Copper foil pressing process for rigid-flex printed circuit board with gasket

Abstract

The invention discloses a copper foil pressing process for a rigid-flex board with a gasket, and relates to the technical field of copper foil pressing, and the process comprises the following steps: S1, carrying out windowing processing on PP2 close to one side of a flexible region, and keeping PP1 close to one side of a copper foil in a non-windowing state; s2, a PTFE glue blocking gasket matched with the PP2 windowing area is prepared; s3, carrying out lamination riveting and lamination according to a preset sequence; s4, adopting a double mask protection mode; s5, processing an annular presplitting groove in the position, corresponding to the flexible area cover, of the exposed PP1 surface after etching; s6, monitoring the size of the micro gap in real time through a laser displacement sensor, and feeding back and adjusting temperature control parameters; and S7, the PTFE glue blocking gaskets are guided and collected from the micro gaps through the guide channels. According to the method, the pre-splitting groove is matched with a directional force coupling uncovering mode, and an existing uncovering scheme of blind groove laser milling and manual prying is replaced. And the pre-splitting groove provides an accurate path for fracture, so that the problems of irregular fracture and burr generation of the PP protective layer can be effectively avoided.

Description

Technical Field

[0001] This invention relates to the field of copper foil lamination technology, and in particular to a process for laminating copper foil onto a rigid-flexible bonded plate with added gaskets. Background Technology

[0002] Rigid-flex PCBs, as a novel electronic interconnect material that combines the load-bearing capacity of rigid substrates with the bending characteristics of flexible substrates, are widely used in high-end electronic fields such as aerospace, consumer electronics, and automotive electronics. The copper foil lamination process is one of the core steps in the fabrication of rigid-flex PCBs, and its process stability and precision directly determine the circuit conductivity reliability, structural load-bearing stability, and long-term service life of the rigid-flex PCB.

[0003] In the process of laminating copper foil onto rigid-flex boards, the flexible area needs to retain excellent bendability, while the rigid area needs to have stable load-bearing and support capabilities. Therefore, the lamination process requires addressing two core issues: precise control of the height difference in the flexible area and adhesive protection. In existing technologies, to prevent adhesive from overflowing into the flexible area and damaging its bending performance during lamination, a common adhesive protection solution is to place gaskets at corresponding positions in the flexible area. The specific process generally includes key steps such as PP windowing, gasket preparation and application, lamination, and exposing the flexible area by opening the cover.

[0004] However, existing technologies mostly employ two methods to open the cover: laser milling of blind grooves or manual prying. Laser milling requires strict control of the milling depth, resulting in an extremely narrow process window; even slight deviations can easily damage the flexible substrate. Manual prying, on the other hand, easily leads to irregular breakage and burrs in the PP protective layer, and is highly prone to scratching the surface of the cover film. Furthermore, manual operation is inefficient and unsuitable for large-scale mass production. In addition, the gasket and cover film interface in existing processes are prone to adhesion due to molecular adsorption, often resulting in gasket residue after opening. This residue not only interferes with subsequent processes but the cleaning process can also further damage the board structure, reducing product yield. Summary of the Invention

[0005] The purpose of this invention is to provide a process for laminating copper foil onto a rigid-flexible bonded board with added gaskets, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a process for laminating copper foil onto a rigid-flexible bonded board with a gasket, comprising the following steps: S1. Perform window opening processing on PP2 on the side closer to the flexible area, while keeping PP1 on the side closer to the copper foil in a closed state. S2. Prepare a PTFE adhesive barrier pad that is compatible with the window opening area of ​​PP2. After pressing the cover film onto the flexible area of ​​the flexible core board, attach the PTFE adhesive barrier pad to the surface of the cover film. The total thickness of the PTFE adhesive barrier pad and the cover film is compatible with the window opening thickness of PP2. S3. Perform stacking and lamination in a preset order to fill the window area of ​​PP2 with PTFE adhesive barrier gasket; S4. A dual mask protection method is used to selectively etch away the copper of the flexible area cover, exposing the underlying PP1 protective layer. S5. A ring-shaped pre-crack groove is machined on the surface of PP1 exposed after etching, corresponding to the flexible area cover position. The ring-shaped pre-crack groove is provided with at least two stress relief branch grooves along the circumferential direction. S6. In the temperature control equipment in the inert gas atmosphere, the ultrasonic vibration is transmitted to the interface between the PTFE resist gasket and the cover film through the flexible conductive medium by gradient temperature control and low frequency ultrasound. The difference in the thermal expansion coefficients of the two is used to form a uniform micro gap. At the same time, the micro gap size is monitored in real time by a laser displacement sensor and the temperature control parameters are adjusted accordingly. S7. Based on the pre-cracked groove and stress relief branch groove processed in step S5, the annular array nozzle with elastic sealing ring is aligned and attached to the annular pre-cracked groove. The PP1 is driven to break along the pre-cracked groove and stress relief branch groove by a coordinated method of pulsed airflow and reverse negative pressure adsorption. At the same time, the PTFE adhesive pad is guided and collected from the micro gap through the guide channel.

[0007] Preferably, in step S1, the windowing process of PP2 adopts CNC adaptive milling, and the window diameter and hole density are dynamically adjusted according to the regional characteristics of the rigid-flex plate. The rigid-flex edge area adopts small-diameter high-density windowing, and the flexible area center adopts large-diameter low-density windowing. The windowing area corresponds to the flexible area position of the flexible core plate, and the window shape is completely adapted to the shape of the PTFE resist gasket.

[0008] Preferably, in step S2, the preparation of the PTFE adhesive barrier includes: Picosecond laser machine is used to laser mill holes in PTFE sheet to form positioning holes and clearance grooves that are compatible with the positioning holes of flexible core board and circuit structure. The surface of PTFE resist gasket is treated with plasma to improve the bonding stability with cover film. The cover film is pressed onto the flexible area of ​​the flexible core board by a high-speed press at a preset temperature and pressure. The PTFE adhesive resist pad is fixed to the surface of the cover film by a vacuum adsorption manual application method. The difference between the total thickness of the PTFE adhesive resist pad and the cover film and the window thickness of PP2 is controlled within ±0.02mm.

[0009] Preferably, in step S3, the sequence of riveting the stacked plates includes: Centered on the flexible core board, a cover film covered with PTFE adhesive pads, a windowed PP2, a windowless PP1, and copper foil are stacked on both sides in sequence. After being aligned and fixed through multiple sets of riveting holes, a segmented temperature-controlled laminator is used for pressing. The pressure distribution on the board surface is monitored in real time during the pressing process.

[0010] Preferably, in step S4, the selective etching with dual mask protection specifically includes: S41. An etch-resistant polyimide physical mask is laminated onto the surface of PP1, exposing only the copper area of ​​the flexible cover. At the same time, photoresist is coated on the copper surface of the cover to form a chemical mask. The etching range is defined by high-precision photolithography development. S42. First, perform low-temperature pre-etching to ensure the etching solution evenly wets the copper surface of the cover; then, perform medium-temperature main etching with ultrasonic stirring to quickly remove most of the copper layer on the cover; finally, perform room-temperature fine etching to remove the remaining copper layer. S43. Use deionized water for ultrasonic cleaning to remove residual etching solution, and then dry with nitrogen gas. Control the nitrogen gas flow rate during the drying process to avoid damaging the PP1 surface.

[0011] Preferably, in step S5, the annular pre-cracked groove is processed by a combination of plasma etching and mechanical micro-milling. The position of the pre-cracked groove is aligned with the edge of the flexible area cover. The depth of the pre-cracked groove is a preset ratio of the thickness of PP1, the width is a preset narrow dimension, and it does not penetrate PP1. The stress relief branch groove is arranged radially along the annular pre-crack groove, with a length that is a preset proportion of the radius of the pre-crack groove, and a depth that is consistent with the pre-crack groove. The included angles of adjacent branch grooves are evenly distributed to disperse stress concentration when the cover is opened.

[0012] Preferably, in step S6, the specific process of the gradient temperature control and low-frequency ultrasound coordination is as follows: S61. In a nitrogen atmosphere temperature control device, the printed circuit board is slowly heated to the preset preheating temperature and kept at that temperature to make the overall temperature of the printed circuit board uniform. S62. Heat to the preset expansion temperature at a constant rate to avoid sudden changes in thermal stress that could damage PP1 or the flexible area. S63. Maintain the above-mentioned preset expansion temperature, attach the flexible conductive medium to the surface of the printed circuit board, apply low-frequency ultrasonic vibration, monitor the micro-gap size in real time through a laser displacement sensor, and automatically adjust the temperature to correct when the gap deviates from the preset range. S64. Cool down at a preset slow rate to the preset stable gap temperature to maintain the stability of the micro-gap.

[0013] Preferably, in step S7, the coordinated opening of the lid is executed using closed-loop control logic based on multi-parameter threshold feedback, specifically including: S71. Precisely align and seal the airflow output structure with the pre-cracked groove. Determine whether the preset sealing threshold is met through sealing detection methods. If it is not met, adjust the parameters until it is qualified. S72. Set the opening driving force threshold according to the pre-crack groove parameters and PP1 characteristics, and adopt the time-series coordinated control of driving force and reverse adsorption force to monitor and dynamically adjust the driving force parameters in real time. S73. Collect stress signals through the stress detection structure, determine whether a preset fracture threshold signal appears, and if the threshold is met, determine fracture and stop the driving force output; if the threshold is not met, adjust the output parameters. S74. Monitor the gasket detachment signal through the detachment detection structure. After confirming that the detachment threshold is met, complete the gasket collection through the preset collection structure.

[0014] Preferably, a closed-loop detection step is included after step S7: The flexible area was inspected using a CCD camera combined with 3D structured light scanning. The inspection included the flatness of the PP1 fracture edge, the residual PTFE adhesive pad, and the cleanliness of the board surface. If residue is detected, adjust the pulse airflow pressure and negative pressure adsorption position according to the location of the residue, and repeat the coordinated opening operation until the test is qualified.

[0015] Preferably, step S7 is followed by a post-opening processing step: First, a plasma cleaner using a mixture of oxygen and argon gas is used to clean the printed circuit board, removing burrs from the broken edges of PP1 and residual adsorbents on the surface. The printed circuit board is then placed in a constant temperature environment under a nitrogen atmosphere for a preset time to release the thermal and mechanical stress generated during the opening process, followed by rinsing with deionized water and vacuum drying.

[0016] The technical effects and advantages of this invention are as follows: (1) This invention replaces the existing laser milling blind groove and manual prying opening schemes by using a pre-fabricated fracture guiding structure (pre-cracked groove) in conjunction with a directional force coupling opening method. The pre-cracked groove provides a precise path for fracture, which can effectively avoid the problem of irregular fracture and burr generation of PP protective layer; at the same time, it eliminates the need for precise laser control of milling depth, solves the defect of laser milling blind grooves that easily damages the flexible substrate, and avoids the risk of scratching the cover film by manual prying, significantly improving the safety and reliability of the opening process; (2) The present invention constructs micro gaps through the synergistic effect of temperature control and vibration, which destroys the molecular adsorption force between the gasket and the cover film, and solves the problem of gasket and cover film adhesion in the existing process; combined with the directional force coupling drive of threshold judgment control, it can ensure that the gasket is detached from the micro gap, avoid the gasket residue from interfering with subsequent processes, and eliminate the residue cleaning step, reducing the secondary damage to the plate structure during the cleaning process. (3) The opening and gasket removal process of the present invention achieves automated collaborative operation through precise structural prefabrication and threshold control logic, which replaces the manual prying method that relies on manual labor in the prior art, improves production efficiency, and can be adapted to the needs of large-scale batch production. At the same time, by avoiding problems such as opening damage and gasket residue, the product scrap caused by process defects is reduced, the production yield of rigid-flex plate is improved, and the production cost is reduced. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the stacked structure of the present invention; Figure 2 This is a schematic block diagram of the process flow of the present invention.

[0018] In the attached image: 100, Copper foil; 200, PP1; 300, PP2; 400, PTFE adhesive barrier; 500, Cover film; 600, Flexible core board. Detailed Implementation

[0019] 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.

[0020] This invention provides, for example Figures 1-2 The process for laminating copper foil onto a rigid-flexible bonded board with added gaskets, as shown, is characterized by including the following steps: S1. Perform window opening processing on the PP2300 side near the flexible area, and keep the PP1200 side near the copper foil 100 in the closed state. S2. Prepare a PTFE adhesive barrier 400 adapted to the window opening area of ​​PP2300. After pressing the cover film 500 onto the flexible area of ​​the flexible core board 600, attach the PTFE adhesive barrier 400 to the surface of the cover film 500. The total thickness of the PTFE adhesive barrier 400 and the cover film 500 is adapted to the window opening thickness of PP2300. S3. Perform stacking and lamination in a preset order to fill the window area of ​​PP2300 with PTFE adhesive barrier gasket 400. S4. A dual mask protection method is used to selectively etch away the copper of the flexible area cover, exposing the underlying PP1200 protective layer. S5. A ring-shaped pre-crack groove is machined on the PP1200 surface exposed after etching, corresponding to the flexible area cover position. The ring-shaped pre-crack groove has at least two stress relief branch grooves along the circumferential direction to provide a fracture path for subsequent cover opening. S6. In the temperature control equipment in the inert gas atmosphere, through the synergistic effect of gradient temperature control and low-frequency ultrasound, the ultrasonic vibration is transmitted to the interface between the PTFE resist gasket 400 and the cover film 500 through the flexible conductive medium. The difference in the thermal expansion coefficients of the two is used to form a uniform micro gap. At the same time, the micro gap size is monitored in real time by a laser displacement sensor and the temperature control parameters are adjusted accordingly. S7. Based on the pre-cracked groove and stress relief branch groove processed in step S5, the annular array nozzle with elastic sealing ring is aligned and attached to the annular pre-cracked groove. The PP1200 is driven to break along the pre-cracked groove and stress relief branch groove by a coordinated method of pulsed airflow and reverse negative pressure adsorption. At the same time, the PTFE adhesive pad 400 is guided and collected from the micro gap through the guide channel to achieve complete exposure of the flexible area.

[0021] In step S1, the window opening process of PP2300 adopts CNC adaptive milling. The opening hole diameter and hole density are dynamically adjusted according to the regional characteristics of the rigid-flex plate. Small-diameter high-density opening is used in the rigid-flex edge area, and large-diameter low-density opening is used in the center of the flexible area. The opening area corresponds to the flexible area position of the flexible core plate 600, and the opening shape is completely adapted to the shape of the PTFE adhesive pad 400.

[0022] Specifically, the design drawings of the rigid-flex PCB are obtained to determine the boundaries of each area. A CNC milling machine equipped with vision positioning is used to perform windowing on the PP sheet. Before processing, the vision positioning module captures the reference points of the sheet and performs precise calibration against the design drawings. The system then automatically identifies the center of the rigid-flex transition zone and the flexible zone, adaptively matching the corresponding aperture and pore density parameters according to the characteristics of different areas. The rigid-flex transition zone uses small-aperture, high-density windows, while the center of the flexible zone uses large-aperture, low-density windows. During milling, the processing status is monitored in real time, and any abnormalities are promptly identified to ensure precise correspondence between the windowed area and the flexible zone, and a perfect fit between the window shape and the 400mm PTFE adhesive resist gasket. Visual comparison is used for final verification, ensuring that the windowing process meets the requirements for subsequent adhesive resisting and lamination. This process, through differentiated windowing design and precise positioning, effectively adapts to the structural requirements of different areas of the rigid-flex PCB, laying the foundation for controlling the height difference during subsequent lamination and pressing.

[0023] In step S2, the preparation of the PTFE adhesive barrier 400 includes: Picosecond laser machine is used to laser mill holes in PTFE sheet to form positioning holes and clearance grooves that are compatible with the positioning holes of flexible core board 600 and circuit structure. The surface of PTFE resist pad 400 is treated with plasma to improve the bonding stability with cover film 500. The cover film 500 is pressed onto the flexible area of ​​the flexible core board 600 by a high-speed press at a preset temperature and pressure. The PTFE adhesive resist pad 400 is fixed to the surface of the cover film 500 by a vacuum adsorption manual application method. The difference between the total thickness of the PTFE adhesive resist pad 400 and the cover film 500 and the opening thickness of the PP2300 is controlled within ±0.02mm.

[0024] Specifically, based on the positioning and circuit structure design drawings of the flexible core board, high-precision laser processing equipment is used to process the PTFE sheet to form suitable positioning holes and clearance grooves. After processing, the surface of the PTFE resist pad 400 is subjected to plasma activation treatment to improve its bonding stability with the cover film 500. Subsequently, the cover film 500 and the flexible core board are laminated using a pressure device, and then the PTFE resist pad 400 is precisely laminated onto the surface of the cover film 500 using a vacuum adsorption lamination method, ensuring that no air bubbles are generated during the lamination process. After lamination, the total thickness of the PTFE resist pad 400 and the cover film 500 is measured to ensure that the difference between it and the PP window depth is controlled within the allowable range. This process, through precise processing and stable lamination design, achieves reliable fabrication of the resist component and effectively avoids the problem of adhesive overflow during subsequent pressing.

[0025] In step S3, the sequence of riveting the stacked plates includes: Centered on the flexible core board 600, a cover film 500 covered with PTFE adhesive resist gasket 400, a windowed PP2300, a windowless PP1200, and a copper foil 100 are stacked on both sides in sequence. After being aligned and fixed through multiple sets of riveting holes, a segmented temperature-controlled laminator is used for pressing. During the pressing process, the pressure distribution on the board surface is monitored in real time to avoid local pressure concentration that could cause the PTFE adhesive resist gasket 400 to shift.

[0026] Specifically, for the rigid-flex PCB structure requirements of the double-sided flexible area, a cover film 500 covered with a PTFE adhesive resist gasket 400, windowed PP, a complete PP, and copper foil 100 are stacked sequentially in a preset order, with the flexible core board as the center. Each layer is precisely aligned using multiple positioning structures, and temporary fixing is used after alignment to ensure no displacement of the layers. The stacked board is then placed in a segmented temperature-controlled pressing machine for pressing. During pressing, the pressure distribution on the board surface is monitored in real time to prevent localized pressure concentration that could cause displacement of the PTFE adhesive resist gasket 400. The segmented temperature control design ensures a stable bond between the layers. After pressing, the board is checked for warping to ensure the PTFE adhesive resist gasket 400 remains in place, guaranteeing the structural stability of the rigid-flex PCB. This process, through precise stacking and stable pressing control, achieves a reliable bond between the layers, improving the overall quality and stability of the product.

[0027] In step S4, the selective etching with dual mask protection specifically includes: S41. An etch-resistant polyimide physical mask is laminated onto the PP1200 surface, exposing only the copper area of ​​the flexible cover. At the same time, photoresist is coated on the copper surface of the cover to form a chemical mask. The etching range is defined by high-precision photolithography development, achieving high-precision etching boundary control. S42. First, perform low-temperature pre-etching to ensure the etching solution evenly wets the copper surface of the cap; then, perform medium-temperature main etching with ultrasonic stirring to quickly remove most of the copper layer on the cap; finally, perform room-temperature fine etching to remove the remaining copper layer and avoid excessive etching that could damage PP1200. S43. Use deionized water for ultrasonic cleaning to remove residual etching solution, and then dry with nitrogen gas. Control the nitrogen gas flow rate during the drying process to avoid damaging the PP1200 surface.

[0028] Specifically, the process begins with precise dual-mask fabrication. First, an etch-resistant physical mask is smoothly bonded to the intact PP surface. After visually aligning the copper boundary of the flexible cap, the physical mask corresponding to the cap copper area is precisely cut and removed, leaving only the non-cap copper areas protected. Next, photoresist is uniformly coated onto the exposed cap copper surface. Precise design data for the cap copper boundary is imported, and exposure is performed using high-precision photolithography equipment. Unexposed photoresist is then removed via a development process, ultimately forming a chemical mask that perfectly matches the etching range, achieving dual precise definition of the etching area. Following this, a three-stage stepped etching process is initiated. The first step involves low-temperature pre-etching, the core purpose of which is to ensure the etching solution smoothly wets the cap copper surface, avoiding etching deviations caused by uneven local etching solution concentration. The second step involves medium-temperature main etching, accelerating the reaction rate by increasing the etching temperature to quickly remove most of the cap copper layer and improve etching efficiency. The third step involves room-temperature fine etching, reducing the etching reaction intensity and precisely removing any remaining cap copper after the main etching, preventing over-etching and damage to the underlying PP protective layer. Immediately after etching, the post-processing stage begins. First, cleaning removes residual etching solution from the board surface to prevent further corrosion of the PP protective layer. Then, drying ensures no moisture remains on the board surface. Finally, resistance testing verifies the removal of the copper cap, while visual inspection checks the accuracy of the etching boundaries and the integrity of the PP protective layer. Resistance testing provides a direct visual assessment of complete copper removal, while visual inspection promptly identifies issues such as etching boundary misalignment and PP layer damage. This process, through precise double-mask definition and a scientifically designed three-stage stepped etching method, achieves thorough and accurate removal of the copper cap while maximizing the protection of the PP protective layer, laying a solid foundation for subsequent processes such as pre-cracked groove fabrication in the flexible area.

[0029] In step S5, the annular pre-cracked groove is processed by a combination of plasma etching and mechanical micro-milling. The position of the pre-cracked groove is aligned with the edge of the flexible area cover. The depth of the pre-cracked groove is a preset ratio of the thickness of PP1200, the width is a preset narrow dimension, and it does not penetrate PP1200. The stress relief branch grooves are arranged radially along the annular pre-crack groove, with a length that is a preset proportion of the radius of the pre-crack groove, and a depth that is consistent with the pre-crack groove. The included angles of adjacent branch grooves are evenly distributed to disperse stress concentration when the cover is opened.

[0030] Specifically, based on the edge coordinates of the flexible cover, an annular pre-cracked groove is fabricated using a combination of plasma etching and mechanical micro-milling. Before processing, the pre-cracked groove's position is calibrated using visual positioning. A shallow groove is first created using plasma etching to prevent PP edge chipping during subsequent mechanical micro-milling. Then, the annular pre-cracked groove is formed along the shallow groove's trajectory using precision mechanical micro-milling. Subsequently, multiple evenly distributed stress-relieving branch grooves are machined radially along the annular pre-cracked groove. The branch grooves have the same depth as the pre-cracked groove and are used to disperse stress concentration during cover opening. After processing, the width and depth of the pre-cracked groove are inspected to ensure it does not penetrate the PP and that there is no edge chipping at the connection between the branch grooves and the annular pre-cracked groove. This process, through precise pre-cracked groove structural design, provides a precise fracture path for subsequent cover opening, improving the reliability of the opening process.

[0031] In step S6, the specific process of gradient temperature control and low-frequency ultrasound coordination is as follows: S61. In a nitrogen atmosphere temperature control device, the printed circuit board is slowly heated to the preset preheating temperature and kept at that temperature to make the overall temperature of the printed circuit board uniform. S62. Heat to the preset expansion temperature at a constant rate to avoid sudden changes in thermal stress that could damage PP1200 or the flexible area. S63. Maintain the above-mentioned preset expansion temperature, attach the flexible conductive medium to the surface of the printed circuit board, apply low-frequency ultrasonic vibration, monitor the micro-gap size in real time through a laser displacement sensor, and automatically adjust the temperature to correct when the gap deviates from the preset range. S64. Cool down at a preset slow rate to the preset stable gap temperature to maintain the stability of the micro-gap and provide continuous operating space for subsequent opening of the cover.

[0032] Specifically, leveraging the difference in thermal expansion characteristics between PTFE and the cover film 500, a micro-gap is constructed using a synergistic effect of temperature control and vibration. First, the sheet material is placed in a temperature-controlled device with an inert gas atmosphere. A flexible conductive medium is then bonded to the sheet surface and connected to a vibration generator. After purging the air from the device, a gradient temperature control program is initiated. The material sequentially passes through a preheating section to ensure uniform temperature across the entire sheet; a heating section to create a significant expansion difference between PTFE and the cover film 500; a heat-insulating vibration section to disrupt molecular adhesion through low-frequency vibration and monitor the micro-gap size in real time. Temperature is dynamically adjusted based on the monitoring results to ensure gap stability; and finally, a micro-cooling section maintains micro-gap stability. By monitoring the uniformity and adhesion of the micro-gap, it is ensured that there is no significant adhesion between PTFE and the cover film 500, providing sufficient space for subsequent gasket removal. This process, through precise temperature control and vibration synergistic design, fundamentally solves the adhesion problem between the gasket and the cover film 500, ensuring efficient subsequent opening of the cover.

[0033] In step S7, the collaborative opening of the lid is executed using closed-loop control logic based on multi-parameter threshold feedback, specifically including: S71. Align the annular array nozzle with elastic sealing ring with the annular pre-cracked groove concentrically. After compressing the elastic sealing ring to the preset compression amount, check the sealing status through the air tightness tester to determine whether the leakage rate is lower than the preset sealing threshold. If the threshold is not reached, adjust the sealing ring compression amount or the nozzle alignment accuracy until the sealing requirements are met. S72. Based on the pre-cracked groove parameters and the material characteristics of PP1200, set the peak pressure threshold range of the pulse airflow, introduce dry inert gas into the nozzle, adopt the timing control of the pulse airflow and the negative pressure adsorption peak synchronously, monitor the actual peak pressure of the pulse airflow in real time, and maintain the stable output of pulse parameters by dynamically adjusting the gas supply pressure. S73. During the bidirectional force coupling process, stress signals are collected in real time by stress sensors attached to the surface of PP1200 to determine whether a preset stress mutation value or fracture threshold has occurred. If the mutation value is detected, it is determined that PP1200 has fractured along the pre-crack groove and stress release branch groove, and the pulse airflow pressurization is stopped. If it is not detected, the pulse period is extended until the fracture threshold is reached or the maximum safe pressurization number limit is triggered. S74. The airflow sensor in the guide channel monitors the gasket passing signal in real time to determine whether the preset detachment confirmation threshold is met, and confirms that the PTFE adhesive barrier gasket 400 is completely detached from the micro gap; then the detached gasket is guided to the sealed collection box through the inclined guide channel, and the buffer pad in the collection box avoids damage to the gasket.

[0034] Specifically, the collaborative opening process employs threshold judgment logic control to ensure precise and reliable operation. First, the airflow output structure is precisely aligned and sealed with the pre-splitting groove. A seal detection method determines whether a preset sealing threshold is met; if not, parameters are adjusted until acceptable. Then, based on the pre-splitting groove parameters and PP material characteristics, an opening driving force threshold range is set. A timing control method synchronizing the peak values ​​of driving force and reverse adsorption force is used to monitor and dynamically adjust the driving force parameters in real time. During force coupling, a stress detection structure collects stress signals to determine if a preset fracture threshold signal has appeared. If the threshold is met, PP fracture is detected, and driving force output stops; otherwise, parameters are adjusted, and operation continues. Finally, a detachment detection structure monitors the gasket detachment signal. Once the detachment threshold is confirmed, a preset collection structure collects the gasket. This process, through full-process threshold control, achieves precise coordination between opening and gasket detachment, avoiding issues such as sheet damage and gasket residue.

[0035] The process includes a closed-loop detection step following step S7. The flexible area was inspected using a CCD camera combined with 3D structured light scanning. The inspection included the flatness of the PP1200 fracture edge, the residue of the PTFE adhesive pad 400, and the cleanliness of the board surface. If residue is detected, adjust the pulse airflow pressure and negative pressure adsorption position according to the location of the residue, and repeat the coordinated opening operation until the test is qualified.

[0036] Specifically, after opening the lid, a comprehensive inspection of the flexible area is conducted using a combination of visual inspection and 3D scanning to ensure that the flexible area is free of gasket residue, burrs, and damage, providing a clean surface for subsequent processes. Before inspection, the board is fixed on the inspection platform and the platform's flatness is adjusted. The flexible area is then fully covered by a visual inspection system to identify any residual foreign objects or excessive burrs. Suspected abnormal areas are precisely verified using 3D scanning equipment. If residue issues are detected, the airflow output and adsorption position parameters are adjusted according to the residue location, and the lid-opening operation is repeated. After the second operation, the inspection is repeated until the inspection is qualified. This closed-loop inspection process effectively ensures the quality of the flexible area after opening the lid and avoids interference from residue issues in subsequent processes.

[0037] The process includes a post-opening processing step after step S7: First, a plasma cleaner using a mixture of oxygen and argon gases is used to clean the printed circuit board, removing burrs from the broken edges of the PP1200 and residual adsorbents on the surface. The printed circuit board is then placed in a constant temperature environment under a nitrogen atmosphere for a preset time to release the thermal and mechanical stress generated during the opening process. Afterward, it is rinsed with deionized water and vacuum dried to ensure stable bending performance in the flexible area.

[0038] Specifically, to ensure the bending performance of the flexible area, a series of post-processing operations are performed on the board after opening the cover. First, a mixed-gas plasma cleaner is used to clean the board, removing tiny burrs and surface adsorbates from the broken edges of the PP. Then, the cleaned board is placed in a constant-temperature environment with an inert gas atmosphere for slow cooling to release the thermal and mechanical stresses generated during the opening process. Finally, the board is rinsed and dried to ensure the cleanliness of the flexible area surface. By testing the surface cleanliness and bending performance of the flexible area, the long-term reliability of the rigid-flex board is ensured. This post-processing effectively improves the structural stability and cleanliness of the flexible area, making the product more adaptable to the stringent requirements of high-end electronics applications.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations 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.

Claims

1. A process for laminating copper foil onto a rigid-flexible bonded plate with gaskets, characterized in that, Includes the following steps: S1. PP2 (300) on the side closer to the flexible area is opened, while PP1 (200) on the side closer to the copper foil (100) remains closed. S2. Prepare a PTFE adhesive barrier pad (400) adapted to the window opening area of ​​PP2 (300). After pressing the cover film (500) onto the flexible area of ​​the flexible core board (600), attach the PTFE adhesive barrier pad (400) to the surface of the cover film (500). The total thickness of the PTFE adhesive barrier pad (400) and the cover film (500) is adapted to the window opening thickness of PP2 (300). S3. Perform stacking and lamination in a preset order so that the PTFE adhesive barrier gasket (400) fills the window area of ​​PP2 (300); S4. Using a dual mask protection method, selective etching is used to remove the copper of the flexible area cover, exposing the underlying PP1 (200) protective layer; S5. An annular pre-crack groove is machined on the surface of PP1 (200) exposed after etching, corresponding to the flexible area cover position. The annular pre-crack groove is provided with at least two stress relief branch grooves along the circumferential direction. S6. In the temperature control equipment in an inert gas atmosphere, through the synergistic effect of gradient temperature control and low-frequency ultrasound, the ultrasonic vibration is transmitted to the interface between the PTFE resist gasket (400) and the cover film (500) via a flexible conductive medium. The difference in the thermal expansion coefficients of the two is used to form a uniform micro gap. At the same time, the size of the micro gap is monitored in real time by a laser displacement sensor and the temperature control parameters are adjusted accordingly. S7. Based on the pre-cracked groove and stress relief branch groove processed in step S5, the annular array nozzle with elastic sealing ring is aligned and attached to the annular pre-cracked groove. The PP1 (200) is driven to break along the pre-cracked groove and stress relief branch groove by a combination of pulsed airflow and reverse negative pressure adsorption sequence. At the same time, the PTFE adhesive pad (400) is guided and collected from the micro gap through the guide channel.

2. The process for laminating copper foil onto a rigid-flexible bonded plate with a gasket according to claim 1, characterized in that, In step S1, the windowing process of PP2 (300) adopts CNC adaptive milling. The window opening diameter and hole density are dynamically adjusted according to the regional characteristics of the rigid-flex plate. The rigid-flex edge area adopts small-diameter high-density windowing, and the flexible area center adopts large-diameter low-density windowing. The windowing area corresponds to the flexible area position of the flexible core plate (600), and the window shape is completely adapted to the shape of the PTFE adhesive pad (400).

3. The process for laminating copper foil onto a rigid-flexible bonded plate with a gasket according to claim 1, characterized in that, In step S2, the preparation of the PTFE adhesive barrier (400) includes: Picosecond laser machine is used to laser mill holes in PTFE sheet to form positioning holes and clearance grooves that are compatible with the positioning holes and circuit structure of flexible core board (600). The surface of PTFE resist pad (400) is treated with plasma to improve the bonding stability with cover film (500). The cover film (500) is pressed onto the flexible area of ​​the flexible core board (600) by a high-speed press at a preset temperature and pressure. The PTFE adhesive resist pad (400) is fixed to the surface of the cover film (500) by a vacuum adsorption manual application method. The difference between the total thickness of the PTFE adhesive resist pad (400) and the cover film (500) and the opening thickness of PP2 (300) is controlled within ±0.02mm.

4. The process for laminating copper foil onto a rigid-flexible bonded plate with a gasket according to claim 1, characterized in that, In step S3, the sequence of riveting the stacked plates includes: Centered on the flexible core board (600), a cover film (500) covered with PTFE adhesive pads (400), a windowed PP2 (300), a windowless PP1 (200), and a copper foil (100) are stacked on both sides in sequence. After being aligned and fixed through multiple sets of riveting holes, a segmented temperature-controlled laminator is used for pressing. The pressure distribution on the board surface is monitored in real time during the pressing process.

5. The process for laminating copper foil onto a rigid-flexible bonded plate with a gasket according to claim 1, characterized in that, In step S4, the selective etching protected by the dual mask specifically includes: S41. An etch-resistant polyimide physical mask is bonded to the surface of PP1 (200), exposing only the copper area of ​​the flexible cover. At the same time, photoresist is coated on the copper surface of the cover to form a chemical mask, and the etching range is defined by high-precision photolithography development. S42. First, perform low-temperature pre-etching to ensure the etching solution evenly wets the copper surface of the cover; then, perform medium-temperature main etching with ultrasonic stirring to quickly remove most of the copper layer on the cover; finally, perform room-temperature fine etching to remove the remaining copper layer. S43. Use deionized water for ultrasonic cleaning to remove residual etching solution, and then dry with nitrogen gas. During the drying process, control the nitrogen gas flow rate to avoid damaging the PP1 (200) surface.

6. The process for laminating copper foil onto a rigid-flexible bonded plate with a gasket according to claim 1, characterized in that, In step S5, the annular pre-cracked groove is processed by a combination of plasma etching and mechanical micro-milling. The position of the pre-cracked groove is aligned with the edge of the flexible area cover. The depth of the pre-cracked groove is a preset ratio of the thickness of PP1 (200), the width is a preset narrow dimension, and it does not penetrate PP1 (200). The stress relief branch groove is arranged radially along the annular pre-crack groove, with a length that is a preset proportion of the radius of the pre-crack groove, and a depth that is consistent with the pre-crack groove. The included angles of adjacent branch grooves are evenly distributed to disperse stress concentration when the cover is opened.

7. The process for laminating copper foil onto a rigid-flexible bonded plate with a gasket according to claim 1, characterized in that, In step S6, the specific process of the gradient temperature control and low-frequency ultrasound coordination is as follows: S61. In a nitrogen atmosphere temperature control device, the printed circuit board is slowly heated to the preset preheating temperature and kept at that temperature to make the overall temperature of the printed circuit board uniform. S62. Heat to the preset expansion temperature at a constant rate to avoid sudden thermal stress that could damage PP1 (200) or the flexible area. S63. Maintain the above-mentioned preset expansion temperature, attach the flexible conductive medium to the surface of the printed circuit board, apply low-frequency ultrasonic vibration, monitor the micro-gap size in real time through a laser displacement sensor, and automatically adjust the temperature to correct when the gap deviates from the preset range. S64. Cool down at a preset slow rate to the preset stable gap temperature to maintain the stability of the micro-gap.

8. The process for laminating copper foil onto a rigid-flexible bonded plate with a gasket according to claim 1, characterized in that, In step S7, the coordinated opening of the lid is executed using closed-loop control logic based on multi-parameter threshold feedback, specifically including: S71. Precisely align and seal the airflow output structure with the pre-cracked groove. Determine whether the preset sealing threshold is met through sealing detection methods. If it is not met, adjust the parameters until it is qualified. S72. Set the opening driving force threshold according to the pre-crack groove parameters and PP1 (200) characteristics, adopt the time-sequential coordinated control of driving force and reverse adsorption force, and monitor and dynamically adjust the driving force parameters in real time. S73. Collect stress signals through the stress detection structure, determine whether a preset fracture threshold signal appears, and if the threshold is met, determine fracture and stop the driving force output; if the threshold is not met, adjust the output parameters. S74. Monitor the gasket detachment signal through the detachment detection structure. After confirming that the detachment threshold is met, complete the gasket collection through the preset collection structure.

9. The process for laminating copper foil onto a rigid-flexible bonded plate with a gasket according to claim 1, characterized in that, Step S7 is followed by a loop closure detection step: The flexible area was inspected using a CCD camera combined with 3D structured light scanning. The inspection included the flatness of the fracture edge of PP1 (200), the residue of PTFE adhesive pad (400), and the cleanliness of the board surface. If residue is detected, adjust the pulse airflow pressure and negative pressure adsorption position according to the location of the residue, and repeat the coordinated opening operation until the test is qualified.

10. The process for laminating copper foil onto a rigid-flexible bonded plate with a gasket according to claim 1, characterized in that, Step S7 is followed by post-opening processing steps: First, a plasma cleaner with a mixture of oxygen and argon gas was used to clean the printed circuit board to remove burrs and surface residues from the broken edges of PP1 (200). The printed circuit board is then placed in a constant temperature environment under a nitrogen atmosphere for a preset time to release the thermal and mechanical stress generated during the opening process, followed by rinsing with deionized water and vacuum drying.

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