Brightener for copper electroplating solution of printed circuit board and preparation method thereof

Abstract

The present invention provides a brightener for copper electroplating solution of a printed circuit board and a preparation method thereof. The brightener of the present invention has a carbonyl disulfide sodium salt structure and can ensure that a soluble anode copper ball obtains a dense and extremely thin film layer during a continuous electroplating process at a high current density, thereby avoiding peeling of the anode film layer to form sludge, slowing down the accumulation of anode sludge in an anode bag, reducing the cleaning frequency of the copper ball, reducing copper ball loss, saving costs, and reducing the cost of anode cleaning. Less sludge reduces contamination of the bath solution, extending the bath solution replacement cycle. By introducing a carbon-based structure into the molecule, the reaction activity of the brightener molecule on the surface of the soluble anode is reduced while ensuring the water solubility of the brightener molecule, thereby slowing down the formation of the anode film layer during the electroplating process, making it more dense, reducing the generation of anode mud, and the dense anode film is more difficult to peel off and can withstand higher current density.

Description

Technical Field

[0001] The invention relates to the technical field of copper plating of printed circuit boards, in particular to a brightener for copper electroplating solution of printed circuit boards and a preparation method thereof. Background Art

[0002] With the diversification of electronic devices, the multi-layering of printed circuit boards, the reduction in through-hole diameters, and the layout and development of the 5G industry, the concepts of efficiency, reliability, cost, production capacity, and environmental protection continue to strengthen.

[0003] The printed circuit board (PCB) industry uses an acidic plating solution containing copper ions and organic additives to perform copper electroplating.

[0004] In order to obtain a glossy and smooth copper coating, the addition of organic additives to the electroplating copper solution is particularly critical. Organic additives in the electroplating copper solution include brighteners (accelerators), leveling agents (leveling agents), and inhibitors (carriers). Among them, brighteners are the main component that contributes to the gloss of the copper coating.

[0005] The main brighteners used in traditional acid copper plating organic additives include sodium polydisulfide propane sulfonate, sodium 3-mercaptopropane sulfonate, sodium N,N-dimethylthiopropane sulfonate, and sodium thiazoline disulfide propane sulfonate. Although these brighteners are highly universal and have good gloss, they cannot fully meet industry requirements. For example, the anodic film layer of soluble anode copper balls in existing electroplating systems is too thick, and the anode film layer easily falls off and clogs the anode bag. The anode copper balls must be cleaned regularly, resulting in significant anode copper ball loss. Some anode sludge dissolves into the bath, contaminating the bath and accelerating the replacement frequency of the copper plating bath. The discharge of waste bath liquid easily pollutes the environment, increasing environmental pressure. Furthermore, traditional electroplating brighteners can cause severe flaking of the anode copper ball film when continuously electroplated at high current density (35-50 ASF). This causes an increase in cuprous ions in the bath, forming copper filament-like plating spots on the copper layer of the electroplated board, affecting the quality of the copper plating. Summary of the Invention

[0006] To address the shortcomings of the prior art, the present invention provides a brightener for copper electroplating solutions for printed circuit boards and a preparation method thereof. The addition of the brightener during the electroplating process produces a thin and dense film layer on the anode copper balls, slowing the formation of anode sludge and reducing its accumulation in anode bags. This reduces the frequency of anode cleaning, contamination of the copper electroplating bath, and the frequency of bath replacement.

[0007] The technical solution of the present invention is: a brightener for copper electroplating solution of printed circuit boards, the chemical structural formula of the brightener is:

[0008] RSSR (I);

[0009] Wherein, the structure of R is:

[0010] NaO3S-(CH2) m -R1-(CH2)n- (II);

[0011] Wherein, m=2-7, n=0-3, and when m=n, m=n=2-3, when m≠n, n=0;

[0012] R1 is the following general formula (III):

[0013]

[0014] The present invention provides a method for preparing a brightener for a copper electroplating solution for a printed circuit board, comprising the following steps:

[0015] S1), reacting halogenated acid chloride or dihalogenated ketone with potassium alkyl xanthate in dichloromethane, evaporating the solvent under reduced pressure after the reaction, and purifying to obtain reaction product a;

[0016] S2), reacting the reaction product a obtained in step S1) with sodium sulfite in an aqueous solution, and cooling to room temperature after the reaction to obtain an aqueous solution of product b;

[0017] S3), adding sodium hydroxide to the aqueous solution of the reaction product b obtained in step S2), stirring the reaction, and cooling after the reaction to obtain an aqueous solution of the reaction product c;

[0018] S4), adding triethylamine to the aqueous solution of the reaction product c obtained in step S2), reacting under ultrasonic conditions, and obtaining the brightener after the reaction is completed.

[0019] Preferably, in step S1), the halogenated acid chloride has a structure represented by general formula (IV):

[0020]

[0021] Wherein, m=2-7, n=0-3, and when m=n, m=n=2-3, when m≠n, n=0, X=Cl, Br.

[0022] Preferably, in step S1), the potassium alkyl xanthate has a structure shown in general formula (V):

[0023]

[0024] Among them, R2 is ethyl, propyl, isopropyl, butyl, or pentyl.

[0025] Preferably, in step S1), the molar ratio of the halogenated acid chloride or dihalogenated ketone to potassium alkyl xanthate is 1 to 3:1, the reaction temperature is 10-80° C., and the reaction time is 2-8 hours;

[0026] The purification method is as follows: after the reaction is completed, the mixed solution is evaporated under reduced pressure to remove the solvent, and then the salt is washed away with DI water to obtain the reaction product a.

[0027] Preferably, in step S2), the molar ratio of the reaction product a to sodium sulfite is 1:0.8-1.5, the reaction temperature is 80-110° C., and the reaction time is 2-8 h.

[0028] Preferably, in step S3), the stirring reaction temperature is 20-100° C., and the reaction time is 2-12 h.

[0029] Preferably, in step S4), the reaction temperature under ultrasonic conditions is 10-50° C., and the reaction time is 1-8 h.

[0030] The present invention also provides a copper electroplating solution for a printed circuit board, wherein the copper electroplating solution comprises a basic copper plating solution and an organic additive;

[0031] The basic copper plating solution is a mixed solution of copper sulfate pentahydrate, sulfuric acid and hydrochloric acid, and the organic additives include brightener, leveler and inhibitor.

[0032] Preferably, the concentration of copper sulfate pentahydrate in the basic copper plating solution is 50 g / L to 100 g / L, the concentration of sulfuric acid is 180 g / L to 250 g / L, and the concentration of hydrochloric acid is 40-80 mg / L.

[0033] As a preference, among the organic additives,

[0034] Brightener 0.1ppm~50ppm;

[0035] Inhibitor 100ppm~1500ppm;

[0036] Leveling agent 1ppm~80ppm.

[0037] Preferably, the inhibitor is selected from one or more of polyethylene glycol with a molecular weight of 3,000-50,000, polypropylene glycol with a molecular weight of 3,000-50,000, and ethylene oxide-propylene oxide block copolymer with a molecular weight of 3,000-50,000.

[0038] Preferably, the leveling agent is polyethyleneimine.

[0039] The beneficial effects of the present invention are:

[0040] 1. The addition of the brightener of the present invention makes the anode copper ball film thin and dense during the electroplating process, which slows down the formation of anode sludge, reduces the accumulation of sludge in the anode bag, reduces the frequency of anode cleaning, reduces the pollution of the electroplating copper bath, and also reduces the frequency of replacing the electroplating bath;

[0041] 2. The brightener provided by the present invention has both disulfide bonds and sulfonate groups. By introducing a carbon-based structure into the molecule, the water solubility of the brightener molecule is ensured while reducing the reactivity of the brightener molecule on the soluble anode surface. This slows down the formation of the anode film during the electroplating process, making it denser and reducing the formation of anode mud. The dense anode film is more difficult to peel off and can withstand higher current density.

[0042] 3. The brightener for copper electroplating provided by the present invention has a good compatibility with the inhibitor and the leveler, can obtain a glossy and smooth copper layer, and has good throwing power, can meet the production of through-hole circuit boards of high-aspect ratio printed circuit boards, has high current density resistance, can be continuously produced at high current density, increases the production capacity of a single machine, improves efficiency, has broad application prospects, and the preparation method is simple and easy to operate, and is easy to achieve mass production;

[0043] 4. The brightener of the present invention is suitable for continuous electroplating at high current density. Under the continuous electroplating at high current density, the problem of film peeling will not occur, and the quality problem of copper wire of the plate caused by cuprous ions is eliminated; DETAILED DESCRIPTION

[0044] The specific embodiments of the present invention are further described below:

[0045] Example 1

[0046] This embodiment provides a method for preparing a brightener for a copper electroplating solution for a printed circuit board, comprising the following steps:

[0047] S1), dissolving 20 mmol of halogenated acid chloride (m=2, n=0) having the structure represented by formula (IV) in 150 ml of dichloromethane solution at 30°C, then adding 10 mmol of potassium alkyl xanthate (R2 is ethyl) having the structure represented by formula (V), and stirring at 30°C for 5 h to react;

[0048] After the reaction was completed, the dichloromethane solvent was evaporated under reduced pressure, and the product was washed with 20 ml of deionized water to remove the salt generated by the reaction, and then dried to obtain a solid to obtain the reaction product a1; the structural formula of the reaction product a1 is:

[0049]

[0050] In the above formula, m=2, R2 is ethyl;

[0051] S2), reacting 5 mmol of the reaction product a1 obtained in step S1) with 5 mmol of sodium sulfite in an aqueous solution at a temperature of 100° C. for 6 h. After the reaction is completed, cooling to room temperature is performed to obtain an aqueous solution of product b1. The structural formula of the reaction product b1 is:

[0052]

[0053] In the above formula, m=2, R2 is ethyl;

[0054] S3), adding 20 mmol of potassium hydroxide to an aqueous solution containing 5 mmol of the reaction product b1, then raising the temperature to 100° C., continuing the reaction for 5 hours, and then cooling to room temperature to obtain an aqueous solution of the reaction product c1, the structural formula of the reaction product c1 being:

[0055]

[0056] In the above formula, m=2;

[0057] S4), adding triethylamine to the aqueous solution of the reaction product c1 obtained in step S3), reacting at a temperature of 30° C. under ultrasonic conditions for 3 hours. After the reaction is completed, the brightener d1 for copper electroplating of printed circuit boards according to claim 1 can be obtained. The structural formula of the brightener d1 is:

[0058]

[0059] In the above formula, m=2.

[0060] Example 2

[0061] This embodiment provides a method for preparing a brightener for a copper electroplating solution for a printed circuit board, comprising the following steps:

[0062] S1), dissolving 20 mmol of halogenated acid chloride (m=7, n=0) having the structure represented by formula (IV) in 150 ml of dichloromethane solution at 30°C, then adding 8 mmol of potassium alkyl xanthate (R2 is ethyl) having the structure represented by formula (V), and stirring at 30°C for 5 hours to react;

[0063] After the reaction was completed, the dichloromethane solvent was evaporated under reduced pressure, and the product was washed with 20 ml of deionized water to remove the salt generated by the reaction, and then dried to obtain a solid to obtain the reaction product a2; the structural formula of the reaction product a2 is:

[0064]

[0065] In the above formula, m=7, R2 is ethyl;

[0066] S2), reacting 5 mmol of the reaction product a2 obtained in step S1) with 5 mmol of sodium sulfite in an aqueous solution at a temperature of 100° C. for 6 h. After the reaction is completed, cooling to room temperature is performed to obtain an aqueous solution of the product b2. The structural formula of the reaction product b2 is:

[0067]

[0068] In the above formula, m=7, R2 is ethyl;

[0069] S3), adding 20 mmol of potassium hydroxide to an aqueous solution containing 5 mmol of the reaction product b2, then raising the temperature to 100° C., continuing the reaction for 5 hours, and then cooling to room temperature to obtain an aqueous solution of the reaction product c2, the structural formula of the reaction product c2 being:

[0070]

[0071] In the above formula, m=7;

[0072] S4), adding triethylamine to the aqueous solution of the reaction product c2 obtained in step S3), reacting at a temperature of 30° C. under ultrasonic conditions for 4 hours. After the reaction is completed, the brightener d2 for copper electroplating on a printed circuit board according to claim 1 can be obtained. The structural formula of the brightener d2 is:

[0073]

[0074] In the above formula, m=7.

[0075] Example 3

[0076] This embodiment provides a method for preparing a brightener for a copper electroplating solution for a printed circuit board, comprising the following steps:

[0077] S1), dissolving 20 mmol of a dihalogenated ketone (m=n=2) having a structure represented by formula (IV) in 150 ml of a dichloromethane solution at 30° C., then adding 7 mmol of potassium alkyl xanthate (R2 is isopropyl) having a structure represented by formula (V), and stirring at 30° C. for 5 h to react;

[0078] After the reaction, the dichloromethane solvent and unreacted dihaloketone were evaporated under reduced pressure, and the product was washed with 20 ml of deionized water to remove the salt generated by the reaction, and then dried to obtain a solid to obtain a reaction product a3; the structural formula of the reaction product a3 is:

[0079]

[0080] In the above formula, m=n=2, R2 is isopropyl;

[0081] S2), reacting 5 mmol of the reaction product a3 obtained in step S1) with 5 mmol of sodium sulfite in an aqueous solution at a temperature of 100° C. for 6 h. After the reaction is completed, cooling to room temperature is performed to obtain an aqueous solution of product b3. The structural formula of the reaction product b3 is:

[0082]

[0083] In the above formula, m=n=2, R2 is isopropyl;

[0084] S3), adding 20 mmol of potassium hydroxide to an aqueous solution containing 5 mmol of the reaction product b3, then raising the temperature to 100° C., continuing the reaction for 5 hours, and then cooling to room temperature to obtain an aqueous solution of the reaction product c3, the structural formula of the reaction product c3 being:

[0085]

[0086] In the above formula, m=n=2;

[0087] S4), adding triethylamine to the aqueous solution of the reaction product c3 obtained in step S3), reacting at a temperature of 30° C. under ultrasonic conditions for 4 hours. After the reaction is completed, the brightener d3 for copper electroplating on a printed circuit board according to claim 1 can be obtained. The structural formula of the brightener d3 is:

[0088]

[0089] In the above formula, m=n=2.

[0090] Example 4

[0091] This embodiment provides a method for preparing a brightener for a copper electroplating solution for a printed circuit board, comprising the following steps:

[0092] S1), dissolving 20 mmol of a dihalogenated ketone (m=n=3) having a structure represented by formula (IV) in 150 ml of a dichloromethane solution at 30° C., then adding 10 mmol of potassium alkyl xanthate (R2 is isopropyl) having a structure represented by formula (V), and stirring at 30° C. for 5 h to react;

[0093] After the reaction, the dichloromethane solvent and unreacted dihaloketone were evaporated under reduced pressure, and the product was washed with 20 ml of deionized water to remove the salt generated by the reaction, and then dried to obtain a solid to obtain a reaction product a4; the structural formula of the reaction product a4 is:

[0094]

[0095] In the above formula, m=n=3, R2 is isopropyl;

[0096] S2), reacting 5 mmol of the reaction product a4 obtained in step S1) with 5 mmol of sodium sulfite in an aqueous solution at a temperature of 100° C. for 6 h. After the reaction is completed, cooling to room temperature is performed to obtain an aqueous solution of the product b4. The structural formula of the reaction product b4 is:

[0097]

[0098] In the above formula, m=n=3, R2 is isopropyl;

[0099] S3), adding 20 mmol of potassium hydroxide to an aqueous solution containing 5 mmol of the reaction product b4, then raising the temperature to 100° C., continuing the reaction for 5 hours, and then cooling to room temperature to obtain an aqueous solution of the reaction product c4, the structural formula of the reaction product c4 being:

[0100]

[0101] In the above formula, m=n=3;

[0102] S4), adding triethylamine to the aqueous solution of the reaction product c4 obtained in step S3), reacting at a temperature of 30° C. under ultrasonic conditions for 4 hours. After the reaction is completed, the brightener d4 for copper electroplating on a printed circuit board according to claim 1 can be obtained. The brightener d4 has the structural formula:

[0103]

[0104] In the above formula, m=n=3.

[0105] Example 5

[0106] A copper electroplating solution was prepared: a mixed solution of copper sulfate pentahydrate and sulfuric acid was used as the copper electroplating base solution, wherein the concentration of copper sulfate pentahydrate was 75 g / L and the concentration of sulfuric acid was 215 g / L; the chloride ion concentration was 60 ppm, the brightener was 2 ppm, the inhibitor was PEG 8000 400 ppm, and the leveler was polyethyleneimine 20 ppm; the brightener prepared in Examples 1-4 was used.

[0107] Comparative Example 1

[0108] A copper plating solution was prepared by using a mixed solution of copper sulfate pentahydrate and sulfuric acid as the copper electroplating base solution, wherein the concentration of copper sulfate pentahydrate was 75 g / L and the concentration of sulfuric acid was 215 g / L; the chloride ion concentration was 60 ppm; the brightener was 2 ppm; the inhibitor PEG8000 was 400 ppm; and the leveling agent polyethyleneimine was 20 ppm; the brightener was commercially available sodium polydisulfide dipropane sulfonate.

[0109] Example 6

[0110] Electroplating samples were tested in a Haring cell with a plate thickness of 1.6 mm and a through-hole diameter of 0.25 mm. Plating was performed at 3.5 ASD for 35 minutes. A phosphorus-containing copper ball was used as the anode, placed in a titanium basket and wrapped in a filter bag. Electroplating was performed using the plating solution prepared in Example 5. The copper layer's gloss, through-hole depth capability, and post-plating anodic film peeling and sludge deposition height were evaluated. Table 1 lists the test components.

[0111] Table 1 Test results:

[0112]

[0113] As can be seen from the table above, the copper electroplating solutions using the brighteners described in Examples 1-4 have anode slime heights of 0.5 cm to 0.8 cm, while the anode slime height in Comparative Example 1, using commercially available sodium polydisulfide bis(propane disulfide) as the brightener, is 2.3 cm. Therefore, the brighteners of Examples 1-4 have significantly superior effects compared to the comparative example. The present invention introduces a carbon-based structure into the molecule, thereby reducing the reactivity of the brightener molecules on the surface of the soluble anode while ensuring the water solubility of the brightener molecules. This slows down the formation of the anode film during the electroplating process, making it denser and reducing the formation of anode slime. Furthermore, the dense anode film is more difficult to peel off and can withstand higher current densities. The addition of the brightener of the present invention results in a thin and dense film layer on the anode copper balls during the electroplating process, slowing the formation of anode slime and reducing the accumulation of slime in the anode bag. This reduces the frequency of anode cleaning, contamination of the copper electroplating bath, and replacement of the electroplating bath.

[0114] The above embodiments and descriptions are only for explaining the principles and best embodiments of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, which shall fall within the scope of the invention to be protected.

Claims

1. A copper electroplating solution for a printed circuit board, comprising a base copper plating solution and an organic additive; The basic copper plating solution is a mixed solution of copper sulfate pentahydrate, sulfuric acid and hydrochloric acid, and the organic additives include brightener, leveler and inhibitor; The concentration of copper sulfate pentahydrate in the basic copper plating solution is 50g / L to 100g / L, the concentration of sulfuric acid is 180g / L to 250g / L, and the concentration of hydrochloric acid is 40-80mg / L; Its characteristics are: The chemical structural formula of the brightener is: RSSR (I); Wherein, the structure of R is: NaO3S-(CH2) m -R1-(CH2) n - (II); Wherein, m=2-7, n=0-3, and when m=n, m=n=2-3, when m≠n, n=0; R1 is the following structure: 。 2. The copper electroplating solution for printed circuit boards according to claim 1, wherein: Among the organic additives, Brightener 0.1ppm~50ppm; Inhibitor 100ppm~1500ppm; Leveling agent 1ppm~80ppm.

3. The copper electroplating solution for printed circuit boards according to claim 1, wherein: The leveling agent is polyethyleneimine; The inhibitor is selected from one or more of polyethylene glycol with a molecular weight of 3,000-50,000, polypropylene glycol with a molecular weight of 3,000-50,000, and ethylene oxide-propylene oxide block copolymer with a molecular weight of 3,000-50,000.

4. The copper electroplating solution for printed circuit boards according to claim 1, wherein: The brightener preparation comprises the following steps: S1), reacting halogenated acid chloride or dihalogenated ketone with potassium alkyl xanthate in dichloromethane, evaporating the solvent under reduced pressure after the reaction, and purifying to obtain reaction product a; S2), reacting the reaction product a obtained in step S1) with sodium sulfite in an aqueous solution, and cooling to room temperature after the reaction to obtain an aqueous solution of product b; S3), adding sodium hydroxide to the aqueous solution of the reaction product b obtained in step S2), stirring the reaction, and cooling after the reaction to obtain an aqueous solution of the reaction product c; S4), adding triethylamine to the aqueous solution of the reaction product c obtained in step S2), reacting under ultrasonic conditions, and obtaining the brightener after the reaction is completed.

5. The copper electroplating solution for printed circuit boards according to claim 4, wherein: In step S1), the halogenated acid chloride has a structure represented by formula (IV): Wherein, m=2-7, n=0-3, and when m=n, m=n=2-3, when m≠n, n=0, X=Cl, Br.

6. The copper electroplating solution for printed circuit boards according to claim 4, wherein: In step S1), the potassium alkyl xanthate has a structure shown in general formula (V): ； Among them, R2 is ethyl, propyl, isopropyl, butyl, or pentyl.

7. The copper electroplating solution for printed circuit boards according to claim 4, wherein: In step S1), the molar ratio of the halogenated acid chloride or dihalogenated ketone to potassium alkyl xanthate is 1 to 3:1, the reaction temperature is 10-80° C., and the reaction time is 2-8 hours; The purification method is as follows: after the reaction is completed, the mixed solution is evaporated under reduced pressure to remove the solvent, and then the salt is washed away with DI water to obtain the reaction product a.

8. The copper electroplating solution for printed circuit boards according to claim 4, wherein: In step S2), the molar ratio of the reaction product a to sodium sulfite is 1:0.8-1.5, the reaction temperature is 80-110° C., and the reaction time is 2-8 h.

9. The copper electroplating solution for printed circuit boards according to claim 4, wherein: In step S3), the stirring reaction temperature is 20-100° C., and the reaction time is 2-12 h.

10. The copper electroplating solution for printed circuit boards according to claim 4, characterized in that: In step S4), the reaction temperature under the ultrasonic condition is 10-50° C., and the reaction time is 1-8 h.

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