Low-stress electroplating high-phosphorus nickel plating solution and electroplating method thereof

Abstract

The embodiment of the present application discloses a kind of low stress electroplating high phosphorus nickel plating solution and its electroplating method, the electroplating high phosphorus nickel plating solution includes the following mass concentration component: nickel salt 300-360g / L, complexing agent 20-40g / L, reducing agent 30-50g / L, leveling agent 0.02-0.08g / L, promoter 0.1-0.5g / L, dispersing agent 0.6-1.2g / L;The complexing agent is amino carboxyl pyridine compound;The leveling agent is amino alkyl hydroxyl sulfonate compound;The dispersing agent is amino alkyl olefin carboxylic acid polymer;The promoter is mercapto alkyl pyrimidine compound.The present application can realize the electroplating process of low stress high phosphorus nickel, it has excellent stability, excellent binding force, phosphorus content can reach 11% or more, can realize the thick nickel electroplating of substrate while containing high phosphorus, and it will not produce the phenomenon of collapse when bending more than 90 degrees.

Description

Technical Field

[0001] This invention relates to the field of nickel electroplating technology, and more particularly to a low-stress high-phosphorus nickel electroplating solution and its electroplating method. Background Technology

[0002] Die-casting modules are primarily made of aluminum and zinc alloys, offering high forming efficiency, complex structures, and excellent precision. They are widely used in high-end manufacturing fields such as precision electronics, automobiles, and molds. However, die-cast substrates often exhibit defects such as oxide films, porosity, silicon phases, and component segregation. These defects require electroplating with high-phosphorus nickel plating to improve corrosion resistance, wear resistance, smoothness, and non-magnetic properties.

[0003] Currently, high-phosphorus nickel plating of die-cast modules generally adopts the nickel aminosulfonate system, combined with conventional complexing agents and phosphorus sources for co-deposition. However, the die-cast substrate has uneven surface and large activity differences. Conventional plating solutions have high deposition stress, and thick plating layers are prone to cracking, warping, and peeling, with poor adhesion. Moreover, traditional processes cannot balance high phosphorus content and low stress characteristics. Reducing stress often sacrifices phosphorus content, which cannot meet the requirements of non-magnetic and high corrosion resistance.

[0004] The industry often tries to improve the situation by simply adjusting process parameters or adding common additives, but the effects are limited and can easily lead to problems such as decreased plating solution stability, low deposition efficiency, and poor coating uniformity, making it difficult to adapt to the large-scale production of high-precision die-casting modules. Therefore, developing a high-phosphorus nickel electroplating process that is suitable for die-casting modules, with low stress, high phosphorus content, and high adhesion has significant engineering application value. Summary of the Invention

[0005] The technical problem to be solved by the embodiments of the present invention is to provide a low-stress electroplating high-phosphorus nickel plating solution and its electroplating method, so as to realize the low-stress high-phosphorus nickel electroplating process, which has excellent stability, excellent adhesion, and phosphorus content of up to 11% or more. It can achieve thick nickel electroplating of substrates while containing high phosphorus, and will not crack when bent more than 90 degrees.

[0006] To address the aforementioned technical problems, embodiments of the present invention provide a low-stress electroplating high-phosphorus nickel plating solution, comprising the following components by mass concentration: Nickel salt 300-360 g / L, complexing agent 20-40 g / L, reducing agent 30-50 g / L, leveling agent 0.02-0.08 g / L, accelerator 0.1-0.5 g / L, dispersant 0.6-1.2 g / L; The complexing agent is an aminocarboxypyridine compound; the leveling agent is an aminoalkylhydroxysulfonate compound; the dispersant is an aminoalkylolefin carboxylic acid polymer; and the accelerator is a mercaptoalkylpyrimidine compound. The reducing agent is sodium hypophosphite.

[0007] The nickel salt is nickel aminosulfonate and nickel chloride, wherein the nickel aminosulfonate is 300-330 g / L and the nickel chloride is 30-60 g / L.

[0008] Furthermore, the aminocarboxypyridine compound is 5-carboxy-2,3-diaminopyridine.

[0009] Furthermore, the aminoalkyl hydroxysulfonate compound is 2-sodium (dimethylamino)-1-hydroxyethanesulfonate.

[0010] Furthermore, the aminoalkyl olefin carboxylic acid polymer is an aminoethylated acrylic acid polymer.

[0011] Furthermore, the mercaptoalkylpyrimidine compound is 2-mercapto-5-n-propanepyrimidine.

[0012] Furthermore, the operating conditions of the low-stress electroplating high-phosphorus nickel plating solution are: temperature 60-70℃, pH value 2.8-3.4, and current density 2.5-4.5A / dm².

[0013] Accordingly, embodiments of the present invention also provide an electroplating method for a low-stress electroplating high-phosphorus nickel plating solution, comprising: Step A: Add ultrapure water to the mixing tank, keep the temperature constant at 35-40℃, stir at 120-150r / min, add nickel aminosulfonate and nickel chloride in sequence, and dissolve in stages to obtain the base solution; Step B: Add a portion of the complexing agent to the base solution for the first time and stir to complete the initial chelation of nickel ions; then mix the remaining complexing agent with the leveling agent and slowly add it dropwise to the base solution; Step C: Dissolve sodium hypophosphite in ultrapure water to prepare a saturated mother liquor, and slowly add it dropwise to the base solution while stirring throughout the process; Step D: Add the dispersant and accelerator sequentially, and mix thoroughly using intermittent stirring; adjust the pH to 2.8-3.4 with sodium hydroxide or sulfuric acid; Step E: Segmented stepped current electroplating.

[0014] Furthermore, in step E, the initial pre-plating is performed at 2.5-2.7 A / dm² for 3 minutes; the intermediate main plating is performed at 2.8-3.5 A / dm²; and the final sealing deposition is performed at 3.0 A / dm². The temperature throughout the process is 60-70℃, the anode-cathode spacing is 12-18cm, and the process is accompanied by circulating filtration and nitrogen stirring.

[0015] The beneficial effects of this invention are as follows: 1) This invention uses an aminocarboxypyridine compound, specifically 5-carboxy-2,3-diaminopyridine, which not only improves the stability of nickel ions but also enhances the fineness of nickel deposition. Traditional complexing agents such as malic acid and EDTA have limited effects, and over time, they can cause slight whitening of the plating and easily lead to the formation of small nickel nodules. In contrast, the complexing agent used in this application exhibits significantly less of this phenomenon.

[0016] 2) This invention uses an aminoalkyl hydroxysulfonate compound as the leveling agent, specifically 2-sodium (dimethylamino)-1-hydroxyethanesulfonate. Traditional leveling agents easily cause coating brittleness, plating leakage in low current areas, and easy decomposition of the plating solution. Some may also cause color difference and impurity accumulation in the coating. 2-sodium (dimethylamino)-1-hydroxyethanesulfonate has excellent leveling ability, good plating solution stability, no by-product accumulation, uniform and bright coating in both high and low current areas, and strong compatibility. This invention represents a formulation innovation in terms of molecular structure and mechanism of action.

[0017] 3) The dispersant used in this invention can improve the current density distribution efficiency and can work synergistically with the leveling agent. Experiments have shown that after the addition of this substance, the coating structure is improved at high current densities, such as those exceeding 2.5 A / dm². 2 Even afterward, a low-stress, bright, and delicate coating can still be achieved. Multiple bending tests exceeding 90 degrees proved that no cracks or coating defects were observed in the coating.

[0018] 4) In the preparation of the plating solution, the low-temperature pre-dissolution treatment of the base solution ensures the stability of nickel ions in their free state; the complexing agent is added in two stages to precisely control the complexation stability constant of the plating solution, suppressing the subsequent efflux of phosphorus source water and laying the foundation for uniform co-deposition of nickel and phosphorus; the slow-release homogeneous doping of phosphorus source avoids local enrichment of high-concentration phosphorus source, achieving uniform dispersion of phosphorus components at the molecular level and ensuring the uniformity of high phosphorus content in the coating; the low-stress composite additive modification of this invention enables the additive to be directionally adsorbed on the surface of nickel ion complex clusters, controlling the charge distribution at the deposition interface and offsetting the tensile stress of the coating deposition from the source. Furthermore, in the electroplating process, a segmented stepped current + constant temperature steady-state deposition process is adopted to avoid the stress accumulation problem caused by constant current deposition. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will be further described in detail below with reference to specific embodiments.

[0020] The low-stress electroplating high-phosphorus nickel plating solution of this invention comprises the following components by mass concentration: Nickel salt 300-360 g / L, complexing agent 20-40 g / L, reducing agent 30-50 g / L, leveling agent 0.02-0.08 g / L, accelerator 0.1-0.5 g / L, dispersant 0.6-1.2 g / L.

[0021] The complexing agent is an aminocarboxypyridine compound; the leveling agent is an aminoalkylhydroxysulfonate compound; the dispersant is an aminoalkylolefin carboxylic acid polymer; and the accelerator is a mercaptoalkylpyrimidine compound.

[0022] The aminocarboxypyridine compound is 5-carboxy-2,3-diaminopyridine. The reducing agent is sodium hypophosphite. The nickel salt is nickel sulfamate and nickel chloride, wherein the nickel sulfamate concentration is 300-330 g / L and the nickel chloride concentration is 30-60 g / L. This invention uses 5-carboxy-2,3-diaminopyridine as the aminocarboxypyridine compound, which not only improves the stability of nickel ions but also enhances the fineness of nickel deposition. Traditional complexing agents such as malic acid and EDTA have limited effects, and over time, these complexing agents can cause slight whitening of the plating and easily lead to the formation of small amounts of nickel nodules. In contrast, the complexing agent used in this invention exhibits significantly less of this phenomenon.

[0023] The aminoalkyl hydroxysulfonate compound is 2-sodium (dimethylamino)-1-hydroxyethanesulfonate. The leveling agent of this invention uses an aminoalkyl hydroxysulfonate compound, specifically 2-sodium (dimethylamino)-1-hydroxyethanesulfonate. Traditional leveling agents such as saccharin, 1,4-butynediol, coumarin, 4-(N-ethyl-N-hydroxyethyl)-2-methylphenylenediamine sulfate, diethyldithiophosphate ammonium salt, and 2-sodium (dimethylamino)-1-hydroxyethanesulfonate, etc., easily cause coating brittleness, plating leakage in low-current areas, easy decomposition of the plating solution, and in some cases, color difference and impurity accumulation in the coating. 2-sodium (dimethylamino)-1-hydroxyethanesulfonate exhibits excellent leveling ability, good plating solution stability, no by-product accumulation, uniform and bright coating in both high and low current areas, and strong compatibility, achieving formulation innovation from the perspectives of molecular structure and mechanism of action.

[0024] The aminoalkyl olefin carboxylic acid polymer is an aminoethylated acrylic acid polymer. Preferably, the mercaptoalkylpyrimidine compound is 2-mercapto-5-n-propanepyrimidine. The dispersant of the present invention can improve current density distribution efficiency and can work synergistically with the leveling agent. Experiments have shown that after the addition of this substance, the coating structure is improved at high current densities, such as those exceeding 2.5 A / dm². 2Even afterward, a low-stress, bright, and fine coating can still be achieved. Multiple bending tests exceeding 90 degrees proved that no cracks or plating defects were observed. The accelerator can increase the transport rate of nickel ions, promoting effective nickel ion deposition. Due to improper pretreatment in certain localized areas, or localized unevenness of the substrate itself, coupled with the adsorption of leveling agents, poor deposition can occur. The accelerator can accelerate the rapid deposition in concave areas, working synergistically with the leveling agent.

[0025] The operating conditions of the low-stress electroplating high-phosphorus nickel plating solution are: temperature 60-70℃, pH value 2.8-3.4, and current density 2.5-4.5A / dm².

[0026] The electroplating method of the low-stress electroplating high-phosphorus nickel plating solution of the present invention includes steps A to E.

[0027] Step A, low-temperature pre-dissolution treatment of the base solution: Add 60% volume of ultrapure water to the mixing tank, keep the temperature constant at 35-40℃, stir at a low speed of 120-150r / min, add nickel aminosulfonate and nickel chloride in sequence, dissolve in stages for 15min to obtain the base solution.

[0028] Step B involves adding the complexing agent in two stages using a compounding method: first, add 65% of the complexing agent to the base solution and stir for 20 minutes to complete the initial chelation of nickel ions; then, slowly add the remaining 35% of the complexing agent, mixed with the leveling agent, to the base solution.

[0029] Step C, slow-release homogeneous doping of phosphorus source: Sodium hypophosphite is dissolved in ultrapure water at a constant temperature of 25°C to prepare a saturated mother liquor, which is then slowly added dropwise to the base liquid, with the stirring rate reduced to 80 r / min throughout the process.

[0030] Step D, modification of low-stress composite additives: add dispersant and accelerator in batches, and mix them by intermittent stirring (stir for 5 minutes, let stand for 3 minutes, cycle 4 times, and stir evenly); adjust the pH to 2.8-3.4 with 10% sodium hydroxide or 10% sulfuric acid; Step E employs a segmented stepped current + constant temperature steady-state deposition process: segmented stepped current electroplating. Initially, a pre-plating of 2.5-2.7 A / dm² for 3 minutes is used to build a dense transition substrate; the middle stage involves steady-state main plating at 2.8-3.5 A / dm²; and the final stage uses 3.0 A / dm² for stabilized voltage sealing deposition. The plating bath temperature remains constant at 60-70℃ throughout the process, with a cathode-cathode spacing of 12-18 cm, coupled with circulating filtration and nitrogen agitation.

[0031] In this invention, during the preparation of the plating solution, low-temperature pre-dissolution of the base solution ensures the stability of nickel ions in their free state; the complexing agent is added in two stages to precisely control the complexation stability constant of the plating solution, suppressing subsequent phosphorus source water leaching and laying the foundation for uniform co-deposition of nickel and phosphorus; slow-release homogeneous doping of the phosphorus source avoids local enrichment of high-concentration phosphorus source, achieving uniform dispersion of phosphorus components at the molecular level and ensuring the uniformity of high phosphorus content in the coating; low-stress composite additive modification: the additive is directionally adsorbed onto the surface of nickel ion complex clusters, regulating the charge distribution at the deposition interface and offsetting the tensile stress of the coating deposition from the source. Furthermore, during the electroplating process, a segmented stepped current + constant-temperature steady-state deposition process is adopted to avoid the stress accumulation problem caused by constant current deposition.

[0032] Example 1:

[0033] The low-stress electroplating high-phosphorus nickel plating bath of this invention comprises: nickel aminosulfonate 315 g / L, nickel chloride 45 g / L, 5-carboxy-2,3-diaminopyridine 30 g / L, sodium hypophosphite 40 g / L, 2-sodium (dimethylamino)-1-hydroxyethanesulfonate 0.06 g / L, 2-mercapto-5-n-propanepyrimidine 0.3 g / L, and aminoethylated acrylic polymer 0.9 g / L. The plating conditions are: 65°C; pH 3.2; initial current density 2.6 A / dm² for 3 min; intermediate current density 3.2 A / dm² for 40 min; and final current density 3.0 A / dm² for 20 min. The test results for Example 1 are as follows: stability is excellent; coating appearance is excellent; bending performance is excellent; and phosphorus content is 12.3%.

[0034] Example 2:

[0035] The low-stress electroplating high-phosphorus nickel plating bath of this invention comprises: nickel aminosulfonate 330 g / L, nickel chloride 30 g / L, 5-carboxy-2,3-diaminopyridine 25 g / L, sodium hypophosphite 40 g / L, 2-sodium (dimethylamino)-1-hydroxyethanesulfonate 0.04 g / L, 2-mercapto-5-n-propanepyrimidine 0.5 g / L, and aminoethylated acrylic polymer 0.9 g / L. The plating conditions are: 65°C; pH 3.2; pre-plating at 2.6 A / dm² for 3 min; mid-plating at 3.2 A / dm² for 40 min; and final plating at 3.0 A / dm² for 20 min. The test results for Example 2 were as follows: stability was excellent; coating appearance was excellent; bending performance was excellent; and phosphorus content was 11.9%.

[0036] Example 3:

[0037] The low-stress electroplating high-phosphorus nickel plating bath of this invention comprises: nickel aminosulfonate 300 g / L, nickel chloride 60 g / L, 5-carboxy-2,3-diaminopyridine 18 g / L, sodium hypophosphite 35 g / L, 2-sodium (dimethylamino)-1-hydroxyethanesulfonate 0.06 g / L, 2-mercapto-5-n-propanepyrimidine 0.3 g / L, and aminoethylated acrylic polymer 1.2 g / L. The plating temperature is 65℃; pH value is 3.2. The initial plating time is 2.6 A / dm² for 3 min; the middle plating time is 3.2 A / dm² for 40 min; and the final plating time is 3.0 A / dm² for 20 min. The test results for Example 3 were as follows: stability was excellent; coating appearance was excellent; bending performance was excellent; and phosphorus content was 12.1%.

[0038] Comparative Example 1: The low-stress electroplating high-phosphorus nickel plating bath of Comparative Example 1 consisted of: nickel aminosulfonate 315 g / L, nickel chloride 45 g / L, sodium hypophosphite 40 g / L, 2-sodium (dimethylamino)-1-hydroxyethanesulfonate 0.06 g / L, 2-mercapto-5-n-propanepyrimidine 0.3 g / L, and aminoethylated acrylic polymer 0.9 g / L. The plating conditions were: 65℃; pH 3.2; initial plating at 2.6 A / dm² for 3 min; intermediate plating at 3.2 A / dm² for 40 min; and final plating at 3.0 A / dm² for 20 min. Compared with Example 1, Comparative Example 1 lacked a complexing agent, and the test results were as follows: stability was excellent; coating appearance was poor; bending phenomenon was poor; and phosphorus content was 9.7%.

[0039] Comparative Example 2: The low-stress electroplating high-phosphorus nickel plating bath of Comparative Example 2 consisted of: nickel aminosulfonate 315 g / L, nickel chloride 45 g / L, 5-carboxy-2,3-diaminopyridine 30 g / L, sodium hypophosphite 40 g / L, 2-mercapto-5-n-propanepyrimidine 0.3 g / L, and aminoethylated acrylic polymer 0.9 g / L. The plating conditions were: 65℃; pH 3.2; initial plating at 2.6 A / dm² for 3 min; intermediate plating at 3.2 A / dm² for 40 min; and final plating at 3.0 A / dm² for 20 min. Compared with Example 1, Comparative Example 2 lacked a leveling agent, and the test results were as follows: stability was good; coating appearance was poor; bending phenomenon was poor; and phosphorus content was 12.7%.

[0040] Comparative Example 3: The low-stress electroplating high-phosphorus nickel plating bath of Comparative Example 3 consisted of: nickel aminosulfonate 315 g / L, nickel chloride 45 g / L, 5-carboxy-2,3-diaminopyridine 30 g / L, sodium hypophosphite 40 g / L, 2-sodium (dimethylamino)-1-hydroxyethanesulfonate 0.06 g / L, and aminoethylated acrylic polymer 0.9 g / L. The plating conditions were: 65℃; pH 3.2; initial current density 2.6 A / dm² for 3 min; intermediate current density 3.2 A / dm² for 40 min; and final current density 3.0 A / dm² for 20 min. Compared with Example 1, Comparative Example 3 lacked an accelerator, and the test results were as follows: stability was excellent; coating appearance was good; bending performance was good; and phosphorus content was 12.5%.

[0041] Comparative Example 4: The low-stress electroplating high-phosphorus nickel plating bath of Comparative Example 4 consisted of: nickel aminosulfonate 315 g / L, nickel chloride 45 g / L, 5-carboxy-2,3-diaminopyridine 30 g / L, sodium hypophosphite 40 g / L, 2-sodium (dimethylamino)-1-hydroxyethanesulfonate 0.06 g / L, and 2-mercapto-5-n-propanepyrimidine 0.3 g / L. The plating conditions were: 65℃; pH 3.2; initial current density 2.6 A / dm² for 3 min; intermediate current density 3.2 A / dm² for 40 min; and final current density 3.0 A / dm² for 20 min. Compared with Example 1, Comparative Example 4 lacked a dispersant, and the test results were as follows: stability was excellent; coating appearance was good; bending performance was good; and phosphorus content was 12.6%.

[0042] The evaluation criteria for the various embodiments and comparative examples of this invention are shown in Table 1:

[0043] This invention enables a low-stress, high-phosphorus nickel electroplating process with excellent stability, superior adhesion, and a phosphorus content of over 11%. It can achieve thick nickel electroplating of substrates while containing high phosphorus, and will not crack when bent at more than 90 degrees.

[0044] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-stress electroplating solution for high-phosphorus nickel, characterized in that, Includes the following components by mass concentration: Nickel salt 300-360 g / L, complexing agent 20-40 g / L, reducing agent 30-50 g / L, leveling agent 0.02-0.08 g / L, accelerator 0.1-0.5 g / L, dispersant 0.6-1.2 g / L; pH value 2.8-3.4; The complexing agent is 5-carboxy-2,3-diaminopyridine; the leveling agent is 2-sodium (dimethylamino)-1-hydroxyethanesulfonate; the dispersant is aminoethylated acrylic polymer; and the accelerator is 2-mercapto-5-n-propanepyrimidine. The reducing agent is sodium hypophosphite; The nickel salt is nickel aminosulfonate and nickel chloride, wherein the nickel aminosulfonate is 300-330 g / L and the nickel chloride is 30-60 g / L.

2. The low-stress electroplating high-phosphorus nickel plating solution as described in claim 1, characterized in that, The operating conditions for the low-stress electroplating high-phosphorus nickel plating solution are: temperature 60-70℃, current density 2.5-4.5A / dm².

3. A method for electroplating a low-stress high-phosphorus nickel plating solution as described in claim 1 or 2, characterized in that, include: Step A: Add ultrapure water to the mixing vessel, maintain the temperature at 35-40℃, stir at 120-150r / min, add nickel aminosulfonate and nickel chloride in sequence, and dissolve in stages to obtain the base solution; Step B: Add a portion of the complexing agent to the base solution for the first time and stir to complete the initial chelation of nickel ions; then mix the remaining complexing agent with the leveling agent and slowly add it dropwise to the base solution; Step C: Dissolve sodium hypophosphite in ultrapure water to prepare a saturated mother liquor, and slowly add it dropwise to the base solution while stirring throughout the process; Step D: Add the dispersant and accelerator sequentially, and mix thoroughly using intermittent stirring; adjust the pH to 2.8-3.4 with sodium hydroxide or sulfuric acid; Step E: Pre-plating at 2.5-2.7 A / dm² for 3 min in the early stage; main plating at 2.8-3.5 A / dm² for 40 min in the middle stage; sealing deposition at 3.0 A / dm² for 20 min in the later stage; the temperature throughout the process is 60-70℃, the distance between the anode and cathode is 12-18 cm, and it is combined with circulating filtration and nitrogen stirring.

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