28. The corrosion and temperature shock resistant composite layer of any of claims 1-11, 14-18, 20-27, wherein, The corrosion-resistant and temperature-shock-resistant composite layer further comprises a watt nickel layer arranged on the surface of the nickel aminosulfonate layer.

29. The corrosion resistant temperature shock resistant composite layer of claim 28, wherein, The thickness of the watt nickel layer is 1-20 μm.

30. The corrosion resistant temperature shock resistant composite layer of claim 29, wherein, The thickness of the watt nickel layer is 3-9 μm.

31. The corrosion and temperature shock resistant composite layer of claim 12, wherein, The corrosion-resistant and temperature-shock-resistant composite layer further comprises a watt nickel layer arranged on the surface of the nickel aminosulfonate layer.

32. The corrosion resistant temperature shock resistant composite layer of claim 31, wherein, The thickness of the watt nickel layer is 1-20 μm.

33. The corrosion resistant temperature shock resistant composite layer of claim 32, wherein, The thickness of the watt nickel layer is 3-9 μm.

34. The corrosion and temperature shock resistant composite layer of claim 13, wherein, The corrosion-resistant and temperature-shock-resistant composite layer further comprises a watt nickel layer arranged on the surface of the nickel aminosulfonate layer.

35. The corrosion and temperature shock resistant composite layer of claim 34, wherein, The thickness of the watt nickel layer is 1-20 μm.

36. The corrosion and temperature shock resistant composite layer of claim 35, wherein, The thickness of the watt nickel layer is 3-9 μm.

37. The corrosion resistant temperature shock resistant composite layer of claim 19, wherein, The corrosion-resistant and temperature-shock-resistant composite layer further comprises a layer of Watt nickel, which is arranged on the surface of the layer of nickel sulfamate.

38. The corrosion resistant temperature shock resistant composite layer of claim 37, wherein, The thickness of the layer of Watt nickel is 1-20 μm.

39. The corrosion resistant temperature shock resistant composite layer of claim 38, wherein, The thickness of the layer of Watt nickel is 3-9 μm.

40. A method for preparing the corrosion-resistant and temperature-shock-resistant composite layer according to any one of claims 1-39, comprising the following steps: forming, on the surface of the substrate, a layer of cupric hydroxide, a layer of cupric pyrophosphate, a layer of nickel sulfamate, and a layer of silver in sequence by electroplating.

41. The method of manufacturing according to claim 40, wherein, The plating solution for the copper layer contains cuprous cyanide: 40-50 g / L, total sodium cyanide: 40-60 g / L, free sodium cyanide: 8-14 g / L, potassium sodium tartrate: 30-45 g / L, sodium hydroxide: 1-3 g / L, and additives: 3-5 mL / L, based on the total volume of the plating solution. The temperature of the plating solution is 40-50°C, the area ratio of the cathode to the anode is 1:1-2, the current density is 0.7-1.2 A / dm 2 , and the plating time is 5-15 min.

42. The method of manufacturing according to claim 41, wherein, The area ratio of the anode to the cathode is 1:1.

5.

43. The method of manufacturing according to claim 40, wherein, The plating solution for the copper layer contains copper pyrophosphate: 50-70 g / L, potassium pyrophosphate: 300-450 g / L, ammonium citrate: 15-30 g / L, and ammonia: 2-5 mL / L, based on the total volume of the plating solution. The temperature for plating the copper layer is 40-50°C, the current density is 0.7-1.2 A / dm 2 , the ratio of anode to cathode area is 1:1-2, and the plating time is 50-90 min.

44. The method of manufacturing according to claim 43, wherein, The area ratio of the anode to the cathode is 1:1.

5.

45. The method of manufacturing according to claim 43, wherein, The electroplating time is 70 min.

46. The method of manufacturing according to claim 40, wherein, The electroplating solution for the sulfamic acid nickel layer contains, based on the total volume of the electroplating solution, 300-500 g / L of sulfamic acid nickel, 10-25 g / L of nickel chloride, 30-40 g / L of boric acid, 100-150 g / L of sulfamic acid, and 5-10 ml / L of an additive; the temperature for electroplating the sulfamic acid nickel layer is 50-60℃, the current density is 0.8-1.2 A / dm 2 , the ratio of anode to cathode area is 1:1-2, and the electroplating time is 1-80 min.

47. The method of manufacturing according to claim 46, wherein, The area ratio of the anode to the cathode is 1:1.

5.

48. The method of manufacturing according to claim 46, wherein, The electroplating time is 40-60 min.

49. The method of manufacturing according to claim 48, wherein, The electroplating time is 50 min.

50. The method of manufacturing according to claim 40, wherein, The silver plating solution contains 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, and additives 20-30 g / L, based on the total volume of the plating solution. The temperature of the silver plating layer is 20-25°C, the area ratio of the cathode to the anode is 1:1-2, the current density is 0.2-0.5 A / dm 2 , and the plating time is 1-90 min.

51. The method of manufacturing according to claim 50, wherein, The area ratio of the anode to the cathode is 1:1.

5.

52. The method of manufacturing according to claim 50, wherein, The electroplating time is 30-60 min.

53. The method of manufacturing according to claim 52, wherein, The electroplating time is 40 min.

54. A method for treating an aluminum substrate to be corrosion-resistant and temperature-shock-resistant, comprising the step of arranging on the surface of the aluminum substrate the corrosion-resistant and temperature-shock-resistant composite layer according to any one of claims 1-39.

55. The method of claim 54, wherein, The corrosion resistance refers to salt spray corrosion resistance, and the temperature-shock resistance refers to temperature cycle shock resistance.

56. The method of claim 54, wherein, The surface roughness of the aluminum substrate is less than Ra 3.

6.

57. The method of claim 56, wherein, The surface roughness of the aluminum substrate is less than Ra 0.

8.

58. A corrosion resistant temperature shock resistant aluminum terminal, wherein, Part or all of the surface of the corrosion-resistant and temperature-shock-resistant aluminum terminal is provided with the corrosion-resistant and temperature-shock-resistant composite layer according to any one of claims 1-39.

59. A method for preparing the corrosion-resistant and temperature-shock-resistant aluminum terminal according to claim 58, comprising the following steps: performing roll processing and polishing processing on the front surface of the aluminum terminal; performing stamping processing on the side surface of the aluminum terminal; forming, on the front surface and the side surface of the processed aluminum terminal, a layer of cupric hydroxide, a layer of cupric pyrophosphate, a layer of nickel sulfamate, and a layer of silver in sequence by electroplating, to obtain the corrosion-resistant and temperature-shock-resistant aluminum terminal.

60. The method of manufacturing according to claim 59, wherein, Before the layer of cupric hydroxide is formed by electroplating, a transition layer is first formed on the front surface and the side surface of the processed aluminum terminal.

61. The method of manufacturing according to claim 59, wherein, The front surface of the aluminum terminal after the roll processing and polishing processing has a surface roughness of less than Ra 3.

6.

62. The method of manufacturing according to claim 61, wherein, The front surface of the aluminum terminal after the roll processing and polishing processing has a surface roughness of less than Ra 0.

8.

63. The method of manufacturing of claim 59, wherein, The side surface of the aluminum terminal after the roll processing has a surface roughness of less than Ra 3.6, and a bright band of greater than 50%.

64. The method of manufacturing according to claim 63, wherein, The side surface of the aluminum terminal after the roll processing has a surface roughness of less than Ra 0.

8.

65. The method of manufacturing according to claim 63, wherein, The bright band of the aluminum terminal after the roll processing is greater than 98%.

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