An acidic hole-filling agent and a method for preparing the same

Abstract

The application relates to the field of copper plating treatment of circuit boards, and discloses an acidic hole-filling agent and a preparation method thereof. The acidic hole-filling agent is prepared from the following raw materials in percentage by weight: 5-10% of organic acid, 12-16% of cationic adsorbent, 4-6% of dispersant, 2-4% of wetting agent, 0.5-1.5% of surfactant, and the balance of water; the cationic adsorbent is composed of heptadecenyl amine ethylimidazoline quaternary ammonium salt, 1-vinyl-3-methyl imidazole acetate and double long-chain quaternary ammonium salt. The acidic hole-filling agent prepared by the application is applied to fine-aperture (such as HDI board and IC carrier board) circuit boards, has good corrosion inhibition, infiltration and adsorption performance on the hole bottom or hole wall of the circuit board, the prepared circuit board is uniformly copper-plated, and the hole metallization quality of the circuit board is improved.

Description

Technical Field

[0001] This application relates to the field of copper plating treatment of circuit boards, and in particular to an acidic hole-forming agent and its preparation method. Background Technology

[0002] Acidic hole-forming agents are used in the cleaning and hole-forming process before chemical copper plating (PTH) on printed circuit boards (PCBs). This is a crucial step after removing adhesive residue / drilling debris and before micro-etching / pre-dip / activation. Its core functions are to clean the hole walls, adjust the surface charge of the hole walls to a positive charge, improve the uniformity of subsequent palladium colloid adsorption, and ensure the continuous, void-free, and strongly bonded chemical copper plating layer.

[0003] Existing acidic pore-forming agents generally consist of inorganic / organic acids, cationic additives, wetting agents, and solvents. Among them, cationic additives are generally selected from bis(trifluoromethanesulfonyl)imide trioctyldodecylammonium and trioctylmethylammonium bis(trifluoromethanesulfonyl)imide salts. Their molecular structure contains long-chain alkyl groups and quaternary ammonium cationic heads, which can form a dense, oriented monolayer on the PCB surface through physical adsorption. This allows the PCB surface potential to rapidly and uniformly change from a negative potential to a strong positive potential, providing adsorption sites for subsequently negatively charged colloidal palladium particles.

[0004] For circuit boards with fine apertures (such as HDI boards and IC substrates), due to the high aspect ratio and small hole wall area, the use of the aforementioned acidic hole-forming agents can easily lead to activation blind spots at the bottom or walls of the holes, resulting in localized copper-free defects. Furthermore, under prolonged high-temperature conditions, the copper plating layer is prone to peeling off, reducing the circuit board's performance. Therefore, existing acidic hole-forming agents require further improvement. Summary of the Invention

[0005] To address the problem that existing acidic hole-forming agents often result in activation blind spots at the bottom or walls of holes in circuit boards with fine apertures, leading to areas without copper, and causing copper plating to peel off under prolonged high-temperature conditions, thus reducing the performance of the circuit board, this application provides an acidic hole-forming agent and its preparation method.

[0006] In a first aspect, this application provides an acidic pore-forming agent, employing the following technical solution: An acidic pore-forming agent is prepared from the following raw materials in weight percentages: Organic acids 5-10% Cationic adsorbent 12-16% Dispersant 4-6% wetting agent 2-4% Surfactant 0.5-1.5% Remaining water; The cationic adsorbent is composed of heptadecanylamine ethyl imidazoline quaternary ammonium salt, 1-vinyl-3-methylimidazolium acetate, and a bis-long-chain quaternary ammonium salt.

[0007] By adopting the above technical solutions, organic acids can adjust the pH of the system, providing a suitable cleaning environment for other components; the heptadecanylamine ethyl imidazoline quaternary ammonium salt, 1-vinyl-3-methylimidazolium acetate, and double long-chain quaternary ammonium salt in the cationic adsorbent work synergistically to form a dense, strongly positively charged thin film on the circuit board surface through physical adsorption, providing uniform and stable adsorption sites for subsequent negatively charged colloidal palladium particles; the dispersant helps to evenly disperse the components, prevents agglomeration, and ensures the stability of the system. The synergistic effect of the cationic adsorbent and the dispersant allows the cationic adsorbent to be more evenly dispersed in the system, making it suitable for the processing of circuit boards with high aspect ratios and small hole wall areas, improving the penetration and adsorption stability of acidic pore-forming agents on fine circuit boards; the wetting agent can reduce surface tension, further enhancing the wetting ability of the acidic pore-forming agent on the hole walls of the circuit board; and the surfactant can improve the emulsification, dispersion, and cleaning performance of the system.

[0008] The acidic hole-forming agent of this application is applied to circuit boards with fine hole diameters. It has good corrosion inhibition, wetting and adsorption properties on the bottom or wall of the hole, which can avoid activation blind spots at the bottom or wall of the hole, improve the uniformity and stability of subsequent colloidal palladium adsorption, and thus make the copper plating of the circuit board uniform. The copper plating layer of the circuit board is not easy to fall off under long-term high temperature conditions, thereby improving the hole metallization quality and long-term high temperature performance of the circuit board.

[0009] Preferably, the cationic adsorbent is composed of heptadecanylamine ethyl imidazoline quaternary ammonium salt, 1-vinyl-3-methylimidazolium acetate and a bis-long-chain quaternary ammonium salt in a weight ratio of 1:(0.4-0.8):(0.5-1).

[0010] By adopting the above technical solution, the long chain of heptadecanylaminoethylimidazoline quaternary ammonium salt can entangle with the alkyl chain of the double long-chain quaternary ammonium salt, enhancing the overall stability of the adsorption layer. At the same time, its imidazoline ring and aminoethyl group can provide additional adsorption sites and hydrogen bonding, filling the gaps after the adsorption of the double long-chain quaternary ammonium salt. 1-Vinyl-3-methylimidazolium acetate can rapidly diffuse into the depths of micropores, preferentially adsorbing on micro-pits or polar sites that are difficult for the double long-chain quaternary ammonium salt to reach, ensuring that the entire pore wall is covered. The two long chains of the double long-chain quaternary ammonium salt provide the main framework and main positive charge sites of the adsorption layer through hydrophobic interaction. The three work synergistically to give the acidic pore-forming agent better corrosion inhibition, wetting and adsorption performance on the bottom or wall of the fine-diameter circuit board. The resulting circuit board has uniform copper plating, improving the hole metallization quality and high-temperature stability of the circuit board.

[0011] Preferably, the dual long-chain quaternary ammonium salt is dic(decyl)dimethylammonium chloride and / or dic(octyl)dimethylammonium chloride.

[0012] By employing the above technical solution, using decyldimethylammonium chloride and / or octyldimethylammonium chloride as long-chain quaternary ammonium salts, the appropriate chain length allows the cationic adsorbent to exhibit good adsorption performance on the surface of the circuit board hole wall, providing more adsorption sites for subsequent negatively charged colloidal palladium particles and improving the uniformity of subsequent palladium colloidal adsorption. If the chain is too long, it will lead to a decrease in the water solubility of the quaternary ammonium salt, affecting the dispersion uniformity of various components in the acidic pore conditioner, and thus reducing the uniformity of the pore wall surface potential adjustment.

[0013] Preferably, the organic acid is at least one of citric acid, malic acid, and glycolic acid.

[0014] By adopting the above technical solution, citric acid, malic acid, and glycolic acid, as organic acids, possess excellent water solubility and acidity, effectively adjusting the pH value of acidic pore-forming agents. Furthermore, they are all green and environmentally friendly organic acids. Simultaneously, these organic acids can undergo complexation reactions with metal ions on the circuit board surface, helping to clean the hole walls, remove impurities and oxides, and improve the cleanliness of the hole walls. This, in turn, enhances the uniformity of subsequent palladium colloid adsorption, ensuring the continuous, void-free, and strongly bonded performance of the chemical copper plating layer.

[0015] Preferably, the dispersant is composed of a polycarboxylic acid ammonium salt dispersant and an acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer in a weight ratio of 1:(2-4).

[0016] By employing the above technical solution, the polycarboxylate ammonium salt dispersant exhibits excellent dispersing properties, enabling uniform dispersion of all components in the acidic pore-forming agent and preventing agglomeration. The acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer enhances the system's stability and improves the dispersion effect. The two work synergistically to further enhance the dispersant's ability to disperse the raw materials in the acidic pore-forming agent, resulting in more uniform dispersion of the raw materials within the system. This improves the performance of the acidic pore-forming agent, giving it better corrosion inhibition, wetting, and adsorption properties on the bottom or walls of fine-diameter circuit boards.

[0017] Preferably, the wetting agent is at least one of polyethylene glycol, propylene glycol block polyether, and acetylenic diol ethoxylate.

[0018] By adopting the above technical solution, the surface tension of acidic hole-forming agent can be effectively reduced, its wetting performance on the bottom or wall of the hole in a circuit board with fine aperture can be enhanced, and the acidic hole-forming agent can be better covered on the surface of the hole wall.

[0019] Preferably, the surfactant is at least one of isomeric decayl alcohol polyoxyethylene ether, isomeric tridecyl alcohol polyoxyethylene ether, and octyl alcohol polyoxyethylene ether.

[0020] By adopting the above technical solution, the wettability and spreadability of acidic hole-forming agent on the surface of circuit board hole walls can be improved, allowing the hole-forming agent to better cover the hole walls and enhance the cleaning and adjustment effect on the hole walls.

[0021] Secondly, this application provides a method for preparing an acidic pore-forming agent, employing the following technical solution: A method for preparing an acidic pore-forming agent includes the following steps: first, adding an organic acid to water and stirring until homogeneous; then adding a cationic adsorbent, a dispersant, a wetting agent, and a surfactant and stirring until homogeneous to obtain the acidic pore-forming agent.

[0022] By adopting the above technical solution, the preparation method is simple and easy to operate. First, add organic acid to water and stir evenly. Then, add cationic adsorbent, dispersant, wetting agent and surfactant in sequence and stir. This can make the raw materials fully mixed and ensure that the acidic pore-forming agent has a uniform and stable composition.

[0023] In summary, this application includes at least one of the following beneficial technical effects: 1. The acidic pore-forming agent of this application is composed of organic acid, cationic adsorbent, dispersant, wetting agent, surfactant and water. The cationic adsorbent is composed of heptadecanylamine ethyl imidazoline quaternary ammonium salt, 1-vinyl-3-methylimidazolium acetate and double long-chain quaternary ammonium salt. It has good corrosion inhibition, wetting and adsorption performance on the bottom or wall of the hole of the circuit board with fine pore size, improves the adsorption uniformity and stability of colloidal palladium, and the copper plating of the obtained circuit board is uniform, thereby improving the hole metallization quality of the circuit board, avoiding the problem of local copper absence, and improving the long-term high temperature use stability of the circuit board.

[0024] 2. The dispersant is composed of polycarboxylate ammonium salt dispersant and acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, which helps to further improve the penetration and dispersion performance of acidic pore-forming agent in the pores of fine circuit boards. Detailed Implementation

[0025] The present application will be further described in detail below with reference to the embodiments.

[0026] The following are some of the sources and specifications of the raw materials used in this application. The raw materials used in the preparation examples and embodiments of this application can all be obtained commercially, including but not limited to the following models and manufacturers of raw materials. Raw materials with equivalent performance can also be used: 1. Heptadecanylaminoethylimidazoline quaternary ammonium salt: Komed ODD, content 70%; 2. 1-Vinyl-3-methylimidazolium acetate: CAS No. 1416358-75-2, purity 99%; 3. Ammonium polycarboxylate dispersant: DAD DISPERSANT 6227; 4. Acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer: Xingyan Chemical, CAS No. 40623-75-4; 5. Propylene glycol block polyether: Haian Petrochemical L-62; 6. Acetylene diol ethoxylates: Evonik Surfynol 485.

[0027] Example Example 1

[0028] Example 1 discloses an acidic pore-forming agent, which is prepared by the following steps: First, add 0.5 kg of organic acid to 7.45 kg of water and stir evenly. Then add 1.2 kg of cationic adsorbent, 0.6 kg of dispersant, 0.2 kg of wetting agent and 0.05 kg of surfactant and stir evenly to obtain an acidic pore-forming agent. The cationic adsorbent is composed of heptadecanylamine ethyl imidazoline quaternary ammonium salt, 1-vinyl-3-methylimidazolium acetate and a bis-long-chain quaternary ammonium salt in a weight ratio of 1:0.4:0.7, wherein the bis-long-chain quaternary ammonium salt is dicedyldimethylammonium chloride; the organic acid is composed of citric acid and malic acid in a weight ratio of 1:0.2; the dispersant is a polycarboxylic acid ammonium salt dispersant; the wetting agent is polyethylene glycol 1000; and the surfactant is isomeric decayl alcohol polyoxyethylene ether.

[0029] Example 2

[0030] The difference between Example 2 and Example 1 lies in the types and amounts of each component: First, add 0.75 kg of organic acid to 6.95 kg of water and stir evenly. Then add 1.4 kg of cationic adsorbent, 0.5 kg of dispersant, 0.3 kg of wetting agent and 0.1 kg of surfactant, and stir evenly to obtain an acidic pore-forming agent. The cationic adsorbent is composed of heptadecanylamine ethyl imidazoline quaternary ammonium salt, 1-vinyl-3-methylimidazolium acetate, and a bis-long-chain quaternary ammonium salt in a weight ratio of 1:0.8:0.5. The bis-long-chain quaternary ammonium salt is composed of dicedyldimethylammonium chloride and dicoctyldimethylammonium chloride in a weight ratio of 1:1. The organic acid is citric acid. The dispersant is maleic acid-acrylic acid copolymer, which was purchased from Juji Chemical Co., Ltd., CAS No. 29132-58-9, with a content of 99%. The wetting agent is propylene glycol block polyether. The surfactant is isotridecyl alcohol polyoxyethylene ether.

[0031] Example 3

[0032] The difference between Example 3 and Example 1 lies in the types and amounts of each component: First, add 1 kg of organic acid to 6.45 kg of water and stir evenly. Then add 1.6 kg of cationic adsorbent, 0.4 kg of dispersant, 0.4 kg of wetting agent and 0.15 kg of surfactant and stir evenly to obtain an acidic pore-forming agent. The cationic adsorbent is composed of heptadecanylamine ethyl imidazoline quaternary ammonium salt, 1-vinyl-3-methylimidazolium acetate and a bis-long-chain quaternary ammonium salt in a weight ratio of 1:0.6:1, with the bis-long-chain quaternary ammonium salt being bis-octyldimethylammonium chloride; the organic acid is composed of citric acid and glycolic acid in a weight ratio of 2:1; the dispersant is a polycarboxylic acid ammonium salt dispersant; the wetting agent is composed of polyethylene glycol 800 and acetylenic glycol ethoxylate in a weight ratio of 4:1; and the surfactant is isomeric tridecyl alcohol polyoxyethylene ether.

[0033] Example 4

[0034] The difference between Example 4 and Example 3 is that the double long-chain quaternary ammonium salt is bis(dodecyl)dimethylammonium chloride, and the rest is the same as in Example 3.

[0035] Example 5

[0036] The difference between Example 5 and Example 3 is that the dispersant is composed of a polycarboxylate ammonium salt dispersant and an acrylic-2-acrylamide-2-methylpropanesulfonic acid copolymer in a weight ratio of 1:2, while the rest is the same as in Example 3.

[0037] Example 6

[0038] The difference between Example 6 and Example 3 is that the dispersant is composed of a polycarboxylate ammonium salt dispersant and an acrylic-2-acrylamide-2-methylpropanesulfonic acid copolymer in a weight ratio of 1:4, while the rest is the same as in Example 3.

[0039] Example 7

[0040] The difference between Example 7 and Example 3 is that the dispersant consists of a polycarboxylate ammonium salt dispersant and a maleic acid-acrylic acid copolymer in a weight ratio of 1:2. The maleic acid-acrylic acid copolymer was purchased from Juji Chemical, CAS No. 29132-58-9, with a content of 99%. The rest is the same as in Example 3.

[0041] Comparative Example Comparative Example 1 The difference between Comparative Example 1 and Example 3 is that the bis-long-chain quaternary ammonium salt was replaced by 1-vinyl-3-methylimidazolium acetate by mass, while the rest is the same as Example 3.

[0042] Comparative Example 2 The difference between Comparative Example 2 and Example 3 is that the heptadecanylamine ethyl imidazoline quaternary ammonium salt was replaced by an equal mass of a bis-long-chain quaternary ammonium salt, while the rest was the same as in Example 3.

[0043] Comparative Example 3 The difference between Comparative Example 3 and Example 3 is that 1-vinyl-3-methylimidazolium acetate was replaced by an equal mass of heptadecanylamine ethylimidazoline quaternary ammonium salt, otherwise it was the same as Example 3.

[0044] Comparative Example 4 The difference between Comparative Example 4 and Example 3 is that the cationic adsorbent is trioctylmethylammonium bis(trifluoromethanesulfonyl)imide salt, while the rest is the same as in Example 3.

[0045] Performance testing The performance of the acidic pore-forming agents prepared in Examples 1-7 and Comparative Examples 1-4 was tested below: A PCB board with a thickness of 2mm, a hole diameter of 0.1mm, and a thickness-to-diameter ratio of 20:1 is selected. Taking chemical electroless copper plating as an example, the chemical electroless copper plating process is as follows: Remove adhesive residue - wash with water - pre-neutralize - wash with water - neutralize - wash with water - expand - degrease - wash with water - acidic pore shaping - wash with water - micro-etching - wash with water - pre-immersion - activation - wash with water - accelerate - chemical copper deposition - wash with water; Among them: the adhesive residue removal agent used is: potassium permanganate 60g / L, sodium hydroxide 40g / L; temperature 70℃, time 15min; Pre-neutralization uses the following pre-neutralizing agent: 2 wt% sulfuric acid, 2 wt% hydrogen peroxide, and the balance water; temperature 25℃, time 5 min. Neutralization: 10wt% sulfuric acid, 15wt% Jinshengxin neutralizing agent BA-102L, balance water; temperature 40℃, time 7min; Bulk Spreading Agent: Jinsheng New Bulk Spreading Agent BA-100L 20wt%, Sodium Hydroxide 1wt%, Balance Water; Temperature 70℃, Time 7min; Degreasing: Jinsheng New Degreasing Agent BA-31A 13wt%, balance water; temperature 60℃, time 7min; Acidic pore-forming agent: 10 wt% acidic pore-forming agent and the balance water prepared in the examples and comparative examples of this application; temperature 45°C, time 2 min; Micro-etching: 3 wt% sulfuric acid, 10 wt% sodium persulfate, balance water; temperature 25℃, time 1 min; Pre-soaking: Jinshengxin pre-soaking salt BA-33R 17wt%, hydrochloric acid 0.5wt%, balance water; temperature 25℃, time 1.5min; Activation: Jinshengxin BA-33R 17wt%, hydrochloric acid 0.8wt%, balance water; temperature 35℃, time 2min.

[0046] Acceleration: Jinshengxin BA-35L 10wt%, Jinshengxin BA-35S 10wt%, balance water; temperature 45℃, time 4min; Chemical copper deposition: copper ions 1.75 g / L, sodium hydroxide 11 g / L, formaldehyde 7 g / L; temperature 31℃, time 12 min, to obtain the finished PCB board; 1. Backlight Level Test Test the backlight level (out of 10) of the finished PCB board. A level of 8 or higher is considered acceptable. Record the test results. 2. High temperature test Place the finished PCB board in a constant temperature and humidity chamber at 85℃ and 85% for 7 days. After drying, observe whether the copper plating layer has peeled off. If it has not peeled off, test the backlight level (out of 10) of the finished PCB board and record the test results. The following are the performance test data of the acidic pore-forming agents prepared in Examples 1-7 and Comparative Examples 1-4, as detailed in Table 1 below.

[0047] Table 1 Performance test data of the acidic pore-forming agents prepared in Examples 1-7 and Comparative Examples 1-4

[0048] From the above experimental data, we can conclude that: Compared to Example 3, Example 4 changed the type of double long-chain quaternary ammonium salt. The backlight level of the finished PCB board decreased from 9.5 to 9. After high-temperature testing, the backlight level decreased from 9 to 8. This may be because the chain length of the double long-chain quaternary ammonium salt was increased, which reduced the dispersion uniformity of the double long-chain quaternary ammonium salt on the overall acidic pore-forming agent.

[0049] Combining Examples 3 and 5-7, it can be concluded that further optimization of the type and proportion of dispersant can further improve the metallization quality and high-temperature stability of the prepared PCB board. Compared to Example 3, Examples 5-6, with optimized dispersant, achieved a backlight level of 10 in the prepared PCB board, and the backlight level remained unchanged after high-temperature testing. In Example 7, compared to Example 3, the backlight level of the prepared PCB board remained unchanged. This further verifies the role of optimized dispersant in the preparation of the acidic pore-forming agent.

[0050] Combining Examples 3 and Comparative Examples 1-4, it can be concluded that by using the cationic adsorbent of this application, composed of heptadecanylaminoethylimidazoline quaternary ammonium salt, 1-vinyl-3-methylimidazolium acetate, and a dual long-chain quaternary ammonium salt, the wetting, penetration, and adsorption performance of the acidic pore-forming agent of this application can be significantly improved, resulting in a marked improvement in the performance of the finished PCB board. Compared to Example 3, Comparative Examples 1-4 changed the type and formulation of the cationic adsorbent, and the backlight level of the finished PCB boards obtained from these examples all failed the test, and the copper plating layer peeled off after high-temperature testing. This further verifies the excellent synergistic effect of the specific components of the cationic adsorbent of this application in the preparation of the acidic pore-forming agent.

[0051] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An acidic pore-forming agent, characterized in that, It is made from the following raw materials by weight percentage: Organic acids 5-10% Cationic adsorbent 12-16% Dispersant 4-6% wetting agent 2-4% Surfactant 0.5-1.5% Remaining water; The cationic adsorbent is composed of heptadecanylamine ethyl imidazoline quaternary ammonium salt, 1-vinyl-3-methylimidazolium acetate, and a bis-long-chain quaternary ammonium salt.

2. The acidic pore-forming agent according to claim 1, characterized in that, The cationic adsorbent is composed of heptadecanylamine ethyl imidazoline quaternary ammonium salt, 1-vinyl-3-methylimidazolium acetate and a bis-long-chain quaternary ammonium salt in a weight ratio of 1:(0.4-0.8):(0.5-1).

3. An acidic pore-forming agent according to claim 1 or 2, characterized in that, The dual long-chain quaternary ammonium salt is dic(decyl)dimethylammonium chloride and / or dic(octyl)dimethylammonium chloride.

4. The acidic pore-forming agent according to claim 1, characterized in that, The organic acid is at least one of citric acid, malic acid, and glycolic acid.

5. The acidic pore-forming agent according to claim 1, characterized in that, The dispersant is composed of a polycarboxylic acid ammonium salt dispersant and an acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer in a weight ratio of 1:(2-4).

6. The acidic pore-forming agent according to claim 1, characterized in that, The wetting agent is at least one of polyethylene glycol, propylene glycol block polyether, and acetylation glycol ethoxylate.

7. The acidic pore-forming agent according to claim 1, characterized in that, The surfactant is at least one of isomeric decayl alcohol polyoxyethylene ether, isomeric tridecyl alcohol polyoxyethylene ether, and octyl alcohol polyoxyethylene ether.

8. A method for preparing an acidic pore-forming agent as described in any one of claims 1-7, characterized in that, Includes the following steps: First, add organic acid to water and stir until homogeneous. Then add cationic adsorbent, dispersant, wetting agent and surfactant, and stir until homogeneous to obtain acidic pore-forming agent.

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