An imidazole ring sulfide quaternary ammonium salt compound, a preparation method and application thereof

Abstract

This invention relates to the field of fine chemicals, and more particularly to an imidazole cyclic sulfide quaternary ammonium salt compound, its preparation method, and its application. The structural formula of the compound is shown in Formula (I). This invention provides a novel imidazole sulfide quaternary ammonium salt compound, its preparation method, and its application in electroplating solutions. This compound, during continuous electroplating at low current densities, can produce a bright and smooth copper-plated surface on the workpiece, while also possessing excellent deep plating capability and a good copper layer lattice structure, thus adapting to the specific needs of current copper plating additive processes.

Description

Technical Field

[0001] This invention relates to the field of fine chemicals, and in particular to an imidazole cyclic sulfide quaternary ammonium salt compound, its preparation method, and its application. Background Technology

[0002] In acidic copper plating processes, the synergistic effect of organic additive systems is crucial for ensuring coating quality. Leveling agents, brighteners, and inhibitors constitute the core functional components. Traditional leveling agents mainly include nitrogen-containing polyether compounds, dye compounds, quaternary ammonium salt compounds, and polymers reacting nitrogen-containing heterocyclic or nitrogen-containing linear compounds with epoxy groups. This type of polymer system represents the classic structure of modern leveling agents, and when used in conjunction with brighteners and wetting agents, it can achieve smooth coatings over a wide current density range. For example, European invention patent EP2562294A3 discloses a reaction product of a cyclodiaza compound and epoxides such as epichlorohydrin; US invention patent US3081240A first proposed adding nitrogen-containing basic dyes such as thiazole dyes and acridine dyes as leveling agents in acidic plating baths, which act on low current density areas, marking the beginning of the systematic application of organic additives. After continuous improvement, dyes such as Genna Green, Crystal Violet, and Direct Black are still partially used in modern additive systems. Chinese invention patent application CN118390125A also discloses a composite system containing chlorobenzenesulfonic acid derivatives, chlorodiphenyl sulfide derivatives, etc., and leveling agents, which is suitable for acidic copper plating of IC substrates and can achieve uniform and smooth plating and blind hole filling.

[0003] With the development of the electronics manufacturing industry, copper plating technology is gradually evolving towards higher aspect ratios and higher densities. For the demand for through-hole copper plating with aspect ratios of 8:1 to 15:1, existing technologies mainly fall into two optimization categories. One is pulse electroplating through-hole technology, which can achieve a plating depth of TP=80-110% or even higher. However, it suffers from problems such as rough and uneven copper surface, a matte finish, and even reddish discoloration in some areas. Furthermore, the brightener consumption rate is 3 to 6 times that of DC electroplating, resulting in extremely unstable brightener concentration in the plating solution. Even slight fluctuations can lead to defects such as dullness, haziness, or streaks in the plating layer. The process window is narrow and its stability is poor. Another type is the low-current DC electroplating process (current density 6-18 ASF). This method has advantages such as good copper layer gloss, flat board surface, high reliability, strong plating solution stability and wide process window. However, due to the high aspect ratio structure, conventional additive systems are difficult to achieve ideal deep plating capability. For example, for through holes with an aspect ratio of 10:1, the copper plating depth capability is mostly less than 60%, which cannot meet the electroplating quality requirements of high aspect ratio workpieces.

[0004] Against this backdrop, there is an urgent need to provide a technical solution that is compatible with low-current DC electroplating, can obtain a bright and smooth plating surface with excellent deep plating capability and good copper layer lattice in high aspect ratio through-hole scenarios. Summary of the Invention

[0005] To optimize the low-current DC copper plating process, this invention provides a novel imidazole sulfide quaternary ammonium salt compound, its preparation method, and its application in electroplating solutions. This compound can produce a bright and smooth copper-plated surface on the workpiece during continuous electroplating at low current density, while also possessing excellent deep plating capability and a good copper layer lattice structure, making it suitable for the specific needs of current copper plating additive processes.

[0006] The first aspect of this invention provides an imidazole cyclic sulfide quaternary ammonium salt compound, the structural formula of which is shown in Formula (I): Equation (Ⅰ) Where m = 1-6, which can be listed as 1, 2, 3, 4, 5, 6; X is a halogen, which can be listed as Cl, Br or I.

[0007] To address the problems of insufficient deep plating capability (mostly below 60%), columnar lattice formation, and poor ductility in conventional additive systems used in low-current DC electroplating processes for high aspect ratio (8-15):1 through-hole plating, the present invention employs imidazole ring sulfide quaternary ammonium salt compounds as shown in formula (Ⅰ) as leveling agents. This achieves technical effects such as a deep plating capability of approximately 75% in copper plating scenarios with high aspect ratio through-holes, a dense lattice without columnar defects, excellent ductility, a wide effective concentration window (0.2-10ppm), and a smooth, glossy surface without whitening at the hole openings. The core reason lies in the synergistic effect of the compound molecule, which simultaneously possesses an imidazole ring, a thioether bond, and a quaternary ammonium salt group: the imidazole ring can regulate the copper ion deposition rate in the low current density region through adsorption, the thioether bond can optimize the crystal orientation of the coating, and the cationic characteristics of the quaternary ammonium salt group can enhance the adsorption stability of the molecule on the pore wall. The three work together to improve the uniformity of current distribution and inhibit the growth of columnar crystals, thus achieving both excellent deep plating capability and comprehensive coating performance in low current electroplating scenarios.

[0008] Optionally, the raw materials for preparing the compound include: 2-mercaptoimidazole, haloquaternary ammonium salt, activator and solvent.

[0009] Optionally, the structural formula of the haloquaternary ammonium salt is shown in formula (II): Formula (II).

[0010] Optionally, the haloquaternary ammonium salt includes one or more combinations of (2-bromoethyl)trimethylammonium bromide, 3-bromopropyltrimethylammonium bromide, (2-chloroethyl)trimethylammonium chloride, 4-bromobutyltrimethylammonium bromide, (3-chloropropyl)trimethylammonium chloride, 5-bromopentyltrimethylammonium bromide, (6-chlorohexyl)trimethylammonium chloride, and 2-iodoethyltrimethylammonium iodide; further optionally, it is (2-bromoethyl)trimethylammonium bromide or 3-bromopropyltrimethylammonium bromide.

[0011] Optionally, the solvent includes one or more combinations of ethanol, acetonitrile, tetrahydrofuran, (N,N-dimethylformamide), and DMSO (dimethyl sulfoxide).

[0012] Optionally, the molar ratio of the 2-mercaptoimidazole to the haloquammonium salt is 1:(1.01-1.03).

[0013] Optionally, the molar ratio of the 2-mercaptoimidazole to the activator is 1:(1.05-1.1).

[0014] Optionally, the activator includes potassium carbonate or sodium carbonate.

[0015] A second aspect of the present invention provides a method for preparing the imidazole cyclic sulfide quaternary ammonium salt compound as described above, wherein the preparation steps of the compound include: 2-Mercaptoimidazole, haloquaternary ammonium salt, solvent and activator are mixed and reacted at high temperature to obtain a liquid containing imidazole cyclic sulfide quaternary ammonium salt compounds. Optionally, the preparation steps of the compound further include: cooling the feed solution and adjusting the pH to neutral after the reaction, and performing post-treatment on the feed solution to obtain the purified imidazole cyclic sulfide quaternary ammonium salt compound.

[0016] Optionally, the post-processing method is extraction; the extractant used in the extraction process can be listed as dichloromethane, trichloromethane, ethyl acetate, dichloroethane, toluene, diethyl ether, etc.; further, dichloromethane can be selected.

[0017] The reaction temperatures can be listed as 30℃, 40℃, 50℃, 60℃, and 70℃.

[0018] Optionally, the reaction conditions are: 30-70℃ for 3-24 hours.

[0019] In some embodiments, the preparation steps of the compound include: S1. Mix 2-mercaptoimidazole, haloquaternary ammonium salt and solvent, add activator, react at 30-70℃ for 3-24h to obtain the solution; S2. Cool the feed solution to room temperature, adjust the pH to neutral, extract the feed solution with an extractant, and remove the extractant to obtain imidazole cyclic sulfide quaternary ammonium salt compounds.

[0020] Optionally, the method for removing the extractant is evaporation.

[0021] The compounds synthesized in this invention offer flexible usage methods. In batch synthesis scenarios, a small amount of water can be directly added to the reaction system to dissolve the solid, and then the pH can be adjusted with dilute sulfuric acid. The product mass fraction can then be directly calculated based on the theoretical volume value and put into use, making the operation simple and efficient. The advantage of the compounds synthesized in this invention is that they can be used directly in batch synthesis without post-treatment such as extraction. This is because the target product synthesized in this invention is mainly used as a leveling agent for electroplating solutions, and it must ultimately dissolve in an aqueous electroplating solution. The reaction system after batch synthesis is essentially a mixture of "organic solvent + solid product + inorganic salt byproduct," which can be directly adapted to the aqueous environment of the electroplating solution. Therefore, no post-treatment is required; it can be used directly after dissolution and pH adjustment, making the operation very convenient.

[0022] Alternatively, the reaction time can be 4-8 hours, which can balance reaction yield and synthesis efficiency.

[0023] A third aspect of the present invention provides an application of the imidazole cyclic sulfide quaternary ammonium salt compound as described above, wherein the imidazole cyclic sulfide quaternary ammonium salt compound is applied to an electroplating solution.

[0024] In some embodiments, the electroplating solution is an acidic copper plating solution.

[0025] Optionally, the raw materials for preparing the electroplating solution include: Copper sulfate pentahydrate: 35-65 g / L; Sulfuric acid: 220-270 g / L; Chloride ions: 40-80 ppm; Brightener: 0.5-5 ppm; Compounds represented by formula (Ⅰ): 0.2-10 ppm; Inhibitor: 300-1200 ppm; The solvent is water.

[0026] Chloride ions are provided by hydrochloric acid.

[0027] Optionally, the brightening agent may include sodium 3-mercaptopropane sulfonate, sodium N,N-dimethyldithioaminopropane sulfonate, sodium thiazoline dithiopropane sulfonate, sodium 2-mercapto-5-benzimidazole sulfonate, sodium polydithiodiethane sulfonate, sodium polydithiodipropane sulfonate, etc.; sodium polydithiodipropane sulfonate may be selected.

[0028] Optionally, the inhibitor may include polyethylene glycol, polyethylene glycol-polypropylene glycol block copolymer, polypropylene glycol monobutyl ether, poly(ethylene glycol-ran-polypropylene glycol) monobutyl ether, etc.; it may be poly(ethylene glycol-ran-polypropylene glycol) monobutyl ether.

[0029] Optionally, the average molecular weight of the inhibitor is 600-4000; examples include 600, 1000, 1500, 1800, and 3000.

[0030] Optionally, the electroplating solution is used for the electroplating copper process of through holes in electronic interconnect substrates, wherein the thickness-to-diameter ratio of the through holes is (8-15):1; for example, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1.

[0031] In some implementations, the electronic interconnect substrate may be exemplified as a PCB (printed circuit board), HDI (high-density interconnect), or IC (integrated circuit) substrate.

[0032] Optionally, the copper electroplating process uses a low-current DC electroplating method, with electroplating conditions of 6-18 ASF for 60-200 min; further optionally, it uses 8 ASF for 150 min.

[0033] Beneficial effects: This invention provides an imidazole cyclic sulfide quaternary ammonium salt compound, its preparation method, and its application, which have the following advantages: (1) This invention successfully synthesized a novel imidazole thioether quaternary ammonium salt compound, whose molecular structure is different from that of traditional copper plating additives, providing a new structural functional molecule selection for copper electroplating and potential related applications; (2) The compound molecules of the present invention simultaneously possess imidazole rings, thioether bonds and quaternary ammonium salt groups. When used as a copper plating additive, it can obtain a good plating lattice structure in the scenario of dense hole areas of substrates with low current density and high aspect ratio. The surface of the plated parts is smooth and glossy, effectively solving the defects such as whitening of the hole openings. (3) For high aspect ratio through-hole electroplating scenarios, the novel compound of the present invention exhibits excellent deep plating performance. Even under a high aspect ratio of 12:1, the deep plating capability can still reach more than 70%, meeting the copper plating requirements of high-difficulty structures. (4) The preparation method of the compound of the present invention is simple to operate, the reaction conditions are mild and easy to scale up, and its application scenarios and concentration windows are highly compatible. It can be flexibly adapted to copper plating systems with different process parameters, which is convenient for industrial promotion and process adjustment. Attached Figure Description

[0034] Figure 1 Example 1: 1H NMR spectrum of imidazole cyclic sulfide quaternary ammonium salt compounds; Figure 2 A cross-sectional view of the plated part from Example 1; Figure 3 SEM lattice image of the copper layer from Example 1; Figure 4 Apply the cross-sectional view of the plated part in Example 8; Figure 5 SEM lattice image of the copper layer from Example 8; Figure 6 A cross-sectional view of the plated part from Example 15; Figure 7 SEM lattice image of the copper layer from Example 15. Detailed Implementation

[0035] Unless otherwise specified, all raw materials, equipment and other consumables involved in this invention are commercially available; the room temperature is 25°C.

[0036] Example 1 This embodiment provides an imidazole cyclic sulfide quaternary ammonium salt compound and its preparation method; the preparation steps include: S1. Synthesis reaction: 0.1 mol of 2-mercaptoimidazole was placed in a reaction vessel, and 0.101 mol of 2-bromoethanetrimethylammonium bromide and 200 ml of solvent (ethanol) were added and mixed evenly; then 0.106 mol of activator (sodium carbonate) was added, and the mixture was stirred and heated to 50 °C for 5 h to obtain the feed solution; S2. Post-processing: After the reaction was completed, the feed solution was cooled to room temperature, the pH of the feed solution was adjusted to 7 with dilute sulfuric acid, and the extractant (dichloromethane) was used for extraction. After evaporating the extractant, the product (imidazolium cyclic sulfide quaternary ammonium salt compound) was obtained; the yield was 78.0%.

[0037] The obtained imidazole cyclic sulfide quaternary ammonium salt compound is 1-((1H-imidazol-2-yl)thio)-N,N,N-trimethylammonium bromide (NMR spectrum shown in [reference needed]). Figure 1 Its structural formula is: (i.e., m=2).

[0038] Example 2 This embodiment provides an imidazole cyclic sulfide quaternary ammonium salt compound and its preparation method; the preparation steps include: S1. Synthesis reaction: 0.1 mol 2-mercaptoimidazole was placed in a reaction vessel, and 0.101 mol 3-bromopropanetrimethylammonium bromide and 200 ml solvent (ethanol) were added and mixed evenly; then 0.106 mol activator (sodium carbonate) was added, and the mixture was stirred and heated to 50 °C for 5 h to obtain the feed solution; S2. Post-processing: After the reaction was completed, the feed solution was cooled to room temperature, the pH of the feed solution was adjusted to 7 with dilute sulfuric acid, and the extractant (dichloromethane) was used for extraction. After evaporating the extractant, the product (imidazolium cyclic sulfide quaternary ammonium salt compound) was obtained; the yield was 81.0%.

[0039] The obtained imidazole ring sulfide quaternary ammonium salt compound is 3-((1H-imidazol-2-yl)thio)-N,N,N-trimethylpropyl-1-ammonium bromide, and its structural formula is: (i.e., m=3).

[0040] Example 3-13 The specific implementation method is the same as in Example 1; the difference is that the reaction conditions in step S1 are different, as shown in Table 1.

[0041] Table 1

[0042] Comparing the synthesis results of Examples 3-13 and Example 1, it can be seen that the optimal reaction temperature for preparing novel imidazole cyclic sulfide quaternary ammonium salt compounds is 30-70℃. If the temperature is too low, the reaction rate is slow, and the reaction time needs to be extended to achieve a higher yield. If the temperature is too high, although the reaction time can be shortened to a certain extent, the yield will decrease, presumably due to side reactions caused by high temperature and deterioration of raw materials and products. Considering both yield and efficiency, a reaction time of 4-8 hours is most suitable. If the reaction time is too long, it will increase the preparation time and reduce production efficiency.

[0043] Application Example 1-18 Application Examples 1-18 each provide an electroplating solution with the following formulation: Copper sulfate pentahydrate: 45 g / L; Sulfuric acid: 255 g / L; Hydrochloric acid: 66 ppm; Brightener: 3 ppm; Leveling agent: 0.2-10 ppm (see Table 2 for details); Inhibitor: 600 ppm; The solvent is water.

[0044] The brightener is sodium polydisulfide dipropane sulfonate, sourced from Aiyan Reagent, model AY67588; the inhibitor is poly(ethylene glycol-ran-polypropylene glycol) monobutyl ether, with an average molecular weight of 1800, sourced from McLean, model P909955.

[0045] Table 2

[0046] Gynura Green B: CAS number is 2869-83-2.

[0047] The preparation method of the electroplating solution is as follows: mix the raw materials evenly to obtain the solution.

[0048] Performance testing 1. Electroplating test The electroplating solution used in Application Examples 1-18 was used to test the copper plating on the Haring tank plate. The test piece was a PCB plated part with a size of 150mm×60mm×3mm, a through hole with a diameter of 0.25mm (i.e., a thickness-to-diameter ratio of 12:1), and a conductive thin layer.

[0049] The test conditions were as follows: 1) Hull bath for rapid evaluation: electroplating at 2A current for 5 minutes; 2) Harlem bath for deep plating evaluation: continuous electroplating at a current density of 8ASF for 150 minutes to test the deep plating capability. The deep plating capability (TP) was calculated as the ratio of the average copper thickness at the center of the hole in the plated part to the average copper layer thickness on the board surface. The test results are shown in Table 3. The cross-sectional images of the plated parts and the SEM lattice images of the copper layers in Application Examples 1, 8, and 15 are shown in Table 3. Figure 2-7 .

[0050] 2. Extensibility Test Referring to the IPC-TM-650 standard for the electronics manufacturing industry, a tensile test (IPC-TM-650 2.4.18 / 2.4.19) was conducted on the electroplated copper foil. The measured elongation at break was used to characterize the ductility of the material and to assess whether the copper foil is prone to breakage or delamination during processing and use.

[0051] Table 3

[0052] In Table 3, " / " indicates that the test was not conducted; the appearance in Table 3 represents the Hull cell test results, while TP, ductility, and lattice represent the Haring cell test results.

[0053] Table 3 and Figure 2-7 The test results show that the imidazole cyclic sulfide quaternary ammonium salts prepared in Examples 1 and 2, when used as leveling agents, have an effective addition range of 0.2-10 ppm. Within this range, they exhibit good deep plating capability, achieving approximately 75% deep plating capability for parts with a thickness-to-diameter ratio of 12:1. Furthermore, the coating exhibits excellent ductility and a dense lattice structure. In contrast, the application example using Janus Green B only yielded a glossy and smooth coating within an addition range of 1-10 ppm, with a maximum deep plating capability of only 52%, low coating ductility (only 18%), and a slightly columnar lattice structure, failing to meet production requirements.

[0054] The embodiments and descriptions above are merely illustrative of the principles and specific implementations of the present invention. Various changes and modifications may be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. An imidazolic ring thioether quaternary ammonium salt compound, characterized by, The structural formula of the compound is shown in formula (Ⅰ): Formula (I) Where m = 1-6, and X is a halogen.

2. The compound of claim 1, wherein The raw materials for preparing the compound include: 2-mercaptoimidazole, haloquaternary ammonium salt, activator and solvent; The structural formula of the haloquaternary ammonium salt is shown in formula (II): Formula (II).

3. The compound of claim 2, wherein The molar ratio of the 2-mercaptoimidazole to the haloquammonium salt is 1:(1.01-1.03).

4. The compound of claim 2, wherein The molar ratio of the 2-mercaptoimidazole to the activator is 1:(1.05-1.1).

5. The compound of claim 2, wherein The haloquaternary ammonium salts include one or more combinations of (2-bromoethyl)trimethylammonium bromide, 3-bromopropyltrimethylammonium bromide, (2-chloroethyl)trimethylammonium chloride, 4-bromobutyltrimethylammonium bromide, (3-chloropropyl)trimethylammonium chloride, 5-bromopentyltrimethylammonium bromide, (6-chlorohexyl)trimethylammonium chloride, and 2-iodoethyltrimethylammonium iodide.

6. A method for producing the imidazolium ring sulfide quaternary ammonium salt compound according to any one of claims 2 to 5, characterized by, The preparation steps of the compound include: mixing 2-mercaptoimidazole, haloquaternary ammonium salt, solvent and activator, and reacting at high temperature to obtain a solution containing imidazole cyclic sulfide quaternary ammonium salt compound.

7. The preparation method according to claim 6, characterized in that, The preparation steps of the compound further include: cooling the feed solution and adjusting the pH to neutral after the reaction is completed, and performing post-treatment on the feed solution to obtain the purified imidazole cyclic sulfide quaternary ammonium salt compound. Preferably, the reaction conditions are: 30-70℃ for 3-24 hours; the post-treatment method is extraction.

8. Use of the imidazolic ring thioether quaternary ammonium salt compound according to any one of claims 1 to 5, characterized in that, The imidazole cyclic sulfide quaternary ammonium salt compound is used in electroplating solutions.

9. Use according to claim 8, characterized in that, The raw materials for preparing the electroplating solution include: Copper sulfate pentahydrate: 35-65 g / L; Sulfuric acid: 220-270 g / L; Chloride ions: 40-80 ppm; Brightener: 0.5-5 ppm; Compounds represented by formula (Ⅰ): 0.2-10 ppm; Inhibitor: 300-1200 ppm; The solvent is water.

10. Use according to claim 8 or 9, characterized in that, The electroplating solution is used for the copper plating process of through holes in electronic interconnect substrates, wherein the thickness-to-diameter ratio of the through holes is (8-15):1.

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