Environmentally friendly acidic tin-plating electrolyte and environmentally friendly tin-plating process using the same

Abstract

The present application relates to the field of metal surface treatment technology, in particular to an environmentally friendly acidic tin-plating electrolyte and an environmentally friendly tin-plating process implemented using the same. An environmentally friendly acidic tin-plating electrolyte includes the following components: 35-40g / L of stannous methanesulfonate, 45-80g / L of methanesulfonic acid, 15-40g / L of citric acid, 80-120g / L of thiourea, 50-80g / L of sodium hypophosphite, 5-20g / L of ammonium hypophosphite, 15-25g / L of compound brightener, 5-15g / L of compound surfactant, 10-20g / L of compound antioxidant, and 5-20g / L of pH regulator. The electrolytic tin coating obtained by the environmentally friendly acidic tin-plating electrolyte in this application is compact and smooth, while reducing the increase in overall production costs, solving the problem of rare earth salt pollution treatment in waste liquid.

Description

Technical Field

[0001] The present application relates to the technical field of metal surface treatment, and in particular to an environmentally friendly acidic tin-plating electrolyte and an environmentally friendly tin-plating process implemented using the same. Background Art

[0002] Tin has the advantages of good corrosion resistance, solderability, softness, ductility, non-toxicity, etc. It has been widely used in the field of metal surface treatment, giving it good corrosion resistance and solderability without affecting its original processing performance. The industrial production method of electroplating tin includes acid tin plating method and alkaline tin plating method. The existing acid tin plating method can be divided into the Rasstein method of stannous fluoroborate system, the Harogen method of halogen shaving system, and the Froststein method of stannous sulfate system.

[0003] In the Frostenberg method of the stannous sulfate system, the electroplating solution is mainly composed of stannous sulfate, phenolsulfonic acid, organic additives, etc. The tin plating solution has good dispersibility and covering ability, high cathode current efficiency, relatively stable plating solution, long working cycle, smooth and delicate coating, but it produces process waste and has poor environmental protection.

[0004] The electroplating solution in the Harogen process of the halogen shaving system is mainly composed of stannous chloride, sodium fluoride, potassium bifluoride, sodium chloride and additives. Its advantages are: it can be plated on one side, can work in a fairly wide range of plating solutions and the electroplating speed is relatively fast, the electroplating solution has high conductivity, and the current density allows a relatively large range of use. However, there are also corresponding defects: since the electroplating solution is highly corrosive to the electroplating equipment, the tin consumption is relatively high.

[0005] The electroplating solution in the Rasstein method of the stannous fluoroborate system is mainly composed of boric acid, sodium hydrogen difluoride, sulfuric acid, stannous oxide, additives, etc. It has the advantages of high conductivity, wide current density range, good wetting ability, etc., but it also has the following defects: fluoroborates are expensive, have certain corrosiveness and toxicity, and the residual waste liquid is highly polluting.

[0006] The alkaline tin plating method is a stannate tin plating system plating solution, which has better dispersibility than the acid tin plating method. The solution is strongly alkaline and does not corrode the steel body. It is particularly suitable for plating parts with complex shapes. However, it has the following defects relative to the acid tin plating method: the current density is relatively low, which makes the electroplating speed slow, and its current efficiency is 60-80%, which is much lower than the current efficiency of the acid tin plating method (>95%).

[0007] At present, in order to meet the requirements of environmentally friendly tin plating development, a new methanesulfonate tin plating technology has been introduced, with the following technical advantages: uniform coating is obtained in a wide current density range, and the production efficiency is equal to or even exceeds that of the halide plating solution system, no fluoride precipitation is produced, the methanesulfonate tin plating solution is non-toxic and completely biodegradable, the wastewater treatment is simple, does not contain toxic substances such as cyanide, fluorine or free phenol, and the sediment generation rate is low. Based on the above technical advantages, the methanesulfonate tin plating system has become the most widely used process in tin plating after more than ten years of industrial development.

[0008] Methanesulfonate tin plating technology has become a research hotspot for researchers from all over the world. Methanesulfonate tin plating solution mainly uses divalent tin main salt + acid + reducing agent + complexing agent + functional additives (such as surfactant and antioxidant). For example, a methanesulfonate tin plating electrolyte disclosed in CN102162110B includes the following ingredients: 30~120g / L stannous methanesulfonate, 60~180g / L methanesulfonic acid, 1~10g cerium sulfate, 0.1~2g / L antioxidant, 5~10g / L brightener and 5~15gL surfactant, the antioxidant is meta-diphenol or catechol or a mixture of the two, the brightener is glutaraldehyde or benzylidene acetone or a mixture of the two, and the surfactant is polyethylene glycol octylphenyl ether or sodium dodecyl sulfonate or a mixture of the two. The introduction of cerium salts into the above-mentioned tin-plating solution expands the cathode current density range, enhances the all-plating ability of the plating solution, widens the bright range of the coating, and improves the corrosion resistance and electrical conductivity of the coating; cerium is easily adsorbed on the active points of crystal growth, which can effectively inhibit crystal growth, refine the coating grains and make the surface bright and delicate, and reduce the consumption of brighteners in the methylsulfonate tin-plating electrolyte; cerium has a strong attraction to electrons, and rare earths easily form ions in the solution. The characteristic adsorption of cerium ions increases the potential of hydrogen ions at the cathode and the selective blocking of hydrogen ions by the adsorption film, which reduces the degree of harm of "hydrogen embrittlement". Although the quality of the coating has been improved, the inevitable introduction of rare earth elements has brought about an increase in production costs and the problem of rare earth salt pollution treatment in waste liquid.

[0009] To this end, the inventors provided an environmentally friendly acidic tin plating electrolyte. By optimizing the distribution ratio of the formula components and optimizing the electroplating process parameters, the overall production cost was reduced while ensuring the density and smoothness of the resulting electrolytic tin plating layer, thereby solving the problem of rare earth salt pollution treatment in the waste liquid. Summary of the invention

[0010] In order to solve the problem of rare earth salt pollution treatment in waste liquid of existing modified methane sulfonate tin plating and the resulting increase in production costs, the present application provides an environmentally friendly acidic tin plating electrolyte and an environmentally friendly tin plating process implemented using the same.

[0011] The environmentally friendly acidic tin plating electrolyte provided in the present application is realized by the following technical solutions:

[0012] An environmentally friendly acidic tin-plating electrolyte comprises the following components: 35-40 g / L of stannous methanesulfonate, 45-80 g / L of methanesulfonic acid, 15-40 g / L of citric acid, 80-120 g / L of thiourea, 50-80 g / L of sodium hypophosphite, 5-20 g / L of ammonium hypophosphite, 15-25 g / L of a compound brightener, 5-15 g / L of a compound surfactant, 10-20 g / L of a compound antioxidant, 5-20 g / L of a pH regulator, and 0.4-0.8 g / L of triethylenetetraaminehexaacetic acid; the pH regulator is composed of methanesulfonic acid, citric acid, and EDTA in a mass ratio of (4-6): (0.8-1.6): (0.4-0.6); and the pH value of the environmentally friendly acidic tin-plating electrolyte is 0.6-0.7.

[0013] The inventors optimized the formulation ratio of the environmentally friendly acidic tin-plating electrolyte and combined it with the optimization of the electroplating process parameters. Under the premise of ensuring the density and smoothness of the obtained electrolytic tin plating layer, the increase in overall production costs was reduced and the problem of rare earth salt pollution treatment in the waste liquid was solved.

[0014] Preferably, the composite surfactant is composed of alkylphenol polyoxyethylene ether OP-10, polyethylene glycol PEG 300, and polyethylene glycol alkyne with a molecular weight of 1000-2000; the structural formula of the polyethylene glycol alkyne is as follows:

[0015] .

[0016] Preferably, the mass ratio of the alkylphenol polyoxyethylene ether OP-10, polyethylene glycol PEG 300, and polyethylene glycol alkyne with a molecular weight of 1000-2000 is 8:(1-2):(0.5-1.6).

[0017] The compound surfactant has excellent adsorption capacity on the cathode (workpiece to be plated) surface and can inhibit the discharge of tin ions (II) and the evolution of hydrogen (Sn 2+ +2H + +1 / 2O2→Sn 4++H2), which can improve the quality of electrolytic tin plating. The main surfactant of alkylphenol polyoxyethylene ether OP-10 controls the morphology and density of the electrolytic tin plating. The polyethylene glycol PEG 300 contained in the compound surfactant can play a role in grain refinement and enhance the sedimentation rate, ensuring the density and smoothness of the electrolytic tin plating. On the one hand, an appropriate amount of polyethylene glycol acetylene can play a role in wetting and dispersing, greatly eliminating the problem of pinhole bubbles in the tin plating layer caused by anode hydrogen evolution, and assisting in improving the density and smoothness of the electrolytic tin plating. In addition, an appropriate amount of polyethylene glycol acetylene contains alcohol acetylene groups that can be adsorbed on the uneven raised parts of the electrode surface, so that the plating speed of the raised parts is reduced relative to the recessed parts, which can further adjust the smoothness of the electrolytic tin plating, the bonding strength of the tin layer and the solderability.

[0018] Preferably, the composite antioxidant is composed of ascorbic acid, catechol and hydroquinone in a mass ratio of (0.1-0.2): (0.8-1.2): (0.8-1.2).

[0019] Preferably, the composite antioxidant is composed of ascorbic acid, catechol and hydroquinone in a mass ratio of 1:5:4.

[0020] By adopting the above technical scheme, the composite antioxidant improves the storage stability of the prepared environmentally friendly acidic tin-plating electrolyte, inhibits the conversion of divalent tin into tetravalent tin, and the tetravalent tin is converted into Sn(OH)4 (a-stannic acid) and precipitated and is closely related to the electrolysis temperature threshold of the electrolytic tin-plating solution, thereby improving the temperature resistance of the environmentally friendly acidic tin-plating electrolyte, which is beneficial to improving the quality of the final electrolytic tin coating. On the other hand, experiments have found that under the above formula system, adding an appropriate amount of ascorbic acid can improve the morphology and density of the coating without affecting the sedimentation rate, and the oxidation of the tin coating surface is also significantly improved, thereby optimizing the quality of the electrolytic tin coating.

[0021] Preferably, the composite brightener is composed of 1-(2-hydroxy-3-sulfopropyl)pyridine betaine salt, hydroxyethyl propargyl ether, and super cinnamaldehyde in a mass ratio of (65-80): (10-25): (5-10).

[0022] Preferably, the composite brightener is composed of 1-(2-hydroxy-3-sulfopropyl)pyridine betaine salt, hydroxyethyl propargyl ether, and super cinnamaldehyde in a mass ratio of 77:15:8.

[0023] The compound brightener in the present application can be relatively quickly adsorbed on the uneven convex part of the surface of the workpiece to be plated, so that the plating speed of the convex part is reduced relative to the concave part, and the convex part is slower than the concave part, thereby playing the role of making the electrode surface flat, and also making the tin in the tin plating layer arranged in the same direction, and the gloss of the tin plating layer with a highly consistent crystal direction arrangement is excellent, that is, the flatness is improved and the light is emitted. In addition, the preferred super cinnamaldehyde is used as a compound brightener to further refine the grains of the tin plating layer, and the bright and flat tin plating layer has good solderability and stable bonding strength with the surface of the plated part, which is conducive to improving the quality of the overall plating layer.

[0024] Preferably, the environmentally friendly acidic tin-plating electrolyte comprises the following components: 38 g / L stannous methanesulfonate, 65 g / L methanesulfonic acid, 25 g / L citric acid, 105 g / L thiourea, 75 g / L sodium hypophosphite, 15 g / L ammonium hypophosphite, 18 g / L compound brightener, 12 g / L compound surfactant, 14 g / L compound antioxidant, and 16 g / L pH adjuster; the pH adjuster is composed of methanesulfonic acid, citric acid, and EDTA in a mass ratio of 6:1.5:0.5; the pH value of the environmentally friendly acidic tin-plating electrolyte is 0.6-0.62.

[0025] By optimizing the formula of the environmentally friendly acidic tin-plating electrolyte, not only can the density and smoothness of the electrolytic tin plating layer be further improved, but also the tin deposition rate can be adjusted, the efficiency of the tin-plating process can be improved, and the overall production cost can be reduced; in addition, the above-mentioned optimized environmentally friendly acidic tin-plating electrolyte formula can inhibit the oxidation of divalent tin to form tin sludge, and improve the quality stability of the tin plating layer.

[0026] The present application provides an environmentally friendly tin plating process using an environmentally friendly acidic tin plating electrolyte, which is achieved through the following technical solutions:

[0027] An environmentally friendly tin-plating process using an environmentally friendly acidic tin-plating electrolyte comprises the following steps:

[0028] Step 1, preparation of an environmentally friendly acidic tin-plating electrolyte: first, 100 parts of deionized water and 0.4-0.8 parts of triethylenetetraaminehexaacetic acid are mixed evenly, and then placed in a reactor for boiling treatment for 5-15 minutes, and after boiling, the air in the reactor is replaced by nitrogen, and after the boiling treatment is completed, the temperature is lowered to 0-20° C. and filtered to obtain a water solvent, and accurately measured stannous methanesulfonate, methanesulfonic acid, citric acid, thiourea, sodium hypophosphite, ammonium hypophosphite, compound brightener, compound surfactant, and compound antioxidant are added into the reactor and stirred evenly with the obtained water solvent, and then a pH adjuster is added dropwise to adjust the pH value of the system to 0.6-0.7, so as to obtain an environmentally friendly acidic tin-plating electrolyte; and at the same time, surface treatment is performed on the workpiece to be plated;

[0029] Step 2: The environmentally friendly acidic tin-plating electrolyte in step 1 is placed in an electrolytic cell, wherein the environmentally friendly acidic tin-plating electrolyte accounts for 60-75% of the volume of the electrolytic cell, a mesh tin sheet is used as an anode, and a workpiece to be plated is used as a cathode, wherein the mesh tin sheet and the workpiece to be plated are in the same length direction, and a circulating pump is connected to both sides of the electrolytic cell through a pipeline, and the circulating pump is used to realize the circulation of the environmentally friendly acidic tin-plating solution and control the flow rate of the environmentally friendly acidic tin-plating solution, wherein the flow direction of the environmentally friendly acidic tin-plating solution is in the same length direction as the mesh tin sheet, and the flow rate of the environmentally friendly acidic tin-plating solution is 0.2- 0.6m / s, the electrolytic cell is filled with conductive fiber cotton, and the conductivity of the conductive fiber cotton is controlled at 0.5-10s / m; the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length direction of the mesh tin sheet and the workpiece to be plated, the conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated, the temperature of the environmentally friendly acidic tin plating electrolyte is 45-50°C, the current density is controlled at 3-5A / dm2, and the electroplating time is 3-15min, so that a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0030] The present invention uses an environmentally friendly tin-plating process implemented by an environmentally friendly acidic tin-plating electrolyte to obtain a dense, smooth and high-quality tin-plated layer. The implementation equipment of the process method is relatively simple, the process flow is low in difficulty, and it is easy to achieve large-scale production. In the above tin-plating process, the invention removes impurities such as dissolved oxygen and iron ions in the water solvent, inhibits the anode side reaction (Sn 2+ +2H + +1 / 2O2→Sn 4+ +H2) to further improve the quality of the tin plating layer.

[0031] In addition, the circulation pump realizes the circulation flow of the environmentally friendly acidic tin plating solution and controls the flow rate of the environmentally friendly acidic tin plating solution, which can improve the overall uniform dispersion of divalent tin in the electrolyte, and also makes the divalent tin produced by the mesh tin sheet connected to the anode quickly diffuse into the environmentally friendly acidic tin plating electrolyte. The stable divalent tin concentration can effectively ensure the density and smoothness of the tin plating layer.

[0032] In addition, the setting of the conductive fiber cotton provides a fast directional movement channel for ion flow, which can effectively accelerate the generation of the anode

[0033] Preferably, in the step 2, the flow rate of the environmentally friendly acidic tin plating is 0.4-0.5m / s, the temperature of the environmentally friendly acidic tin plating electrolyte is 50°C, the current density is controlled to be 4A / dm2, and the electroplating time is 8-12min, so that a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0034] The density, smoothness and solderability of the tin-plated layer can be further improved by optimizing the process parameters.

[0035] In summary, this application has the following advantages:

[0036] 1. This application optimizes the formulation ratio of the environmentally friendly acidic tin-plating electrolyte and combines it with the optimization of the electroplating process parameters. On the premise of ensuring the density and smoothness of the obtained electrolytic tin plating layer, it reduces the increase in overall production costs and solves the problem of rare earth salt pollution treatment in the waste liquid.

[0037] 2. The environmentally friendly tin-plating process implemented by the present application using an environmentally friendly acidic tin-plating electrolyte can obtain a dense, smooth and flat high-quality tin-plating layer, and the implementation equipment of the process method is relatively simple, the process flow is of low difficulty, and it is easy to achieve large-scale production. DETAILED DESCRIPTION

[0038] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples and comparative examples.

[0039] Example

[0040] An environmentally friendly acidic tin plating electrolyte comprises the following components: 35-40 g / L of stannous methanesulfonate, 45-80 g / L of methanesulfonic acid, 15-40 g / L of citric acid, 80-120 g / L of thiourea, 50-80 g / L of sodium hypophosphite, 5-20 g / L of ammonium hypophosphite, 15-25 g / L of a compound brightener, 5-15 g / L of a compound surfactant, 10-20 g / L of a compound antioxidant, 5-20 g / L of a pH regulator, and 0.4-0.8 g / L of triethylenetetraaminehexaacetic acid.

[0041] The pH adjuster is composed of methanesulfonic acid, citric acid, and EDTA in a mass ratio of (4-6): (0.8-1.6): (0.4-0.6). Preferably, the pH adjuster is composed of methanesulfonic acid, citric acid, and EDTA in a mass ratio of 6:1.5:0.5.

[0042] The pH value of environmentally friendly acidic tin plating electrolyte is 0.6-0.7.

[0043] Preferably, the pH value of the environmentally friendly acidic tin plating electrolyte is 0.6-0.62.

[0044] The compound surfactant is composed of alkylphenol polyoxyethylene ether OP-10, polyethylene glycol PEG 300, and polyethylene glycol alkyne with a molecular weight of 1000-2000. The structural formula of polyethylene glycol alkyne is as follows:

[0045]

[0046] Preferably, the mass ratio of alkylphenol polyoxyethylene ether OP-10, polyethylene glycol PEG 300, and polyethylene glycol alkyne with a molecular weight of 1000-2000 is 8:(1-2):(0.5-1.6). Optimal formula: the mass ratio of alkylphenol polyoxyethylene ether OP-10, polyethylene glycol PEG300, and polyethylene glycol alkyne with a molecular weight of 1000-2000 is 8:1.4:0.6.

[0047] The compound antioxidant is composed of ascorbic acid, catechol and hydroquinone in a mass ratio of (0.1-0.2):(0.8-1.2):(0.8-1.2). Preferably, ascorbic acid, catechol and hydroquinone are composed in a mass ratio of 1:5:4.

[0048] The compound brightener is composed of 1-(2-hydroxy-3-sulfopropyl)pyridine betaine salt, hydroxyethyl propargyl ether, and super cinnamaldehyde in a mass ratio of (65-80): (10-25): (5-10). Preferably, the compound brightener is composed of 1-(2-hydroxy-3-sulfopropyl)pyridine betaine salt, hydroxyethyl propargyl ether, and super cinnamaldehyde in a mass ratio of 77:15:8.

[0049] Preferred formula: The environmentally friendly acidic tin plating electrolyte includes the following components: 38g / L stannous methanesulfonate, 65g / L methanesulfonic acid, 25g / L citric acid, 105g / L thiourea, 75g / L sodium hypophosphite, 15g / L ammonium hypophosphite, 18g / L compound brightener, 12g / L compound surfactant, 14g / L compound antioxidant, and 16g / L pH adjuster.

[0050] A method for preparing an environmentally friendly acidic tin-plating electrolyte comprises the following steps:

[0051] Step 1, preparation of an environmentally friendly acidic tin-plating electrolyte: first, 100 parts of deionized water and 0.4-0.8 parts of triethylenetetraaminehexaacetic acid are mixed evenly, and then placed in a reactor for boiling treatment for 5-15 minutes, and after boiling, the air in the reactor is replaced by nitrogen, and after the boiling treatment is completed, the temperature is lowered to 0-20° C. and filtered to obtain a water solvent, and accurately measured stannous methanesulfonate, methanesulfonic acid, citric acid, thiourea, sodium hypophosphite, ammonium hypophosphite, compound brightener, compound surfactant, and compound antioxidant are added into the reactor and stirred evenly with the obtained water solvent, and then a pH adjuster is added dropwise to adjust the pH value of the system to 0.6-0.7, so as to obtain an environmentally friendly acidic tin-plating electrolyte; and at the same time, surface treatment is performed on the workpiece to be plated;

[0052] Step 2: The environmentally friendly acidic tin-plating electrolyte in step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 60-75% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, the workpiece to be plated is used as the cathode, the mesh tin sheet and the workpiece to be plated are in the same length direction, the two sides of the electrolytic cell are connected to a circulation pump through a pipeline, the circulation of the environmentally friendly acidic tin-plating solution and the control of the flow rate of the environmentally friendly acidic tin-plating solution are achieved through the circulation pump, the flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet, and the flow rate of the environmentally friendly acidic tin-plating is 0 .2-0.6m / s, the electrolytic cell is filled with conductive fiber cotton, and the conductivity of the conductive fiber cotton is controlled at 0.5-10s / m; the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length direction of the mesh tin sheet and the workpiece to be plated, and the conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acidic tin plating electrolyte is 45-50℃, the current density is controlled at 3-5A / dm2, and the electroplating time is 3-15min, so that a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0053] Optimum electrolytic tinning parameters are: environmentally friendly acidic tinning flow rate is 0.4-0.5m / s, environmentally friendly acidic tinning electrolyte temperature is 50°C, current density is controlled at 4A / dm2, and electroplating time is 8-12min.

[0054] Example 1: An environmentally friendly acidic tin plating electrolyte comprises the following components: 35 g / L stannous methanesulfonate, 45 g / L methanesulfonic acid, 40 g / L citric acid, 100 g / L thiourea, 60 g / L sodium hypophosphite, 15 g / L ammonium hypophosphite, 15 g / L compound brightener, 10 g / L compound surfactant, 20 g / L compound antioxidant, and 8 g / L pH adjuster.

[0055] The pH regulator is composed of methanesulfonic acid, citric acid, and EDTA in a mass ratio of 4:1.5:0.5. The compound surfactant is composed of alkylphenol polyoxyethylene ether OP-10, polyethylene glycol PEG 300, and polyethylene glycol alkyne with a molecular weight of 2000 (customized by Xiamen Sinobon Biotechnology Co., Ltd.) in a mass ratio of 8:1:1. The compound antioxidant is composed of ascorbic acid, catechol, and hydroquinone in a mass ratio of 0.1:1.1:0.8. The compound brightener is composed of 1-(2-hydroxy-3-sulfopropyl) pyridine betaine salt, hydroxyethyl propargyl ether, and super cinnamaldehyde in a mass ratio of 77:15:8.

[0056] A method for preparing an environmentally friendly acidic tin-plating electrolyte comprises the following steps:

[0057] Step 1, preparation of an environmentally friendly acidic tin-plating electrolyte: first, 100 parts of deionized water and 0.6 parts of triethylenetetraaminehexaacetic acid are mixed evenly, and then placed in a reactor for boiling treatment for 8 minutes, and after boiling, the air in the reactor is replaced by nitrogen. After the boiling treatment is completed, the temperature is lowered to 20° C. and filtered to obtain a water solvent, and accurately measured stannous methanesulfonate, methanesulfonic acid, citric acid, thiourea, sodium hypophosphite, ammonium hypophosphite, compound brightener, compound surfactant, and compound antioxidant are added into the reactor and stirred evenly with the obtained water solvent, and then a pH adjuster is added dropwise and mixed. After the pH value of the system is 0.7, an environmentally friendly acidic tin-plating electrolyte is obtained;

[0058] At the same time, the workpiece to be plated - iron sheet (36mm×18mm×1.5 mm) was surface treated: 200# sandpaper / 500# sandpaper / 2000# sandpaper were used to polish and remove the oxide layer, and after polishing, acetone aqueous solution (acetone / water volume ratio 1:4) was used to clean three times to remove residual oil stains, and then immersed in 5g / L OP-10 aqueous solution for ultrasonic dispersion treatment for 10min, and then immersed in activation solution (40g / L stannous methanesulfonate, 60g / L methanesulfonic acid) for 30s ultrasonic dispersion treatment;

[0059] Step 2: The environmentally friendly acidic tin-plating electrolyte in step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent. The two sides of the electrolytic cell are connected to a circulation pump through a pipeline. The circulation pump is used to realize the circulation of the environmentally friendly acidic tin-plating solution and control the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin-plating is 0.5m / s. The electrolytic cell is filled with conductive fiber cotton, the conductivity of the conductive fiber cotton is 3.6s / m, the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length direction of the mesh tin sheet and the workpiece to be plated, the conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated, the temperature of the environmentally friendly acidic tin-plating electrolyte is 45°C, and the current density is controlled to be 3A / dm 2 The electroplating time is 5 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0060] The difference between Example 2 and Example 1 is that an environmentally friendly acidic tin plating electrolyte includes the following components: 38 g / L stannous methanesulfonate, 65 g / L methanesulfonic acid, 25 g / L citric acid, 105 g / L thiourea, 75 g / L sodium hypophosphite, 15 g / L ammonium hypophosphite, 18 g / L compound brightener, 12 g / L compound surfactant, 14 g / L compound antioxidant, and 16 g / L pH adjuster.

[0061] The difference between Example 3 and Example 1 is that an environmentally friendly acidic tin plating electrolyte includes the following components: 40 g / L stannous methanesulfonate, 80 g / L methanesulfonic acid, 15 g / L citric acid, 120 g / L thiourea, 55 g / L sodium hypophosphite, 20 g / L ammonium hypophosphite, 24 g / L compound brightener, 15 g / L compound surfactant, 18 g / L compound antioxidant, and 8 g / L pH adjuster.

[0062] The difference between Example 4 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to the circulation pump through a pipeline. The circulation pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin plating is 0.5m / s, and the electrolytic cell is filled with conductive fiber cotton. The conductivity of the conductive fiber cotton is 1.6s / m, and the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acidic tin-plating electrolyte is 45°C, and the current density is controlled to be 3A / dm 2 The electroplating time is 5 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0063] The difference between Example 5 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to the circulation pump through a pipeline. The circulation pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin plating is 0.5m / s, and the electrolytic cell is filled with conductive fiber cotton. The conductivity of the conductive fiber cotton is 7.8s / m, and the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acidic tin-plating electrolyte is 45°C, and the current density is controlled to be 3A / dm 2 The electroplating time is 5 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0064] The difference between Example 6 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to the circulation pump through a pipeline. The circulation pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin plating is 0.2m / s, and the electrolytic cell is filled with conductive fiber cotton. The conductivity of the conductive fiber cotton is 3.6s / m. The length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acidic tin-plating electrolyte is 45°C, and the current density is controlled to be 3A / dm 2 The electroplating time is 5 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0065] The difference between Example 7 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, the workpiece to be plated is used as the cathode, the length direction of the mesh tin sheet and the workpiece to be plated are consistent, the two sides of the electrolytic cell are connected to the circulation pump through a pipeline, the circulation pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution, and the flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet. The flow rate of environmentally friendly acid tin plating is 0.3m / s. The electrolytic cell is filled with conductive fiber cotton. The conductivity of the conductive fiber cotton is 3.6s / m. The length of the conductive fiber cotton is perpendicular to the length direction of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acid tin plating electrolyte is 45°C, the current density is controlled to 3A / dm2, and the electroplating time is 5min. A dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0066] The difference between Example 8 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, the workpiece to be plated is used as the cathode, the length direction of the mesh tin sheet and the workpiece to be plated are consistent, the two sides of the electrolytic cell are connected to the circulation pump through a pipeline, the circulation pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution, and the flow direction of the environmentally friendly acidic tin-plating solution is consistent with the length direction of the mesh tin sheet. The flow rate of environmentally friendly acid tin plating is 0.4m / s. The electrolytic cell is filled with conductive fiber cotton. The conductivity of the conductive fiber cotton is 3.6s / m. The length of the conductive fiber cotton is perpendicular to the length direction of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acid tin plating electrolyte is 45°C, the current density is controlled to 3A / dm2, and the electroplating time is 5min. A dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0067] The difference between Example 9 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, the workpiece to be plated is used as the cathode, the length direction of the mesh tin sheet and the workpiece to be plated are consistent, the two sides of the electrolytic cell are connected to the circulation pump through a pipeline, the circulation pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution, and the flow direction of the environmentally friendly acidic tin-plating solution is consistent with the length direction of the mesh tin sheet. The flow rate of environmentally friendly acid tin plating is 0.6m / s. The electrolytic cell is filled with conductive fiber cotton. The conductivity of the conductive fiber cotton is 3.6s / m. The length of the conductive fiber cotton is perpendicular to the length direction of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acid tin plating electrolyte is 45°C, the current density is controlled to 3A / dm2, and the electroplating time is 5min. A dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0068] The difference between Example 10 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to a circulation pump through a pipeline. The circulation pump is used to realize the circulation of the environmentally friendly acidic tin-plating solution and control the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin-plating is 0.5m / s, and the electrolytic cell is filled with conductive fiber cotton, the conductivity of the conductive fiber cotton is 3.6s / m, the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated, the conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated, the temperature of the environmentally friendly acidic tin-plating electrolyte is 50°C, and the current density is controlled to be 3A / dm2 The electroplating time is 5 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0069] The difference between Example 11 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to a circulation pump through a pipeline. The circulation pump is used to realize the circulation of the environmentally friendly acidic tin-plating solution and control the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin-plating is 0.5m / s, and the electrolytic cell is filled with conductive fiber cotton, the conductivity of the conductive fiber cotton is 3.6s / m, the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated, the conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated, the temperature of the environmentally friendly acidic tin-plating electrolyte is 50°C, and the current density is controlled to be 4A / dm 2 The electroplating time is 5 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0070] The difference between Example 12 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to a circulation pump through a pipeline. The circulation pump is used to realize the circulation of the environmentally friendly acidic tin-plating solution and control the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin-plating is 0.5m / s, and the electrolytic cell is filled with conductive fiber cotton, the conductivity of the conductive fiber cotton is 3.6s / m, the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated, the conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated, the temperature of the environmentally friendly acidic tin-plating electrolyte is 50°C, and the current density is controlled to be 5A / dm 2 The electroplating time is 5 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0071] The difference between Example 13 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode, the length directions of the mesh tin sheet and the workpiece to be plated are consistent, the two sides of the electrolytic cell are connected to the circulation pump through a pipeline, and the circulation pump is used to realize the circulation of the environmentally friendly acidic tin-plating solution and control the flow rate of the environmentally friendly acidic tin-plating solution, the flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet, the flow rate of the environmentally friendly acidic tin-plating is 0.5m / s, the electrolytic cell is filled with conductive fiber cotton, the conductivity of the conductive fiber cotton is 3.6s / m, the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated, the conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated, the temperature of the environmentally friendly acidic tin-plating electrolyte is 50°C, and the current density is controlled to be 4A / dm 2 The electroplating time is 3 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0072] The difference between Example 14 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to a circulation pump through a pipeline. The circulation pump is used to realize the circulation of the environmentally friendly acidic tin-plating solution and control the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin-plating is 0.5m / s, and the electrolytic cell is filled with conductive fiber cotton, the conductivity of the conductive fiber cotton is 3.6s / m, the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated, the conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated, the temperature of the environmentally friendly acidic tin-plating electrolyte is 50°C, and the current density is controlled to be 4A / dm 2 The electroplating time is 8 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0073] The difference between Example 15 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode, the length directions of the mesh tin sheet and the workpiece to be plated are consistent, the two sides of the electrolytic cell are connected to the circulation pump through a pipeline, and the circulation pump is used to realize the circulation of the environmentally friendly acidic tin-plating solution and control the flow rate of the environmentally friendly acidic tin-plating solution, the flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet, the flow rate of the environmentally friendly acidic tin-plating is 0.5m / s, the electrolytic cell is filled with conductive fiber cotton, the conductivity of the conductive fiber cotton is 3.6s / m, the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated, the conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated, the temperature of the environmentally friendly acidic tin-plating electrolyte is 50°C, and the current density is controlled to be 4A / dm 2 The electroplating time is 12 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0074] The difference between Example 16 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode, the length directions of the mesh tin sheet and the workpiece to be plated are consistent, the two sides of the electrolytic cell are connected to the circulation pump through a pipeline, and the circulation pump is used to realize the circulation of the environmentally friendly acidic tin-plating solution and control the flow rate of the environmentally friendly acidic tin-plating solution, the flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet, the flow rate of the environmentally friendly acidic tin-plating is 0.5m / s, the electrolytic cell is filled with conductive fiber cotton, the conductivity of the conductive fiber cotton is 3.6s / m, the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated, the conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated, the temperature of the environmentally friendly acidic tin-plating electrolyte is 50°C, and the current density is controlled to be 4A / dm 2 The electroplating time is 15 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0075] The difference between Example 17 and Example 1 is that the pH adjuster consists of methanesulfonic acid, citric acid, and EDTA in a mass ratio of 5:1.5:0.5.

[0076] The difference between Example 18 and Example 1 is that the pH adjuster consists of methanesulfonic acid, citric acid, and EDTA in a mass ratio of 6:1.5:0.5.

[0077] The difference between Example 19 and Example 1 is that the mass ratio of the compound surfactant composed of alkylphenol polyoxyethylene ether OP-10, polyethylene glycol PEG 300, and polyethylene glycol alkyne with a molecular weight of 2000 is 8:2:0.5.

[0078] The difference between Example 20 and Example 1 is that the mass ratio of the composite surfactant composed of alkylphenol polyoxyethylene ether OP-10, polyethylene glycol PEG 300, and polyethylene glycol alkyne with a molecular weight of 2000 is 8:1:1.6.

[0079] The difference between Example 21 and Example 1 is that the compound antioxidant is composed of ascorbic acid, catechol and hydroquinone in a mass ratio of 0.2:1.2:0.8.

[0080] The difference between Example 22 and Example 1 is that the compound antioxidant is composed of ascorbic acid, catechol and hydroquinone in a mass ratio of 0.15:1:0.85.

[0081] The difference between Example 23 and Example 1 is that the composite antioxidant is composed of ascorbic acid, catechol and hydroquinone in a mass ratio of 1:5:4.

[0082] The difference between Example 24 and Example 1 is that the compound brightener is composed of 1-(2-hydroxy-3-sulfopropyl)pyridine amine salt, hydroxyethyl propargyl ether, and super cinnamaldehyde in a mass ratio of 65:25:10.

[0083] The difference between Example 25 and Example 1 is that the compound brightener is composed of 1-(2-hydroxy-3-sulfopropyl)pyridine amine salt, hydroxyethyl propargyl ether, and super cinnamaldehyde in a mass ratio of 80:15:5.

[0084] The difference between Example 26 and Example 1 is: An environmentally friendly acidic tin plating electrolyte includes the following components: 38 g / L stannous methanesulfonate, 65 g / L methanesulfonic acid, 25 g / L citric acid, 105 g / L thiourea, 75 g / L sodium hypophosphite, 15 g / L ammonium hypophosphite, 18 g / L compound brightener, 12 g / L compound surfactant, 14 g / L compound antioxidant, and 16 g / L pH adjuster.

[0085] The pH adjuster is composed of methanesulfonic acid, citric acid and EDTA in a mass ratio of 6:1.5:0.5.

[0086] The compound surfactant is composed of alkylphenol polyoxyethylene ether OP-10, polyethylene glycol PEG 300 and polyethylene glycol alkyne with a molecular weight of 2000 in a mass ratio of 8:1.2:0.8.

[0087] The compound antioxidant is composed of ascorbic acid, catechol and hydroquinone in a mass ratio of 1:5:4.

[0088] The difference in the preparation process is: step 2, the environmentally friendly acidic tin-plating electrolyte in step 1 is placed in the electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length direction of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to the circulation pump through a pipeline. The circulation pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin plating is 0.5m / s. The electrolytic cell is filled with conductive fiber cotton, and the conductivity of the conductive fiber cotton is 3.6s / m. The length of the conductive fiber in the conductive fiber cotton is perpendicular to the length direction of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acidic tin-plating electrolyte is 50°C, and the current density is controlled to be 4A / dm 2 The electroplating time is 10 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0089] The difference between Comparative Example 1 and Example 1 is as follows: Step 2: the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, the workpiece to be plated is used as the cathode, the length direction of the mesh tin sheet and the workpiece to be plated are consistent, the temperature of the environmentally friendly acidic tin-plating electrolyte is 45°C, and the current density is controlled to be 3A / dm 2 The electroplating time is 5 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0090] The difference between Comparative Example 2 and Example 1 is: Step 2, the environmentally friendly acidic tin-plating electrolyte in step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to the circulating pump through a pipeline. The circulating pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin-plating is 0.5m / s, the temperature of the environmentally friendly acidic tin-plating electrolyte is 45°C, the current density is controlled to be 3A / dm2, and the electroplating time is 5min, so that a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0091] The difference between Comparative Example 3 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to the circulation pump through a pipeline. The circulation pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin plating is 0.5m / s, and the electrolytic cell is filled with conductive fiber cotton, the conductivity of the conductive fiber cotton is 0.05s / m, the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated, the conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated, the temperature of the environmentally friendly acidic tin-plating electrolyte is 45°C, and the current density is controlled to be 3A / dm 2 The electroplating time is 5 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0092] The difference between Comparative Example 4 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to the circulation pump through a pipeline. The circulation pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin plating is 0.5m / s, and the electrolytic cell is filled with conductive fiber cotton. The conductivity of the conductive fiber cotton is 10.8s / m, and the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acidic tin-plating electrolyte is 45°C, and the current density is controlled to be 3A / dm 2 The electroplating time is 5 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0093] The difference between Comparative Example 5 and Example 1 is: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode, the length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the electrolytic cell is filled with conductive fiber cotton, the conductivity of the conductive fiber cotton is 3.6s / m, the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated, the conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated, the temperature of the environmentally friendly acidic tin-plating electrolyte is 45°C, the current density is controlled to be 3A / dm2, and the electroplating time is 5min, so that a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0094] The difference between Comparative Example 6 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, the workpiece to be plated is used as the cathode, the length direction of the mesh tin sheet and the workpiece to be plated are consistent, the two sides of the electrolytic cell are connected to the circulation pump through a pipeline, the circulation pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution, and the flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet. The flow rate of environmentally friendly acid tin plating is 0.1m / s. The electrolytic cell is filled with conductive fiber cotton. The conductivity of the conductive fiber cotton is 3.6s / m. The length of the conductive fiber cotton is perpendicular to the length direction of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acid tin plating electrolyte is 45°C, the current density is controlled to 3A / dm2, and the electroplating time is 5min. A dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0095] The difference between Comparative Example 7 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, the workpiece to be plated is used as the cathode, the length direction of the mesh tin sheet and the workpiece to be plated are consistent, the two sides of the electrolytic cell are connected to the circulating pump through a pipeline, the circulating pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution, and the flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet. The flow rate of environmentally friendly acid tin plating is 1m / s. The electrolytic cell is filled with conductive fiber cotton. The conductivity of the conductive fiber cotton is 3.6s / m. The length of the conductive fiber cotton is perpendicular to the length direction of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acid tin plating electrolyte is 45°C, the current density is controlled to be 3A / dm2, and the electroplating time is 5min. A dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0096] The difference between Comparative Example 8 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to the circulation pump through a pipeline. The circulation pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin plating is 0.5m / s, and the electrolytic cell is filled with conductive fiber cotton. The conductivity of the conductive fiber cotton is 3.6s / m, and the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acidic tin-plating electrolyte is 35°C, and the current density is controlled to be 3A / dm2 The electroplating time is 5 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0097] The difference between Comparative Example 9 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to the circulation pump through a pipeline. The circulation pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin plating is 0.5m / s, and the electrolytic cell is filled with conductive fiber cotton. The conductivity of the conductive fiber cotton is 3.6s / m, and the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acidic tin-plating electrolyte is 55°C, and the current density is controlled to be 3A / dm 2 The electroplating time is 5 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0098] The difference between Comparative Example 10 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to the circulation pump through a pipeline. The circulation pump realizes the circulation of the environmentally friendly acidic tin-plating solution and controls the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin plating is 0.5m / s, and the electrolytic cell is filled with conductive fiber cotton. The conductivity of the conductive fiber cotton is 3.6s / m, and the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acidic tin-plating electrolyte is 50°C, and the current density is controlled to be 1A / dm 2 The electroplating time is 5 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0099] The difference between Comparative Example 11 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to a circulation pump through a pipeline. The circulation pump is used to realize the circulation of the environmentally friendly acidic tin-plating solution and control the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet, and the flow rate of the environmentally friendly acidic tin-plating is 0.5m / s. The electrolytic cell is filled with conductive fiber cotton, and the conductivity of the conductive fiber cotton is 3.6s / m. The length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acidic tin-plating electrolyte is 50°C, and the current density is controlled to be 6A / dm 2 The electroplating time is 5 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0100] The difference between Comparative Example 12 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to a circulation pump through a pipeline. The circulation pump is used to realize the circulation of the environmentally friendly acidic tin-plating solution and control the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet, and the flow rate of the environmentally friendly acidic tin-plating is 0.5m / s. The electrolytic cell is filled with conductive fiber cotton, and the conductivity of the conductive fiber cotton is 3.6s / m. The length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acidic tin-plating electrolyte is 50°C, and the current density is controlled to be 4A / dm 2 The electroplating time is 1 minute, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0101] The difference between Comparative Example 13 and Example 1 is as follows: Step 2, the environmentally friendly acidic tin-plating electrolyte in Step 1 is placed in an electrolytic cell, the environmentally friendly acidic tin-plating electrolyte accounts for 67% of the volume of the electrolytic cell, the mesh tin sheet is used as the anode, and the workpiece to be plated is used as the cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent, and the two sides of the electrolytic cell are connected to a circulation pump through a pipeline. The circulation pump is used to realize the circulation of the environmentally friendly acidic tin-plating solution and control the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet, and the flow rate of the environmentally friendly acidic tin-plating is 0.5m / s. The electrolytic cell is filled with conductive fiber cotton, and the conductivity of the conductive fiber cotton is 3.6s / m. The length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated. The conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acidic tin-plating electrolyte is 50°C, and the current density is controlled to be 4A / dm 2 The electroplating time is 20 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

[0102] The difference between Comparative Example 14 and Example 1 is that the pH adjuster consists of methanesulfonic acid and citric acid in a mass ratio of 4:2.

[0103] The difference between Comparative Example 15 and Example 1 is that the compound surfactant is alkylphenol polyoxyethylene ether OP-10.

[0104] The difference between Comparative Example 16 and Example 1 is that the compound surfactant is polyethylene glycol PEG 300.

[0105] The difference between Comparative Example 17 and Example 1 is that the compound surfactant is polyethylene glycol alkyne with a molecular weight of 2000.

[0106] The difference between Comparative Example 18 and Example 1 is that the compound surfactant is alkylphenol polyoxyethylene ether OP-10 and polyethylene glycol PEG 300, and the mass ratio of alkylphenol polyoxyethylene ether OP-10 to polyethylene glycol PEG 300 is 4:1.

[0107] The difference between Comparative Example 19 and Example 1 is that the compound antioxidant is ascorbic acid.

[0108] The difference between Comparative Example 20 and Example 1 is that the compound antioxidant is catechol.

[0109] The difference between Comparative Example 21 and Example 1 is that the compound antioxidant is hydroquinone.

[0110] The difference between Comparative Example 22 and Example 1 is that the composite antioxidant is hydroquinone and catechol in a mass ratio of 1:1.

[0111] The difference between Comparative Example 23 and Example 1 is that the compound brightener is 1-(2-hydroxy-3-sulfopropyl)pyridine amine salt.

[0112] The difference between Comparative Example 24 and Example 1 is that the compound brightener is hydroxyethyl propargyl ether.

[0113] The difference between Comparative Example 25 and Example 1 is that the compound brightener is super cinnamaldehyde.

[0114] The difference between Comparative Example 26 and Example 1 is that the compound brightener is composed of 1-(2-hydroxy-3-sulfopropyl)pyridine amine salt and hydroxyethyl propargyl ether in a mass ratio of 75:25.

[0115] The difference between Control Group 1 and Example 1 is: Step 1, preparation of an environmentally friendly acidic tin-plating electrolyte: accurately measured stannous methanesulfonate, methanesulfonic acid, citric acid, thiourea, sodium hypophosphite, ammonium hypophosphite, a compound brightener, a compound surfactant, a compound antioxidant, and deionized water are put into a reaction kettle and stirred evenly, and then a pH adjuster is added dropwise and the pH value of the system is 0.7 after mixing, thereby obtaining an environmentally friendly acidic tin-plating electrolyte.

[0116] The difference between Control Group 2 and Example 1 is that the environmentally friendly acidic tin plating electrolyte is composed of 30 g / L stannous methanesulfonate, 60 g / L methanesulfonic acid, 1 g / L cerium sulfate, 0 g / L meta-diphenol, 0.5 g / L catechol, 5 g / L benzalketone, 5 g / L glutaraldehyde, 5 g / L O-10, 5 g / L sodium dodecyl sulfate, and the rest is deionized water.

[0117] Performance testing:

[0118] 1. Determination of electroplating rate of plating solution: Determine the deposition rate of electroplated tin in tin plating solution by weighing method. Deposition rate v=100(m2-m1) / ρSt, v is deposition rate (μm / min); m1 is the mass of unplated sample (g); m2 is the mass of plated sample (g); ρ is the density of tin (7.28g / cm); S is the coating area; t is the plating time (min).

[0119] 2. Test of coating salt spray corrosion resistance - neutral salt spray test (NSS test): Refer to GB / T6461-2002, specimens and ratings of metal and other inorganic coatings on metal substrates after corrosion tests. According to GB5944-86 (Evaluation of corrosion test results of metal coatings on light industrial products), the evaluation method of corrosion results of electroplated coating specimens after corrosion tests (neutral salt spray test) can be evaluated. After the neutral salt spray corrosion test, count the number of substrate corrosion points and coating corrosion grids (n), and then count the total number of grids on the test piece (N), and then calculate according to the corrosion rate (%) = n*100 / N to obtain the corrosion rate of the coating.

[0120] 3. To measure the bonding strength of the coating, use the 3M tin-removal tape specially used for PCB to firmly stick the tape on the coating, then quickly tear off the tape, and then visually observe the amount of metal remaining on the tape. The less metal residue, the better the bonding strength of the coating.

[0121] 4. Evaluation method of plating solution stability: Place the tin plating solution in a 60℃ constant temperature water bath to accelerate the oxidation of the electrolytic tin plating solution, and record the time for the electrolytic tin plating solution to become turbid. The longer the time for the plating solution to become turbid, the better the stability of the plating solution.

[0122] The performance test results are shown in Table 1.

[0123] Table 1: Test parameter table of tin / iron sheet samples in Examples 1-26 and Comparative Examples 1-26

[0124]

[0125]

[0126]

[0127]

[0128]

[0129] Combining Example 1 and Control Group 1 and Table 1, it can be seen that the environmentally friendly acidic tin-plating electrolyte prepared by using the water solvent for removing oxygen and ferrous impurities in the present application has better stability and the prepared tin-plated layer has excellent density and smoothness.

[0130] Combining Example 1 and Control Group 2 and Table 1, it can be seen that the density and smoothness of the tin-plated layers obtained by the two are similar, but the environmentally friendly acidic tin-plating electrolyte prepared in the present application has better stability, deposition rate and corrosion resistance.

[0131] Combining Example 1 and Examples 2-3 and Table 1, it can be seen that the quality of the tin-plated layer obtained by the formula in Example 2 is relatively good. Correspondingly, from the cost analysis, Example 3> Example 2> Example 1, and Example 2 is preferred for mass production.

[0132] It can be seen from Example 1 and Comparative Examples 1-5 and Table 1 that the preparation process uses a circulating pump to achieve the circulation of the environmentally friendly acidic tin plating solution and controls the flow rate of the environmentally friendly acidic tin plating solution in combination with setting conductive fiber cotton between the mesh tin sheet and the workpiece to be plated, which can improve the density, smoothness and corrosion resistance of the resulting tin plating layer.

[0133] It can be seen from Example 1, Examples 4-5 and Comparative Examples 3-4 and Table 1 that the tin-plated layer prepared by controlling the conductivity of the conductive fiber cotton to 1.5-8s / m has relatively good density, smoothness, and corrosion resistance, and a faster sedimentation rate, which can improve the overall tin-plating production efficiency and thereby reduce production costs.

[0134] It can be seen from Example 1, Examples 6-9 and Comparative Examples 5-7 and Table 1 that the circulation of the environmentally friendly acidic tin plating solution is achieved by a circulation pump, and the flow rate of the environmentally friendly acidic tin plating solution is controlled to be 0.2-0.6 m / s, which can improve the quality of the obtained tin plating layer.

[0135] Combining Example 1, Examples 10-17 and Comparative Examples 10-13 and Table 1, it can be seen that the optimal electrolytic tin plating parameters are: the environmentally friendly acidic tin plating flow rate is 0.5m / s, the environmentally friendly acidic tin plating electrolyte temperature is 50°C, the current density is controlled to 4A / dm2, and the electroplating time is 8-12min.

[0136] It can be seen from Example 1, Examples 18-19 and Comparative Example 14 and Table 1 that the pH adjuster is composed of methanesulfonic acid, citric acid and EDTA in a mass ratio of (4-6): (0.8-1.6): (0.4-0.6), which can improve the quality of the obtained tin-plated layer.

[0137] It can be seen from Example 1, Examples 20-21 and Comparative Examples 15-18 and Table 1 that the composite surfactant is composed of alkylphenol polyoxyethylene ether OP-10, polyethylene glycol PEG 300, and polyethylene glycol alkyne with a molecular weight of 1000-2000 in a mass ratio of 8:(1-2):(0.5-1.6), which can improve the quality of the obtained tin-plated layer.

[0138] It can be seen from Example 1, Examples 21-23 and Comparative Examples 19-22 and Table 1 that the composite antioxidant is composed of ascorbic acid, catechol and hydroquinone in a mass ratio of (0.1-0.2): (0.8-1.2): (0.8-1.2), which can improve the quality of the obtained tin plating layer and enhance the storage stability of the environmentally friendly acidic tin plating solution.

[0139] It can be seen from Example 1, Examples 24-26 and Comparative Examples 23-26 and Table 1 that the composite brightener is composed of 1-(2-hydroxy-3-sulfopropyl)pyridine amine salt, hydroxyethyl propargyl ether, and super cinnamaldehyde in a mass ratio of (65-80): (10-25): (5-10), which can improve the density, smoothness, and corrosion resistance of the resulting tin-plated layer.

[0140] In summary, the electrolytic tin coating obtained by the environmentally friendly acidic tin plating electrolyte in the present application is dense, smooth and flat, while reducing the increase in overall production costs and solving the problem of rare earth salt pollution treatment in waste liquid.

[0141] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. An environmentally friendly acidic tin-plating electrolyte, characterized in that: The invention comprises the following components: 35-40 g / L stannous methanesulfonate, 45-80 g / L methanesulfonic acid, 15-40 g / L citric acid, 80-120 g / L thiourea, 50-80 g / L sodium hypophosphite, 5-20 g / L ammonium hypophosphite, 15-25 g / L compound brightener, 5-15 g / L compound surfactant, 10-20 g / L compound antioxidant, 5-20 g / L pH regulator, 0.4-0.8 g / L triethylenetetraaminehexaacetic acid; the pH regulator is composed of methanesulfonic acid, citric acid and EDTA in a mass ratio of (4-6): (0.8-1.6): (0.4-0.6); the pH value of the environmentally friendly acidic tin plating electrolyte is 0.6-0.7; The composite surfactant is composed of alkylphenol polyoxyethylene ether OP-10, polyethylene glycol PEG 300, and polyethylene glycol alkyne with a molecular weight of 1000-2000; the structural formula of the polyethylene glycol alkyne is as follows: ； The mass ratio of the alkylphenol polyoxyethylene ether OP-10, polyethylene glycol PEG 300, and polyethylene glycol alkyne with a molecular weight of 1000-2000 is 8:(1-2):(0.5-1.6); The composite antioxidant is composed of ascorbic acid, catechol and hydroquinone in a mass ratio of (0.1-0.2): (0.8-1.2): (0.8-1.2); The composite brightener is composed of 1-(2-hydroxy-3-sulfopropyl)pyridine betaine salt, hydroxyethyl propargyl ether and super cinnamaldehyde in a mass ratio of (65-80): (10-25): (5-10).

2. The environmentally friendly acidic tin-plating electrolyte according to claim 1, characterized in that: The composite antioxidant is composed of ascorbic acid, catechol and hydroquinone in a mass ratio of 1:5:

4.

3. The environmentally friendly acidic tin-plating electrolyte according to claim 1, characterized in that: The composite brightener is composed of 1-(2-hydroxy-3-sulfopropyl)pyridine amine salt, hydroxyethyl propargyl ether, and super cinnamaldehyde in a mass ratio of 77:15:

8.

4. An environmentally friendly tin-plating process implemented by using the environmentally friendly acidic tin-plating electrolyte according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1, preparation of an environmentally friendly acidic tin-plating electrolyte: first, 100 parts of deionized water and 0.4-0.8 parts of triethylenetetraaminehexaacetic acid are mixed evenly, and then placed in a reactor for boiling treatment for 5-15 minutes, and after boiling, the air in the reactor is replaced by nitrogen, and after the boiling treatment is completed, the temperature is lowered to 0-20° C. and filtered to obtain a water solvent, and accurately measured stannous methanesulfonate, methanesulfonic acid, citric acid, thiourea, sodium hypophosphite, ammonium hypophosphite, compound brightener, compound surfactant, and compound antioxidant are added into the reactor and stirred evenly with the obtained water solvent, and then a pH adjuster is added dropwise to adjust the pH value of the system to 0.6-0.7, so as to obtain an environmentally friendly acidic tin-plating electrolyte; and at the same time, surface treatment is performed on the workpiece to be plated; Step 2: The environmentally friendly acidic tin-plating electrolyte in step 1 is placed in an electrolytic cell, wherein the environmentally friendly acidic tin-plating electrolyte accounts for 60-75% of the volume of the electrolytic cell. A mesh tin sheet is used as an anode, and a workpiece to be plated is used as a cathode. The length directions of the mesh tin sheet and the workpiece to be plated are consistent. A circulating pump is connected to both sides of the electrolytic cell through a pipeline. The circulating pump is used to realize the circulation of the environmentally friendly acidic tin-plating solution and control the flow rate of the environmentally friendly acidic tin-plating solution. The flow direction of the environmentally friendly acidic tin-plating is consistent with the length direction of the mesh tin sheet. The flow rate of the environmentally friendly acidic tin-plating is 0.2-0.6m / s. Conductive fiber cotton is filled in the electrolytic cell, and the conductivity of the conductive fiber cotton is controlled at 0.5-10s / m; the length of the conductive fiber in the conductive fiber cotton is perpendicular to the length directions of the mesh tin sheet and the workpiece to be plated, and the conductive fiber cotton is located between the mesh tin sheet and the workpiece to be plated. The temperature of the environmentally friendly acidic tin-plating electrolyte is 45-50°C, and the current density is controlled to be 3-5A / dm 2 The electroplating time is 3-15 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

5. The environmentally friendly tin plating process according to claim 4, characterized in that: In the step 2, the flow rate of the environmentally friendly acidic tin plating is 0.4-0.5 m / s, the temperature of the environmentally friendly acidic tin plating electrolyte is 50° C., and the current density is controlled to be 4 A / dm 2 The electroplating time is 8-12 minutes, and a dense, smooth and flat tin layer can be plated on the surface of the workpiece to be plated.

Images