An alkali-free developing solution and its developing method

Abstract

This invention discloses an alkali-free developing solution and its developing method, relating to the field of circuit board manufacturing technology. The alkali-free developing solution comprises the following components by mass concentration: developer 3.0-6.0%; accelerator 1.0-3.0%; wetting agent 0.5-2.0%; penetration enhancer 1.0-3.0%; and stabilizer 0.2-1.0%. The alkali-free developing solution of this invention possesses core advantages such as alkali-free corrosion, low foaming, rapid defoaming, fine developing, stable performance, and excellent anti-plating properties. It is particularly suitable for developing circuits with line widths and spacings of 5μm, significantly improving pattern clarity and integrity, effectively reducing developing residue, and facilitating high-precision circuit forming.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing technology, and in particular to an alkali-free developing solution and its developing method. Background Technology

[0002] In semiconductor manufacturing, flat panel displays, and printed circuit boards (PCBs), photolithography is the core process for pattern transfer, and the performance of the developer directly determines the quality and yield of the final product. Taking the PCB developing process as an example, its complete process includes: substrate cleaning (removal of oxides and contaminants) → coating with photoresist (dry film / liquid) → pre-baking (90-110℃) → exposure → development → deionized water rinsing → drying → post-processing (etching / electroplating).

[0003] Traditional PCB developers face multiple bottlenecks in practical applications: First, there are precision limitations in the manufacturing process. The developing speed is difficult to control precisely; too fast a speed leads to poor uniformity and rough circuit edges, failing to meet the demands of high-precision pattern transfer; too slow a speed results in incomplete development and residual adhesive. Second, there are challenges to product stability. Recycling the developer generates numerous air bubbles, interfering with the stability of the developing process and shortening the solution's lifespan. Finally, there is significant environmental pressure. Some developers are highly corrosive, resulting in costly and difficult wastewater treatment, making it difficult to meet the environmental requirements of current green manufacturing.

[0004] In response to the trend of electronic products moving towards higher density and miniaturization, the technological iteration of PCB developers presents four main directions: First, higher precision, requiring adaptation to the transfer of finer circuit patterns, improving resolution and development uniformity, and ensuring the integrity of complex patterns; second, green and environmentally friendly, simplifying wastewater treatment processes by reducing toxicity and corrosiveness and designing biodegradable formulas, while improving the recycling rate of developers and reducing resource consumption; third, high efficiency and stability, developing long-cycle stable formulas to maintain consistent development effects under different production conditions such as temperature and pressure, while increasing development speed to meet the needs of large-scale mass production; and fourth, material and process compatibility, optimizing developer composition to enhance compatibility with new processes such as new photoresists and laser direct imaging.

[0005] Alkali-free developer is a type of developer that does not contain traditional alkaline components. It typically uses other types of compounds to achieve its developing function. Alkali-free developer offers the following advantages: First, it avoids the environmental pollution caused by alkaline substances, and its wastewater treatment is relatively simple, reducing environmental pressure. Second, alkali-free developer generally has lower toxicity and corrosiveness, posing a relatively lower safety risk to operators. Furthermore, because it does not contain strong alkali, it is less corrosive to developing equipment, extending equipment lifespan and reducing maintenance costs. Third, in some specialized PCB manufacturing processes, such as for certain sensitive materials or high-precision photolithography, alkali-free developer can provide better developing results, avoiding the impact of alkaline substances on material properties, and helping to improve product yield and performance.

[0006] Currently, there are several technical solutions for developing solutions. CN109375482A proposes a PCB developing solution and its preparation method. This developing solution contains 5-20 parts diethylene glycolamine, 2-6 parts citric acid, 0.5-5 parts polyetheramine, 3-10 parts hexanediol, and 60-80 parts water. It can reduce the developing defect rate, increase the service life of the developing solution, and eliminate the need for tank replacement for a longer period of time. CN113419410A discloses an environmentally friendly developing solution and its preparation method. Its composition is: 10-20% ethylene glycol, 8-10% sodium carbonate, 12-15% tetramethylammonium hydroxide, 0.5-1.5% p-phenylenediamine, 2-5% anti-aging agent, and the balance being water. This can prevent the developing solution from aging, ensure the service life of the developing solution, and not affect the performance. CN115657429B discloses a high-efficiency and environmentally friendly developer for PCB boards, which consists of: 60-100 parts of an organic alkali composition, 30-80 parts of a cosolvent, 30-70 parts of a defoamer, 40-70 parts of a surfactant, 20-50 parts of an antioxidant, 15-45 parts of a penetrant, 30-50 parts of a buffer, 10-20 parts of an inhibitor, and the balance being water. This developer can improve the antioxidant capacity of both the developer and the PCB board, and ensure the stability of the developer during use.

[0007] Existing developers can generally meet the needs of conventional PCB manufacturing processes. Traditional developers often use alkaline systems (such as sodium carbonate and potassium carbonate), which can effectively dissolve photosensitive resin in unexposed areas. However, their technical shortcomings are gradually becoming a bottleneck restricting the industry's development. On the one hand, alkaline environments easily corrode substrate materials (such as aluminum, copper, and other metal layers and sensitive photoresists), causing problems such as metal layer damage and photoresist pattern deformation. Moreover, when processing chemically amplified photoresists and high aspect ratio patterns, alkaline developers are prone to uneven development and residues, making it difficult to meet the requirements of high-precision photolithography processes. Especially in emerging fields such as flexible electronics and microelectromechanical systems (MEMS), flexible substrate materials (such as polyimide and polyester films) are extremely sensitive to alkaline environments, and the corrosiveness of traditional developers can damage the substrate structure, limiting the development of related industries. On the other hand, the waste liquid generated after the use of alkaline developers is difficult and costly to treat, which is inconsistent with the current development trend of green manufacturing and environmentally friendly production.

[0008] Therefore, developing an alkali-free developer that maintains high-efficiency developing performance, reduces the risk of corrosion to the substrate and photoresist, and meets environmental protection requirements has become a pressing technical challenge in the current photolithography field. The semiconductor and printing industries have an urgent need for "green chemical processes," requiring developers to possess the following characteristics: first, environmental friendliness, containing no strong alkalis and low-toxicity components; second, high precision compatibility, adapting to photolithography developing processes with linewidths / spacings ≤5μm; and third, long-term stability, avoiding component decomposition or precipitation to reduce the risk of production downtime. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides an alkali-free developer and its development method, applicable to the development process of PCBs. This alkali-free developer contains effective components such as a developer, accelerator, wetting agent, penetration enhancer, and stabilizer. The developer is a class of compounds containing functional groups such as sulfonyl and hydroxyl groups, achieving development primarily through hydrogen bonding, redox activity, and polarity regulation. The accelerator increases the development rate by accelerating the hydrolysis or saponification reaction of soluble substances in the photoresist. The wetting agent accelerates the penetration of the developer into the pores of the dry film, improving penetration efficiency. The protectant prevents the developer from oxidation, extending the developer's lifespan. The penetration enhancer is a key auxiliary agent for achieving high-precision pattern transfer by reducing interfacial tension, enhancing the developer's penetration capacity, and optimizing dissolution kinetics through surface activity. The stabilizer primarily maintains the stability of the developer system and extends its lifespan.

[0010] Specifically, the present invention provides an alkali-free developer solution comprising the following components at the following mass concentrations:

[0011] Developer 3.0-6.0%;

[0012] Accelerator 1.0-3.0%;

[0013] Wetting agent 0.5-2.0%;

[0014] Penetration enhancer 1.0-3.0%;

[0015] Stabilizer 0.2-1.0%;

[0016] The developer is selected from one or a mixture of more than one of 1-(phenylsulfonyl)cycloprop-1-ol (CAS No.: 1006613-82-6), 1-(methanesulfonyl)piperidin-4-ol (CAS No.: 141482-19-1), and 3-(methanesulfonyl)benzyl alcohol (CAS No.: 220798-39-0);

[0017] The accelerator is selected from one or a mixture of more of the following: 1,3-bis(hydroxymethyl)-5,5-dimethylimidazoline-2,4-dione (CAS No.: 6440-58-0), imidazoline-2,4-dione (CAS No.: 461-72-3), and 3-methylimidazoline-2,4-dione (CAS No.: 6843-45-4);

[0018] The wetting agent is selected from one or a mixture of more of 2,7-dihydroxynaphthalene (CAS No.: 582-17-2), 2,3-dihydroxynaphthalene (CAS No.: 92-44-4), and 2,6-dihydroxynaphthalene (CAS No.: 581-43-1);

[0019] The penetration enhancer is selected from one or a mixture of more of the following: 6-azidohexane-1-ol (CAS No.: 146292-90-2), 3-azido-1-propanol (CAS No.: 72320-38-8), and 4-azidobenzyl alcohol (CAS No.: 31499-54-4);

[0020] The stabilizer is selected from one or a mixture of more of the following: methylpyridinium phosphate (CAS No.: 35575-96-3), chlorpyrifos (CAS No.: 42509-80-8), and triazophos (CAS No.: 24017-47-8).

[0021] Preferably, the alkali-free developing solution is composed of the following components at the following mass concentrations:

[0022] Developer 3.0-6.0%;

[0023] Accelerator 1.0-3.0%;

[0024] Wetting agent 0.5-2.0%;

[0025] Penetration enhancer 1.0-3.0%;

[0026] Stabilizer 0.2-1.0%;

[0027] The remainder is water.

[0028] More preferably, the alkali-free developing solution is composed of the following components at the following mass concentrations:

[0029] Developer 4.5%;

[0030] Accelerator 2.0%;

[0031] Wetting agent 1.0%;

[0032] Penetration enhancer 2.0%;

[0033] Stabilizer 0.5%;

[0034] The remainder is water.

[0035] The preparation method of the above-mentioned alkali-free developing solution of the present invention is as follows: according to the required mass concentration, weigh the developing agent, accelerator, wetting agent, penetration aid and stabilizer, add them to water, and mix them evenly at room temperature to obtain the solution.

[0036] The alkali-free developing solution described above is used for developing circuit boards with a linewidth and spacing of 5μm.

[0037] The present invention also provides a developing method, comprising the following developing steps: spraying the circuit board to be developed with the above-mentioned alkali-free developing solution with a mass concentration of 2-5% to make the circuit pattern appear on the circuit board.

[0038] Preferably, in the developing step, the spray pressure is 1.5 ± 0.5 kg / cm². 2 Spraying time: 15±2s.

[0039] Furthermore, the above-described developing method includes a pre-immersion step before the developing stage: the exposed circuit board is immersed in the pre-immersion solution for 15±2 seconds; the pre-immersion solution consists of the above-mentioned alkali-free developing solution with a mass concentration of 0.8-1.2% and the remainder water. The purpose of the pre-immersion stage is to pre-soak and expand the film, which helps the dry film to be removed quickly in the developing stage.

[0040] In some specific embodiments, the developing method of the present invention sequentially includes the following steps: a pre-immersion stage and a developing stage:

[0041] Pre-immersion stage: The exposed circuit board is immersed in the pre-immersion stage solution for 15±2s; the pre-immersion stage solution consists of the above-mentioned alkali-free developing solution with a mass concentration of 1.0% and the remainder water;

[0042] Developing section: The pre-impregnated circuit boards are sprayed with a 3% (w / w) alkali-free developing solution as described above, at a spray pressure of 1.5 ± 0.5 kg / cm². 2Spraying time: 15±2s.

[0043] The alkali-free developer of this invention possesses core advantages such as alkali-free corrosion, low foaming, rapid defoaming, fine development, stable performance, and excellent anti-plating properties. It is particularly suitable for developing lines with line widths and spacings of up to 5μm, significantly improving pattern clarity and integrity, effectively reducing developer residue, and facilitating high-precision circuit formation. This alkali-free developer exhibits high stability, reducing the defect rate of fine line development and improving overall manufacturing efficiency. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 The image shown under an optical microscope after development in Example 1;

[0046] Figure 2 This is the developed pattern observed under an optical microscope after development, as shown in Comparative Example 11. Detailed Implementation

[0047] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] It should be noted that the contents or concentrations mentioned in the following examples / comparative examples are all mass concentrations.

[0049] The preparation methods of the alkali-free developing solutions in Examples 1-5 are as follows: According to the formula of Examples 1-5, the developer, accelerator, wetting agent, penetration aid, stabilizer and the remaining water are weighed in sequence and added to the reaction vessel. The mixture is stirred and mixed at room temperature for 30 minutes to obtain the alkali-free developing solution of the corresponding example. The obtained alkali-free developing solution is sealed and stored for later use.

[0050] Example 1:

[0051] The alkali-free developer solution in this embodiment consists of the following components by mass concentration:

[0052] The developer content is 4.5%, specifically 1-(phenylsulfonyl)cycloprop-1-ol;

[0053] The accelerator content is 2.0%, specifically 1,3-bis(hydroxymethyl)-5,5-dimethylimidazoline-2,4-dione;

[0054] The wetting agent content is 1.0%, specifically 2,7-dihydroxynaphthalene;

[0055] The penetration enhancer content is 2.0%, specifically 6-azidohexane-1-ol;

[0056] The stabilizer content is 0.5%, specifically methylpyridinium phosphate;

[0057] The remainder is water.

[0058] Example 2:

[0059] The alkali-free developer solution in this embodiment consists of the following components by mass concentration:

[0060] The developer content is 4.5%, specifically 1-(methylsulfonyl)piperidine-4-ol;

[0061] The accelerator content is 2.0%, specifically imidazoline-2,4-dione;

[0062] The wetting agent content is 1.0%, specifically 2,3-dihydroxynaphthalene;

[0063] The penetration enhancer content is 2.0%, specifically 3-azido-1-propanol;

[0064] The stabilizer content is 0.5%, specifically chlorpyrifos;

[0065] The remainder is water.

[0066] Example 3:

[0067] The alkali-free developer solution in this embodiment consists of the following components by mass concentration:

[0068] The developer content is 4.5%, specifically 3-(methylsulfonyl)benzyl alcohol;

[0069] The accelerator content is 2.0%, specifically 3-methylimidazolidine-2,4-dione;

[0070] The wetting agent content is 1.0%, specifically 2,6-dihydroxynaphthalene;

[0071] The penetration enhancer content is 2.0%, specifically 4-azidobenzyl alcohol;

[0072] The stabilizer content is 0.5%, specifically triazophos;

[0073] The remainder is water.

[0074] Example 4:

[0075] The alkali-free developer solution in this embodiment consists of the following components by mass concentration:

[0076] The developer content is 3.0%, specifically 1-(phenylsulfonyl)cycloprop-1-ol;

[0077] The accelerator content is 1.0%, specifically 1,3-bis(hydroxymethyl)-5,5-dimethylimidazoline-2,4-dione;

[0078] The wetting agent content is 0.5%, specifically 2,7-dihydroxynaphthalene;

[0079] The penetration enhancer content is 1.0%, specifically 6-azidohexane-1-ol;

[0080] The stabilizer content is 0.2%, specifically methylpyridinium phosphate;

[0081] The remainder is water.

[0082] Example 5:

[0083] The alkali-free developer solution in this embodiment consists of the following components by mass concentration:

[0084] The developer content is 6.0, specifically 1-(phenylsulfonyl)cycloprop-1-ol;

[0085] The accelerator content is 3.0%, specifically 1,3-bis(hydroxymethyl)-5,5-dimethylimidazoline-2,4-dione;

[0086] The wetting agent content is 2.0%, specifically 2,7-dihydroxynaphthalene;

[0087] The penetration enhancer content is 3.0%, specifically 6-azidohexane-1-ol;

[0088] The stabilizer content is 1.0%, specifically methylpyridinium phosphate;

[0089] The remainder is water.

[0090] Comparative Example 1

[0091] The only difference between Comparative Example 1 and Example 1 is that the components do not contain a developer.

[0092] Comparative Example 2

[0093] The only difference between Comparative Example 2 and Example 1 is that the components do not contain accelerators.

[0094] Comparative Example 3

[0095] The only difference between Comparative Example 3 and Example 1 is that the components do not contain a wetting agent.

[0096] Comparative Example 4

[0097] The only difference between Comparative Example 4 and Example 1 is that the components do not contain a penetration enhancer.

[0098] Comparative Example 5

[0099] The only difference between Comparative Example 5 and Example 1 is that the components do not contain stabilizers.

[0100] Comparative Example 6

[0101] The only difference between Comparative Example 6 and Example 1 is that the concentration of developer in the components is 12.0%.

[0102] Comparative Example 7

[0103] The only difference between Comparative Example 7 and Example 1 is that the accelerator concentration in the component is 6.0%.

[0104] Comparative Example 8

[0105] The only difference between Comparative Example 8 and Example 1 is that the concentration of wetting agent in the components is 4.0%.

[0106] Comparative Example 9

[0107] The only difference between Comparative Example 9 and Example 1 is that the concentration of the penetration enhancer in the component is 6.0%.

[0108] Comparative Example 10

[0109] The only difference between Comparative Example 10 and Example 1 is that the concentration of stabilizer in the component is 2.0%.

[0110] Comparative Example 11

[0111] The developer described in the prior art CN109375482A is specifically composed of: 5% diethylene glycolamine, 2% citric acid, 0.5% polyetheramine, 3% hexanediol, and the balance being water.

[0112] The developing solutions of the above examples / comparative examples were tested for foaming performance, developing performance, stability performance, and anti-plating performance. The specific testing methods are as follows:

[0113] 1) Foam performance: Take the developer of the example / comparative example and add tap water to prepare a 0.6% concentration solution; use RM-2 digital display Roche foam analyzer for testing. The test temperature is 25℃. Avoid ventilation or vibration during the test to prevent it from affecting the foam stability. Record the initial foam height (unit: mm, denoted as H0) and the time (T) for the foam to disappear to half its height. Each sample is tested in parallel at least 3 times and the average value is taken.

[0114] 2) Development performance: The developer solution of the example / comparative example was used to develop an IC substrate with a line width / spacing of 5μm according to the following development process; the ability to clearly develop the pattern was observed, and the proportion of dry film remaining on the surface of the circuit board after development was tested using a SU1510 scanning electron microscope, i.e., the development residue rate. The development residue rate should be ≤0.5%.

[0115] The developing process is as follows: degreasing → water washing → drying → film application → exposure → developing → water washing → etching → water washing → film removal → water washing → drying; the developing solution used in the examples / comparative examples is used in the developing process, which is divided into two processing stages: pre-immersion stage and developing stage.

[0116] The process for the pre-immersion section is as follows: this section is an immersion type; the solution composition in the pre-immersion tank is 1.0% of the developer solution of the example / comparative example, and the remainder is water; the pre-immersion temperature is 25±1℃, the length of the pre-immersion section is 0.5m, and the linear velocity is 2.0±0.2m / min;

[0117] The developing section process is as follows: this section is a spray type; the solution composition in the developing tank is 3.0% developing solution from the examples / comparative examples, with the remainder being tap water; the developing temperature is 25±1℃, the developing section length is 0.5m; the linear velocity is 2.0±0.2m / min, and the pressure is 1.5±0.5kg / cm. 2 ;

[0118] 3) Stability: The developer solutions from the examples / comparative examples were stored at 40°C for 7 days, and the changes in surface tension were observed on the first and seventh days. The surface tension was tested using the capillary rise method. Specifically, a clean capillary was vertically inserted into the developer solutions of the examples / comparative examples. Due to surface tension, the solution would rise to a certain height within the capillary. Based on parameters such as capillary radius, solution density, gravitational acceleration, and the height the solution rose within the capillary, the surface tension of the solution could be calculated using relevant formulas. The calculation formula is as follows: Where γ is the surface tension; r is the capillary radius; h is the height the solution rises in the capillary; ρ is the density of the solution; g is the acceleration due to gravity; and θ is the contact angle.

[0119] 4) Anti-plating performance: The developer solution of the example / comparative example is evenly applied to the test board, washed with water and then electroplated. The electroplating condition of the test board is observed. The present invention requires that the electroplating solution does not penetrate into the non-patterned area (substrate) or under the photoresist, causing problems such as plating penetration.

[0120] The performance test results of the developing solutions in Examples 1-5 and Comparative Examples 1-11 are shown in Table 1:

[0121] Table 1 Performance test results of the developer

[0122]

[0123] Example 1: The developed pattern observed under an optical microscope after development is as follows. Figure 1 As shown; the developed pattern observed under an optical microscope after development in Comparative Example 11 is as follows. Figure 2 As shown.

[0124] As can be seen from the test results of Examples 1-5 in Table 1, the foam height of the alkali-free developer of this invention is 2.0-2.5 mm, and the time to eliminate half of the foam is 1.5-2.0 s, indicating excellent foam performance. The residual development rate of circuit boards with a line width and spacing of 5 μm is 0.02-0.06%, indicating excellent development performance. The surface tension of the product remains unchanged on the first and seventh days, with a surface tension of 14.2-14.7 mN / m, indicating excellent stability. Anti-plating tests using the developer of this invention show no plating penetration, indicating excellent anti-plating performance. This demonstrates that the alkali-free developer of this invention has advantages such as alkali-free corrosion, low foam, rapid foam elimination, fine development, stable performance, and excellent anti-plating effect. It can be applied to the development process of fine lines with a line width and spacing of 5 μm. After development, the pattern is clear and complete, with a low residual development rate, which is beneficial for high-precision forming of fine lines. The product has good stability, reduces the defect rate of fine line development, and improves manufacturing efficiency.

[0125] The difference between Comparative Examples 1-5 and Example 1 is that they lacked one of the following components: developer, accelerator, wetting agent, penetration enhancer, and stabilizer, respectively. Test results show that the developer is a crucial component for development; its absence significantly reduces the developing performance of the developer, affecting foaming properties, stability, and anti-plating properties. The accelerator, wetting agent, and penetration enhancer primarily assist the developer; their absence slightly reduces the developer's performance. The stabilizer mainly maintains the stability of the developer; its absence significantly reduces the product's stability. Therefore, the superior performance of the developer of this invention is the result of the interaction of its components; the absence of any one component will affect the product's performance.

[0126] The difference between Comparative Examples 6-10 and Example 1 is that the developer, accelerator, wetting agent, penetration enhancer, and stabilizer in the alkali-free developer solution of the present invention are all higher than the upper limit of the concentration of the present invention. The test results show that, compared with Examples 1-5, excessively high concentrations of developer, accelerator, wetting agent, penetration enhancer, and stabilizer will not affect the developing performance, but excessively high concentrations will increase the cost of the solution. Therefore, the concentration of each component in the developer solution of the present invention should not be too high. Within the concentration range defined by the present invention, a stable developing effect of the solution can be guaranteed.

[0127] Comparative Example 11 illustrates a developing solution using existing technology. Test results show that the developer of this invention has lower foam height, faster defoaming time, better development residue rate, lower surface tension and stability, and better anti-plating performance, making it suitable for alkali-free developing processes for fine lines.

[0128] In summary, the alkali-free developer provided by this invention possesses core advantages such as alkali-free corrosion, low foaming, rapid defoaming, fine development, stable performance, and excellent anti-plating properties. It is particularly suitable for developing fine lines with line widths and spacings down to 5μm, significantly improving pattern clarity and integrity, effectively reducing developer residue, and facilitating high-precision circuit formation. This product exhibits high stability, reducing the defect rate of fine line development and improving overall manufacturing efficiency.

[0129] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An alkali-free developing solution, characterized in that, Components including the following mass concentrations: Developer 3.0-6.0%; Accelerator 1.0-3.0%; Wetting agent 0.5-2.0%; Penetration enhancer 1.0-3.0%; Stabilizer 0.2-1.0%; The developer is selected from one or a mixture of more than one of 1-(phenylsulfonyl)cycloprop-1-ol, 1-(methylsulfonyl)piperidin-4-ol, and 3-(methylsulfonyl)benzyl alcohol; The accelerator is selected from one or a mixture of more of 1,3-bis(hydroxymethyl)-5,5-dimethylimidazoline-2,4-dione, imidazoline-2,4-dione, and 3-methylimidazoline-2,4-dione; The wetting agent is selected from one or a mixture of more than one of 2,7-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, and 2,6-dihydroxynaphthalene; The penetration enhancer is selected from one or a mixture of more than one of 6-azidohexane-1-ol, 3-azido-1-propanol, and 4-azidobenzyl alcohol; The stabilizer is selected from one or a mixture of more than one of methylpyridinium phosphate, chlorpyrifos, and triazophos.

2. The alkali-free developing solution according to claim 1, characterized in that, It consists of components with the following mass concentrations: Developer 3.0-6.0%; Accelerator 1.0-3.0%; Wetting agent 0.5-2.0%; Penetration enhancer 1.0-3.0%; Stabilizer 0.2-1.0%; The remainder is water.

3. The alkali-free developing solution according to claim 1, characterized in that, It consists of components with the following mass concentrations: Developer 4.5%; Accelerator 2.0%; Wetting agent 1.0%; Penetration enhancer 2.0%; Stabilizer 0.5%; The remainder is water.

4. The method for preparing the alkali-free developing solution according to any one of claims 1-3, characterized in that, Weigh out the developer, accelerator, wetting agent, penetration enhancer, and stabilizer according to the required mass concentration, add them to water, and mix evenly at room temperature.

5. The alkali-free developing solution according to any one of claims 1-3, characterized in that, Line development for circuit boards with 5μm linewidth and spacing.

6. A developing method, characterized in that, The development step includes the following steps: spraying the circuit board to be developed with a 2-5% mass concentration of the alkali-free developing solution as described in any one of claims 1-3, so that the circuit pattern appears on the circuit board.

7. The developing method according to claim 6, characterized in that, In the developing step, the spray pressure is 1.5 ± 0.5 kg / cm². 2 Spraying time: 15±2s.

8. The developing method according to claim 6, characterized in that, The development stage is preceded by a pre-immersion stage: the exposed circuit board is immersed in the pre-immersion solution for 15±2s; the pre-immersion solution consists of a 0.8-1.2% alkali-free developing solution as described in any one of claims 1-3 and the remainder water.

9. A developing method, characterized in that, The process includes the following steps in sequence: pre-impregnation and developing. Pre-immersion section: The exposed circuit board is immersed in the pre-immersion section solution for 15±2s; the pre-immersion section solution is composed of 1.0% by mass of the alkali-free developing solution as described in any one of claims 1-3 and the remainder water; Developing section: The pre-impregnated circuit boards are sprayed with a 3% (w / w) alkali-free developing solution as described in any one of claims 1-3, at a spraying pressure of 1.5 ± 0.5 kg / cm². 2 Spraying time: 15±2s.

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