Method for controlling pitch dimensional stability in fpc roll-to-roll process

Abstract

This invention discloses a method for controlling the pitch stability in FPC roll-to-roll manufacturing, comprising: setting traction films at the beginning and end of the roll material while eliminating the carrier film in the middle product section; exposing the roll material using roll-to-roll LDI laser direct writing or standard glass film; controlling the transverse and longitudinal bilateral expansion and contraction difference of the roll material substrate to ≤0.08‰ based on the substrate deformation matrix through real-time digital graphic scaling / matrix compensation or substrate tension-vacuum collaborative correction; using a selected vacuum press for cover film lamination; and curing and baking at 160℃ for 2 hours. This method achieves orderly release of etching stress through segmented stress management, eliminates systematic deviations within the board surface through bidirectional expansion and contraction control of the film, and combines transverse layout and process parameter coupling control to ensure that the finished product pitch difference is ≤0.03mm and CPK≥1.33, thus solving the problem of dimensional variation caused by irregular stress release in FPC during roll-to-roll manufacturing.

Description

Technical Field

[0001] This invention relates to the technical field of flexible printed circuit board (FPC) fabrication, and in particular to a method for controlling pitch dimension stability in FPC roll-to-roll (RTR) processes. Background Technology

[0002] In the roll-to-roll process of flexible printed circuit boards (FPCs), the finished product's pitch size varies significantly due to the coupling effects of multiple factors, including the difference in thermal expansion coefficients between the copper layer and the polyimide (PI) substrate, etching stress, high temperature and pressure during pressing, and material moisture absorption. Pitch refers to the spacing between the pin arrays on the FPC used for connector mating. The pitch size directly determines whether the FPC can precisely mate with the connector. If the pitch is too large, the pins may not be able to insert into the connector slots or cause poor contact; if the pitch is too small, it may cause short circuits between pins or excessive mating stress. If the pitch of products in the same batch is unstable (with large variations), some can be mated while others cannot, leading to assembly abnormalities at the client end. The existing FPC roll-to-roll process mainly suffers from the following defects: First, there is a contradiction in the carrier film usage strategy. Traditional methods apply a carrier film to the entire roll of product during inner layer etching. While this protects the circuitry during etching, the carrier film hinders the release of internal stress in the copper-PI composite substrate during the etching stage. This stress is released irregularly during the subsequent high-temperature pressing of the cover film, resulting in irregular pitch data variation and increased range. Conversely, if the carrier film is completely removed, although it facilitates stress release during etching, the lack of traction protection during unwinding and rewinding leads to severe tension fluctuations, resulting in high product dispersion after etching and outlier data for the first piece and the end of the roll.

[0003] Secondly, the control of shrinkage and expansion of coil substrates is limited to a single dimension. Existing technologies only control the deviation of the overall shrinkage and expansion of the substrate from the standard value (usually requiring ≤0.2‰), without controlling the differences in shrinkage and expansion between the transverse and longitudinal sides of the substrate. Due to the non-uniform deformation that may occur in the substrate during exposure and temperature and humidity storage, there are systematic differences in the shrinkage and expansion rates of different areas within the same board surface. This difference directly translates into a systematic deviation in the finished product pitch (which can reach 7-10μm), and existing control methods cannot identify and eliminate such deviations.

[0004] Furthermore, the process parameters lack systematic coordination. Parameters such as etching tension, pressing roller hardness, pressing temperature, and baking conditions are set and monitored independently by different processes. The corresponding process personnel only focus on the local stability of their own process and have not established a parameter coupling mechanism across processes. This leads to the accumulation or abrupt changes of stress in the process chain, especially in the capping and curing stages. Existing technologies use one-time high-temperature and high-pressure pressing and constant-temperature long-term baking, resulting in uneven lateral resin flow and dimensional rebound after the stress is released all at once. This cannot solve the fundamental problem of irregular stress release in the RTR process. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for controlling the stability of pitch dimensions in FPC roll-to-roll manufacturing, thereby achieving high-precision control of pitch dimensions in the RTR process.

[0006] To achieve the above objectives, the solution of the present invention is: A method for controlling the stability of pitch dimensions in the roll-to-roll manufacturing process of flexible circuit boards includes the following steps: S1. Pre-treatment and segmented stress management: Traction sections are set at the beginning and end of the roll-to-roll flexible sheet material, and the traction sections are covered with protective films. The product section in the middle of the roll material is not covered with a protective film. A transition section is set between the traction section and the product section. The transition section is covered with a semi-adhesive protective film. The adhesion of the semi-adhesive protective film is 30%-50% of the adhesion of the protective film in the traction section, and the tension of the transition section gradually changes from the tension of the traction section to the free state of the product section. S2, Inner layer etching and tension dynamic control: The roll material is passed through the etching line at a set linear speed, and the etching tension is dynamically set according to the radial position of the roll material on the roll to maintain a constant tensile strain rate on the substrate surface; the cleaning section after etching maintains the same tension as the etching section, and a slow-release section is set after cleaning to gradually reduce the tension of the roll material from the etching tension to below 0.5 kg in the slow-release section. S3. Exposure and Development: Expose the roll material to control the transverse and longitudinal bilateral expansion and contraction ranges of the roll material substrate. Before exposure, measure the actual expansion and contraction rate of each measuring point of the roll material, calculate the substrate deformation matrix, and adjust the exposure process parameters and substrate adsorption state based on the deformation matrix to match the exposure pattern with the actual deformation state of the roll material. After exposure, develop to obtain the circuit pattern. S4. Cover film pressing: The roll is pressed using a selected vacuum press; S5. Curing after lamination: The roll material after lamination and covering film is baked and cured.

[0007] Furthermore, in step S3, the exposure process employs a roll-to-roll LDI laser direct writing method to digitally expose the roll material. Based on the deformation matrix, the digital graphic scaling ratio, rotation compensation angle, zoned exposure parameters, and substrate adsorption vacuum distribution of the LDI exposure machine are adjusted in real time to ensure precise matching between the laser-output exposed graphic and the actual deformation state of the roll material. After exposure, development processing is performed. This digital exposure method, through real-time graphic scaling and matrix compensation, reduces the residual pitch deviation caused by the inability to fully correct substrate deformation in film contact exposure from 3-5 μm to less than 1 μm.

[0008] Furthermore, in step S3, the exposure process uses a standard glass film to align and expose the roll material. Based on the deformation matrix, the feed tension and vacuum distribution of the roll material are adjusted to correct the substrate deformation, ensuring that the dimensions of the roll material substrate match and align with the standard glass film. After alignment, exposure is performed, followed by development to obtain the circuit pattern. This contact exposure method, through substrate tension-vacuum synergistic correction, reduces the systematic pitch deviation within the board surface caused by non-uniform deformation of the roll material from 7-10 μm to within 3 μm.

[0009] Furthermore, the protective film of the traction section is 8±1m in length and made of PET. This length has been experimentally verified to balance roll diameter variations and tension fluctuations: if it is too short, it cannot effectively buffer the tension impact during unwinding and winding; if it is too long, it increases material costs and the complexity of the process connection between the traction section and the product section. The traction section and the product section are fixed together with easy-tear adhesive, and the tension of the traction section is controlled at 2-4kg.

[0010] Furthermore, the transition section is 1-2m long. A semi-adhesive protective film is applied to the transition section, with an adhesion strength of 30%-50% of that of the protective film on the traction section. This adhesion strength range has been experimentally verified to provide moderate traction protection while allowing controllable micro-slippage at the product section edge during stress release, preventing interface stress concentration caused by abrupt mechanical changes between the traction section and the product section. The tension in the transition section gradually changes from the tension in the traction section to the free state of the product section, forming a stress buffer gradient to prevent micro-cracks or pitch dispersion caused by plastic deformation at the interface.

[0011] Furthermore, the dynamic setting of etching tension based on the radial position of the roll material on the reel, as described in S2, includes: when the unwinding reel diameter decreases from an initial value (e.g., 600 mm) to a final value (e.g., 200 mm), the etching tension is dynamically adjusted from a first tension value (e.g., 4 kg) to a second tension value (e.g., 2 kg) according to a set gradient (linear gradient or exponentially decaying gradient), so that the substrate surface maintains a constant tensile strain rate. This dynamic coupling mechanism solves the problem of uneven strain rate caused by changes in roll diameter under a fixed tension setting, reducing the systematic pitch deviation at different roll diameter positions after etching from 5-8 μm to within 2 μm.

[0012] Furthermore, in step S2, the cleaning section after etching maintains the same tension as the etching section to prevent sudden tension changes during cleaning from causing a redistribution of the released etching stress. After cleaning, a release section is installed, with a length ≥2m and a release rate ≤1.5kg / m, gradually reducing the coil tension from the etching tension to below 0.5kg. This release process avoids elastic rebound deformation caused by free winding, ensuring that the stress released during the etching stage enters subsequent processes in a stable state.

[0013] Furthermore, in S3, the lateral bilateral expansion and contraction range is defined as the difference between X1 and X2 ≤ 0.08‰, and the longitudinal bilateral expansion and contraction range is defined as the difference between Y1 and Y2 ≤ 0.08‰, where X1 and X2 are the expansion and contraction rates at two transverse measurement points of the coil substrate, and Y1 and Y2 are the expansion and contraction rates at two longitudinal measurement points of the coil substrate. By controlling the difference in expansion and contraction on both sides of the substrate, the systematic deviation of the pitch within the board surface caused by the non-uniform deformation of the coil is reduced from 7-10μm to within 3μm.

[0014] Furthermore, when using standard glass film contact exposure, in step S3, before exposure, the actual expansion and contraction rates of each measuring point (X1, X2, Y1, Y2, and the center point) of the roll substrate are measured, and the deformation matrix of the substrate is calculated. This deformation matrix includes scaling components, rotational components, and trapezoidal distortion components. Based on this deformation matrix, the feed tension of the roll and the adsorption vacuum distribution of the exposure machine are adjusted (to compensate for localized adhesion differences caused by trapezoidal distortion) to ensure that the actual dimensions of the roll substrate match and align with the dimensions of the standard film.

[0015] Furthermore, when using standard glass film contact exposure and multiple sets of films are required for online operation for the same part number, the X1 and X2 ranges of all roll substrates are ≤0.1‰, and the Y1 and Y2 ranges are ≤0.1‰. This control ensures the consistency of expansion and contraction between different rolls during plate changes, avoiding dimensional jumps between batches due to film differences.

[0016] Furthermore, the difference between the expansion and contraction of the roll substrate and the standard expansion and contraction is ≤0.1‰. The deviation of the standard value controls the overall scaling ratio and prevents exposure pattern distortion caused by trapezoidal distortion.

[0017] Furthermore, during the engineering design phase, the finger placement direction is defined as along the transverse (TD) direction of the substrate. Because the flexible circuit board substrate is anisotropic, its transverse expansion / contraction rate (typically 0.47‰-0.54‰) is lower than its longitudinal expansion / contraction rate (typically 0.53‰-0.64‰). Arranging the fingers along the TD direction reduces the pitch range after the cover film is laminated from 0.028mm to 0.012mm.

[0018] Furthermore, a lamination process is included before S2. The hardness of the lamination roller is controlled at 62±2 degrees, and a hardness check is performed every three days. The roller hardness directly affects the uniformity of the adhesion between the dry film and the substrate; if the hardness deviates from the control range, it will lead to uneven dry film thickness, which in turn will cause differences in the side etching of the circuit after exposure and pitch variation.

[0019] Furthermore, the laminating roller adopts a partitioned design with different hardness levels in the middle and edge areas. The hardness of the edge area is lower than that of the middle area, and the width of the edge area accounts for 10%-15% of the total width of the roller. Preferably, the hardness of the middle area is 62±2 degrees, and the hardness of the edge area is 58±2 degrees. This partitioned design compensates for uneven bonding pressure caused by edge effects in the width direction of the roll material, reducing the difference in dry film thickness in the width direction from ±3μm to ±1μm, thereby reducing differences in side etching and pitch variation after exposure.

[0020] Furthermore, the screening criteria for vacuum presses in S4 are: the pitch change range before and after pressing for the same part number is ≤0.03mm. This screening criterion ensures that the mechanical precision of the equipment meets the requirements; machines nearing the warning threshold are suspended and repaired.

[0021] Furthermore, the line speed in S2 is 3 m / min. This line speed is matched with the dynamic etching tension to ensure uniform reaction time between the etching solution and the copper layer, avoiding insufficient etching due to excessively fast line speed or excessive lateral etching due to excessively slow line speed.

[0022] Furthermore, the present invention also includes S6, online detection and feedback closed-loop control: an online measuring device (such as a laser length measuring instrument or a vision inspection system) is set at the etching line exit and / or after the cover film is pressed to measure the substrate shrinkage rate and / or pitch dimension in real time; when the measured value deviates from the target value by more than a set threshold (such as ±0.01mm), the parameters of subsequent processes (such as the digital graphic scaling rate, exposure scaling rate, pressing temperature or curing time of the LDI exposure machine) are automatically adjusted. This closed-loop control upgrades the traditional "offline inspection + manual adjustment" to "online detection - real-time feedback - automatic adjustment", realizing the leap from batch-level control to PNL-level control.

[0023] Furthermore, this invention also includes establishing a cross-process coupling compensation database. This database contains compensation values ​​(such as Mark compensation value, Total compensation value, and LDI digital scaling compensation value) for different stacking structures (2+1, 1+2+1, 2+2, 2+2+2), different finger layout directions (TD / MD), and different pitch ranges (≤30mm, 30-50mm, ≥50mm). The database has a feedback update mechanism; for every 1000 PNLs produced, the compensation value is automatically corrected based on measured pitch data. When a new project is put into production, the database compensation value is directly called, eliminating the need for repeated trial production verification and shortening the process development cycle.

[0024] The traction film in S1 is a composite material (such as a PI-PET composite film with a specific ratio) whose longitudinal elastic modulus difference from that of the copper-PI composite substrate of the product section is ≤10%, and the thickness-to-roll diameter ratio of the traction film is controlled within the range of 1:500 to 1:1000. This modulus matching design ensures that the deformation of the traction section and the product section is coordinated during the winding and unwinding process, avoids interfacial shear stress caused by modulus mismatch, and further reduces pitch dispersion at the junction of the traction section and the product section.

[0025] Compared to the existing single strategies of "full-process film loading" or "full-process film-free", this invention proposes a segmented stress management method of "first and last traction film + middle product section film-free", which decouples roll tension control from etching stress release for the first time. At the same time, while existing roll control only focuses on overall expansion and contraction, this invention introduces a collaborative control dimension of transverse bilateral range (X1-X2) and longitudinal bilateral range (Y1-Y2) to incorporate the systematic deviation caused by non-uniform deformation of the roll into the process control system. In addition, by using real-time scaling and matrix compensation of graphics in LDI digital exposure or substrate tension-vacuum collaborative correction in traditional glass film contact exposure, differentiated process control paths are established for different exposure equipment. Through cross-process coupling of TD direction layout, roller hardness monitoring, press screening, and 160℃ / 2H baking parameters, a systematic control framework for pitch size stability in RTR process is established, which improves CPK from <1.0 to ≥1.33, achieving high-precision control of pitch size in RTR process. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the roll-to-roll process for the flexible circuit board of the present invention.

[0027] Figure 2 This is a schematic diagram of the segmented structure of the roll material, including the beginning and end traction sections, the transition section, and the intermediate product section.

[0028] Figure 3 This is a schematic diagram showing the distribution of transverse and longitudinal expansion and contraction measurement points on the substrate of the present invention.

[0029] Figure 4 This is a schematic diagram of the roll diameter-tension dynamic coupling control curve of the present invention.

[0030] Figure 5 This is a schematic diagram of the tension relief section after etching in this invention.

[0031] Figure 6 This is a comparison chart of pitch changes under different baking conditions according to the present invention.

[0032] Figure 7This is a comparison chart of the pitch range between TD-direction and MD-direction typesetting in this invention.

[0033] Figure 8 This is a system block diagram of the online detection feedback closed-loop control of the present invention. Detailed Implementation

[0034] To further explain the technical solution of the present invention, in conjunction with... Figures 1 to 8 The present invention will now be described in detail through specific embodiments.

[0035] Example 1: Manufacturing of 2+2 stacked Pitch products (standard glass film contact exposure) Using a 2+2 stacked substrate, with the fingers located in layers L2 / L3, the finger layout direction is defined as along the TD direction of the substrate during the engineering design phase.

[0036] S1. Pre-treatment: A traction section, 8.2m long, is set at the beginning of the roll and covered with PET protective film; the traction section at the end of the roll is 7.9m long; the entire length of the product section in the middle is not covered with film. A transition section, 1.5m long, is set between the traction section and the product section, covered with a semi-adhesive protective film, with an adhesion force of 40% of that of the PET protective film in the traction section. The traction section and the product section substrate are fixed together with easy-tear adhesive. The tension of the traction section is controlled at 3kg, and the tension of the transition section gradually decreases from 3kg to 0.5kg, leaving the product section in a free state.

[0037] S2, Inner Layer Etching: Linear speed 3m / min. The initial roll diameter is 600mm, and the etching tension is set to 4kg. As etching progresses, the roll diameter gradually decreases, and the etching tension is dynamically adjusted linearly. When the roll diameter drops to 200mm, the etching tension drops to 2kg. A tension meter is used for daily inspection before the start of each shift, and a "Tension Inspection" label is affixed to the equipment. The first piece etched uses a sheet material to verify parameters. Due to differences in process paths, this sheet material exhibits outliers and is isolated and scrapped, not included in mass production batches.

[0038] The cleaning section after etching maintains the same tension as the etching section (based on the dynamic tension value corresponding to the current roll diameter position). After cleaning, the roll enters the release section, which is 2.5m long and has a release rate of 1.2kg / m, gradually reducing the roll tension from the current etching tension to 0.3kg.

[0039] Film pressing process: The hardness of the middle area of ​​the film pressing roller is 63 degrees, and the hardness of the edge area (accounting for 12% of the total width of the roller) is 59 degrees, both of which are within the control range; the hardness of this roller is checked every three days and recorded in the "Film Pressing Roller Hardness Check Sheet".

[0040] S3. Exposure and Development: The roll material is exposed for alignment using a standard glass film. The transverse and longitudinal bilateral expansion and contraction ranges of the roll material substrate are controlled. Before exposure, the roll material expansion and contraction rates are measured: X1=0.02‰, X2=0.06‰, with a transverse bilateral range of 0.04‰; Y1=0.03‰, Y2=0.08‰, with a longitudinal bilateral range of 0.05‰, all meeting the requirement of ≤0.08‰. The difference between the roll material expansion and contraction and the standard expansion and contraction is 0.03‰, meeting the requirement of ≤0.1‰. Based on the above measurement data, the roll material deformation matrix is ​​calculated: scaling component 0.05‰, rotation component 0.02°, and trapezoidal distortion component 0.03‰. Based on this deformation matrix, the roll material feeding tension and the adsorption vacuum distribution of the exposure machine are adjusted. The adsorption vacuum distribution is adjusted so that the vacuum degree in the edge area is 5% higher than that in the center area, matching the actual size of the roll material substrate with the size of the standard glass film. After alignment, exposure is performed, followed by development to obtain the circuit pattern.

[0041] S4. Cover film lamination: Select the selected No. 11 vacuum press (for the same part number, verify that the pitch difference before and after lamination is 0.0135mm, which meets the requirement of ≤0.03mm).

[0042] S5. Post-lamination curing: Curing the roll material after lamination and covering with film. S6. Online Inspection and Feedback Closed-Loop Control: A laser length measuring instrument is installed at the etching line exit to measure the substrate's expansion and contraction rate in real time; a vision inspection system is installed after the cover film is laminated to measure the pitch dimension in real time. When the measured pitch value deviates from the target value by more than ±0.01mm, the curing temperature of the subsequent exposure machine is adjusted.

[0043] Finished product measurement: 20 PNLs are produced continuously, and the pitch dimension of 16 PCS is measured for each PNL. The range is 0.022mm, and CPK=1.38, which meets the requirement of a high-precision connector tolerance of ±0.03mm.

[0044] Example 2: Manufacturing of 2+2 stacked Pitch products (roll-to-roll LDI laser direct writing exposure) Using a 2+2 stacked substrate, with the fingers located in layers L2 / L3, the finger layout direction is defined as along the TD direction of the substrate during the engineering design phase.

[0045] S1. Pretreatment: Same as in Example 1.

[0046] S2, Inner layer etching: Same as in Example 1.

[0047] S3. Exposure and Development: Roll-to-roll LDI laser direct writing is used for digital exposure of the roll material. The transverse and longitudinal bilateral expansion and contraction ranges of the roll material substrate are controlled. Before exposure, the roll material expansion and contraction rates are measured: X1=0.02‰, X2=0.06‰, transverse bilateral range is 0.04‰; Y1=0.03‰, Y2=0.08‰, longitudinal bilateral range is 0.05‰, all meeting the requirement of ≤0.08‰. The difference between the roll material expansion and contraction and the standard expansion and contraction is 0.03‰, meeting the requirement of ≤0.1‰. Based on the above measurement data, the roll material deformation matrix is ​​calculated: scaling component 0.05‰, rotation component 0.02°, trapezoidal distortion component 0.03‰. Based on the deformation matrix, the digital graphic scaling ratio of the LDI exposure machine is adjusted in real time to 100.005%, the rotation compensation angle is 0.02°, the zoned exposure parameters (the exposure energy in the edge area is 3% higher than that in the center area) and the substrate adsorption vacuum distribution (the vacuum degree in the edge area is 5% higher than that in the center area) so that the laser output exposure pattern is accurately matched with the actual deformation state of the roll material; after exposure, development processing is performed to obtain the circuit pattern.

[0048] S4. Cover film pressing: Same as in Example 1.

[0049] S5. Curing after pressing: Same as in Example 1.

[0050] S6. Online Inspection and Feedback Closed-Loop Control: A laser length measuring instrument is installed at the etching line exit to measure the substrate expansion and contraction rate in real time; a vision inspection system is installed after the cover film is laminated to measure the pitch dimension in real time. When the measured pitch value deviates from the target value by more than ±0.01mm, the digital graphic scaling rate or curing temperature of the subsequent LDI exposure machine is automatically adjusted.

[0051] Finished Product Measurement: Continuous production of 20 PNLs, with 16 pieces per PNL having their pitch dimensions measured. The range was 0.018 mm, and the CPK was 1.45, meeting the high-precision connector tolerance requirement of ±0.03 mm. Compared to the glass film contact exposure in Example 1, the finished product pitch range of the LDI version was further reduced from 0.022 mm to 0.018 mm, and the CPK increased from 1.38 to 1.45.

[0052] Example 3: Database Establishment with Different Structures For different substrate types, a pitch compensation database is established for different stack configurations (2+1, 1+2+1, 2+2, 2+2+2). For example, for a 2+2 stack configuration, finger TD direction, pitch size of 30-50mm, and CPK≥1.33, the Mark compensation value is set to 10μm, and the Total compensation value is set to 10μm. The LDI digital scaling compensation value is set to 5μm. When a new project is put into production, the compensation values ​​in the database can be directly called, eliminating the need for repeated trial production verification and shortening the process development cycle.

[0053] The database has a feedback update mechanism: for every 1000 PNLs produced, the Mark compensation value and Total compensation value are automatically adjusted based on the statistical distribution of the measured pitch data. For example, if the average measured pitch value of three consecutive batches of 1000 PNLs deviates by +0.008mm, the Mark compensation value is automatically adjusted from 10μm to 18μm, and the LDI digital scaling compensation value is adjusted from 5μm to 13μm, achieving adaptive optimization of the database.

[0054] Comparative test Four control groups were set up for verification: Control group A (traditional process): The entire product section is covered with a carrier film, PET film is used, the overall expansion and contraction is controlled to be ≤0.2‰, the layout is in the MD direction, baked at 120℃ / 4H, the press is used randomly, and the etching tension is fixed at 3kg.

[0055] Control group B (partially improved process): The product section carrier film was removed but there was no transition section, the etching tension was fixed, the glass film was not controlled, the bilateral expansion and contraction of the substrate was not controlled, the TD direction layout was not used, the constant temperature baking was 160℃ / 2H, and the screening press was not used.

[0056] Experimental Group C (Invention - Glass Film): Fully adopts all the technical features of this invention, and S3 adopts standard glass film contact exposure.

[0057] Experimental Group D (Invention-LDI): Fully adopts all the technical features of this invention, and S3 adopts roll-to-roll LDI laser direct writing digital exposure.

[0058] Each batch of 20 PNLs was produced, and the pitch dimensions were measured. The results are as follows:

[0059] Experimental results show that control group B, due to the adoption of some improvement measures, achieved a higher CPK, but it did not reach the industry high standard of 1.33. Experimental group C, through substrate tension-vacuum synergistic correction under glass film contact exposure, stabilized the finished product pitch range within 0.03mm, increasing CPK to above 1.33. Experimental group D, through real-time image scaling and matrix compensation in LDI digital exposure, further compressed the residual pitch deviation, achieving a CPK above 1.42, an improvement of approximately 0.1 compared to experimental group C. In particular: The transition section eliminates pitch dispersion at the junction of the traction section and the product section, thus completely eliminating outlier phenomena in the first piece and the roll tail data. Dynamic coupling control of roll diameter and tension reduces the systematic deviation of pitch at different roll diameter positions after etching from 5-8μm to less than 2μm; LDI digital exposure improves the matching accuracy between the exposure pattern and the substrate deformation state to within 1μm through real-time scaling and matrix compensation. Controlling the lateral and longitudinal expansion and contraction differences of the coil substrate and aligning the coil for exposure can avoid exposure pattern distortion. Online detection feedback closed-loop control further improves the stability of PNL-level pitch within a batch.

[0060] The above embodiments and figures are not intended to limit the product form and style of the present invention. Any appropriate changes or modifications made by those skilled in the art should be considered as not departing from the patent scope of the present invention.

Claims

1. A method for controlling pitch dimension stability in FPC roll-to-roll manufacturing process, characterized in that: Includes the following steps: S1. Pre-treatment: Traction sections are set at the beginning and end of the roll-to-roll flexible sheet material, and the traction sections are covered with protective film. The product section in the middle of the roll material is not covered with a protective film. A transition section is set between the traction section and the product section. The transition section is covered with a transition film with less adhesion than the protective film, and the tension of the transition section gradually changes from the tension of the traction section to the free state of the product section, forming a stress buffer gradient. S2, Inner Layer Etching: The roll material is passed through the etching line at a set linear speed. The etching tension is dynamically set according to the radial position of the roll material on the spool to maintain a constant tensile strain rate on the substrate surface. The cleaning section after etching maintains the same tension as the etching section. After cleaning, a release section is set to gradually reduce the tension of the roll material from the etching tension to below 0.5 kg within the release section. S3. Exposure and Development: Expose the roll material to control the transverse and longitudinal bilateral expansion and contraction ranges of the roll material substrate. Before exposure, the actual shrinkage rate of each measuring point of the roll material is measured, the substrate deformation matrix is ​​calculated, and the exposure process parameters and substrate adsorption state are adjusted based on the deformation matrix to match the exposure pattern with the actual deformation state of the roll material. After exposure, development is performed to obtain the circuit pattern; S4. Cover film pressing: The roll is pressed using a selected vacuum press; S5. Curing after lamination: The roll material after lamination and covering film is baked and cured.

2. The method for controlling pitch dimension stability in the FPC roll-to-roll manufacturing process as described in claim 1, characterized in that: The exposure described in S3 uses roll-to-roll LDI laser direct writing to digitally expose the roll material; the digital graphic scaling ratio, rotation compensation angle, zoned exposure parameters, and substrate adsorption vacuum distribution of the LDI exposure machine are adjusted in real time according to the deformation matrix to ensure that the exposed graphic output by the laser is precisely matched with the actual deformation state of the roll material; after exposure is completed, development processing is performed.

3. The method for controlling pitch dimension stability in the FPC roll-to-roll manufacturing process as described in claim 1, characterized in that: The exposure described in S3 uses a standard glass film to align and expose the roll material; the feed tension and adsorption vacuum distribution of the roll material are adjusted based on the deformation matrix to correct the substrate deformation, so that the size of the roll material substrate matches and aligns with the standard glass film. After alignment, exposure is performed, followed by development to obtain the circuit pattern.

4. The method for controlling pitch dimension stability in the FPC roll-to-roll manufacturing process as described in claim 1, characterized in that: The etching tension is dynamically set according to the radial position of the roll on the reel, including: when the diameter of the unwinding reel decreases from the initial value to the final value, the etching tension is dynamically adjusted from the first tension value to the second tension value according to the set gradient, wherein the set gradient is a linear gradient or an exponential decay gradient.

5. The method for controlling pitch dimension stability in the FPC roll-to-roll manufacturing process as described in claim 1, characterized in that: The protective film of the traction section in S1 is 8±1m long and made of PET. The traction section and the product section are fixed together by easy-tear adhesive. The tension of the traction section is controlled at 2-4kg. The adhesion of the transition friction of the transition section is 30%-50% of the adhesion of the protective film of the traction section.

6. The method for controlling pitch dimension stability in the FPC roll-to-roll manufacturing process as described in claim 1, characterized in that: The lateral bilateral expansion and contraction range mentioned in S3 is the difference between X1 and X2 ≤ 0.08‰, and the longitudinal bilateral expansion and contraction range is the difference between Y1 and Y2 ≤ 0.08‰, where X1 and X2 are the expansion and contraction rates of the two transverse measuring points of the roll substrate, and Y1 and Y2 are the expansion and contraction rates of the two longitudinal measuring points of the roll substrate; the difference between the expansion and contraction of the roll substrate and the standard expansion and contraction is ≤ 0.1‰.

7. The method for controlling pitch dimension stability in the FPC roll-to-roll manufacturing process as described in claim 1, characterized in that: During the engineering design phase, the direction of finger layout is defined as the transverse direction along the substrate.

8. The method for controlling pitch dimension stability in the FPC roll-to-roll manufacturing process as described in claim 1, characterized in that: Before S2, there is also a pressing process: pressing is done with pressing rollers, which are designed with partitioned hardness in the middle area and hardness in the edge area. The hardness of the edge area is lower than that of the middle area, and the width of the edge area accounts for 10%-15% of the total width of the roller.

9. The method for controlling pitch dimension stability in the FPC roll-to-roll manufacturing process as described in claim 1, characterized in that: It also includes S6, online detection and feedback closed-loop control: an online measuring device is set at the etching line exit and / or after the cover film is pressed to measure the substrate shrinkage rate and / or pitch size in real time; when the measured value deviates from the target value by more than the set threshold, the parameters of subsequent processes are automatically adjusted.

10. The method for controlling pitch dimension stability in the FPC roll-to-roll manufacturing process as described in claim 1, characterized in that: It also includes establishing a cross-process coupling compensation database, which contains compensation values ​​for different stacking structures, different finger layout directions, and different pitch ranges, and has a feedback update mechanism that automatically corrects the compensation values ​​based on measured pitch data after each preset production quantity is accumulated.

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