Non-toxic sodium cyanide or potassium cyanide complexing agent, preparation method therefor, and use thereof

Description

Non-poisonous sodium cyanide or potassium cyanide complexing agent, its preparation method and application TECHNICAL FIELD

[0001] The present application relates to a compound, its preparation method and application, in particular to a non-poisonous sodium cyanide or potassium cyanide complexing agent, its preparation method and application. BACKGROUND

[0002] The complexing agent is a compound capable of forming complex ions with metal ions. In electroplating solutions, except for a few electroplating solutions such as acid solution plating iron, plating nickel, plating chromium, and plating copper, which do not use or do not need to use complexing agents, most electroplating solutions such as alkaline solution plating silver, plating gold, plating copper, plating zinc, plating tin, and plating copper-tin alloy all need to use complexing agents.

[0003] The commonly used complexing agent such as cyanide has excellent complexing ability due to the cyanide ion. Cyanide electroplating is the best electroplating method and is widely used in the electroplating industry. However, NaCN, KCN, CuCN and other compounds used in cyanide electroplating are highly toxic, and the lethal dose for humans is only 0.005g. Cyanide not only harms the health of operators, but also pollutes the environment. In addition, the treatment of wastewater is difficult, and the cost of wastewater treatment is extremely high. Therefore, in order to protect the environment and reduce public hazards, it is urgent to develop a complexing agent to replace cyanide for cyanide-free electroplating process.

[0004] At present, the cyanide-free electroplating process and the cyanide-free complexing agent used mainly have the following types: 1. Pyrophosphate copper plating: potassium pyrophosphate is used as a complexing agent. Potassium pyrophosphate has good complexing performance. The complex of copper ions and pyrophosphate has a stable constant K1=6.7 and K2=9.0. The electroplating solution using potassium pyrophosphate as a complexing agent has stable quality and a wide range of applicable processes. However, the application range of the electroplating solution using potassium pyrophosphate as a complexing agent is limited because the electroplating cannot be directly performed on a steel substrate, otherwise the surface of the substrate will be replaced to cause poor adhesion. 2. Citrate copper plating: citric acid has strong complexing ability and can produce very stable substances with copper ions in the plating solution. The complex of copper ions and citric acid has a stable constant K2=19.30. The copper plated on the iron substrate does not have replacement phenomenon. However, the electroplating solution using citric acid as a complexing agent has unstable quality, and the dispersibility of the electroplating solution needs to be improved. The electroplating solution will deteriorate at high temperature. 3. HEDP copper plating: HEDP is an organic phosphonate with good complexing ability. When it reacts with various metals, it can form relatively stable substances. The electroplating solution prepared by using HEDP as a complexing agent has stable quality and good dispersibility. However, the electroplating solution has a narrow current density range in actual production, the plated layer is prone to copper powder, and the iron impurities in the plating solution reduce the deposition rate and make the adhesion between the plated layer and the substrate poor. Therefore, the electroplating solution prepared by using HEDP as a complexing agent has not been widely applied.

[0005] CN103755738B, published on June 01, 2016 discloses a kind of complexing agent and preparation method and use of complexing agent, and the complexing agent is applied to the production of electroplating solution, convenient processing, the complexing ability of the electroplating solution prepared is strong to metal, the complexing constant of copper ion can reach 10 26～27 , far superior to the non-cyanide complexing agent in the prior art, the quality of the electroplating solution prepared from the complexing agent is stable, the dispersibility is good, the process current density range that can be used is wider, and the application range of the electroplating solution is wide. With higher requirements for the quality of electroplated products, after meeting the higher complexing force, the throwing power of the complexing agent also needs to be considered, the plating layer needs to be more compact, and the electroplating efficiency needs to be improved to achieve energy saving of electroplating process. Based on the problems to be solved in the newly proposed non-cyanide electroplating, the inventors of the present application have developed a new complexing agent and disclosed its preparation method and application. SUMMARY

[0006] One of the purposes of the present application is to solve the defects of the complexing agent for non-cyanide electroplating in the prior art and provide a new complexing agent. The complexing agent has strong complexing ability and strong throwing power when used for non-cyanide electroplating, the plating layer is more delicate and compact, the electroplating efficiency is high, and energy saving of electroplating process can be achieved.

[0007] The second purpose of the present application is to provide a new preparation method of complexing agent. The method is easy to realize industrial production, and the quality of the produced complexing agent product is stable.

[0008] The third purpose of the present application is to provide a new application of complexing agent, which is used for non-cyanide electroplating and can well replace the commonly used cyanide electroplating in the prior art and also well meet the higher requirements of non-cyanide electroplating target.

[0009] The technical solution adopted by the present application to solve the technical problems is:

[0010] A non-toxic sodium cyanide or potassium cyanide complexing agent, the general formula of the complexing agent is R n [C 2n N 2n+1 S n O n H n+3 ], and the structural formula is as follows:

[0011] Wherein, R is K or Na, n is 1, 2, 3, …, 50.

[0012] The foregoing technical solution is explained below with several examples:

[0013] A: when R is K and n is 1, the general formula of the complexing agent is K[C2N3SOH4], and the structural formula is as follows:

[0014] B: when R is K, n is 20, the complexing agent has the general formula of K 20 [C 40 N 41 S 20 O 20 H 23 ], and its structural formula is as follows:

[0015] C: when R is Na, n is 50, the complexing agent has the general formula of Na 50 [C 100 N 101 S 50 O 50 H 53 ], and its structural formula is as follows:

[0016] Preferably, R is K, n is 1, 2, 3, and its structural formula is as follows, respectively:

[0017] Preferably, the complexing agent is prepared from yellow vitriol, sodium thiosulfate or potassium thiosulfate (when R is K, potassium thiosulfate is used, and when R is Na, sodium thiosulfate is used) and urea as raw materials, in an oxygen-containing atmosphere, with rhodium and / or platinum as catalyst, through solid-state polymineral salt reaction, dissolution in water, separation, concentration and drying of the separated liquid.

[0018] The reaction formula of the preparation method of the complexing agent of the present application 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+(5n / 12)C+(n / 4)N2+nNa2SO3+(n-1)NH3,

[0019] 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;

[0020] The present application also discloses a preparation method of a non-poisonous sodium cyanide or potassium cyanide complexing agent, and the steps of the preparation method are as follows:

[0021] The yellow prussiate, sodium or potassium thiosulfate and urea are placed in a rotary reaction kiln, which is fixed with catalyst rhodium and / or platinum, and reacted in an oxygen-containing atmosphere at 450-650℃ for 5-7 hours; the polymerized polymineral salt is dissolved in water, separated, and the insoluble matter is removed to obtain a separation liquid, which is dried to obtain the finished complexing agent.

[0022] Preferably, the separation is performed by any one or several of suction filtration, plate-frame pressure filtration and centrifugal separation.

[0023] Preferably, the separation liquid is concentrated before drying, and the separation liquid is concentrated to a water content of 30-40%, and the concentrated material is dried to a water content of less than 5%, and the concentration is performed by vacuum concentration.

[0024] Preferably, the drying is performed by spray drying, and the inlet air temperature of the spray drying is 100-200℃.

[0025] In addition, based on the complexing agent of the present application, the present application also discloses an application of the complexing agent in preparing a cyanide-free electroplating solution.

[0026] Specifically, the electroplating solution is any one of copper plating, tin plating, silver plating, copper-zinc alloy plating, copper-tin alloy plating, copper-tin-zinc alloy plating, nickel-tin alloy plating, nickel-cobalt alloy plating, tin-cobalt alloy plating and nickel-tin-cobalt alloy plating, and the amount of the complexing agent in the electroplating solution is 15-25% by mass.

[0027] The present application has the following advantages:

[0028] The raw materials for preparing the complexing agent of the present application are widely available and low in price, and the preparation process, transportation, storage and use are simple, and the production cost is low; the complexing agent of the present application is applied to the production of an electroplating solution, which is convenient to process, and the prepared electroplating solution has strong complexing ability to metals, for example, the complexing constant of the complexing agent of the present application to copper ions can reach 10 26-27 (which is equivalent to the cyanide-free complexing agent of the prior art), which is much better than the conventional complexing agents (especially potassium pyrophosphate, citric acid and HEDP) in the prior art, the electroplating solution prepared from the complexing agent of the present application is stable in quality, has good dispersibility, a wide range of process current density can be used, and has a wide application range (the listed performances are equivalent to the electroplating solution prepared from the cyanide-free complexing agent of the prior art), in addition, the deep plating capacity is strong, the plated layer is more delicate and denser, the electroplating efficiency is high, and energy saving of the electroplating process can be achieved. DETAILED DESCRIPTION

[0029] The technical solutions of the present application are further described in detail below through specific examples. The reagents, raw materials and devices and facilities used in the following examples are all commercially available conventional reagents, raw materials, devices and facilities.

[0030] Example 1

[0031] A non-toxic sodium cyanide or potassium cyanide complexing agent, the structural formula of which is as follows:

[0032] The polymineral salt reaction formula of the complexing agent is as follows:

[0033] (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:

[0034] The yellow prussiate, sodium or potassium thiosulfate and urea are placed in a rotary reaction kiln, which is fixed with a catalyst rhodium and / or platinum, in an oxygen-containing atmosphere, at 450-460℃, and reacted for 7 hours; the polymeric polymineral salt is dissolved in water, separated, and the insoluble substances are removed to obtain a separation liquid, which is dried to obtain the complexing agent finished product.

[0035] In Example 1, the separation uses suction filtration, and the separation liquid is concentrated before drying, and the separation liquid is concentrated to a water content of 30%, and the concentrated material is dried to a water content of less than 5%, the concentration uses vacuum concentration, and the drying uses spray drying, and the inlet air temperature of the spray drying is 100-110℃.

[0036] Example 2

[0037] A non-toxic sodium cyanide or potassium cyanide complexing agent, the structural formula of which is as follows:

[0038] The polymineral salt reaction formula of the complexing agent is as follows:

[0039] (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:

[0040] The yellow prussiate, sodium or potassium thiosulfate and urea are put into a rotary reaction kiln, which is fixed with catalyst rhodium and / or platinum, and reacted for 5 hours at 640-650℃ in an oxygen-containing atmosphere; the polymerized polymineral salt is dissolved in water, separated, and the insoluble matter is removed to obtain a separated liquid, which is dried to obtain the complexing agent product.

[0041] In Example 1, the separation uses plate-frame pressure filtration, and the separated liquid is concentrated before drying, and the separated liquid is concentrated to a water content of 40%, and the concentrated material is dried to a water content of less than 5%, the concentration uses vacuum concentration, and the drying uses spray drying, and the inlet air temperature of the spray drying is 190-200℃.

[0042] Example 3

[0043] A non-toxic sodium or potassium cyanide complexing agent, and the structural formula of the complexing agent is as follows:

[0044] The reaction formula of the polymineral salt 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, and the preparation method steps are as follows:

[0045] The yellow prussiate, sodium or potassium thiosulfate and urea are put into a rotary reaction kiln, which is fixed with catalyst rhodium and / or platinum, and reacted for 6 hours at 590-600℃ in an oxygen-containing atmosphere; the polymerized polymineral salt is dissolved in water, separated, and the insoluble matter is removed to obtain a separated liquid, which is dried to obtain the complexing agent product.

[0046] In Example 3, the separation uses centrifugal separation, and the separated liquid is concentrated before drying, and the separated liquid is concentrated to a water content of 35%, and the concentrated material is dried to a water content of less than 5%, the concentration uses vacuum concentration, and the drying uses spray drying, and the inlet air temperature of the spray drying is 160-170℃.

[0047] Example 4

[0048] A non-toxic sodium or potassium cyanide complexing agent, and the structural formula and preparation method of the complexing agent are the same as those in Example 3, except that n = 50.

[0049] Example 5

[0050] A non-toxic sodium or potassium cyanide complexing agent, and the structural formula and preparation method of the complexing agent are the same as those in Example 1, except that Na is used instead of K.

[0051] Example 6

[0052] A non-toxic sodium cyanide or potassium cyanide complexing agent, the structural formula of the complexing agent is the same as that of Example 2, except that Na is used instead of K.

[0053] Example 7

[0054] A non-toxic sodium cyanide or potassium cyanide complexing agent, the structural formula of the complexing agent is the same as that of Example 3, except that Na is used instead of K.

[0055] Example 8

[0056] A non-toxic sodium cyanide or potassium cyanide complexing agent, the structural formula of the complexing agent is the same as that of Example 4, except that Na is used instead of K.

[0057] The complexing agent of Examples 1-8 of the present application is used for electroplating, and the electroplating solution for pre-plating copper is taken as an example, the amount of the complexing agent in the electroplating solution is 15-25%, preferably 20%. The application of the complexing agent of the present application is illustrated by taking the amount of 20% as an example.

[0058] The reaction formula for preparing the complexing agent copper salt from the complexing agent is as follows, taking n=2 and R=K as an example;

[0059] 2CuSO4+K2[C4N5S2O2H5]+Na2SO3+2NaOH=K2SO4+2Na2SO4+H2O+Cu2[C4N5S2O2H5]. The reaction condition is normal temperature and pressure.

[0060] Example 9: The complexing agent of Example 1 is used in the electroplating solution for pre-plating copper

[0061] Water is added to a reaction kettle, the complexing agent of Example 1 is added according to the molar ratio, a molar amount of copper salt (copper sulfate or copper chloride) is added, and a molar amount of sodium sulfite and sodium hydroxide is added, stirring is performed to react, after the reaction is completed, the precipitate is filtered to obtain the complexing agent copper salt after rinsing and drying.

[0062] The electroplating solution is configured: the complexing agent is 20%, the complexing agent copper salt is 3.0%, and the balance is water, which is mixed uniformly, and the pH is adjusted to 11 by sodium hydroxide.

[0063] Example 10: The complexing agent of Example 2 is used in the electroplating solution for pre-plating copper

[0064] Water is added to a reaction kettle, the complexing agent of Example 2 is added according to the molar ratio, a molar amount of copper salt (copper sulfate or copper chloride) is added, and a molar amount of sodium sulfite and sodium hydroxide is added, stirring is performed to react, after the reaction is completed, the precipitate is filtered to obtain the complexing agent copper salt after rinsing and drying.

[0065] Preparation of plating solution: 20% of complexing agent, 3.0% of complexing agent copper salt, the rest is water, mix well, adjust pH to 12 with sodium hydroxide.

[0066] Example 11: Complexing agent of Example 3 for pre-plating copper plating solution

[0067] Into the reactor, add water, add complexing agent of Example 3 according to molar ratio, add copper salt (copper sulfate or copper chloride) according to molar ratio, then add sodium sulfite and sodium hydroxide according to molar ratio, stir and react, after the reaction is completed, filter the precipitate, rinse, dry, and obtain the complexing agent copper salt.

[0068] Preparation of plating solution: 20% of complexing agent, 3.0% of complexing agent copper salt, the rest is water, mix well, adjust pH to 11.5 with sodium hydroxide.

[0069] Example 12-16: Complexing agent of Example 4-8 for pre-plating copper plating solution

[0070] Into the reactor, add water, add complexing agent of Example 4-8 according to molar ratio, add copper salt (copper sulfate or copper chloride) according to molar ratio, then add sodium sulfite and sodium hydroxide according to molar ratio, stir and react, after the reaction is completed, filter the precipitate, rinse, dry, and obtain the complexing agent copper salt.

[0071] Preparation of plating solution: 20% of complexing agent, 3.0% of complexing agent copper salt, the rest is water, mix well, adjust pH to 11-12 with sodium hydroxide.

[0072] Comparative Example 17: Potassium pyrophosphate complexing agent

[0073] Preparation of plating solution: 20% of complexing agent, 3.0% of complexing agent copper salt, the rest is water, mix well, adjust pH to 12 with sodium hydroxide.

[0074] Comparative Example 18: Complexing agent of Patent No. 2014100151872

[0075] Preparation of plating solution: 20% of complexing agent, 3.0% of complexing agent copper salt, the rest is water, mix well, adjust pH to 12 with sodium hydroxide.

[0076] Performance test:

[0077] The above Examples 9-16, Comparative Examples 17-18 were tested for performance according to the following method.

[0078] The cyanide-free pre-plating copper plating solution prepared from Examples 9-16 and Comparative Examples 17-18 was subjected to the following studies:

[0079] 1. Hull cell test (267 ml)

[0080] 1.1 Preliminary test: The cyanide-free pre-plating copper plating solution prepared in Examples 9-16 and Comparative Examples 17-18 was sheeted under the conditions of temperature 25°C, circuit 1A (constant current), air agitation, time 5 min. It was observed during sheeting of the plating solution of Examples 9-16 that the tank voltage was also relatively stable under constant current conditions and the plated sheet exhibited the characteristics of half-spot, fine crystals on a large area. Examples 9-16 were all superior to Comparative Example 18, and Comparative Example 18 was superior to Comparative Example 17.

[0081] 1.2 Hull tank test to determine the current density range:

[0082] The cyanide-free pre-plating copper plating solution prepared in Examples 9-16 and Comparative Examples 17-18 was sheeted by Hull under the conditions of temperature 55°C, current 1A, time 10 min, and the best current density range was determined. The sheet material used for sheeting was A3 steel sheet of 0.5*70*100, polished with 600# water sandpaper. The current density at each point of the test sheet was calculated according to the empirical formula Jk = I (5.1-5.24LgL). It was found from sheeting and current density calculation that the current density range of the plating solution prepared in Examples 9-16 was 0.5 A / dm 2 to 5 A / dm 2 .

[0083] 2 Test of plating solution and plating performance

[0084] 2.1 Measurement of current efficiency: The current efficiency of the plating solution prepared in Examples 9-16 was measured by copper coulomb meter and was 94.6% on average. The current efficiency of the plating solution prepared in Example 17 was 89.8%, and the current efficiency of the plating solution prepared in Example 18 was 92.8%.

[0085] 2.2 Measurement of throwing power of plating solution

[0086] The throwing power of the plating solution was measured by the bending cathode method under the conditions of current 1A, no oil air agitation, temperature 55°C, time 30 min, and the test material was A3 copper sheet of 0.5*70*100, polished with 600# water sandpaper.

[0087] The average throwing power of the plating solution of Examples 9-16 was measured to be 94.5%, the throwing power of the plating solution of Example 17 was 90.1%, and the throwing power of the plating solution of Example 18 was 92.1%.

[0088] 2.3 Measurement of covering power

[0089] The covering power of the plating solution was measured by the inner hole method, the size of the copper pipe was 10 mm*100 mm, the through hole and blind hole method was used, the temperature of the plating solution was 55°C, and the cathode current density was 0.5 A / dm 2, time 5 min. After the experiment, the iron pipe was dissected to observe the plated layer inside the pipe.

[0090] The cyanide-free pre-plating copper plating solution prepared in Examples 9-16 and Comparative Examples 17-18 was used as the experimental plating solution. After the experiment, it was found that the through holes and blind holes were all plated with copper layer, indicating that the plating solution prepared in Examples 9-16 has excellent covering capacity, which is superior to Example 18, and more superior to Example 17.

[0091] 2.4 Bonding force test

[0092] 2.4.1 Bending experiment: polished iron sheet (A3) with a thickness of 0.5 mm was used, the temperature of the plating solution was 55°C, the cathode current density was 2 A / dm 2 , time 15 min.

[0093] The cyanide-free pre-plating copper plating solution prepared in Examples 9-16 and Comparative Examples 17-18 was used as the experimental plating solution. After the experiment, the plated test piece was repeatedly bent until it broke, and there was no peeling phenomenon at the crack, proving that the plated layer and the substrate were not separated.

[0094] 2.4.2 Thermal shock experiment: polished iron sheet (A3) with a thickness of 0.5 mm was used, the temperature of the plating solution was 55°C, the cathode current density was 2 A / dm 2 , time 15 min.

[0095] The cyanide-free pre-plating copper plating solution prepared in Examples 9-16 and Comparative Examples 17-18 was used as the experimental plating solution. After the experiment, the plated test piece was placed in an oven and baked to 200°C for 1 h, and then immediately immersed in 0°C water for quenching. No blistering and peeling phenomenon of the plated layer was found.

[0096] 2.5 Plated layer toughness experiment: A3 steel sheet with a thickness of 1 mm was passivated with chromium acid, and after cleaning, it was directly hung in the plating solution of Examples 9-16 and Comparative Examples 17-18. After the thickness of the plated layer reached 20 μm, the plated layer was peeled off, bent at 180°C, and squeezed at the bending part. The plated layer did not break, indicating that the plated layer has good toughness. Among them, Examples 9-16 are superior to Example 18, and more superior to Example 17.

[0097] 2.6 Plated layer porosity experiment: polished iron sheet (A3) with a thickness of 0.5 mm was used, the temperature of the plating solution was 55°C, the cathode current density was 1 A / dm 2 , time 20 min, and the porosity experiment was performed using the filter paper test method with potassium ferricyanide solution.

[0098] Potassium ferricyanide 10 g / L; sodium chloride 20 g / L.

[0099] The experimental results show that the porosity of the plated layer formed by the plating solution prepared in Examples 9-16 as the experimental object is ≤0.5 pieces / dm2 , better than 1 A / dm of Example 18 2 , better than 2 A / dm of Example 17 2 .

[0100] 2.7 Determination of deposition rate: Current 1 A, temperature 55°C, time 30 min. The results show that the deposition rate of the plating solution prepared in Examples 9-16 is 0.75 μm / min, the deposition rate of the plating solution prepared in Example 17 is 0.55 μm / min, and the deposition rate of the plating solution prepared in Example 18 is 0.62 μm / min.

[0101] The plating solutions prepared in Examples 9-16 were further subjected to pilot experiments, and the pilot process parameters are as follows:

[0102] Process flow: steel workpiece → ultrasonic oil removal → water washing 1 → water washing 2 → anode electrolytic oil removal → water washing 1 → water washing 2 → acid pickling oil removal → water washing 1 → water washing 2 → hydrochloric acid washing → water washing 1 → water washing 2 → terminal electrolytic oil removal → water washing 1 → water washing 2 → acid activation → water washing 1 → water washing 2 → the plating solution of Examples 9-16 → recovery → water washing 1 → water washing 2 → acid activation → acid copper.

[0103] Ultrasonic oil removal: oil removal powder concentration 50±5 g / L, temperature 70±5°C, current density 1-5 A / dm 2 , time 5 min.

[0104] Cathode electrolytic oil removal: electrolytic oil removal powder concentration 50±5 g / L, temperature 70±5°C, current density 1-5 A / dm 2 , time 5-7 min.

[0105] Anode electrolytic oil removal: electrolytic oil removal powder concentration 50±5 g / L, temperature 70±5°C, current density 1-5 A / dm 2 , time 3-5 min.

[0106] Acid pickling: industrial hydrochloric acid concentration 15-20%, time 8-10 min, room temperature.

[0107] Activation: industrial hydrochloric acid concentration 5-10%, time 3-5 min, room temperature.

[0108] The plating solution of Examples 9-16: Baume degree 32-36, pH value 8.0, temperature 50-55°C, current density 0.5-5 A / dm 2 , time 5 min to several hours, and it has been proved that the leveling and brightness are still very good when plated to 100 μm. It is better than Comparative Example 18, and better than Comparative Example 17.

[0109] The plating solution prepared in Examples 9-16 was verified to have reliability and stable performance by continuously running a 50 L pilot plating production line for 20 months and a 350 L pilot plating production line for 11 months. The consumption of the plating solution was 10-50 ml / KAH. Based on the above pilot experiments, the process conditions for industrial production of the plating solution prepared in Examples 9-16 were obtained.

[0110] 1. Steel workpiece:

[0111] Process flow: Steel workpiece → ultrasonic oil removal → water washing 1 → water washing 2 → anode electrolytic oil removal → water washing 1 → water washing 2 → acid pickling oil removal → water washing 1 → water washing 2 → hydrochloric acid washing → water washing 1 → water washing 2 → terminal electrolytic oil removal → water washing 1 → water washing 2 → acid activation → water washing 1 → water washing 2 → pre- immersion → the plating solution of Examples 9-16 → recovery → water washing 1 → water washing 2 → acid activation → acid copper.

[0112] Process conditions:

[0113] Density of plating solution: 32-36 Baume

[0114] Temperature: 45-60°C

[0115] pH value: 11.00-12.0

[0116] Agitation: air agitation plus cathode movement

[0117] Anode: electrolytic copper or oxygen-free electrolytic copper

[0118] Anode / cathode area ratio: 1:1.5-2.

[0119] Current: 0.5-5 A / dm 2

[0120] 2. Zinc alloy workpiece:

[0121] Process flow: Zinc alloy workpiece → hot dipping wax removal → ultrasonic wax removal → water washing 1 → water washing 2 → ultrasonic oil removal → water washing 1 → water washing 2 → anode electrolytic oil removal → water washing 1 → water washing 2 → acid salt activation → water washing 1 → water washing 2 → ultrasonic pre- immersion liquid pre- immersion for 30 s → the plating solution of Examples 9-16 (charged into the tank at 25-35°C) → recovery → water washing 1 → water washing 2 → acid activation → acid copper.

[0122] Process conditions:

[0123] Density of plating solution: 32-38 Baume

[0124] Temperature: 25-35°C

[0125] pH value: 11.00-12.0

[0126] Agitation: air agitation plus cathode movement

[0127] Anode: Electrolytic copper or oxygen free electrolytic copper

[0128] Anode to cathode area ratio: 1:1.5-2.

[0129] Current: 0.5-1.5 A / dm 2 .

[0130] The above described embodiments are only a preferred solution of the present application, and do not limit the present application in any form, and other variants and modifications are possible without departing from the technical solution recited in the claims.

Claims

1. A non-poisonous sodium cyanide or potassium cyanide complexing agent, characterized in that: wherein R is K or Na, n is 1, 2, 3, …, 50. The complexing agent has a general formula of R n [C 2n N 2n+1 S n O n H n+3 ] and a structural formula as follows: The n is 1, 2, 3, and the R is K.

2. The complexing agent according to claim 1, characterized in that: The complexing agent is prepared from ferric ferrocyanide, sodium or potassium thiosulfate and urea as raw materials, in an oxygen-containing atmosphere, with rhodium and / or platinum as catalyst, through solid-state polymeric inorganic salt reaction, dissolution in water, separation, separation liquid concentration and drying.

3. The complexing agent of claim 1, wherein: The preparation method steps are as follows:

4. The method of preparing the complexing agent of claim 3, characterized in that: The ferric ferrocyanide, sodium or potassium thiosulfate and urea are placed in a rotary kiln, which is fixed with rhodium and / or platinum catalyst, in an oxygen-containing atmosphere, at 450-650℃, for 5-7 hours; the polymeric inorganic salt is dissolved in water, separated by removing insoluble substances, to obtain a separation liquid, which is dried to obtain the complexing agent product. The separation uses any one or several of suction filtration, plate and frame pressure filtration and centrifugal separation.

5. The method for preparing the complexing agent according to claim 4, characterized in that: The separation liquid is concentrated before drying, to a water content of 30-40%, and the concentrated material is dried to a water content of less than 5%, the concentration using vacuum concentration.

6. The method of claim 4, wherein the complexing agent is prepared by the process comprising: The drying uses spray drying, with an air inlet temperature of 100-200℃.

7. The method for preparing the complexing agent according to claim 6, characterized in that:

8. Use of the complexing agent of any one of claims 1-7 in the preparation of a cyanide-free electroplating solution. The electroplating solution is any one of copper plating, tin plating, silver plating, copper-zinc alloy plating, copper-tin alloy plating, copper-tin-zinc alloy plating, nickel-tin alloy plating, nickel-cobalt alloy plating, tin-cobalt alloy plating and nickel-tin-cobalt alloy plating.

9. Use according to claim 8, characterized in that: The amount of complexing agent in the electroplating solution is 15-25% by mass.

10. Use according to claim 9, characterized in that: ​

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