A low-ammonia nitrogen treating agent for copper surface super-roughening of a circuit board and application thereof

Abstract

The application relates to the technical field of printed circuit board manufacturing, in particular to a low-ammonia-nitrogen treatment agent for copper surface super-roughening of a circuit board and an application method thereof. The application method comprises the following steps: pretreating a copper surface of a circuit board, preparing a working solution which does not contain additional ammonium chloride and takes sodium chloride as a main chlorine ion source, controlling the concentration window of divalent copper ions, sodium chloride, formic acid and sodium formate in the working solution, making the copper surface contact with the working solution to perform super-roughening treatment, and monitoring the concentration of divalent copper ions, acidity, pH value and micro-etching amount in real time in a continuous production process, dynamically adding a supplement liquid B containing sodium chloride, formic acid and sodium formate or performing dilution adjustment according to the monitoring result, and finally performing post-treatment. The application can significantly reduce ammonia-nitrogen emission while maintaining the stability of micro-etching speed and the uniformity of the roughening structure of the copper surface, and meets the strict requirements of communication circuit boards on passive intermodulation performance.

Description

Technical Field

[0001] This application relates to the field of printed circuit board manufacturing technology, and in particular to a low ammonia nitrogen treatment agent for roughening the copper surface of circuit boards and its application. Background Technology

[0002] In PCB manufacturing, roughening or ultra-roughening of the copper surface is a critical process for ensuring interlayer adhesion, solder resist adhesion, and pattern transfer quality. Existing copper surface treatment technologies typically employ acidic micro-etching systems, removing the surface layer of copper and creating a microscopically roughened structure through redox reactions. To adjust the etching rate and control the roughening morphology, traditional techniques generally introduce ammonium chloride into the treatment solution as a chloride ion source and complexing stabilizer, in conjunction with hydrogen peroxide, sulfuric acid, organic acids, and various nitrogen-containing surfactants. These existing technologies can achieve high micro-etching rates on continuous production lines and maintain the chemical balance of the bath solution through the ammonium salt system. They are widely used in pretreatment before inner layer lamination, pretreatment before outer layer pattern plating, and surface modification processes for communication circuit boards.

[0003] However, existing technologies rely heavily on ammonium chloride and nitrogen-containing additives, resulting in persistently high ammonia nitrogen content in the treatment solution and subsequent wastewater, placing enormous pressure on environmental protection. Furthermore, during long-term continuous operation, factors such as copper ion accumulation, acidity changes, and uneven component consumption can lead to large fluctuations in micro-etching amounts and inconsistent board appearances in existing systems. This makes it difficult to simultaneously meet the increasingly stringent requirements for both low ammonia nitrogen emissions and highly stable production processes. Particularly in the field of communication circuit board manufacturing, which is sensitive to passive intermodulation performance, a solution that can effectively control ammonia nitrogen emissions and precisely regulate the micro-etching window is lacking. Summary of the Invention

[0004] This application provides a low-ammonia nitrogen treatment agent for roughening the copper surface of circuit boards and its application, in order to solve the above-mentioned problems.

[0005] In a first aspect, this application provides a method for applying a low-ammonia nitrogen treatment agent for roughening the copper surface of a circuit board, the method comprising:

[0006] S1. Perform degreasing, water washing and acid pickling pretreatment on the copper surface of the circuit board to be processed to remove oil stains, oxides and particulate contaminants from the copper surface;

[0007] S2. Prepare the starting solution A of the low ammonia nitrogen treatment agent as the working solution, wherein the working solution contains divalent copper ions, sodium chloride, formic acid, sodium formate, acidity regulator, nitrogen-free wetting and leveling agent, stabilizer and water, and the concentration of divalent copper ions in the working solution is 10-40 g / L, the concentration of sodium chloride is 50-130 g / L, the concentration of formic acid is 35-100 g / L, the concentration of sodium formate is 40-130 g / L, the acidity is 1.6-2.4 N, and the pH value is 2.8-3.8;

[0008] S3. The pretreated copper surface of the circuit board is brought into contact with the working fluid. The contact method is spraying, immersion, or a combination of spraying and immersion. The treatment temperature is 25-38°C and the treatment time is 30-90 seconds, so as to form an ultra-coarsened microstructure on the copper surface of the circuit board.

[0009] S4. During the continuous processing of the circuit board, the concentration of divalent copper ions, acidity, pH value and micro-etching amount of the copper surface of the circuit board are detected in the working solution.

[0010] S5. When the concentration of divalent copper ions is between 25 and 35 g / L and the micro-etching amount is lower than the target micro-etching amount, add supplementary solution B to the working solution. Supplementary solution B contains sodium chloride, formic acid, sodium formate, a nitrogen-free wetting and leveling agent, a stabilizer, and water. When the micro-etching amount is higher than the target micro-etching amount, reduce the amount of supplementary solution B or add low-chlorine diluent. The target micro-etching amount is preset according to the circuit board type; the target micro-etching amount for ordinary circuit boards is 20–28 uin, and the target total micro-etching amount for communication circuit boards is 45–60 uin. The low-chlorine diluent includes deionized water, sodium formate, and an optional stabilizer, wherein the sodium chloride concentration is less than 30% of the sodium chloride concentration in the working solution.

[0011] S6. After the ultra-roughened circuit board is washed with water, acid-washed or treated with anti-oxidation, the treated copper surface can be used for subsequent lamination, solder masking, pattern transfer or communication circuit board assembly processes.

[0012] The working fluid does not contain added ammonium chloride, and the added ammonium salt type chloride ion source is replaced by sodium chloride. Sodium chloride serves as the main non-ammonium salt type chloride ion compensation component, and through the synergistic effect of sodium chloride, divalent copper ions, and formic acid / sodium formate buffer system, it enables the copper surface of the circuit board to maintain a stable micro-etching amount under low ammonia nitrogen conditions.

[0013] Through the above technical solution, by constructing a system without added ammonium chloride and utilizing sodium chloride to provide a stable chloride ion environment, the volatilization of ammonium ions under high temperature and acidic conditions and the ammonia nitrogen load in subsequent wastewater treatment are avoided. At the same time, the buffer system composed of formic acid and sodium formate can effectively suppress the drastic fluctuations in pH value caused by reaction consumption and prevent the micro-etching rate from getting out of control. Combined with a dynamic replenishment mechanism based on real-time micro-etching amount and divalent copper ion concentration, the precise control of the copper surface etching rate under low ammonia nitrogen conditions is achieved. This solves the technical problems of "loss of etching upon removal of ammonium" or large fluctuations in micro-etching amount leading to substandard CPK in existing technologies. Its beneficial effects are that it significantly reduces the ammonia nitrogen content in wastewater, maintains the long-term stability of micro-etching amount, and ensures that a uniform honeycomb-like ultra-coarsened structure is formed on the copper surface.

[0014] Optionally, in step S2, the working solution has a divalent copper ion concentration of 20–32 g / L, a sodium chloride concentration of 70–100 g / L, a formic acid concentration of 45–80 g / L, a sodium formate concentration of 60–100 g / L, and a pH value of 3.0–3.5.

[0015] By limiting the concentration of divalent copper ions to a plateau range of 20–32 g / L, the risk range of insufficient reaction kinetics due to excessively low concentrations of divalent copper ions or disproportionation precipitation due to excessively high concentrations is avoided. Controlling the sodium chloride concentration to 70–100 g / L ensures sufficient chloride ion activity to maintain the micro-etching rate while preventing high-concentration sodium salt precipitation and crystallization that could clog the spray pipes. Combined with a narrow pH window of 3.0–3.5, the ratio of formic acid to sodium formate buffer is kept within a suitable buffer capacity range, effectively resisting acidity drift during production. This reduces the standard deviation of micro-etching in applications with extremely high surface consistency requirements, such as communication circuit boards.

[0016] Optionally, in step S2, the divalent copper ions are derived from one or more of copper chloride, copper sulfate, and copper formate;

[0017] The acidity regulator is sulfuric acid;

[0018] Sodium chloride, as a non-ammonium salt chloride ion compensating component, is used to replace ammonium chloride in regulating the micro-corrosion ability of the working fluid.

[0019] By employing the aforementioned technical solutions and selecting copper chloride, copper sulfate, or copper formate as the copper source, the introduction of ammonium ions is eliminated at the source, ensuring the system's low ammonia nitrogen characteristics. Using sulfuric acid as an acidity regulator avoids the side reaction risks associated with the introduction of nitrate or additional chloride ions, maintaining the purity and stability of the system's ionic strength. Specifically, sodium chloride is clarified not only as a simple chloride ion provider but also as a non-ammonium salt chloride ion compensating component. Its sodium ions participate in reconstructing the double-layer structure of the copper surface, weakening the hydrated shell of copper ions, and accelerating the dissolution kinetics of copper under conditions without ammonium salt promotion. This specific synergistic mechanism allows the system to maintain or even enhance its micro-etching ability after complete removal of ammonium chloride, overcoming the precipitous drop in etching rate caused by simple replacement.

[0020] Optionally, in step S2, the nitrogen-free wetting and leveling agent is one or more of polyacrylate, maleic acid-acrylic acid copolymer, and polyether-modified carboxylate.

[0021] The stabilizer is one or more of the following: sugar alcohol stabilizers, polyhydroxycarboxylate stabilizers, or low-phosphorus organic acid salt stabilizers.

[0022] The above technical solution introduces nitrogen-free polymer additives such as polyacrylates or maleic acid-acrylic acid copolymers. These additives utilize their carboxyl functional groups to selectively adsorb onto the specific orientation of the copper crystal surface, slowing down the dissolution rate of the surface and guiding anisotropic corrosion to form a regular honeycomb microstructure. Simultaneously, it improves the wetting and spreading properties of the solution on the copper surface, eliminating the risk of over-etching caused by localized dry spots. Combined with sugar alcohols or polyhydroxycarboxylate stabilizers, the polyhydroxy chelation effect inhibits the disproportionation reaction of divalent copper ions under acidic high-temperature conditions and the formation of cuprous oxide precipitate, extending the service life of the bath solution and avoiding the COD spike problem caused by nitrogen-containing surfactants. This achieves a balance between environmental friendliness and functionality.

[0023] Optionally, in step S3, for the copper surface of the communication circuit board, the total micro-etching amount of the copper surface of the circuit board is controlled to be 45-60uin;

[0024] When the total micro-erosion amount is less than 45uin, increase the replenishment ratio of replenishment solution B or extend the treatment time;

[0025] When the total micro-erosion amount is higher than 60uin, reduce the replenishment ratio of replenishment solution B or shorten the treatment time.

[0026] Through the above technical solution, addressing the sensitivity of communication circuit boards to passive intermodulation performance, by strictly locking the total micro-etching amount within the optimal window of 45-60 uin, a good balance between the micro-roughness and bonding force of the copper surface is ensured. This avoids the weak interface bonding caused by excessively low micro-etching amount or the current concentration effect caused by excessively high micro-etching amount. A negative feedback adjustment rule based on micro-etching amount deviation is established. When the micro-etching amount is detected to deviate from the target window, the replenishment strategy or contact time of the replenishing fluid B is adjusted in real time, directly changing the effective chloride ion concentration and reaction time in the working fluid. This helps to improve the stability of replenishment control and reduce the risk of PIM failure caused by micro-etching amounts of 42 uin and below or 68 uin and above.

[0027] Optionally, in step S5, the content of sodium chloride in the replenishing solution B is 150-300 g / L, the content of formic acid is 60-180 g / L, the content of sodium formate is 30-120 g / L, the content of nitrogen-free wetting and leveling agent is 0.05-0.50 g / L, and the content of stabilizer is 0.1-2.0 g / L.

[0028] Through the above technical solution, by designing a high-concentration replenishment solution B with a sodium chloride concentration as high as 150-300 g / L, it is ensured that a single small-volume replenishment can significantly increase the chloride ion concentration in the working solution, reducing the volume expansion and temperature fluctuations of the tank solution caused by large-volume replenishment. The formic acid and sodium formate are configured in a specific molar ratio, so that the replenishment operation can maintain the original pH buffer capacity of the working solution without decay while replenishing the consumed components. The high-concentration design of the wetting and leveling agent and the stabilizer compensates for their decomposition loss and carry-over loss during continuous production, ensuring the balance of each component of the working solution after replenishment, and avoiding sudden changes in micro-etching rate or darkening of the plate surface caused by the imbalance of the replenishment solution itself.

[0029] Optionally, in step S5, supplementary control is performed according to the following rules:

[0030] When the concentration of divalent copper ions is below 20 g / L and the micro-etching amount is below the target micro-etching amount, add copper-containing starter solution A;

[0031] When the concentration of divalent copper ions is 25-35 g / L and the micro-etching amount is lower than the target micro-etching amount, add supplementary solution B.

[0032] When the pH value is below 2.8 or the acidity is above 2.4N, reduce the amount of formic acid added and add deionized water or a low-chlorine diluent containing sodium formate.

[0033] When the pH is higher than 3.8 or the acidity is lower than 1.6N, add an acidity adjusting solution containing formic acid;

[0034] When the micro-etching amount is higher than the target micro-etching amount and the plate surface shows a darkening or over-etching trend, stop adding replenishing solution B and add deionized water or low-chlorine diluent.

[0035] Through the above technical solution, by establishing a three-level intelligent replenishment decision logic, the causes of insufficient micro-etching are accurately distinguished: if the copper source is depleted, the start-up solution A is replenished from the source; if chloride ions or acidity are depleted, replenishment solution B is precisely replenished; if chloride ions are excessive or acidity is too high, resulting in over-etching, a dilution strategy is adopted. This multi-parameter coupled control method overcomes the blindness of single-parameter replenishment, improves the accuracy of replenishment decisions, reduces batch plate scrapping accidents caused by misjudgment, and extends the overall service life of the tank solution.

[0036] Optionally, in step S1, after pre-treating the copper surface of the communication circuit board, high-frequency circuit board or thick copper circuit board by degreasing, washing and pickling, a light brushing or spraying pre-cleaning step is also included.

[0037] After step S3, the copper surface of the circuit board will appear uniformly red or form a honeycomb-like roughened microstructure.

[0038] Through the above technical solution, by adding a light mechanical brushing or high-pressure spray pre-cleaning step after chemical pretreatment, stubborn organic contaminants and micron-sized particles are physically removed, eliminating the hydrophobic barrier formed in the acidic working solution and ensuring all-round contact between the solution and the copper surface. This pretreatment enhancement measure works synergistically with the subsequent ultra-roughening treatment, resulting in a uniform red color on the treated copper surface that indicates sufficient oxidation. This solves the problem of uneven roughening and etching blind spots caused by surface contamination in high-reliability circuit boards, providing an ideal interface foundation for subsequent lamination or solder resist processes.

[0039] Secondly, this application provides a low-ammonia nitrogen treatment agent for roughening the copper surface of circuit boards, comprising:

[0040] The low ammonia nitrogen treatment agent includes starter solution A and replenishment solution B;

[0041] The starter solution A is diluted 5 to 20 times to form a working solution, which includes the following components:

[0042] Divalent copper ions 10-40 g / L, sodium chloride 50-130 g / L, formic acid 35-100 g / L, sodium formate 40-130 g / L, acidity regulator, nitrogen-free wetting and leveling agent 0.01-0.20 g / L, stabilizer 0.05-1.0 g / L, and water;

[0043] The acidity regulator is used to adjust the acidity of the working solution to 1.6–2.4N, and the pH value of the working solution is 2.8–3.8;

[0044] The replenishing solution B includes sodium chloride, formic acid, sodium formate, nitrogen-free wetting and leveling agent, stabilizer and water;

[0045] The low ammonia nitrogen treatment agent does not contain added ammonium chloride, and the replenishment solution B is used to replenish the working solution during the continuous ultra-roughening treatment of the circuit board according to the concentration of divalent copper ions, acidity, pH value and micro-etching amount.

[0046] Through the above technical solution, by dividing the reagent into a two-component architecture of start-up solution A and replenishment solution B, the functions of initial bath setup and operation and maintenance are decoupled. Start-up solution A provides a broad and robust basic reaction environment, covering the needs of different production line loads. Replenishment solution B, as a precise regulator, is designed to be ammonium-free, ensuring that no ammonia nitrogen accumulates during continuous replenishment. This close cooperation between the reagent and the method results in the reagent itself having extremely low background ammonia nitrogen (≤5ppm), and significantly outperforming traditional single-component or ammonium-containing reagents in terms of first-time start-up success rate and long-term operational stability, providing a solid material basis for achieving green manufacturing.

[0047] Optionally, after the starter solution A is prepared into a working solution, the concentration of divalent copper ions in the working solution is 20-32 g / L, the concentration of sodium chloride is 70-100 g / L, the concentration of formic acid is 45-80 g / L, and the concentration of sodium formate is 60-100 g / L.

[0048] The replenishment solution B contains 150–300 g / L sodium chloride, 60–180 g / L formic acid, 30–120 g / L sodium formate, 0.05–0.50 g / L nitrogen-free wetting and leveling agent, and 0.1–2.0 g / L stabilizer.

[0049] By further solidifying the optimal ratio parameters of the start-up solution A and the replenishment solution B through the above technical solution, the concentrations of copper ions, sodium chloride, and organic acid salts are locked within the optimal window verified by a large number of production lines, avoiding the inflection point region of the response curve and balancing the micro-etching rate and crystallization risk. The concentration of the replenishment solution B is designed to be 2 to 3 times the upper limit of the start-up solution, which not only ensures the high efficiency of replenishment but also reserves sufficient safety margin to cope with unexpected working conditions. This optimized solution improves the first-time pass rate of start-up, enhances the efficiency of replenishment solution per unit volume, simplifies on-site operation, and reduces the overall operating cost. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0051] Figure 1 A flowchart illustrating the application method of a low-ammonia nitrogen treatment agent for roughening the copper surface of a circuit board, provided in one embodiment of this application;

[0052] Figure 2 This is a SEM image of the uniform honeycomb microporous structure after treatment with a low ammonia nitrogen system according to an embodiment of this application.

[0053] Figure 3 SEM image of a shallow honeycomb coarsening structure under low copper ion concentration conditions provided in an embodiment of this application;

[0054] Figure 4 SEM image of a deep honeycomb coarsening structure under high copper ion concentration conditions provided in an embodiment of this application;

[0055] Figure 5 SEM image of a regular honeycomb-like coarsened structure under the condition of an alternative wetting and leveling agent provided in an embodiment of this application;

[0056] Figure 6 This is a SEM image of the localized etched blind area and uneven coarsening after conventional preprocessing, provided in an embodiment of this application.

[0057] Figure 7 SEM image of a uniform honeycomb-like roughened structure across the entire board surface after light brushing pretreatment, as provided in an embodiment of this application. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0059] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0060] The embodiments of this application will now be described in further detail with reference to the accompanying drawings.

[0061] Example 1

[0062] This embodiment aims to provide a low ammonia nitrogen ultra-coarsening treatment scheme under optimal process conditions, and to verify the feasibility and excellent performance of the system after sodium chloride replaces ammonium chloride.

[0063] Preparation of the start-up solution: Add copper chloride (to achieve a divalent copper ion concentration of 25 g / L), sodium chloride (85 g / L), formic acid (60 g / L), and sodium formate (80 g / L) sequentially to deionized water. After stirring and dissolving, slowly add sulfuric acid to adjust the acidity to 2.0 N, at which point the pH value is approximately 3.2. Then add sodium polyacrylate (0.05 g / L) as a nitrogen-free wetting and leveling agent, and sorbitol (0.2 g / L) as a stabilizer. Add deionized water to a final volume of 1 L to obtain the working solution.

[0064] The acidity in this application refers to the total acidity or titratable acidity obtained by titrating with a sodium hydroxide standard solution to a specified endpoint, and is not directly equivalent to the free hydrogen ion concentration; the pH value is the real-time pH of the working solution measured by the glass electrode method.

[0065] Pretreatment: Take FR-4 substrate copper-clad laminate and electroplated copper board, and successively pass them through alkaline degreasing (60℃, 3min), water washing, 10% sulfuric acid activation (30s), water washing, and finally light brushing treatment (brushing wheel speed 1200rpm, pressure 0.3mm) to remove surface fingerprints and oxide layer.

[0066] Ultra-roughening treatment: The pre-treated board is placed in a working liquid at a constant temperature of 30°C and treated by spraying for 60 seconds at a spraying pressure of 0.2 MPa.

[0067] Process monitoring and replenishment: After continuously treating 500 square meters of board surface, the concentration of divalent copper ions was found to have increased to 28 g / L, and the micro-etching amount was measured at 22 uin (target value 24 ± 2 uin). At this point, the replenishment procedure was initiated, adding 150 mL of replenishment solution B per 100 square meters of board surface. The composition of replenishment solution B is: sodium chloride 200 g / L, formic acid 120 g / L, sodium formate 60 g / L, sodium polyacrylate 0.2 g / L, and sorbitol 0.5 g / L.

[0068] Post-treatment: The treated boards are washed with water, neutralized with 1% sulfuric acid, rinsed with pure water, and dried with hot air.

[0069] Testing revealed that the working solution contained 45 ppm ammonia nitrogen and 38,000 ppm COD. The micro-etching depth of the electroplated board was 23.8 uin, and that of the substrate board was 24.2 uin, resulting in a uniform bright red surface. Figure 2As shown, SEM observation revealed a relatively uniform honeycomb micropore structure on the copper surface, with pore sizes mainly ranging from approximately 0.3 to 1.5 μm, and locally reaching around 2 μm. After 8 hours of continuous operation, the micro-etching amount fluctuated between 23.5 and 24.5 μm.

[0070] This embodiment demonstrates that, under conditions completely free of added ammonium chloride, a stable and excellent ultra-roughening effect can be achieved through the synergistic effect of sodium chloride, copper ions, and the formic acid / sodium formate system, combined with a precise replenishment strategy. The amount of micro-etching is controllable and the surface morphology is ideal, meeting the environmental protection requirements for low ammonia nitrogen.

[0071] Example 2

[0072] This embodiment aims to verify the feasibility and technical effectiveness of keeping the concentration of divalent copper ions in the working solution near the lower limit.

[0073] The method is the same as in Example 1, except that the amount of copper chloride added is adjusted in step 1 so that the concentration of divalent copper ions in the working solution is 10 g / L. The concentrations of other components and process conditions (temperature 30°C, time 60 s, replenishment strategy, etc.) are the same as in Example 1.

[0074] Test results showed that under these conditions, the micro-etching amount of the electroplated board was 18.5 uin, and the micro-etching amount of the substrate board was 19.2 uin. Although the micro-etching rate was slightly lower than that of Example 1, it was still within the range where effective roughening was possible. The board surface color was slightly lighter than that of Example 1, appearing as a pale red. Figure 3 As shown, the SEM morphology reveals a slightly shallow but still continuous and intact honeycomb structure. During continuous operation, by appropriately extending the treatment time to 75 seconds or fine-tuning the ratio of replenishing solution B, the micro-etching amount can be stably controlled within the target range.

[0075] The results show that even under conditions where the concentration of divalent copper ions is as low as 10 g / L, the technical solution of the present invention can still achieve ultra-roughening of the copper surface, proving the feasibility of the lower limit of the concentration range and demonstrating the good adaptability of the system to low copper concentrations.

[0076] Example 3

[0077] This embodiment aims to verify the feasibility and technical effectiveness of maintaining a divalent copper ion concentration near the upper limit in the working solution.

[0078] The method is the same as in Example 1, except that the amount of copper chloride added is adjusted in step 1 so that the concentration of divalent copper ions in the working solution is 40 g / L, while the concentrations of other components and process conditions remain the same as in Example 1.

[0079] Test results showed that under these conditions, the micro-etching amount of the electroplated board was 26.5 uin, and that of the substrate board was 27.1 uin. The micro-etching rate was high, but no excessive corrosion or blackening of the board surface was observed. The board surface appeared deep red, as... Figure 4 As shown in the SEM image, the honeycomb pores are quite deep. By reducing the replenishment frequency of the replenishment fluid B, the micro-etching rate in continuous production was successfully stabilized in the range of 26-27 μin.

[0080] The results show that even under conditions where the concentration of divalent copper ions is as high as 40 g / L, the system of the present invention can still maintain stable micro-etching performance and good plate appearance, without copper salt precipitation or uncontrolled reaction, proving the effective support of the upper limit of the concentration range.

[0081] Example 4

[0082] This embodiment aims to verify the feasibility and technical effectiveness of sodium chloride concentrations near the lower limit.

[0083] The method is the same as in Example 1, except that the amount of sodium chloride added is adjusted in step 1 so that the concentration of sodium chloride in the working solution is 50 g / L, while the concentrations of other components and process conditions remain the same as in Example 1.

[0084] Test results showed that the micro-etching amount decreased under these conditions, with the electroplated board's micro-etching amount being approximately 20.5 uin. The board surface color was normal, but the roughening depth was slightly shallow. By slightly increasing the processing temperature to 35℃ or extending the processing time to 70s, the rate loss caused by the low chloride ion concentration could be compensated, allowing the final micro-etching amount to reach the target value of approximately 24 uin.

[0085] The results show that, under the edge condition of sodium chloride concentration of 50 g / L, the present invention can still achieve the expected ultra-coarsening effect by adjusting the process parameters in a coordinated manner, thus verifying the feasibility of this parameter range.

[0086] Example 5

[0087] This embodiment aims to verify the feasibility and technical effectiveness of sodium chloride concentrations near the upper limit.

[0088] The method is the same as in Example 1, except that the amount of sodium chloride added is adjusted in step 1 so that the concentration of sodium chloride in the working solution is 130 g / L, while the concentrations of other components and process conditions remain the same as in Example 1.

[0089] Test results showed that the micro-etching rate was significantly improved under these conditions, with the micro-etching amount on the electroplated plate reaching approximately 28.5 uin. The plate surface showed significant roughening, but no localized over-etching or pitting was observed. By reducing the amount of replenishing solution B and adding deionized water as needed for dilution, the micro-etching amount was successfully brought back and stabilized within the target window.

[0090] The results show that under high concentration of sodium chloride (130 g / L), the system of the present invention has good buffering capacity and controllability, and can effectively suppress the disorderly growth of micro-erosion by the replenishment strategy, which proves the rationality of the upper limit of the parameter.

[0091] Example 6

[0092] This embodiment aims to verify the feasibility and technical effectiveness of processing at temperatures near the lower limit.

[0093] The method is the same as in Example 1, except that the processing temperature is adjusted to 25°C in step 3, while the concentrations of other components and process conditions remain the same as in Example 1.

[0094] Test results showed that the reaction rate slowed down at low temperatures, with a micro-etching amount of approximately 21.0 uin. By extending the processing time to 80 s, a micro-etching amount (24.1 uin) and plate morphology comparable to those in Example 1 could be obtained.

[0095] The results show that, under low temperature conditions of 25℃, the technical solution of the present invention can still achieve effective ultra-coarsening treatment by adjusting the time parameter, proving the feasibility of the lower limit of the process temperature range.

[0096] Example 7

[0097] This embodiment aims to verify the feasibility and technical effectiveness of processing temperatures near the upper limit.

[0098] The method is the same as in Example 1, except that the processing temperature is adjusted to 38°C in step 3, while the concentrations of other components and process conditions remain the same as in Example 1.

[0099] Test results show that the reaction rate is accelerated at high temperatures, with a micro-etching amount of approximately 27.8 uin. By shortening the processing time to 45 seconds, the micro-etching amount can be precisely controlled at 24.5 uin, with good board surface uniformity and no signs of over-etching.

[0100] The results show that the system of the present invention reacts rapidly and is controllable under high temperature conditions of 38℃, proving the effectiveness of the upper limit of the process temperature range.

[0101] Example 8

[0102] This embodiment aims to verify the feasibility and technical effectiveness of keeping the sodium chloride concentration in replenishment solution B near the lower limit.

[0103] The method is the same as in Example 1, except that when preparing the replenishment solution B, the sodium chloride content is adjusted to 150 g / L, while the other components and replenishment logic remain the same as in Example 1.

[0104] During continuous production replenishment, it was found that the volume of replenishment liquid required to achieve the same chloride ion compensation effect increased by about 30% compared to Example 1, but the stability of the micro-corrosion amount of the working fluid was not significantly affected and could still be maintained within the target range.

[0105] The results showed that when the sodium chloride concentration in the replenishment solution B was 150 g / L, although the replenishment efficiency was slightly reduced, the replenishment function could still be effectively performed, verifying the feasibility of this lower concentration limit.

[0106] Example 9

[0107] This embodiment aims to verify the feasibility and technical effectiveness of maintaining a sodium chloride concentration near the upper limit in replenishment solution B.

[0108] The method is the same as in Example 1, except that when preparing the replenishment solution B, the sodium chloride content is adjusted to 300 g / L, while the other components and replenishment logic remain the same as in Example 1.

[0109] During continuous production replenishment, even a very small amount of replenishment solution can significantly increase the chloride ion concentration of the working fluid, making replenishment control more sensitive. Precise metering is necessary to prevent excessively high local concentrations, but under automated control, the micro-etching volume exhibits excellent stability.

[0110] The results showed that when the sodium chloride concentration in the replenishment solution B was 300 g / L, the replenishment efficiency was extremely high, verifying the feasibility and advantages of this upper concentration limit.

[0111] Example 10

[0112] This embodiment aims to verify the feasibility of using nitrogen-free wetting and leveling agents and stabilizers.

[0113] The method is the same as in Example 1, except that the nitrogen-free wetting and leveling agent is replaced with maleic acid-acrylic acid copolymer (0.08 g / L), and the stabilizer is replaced with sodium citrate (0.3 g / L), while the other conditions remain unchanged.

[0114] Test results showed that the micro-etching amount was 23.9 uin, and the board surface was uniformly red, as... Figure 5 As shown, the SEM morphology reveals a regular honeycomb structure with smooth pore walls. Environmental indicators tested showed ammonia nitrogen of 42 ppm and COD of 36,500 ppm.

[0115] The results show that other types of nitrogen-free wetting and leveling agents and stabilizers listed in this application can also achieve the technical effects of the present invention, demonstrating the wide applicability of component selection.

[0116] Example 11

[0117] This embodiment aims to verify the impact and control effect of a specific micro-etching window on the PIM performance of a communication circuit board.

[0118] In this application, the single-sided micro-etching amount of the copper surface of a conventional circuit board can be controlled to be 20-28 uin; for communication circuit boards, when measured by cumulative micro-etching amount on both sides or total micro-etching amount, it is preferably controlled to be 45-60 uin. Unless otherwise specified, the micro-etching amount in Examples 1-10 is the single-sided micro-etching amount, and the micro-etching amount in Example 11 is the total micro-etching amount of the communication circuit board.

[0119] High-frequency communication circuit board samples were selected and treated using the reagents and methods described in Example 1. Four different target micro-etching control points were set: 42 uin, 48 uin, 59 uin, and 68 uin. Different micro-etching amounts were achieved by adjusting the addition ratio of replenishing solution B and the treatment time. After treatment, the samples were subjected to PIM testing in the 28 GHz band.

[0120] The test results are shown in Table 1:

[0121] Table 1. PIM test results of communication board under different micro-etching amounts

[0122]

[0123] Data analysis shows that when the micro-etching amount is controlled within the range of 45–60 uin (samples B and C), the PIM test values ​​are all better than the industry high standard of -160 dBc, and are deemed qualified. However, when the micro-etching amount is below 45 uin (sample A) or above 60 uin (sample D), the PIM performance deteriorates significantly, posing a risk of non-compliance. The performance is best around 48 uin, comparable to the effect of commercially available benchmark solutions.

[0124] This embodiment strongly demonstrates the necessity of controlling the micro-etching amount of communication circuit boards within a window of 45 to 60 μin, and verifies the significant effect of the technical solution of this application in solving the PIM stability problem of high-end communication boards. This window is a key process parameter for achieving low PIM.

[0125] Example 12

[0126] This embodiment aims to verify the effect of light brushing pretreatment on the uniformity of copper surface roughening.

[0127] Two identical thick copper circuit board substrates were selected. The first group (control group) underwent only routine degreasing, water washing, and acid pickling pretreatment; the second group (experimental group) underwent a slight abrasion step after acid pickling (brush wheel speed 1200 rpm, indentation 0.3 mm). Both groups were then subjected to ultra-roughening treatment using the reagents and processes described in Example 1.

[0128] After treatment, macroscopic observation of the control group boards revealed localized oil stains or fingerprint residue; further investigation revealed... Figure 6As shown, SEM morphology reveals that this type of area does not form a continuous honeycomb-like coarsening structure, and there are localized areas of insufficient etching. Water-break time tests showed that some points exceeded 60 seconds (poor wetting). After treatment, the experimental group of boards exhibited a uniform red surface with no visible stains. Figure 7 As shown, SEM observation revealed that the honeycomb structure was uniformly distributed across the entire board, with a coverage rate of >99% and a water-break time of <30s.

[0129] Figure 6 and Figure 7 Typical morphologies are shown at different magnifications. These two images are mainly used to illustrate the differences in coarsening continuity and are not used as a direct basis for comparing aperture sizes.

[0130] The results show that for communication boards, high-frequency boards, or thick copper plates, adding a light brushing or spraying pre-cleaning step can significantly eliminate the interference of surface contaminants on the roughening reaction, greatly improve the uniformity and reliability of copper surface treatment, and verify the technical value of pretreatment enhancement measures.

[0131] Example 13

[0132] This embodiment aims to compare the environmental performance and micro-corrosion stability of the low ammonia nitrogen system of the present invention with those of the traditional ammonium chloride-containing system.

[0133] Comparative Example 1: A traditional micro-etching solution containing ammonium chloride (60 g / L ammonium chloride, with other parameters such as copper ions and acidity consistent with the working solution in Example 1, without sodium chloride substitution) was used.

[0134] Comparative Example 2: A solution with simple ammonium chloride removal but without optimized buffer and replenishment system (containing only copper ions, sulfuric acid, a small amount of chloride ions, and no sodium formate buffer or special replenishment solution B).

[0135] Set up the sample of Example 1.

[0136] All three systems were operated continuously for 12 hours under the same production line conditions, with the fluctuation of micro-corrosion and the ammonia nitrogen and COD indicators of the discharged wastewater being detected every hour.

[0137] The specific test results are shown in Table 2. As can be seen from the data trend, Embodiment 1 of the present invention is significantly better than the comparative embodiment in all indicators.

[0138] Table 2 Comparison of Performance and Environmental Indicators of Different Systems

[0139]

[0140] Analysis shows that although Comparative Example 1 met the micro-corrosion standard, its ammonia nitrogen level was severely excessive, failing to meet environmental protection requirements. Comparative Example 2, while having extremely low ammonia nitrogen, had a severely insufficient and highly fluctuating micro-corrosion level, unable to meet production needs. Only Example 1, through the synergistic effect of sodium chloride substitution, buffer system construction, and dynamic replenishment control, simultaneously achieved low ammonia nitrogen (45ppm < 100ppm), significantly reduced ammonia nitrogen while maintaining COD within the range treatable by conventional wastewater treatment processes, and high stability of micro-corrosion level (fluctuation only ±1.2uin).

[0141] This embodiment fully demonstrates the progress of the present invention compared with the prior art, proves the unique advantages of the "sodium chloride substitution + buffer system + feedback replenishment" combination scheme, and solves the problem that a single technical means cannot take into account both environmental protection and performance.

[0142] Example 14

[0143] In this embodiment, the test samples include the products prepared in each of Examples 1 to 10 (i.e., the copper surface of the circuit board after being treated under the corresponding conditions). The above samples are then used for subsequent solder resist coating and lamination processes.

[0144] Experimental results show that all copper surfaces prepared within the specified range achieved a solder resist adhesion test (3M tape tear) grade of 5B (no peeling), and the peel strength after lamination was greater than 0.9 kN / m, meeting IPC level 2 or higher standards. In particular, for the communication circuit board (Example 11), the samples treated within the 45-60 μin micro-etching window maintained excellent PIM performance after assembly.

[0145] Therefore, the low ammonia nitrogen treatment agent and its application method of this application can be used for the copper surface roughening treatment of high-performance printed circuit boards, high-frequency communication substrates and thick copper power boards to improve solder resist adhesion, interlayer bonding and passive intermodulation performance stability of communication circuit boards. It can be widely used in the manufacturing process of high-performance printed circuit boards, high-frequency communication substrates and thick copper power boards, especially in fields with strict requirements for environmental protection indicators and signal integrity.

[0146] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for applying a low-ammonia nitrogen treatment agent for ultra-roughening the copper surface of a circuit board, characterized in that, include: S1. Perform degreasing, water washing and acid pickling pretreatment on the copper surface of the circuit board to be processed to remove oil stains, oxides and particulate contaminants from the copper surface; S2. Prepare the starting solution A of the low ammonia nitrogen treatment agent as the working solution, wherein the working solution contains divalent copper ions, sodium chloride, formic acid, sodium formate, acidity regulator, nitrogen-free wetting and leveling agent, stabilizer and water, and the concentration of divalent copper ions in the working solution is 10-40 g / L, the concentration of sodium chloride is 50-130 g / L, the concentration of formic acid is 35-100 g / L, the concentration of sodium formate is 40-130 g / L, the acidity is 1.6-2.4 N, and the pH value is 2.8-3.8; S3. The pretreated copper surface of the circuit board is brought into contact with the working fluid. The contact method is spraying, immersion, or a combination of spraying and immersion. The treatment temperature is 25-38°C and the treatment time is 30-90 seconds, so as to form an ultra-coarsened microstructure on the copper surface of the circuit board. S4. During the continuous processing of the circuit board, the concentration of divalent copper ions, acidity, pH value and micro-etching amount of the copper surface of the circuit board are detected in the working solution. S5. When the concentration of divalent copper ions is between 25 and 35 g / L and the micro-etching amount is lower than the target micro-etching amount, add supplementary solution B to the working solution. Supplementary solution B contains sodium chloride, formic acid, sodium formate, a nitrogen-free wetting and leveling agent, a stabilizer, and water. When the micro-etching amount is higher than the target micro-etching amount, reduce the amount of supplementary solution B or add low-chlorine diluent. The target micro-etching amount is preset according to the circuit board type; the target micro-etching amount for ordinary circuit boards is 20–28 μin, and the target total micro-etching amount for communication circuit boards is 45–60 μin. The low-chlorine diluent includes deionized water, sodium formate, and an optional stabilizer. The sodium chloride concentration in the low-chlorine diluent is less than 30% of the sodium chloride concentration in the working solution prepared from the starter solution A in step S2. S6. After the ultra-roughened circuit board is washed with water, acid-washed or treated with anti-oxidation, the treated copper surface can be used for subsequent lamination, solder masking, pattern transfer or communication circuit board assembly processes. The working fluid does not contain added ammonium chloride, and the added ammonium salt type chloride ion source is replaced by sodium chloride. Sodium chloride serves as the main non-ammonium salt type chloride ion compensation component, and through the synergistic effect of sodium chloride, divalent copper ions, and formic acid / sodium formate buffer system, it enables the copper surface of the circuit board to maintain a stable micro-etching amount under low ammonia nitrogen conditions.

2. The method according to claim 1, characterized in that, In step S2, the working solution has a copper ion concentration of 20-32 g / L, a sodium chloride concentration of 70-100 g / L, a formic acid concentration of 45-80 g / L, a sodium formate concentration of 60-100 g / L, and a pH value of 3.0-3.

5.

3. The method according to claim 1, characterized in that, In step S2, the divalent copper ions are derived from one or more of copper chloride, copper sulfate, and copper formate. The acidity regulator is sulfuric acid; Sodium chloride, as a non-ammonium salt chloride ion compensating component, is used to replace ammonium chloride in regulating the micro-corrosion ability of the working fluid.

4. The method according to claim 1, characterized in that, In step S2, the nitrogen-free wetting and leveling agent is one or more of polyacrylate, maleic acid-acrylic acid copolymer, and polyether modified carboxylate; The stabilizer is one or more of the following: sugar alcohol stabilizers, polyhydroxycarboxylate stabilizers, or low-phosphorus organic acid salt stabilizers.

5. The method according to claim 1, characterized in that, In step S3, for the copper surface of the communication circuit board, the total micro-etching amount of the copper surface of the control circuit board is controlled to be 45-60 μin; When the total micro-erosion amount is less than 45 μin, increase the addition ratio of replenishing solution B or extend the treatment time; When the total micro-etching amount is higher than 60 μin, reduce the addition ratio of replenishing solution B or shorten the treatment time.

6. The method according to claim 1, characterized in that, In step S5, the content of sodium chloride in the replenishing solution B is 150-300 g / L, the content of formic acid is 60-180 g / L, the content of sodium formate is 30-120 g / L, the content of nitrogen-free wetting and leveling agent is 0.05-0.50 g / L, and the content of stabilizer is 0.1-2.0 g / L.

7. The method according to claim 1, characterized in that, In step S5, supplementary control is performed according to the following rules: When the concentration of divalent copper ions is below 20 g / L and the micro-corrosion amount is below the target micro-corrosion amount, add copper-containing starter solution A; When the concentration of divalent copper ions is 25-35 g / L and the micro-etching amount is lower than the target micro-etching amount, add supplementary solution B. When the pH value is below 2.8 or the acidity is above 2.4N, reduce the amount of formic acid added and add deionized water or a low-chlorine dilution containing sodium formate. When the pH is higher than 3.8 or the acidity is lower than 1.6N, add an acidity adjusting solution containing formic acid; When the micro-etching amount is higher than the target micro-etching amount and the plate surface shows a darkening or over-etching trend, stop adding replenishing solution B and add deionized water or low-chlorine diluent.

8. The method according to claim 1, characterized in that, In step S1, after pre-treatment of the copper surface of the communication circuit board, high-frequency circuit board or thick copper circuit board by degreasing, water washing and acid washing, a light brushing or spraying pre-cleaning step is also included. After step S3, the copper surface of the circuit board will appear uniformly red or form a honeycomb-like roughened microstructure.

9. A low-ammonia nitrogen treatment agent for roughening the copper surface of circuit boards, characterized in that, The method applied to any one of claims 1-8 includes: The low ammonia nitrogen treatment agent includes starter solution A and replenishment solution B; The starter solution A is diluted 5 to 20 times to form the working solution, which includes the following components: Divalent copper ions 10-40 g / L, sodium chloride 50-130 g / L, formic acid 35-100 g / L, sodium formate 40-130 g / L, acidity regulator, nitrogen-free wetting and leveling agent 0.01-0.20 g / L, stabilizer 0.05-1.0 g / L, and water; The acidity regulator is used to adjust the acidity of the working solution to 1.6–2.4N, and the pH value of the working solution is 2.8–3.8; The replenishing solution B includes sodium chloride, formic acid, sodium formate, nitrogen-free wetting and leveling agent, stabilizer and water; The low ammonia nitrogen treatment agent does not contain added ammonium chloride, and the replenishment solution B is used to replenish the working solution during the continuous ultra-roughening treatment of the circuit board according to the concentration of divalent copper ions, acidity, pH value and micro-etching amount.

10. The pharmaceutical preparation according to claim 9, characterized in that, After the starter solution A is prepared into a working solution, the concentration of divalent copper ions in the working solution is 20-32 g / L, the concentration of sodium chloride is 70-100 g / L, the concentration of formic acid is 45-80 g / L, and the concentration of sodium formate is 60-100 g / L. The replenishment solution B contains 150–300 g / L sodium chloride, 60–180 g / L formic acid, 30–120 g / L sodium formate, 0.05–0.50 g / L nitrogen-free wetting and leveling agent, and 0.1–2.0 g / L stabilizer.

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