阅读说明：本技术 一种不含铅的环保化学镍溶液及使用其的化学镀镍工艺 (Lead-free environment-friendly chemical nickel solution and chemical nickel plating process using same ) 是由 林小华 于 2021-09-16 设计创作，主要内容包括：本申请涉及化学镀镍领域,涉及一种不含铅的环保化学镍溶液及使用其的化学镀镍工艺,不含铅的环保化学镍溶液包括以下重量份的原料混合而成：硫酸镍35-40份、还原剂10-15份、络合剂5-9份、2.857mol/L氨水12-18份、铜盐0.59-3.03份和水235-320份；在镀液中加入铜盐,铜离子被转化后附着在新生的镀层表面,继续催化镍还原,在镀层厚和长时间沉积的情况下,依旧有较高的镀层沉积速率,且铜晶粒与镍离子直接置换反应,使镀层中减小掺杂铜,保证镀层性能稳定,镀液中不含铅,减小对环境的污染；使用本申请不含铅的环保化学镍溶液进行的化学镀镍工艺,制件表面的镀层沉积速率快,对厚镀层制件加工效率高。(The application relates to the field of chemical nickel plating, and relates to a lead-free environment-friendly chemical nickel solution and a chemical nickel plating process using the same, wherein the lead-free environment-friendly chemical nickel solution is formed by mixing the following raw materials in parts by weight: 35-40 parts of nickel sulfate, 10-15 parts of reducing agent, 5-9 parts of complexing agent, 12-18 parts of 2.857mol/L ammonia water, 0.59-3.03 parts of copper salt and 320 parts of 235-containing water; copper salt is added into the plating solution, copper ions are attached to the surface of a newly-generated plating layer after being converted, nickel reduction is continuously catalyzed, the deposition rate of the plating layer is still higher under the conditions of thick plating layer and long-time deposition, and copper crystal grains and nickel ions are directly subjected to displacement reaction, so that doped copper in the plating layer is reduced, the performance stability of the plating layer is ensured, lead is not contained in the plating solution, and the pollution to the environment is reduced; by the chemical nickel plating process using the lead-free environment-friendly chemical nickel solution, the deposition rate of the plating layer on the surface of the workpiece is high, and the processing efficiency of the workpiece with the thick plating layer is high.)

1. The lead-free environment-friendly chemical nickel solution is characterized by being prepared by mixing the following raw materials in parts by weight:

35-40 parts of nickel sulfate;

10-15 parts of a reducing agent, wherein the reducing agent is one of sodium hypophosphite, potassium hypophosphite or sodium borohydride;

5-9 parts of a complexing agent, wherein the complexing agent is one of sodium citrate, lactic acid or malic acid;

12-18 parts of 2.857mol/L ammonia water;

0.59-3.03 parts of copper salt;

320 portions of 235 portions of water.

2. The lead-free environment-friendly chemical nickel solution as claimed in claim 1, wherein: the molar ratio of the ionic copper to the ionic nickel in the chemical nickel solution is (1.26-3.68): 100.

3. The lead-free environment-friendly chemical nickel solution as claimed in claim 1, wherein: the copper salt is copper ammonia salt.

4. The lead-free environment-friendly chemical nickel solution as claimed in claim 3, wherein: the copper ammonia salt is copper tetraammine sulfate.

5. The lead-free environment-friendly chemical nickel solution as claimed in claim 4, wherein: the weight portion of the copper tetraammine sulfate is 1.53-3.03 portions.

6. The lead-free environment-friendly chemical nickel solution as claimed in claim 1, wherein: the copper salt is copper acetate.

7. The lead-free environment-friendly chemical nickel solution as claimed in claim 5, wherein: the weight portion of the copper acetate is 0.59-1.73.

8. The lead-free environmentally friendly chemical nickel solution as claimed in claim 7, wherein: the nickel plating temperature of the chemical nickel solution is 80-85 ℃.

9. The chemical nickel plating process is characterized by comprising the following steps:

degreasing, washing, activating, washing, chemical plating, washing and heat treatment are carried out on the workpiece;

the plating solution used in the electroless plating is the environment-friendly chemical nickel solution as claimed in any one of claims 1 to 8.

Technical Field

The application relates to the field of chemical nickel plating, in particular to a lead-free environment-friendly chemical nickel solution and a chemical nickel plating process using the same.

Background

The surface of the circuit board is usually protected by nickel plating, and the chemical nickel plating method is mostly adopted at present.

The chemical nickel plating uses nickel sulfate, nickel acetate and the like as main salts, hypophosphite, sodium borohydride, borane, hydrazine and the like as reducing agents, various auxiliary agents are added to prepare plating solution, the workpiece is pretreated firstly, then the workpiece is immersed in the plating solution and is changed under certain alkalinity and temperature, nickel ions in the solution and the sodium hypophosphite undergo redox reaction, and generated nickel atoms are deposited on the surface of the workpiece to form a fine and bright nickel plating layer.

In view of the above-mentioned related technologies, when a plating layer is formed on a surface of a workpiece, nickel ions near the surface of the workpiece are replaced to form nickel atoms to be deposited on the surface of the workpiece, the concentration of the nickel ions near the workpiece is reduced, although the concentration of the nickel ions in a solution at a far position of the workpiece is higher, the moving speed of the nickel ions in the solution is limited, and the concentration of the nickel ions near the workpiece and the concentration of the nickel ions in solutions at other positions are continuously different, so that the deposition rate of the nickel atoms on the surface of the workpiece is reduced, and meanwhile, the plating layer on the surface of the workpiece is continuously extended and thickened, active catalytic sites obtained after the surface pretreatment of the workpiece are continuously covered by the plating layer, the catalytic effect is reduced, and the deposition rate of the plating layer is also reduced.

In summary, in the conventional electroless nickel plating process, the plating deposition rate decreases with the increase of the plating deposition time and the plating deposition thickness, and the production efficiency based on the same unit plating thickness is low for obtaining a thinner plating layer with a thicker plating layer.

Disclosure of Invention

In order to increase the deposition rate of a plating layer on the surface of a workpiece, the application provides a lead-free environment-friendly chemical nickel solution and an electroless nickel plating process using the same.

In a first aspect, the application provides a lead-free environment-friendly chemical nickel solution, which is realized by adopting the following technical scheme: the lead-free environment-friendly chemical nickel solution is prepared by mixing the following raw materials in parts by weight: 35-40 parts of nickel sulfate; 10-15 parts of a reducing agent, wherein the reducing agent is one of sodium hypophosphite, potassium hypophosphite or sodium borohydride; 5-9 parts of a complexing agent, wherein the complexing agent is one of sodium citrate, lactic acid or malic acid; 12-18 parts of 2.857mol/L ammonia water; 0.59-3.03 parts of copper salt; 320 portions of 235 portions of water.

By adopting the technical scheme, when the chemical nickel solution is used, a workpiece is immersed in the chemical nickel solution, the nickel in the complex state is reduced by the reducing agent under the action of the catalytic activity surface obtained by surface treatment of the workpiece and covers the catalytic activity surface, and the concentration of the nickel near the surface of the workpiece is reduced along with the deposition process of the coating.

When the nickel concentration is reduced below the threshold value, the reaction product constant of copper reduction is larger than that of nickel reduction, and at the moment, copper ions begin to be reduced into copper atoms, and meanwhile, the copper ion concentration is specially adjusted in the application, so that the copper atoms are scattered and attached to the surface of a new nickel layer in the form of grains. The method has the advantages that a new catalytic active site is formed after copper crystal grains are generated, the catalytic active site is linked and covered on a catalytic active surface which cannot be catalyzed continuously, nickel is reduced continuously by a reducing agent, and the deposition speed of a nickel coating is ensured under the condition of low concentration or untimely ion migration, so that the higher deposition rate of the coating is still kept under the process requirements of thick coating thickness and long-time coating deposition, and the method has the advantages of no triggering under the early-stage high coating deposition rate, low local nickel concentration or automatic triggering of later-stage coating deposition because the method takes nickel concentration as a trigger point.

Moreover, the copper crystal grains are small and distributed and dispersed, and the copper crystal grains can directly perform a displacement reaction with nickel ions, so that the nickel deposition is accelerated, the doping of copper into the coating is reduced, and the stable performance of the coating is ensured.

And the mixed raw materials in the chemical nickel plating solution do not contain lead, so that the plating layer on the surface of the workpiece does not contain lead, the pollution of the chemical nickel plating solution to the environment can be reduced, and the environment-friendly effect is achieved.

To sum up, the chemical nickel plating solution of this application provides high cladding material deposition efficiency and maintains the stable effect of cladding material performance to thick cladding material thickness and the sedimentary technology demand of long-time cladding material, and does not contain lead in the chemical nickel plating solution, can reduce the pollution to the environment.

Optionally, the molar ratio of the ionic copper to the ionic nickel in the chemical nickel solution is (1.26-3.68): 100.

By adopting the technical scheme, the molar ratio of the ionic copper to the ionic nickel in the chemical nickel solution is an important factor influencing the site for starting the catalytic action by reduction, the molar ratio of the ionic copper to the ionic nickel in the chemical nickel solution is too small, the nickel concentration is too low when the site is activated, the catalytic benefit is poor or the ionic copper is replaced by nickel too quickly, and the catalytic effect is poor; the molar ratio of the ionic copper to the ionic nickel in the chemical nickel solution is too large, the amount of copper atoms mixed into the plating layer is too large, and the plating performance is deviated.

The mole ratio of the ionic copper to the ionic nickel in the electroless nickel solution is (1.26-3.68):100 is the preferred embodiment.

Optionally, the copper salt is a copper ammonia salt.

Optionally, the copper ammonium salt is copper tetraammine sulfate.

Optionally, the weight part of the copper tetraammine sulfate is 1.53-3.03 parts.

By adopting the technical scheme, in the chemical nickel plating solution, the copper ammonium salt reacts with the reducing agent to generate the ammonia ions, and the ammonia ions react with the nickel to promote the complexation of the nickel ions, so that the catalytic reduction of the nickel is promoted, and the deposition rate of nickel atoms is accelerated.

Meanwhile, the copper tetrammine sulfate has a good effect, and other anions are prevented from being introduced.

And the scheme that the weight part of the copper tetraammine sulfate is 1.53-3.03 parts is preferably adopted.

Optionally, the copper salt is copper acetate.

Optionally, the weight part of the copper acetate is 0.59-1.73.

By adopting the technical scheme, the copper acetate reacts with hydrogen ions in the chemical nickel plating solution, the pH value is increased, an alkaline environment is provided for the chemical nickel solution, and the possibility of reducing the deposition rate of the plating layer due to the hydrogen ions is further reduced.

And the scheme that the weight part of copper acetate is 0.59-1.73 parts is preferred.

Optionally, the nickel plating temperature of the chemical nickel solution is 80-85 ℃.

By adopting the technical scheme, the activity of copper ammonia ions is higher within the temperature of 80-85 ℃, and the copper ammonia ions are easy to react with other substances.

In a second aspect, the present application provides the above chemical nickel plating process using the environmentally friendly chemical nickel solution, which adopts the following technical scheme:

the chemical nickel plating process comprises the following steps: degreasing, washing, activating, washing, chemical plating, washing and heat treatment are carried out on the workpiece;

the plating solution used in the chemical plating is the environment-friendly chemical nickel solution.

By adopting the technical scheme, after the workpiece is subjected to degreasing, washing, activation, washing, chemical plating, washing and heat treatment, stains and oxidation films on the surface of the workpiece are removed, the hydrophilicity and the uniformity of the surface of the workpiece are improved, the selectivity of a plating solution on the workpiece is increased, a plating layer is chemically plated on the workpiece, and finally the workpiece is subjected to heat treatment; in the process of plating the workpiece, the deposition rate of the plating layer on the surface of the workpiece is high, and the processing efficiency of the workpiece with the thick plating layer is high.

In summary, the present application includes at least one of the following beneficial technical effects:

1. copper salt is added into the plating solution, copper ions are converted and then attached to the surface of a newly-generated nickel plating layer in a crystal grain form, nickel is continuously catalyzed to be reduced by a reducing agent, under the conditions of thick plating layer thickness and long-time plating layer deposition, higher plating layer deposition rate is still kept, and copper crystal grains can directly perform replacement reaction with nickel ions, so that the doping of copper in the plating layer is reduced, the performance stability of the plating layer is ensured, and the chemical nickel plating solution does not contain lead element, so that the pollution to the environment can be reduced;

2. the mole ratio of the ionic copper to the ionic nickel in the chemical nickel solution is (1.26-3.68):100, so that the poor catalytic effect caused by small mole ratio can be reduced, and the possibility of deviation of the coating performance caused by large mole ratio can be reduced;

3. through the chemical nickel plating process using the environment-friendly chemical nickel solution, the deposition rate of the plating layer on the surface of the workpiece is high, and the processing efficiency of the workpiece with the thick plating layer is high.

Detailed Description

Example 1

The lead-free environment-friendly chemical nickel solution is prepared by mixing the following raw materials in parts by weight:

35kg of nickel sulfate;

10kg of reducing agent, wherein the reducing agent is sodium hypophosphite;

5kg of complexing agent, wherein the complexing agent is sodium citrate;

12kg of 2.857mol/L ammonia water;

0.59kg of copper salt, wherein the copper salt is copper tetraammine sulfate;

235kg of water.

The preparation method of the environment-friendly chemical nickel solution is as follows,

s1: mixing nickel sulfate, sodium hypophosphite, sodium citrate, 2.857mol/L ammonia water, copper tetraammine sulfate and water according to weight percentage, and obtaining the environment-friendly chemical nickel solution after uniformly mixing.

The chemical nickel process of the environment-friendly chemical nickel solution provided by the embodiment 1 is as follows:

before chemical plating, a workpiece is pretreated, and the workpiece is cleaned and degreased;

then washing the workpiece with clear water, and immersing the washed workpiece into a palladium chloride solution of 0.1g/L for activation for 5 s;

then washing the workpiece with clear water, putting the washed workpiece into a prepared environment-friendly chemical nickel solution, treating at 82 ℃ for 14min, and taking out the workpiece after 14 min;

finally, the processed workpiece is washed by clean water, and the workpiece is thermally treated by heat, so that the workpiece is dried.

Examples 2 to 5

An environmentally friendly chemical nickel solution containing no lead was different from example 1 in the ratio of the amount of raw materials and the temperature at which the article was plated.

The ratios of the amounts of the raw materials used and the temperatures at which the articles were plated in examples 1 to 5 are shown in Table 1.

TABLE 1 raw material ratio and plating temperature for examples 1 to 5

The raw materials used in examples 1 to 5 of the present application and in the following examples are used in a proportion of the amount of the non-crystallization water, i.e., the amount is not counted by the quality of the crystallization water.

Examples 6 to 13

A lead-free, environmentally friendly chemical nickel solution which differs from example 1 in that a different reducing agent or complexing agent is used.

The ratios of the used raw materials and the temperatures at which the articles were plated in examples 6 to 13 are shown in Table 2.

TABLE 2 raw material ratio and plating temperature for examples 6 to 13

Example 14

In contrast to example 5, the temperature for plating the article was 86.7 ℃.

Example 15

In contrast to example 5, the temperature for plating the article was 76 ℃.

Example 16

In contrast to example 5, the amount of copper tetraammine sulfate used in the starting material was 1.32 kg.

Example 17

In contrast to example 5, the amount of copper tetraammine sulfate used in the feed was 3.45 kg.

Example 18

In contrast to example 5, the amount of the cuprammonium salt in the raw material was changed to the amount of cuprammonium chloride or the like.

Example 19

In contrast to example 5, the amount of copper salt in the raw material was changed to copper tetraammine sulfate by the amount of copper acetate or the like.

Example 20

In contrast to example 19, copper acetate was used in an amount of 1.46 kg.

Example 21

In contrast to example 20, copper acetate was used in an amount of 0.59 kg.

Example 22

In contrast to example 21, copper acetate was used in an amount of 0.29 kg.

Example 23

In contrast to example 21, copper acetate was used in an amount of 1.82 kg.

Example 24

Unlike example 21, the reducing agent replaced sodium hypophosphite with the amount of potassium hypophosphite or the like.

Example 25

Unlike example 24, the reducing agent was used in an amount of sodium borohydride or the like instead of potassium hypophosphite.

Example 26

Unlike example 21, the complexing agent replaced sodium citrate with the amount of lactic acid or the like.

Example 27

Unlike example 26, the reducing agent replaced sodium hypophosphite with the amount of potassium hypophosphite or the like.

Example 28

Unlike example 27, the reducing agent was used in an amount of sodium borohydride or the like instead of potassium hypophosphite.

Example 29

Unlike example 26, the complexing agent replaced lactic acid with the amount of malic acid or the like.

Example 30

Unlike example 29, the reducing agent replaced sodium hypophosphite with the amount of potassium hypophosphite or the like.

Example 31

Unlike example 30, the reducing agent was used in an amount of sodium borohydride or the like instead of potassium hypophosphite.

Comparative example

Comparative example 1

An environmentally friendly chemical nickel solution free of lead, which differs from example 1 in that copper salts are not included in the starting materials.

S1: mixing nickel sulfate, sodium hypophosphite, sodium citrate, 2.857mol/L ammonia water and water according to weight, and uniformly mixing to obtain the environment-friendly chemical nickel solution.

Performance detection

The following performance tests were performed for the plating baths of examples 1 to 31 of the present application and comparative example 1.

In each case, 50 workpiece samples with the specification of 2mm 20mm 100mm are selected, after the 50 workpiece samples are pretreated, the workpiece samples are placed in a prepared plating solution, the deposition time of a plating layer is 2 hours, after the time is reached, the workpiece is taken out, then the workpiece is washed by clean water, and finally the workpiece is dried.

And randomly selecting 10 points on each processed part, detecting the thickness of the coating, and expressing the test result by the average thickness of the coating.

The test results of examples 1-31 and comparative example 1 are shown below.

TABLE 3 coating thickness detection data sheet

The present application is described in detail below with reference to the test data provided in table 3.

Examples 1-5 compared to comparative example 1 the effect of copper salts was examined. As a result, it was found that in examples 1 to 5, since the average thickness of the plating layer of the plated article was larger than that of the plated article in comparative example 1 by adding the copper salt, the copper salt added in the present application can increase the deposition rate of the plating layer.

In addition to examples 1-5, there were other experimental groups during the development of this application, where example 5 was the relatively superior group of all experimental groups and was taken out separately.

The effect of different reducing or complexing agents in amounts of these substances on the coating thickness of the articles was examined in examples 6-13. As a result, compared with example 5, the average thicknesses of the coatings of the articles of examples 6 to 13 and example 5 are similar, and the combination of the reducing agent and the complexing agent can ensure the effect of improving the deposition rate of the copper salt coating.

In examples 14 and 15, the influence of the plating deposition temperature was examined. As a result, it was found that the temperature of example 14 was higher than that of example 5, and the average thickness of the plating layer of example 14 was smaller than that of example 5; the temperature of example 15 is lower than that of example 5, and the average thickness of the plating layer of example 15 is smaller than that of example 5, so when the copper salt is copper ammonia salt in the application, the plating temperature is preferably 82 ℃.

In examples 16 and 17, the influence of the weight part of copper tetraammine sulfate was examined. As a result, it was found that the amount of example 16 used was small as compared with example 5, and the average thickness of the plating layer of example 16 was small as compared with example 5; the amount of the embodiment 17 is larger than that of the embodiment 5, the average thickness of the plating layer of the embodiment 17 is larger than that of the embodiment 5, but after the detection of the plating layer composition, the content of copper element in the plating layer of the embodiment 5 is 12 ppm; the coating of example 17, which contains 1508ppm of Cu, adversely affects the coating properties and reduces the coating life compared to example 5. Therefore, the dosage of the copper tetrammine sulfate in the application is preferably 1.53-3.03 kg.

The effect of using different cuprammonium salts was examined in example 18. As a result, it was found that in example 18, when copper ammonium chloride was used in an amount equivalent to that of the copper ammonium salt, the average thickness of the plated layer was 30.2 μm, and the average thickness of the plated layer was smaller than that of example 5, so that copper tetraammine sulfate was preferable as the copper ammonium salt of the present invention.

The effect of using copper acetate and the amount of copper acetate for the copper salt was examined in examples 19-23. As a result, it was found that:

the dosage of the copper acetate is from 0.2kg to 1.82kg, and the thickness of the plating layer increases along with the dosage, namely, the deposition rate of the plating layer increases along with the dosage of the copper acetate. Wherein when the amount is less than 0.59kg (example 22), the deposition rate of the coating is similar to that of the comparative example 1; when the amount is more than 1.73kg (example 24), the deposition rate of the plating layer is faster, but the content of copper element in the plating layer of example 22 is 752ppm, which is detected to affect the performance of the plating layer, and the plating rate is improved with the increase of the concentration, which is not as good as that of copper sulfate and tetramine, so the amount of copper acetate used as copper salt in the application is preferably 0.59-1.73 kg.

With reference to example 5, example 16, example 17, and examples 19-23, the amount of copper-nickel species in the plating solution is as follows:

TABLE 4 quantitative ratio of Cu/Ni species in plating solution

Therefore, the copper salt in the application ensures that the plating layer has stable performance and better effect of promoting the deposition rate of the plating layer, and the quantity ratio of the copper-nickel substance in the plating solution is (1.26-3.68):100 is better.

Examples 24 to 31 have examined that, in the case of copper acetate containing copper salt in an equal amount, the average thickness of the plating layer is similar when reducing agents or complexing agents in different amounts are used, and the combination of the reducing agents and the complexing agents can ensure the effect of increasing the deposition rate of the copper salt plating layer.

After the above-described test methods were carried out for examples 1 to 31, the results showed that the average thickness of the plated layer of the fabricated article was 25.54 to 38.7 μm and the deposition rate of the plated layer was 12.77 to 19.35. mu.m/h.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.