Ultra-fine circuit stripping liquid and preparation method thereof

Abstract

The present invention relates to the technical field of removing metal materials on a surface by non-mechanical methods, and in particular to an ultra-fine circuit stripping solution and a preparation method thereof. The stripping solution comprises the following components: an alkaline substance, a stripping agent, a wetting agent, a tin protecting agent and a solvent. The present invention also provides a preparation method thereof. Compared with the prior art, the stripping solution prepared by the present invention has the advantages of good stripping effect, strong tin protecting performance and the like.

Description

Technical Field

[0001] The invention relates to the technical field of removing metal materials on a surface by non-mechanical methods, and in particular to an ultra-fine circuit stripping liquid and a preparation method thereof. Background Art

[0002] As the core component of electronic products, the production technology standards of printed circuit boards (PCBs) are increasingly improved. In the production process of PCBs, the pattern transfer process plays a key role. It involves transferring a specific CAD design pattern to a substrate through multiple processes to form a conductive path for the circuit. At present, a method widely used in the industry is to use photosensitive resist dry film (referred to as "dry film") as a medium to achieve pattern transfer through steps such as lamination, exposure, development, electroplating, film stripping and etching. The main body of the dry film is a photosensitive adhesive layer, which is composed of components such as photoinitiators, photopolymerization monomers and film-forming resins. During the exposure process, the photoinitiator in the photosensitive adhesive layer will generate active free radicals under the action of light. These free radicals trigger polymerization reactions, causing the molecular structure of the dry film to change from linear to network, and some unsaturated bonds to saturated bonds, thereby changing its solubility in the solvent.

[0003] The main components of the dry film are high molecular weight esters. In an alkaline environment, these esters will undergo hydrolysis to generate carboxylates and alcohols. During the development process, the unexposed area has a higher solubility and is therefore easily dissolved in a weakly alkaline developer. In contrast, the exposed area has a lower solubility and requires a strongly alkaline stripping solution to remove.

[0004] CN201910597191.7 discloses an environmentally friendly film stripping liquid, characterized in that the components of the environmentally friendly film stripping liquid include, by mass percentage: 35% to 45% of composite alkali, 3% to 5% of polyether surfactant, and 50% to 62% of water. The invention also discloses a method for preparing an environmentally friendly film stripping liquid. Using the environmentally friendly film stripping liquid provided by the invention for film stripping treatment can not only improve the effect of the film stripping treatment, but also greatly save water and reduce emissions, saving water and reducing emissions by more than 90%, making a great social contribution to water saving and emission reduction. At the same time, the waste liquid obtained after treatment has a lower chemical oxygen demand, which reduces the treatment cost of the waste liquid.

[0005] CN202210203518.X provides an environmentally friendly organic film stripping liquid suitable for the film stripping process of printed circuit boards, and its components are classified as 8-20% organic alkali content, 12-20% organic solvent, 0.1-0.5% corrosion inhibitor, 5-10% accelerator, and 49.5-75% deionized water. The invention has a good film stripping effect for line width / line spacing above 3mil / 3mil, has no odor, does not attack the tin layer, and has obvious advantages in improving line gaps, film clamping, and reducing tin plating costs.

[0006] However, in an alkaline environment, some tin will dissolve on the printed circuit board, so a thicker tin plating layer is often required to provide protection, which is relatively expensive and may also cause circuit corrosion. Summary of the invention

[0007] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide an ultra-fine circuit stripping solution and a preparation method thereof.

[0008] The function of the tin protecting agent is to form a protective film on the tin surface to reduce the degree of corrosion, isolate the tin from contacting with the oxide to prevent the tin from dissolving, and have an anti-etching effect. The current tin protecting agent still has the defects of poor tin protecting effect and instability in alkaline environment. In the present invention, a tin protecting agent is prepared, and its structure has thiazole and thiourea groups. Thiazole is a five-membered heterocyclic compound containing sulfur and nitrogen. In its structure, nitrogen and sulfur atoms both contain unshared lone pairs of electrons. These lone pairs of electrons can participate in coordination with metallic tin to form a complex, and the sulfur atom in thiourea also has a pair of unshared lone pairs of electrons, which can form a coordination bond with the empty orbit of metallic tin. Therefore, the tin protecting agent can form a protective layer on the tin surface to prevent the occurrence of tin dissolution and achieve an anti-etching effect. In the present invention, alkaline substances are used as the main components to destroy the chain structure in the dry film, so that the dry film falls off and achieves the film stripping effect. The film breaking agent dissolves the polymer segments in the dry film molecules to control the size of the film fragments. The wetting agent inhibits the generation of foam, increases the contact area between the film stripping liquid and the dry film, and foams the photoresist, making the molecular gap larger, increasing the contact area between the photoresist layer and the film stripping liquid, and increasing the solubility. The film stripping liquid prepared by the present invention can effectively inhibit metal corrosion and has a good film stripping effect.

[0009] To achieve the above object, the present invention provides an ultra-fine circuit stripping solution, comprising the following components in mass percentage: 0.5-5% alkaline substance, 1-5% stripping agent, 0.5-4% wetting agent, 1-3% tin protecting agent, and the balance being solvent.

[0010] Furthermore, the alkaline substance is sodium hydroxide or potassium hydroxide.

[0011] Furthermore, the stripping agent is one of triethanolamine, N,N-diethylethanolamine or diethylene glycol monobutyl ether.

[0012] Furthermore, the wetting agent is one of tripropylene glycol, 1,2,3-hexanetriol or propylene glycol.

[0013] Furthermore, the solvent is water.

[0014] The preparation method of the tin protecting agent comprises the following steps:

[0015] Add 1,1-diethylhydrazine to anhydrous tetrahydrofuran, then add bis(1,2,4-triazol-1-yl)methylthione, stir at room temperature for 0.5-1h to mix evenly, continue to add N-(4-aminophenyl)-4-thiadiazolecarboxamide and stir for 5-8h. After the stirring is completed, concentrate under reduced pressure to remove the solvent to obtain a residue. After the residue is diluted with acetonitrile, heat and stir for 10-20h, cool and filter, wash the filter cake with acetonitrile and dry.

[0016] Furthermore, the molar ratio of the 1,1-diethylhydrazine, bis(1,2,4-triazol-1-yl)methanethione and N-(4-aminophenyl)-4-thiadiazolecarboxamide is 1:1.1 to 1.5:1.

[0017] Furthermore, the temperature range of the heating and stirring is 30-50°C.

[0018] Preferably, the preparation method of the tin protecting agent comprises the following steps:

[0019] Add 1,1-diethyl-hydrazine to anhydrous tetrahydrofuran, then add bis(1,2,4-triazol-1-yl)methylthione, stir at room temperature for 0.5-1h to mix evenly, continue to add N-(4-aminophenyl)-4-thiadiazolecarboxamide and stir for 5-8h, the molar ratio of 1,1-diethyl-hydrazine, bis(1,2,4-triazol-1-yl)methylthione and N-(4-aminophenyl)-4-thiadiazolecarboxamide is 1:1.1-1.5:1, after stirring, concentrate under reduced pressure to remove the solvent to obtain a residue, dilute the residue with acetonitrile, heat to 30-50°C and stir for 10-20h, cool and filter, wash the filter cake with acetonitrile and dry.

[0020] A method for preparing an ultra-fine circuit stripping solution comprises the following steps:

[0021] Mix the above components according to the proportions, and stir to mix evenly.

[0022] Beneficial effects of the present invention:

[0023] In the present invention, the alkaline substance is the main component, and its function is to destroy the chain structure in the dry film, so that the dry film falls off and achieves the film stripping effect. The stripping agent dissolves the polymer segment in the dry film molecule to control the film stripping effect. The wetting agent inhibits the generation of foam, increases the contact area between the film stripping liquid and the dry film, and foams the photoresist, so that the molecular gap is larger, the contact area between the photoresist layer and the film stripping liquid is increased, and the solubility is increased. The tin protecting agent can form a protective layer on the tin surface to prevent the occurrence of tin dissolution and achieve the effect of anti-etching. The film stripping liquid prepared by the present invention can effectively inhibit metal corrosion and has a good film stripping effect. DETAILED DESCRIPTION

[0024] Bis(1,2,4-triazol-1-yl)methanethione, CAS No.: 63976-76-1.

[0025] N-(4-aminophenyl)-4-thiadiazolecarboxamide, CAS No.: 273735-27-6.

[0026] The preparation method of the tin protecting agent comprises the following steps:

[0027] Add 1,1-diethylhydrazine to anhydrous tetrahydrofuran, then add bis(1,2,4-triazol-1-yl)methylthione, stir at room temperature for 0.5-1h to mix evenly, continue to add N-(4-aminophenyl)-4-thiadiazolecarboxamide and stir for 5-8h. After the stirring is completed, concentrate under reduced pressure to remove the solvent to obtain a residue. After the residue is diluted with acetonitrile, heat and stir for 10-20h, cool and filter, wash the filter cake with acetonitrile and dry.

[0028] 1,1-Diethyl-hydrazine is used as a starting material to couple with bis(1,2,4-triazol-1-yl)methylthione in tetrahydrofuran as a medium, and then further coupled with N-(4-aminophenyl)-4-thiadiazolecarboxamide. After the reaction is completed, the final product is crystallized and impurities are removed through acetonitrile.

[0029] Comparative Example 1

[0030] A method for preparing an ultra-fine circuit stripping solution comprises the following steps:

[0031] Mix 20 g of sodium hydroxide, 50 g of diethylene glycol monobutyl ether, 30 g of 1,2,3-hexanetriol, 15 g of potassium citrate and 885 mL of water, and stir well to obtain the product.

[0032] Example 1

[0033] A method for preparing an ultra-fine circuit stripping solution comprises the following steps:

[0034] Mix 20 g of sodium hydroxide, 50 g of diethylene glycol monobutyl ether, 30 g of 1,2,3-hexanetriol, 15 g of tin protecting agent and 885 mL of water, and stir evenly to obtain the product.

[0035] The preparation method of the tin protecting agent comprises the following steps:

[0036] Add 1,1-diethyl-hydrazine to anhydrous tetrahydrofuran, then add bis(1,2,4-triazol-1-yl)methylthione, stir at room temperature for 0.5h to mix evenly, continue to add N-(4-aminophenyl)-4-thiadiazolecarboxamide and stir for 7h, the molar ratio of 1,1-diethyl-hydrazine, bis(1,2,4-triazol-1-yl)methylthione and N-(4-aminophenyl)-4-thiadiazolecarboxamide is 1:1.2:1. After stirring, concentrate under reduced pressure to remove the solvent to obtain a residue, dilute the residue with acetonitrile, heat to 40°C and stir for 16h, cool and filter, wash the filter cake with acetonitrile and dry.

[0037] Example 2

[0038] A method for preparing an ultra-fine circuit stripping solution comprises the following steps:

[0039] Mix 20 g of sodium hydroxide, 50 g of diethylene glycol monobutyl ether, 30 g of 1,2,3-hexanetriol, 15 g of tin protecting agent and 885 mL of water, and stir evenly to obtain the product.

[0040] The preparation method of the tin protecting agent comprises the following steps:

[0041] Aniline was added to anhydrous tetrahydrofuran, and then bis(1,2,4-triazol-1-yl)methylthione was added, and the mixture was stirred at room temperature for 0.5 h to mix evenly. N-(4-aminophenyl)-4-thiadiazolecarboxamide was added and stirred for 7 h. The molar ratio of aniline, bis(1,2,4-triazol-1-yl)methylthione and N-(4-aminophenyl)-4-thiadiazolecarboxamide was 1:1.2:1. After the stirring was completed, the solvent was removed by concentration under reduced pressure to obtain a residue. The residue was diluted with acetonitrile, heated to 40°C and stirred for 16 h. After cooling, it was filtered, and the filter cake was washed with acetonitrile and dried.

[0042] Example 3

[0043] A method for preparing an ultra-fine circuit stripping solution comprises the following steps:

[0044] Mix 20 g of sodium hydroxide, 50 g of diethylene glycol monobutyl ether, 30 g of 1,2,3-hexanetriol, 15 g of tin protecting agent and 885 mL of water, and stir evenly to obtain the product.

[0045] The preparation method of the tin protecting agent comprises the following steps:

[0046] Add p-chloroaniline to anhydrous tetrahydrofuran, then add bis(1,2,4-triazol-1-yl)methylthione, stir at room temperature for 0.5h to mix evenly, continue to add N-(4-aminophenyl)-4-thiadiazolecarboxamide and stir for 7h, the molar ratio of p-chloroaniline, bis(1,2,4-triazol-1-yl)methylthione and N-(4-aminophenyl)-4-thiadiazolecarboxamide is 1:1.2:1, after stirring, concentrate under reduced pressure to remove the solvent to obtain a residue, dilute the residue with acetonitrile, heat to 40°C and stir for 16h, cool and filter, wash the filter cake with acetonitrile and dry.

[0047] Example 4

[0048] The same as Example 1, the only difference is that the addition amount of sodium hydroxide is 10g.

[0049] Example 5

[0050] The same as Example 1, the only difference is that the addition amount of sodium hydroxide is 30g.

[0051] Test Example 1

[0052] The dry film plate was clamped with tweezers and completely immersed in the stripping solution prepared in the comparative example and the example, and swung back and forth at the same frequency, and the time required for the dry film from immersion in the solution to complete stripping was recorded by a stopwatch. The dry film plate was weighed before and after stripping, and the weight difference before and after stripping was calculated.

[0053] Table 1 Stripping test of stripping solution

[0054] Experimental protocol Defilming time / s Weight difference before and after film removal / g Comparative Example 1 30 0.1012 Example 1 32 0.0041 Example 2 33 0.0069 Example 3 35 0.0075 Example 4 38 0.0040 Example 5 28 0.1623

[0055] From the film stripping test, it can be seen that the film stripping liquid prepared by the present invention has a good film stripping effect, and the dry film can be removed in a short time, while the weight difference before and after the film stripping of the same film stripping liquid shows a difference. This is because the tin dissolution phenomenon may also occur while the dry film is falling off, so the weight difference before and after the film stripping of each sample is relatively large. Compared with the conventional tin-protecting agent in the control example 1, the weight difference of the samples of Examples 1 to 4 is smaller, which shows that the tin-protecting agent in the embodiment has a better tin-protecting effect, so the probability of the occurrence of the tin dissolution phenomenon may be lower. This is because the tin-protecting agent in the embodiment has thiazole and thiourea groups in its structure. Thiazole is a five-membered heterocyclic compound containing sulfur and nitrogen. The nitrogen and sulfur atoms in its structure contain unshared lone pairs of electrons. These lone pairs of electrons can participate in coordination with metal tin to form a complex, and the sulfur atom in thiourea also has a pair of unshared lone pairs of electrons, which can form a coordination bond with the empty orbit of metal tin. Therefore, the tin-protecting agent can form a protective layer on the tin surface to prevent the occurrence of tin dissolution and achieve an anti-etching effect. Therefore, compared with the control example, the weight difference of the samples in the embodiment before and after the film stripping is smaller. Compared with Examples 2 to 3, Example 1 has a strong electron-withdrawing group - diethyl nitrogen in its structure, so the electron cloud density is greatly enhanced, and its complexing ability with metallic tin is enhanced, so the tin protection effect is better, while the phenyl and chlorine atoms in Examples 2 and 3 do not have strong electron-withdrawing properties that match them. In the embodiment, the alkaline substance is the main component, and its function is to destroy the chain structure in the dry film, so that the dry film falls off and achieves the film stripping effect. The stripping agent dissolves the polymer segment in the dry film molecule to control the film stripping effect. The wetting agent inhibits the generation of foam, increases the contact area between the film stripping liquid and the dry film, and foams the photoresist, making the molecular gap larger, increasing the contact area between the photoresist layer and the film stripping liquid, and increasing the solubility. The alkaline substance sodium hydroxide is the main active component of the film stripping, and its addition amount greatly affects the film stripping effect. Too little addition may lead to incomplete film stripping, while too much addition will lead to the occurrence of tin surface corrosion. Therefore, the formula in Example 1 is relatively optimal.

[0056] Test Example 2

[0057] The thickness of the tin-plated layer on the surface of the dry film board in Test Example 1 was measured, and the degree of corrosion caused by the stripping solution to the tin surface was determined by comparing the thickness change of the tin surface before and after immersion.

[0058] Table 2 Tin protection test of stripping solution

[0059] Experimental protocol Tin surface thickness variation / μm Comparative Example 1 ﹣0.156 Example 1 ﹣0.106 Example 2 ﹣0.124 Example 3 ﹣0.131 Example 4 ﹣0.101 Example 5 ﹣0.182

[0060] The difference between the tin protection effects can be more intuitively seen from the change in the thickness of the tin surface. The tin protection of Examples 1 to 4 is significantly better than that of Control Example 1, while Example 1 is the best. This may be because there are thiazole and thiourea groups in its structure. Thiazole is a five-membered heterocyclic compound containing sulfur and nitrogen. Both nitrogen and sulfur atoms in its structure contain unshared lone pairs of electrons. These lone pairs of electrons can participate in coordination with metallic tin to form a complex, and the sulfur atom in thiourea also has a pair of unshared lone pairs of electrons, which can form a coordination bond with the empty orbit of metallic tin. Therefore, the tin protection agent can form a protective layer on the tin surface to prevent the occurrence of tin dissolution and achieve an anti-etching effect. In addition, compared with Examples 2 to 3, Example 1 has a strong electron-withdrawing group-diethyl nitrogen in the structure, so the electron cloud density is greatly enhanced, and its complexing ability with metallic tin is enhanced, so the tin protection effect is better. The data in Examples 4 to 5 are also consistent with those in Test Example 1.

[0061] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. An ultra-fine circuit stripping solution, characterized in that: The composition comprises the following components in percentage by weight: 2% alkaline substance, 1-5% stripping agent, 0.5-4% wetting agent, 1-3% tin protecting agent, and the balance being solvent; The preparation method of the tin protecting agent is: Add 1,1-diethyl-hydrazine to anhydrous tetrahydrofuran, then add bis(1,2,4-triazol-1-yl)methylthione, stir at room temperature for 0.5-1h to mix evenly, continue to add N-(4-aminophenyl)-4-thiadiazolecarboxamide and stir for 5-8h, the molar ratio of 1,1-diethyl-hydrazine, bis(1,2,4-triazol-1-yl)methylthione and N-(4-aminophenyl)-4-thiadiazolecarboxamide is 1:1.1-1.5:1, after the stirring is completed, concentrate under reduced pressure to remove the solvent to obtain a residue, dilute the residue with acetonitrile, heat to 30-50°C and stir for 10-20h, cool and filter, wash the filter cake with acetonitrile and dry to obtain; The alkaline substance is sodium hydroxide or potassium hydroxide; The stripping agent is one of triethanolamine, N,N-diethylethanolamine or diethylene glycol monobutyl ether; The wetting agent is one of tripropylene glycol, 1,2,3-hexanetriol or propylene glycol; The solvent is water.

2. A method for preparing an ultra-fine circuit stripping solution as claimed in claim 1, characterized in that: The steps include: Mix the above components according to the proportions, and stir to mix evenly.