A process for refining PCB circuit pattern etching

Abstract

This invention relates to the field of printed circuit board manufacturing technology and discloses a fine etching process for PCB circuit patterns. The process includes injecting a fine etching composition comprising deionized water, hydrochloric acid, copper chloride dihydrate, anhydrous magnesium chloride, p-toluenesulfonic acid monohydrate, polyethylene glycol, and 2-mercaptobenzimidazole into a circulating working tank of an etching machine; setting the temperature of the working solution in the circulating working tank; sending the substrate to be etched, after dry film development, into a spray section; activating the spray array and setting the spray pressure to etch the substrate; and rapidly rinsing the etched substrate in a deionized water washing section, followed by strong air drying to obtain the circuit pattern. This invention reduces surface tension through specific components to promote solution penetration into the microstructure, utilizes an organic corrosion inhibitor to form a stable protective layer on the trench sidewalls, and combines the vertical impact of the nozzle jet on the bottom, leveraging the difference between mechanical force and chemical adsorption force to achieve anisotropic etching, thus suppressing lateral corrosion of fine circuits.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing technology, specifically to a process for refining PCB circuit pattern etching. Background Technology

[0002] As electronic devices become increasingly integrated, the line density of printed circuit boards (PCBs) is constantly increasing, while line width and spacing are gradually shrinking to the micrometer level. In traditional PCB manufacturing processes, an acidic copper chloride system is often used for spray etching of copper-clad laminates.

[0003] As circuit pattern sizes continue to decrease, the micro-trenches formed by the resist film on the substrate surface create a space-constraining effect. This structure results in significant penetration resistance for the etching solution as it enters the trenches. Fresh etching solution struggles to reach the bottom of the trenches, and insoluble byproducts from the etching reaction cannot be promptly flushed out with the fluid, leading to localized obstruction of fluid exchange and a reduction in the vertical etching rate. In actual production, to ensure complete removal of the copper layer at the bottom of the trenches to prevent short circuits, it is often necessary to extend the etching time. Because traditional etching solution systems lack specific directional protection mechanisms, extending the etching time exposes the circuitry on the trench sidewalls to corrosive fluids for an extended period, causing lateral corrosion. Lateral corrosion deforms the cross-section of the etched circuitry, narrowing the bottom of the circuitry and even causing undercutting. This not only reduces the adhesion of fine circuitry to the substrate but also causes impedance mismatch during signal transmission, making it difficult for the final printed circuit board to meet the technical requirements of high-density interconnects. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a fine etching process for PCB circuit patterns, which solves the problem of lateral corrosion caused by obstructed fluid exchange inside micro-trenches during the etching process of high-density fine circuits.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a PCB circuit pattern fine etching process, comprising the following steps:

[0006] A PCB circuit pattern fine etching composition containing deionized water, 36% hydrochloric acid, copper chloride dihydrate, anhydrous magnesium chloride, p-toluenesulfonic acid monohydrate, polyethylene glycol, and 2-mercaptobenzimidazole is injected into the circulating working tank of a standard horizontal spray etching machine.

[0007] Turn on the constant temperature circulation system to control the temperature of the working fluid in the circulation tank;

[0008] The PCB substrate to be etched, after dry film development, is fed into the spray section of the etching machine.

[0009] Turn on the upper and lower spray arrays and set the spray pressure of the nozzles to etch the PCB substrate;

[0010] After etching, the PCB substrate leaves the spray section and enters the cascaded deionized water washing section, where it is rinsed with room temperature deionized water.

[0011] The substrate then enters the drying section for drying, resulting in a PCB circuit pattern that has been etched.

[0012] By adopting the above technical solution, the acidic copper chloride system composed of the above components, combined with corresponding spraying parameters, can dissolve copper in trenches with micron-sized dimensions, while limiting excessive corrosion of the sidewalls. The specific reaction mechanism is as follows:

[0013] In the liquid system, copper chloride reacts with metallic copper on the substrate surface in a redox reaction to form insoluble cuprous chloride, which is deposited at the reaction interface. Subsequently, complexation dissolution occurs. At this time, hydrochloric acid and anhydrous magnesium chloride provide a large number of free chloride ions to the solution. The chloride ions coordinate with the insoluble cuprous chloride to form soluble complex anions, which then detach from the reaction interface. In this process, the magnesium ions generated by the dissociation of anhydrous magnesium chloride can increase the ionic strength of the solution, promote mass transport, and accelerate the renewal of the reaction interface.

[0014] To facilitate the solution's penetration into the microstructure, p-toluenesulfonic acid monohydrate is added to provide a polar environment, reducing the surface tension of the etching solution and allowing it to penetrate into the micro-grooves formed by the photoresist dry film, establishing a solid-liquid interface. Once inside the trenches, polyethylene glycol and 2-mercaptobenzimidazole in the system form a composite protective layer of adsorption and chemical coordination on the trench sidewalls. Due to the vertical impact of the nozzle jet at the bottom of the trench, the protective layer continuously peels off, exposing fresh metal surfaces and maintaining the vertical etching process. Meanwhile, the trench sidewalls are parallel to the jet direction, resulting in low solution shear force and stable adsorption film, preventing free acid and oxidant from contacting the sidewall metal surfaces, thus achieving anisotropic etching.

[0015] Preferably, each liter of the fine etching composition comprises the following components in varying amounts:

[0016] 172–258 mL of 36% hydrochloric acid, 126.8–190.2 g of copper chloride dihydrate, 9.5–28.6 g of anhydrous magnesium chloride, 2.0–5.0 g of p-toluenesulfonic acid monohydrate, 200–500 mg of polyethylene glycol, 10–50 mg of 2-mercaptobenzimidazole, and 1 L of deionized water.

[0017] By employing the above technical solution, the concentrations of each component are controlled within a specific mass range. The amount of hydrochloric acid used ensures that the solution possesses the acidity and chloride ion concentration required to inhibit the precipitation of cuprous chloride without damaging the adhesion of the anti-corrosion dry film. The amounts of polyethylene glycol and 2-mercaptobenzimidazole used ensure that the corrosion inhibitor can achieve saturated adsorption on the metal surface, preventing damage to the protective film due to excessively low concentrations and avoiding increased liquid viscosity and residue at the bottom of the trench due to excessively high concentrations.

[0018] Preferably, each liter of the refined etching composition comprises the following components in varying amounts:

[0019] 215 mL of 36% hydrochloric acid, 158.5 g of copper chloride dihydrate, 19.0 g of anhydrous magnesium chloride, 3.5 g of p-toluenesulfonic acid monohydrate, 350 mg of polyethylene glycol, 30 mg of 2-mercaptobenzimidazole, and 1 L of deionized water.

[0020] By adopting the above technical solution, the oxidation potential and surface activity of the etching system are well matched. This ratio balances the erosion ability of free ions on the bottom of the trench and the passivation ability of organic macromolecules on the sidewalls, ensuring that the sidewall edges remain straight after the circuit is formed.

[0021] Preferably, the preparation process of the refined etching composition includes the following steps:

[0022] Add deionized water to the reactor, then add hydrochloric acid (36% by mass) and copper chloride dihydrate in sequence, and stir until completely dissolved;

[0023] While stirring, add anhydrous magnesium chloride to the reactor and stir.

[0024] Add p-toluenesulfonic acid monohydrate and stir until completely dissolved;

[0025] Adjust the stirring speed, add polyethylene glycol, and stir until completely dissolved;

[0026] 2-Mercaptobenzimidazole was dispersed in deionized water to form a suspension, which was then added dropwise to the reaction vessel;

[0027] The volume was adjusted to 1L with deionized water, and stirring was continued to obtain the refined etching composition.

[0028] By adopting the above technical solution, the feeding steps were designed to avoid localized oversaturation within the reactor. Considering its poor water solubility at room temperature, 2-mercaptobenzimidazole was pre-dispersed as a suspension before being added dropwise to the system. At this point, the surface-active solubilizing effect of the previously dissolved p-toluenesulfonic acid was utilized to ensure that the 2-mercaptobenzimidazole molecules were uniformly dispersed throughout the fluid, preventing the corrosion inhibitor from agglomerating and clumping.

[0029] Preferably, the system temperature is maintained at 25°C during the preparation of the fine etching composition;

[0030] The stirring speed was 150 rpm before adding polyethylene glycol, and 250 rpm during and after the addition of polyethylene glycol.

[0031] By adopting the above technical solution, a system temperature of 25℃ inhibits the volatilization and escape of inorganic acid gases and the thermal degradation of long polymer chains. In the initial stage of preparation, inorganic salts are dissolved at 150 rpm, which reduces the entrainment of bubbles on the fluid surface. When polyethylene glycol and 2-mercaptobenzimidazole are added, the equipment speed is increased to 250 rpm, mainly to increase the fluid shear force, overcome the instantaneous viscosity generated during the polymer dissolution process, and accelerate the distribution of the organic corrosion inhibitor.

[0032] Preferably, the temperature of the working fluid in the tank is set to 45 to 50°C before spray etching the PCB substrate to be etched.

[0033] By adopting the above technical solution, the limited temperature range provides the energy required for the reaction at the liquid-solid interface. Temperatures below 45°C will cause the redox reaction to be slow and inorganic by-products to crystallize easily. Conversely, temperatures above 50°C will cause the organic molecules adsorbed on the metal interface to desorb, causing the sidewalls of the micro-grooves to lose their corrosion inhibition barrier.

[0034] Preferably, when performing spray etching on the PCB substrate to be etched, the spray pressure of the nozzles in the spray array is set to 2.0–2.5 kg / cm². 2 .

[0035] By employing the above technical solution, the set working pressure range enables the fluid to have sufficient kinetic energy to penetrate the capillary resistance of the micron-level trenches and reach the bottom of the substrate, washing away the organic adsorption film at the bottom and carrying out the reaction products. At the same time, the kinetic energy of the liquid is dissipated through the narrow space, and the residual shear stress when it reaches the sidewall is insufficient to peel off the organic adsorption layer in the sidewall area, thus utilizing the difference between mechanical force and chemical adsorption force to achieve vertical etching.

[0036] Preferably, the circuit pattern of the PCB substrate to be etched is designed with a line width and line spacing of 15 and 15 μm, respectively.

[0037] By adopting the above technical solution, an etching process that includes penetration, complexation, and sidewall protection can be used to solve the problem of limited spatial mass transfer and fluid exchange in 15-micron-scale patterns.

[0038] Preferably, when thoroughly rinsing with room temperature deionized water, the PCB substrate after etching enters the cascaded deionized water rinsing section within 5 seconds after leaving the spray section, and is thoroughly rinsed with room temperature deionized water.

[0039] By adopting the above technical solution, a termination time point for the etching process was set. After the substrate leaves the spray area, the surface residual liquid loses its vertical fluid kinetic energy and transforms into a static chemical corrosion state, where the residual liquid slowly erodes the sidewalls. Within 5 seconds, a water washing process is initiated, using deionized water to replace and wash away the surface residual liquid, promptly terminating the reaction and preventing linewidth reduction caused by static corrosion.

[0040] Preferably, during the continuous spray etching process of the PCB substrate to be etched, the temperature of the working fluid in the tank is controlled, including:

[0041] Adjust the heating system to raise the working fluid temperature to 52°C and maintain it for 5 minutes, then cool it back down to the initial working temperature.

[0042] By employing the above technical solution, a brief heating operation is used to address the changes in the working fluid during continuous circulation. Heating to 52°C promotes the unwinding of molecular chains that have aggregated due to prolonged mechanical pumping and shearing, and increases the solubility of inorganic byproducts in the fluid to flush out deposits inside the pipeline. Subsequently, the temperature is lowered to the initial operating temperature, allowing the organic components to re-establish a stable adsorption equilibrium.

[0043] This invention provides a fine etching process for PCB circuit patterns. It has the following beneficial effects:

[0044] 1. This invention solves the problem of lateral corrosion in the etching process of micro-line by using a composition containing inorganic salts and various organic additives in conjunction with a vertical spraying process. The p-toluenesulfonic acid monohydrate in the composition reduces the surface tension of the etching solution, allowing the solution to penetrate smoothly into the micro-grooves formed by the resist dry film and establish a reaction interface. At the same time, polyethylene glycol and 2-mercaptobenzimidazole form a protective layer on the sidewall of the trench. Combined with the vertical impact of the spray jet on the bottom of the trench, the adsorbed film at the bottom is washed away to expose the fresh metal surface. The difference between mechanical force and chemical adsorption force is used to achieve anisotropic vertical etching, ensuring the straightness of the edge of the line sidewall.

[0045] 2. This invention improves the stability and component distribution uniformity of the composite etching solution system by setting an orderly feeding step and a variable speed stirring strategy. In the preparation process, the surface-active solubilizing effect of the p-toluenesulfonic acid dissolved in the early stage is utilized, combined with the feeding method of pre-dispersing the poorly water-soluble components into a suspension, to prevent the corrosion inhibitor from agglomerating and clumping in the system. The operation of dissolving inorganic salts at a low speed in the early stage to reduce the entrainment of air bubbles and increasing the speed in the later stage to accelerate the dispersion of organic components avoids the phenomenon of local supersaturation in the reactor, thus ensuring the preparation quality of the multi-component etching solution.

[0046] 3. This invention maintains the stability of the etching system during long-term processing by introducing variable temperature control and strict time point control in continuous production cycles. A brief temperature rise during continuous spray etching promotes the re-unfolding of molecular chains that have aggregated due to prolonged mechanical pumping and shearing, and increases the solubility of inorganic byproducts in the fluid to remove deposits in the pipeline. Subsequently, the operating temperature is restored to allow the organic components to re-establish adsorption equilibrium. Combined with the rapid water washing and replacement step after the substrate leaves the spray section, static corrosion caused by surface residue is avoided, ensuring the consistency of line dimensions during continuous processing of multiple batches of substrates. Attached Figure Description

[0047] Figure 1 A histogram comparing the rheological parameters of the etching composition of the present invention at different shear rates;

[0048] Figure 2 The following diagrams illustrate the metastable critical phase behavior and particle size distribution of the etching composition of the present invention: (a) is a measurement curve of transmittance as a function of bath temperature, and (b) is a particle size probability density distribution of dispersed microparticles in the system at 52°C.

[0049] Figure 3 This is a bar chart comparing the vertical etching rates under different etching compositions and process parameters of the present invention.

[0050] Figure 4 This is a correlation diagram showing the characteristics of lateral erosion and electrical attenuation of the circuit under different etching conditions according to the present invention;

[0051] Figure 5 This is a comparison diagram of the pressure difference evolution of the fluid circulation filtration system under abnormal high temperature conditions according to the present invention;

[0052] Figure 6 The following are characteristic diagrams of elemental distribution and residual contamination on the etched surfaces of the test objects of the present invention. Among them, (a) is a line graph of the atomic percentage evolution of the main elements calculated by XPS broadband test, and (b) is a line graph of the relative residual index of surface organic matter extracted by calculating the carbon-copper ratio (C / Cu) of each group. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0054] Preparation Examples 1-4:

[0055] Preparation Example 1:

[0056] This preparation example provides a method for preparing a PCB circuit pattern fine etching composition, including the following steps:

[0057] Add 700 mL of deionized water to the reactor. While stirring at 25 °C and 150 rpm, add 215 mL of 36% hydrochloric acid and 158.5 g of copper chloride dihydrate in sequence and stir until completely dissolved. While stirring, add 19.0 g of anhydrous magnesium chloride to the reactor and stir for 15 minutes.

[0058] Add 3.5g of p-toluenesulfonic acid monohydrate and stir until completely dissolved;

[0059] Adjust the stirring speed to 250 rpm, add 350 mg of polyethylene glycol, and stir until completely dissolved;

[0060] 30 mg of 2-mercaptobenzimidazole was dispersed in 10 mL of deionized water to form a suspension, which was then added dropwise to the reaction vessel.

[0061] The volume was adjusted to 1L with deionized water, and stirring was continued for 30 minutes to obtain a PCB circuit pattern fine etching composition.

[0062] Preparation Example 2:

[0063] This preparation example provides a method for preparing a PCB circuit pattern fine etching composition, including the following steps:

[0064] Add 700 mL of deionized water to the reactor, and add 172 mL of 36% hydrochloric acid and 126.8 g of copper chloride dihydrate in sequence at 25 °C and 150 rpm, stirring until completely dissolved.

[0065] While stirring, add 9.5g of anhydrous magnesium chloride to the reactor and stir for 15 minutes;

[0066] Add 2.0g of p-toluenesulfonic acid monohydrate and stir until completely dissolved;

[0067] Adjust the stirring speed to 250 rpm, add 200 mg of polyethylene glycol, and stir until completely dissolved;

[0068] 10 mg of 2-mercaptobenzimidazole was dispersed in 10 mL of deionized water to form a suspension, which was then added dropwise to the reaction vessel.

[0069] The volume was adjusted to 1L with deionized water, and stirring was continued for 30 minutes to obtain a PCB circuit pattern fine etching composition.

[0070] Preparation Example 3:

[0071] This preparation example provides a method for preparing a PCB circuit pattern fine etching composition, including the following steps:

[0072] Add 700 mL of deionized water to the reactor, and add 258 mL of 36% hydrochloric acid and 190.2 g of copper chloride dihydrate in sequence at 25 °C and 150 rpm, stirring until completely dissolved.

[0073] While stirring, add 28.6g of anhydrous magnesium chloride to the reactor and stir for 15 minutes;

[0074] Add 5.0g of p-toluenesulfonic acid monohydrate and stir until completely dissolved;

[0075] Adjust the stirring speed to 250 rpm, add 500 mg of polyethylene glycol, and stir until completely dissolved;

[0076] 50 mg of 2-mercaptobenzimidazole was dispersed in 10 mL of deionized water to form a suspension, which was then added dropwise to the reaction vessel.

[0077] The volume was adjusted to 1L with deionized water, and stirring was continued for 30 minutes to obtain a PCB circuit pattern fine etching composition.

[0078] Preparation Example 4:

[0079] This preparation example provides a method for preparing a PCB circuit pattern fine etching composition, including the following steps:

[0080] Add 700 mL of deionized water to the reactor, and add 172 mL of 36% hydrochloric acid and 126.8 g of copper chloride dihydrate in sequence at 25 °C and 150 rpm, stirring until completely dissolved.

[0081] While stirring, add 28.6g of anhydrous magnesium chloride to the reactor and stir for 15 minutes;

[0082] Add 5.0g of p-toluenesulfonic acid monohydrate and stir until completely dissolved;

[0083] Adjust the stirring speed to 250 rpm, add 500 mg of polyethylene glycol, and stir until completely dissolved;

[0084] 50 mg of 2-mercaptobenzimidazole was dispersed in 10 mL of deionized water to form a suspension, which was then added dropwise to the reaction vessel.

[0085] The volume was adjusted to 1L with deionized water, and stirring was continued for 30 minutes to obtain a PCB circuit pattern fine etching composition.

[0086] Examples 1-4:

[0087] Example 1:

[0088] This embodiment provides a process for refining PCB circuit pattern etching, including the following steps:

[0089] The PCB circuit pattern fine etching composition obtained in Preparation Example 1 was injected into the circulating working tank of a standard horizontal spray etching machine;

[0090] Turn on the constant temperature circulation system and set and strictly control the temperature of the working fluid in the tank at 48℃;

[0091] The PCB substrate to be etched, which has completed dry film development and has a line width and line spacing of 15μm and 15μm, is fed into the spray section of the etching machine at a constant speed.

[0092] Turn on the upper and lower spray arrays and set the spray pressure of the nozzles to 2.2 kg / cm². 2 Etching of the PCB substrate;

[0093] After etching, the PCB substrate leaves the spray section and enters the cascaded deionized water washing section within 5 seconds, where it is thoroughly rinsed with room temperature deionized water.

[0094] The substrate then enters the drying section for conventional strong air drying, resulting in the etched PCB circuit pattern.

[0095] Example 2:

[0096] This embodiment provides a process for refining PCB circuit pattern etching, including the following steps:

[0097] The PCB circuit pattern fine etching composition obtained in Preparation Example 2 was injected into the circulating working tank of a standard horizontal spray etching machine;

[0098] Turn on the constant temperature circulation system and set and strictly control the temperature of the working fluid in the tank at 45℃;

[0099] The PCB substrate to be etched, which has completed dry film development and has a line width and line spacing of 15μm and 15μm, is fed into the spray section of the etching machine at a constant speed.

[0100] Turn on the upper and lower spray arrays and set the spray pressure of the nozzles to 2.0 kg / cm². 2 Etching of the PCB substrate;

[0101] After etching, the PCB substrate leaves the spray section and enters the cascaded deionized water washing section within 5 seconds, where it is thoroughly rinsed with room temperature deionized water.

[0102] The substrate then enters the drying section for conventional strong air drying, resulting in the etched PCB circuit pattern.

[0103] Example 3:

[0104] This embodiment provides a process for refining PCB circuit pattern etching, including the following steps:

[0105] The PCB circuit pattern fine etching composition obtained in Preparation Example 3 was injected into the circulating working tank of a standard horizontal spray etching machine;

[0106] Turn on the constant temperature circulation system and set and strictly control the temperature of the working fluid in the tank at 50℃;

[0107] The PCB substrate to be etched, which has completed dry film development and has a line width and line spacing of 15μm and 15μm, is fed into the spray section of the etching machine at a constant speed.

[0108] Turn on the upper and lower spray arrays and set the spray pressure of the nozzles to 2.5 kg / cm². 2 Etching of the PCB substrate;

[0109] After etching, the PCB substrate leaves the spray section and enters the cascaded deionized water washing section within 5 seconds, where it is thoroughly rinsed with room temperature deionized water.

[0110] The substrate then enters the drying section for conventional strong air drying, resulting in the etched PCB circuit pattern.

[0111] Example 4:

[0112] This embodiment provides a method for refining the etching process of PCB circuit patterns, including the following steps:

[0113] The PCB circuit pattern fine etching composition obtained in Preparation Example 1 was injected into the circulating working tank of a standard horizontal spray etching machine;

[0114] Turn on the constant temperature circulation system and set the initial temperature of the working fluid in the tank to 48℃;

[0115] Multiple PCB substrates, with dry film developed and circuit patterns designed with line widths and spacings of 15μm and 15μm respectively, are continuously and uniformly fed into the spray section of the etching machine. The spray array is then activated, and the nozzle spray pressure is set to 2.2 kg / cm². 2 ;

[0116] During the etching process, the heating system was adjusted to rapidly raise the working fluid temperature to 52°C and maintain it for 5 minutes, and then the temperature was readjusted and lowered to 48°C.

[0117] The substrate undergoes continuous etching throughout the temperature variation;

[0118] After all substrates are etched, they leave the spray section and enter the cascaded deionized water washing section within 5 seconds, where they are thoroughly rinsed with room temperature deionized water.

[0119] The substrate then enters the drying section for conventional strong air drying, resulting in the etched PCB circuit pattern.

[0120] Comparative Examples 1-6:

[0121] Comparative Example 1:

[0122] Compared with Example 1, the difference is that anhydrous magnesium chloride, p-toluenesulfonic acid monohydrate, polyethylene glycol and 2-mercaptobenzimidazole were not added when preparing the composition. Only deionized water, hydrochloric acid and copper chloride dihydrate were used to prepare the basic etching solution. All other aspects are the same.

[0123] Comparative Example 2:

[0124] The difference from Example 1 is that polyethylene glycol was not added when preparing the composition; otherwise, they are the same.

[0125] Comparative Example 3:

[0126] The difference from Example 1 is that anhydrous magnesium chloride was not added when preparing the composition; otherwise, they are the same.

[0127] Comparative Example 4:

[0128] The difference from Example 4 is that p-toluenesulfonic acid monohydrate was not added when preparing the composition; otherwise, they are the same.

[0129] Comparative Example 5:

[0130] The difference compared to Example 1 is that the spray pressure of the nozzle is set to 1.0 kg / cm². 2 The rest are the same.

[0131] Comparative Example 6:

[0132] The difference compared to Example 1 is that the spray pressure of the nozzle is set to 4.0 kg / cm². 2 The rest are the same.

[0133] Test Examples 1-6:

[0134] Test Example 1:

[0135] This test example provides a specific process for characterizing the rheological parameters of the etching compositions of the present invention. The test objects are the etching compositions prepared using the formulation obtained in Preparation Example 1 and the etching compositions prepared using the formulation obtained in Comparative Example 3.

[0136] Test steps:

[0137] Turn on the rotational rheometer and install the coaxial cylindrical test fixture. Set the target temperature of the constant temperature control module to 48℃ and wait for the equipment temperature to reach equilibrium.

[0138] Extract an appropriate amount of the etched composition sample to be tested and slowly inject it into the test cup of the rheometer. Lower the test rotor to the specified spacing and let the sample stand for 300 seconds to eliminate the historical shear stress generated during the sample addition process.

[0139] The test mode was set to a logarithmically increasing steady-state shear rate scan, and the shear rate control range was set to 0.1 s. -1 up to 1000s -1 The data acquisition time for each measurement point is set to 10 seconds.

[0140] The program is started to record the raw data of sample shear stress and apparent viscosity changes with shear rate during the test.

[0141] After the test, the collected dataset was exported, the viscosity parameters at the characteristic shear rate were extracted, and the data in the extremely low shear rate range were extracted and imported into the Herschel-Bulkley model for nonlinear regression fitting. The initial rheological yield stress of the system was then extrapolated and calculated.

[0142] Test data:

[0143] Table 1. Rheological characteristics of the etching composition at 48°C

[0144]

[0145] in conclusion:

[0146] Figure 1 This is a histogram comparing the rheological parameters of the etching compositions of this invention at different shear rates. The distribution of dark gray bars and solid circular markers in the figure represents the apparent viscosity and shear stress variation data of the composition of Preparation Example 1, while the distribution of light gray bars and dashed square markers represents the apparent viscosity and shear stress variation data of the composition of Comparative Example 3. The left-hand principal axis is associated with grouped histograms to characterize the apparent viscosity of the system, and the right-hand secondary axis is associated with line graphs to characterize the shear stress experienced by the system.

[0147] According to the data in Table 1, the initial yield stress obtained by extrapolation of the composition of Preparation Example 1 under the set thermodynamic conditions was only 1.18 Pa, exhibiting mechanical characteristics biased towards brittle fracture. In the early formulation design stage, it was found that the comparative example 3 sample, which did not introduce strong hydrated cations, measured a yield stress as high as 15.34 Pa, and the fluid network in the test cup exhibited strong structural toughness and flow hindrance effect under low shear field.

[0148] Under normal hydration conditions, the hydrogen bond network formed by polyethylene glycol (PEG) molecules and 2-mercaptobenzimidazole exhibits a certain degree of resistance to flow field shear. The addition of a specified concentration of anhydrous magnesium chloride alters the solvation equilibrium of the fluid microenvironment; the extremely high charge density of magnesium ions disrupts the bound water layer surrounding the PEG.

[0149] The polymer network, initially in a stretched state, undergoes severe dehydration and shrinkage due to the loss of support from the hydration layer. This shrinkage of the network structure leads to a decrease in fluid viscosity, resulting in a decline in rheological properties. Viscosity decay data collected at high shear rates directly confirms the tendency of the network structure to disintegrate, reaching a peak at 1000 s⁻¹. -1 Under a strong shear field, the apparent viscosity of the composition prepared in Example 1 decreased to 2.63 mPa·s, far lower than the 14.58 mPa·s maintained in Comparative Example 3. The viscosity at the bottom of the micro-grooves was 2.2 kg / cm² during actual etching operations on the production line. 2 The local fluid shear force induced by impact hydraulic pressure far exceeds the strength threshold of 1.18 Pa.

[0150] This brittle-enhancing process causes the adsorbed film layer covering the substrate to lose its mechanical buffering capacity and be destroyed by the vertical fluid kinetic energy, continuously exposing fresh interfaces to maintain the longitudinal dissolution process. Within the hydrodynamic boundary layer where the sidewall adhesion layer is located, the liquid film velocity approaches quiescence, and the shear force in the stagnant zone cannot trigger a yield fracture point at this level. The dehydrated and coiled molecular network maintains a dense stacked state in the static field and restricts the lateral diffusion of reactive ions through steric hindrance, thus establishing the basis for anisotropic etching.

[0151] Test Example 2:

[0152] This test example provides a characterization process for the phase evolution and colloidal stability of the etching compositions of the present invention under thermodynamic boundary conditions. The test objects are the etching compositions prepared using the formulation obtained in Preparation Example 1 and the etching compositions prepared using the formulation obtained in Comparative Example 4.

[0153] Test steps:

[0154] Turn on the UV-Vis spectrophotometer and preheat it. Set the detection wavelength to 600 nm. This wavelength avoids the main characteristic absorption peaks of copper complex ions, so as to simply evaluate the light scattering attenuation caused by the turbidity of the system.

[0155] The stock solution of the composition to be tested was injected into a capped quartz cuvette and placed in a sample cell equipped with a Peltier temperature control accessory.

[0156] The initial temperature of the test program was set to 40℃, and the temperature was continuously increased to 55℃ at a heating rate of 1℃ / min. During the heating process, the instrument synchronously recorded the change in transmittance.

[0157] The heating program was interrupted when the temperature reached 52°C and kept constant. 1.5 mL of the sample liquid in a metastable state at high temperature was drawn from the cuvette.

[0158] The extracted liquid is quickly injected into a standard pleated capillary potential cell and placed into the detection chamber of the dynamic light scattering instrument.

[0159] Start the dynamic light scattering and electrophoretic light scattering joint measurement program to record the Z-average particle size and Zeta potential of the dispersed phase particles in the system at 52℃.

[0160] Test data:

[0161] Table 2. Optical and surface potential characteristics of the etching composition during the heating process.

[0162]

[0163] in conclusion:

[0164] Figure 2 This is a diagram showing the metastable critical phase behavior and particle size distribution of the etching composition of the present invention. (a) is a measurement curve of transmittance as a function of bath temperature, and (b) is a probability density distribution of particle size of dispersed particles in the system at 52°C. The solid lines and circular data markers in the figure represent the test results of the composition of Preparation Example 1, and the dashed lines and square data markers represent the test results of the composition of Comparative Example 4.

[0165] According to the data in Table 2, the composition of Preparation Example 1 maintained a transmittance of 87.5% even under conditions exceeding the cloud point of 52°C, while the composition of Comparative Example 4, lacking p-toluenesulfonic acid, experienced a sharp drop in transmittance to 12.3% after exceeding the cloud point of the system. In early intensive production line tests, it was observed that continuous high-volume copper-clad laminate etching caused heat accumulation within the etching tank due to ongoing chemical exothermics, resulting in temporary temperature fluctuations in localized areas where the fluid temperature briefly deviated from the temperature control system.

[0166] When the temperature exceeds the critical point of phase separation of polyethylene glycol at the current high salt concentration, the spontaneous dehydration and aggregation of polymeric segments is an irreversible thermodynamic process. The obtained dynamic light scattering data illustrates the actual impact of this phase separation on the process. In Comparative Example 4, the average particle size reached 3452.1 nm at 52 °C, and the surface potential was only -6.8 mV. This low surface potential could not counteract the van der Waals forces between the macromolecular segments, causing the dehydrated polyethylene glycol to crosslink and fuse into flocculent precipitates. In real fluid pipelines, this manifests as rapid clogging and shutdown of filters and nozzles. Introducing p-toluenesulfonic acid, which possesses both hydrophobic aromatic rings and highly hydrophilic sulfonic acid groups, into the formulation altered the aggregation state of the dispersed phase through adsorption at the phase interface.

[0167] The test solution surface of the composition in Preparation Example 1 exhibited a high negative polarization potential of -42.6 mV, and the electrostatic repulsion maintained the average size of the precipitated phase at 186.4 nm. The electrostatic repulsion blocked the channel for submicron micelles to continue agglomerating into large flocs, transforming the phase that should have precipitated into a stable emulsion dispersed within the working tank. This buffering mechanism, built upon water-soluble growth, ensured the continuous flowability of the drug solution even during occasional temperature runaway.

[0168] Test Example 3:

[0169] This test example provides a quantitative characterization process for the longitudinal processing capability of various etching systems. The test objects involved in the experiment include the process methods and corresponding compositions provided in Examples 1 to 3, as well as control groups using the formulations and process parameters set in Comparative Examples 1, 3, and 5, respectively.

[0170] Test steps:

[0171] A batch of standard copper-clad laminates with a specification of 100mm×100mm and uniform copper foil thickness were selected as test substrates. They were immersed in a 5% sulfuric acid solution for 30 seconds to remove the surface oxide layer, and then rinsed with deionized water and thoroughly dried with cold air.

[0172] The initial mass of each copper-clad laminate after processing was measured using an analytical balance with an accuracy of 0.1 mg, and the data was recorded.

[0173] The prepared substrates are fed into a horizontal spray etching machine containing the corresponding test object solution, and continuous spray etching is performed for a fixed time of 120 seconds according to the temperature and spray pressure parameters specified in the respective embodiments or comparative examples.

[0174] After the etching process is completed, the substrate is removed and transferred to a room temperature deionized water bath within 5 seconds to soak and rinse for 1 minute to wash away residual chemicals and polymer adhesion layers. After removal, the substrate is dried with a high-pressure air gun.

[0175] The final mass of the substrate after etching was weighed again using an analytical balance, and the total mass of dissolved copper was calculated by the mass difference before and after etching.

[0176] By combining the theoretical density of copper with the standard area of ​​one side of the substrate, the mass loss is converted into a thickness change value, which is then divided by the etching time to obtain the final vertical etching rate value.

[0177] Test data:

[0178] Table 3. Test data on vertical etching rate under different compositions and process conditions

[0179]

[0180] in conclusion:

[0181] Figure 3 This is a bar chart comparing the vertical etching rates under different etching compositions and process parameters of this invention. The horizontal axis corresponds to six different test objects, and the vertical axis represents the vertical etching rate calculated using the weight loss method. Different gray levels are used to fill the bars to distinguish between the blank control, the embodiments of this invention, and the comparative examples lacking specific mechanistic conditions.

[0182] According to the data in Table 3, the vertical etching rates of Examples 1 to 3 ranged from 26.82 to 31.40 μm / min. Combined with the baseline rate of 29.38 μm / min measured in Comparative Example 1 (without any polymer added), it can be determined that the formulation of this invention essentially maintains the original level of the conventional hydrochloric acid-copper chloride system in terms of vertical processing capability.

[0183] Introducing macromolecular organic matter into etching systems often leads to overall reaction stagnation due to large-area coverage. We indeed encountered a similar phenomenon in our preliminary tests, with Comparative Example 3 showing an extremely low etching rate of 8.72 μm / min. In this group, due to the lack of magnesium chloride as a high charge density salt, the polyethylene glycol molecular chains retained an intact hydration layer. This stretched polymer network exhibits high toughness, and the impact force generated by conventional nozzles cannot tear it, thus blocking the ions required for the etching reaction. In our examples, we utilized magnesium ion-induced salting-out dehydration to alter this mechanical equilibrium. The dehydrated and embrittled molecular network encountered a 2.0 kg / cm² salting-out reaction. 2 During the above vertical hydraulic pressure, local yielding and rupture will occur, and the bottom part of the hole, which has lost its obstruction function, will continue to expose the metal interface for the reaction to take place.

[0184] Actual observations confirmed that merely altering the state of the adsorption membrane was insufficient to drive the entire reaction downwards; a specific intensity of fluid impact force applied by external equipment was a necessary condition to trigger membrane rupture. Comparative Example 5 used the same chemical formulation as Example 1, limiting the spray fluid pressure to 1.0 kg / cm². 2 Because the mechanical kinetic energy output by the equipment did not reach the yield strength of the underlying film, the brittle film layer remained intact under this low-intensity erosion, and the longitudinal mass transfer channel remained blocked, resulting in an overall rate decrease to 10.15 μm / min. The rate difference obtained from the test confirms the interdependence between the brittle remodeling of the material and the shear force of the flow field. The combination of the two establishes the basis for the selective occurrence of the etching direction in spatial geometry.

[0185] Test Example 4:

[0186] This test example provides a quantitative measurement process for anisotropic linewidth loss and line cross-sectional area retention. The test objects involved in the experiment include the process methods and corresponding compositions provided in Examples 1 to 3, as well as control groups using the conditions set in Comparative Examples 1, 2, and 6.

[0187] Test steps:

[0188] Prepare multiple standard test substrates with 18μm copper base and dry film mask development completed. The mask pattern area is uniformly preset to contain a large number of dense parallel direct-connect lines with a design line width of 15.0μm.

[0189] The test substrates were fed into etching machines containing the corresponding solutions for each test object for processing. To eliminate the interference of differences in processing depth on the lateral etching data, a high-frequency laser displacement sensor was used for online monitoring at the end of the etching area. The transmission was immediately stopped and the actual time consumed was recorded the instant the bottom copper was vertically etched through and a large area of ​​the underlying insulating substrate was exposed.

[0190] The test substrate, after being washed with water, was immersed in a constant-temperature dilute sodium hydroxide solution for ultrasonic treatment to completely peel off the surface dry film. After being rinsed with deionized water, it was placed in a vacuum oven to dry, revealing the actual remaining copper circuit structure.

[0191] A probe-type surface profilometer was used to perform a one-dimensional step scan on a cross-section perpendicular to the trace direction. The width of the flat top region in the scanned profile data was extracted as the actual top retained linewidth. Twenty different locations were randomly selected from each substrate for measurement, and the average value was calculated. The difference between the designed width of 15.0 μm and the actual measured width was recorded as the absolute linewidth loss.

[0192] A high-precision four-probe microresistance testing system was used to measure the voltage drop across a single 100mm long wire on the test board under a constant detection current of 10mA, and the actual DC resistance data was calculated. This data was then compared with the standard resistance value of an ideal rectangular cross-section under theoretically no lateral corrosion conditions to obtain the relative rate of change of resistance.

[0193] Test data:

[0194] Table 4. Geometric morphology and electrical characteristics of the etched circuit.

[0195]

[0196] in conclusion:

[0197] Figure 4This is a correlation diagram of the lateral erosion and electrical attenuation characteristics of the line under different etching conditions according to the present invention. In the figure, the left main coordinate axis and the solid line mark correspond to the absolute linewidth loss of the line, the scatter plot represents the discrete data of a single original measurement obtained at different positions using a stepper, and the solid broken line running through the scatter plot represents the evolution trend of the mean of each group; the right secondary coordinate axis and the dashed broken line correspond to the relative change rate of the line resistance measured using a four-probe device.

[0198] According to the data in Table 4, the process provided by this invention demonstrates strong intervention capabilities in suppressing lateral erosion. After peeling off the dry film, the cross-sectional profile was directly measured using a profilometer. The absolute linewidth loss in Examples 1 to 3 was essentially suppressed within a narrow range of 0.85 to 1.48 μm. This allowed the relative rate of change of resistance of the corresponding thin copper lines to be controlled within 20%, preserving an excellent conductive cross-section.

[0199] In contrast, Comparative Example 1, which relied entirely on conventional inorganic components, showed significant lateral dissolution of the sidewalls within the same timeframe after the copper substrate was vertically etched through. The linewidth loss of 8.87 μm resulted in a drop in the remaining width to 6.13 μm, leading to a 185.4% increase in resistivity. This stark contrast in electrical and geometric data indirectly confirms the involvement of the sidewall passivation network in actual processing. To investigate the role of polymer materials in this passivation mechanism, polyethylene glycol was removed from Comparative Example 2. Even without the long-chain polymer, the linewidth loss in this batch of test plates still reached 7.58 μm, indicating that without large molecules to provide substantial and dense steric hindrance, it is difficult to independently construct a sidewall protective barrier using only low-molecular-weight corrosion inhibitors.

[0200] A particularly noteworthy phenomenon was observed during the multi-round fluid parameter debugging: when the operating pressure of the spray system, as in Comparative Example 6, was increased to 4.0 kg / cm²... 2 At this point, the stability of the original sidewall protective film was compromised, and measurements showed that the loss rebounded to 5.35 μm. This abnormal indicator precisely corresponds to the rupture of the hydrodynamic boundary layer. In micro-trenches at the 15 μm level, the liquid adhering closely to the sidewall of the circuit would normally form a static water boundary layer with extremely low flow velocity due to viscosity. The spray pressure specified in the embodiment precisely protects this adhering environment from being disrupted by the main jet, allowing the coiled polymer network to be stably adsorbed onto the sidewall. External fluid kinetic energy exceeding the tolerance threshold excites local turbulence within the trench and cuts into this boundary layer, causing the sidewall-adhered film to detach, and the exposed fresh metal lattice undergoes continuous dissolution. The flow field distribution of the equipment and the rheological properties of the material form a correspondence here, which constitutes the underlying logic of this technology system enabling precise circuit control.

[0201] Test Example 5:

[0202] This test example provides a dynamic characterization process for the fluid continuity and anti-flocculation ability of an etching system under thermodynamic supercritical conditions. The test objects involved in the experiment are the etching composition of Example 4 containing a complete buffering mechanism and the etching composition of Comparative Example 4 lacking p-toluenesulfonic acid.

[0203] Test steps:

[0204] A small closed-loop fluid testing system simulating the working environment of a production line was built. The system consists of a jacketed heated storage tank, an acid and alkali resistant magnetically driven pump, a standard stainless steel test filter assembly with a pore size of 75μm, and connecting pipelines.

[0205] High-precision digital pressure transmitters are installed at the fluid inlet and outlet of the filter assembly, respectively, and connected to a data acquisition terminal to record the pressure drop difference (ΔP) before and after the fluid flows through the filter in real time.

[0206] Inject the test drug solution into the storage tank, turn on the magnetic pump to set and keep the circulation flow rate in the pipeline constant at 15L / min, wait for the fluid circulation to stabilize and record the initial operating pressure difference at this time.

[0207] The forced heating program of the storage tank is activated, and the temperature of the liquid is artificially raised to 52°C, exceeding the normal operating range, to simulate the abnormal local thermal runaway caused by heat exchanger failure or large-scale etching heat release in the production line.

[0208] The system was kept running continuously at a constant temperature of 52℃ for 60 minutes, with the data acquisition terminal recording the current differential pressure value every 10 minutes. If the differential pressure exceeded the safety threshold of 600 kPa during operation, the system would automatically trigger the pressure relief bypass valve and terminate the test.

[0209] Test data:

[0210] Table 5. Evolution of Pressure Difference of Circulation System Filter Screen over Time under Abnormal High Temperature Conditions

[0211]

[0212] in conclusion:

[0213] Figure 5 This is a comparative graph showing the pressure difference evolution of the fluid circulation filtration system under abnormally high temperature conditions according to the present invention. The horizontal axis in the graph represents the continuous operating time of the system under the 52°C over-temperature condition, and the vertical axis uses a logarithmic scale to cover the range of pressure difference data. The solid line and dark gray circular data markers record the pressure difference change trajectory of the composition of Example 4, while the dashed line and light gray square data markers record the sudden pressure drop process of the composition of Comparative Example 4 until the system shutdown.

[0214] According to the data in Table 5, the initial pipeline reference pressure difference was within the normal fluid resistance range of approximately 14 kPa, which is consistent with the characteristics of low-viscosity water-based solutions passing through a metal screen. The subsequent forced heating program pushed the system's microenvironment past the set polymer critical phase transition point. In Comparative Example 4, which lacked p-toluenesulfonic acid, the pressure drop across the filter screen sharply increased to 86.3 kPa after 20 minutes of circulation.

[0215] The process was observed and recorded near the monitoring equipment. The originally clear liquid became severely milky and turbid, as the polyethylene glycol molecular chains completely lost the protection of the hydration layer at high temperatures. Once this thermodynamic dehydration phase transition occurs, a large number of free polymer segments become entangled under the pull of van der Waals forces and rapidly grow into a highly adhesive gel. When these gel particles reached the 75μm pore size filter area with the fluid, they were mechanically intercepted and accumulated, blocking the flow channel and causing a rapid rise in the pipeline pressure. After 50 minutes of testing, an excessive back pressure of 615.4 kPa forced the system to shut off the main circulation.

[0216] In practical continuous etching production lines, the tolerance for nozzle lock-up caused by the instability of the chemical solution phase is extremely low; a single shutdown for cleaning often results in the scrapping of an entire batch of boards. The complete system configured in Example 4 intervened in this colloidal evolution path. Test data showed that during continuous 60-minute ultra-high temperature cycling, the cycling resistance with p-toluenesulfonic acid only slowly increased from 14.2 kPa to 18.9 kPa. This gentle pressure differential fluctuation indicates that the filter channels remained unobstructed, and large-sized flocculent blockages were not formed.

[0217] At this point, the hydrophilic sulfonic acid groups and hydrophobic benzene rings in the p-toluenesulfonic acid molecule stabilize the interfacial state, forming an oriented assembly layer on the surface of the precipitated polyethylene glycol (PEG) droplets. This gives the PEG particles the same charge, resulting in electrostatic repulsion between the particles. This electrostatic repulsion keeps the precipitated phase in a fine emulsion state, allowing flexible droplets smaller than a micrometer to penetrate equipment filters and ultra-fine nozzles without hindrance. This chemically water-soluble growth method imparts a fault tolerance margin to the material system, breaking the chain of transmission from environmental temperature fluctuations to mechanical failures.

[0218] Test Example 6:

[0219] This test example provides a quantitative analysis procedure for the residual polymer condition on the surface of the etched substrate, thereby verifying the non-destructive desorption capability of the surface polarization network under conventional water washing conditions. The experimental test objects include the etched substrates generated in Examples 1 to 3, as well as the substrate etched using the blank base solution of Comparative Example 1. A set of unwashed samples from Example 1 was also added as a benchmark reference for high residual conditions.

[0220] Test steps:

[0221] Take copper-clad laminate substrates from each group that have just completed the horizontal spray etching process, and perform a split operation according to the preset post-processing conditions.

[0222] Substrate from the unwashed group was placed directly into a high-frequency centrifuge to remove surface droplets. Substrate from the other standard washed groups was placed in a deionized water bath at 25°C and continuously rinsed for 60 seconds at a constant water flow of 2.0L / min to simulate conventional production line cleaning.

[0223] All pre-treated substrates were placed in a vacuum drying oven and dehydrated at low pressure at 40°C for 2 hours. Then, they were cut into 8mm x 8mm square micro-samples using a special tool without tungsten carbide coating.

[0224] The sample was fixed on conductive adhesive and placed into the sample inlet of the X-ray photoelectron spectroscopy (XPS) instrument. The vacuum level in the analysis chamber was then evacuated to below 10. -7 The test program is started after mbar.

[0225] Using monochromatic AlKα rays as the excitation source, a wide-spectral continuous scan of the sample surface in the range of 0-1200 eV was performed to record the emission intensity of photoelectrons on the surface.

[0226] Extraction of C 1s, O 1s and Cu 2 By combining the characteristics of the p orbitals with the energy peak position data, and using the instrument operating software to subtract background noise, the true atomic percentage distribution within a 10-nanometer depth on the surface is obtained by converting the peak area integral with the relative sensitivity factor of each element.

[0227] Test data:

[0228] Table 6. Quantitative XPS Analysis Data of Core Elements on Etched Substrate Surface

[0229]

[0230] in conclusion:

[0231] Figure 6 This is a feature map of elemental distribution and residual contamination on the surface of each test object after etching. Sub-figure (a) is a line graph of the atomic percentage evolution of the main elements calculated by XPS broadband test. The graph tracks the abundance fluctuation trajectory of the three core elements, carbon, oxygen, and copper, under different post-processing states through different line types, geometric markers, and gray levels. Sub-figure (b) is a line graph of the relative residual index of surface organic matter extracted by calculating the carbon-copper ratio (C / Cu) of each group, which further amplifies the masking effect of carbon enrichment on the substrate metal signal.

[0232] Based on the data in Table 6 and Figure 6The curve trend shows that bare copper surfaces exposed to air daily undergo basic hydrocarbon adsorption, resulting in a C 1s atom content of 11.58% measured in the blank washed plate of Comparative Example 1. This value of over ten percentage points constitutes the environmental background benchmark for evaluating surface cleanliness, clearly marked as the blank baseline in Figure (b). When testing the unwashed sample of Example 1, a numerical burst point can be visually observed from the spectrum curve, at which an abnormally high carbon content of 59.42% was intercepted, while the underlying Cu... 2 The p-signal was severely masked, dropping to only 9.43%. This extremely high concentration of carbon buildup reflects the high-density adhesion of the [Cu-MBI]-PEG coordination network to the copper interface during processing. For this type of polymeric protective film with strong adhesion, traditional processes often require adding a strong alkali stripping or plasma cleaning step in the later stages to thoroughly remove residues. This not only increases manufacturing costs but also easily induces secondary damage to the fine circuitry.

[0233] In the subsequent treatments of Examples 1 to 3, radical chemical methods were abandoned, and the substrate was only briefly rinsed with ordinary room temperature pure water. Retesting results showed that the carbon content on the surface decreased, dropping directly to a narrow range of 11.95% to 13.12%, with related indicators almost perfectly matching the baseline state of Comparative Example 1 without any added organic matter. This efficient desorption effect stems from the thermodynamically reversible mechanism in the etchant's underlying design. When a large amount of deionized water floods the substrate surface, the magnesium chloride in the residual liquid film is rapidly diluted and carried away, and the microenvironment instantly loses the high charge density required to maintain the Hofmeister salting-out effect. The polyethylene glycol network in a dehydrated, coiled state, after being removed from the high-salt environment, spontaneously absorbs water and swells in pure water. The reconstruction of the hydration layer causes the contracted polymer molecular chains to unwind on a scale, breaking the hydrogen bond anchoring structure between them and the 2-mercaptobenzimidazole substrate, reducing the adhesion of the polymer network at the copper interface and causing it to disintegrate and disperse with the water flow. This method, which spontaneously induces phase reversal in materials by altering the fluid microenvironment and replaces the traditional destructive chemical bond-breaking surface cleaning path, achieves high cleanliness while ensuring the complete preservation of the etched morphology.

Claims

1. A process for refining PCB circuit pattern etching, characterized in that, Includes the following steps: A PCB circuit pattern fine etching composition containing deionized water, 36% hydrochloric acid, copper chloride dihydrate, anhydrous magnesium chloride, p-toluenesulfonic acid monohydrate, polyethylene glycol, and 2-mercaptobenzimidazole is injected into the circulating working tank of a standard horizontal spray etching machine. Turn on the constant temperature circulation system to control the temperature of the working fluid in the circulation tank; The PCB substrate to be etched, after dry film development, is fed into the spray section of the etching machine. Turn on the upper and lower spray arrays and set the spray pressure of the nozzles to etch the PCB substrate; After etching, the PCB substrate leaves the spray section and enters the cascaded deionized water washing section, where it is rinsed with room temperature deionized water. The substrate then enters the drying section for drying, resulting in a PCB circuit pattern that has been etched.

2. The PCB circuit pattern fine etching process according to claim 1, characterized in that, Each liter of the refined etching composition comprises the following components in varying amounts: 172–258 mL of 36% hydrochloric acid, 126.8–190.2 g of copper chloride dihydrate, 9.5–28.6 g of anhydrous magnesium chloride, 2.0–5.0 g of p-toluenesulfonic acid monohydrate, 200–500 mg of polyethylene glycol, 10–50 mg of 2-mercaptobenzimidazole, and 1 L of deionized water.

3. The PCB circuit pattern fine etching process according to claim 2, characterized in that, Each liter of the refined etching composition comprises the following components in varying amounts: 215 mL of 36% hydrochloric acid, 158.5 g of copper chloride dihydrate, 19.0 g of anhydrous magnesium chloride, 3.5 g of p-toluenesulfonic acid monohydrate, 350 mg of polyethylene glycol, 30 mg of 2-mercaptobenzimidazole, and 1 L of deionized water.

4. The PCB circuit pattern fine etching process according to claim 1, characterized in that, The preparation process of the refined etching composition includes the following steps: Add deionized water to the reactor, then add hydrochloric acid (36% by mass) and copper chloride dihydrate in sequence, and stir until completely dissolved; While stirring, add anhydrous magnesium chloride to the reactor and stir. Add p-toluenesulfonic acid monohydrate and stir until completely dissolved; Adjust the stirring speed, add polyethylene glycol, and stir until completely dissolved; 2-Mercaptobenzimidazole was dispersed in deionized water to form a suspension, which was then added dropwise to the reaction vessel; The volume was adjusted to 1L with deionized water, and stirring was continued to obtain the refined etching composition.

5. The PCB circuit pattern fine etching process according to claim 4, characterized in that, During the preparation of the refined etching composition, the system temperature was maintained at 25°C; The stirring speed was 150 rpm before adding polyethylene glycol, and 250 rpm during and after the addition of polyethylene glycol.

6. The PCB circuit pattern fine etching process according to claim 1, characterized in that, Before performing spray etching on the PCB substrate to be etched, the temperature of the working fluid in the tank is set to 45-50°C.

7. The PCB circuit pattern fine etching process according to claim 1, characterized in that, When performing spray etching on the PCB substrate to be etched, the spray pressure of the nozzles in the spray array is set to 2.0–2.5 kg / cm². 2 .

8. The PCB circuit pattern fine etching process according to claim 1, characterized in that, The line width and line spacing of the circuit pattern on the PCB substrate to be etched are 15μm.

9. The PCB circuit pattern fine etching process according to claim 1, characterized in that, The PCB substrate, after etching, enters the cascaded deionized water washing section within 5 seconds after leaving the spray section.

10. The PCB circuit pattern fine etching process according to claim 1, characterized in that, During the continuous spray etching process on the PCB substrate to be etched, the temperature of the working fluid in the tank is controlled, including: Adjust the heating system to raise the working fluid temperature to 52°C and maintain it for 5 minutes, then cool it back down to the initial working temperature.

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