阅读说明：本技术 一种厚镀层的长效化学镀锡液以及镀锡方法 (Long-acting chemical tin plating solution for thick plating layer and tin plating method ) 是由 朱祖光 王世雄 于 2020-07-15 设计创作，主要内容包括：本发明属于化学镀技术领域,特别涉及一种厚镀层的长效化学镀锡液以及镀锡方法,包括A液和B液,分别含有以下组分：A液：硫酸亚锡、络合剂、pH调节剂和稳定剂；B液：促进剂、分散剂、pH调节剂、光亮剂和还原剂；使用过程包括S1.配置、S2.添加、S3.预实验、S4.补液、S6.换液五个步骤。本发明的有益效果为：提供了一种能镀厚度层的长效化学镀锡液,其稳定期相较于现有技术大大延长,镀锡速率快,镀锡效果好,并且各组分使用量较低、使用率较高,所以废水排放量较低,对环境十分友好。(The invention belongs to the technical field of chemical plating, and particularly relates to a long-acting chemical tin plating solution for a thick plating layer and a tin plating method, wherein the long-acting chemical tin plating solution comprises a solution A and a solution B, which respectively comprise the following components: solution A: stannous sulfate, complexing agent, pH regulator and stabilizer; and B, liquid B: accelerator, dispersant, pH regulator, brightener and reducer; the using process comprises the five steps of S1. configuration, S2. addition, S3. preliminary experiment, S4. liquid supplement and S6. liquid change. The invention has the beneficial effects that: the long-acting chemical tin plating solution capable of plating the thick layer is provided, the stabilization period is greatly prolonged compared with the prior art, the tin plating speed is high, the tin plating effect is good, the using amount of each component is low, the using rate is high, the discharge amount of waste water is low, and the long-acting chemical tin plating solution is very environment-friendly.)

1. A long-acting chemical tin plating solution for thick plating layers is characterized in that: comprises a solution A and a solution B, which respectively contain the following components:

solution A: the complexing agent at least contains EDTA, and the stannous sulfate is used;

and B, liquid B: the environment-friendly polishing agent comprises an accelerant, a dispersing agent, a pH regulator, a brightening agent and a reducing agent, wherein the accelerant comprises one or more of thiourea and N-monosubstituted derivatives of which the carbon atom number is less than 5, and the reducing agent is sodium hypophosphite;

and 6-10 parts of the solution B is prepared from the solution A in parts by mass.

2. The long-acting electroless tin plating solution for thick plating according to claim 1, wherein: the complexing agent also comprises one or more of citric acid and sodium, potassium and ammonium salts thereof.

3. The long-acting electroless tin plating solution for thick plating according to claim 2, wherein: the content of the EDTA is as follows: 5-20 g/L;

the total content of the citric acid and the sodium, potassium and ammonium salts thereof is calculated in the following way: and calculating equivalent mass volume concentration by converting citrate into equimolar citric acid, wherein the total equivalent mass volume concentration of the citric acid and sodium, potassium and ammonium salts thereof is 20-80 mg/L.

4. The long-acting electroless tin plating solution for thick plating according to claim 1, wherein: the pH regulator is one or more of dilute hydrochloric acid or ammonia water, and is regulated until the pH of the solution A and the pH of the solution B are both below 2.4.

5. The long-acting electroless tin plating solution for thick plating according to claim 1, wherein: the stabilizer comprises one or more of sodium thiosulfate and ascorbic acid, and the content of the stabilizer is respectively

Sodium thiosulfate: 10-50g/L

Ascorbic acid: 0.1-0.5 g/L.

6. The long-acting electroless tin plating solution for thick plating according to claim 1, wherein: the thiourea and the mixture of one or more of the N-monosubstituted derivatives with the carbon atom number less than 5 comprise the following components in percentage by weight: converting the selected reagent into thiourea with equal sulfur atom number by calculating sulfur atom number, and recording as equivalent thiourea, wherein the content of the equivalent thiourea is 50-150 mg/L.

7. The long-acting electroless tin plating solution for thick plating according to claim 1, wherein: the dispersant comprises one or more of fluorocarbon surfactant lauryl sodium sulfate, and the content of the dispersant is as follows:

fluorocarbon surfactant: 0.1-1ml/L

Sodium lauryl sulfate: 1-5 g/L.

8. The long-acting electroless tin plating solution for thick plating according to claim 1, wherein: the brightening agent comprises one or more of gelatin, benzalacetone, sodium fluoride and 1, 4-butynediol, and the content of each is as follows:

gelatin: 0.1-1g/L

Benzylidene acetone: 1-5g/L

Sodium fluoride: 0.5-5g/L

1. 4-butynediol: 1-10 g/L. .

9. A method of plating tin using the long-life electroless tin plating solution for thick plating according to claim 1, characterized by comprising: the method comprises the following steps:

s1, preparation: preparing solution A and solution B according to the components;

s2, adding: mixing A, B liquid in a plating tank according to the proportion that one part of the liquid A is added into 6-10 parts of the liquid B in parts by mass, and rapidly heating to 50 ℃;

s3, pre-experiment: sending the workpieces into the prepared chemical plating solution for continuous chemical plating, recording the chemical plating completion time of each workpiece, simultaneously checking the surface plating layer of each plated workpiece until one workpiece surface plating layer does not meet the requirement, and recording the chemical plating completion time of the previous workpiece, namely the continuous chemical plating period;

s4, tinning: sending the workpiece into a plating tank for tinning;

s5, liquid supplementing: after each continuous chemical plating period, cooling the plating solution to room temperature, pumping the plating solution into another plating tank, removing sediments in the original plating tank, analyzing the proportion of the plating solution pumped into the other plating tank, adding corresponding solution A or solution B, returning the proportion of the stannous sulfate and the accelerator to the proportion configured in the step S1, heating to 50 ℃, continuing to perform the step S4,

s6, liquid changing: when the replenishment is performed at S4, if the component contents of the bath after the calculation of the solution A or the solution B exceed the range defined in claims 1 to 8, the whole bath is discarded and the step S1 is performed again.

10. The long-acting electroless tin plating solution for thick plating according to claim 9, wherein: in the step S2 and the step S4, after the chemical tin plating solution is mixed, sampling is carried out to detect the pH, and dilute sulfuric acid or ammonia water is added to make the pH within 1-2.

Technical Field

The invention belongs to the technical field of chemical plating, and particularly relates to a long-acting chemical tin plating solution for a thick plating layer and a tin plating method.

Background

In recent years, tin-plated layers have been widely used as solderable plating layers in the fields of electronic components and semiconductor packages using copper and copper alloys as a base, and tin-plated layers have also been widely used as protective plating layers for plating the inner surfaces of copper and copper alloy pipes in water supply systems. The use of tin-lead alloy coatings is increasingly restricted due to the increasing pollution caused by lead. The lead-free solderable tin-based alloy plating technology is rarely reported at home and abroad. Therefore, tin plating is still the preferred solderable plating on typical electronic components.

Compared with electroplating, the chemical plating process has good dispersing capacity and deep plating capacity, is not limited by the geometric shape of a workpiece, and can solve certain problems which cannot be solved by electroplating. Whether as a solderable plating or a protective plating, the tin plating requires a certain thickness to satisfy the requirements of brazing performance or corrosion resistance. The patent publication number is 'CN 104746057A', the name is 'an chemical tinning liquid and a preparation method thereof and an chemical tinning method', a tinning liquid and a tinning method using the tinning liquid are provided, the plating thickness is improved and the stability of the chemical plating liquid is improved by using a titanium chloride system and matching with a sulfonic acid promoter, but the stability of the chemical plating liquid prepared by the method is only 6 hours at most, turbidity is generated after the time, the chemical plating effect is influenced, and the industrial continuous production needs are not supported sufficiently.

Disclosure of Invention

The invention aims to provide a long-acting chemical tin plating solution for a thick plating layer and a tin plating method, which have the effects of long-acting stability and large plating layer thickness.

The technical purpose of the invention is realized by the following technical scheme: comprises a solution A and a solution B, which respectively contain the following components:

solution A: stannous sulfate, a complexing agent, a pH regulator and a stabilizer, wherein the complexing agent at least contains EDTA;

and B, liquid B: the environment-friendly polishing agent comprises an accelerant, a dispersing agent, a pH regulator, a brightening agent and a reducing agent, wherein the accelerant comprises one or more of thiourea and N-monosubstituted derivatives of which the carbon atom number is less than 5, and the reducing agent is sodium hypophosphite;

and 6-10 parts of the solution B is prepared from the solution A in parts by mass.

The invention is further provided with: the complexing agent also comprises one or more of citric acid and sodium, potassium and ammonium salts thereof.

The invention is further provided with: the content of the EDTA is as follows: 5-20g/L, and the total content of the citric acid and the sodium, potassium and ammonium salts thereof is calculated in the following way: and calculating equivalent mass volume concentration by converting citrate into equimolar citric acid, wherein the total content of citric acid and sodium, potassium and ammonium salts thereof is 20-80 mg/L.

The invention is further provided with: the pH regulator is one or more of dilute hydrochloric acid or ammonia water, and is regulated until the pH of the solution A and the pH of the solution B are both below 2.4.

The invention is further provided with: the stabilizer comprises one or more of sodium thiosulfate and ascorbic acid, and the content of the stabilizer is respectively

Sodium thiosulfate: 10-50g/L

Ascorbic acid: 0.1-0.5 g/L.

The invention is further provided with: the thiourea and the mixture of one or more of the N-monosubstituted derivatives with the carbon atom number less than 5 comprise the following components in percentage by weight: converting the selected reagent into thiourea with equal sulfur atom number by calculating sulfur atom number, and recording as equivalent thiourea, wherein the content of the equivalent thiourea is 50-150 mg/L.

The invention is further provided with: the dispersant comprises one or more of fluorocarbon surfactant lauryl sodium sulfate, and the content of the dispersant is as follows:

fluorocarbon surfactant: 0.1-1ml/L

Sodium lauryl sulfate: 1-5 g/L.

The invention is further provided with: the brightening agent comprises one or more of gelatin, benzalacetone, sodium fluoride and 1, 4-butynediol, and the content of each is as follows:

gelatin: 0.1-1g/L

Benzylidene acetone: 1-5g/L

Sodium fluoride: 0.5-5g/L

1. 4-butynediol: 1-10 g/L.

The invention is further provided with: a tin plating method of long-acting chemical tin plating solution using thick plating is characterized in that: the method comprises the following steps:

s1, preparation: preparing solution A and solution B according to the components;

s2, adding: mixing A, B liquid in a plating tank according to the proportion that one part of the liquid A is added into 6-10 parts of the liquid B in parts by mass, and rapidly heating to 50 ℃;

s3, pre-experiment: sending the workpieces into the prepared chemical plating solution for continuous chemical plating, recording the chemical plating completion time of each workpiece, simultaneously checking the surface plating layer of each plated workpiece until one workpiece surface plating layer does not meet the requirement, and recording the chemical plating completion time of the previous workpiece, namely the continuous chemical plating period;

s4, tinning: sending the workpiece into a plating tank for tinning;

s5, liquid supplementing: after each continuous chemical plating period, cooling the plating tank to room temperature, pumping the plating solution into another plating tank, removing the sediments in the original plating tank, analyzing the proportion of the plating solution pumped into another plating tank, adding corresponding solution A or solution B to restore the proportion of the stannous sulfate and the accelerator to the proportion configured in the step S1, heating to 50 ℃, continuing to perform the step S4,

s6, liquid changing: when the replenishment is performed at S4, if the component contents of the plating bath after the calculation of the solution A or the solution B exceed the range limited by the above contents, the whole plating bath is discarded and the step S1 is performed again.

By adopting the technical scheme, because the plating solution needs to be chemically plated at a certain temperature, the plating solution per se has transpiration, so that the liquid is reduced and a part of volatile substances in the plating solution are lost; after continuous chemical plating for a period of time, the plating solution needs to be reduced to room temperature, by-products of the chemical plating, such as substances such as complexed copper ions and the like, can be rapidly settled to form sediments which are separated from the plating solution, and then clear liquid is extracted, and most of the by-products can be removed by removing the sediments; the combined action of the transpiration and the sediment removal causes certain loss of the plating solution, so that the plating solution is still in a volume and a state similar to the mixed state of the A, B solution in the step S2 after A, B solution is supplemented, and the plating solution can be continuously produced for a long time without frequent replacement.

The invention is further provided with: after chemical plating is continuously carried out for at least 40h, the plating solution is pumped into another plating tank, the sediment in the original plating tank is removed, the proportion of the plating solution pumped into the other plating tank is analyzed, the corresponding solution A or solution B is supplemented, the proportion of the stannous sulfate and the accelerator is returned to the proportion of the stannous sulfate and the accelerator prepared in the step S1, the temperature is raised to 50 ℃, the step S4 is continued until the content of the components exceeds the range limited by the claims 1 to 8 after the solution A or the solution B is supplemented, and the whole plating solution is discarded and the step S1 is carried out again.

The invention has the beneficial effects that:

1. according to the invention, the compound of EDTA, citrate and thiourea is added, so that copper ions are quickly complexed after being displaced, the displaced copper ions are not easy to form precipitates and are attached to the surface of a plated part to influence the plating effect, and meanwhile, the compound complexing agent also has stable divalent tin ions, so that divalent tin is not easy to be excessively reduced by a reducing agent and oxidized by dissolved oxygen to form tetravalent tin precipitates under the dissolving condition, the turbid failure time of the plating solution can be effectively delayed, in the best embodiment, the solution needs to be cleaned and replenished after long-time chemical plating for about 48 hours, the chemical plating change interval time is greatly prolonged, and the industrial cost of chemical plating tin is greatly reduced.

2. According to the invention, sodium hypophosphite and ascorbic acid jointly form a reducing component, the reducing capacity of ascorbic acid is insufficient, a stannous tin complex cannot be reduced into elemental tin when A, B liquid is not mixed, but the phenomenon that the stannous tin complex is oxidized into tetravalent tin by dissolved oxygen can be effectively avoided, so that the shelf life of the A liquid is greatly prolonged, and after A, B liquid is mixed, the phenomenon that the dissolved oxygen oxidizes sodium hypophosphite can be avoided, so that the effective time of the reaction liquid is greatly prolonged.

3. The fluorocarbon surfactant and the lauryl sodium sulfate are added as surface active ingredients, so that a stronger surface active effect can be obtained with a smaller addition amount, and stannous ions near a plating layer are controlled by matching with the added sodium fluoride and other brightening agents, so that the brightness of the surface of the plating layer is greatly improved.

4. Compared with the stabilization period of 6 hours at the longest in the prior art, the required content range of each added component is lower, but the tin plating speed can reach 3-5 mu m/h, liquid supplement is carried out after continuous 48h plating in the optimal embodiment, and liquid replacement is needed after dozens of times of liquid supplement, namely the scheme greatly reduces the treatment times, treatment amount and treatment difficulty of treating the waste plating solution under the condition of not reducing the quality of a plating layer, and is more environment-friendly.

Detailed Description

The technical solutions in the examples will be clearly and completely described below.