Electroless nickel plating solution and preparation method thereof

Abstract

The application belongs to the technical field of electroless nickel plating and particularly relates to an electroless nickel plating solution and a preparation method thereof. Raw materials of the electroless nickel plating solution include: 30-50 parts of a nickel source, 20-40 parts of a reducing agent, 10-20 parts of a complexing agent, 3-10 parts of a pH buffer, 5-10 parts of a thiourea stabilizer, 0.5-2 parts of a bipyridine ionic liquid surfactant and 1000 parts of deionized water. The electroless nickel plating solution has the advantages of fast plating speed, dense and uniform plating layer, good wear resistance and salt resistance and the like.

Description

Technical Field

[0001] This invention belongs to the field of electroless nickel plating technology, specifically relating to an electroless nickel plating solution and its preparation method. Background Technology

[0002] Electroless plating, also known as autocatalytic plating, is a process in which metal ions in a plating bath are reduced and deposited onto the substrate without an external current, aided by a reducing agent. The resulting metal coating is continuous, and the metal itself possesses catalytic capabilities. Electroless plating uses the metal already reduced and deposited on the substrate surface as new catalytic active sites, allowing the reaction to continue on the deposited metal surface, resulting in a continuous metal coating. Electroless nickel plating technology has developed rapidly. Initially, the purpose of researching electroless nickel plating was to solve certain problems that electroplating could not achieve, using it as a substitute for electroplating. Later, with in-depth research and increasing demand, many other functional coatings for various applications were gradually developed, such as corrosion resistance, wear resistance, coating uniformity, and electromagnetic shielding. Electroless nickel plating also features zero emissions and is suitable for plating complex parts made of various materials (including non-metallic materials). It has been widely used in aerospace, petrochemical, electronics, transportation, and IT industries.

[0003] To obtain a high-performance electroless nickel plating layer, additives (including buffers, surfactants, brighteners, complexing agents, etc.) are essential. Surfactants play a significant role in the electroless plating process. Appropriate surfactants are typically selected in electroless plating surface treatment technologies to increase the reaction rate, improve coating uniformity, and maintain the stability of the plating solution. Widely used surfactants include dodecyl sulfate, dodecyl sulfonate, polyethylene glycol, and OP-10. Furthermore, electroless nickel plating solutions are thermodynamically unstable systems, often containing particles such as colloidal particles and solid impurities. Without stabilizers, nickel ions react with these particles, leading to significant nickel ion consumption. When the amount of particles in the plating solution is high, it can even cause spontaneous decomposition of the plating solution.

[0004] Compared to electroplating, electroless nickel plating has a slower plating rate. Furthermore, the electroless nickel plating solution used in electroless plating has poor stability, leading to uneven coating quality and even defects during the plating process, which limits its application in large-scale production. In recent years, with advancements in materials science and chemical engineering technology, researchers have focused on developing novel electroless nickel plating solution formulations to improve the overall performance of the plating solution. These methods mainly include optimizing the type and concentration of nickel salts, introducing highly efficient corrosion inhibitors and complexing agents, selecting novel environmentally friendly stabilizers, and adding surfactants with specific functions. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a chemical nickel plating solution and its preparation method, thereby solving problems such as slow nickel plating rate and poor coating quality. To achieve the above objective, this invention adopts the following technical solution: A chemical nickel plating solution, by weight, comprises the following raw materials: 30-50 parts nickel source, 20-40 parts reducing agent, 10-20 parts complexing agent, 3-10 parts pH buffer, 5-10 parts thiourea stabilizer, 0.5-2 parts bispyridine ionic liquid surfactant, and 1000 parts deionized water. The structural formula of the bispyridine ionic liquid surfactant is: or ; The structural formula of the thiourea stabilizer is: .

[0006] In some embodiments, the nickel source is selected from one or more of nickel sulfate, nickel chloride, nickel carbonate, nickel hypophosphite, nickel methanesulfonate, nickel acetate, nickel nitrate, and nickel aminosulfonate.

[0007] In some embodiments, the reducing agent is selected from one or more of sodium hypophosphite, sodium hypophosphite, potassium hypophosphite, sodium formaldehyde bisulfite, sodium borohydride, ascorbic acid, dimethylamine borane, and formaldehyde.

[0008] In some embodiments, the complexing agent is selected from one or more of succinic acid, citric acid, sodium citrate, lactic acid, malic acid, glycine, tetrasodium ethylenediaminetetraacetic acid, and ethylenediaminetetraacetic acid.

[0009] In some embodiments, the pH buffer is selected from one or more of glacial acetic acid, sodium acetate, sodium succinate, and sodium citrate.

[0010] In some implementation schemes, the raw materials, by weight, include: 40 parts nickel sulfate (nickel source), 25 parts sodium hypophosphite (reducing agent), 15 parts citric acid (complexing agent), 5 parts sodium acetate (pH buffer), 10 parts thiourea stabilizer, 2 parts bispyridine ionic liquid surfactant, and 1000 parts deionized water.

[0011] In some implementation schemes, the raw materials, by weight, include: 50 parts nickel chloride (nickel source), 20 parts sodium hypophosphite (reducing agent), 10 parts lactic acid (complexing agent), 7 parts sodium acetate (pH buffer), 8 parts thiourea stabilizer, 1.5 parts bispyridine ionic liquid surfactant, and 1000 parts deionized water.

[0012] In some implementation schemes, the raw materials, by weight, include: 35 parts nickel aminosulfonate (nickel source), 20 parts sodium hypophosphite (reducing agent), 20 parts malic acid (complexing agent), 8 parts sodium succinate (pH buffer), 6 parts thiourea stabilizer, 2 parts bispyridine ionic liquid surfactant, and 1000 parts deionized water.

[0013] The present invention also provides a method for preparing the above-mentioned electroless nickel plating solution, comprising the following steps: Add nickel source, reducing agent, complexing agent, pH buffer, thiourea stabilizer, bispyridine ionic liquid surfactant, and deionized water to the reactor according to the specified weight parts, stir well, and then adjust the pH value to 5.0 with sulfuric acid to obtain the electroless nickel plating solution. Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The electroless nickel plating solution of the present invention has the properties of fast nickel plating speed, dense and uniform nickel plating layer, good wear resistance and salt resistance.

[0014] 2) The thiourea stabilizer used in this invention It can efficiently adsorb microparticles, inhibit the interaction between microparticles and nickel ions, prevent spontaneous decomposition of electroless nickel plating solution, improve the stability of plating solution, accelerate the nickel plating rate, and obtain a bright and uniform coating.

[0015] 3) The bispyridine ionic liquid surfactant used in this invention has a stronger wetting effect than sodium dodecyl sulfonate commonly used in the field. It can make the nickel plating solution fully contact the metal to be plated, and make the generated bubbles escape quickly, thereby reducing the plating defects caused by bubbles and improving the nickel plating rate and the uniformity and wear resistance of the nickel plating layer. Detailed Implementation

[0016] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0017] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0018] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments of the present invention are obtained through conventional commercial means.

[0019] Example 1 A chemical nickel plating solution, by weight, comprises the following raw materials: 40 parts nickel sulfate (nickel source), 25 parts sodium hypophosphite (reducing agent), 15 parts citric acid (complexing agent), 5 parts sodium acetate (pH buffer), and thiourea stabilizer. 10 parts, bispyridine ionic liquid surfactant 2 portions, 1000 portions of deionized water.

[0020] The preparation method of the above-mentioned electroless nickel plating solution includes the following steps: Add nickel source, reducing agent, complexing agent, pH buffer, thiourea stabilizer, bispyridine ionic liquid surfactant and deionized water to the reactor according to the weight parts, stir evenly, and then adjust the pH value to 5.0 with sulfuric acid to obtain electroless nickel plating solution.

[0021] Example 2 A chemical nickel plating solution, by weight, comprises the following raw materials: 50 parts nickel chloride (nickel source), 20 parts sodium hypophosphite (reducing agent), 10 parts lactic acid (complexing agent), 7 parts sodium acetate (pH buffer), and thiourea stabilizer. 8 parts, bispyridine ionic liquid surfactant 1.5 parts, 1000 parts deionized water.

[0022] The preparation method of the above-mentioned electroless nickel plating solution includes the following steps: Add nickel source, reducing agent, complexing agent, pH buffer, thiourea stabilizer, bispyridine ionic liquid surfactant and deionized water to the reactor according to the weight ratio, stir evenly, and then adjust the pH value to 4.5 with sulfuric acid to obtain electroless nickel plating solution.

[0023] Example 3 A chemical nickel plating solution, by weight, comprises the following raw materials: 35 parts nickel aminosulfonate (nickel source), 20 parts sodium hypophosphite (reducing agent), 20 parts malic acid (complexing agent), 8 parts sodium succinate (pH buffer), and thiourea stabilizer. 6 parts, bispyridine ionic liquid surfactant 2 portions, 1000 portions of deionized water.

[0024] The preparation method of the above-mentioned electroless nickel plating solution includes the following steps: Add nickel source, reducing agent, complexing agent, pH buffer, thiourea stabilizer, bispyridine ionic liquid surfactant and deionized water to the reactor according to the weight parts, stir evenly, and then adjust the pH value to 4.0 with sulfuric acid to obtain electroless nickel plating solution.

[0025] Comparative Example 1 Based on Example 1, thiourea stabilizer was added. The common stabilizer 2,4-dithiobiuret was replaced, and other operations and conditions were the same as in Example 1.

[0026] Comparative Example 2 Based on Example 1, a bispyridine ionic liquid surfactant was used. The sodium dodecyl sulfonate was substituted, and other operations and conditions were the same as in Example 1.

[0027] Comparative Example 3 Based on Example 1, a bispyridine ionic liquid surfactant was used. Replace with Other operations and conditions are the same as in Example 1.

[0028] Performance testing The nickel plating process steps adopted in this invention are as follows: grinding of magnesium alloy sample---deionized water cleaning---ultrasonic cleaning---alkaline washing (ammonia water)---deionized water cleaning---one-step acid washing activation (10% H2SO4 solution)---deionized water rinsing---nickel plating in chemical nickel plating solution to form Ni-P coating (temperature is 80℃).

[0029] Nickel plating rate: Nickel plating was continuously performed in the electroless nickel plating solution for 1 hour, and then the coating thickness was measured at 5-8 points using an X-ray fluorescence spectrometer (XRF). The average value was taken, and the unit was μm / h.

[0030] Visual inspection: Observe whether the nickel plating layer is bright and whether the brightness is uniform.

[0031] Salt spray test: Conducted according to GB / T2423.17-93, the standard for medium-sized salt spray test (NSS). Conditions: 5% sodium chloride solution, pH between 6.5 and 7.2, continuous atomization, temperature maintained at 35℃, and salt spray deposition rate maintained at 1.5 mL / (h·80 cm). 2 Observe whether there are any peeling, cracking, wrinkling, or bubbles.

[0032] Hardness Testing: The hardness of the Ni-P coating was measured using an HVS-1000A microhardness tester. The load was 100g, and the loading time was 20s. Five tests were performed on each sample, and the average value was taken. The microhardness value was calculated using the following formula: HV = 1854.4P / d 2 ; d = NV; where HV is the microhardness value of the Ni-P coating; P is the load; d is the diagonal length of the indentation; N is the diagonal length in the eyepiece; V is the magnification of the objective lens. The results are shown in Table 1.

[0033] Therefore, the electroless nickel plating solution prepared by this invention has the properties of fast nickel plating speed, dense and uniform nickel plating layer, and good wear resistance and salt resistance. On the one hand, because the electroless nickel plating solution contains particles such as colloidal particles and solid impurities, these particles have high surface activity, while the thiourea stabilizer used in this invention... It can efficiently adsorb microparticles, inhibit the interaction between microparticles and nickel ions, avoid spontaneous decomposition of the electroless nickel plating solution, improve the stability of the plating solution, accelerate the nickel plating rate, and obtain a bright and uniform coating. On the other hand, the bispyridine ionic liquid surfactant used in this invention has a stronger wetting effect than sodium dodecyl sulfonate commonly used in the field, enabling the nickel plating solution to fully contact the metal to be plated, allowing generated bubbles to escape quickly, thereby reducing coating defects caused by bubbles, and improving the nickel plating rate and the uniformity and wear resistance of the nickel plating layer.

[0034] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A chemical nickel plating solution, comprising, by weight, the following raw materials: 30-50 parts nickel source, 20-40 parts reducing agent, 10-20 parts complexing agent, 3-10 parts pH buffer, 5-10 parts thiourea stabilizer, 0.5-2 parts bispyridine ionic liquid surfactant, and 1000 parts deionized water; The structural formula of the bispyridine ionic liquid surfactant is: or ; The structural formula of the thiourea stabilizer is: .

2. The electroless nickel plating solution according to claim 1, characterized in that, The nickel source is selected from one or more of nickel sulfate, nickel chloride, nickel carbonate, nickel hypophosphite, nickel methanesulfonate, nickel acetate, nickel nitrate, and nickel aminosulfonate.

3. The electroless nickel plating solution according to claim 1, characterized in that, The reducing agent is selected from one or more of sodium hypophosphite, sodium hypophosphite, potassium hypophosphite, sodium formaldehyde bisulfite, sodium borohydride, ascorbic acid, dimethylamine borane, and formaldehyde.

4. The electroless nickel plating solution according to claim 1, characterized in that, The complexing agent is selected from one or more of succinic acid, citric acid, sodium citrate, lactic acid, malic acid, glycine, tetrasodium ethylenediaminetetraacetic acid, and ethylenediaminetetraacetic acid.

5. The electroless nickel plating solution according to claim 1, characterized in that, The pH buffer is selected from one or more of glacial acetic acid, sodium acetate, sodium succinate, and sodium citrate.

6. The electroless nickel plating solution according to claim 1, characterized in that, The raw materials, calculated by weight, include: 40 parts nickel sulfate (nickel source), 25 parts sodium hypophosphite (reducing agent), 15 parts citric acid (complexing agent), 5 parts sodium acetate (pH buffer), 10 parts thiourea stabilizer, 2 parts bispyridine ionic liquid surfactant, and 1000 parts deionized water.

7. The electroless nickel plating solution according to claim 1, characterized in that, The raw materials, calculated by weight, include: 50 parts nickel chloride (nickel source), 20 parts sodium hypophosphite (reducing agent), 10 parts lactic acid (complexing agent), 7 parts sodium acetate (pH buffer), 8 parts thiourea stabilizer, 1.5 parts bispyridine ionic liquid surfactant, and 1000 parts deionized water.

8. The electroless nickel plating solution according to claim 1, characterized in that, The raw materials, calculated by weight, include: 35 parts nickel aminosulfonate (nickel source), 20 parts sodium hypophosphite (reducing agent), 20 parts malic acid (complexing agent), 8 parts sodium succinate (pH buffer), 6 parts thiourea stabilizer, 2 parts bispyridine ionic liquid surfactant, and 1000 parts deionized water.

9. A method for preparing a chemical nickel plating solution according to any one of claims 1-8, comprising the following steps: Add nickel source, reducing agent, complexing agent, pH buffer, thiourea stabilizer, bispyridine ionic liquid surfactant and deionized water to the reactor according to the weight parts, stir evenly, and then adjust the pH value to 5.0 with sulfuric acid to obtain electroless nickel plating solution.

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