Nickel melting tank cleaning agent as well as preparation method and application thereof

Abstract

The invention discloses a nickel melting tank cleaning agent as well as a preparation method and application thereof, and relates to the technical field of cleaning agents. According to the chemical nickel tank cleaning agent provided by the invention, the specific dispersing agent and the amino acid complexing agent are compounded in an alkaline environment, so that the dispersity of a nickel-containing black compound formed on the surface of a chemical nickel tank after a subsequent nitrate tank can be improved, and nickel ions stably exist in a water phase. The cleaning agent is used for replacing a conventional alkali washing agent to clean the nickel melting tank, after a conventional nitration tank and water washing process, the conductivity of the nickel melting tank is not higher than 4 microseconds / cm, the corrosion current density is not higher than 0.14 microamperes / cm < 2 >, and after the surface of the nickel melting tank is wiped by dust-free cloth, the residual quantity of black substances on the dust-free cloth is low, so that the impurity content is low, and the removal effect is excellent. Meanwhile, the cleaning agent does not corrode the nickel melting tank, and the surface of the nickel melting tank can be kept smooth.

Description

Technical Field

[0001] The present invention relates to the technical field of cleaning agents, and in particular to a cleaning agent for a nickel bath, a preparation method thereof, and an application thereof. Background Art

[0002] The electroless nickel-gold plating process for PCBs (printed circuit boards) is used to improve the surface conductivity of PCBs. It involves two main steps: first, a nickel layer is formed on the PCB surface through electroless plating (referred to as electroless nickel plating), followed by an electroless gold layer. The electroless nickel plating process is typically performed in a stainless steel or polypropylene bath. However, prolonged reaction time can result in residual nickel on the bath walls and electrode rods. Cleaning the bath walls is necessary to prevent this from affecting the quality of the resulting nickel-gold-plated PCB.

[0003] The cleaning process of industrial nickel baths typically includes a nitrate bath step. The most commonly used system for this process is sulfuric acid-hydrogen peroxide. This highly oxidizing agent readily oxidizes elemental nickel on the bath's surface into nickel ions. These nickel ions readily react with other elements in the system, such as O and H, to form substances such as NiO, Ni(OH)2, and NiOOH. These nickel oxygenates readily aggregate on the bath's surface, forming black, granular substances that are insoluble in water and cannot be removed by simple water washing. Their presence severely impacts the subsequent nickel bathing process for PCBs. To prevent the formation of these nickel oxygenates, existing processes often incorporate an alkaline wash step before the nitrate bath. However, alkaline washes are limited in their effectiveness against these substances, and to maximize the solubility of these subsequently generated black substances, a large amount of alkali is required, increasing costs and potentially corrosive to the stainless steel bath walls. To address this issue, researchers have proposed adding organic detergents to the alkaline wash process to enhance cleaning effectiveness while preventing severe corrosion of the bath's surface. However, most existing organic cleaning agents do not improve cleaning performance. Their introduction only slightly alters the surface properties of these black substances, but does not improve their removal efficiency. Therefore, in order to improve the removal of these black nickel oxides while avoiding corrosion in nickel baths, a new nickel bath cleaning agent is urgently needed. Summary of the Invention

[0004] In order to address the shortcomings of the existing technology, the present invention provides a nickel bath cleaning agent. By adding specific dispersants and complexing agents in an alkaline environment, the nickel ions generated in the subsequent nitrate bath process can be fully dispersed, complexed and stably present in the aqueous phase, thereby not only achieving sufficient cleaning of the nickel bath, but also preventing serious corrosion to the nickel bath.

[0005] Another object of the present invention is to provide a method for preparing a nickel bath cleaning agent.

[0006] Another object of the present invention is to provide an application of a nickel bath cleaning agent.

[0007] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0008] A nickel bath cleaning agent comprising the following raw materials calculated by mass:

[0009] 1-30 parts of dispersant, 1-10 parts of complexing agent, 40-97 parts of water;

[0010] The dispersant includes at least one of trisodium citrate, sodium stannate, sodium hexametaphosphate, sodium pyrophosphate, potassium tartrate, and sodium tartrate;

[0011] The complexing agent includes an amino acid;

[0012] The pH value of the nickel bath cleaning agent is 9.5-14.

[0013] The nickel-plating tank cleaning agent provided by the present invention can form a layer of organic film on the surface of the nickel-plating tank before the nitrate tank, thereby allowing the nickel ions generated in the subsequent nitrate tank process to be stably present in the aqueous phase by forming a complex and being removed through a simple water washing step. However, the inventors of the present application have found through a large number of experimental studies that the nickel ions generated in the nitrate tank process compete with each other in the precipitation process and the complexing process. Even if a complexing agent is added, a partial nickel oxide precipitate will still be produced after the nitrate tank. Therefore, a dispersant is also added in the present invention, and the dispersant can improve the dispersibility of the nickel oxygen compound precipitation (materials such as NiO, Ni(OH)2, NiOOH), so that the nickel ions in the precipitation can also be fully exposed and undergo complexation reaction, and the complex formed can then be directly discharged with the water washing solution; meanwhile, the introduction of the dispersant can further promote complexation by reducing the precipitation formation trend and improving the precipitation solubility. Based on this, the nickel bath cleaning agent provided by the present invention can fully improve the ability to remove black nickel oxide precipitates on the surface of the nickel bath, and the substances selected in the present invention all have high temperature and resistance, and the required amount of reagent addition is also less, so it is not easy to cause corrosion to the surface of the stainless steel nickel bath.

[0014] It should be noted that the pH of the nickel bath cleaning agent in the present invention needs to be controlled at 9.5 to 14 in order to optimize the activity of the dispersant and the complexing agent and to fully reduce the corrosion on the nickel bath surface. First, under alkaline conditions (pH ≥ 9.5), the acid radical part (such as -COO - ) is completely ionized, which can soften water, reduce interfacial tension and enhance dispersion ability. Amino acids, as complexing agents, are in the deprotonated form (-NH- and -COO - ) exists, forming bidentate or multidentate coordination, which can significantly improve the Ni 2+ The complexing ability of metal ions; secondly, nickel ions are easy to form hydroxide precipitation under near neutral or weak acidic conditions, and high pH (9.5-14) can make the metal ion form a hydroxyl complex (such as Ni(OH)3 - ) exists stably, and the chelating effect of the complexing agent can lock the metal ions in a soluble state; finally, a dense passivation film (Cr2O3) is formed on the surface of the stainless steel in a strong alkaline environment (pH 9.5-14), and the corrosion rate is significantly lower than that under acidic conditions, thus avoiding corrosion of the equipment by the cleaning agent. In a specific embodiment of the present invention, after the pH of the nickel bath cleaning agent is controlled to 9.5-14, since the process of cleaning the nickel bath using the nickel bath cleaning agent is carried out under alkaline conditions, it can replace the conventional process of alkaline washing with sodium hydroxide, that is, the nickel bath cleaning agent of the present invention can replace the conventional alkaline washing agent.

[0015] It should be noted that the specific dispersants and complexing agents selected in the present invention are obtained after specific screening and combination. Among them, the selection of amino acids as complexing agents is mainly based on functional adaptability, system compatibility and cost issues. First, amino acids have better pH adaptability and moderate complexing ability. While other complexing agents such as EDTA (ethylenediaminetetraacetic acid) can theoretically form more stable complexes (log K≈18.6) under the strong alkaline conditions of the present invention (pH>10), in actual use, they lack synergy with the specific dispersants selected in the present invention, and the two components cannot form a good combination, but instead tend to form more precipitation. Secondly, amino acids have better system compatibility and are much less corrosive to stainless steel on the tank wall than EDTA. Amino acids are more stable in alkaline environments and strong oxidizing environments, and their degradation products are easier to handle. Finally, the cost of amino acids is much lower than that of EDTA.

[0016] The types of dispersants are also obtained through specific screening. The main reason why specific dispersants such as trisodium citrate are selected in the present invention is that the carboxylate group of trisodium citrate can stabilize the black matter particles through electrostatic repulsion and steric hindrance to prevent them from aggregating. In order to improve the dispersibility, technicians usually use the method of adding surfactants. However, common surfactants such as SDS (sodium dodecyl sulfate) only rely on hydrophobic chain adsorption and are easily ineffective due to the charge shielding effect in strong alkaline systems. Dispersants such as trisodium citrate and sodium stannate can maintain stable existence within the pH range of 9.5 to 14 in the present invention, and their weak alkalinity can help maintain the pH of the system. In short, the selection of specific dispersants and complexing agents in the present invention is not accidental, but is based on a refined design of functional complementarity, system adaptability and comprehensive cost, ultimately achieving the optimal balance between cleaning efficiency and engineering feasibility.

[0017] It should be noted that the ratio of each component in the present invention also needs to be controlled within a certain range. Among them, the mass fraction of the dispersant is controlled to be 1 to 30 parts, which can ensure sufficient dispersing ability, prevent the aggregation of black matter, and avoid excessive foaming or corrosion. The mass fraction of the complexing agent is controlled to be 1 to 10 parts in order to provide sufficient complexing ability to dissolve metal ions, but not too much to affect the coordination between it and the dispersant. Controlling the mass fraction of water can control the concentration of the dispersant and complexing agent in water. If the amount of water added is too little, the dispersant and complexing agent with too high a concentration will easily cause the nickel element to be passivated and difficult to react. If the amount of water added is too high, the dispersant and complexing agent will not be able to fully play their role.

[0018] Preferably, the pH of the nickel bath cleaning agent is adjusted by adding an alkali, wherein the alkali comprises at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate.

[0019] After adding the above-mentioned alkali, the pH of the nickel bath cleaning agent of the present invention can be adjusted to 9.5-14.

[0020] More preferably, the base comprises sodium hydroxide.

[0021] More preferably, the nickel bath cleaning agent comprises the following raw materials calculated by mass:

[0022] 1-30 parts of dispersant, 1-10 parts of complexing agent, 40-97 parts of water, 1-20 parts of alkali.

[0023] Controlling the mass fraction of alkali is more conducive to adjusting the pH of the nickel bath cleaning agent to 9.5-14.

[0024] Preferably, the amino acid includes at least one of glycine, methionine, and L-cystine.

[0025] More preferably, the dispersant comprises trisodium citrate.

[0026] More preferably, the mass ratio of the complexing agent to the dispersant is (2-5):(10-28).

[0027] Controlling the mass ratio of the complexing agent to the dispersant within the above range is conducive to fully exerting the synergistic effect of the two.

[0028] The present invention also provides a method for preparing the above-mentioned nickel bath cleaning agent, comprising the following steps:

[0029] Mix all the prepared raw materials and adjust the pH to 9.5-14 to obtain the product.

[0030] In a specific embodiment of the present invention, when the raw materials for preparing the nickel bath cleaning agent include alkali, the pH of the nickel bath cleaning agent can be adjusted to 9.5-14 by mixing the raw materials, without adding additional reagents capable of adjusting the pH.

[0031] The present invention also protects the use of the above-mentioned nickel bath cleaning agent in cleaning a PCB nickel bath.

[0032] Preferably, the volume ratio of the nickel bath cleaning agent to the PCB nickel bath is (5-15):100.

[0033] In a specific embodiment of the present invention, the method for cleaning the PCB nickel bath comprises the following steps:

[0034] The nickel bath cleaning agent is added to clean the PCB nickel bath, and then the nitrate bath is carried out, and the nitrate bath adopts a sulfuric acid-hydrogen peroxide nitrate bath system.

[0035] More specifically, the cleaning time is 1 to 2 hours.

[0036] More specifically, the temperature of the saltpeter tank is 50-70° C., and the saltpeter tank time is 8-12 hours.

[0037] Existing industrial cleaning processes typically include two steps: alkaline washing and a saltpeter bath. The nickel bath cleaning agent and corresponding cleaning method provided by the present invention can replace the conventional alkaline washing method before the saltpeter bath. After cleaning with the cleaning agent provided by the present invention, the saltpeter bath can be performed, which can achieve a thorough cleaning of the nickel bath surface and avoid the formation of nickel oxygen compounds.

[0038] More specifically, the saltpeter tank further comprises a water washing step. More specifically, the water washing is rinsing.

[0039] After the nitrate tank, simply rinse the nickel bath with water to remove the residual cleaning agents, nitrate bath agents and other chemicals on the surface of the nickel bath.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The cleaning agent of the present invention is used to replace the conventional alkaline cleaning agent for alkaline cleaning of the nickel bath. After the conventional nitrate bath and water washing process, the conductivity of the nickel bath is not higher than 4μs / cm, and the corrosion current density is not higher than 0.14μA / cm 2 After wiping the surface of the nickel bath with a dust-free cloth, the amount of black matter remaining on the dust-free cloth is low, indicating low impurity content and excellent removal effect. At the same time, the cleaning agent of the present invention does not corrode the nickel bath and can keep the surface of the nickel bath smooth. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1The present invention provides a flow chart of a method for cleaning a PCB nickel bath. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with specific embodiments, but the examples do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the examples of the present invention are conventionally purchased raw materials and reagents.

[0044] Examples 1 to 17

[0045] This embodiment provides a series of nickel bath cleaning agents with different components and proportions, and the preparation method includes the following steps:

[0046] Mix all the prepared raw materials to obtain the product.

[0047] The specific raw materials and their quantities in this embodiment are shown in Table 1 below:

[0048] Table 1. Specific ingredients and their quantities in Examples 1 to 17

[0049]

[0050]

[0051] Comparative Example 1

[0052] This comparative example provides a nickel bath cleaning agent, which differs from Example 4 only in that:

[0053] Replace glycine with EDTA and set the pH of the nickel bath cleaner to 12.80.

[0054] The preparation method of the nickel bath cleaning agent in this comparative example is carried out according to Example 1.

[0055] Comparative Example 2

[0056] This comparative example provides a nickel bath cleaning agent, which differs from Example 4 only in that:

[0057] Without adding alkali, the pH of the nickel bath cleaner is 9.30.

[0058] The preparation method of the nickel bath cleaning agent in this comparative example is carried out according to Example 1.

[0059] Comparative Example 3

[0060] This comparative example provides a nickel bath cleaning agent, which differs from Example 4 only in that:

[0061] The pH of the nickel bath cleaner was 11.20 when trisodium citrate was replaced with L-cystine.

[0062] The preparation method of the nickel bath cleaning agent in this comparative example is carried out according to Example 1.

[0063] Comparative Example 4

[0064] This comparative example provides a nickel bath cleaning agent, which differs from Example 4 only in that:

[0065] The mass fraction of trisodium citrate is 0.1 parts, the mass fraction of glycine is 0.1 parts, the mass fraction of water is 79.8 parts, and the pH value of the nickel bath cleaning agent is 13.15.

[0066] The preparation method of the nickel bath cleaning agent in this comparative example is carried out according to Example 1.

[0067] Comparative Example 5

[0068] This comparative example provides a nickel bath cleaning agent, which differs from Example 4 only in that:

[0069] The mass fraction of trisodium citrate is 0.1 parts, the mass fraction of glycine is 4.5 parts, the mass fraction of water is 75.4 parts, and the pH value of the nickel bath cleaning agent is 11.90.

[0070] The preparation method of the nickel bath cleaning agent in this comparative example is carried out according to Example 1.

[0071] Comparative Example 6

[0072] This comparative example provides a nickel bath cleaning agent, which differs from Example 4 only in that:

[0073] The mass fraction of trisodium citrate is 4.5 parts, the mass fraction of glycine is 0.1 parts, the mass fraction of water is 75.4 parts, and the pH value of the nickel bath cleaning agent is 12.60.

[0074] The preparation method of the nickel bath cleaning agent in this comparative example is carried out according to Example 1.

[0075] Comparative Example 7

[0076] This comparative example provides a nickel bath cleaning agent, which differs from Example 4 only in that:

[0077] Glycine was replaced with sodium lauryl-N-methylglycinate, and the pH of the nickel bath cleaner was 12.60.

[0078] The preparation method of the nickel bath cleaning agent in this comparative example is carried out according to Example 1.

[0079] Comparative Example 8

[0080] This comparative example provides a nickel bath cleaning agent, which differs from Example 4 only in that:

[0081] The pH of the nickel bath cleaner was set to 12.30 by replacing trisodium citrate with sodium lauryl-N-methylglycinate.

[0082] The preparation method of the nickel bath cleaning agent in this comparative example is carried out according to Example 1.

[0083] Performance Testing

[0084] Cleaning effect test: The cleaning agents obtained in the examples and comparative examples were added to a stainless steel PCB nickel bath at a volume ratio of 10:100. The cleaning time was 1.5 hours. After cleaning, sulfuric acid-hydrogen peroxide bath was added and the bath was kept at 60°C for 10 hours. After the bath was completed, the conductivity and corrosion current density were tested, and the cleaning effect and the corrosion condition of the bath surface were observed and tested. The test indicators and methods are as follows:

[0085] Conductivity Test: After the nitrate bath is complete, rinse the nickel bath with water. Take approximately 100 mL of the wastewater from the rinse and place it in a clean beaker, avoiding interference from bubbles and suspended matter. Then, use a portable conductivity meter (Mettler Toledo FiveGo series) to test. Immerse the electrode at least 2 cm below the sample liquid surface and gently shake to remove any bubbles on the electrode surface. Wait for the reading to stabilize (usually 10-15 seconds) before recording the conductivity value. Conductivity can assess the residual ions in the wastewater after cleaning, indirectly reflecting the residual amount of cleaning agent and water purity. Lower conductivity indicates a cleaner cleaning process.

[0086] Corrosion Current Density Test: This electrochemical method quantifies the corrosion current of the stainless steel PCB nickel bath wall after cleaning to assess the corrosion risk of the cleaning agent to the equipment. The lower the corrosion current density, the better. The specific steps are as follows: After the salt bath is completed and during the water rinse, start the nickel bath's built-in electrochemical workstation and record the corrosion current density after the reading stabilizes.

[0087] Evaluation of cleaning effect: After the saltpeter tank is completed, it is washed with water, and then the surface of the tank is wiped with a clean dust-free cloth. Check whether there is any black matter residue on the dust-free cloth. If the residue is ≤3g, it is evaluated as excellent; if there is a small amount of black matter residue (>3g, ≤15g), it is evaluated as good; if there is a large amount of black matter residue or accumulation on the dust-free cloth (>15g), it is evaluated as poor.

[0088] Detection of corrosion on the tank surface: Take a stainless steel test sample that is consistent with the tank material, first weigh and record the data m1, and then weigh and record the data m2 after the same treatment as the nickel bath (cleaning + nitrate bath + water washing), and record the corrosion amount m=m1-m2. ≤0.1mg means no corrosion, >0.1mg and ≤0.5mg means slight corrosion, and >0.5mg means severe corrosion.

[0089] The specific performance test data is shown in Table 2 below:

[0090] Table 2. Performance test data of nickel bath cleaning agents obtained in Examples and Comparative Examples

[0091]

[0092]

[0093] As shown in Table 2, the cleaning agent of the present invention is used to replace the conventional alkaline cleaning agent for alkaline cleaning of the nickel bath. After the conventional nitrate bath and water washing process, the conductivity of the nickel bath is not higher than 4 μs / cm, and the corrosion current density is not higher than 0.14 μA / cm. 2 After wiping the surface of the nickel bath with a dust-free cloth, the amount of black matter remaining on the dust-free cloth is low, indicating low impurity content and excellent removal effect. At the same time, the cleaning agent of the present invention does not corrode the nickel bath and can keep the surface of the nickel bath smooth.

[0094] According to the comparison of the data of Examples 4 and 8 to 9, it can be seen that using trisodium citrate as a dispersant and compounding it with an amino acid complexing agent can obtain a better cleaning effect.

[0095] According to the comparison of Examples 4, 10 to 13, it can be seen that the three amino acids of methionine, glycine and L-cystine preferred in the present invention are used as complexing agents (Examples 4, 10 to 11). Since the three preferred amino acids have better interaction with the dispersant, the cleaning effect is better.

[0096] According to the data of Examples 4, 14 to 17, when the mass ratio of the complexing agent to the dispersant is (2 to 5): (10 to 28) as preferred in the present invention (Examples 4, 14, and 17), the two additives can better cooperate and fully exert their effects, thereby achieving a better cleaning effect.

[0097] According to the data of Comparative Example 2, it can be seen that it is difficult to ensure that the pH is within the range of 9.5 to 14 without adding alkali to the cleaning agent, and the insufficient pH condition causes the dispersant and complexing agent to be unable to fully exert their effects.

[0098] According to Comparative Examples 1, 3, 7, and 8, the dispersant and complexing agent amino acids were replaced with similar substances. Since the similar substances do not have the synergistic effect between the specific dispersant such as trisodium citrate and the amino acid in the present invention, the cleaning effect is reduced.

[0099] According to Comparative Examples 4 to 6, the ratio of the dispersant to the complexing agent is not appropriate, and it is also impossible to ensure that the combination of the two can achieve the optimal effect.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A nickel bath cleaning agent, characterized in that: Including the following preparation raw materials calculated by mass: 1-30 parts of dispersant, 1-10 parts of complexing agent, 40-97 parts of water; The dispersant includes at least one of trisodium citrate, sodium stannate, sodium hexametaphosphate, sodium pyrophosphate, potassium tartrate, and sodium tartrate; The complexing agent includes an amino acid; The pH value of the nickel bath cleaning agent is 9.5-14.

2. The nickel bath cleaning agent according to claim 1, wherein The pH of the nickel bath cleaning agent is adjusted by adding alkali, wherein the alkali includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate.

3. The nickel bath cleaning agent according to claim 2, wherein: The base includes sodium hydroxide.

4. The nickel bath cleaning agent according to claim 2, wherein Including the following preparation raw materials calculated by mass: 1-30 parts of dispersant, 1-10 parts of complexing agent, 40-97 parts of water, 1-20 parts of alkali.

5. The nickel bath cleaning agent according to claim 1, wherein The amino acid includes at least one of glycine, methionine, and L-cystine.

6. The nickel bath cleaning agent according to claim 1, wherein The dispersant includes trisodium citrate.

7. The nickel bath cleaning agent according to claim 5 or 6, wherein: The mass ratio of the complexing agent to the dispersant is (2-5): (10-28).

8. The method for preparing the nickel bath cleaning agent according to any one of claims 1 to 7, characterized in that: The steps include: Mix all the prepared raw materials and adjust the pH to 9.5-14 to obtain the product.

9. Use of the nickel bath cleaning agent according to any one of claims 1 to 7 in cleaning a nickel bath for PCBs.

10. The use according to claim 9, characterized in that The volume ratio of the nickel bath cleaning agent to the PCB nickel bath is (5-15):100.

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