A developing solution control method for preventing PCB from being plated in a non-copper hole
Patent Information
- Application Number
- CN202611050639.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-15
- Publication Date
- 2026-10-23
AI Technical Summary
[0005]针对现有技术的不足，本发明提供了一种防止PCB抗镀型孔无铜的显影液控制方法，解决现有技术中显影副产物无定量监控标准、抗镀型孔无铜缺陷管控依赖人工经验、良率不稳定的问题，通过量化管控阈值实现显影液状态的闭环管控，从源头抑制缺陷产生
1.本发明提供了一种防止PCB抗镀型孔无铜的显影液控制方法，本方法首次定量明确显影液安全工艺窗口，通过系统的再现性测试验证，确立pH值≥10.6为防止抗镀型孔无铜的临界管控阈值，量化了显影副产物积累的安全边界，为工艺管控提供了科学、可落地的判断标准，解决了传统依赖人工经验、管控标准模糊的问题。
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Abstract
Description
Technical Field
[0001] This invention relates to the field of printed circuit board manufacturing technology, specifically to a method for controlling the developer solution to prevent copper-free holes in PCB anti-plating vias. Background Technology
[0002] In the PCB positive film manufacturing process, the core steps typically involve outer layer pretreatment, dry film lamination, exposure, development, pattern electroplating, and alkaline etching. Among these, copper-free vias are a common and serious quality defect, directly causing electrical conduction failure in PCB metallized vias and leading to mass product scrapping. Current development processes generally use sodium carbonate solution as the developer, with the concentration monitored and adjusted online using a pH meter to maintain development capability. However, in actual production, the photosensitive polymers in the dry film react with sodium carbonate to continuously generate -COO⁻Na⁺ organic byproducts that accumulate in the developing tank. Simultaneously, hydrogen foam generated during dry film dissolution hinders tank overflow and renewal, further exacerbating byproduct accumulation.
[0003] The current process only indirectly controls the concentration of sodium carbonate solution through pH value, and does not establish quantitative monitoring standards and control mechanisms for the accumulation of developing by-products. When the developing solution rich in by-products is applied to the PCB board through the spray system, the by-products will enter the metallized holes with the solution. Moreover, the water washing effect in the center of the hole is weaker than that at the hole opening, and the by-products are more likely to remain and be adsorbed on the hole wall. In the subsequent pattern electroplating process, the by-products remaining on the hole wall will form a resist layer, causing uneven thickness of copper and tin plating layers or even local failure to deposit, which manifests as thinning and discontinuity of the plating layer and other anti-plating phenomena. Finally, after alkaline stripping and etching processes, the copper layer on the hole wall is eroded by the etching solution, forming three typical types of copper-free defects in anti-plating holes: completely broken, gradually thinning, and jagged.
[0004] Currently, the industry relies heavily on manual experience to adjust developing parameters to address this type of defect, lacking clear quantitative control thresholds. This results in poor process stability and difficulty in effectively preventing batch scrapping of copper-free holes, becoming a key bottleneck restricting the improvement of PCB positive film process yield. Therefore, this invention proposes a developing solution control method to prevent copper-free holes in PCB anti-plating type holes, thereby effectively solving the above-mentioned problems and difficulties. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a developer control method to prevent copper-free through-holes in PCB anti-plating systems. This method solves the problems of lack of quantitative monitoring standards for development byproducts, reliance on manual experience for controlling copper-free through-hole defects, and unstable yield in existing technologies. By quantifying control thresholds, a closed-loop control of the developer state is achieved, suppressing defect generation at the source.
[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for controlling the developer solution to prevent copper-free through-holes in PCB plating, the method specifically includes the following steps: Step 1: Device setup; An online pH detection device is installed in the developing tank of the PCB dry film developing line, and an early warning device electrically connected to the pH detection device is set up; the original sodium carbonate automatic replenishment system is retained, and its automatic replenishment logic based on the melt volume is maintained. Step 2: Threshold setting; The lower limit of the safe control of the pH value of the developer is set at 10.6, and this pH value is used as the critical control threshold for anti-copper defects in the plated holes; Step 3: Real-time monitoring; During the production process, the real-time pH value of the developer is continuously collected by an online pH detection device, and an automatic sodium carbonate replenishment system is run simultaneously to maintain the basic developing capacity. Step 4: Early Warning and Control; When the real-time monitored pH value is lower than 10.6, the early warning device triggers an alarm and performs a developer replacement operation. After the replacement is completed, normal production resumes. Step 5: Process Validation; Periodically conduct reproducible simulation tests to establish and verify the correspondence between different pH values and copper-free defect types in the pores, and continuously confirm the effectiveness of the control threshold.
[0007] Furthermore, in step 5, during process verification, the specific procedure for reproducibility simulation testing is as follows: Step 501: Prepare the test sample; Select a PCB substrate that has undergone copper plating and has completed one copper plating process, and cut it into a standard-sized test board. Step 502: Gradient immersion; The test plates were immersed in developer solutions with different preset pH values for a set time to simulate the adhesion process of developer byproducts in production. Step 503: Simulate subsequent processes; After immersion, the test board undergoes a series of processes including water washing and drying, degreasing, micro-etching, secondary copper plating, tin plating, and alkaline etching, replicating the entire process of the positive film process. Step 504: Slice verification; Metallographic sections were prepared on the treated test board to observe the morphology of the copper layer on the hole wall and to statistically analyze the types and severity of copper-free defects in the holes corresponding to different pH values. Step 505: Threshold verification; Based on the slicing results, it was confirmed that there were no anti-plating holes and no copper defects when pH≥10.6, thus verifying the reliability of the control threshold.
[0008] Furthermore, during the setup of the device in step 1, the sampling point of the online pH detection device is located on the circulation loop of the developing tank.
[0009] Furthermore, in the process of setting the threshold in step 2, the safety control lower limit of 10.6 reserves a measurement error margin of ±0.1 for the pH meter.
[0010] Furthermore, during the early warning and control process in step 4, the developer solution is replaced entirely. After replacement, the pH detection device is recalibrated, and production can only resume after confirming that the pH value is within the safe range.
[0011] Furthermore, in step 501, during the preparation of the test sample, the thickness of the test sample is 1.2mm-2.0mm, the aperture range is 0.2mm-0.35mm, and the copper plating time is 30min.
[0012] Furthermore, during step 502, the pH gradient of the developing solution is set to six levels: 9.0, 9.5, 10.0, 10.3, 10.6, and 11.0, with a soaking time of 60 seconds.
[0013] This invention provides a method for controlling the developer solution to prevent copper-free through-holes in PCB anti-plating systems. It has the following beneficial effects: 1. This invention provides a method for controlling the developer solution to prevent copper-free through-holes in PCB anti-plating systems. This method is the first to quantitatively define the safe process window for the developer solution. Through systematic reproducibility testing, it establishes a pH value ≥10.6 as the critical control threshold for preventing copper-free through-holes in anti-plating systems. It quantifies the safe boundary for the accumulation of development by-products, providing a scientific and practical judgment standard for process control, and solving the problems of traditional reliance on manual experience and vague control standards.
[0014] 2. This invention provides a developer solution control method to prevent copper-free holes in PCB anti-plating vias. It achieves closed-loop management of the developer solution status. Through the closed-loop control logic of online real-time monitoring, threshold warning, and solution replacement, the excessive accumulation of developer solution byproducts can be detected in a timely manner, effectively avoiding anti-plating problems on the hole walls caused by byproduct residues. This significantly improves the process stability of the developing process and reduces the risk of batch scrap caused by human negligence.
[0015] 3. This invention provides a developer control method to prevent copper-free PCB anti-plating vias, which improves yield and has low modification costs. This method can reduce the generation of copper-free defects in anti-plating vias from the source, reduce material, labor and time costs caused by product rework and scrap, and retain the original automatic sodium carbonate replenishment logic without major modifications to existing equipment, making it easy to quickly promote and implement on the production line. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the developer control system corresponding to the control method of the present invention; Figure 2This is a comparison of metallographic section results corresponding to different pH values in the reproducibility simulation test of this invention; Figure 3 The diagram shows the three types of copper-free defects in anti-plating holes involved in this invention. The top three diagrams are completely broken, the middle three diagrams are gradually thinning, and the bottom three diagrams are dog-tooth shaped. Detailed Implementation
[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0018] Example 1:
[0019] like Figure 1-3 As shown, this embodiment provides a developer solution control method to prevent copper-free defects in PCB anti-plating holes. This method is applied to the dry film development process of PCB positive film manufacturing. By quantitatively controlling the pH value of the developer solution, the method suppresses the copper-free defects in anti-plating holes caused by the residue of development byproducts on the hole walls. The control system for implementing this method includes a developing tank, an online pH meter, an early warning device, and an automatic sodium carbonate replenishment unit. The online pH meter is connected to the circulation loop of the developing tank via a sampling tube to collect real-time pH data of the tank solution. The early warning device is electrically connected to the pH meter and has a preset pH threshold. When the detected value falls below the threshold, an audible and visual alarm is triggered. The automatic sodium carbonate replenishment unit operates independently, automatically replenishing the sodium carbonate solution according to the melting volume of the production line to maintain the basic developing concentration. The specific control method includes the following steps: Step 1: Device installation and parameter initialization; An online pH monitoring device is installed on the circulating pipeline of the developing tank to ensure that the sampled tank solution is representative and can accurately reflect the state of the entire developing tank. The early warning device is connected to the pH meter signal, while the original automatic sodium carbonate addition system of the production line is retained, and its replenishment logic remains unchanged. It still automatically replenishes according to the melting amount of the film in the production process. The pH meter is calibrated to ensure that the detection error is controlled within ±0.1. Step 2: Set security control thresholds; Based on extensive process testing and defect statistics in the early stages, the lower limit of the safe control of the developer pH value was set at 10.6. That is, when the developer pH is ≥ 10.6, the accumulation of developing by-products is at a safe level and will not cause copper-free defects in anti-plating holes; when pH < 10.6, the accumulation of by-products exceeds the standard, and there is a risk of copper-free hole quality. The threshold setting takes into account the measurement error of the pH meter itself (approximately 0.1 pH unit), and reserves an error margin on the basis of the critical safety value to ensure the reliability of production process control; Step 3: Real-time monitoring of the production process; During the production of PCB positive film, the developing process runs continuously. An online pH meter collects the pH value of the developer solution in real time at a fixed frequency and uploads it to the control system. During the production process, the automatic sodium carbonate replenishment system replenishes the solution according to the amount of dry film dissolved, maintaining the basic dissolving capacity of the developer solution. The pH value shows a slow downward trend as byproducts accumulate. Step 4: Threshold warning and medicine replacement; When the online pH meter detects that the pH value of the developer is lower than 10.6, the warning device immediately triggers an audible and visual alarm, prompting the operator that the developer has exceeded the safe control range. After receiving the alarm, the operator suspends the production of the corresponding developing tank and performs a complete replacement of the developer. After the replacement is completed, the pH value of the newly prepared developer is tested and calibrated. After confirming that the pH value is within the safe range, normal production is resumed. Step 5: Periodic reproducibility verification; To ensure the continued effectiveness of the control thresholds, a reproducibility simulation test is conducted quarterly or whenever the production line's chemical system or dry membrane model changes. This test verifies the correlation between pH value and copper-free defects in the pores. The test procedure is as follows: Sample preparation: Select a PCB test board with a standard substrate, 1.5mm thick, and hole diameter covering 0.2-0.35mm; first, perform a copper plating process, followed by a 30-minute copper plating (board electroplating) to form a uniform primary copper layer on the hole walls. Cut the test board into standard 5cm×10cm samples; Gradient immersion test: Prepare developing solutions with pH values of 9.0, 9.5, 10.0, 10.3, 10.6 and 11.0 respectively, and immerse the test plates of different groups in the corresponding developing solutions for 60 seconds to simulate the adsorption process of developing solution by-products on the pore walls during production. Process replication: After soaking, the test board is taken out, washed and dried, and then sequentially goes through degreasing for 15 seconds, micro-etching for 15 seconds, secondary copper plating for 30 minutes, normal tin plating, and alkaline etching processes to completely replicate the pattern electroplating and etching process of the positive film process. Metallographic section analysis: Metallographic sections were prepared from samples of each group of test plates, and the morphology and continuity of the copper layer on the hole walls were observed under a microscope. The test results are as follows: pH=8.93 (nominal 9.0): Blocky anti-plating material exists on the hole wall, secondary copper anti-plating is obvious, tin thickness is only 2.13μm, after etching, the first copper and the second copper are completely separated, which is a completely separated hole with no copper. pH=9.49 (nominal 9.5): The hole wall has blocky anti-plating material, secondary copper anti-plating, tin thickness 2.66μm, and the copper layer after etching is in a state of broken threads. pH=10.0: The hole wall is densely covered with anti-plating material, the secondary copper thickness gradually decreases, the tin thickness is 2.72μm, which is a gradually thinning hole with no copper. pH=10.32 (nominal 10.3): Anti-plating material is present on the hole wall, the secondary copper is gradually thinning, the tin thickness is 3.19μm, and it is still a gradually thinning defect; pH=10.5: The hole wall has only a very small amount of anti-plating material, the secondary copper deposition is normal, the tin thickness is 3.58μm, and there are no holes or copper defects after etching. pH=11.16 (nominal 11.0): The hole wall is clean and free of residue, the secondary copper and tin layers are deposited evenly, there is no anti-plating phenomenon, and the copper in the hole is intact and continuous after etching. Test results show that the lower the pH value, the higher the content of by-products in the developer, the more anti-plating material adheres to the hole wall, and the more serious the copper-free hole defect. When pH ≥ 10.6, the generation of anti-plating copper-free hole defects can be completely avoided, verifying the accuracy and reliability of the control threshold. Using the control method of this embodiment, in actual production line applications, for a certain type of PCB board with a large thickness-to-diameter ratio, the defect rate of copper-free holes reached 3.8% when the pH of the developing solution was 10.2 before the tank was changed, and the defect rate dropped to 1% when the pH was increased to 11.4 after the tank was changed; on another production line, the defect rate of copper-free holes was 14.2% when the pH of the developing solution was 10.3 before the tank was changed, and the defect rate dropped to 2.12% when the pH of the developing solution was 11.5 after the tank was changed, demonstrating significant control effectiveness.
[0020] The following points should be noted in this article: 1. The accompanying drawings of the embodiments disclosed herein only relate to the structures involved in the embodiments disclosed herein; other structures can be referred to in general design.
[0021] 2. Where there is no conflict, the embodiments of this disclosure and the features in the embodiments can be combined with each other to obtain new embodiments.
[0022] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
Claims
1. A method for controlling the developer solution to prevent copper absence in PCB anti-plating vias, characterized in that: The method specifically includes the following steps: Step 1: Device setup; An online pH detection device is installed in the developing tank of the PCB dry film developing line, and an early warning device electrically connected to the pH detection device is set up; the original sodium carbonate automatic replenishment system is retained, and its automatic replenishment logic based on the melt volume is maintained. Step 2: Threshold setting; The safety control lower limit of the developer pH value is set at 10.6, and this pH value is used as the critical control threshold for anti-copper defects in the plated holes. Step 3: Real-time monitoring; During the production process, the real-time pH value of the developer is continuously collected by an online pH detection device, and an automatic sodium carbonate replenishment system is run simultaneously to maintain the basic developing capacity. Step 4: Early Warning and Control; When the real-time monitored pH value is lower than 10.6, the early warning device triggers an alarm and performs a developer replacement operation. After the replacement is completed, normal production resumes. Step 5: Process Validation; Periodically conduct reproducible simulation tests to establish and verify the correspondence between different pH values and copper-free defect types in the pores, and continuously confirm the effectiveness of the control threshold.
2. The developing solution control method for preventing copper absence in PCB anti-plating vias according to claim 1, characterized in that: In the process verification of step 5, the specific procedure for reproducibility simulation testing is as follows: Step 501: Prepare the test sample; Select a PCB substrate that has undergone copper plating and has completed one copper plating process, and cut it into a standard-sized test board. Step 502: Gradient immersion; The test plates were immersed in developer solutions with different preset pH values for a set time to simulate the adhesion process of developer byproducts in production. Step 503: Simulate subsequent processes; After immersion, the test board undergoes a series of processes including water washing and drying, degreasing, micro-etching, secondary copper plating, tin plating, and alkaline etching, replicating the entire process of the positive film process. Step 504: Slice verification; Metallographic sections were prepared on the treated test board to observe the morphology of the copper layer on the hole wall and to statistically analyze the types and severity of copper-free defects in the holes corresponding to different pH values. Step 505: Threshold verification; Based on the slicing results, it was confirmed that there were no anti-plating holes and no copper defects when pH≥10.6, thus verifying the reliability of the control threshold.
3. The developer control method for preventing copper absence in PCB anti-plating vias according to claim 1, characterized in that: During the setup of the device in step 1, the sampling point of the online pH detection device is located on the circulation loop of the developing tank.
4. The developing solution control method for preventing copper absence in PCB anti-plating holes according to claim 1, characterized in that: In the process of setting the threshold in step 2, the safety control lower limit of 10.6 reserves a measurement error margin of ±0.1 for the pH meter.
5. The developer control method for preventing copper absence in PCB anti-plating holes according to claim 1, characterized in that: In step 4, during the early warning and control process, the developer solution is replaced by replacing the entire tank. After replacement, the pH detection device is recalibrated, and production can only resume after confirming that the pH value is within the safe range.
6. The developer control method for preventing copper absence in PCB anti-plating vias according to claim 1, characterized in that: In step 501, during the preparation of the test sample, the test sample thickness is 1.2mm-2.0mm, the hole diameter range is 0.2mm-0.35mm, and the copper plating time is 30min.
7. The developer control method for preventing copper absence in PCB anti-plating vias according to claim 1, characterized in that: During the gradient soaking process in step 502, the pH gradient of the developing solution is divided into six steps: 9.0, 9.5, 10.0, 10.3, 10.6, and 11.0, and the soaking time is 60 seconds.