Cyanide-free alkaline copper deposition process

Abstract

The invention provides a cyanide-free alkaline copper deposition process, which belongs to the technical field of metal deposition, and comprises the following steps: preparing a cyanide-free alkaline copper surface treatment solution containing a composite main complexing agent, an auxiliary complexing agent, silane modified nano TiO2 and other components; the metal base material is subjected to degreasing, micro-etching and electrolytic activation pretreatment; the pretreated base material serves as a cathode, electrolytic copper serves as an anode, electrolysis parameters are controlled through a pulse power source, ultrasonic assistance is combined, and copper ion directional deposition is achieved; and a cyanide-free alkaline copper layer is formed through graded washing and post-treatment. The problems of cyanide pollution, poor coating binding force and insufficient plating solution stability of a traditional copper plating process are solved, cyaniding-free production is achieved, the binding force of an alkaline copper layer reaches grade 0, the salt spray resistance is excellent, the service life of a surface treatment solution is long, and the surface treatment solution can be adapted to various base materials such as aluminum alloy, magnesium alloy and stainless steel and has good application prospects. The method is suitable for the fields of electronic interconnection, automobile corrosion prevention, aerospace equipment surface treatment and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal deposition, in particular to a cyanide-free alkaline copper deposition process. BACKGROUND

[0002] Traditional cyanide electroplating process has gradually withdrawn from the mainstream application market due to the high toxicity of cyanide and the difficulty of waste liquid treatment. Cyanide-free, low pollution and high precision have become the main development trend of electroplating technology. Currently, cyanide-free electroplating process has been applied on a large scale in scenes such as electronic component interconnection, automobile part corrosion prevention, hardware decoration coating, etc. In the industry, by optimizing the complexing agent system, improving equipment configuration (such as pulse power, ultrasonic auxiliary device) and refining process parameters, the performance of the coating and the environmental protection level are continuously improved, trying to meet the stringent requirements of high-end manufacturing on surface treatment.

[0003] Especially in the field of high-end manufacturing, electronic packaging, aerospace, high-end automobile parts and other scenes have put forward standards far beyond conventional applications on the performance, stability and environmental protection of metal surface deposition layer. However, even after several rounds of technical optimization, the existing cyanide-free copper deposition process has not broken through the inherent limitations brought by its own technical principles, making it difficult to adapt to the special needs of high-end manufacturing, and also exposing many problems in actual production that need to be solved: First, the contradiction between environmental protection and compliance is prominent. Although the existing cyanide-free process has abandoned cyanide, high-concentration heavy metal wastewater and difficult-to-biodegrade complexing agent pollutants will still be produced during the deposition process. Such substances are easy to accumulate in the environment, posing significant ecological risks, and the cost of wastewater treatment is high; some processes also rely on harmful auxiliary reagents such as formaldehyde, which not only threatens the health of operators, but also cannot meet the strict requirements of high-end markets for environmental access, limiting the market expansion of products.

[0004] Secondly, the deposited layer has poor performance stability and is difficult to meet the performance requirements of high-end manufacturing. From the basic performance, the existing process has inherent shortcomings in the complex system: the single component of pyrophosphate in the alkaline system has weak complexing ability for copper ions, the structure of the complex ions formed is unstable, and the cathode polarization is insufficient during the discharge reduction process, which makes it difficult to meet the basic use requirements of the adhesion between the deposited layer and the substrate such as steel and aluminum alloy; the acidic sulfate system is prone to displacement reaction with active substrates such as iron, aluminum and zinc, forming a rough and loose copper layer, which is prone to defects such as pinholes and peeling. From the high-end requirements, the existing deposited layer cannot meet the performance requirements of special scenarios: in the field of electronic interconnection, the deposited layer needs to have stable interface contact performance to ensure the reliability of signal transmission, and the uneven surface state of the existing deposited layer can easily cause connection failure; in the field of high-end automobile parts, the deposited layer needs to have excellent corrosion resistance and impact resistance to cope with complex working conditions, and the existing deposited layer has insufficient environmental erosion resistance and structural strength; in the field of aerospace, the deposited layer needs to maintain performance stability in extreme temperature changes and strong radiation, and the existing deposited layer is prone to cracking and peeling, which cannot guarantee the long-term service safety of the parts.

[0005] Thirdly, the process has narrow adaptability and insufficient processing capacity for high-end substrates and complex structures. The treatment solution of the existing cyanide-free copper deposition process cannot directly realize stable deposition on high-end substrates such as high-strength aluminum alloy, magnesium alloy and special stainless steel, and needs to rely on multiple pretreatment processes such as degreasing, pickling, alkaline washing and activation, which is complicated and easy to cause over-corrosion of the substrate, affecting the mechanical properties of the substrate; for complex structures such as PCB micro-pitch lines and rocket engine curved parts, the existing treatment solution has limited deep plating capacity, making it difficult to achieve uniform deposition, resulting in large local performance differences of the parts, which cannot meet the requirements of high-end manufacturing for precision uniformity. At the same time, the deposition process needs to accurately match multiple parameters such as current density, temperature and pH value, and the existing system has very low tolerance to parameter fluctuations, and small deviations can cause a sharp decline in the performance of the deposited layer, making it difficult to guarantee the product qualification rate in large-scale production of high-end manufacturing.

[0006] Fourthly, the equipment and maintenance cost is high. The high requirements of high-end manufacturing for deposition accuracy force enterprises to invest in high-precision deposition equipment, online detection systems and other high-end equipment, which requires huge initial investment; and the existing cyanide-free treatment solution has poor stability, is prone to copper ion hydrolysis and precipitation, and complexing agent failure, which shortens the service life and increases the cost of subsequent maintenance and replacement, further increasing the production burden of enterprises.

[0007] The above problems seriously restrict the large-scale application of cyanide-free alkaline copper deposition process in the field of high-end manufacturing surface treatment, and it is urgent to develop a more stable, efficient and environmentally friendly cyanide-free alkaline copper deposition process to break through the technical bottlenecks and meet the diversified needs of high-end manufacturing. SUMMARY

[0008] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a cyanide-free alkaline copper deposition process, which solves the problems of serious environmental pollution risk caused by cyanide in the existing copper plating technology, insufficient stability of copper ions caused by single complexing agent system, poor adhesion and insufficient density of the plating layer to active substrates such as aluminum alloy and magnesium alloy, and narrow range of process adapted substrates, and cannot meet the needs of high-end manufacturing, realizes long-term stable and durable surface treatment fluid under the premise of no cyanide pollution, can efficiently deposit a cyanide-free alkaline copper layer with high density, uniformity, strong adhesion and excellent corrosion resistance on various substrates such as aluminum alloy, magnesium alloy, zinc alloy and stainless steel, and can be widely applied in the fields of electronic component interconnection, automobile part corrosion prevention, aerospace equipment surface pretreatment and the like, and is suitable for functional deposition layer requirements of various substrates.

[0009] In order to achieve the above-mentioned purpose, the present application provides the following scheme: A cyanide-free alkaline copper deposition process, comprising the following steps: S1, sequentially dissolving a composite main complexing agent, an auxiliary complexing agent, a soluble copper salt, a functional enhancer and a conductive salt in deionized water, and adding a compounded additive after adjusting the pH value, and preparing a cyanide-free alkaline copper surface treatment fluid through dispersion and stability adjustment; S2, carrying out degreasing, surface etching and electrolytic activation treatment on the metal substrate to obtain a pretreated metal substrate; S3, taking the pretreated metal substrate as a cathode, taking electrolytic copper as an anode, and placing them together in the cyanide-free alkaline copper surface treatment fluid, connecting a pulse power supply and controlling electrolysis parameters, realizing directional deposition of copper ions on the cathode surface through electrolysis to complete deposition of the cyanide-free alkaline copper layer; S4, carrying out graded water washing and post-treatment on the metal substrate after electrolytic deposition to finally form a cyanide-free alkaline copper layer on the metal substrate.

[0010] Preferably, in S1, the cyanide-free alkaline copper surface treatment fluid comprises: a composite main complexing agent 150-300 g / L, an auxiliary complexing agent 40-90 g / L, a soluble copper salt 8-22 g / L, a functional enhancer 1.0-2.5 g / L, a conductive salt 30-50 g / L, and a compounded additive 3-15 mL / L, wherein the pH value of the cyanide-free alkaline copper surface treatment fluid is 9.0-10.0; the composite main complexing agent is a mixture composed of a modified hydroxyethylidene diphosphonic acid derivative and pyrophosphate in a mass ratio of 1-2:2-3.

[0011] Preferably, the modified hydroxyethylidene diphosphonic acid derivative is a hydroxyethylidene diphosphonic acid grafted with a terminal sulfonic acid group; the auxiliary complexing agent is a complex of sodium gluconate and aminotri(methylene) phosphonic acid at a mass ratio of 3-5:1; and the functional enhancer is a silane-modified nano-TiO2 with a particle size of 30-80 nm and a surface modifier of γ-(2,3-epoxypropoxy) propyl trimethoxysilane.

[0012] Preferably, the complex additive is composed of component X, component Y, and component Z at a mass ratio of 3-25:2-18:4-22; the component X is a compound containing a sulfide structure, selected from one or more of 2,2'-thiodiethanol and bis(2-hydroxyethyl) sulfide; the component Y is a polyetheramine polymer, selected from one of polyetheramine D230 and polyetheramine T403; and the component Z is a nitrogen-containing compound containing a heterocyclic ring, selected from one or more of 1-hydroxyethyl-2-imidazolinone and 2-aminobenzimidazole.

[0013] Preferably, the composite pH regulator is a mixed solution of potassium hydroxide and potassium bicarbonate at a mass ratio of 4-6:1; the soluble copper salt is a complex of copper 2-hydroxypropanesulfonate and copper pyrophosphate at a mass ratio of 1-3:1; and the conductive salt is a mixture of potassium carbonate and potassium chloride at a mass ratio of 5-7:1.

[0014] Preferably, in S1, the specific preparation process of the cyanide-free alkaline copper surface treatment solution is as follows: the temperature of deionized water is adjusted to 40-50℃, the composite main complexing agent is first added and stirred for 25-35 min, the auxiliary complexing agent is then added and stirred for 10-20 min, the soluble copper salt is added until completely dissolved, the functional enhancer is subsequently added and ultrasonically dispersed for 15-25 min, the conductive salt is added and stirred to dissolve, the composite pH regulator is used to adjust the pH value to 9.0-10.0, and finally the complex additive is added, and the solution is left to stand and age for 1-2 h, thereby obtaining the cyanide-free alkaline copper surface treatment solution.

[0015] Preferably, in S2, the degreasing is performed in a double-gradient mode of weak alkali pre-degreasing and solvent fine degreasing, wherein the temperature of the weak alkali pre-degreasing is 35-40℃, and the degreasing time is 4-6 min, and the temperature of the solvent fine degreasing is room temperature, and the degreasing time is 2-4 min; the surface micro-etching is performed using an acid micro-etching solution containing fluoride, and the etching amount is controlled to be 0.5-1.0 μm; and the electrolytic activation treatment is performed using an electrolyte solution containing sulfuric acid, with the substrate as the cathode and a platinum sheet as the anode, and a cathode current of 0.5-1.0 A / dm 2 is applied, and the activation temperature is 25-35℃, and the treatment time is 2-4 min.

[0016] Preferably, in step S3, the electrolysis parameters are: pulse power supply frequency 1000-3000Hz, duty cycle 30%-60%, and cathode current density 1.0-3.0A / dm³. 2 The electrolysis temperature is 35-45℃ and the electrolysis time is 10-60min. Ultrasonic dispersion is used during the deposition process, with an ultrasonic power of 200-300W and an ultrasonic frequency of 25-40kHz.

[0017] Preferably, in S3, the specific process of stirring and anode configuration during the electrolytic deposition process is as follows: a combined stirring mode of bottom aeration stirring and side mechanical stirring is adopted, wherein the aeration rate is adjusted to 0.5-0.7 m / s and the mechanical stirring speed is 120-180 r / min; the anode uses a titanium basket to load an electrolytic copper plate, and the titanium basket is covered with a polypropylene anode bag, and the area ratio of the anode to the cathode is 1.5-2.5:1.

[0018] Preferably, in S4, the specific process of the graded water washing and post-treatment is as follows: first, perform a room temperature water wash for 1-2 minutes, then a hot water wash at 45-55℃ for 1-2 minutes, and finally a deionized water wash for 2-3 minutes; the post-treatment involves soaking in a passivation solution containing benzotriazole for 10-15 minutes.

[0019] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: (1) This invention completely eliminates the use of cyanide by using a graded synergistic treatment of a composite main complexing agent and an auxiliary complexing agent, thus eliminating the environmental and safety risks caused by highly toxic substances from the source. At the same time, the composite complexing system can stabilize copper ions in the surface treatment solution by means of the synergistic effect of multiple ligands, avoiding their hydrolysis and precipitation, thus solving the problem of poor stability caused by insufficient coordination ability of a single complexing agent in existing cyanide-free plating solutions. In addition, the buffering mechanism formed by the composite pH adjuster can maintain the pH value of the surface treatment solution, reduce the impact of process fluctuations on the performance of the surface treatment solution, and significantly improve the durability of the surface treatment solution.

[0020] (2) The present invention uses a combination of pretreatments, including dual-gradient degreasing, surface micro-etching and electrolytic activation, to construct uniform conductive active sites on the surface of substrates with different properties, such as aluminum alloys, magnesium alloys, zinc alloys and stainless steel, laying the foundation for electrolytic deposition. The introduction of functional enhancers can strengthen the structure of alkaline copper layers. Combined with ultrasonic-assisted dispersion, composite stirring and optimized electrolytic parameters during the deposition process, the uniformity of copper ion mass transfer is effectively improved. This solves the problems of weak bonding between the coating and the substrate, loose structure and easy pinhole defects in the prior art, and significantly improves the density and corrosion resistance of alkaline copper layers.

[0021] (3) By combining the synergistic regulation of compound additives with pulse electrolysis technology, this invention can accurately balance the brightness and uniformity of alkaline copper layer, which is suitable for the surface treatment needs of complex shaped parts. No highly toxic raw materials are involved in the entire process, and the by-products are easily degraded, which reduces the pressure of environmental treatment. Moreover, it can meet the stringent requirements in fields such as electronic component interconnection, automotive parts corrosion protection, and aerospace equipment surface treatment, which improves the application potential of cyanide-free alkaline copper deposition technology, realizes the synergistic improvement of environmental protection and functionality, and provides a better solution for surface treatment in the high-end manufacturing field. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a flowchart of a cyanide-free alkaline copper deposition process according to the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] like Figure 1 As shown, the present invention provides a cyanide-free alkaline copper deposition process, comprising the following steps: S1. The composite main complexing agent, auxiliary complexing agent, soluble copper salt, functional enhancer, and conductive salt are dissolved in deionized water in sequence, and the pH value is adjusted before adding compound additives. After dispersion and stability adjustment, a cyanide-free alkaline copper surface treatment solution is prepared.

[0027] In the above steps, the composite main complexing agent is a mixture of modified hydroxyethylidene diphosphonic acid derivative and pyrophosphate in a mass ratio of 1-2:2-3. The modified hydroxyethylidene diphosphonic acid derivative is prepared by the following method: 1 mol of hydroxyethylidene diphosphonic acid is dissolved in 2 L of deionized water, 1.2 mol of sodium sulfite is added at 60 °C and activated for 30 min, followed by the dropwise addition of 1.1 mol of 1,3-propanesulfonic acid lactone at a dropping rate of 1 mL / min. The reaction is carried out at 80 °C for 4 h, and the pH is adjusted to 7.0 before distillation and drying to obtain the final product.

[0028] The auxiliary complexing agent is a compound composed of sodium gluconate and aminotrimethylene phosphonic acid in a mass ratio of 3-5:1; the functional enhancer is silane-modified nano-TiO2 with a particle size of 30-80 nm, and the surface modifier is γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0029] The dispersion process employs ultrasonic dispersion with a power of 200-300W, a frequency of 25-40kHz, and a dispersion time of 15-25min. Stability adjustment involves static aging for 1-2 hours at a temperature maintained within the range of 40-50℃. Furthermore, pH adjustment utilizes a composite pH adjuster, which is a mixture of potassium hydroxide and potassium bicarbonate in a mass ratio of 4-6:1, with the pH value controlled between 9.0 and 10.0.

[0030] S2. The metal substrate is subjected to degreasing, surface micro-etching and electrolytic activation treatment to obtain the pretreated metal substrate.

[0031] In the above steps, the degreasing adopts a dual-gradient mode of weak alkali pre-degreasing and solvent degreasing: the temperature range of weak alkali pre-degreasing is 35-40℃ and the treatment time is 4-6 min; the treatment temperature of solvent degreasing is room temperature and the treatment time is 2-4 min.

[0032] Surface micro-etching was performed using an acidic micro-etching solution containing fluoride, with the etching depth controlled within the range of 0.5-1.0 μm. After micro-etching, the surface was rinsed three times with deionized water, each rinsing time being 1 min. Electrolytic activation treatment was performed using a 5%-8% (mass fraction) sulfuric acid solution, with the substrate as the cathode and a platinum sheet as the anode, applying an A / dm² pressure of 0.5-1.0 A. 2 The cathode current is set, the activation temperature is 25-35℃, the treatment time is 2-4 minutes, and after activation, it is immediately immersed in deionized water for later use.

[0033] S3. The pretreated metal substrate is used as the cathode, and electrolytic copper is used as the anode. They are placed together in a cyanide-free alkaline copper surface treatment solution, connected to a pulse power supply and the electrolysis parameters are controlled. Through electrolysis, copper ions are directionally deposited on the cathode surface to complete the deposition of a cyanide-free alkaline copper layer.

[0034] In the above steps, the electrolysis parameters are: pulse power supply frequency 1000-3000Hz, duty cycle 30%-60%, and cathode current density 1.0-3.0A / dm³. 2 Electrolysis temperature 35-45℃, electrolysis time 10-60min.

[0035] The deposition process employs a combination of ultrasonic-assisted dispersion and composite stirring: the ultrasonic power is 200-300W and the ultrasonic frequency is 25-40kHz; the composite stirring combines bottom aeration and side mechanical stirring, with an aeration rate of 0.5-0.7m / s and a mechanical stirring speed controlled within the range of 120-180r / min.

[0036] The anode uses a titanium basket to load electrolytic copper plates, and the titanium basket is covered with a polypropylene anode bag to filter the anode mud. The area ratio of the anode to the cathode is 1.5-2.5:1.

[0037] S4. The electrolytically deposited metal substrate is subjected to graded water washing and post-treatment to finally form a cyanide-free alkaline copper layer on the metal substrate.

[0038] In the above steps, the graded water washing is as follows: first, wash with room temperature water for 1-2 minutes, then wash with hot water at 45-55℃ for 1-2 minutes, and then wash with deionized water for 2-3 minutes. After each water washing step, the surface water droplets are dried with compressed air. The post-treatment involves soaking in a passivation solution containing benzotriazole for 10-15 minutes. The passivation solution concentration is 4-6 g / L, and the temperature is room temperature. After soaking, the product is air-dried naturally or dried at a drying temperature of 60℃.

[0039] When preparing a cyanide-free alkaline copper layer according to the above process, the cyanide-free alkaline copper surface treatment solution used includes the following components: 150-300 g / L of composite main complexing agent, 40-90 g / L of auxiliary complexing agent, 8-22 g / L of soluble copper salt, 1.0-2.5 g / L of functional enhancer, 30-50 g / L of conductive salt, and 3-15 mL / L of compound additives.

[0040] The soluble copper salt is a compound composed of copper 2-hydroxypropanesulfonate and copper pyrophosphate in a mass ratio of 1-3:1; the conductive salt is a mixture composed of potassium carbonate and potassium chloride in a mass ratio of 5-7:1.

[0041] The compound additive is composed of component X, component Y, and component Z in a mass ratio of 3-25:2-18:4-22: component X is a compound containing a sulfide structure, selected from one or more of 2,2'-thiodiethanol and bis(2-hydroxyethyl) sulfide; component Y is a polyetheramine polymer, selected from one of polyetheramine D230 and polyetheramine T403; component Z is a nitrogen-containing compound containing a heterocyclic ring, selected from one or more of 1-hydroxyethyl-2-imidazolinone and 2-aminobenzimidazole.

[0042] It should be noted that the pyrophosphate in the composite main complexing agent and the sodium gluconate in the auxiliary complexing agent used in this invention are both conventional reagents known in the field of surface treatment. Pyrophosphate is a commonly used complexing agent in traditional cyanide-free surface treatment solutions. It has the characteristics of moderate coordination ability and low cost, but when used alone, its stabilizing effect on copper ions is limited, which can easily lead to the failure of the surface treatment solution.

[0043] To address this issue, this invention optimizes the complex complex system by modifying hydroxyethylidene diphosphonic acid with a terminal sulfonic acid group, thereby increasing its affinity for Cu. 2+ The coordination sites are specifically formed by the sulfonic acid group and the hydroxyl and phosphonic acid groups to form multidentate coordination, which improves the stability constant (lgK) of the composite main complexing agent. At the same time, the combination of sodium gluconate and aminotrimethylene phosphonic acid as auxiliary complexing agents forms a hierarchical synergistic effect of main complexing and auxiliary coordination, which effectively inhibits the hydrolysis and precipitation of copper ions in alkaline environment and solves the problem of poor stability of traditional cyanide-free plating solutions.

[0044] Furthermore, this invention introduces a functional enhancer, silane, to modify nano-TiO2: unmodified nano-TiO2 is prone to agglomeration and cannot be uniformly dispersed in the surface treatment solution; while the epoxy and hydroxyl groups of γ-(2,3-epoxypropoxy)propyltrimethoxysilane can form hydrogen bonds with the complexing agent to achieve stable suspension of nanoparticles. At the same time, it can be dispersed in the alkaline copper layer during the deposition process, refining the crystal grains and significantly improving the density and corrosion resistance of the alkaline copper layer.

[0045] In the electrolytic deposition process, the synergistic process of pulse power supply, ultrasonic assistance and compound stirring is also indispensable: pulse electrolysis can reduce concentration polarization and hydrogen evolution reaction, and reduce pinhole defects in alkaline copper layer; ultrasonic action can break the diffusion boundary layer of copper ions, and compound stirring promotes macroscopic mass transfer of surface treatment solution. The combination of the two solves the problem of uneven alkaline copper layer; optimized anode configuration and filtration device can avoid anode mud contamination of surface treatment solution and maintain long-term stability of surface treatment solution.

[0046] The above content will be further described below through specific implementation methods. The listed embodiments are only some embodiments of the present invention.

[0047] Example 1 This embodiment provides a cyanide-free alkaline copper deposition process. Specifically, a 5052 aluminum alloy substrate is selected, a cyanide-free alkaline copper surface treatment solution is prepared, and electrolytic deposition is performed. The process includes: First, a cyanide-free alkaline copper surface treatment solution was prepared: 500 ml of deionized water was taken and heated to 45°C. Then, 225 g of a composite primary complexing agent was added, comprising 90 g of modified hydroxyethylidene diphosphonic acid derivative and 135 g of potassium pyrophosphate, in a mass ratio of 1:1.5, and stirred for 30 min until completely dissolved. Next, 65 g of an auxiliary complexing agent was added, comprising 50 g of sodium gluconate and 15 g of aminotrimethylene phosphonic acid, in a mass ratio of 3.3:1, and stirred for 15 min. Then, 15 g of a soluble copper salt was added, comprising 10 g of copper 2-hydroxypropanesulfonate and 5 g of copper pyrophosphate, in a mass ratio of 2:1, and stirred until completely dissolved. Finally, 1.8 g of silane-modified nano-TiO2 with a particle size of 50 nm was added, and ultrasonic dispersion was initiated for 20 min at a power of 250 W and a frequency of 30 kHz. Next, 40g of conductive salt was added, comprising 34g of potassium carbonate and 6g of potassium chloride in a mass ratio of 5.7:1, and the mixture was stirred for 10 minutes. Then, the pH of the surface treatment solution was adjusted to 9.5 using a composite pH adjuster, wherein the mass ratio of potassium hydroxide to potassium bicarbonate in the composite pH adjuster was 5:1. Finally, 9mL of a compound additive was added, comprising 4.5g of 2,2'-thiodiethanol, 3g of polyetheramine D230, and 1.5g of 2-aminobenzimidazole in a mass ratio of 15:10:5. Finally, 500ml of deionized water was poured into the mixture, and the surface treatment solution was allowed to stand for 1.5 hours to age, yielding a cyanide-free alkaline copper surface treatment solution.

[0048] Secondly, the 5052 aluminum alloy substrate underwent pretreatment: weak alkali pre-degreasing and solvent degreasing were performed sequentially. The weak alkali pre-degreasing temperature was 38℃ for 5 minutes; the solvent degreasing temperature was room temperature for 3 minutes. Then, the substrate was treated with a hydrofluoric acid-nitric acid micro-etching solution, controlling the etching depth to 0.8 μm. Finally, the substrate was placed in a 7% sulfuric acid solution for electrolytic activation, with the substrate as the cathode and a platinum sheet as the anode, and an application rate of 0.8 A / dm² was applied. 2 The cathode current was set, the activation temperature was 30℃, and the time was 3min. After rinsing with deionized water, the pretreated 5052 aluminum alloy substrate was obtained.

[0049] Electrolytic deposition is then performed, following this process: A pretreated 5052 aluminum alloy substrate is used as the cathode, and an electrolytic copper plate is loaded in a titanium basket as the anode (anode to cathode area ratio 2:1). Both are immersed in a prepared cyanide-free alkaline copper surface treatment solution, with the solution temperature controlled at 40℃. A pulsed power supply is connected, with a frequency of 2000Hz, a duty cycle of 45%, and a cathode current density of 2.0A / dm³. 2Ultrasonic-assisted dispersion was activated with an ultrasonic power of 250W and an ultrasonic frequency of 30kHz. Simultaneously, a combined stirring mode was activated, including bottom aeration and side mechanical stirring. The aeration rate for bottom aeration was 0.6m / s, and the rotation speed for side mechanical stirring was 150r / min. Electrolytic deposition was maintained under these conditions for 30 minutes.

[0050] Finally, post-processing is performed as follows: the deposited 5052 aluminum alloy substrate is subjected to graded water washing, first washed with room temperature water for 1.5 min, then washed with 50℃ hot water for 1.5 min, and finally washed with deionized water for 2.5 min. After washing, the substrate surface is dried with compressed air, and then the substrate is immersed in 5 g / L benzotriazole passivation solution at room temperature for 12 min, followed by natural air drying, forming an alkaline copper layer on the 5052 aluminum alloy substrate.

[0051] Example 2 This embodiment provides a cyanide-free alkaline copper deposition process. Specifically, this embodiment selects an AZ31B type magnesium alloy substrate, prepares a cyanide-free alkaline copper surface treatment solution, and performs electrolytic deposition. The process includes: First, a cyanide-free alkaline copper surface treatment solution was prepared: 500 ml of deionized water was taken and heated to 50°C. Then, 300 g of a composite primary complexing agent was added, comprising 120 g of modified hydroxyethylidene diphosphonic acid derivative and 180 g of potassium pyrophosphate, in a mass ratio of 1:1.5, and stirred for 35 min until completely dissolved. Next, 90 g of an auxiliary complexing agent was added, comprising 75 g of sodium gluconate and 15 g of aminotrimethylene phosphonic acid, in a mass ratio of 5:1, and stirred for 20 min. Then, 22 g of a soluble copper salt was added, comprising 16.5 g of copper 2-hydroxypropanesulfonate and 5.5 g of copper pyrophosphate, in a mass ratio of 3:1, and stirred until completely dissolved. Finally, 2.5 g of silane-modified nano-TiO2 with a particle size of 80 nm was added, and ultrasonic dispersion was initiated for 25 min at a power of 300 W and a frequency of 40 kHz. Next, add 50g of conductive salt, which includes 43g of potassium carbonate and 7g of potassium chloride in a mass ratio of 6.1:1, and stir for 15 minutes. Then, adjust the pH of the surface treatment solution to 10.0 using a composite pH adjuster, wherein the mass ratio of potassium hydroxide to potassium bicarbonate in the composite pH adjuster is 5:1. Finally, add 15mL of compound additive and 500mL of deionized water to the mixture. Then, let the surface treatment solution stand for 2 hours to obtain a cyanide-free alkaline copper surface treatment solution.

[0052] Secondly, the AZ31B magnesium alloy substrate underwent pretreatment: weak alkali pre-degreasing and solvent degreasing were performed sequentially. The weak alkali pre-degreasing temperature was 40℃ for 6 minutes; the solvent degreasing temperature was room temperature for 4 minutes. Then, the substrate was subjected to micro-etching treatment, with the etching depth controlled at 1.0 μm. Finally, the substrate was placed in an 8% sulfuric acid solution for electrolytic activation, using the substrate as the cathode and a platinum sheet as the anode, with an application rate of 1.0 A / dm². 2 The cathode current was set, the activation temperature was 35℃, and the time was 4 min. After rinsing with deionized water, the pretreated AZ31B magnesium alloy substrate was obtained.

[0053] Electrolytic deposition is then performed as follows: A pretreated AZ31B magnesium alloy substrate is used as the cathode, and an electrolytic copper plate is loaded in a titanium basket as the anode (anode to cathode area ratio 2.5:1). Both are immersed in a prepared cyanide-free alkaline copper surface treatment solution, with the solution temperature controlled at 45℃. A pulsed power supply is connected, with a frequency of 3000Hz, a duty cycle of 60%, and a cathode current density of 3.0A / dm³. 2 Ultrasonic-assisted dispersion was activated with an ultrasonic power of 300W and an ultrasonic frequency of 40kHz. Simultaneously, a combined stirring mode was activated, including bottom aeration and side mechanical stirring. The aeration rate for bottom aeration was 0.7m / s, and the rotation speed for side mechanical stirring was 180r / min. Electrolytic deposition was maintained under these conditions for 60 minutes.

[0054] Finally, post-processing is performed as follows: the deposited AZ31B magnesium alloy substrate is subjected to graded water washing, first washed with room temperature water for 2 minutes, then washed with 55℃ hot water for 2 minutes, and finally washed with deionized water for 3 minutes. After washing, the substrate surface is dried with compressed air, and then the substrate is immersed in 5 g / L benzotriazole passivation solution at room temperature for 15 minutes, followed by natural air drying, forming an alkaline copper layer on the AZ31B magnesium alloy substrate.

[0055] Example 3 This embodiment provides a cyanide-free alkaline copper deposition process. Specifically, this embodiment selects a Zamak 5 type zinc alloy substrate, prepares a cyanide-free alkaline copper surface treatment solution, and performs electrolytic deposition. The process includes: First, a cyanide-free alkaline copper surface treatment solution was prepared: 500 ml of deionized water was taken and heated to 42 °C. Then, 200 g of a composite primary complexing agent was added, comprising 80 g of modified hydroxyethylidene diphosphonic acid derivative and 120 g of potassium pyrophosphate, in a mass ratio of 1:1.5, and stirred for 28 min until completely dissolved. Next, 70 g of an auxiliary complexing agent was added, comprising 55 g of sodium gluconate and 15 g of aminotrimethylene phosphonic acid, in a mass ratio of 3.7:1, and stirred for 18 min. Then, 12 g of a soluble copper salt was added, comprising 9 g of copper 2-hydroxypropanesulfonate and 3 g of copper pyrophosphate, in a mass ratio of 3:1, and stirred until completely dissolved. Finally, 1.5 g of silane-modified nano-TiO2 with a particle size of 60 nm was added, and ultrasonic dispersion was initiated for 22 min at a power of 260 W and a frequency of 35 kHz. Next, 45g of conductive salt was added, comprising 38g of potassium carbonate and 7g of potassium chloride in a mass ratio of 5.4:1, and the mixture was stirred for 12 minutes. Then, the pH of the surface treatment solution was adjusted to 9.3 using a composite pH adjuster, wherein the mass ratio of potassium hydroxide to potassium bicarbonate in the composite pH adjuster was 5:1. Finally, 7mL of compound additive was added, and 500mL of deionized water was added to the mixture. The surface treatment solution was then allowed to stand for 1.2 hours to age, yielding a cyanide-free alkaline copper surface treatment solution.

[0056] Secondly, the Zamak 5 zinc alloy substrate underwent pretreatment: weak alkali pre-degreasing and solvent degreasing were performed sequentially. The weak alkali pre-degreasing temperature was 37℃ for 5 minutes; the solvent degreasing temperature was room temperature for 3 minutes. Then, the substrate was micro-etched, with the etching depth controlled at 0.7 μm. Finally, the substrate was placed in a 6% sulfuric acid solution for electrolytic activation, using the substrate as the cathode and a platinum sheet as the anode, with an application rate of 0.7 A / dm. 2 The cathode current was set, the activation temperature was 32℃, and the time was 3min. After rinsing with deionized water, the pretreated Zamak5 type zinc alloy substrate was obtained.

[0057] Electrolytic deposition is then performed, following this process: A pretreated Zamak 5 type zinc alloy substrate is used as the cathode, and an electrolytic copper plate loaded in a titanium basket is used as the anode (anode to cathode area ratio 2:1). Both are immersed in a prepared cyanide-free alkaline copper surface treatment solution, with the solution temperature controlled at 38℃. A pulsed power supply is connected, with a frequency of 2500Hz, a duty cycle of 50%, and a cathode current density of 1.8A / dm³. 2 Ultrasonic-assisted dispersion was activated with an ultrasonic power of 260W and an ultrasonic frequency of 35kHz. Simultaneously, a combined stirring mode was activated, including bottom aeration and side mechanical stirring. The aeration rate for bottom aeration was 0.55m / s, and the rotation speed for side mechanical stirring was 140r / min. Electrolytic deposition was maintained under these conditions for 20 minutes.

[0058] Finally, post-processing is performed as follows: the deposited Zamak 5 type zinc alloy substrate is subjected to graded water washing, first washed with room temperature water for 1.2 min, then washed with 48℃ hot water for 1.2 min, and finally washed with deionized water for 2.3 min. After washing, the substrate surface is dried with compressed air, and then the substrate is immersed in 5 g / L benzotriazole passivation solution at room temperature for 13 min, followed by natural air drying, forming an alkaline copper layer on the Zamak 5 type zinc alloy substrate.

[0059] Comparative Example 1 The only difference between this comparative example and Example 1 is that ordinary hydroxyethylidene diphosphonic acid is used instead of the modified hydroxyethylidene diphosphonic acid derivative; the amounts of all other materials and process parameters are the same, specifically including: First, a cyanide-free alkaline copper surface treatment solution was prepared: 500 ml of deionized water was taken and then heated to 45°C. Next, 225 g of a composite primary complexing agent was added, comprising 90 g of common hydroxyethylidene diphosphonic acid and 135 g of potassium pyrophosphate in a mass ratio of 1:1.5, and stirred for 30 min until completely dissolved. Subsequent steps, including adding auxiliary complexing agents, soluble copper salts, silane-modified nano-TiO2, conductive salts, composite pH adjusters, compound additives, and replenishing deionized water, as well as stirring, ultrasonic dispersion, and aging, were performed according to Example 1 to obtain the cyanide-free alkaline copper surface treatment solution.

[0060] Secondly, the 5052 aluminum alloy substrate was pretreated: all steps were performed in accordance with Example 1 to obtain the pretreated 5052 aluminum alloy substrate.

[0061] Then, electrolytic deposition is performed, and the process is as follows: all steps are performed in accordance with Example 1.

[0062] Finally, post-processing is performed, and the process is as follows: all steps are carried out in accordance with Example 1, and an alkaline copper layer is formed on the 5052 type aluminum alloy substrate.

[0063] Comparative Example 2 The only difference between this comparative example and Example 1 is that silane-modified nano-TiO2 was not added to the surface treatment solution; the amounts of other materials and process parameters are the same, specifically including: First, a cyanide-free alkaline copper surface treatment solution was prepared: 500 ml of deionized water was taken and its temperature was raised to 45°C. Then, 225 g of the composite primary complexing agent was added and stirred for 30 min until completely dissolved. Next, 65 g of the auxiliary complexing agent was added and stirred for 15 min. Then, 15 g of soluble copper salt was added and stirred until completely dissolved. Subsequently, 40 g of conductive salt was added directly and stirred for 10 min. Subsequent steps, including pH adjustment, addition of compound additives, replenishment of deionized water, and aging, were performed according to Example 1 to obtain the cyanide-free alkaline copper surface treatment solution.

[0064] Secondly, the 5052 aluminum alloy substrate was pretreated: all steps were performed in accordance with Example 1 to obtain the pretreated 5052 aluminum alloy substrate.

[0065] Then, electrolytic deposition is performed, and the process is as follows: all steps are performed in accordance with Example 1.

[0066] Finally, post-processing is performed, and the process is as follows: all steps are carried out in accordance with Example 1, and an alkaline copper layer is formed on the 5052 type aluminum alloy substrate.

[0067] Comparative Example 3 The only difference between this comparative example and Example 1 is that a DC power supply is used instead of a pulse power supply during the deposition process; all other material quantities and process parameters are the same, specifically including: First, a cyanide-free alkaline copper surface treatment solution was prepared: all steps were performed according to Example 1 to obtain a cyanide-free alkaline copper surface treatment solution.

[0068] Secondly, the 5052 aluminum alloy substrate was pretreated: all steps were performed in accordance with Example 1 to obtain the pretreated 5052 aluminum alloy substrate.

[0069] Electrolytic deposition is then performed. The process is as follows: a pretreated 5052 aluminum alloy substrate is used as the cathode, and an electrolytic copper plate loaded in a titanium basket is used as the anode. Both are immersed in a prepared cyanide-free alkaline copper surface treatment solution, with the temperature of the solution controlled at 40°C. A DC power supply is connected, with a cathode current density of 2.0 A / dm³. 2 Ultrasonic-assisted dispersion was activated at a power of 250W and a frequency of 30kHz. Mechanical stirring was activated only at a speed of 150r / min, and electrolytic deposition was carried out under the above conditions for 30min.

[0070] Finally, post-processing is performed, and the process is as follows: all steps are carried out in accordance with Example 1, and an alkaline copper layer is formed on the 5052 type aluminum alloy substrate.

[0071] Comparative Example 4 The only difference between this comparative example and Example 1 is the use of a traditional single pyrophosphate cyanide-free electroplating process; the remaining substrate pretreatment and post-treatment steps are the same, specifically including: First, prepare a traditional cyanide-free electroplating surface treatment solution: Take 500ml of deionized water, add 200g of potassium pyrophosphate, 20g of citric acid, 20g of potassium sodium tartrate, and 15g of copper acetate, and stir until completely dissolved. Adjust the pH of the plating solution to 9.0 using a pH adjuster, add 4.6mL of compound additive and 500ml of deionized water to obtain the traditional cyanide-free electroplating surface treatment solution.

[0072] Secondly, the 5052 aluminum alloy substrate was pretreated: all steps were performed in accordance with Example 1 to obtain the pretreated 5052 aluminum alloy substrate.

[0073] Then, electrolytic deposition is performed. The process is as follows: the pretreated 5052 aluminum alloy substrate is used as the cathode, and electrolytic copper is selected as the anode. Both are immersed in a prepared traditional cyanide-free electroplating surface treatment solution. The cathode current density is set to 2A / dm³. 2 Turn on the air agitator, control the plating solution temperature to 40℃, and electroplate for 30 minutes.

[0074] Finally, post-processing is performed, and the process is as follows: all steps are carried out in accordance with Example 1, and an alkaline copper layer is formed on the 5052 type aluminum alloy substrate.

[0075] The performance of the alkaline copper layers prepared in Examples 1-3 and Comparative Examples 1-4 was tested below. The test standard was in accordance with the "Metallic Coating Electroplating of Copper and Copper Alloy Layers" (GB / T 12334-2008). The results are shown in Table 1.

[0076] Table 1 Performance Test Results

[0077] Referring to Table 1, it can be found that compared with Comparative Examples 1-4, Examples 1-3 of the present invention achieve a bonding strength (cross-cut test) of 0, while the Comparative Examples are 1-3; in terms of salt spray resistance, Examples 1-3 achieve 48-96 hours, while Comparative Examples 1-4 achieve 30-48 hours; in terms of surface roughness (Ra), Examples 1-3 achieve 0.06-0.10 μm, while Comparative Examples 1-4 achieve 0.12-0.30 μm; in terms of plating bath life, Examples 1-3 achieve 10-14 months, while Comparative Examples 1-4 achieve 5-8 months; and in terms of deep plating capability (depth-to-diameter ratio), Examples 1-3 achieve a ratio of 3:1, while Comparative Examples 1-4 achieve a ratio of 1.5:1-2.8:1. This further demonstrates that the present invention exhibits significant advantages in all performance indicators.

[0078] Therefore, the above-mentioned cyanide-free alkaline copper deposition process solves the problems of serious environmental pollution risks caused by cyanide in existing copper plating technologies, insufficient stability of copper ions by a single complexing agent system leading to easy failure of the plating solution, poor adhesion and insufficient density of the coating with active substrates such as aluminum alloys and magnesium alloys, as well as the narrow range of substrates that the process can adapt to and cannot meet the needs of high-end manufacturing. It achieves long-term stability and durability of the surface treatment solution under the premise of cyanide-free pollution, and can efficiently deposit dense, uniform, strong adhesion and excellent corrosion resistance alkaline copper layers on various substrates such as aluminum alloys, magnesium alloys, zinc alloys and stainless steel. It can be widely used in fields such as electronic component interconnection, corrosion protection of automotive parts, and surface pretreatment of aerospace equipment, and is suitable for the functional deposition layer requirements of various substrates.

[0079] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0080] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A cyanide-free alkaline copper deposition process, characterized in that, Includes the following steps: S1. The composite main complexing agent, auxiliary complexing agent, soluble copper salt, functional enhancer and conductive salt are dissolved in deionized water in sequence, and the pH value is adjusted before adding compound additives. After dispersion and stability adjustment, a cyanide-free alkaline copper surface treatment solution is prepared. S2. Degreasing, surface micro-etching and electrolytic activation treatment are performed on the metal substrate to obtain the pretreated metal substrate. S3. The pretreated metal substrate is used as the cathode, and electrolytic copper is used as the anode. They are placed together in a cyanide-free alkaline copper surface treatment solution, connected to a pulse power supply and the electrolysis parameters are controlled. Through electrolysis, copper ions are directionally deposited on the cathode surface to complete the deposition of a cyanide-free alkaline copper layer. S4. The electrolytically deposited metal substrate is subjected to graded water washing and post-treatment to finally form a cyanide-free alkaline copper layer on the metal substrate.

2. The cyanide-free alkaline copper deposition process according to claim 1, characterized in that, In S1, the cyanide-free alkaline copper surface treatment solution comprises: a composite primary complexing agent of 150-300 g / L, an auxiliary complexing agent of 40-90 g / L, a soluble copper salt of 8-22 g / L, a functional enhancer of 1.0-2.5 g / L, a conductive salt of 30-50 g / L, and a compound additive of 3-15 mL / L, wherein the pH value of the cyanide-free alkaline copper surface treatment solution is 9.0-10.0; the composite primary complexing agent is a mixture of modified hydroxyethylidene diphosphonic acid derivative and pyrophosphate in a mass ratio of 1-2:2-3.

3. The cyanide-free alkaline copper deposition process according to claim 2, characterized in that, The modified hydroxyethylidene diphosphonic acid derivative is hydroxyethylidene diphosphonic acid with terminal grafted sulfonic acid groups; the auxiliary complexing agent is a compound composed of sodium gluconate and aminotrimethylene phosphonic acid in a mass ratio of 3-5:1; the functional enhancer is silane-modified nano-TiO2 with a particle size of 30-80 nm, and the surface modifier is γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

4. The cyanide-free alkaline copper deposition process according to claim 2, characterized in that, The compound additive is composed of component X, component Y, and component Z in a mass ratio of 3-25:2-18:4-22; component X is a compound containing a thioether structure, selected from one or more of 2,2'-thiodiethanol and bis(2-hydroxyethyl) thioether; component Y is a polyetheramine polymer, selected from one of polyetheramine D230 and polyetheramine T403; component Z is a nitrogen-containing compound containing a heterocyclic ring, selected from one or more of 1-hydroxyethyl-2-imidazolinone and 2-aminobenzimidazole.

5. The cyanide-free alkaline copper deposition process according to claim 2, characterized in that, The composite pH adjuster is a mixture of potassium hydroxide and potassium bicarbonate in a mass ratio of 4-6:1; the soluble copper salt is a compound of copper 2-hydroxypropanesulfonate and copper pyrophosphate in a mass ratio of 1-3:1; and the conductive salt is a mixture of potassium carbonate and potassium chloride in a mass ratio of 5-7:

1.

6. The cyanide-free alkaline copper deposition process according to claim 1, characterized in that, In S1, the specific preparation process of the cyanide-free alkaline copper surface treatment solution is as follows: the temperature of deionized water is adjusted to 40-50℃, the composite main complexing agent is added and stirred for 25-35 minutes, the auxiliary complexing agent is added and stirred for 10-20 minutes, the soluble copper salt is added until completely dissolved, the functional enhancer is added and ultrasonically dispersed for 15-25 minutes, the conductive salt is added and stirred to dissolve, the pH value is adjusted to 9.0-10.0 with the composite pH adjuster, the compound additive is added, and the mixture is allowed to stand and age for 1-2 hours to finally obtain the cyanide-free alkaline copper surface treatment solution.

7. The cyanide-free alkaline copper deposition process according to claim 1, characterized in that, In step S2, the degreasing employs a dual-gradient mode of weak alkali pre-degreasing and solvent degreasing. The weak alkali pre-degreasing temperature is 35-40℃, and the degreasing time is 4-6 min. The solvent degreasing temperature is room temperature, and the degreasing time is 2-4 min. The surface micro-etching uses an acidic micro-etching solution containing fluoride, with the etching depth controlled at 0.5-1.0 μm. The electrolytic activation treatment uses an electrolyte solution containing sulfuric acid, with the substrate as the cathode and a platinum sheet as the anode, applying an A / dm² solution. 2 The cathode current is set at an activation temperature of 25-35℃ and a treatment time of 2-4 minutes.

8. The cyanide-free alkaline copper deposition process according to claim 1, characterized in that, In step S3, the electrolysis parameters are: pulse power supply frequency 1000-3000Hz, duty cycle 30%-60%, and cathode current density 1.0-3.0A / dm³. 2 The electrolysis temperature is 35-45℃ and the electrolysis time is 10-60min. Ultrasonic dispersion is used during the deposition process, with an ultrasonic power of 200-300W and an ultrasonic frequency of 25-40kHz.

9. The cyanide-free alkaline copper deposition process according to claim 1, characterized in that, In S3, the specific process of stirring and anode configuration during the electrolytic deposition process is as follows: a combined stirring mode of bottom aeration stirring and side mechanical stirring is adopted, wherein the aeration rate is adjusted to 0.5-0.7 m / s and the mechanical stirring speed is 120-180 r / min; the anode uses a titanium basket to load the electrolytic copper plate, and the titanium basket is covered with a polypropylene anode bag, and the area ratio of the anode to the cathode is 1.5-2.5:

1.

10. The cyanide-free alkaline copper deposition process according to claim 1, characterized in that, In S4, the specific process of the graded water washing and post-treatment is as follows: first, perform a room temperature water wash for 1-2 minutes, then a hot water wash at 45-55℃ for 1-2 minutes, and finally a deionized water wash for 2-3 minutes; the post-treatment involves soaking in a passivation solution containing benzotriazole for 10-15 minutes.

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