A high-precision electroplating method and system for local selective gold plating of aluminum alloy

Abstract

The present invention relates to the technical field of high-precision electroplating of aluminum alloys. In view of the problem that existing mask materials are difficult to achieve high-precision local gold plating, a high-precision electroplating method and system for local selective gold plating of aluminum alloys are proposed. The aluminum alloy to be electroplated is passivated and heterogeneous seed deposited to improve the bonding strength with the zinc layer and the uniformity of the coating; the bonding strength between the zinc layer and the mask is improved by modifying silicon dioxide with mercapto groups and silanes; the non-gold-plated area is protected by a photothermal dual-responsive polymer mask polymerized by fluorine-containing segments and azobenzene monomers, and the hydrophilic state is locked by ultraviolet laser scanning and heating to achieve micron-level selective regional activation; after local gold plating, the mask is removed by a stripping solution. This method significantly improves the bonding strength, uniformity and edge clarity of the coating, and is suitable for the high-precision gold plating requirements of aluminum alloy parts with complex structures.

Description

Technical Field

[0001] The present application relates to the field of high-precision electroplating of aluminum alloys, and in particular to a high-precision electroplating method and system for local selective gold plating of aluminum alloys. Background Art

[0002] Aluminum alloys are lightweight, high-strength, and have good electrical conductivity, and are widely used in electronics, aerospace, automotive, and other fields. Local selective gold plating is commonly used to improve the electrical conductivity, corrosion resistance, and welding properties of aluminum alloys. Among them, high-precision local selective gold plating technology has important applications in the microelectronics, aerospace, and automotive industries. High-precision gold plating technologies mainly include chemical plating, electroplating, and laser-assisted gold plating. Although chemical plating can achieve uniform coating, it has a slow plating speed, high cost, and is difficult to achieve local selective gold plating. Electroplating technology can achieve local gold plating, but it has extremely high requirements for surface cleanliness and conductivity, and the coating uniformity is poor. Laser-assisted local gold plating technology has high precision and controllability, and can achieve local gold plating at the micron level.

[0003] Mask materials can provide protection for non-gold-plated areas during local selective gold plating, thereby assisting in achieving local selectivity in gold plating. In the prior art, mask materials are mainly divided into two categories: photoresponsive materials and chemically responsive materials. Photoresponsive materials (such as photoresists) activate local areas through ultraviolet light irradiation, but the process is complex and requires exposure and development equipment. Chemically responsive materials (such as self-assembled monolayers) protect local areas through chemical modification, but their response speed is slow and they have extremely high requirements for surface cleanliness. Most existing mask materials are single-responsive materials, which makes it difficult to simultaneously meet the requirements of high-precision and complex-shaped gold plating, resulting in unclear boundaries and insufficient precision in the gold-plated areas. Problems such as poor adhesion and easy peeling of mask materials also limit their application in high-precision gold plating. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, this application proposes a high-precision electroplating method and system for local selective gold plating of aluminum alloys. The aluminum alloy to be electroplated is passivated and heterogeneous seed deposited to improve the bonding strength with the zinc layer and the uniformity of the coating; the bonding strength between the zinc layer and the mask is improved by modifying silicon dioxide with mercapto groups and silanes; the non-gold-plated area is protected by a photothermal dual-responsive polymer mask polymerized by fluorine-containing segments and azobenzene monomers, and the hydrophilic state is locked by combining ultraviolet laser scanning and heating to achieve micron-level selective regional activation; after local gold plating, the mask is removed by stripping liquid. This method significantly improves the bonding strength, uniformity and edge clarity of the coating, and is suitable for the high-precision gold plating needs of aluminum alloy parts with complex structures.

[0005] To achieve the above objectives, this application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a high-precision electroplating method for local selective gold plating of aluminum alloy, comprising the following steps:

[0007] Performing a first electroplating on the aluminum alloy to be electroplated to obtain an aluminum alloy plated with a first electroplated surface, wherein the first electroplated surface includes zinc;

[0008] Coating a photothermal dual-responsive polymer on the aluminum alloy plated with the first electroplating surface to form an aluminum alloy covered with a mask surface, wherein the photothermal dual-responsive polymer is polymerized from a thermal response monomer and an azobenzene monomer;

[0009] Controlling an ultraviolet laser of a set wavelength to scan the area to be gold-plated on the surface of the aluminum alloy covered with the mask surface, and heating the scanned aluminum alloy to a first set temperature range;

[0010] After the heated and scanned aluminum alloy is cooled to a second set temperature range, a second electroplating is performed to obtain an aluminum alloy plated with a second electroplated surface, where the second electroplated surface is a gold-plated layer formed on the area to be gold-plated.

[0011] In a second aspect, the present application provides a high-precision electroplating system for local selective gold plating of aluminum alloys, comprising:

[0012] a first electroplating module for performing a first electroplating on the aluminum alloy to be electroplated to obtain the aluminum alloy plated with a first electroplated surface, wherein the first electroplated surface comprises zinc;

[0013] a mask coating module, coating a photothermal dual-responsive polymer on the aluminum alloy plated with the first electroplating surface to form an aluminum alloy covered with a mask surface, wherein the photothermal dual-responsive polymer is polymerized from a thermal responsive monomer and an azobenzene monomer;

[0014] A scanning module controls an ultraviolet laser of a set wavelength to scan the area to be gold-plated on the aluminum alloy covered with the mask surface, and heats the scanned aluminum alloy to a first set temperature range;

[0015] The second electroplating module cools the heated and scanned aluminum alloy to a second set temperature range and then performs a second electroplating to obtain an aluminum alloy plated with a second electroplated surface, where the second electroplated surface is a gold-plated layer formed on the area to be gold-plated.

[0016] Beneficial technical effects:

[0017] A photothermal dual-responsive polymer mask achieves micron-level precision control of gold-plated areas. This polymer, a copolymer of fluoromethacrylate and azobenzene monomers, transforms its hydrophobic state into a hydrophilic state under 355nm UV light. This state is locked in place by heating, preventing performance degradation caused by ambient light or temperature fluctuations. Combined with high-speed UV laser scanning, precise activation of complex patterns is achieved, with gold-plated edge sharpness as low as 1.0μm. The fluorine segments in the photothermal dual-responsive polymer impart hydrophobicity and acid corrosion resistance to the mask, ensuring that non-gold-plated areas remain fully protected in the electrolyte. Spray coating, spin coating, and immersion-coating methods, combined with different solvents (acetone / ethylene glycol) and the leveling agent BYK-333, ensure uniform mask coating on complex surfaces. During the pretreatment process, the passivation solution forms a dense passivation film on the aluminum alloy surface, inhibiting aluminum oxide regeneration. Heterogeneous seed deposition provides a conductive substrate, stabilizing the subsequent zinc layer. During the surface functionalization treatment, mercaptobenzimidazole (-SH) forms Zn-S bonds with the zinc layer, and silane-modified nano-silica creates a micron-scale rough structure, enhancing mask adhesion. The stripping solution, ethanol / tetrahydrofuran, efficiently removes the mask without being highly corrosive, reducing waste liquid disposal costs. Gold nanoclusters serve as seed crystals, lowering the activation energy for electroplating and reducing precious metal usage. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of a high-precision electroplating system for local selective gold plating of aluminum alloy according to the present invention.

[0019] Figure 2 This is a partial enlarged view of the partially gold-plated aluminum alloy prepared in Example 1 of the present invention.

[0020] Figure numerals: 1. first electroplating surface; 2. second electroplating surface; 3. cavity. DETAILED DESCRIPTION

[0021] In order to make the technical problems, technical solutions, and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below with reference to the following examples. However, this should not be construed as limiting the scope of this application to the following examples. Without departing from the above-mentioned method concepts of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0022] In this application, the terms used in this application are for the purpose of describing specific embodiments only and are not intended to be limiting of the application.

[0023] As used in this application, the singular forms "for," "or," "an," "any," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0024] In addition, the terms “first” and “second”, if used, are only used for descriptive purposes and should not be understood as indicating or implying relative importance.

[0025] In a first aspect, the present application provides a high-precision electroplating method for local selective gold plating of aluminum alloy, comprising the following steps:

[0026] In a first aspect, the present application provides a high-precision electroplating method for local selective gold plating of aluminum alloy, comprising the following steps:

[0027] Performing a first electroplating on the aluminum alloy to be electroplated to obtain an aluminum alloy plated with a first electroplated surface 1, wherein the first electroplated surface 1 comprises zinc;

[0028] A photothermal dual-responsive polymer is coated on the aluminum alloy plated with the first electroplating surface 1 to form an aluminum alloy covered with a mask surface, wherein the photothermal dual-responsive polymer is polymerized from a thermal response monomer and an azobenzene monomer;

[0029] Controlling an ultraviolet laser of a set wavelength to scan the area to be gold-plated on the surface of the aluminum alloy covered with the mask surface, and heating the scanned aluminum alloy to a first set temperature range;

[0030] After the heated and scanned aluminum alloy is cooled to a second set temperature range, a second electroplating is performed to obtain an aluminum alloy plated with a second electroplated surface 2 , where the second electroplated surface 2 is a gold-plated layer formed on the area to be gold-plated.

[0031] In a feasible implementation scenario, the method further includes performing surface pretreatment on the aluminum alloy to be electroplated before performing the first electroplating:

[0032] The aluminum alloy to be electroplated is immersed in a passivation solution for passivation treatment; the passivation solution contains 90-100 mL / L of phosphoric acid, 5.1-5.3 g / L of sodium fluoride, 2.9-3.2 g / L of ammonium molybdate, and 0.45-0.55 g / L of sodium dodecyl sulfate; the temperature of the passivation solution is 50-60° C.;

[0033] The aluminum alloy to be electroplated after passivation treatment is placed in a seed solution to deposit heterogeneous seed crystals, which are then soaked at 40-45°C and then washed and dried; the seed solution contains 24.8-25.5g / L of zinc sulfate, 0.78-0.83g / L of ascorbic acid and 0.09-0.11wt% of gold nanoclusters; and the pH of the seed solution is 9.0-9.2.

[0034] The aluminum alloy to be electroplated was subjected to passivation treatment and heterogeneous seed deposition treatment. The aluminum oxide on the surface of the aluminum alloy to be electroplated was removed by pickling with a passivation solution. Sodium fluoride and ammonium molybdate synergistically formed a dense passivation film on the surface of the aluminum alloy, avoiding the defects of unstable coating bonding and easy falling off caused by direct electroplating on the aluminum oxide layer. The passivation film has stable performance, inhibits the regeneration of aluminum oxide, and is easy to stably combine with the zinc layer. The heterogeneous seed deposition treatment provides zinc ions that can be adsorbed on the surface of the aluminum alloy, forming a zinc seed layer to provide a conductive base for zinc plating. Gold nanoclusters are anchored on the surface of the aluminum alloy through electrostatic action, serving as conductive crystal nuclei to reduce the activation energy for subsequent electroplating and promote the uniform deposition of electroplated metal particles.

[0035] In a feasible implementation scenario, the method also includes performing surface functionalization treatment on the first electroplating surface 1, specifically: immersing the aluminum alloy plated with the first electroplating surface 1 in a modification solution, pulling it at a speed of 4-5 cm / min, and solidifying it after taking it out; the modification solution includes: adding nano-silica powder, KH-550 and mercaptobenzimidazole to anhydrous ethanol in sequence and mixing them evenly; the mass ratio of anhydrous ethanol, nano-silica powder, KH-550 and mercaptobenzimidazole is 90: (5-5.5): 1.5: (1.0-1.2).

[0036] During the first electroplating zinc process, pulse plating is used to reduce internal stress in the coating and improve deposition efficiency. Subsequent surface functionalization treatment uses a modified solution. Mercaptobenzimidazole, a coupling agent containing a thiol group (-SH), forms a Zn-S bond with the zinc layer surface, enhancing the adhesion between the mask and the zinc layer. Silane-modified nanosilica is linked to the zinc layer via Si-O-Si or Si-O-Zn covalent bonds. The nanosilica forms a micron-scale rough structure on the zinc layer surface, providing strong binding sites for the photothermal dual-responsive polymer and preventing the mask surface from peeling during the electroplating process. The corrosion resistance of mercaptobenzimidazole synergizes with the hydrophobicity of the fluorine chain to protect non-gold-plated areas from electrolyte corrosion.

[0037] In a feasible implementation scenario, the preparation method of the photothermal dual-responsive polymer is:

[0038] 4-aminoazobenzene was dissolved in dichloromethane, triethylamine was added, and the mixture was placed in an ice bath. Acryloyl chloride was then added dropwise to react. The mass ratio of 4-aminoazobenzene, dichloromethane, triethylamine, and acryloyl chloride was 1:(18-20):1:(0.4-0.5). After the reaction, the mixture was purified by silica gel chromatography and recrystallized from ethanol to obtain the azobenzene monomer.

[0039] The thermal response monomer and the azobenzene monomer are mixed in a molar ratio of (6-7): (3-4), and 0.4% to 0.6% of the total molar number of the reactants of azobisisobutyronitrile is added as an initiator under nitrogen protection. The mixture is reacted in tetrahydrofuran at 65-75°C for 13-18 hours, and a photothermal dual response polymer is obtained after purification.

[0040] The thermal response monomer is one of hexafluorobutyl methacrylate, dodecafluoroheptyl methacrylate and tridecafluorooctyl methacrylate.

[0041] The amino group of 4-aminoazobenzene undergoes an esterification reaction with acryloyl chloride to replace the chlorine atom of acryloyl chloride to generate an acrylate azobenzene monomer. The acrylate azobenzene monomer and the thermal response monomer undergo free radical chain polymerization to obtain a photothermal dual-responsive polymer. Hexafluorobutyl methacrylate, dodecafluoroheptyl methacrylate or tridecafluorooctyl methacrylate provide fluorine-containing chain segments for the photothermal dual-responsive polymer, giving the photothermal dual-responsive polymer hydrophobicity and acid corrosion resistance, so that the mask surface can protect the non-gold-plated area in the electrolyte; the azobenzene segment gives the polymer photoresponsive properties. Ultraviolet light (355nm) can induce the N=N bond to rotate or flip, resulting in trans-cis isomerization, causing the polymer to change from a hydrophobic state to a hydrophilic state. Dark conditions or visible light greater than 450nm can reversibly restore the cis structure to a trans structure, and the polymer returns to a hydrophobic state. To avoid this interference factor, the cis structure is locked by heating to inhibit the reversible transformation. The locked hydrophilic state remains stable during the second electroplating zinc plating process, ensuring that the gold plating solution is accurately deposited in the gold-plated area.

[0042] In a feasible implementation scenario, the method of coating the photothermal dual-responsive polymer on the first electroplating surface 1 includes:

[0043] The photothermal dual-responsive polymer is dissolved in an organic solvent to obtain a mask coating liquid; the organic solvent is acetone or a mixed solvent of acetone and ethylene glycol; the mask coating liquid also includes a leveling agent;

[0044] Applying the mask coating liquid to the first electroplating surface 1; the specific coating method is one or more of spin coating, spray coating and immersion-coating method;

[0045] The volume ratio of acetone to ethylene glycol in the mixed solvent of acetone and ethylene glycol is (7.8-8):2; the leveling agent is polyether-modified siloxane BYK-333, and its weight fraction in the mask coating liquid is 0.5-0.6wt%; the concentration of the photothermal dual-responsive polymer in the mask coating liquid is 6-10wt%.

[0046] The mask coating solution for both the spray and immersion-coating methods utilizes an acetone / ethylene glycol mixture as the acetone evaporates quickly, while the ethylene glycol slows curing, ensuring uniform coating. BYK-333 leveling agent reduces surface tension and eliminates coating defects such as bubbles and orange peel. Spin coating is suitable for smooth surfaces, spray coating for curved surfaces, and immersion-coating for structures with deep holes or cavities. Combining these three mask coating methods enables selective electroplating of complex aluminum alloy structures.

[0047] In a feasible implementation, the scanning wavelength of the ultraviolet solid laser is 355 nm.

[0048] In a feasible implementation scenario, in the first electroplating, a pulse power supply is used that can emit a pulse current of 10ms / -1.5V in the forward direction and 2ms / +0.2V in the reverse direction; the ultraviolet solid laser scanning time is 5-8min; the first set temperature range is 65-80℃; the second set temperature range is 25-30℃; the plating solution pH in the second electroplating process is 5.0-5.2.

[0049] During the first electroplating zinc plating process, pulse electroplating is used to reduce the internal stress of the coating and improve the deposition efficiency.

[0050] In a feasible implementation, the method further includes immersing the aluminum alloy plated with the second electroplating surface 2 in a stripping solution, and ultrasonically removing the mask surface of the non-gold-plated area.

[0051] After the gold plating of the second electroplating is completed, the mask surface of the non-gold-plated area is automatically stripped under the combination of stripping liquid and ultrasonic treatment, retaining the complete plating layer boundary.

[0052] In the second aspect, the present application provides a high-precision electroplating system for local selective gold plating of aluminum alloys, such as Figure 1 Shown, including:

[0053] a first electroplating module for performing a first electroplating on the aluminum alloy to be electroplated to obtain an aluminum alloy plated with a first electroplating surface 1, wherein the first electroplating surface 1 comprises zinc;

[0054] A mask coating module is used to coat a photothermal dual-responsive polymer on the aluminum alloy plated with the first electroplating surface 1 to form an aluminum alloy covered with a mask surface, wherein the photothermal dual-responsive polymer is polymerized from a thermal responsive monomer and an azobenzene monomer;

[0055] A scanning module controls an ultraviolet laser of a set wavelength to scan the area to be gold-plated on the aluminum alloy covered with the mask surface, and heats the scanned aluminum alloy to a first set temperature range;

[0056] The second electroplating module cools the heated and scanned aluminum alloy to a second set temperature range and then performs a second electroplating to obtain an aluminum alloy plated with a second electroplating surface 2, where the second electroplating surface 2 is a gold-plated layer formed on the area to be gold-plated.

[0057] In one feasible implementation scenario, the system further comprises a pretreatment module, a surface functionalization module, and a stripping module;

[0058] The pretreatment module includes a passivation unit and a seed loading unit; the passivation unit is used to passivate the surface of the aluminum alloy to be electroplated to obtain a passivated aluminum alloy; the seed loading unit is used to deposit zinc seeds on the surface of the passivated aluminum alloy, and the obtained aluminum alloy serves as an updated aluminum alloy to be electroplated;

[0059] The surface functionalization module is used to modify the aluminum alloy plated with the first electroplating surface 1, and the obtained modified aluminum alloy serves as the updated aluminum alloy plated with the first electroplating surface 1;

[0060] The stripping module is used to strip the mask surface on the aluminum alloy plated with the second electroplating surface 2

[0061] The following will describe in detail a high-precision electroplating method and system for local selective gold plating of aluminum alloy provided by the present application in combination with different embodiments.

[0062] Example 1

[0063] A high-precision electroplating method for local selective gold plating of aluminum alloy comprises the following steps:

[0064] 1. Prepare a passivation solution containing 90 mL / L phosphoric acid, 5.1 g / L sodium fluoride, 2.9 g / L ammonium molybdate and 0.45 g / L sodium dodecylsulfonate, pour it into the passivation solution tank, maintain a constant temperature of 60 ° C, immerse the aluminum alloy to be electroplated in the passivation solution for passivation treatment, and wash and dry it after 5 minutes;

[0065] 2. Stir 4 mM chloroauric acid and 6 mM glutathione solution at 500 rpm, heat to 90 ° C and stir for 7 hours, add isopropanol, the mass ratio of chloroauric acid, glutathione solution and isopropanol is 1:1:6, centrifuge at 10000 rpm for 10 minutes after 5 minutes, wash, and freeze-dry to obtain gold nanoclusters; prepare a seed solution containing 24.8 g / L zinc sulfate, 0.78 g / L ascorbic acid and 0.09 wt% gold nanoclusters, adjust the pH to 9.0, pour into the seed solution tank, and maintain a constant temperature of 40 ° C; put the passivated aluminum alloy to be electroplated into the seed solution for seed deposition, soak for 2 minutes, and then wash and dry;

[0066] 3. Prepare a zinc plating solution containing 100 g / L zinc chloride, 30 g / L citric acid, 3 g / L polyethylene glycol PEG-8000, 0.2 g / L thiourea and 20 g / L sodium citrate, pour the solution into a zinc plating tank, place the aluminum alloy to be electroplated after seed crystal deposition into the zinc plating solution, start a pulse power supply, and pass a pulse current of 10 ms / -1.5 V in the forward direction and 2 ms / +0.2 V in the reverse direction for 5 minutes to perform the first electroplating, thereby obtaining an aluminum alloy plated with a first electroplated surface 1;

[0067] 4. Add nano-silica powder to anhydrous ethanol, add KH-550 after ultrasonic dispersion, react at 70°C for 6 hours, add mercaptobenzimidazole, and mix evenly to obtain a modified solution. Pour the solution into a modification tank, place the aluminum alloy plated with the first electroplating surface 1 into the modified solution, pull it at a speed of 5 cm / min for 2 minutes, take it out, and cure it at 80°C for 10 minutes to obtain a modified aluminum alloy.

[0068] 5. Dissolve 4-aminoazobenzene in dichloromethane, add triethylamine, place in an ice bath, and dropwise add acryloyl chloride to react. The mass ratio of 4-aminoazobenzene, dichloromethane, triethylamine, and acryloyl chloride is 1:18:1:0.5. React for 12 hours, purify by silica gel chromatography, and recrystallize from ethanol to obtain an azobenzene monomer.

[0069] Hexafluorobutyl methacrylate and azobenzene monomer were mixed in a molar ratio of 7:3, and 0.6% of the total molar number of azobisisobutyronitrile was added as an initiator under nitrogen protection. The mixture was reacted in tetrahydrofuran at 75°C for 13 hours, and a photothermal dual-responsive polymer was obtained after purification.

[0070] 6. The photothermal dual-responsive polymer solution was mixed with acetone at a mass ratio of 1:9 to obtain a mask coating liquid with a photothermal dual-responsive polymer concentration of 10 wt%, and the solution was placed in a photothermal dual-responsive polymer mask coating liquid supply device. The mask coating liquid was applied to the modified surface of the modified aluminum alloy using a spin coater at 3000 rpm, and cured at 60°C for 10 min to obtain a mask surface;

[0071] 7. Control the UV solid-state laser to scan the area to be gold-plated on the aluminum alloy covered with the mask surface, with a scanning wavelength of 355nm, a maximum power of 3W, a power density of 10mW / μm², a high-speed scanning galvanometer, a scanning speed of 200mm / s, a single exposure time of ≤50μs, a pulse frequency of 50kHz, and a scanning time of 5min;

[0072] 8. Place the scanned aluminum alloy in a heating device and keep it at a constant temperature of 80℃ for 5 minutes. After taking it out, cool it naturally to 25-30℃. Prepare a solution containing 5g / L potassium gold sulfite, 10g / L citric acid, 0.5g / L benzotriazole, 0.1g / L cerium nitrate and 0.1g / L thiourea, adjust the pH to 5.0, and obtain a gold plating solution. Pour it into the gold plating tank and keep it at a constant temperature of 60℃. Place the cooled aluminum alloy in the gold plating solution for the second electroplating. The current density is 1A / dm² and the electroplating time is 8 minutes.

[0073] 9. Ethanol and tetrahydrofuran were mixed in a volume ratio of 1:4 to obtain a stripping solution. The container containing the stripping solution was placed in an ultrasonic cleaner, ensuring that the liquid level of the ultrasonic cleaner was lower than the edge of the container. The aluminum alloy plated with the second electroplated surface 2 was placed in the stripping solution. The mask was stripped by ultrasonication for 3 minutes to obtain the following: Figure 2 Aluminum alloy with partial gold plating shown.

[0074] Example 2

[0075] A high-precision electroplating method for local selective gold plating of aluminum alloy comprises the following steps:

[0076] 1. Prepare a passivation solution containing 100 mL / L phosphoric acid, 5.2 g / L sodium fluoride, 3.0 g / L ammonium molybdate and 0.5 g / L sodium dodecylsulfonate, pour it into the passivation solution tank, maintain a constant temperature of 55 ° C, immerse the aluminum alloy to be electroplated in the passivation solution for passivation treatment, and wash and dry it after 5 minutes;

[0077] 2. Mix 4 mM chloroauric acid and 6 mM glutathione solution at 500 rpm, heat to 90 ° C and stir for 7 hours, add isopropanol, the mass ratio of chloroauric acid, glutathione solution and isopropanol is 1:1:6, centrifuge at 10000 rpm for 10 minutes after 5 minutes, wash and freeze-dry to obtain gold nanoclusters; prepare a seed solution containing 25 g / L zinc sulfate, 0.8 g / L ascorbic acid and 0.1 wt% gold nanoclusters, adjust the pH to 9.1, pour into the seed solution tank, and maintain a constant temperature of 45 ° C; put the passivated aluminum alloy to be electroplated into the seed solution for seed deposition, soak for 2 minutes, and then wash and dry;

[0078] 3. Prepare a zinc plating solution containing 100 g / L zinc chloride, 30 g / L citric acid, 3 g / L polyethylene glycol PEG-8000, 0.2 g / L thiourea and 20 g / L sodium citrate, pour the solution into a zinc plating tank, place the aluminum alloy to be electroplated after seed crystal deposition into the zinc plating solution, start a pulse power supply, and pass a pulse current of 10 ms / -1.5 V in the forward direction and 2 ms / +0.2 V in the reverse direction for 5 minutes to perform the first electroplating, thereby obtaining an aluminum alloy plated with a first electroplated surface 1;

[0079] 4. Add nano-silica powder to anhydrous ethanol, add KH-550 after ultrasonic dispersion, react at 70°C for 6 hours, add mercaptobenzimidazole, and mix evenly to obtain a modified solution. Pour the solution into a modification tank, place the aluminum alloy plated with the first electroplating surface 1 into the modified solution, pull it at a speed of 4 cm / min for 2 minutes, take it out, and cure it at 80°C for 10 minutes to obtain a modified aluminum alloy.

[0080] 5. Dissolve 4-aminoazobenzene in dichloromethane, add triethylamine, place in an ice bath, and dropwise add acryloyl chloride to react. The mass ratio of 4-aminoazobenzene, dichloromethane, triethylamine, and acryloyl chloride is 1:20:1:0.4. React for 12 hours, purify by silica gel chromatography, and recrystallize from ethanol to obtain an azobenzene monomer.

[0081] Dodecafluoroheptyl methacrylate and azobenzene monomer were mixed in a molar ratio of 7:3, and 0.5% of the total molar number of azobisisobutyronitrile was added as an initiator under nitrogen protection. The mixture was reacted in tetrahydrofuran at 70°C for 16 hours, and a photothermal dual-responsive polymer was obtained after purification.

[0082] 6. The photothermal dual-responsive polymer solution was mixed with acetone at a mass ratio of 1:9 to obtain a mask coating liquid with a photothermal dual-responsive polymer concentration of 10 wt%, and the solution was placed in a photothermal dual-responsive polymer mask coating liquid supply device. The mask coating liquid was applied to the modified surface of the modified aluminum alloy using a spin coater at 3000 rpm, and cured at 60°C for 10 min to obtain a mask surface;

[0083] 7. Control the UV solid-state laser to scan the area to be gold-plated on the aluminum alloy covered with the mask surface, with a scanning wavelength of 355nm, a maximum power of 3W, a power density of 10mW / μm², a high-speed scanning galvanometer, a scanning speed of 200mm / s, a single exposure time of ≤50μs, a pulse frequency of 50kHz, and a scanning time of 5min;

[0084] 8. Place the scanned aluminum alloy in a heating device and keep it at a constant temperature of 75℃ for 5 minutes. After taking it out, cool it naturally to 25-30℃. Prepare a solution containing 5g / L potassium gold sulfite, 10g / L citric acid, 0.5g / L benzotriazole, 0.1g / L cerium nitrate and 0.1g / L thiourea, adjust the pH to 5.1, and obtain a gold plating solution. Pour it into the gold plating tank and keep it at a constant temperature of 60℃. Place the cooled aluminum alloy in the gold plating solution for the second electroplating. The current density is 1A / dm² and the electroplating time is 8 minutes.

[0085] 9. Mix ethanol and tetrahydrofuran in a volume ratio of 1:4 to obtain a stripping solution. Place the container containing the stripping solution in an ultrasonic cleaner, ensuring that the liquid level of the ultrasonic cleaner is lower than the edge of the container. Place the aluminum alloy plated with the second electroplated surface 2 into the stripping solution, and ultrasonically strip the mask for 3 minutes to obtain a partially gold-plated aluminum alloy.

[0086] Example 3

[0087] A high-precision electroplating method for local selective gold plating of aluminum alloy comprises the following steps:

[0088] 1. Prepare a passivation solution containing 90mL / L phosphoric acid, 5.3g / L sodium fluoride, 3.2g / L ammonium molybdate and 0.55g / L sodium dodecylsulfonate, pour it into the passivation solution tank, maintain a constant temperature of 50℃, immerse the aluminum alloy to be electroplated in the passivation solution for passivation treatment, and wash and dry it after 5 minutes;

[0089] 2. Stir 4 mM chloroauric acid and 6 mM glutathione solution at 500 rpm, heat to 90 ° C and stir for 7 hours, add isopropanol, the mass ratio of chloroauric acid, glutathione solution and isopropanol is 1:1:6, centrifuge at 10000 rpm for 10 minutes after 5 minutes, wash and freeze-dry to obtain gold nanoclusters; prepare a seed solution containing 25.5 g / L zinc sulfate, 0.83 g / L ascorbic acid and 0.11 wt% gold nanoclusters, adjust the pH to 9.2, pour into the seed solution tank, and maintain a constant temperature of 45 ° C; put the passivated aluminum alloy to be electroplated into the seed solution for seed deposition, soak for 2 minutes, and then wash and dry;

[0090] 3. Prepare a zinc plating solution containing 100 g / L zinc chloride, 30 g / L citric acid, 3 g / L polyethylene glycol PEG-8000, 0.2 g / L thiourea and 20 g / L sodium citrate, pour the solution into a zinc plating tank, place the aluminum alloy to be electroplated after seed crystal deposition into the zinc plating solution, start a pulse power supply, and pass a pulse current of 10 ms / -1.5 V in the forward direction and 2 ms / +0.2 V in the reverse direction for 5 minutes to perform the first electroplating, thereby obtaining an aluminum alloy plated with a first electroplated surface 1;

[0091] 4. Add nano-silica powder to anhydrous ethanol, add KH-550 after ultrasonic dispersion, react at 70°C for 6 hours, add mercaptobenzimidazole, and mix evenly to obtain a modified solution. Pour the solution into a modification tank, place the aluminum alloy plated with the first electroplating surface 1 into the modified solution, pull it at a speed of 5 cm / min for 2 minutes, take it out, and cure it at 80°C for 10 minutes to obtain a modified aluminum alloy.

[0092] 5. Dissolve 4-aminoazobenzene in dichloromethane, add triethylamine, place in an ice bath, and dropwise add acryloyl chloride to react. The mass ratio of 4-aminoazobenzene, dichloromethane, triethylamine, and acryloyl chloride is 1:20:1:0.5. React for 12 hours, purify by silica gel chromatography, and recrystallize from ethanol to obtain an azobenzene monomer.

[0093] Tridecafluorooctyl methacrylate and azobenzene monomer were mixed in a molar ratio of 6:4, and 0.4% of the total molar number of azobisisobutyronitrile was added as an initiator under nitrogen protection. The mixture was reacted in tetrahydrofuran at 65°C for 18 hours, and a photothermal dual-responsive polymer was obtained after purification.

[0094] 6. The photothermal dual-responsive polymer solution was mixed with acetone at a mass ratio of 1:9 to obtain a mask coating liquid with a photothermal dual-responsive polymer concentration of 10 wt%, and the solution was placed in a photothermal dual-responsive polymer mask coating liquid supply device. The mask coating liquid was applied to the modified surface of the modified aluminum alloy using a spin coater at 3000 rpm, and cured at 60°C for 10 min to obtain a mask surface;

[0095] 7. Control the UV solid-state laser to scan the area to be gold-plated on the aluminum alloy covered with the mask surface, with a scanning wavelength of 355nm, a maximum power of 3W, a power density of 10mW / μm², a high-speed scanning galvanometer, a scanning speed of 200mm / s, a single exposure time of ≤50μs, a pulse frequency of 50kHz, and a scanning time of 5min;

[0096] 8. Place the scanned aluminum alloy in a heating device and keep it at a constant temperature of 65℃ for 5 minutes. After taking it out, cool it naturally to 25-30℃. Prepare a solution containing 5g / L potassium gold sulfite, 10g / L citric acid, 0.5g / L benzotriazole, 0.1g / L cerium nitrate and 0.1g / L thiourea, adjust the pH to 5.2, and obtain a gold plating solution. Pour it into the gold plating tank and keep it at a constant temperature of 60℃. Place the cooled aluminum alloy in the gold plating solution for the second electroplating. The current density is 1A / dm² and the electroplating time is 8 minutes.

[0097] 9. Mix ethanol and tetrahydrofuran in a volume ratio of 1:4 to obtain a stripping solution. Place the container containing the stripping solution in an ultrasonic cleaner, ensuring that the liquid level of the ultrasonic cleaner is lower than the edge of the container. Place the aluminum alloy plated with the second electroplated surface 2 into the stripping solution, and ultrasonically strip the mask for 3 minutes to obtain a partially gold-plated aluminum alloy.

[0098] Example 4

[0099] A high-precision electroplating method for local selective gold plating of aluminum alloy comprises the following steps:

[0100] 1. Prepare a passivation solution containing 100 mL / L phosphoric acid, 5.2 g / L sodium fluoride, 3.0 g / L ammonium molybdate and 0.5 g / L sodium dodecylsulfonate, pour it into the passivation solution tank, maintain a constant temperature of 55 ° C, immerse the aluminum alloy to be electroplated in the passivation solution for passivation treatment, and wash and dry it after 5 minutes;

[0101] 2. Mix 4 mM chloroauric acid and 6 mM glutathione solution at 500 rpm, heat to 90 ° C and stir for 7 hours, add isopropanol, the mass ratio of chloroauric acid, glutathione solution and isopropanol is 1:1:6, centrifuge at 10000 rpm for 10 minutes after 5 minutes, wash and freeze-dry to obtain gold nanoclusters; prepare a seed solution containing 25 g / L zinc sulfate, 0.8 g / L ascorbic acid and 0.1 wt% gold nanoclusters, adjust the pH to 9.1, pour into the seed solution tank, and maintain a constant temperature of 45 ° C; put the passivated aluminum alloy to be electroplated into the seed solution for seed deposition, soak for 2 minutes, and then wash and dry;

[0102] 3. Prepare a zinc plating solution containing 100 g / L zinc chloride, 30 g / L citric acid, 3 g / L polyethylene glycol PEG-8000, 0.2 g / L thiourea and 20 g / L sodium citrate, pour the solution into a zinc plating tank, place the aluminum alloy to be electroplated after seed crystal deposition into the zinc plating solution, start a pulse power supply, and pass a pulse current of 10 ms / -1.5 V in the forward direction and 2 ms / +0.2 V in the reverse direction for 5 minutes to perform the first electroplating, thereby obtaining an aluminum alloy plated with a first electroplated surface 1;

[0103] 4. Add nano-silica powder to anhydrous ethanol, add KH-550 after ultrasonic dispersion, react at 70°C for 6 hours, add mercaptobenzimidazole, and mix evenly to obtain a modified solution. Pour the solution into a modification tank, place the aluminum alloy plated with the first electroplating surface 1 into the modified solution, pull it at a speed of 4 cm / min for 2 minutes, take it out, and cure it at 80°C for 10 minutes to obtain a modified aluminum alloy.

[0104] 5. Dissolve 4-aminoazobenzene in dichloromethane, add triethylamine, place in an ice bath, and dropwise add acryloyl chloride to react. The mass ratio of 4-aminoazobenzene, dichloromethane, triethylamine, and acryloyl chloride is 1:20:1:0.4. React for 12 hours, purify by silica gel chromatography, and recrystallize from ethanol to obtain an azobenzene monomer.

[0105] 6. Acetone and ethylene glycol were mixed in a volume ratio of 7.8:2 to obtain a mixed solvent, the photothermal dual response polymer was dissolved in the mixed solvent, and polyether modified siloxane BYK-333 was added. The mass ratio of the photothermal dual response polymer, the mixed solvent and the polyether modified siloxane BYK-333 was 8:91.5:0.5 to obtain a mask coating liquid with a photothermal dual response polymer concentration of 8wt%, which was placed in a photothermal dual response polymer mask coating liquid supply device. The mask coating liquid was sprayed on the modified surface of the modified aluminum alloy, specifically using an airless spray gun with a nozzle diameter of 0.3mm, a spraying pressure of 30psi, a spraying distance of 15-20cm, a single spraying thickness of 0.5μm, and standing at room temperature for 1 minute after each spraying. A total of 4 sprayings were performed, and the mixture was cured at 60°C for 10min to obtain a mask surface.

[0106] 7. Control the UV solid-state laser to scan the area to be gold-plated on the aluminum alloy covered with the mask surface, with a scanning wavelength of 355nm, a maximum power of 3W, a power density of 10mW / μm², a high-speed scanning galvanometer, a scanning speed of 200mm / s, a single exposure time of ≤50μs, a pulse frequency of 50kHz, and a scanning time of 5min;

[0107] 8. Place the scanned aluminum alloy in a heating device and keep it at a constant temperature of 75℃ for 5 minutes. After taking it out, cool it naturally to 25-30℃. Prepare a solution containing 5g / L potassium gold sulfite, 10g / L citric acid, 0.5g / L benzotriazole, 0.1g / L cerium nitrate and 0.1g / L thiourea, adjust the pH to 5.1, and obtain a gold plating solution. Pour it into the gold plating tank and keep it at a constant temperature of 60℃. Place the cooled aluminum alloy in the gold plating solution for the second electroplating. The current density is 1A / dm² and the electroplating time is 8 minutes.

[0108] 9. Mix ethanol and tetrahydrofuran in a volume ratio of 1:4 to obtain a stripping solution. Place the container containing the stripping solution in an ultrasonic cleaner, ensuring that the liquid level of the ultrasonic cleaner is lower than the edge of the container. Place the aluminum alloy plated with the second electroplated surface 2 into the stripping solution, and ultrasonically strip the mask for 3 minutes to obtain a partially gold-plated aluminum alloy.

[0109] Example 5

[0110] A high-precision electroplating method for local selective gold plating of aluminum alloy comprises the following steps:

[0111] 1. Prepare a passivation solution containing 100 mL / L phosphoric acid, 5.2 g / L sodium fluoride, 3.0 g / L ammonium molybdate and 0.5 g / L sodium dodecylsulfonate, pour it into the passivation solution tank, maintain a constant temperature of 55 ° C, immerse the aluminum alloy to be electroplated in the passivation solution for passivation treatment, and wash and dry it after 5 minutes;

[0112] 2. Mix 4 mM chloroauric acid and 6 mM glutathione solution at 500 rpm, heat to 90 ° C and stir for 7 hours, add isopropanol, the mass ratio of chloroauric acid, glutathione solution and isopropanol is 1:1:6, centrifuge at 10000 rpm for 10 minutes after 5 minutes, wash and freeze-dry to obtain gold nanoclusters; prepare a seed solution containing 25 g / L zinc sulfate, 0.8 g / L ascorbic acid and 0.1 wt% gold nanoclusters, adjust the pH to 9.1, pour into the seed solution tank, and maintain a constant temperature of 45 ° C; put the passivated aluminum alloy to be electroplated into the seed solution for seed deposition, soak for 2 minutes, and then wash and dry;

[0113] 3. Prepare a zinc plating solution containing 100 g / L zinc chloride, 30 g / L citric acid, 3 g / L polyethylene glycol PEG-8000, 0.2 g / L thiourea and 20 g / L sodium citrate, pour the solution into a zinc plating tank, place the aluminum alloy to be electroplated after seed crystal deposition into the zinc plating solution, start a pulse power supply, and pass a pulse current of 10 ms / -1.5 V in the forward direction and 2 ms / +0.2 V in the reverse direction for 5 minutes to perform the first electroplating, thereby obtaining an aluminum alloy plated with a first electroplated surface 1;

[0114] 4. Add nano-silica powder to anhydrous ethanol, add KH-550 after ultrasonic dispersion, react at 70°C for 6 hours, add mercaptobenzimidazole, and mix evenly to obtain a modified solution. Pour the solution into a modification tank, place the aluminum alloy plated with the first electroplating surface 1 into the modified solution, pull it at a speed of 4 cm / min for 2 minutes, take it out, and cure it at 80°C for 10 minutes to obtain a modified aluminum alloy.

[0115] 5. Dissolve 4-aminoazobenzene in dichloromethane, add triethylamine, place in an ice bath, and dropwise add acryloyl chloride to react. The mass ratio of 4-aminoazobenzene, dichloromethane, triethylamine, and acryloyl chloride is 1:20:1:0.4. React for 12 hours, purify by silica gel chromatography, and recrystallize from ethanol to obtain an azobenzene monomer.

[0116] 6. Acetone and ethylene glycol are mixed in a volume ratio of 8:2 to obtain a mixed solvent, the photothermal dual response polymer is dissolved in the mixed solvent, and polyether modified siloxane BYK-333 is added. The mass ratio of the photothermal dual response polymer, the mixed solvent and the polyether modified siloxane BYK-333 is 6:93.4:0.6, and a mask coating liquid with a photothermal dual response polymer concentration of 6 wt% is obtained. The mask coating liquid is placed in a photothermal dual response polymer mask coating liquid supply device, and the mask coating liquid is applied to the surface of the surface functionalized galvanized aluminum alloy by an immersion-pulling method. Specifically, the modified aluminum alloy is immersed in a mask coating liquid tank filled with the mask coating liquid, and leached at a speed of 3 mm / s for 2 minutes; after taking out, it is hung vertically, evaporated at room temperature for 5 minutes, and cured at 60°C for 10 minutes to obtain a mask surface;

[0117] 7. Control the UV solid-state laser to scan the area to be gold-plated on the aluminum alloy covered with the mask surface, with a scanning wavelength of 355nm, a maximum power of 3W, a power density of 10mW / μm², a high-speed scanning galvanometer, a scanning speed of 200mm / s, a single exposure time of ≤50μs, a pulse frequency of 50kHz, and a scanning time of 8min;

[0118] 8. Place the scanned aluminum alloy in a heating device and keep it at a constant temperature of 75℃ for 5 minutes. After taking it out, cool it naturally to 25-30℃. Prepare a solution containing 5g / L potassium gold sulfite, 10g / L citric acid, 0.5g / L benzotriazole, 0.1g / L cerium nitrate and 0.1g / L thiourea, adjust the pH to 5.1, and obtain a gold plating solution. Pour it into the gold plating tank and keep it at a constant temperature of 60℃. Place the cooled aluminum alloy in the gold plating solution for the second electroplating. The current density is 1A / dm² and the electroplating time is 8 minutes.

[0119] 9. Mix ethanol and tetrahydrofuran in a volume ratio of 1:4 to obtain a stripping solution. Place the container containing the stripping solution in an ultrasonic cleaner, ensuring that the liquid level of the ultrasonic cleaner is lower than the edge of the container. Place the aluminum alloy plated with the second electroplated surface 2 into the stripping solution, and ultrasonically strip the mask for 3 minutes to obtain a partially gold-plated aluminum alloy.

[0120] Comparative Example 1

[0121] A high-precision electroplating method for local selective gold plating of aluminum alloy, wherein the implementation steps and parameters are the same as those of Example 2, except that the heating step is not performed to lock the hydrophilic state of the mask.

[0122] Comparative Example 2

[0123] A high-precision electroplating method for local selective gold plating of aluminum alloy, wherein the implementation steps and parameters are the same as those of Example 2, except that methacrylic acid is used instead of the thermal responsive monomer.

[0124] Comparative Example 3

[0125] A high-precision electroplating method for local selective gold plating of aluminum alloy, wherein the implementation steps and parameters are the same as those of Example 2, except that the surface of the aluminum alloy to be electroplated is not pretreated and the first electroplating is directly performed.

[0126] Comparative Example 4

[0127] A high-precision electroplating method for local selective gold plating of aluminum alloy, wherein the implementation steps and parameters are the same as those of Example 2, except that the aluminum alloy is not subjected to surface functionalization treatment after zinc plating.

[0128] Performance testing:

[0129] Original appearance: In accordance with the Finished Product Inspection Specifications, staff observed the partially gold-plated aluminum alloy surface under a microscope. The surface was considered qualified if there was no dirt, peeling, blistering, or dulling of the gloss. The results are shown in Table 1.

[0130] Coating adhesion: The coating adhesion of the partially gold-plated aluminum alloys of Examples 1 to 5 and Comparative Examples 1 to 4 was tested according to ISO 2409:2013. The test results were graded into 6 levels, 0-5, respectively. The smaller the number, the higher the grade and the stronger the coating adhesion. The results are shown in Table 1.

[0131] Coating uniformity: X-ray spectroscopy was used to measure the coating thickness of the partially gold-plated aluminum alloys used in Examples 1-5 and Comparative Examples 1-4 in accordance with GB / T 16921-2005. Nine measurement points were selected (1 at the center, 8 at the edges, and 3 mm from the edges) to calculate the average thickness, standard deviation, and coefficient of variation (CV): CV = standard deviation / average × 100%. The results are shown in Table 1.

[0132] Gold-plated layer edge clarity: According to ISO 4518, the steepness of the gold-plated layer edge of the second electroplated surface 2 of the partially gold-plated aluminum alloy of Examples 1 to 5 and Comparative Examples 1 to 4 was tested using a step profiler. The results are shown in Table 1.

[0133] Corrosion resistance of the coating: According to GB / T 10125-2021, the partially gold-plated aluminum alloys of Examples 1 to 5 and Comparative Examples 1 to 4 were subjected to a neutral salt spray test for 96 h. The corrosion level was divided into 0-3 levels, where the smaller the number, the higher the level and the stronger the corrosion resistance. The results are shown in Table 1.

[0134] Table 1 Performance test results of partially gold-plated aluminum alloy

[0135]

[0136] From Table 1 and Figure 2It can be seen that the appearance qualification rate, coating adhesion level and coating corrosion level of the partially gold-plated aluminum alloys of Examples 1 to 5 are higher than those of Comparative Examples 1 to 4, and the coefficient of variation and steepness are lower than those of the partially gold-plated aluminum alloys of Comparative Examples 1 to 4. This shows that the coating uniformity and gold-plated layer edge clarity of the partially gold-plated aluminum alloys of Examples 1 to 5 are better than those of Comparative Examples 1 to 4. Figure 2 The partially gold-plated aluminum alloy layer of Example 1 is uniform and has clear edges.

[0137] In Comparative Example 1, the heating step to lock the mask's hydrophilic state was omitted. As a result, the photothermal dual-responsive polymer forming the mask surface temporarily became hydrophilic after UV laser scanning, but this state was not locked by heating. During the subsequent electroplating process, the mask gradually reverted to a hydrophobic state due to ambient temperature or lighting conditions, hindering contact between the gold plating solution and the area to be gold-plated, thus affecting the gold plating process. Fluctuations in the mask's surface state led to uneven local current distribution, reduced bonding between the gold-plated and zinc-plated layers, significant variations in gold-plated layer thickness, the presence of microcracks in the coating, and reduced corrosion resistance.

[0138] Comparative Example 2 uses a photoresponsive polymer synthesized from methacrylic acid and azobenzene monomers, without the addition of a thermally responsive fluorinated segment. The photoresponsive polymer relies solely on ultraviolet light to induce a hydrophilic state, but lacks a thermoresponsive group, making it impossible to stabilize the hydrophilic state by heating. During the electroplating process, the mask may revert to a hydrophobic state due to ambient light or temperature fluctuations. Fluctuations in the mask's surface state hinder contact between the gold plating solution and the area to be gold-plated, resulting in uneven local current distribution, reduced bonding between the gold-plated layer and the zinc-plated layer, and significant variations in the thickness of the gold-plated layer.

[0139] Comparative Example 1 and Comparative Example 2 together illustrate that the thermal response effect of the photothermal dual-responsive polymer in the present invention is achieved by the thermal response group and the heating step. Neither the thermal response group nor the heating step alone can provide the mask surface with a thermally locked hydrophilic state.

[0140] In Comparative Example 3, the surface of the aluminum alloy to be electroplated was not pretreated, and the first electroplating was directly performed. A layer of aluminum oxide existed on the surface of the aluminum alloy. The aluminum oxide had poor conductivity and was relatively loose, resulting in uneven conductivity on the surface of the aluminum alloy, reduced bonding strength of the coating, and shedding and blistering. The corrosion resistance was reduced, and the coating had defects such as discontinuity and uneven thickness.

[0141] In Comparative Example 4, the aluminum alloy was not subjected to surface functionalization treatment after galvanizing. The surface of the zinc layer lacked the thiol group provided by mercaptobenzimidazole, the bonding strength with the mask surface decreased, and the adhesion of the mask deteriorated, resulting in the edge of the gold-plated layer warping and partial mask falling off. The gold plating solution laterally penetrated into the non-gold-plated area, and part of the non-gold-plated area was exposed to the gold plating solution, and the selectivity accuracy of the local gold plating was significantly reduced.

[0142] In addition, the present application further provides a high-precision electroplating system for local selective gold plating of aluminum alloys, such as Figure 1 Shown, including:

[0143] A first electroplating module, performing a first electroplating on the aluminum alloy to be electroplated to obtain a first electroplated surface 1, wherein the first electroplated surface 1 includes zinc;

[0144] A mask coating module is used to coat a photothermal dual-responsive polymer on the first electroplating surface 1 to form a mask surface. The photothermal dual-responsive polymer is formed by polymerizing a thermal response monomer and an azobenzene monomer.

[0145] A scanning module controls an ultraviolet laser of a set wavelength to scan the area to be gold-plated on the surface of the mask, and heats the scanned aluminum alloy to a first set temperature range;

[0146] The second electroplating module cools the heated aluminum alloy to be electroplated to a second set temperature range and then performs a second electroplating to obtain a second electroplated surface 2. The second electroplated surface 2 is a gold-plated layer formed on the area to be gold-plated.

[0147] The system also includes a pretreatment module, a surface functionalization module, and a stripping module;

[0148] The pretreatment module includes a passivation unit and a seed loading unit; the passivation unit is used to passivate the surface of the aluminum alloy to be electroplated to obtain a passivated aluminum alloy; the seed loading unit is used to deposit zinc seeds on the surface of the passivated aluminum alloy, and the obtained aluminum alloy serves as an updated aluminum alloy to be electroplated;

[0149] The surface functionalization module is used to modify the first electroplating surface 1, and the obtained modified surface serves as the updated first electroplating surface 1;

[0150] The stripping module is used to strip the mask surface after the second electroplating.

[0151] Based on the same inventive concept, the system provided in this application can also improve the bonding strength, uniformity and edge clarity of the coating, and is suitable for the high-precision gold plating requirements of aluminum alloy parts with complex structures.

[0152] The above results show and describe the basic principles and main features of this application as well as the advantages of this application.

[0153] Those skilled in the art should understand that the present application is not limited to the above-described embodiments. The above-described embodiments and descriptions are merely illustrative of the principles of the present application. Various changes and improvements may be made to the present application without departing from the spirit and scope of the present application. Such changes and improvements are intended to fall within the scope of the present application. The scope of protection claimed in the present application is defined by the equivalents of the appended claims.

Claims

1. A high-precision electroplating method for local selective gold plating of aluminum alloy, characterized in that: The following steps are involved: Immersing the aluminum alloy to be electroplated in a passivation solution containing phosphoric acid, sodium fluoride, ammonium molybdate and sodium dodecylsulfonate for passivation treatment; placing the passivated aluminum alloy to be electroplated into a seed solution containing zinc sulfate, ascorbic acid, and gold nanoclusters to deposit heterogeneous seeds; the gold nanoclusters are obtained by reacting chloroauric acid, glutathione, and isopropyl alcohol; Performing a first electroplating on the aluminum alloy to be electroplated after the seed crystal is deposited to obtain an aluminum alloy plated with a first electroplating surface (1), wherein the first electroplating surface (1) is zinc; The aluminum alloy plated with the first surface (1) is subjected to a surface functionalization treatment to obtain a modified aluminum alloy; the surface functionalization treatment specifically comprises: immersing the aluminum alloy plated with the first surface (1) in a modification solution, pulling it, taking it out and solidifying it; the modification solution is obtained by sequentially adding nano-silica powder, KH-550 and mercaptobenzimidazole into anhydrous ethanol and mixing them uniformly; A photothermal dual-responsive polymer is coated on the modified aluminum alloy to form an aluminum alloy covered with a mask surface, wherein the photothermal dual-responsive polymer is polymerized by a thermal response monomer and an azobenzene monomer; the thermal response monomer is one of hexafluorobutyl methacrylate, dodecafluoroheptyl methacrylate, and tridecafluorooctyl methacrylate; and the azobenzene monomer is obtained by esterification of 4-aminoazobenzene with acryloyl chloride; Controlling an ultraviolet laser of a set wavelength to scan the area to be gold-plated on the aluminum alloy covered with the mask surface, and heating the scanned aluminum alloy to a first set temperature range; the first set temperature range is 65-80° C.; After the heated scanned aluminum alloy is cooled to a second set temperature range, a second electroplating is performed to obtain an aluminum alloy plated with a second electroplated surface (2), wherein the second electroplated surface (2) is a gold-plated layer formed on the area to be gold-plated; The aluminum alloy plated with the second electroplated surface (2) is placed in a stripping solution, and the mask is ultrasonically stripped to obtain a partially gold-plated aluminum alloy, wherein the stripping solution is a mixture of ethanol and tetrahydrofuran.

2. The high-precision electroplating method for local selective gold plating of aluminum alloy according to claim 1, characterized in that: The passivation solution contains 90-100 mL / L of phosphoric acid, 5.1-5.3 g / L of sodium fluoride, 2.9-3.2 g / L of ammonium molybdate, and 0.45-0.55 g / L of sodium dodecyl sulfate; the passivation solution temperature is 50-60° C.; the seed solution contains 24.8-25.5 g / L of zinc sulfate, 0.78-0.83 g / L of ascorbic acid, and 0.09-0.11 wt % of gold nanoclusters; and the seed solution has a pH of 9.0-9.

2.

3. The high-precision electroplating method for local selective gold plating of aluminum alloy according to claim 1, characterized in that: The pulling speed is 4-5 cm / min; the mass ratio of the anhydrous ethanol, nano-silica powder, KH-550 and thiobenzimidazole is 90: (5-5.5): 1.5: (1.0-1.2).

4. The high-precision electroplating method for local selective gold plating of aluminum alloy according to claim 1, characterized in that: The preparation method of the photothermal dual-responsive polymer is as follows: 4-aminoazobenzene was dissolved in dichloromethane, triethylamine was added, and the mixture was placed in an ice bath. Acryloyl chloride was then added dropwise to react. The mass ratio of 4-aminoazobenzene, dichloromethane, triethylamine, and acryloyl chloride was 1:(18-20):1:(0.4-0.5). After the reaction, the mixture was purified by silica gel chromatography and recrystallized from ethanol to obtain the azobenzene monomer. The thermal responsive monomer and the azobenzene monomer are mixed in a molar ratio of (6-7): (3-4), and 0.4% to 0.6% of the total molar number of azobisisobutyronitrile based on the reactants is added as an initiator under nitrogen protection. The mixture is reacted in tetrahydrofuran at 65-75° C. for 13-18 hours, and the photothermal dual responsive polymer is obtained after purification.

5. The high-precision electroplating method for local selective gold plating of aluminum alloy according to claim 1, characterized in that: The method of coating the photothermal dual-responsive polymer on the first electroplating surface (1) comprises: dissolving the photothermal dual-responsive polymer in an organic solvent to obtain a mask coating liquid; the organic solvent is acetone or a mixed solvent of acetone and ethylene glycol; the mask coating liquid also includes a leveling agent; The mask coating liquid is applied to the first electroplating surface (1); the specific coating method is one of spin coating, spray coating and immersion-coating; The volume ratio of acetone to ethylene glycol in the mixed solvent of acetone and ethylene glycol is (7.8-8):2; the leveling agent is polyether-modified siloxane BYK-333, and its concentration in the mask coating liquid is 0.5-0.6wt%; the concentration of the photothermal dual-responsive polymer in the mask coating liquid is 6-10wt%.

6. The high-precision electroplating method for local selective gold plating of aluminum alloy according to claim 1, characterized in that: The set wavelength is 355 nm.

7. The high-precision electroplating method for partial selective gold plating of aluminum alloy according to claim 1, characterized in that: In the first electroplating process, a pulse power supply is used that can emit a pulse current of 10ms / -1.5V in the forward direction and 2ms / +0.2V in the reverse direction; the scanning time of the ultraviolet solid laser is 5-8min; the second set temperature range is 25-30℃; the pH of the plating solution in the second electroplating process is 5.0-5.

2.

8. The high-precision electroplating method for partial selective gold plating of aluminum alloy according to claim 1, characterized in that: The method further comprises immersing the aluminum alloy plated with the second electroplated surface (2) in a stripping solution, and ultrasonically removing the mask surface of the non-gold-plated area.

9. A system for implementing a high-precision electroplating method for local selective gold plating of aluminum alloy according to any one of claims 1 to 8, characterized in that: include: A first electroplating module, performing a first electroplating on the aluminum alloy to be electroplated to obtain an aluminum alloy plated with a first electroplating surface (1), wherein the first electroplating surface (1) includes zinc; A mask coating module is used to coat a photothermal dual-responsive polymer on the aluminum alloy plated with the first electroplating surface (1) to form an aluminum alloy covered with a mask surface, wherein the photothermal dual-responsive polymer is polymerized from a thermal response monomer and an azobenzene monomer; a scanning module, controlling an ultraviolet laser of a set wavelength to scan the area to be gold-plated on the aluminum alloy covered with the mask surface, and heating the scanned aluminum alloy to a first set temperature range; The second electroplating module cools the heated scanned aluminum alloy to a second set temperature range and then performs a second electroplating to obtain an aluminum alloy plated with a second electroplating surface (2), wherein the second electroplating surface (2) is a gold-plated layer formed on the area to be gold-plated.

10. The system according to claim 9, characterized in that The system also includes a pretreatment module, a surface functionalization module and a stripping module; The pretreatment module includes a passivation unit and a seed crystal loading unit; the passivation unit is used to passivate the surface of the aluminum alloy to be electroplated to obtain a passivated aluminum alloy; the seed crystal loading unit is used to deposit zinc seeds on the surface of the passivated aluminum alloy, and the obtained aluminum alloy is used as an updated aluminum alloy to be electroplated; The surface functionalization module is used to modify the aluminum alloy plated with the first electroplating surface (1), and the obtained modified aluminum alloy is used as an updated aluminum alloy plated with the first electroplating surface (1); The stripping module is used for stripping the mask surface on the aluminum alloy plated with the second electroplating surface (2).

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