Aluminum-based neutral nickel plating solution

Abstract

The invention discloses an aluminum-based neutral nickel plating solution, relating to the technical field of chemical nickel plating, comprising the following components by mass fraction: 5-10 parts of a nickel salt; 15-30 parts of a complexing agent; 12-18 parts of a reducing agent; 0.1-0.4 parts of a composite stabilizer; 1-5 parts of a composite accelerator; and 0.1-0.5 parts of a composite wetting agent. The stabilizer of the present invention can increase the service life of the plating solution; the reducing agent can not only increase the reduction rate but also not introduce other elements into the coating, thus not adversely affecting the bonding strength; the composite accelerator improves the coverage of the coating; the composite wetting agent improves the dispersibility of nickel ions, thereby improving corrosion resistance for aluminum surface gaps that have not yet been covered with nickel, and under the action of the composite accelerator, promotes the continuous growth of nickel nuclei in the region.

Description

Technical Field

[0001] The invention relates to the technical field of chemical nickel plating, in particular to an aluminum-based neutral nickel plating solution. Background Art

[0002] Electroless nickel plating on aluminum is an important surface treatment technology, serving as an intermediate step in the subsequent electroless palladium-gold treatment of aluminum substrates. Generally, electroless nickel plating on aluminum substrates requires first electroless zinc plating as a protective layer, followed by electroless nickel plating. This is done to protect the aluminum substrate from corrosion and improve bonding strength. However, this process requires multiple zinc immersion and stripping steps during the zinc immersion process, making it extremely tedious and complex.

[0003] Currently, there is a chemical nickel plating method developed on the market that directly coats aluminum substrates. This chemical nickel plating solution is prepared with ammonia water to obtain a solution with a pH of 10-12. The ammonia concentration is high, and the entire production process has a strong ammonia smell. Ammonia is also toxic and has adverse effects on the health of workers. Therefore, it is urgent to develop a process technology that is both environmentally friendly and can shorten the process flow to solve these problems. Summary of the Invention

[0004] In view of the problems in the related art, the present invention proposes an aluminum-based neutral nickel plating solution to overcome the above technical problems existing in the existing related art.

[0005] To this end, the specific technical solutions adopted in the present invention are as follows:

[0006] An aluminum-based neutral nickel plating solution comprises the following components in mass fractions:

[0007] 5-10 parts of nickel salt;

[0008] 15-30 parts of complexing agent;

[0009] 12-18 parts of reducing agent;

[0010] Composite stabilizer 0.1-0.4 parts;

[0011] 1-5 parts of composite accelerator;

[0012] 0.1-0.5 parts of composite wetting agent.

[0013] Furthermore, the nickel salt includes nickel sulfate; the complexing agent includes malic acid; and the reducing agent includes citral. Traditional reducing agents, such as sodium hypophosphite or DMAB, are weak under low-temperature neutral conditions and cannot be used in production. When electroless nickel plating is performed on aluminum substrates, these reducing agents can result in poor bonding strength due to the presence of P and B impurities, which lead to unstable deposition of the coating. The reducing agent used in the present invention not only increases the reduction rate but also does not introduce other elements into the coating, thus not adversely affecting bonding strength.

[0014] Furthermore, composite stabilizers include oxazole carboxylic acid compounds and thiazolylpyridine hydroxycarboxylalkyl compounds. Composite stabilizers can increase the service life of the plating solution. They improve the density of the coating by controlling the growth of nickel crystal nuclei and preventing excessive and irregular growth of nickel nuclei. Traditional nickel plating stabilizers generally contain heavy metal ions such as lead and cadmium, which are difficult to handle. Increasing the concentration of lead ions and spacers can lead to plating leakage or even plating cessation. When used on high-end aluminum substrates such as chips, it can cause slight corrosion of the substrate and reduce bonding strength.

[0015] Furthermore, the oxazole carboxylic acid compound includes 5-oxazolecarboxylic acid, and the thiazolylpyridine hydroxycarboxylalkyl compound includes 2-hydroxy-4-methylthiazole-5-carboxylic acid.

[0016] Furthermore, the concentration ratio of the oxazole carboxylic acid compound to the thiazolylpyridine hydroxycarboxylalkyl compound during use is 1:1.

[0017] Furthermore, the composite accelerator includes aminopurine carboxylic acid compounds and hydroxythiazolyl ester compounds.

[0018] Furthermore, the aminopurine carboxylic acid compound includes 6-amino-9H-purine-9-propionic acid; and the hydroxythiazolyl ester compound includes 4-hydroxy-2-methylthiazole-5-carboxylic acid ethyl ester.

[0019] Furthermore, the concentration ratio of the aminopurine carboxylic acid compound to the hydroxythiazolyl ester compound during use is 1:1.

[0020] Composite accelerators can improve the coverage of the coating. The poor coverage of aluminum-based chemical nickel is the main reason for the poor bonding strength. The introduction of accelerators can greatly improve the coverage of the coating, which is also the key point to solve and improve the formula. The specific reason is that this type of substance is beneficial to the selectivity of nickel ions on the aluminum substrate and accelerates the continuous nucleation of nickel ions.

[0021] Furthermore, the composite wetting agent includes poly(ethylene glycol)-block-polyethylene imine and poly(methyl methacrylate), and the concentration ratio of poly(ethylene glycol)-block-polyethylene imine to poly(methyl methacrylate) during use is 1:1.

[0022] On the one hand, the composite wetting agent can improve the dispersion of nickel ions, while at the same time improving the corrosion resistance of the aluminum surface gaps that have not yet been covered with nickel, inhibiting the excessive attack of nickel ions, and promoting the continuous growth of nickel nuclei in this area under the action of the promoter. Poly(ethylene glycol)-block-polyethyleneimine can be adsorbed onto the surface of the substrate, changing the different concentrations of nickel ions at high and low points, thereby improving the deposition effect of local micro-areas. Polymethyl methacrylate accelerates the nucleation rate of nickel, thus playing a synergistic role.

[0023] Furthermore, the operating conditions of the aluminum-based neutral nickel plating solution are a temperature of 58-68° C. and a pH value of 6.8-7.8.

[0024] The beneficial effects of the present invention are:

[0025] 1) The stabilizer used in this invention can extend the service life of the plating solution. It improves the density of the coating by controlling the growth of nickel crystal nuclei and preventing excessive and irregular growth of nickel nuclei. Traditional nickel plating stabilizers generally contain heavy metal ions such as lead and cadmium, which are difficult to handle. Increasing the concentration of lead ions and spacers can lead to plating skipping or even plating cessation. When used on high-end aluminum substrates such as chips, it can cause minor corrosion of the substrate and reduce bonding strength.

[0026] 2) The reducing agent used in the present invention is citral. Traditional reducing agents, such as sodium hypophosphite or amines such as DMAB, are weak under low-temperature neutral conditions and cannot be used in production. When performing electroless nickel plating on aluminum substrates, these reducing agents result in poor bonding strength due to the presence of P and B impurities, which leads to unstable deposition of the coating. The reducing agent used in the present invention not only increases the reduction rate but also does not introduce other elements into the coating, thus preventing adverse effects on bonding strength.

[0027] 3) The accelerators used in the present invention, 6-amino-9H-purine-9-propionic acid and ethyl 4-hydroxy-2-methylthiazole-5-carboxylate, can improve the coverage of the coating. Experimental studies have found that the poor coverage of aluminum-based chemical nickel is the main reason for the poor bonding strength. The introduction of accelerators can greatly improve the coverage of the coating and is also the key point to solve and improve the formula. The specific reason may be that such substances are beneficial to the selectivity of nickel ions on the aluminum substrate and accelerate the continuous nucleation of nickel ions.

[0028] 4) The composite wetting agent used in the present invention can improve the dispersibility of nickel ions on the one hand, and at the same time improve the corrosion resistance of the aluminum surface gaps that have not yet been covered with nickel, inhibit the excessive attack of nickel ions, and promote the continuous growth of nickel crystal nuclei in this area under the action of the accelerator. DETAILED DESCRIPTION

[0029] According to an embodiment of the present invention, an aluminum-based neutral nickel plating solution is provided, which can realize the chemical nickel plating process of an aluminum substrate. It has the characteristics of fast deposition rate, excellent stability, good bonding strength, and can realize reduction plating of aluminum substrates.

[0030] The present invention is now further described through specific embodiments. According to an embodiment of the present invention, the aluminum-based neutral nickel plating solution includes the following components by mass fraction:

[0031] 5-10 parts of nickel salt;

[0032] 15-30 parts of complexing agent;

[0033] 12-18 parts of reducing agent;

[0034] Composite stabilizer 0.1-0.4 parts;

[0035] 1-5 parts of composite accelerator;

[0036] 0.1-0.5 parts of composite wetting agent.

[0037] In one embodiment, the nickel salt comprises nickel sulfate; the complexing agent comprises malic acid; and the reducing agent comprises citral.

[0038] Conventional reducing agents, such as sodium hypophosphite or amines like DMAB, are weak under low-temperature, neutral conditions and therefore impractical for production. Furthermore, these reducing agents can lead to poor bonding when used directly for electroless nickel plating on aluminum substrates due to P and B impurities, resulting in unstable deposition of the coating. The reducing agent employed in the present invention not only increases the reduction rate but also prevents the introduction of other elements into the coating, thus negatively impacting bonding.

[0039] In one embodiment, the composite stabilizer includes an oxazole carboxylic acid compound and a thiazolylpyridine hydroxycarboxyl alkyl compound.

[0040] Composite stabilizers can extend the life of the plating solution. They improve the density of the coating by controlling the growth of nickel crystal nuclei and preventing excessive and irregular growth of nickel nuclei. Traditional nickel plating stabilizers generally contain heavy metal ions such as lead and cadmium, which are difficult to handle. Furthermore, increasing the concentration of lead ions and spacers can lead to plating leakage or even plating cessation. When used on high-end aluminum substrates such as chips, they can cause minor corrosion of the substrate and reduce bonding strength.

[0041] In one embodiment, the oxazole carboxylic acid compound includes 5-oxazolecarboxylic acid, and the thiazolylpyridine hydroxycarboxylalkyl compound includes 2-hydroxy-4-methylthiazole-5-carboxylic acid.

[0042] In one embodiment, the concentration ratio of the oxazole carboxylic acid compound to the thiazolylpyridine hydroxycarboxylalkyl compound is 1:1.

[0043] In one embodiment, the composite accelerator includes an aminopurine carboxylic acid compound and a hydroxythiazolyl ester compound.

[0044] In one embodiment, the aminopurine carboxylic acid compound includes 6-amino-9H-purine-9-propionic acid; and the hydroxythiazolyl ester compound includes 4-hydroxy-2-methylthiazole-5-carboxylic acid ethyl ester.

[0045] In one embodiment, the concentration ratio of the aminopurine carboxylic acid compound to the hydroxythiazolyl ester compound during use is 1:1.

[0046] Composite accelerators can improve the coverage of the coating. Experimental studies have found that the poor coverage of aluminum-based chemical nickel is the main reason for poor bonding. The introduction of accelerators can greatly improve the coverage of the coating, which is also the key point to solve and improve the formula. The specific reason is that this type of substance is beneficial to the selectivity of nickel ions on the aluminum substrate and accelerates the continuous nucleation of nickel ions.

[0047] In one embodiment, the composite wetting agent includes poly(ethylene glycol)-block-polyethyleneimine and poly(methyl methacrylate), and the concentration ratio of poly(ethylene glycol)-block-polyethyleneimine to poly(methyl methacrylate) when used is 1:1.

[0048] On the one hand, the composite wetting agent can improve the dispersion of nickel ions, while at the same time improving the corrosion resistance of the aluminum surface gaps that have not yet been covered with nickel, inhibiting the excessive attack of nickel ions, and promoting the continuous growth of nickel nuclei in this area under the action of the promoter. Poly(ethylene glycol)-block-polyethyleneimine can be adsorbed onto the surface of the substrate, changing the different concentrations of nickel ions at high and low points, thereby improving the deposition effect of local micro-areas. Polymethyl methacrylate accelerates the nucleation rate of nickel, thus playing a synergistic role.

[0049] In one embodiment, the operating conditions of the aluminum-based neutral nickel plating solution are a temperature of 58-68° C. and a pH value of 6.8-7.8.

[0050] In order to facilitate understanding of the above technical solutions of the present invention, the working principle of the present invention in actual process is described in detail below.

[0051] The following are several specific embodiments of the present invention.

[0052] In the evaluation criteria of the results of the embodiments and comparative examples, MTO stands for metal replacement cycle.

[0053] Table 1: Evaluation criteria

[0054] Example

[0055] An aluminum-based neutral nickel plating solution comprising the following components in the following concentrations:

[0056] Based on 1 L: Nickel sulfate 7.5 g / L, malic acid 25 g / L, citral 15 g / L, 5-oxazolecarboxylic acid 0.125 g / L, 2-hydroxy-4-methylthiazole-5-carboxylic acid 0.125 g / L, 6-amino-9H-purine-9-propionic acid 1.75 g / L, ethyl 4-hydroxy-2-methylthiazole-5-carboxylate 1.75 g / L, poly(ethylene glycol)-block-polyethyleneimine 0.15 g / L, and polymethyl methacrylate 0.15 g / L.

[0057] The operating conditions of the aluminum-based neutral nickel plating solution are: 62°C; pH value 7.2; time 20 minutes.

[0058] The test results of Example 1 are: excellent bonding strength; excellent stability; excellent permeation phenomenon; and excellent deposition rate. Example

[0059] An aluminum-based neutral nickel plating solution comprising the following components in the following concentrations:

[0060] Based on 1 L: Nickel sulfate 5 g / L, malic acid 15 g / L, citral 12 g / L, 5-oxazolecarboxylic acid 0.05 g / L, 2-hydroxy-4-methylthiazole-5-carboxylic acid 0.05 g / L, 6-amino-9H-purine-9-propionic acid 0.5 g / L, ethyl 4-hydroxy-2-methylthiazole-5-carboxylate 0.5 g / L, poly(ethylene glycol)-block-polyethyleneimine 0.05 g / L, and polymethyl methacrylate 0.05 g / L.

[0061] The operating conditions of the aluminum-based neutral nickel plating solution are: 62°C; pH value 7.2; time 20 minutes.

[0062] The test results of Example 2 are: excellent bonding strength; excellent stability; excellent permeation phenomenon; and excellent deposition rate. Example

[0063] An aluminum-based neutral nickel plating solution comprising the following components in the following concentrations:

[0064] Based on 1L: Nickel sulfate 10g / L, malic acid 30g / L, citral 18g / L, 5-oxazolecarboxylic acid 0.2g / L, 2-hydroxy-4-methylthiazole-5-carboxylic acid 0.2g / L, 6-amino-9H-purine-9-propionic acid 2.5g / L, ethyl 4-hydroxy-2-methylthiazole-5-carboxylate 2.5g / L, poly(ethylene glycol)-block-polyethyleneimine 0.25g / L, and polymethyl methacrylate 0.25g / L.

[0065] The operating conditions of the aluminum-based neutral nickel plating solution are: 62°C; pH value 7.2; time 20 minutes.

[0066] The test results of Example 3 are: excellent bonding strength; excellent stability; excellent permeation phenomenon; and excellent deposition rate.

[0067] Comparative Example 1

[0068] An aluminum-based neutral nickel plating solution comprising the following components in the following concentrations:

[0069] Based on 1 L: Nickel sulfate 7.5 g / L, malic acid 25 g / L, 5-oxazolecarboxylic acid 0.125 g / L, 2-hydroxy-4-methylthiazole-5-carboxylic acid 0.125 g / L, 6-amino-9H-purine-9-propionic acid 1.75 g / L, ethyl 4-hydroxy-2-methylthiazole-5-carboxylate 1.75 g / L, poly(ethylene glycol)-block-polyethyleneimine 0.15 g / L, and polymethyl methacrylate 0.15 g / L.

[0070] The operating conditions of the aluminum-based neutral nickel plating solution are: 62°C; pH value 7.2; time 20 minutes.

[0071] Compared with Example 1, Comparative Example 1 lacks a reducing agent, and the test results are: good bonding strength; excellent stability; poor permeation phenomenon; and poor deposition rate.

[0072] Comparative Example 2

[0073] An aluminum-based neutral nickel plating solution comprising the following components in the following concentrations:

[0074] Based on 1 L: nickel sulfate 7.5 g / L, malic acid 25 g / L, citral 15 g / L, 6-amino-9H-purine-9-propionic acid 1.75 g / L, ethyl 4-hydroxy-2-methylthiazole-5-carboxylate 1.75 g / L, poly(ethylene glycol)-block-polyethyleneimine 0.15 g / L, and polymethyl methacrylate 0.15 g / L.

[0075] Comparative Example 2 lacks a stabilizer compared to Example 1, and the test results are: good bonding strength; good stability; good permeation phenomenon; and excellent deposition rate.

[0076] Comparative Example 3

[0077] An aluminum-based neutral nickel plating solution comprising the following components in the following concentrations:

[0078] Based on 1 L: Nickel sulfate 7.5 g / L, malic acid 25 g / L, citral 15 g / L, 5-oxazolecarboxylic acid 0.125 g / L, ethyl 4-hydroxy-2-methylthiazole-5-carboxylate 1.75 g / L, poly(ethylene glycol)-block-polyethyleneimine 0.15 g / L, and polymethyl methacrylate 0.15 g / L.

[0079] The operating conditions of the aluminum-based neutral nickel plating solution are: 62°C; pH value 7.2; time 20 minutes.

[0080] Compared with Example 1, Comparative Example 3 lacks a promoter, and the test results are: the bonding force is poor; the stability is excellent; the plating phenomenon is excellent; and the deposition rate is poor.

[0081] Comparative Example 4

[0082] An aluminum-based neutral nickel plating solution comprising the following components in the following concentrations:

[0083] Based on 1 L: Nickel sulfate 7.5 g / L, malic acid 25 g / L, citral 15 g / L, 5-oxazolecarboxylic acid 0.125 g / L, 2-hydroxy-4-methylthiazole-5-carboxylic acid 0.125 g / L, 6-amino-9H-purine-9-propionic acid 1.75 g / L, ethyl 4-hydroxy-2-methylthiazole-5-carboxylate 1.75 g / L.

[0084] The operating conditions of the aluminum-based neutral nickel plating solution are: 62°C; pH value 7.2; time 20 minutes.

[0085] Compared with Example 1, Comparative Example 4 lacks the composite wetting agent, and the test results are: good bonding strength; excellent stability; good permeation phenomenon; and excellent deposition rate.

[0086] In summary, the stabilizer used in the present invention can improve the service life of plating solution, and it improves coating density by controlling the growth of nickel nuclei, prevents the excessive irregular growth of nickel nuclei. Traditional nickel plating stabilizer generally adopts heavy metal ions such as lead, cadmium, and processing difficulty is large, and along with the increase of lead ion, isolator concentration addition amount, coating leakage plating can be caused, even stop plating and other phenomena, when using on high-end product aluminum substrate such as chip, substrate can be caused to have slight corrosion, reduce bonding strength. The reducing agent used in the present invention is citral, and traditional reducing agent adopts amine substances such as sodium hypophosphite or DMAB, which is weaker under low temperature neutral conditions, and production cannot be achieved. When carrying out chemical nickel plating on aluminum base, these reducing agents can cause bonding strength to be poor when carrying out direct chemical nickel plating, because there are P, B mixed to cause unstable deposition of coating. And the reducing agent used in the present invention, not only can improve reduction speed, other elements are not introduced into the coating, bonding strength can not be adversely affected. The accelerators used in the present invention, 6-amino-9H-purine-9-propionic acid and ethyl 4-hydroxy-2-methylthiazole-5-carboxylate, can improve the coverage of the coating. Experimental studies have found that the poor coverage of aluminum-based chemical nickel is the main reason for the poor bonding strength. After the accelerator is introduced, the coverage of the coating can be greatly improved, which is also a key point for solving and improving the formula. The specific reason may be that such substances are beneficial to the selectivity of nickel ions on the aluminum substrate and accelerate the continuous nucleation of nickel ions. The composite wetting agent used in the present invention can improve the dispersibility of nickel ions on the one hand, while improving the corrosion resistance for the aluminum surface gaps that have not yet been covered with nickel, suppressing the excessive attack of nickel ions, and promoting the continuous growth of nickel nuclei in the region under the action of the accelerator.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An aluminum-based neutral nickel plating solution, characterized in that The following components are included in mass fraction: 5-10 parts of nickel salt, wherein the nickel salt is nickel sulfate; 15-30 parts of complexing agent, the complexing agent is malic acid; 12-18 parts of reducing agent, the reducing agent is citral; 0.1-0.4 parts of a composite stabilizer, comprising 5-oxazolecarboxylic acid and 2-hydroxy-4-methylthiazole-5-carboxylic acid; 1-5 parts of a composite accelerator, including 6-amino-9H-purine-9-propionic acid and ethyl 4-hydroxy-2-methylthiazole-5-carboxylate; 0.1-0.5 parts of a composite wetting agent, comprising poly (ethylene glycol) - block - polyethylene imine and polymethyl methacrylate.

2. The aluminum-based neutral nickel plating solution according to claim 1, characterized in that: The concentration ratio of the 5-oxazolecarboxylic acid to the 2-hydroxy-4-methylthiazole-5-carboxylic acid during use is 1:

1.

3. The aluminum-based neutral nickel plating solution according to claim 1, characterized in that: The concentration ratio of the 6-amino-9H-purine-9-propionic acid to the 4-hydroxy-2-methylthiazole-5-carboxylic acid ethyl ester during use is 1:

1.

4. The aluminum-based neutral nickel plating solution according to claim 1, characterized in that: The concentration ratio of the poly(ethylene glycol)-block-polyethyleneimine to the polymethyl methacrylate during use is 1:

1.

5. The aluminum-based neutral nickel plating solution according to claim 1, characterized in that: The operating conditions of the aluminum-based neutral nickel plating solution are a temperature of 58-68° C. and a pH value of 6.8-7.8.

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