A method for improving the rate and corrosion resistance of electroless nickel plating

Abstract

The application discloses a chemical nickel plating method and belongs to the technical field of nickel plating methods. The chemical nickel plating method comprises the following steps: S1, placing a workpiece to be plated into a chemical nickel plating solution to perform chemical nickel plating, and obtaining a plated workpiece with a primary plating layer; S2, adding a cathode into the chemical nickel plating solution in step S1, taking the plated workpiece with the primary plating layer as an anode, and performing power supply, wherein the anode current density is controlled to be less than 0.5 A / dm 2 , the power supply time is less than 40 s, and the chemical nickel plating process is completed. By adopting the chemical nickel plating method, the chemical nickel plating rate can be significantly improved under the action of the anode current, and the corrosion resistance of the obtained chemical nickel plating layer is significantly enhanced.

Description

Technical Field

[0001] This invention belongs to the field of nickel plating methods, and more specifically, relates to a method for improving the rate and corrosion resistance of electroless nickel plating. Background Technology

[0002] Electroless nickel plating technology has become an important technological choice in the manufacture of many industrial and consumer products due to its excellent corrosion resistance, good plating uniformity, and ability to enhance the hardness and wear resistance of the substrate. However, the current industrial application of electroless nickel plating technology results in a relatively low nickel deposition rate, and with the development of modern technology, the requirements for new materials are becoming increasingly stringent. Further improving the corrosion resistance of nickel plating layers has become a key research focus. Existing technologies can accelerate the deposition rate and improve the corrosion resistance of nickel layers by adding various organic or inorganic additives. However, the addition of additives can easily produce various side effects, such as high plating temperature, difficulty in process control, high energy consumption, poor stability of the plating solution, easy volatility, and short service life.

[0003] To improve the electroless nickel plating rate, patent CN201710730006.8 proposes using an accelerator to speed up the plating process. However, the ferrous sulfate used pollutes the electroless nickel plating solution, is irritating and environmentally unfriendly, and requires a plating temperature of 90℃, consuming a large amount of energy. Furthermore, the nickel plating solution is prone to evaporation. Patent CN201911334558.2 proposes using a combination of organic acids, amino acid accelerators, sodium fluoride, and ammonium chloride to improve the electroless nickel plating rate. However, excessive additives can pollute the nickel plating solution, and it is difficult to control the appropriate compounding ratio and pH of the plating solution.

[0004] To improve the corrosion resistance of electroless nickel plating, patent CN202310818483.5 proposes using a combination of electroless nickel plating solution and a composite stabilizer to enhance the corrosion resistance of the electroless nickel plating layer. The composite stabilizer includes modified naphthiourea, chromium sulfate, and thiodipropionic acid. However, the preparation process of modified naphthiourea is complex, and the chloroform and dichloromethane used in the preparation process are toxic and environmentally unfriendly. Patent CN202410633397.1 proposes using a composite complexing agent, iodate, and rare earth compounds to improve the corrosion resistance of electroless nickel plating, but the plating temperature needs to be 85–90℃, resulting in high energy consumption, and the nickel plating solution is prone to evaporation. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the purpose of this invention is to provide a method for improving the electroless nickel plating rate and corrosion resistance.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution:

[0007] A method for electroless nickel plating includes the following steps:

[0008] S1. The workpiece to be plated is placed in a chemical nickel plating solution for chemical nickel plating to obtain a workpiece with a primary coating.

[0009] S2. Add a cathode to the electroless nickel plating solution from step S1, using the workpiece with the primary plating layer as the anode, and apply current, controlling the anode current density to be <0.5 A / dm³. 2 The energizing time is less than 40 seconds to complete the electroless nickel plating process.

[0010] This invention involves electroless nickel plating of the workpiece to be plated, forming a nickel plating layer on the workpiece, then using the workpiece as the anode and connecting it to the positive terminal of a power source, and using an inert electrode or a nickel electrode as the cathode. After current is applied, electroless nickel plating continues. Under the selected current density and current-carrying time, the electroless nickel plating rate and the corrosion resistance of the electroless nickel plating layer are significantly improved.

[0011] Furthermore, in step S2, the anode current density is controlled to be 0.1–0.3 A / dm³. 2 .

[0012] Furthermore, the energizing time in step S2 is 5 to 35 seconds.

[0013] Furthermore, the cathode in step S2 is an inert electrode or a nickel electrode, preferably a platinum electrode.

[0014] In this invention, the conditions for electroless nickel plating in step S1 can refer to existing technologies.

[0015] Furthermore, the electroless nickel plating time in step S1 is 5 to 60 minutes.

[0016] Furthermore, the temperature for electroless nickel plating in step S1 is 70–75°C.

[0017] Furthermore, the pH value of the electroless nickel plating solution in step S1 is 4.5 to 5.0.

[0018] Furthermore, the pH value of the electroless nickel plating solution in step S1 can be adjusted by adding acid or alkali, such as dilute sulfuric acid, sodium hydroxide, ammonia, etc.

[0019] Furthermore, the electroless nickel plating solution in step S1 includes nickel salt, reducing agent, complexing agent, and stabilizer components. It may also include accelerator, wetting agent, and other components.

[0020] Furthermore, the nickel salt is one or more of nickel sulfate, nickel chloride, nickel acetate, and nickel carbonate.

[0021] Furthermore, the reducing agent in the electroless nickel plating solution in step S1 is sodium hypophosphite and / or sodium hypophosphite.

[0022] In some embodiments of the present invention, the composition of the electroless nickel plating solution is: NiSO4·6H2O 18-25 g / L, NaH2PO2·H2O 15-25 g / L, sodium succinate 5-15 g / L, malic acid 5-15 g / L, CH3COONa 15 g / L, lactic acid 5-15 mL / L, lead acetate 0.5-1.5 mg / L, and the solvent is deionized water.

[0023] In step S1, the workpiece to be electroless nickel plating undergoes pretreatment, including degreasing, micro-etching, and activation steps. The degreasing, micro-etching, and activation steps can be performed with reference to existing technologies.

[0024] Furthermore, the degreasing process involves immersing the workpiece to be plated in a degreasing solution at a temperature of 50°C for 1 to 10 minutes, followed by rinsing the workpiece with water.

[0025] Furthermore, the degreasing solution comprises the following components: NaOH 5-10 g / L, NaCO3 5-15 g / L, Na3PO4 15-25 g / L, and deionized water as the solvent.

[0026] Furthermore, the micro-etching involves immersing the workpiece to be plated in a micro-etching solution for 1-2 minutes, followed by rinsing the workpiece with water.

[0027] Furthermore, the micro-etching solution comprises the following components: Na2S2O8 25-35 g / L, concentrated sulfuric acid 50-100 mL / L, and deionized water as the solvent.

[0028] Furthermore, the activation involves immersing the workpiece to be plated in the activation solution for 1-2 minutes, followed by rinsing the workpiece with water.

[0029] Furthermore, the activation solution comprises the following components: PdCl2 0.1-0.5 g / L, NH4Cl 0.5-2.0 g / L, and deionized water as the solvent.

[0030] Furthermore, the workpiece to be plated in this invention is a copper sheet.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] This invention involves forming a primary nickel plating layer on a workpiece through electroless nickel plating, then using the workpiece as the anode and applying an anodic current. By controlling the anodic current density and the energizing time, electroless nickel plating continues. Under the influence of the anodic current, the deposition rate of electroless nickel plating and the corrosion resistance of the plating layer can be significantly improved. Furthermore, the lower temperature facilitates the maintenance of the plating solution's stability. This invention features a simple process, requires no additional additives, is low in cost, and is suitable for industrial production. Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in this embodiment are conventional reagents, methods and equipment in this technical field.

[0034] The degreasing solution used in the following examples comprises 5 g / L sodium hydroxide, 10 g / L sodium carbonate, and 20 g / L trisodium phosphate, with deionized water as the solvent; the micro-etching solution comprises 30 g / L sodium persulfate and 50 mL / L 98% concentrated sulfuric acid, with deionized water as the solvent; and the activation solution comprises 0.1 g / L palladium chloride and 1 g / L ammonium chloride, with deionized water as the solvent.

[0035] The workpiece to be plated in the following examples is a 2cm×2cm copper sheet. The pretreatment steps for the workpiece before electroless nickel plating are as follows: the copper sheet is immersed in the above degreasing solution at a temperature of 50°C for 1 minute, rinsed with water, then immersed in the above micro-etching solution for 1 minute, rinsed with water, then immersed in the above activation solution for 1 minute, and finally rinsed with water to obtain the copper sheet to be plated used in each example and comparative example.

[0036] The electroless nickel plating solution used in the following examples comprises NiSO4·6H2O 20 g / L, NaH2PO2·H2O 25 g / L, sodium succinate 10 g / L, sodium acetate 15 g / L, malic acid 5 g / L, lactic acid 8 mL / L, and lead acetate 0.8 mg / L, with deionized water as the solvent. The solution was prepared according to the above formula and then adjusted to pH 4.8 to obtain the electroless nickel plating solution.

[0037] Example 1

[0038] A method for electroless nickel plating includes the following steps: immersing a copper sheet to be plated in an electroless nickel plating solution at 75°C for 20 minutes, without removing the copper sheet, applying an anodic current using a platinum electrode as the cathode and the copper sheet as the anode, controlling the anodic current density to be 0.25 A / dm³. 2 The energizing time is 10 seconds, followed by water washing and drying to obtain a nickel plating layer.

[0039] Example 2

[0040] A method for electroless nickel plating includes the following steps: immersing a copper sheet to be plated in an electroless nickel plating solution at 75°C for 20 minutes, without removing the copper sheet, applying an anodic current using a platinum electrode as the cathode and the copper sheet as the anode, controlling the anodic current density to be 0.25 A / dm³. 2 The energizing time is 20 seconds, followed by water washing and drying to obtain a nickel plating layer.

[0041] Example 3

[0042] A method for electroless nickel plating includes the following steps: immersing a copper sheet to be plated in an electroless nickel plating solution at 75°C for 20 minutes, without removing the copper sheet, applying an anodic current using a platinum electrode as the cathode and the copper sheet as the anode, controlling the anodic current density to be 0.25 A / dm³. 2 The energizing time is 30 seconds, followed by water washing and drying to obtain a nickel plating layer.

[0043] Example 4

[0044] A method for electroless nickel plating includes the following steps: immersing a copper sheet to be plated in an electroless nickel plating solution at 75°C for 5 minutes, without removing the copper sheet, applying an anodic current using a platinum electrode as the cathode and the copper sheet as the anode, controlling the anodic current density to be 0.25 A / dm³. 2 The energizing time is 10 seconds, followed by water washing and drying to obtain a nickel plating layer.

[0045] Example 5

[0046] A method for electroless nickel plating includes the following steps: immersing a copper sheet to be plated in an electroless nickel plating solution at 75°C for 5 minutes, without removing the copper sheet, applying an anodic current using a platinum electrode as the cathode and the copper sheet as the anode, controlling the anodic current density to be 0.25 A / dm³. 2 The energizing time is 30 seconds, followed by water washing and drying to obtain a nickel plating layer.

[0047] Comparative Example 1

[0048] The copper sheet to be plated is placed in a chemical nickel plating solution at 75°C for 20 minutes and 30 seconds, followed by rinsing with water and drying to obtain a nickel plating layer.

[0049] Comparative Example 2

[0050] The copper sheet to be plated is immersed in a chemical nickel plating solution at 75°C for 20 minutes. Without removing the copper sheet, an anodic current is applied using a platinum electrode as the cathode and the copper sheet as the anode, with the anodic current density controlled at 0.25 A / dm³. 2 The energizing time is 40 seconds, followed by water washing and drying to obtain a nickel plating layer.

[0051] Comparative Example 3

[0052] The copper sheet to be plated is immersed in a chemical nickel plating solution at 75°C for 20 minutes. Without removing the copper sheet, an anodic current is applied using a platinum electrode as the cathode and the copper sheet as the anode, with the anodic current density controlled at 0.5 A / dm³. 2 The energizing time is 30 seconds, followed by water washing and drying to obtain a nickel plating layer.

[0053] Performance testing

[0054] Coating thickness test: The nickel coatings obtained in the examples and comparative examples were measured using a thickness gauge, and the results are shown in Table 1.

[0055] Corrosion resistance test of coating: A nitric acid solution with a nitric acid:water ratio of 1:2 (volume ratio concentration) was dropped onto the surface of the nickel coating obtained in the examples and comparative examples, and the time when bubbles began to appear on the coating surface (i.e. corrosion began) was recorded. The test results are shown in Table 2.

[0056] Table 1

[0057]

[0058] Table 2

[0059]

[0060] As can be seen from the data in Table 1, the present invention can promote the deposition rate of electroless nickel plating and increase the thickness of the nickel plating layer by passing an anodic current after forming a nickel plating layer on the workpiece to be plated. As can be seen from the data of Example 3, Comparative Example 2 and Comparative Example 3, an excessively high anodic current density or an excessively long energizing time is not conducive to improving the deposition rate of electroless nickel plating.

[0061] As shown in Table 2, the present invention enhances the corrosion resistance of the electroless nickel plating layer by applying an anodic current after forming a nickel plating layer on the workpiece. Data from Example 3, Comparative Examples 2 and 3 show that excessively high anodic current density or excessively long energizing time is detrimental to improving the corrosion resistance of the electroless nickel plating layer. The electroless nickel plating method of the present invention is simple, requires no additional additives, and has good application prospects.

[0062] The above embodiments are preferred experimental methods of the present invention, but the implementation of the present invention is 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 method for electroless nickel plating, characterized in that, Includes the following steps: S1. The workpiece to be plated is placed in a chemical nickel plating solution for chemical nickel plating to obtain a workpiece with a primary coating. S2. Add a cathode to the electroless nickel plating solution from step S1, using the workpiece with the primary plating layer as the anode, and apply current, controlling the anode current density to be 0.1~0.3 A / dm³. 2 The energizing time is less than 40 seconds to complete the electroless nickel plating process.

2. The electroless nickel plating method according to claim 1, characterized in that, The energizing time in step S2 is 5~35s.

3. The electroless nickel plating method according to claim 1, characterized in that, In step S2, the cathode is either an inert electrode or a nickel electrode.

4. The electroless nickel plating method according to claim 1, characterized in that, The electroless nickel plating time in step S1 is 5-60 minutes.

5. The electroless nickel plating method according to claim 1, characterized in that, The temperature for electroless nickel plating in step S1 is 70~75℃.

6. The electroless nickel plating method according to claim 1, characterized in that, The pH value of the electroless nickel plating solution in step S1 is 4.5~5.

0.

7. The electroless nickel plating method according to claim 1, characterized in that, The electroless nickel plating solution in step S1 includes nickel salt, reducing agent, complexing agent, and stabilizer components.

8. The electroless nickel plating method according to claim 7, characterized in that, The nickel salt is one or more of nickel sulfate, nickel chloride, nickel acetate, and nickel carbonate.

9. The electroless nickel plating method according to claim 7, characterized in that, The reducing agent is sodium hypophosphite and / or sodium hypophosphite.

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