A lamination method and system for a multilayer flexible circuit board

Abstract

The application belongs to the technical field of electronic manufacturing and printed circuit board, and particularly relates to a laminating method and system for a multilayer flexible circuit board, which comprises the following steps: providing a flexible substrate layer, forming a patterned photosensitive layer, arranging an adhesive layer, stacking a multilayer structure, performing exposure and development, and laminating, etc. The system comprises a material supply unit, a patterned photosensitive layer forming unit, a laminated stacking unit, a patterned processing unit and a laminating unit, and realizes full-process automation through a central control unit. The application can improve positioning and alignment accuracy, optimize material compatibility, enhance process integration, improve laminating quality, and thus significantly improve the production efficiency and product yield of the multilayer flexible circuit board.

Description

Technical Field

[0001] This invention belongs to the field of electronic manufacturing and printed circuit board technology, specifically a lamination method and system for multilayer flexible circuit boards. Background Technology

[0002] Multilayer flexible circuit boards (FPCBs) have demonstrated significant application value in the electronics industry due to their flexibility, thinness, and ability to adapt to complex spaces, driving the miniaturization, multifunctionality, and portability of electronic products. In their manufacturing process, photolithography and lamination are two key steps. Photolithography transforms a pre-set circuit pattern into a photoresist pattern through exposure and development operations, achieving patterning; lamination, on the other hand, forms a complete circuit board structure by pressing together multiple layers of materials.

[0003] However, in the current manufacturing of multilayer flexible circuit boards, there are some issues that need improvement between photolithography and lamination processes. First, regarding accuracy, deviations in the positioning and bonding of the pattern and laminating material can lead to pattern offsets or dimensional errors, making it difficult to meet the requirements of high-precision circuitry and thus affecting electrical performance and functionality. Second, alignment presents challenges; insufficient alignment between the pattern after photolithography and the layers during lamination can cause poor circuit connections or signal transmission obstruction, impacting product quality and reliability. Furthermore, regarding material compatibility, the photolithography material may not interact well with the flexible substrate and adhesives used in the lamination process, resulting in delamination or air bubbles, weakening mechanical properties and potentially causing functional problems. Finally, insufficient process integration, with relatively independent stages in the manufacturing process and limited collaborative optimization capabilities, restricts production efficiency and affects product yield and the realization of complex, high-precision patterned structures.

[0004] In summary, the existing photolithography and lamination processes in the manufacturing of multilayer flexible circuit boards have these problems. Therefore, this invention provides a lamination method and system for multilayer flexible circuit boards. Summary of the Invention

[0005] The purpose of this invention is to provide a lamination method and system for multilayer flexible circuit boards, which solves the technical problems of limited product performance and reduced yield caused by insufficient positioning accuracy, alignment difficulties, poor material compatibility and low process integration in the existing photolithography and lamination processes.

[0006] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0007] In a first aspect, embodiments of the present invention provide a lamination method for a multilayer flexible circuit board, the method comprising: providing at least one flexible substrate layer and forming a patterned photosensitive layer on a first surface of the flexible substrate layer; providing at least one adhesive layer having photosensitive properties and disposed above or below the patterned photosensitive layer; stacking a cover film layer or another flexible substrate layer with the patterned photosensitive layer and the adhesive layer to form a multilayer stacked structure; during the lamination process, performing patterning processing on the multilayer stacked structure, the patterning processing including exposure and development operations on the adhesive layer; after completing the patterning processing, laminating the multilayer stacked structure, the lamination process including vacuuming, heating, applying pressure, and cooling steps; and removing the laminated multilayer flexible circuit board from the lamination equipment to obtain precisely aligned and integrated patterned layers.

[0008] As an optional embodiment of the first aspect of the present invention, the formation of a patterned photosensitive layer on the first surface of the flexible substrate layer specifically involves: forming a layer of liquid or dry film photoresist on the first surface of the flexible substrate layer by coating or lamination; controlling the uniformity of the photoresist thickness by methods such as slot coating, spin coating, or roll coating; or, eliminating air bubbles by hot pressing or vacuum lamination technology to ensure a tight bond between the photoresist and the flexible substrate layer; subsequently, converting the preset circuit pattern into a photoresist pattern through exposure and development operations to form the patterned photosensitive layer.

[0009] As an optional embodiment of the first aspect of the present invention, the exposure and development operation of the adhesive layer specifically includes: before exposure, pre-baking the adhesive layer at a temperature between 80°C and 120°C for 10 to 30 minutes to remove solvent and improve photosensitivity; aligning a preset pattern mask with the adhesive layer using machine vision recognition technology with an alignment accuracy of ±5 micrometers; exposing the adhesive layer with an ultraviolet light source at an energy density between 50 mJ / cm² and 500 mJ / cm², adjusting the exposure time according to the thickness and photosensitivity of the adhesive layer; after exposure, developing the adhesive layer with a specific developer, controlling the temperature, concentration, and development time of the developer within ±0.5°C, ±1%, and ±5 seconds, respectively, to ensure uniform and thorough development; and after development, post-curing the adhesive layer at a temperature between 130°C and 180°C for 30 to 60 minutes to enhance the physical and chemical stability of the pattern structure.

[0010] As an optional embodiment of the first aspect of the present invention, the lamination of the multilayer stacked structure specifically involves: placing the multilayer stacked structure in a lamination apparatus, the lamination apparatus including an upper heating plate, a lower heating plate, and a cavity capable of generating a vacuum environment; and subjecting the cavity to vacuum treatment to a vacuum degree of 10. -3 The vacuuming rate is 0.1 Pa to 1 Pa per second, and the holding time is 10 to 30 minutes, to remove air and volatile substances from the laminated structure. The upper and lower heating plates are heated at a rate of 5°C to 10°C per minute, with the target temperature set between 150°C and 200°C. Temperature sensors of the heating system are distributed in multiple areas on the surface of the plates, and PID algorithm control is used to ensure that the temperature uniformity deviation is less than ±1.5°C. Lamination pressure is applied, ranging from 1 MPa to 5 MPa, with a pressure rise rate of 0.1 MPa to 0.5 MPa per second, and the pressure holding time is 30 to 90 minutes. The pressure control system is implemented through hydraulic or servo electric cylinders, and the pressure uniformity is monitored and adjusted in real time by multiple pressure sensors. After lamination, slow cooling is performed using cooling water circulation or forced air convection at a rate of 2°C to 5°C per minute until room temperature.

[0011] As an optional embodiment of the first aspect of the present invention, the removal of the laminated multilayer flexible circuit board from the laminating equipment specifically involves: after cooling, opening the cavity of the laminating equipment and using a robotic arm or vacuum suction cup gripping mechanism to remove the multilayer flexible circuit board; the repeatability of the robotic arm is ±2 micrometers, and the vacuum suction cup is made of flexible material to avoid damage to the circuit board; the removed multilayer flexible circuit board undergoes dimensional stability testing, the testing method including a non-contact laser rangefinder or machine vision system, with a testing accuracy of ±1 micrometer; if the test result meets the design requirements, the process proceeds to the next step; if it does not meet the requirements, the defect location and type are recorded, and the cause is analyzed using an image recognition algorithm.

[0012] Secondly, embodiments of the present invention provide a lamination system for a multilayer flexible circuit board. The system includes: a material supply unit for providing a flexible substrate layer, an adhesive layer, and a cover film layer; a patterned photosensitive layer forming unit connected to the material supply unit for forming a patterned photosensitive layer on a first surface of the flexible substrate layer; a stacking unit connected to the patterned photosensitive layer forming unit for stacking the flexible substrate layer, the patterned photosensitive layer, the adhesive layer, and the cover film layer into a multilayer stacked structure; a patterning processing unit connected to the stacking unit for performing exposure and development operations on the multilayer stacked structure; a lamination unit connected to the patterning processing unit for laminating the multilayer stacked structure; and a central control unit electrically connected to the material supply unit, the patterned photosensitive layer forming unit, the stacking unit, the patterning processing unit, and the lamination unit for centralized control and status monitoring of the entire lamination system.

[0013] As an optional embodiment of the second aspect of the present invention, the material supply unit includes a roll unwinding mechanism, a tension control mechanism, and a cutting mechanism; the roll unwinding mechanism ensures the smoothness of material transmission through a non-contact correction function; the tension control mechanism achieves closed-loop control through a force sensor and a servo motor, with a tension fluctuation range of less than ±0.1N; the cutting mechanism uses a high-precision cutter or a laser cutting head, with a cutting accuracy of ±0.01mm.

[0014] As an optional embodiment of the second aspect of the present invention, the patterning processing unit includes an exposure module and a developing module; the exposure module includes a high-power ultraviolet light source, a movable pattern mask stage, and a high-precision alignment mechanism, the alignment mechanism consisting of two sets of machine vision cameras and an image processing system, with an alignment accuracy of ±3 micrometers; the developing module includes a developer spray chamber, a developer circulation filtration system, a developer temperature control system, and a rinsing and drying unit, the spray chamber being designed with uniform nozzles, and the developer flow rate control accuracy being ±0.1L / min.

[0015] Thirdly, embodiments of the present invention provide an electronic device, the electronic device including a processor, a memory, and a program or instructions stored in the memory and executable on the processor, wherein when the program or instructions are executed by the processor, they implement the steps of the method described in the first aspect.

[0016] Fourthly, embodiments of the present invention provide a readable storage medium on which a program or instructions are stored, which, when executed by a processor, implement the steps of the method described in the first aspect.

[0017] The beneficial effects of this invention are as follows:

[0018] 1. The lamination method and system for multilayer flexible circuit boards described in this invention utilizes machine vision recognition technology and high-precision alignment mechanisms in key steps. For example, during the exposure and development of the adhesive layer, a preset pattern mask can be aligned with the adhesive layer with an alignment accuracy of ±5 micrometers. High-precision alignment between layers can also be ensured during stacking and other processes, thereby effectively reducing problems such as poor circuit connection and signal transmission obstruction caused by alignment deviations, and ensuring the good realization of the electrical performance and functions of the multilayer flexible circuit board.

[0019] 2. The lamination method and system for multilayer flexible circuit boards described in this invention addresses the issue of unsatisfactory interactions between photolithography materials and materials such as flexible substrates and adhesives in the lamination process by implementing a series of measures. For example, pre-baking the adhesive layer removes solvents and improves photosensitivity; precisely controlling parameters such as the temperature, concentration, and development time of the developing solution; and performing post-curing treatment after development to enhance the stability of the pattern structure. This effectively avoids delamination or bubble formation, significantly improves the bonding strength between materials, enhances the mechanical properties of the multilayer flexible circuit board, and reduces functional failures caused by material compatibility issues.

[0020] 3. The lamination method and system for multilayer flexible circuit boards described in this invention features precise control parameters for key steps such as vacuuming, heating, pressure application, and cooling during the lamination process. For example, the vacuuming of the lamination equipment cavity can achieve a high vacuum level (10). -3 The temperature uniformity deviation during heating can be controlled to less than ±1.5°C. The applied lamination pressure has a reasonable range and can be monitored and adjusted in real time through a precise pressure control system. During cooling, it is slowly cooled to room temperature at an appropriate rate. These precise controls ensure the uniformity and stability of the multilayer stacked structure during lamination, meet the strict requirements of high-performance multilayer flexible circuit boards for lamination quality, and ensure the high-quality output of the final product.

[0021] 4. The lamination method and system for multilayer flexible circuit boards described in this invention, after removing the laminated multilayer flexible circuit board from the lamination equipment, uses a robotic arm with a repeatability accuracy of ±2 micrometers or a vacuum suction cup made of flexible material to grasp it, avoiding damage to the circuit board. It is also equipped with dimensional stability detection with an accuracy of ±1 micrometer (detection methods include non-contact laser rangefinders or machine vision systems). If the detection results do not meet the requirements, the cause can be analyzed through image recognition algorithms. Such detection and subsequent processing mechanisms help to discover product defects in a timely manner, accurately locate the problem, provide a strong basis for improving production processes and enhancing the overall quality of products, and ensure that the products entering the next process meet high-quality standards. Attached Figure Description

[0022] The invention will now be further described with reference to the accompanying drawings.

[0023] Figure 1 This is a flowchart of the lamination method for multilayer flexible circuit boards in this invention;

[0024] Figure 2 This is a structural block diagram of the lamination system of the multilayer flexible circuit board in this invention. Detailed Implementation

[0025] This invention provides a lamination method and system for multilayer flexible circuit boards, combined with... Figure 1 and Figure 2 The specific embodiments of the present invention will be described in detail below. Figure 1 This is a schematic flowchart of a lamination method for a multilayer flexible circuit board provided in an embodiment of the present invention. Figure 2 This is a structural block diagram of a lamination system for a multilayer flexible circuit board provided in an embodiment of the present invention.

[0026] In this embodiment, at least one flexible substrate layer, at least one adhesive layer, and a cover film layer or another flexible substrate layer are first provided by a material supply unit. The flexible substrate layer is conveyed by a roll unwinding mechanism, which ensures smooth material transport through a non-contact correction function. A tension control mechanism achieves closed-loop control through a force sensor and a servo motor, with tension fluctuations within a range of less than ±0.1N. A cutting mechanism uses high-precision blades or a laser cutting head, with a cutting accuracy of ±0.01mm, thereby ensuring the dimensional accuracy and surface quality of the flexible substrate layer. The adhesive layer has photosensitive properties, and its thickness uniformity is controlled by slot coating, spin coating, or roll coating methods in a coating equipment. Simultaneously, hot pressing or vacuum lamination technology is used to eliminate air bubbles to ensure a tight bond with the flexible substrate layer. The cover film layer or another flexible substrate layer is also provided by the roll unwinding mechanism and, after tension control and cutting, enters the subsequent processes.

[0027] Subsequently, the flexible substrate layer is fed into the patterned photosensitive layer forming unit, where a patterned photosensitive layer is formed on the first surface of the flexible substrate layer. This process specifically includes forming a layer of liquid or dry film photoresist on the first surface of the flexible substrate layer using coating or lamination methods. The uniformity of the photoresist thickness is controlled through methods such as slot coating, spin coating, or roll coating, or hot pressing or vacuum lamination techniques are used to eliminate air bubbles and ensure a tight bond between the photoresist and the flexible substrate layer. After the photoresist layer is formed, the preset circuit pattern is converted into a photoresist pattern through exposure and development operations, forming the patterned photosensitive layer. An ultraviolet light source is used during exposure, with the energy density set between 50 mJ / cm² and 500 mJ / cm². The exposure time is adjusted according to the thickness and photosensitivity of the photoresist layer. The temperature, concentration, and development time of the developer are controlled within ±0.5°C, ±1%, and ±5 seconds, respectively, to ensure uniform and thorough development. After development, the patterned photosensitive layer undergoes post-curing treatment at a temperature between 130°C and 180°C for 30 to 60 minutes to enhance the physical and chemical stability of the pattern structure.

[0028] Next, the flexible substrate layer, adhesive layer, and cover film layer or another flexible substrate layer are fed into the stacking unit and stacked in a predetermined order to form a multilayer structure. During the stacking process, the adhesive layer is positioned above or below the patterned photosensitive layer, and the cover film layer or another flexible substrate layer is tightly bonded to the patterned photosensitive layer and the adhesive layer. The stacking unit ensures that the alignment accuracy between each layer reaches ±5 micrometers through a precise positioning device, avoiding poor circuit connection problems caused by alignment deviations. After stacking, the multilayer structure is sent to the patterning processing unit for exposure and development operations. The patterning processing unit includes an exposure module and a development module. The exposure module includes a high-power ultraviolet light source, a movable pattern mask stage, and a high-precision alignment mechanism. The alignment mechanism consists of two sets of machine vision cameras and an image processing system, with an alignment accuracy of ±3 micrometers. The development module includes a developer spray chamber, a developer circulation filtration system, a developer temperature control system, and a rinsing and drying unit. The spray chamber is designed with uniform nozzles, and the developer flow rate control accuracy is ±0.1L / min. Before exposure, the adhesive layer is pre-baked at a temperature between 80°C and 120°C for 10 to 30 minutes to remove solvent and improve photosensitivity. After exposure, the adhesive layer is developed using a specific developer, with the developer temperature, concentration, and development time controlled within ±0.5°C, ±1%, and ±5 seconds, respectively, to ensure uniform and thorough development. After development, the adhesive layer undergoes post-curing at a temperature between 130°C and 180°C for 30 to 60 minutes to enhance the physical and chemical stability of the pattern structure.

[0029] After graphical processing, the multi-layered structure is fed into the lamination unit for lamination. The lamination unit includes an upper heating plate, a lower heating plate, and a cavity capable of generating a vacuum environment. The cavity is designed to ensure a vacuum rate of 0.1 Pa to 1 Pa per second and a vacuum level of 10. -3 The pressure is maintained above 10 Pa for 10 to 30 minutes to remove air and volatile substances from the laminated structure. The upper and lower heating plates are heated by a heating system at a rate of 5°C to 10°C / min, with a target temperature set between 150°C and 200°C. Temperature sensors are distributed across multiple areas of the platen surface, and a PID algorithm is used for control to ensure temperature uniformity deviation is less than ±1.5°C. Lamination pressure is applied at a range of 1 MPa to 5 MPa, with a pressure rise rate of 0.1 MPa to 0.5 MPa per second, and a pressure holding time of 30 to 90 minutes. The pressure control system is implemented via hydraulic or servo electric cylinders, and pressure uniformity is monitored and adjusted in real-time by multiple pressure sensors. After lamination, slow cooling is performed using cooling water circulation or forced air convection at a rate of 2°C to 5°C / min until room temperature is reached.

[0030] After cooling, the lamination chamber is opened, and the multilayer flexible circuit board is removed using a robotic arm or vacuum suction cup gripper. The robotic arm has a repeatability accuracy of ±2 micrometers, and the vacuum suction cup is made of flexible material to avoid damage to the circuit board. The removed multilayer flexible circuit board undergoes dimensional stability testing using methods including non-contact laser rangefinders or machine vision systems, with a testing accuracy of ±1 micrometer. If the test results meet design requirements, the board proceeds to the next process; otherwise, the defect location and type are recorded, and the cause is analyzed using image recognition algorithms. The central control unit is electrically connected to the material supply unit, patterned photosensitive layer forming unit, stacking unit, patterning processing unit, and lamination unit, providing centralized control and status monitoring of the entire lamination system. The central control unit acquires the working status and parameter information of each unit in real time through a data acquisition module and coordinates and optimizes the operation of each unit through control algorithms to ensure the stability and consistency of the entire process.

[0031] Throughout the entire process, the connections and coordination between the functional units are as follows: The material supply unit feeds the flexible substrate layer, adhesive layer, and cover film layer into the patterning photosensitive layer forming unit via a conveyor belt or robotic arm. The patterning photosensitive layer forming unit ensures the alignment accuracy between the flexible substrate layer and the coating equipment through a positioning device, and completes the formation of the patterned photosensitive layer through exposure and development equipment. The stacking unit uses a robotic arm or vacuum suction cup gripping mechanism to stack the flexible substrate layer, patterned photosensitive layer, adhesive layer, and cover film layer into a multi-layered structure in a predetermined order. During the stacking process, the alignment accuracy between each layer is ensured through a positioning device. The patterning processing unit performs exposure and development operations on the multi-layered structure through an exposure module and a development module. The exposure module ensures the alignment accuracy between the pattern mask and the adhesive layer through a high-precision alignment mechanism, and the development module ensures the uniformity and thoroughness of development through a developer spray chamber and a developer circulation filtration system. The lamination unit performs lamination operations on the multi-layered structure through vacuuming, heating, applying pressure, and cooling steps, ensuring the uniformity and stability of the multi-layered structure. The central control unit uses data acquisition modules and control algorithms to centrally control and monitor the operation and status of each functional unit, ensuring the stability and consistency of the entire process.

[0032] Through the above-described process flow and system structure, the embodiments of the present invention achieve efficient and precise manufacturing of multilayer flexible circuit boards, solving the technical problems of limited product performance and decreased yield caused by insufficient positioning accuracy, alignment difficulties, poor material compatibility, and low process integration in the prior art between photolithography and lamination processes. To better enable those skilled in the art to fully understand and implement the present invention, the specific implementation principles and operating steps of the present invention are further explained below in conjunction with a specific application scenario.

[0033] In the actual manufacturing of flexible printed circuit boards (FPCBs), the material supply unit first provides a flexible substrate layer, an adhesive layer, and a cover film layer or another flexible substrate layer. When the flexible substrate layer is conveyed by the unwinding mechanism, a non-contact correction function ensures smooth material transport, while the tension control mechanism uses force sensors and servo motors to achieve closed-loop control, ensuring tension fluctuations are less than ±0.1N. The cutting mechanism uses high-precision blades or laser cutting heads for dimensional cutting with a precision of ±0.01mm, ensuring the surface quality and dimensional accuracy of the flexible substrate layer. The adhesive layer's thickness uniformity is controlled through slot coating, spin coating, or roll coating methods in the coating equipment, and air bubbles are eliminated using hot pressing or vacuum lamination technology to ensure a tight bond with the flexible substrate layer. The cover film layer or another flexible substrate layer undergoes the same process before proceeding to subsequent steps. This step, through rigorous material preparation and parameter control, lays a precise foundation for subsequent processes, avoiding performance degradation due to material quality issues.

[0034] Subsequently, the flexible substrate layer is fed into the patterned photosensitive layer forming unit, where a layer of liquid or dry film photoresist is formed on the first surface of the flexible substrate layer by coating or lamination. During this process, methods such as slot coating, spin coating, or roll coating are used to control the uniformity of the photoresist thickness, while hot pressing or vacuum lamination techniques are used to eliminate air bubbles and ensure a tight bond between the photoresist and the flexible substrate layer. Next, the photoresist layer is exposed using an ultraviolet light source, with the light source energy density set between 50 mJ / cm² and 500 mJ / cm², and the exposure time adjusted according to the thickness and photosensitivity of the photoresist layer. The temperature, concentration, and development time of the developer are controlled within ±0.5°C, ±1%, and ±5 seconds, respectively, to ensure uniform and thorough development. After development, the patterned photosensitive layer undergoes post-curing treatment, with the temperature set between 130°C and 180°C for 30 to 60 minutes to enhance the physical and chemical stability of the patterned structure. This step, through precise control of exposure and development parameters, transforms the preset circuit pattern into a photoresist pattern, achieving high-precision patterned photosensitive layer formation.

[0035] Next, the flexible substrate layer, adhesive layer, and cover film layer or another flexible substrate layer are fed into the stacking unit and stacked in a predetermined order to form a multilayer structure. During stacking, the adhesive layer is positioned above or below the patterned photosensitive layer, and the cover film layer or another flexible substrate layer is tightly bonded to the patterned photosensitive layer and the adhesive layer. The stacking unit uses a positioning device to ensure an alignment accuracy of ±5 micrometers between each layer, avoiding poor circuit connections caused by alignment deviations. After stacking, the multilayer structure is sent to the patterning processing unit for exposure and development. The exposure module includes a high-power ultraviolet light source, a movable pattern mask stage, and a high-precision alignment mechanism. The alignment mechanism consists of two sets of machine vision cameras and an image processing system, with an alignment accuracy of ±3 micrometers. The development module includes a developer spray chamber, a developer circulation and filtration system, a developer temperature control system, and a rinsing and drying unit. The spray chamber is designed with uniform nozzles, and the developer flow rate control accuracy is ±0.1 L / min. This step ensures the patterning quality of the adhesive layer through high-precision alignment and uniform developer spraying.

[0036] After graphical processing, the multi-layered structure is fed into the lamination unit for lamination. The lamination unit includes an upper heating plate, a lower heating plate, and a cavity capable of generating a vacuum environment. The cavity is designed to ensure a vacuum rate of 0.1 Pa to 1 Pa per second and a vacuum level of 10. -3The pressure is maintained above a certain pressure for 10 to 30 minutes to remove air and volatile substances from the laminated structure. The upper and lower heating plates are heated by a heating system at a rate of 5°C to 10°C / min, with a target temperature set between 150°C and 200°C. Temperature sensors are distributed across multiple areas of the platen surface, and a PID algorithm is used for control to ensure temperature uniformity deviation is less than ±1.5°C. Lamination pressure is applied at a range of 1 MPa to 5 MPa, with a pressure rise rate of 0.1 MPa to 0.5 MPa per second, and a pressure holding time of 30 to 90 minutes. The pressure control system is implemented via hydraulic or servo electric cylinders, and pressure uniformity is monitored and adjusted in real-time by multiple pressure sensors. After lamination, slow cooling is performed using cooling water circulation or forced air convection at a rate of 2°C to 5°C / min until room temperature. This step, through precise control of vacuum, temperature, and pressure parameters, ensures the uniformity and stability of the multilayer laminated structure.

[0037] After cooling, the lamination chamber is opened, and the multilayer flexible circuit board is removed using a robotic arm or vacuum suction cup gripper. The robotic arm has a repeatability accuracy of ±2 micrometers, and the vacuum suction cup is made of flexible material to avoid damage to the circuit board. The removed multilayer flexible circuit board undergoes dimensional stability testing using methods including non-contact laser rangefinders or machine vision systems, with a testing accuracy of ±1 micrometer. If the test results meet design requirements, the board proceeds to the next process; otherwise, the defect location and type are recorded, and the cause is analyzed using image recognition algorithms. The central control unit is electrically connected to the material supply unit, patterned photosensitive layer forming unit, stacking unit, patterning processing unit, and lamination unit, providing centralized control and status monitoring of the entire lamination system. The central control unit acquires the working status and parameter information of each unit in real time through a data acquisition module and coordinates and optimizes the operation of each unit through control algorithms to ensure the stability and consistency of the entire process.

[0038] Throughout the entire process, the connections and coordination between the functional units are as follows: The material supply unit feeds the flexible substrate layer, adhesive layer, and cover film layer into the patterning photosensitive layer forming unit via a conveyor belt or robotic arm. The patterning photosensitive layer forming unit ensures the alignment accuracy between the flexible substrate layer and the coating equipment through a positioning device, and completes the formation of the patterned photosensitive layer through exposure and development equipment. The stacking unit uses a robotic arm or vacuum suction cup gripping mechanism to stack the flexible substrate layer, patterned photosensitive layer, adhesive layer, and cover film layer into a multi-layered structure in a predetermined order. During the stacking process, the alignment accuracy between each layer is ensured through a positioning device. The patterning processing unit performs exposure and development operations on the multi-layered structure through an exposure module and a development module. The exposure module ensures the alignment accuracy between the pattern mask and the adhesive layer through a high-precision alignment mechanism, and the development module ensures the uniformity and thoroughness of development through a developer spray chamber and a developer circulation filtration system. The lamination unit performs lamination operations on the multi-layered structure through vacuuming, heating, applying pressure, and cooling steps, ensuring the uniformity and stability of the multi-layered structure. The central control unit uses data acquisition modules and control algorithms to centrally control and monitor the operation and status of each functional unit, ensuring the stability and consistency of the entire process.

[0039] Through the above-described process flow and system structure, the embodiments of the present invention achieve efficient and precise manufacturing of multilayer flexible circuit boards, and solve the technical problems of limited product performance and reduced yield caused by insufficient positioning accuracy, difficult alignment, poor material compatibility and low process integration in the prior art between photolithography and lamination processes.

[0040] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A lamination method for a multilayer flexible circuit board, characterized in that, Includes the following steps: S1. Provide at least one flexible substrate layer, the flexible substrate layer having a first surface and a second surface; S2. At least one patterned photosensitive layer is formed on the first surface of the flexible substrate layer, the patterned photosensitive layer comprising a preset pattern structure formed by a photolithography process. S3. Provide at least one adhesive layer with photosensitive properties, and place it above or below the patterned photosensitive layer; S4. Provide at least one cover film layer or another flexible substrate layer, which is stacked with the patterned photosensitive layer and adhesive layer to form a multilayer stacked structure; S5. During the lamination process, the multilayer stacked structure is graphically processed, including: S51. Based on a preset graphic mask or direct imaging technology, after aligning with the preset graphic structure, the adhesive layer is exposed to selectively cure or soften specific areas. The exposure unit is used to adjust the light source intensity and exposure time to adapt to different adhesive layers. S52. Develop the exposed binder layer by controlling the temperature, concentration and time of the developer to remove or retain binder material in specific areas, thereby forming or enhancing graphic features. The developing unit includes a spraying mechanism and a waste liquid recovery system. S6. After completing the graphical processing or in parallel with it, laminating the multi-layered structure includes: S61. Place the multi-layered structure in a laminating equipment containing an upper heating plate, a lower heating plate, and a vacuum cavity; S62. Evacuate the cavity to a vacuum of at least 10⁻³ Pa to remove air and volatile substances from between layers and inside the material; S63. Heat to 150°C~200°C, control the heating rate to 5°C / min~10°C / min, and ensure that the temperature uniformity deviation is ≤±2°C; S64. Apply lamination pressure of 1MPa~5MPa, control the pressure rise rate and holding time, and do not damage the patterned photosensitive layer. S7. Maintain at the preset temperature and pressure for 30 to 90 minutes, then cool to room temperature at a rate of 2°C / min to 5°C / min; S8. Remove the laminated multilayer flexible circuit board, which contains precisely aligned and interconnected patterned layers.

2. The method according to claim 1, characterized in that, The method for forming the patterned photosensitive layer in S2 includes at least one of the following: S21. Coating or laminating a layer of liquid or dry film photoresist on the first surface of the flexible substrate layer, wherein the photoresist has preset photosensitivity and thickness uniformity, and the coating method is any one of slot coating, spin coating or roll coating, and the dry film lamination method uses hot pressing or vacuum lamination technology to eliminate air bubbles. S22. A metal layer or conductive material layer is deposited on the first surface of the flexible substrate layer, and the preset pattern structure is formed on the metal layer or conductive material layer by photolithography and etching processes. The deposition method is any one of sputtering, evaporation or electroplating. The composition, temperature and time of the etching solution are precisely controlled to achieve high-precision etching. S23. Directly use a flexible substrate layer or adhesive layer with patterning characteristics, wherein the flexible substrate layer or adhesive layer has been pre-embedded or has a specific pattern formed on its surface during manufacturing, wherein the pattern is any one of conductive lines, insulating areas or functional patterns, and the accuracy and stability of the pre-formed pattern meet the requirements of subsequent processing.

3. The method according to claim 1, characterized in that, The graphical processing of S5 also includes at least the following step: S511. Before exposing the adhesive layer, a pre-baking step is performed to remove the solvent in the adhesive layer and improve its photosensitivity. The pre-baking temperature is between 80°C and 120°C, and the time is between 10 minutes and 30 minutes. S512. After developing the adhesive layer, a post-curing or post-baking step is performed to enhance the physical and chemical stability of the developed pattern structure. Post-curing is performed by either ultraviolet light irradiation or heat treatment. The post-baking temperature is between 130°C and 180°C, and the time is between 30 minutes and 60 minutes. S513. After development, the exposed non-cured or non-bonded areas are etched or laser-ablated to form a finer or deeper graphic structure. S514. During or after lamination, laser drilling or mechanical drilling is performed to form through holes, blind holes or buried holes in the multilayer flexible circuit board, wherein the drilling position is precisely aligned with the graphic structure.

4. The lamination method for a multilayer flexible circuit board according to claim 1, characterized in that, The flexible substrate layer is selected from at least one of polyimide, polyester, liquid crystal polymer and polyethylene naphthalate, with a thickness of 12~100μm; the adhesive layer is selected from thermosetting epoxy resin, acrylic resin, polyimide resin or mixtures thereof, containing photoinitiator components, with a thickness of 5~50μm, and its glass transition temperature and coefficient of thermal expansion are matched with those of the flexible substrate layer; the cover film layer is an insulating flexible polymer film with a thickness of 12~50μm, and its surface is coated with adhesive.

5. The lamination method for a multilayer flexible circuit board according to claim 1, characterized in that, The alignment accuracy of S5 is ±5μm. It uses machine vision to identify alignment marks and fine-tunes them through an XY-θ precision platform. The exposure light source is ultraviolet light, deep ultraviolet light, or X-rays with an energy density of 50~500mJ / cm². Exposure is carried out in a clean environment.

6. The lamination method for a multilayer flexible circuit board according to claim 1, characterized in that: The laminating equipment has multi-layer lamination capability, capable of simultaneously processing multiple multi-layer stacked structures. Each lamination unit of the multi-layer lamination has an independent temperature and pressure control system. The laminating equipment is equipped with an inert gas protection device inside its cavity. After vacuuming, it is filled with either nitrogen or argon to further prevent material oxidation and improve lamination quality. The surface of the laminating plate undergoes fine grinding and plating treatment to ensure its flatness is less than ±5 micrometers.

7. A lamination system for a multilayer flexible circuit board, applicable to the lamination method for a multilayer flexible circuit board according to any one of claims 1-6, characterized in that, include: A material supply unit for supplying a flexible substrate layer, an adhesive layer, and a cover film layer / another flexible substrate layer, including unwinding, tension control, and cutting mechanisms; A patterned photosensitive layer forming unit, connected to a material supply unit, is used to form a patterned photosensitive layer with a preset pattern structure, including an automatic coating device or a dry film laminator. The stacking unit, connected to the patterned photosensitive layer forming unit, is used to stack and form a multi-layered structure, including a multi-axis robotic arm and a vacuum suction cup; An integrated graphics processing unit, connected to a stacking unit, is used to perform graphics processing on the multilayer stacked structure during the lamination process, including: An exposure module is used to expose the adhesive layer to selectively cure or soften specific areas of the adhesive layer. The exposure module includes a high-power ultraviolet light source, a pattern mask stage / digital micromirror array, and an alignment mechanism. The developing module is used to develop the exposed adhesive layer, and includes a developer spray chamber, a circulating filtration system and a rinsing and drying unit; The lamination unit, connected to the integrated graphics processing unit, includes: A vacuum chamber is used to house the multi-layered structure and provide a vacuum environment. The vacuum chamber has a double-layer sealing structure and a high-efficiency vacuum pump assembly. A heating plate, comprising an upper plate and a lower plate, wherein the plate is internally equipped with an electric heating element and a heat spreader, and the temperature uniformity is ≤±1.5°C; A pressure application mechanism is used to apply a preset lamination pressure to the heated pressure plate. The pressure application mechanism adopts a high-precision hydraulic system or a servo electric cylinder, and the pressure sensor has a measurement accuracy of 0.1%. A cooling system is provided for slowly cooling the laminating equipment and the multilayer stacked structure after lamination is completed. The cooling system is achieved through cooling water circulation or forced air convection. The central control unit is electrically connected to the material supply unit, the patterned photosensitive layer forming unit, the stacking unit, the integrated patterning processing unit, and the lamination unit, and is used for centralized control, data acquisition, status monitoring, and fault diagnosis of the entire lamination system.

8. The lamination system for a multilayer flexible circuit board according to claim 7, characterized in that, The integrated graphical processing unit also includes an etching module or a laser ablation module. The etching module includes one or more etching chambers, an etching solution supply and recovery system, and a gas purification system. The etching chamber has a corrosion-resistant lining and temperature control function. The flow rate, concentration, and temperature of the etching solution are precisely regulated. The etching module realizes wet etching or plasma dry etching. The laser ablation module includes a high-precision laser, a galvanometer scanning system, and a dust collection system.

9. The lamination system for a multilayer flexible circuit board according to claim 7, characterized in that, The system also includes: A cleaning and pretreatment unit is disposed after the material supply unit and before the patterned photosensitive layer forming unit, and is used to clean and pretreat the surface of the flexible substrate layer. A dimensional stability control unit, integrated in the lamination unit, is used to monitor and control the dimensional changes of the multilayer stacked structure during the lamination process; A graphic defect detection unit is disposed after the integrated graphic processing unit and before the lamination unit, and is used to detect defects in the graphicized stacked structure. An automatic transfer and buffering unit is used to efficiently transfer and buffer the flexible substrate layer, semi-finished stack, and final product multilayer flexible circuit board between various units within the system.

10. The lamination system for a multilayer flexible circuit board according to claim 7, characterized in that, The flexible substrate layer is continuously supplied in the material supply unit via a flexible roll-to-roll method. The lamination unit is designed with a modular structure, allowing for flexible configuration of different quantities and types of heating plates and vacuum chambers according to production needs and product types. The central control unit integrates artificial intelligence and machine learning algorithms, and through the analysis of historical production data and real-time monitoring data, it achieves intelligent optimization and predictive maintenance of lamination parameters.

Images