A method for micro-etching a copper surface of a printed circuit board

Abstract

This invention discloses a method for micro-etching the copper surface of printed circuit boards, relating to the field of printed circuit board processing technology. The specific steps of the method are as follows: first, sulfuric acid and hydrogen peroxide are mixed, and a chlorine-resistant interface modifier is added and stirred evenly to prepare a single-type micro-etching working solution. Then, the board is subjected to acid degreasing, deionized water rinsing, static immersion in the working solution at 25~35℃, and finally sprayed and countercurrent rinsing and hot air drying to achieve gentle and uniform micro-etching of the copper surface and ensure consistent processing. This invention uses a single-type micro-etching working solution with optimized components, combined with closed temperature control preparation, to improve stability and chlorine resistance, achieve gentle and uniform etching of the copper surface, and optimize the microstructure to enhance the adhesion of the plating layer. At the same time, it standardizes the entire process of acid degreasing, static immersion, graded rinsing and hot air drying, adapts to automated production, ensures the consistency and reliability of copper surface treatment, and improves the quality of circuit board processing.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board processing technology, specifically to a method for micro-etching the copper surface of a printed circuit board. Background Technology

[0002] As a core component and signal transmission carrier in electronic devices, the quality of copper surface treatment directly determines the overall performance and lifespan of the circuit board. Copper surface micro-etching is an indispensable key pretreatment process in circuit board manufacturing. This process is mainly used to remove the oxide layer and impurities on the copper surface, control the microstructure of the copper surface, improve the bonding strength between the copper surface and subsequent plating layers, and ensure the conductivity, structural stability, and process adaptability of the circuit board. With the rapid development of the electronics industry towards high precision, high density, and miniaturization, various electronic devices have placed higher demands on the processing precision and reliability of printed circuit boards. The uniformity, stability, and process adaptability of copper surface micro-etching have become core concerns in the industry. Currently, micro-etching technology in the industry needs to simultaneously consider processing effect, production efficiency, and cost control, adapt to the high-efficiency operation requirements of automated production lines, and provide process support for the large-scale production of high-end printed circuit boards.

[0003] Traditional micro-etching technology for copper surfaces of printed circuit boards (PCBs) has many limitations and cannot meet the stringent requirements of modern production. Traditional micro-etching working fluid systems have complex compositions and insufficient chemical stability, making them prone to component decomposition and performance degradation during preparation and use. This makes it difficult to consistently guarantee the micro-etching effect. The pretreatment stage of traditional processes has limited cleaning effectiveness, easily leaving oil and impurities that affect the uniformity of subsequent micro-etching reactions. The immersion process lacks stable environmental and attitude control, easily causing defects such as uneven copper etching, over-etching, or under-etching. Post-treatment stages struggle to completely remove chemical residues from the board surface, and imperfect drying processes can lead to board defects. Furthermore, traditional processes have weak adaptability to automated production, cumbersome operation procedures, high material consumption, short service life, and low overall yield, severely restricting the improvement of PCB processing quality and the large-scale development of the industry. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for micro-etching of copper surfaces on printed circuit boards. By optimizing the preparation process of the micro-etching working solution, combining it with chlorine-resistant composite interface modifiers, and using a closed-loop temperature control, light-shielding stirring, and filtration storage method, a stable and uniform single-type micro-etching working solution is obtained. This method standardizes the entire process of copper surface pretreatment, constant temperature immersion, graded rinsing, and closed-loop drying, and can be adapted to continuous operation on automated production lines. This invention can achieve gentle and uniform etching of the copper surface, avoiding defects such as over-etching and uneven etching, optimizing the microstructure and surface activity of the copper surface, improving the adhesion of the plating layer, simplifying the treatment system, extending the service life of the working solution, and reducing consumable consumption, effectively improving the yield rate and production stability of printed circuit boards, meeting the needs of large-scale production of high-precision printed circuit boards, and providing efficient and reliable micro-etching technology support for the industry.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for micro-etching the copper surface of a printed circuit board, the specific steps of which are as follows: S1, Preparation of working solution: Electronic grade sulfuric acid and electronic grade hydrogen peroxide are mixed to form a basic reaction system. Chlorine-resistant composite interface modifier is added to the basic reaction system. The mixture is continuously stirred until it becomes homogeneous, thus obtaining a single type of micro-etching working solution. S2, Copper surface pretreatment: Fix the board to be treated at the processing station, use an acidic degreasing agent to treat the copper surface of the board, rinse the copper surface with deionized water after treatment, and then remove the residual moisture on the surface of the board. S3, Copper surface immersion treatment: The board body with residual moisture removed is placed inside the single type micro-etching working solution, and the copper surface of the board body is immersed under a constant temperature condition of 20℃~35℃. S4, Post-treatment of board surface: After the impregnation operation is completed, the board body is subjected to spray rinsing and countercurrent rinsing in sequence. After the rinsing operation is completed, the board body is thoroughly dried with hot air.

[0006] Further, in step S1, electronic-grade sulfuric acid with a concentration of 98 wt% and electronic-grade hydrogen peroxide with a concentration of 27.5 wt% are selected as raw materials for preparation; sulfuric acid is injected into the bottom of a polytetrafluoroethylene-lined sealed stirring container at a rate of 5-15 mL / s, and hydrogen peroxide is added into the container at a rate of 10-20 mL / s; the temperature of the mixing system is maintained at 15℃-25℃ by the water-cooling jacket on the outer wall of the container.

[0007] Furthermore, in step S1, the chlorine-resistant composite interface modifier is divided into two to four equal parts and added in stages. After each part is added, a stirring operation is performed for 3 to 8 minutes. After all the additives are added, a stirring operation is performed for another 30 to 40 minutes. The stirring operation is performed using a closed magnetic stirring device with a constant speed of 50 to 90 r / min and in a light-proof environment. The chlorine-resistant composite interface modifier is composed of the following components in parts by mass: 5 to 10 parts of benzotriazole, 10 to 20 parts of polyethylene glycol, 2 to 5 parts of alkyl glycoside, and 65 to 83 parts of deionized water.

[0008] Furthermore, in step S1, after the working solution is prepared, the single-type micro-etching working solution is subjected to negative pressure filtration using a 150-250 mesh polypropylene filter cloth, with the pressure value of the negative pressure filtration controlled at 0.05-0.2 MPa; after filtration, the single-type micro-etching working solution is transferred to an opaque, sealed container for storage, and the storage environment is kept at normal pressure.

[0009] Furthermore, in step S2, the plate to be processed is horizontally fixed in an automated conveyor processing station by a vacuum suction cup; the acidic degreasing agent is applied to both the front and back surfaces of the copper surface through a fan-shaped atomizing nozzle, the spray pressure of the fan-shaped atomizing nozzle is set to 0.2-0.3 MPa, and the spray coverage angle is set to 100°-140°; the moving speed of the automated conveyor station is constant at 0.3-0.7 m / s.

[0010] Furthermore, in step S2, the contact treatment time between the acidic degreasing agent and the copper surface is set to 60-90 seconds, and the ambient temperature during the contact treatment is maintained at 20-30°C; the resistivity of the deionized water used to rinse the copper surface is not less than 15 MΩ·cm, and the rinsing is performed in two stages, with the first rinsing lasting 20-40 seconds and the second rinsing lasting 15-25 seconds; after rinsing, the board is placed at an angle of 60°-90° to remove residual moisture from the surface; the acidic degreasing agent is a mixed aqueous solution containing 5-10 wt% sulfuric acid, 3-8 wt% sodium dodecyl sulfate, and the remainder deionized water.

[0011] Furthermore, in step S3, the plate is placed vertically inside the single-type micro-etching working fluid, the immersion speed of the plate in the working fluid is controlled at 3-7 cm / s, and the distance between adjacent plates is maintained at 2-5 cm; the immersion operation is temperature controlled by a dual-loop water bath device, the temperature is controlled at 20-35℃, and the immersion operation time is set to 30-60 seconds.

[0012] Furthermore, in step S3, the single-type micro-etching working fluid is kept in a static state without stirring or circulation; after the immersion operation is completed, the plate is moved out of the working fluid in a vertical direction at a speed of 2-5 cm / s. After the plate is moved out of the working fluid, it passes through the anti-drip baffle and stays above the liquid tank for 3-10 seconds to remove the working fluid adhering to the plate surface.

[0013] Furthermore, in step S4, the spray rinsing operation uses deionized water with a resistivity of not less than 18 MΩ·cm, the spray rinsing pressure is set to 0.2 to 0.4 MPa, and the spray rinsing duration is set to 20 to 30 seconds; the spray rinsing is performed using a matrix arrangement of nozzles, with the nozzles evenly covering the entire area of ​​the copper surface of the board.

[0014] Furthermore, in step S4, the pure water flow rate for countercurrent rinsing is set to 1-3 L / min, and the countercurrent rinsing duration is set to 30-50 seconds, wherein the flow direction of the pure water is opposite to the transport direction of the board; the drying operation is performed using a closed-loop circulating hot air device, the wind speed of the hot air device is set to 1-2 m / s, the drying operation duration is set to 30-40 seconds, and the hot air is simultaneously blown on both the front and back surfaces of the copper surface of the board.

[0015] Compared with existing technologies, this micro-etching method for the copper surface of printed circuit boards has the following advantages: I. This invention optimizes the preparation process and component system of the micro-etching working solution, and combines it with a stepwise addition and uniform stirring process of chlorine-resistant composite interface modifiers to form a uniform and stable single-type micro-etching working solution. Combined with a closed-loop temperature control and light-shielding filtration preparation method, the chemical stability and chlorine resistance of the working solution are effectively improved, avoiding component decomposition or failure. This working solution can achieve a gentle and uniform etching effect on the copper surface of printed circuit boards, precisely controlling the etching degree and preventing over-etching or uneven etching. Simultaneously, the interface modification effect optimizes the microstructure of the copper surface, improving the adhesion between the copper surface and subsequent plating layers. The single-type working solution simplifies the configuration of the treatment system, reduces the cumbersome operation of mixing multiple solutions, and the closed-loop preparation and filtration storage can extend the service life of the working solution, reduce consumable consumption, and make copper surface micro-etching treatment more suitable for industrial production needs, ensuring the consistency and reliability of copper surface treatment on circuit boards.

[0016] II. This invention standardizes the entire process of copper surface pretreatment, immersion treatment, and post-processing. First, the copper surface is cleaned with acidic degreasing to remove oil and impurities. Then, it is thoroughly rinsed with high-purity deionized water to avoid residue. With appropriate immersion posture and temperature control, the copper surface is fully and evenly contacted with the micro-etching working solution. The static immersion mode avoids etching deviations caused by fluid scouring. Subsequently, a graded rinsing and comprehensive hot air drying process is used to thoroughly remove residual agents and moisture from the board surface, ensuring that the copper surface is clean, dry, and free of impurities. The entire process is seamlessly connected, adaptable to automated production equipment, improving processing efficiency while optimizing the micro-roughness and surface activity of the copper surface. This enhances the adaptability of the circuit board to subsequent processes, reduces board surface defects and defective products, improves the processing quality and stability of printed circuit boards, and meets the production and processing requirements of high-precision circuit boards.

[0017] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0019] Figure 1 A flowchart of a method for micro-etching copper surfaces of printed circuit boards; Figure 2 This is a schematic diagram illustrating data transmission between the various steps of a micro-etching process for the copper surface of a printed circuit board. Detailed Implementation

[0020] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0021] Example 1: A complete implementation process of a micro-etching method for the copper surface of a printed circuit board.

[0022] S1, Preparation of working solution: 98wt% electronic-grade sulfuric acid and 27.5wt% electronic-grade hydrogen peroxide were selected as raw materials. Sulfuric acid was injected into the bottom of a polytetrafluoroethylene-lined, sealed stirred container at a rate of 10 mL / s, followed by the addition of hydrogen peroxide at a rate of 15 mL / s. The temperature of the mixture was maintained between 20°C and 25°C using a water-cooling jacket on the outer wall of the container. A chlorine-resistant composite interface modifier was added to the basic reaction system. The additive was divided into three equal parts and added in stages, with stirring for 5 minutes after each addition. After all the additives were added, stirring continued for 35 minutes. Stirring was performed using a sealed magnetic stirrer at a constant speed of 70 r / min under light-protected conditions. The chlorine-resistant composite interface modifier consisted of the following components in parts by weight: 7 parts benzotriazole, 15 parts polyethylene glycol, 3 parts alkyl glycoside, and 75 parts deionized water. After the working solution is prepared, it is filtered under negative pressure using a 200-mesh polypropylene filter cloth. The pressure during filtration is controlled at 0.1 MPa. The filtered working solution is then transferred to an opaque, sealed container and stored at atmospheric pressure. Figure 1 As shown.

[0023] S2, Copper surface pretreatment: The board to be treated is horizontally fixed in the automated conveyor processing station using a vacuum suction cup. An acidic degreasing agent is applied to the copper surface of the board through a fan-shaped atomizing nozzle, which is used on both sides of the copper surface. The spray pressure of the fan-shaped atomizing nozzle is set to 0.25 MPa, and the spray coverage angle is set to 120°. The moving speed of the automated conveyor station is kept constant at 0.5 m / s. The contact treatment time between the acidic degreasing agent and the copper surface is set to 75 seconds, and the ambient temperature is maintained at 25°C. After treatment, the copper surface is rinsed with deionized water. The resistivity of the deionized water used for rinsing the copper surface is not less than 15 MΩ·cm. Rinsing is performed twice: the first rinse lasts 30 seconds, and the second rinse lasts 20 seconds. After rinsing, the board is placed at a 75° angle to remove residual moisture from the surface. The acidic degreasing agent is a mixed aqueous solution containing 7 wt% sulfuric acid, 5 wt% sodium dodecyl sulfate, and the remainder deionized water.

[0024] S3, Copper surface impregnation treatment: The board, after removing residual moisture, is placed vertically into a single-type micro-etching working solution. The immersion speed is controlled at 5 cm / s, and the spacing between adjacent boards is 3 cm. The copper surface of the board is immersed at a constant temperature of 30°C, controlled by a dual-loop water bath, for 45 seconds. The single-type micro-etching working solution is kept static, without stirring or circulation. After immersion, the board is removed vertically from the working solution at a speed of 3 cm / s. After removal, the board passes over an anti-drip baffle and remains above the solution for 5 seconds to remove any remaining working solution from the surface.

[0025] S4, Post-processing of the board surface: After the impregnation process, the board is subjected to a series of spray rinsing and counter-current rinsing operations. For spray rinsing, deionized water with a resistivity of at least 18 MΩ·cm is used, with a pressure of 0.3 MPa and a duration of 25 seconds. A matrix-arranged nozzle is used for spray rinsing, evenly covering the entire copper surface of the board. For counter-current rinsing, the pure water flow rate is set to 2 L / min, and the rinsing duration is 40 seconds, with the pure water flowing in the opposite direction to the board's transport direction. After rinsing, the board is thoroughly dried using a closed-loop circulating hot air system. The air velocity is set to 1.5 m / s, and the drying time is 35 seconds. The hot air is simultaneously blown onto both the front and back surfaces of the copper surface of the board. Figure 2 As shown.

[0026] Example 2: Comparative test of micro-etching working fluid preparation process.

[0027] Comparison of the order in which raw materials are added: Three parallel experiments were conducted according to the raw material ratio in Example 1, using three methods: sulfuric acid added before hydrogen peroxide, hydrogen peroxide added before sulfuric acid, and simultaneous addition. The raw material addition rate and mixing system temperature were strictly controlled during the experiments, and the highest temperature and hydrogen peroxide decomposition rate during the mixing process were recorded.

[0028] Comparison of additive application methods: The chlorine-resistant composite interface modifier additive was tested using three methods: single-dose addition, two-part addition, and three-part addition. Stirring was performed for 5 minutes after each addition, and then for another 35 minutes after all additives were added. The dispersion uniformity of the additive and the stability of the working solution were tested under different addition methods.

[0029] Comparison of working fluid storage conditions: The prepared working solution was subjected to negative pressure filtration using 100-mesh, 200-mesh, and 300-mesh polypropylene filter cloths, with the pressure controlled at 0.1 MPa for each filtration. After filtration, the working solution was transferred to transparent plastic containers, opaque plastic containers, and opaque glass containers for storage, all under normal atmospheric pressure. The micro-etching rate of the working solution was periodically tested.

[0030] Comparative test results of micro-etching working fluid preparation processes: Table 1 Raw material addition order Add hydrogen peroxide to sulfuric acid first, then add 0.82 3.2% 7.1% Raw material addition order Hydrogen peroxide is added first, followed by sulfuric acid. 0.75 12.6% 21.3% Raw material addition order Add at the same time 0.71 15.8% 27.5% Additive application method One-time delivery 0.78 11.2% 19.7% Additive application method Dispose of in two equal portions 0.80 6.5% 12.8% Additive application method Distribute in three equal portions 0.82 3.2% 7.1% Storage conditions Translucent plastic containers 0.82 18.7% 32.4% Storage conditions Opaque plastic containers 0.82 3.2% 7.1% Storage conditions Opaque glass container 0.82 3.5% 7.4% Test Result Analysis: The test results show that the initial micro-etching rate was highest when sulfuric acid was added first, followed by hydrogen peroxide, and the rate of change in micro-etching rate was lowest at 7 and 14 days. This is because sulfuric acid has a higher density than hydrogen peroxide; adding sulfuric acid first allows hydrogen peroxide to mix slowly on top of the sulfuric acid, avoiding localized violent reactions that could lead to hydrogen peroxide decomposition. Adding the additive in three equal parts resulted in the best stability of the working solution, as this stepwise addition allows for more uniform dispersion of the additive in the mixed system, reducing localized agglomeration. Storing the working solution in an opaque container resulted in the longest retention of its micro-etching activity, as light exposure accelerates the decomposition of hydrogen peroxide and the oxidative deterioration of the additive. In summary, the combined process of adding sulfuric acid first, followed by hydrogen peroxide, adding the additive in three equal parts, and storing in an opaque, sealed container yielded the best results.

[0031] Example 3: Comparison and testing of copper surface pretreatment process parameters.

[0032] Comparison of contact time for acidic degreasing agents: Under the conditions of an acidic degreasing agent spraying pressure of 0.25 MPa, a spray coverage angle of 120°, and an ambient temperature of 25°C, the contact treatment time between the acidic degreasing agent and the copper surface was set to 60 seconds, 75 seconds, and 90 seconds, respectively. The oil removal rate and corrosion of the copper surface were tested under different contact times.

[0033] Comparison of deionized water rinsing parameters: The degreased copper surface was rinsed with deionized water with resistivity of 15 MΩ·cm and 18 MΩ·cm, respectively. The rinsing was performed twice, with the first rinse lasting 30 seconds and the second rinse lasting 20 seconds. The removal rate of residual degreaser and the amount of residual ions on the copper surface were tested under different rinsing parameters.

[0034] Comparison of water control angles on the plates: After rinsing, the boards were tilted at 60°, 75°, and 90° to remove residual moisture from the surface. The removal rate of residual moisture and the stability of the boards were tested at different tilt angles.

[0035] Comparison of copper surface pretreatment process parameters test results: Table 2 Degreasing agent contact time 60 seconds 91.2% 92.5% 32 Degreasing agent contact time 75 seconds 96.8% 95.7% 31 Degreasing agent contact time 90 seconds 98.5% 97.2% 30 Deionized water resistivity 15MΩ·cm 96.8% 95.7% 31 Deionized water resistivity 18MΩ·cm 96.8% 99.1% 31 Plate water control angle 60° 96.8% 95.7% 45 Plate water control angle 75° 96.8% 95.7% 31 Plate water control angle 90° 96.8% 95.7% 28 Test Result Analysis: The test results show that the removal rate of oil stains and the removal rate of residual degreaser on the copper surface both increased with the increase of the contact time of the acidic degreaser. At a contact time of 90 seconds, the oil stain removal rate reached 98.5%, effectively removing various oil stains from the copper surface. When rinsing with deionized water with a resistivity of 18 MΩ·cm, the removal rate of residual degreaser was even higher. This is because the high-resistivity deionized water has a lower ion content, allowing for a more thorough rinsing away of residual ionic degreaser on the copper surface. When the water control angle of the board was 75°, the surface residual water was removed quickly, and the board maintained good stability, preventing slippage. While the water removal speed was fastest at a water control angle of 90°, the board was prone to slippage, posing a safety hazard. In summary, the combined process of a 90-second contact time with the acidic degreaser, rinsing with deionized water with a resistivity of at least 15 MΩ·cm, and water control at a 75° tilt angle yielded the best results.

[0036] Example 4: Comparison and testing of copper surface immersion treatment process parameters.

[0037] Comparison of immersion temperatures: Under conditions of immersion time of 45 seconds, vertical placement of the board, immersion speed of 5 cm / s, and board spacing of 3 cm, immersion temperatures of 25℃, 30℃, and 35℃ were set respectively. The micro-etching thickness and uniformity of the copper surface were tested at different immersion temperatures.

[0038] Comparison of soaking time: Under the conditions of immersion temperature of 30℃, vertical placement of the board, immersion speed of 5cm / s, and board spacing of 3cm, immersion times of 30 seconds, 45 seconds, and 60 seconds were set respectively. The micro-etching thickness and surface roughness of the copper surface were tested under different immersion times.

[0039] Comparison of plate movement speeds: The immersion speed of the plate in the working fluid was set to 5 cm / s, and the removal speed from the working fluid was set to 3 cm / s. The generation of bubbles on the plate surface and the amount of working fluid adhering to the plate surface were tested at different moving speeds.

[0040] Comparison of copper surface immersion treatment process parameters test results: Table 3 Immersion temperature 25℃ 0.42 92.3 0.18 Immersion temperature 30℃ 0.61 95.7 0.21 Immersion temperature 35℃ 0.83 91.5 0.25 Soaking time 30 seconds 0.41 95.2 0.17 Soaking time 45 seconds 0.61 95.7 0.21 Soaking time 60 seconds 0.79 94.8 0.24 Plate movement speed Immersion 5cm / s, removal 3cm / s 0.61 95.7 0.21 Plate movement speed Immersion 7cm / s, removal 4cm / s 0.58 89.2 0.23 Plate movement speed Immersion 3cm / s, removal 2cm / s 0.63 94.5 0.22 Test Result Analysis: The test results show that the average micro-etching thickness on the copper surface gradually increases with increasing immersion temperature. The best uniformity of micro-etching thickness, reaching 95.7%, is achieved at an immersion temperature of 30℃. Both excessively high and low immersion temperatures lead to decreased micro-etching uniformity. This is because excessively high temperatures result in an overly rapid reaction rate, leading to uneven local reactions; while excessively low temperatures result in an overly slow reaction rate, making the surface more susceptible to impurities and surface conditions. With increasing immersion time, both the average micro-etching thickness and roughness of the copper surface increase. An immersion time of 45 seconds results in both micro-etching thickness and roughness within a relatively ideal range. The best uniformity of micro-etching thickness is achieved when the board immersion speed is 5 cm / s and the removal speed is 3 cm / s, with no bubbles forming on the board surface and minimal adhering working fluid. Excessively fast immersion speeds cause bubbles to form on the board surface, affecting micro-etching uniformity; excessively fast removal speeds result in the board surface carrying excessive working fluid, causing waste and affecting subsequent rinsing effects. In summary, the optimal combination of immersion temperature (30℃), immersion time (45 seconds), immersion speed (5cm / s), and removal speed (3cm / s) yields the best results.

[0041] Example 5: Comparison and testing of post-processing parameters for board surface.

[0042] Comparison of spray rinsing parameters: Deionized water with a resistivity of 18 MΩ·cm was used for spray rinsing, with spray pressures set to 0.2 MPa, 0.3 MPa, and 0.4 MPa, and spray durations set to 25 seconds for each. The removal rate of residual micro-etching working fluid and the cleanliness of the board surface were tested under different spray parameters.

[0043] Comparison of countercurrent rinsing parameters: The pure water flow rate for countercurrent rinsing was set to 1 L / min, 2 L / min, and 3 L / min, respectively, and the countercurrent rinsing time was set to 40 seconds for each. The residual ion content and water consumption on the plate surface were tested under different countercurrent rinsing parameters.

[0044] Comparison of hot air drying parameters: The hot air velocity was set to 1.5 m / s, and the drying time was set to 30 seconds, 35 seconds, and 40 seconds, respectively. The degree of drying and the oxidation of the copper surface were tested under different drying parameters.

[0045] Comparison of test results for post-processing parameters of board surface: Table 4 Spray rinsing pressure 0.2MPa 96.8% 0.32 Completely dry Spray rinsing pressure 0.3MPa 99.5% 0.11 Completely dry Spray rinsing pressure 0.4MPa 99.7% 0.09 Completely dry Countercurrent rinsing flow 1L / min 97.2% 0.25 Completely dry Countercurrent rinsing flow 2L / min 99.5% 0.11 Completely dry Countercurrent rinsing flow 3L / min 99.6% 0.10 Completely dry Hot air drying time 30 seconds 99.5% 0.11 Basic drying Hot air drying time 35 seconds 99.5% 0.11 Completely dry Hot air drying time 40 seconds 99.5% 0.11 Completely dry Test Result Analysis: The test results show that as the spray rinsing pressure increases, the removal rate of residual working fluid on the board surface gradually improves, and the amount of residual ions on the board surface gradually decreases. At a spray pressure of 0.3 MPa, the removal rate of residual working fluid reaches 99.5%, which meets the requirements of subsequent processes. Further increasing the spray pressure has no significant effect on improving the removal rate; instead, it increases energy consumption and the risk of board surface damage. As the flow rate of the countercurrent rinsing pure water increases, the amount of residual ions on the board surface gradually decreases. At a pure water flow rate of 2 L / min, the amount of residual ions on the board surface has already dropped to a low level; further increasing the flow rate would waste water resources. A hot air drying time of 35 seconds ensures complete drying of the board surface without copper oxidation. Too short a drying time will result in incomplete drying and easily cause copper oxidation; too long a drying time will waste energy and may cause board deformation. In summary, the combined process of a spray rinsing pressure of 0.3 MPa, a countercurrent rinsing pure water flow rate of 2 L / min, and a hot air drying time of 35 seconds yields the best results.

[0046] Example 6: Comparative test of the stability of micro-etching treatment effect.

[0047] Comparison of working fluid storage stability: The prepared single-type micro-etching working solution was stored under the storage conditions described in Example 1. The working solution was then removed on day 1, day 7, and day 14 of storage, and micro-etched onto the same batch of printed circuit boards according to the process parameters described in Example 1. The micro-etching rate and treatment effect of the working solution under different storage times were tested.

[0048] Batch processing stability comparison: Using the same batch of micro-etching working solution, 100 printed circuit boards were continuously processed according to the process parameters in Example 1. The micro-etching thickness and copper surface roughness were tested after processing every 20 boards. The stability of the micro-etching effect during continuous processing was tested.

[0049] Comparison of consistency between different batches of working fluid: Five different batches of micro-etching working solution were prepared according to the process parameters in Example 1, and micro-etched on printed circuit boards of the same batch. The consistency of the treatment effect of different batches of working solution was tested.

[0050] Results of the stability comparison test of micro-etching treatment effect: Table 5 Working fluid storage time Day 1 0.61 2.1 0.21 1.8 Working fluid storage time Day 7 0.59 2.3 0.22 1.9 Working fluid storage time Day 14 0.56 2.7 0.23 2.2 Continuous batch processing Blocks 1-20 0.61 2.1 0.21 1.8 Continuous batch processing Blocks 41-60 0.60 2.4 0.21 2.0 Continuous batch processing Blocks 81-100 0.58 2.6 0.22 2.1 Different working fluid batches Batch 1 0.61 2.1 0.21 1.8 Different working fluid batches Batch 3 0.60 2.5 0.22 2.1 Different working fluid batches Batch 5 0.59 2.3 0.21 1.9 Test Result Analysis: The test results show that within 14 days of storage with the working solution, the average micro-etching thickness decreased from 0.61 μm to 0.56 μm, the relative standard deviation of the micro-etching thickness increased from 2.1% to 2.7%, and the copper surface roughness increased from 0.21 μm to 0.23 μm, with the relative standard deviation of roughness increasing from 1.8% to 2.2%. This indicates that the working solution maintains good micro-etching activity and treatment effect within 14 days of storage. After continuously treating 100 boards, the average micro-etching thickness decreased from 0.61 μm to 0.58 μm, the relative standard deviation of the micro-etching thickness increased from 2.1% to 2.6%, and the copper surface roughness remained basically stable. This indicates that the same batch of working solution can stably treat at least 100 printed circuit boards. The average micro-etching thickness after treatment with different batches of working solution ranged from 0.59 μm to 0.61 μm, with a relative standard deviation of 2.1% to 2.5%. The copper surface roughness ranged from 0.21 μm to 0.22 μm, with a relative standard deviation of 1.8% to 2.1%. This indicates that the treatment effect of different batches of working solution has good consistency, ensuring the stability of product quality.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for micro-etching the copper surface of a printed circuit board, characterized in that, The specific steps of this method are as follows: S1, Preparation of working solution: Electronic grade sulfuric acid and electronic grade hydrogen peroxide are mixed to form a basic reaction system. Chlorine-resistant composite interface modifier is added to the basic reaction system. The mixture is continuously stirred until it becomes homogeneous, thus obtaining a single type of micro-etching working solution. S2, Copper surface pretreatment: Fix the board to be treated at the processing station, use an acidic degreasing agent to treat the copper surface of the board, rinse the copper surface with deionized water after treatment, and then remove the residual moisture on the surface of the board. S3, Copper Surface Immersion Treatment: The board, after removing residual moisture, is placed vertically into the single-type micro-etching working solution at a speed of 3–7 cm / s, with a spacing of 2–5 cm between adjacent boards. The copper surface of the board is statically immersed at a constant temperature of 20°C–35°C. During immersion, the single-type micro-etching working solution remains static without stirring or circulation. The immersion duration is set to 30–60 seconds. After immersion, the board is removed vertically from the working solution at a speed of 2–5 cm / s. After removal, the board passes through an anti-drip baffle and remains above the solution tank for 3–10 seconds to remove any adhering working solution from the board surface. S4, Post-treatment of board surface: After the impregnation operation is completed, the board body is subjected to spray rinsing and countercurrent rinsing in sequence. After the rinsing operation is completed, the board body is thoroughly dried with hot air. In step S1, sulfuric acid is injected into the bottom of the container at a rate of 5-15 mL / s, and hydrogen peroxide is added into the container at a rate of 10-20 mL / s. After each addition of additive, stirring is performed for 3-8 minutes. After all additives are added, stirring is continued for 30-40 minutes, with the stirring speed kept constant at 50-90 r / min. Negative pressure filtration uses 150-250 mesh polypropylene filter cloth, and the pressure is controlled at 0.05-0.2 MPa. The chlorine-resistant composite interface modifier is composed of the following components in parts by weight: 5-10 parts benzotriazole, 10-20 parts polyethylene glycol, 2-5 parts alkyl glycoside, and 65-83 parts deionized water.

2. The method for micro-etching copper surface of a printed circuit board according to claim 1, characterized in that, In step S1, the chlorine-resistant composite interface modifier is divided into three equal parts and added in stages. After each part is added, a stirring operation is performed for 5 minutes. After all the additives are added, a stirring operation is performed for another 35 minutes. The stirring speed is kept constant at 70 r / min. The negative pressure filter uses 200-mesh polypropylene filter cloth, and the pressure value is controlled at 0.1 MPa.

3. The method for micro-etching copper surface of a printed circuit board according to claim 1, characterized in that, In step S2, the spray pressure of the fan-shaped atomizing nozzle is set to 0.2-0.3 MPa, the spray coverage angle is set to 100°-140°, and the moving speed of the automated transmission station is constant at 0.3-0.7 m / s; the first rinsing time is 20-40 seconds, and the second rinsing time is 15-25 seconds.

4. The method for micro-etching copper surface of a printed circuit board according to claim 1, characterized in that, In step S2, the acidic degreasing agent is a mixed aqueous solution containing 5-10 wt% sulfuric acid, 3-8 wt% sodium dodecyl sulfate and the remainder deionized water; the plate is placed at a 75° tilt angle to remove residual moisture from the surface.

5. The method for micro-etching copper surface of a printed circuit board according to claim 1, characterized in that, In step S3, the immersion operation is temperature controlled by a dual-loop water bath device, with the temperature controlled at 30°C and the immersion time set to 45 seconds; the speed at which the plate is immersed in the working liquid is controlled at 5 cm / s, the speed at which it is removed from the working liquid is controlled at 3 cm / s, and it stays above the liquid tank for 5 seconds.

6. The method for micro-etching copper surface of a printed circuit board according to claim 1, characterized in that, In step S4, the spray rinsing pressure is set to 0.2-0.4 MPa, and the spray rinsing time is set to 20-30 seconds; the pure water flow rate for countercurrent rinsing is set to 1-3 L / min, and the countercurrent rinsing time is set to 30-50 seconds; the wind speed of the hot air equipment is set to 1-2 m / s, and the drying operation time is set to 30-40 seconds.

7. The method for micro-etching copper surface of a printed circuit board according to claim 1, characterized in that, In step S4, the spray rinsing pressure is set to 0.3 MPa and the duration is set to 25 seconds; the pure water flow rate for countercurrent rinsing is set to 2 L / min and the duration is set to 40 seconds; the wind speed of the hot air equipment is set to 1.5 m / s and the drying time is set to 35 seconds.

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