Non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution and preparation method therefor

Description

A non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution and its preparation method Technical Field

[0001] This invention relates to a non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution and its preparation method, belonging to the technical field of electroplating solutions and their preparation. Background Technology

[0002] Complexing agents are compounds that can form complex ions with metal ions. In electroplating solutions, except for a few electroplating solutions such as acidic solutions for iron, nickel, chromium, and copper plating which do not use or do not need to use complexing agents, most other electroplating solutions, such as alkaline solutions for silver, gold, copper, zinc, tin, and copper-tin alloy plating, require the use of complexing agents.

[0003] Commonly used complexing agents include cyanide. Due to the excellent complexing ability of cyanide ions, cyanide electroplating is the best electroplating method and is widely used in the electroplating industry. However, cyanide electroplating uses highly toxic compounds such as NaCN, KCN, and CuCN. The lethal dose for humans is only 0.005g. Cyanide not only harms the health of operators but also pollutes the environment. Moreover, the wastewater is difficult to treat, and the wastewater treatment cost is extremely high. Therefore, in order to protect the environment and reduce pollution, it is urgent to develop a complexing agent to replace cyanide for cyanide-free electroplating processes.

[0004] Currently, the main cyanide-free electroplating processes and cyanide-free complexing agents used are as follows: 1. Pyrophosphate copper plating: Potassium pyrophosphate is used as the complexing agent. Potassium pyrophosphate has good complexing properties. The stability constants of the complexes formed by copper ions and pyrophosphate are K1 = 6.7 and K2 = 9.0. Electroplating solutions using potassium pyrophosphate as the complexing agent have stable quality and a wide range of applicable processes. However, the drawback is that electroplating cannot be performed directly on steel substrates, otherwise, displacement will occur on the substrate surface, resulting in poor adhesion. Therefore, the application range of electroplating solutions using potassium pyrophosphate as the complexing agent is limited; 2. Citrate copper plating: Citric acid has strong complexing ability and can produce very stable substances with copper ions in the plating solution. The stability constant of the complexes formed by copper ions and citrate is K2 = 19.30. The process of copper plating on iron substrates does not result in displacement. However, it has several drawbacks: the quality of the electroplating solution using citric acid as a complexing agent is not stable enough, the dispersibility of the solution needs improvement, and the solution deteriorates at high temperatures. 3. HEDP copper plating: HEDP is an organophosphonate with excellent complexing ability. It can form relatively stable substances when reacting with various metals. Electroplating solutions prepared using HEDP as a complexing agent are stable in quality and have good dispersibility. However, in actual production, it has been found that the process current density range of this electroplating solution is narrow, copper powder is easily generated in the plating layer, and iron impurities in the solution reduce the deposition rate, resulting in poor adhesion between the plating layer and the substrate. Therefore, electroplating solutions prepared using HEDP as a complexing agent have not been widely used.

[0005] Publication No. CN103755738B, published on June 1, 2016, discloses a complexing agent, its preparation method, and its uses. This complexing agent is used in the production of electroplating solutions, is easy to process, and produces electroplating solutions with strong complexing ability for metals, achieving a complexing constant of up to 10 for copper ions. 26～27 This new cyanide-free complexing agent is far superior to existing cyanide-free complexing agents. The electroplating solution prepared with this complexing agent exhibits stable quality, good dispersibility, a wide range of applicable process current densities, and broad application scope. With increasingly higher requirements for electroplated product quality, in addition to meeting high complexing strength, it is also necessary to consider the deep plating capability of the complexing agent, requiring a denser coating and improved electroplating efficiency to achieve energy savings in the electroplating process. Based on the problems to be solved by the newly proposed cyanide-free electroplating, the inventors of this application have developed a new non-highly toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution and disclosed its preparation method. Summary of the Invention

[0006] One of the objectives of this invention is to overcome the shortcomings of existing technologies and provide a new non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution. This electroplating solution has strong deep plating capability, produces finer and denser crystal coatings, has high electroplating efficiency, and can achieve energy saving in the electroplating process.

[0007] The second objective of this invention is to provide a novel method for preparing non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solutions. This method is easily scalable for industrial production, and the resulting electroplating solution products exhibit stable quality.

[0008] The technical solution adopted by this invention to solve its technical problem is:

[0009] A non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution, wherein the complexing agent copper salt in the non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution has the general formula Cu. n [C 2n N 2n+1 S n O n H n+3 Its structural formula is as follows:

[0010] Where n is 1, 2, 3, ..., 50.

[0011] Preferably, the complexing agent in the non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution has the general formula R. m [C 2m N 2m+1 S m O m H m+3 Its structural formula is as follows:

[0012] Where R is K or Na, and m is 1, 2, 3, ..., 50.

[0013] The following examples illustrate the aforementioned technical solution:

[0014] A: When R is K and m is 1, the general formula of the complexing agent is K[C2N3SOH4], and its structural formula is as follows:

[0015] The structural formula of the copper salt obtained by processing this complexing agent is: Cu[C2N3SOH4], n=m, and its structural formula is as follows:

[0016] B: When R is K and n is 20, the general formula of the complexing agent is K. 20 [C 40 N 41 S 20 O 20 H 23 Its structural formula is as follows:

[0017] The structural formula of the copper salt of the complexing agent obtained by processing this complexing agent is as follows:

[0018] C: When R is Na and n is 50, the general formula of the complexing agent is Na. 50 [C 100 N 101 S 50 O 50 H 53 Its structural formula is as follows:

[0019] The structural formula of the copper salt of the complexing agent obtained by processing this complexing agent is as follows:

[0020] Preferably, R is K, and n is 1, 2, or 3, and their structural formulas are as follows:

[0021] Preferably, in the non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution, the mass fraction of the complexing agent is 15-25%, the mass fraction of the complexing agent copper salt is 2.5-3.5%, and the balance is water.

[0022] More preferably, in the non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution, the mass fraction of the complexing agent is 20%, the mass fraction of the complexing agent copper salt is 3%, and the remainder is water.

[0023] In the non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution of the present invention, at least the complexing agent copper salt is prepared by reacting the complexing agent of the present invention with a soluble copper salt. Further mixing is used to prepare the complexing agent in the electroplating solution. Conventional complexing agents can be used, as can the complexing agent of the present invention, and preferably the complexing agent of the present invention. The value of m in the complexing agent copper salt can be the same as or different from the value of n in the complexing agent. For example, mixing the complexing agent from A above with the complexing agent copper salt from A above, or mixing it with the complexing agent copper salt from B above, can all produce the non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution of the present invention.

[0024] Preferably, the complexing agent is made from ferrous sulfate, sodium thiosulfate or potassium thiosulfate (potassium thiosulfate is used when R is K, and sodium thiosulfate is used when R is Na) and urea as raw materials, and is obtained by reacting solid polymeric inorganic salts in an oxygen-containing atmosphere with rhodium and / or platinum as catalysts, dissolving in water, and then separating, concentrating the separated liquid and drying.

[0025] The reaction formula for the preparation method of the complexing agent of the present invention is as follows: (n / 4)[K4Fe(CN)6]+nNa2S2O3+nCH4N2O+20 / nO2=K n [C 2n N 2n+1 S n O n H n+3 ]+(n / 12)Fe3C+(5 n / 12)C+(n / 4)N2+nNa2SO3+(n-1)NH3,

[0026] Or; (n / 4)[K4Fe(CN)6]+nK2S2O3+nCH4N2O+20 / nO2=K n [C 2n N 2n+1 S n O n H n+3 ]+(n / 12)Fe3C+(5n / 12)C+(n / 4)N2+nK2SO3+(n-1)NH3;

[0027] This invention also discloses a specific method for preparing a complexing agent, the steps of which are as follows:

[0028] Salt, sodium thiosulfate or potassium thiosulfate and urea are placed in a rotary kiln containing a fixed catalyst of rhodium and / or platinum. The reaction is carried out at 450-650℃ for 5-7 hours in an oxygen-containing atmosphere. The polymerized inorganic salt is dissolved in water, separated, and the insoluble matter is removed to obtain a separated liquid. The separated liquid is dried to obtain the complexing agent product.

[0029] Preferably, the separation is performed using one or more of the following methods: vacuum filtration, plate and frame filtration, and centrifugal separation.

[0030] Preferably, the separated liquid is concentrated before drying, and the separated liquid is concentrated to a water content of 30-40%. The concentrated material is then dried to a water content of less than 5%. The concentration is carried out by vacuum concentration.

[0031] Preferably, the drying is carried out by spray drying, and the inlet air temperature of the spray drying is 100-200℃.

[0032] Preferably, the preparation method of the complexing agent copper salt is as follows: water is added to a reactor, then molar amounts of complexing agent and water-soluble copper salt are added, then molar amounts of sodium sulfite and sodium hydroxide are added, the mixture is stirred to carry out the reaction, and after the reaction is completed, the precipitate is filtered, washed, and dried to obtain the complexing agent copper salt.

[0033] The preparation method of the non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution of the present invention is as follows: the complexing agent copper salt, the complexing agent and water are mixed in proportion, stirred and dissolved, and then the pH value is adjusted to 11-12 to obtain the non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution.

[0034] The beneficial effects of this invention are:

[0035] The complexing agent of this invention uses widely available and inexpensive raw materials, and its preparation process, transportation, storage, and use are simple, resulting in low production costs. When applied to the production of electroplating solutions, the complexing agent is easy to process, and the resulting electroplating solution exhibits strong complexing ability towards metals; for example, the complexation constant of the complexing agent for copper ions can reach 10. 26～27 (Comparable to existing cyanide-free complexing agents), far superior to conventional complexing agents in the prior art (especially potassium pyrophosphate, citric acid, and HEDP complexing agents). Electroplating solutions prepared with the complexing agent of this invention have stable quality, good dispersibility, a wide range of applicable process current densities, and a wide range of applications (these listed properties are comparable to those of electroplating solutions prepared with existing cyanide-free complexing agents). In addition, it has strong deep plating capability, finer and denser coating crystals, high electroplating efficiency, and can achieve energy saving in the electroplating process. Detailed Implementation

[0036] The technical solution of the present invention will be further described in detail below through specific embodiments. The reagents, raw materials, and apparatus used in the following embodiments are all commercially available conventional reagents, raw materials, apparatus, and facilities.

[0037] Example 1:

[0038] A complexing agent, the structural formula of which is as follows:

[0039] The reaction formula of the polymeric inorganic salt of the complexing agent is as follows:

[0040] (1 / 4)[K4Fe(CN)6]+K2S2O3+CH4N2O+20O2=K[C2N3SOH4]+(1 / 12)Fe3C+(5 / 12)C+(1 / 4)N2+K2SO3; The preparation method steps are as follows:

[0041] Salt, sodium thiosulfate or potassium thiosulfate and urea are placed in a rotary kiln containing a fixed catalyst of rhodium and / or platinum. The reaction is carried out at 450-460°C for 7 hours in an oxygen-containing atmosphere. The polymerized inorganic salt is dissolved in water, separated, and the insoluble matter is removed to obtain a separated liquid. The separated liquid is dried to obtain the complexing agent product.

[0042] In Example 1, the separation is performed by vacuum filtration, the separated liquid is concentrated before drying, the separated liquid is concentrated to a water content of 30%, the concentrated material is dried to a water content of less than 5%, the concentration is performed by vacuum concentration, and the drying is performed by spray drying, the inlet air temperature of spray drying is 100-110℃.

[0043] Example 2

[0044] A complexing agent, the structural formula of which is as follows:

[0045] The reaction formula of the polymeric inorganic salt of the complexing agent is as follows:

[0046] (1 / 2)[K4Fe(CN)6]+2K2S2O3+2CH4N2O+10O2=K2[C4N5S2O2H5]+(1 / 6)Fe3C+(5 / 6)C+(1 / 2)N2+2K2SO3+NH3; The preparation method steps are as follows:

[0047] Salt, sodium thiosulfate or potassium thiosulfate and urea are placed in a rotary kiln containing fixed catalysts of rhodium and / or platinum. The reaction is carried out at 640-650℃ for 5 hours in an oxygen-containing atmosphere. The polymerized inorganic salt is dissolved in water, separated, and the insoluble matter is removed to obtain a separated liquid. The separated liquid is dried to obtain the complexing agent product.

[0048] In Example 1, the separation is carried out by plate and frame filter press. The separated liquid is concentrated before drying. The separated liquid is concentrated to a water content of 40%. The concentrated material is dried to a water content of less than 5%. The concentration is carried out by vacuum concentration. The drying is carried out by spray drying. The inlet air temperature of spray drying is 190-200℃.

[0049] Example 3

[0050] A complexing agent, the structural formula of which is as follows:

[0051] The polymeric inorganic salt reaction formula of the complexing agent is as follows: (3 / 4)[K4Fe(CN)6]+3K2S2O3+3CH4N2O+20 / 3O2=K3[C6N7S3O3H6]+(1 / 4)Fe3C+(5 / 4)C+(3 / 4)N2+3K2SO3+2NH3; the preparation method steps are as follows:

[0052] Salt, sodium thiosulfate or potassium thiosulfate and urea are placed in a rotary kiln containing a fixed catalyst of rhodium and / or platinum. The reaction is carried out at 590-600℃ for 6 hours in an oxygen-containing atmosphere. The polymerized inorganic salt is dissolved in water, separated, and the insoluble matter is removed to obtain a separated liquid. The separated liquid is dried to obtain the complexing agent product.

[0053] In Example 3, the separation is carried out by centrifugal separation, the separated liquid is concentrated before drying, the separated liquid is concentrated to a water content of 35%, the concentrated material is dried to a water content of less than 5%, the concentration is carried out by vacuum concentration, and the drying is carried out by spray drying, the inlet air temperature of spray drying is 160-170℃.

[0054] Example 4

[0055] A complexing agent, the structural formula and preparation method of which are the same as in Example 3, except that n = 50 is used.

[0056] Example 5

[0057] A complexing agent, the structural formula and preparation method of which are the same as in Example 1, except that Na is used instead of K.

[0058] Example 6

[0059] A complexing agent, the structural formula and preparation method of which are the same as in Example 2, except that Na is used instead of K.

[0060] Example 7

[0061] A complexing agent, the structural formula and preparation method of which are the same as in Example 3, except that Na is used instead of K.

[0062] Example 8

[0063] A complexing agent, the structural formula and preparation method of which are the same as in Example 4, except that Na is used instead of K.

[0064] The complexing agents of Examples 1-8 of this invention are used for electroplating. Taking a pre-plated copper electroplating solution as an example, the amount of complexing agent in the electroplating solution is 15-25%, preferably 20%. The examples of this invention use a 20% dosage as an example to illustrate the application of the complexing agent of this invention.

[0065] The reaction formula for preparing copper salt of complexing agent from complexing agent is as follows, taking n=2 and R=K as an example;

[0066] 2CuSO4 + K2[C4N5S2O2H5] + Na2SO3 + 2NaOH = K2SO4 + 2Na2SO4 + H2O + Cu2[C4N5S2O2H5]. The reaction is carried out at room temperature and pressure.

[0067] Example 9: The complexing agent of Example 1 used in the electroplating solution for pre-plating copper.

[0068] Water was added to the reaction vessel, and the complexing agent of Example 1 was added in molar amounts. Then, molar amounts of copper salt (copper sulfate or copper chloride) were added, followed by molar amounts of sodium sulfite and sodium hydroxide. The mixture was stirred to carry out the reaction. After the reaction was completed, the precipitate was filtered, washed, and dried to obtain the complexing agent copper salt.

[0069] Preparation of electroplating solution: 20% complexing agent, 3.0% copper salt complexing agent, and the balance is water. Mix well and adjust the pH to 11 with sodium hydroxide.

[0070] Example 10: The complexing agent of Example 2 used in the electroplating solution for pre-plating copper.

[0071] Water was added to the reaction vessel, and the complexing agent of Example 2 was added in molar amounts. Then, molar amounts of copper salt (copper sulfate or copper chloride) were added, followed by molar amounts of sodium sulfite and sodium hydroxide. The mixture was stirred to carry out the reaction. After the reaction was completed, the precipitate was filtered, washed, and dried to obtain the complexing agent copper salt.

[0072] Preparation of electroplating solution: 20% complexing agent, 3.0% copper salt complexing agent, and the balance is water. Mix well and adjust the pH to 12 with sodium hydroxide.

[0073] Example 11: The complexing agent of Example 3 is used in the electroplating solution for pre-plating copper.

[0074] Water was added to the reaction vessel, and the complexing agent of Example 3 was added in molar amounts. Then, molar amounts of copper salt (copper sulfate or copper chloride) were added, followed by molar amounts of sodium sulfite and sodium hydroxide. The mixture was stirred to carry out the reaction. After the reaction was completed, the precipitate was filtered, washed, and dried to obtain the complexing agent copper salt.

[0075] Preparation of electroplating solution: 20% complexing agent, 3.0% copper salt complexing agent, and the balance is water. Mix well and adjust the pH to 11.5 with sodium hydroxide.

[0076] Examples 12-16: Using the complexing agents of Examples 4-8 respectively in the electroplating solutions for pre-plating copper.

[0077] Water was added to the reaction vessel, and the complexing agent of Examples 4-8 was added in molar amounts. A molar amount of copper salt solution (copper sulfate solution or copper chloride solution) was added, followed by molar amounts of sodium sulfite and sodium hydroxide. The mixture was stirred to carry out the reaction. After the reaction was completed, the precipitate was filtered, washed, and dried to obtain the complexing agent copper salt.

[0078] Preparation of electroplating solution: 20% complexing agent, 3.0% copper salt complexing agent, and the balance is water. Mix well and adjust the pH to 11-12 with sodium hydroxide.

[0079] Comparative Example 17: Potassium Pyrophosphate Complex

[0080] Preparation of electroplating solution: 20% complexing agent, 3.0% copper salt complexing agent, and the balance is water. Mix well and adjust the pH to 12 with sodium hydroxide.

[0081] Comparative Example 18: Complexing agent of patent No. 2014100151872

[0082] Preparation of electroplating solution: 20% complexing agent, 3.0% copper salt complexing agent, and the balance is water. Mix well and adjust the pH to 12 with sodium hydroxide.

[0083] Performance testing:

[0084] The performance of Examples 9-16 and Comparative Examples 17-18 described above was tested according to the following method.

[0085] The following studies were conducted on the cyanide-free pre-plating copper electroplating solutions prepared in Examples 9-16 and Comparative Examples 17-18:

[0086] 1. Hull tank test (267ml)

[0087] 1.1 Preliminary Experiments: The cyanide-free pre-plated copper electroplating solutions prepared in Examples 9-16 and Comparative Examples 17-18 were plated under the conditions of 25°C, 1A (constant current), and air stirring for 5 minutes. During the plate-plating process of the electroplating solutions in Examples 9-16, it was observed that under constant current conditions, the tank voltage was relatively stable, and the plated sheets exhibited characteristics of semi-glossy spots and fine crystals over a large area. Examples 9-16 were all superior to Comparative Example 18, and Comparative Example 18 was superior to Comparative Example 17.

[0088] 1.2 Hull tank test to determine the current density range:

[0089] The cyanide-free pre-plated copper electroplating solutions prepared in Examples 9-16 and Comparative Examples 17-18 were tested at 55°C, 1A current, and 10min. The optimal current density range was determined using Hull test strips. The test strips were made of 0.5*70*100mm A3 steel sheets and polished with 600# wet sandpaper. The current density at each point on the test strip was calculated using the empirical formula Jk = I(5.1-5.24LgL). Through test strip testing and current density calculations, it was determined that the current density range of the electroplating solutions prepared in Examples 9-16 is 0.5A / dm³. 2 Up to 5A / dm 2 between.

[0090] 2. Electroplating solution and electroplating performance testing

[0091] 2.1 Determination of current efficiency: The current efficiency of the electroplating solutions prepared in Examples 9-16 was 94.6% on average, that of the electroplating solution prepared in Example 17 was 89.8%, and that of the electroplating solution prepared in Example 18 was 92.8%.

[0092] 2.2 Determination of the dispersibility of electroplating solution

[0093] The dispersion ability of the electroplating solution was measured using the bent cathode method. The conditions were: current 1A, oil-free air stirring, temperature 55℃, time 30min. The test material was a 0.5*70*100 A3 copper sheet, which was polished with 600# wet sandpaper.

[0094] The average dispersion ability of the electroplating solutions in Examples 9-16 was measured to be 94.5%, the dispersion ability of the electroplating solution in Example 17 was 90.1%, and the dispersion ability of the electroplating solution in Example 18 was 92.1%.

[0095] 2.3 Measurement of Coverage Capacity

[0096] The coverage capacity of the plating solution was measured using the internal hole method. The copper tube dimensions were 10mm*100mm. Both through-hole and blind-hole methods were employed. The plating solution temperature was 55℃, and the cathode current density was 0.5A / dm³. 2 The experiment lasted 5 minutes. After the experiment, the iron pipe was cut open to observe the coating inside.

[0097] The cyanide-free pre-plated copper electroplating solutions prepared in Examples 9-16 and Comparative Examples 17-18 were used as experimental electroplating solutions. After the experiment, it was found that all through holes and blind holes were plated with copper layers, indicating that the electroplating solutions prepared in Examples 9-16 have excellent coverage ability, which is better than Example 18 and even better than Example 17.

[0098] 2.4 Bonding strength test

[0099] 2.4.1 Bending Test: A polished iron sheet (A3) with a thickness of 0.5 mm was used. The temperature of the electroplating solution was 55℃, and the cathode current density was 2 A / dm³. 2 Time: 15 minutes.

[0100] The cyanide-free pre-plated copper electroplating solutions prepared in Examples 9-16 and Comparative Examples 17-18 were used as experimental electroplating solutions. After the experiment, the plated test pieces were repeatedly bent until they broke. There was no peeling at the crack, which proved that the plating layer and the substrate did not separate.

[0101] 2.4.2 Thermal shock test: A polished iron sheet (A3) with a thickness of 0.5 mm was used, the temperature of the electroplating solution was 55℃, and the cathode current density was 2 A / dm³. 2 Time: 15 minutes.

[0102] The cyanide-free pre-plated copper electroplating solutions prepared in Examples 9-16 and Comparative Examples 17-18 were used as experimental electroplating solutions. After the experiment, the plated test pieces were placed in an oven and baked at 200°C for 1 hour. After being taken out, they were immediately immersed in 0°C water for rapid cooling. No blistering or peeling of the plating layer was found.

[0103] 2.5 Coating Toughness Test: 1mm thick A3 steel sheets were passivated with chromic acid, cleaned, and then directly hung in the electroplating solutions of Examples 9-16 and Comparative Examples 17-18. After the coating thickness reached 20μm, the coating was peeled off, bent at 180°, and the bent area was pressed. The coating did not crack, indicating good coating toughness. Examples 9-16 were superior to Example 18, and even more superior to Example 17.

[0104] 2.6 Coating Porosity Experiment: A polished iron sheet (A3) with a thickness of 0.5 mm was used. The electroplating solution temperature was 55℃, and the cathode current density was 1 A / dm³. 2 The porosity experiment was conducted using a potassium ferricyanide solution filter paper method for 20 minutes.

[0105] Potassium ferricyanide 10 g / L; Sodium chloride 20 g / L.

[0106] Experimental results show that the porosity of the electroplating layers formed by the electroplating solutions prepared in Examples 9-16 is ≤0.5 porosities / dm³. 2 1 unit / dm, superior to Example 18 2 It is superior to the 2 / dm of Example 17. 2 .

[0107] 2.7 Determination of deposition rate: The current was set to 1A, the temperature to 55℃, and the time to 30min. The results showed that the deposition rate of the electroplating solution prepared in Examples 9-16 was 0.75μm / min, the deposition rate of the electroplating solution prepared in Example 17 was 0.55μm / min, and the deposition rate of the electroplating solution prepared in Example 18 was 0.62μm / min.

[0108] The electroplating solutions obtained in Examples 9-16 were further subjected to pilot-scale experiments. The pilot-scale process parameters are as follows:

[0109] Process flow: Steel workpiece → Ultrasonic degreasing → Water wash 1 → Water wash 2 → Anodic electrolytic degreasing → Water wash 1 → Water wash 2 → Acid pickling degreasing → Water wash 1 → Water wash 2 → Hydrochloric acid pickling → Water wash 1 → Water wash 2 → Terminal electrolytic degreasing → Water wash 1 → Water wash 2 → Acid activation → Water wash 1 → Water wash 2 → Electroplating solution of Examples 9-16 → Recovery → Water wash 1 → Water wash 2 → Acid activation → Acid copper.

[0110] Ultrasonic degreasing: degreasing powder concentration 50±5g / L, temperature 70±5℃, current density 1-5A / dm³ 2 Time: 5 minutes.

[0111] Electrolytic oil removal at cathodes: oil removal powder concentration 50±5 g / L, temperature 70±5℃, current density 1-5 A / dm³ 2 The time is 5 to 7 minutes.

[0112] Anodic electrolytic oil removal: oil removal powder concentration 50±5 g / L, temperature 70±5℃, current density 1-5 A / dm³ 2 The time is 3 to 5 minutes.

[0113] Pickling: Industrial hydrochloric acid concentration 15-20%, time 8-10 min, room temperature.

[0114] Activation: 5-10% industrial hydrochloric acid concentration, 3-5 min, room temperature.

[0115] Electroplating solutions in Examples 9-16: Baumé degree 32-36, pH 8.0, temperature 50-55°C, current density 0.5-5 A / dm³ 2 The time varies from 5 minutes to several hours. Practical experience has shown that even after plating to 100μm, the leveling and gloss are still excellent, superior to Comparative Example 18 and even better than Comparative Example 17.

[0116] The electroplating solutions prepared in Examples 9-16 were verified to be reliable and stable after 20 months of continuous operation on a 50L pilot-scale electroplating production line and 11 months of continuous operation on a 350L pilot-scale electroplating production line. The consumption of the electroplating solutions was 10-50 ml / kWh. Based on the above pilot-scale experiments, the process conditions for industrial production of the electroplating solutions prepared in Examples 9-16 were obtained.

[0117] 1. Steel workpieces:

[0118] Process flow: Steel workpiece → Ultrasonic degreasing → Water wash 1 → Water wash 2 → Anodic electrolytic degreasing → Water wash 1 → Water wash 2 → Acid pickling degreasing → Water wash 1 → Water wash 2 → Hydrochloric acid pickling → Water wash 1 → Water wash 2 → Terminal electrolytic degreasing → Water wash 1 → Water wash 2 → Acid activation → Water wash 1 → Water wash 2 → Pre-immersion → Electroplating solution of Examples 9-16 → Recovery → Water wash 1 → Water wash 2 → Acid activation → Acid copper.

[0119] Process conditions:

[0120] Electroplating solution density: 32-36 Baume

[0121] Temperature 45~60℃

[0122] pH value: 8.00~8.50

[0123] Stirring: Air stirring plus cathode movement

[0124] Anode: Electrolytic copper or oxygen-free electrolytic copper

[0125] Yin-Yang area ratio: 1:1.5~2.

[0126] Current: 0.5~2.5A / dm 2

[0127] 2. Zinc alloy workpieces:

[0128] Process flow: Zinc alloy workpiece → hot dip dewaxing → ultrasonic dewaxing → water wash 1 → water wash 2 → ultrasonic degreasing → water wash 1 → water wash 2 → anodic electrolytic degreasing → water wash 1 → water wash 2 → acid salt activation → water wash 1 → water wash 2 → ultrasonic pre-immersion solution for 30s → electroplating solution of Examples 9-16 (charged into the tank at 25-35℃) → recovery → water wash 1 → water wash 2 → acid activation → acid copper.

[0129] Process conditions:

[0130] Electroplating solution density: 32-38 Baume

[0131] Temperature 25~35℃

[0132] pH value: 8.00~8.50

[0133] Stirring: Air stirring plus cathode movement

[0134] Anode: Electrolytic copper or oxygen-free electrolytic copper

[0135] Yin-Yang area ratio: 1:1.5~2.

[0136] Current: 0.5~1.5A / dm2.

[0137] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. A non-highly toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution, characterized in that: The general formula for the complexing agent copper salt in the non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution is Cu. n [C 2n N 2n+1 S n O n H n+3 Its structural formula is as follows: Where n is 1, 2, 3, ..., 50.

2. The non-highly toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution according to claim 1, characterized in that: The general formula for the complexing agent in the non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution is R. m [C 2m N 2m+1 S m O m H m+3 Its structural formula is as follows: Where R is K or Na, and m is 1, 2, 3, ..., 50.

3. The non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution according to claim 1 or 2, characterized in that: In the non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution, the mass fraction of the complexing agent is 15-25%, the mass fraction of the complexing agent copper salt is 2.5-3.5%, and the balance is water.

4. The non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution according to claim 3, characterized in that: In the non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution, the mass fraction of the complexing agent is 20%, the mass fraction of the complexing agent copper salt is 3.0%, and the balance is water.

5. The non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution according to claim 1 or 2, characterized in that: The preparation method of the complexing agent copper salt is as follows: water is added to the reactor, then molar amounts of complexing agent and water-soluble copper salt are added, then molar amounts of sodium sulfite and sodium hydroxide are added, the mixture is stirred to carry out the reaction, and after the reaction is completed, the precipitate is filtered, washed and dried to obtain the complexing agent copper salt.

6. The non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution according to claim 2, characterized in that, The preparation method of the complexing agent is as follows: using ferrous sulfate, sodium thiosulfate or potassium thiosulfate and urea as raw materials, in an oxygen-containing atmosphere, with rhodium and / or platinum as catalysts, the solid polymeric inorganic salts are reacted and dissolved in water, and then the complexing agent is obtained by separation, concentration of the separation liquid and drying.

7. The non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution according to claim 6, characterized in that: The preparation method of the complexing agent is as follows: Salt, sodium thiosulfate or potassium thiosulfate and urea are placed in a rotary kiln containing a fixed catalyst of rhodium and / or platinum. The reaction is carried out at 450-650℃ for 5-7 hours in an oxygen-containing atmosphere. The polymerized inorganic salt is dissolved in water, separated, and the insoluble matter is removed to obtain a separated liquid. The separated liquid is dried to obtain the complexing agent product.

8. The non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution according to claim 6 or 7, characterized in that: The separation is achieved by one or more of the following methods: vacuum filtration, plate and frame filtration, and centrifugal separation.

9. The method for preparing the non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution according to claim 6 or 7, characterized in that: The separated liquid is concentrated before drying, and the water content is concentrated to 30-40%. The concentrated material is then dried to a water content of less than 5%. The concentration is carried out by vacuum concentration, and the drying is carried out by spray drying. The inlet air temperature of the spray drying is 100-200℃.

10. The method for preparing the non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution according to any one of claims 1-9, characterized in that: The complexing agent, copper salt, complexing agent, and water are mixed in the specified proportions, stirred and dissolved, and then the pH value is adjusted to 11-12 to obtain a non-toxic sodium cyanide or potassium cyanide alkaline copper electroplating solution.

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