An environmentally friendly film-removing liquid and its preparation method

Abstract

This application relates to the field of environmentally friendly PCB processing, disclosing an environmentally friendly film removal solution and its preparation method. The environmentally friendly film removal solution is prepared from the following raw materials in weight percentages: 2-4% alkaline hydroxide, 3-5% diethylene glycol butyl ether, 3.5-5.5% tetrahydrofurfuryl alcohol, 2-4% ethylene glycol hexyl ether, 3-5% accelerator, 4-6% stabilizer, and water as the balance; the stabilizer is prepared from hydroxypropyl chitosan, N-tris(hydroxymethyl)methylglycine, quaternary ammonium salt, and water. The environmentally friendly film removal solution of this application is suitable for high-precision PCB board processing, exhibiting good environmental friendliness and dry film removal efficiency, while reducing corrosion of the PCB board's circuit patterns.

Description

Technical Field

[0001] This application relates to the field of environmentally friendly circuit board processing, and more specifically, it relates to an environmentally friendly film-removing solution and its preparation method. Background Technology

[0002] With the rapid development of the electronics industry, electronic products are pursuing miniaturization and lightweighting, leading to increasingly precise wiring on PCBs. As a fundamental component of electronic products, the manufacturing process of PCBs directly affects product performance and reliability. In PCB manufacturing, dry film technology is widely used for pattern transfer. By using ultraviolet light to adhere a dry film to the PCB, precise transfer of circuit patterns is achieved, and the film also provides protection during subsequent electroplating and etching processes. However, the removal of the dry film is a critical step in PCB manufacturing, directly impacting production efficiency and product quality.

[0003] Existing PCB dry film removal agents generally use large amounts of strong alkaline substances, such as sodium hydroxide and potassium hydroxide. These strong alkaline substances are highly corrosive and will corrode the surface of the circuit patterns while removing the dry film. Alternatively, they may contain alkanolamines, such as amine solvents like monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, and ethylenediamine. Alkanolamines have a strong odor, and when added to the removal solution, they can easily emit an irritating smell during use, affecting the production workshop environment and the health of personnel, thus reducing the environmental friendliness of the removal agent.

[0004] To address the aforementioned environmental concerns, existing technologies employ some milder stripping agents. These agents utilize corrosion inhibitors, such as benzotriazole and mercaptobenzothiazole, to reduce the corrosion inhibition effect on circuit patterns. However, the addition of corrosion inhibitors reduces the removal rate of the dry film by the stripping solution. This is especially true for high-precision PCBs, where the circuit patterns are more densely arranged, resulting in lower dry film removal efficiency and consequently impacting PCB processing efficiency. Summary of the Invention

[0005] To address the issue that existing film-removing solutions cannot adequately balance environmental friendliness and film-removing efficiency, this application provides an environmentally friendly film-removing solution and its preparation method.

[0006] Firstly, this application provides an environmentally friendly film-removing solution, employing the following technical solution:

[0007] An environmentally friendly film-removing liquid is prepared from the following raw materials by weight percentage:

[0008] 2-4% alkaline hydroxide

[0009] Diethylene glycol butyl ether 3-5%

[0010] Tetrahydrofurfuryl alcohol 3.5-5.5%

[0011] 2-4% ethylene glycol hexyl ether

[0012] Accelerator 3-5%

[0013] stabilizer 4-6%

[0014] Water balance;

[0015] The stabilizer is prepared from hydroxypropyl chitosan, N-tris(hydroxymethyl)methylglycine, quaternary ammonium salt and water.

[0016] By adopting the above technical solution, the environmentally friendly film removal solution of this application is suitable for processing high-precision PCB boards, exhibiting good dry film removal efficiency without corroding the circuit patterns on the PCB board. The synergistic effect of alkaline hydroxide with diethylene glycol butyl ether, tetrahydrofurfuryl alcohol, and ethylene glycol hexyl ether enhances the penetration performance of the dry film. The accelerator improves the dissolution and removal efficiency of the dry film. The stabilizer, composed of hydroxypropyl chitosan, N-tris(hydroxymethyl)methylglycine, and quaternary ammonium salt, can form a uniform adsorption film on the dry film surface, further enhancing the penetration performance of the environmentally friendly film removal solution, thereby strengthening the removal effect. Simultaneously, it provides good protection for the circuit patterns, reducing corrosiveness. The overall formula does not contain strong alkaline substances, alkanolamines, or corrosion inhibitors, avoiding corrosion of the circuit patterns and the generation of irritating odors, thus improving environmental friendliness and safety.

[0017] Preferably, the stabilizer is prepared from the following raw materials by weight percentage:

[0018] Hydroxypropyl chitosan 4-6%

[0019] N-Tris(hydroxymethyl)methylglycine 2-4%

[0020] Quaternary ammonium salts 8-10%

[0021] Water balance.

[0022] By adopting the above technical solution, the dosage of each component in the stabilizer is further optimized, the synergistic effect of each component is enhanced, and a uniformly interwoven dispersion system is formed. This system can be uniformly dispersed on the surface of the dry film and form an interwoven adsorption film, thereby increasing the contact area between the environmentally friendly film removal liquid and the surface of the dry film. It can also uniformly penetrate into the gaps of high-precision circuit patterns, further improving the removal efficiency of the dry film.

[0023] Preferably, the stabilizer is prepared by the following steps:

[0024] S1. Hydroxypropyl chitosan and N-tris(hydroxymethyl)methylglycine are added to water and heated to react, thus obtaining reactant A; S2. A quaternary ammonium salt is added to reactant A, and the mixture is stirred to obtain a stabilizer.

[0025] By adopting the above technical solution, hydroxypropyl chitosan and N-tris(hydroxymethyl)methylglycine are heated in water to form a stable colloidal dispersion system. After being mixed and stirred with quaternary ammonium salt, the molecular chain segments intertwine and adsorb, thus obtaining a stabilizer with good adsorption stability.

[0026] Preferably, the reaction temperature in step S1 is 45-65℃ and the reaction time is 1-2h.

[0027] By adopting the above technical solution, controlling the reaction temperature in the stabilizer preparation process to 45-65℃ and the reaction time to 1-2h, it can be ensured that hydroxypropyl chitosan and N-tris(hydroxymethyl)methylglycine react fully to form a uniformly dispersed gel-like system.

[0028] Preferably, the quaternary ammonium salt is one or a combination of polyquaternary ammonium salt-7, polyquaternary ammonium salt-39, and organosilicon long-chain quaternary ammonium salt.

[0029] By adopting the above technical solution, selecting one or a combination of polyquaternium-7, polyquaternium-39, and organosilicon long-chain quaternium salts as quaternary ammonium salts can effectively improve the stability of the stabilizer, enhance the adsorption capacity of the stabilizer on the dry film surface, and further improve the permeability and removal efficiency of the film removal solution.

[0030] Preferably, the quaternary ammonium salt is composed of quaternary ammonium salt-39 and organosilicon long-chain quaternary ammonium salt in a weight ratio of 1:(1-2).

[0031] By adopting the above technical solution, quaternary ammonium salt-39 has good penetration and corrosion inhibition effects, while organosilicon long-chain quaternary ammonium salt can effectively improve the wettability and dispersibility of the stabilizer. The two work synergistically to improve the penetration and removal performance of the film removal solution on the dry film, while reducing the risk of corrosion to the circuit pattern.

[0032] Preferably, the accelerator is composed of potassium silicate, potassium persulfate and sodium N-hydroxymethylglycinate in a weight ratio of (1-2):1:(2-3).

[0033] By adopting the above technical solution, potassium silicate, potassium persulfate, and sodium N-hydroxymethylglycinate in a relatively optimal weight ratio are used as accelerators and stabilizers, exhibiting a good synergistic effect. This accelerates the etching process of the dry film and improves its removal efficiency. Simultaneously, it maintains the stability of the stripping solution, reduces adverse reactions between chemical components, and lowers the corrosive properties to the circuit pattern. Preferably, the alkaline hydroxide is one or a combination of sodium hydroxide, potassium hydroxide, and barium hydroxide.

[0034] By adopting the above technical solution, the alkaline hydroxide can increase the alkalinity of the film-removing solution with a small amount of addition, so that the film-removing solution has good environmental protection and good film-removing efficiency.

[0035] Secondly, this application provides a method for preparing an environmentally friendly film-removing solution, which adopts the following technical solution:

[0036] A method for preparing an environmentally friendly film-removing solution includes the following steps: adding an alkaline hydroxide and an accelerator to water, stirring to dissolve, then adding diethylene glycol butyl ether, ethylene glycol hexyl ether and tetrahydrofurfuryl alcohol, stirring until uniform, then adding a stabilizer, stirring until uniform, to obtain the environmentally friendly film-removing solution.

[0037] By adopting the above technical solution, the preparation method of this environmentally friendly film removal liquid can ensure that all components are fully and uniformly mixed. The entire preparation process is simple and efficient, and the resulting environmentally friendly film removal liquid system is uniformly dispersed and stable.

[0038] In summary, this application has the following beneficial effects:

[0039] 1. An environmentally friendly film removal solution is prepared by compounding alkaline hydroxide, diethylene glycol butyl ether, tetrahydrofurfuryl alcohol, ethylene glycol hexyl ether, accelerator and stabilizer. It is suitable for the processing of high-precision PCB boards, has good environmental protection and dry film removal efficiency, and will not corrode the circuit pattern.

[0040] 2. A stabilizer is prepared by compounding hydroxypropyl chitosan, N-tris(hydroxymethyl)methylglycine, quaternary ammonium salt and water. It can form a uniform adsorption film on the surface of the dry film, enhance the penetration ability of the film removal solution, further improve the removal efficiency of the dry film, and at the same time prevent corrosion of the PCB circuit pattern during the film removal process.

[0041] 3. The accelerator and stabilizer are composed of potassium silicate, potassium persulfate and sodium N-hydroxymethylglycinate, which have a good synergistic effect, can accelerate the etching process of dry film, improve the removal efficiency of dry film, and prevent corrosion of PCB circuit patterns during the film removal process. Detailed Implementation

[0042] The present application will be further described in detail below with reference to the embodiments.

[0043] 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:

[0044] 1. Hydroxypropyl chitosan: Pingju Biotechnology, degree of deacetylation 95%, content 98%;

[0045] 2. N-Tris(hydroxymethyl)methylglycine: CAS No. 5704-04-1, content 99%;

[0046] 3. Organosilicon long-chain quaternary ammonium salt: octadecyl dimethyltrimethylsilylpropylammonium chloride, CAS No. 27668-52-6;

[0047] 4. Sodium N-hydroxymethylglycine: CAS No. 70161-44-3, content ≥99%.

[0048] Example of stabilizer preparation

[0049] Preparation Example 1

[0050] Preparation Example 1 provides a stabilizer prepared by the following steps:

[0051] S1. Add 0.4 kg of hydroxypropyl chitosan and 0.4 kg of N-tris(hydroxymethyl)methylglycine to 8.2 kg of water, heat to 45 °C, and react for 2 h to obtain reactant A;

[0052] S2. Add 1 kg of quaternary ammonium salt (composed of 0.5 kg tetramethylammonium hydroxide and 0.5 kg dodecyl dimethyl benzyl ammonium chloride) to reactant A, and mix for 45 min at a mixing rate of 300 r / min to obtain the stabilizer.

[0053] Preparation Examples 2-3

[0054] The difference between Preparation Example 2-3 and Preparation Example 1 lies in the amount of raw materials used and the preparation conditions, as detailed in Table 1 below.

[0055] Table 1. Parameters for Preparation Examples 1-3

[0056]

[0057]

[0058] Preparation Example 4

[0059] The difference between Preparation Example 4 and Preparation Example 1 is that the quaternary ammonium salt is different. The quaternary ammonium salt in Preparation Example 4 is composed of 0.5 kg tetramethylammonium hydroxide and 0.5 kg polyquaternary ammonium salt-39. Everything else is the same as in Preparation Example 1.

[0060] Preparation Example 5

[0061] The difference between Preparation Example 5 and Preparation Example 4 is that the quaternary ammonium salt in Preparation Example 5 is composed of 0.5 kg of organosilicon long-chain quaternary ammonium salt and 0.5 kg of polyquaternary ammonium salt-39, while the rest is the same as Preparation Example 4.

[0062] Preparation Example 6

[0063] The difference between Preparation Example 6 and Preparation Example 4 is that the quaternary ammonium salt in Preparation Example 4 is composed of 0.67 kg of organosilicon long-chain quaternary ammonium salt and 0.33 kg of polyquaternary ammonium salt-39, while the rest is the same as Preparation Example 4.

[0064] Preparation of Comparative Example 1

[0065] The difference between Comparative Example 1 and Preparation Example 5 is that N-tris(hydroxymethyl)methylglycine was replaced with an equal amount of hydroxypropyl chitosan, while the rest was the same as Preparation Example 5.

[0066] Preparation of Comparative Example 2

[0067] The difference between Comparative Example 2 and Preparation Example 5 is that the quaternary ammonium salt was replaced with an equal amount of hydroxypropyl chitosan, while the rest was the same as Preparation Example 5.

[0068] Example

[0069] Example 1

[0070] Example 1 discloses an environmentally friendly film-removing solution, prepared by the following steps: 0.3 kg of potassium hydroxide as an alkaline hydroxide and 0.5 kg of accelerator (composed of ammonium persulfate and potassium silicate in a weight ratio of 1:1) are added to 7.65 kg of water and stirred until dissolved. Then, 0.5 kg of diethylene glycol butyl ether, 0.2 kg of ethylene glycol hexyl ether, and 0.45 kg of tetrahydrofurfuryl alcohol are added and stirred until homogeneous. Finally, 0.4 kg of the stabilizer prepared in Example 1 is added and stirred until homogeneous to obtain the environmentally friendly film-removing solution.

[0071] Example 2-3

[0072] The difference between Examples 2-3 and Example 1 lies in the amount of raw materials used and the preparation process, as detailed in Table 2 below.

[0073] Table 2 Parameter table for Examples 1-3

[0074]

[0075] Examples 4-6

[0076] The difference between Examples 4-6 and Example 1 is that the source of the stabilizer is different, as detailed in Table 3 below.

[0077] Table 3. Source of stabilizers in Examples 4-6

[0078] Example stabilizer source table Example 4 Preparation Example 4 Example 5 Preparation Example 5 Example 6 Preparation Example 6

[0079] Example 7

[0080] The difference between Example 7 and Example 5 is that the accelerator in Example 7 is composed of potassium silicate, potassium persulfate and sodium N-hydroxymethylglycinate in a weight ratio of 1:1:2, while the rest is the same as in Example 5.

[0081] Example 8

[0082] The difference between Example 8 and Example 5 is that the accelerator in Example 8 is composed of potassium silicate, potassium persulfate and sodium N-hydroxymethylglycinate in a weight ratio of 1:2:3, while the rest is the same as in Example 5.

[0083] Example 9

[0084] The difference between Example 9 and Example 8 is that the accelerator in Example 8 is composed of potassium silicate and sodium N-hydroxymethylglycine in a weight ratio of 1:1, while the rest is the same as in Example 8.

[0085] Comparative Example

[0086] Comparative Example 1

[0087] The difference between Comparative Example 1 and Example 5 is that the stabilizer was derived from the preparation of Comparative Example 1, while the rest is the same as Example 5.

[0088] Comparative Example 2

[0089] The difference between Comparative Example 2 and Example 5 is that the stabilizer was derived from the preparation of Comparative Example 2, while the rest is the same as Example 5.

[0090] Comparative Example 3

[0091] The difference between Comparative Example 3 and Example 8 is that the stabilizer was replaced with an equal amount of diethylene glycol butyl ether, otherwise it was the same as Example 8.

[0092] Comparative Example 4

[0093] The difference between Comparative Example 4 and Example 8 is that the accelerator was replaced with an equal amount of diethylene glycol butyl ether, otherwise it was the same as Example 8.

[0094] Comparative Example 5

[0095] The difference between Comparative Example 5 and Example 8 is that tetrahydrofurfuryl alcohol is replaced with diethylene glycol butyl ether in equal amounts, while the rest is the same as Example 8.

[0096] Performance testing

[0097] The following performance tests were conducted on the environmentally friendly film-removing solutions prepared in Examples 1-9 and Comparative Examples 1-5:

[0098] 1. Dry film removal time test

[0099] Immerse the PCB board (copper-plated PCB board, circuit pattern width 0.15mm, dry film thickness 30μm, circuit board size 50.8mm*50.8mm) to be de-coated in environmentally friendly de-coating solution, heat to 55℃, and stop timing after the dry film is completely removed (dry film removal rate greater than 99.5% is qualified), record the time for de-coating (unit: s), and record the test results.

[0100] 2. PCB board circuit pattern dry film removal etching test:

[0101] The PCB board after removing the dry film is tested using AOI equipment. The standard circuit pattern is compared with the AIO scan and the number of etched points on the PCB board circuit pattern is calculated (unit: points). Less than 5 etched points are considered qualified. The test results are recorded.

[0102] 3. Long-term corrosion test of PCB circuit patterns

[0103] The PCB board (copper-plated PCB board, circuit pattern width 0.15mm, dry film thickness 30μm, circuit board size 50.8mm*50.8mm) to be de-coated was immersed at 55℃ for 10 minutes. After being taken out, washed with water and dried, it was tested using AOI equipment. The standard circuit pattern was compared with the AIO scan and the number of etch points (unit: number) of the PCB board circuit pattern was calculated. The test results were recorded.

[0104] The following are the performance test data of the environmentally friendly film-removing solutions prepared in Examples 1-9 and Comparative Examples 1-5, as detailed in Table 4 below.

[0105] Table 4 Performance test data of Examples 1-9 and Comparative Examples 1-5

[0106]

[0107] The " / " indicates obvious corrosion.

[0108] Based on Examples 1-6 and Comparative Examples 1-2, and referring to Table 4, it can be concluded that using the stabilizer prepared from hydroxypropyl chitosan, N-tris(hydroxymethyl)methylglycine, and quaternary ammonium salt of this application, and further optimizing the composition of the quaternary ammonium salt (composed of polyquaternary ammonium salt-39 and organosilicon long-chain quaternary ammonium salt), can improve the film removal efficiency of the prepared environmentally friendly film removal solution. The environmentally friendly film removal solution prepared in Example 5 achieved a dry film removal time of 105s with only 6 corrosion points, and 13 corrosion points were found after long-term corrosion testing. The environmentally friendly film removal solution prepared in Example 4 had a dry film removal time of 111s and 10 corrosion points. Furthermore, after long-term corrosion testing, 18 corrosion points were found. The dry film removal time of the environmentally friendly film removal solution prepared in Example 1 was 113s, with 11 corrosion points. After long-term corrosion testing, 21 corrosion points were found. This indicates that in Examples 1-4, the use of polyquaternium-39 and organosilicon long-chain quaternary ammonium salt for compounding resulted in an increase in the film removal time and corrosion points of the environmentally friendly film removal solution. In contrast, in Comparative Examples 1 and 2, the composition of hydroxypropyl chitosan, N-tris(hydroxymethyl)methylglycine, and quaternary ammonium salt was changed. Compared to Example 4, the dry film removal time was significantly improved, and the number of corrosion points was also significantly increased.

[0109] Based on Examples 5 and 7-9 and Table 4, it can be concluded that further optimization of the accelerator composition, using potassium silicate, potassium persulfate, and sodium N-hydroxymethylglycinate as accelerators, can significantly improve the dry film removal efficiency of the prepared environmentally friendly film removal solution, while also mitigating the corrosion performance on circuit patterns.

[0110] Based on Examples 8 and Comparative Examples 3-5, and referring to Table 4, it can be concluded that the combination of the stabilizer, accelerator, diethylene glycol ethyl ether, hexanediol ethyl ether, and tetrahydrofurfuryl alcohol of this application can produce a good synergistic effect, improving the film removal efficiency of the prepared environmentally friendly film remover while reducing the corrosion performance on the circuit patterns of the PCB board. Compared with Example 8, Comparative Example 3, without the addition of the stabilizer, showed a decrease in the film removal efficiency of the prepared environmentally friendly film remover and a significant increase in corrosivity; compared with Example 8, Comparative Example 4, without the addition of the accelerator, showed a significant decrease in the film removal efficiency of the prepared environmentally friendly film remover; in Comparative Example 5, replacing an equal amount of tetrahydrofurfuryl alcohol with diethylene glycol ethyl ether resulted in a decrease in the film removal efficiency of the prepared environmentally friendly film remover.

[0111] 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 environmentally friendly film-removing liquid, characterized in that, It is made from the following raw materials by weight percentage: alkaline hydroxide 2-4% Diethylene glycol butyl ether 3-5% Tetrahydrofurfuryl alcohol 3.5-5.5% 2-4% ethylene glycol hexyl ether Accelerator 3-5% stabilizer 4-6% Water balance; The stabilizer is prepared from the following raw materials by weight percentage: Hydroxypropyl chitosan 4-6% N-Tris(hydroxymethyl)methylglycine 2-4% Quaternary ammonium salts 8-10% Water balance; The stabilizer is prepared by the following steps: S1. Hydroxypropyl chitosan and N-tris(hydroxymethyl)methylglycine are added to water and heated to react, thus obtaining reactant A; S2. Add quaternary ammonium salt to reactant A, mix and stir to obtain stabilizer; the reaction temperature in step S1 is 45-65℃, the reaction time is 1-2h, and the quaternary ammonium salt is one or a combination of polyquaternary ammonium salt-7, polyquaternary ammonium salt-39, and organosilicon long-chain quaternary ammonium salt. The accelerator is composed of potassium silicate, potassium persulfate and sodium N-hydroxymethylglycinate in a weight ratio of (1-2):1:(2-3); The alkaline hydroxide is one or a combination of sodium hydroxide, potassium hydroxide, and barium hydroxide.

2. The environmentally friendly film-removing liquid according to claim 1, characterized in that, The quaternary ammonium salt is composed of polyquaternary ammonium salt-39 and organosilicon long-chain quaternary ammonium salt in a weight ratio of 1:(1-2).

3. A method for preparing an environmentally friendly film-removing liquid as described in claim 1 or 2, characterized in that, Alkaline hydroxide and accelerator are added to water and stirred to dissolve. Then, diethylene glycol butyl ether, ethylene glycol hexyl ether and tetrahydrofurfuryl alcohol are added and stirred evenly. Finally, a stabilizer is added and stirred evenly to obtain an environmentally friendly film-removing solution.

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