Uncovering processing method of embedded device printed circuit board and printed circuit board

Abstract

The invention relates to an uncovering processing method of an embedded device printed circuit board and the printed circuit board. The uncovering processing method comprises the following steps: providing the printed circuit board with an inner layer bonding pad; a PI composite film is arranged on the surface of the inner layer bonding pad, and the PI composite film at least comprises a non-viscous PI film layer; carrying out lamination and pressing on the printed circuit board provided with the PI composite film; removing a part of the dielectric layer covering the PI composite film by adopting a depth control mode so as to expose the PI composite film; and laser cutting is carried out on the exposed PI composite film, and the cut PI composite film is removed, so that the PI composite film is separated from the inner layer bonding pad. The invention provides an uncovering processing method of an embedded device printed circuit board and the printed circuit board, and aims to improve the uncovering quality and processing controllability of an inner layer bonding pad.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printed circuit board manufacturing, in particular to a cover opening processing method of a buried device printed circuit board and a printed circuit board prepared by the method. BACKGROUND

[0002] Under the development trend of miniaturization and high density of electronic devices, burying components into the interior of a printed circuit board has become an important technical path to realize product integration. In such a process, the cover needs to be opened on the completed laminated board to expose the inner layer pads, so as to realize electrical connection with the buried components. Some existing cover opening methods may face problems such as complex operation steps, high precision control requirements, and the risk of residues on the surface of the inner layer pads after opening, etc. For example, some methods use chemical etching or mechanical force peeling, which may cause damage to the surface of the pads or introduce contaminants, affecting the reliability of subsequent device welding. In addition, the effect of some methods in protecting the inner layer pads from the influence of resin overflow during lamination still has room for improvement. Therefore, the industry expects a cover opening solution that can better balance processing efficiency, precision, and pad surface quality. SUMMARY

[0003] Therefore, the present application provides a cover opening processing method of a buried device printed circuit board and a printed circuit board, in order to improve the cover opening quality and processing controllability of the inner layer pads.

[0004] The object of the present application is achieved by the following technical solutions: A cover opening processing method of a buried device printed circuit board, comprising the following steps: providing a printed circuit board having an inner layer pad; setting a PI composite film on the surface of the inner layer pad, wherein the PI composite film comprises at least one layer of non-adhesive PI film layer; laminating the printed circuit board provided with the PI composite film; removing part of the dielectric layer covering the PI composite film in a depth control manner to expose the PI composite film; laser cutting the exposed PI composite film and removing the cut PI composite film to separate it from the inner layer pad.

[0005] This capping process achieves high precision and non-destructive processing through a systematic procedure. Starting with a printed circuit board (PCB) containing inner pads, it ensures the stability of the processing foundation. A PI composite film is placed on the surface of the inner pads; the non-adhesive PI film layer facilitates smooth removal, eliminating the risk of residual adhesive and ensuring pad cleanliness and electrical performance. A lamination step integrates the composite film into the board, forming a stable structure and creating space for device embedding. Controlled-depth milling removes the dielectric layer with precise depth control, exposing the PI composite film without damaging the pads, ensuring the flatness of the capping area. Laser cutting of the exposed PI film layer achieves micron-level cuts to meet high-density requirements. The removal step simplifies separation based on the non-adhesive properties, reducing cleaning intervention and improving efficiency. The overall method is seamlessly integrated, enhancing production consistency and yield, and is suitable for large-scale manufacturing.

[0006] Preferably, the PI composite film further includes an AD epoxy adhesive layer, which is located between the PI film layer and the printed circuit board, and bonds the PI film layer to the surface of the printed circuit board; the laser cutting step includes cutting the PI film layer and the AD epoxy adhesive layer.

[0007] By introducing an AD epoxy adhesive layer, the bonding strength and sealing effect of the PI composite film are enhanced. This ensures the PI film layer remains in place during processing, preventing deviations. The epoxy adhesive material has excellent adhesion, maintaining its bond strength even at high lamination temperatures, preventing delamination. Simultaneously, the adhesive layer fills microscopic unevenness on the board surface, forming a continuous seal that effectively prevents external media intrusion, thus protecting the cleanliness of the inner layer pads. This structure creates ideal conditions for subsequent processing steps, simplifying the film application process and improving the overall process stability.

[0008] Preferably, the projected area of ​​the PI film layer on the inner layer pad is smaller than the projected area of ​​the AD epoxy adhesive layer on the inner layer pad.

[0009] This dimensional relationship ensures that the PI film layer is completely surrounded by the AD epoxy adhesive layer, providing uniform sealing and protection, reducing edge exposure stress, lowering the risk of cutting tearing, increasing the bonding area to enhance structural stability, adapting to uneven board surfaces, preventing media leakage, providing clear boundaries for laser cutting, improving processing accuracy and consistency, reducing quality issues, and making it suitable for high-precision manufacturing.

[0010] Preferably, the orthographic projection area of ​​the PI film layer on the inner layer pad is located inside the orthographic projection area of ​​the AD epoxy adhesive layer on the inner layer pad.

[0011] This layout optimizes sealing and bonding effects. The PI film layer is embedded inside the adhesive layer to form double protection, isolating the pads from the external environment, preventing resin intrusion, ensuring the original state of the pads, enhancing mechanical strength, reducing the risk of processing deformation, providing a smooth separation interface for removal, improving process reliability and efficiency, and is suitable for embedding complex devices.

[0012] Preferably, the depth control method is depth-controlled groove or depth-controlled laser ablation.

[0013] Offering a variety of processing options to meet different needs, the depth-controlled groove achieves high-precision depth control, suitable for large-area opening and ensuring uniform removal, while the depth-controlled laser ablation performs non-contact processing, reducing mechanical stress and suitable for micro-shapes. Both methods accurately expose the PI composite film, improving flexibility and adaptability, and optimizing production efficiency and cost.

[0014] Preferably, after removing the dielectric layer using a depth-controlled method, the remaining dielectric layer thickness above the PI composite film is not less than 0.1 mm.

[0015] Controlling the remaining thickness protects the PI composite film, buffers processing stress, prevents pad damage, provides working space for laser cutting, reduces penetration risk, enhances structural mechanical strength, avoids fragility issues, and improves product durability and reliability.

[0016] Preferably, the increased lamination thickness from the lamination is adapted to the height of the device to be embedded.

[0017] Adaptive design ensures spatial matching of components, avoids installation difficulties, adjusts thickness to accommodate different sizes, improves versatility, optimizes lamination structure to enhance mechanical stability and thermal management, reduces stress risks, simplifies production planning, and improves efficiency and consistency.

[0018] Preferably, in the removal step, the PI composite film is separated from the inner layer pads based on the non-adhesive nature of the PI film layer and the laser cutting of the AD epoxy adhesive layer.

[0019] It achieves efficient and clean separation by utilizing non-stick properties, requiring no additional assistance, reducing operational complexity, eliminating residual adhesive issues, ensuring pad quality and electrical performance, improving production speed and yield, reducing human error, and enhancing automation.

[0020] Preferably, the laser cutting path is determined based on the boundary of the inner layer pad.

[0021] Setting paths based on pad boundaries ensures precise alignment and dimensional control, avoids cutting deviations, improves processing accuracy and consistency, reduces material waste and time, increases efficiency, simplifies operation processes, and reduces the risk of errors.

[0022] A printed circuit board having an embedded device cavity formed by the method of any one of claims 1 to 9.

[0023] This printed circuit board uses a method to form cavities, enabling high-precision device integration. The cavity dimensions are accurate and the boundaries are clear, ensuring device fit and reducing stress or signal loss. The non-adhesive PI film layer avoids adhesive residue, keeps the pads clean, and ensures electrical connection stability. The robust structure is suitable for high-density applications, improving functionality and lifespan. The consistent method ensures uniform quality.

[0024] The advantages of this invention compared to the prior art are: The present invention provides a systematic method for opening the inner layer pads of a printed circuit board with embedded devices. This method employs a composite film structure including a non-adhesive PI film layer, followed by controlled-depth processing and laser cutting after lamination. In this method, the PI composite film pre-placed on the pad surface acts as an isolation and protection during the lamination process. This design effectively reduces the direct impact of external media (such as lamination resin) on the pad area, thus protecting the cleanliness of the pad surface. The subsequent controlled-depth processing step helps to precisely control the removal depth of the dielectric layer, creating conditions for subsequent operations. Laser cutting specifically treats the exposed PI film layer. Combined with its non-adhesive material properties, this makes subsequent film removal operations relatively simple, reducing the risk of residues on the pad surface caused by mechanical peeling or chemical treatment. The entire process flow is smooth, significantly improving the controllability and consistency of the processing. Therefore, this method effectively improves the opening quality of the embedded device area and reliably ensures the cleanliness of the inner layer pad surface. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the open-cap stacked structure design of the embedded device area of ​​the present invention. It specifically shows the lamination structure of the pre-attached PI composite film in the L5 layer pad area on the FR4 substrate, as well as the thickness matching relationship between the L2 layer and the L5 layer, which reflects the configuration of the interlayer structure and the corresponding design of the device height.

[0027] Figure 2This is a schematic diagram of the PI composite film structure of the present invention, which clearly shows the dimensional fit between the PI film and the AD epoxy adhesive. The PI film has a single-sided dimension smaller than the pad opening area, while the AD epoxy adhesive has a single-sided dimension larger than the PI film, demonstrating the multi-layer structure formed by die-cutting and its sealing and bonding mechanism.

[0028] Figure 3 This is a schematic diagram of the PI composite film pre-attachment process of the present invention, showing the precise positioning of the PI composite film on the surface of the inner layer pad, reflecting the alignment relationship between the composite film and the pad opening area and the surface bonding effect.

[0029] Figure 4 This is a schematic diagram of the lamination process of the present invention, showing the structural morphology after lamination of PP and copper foil on the basis of pre-attached PI composite film, presenting the correspondence between lamination thickness and opening depth and the overall lamination structure characteristics.

[0030] Figure 5 This is a schematic diagram of the depth-controlled groove process of the present invention. It clearly shows the safe medium thickness remaining after removing the covering medium layer through depth-controlled machining, as well as the exposure state of the PI composite film, demonstrating the precision of depth control and the integrity of the machining interface.

[0031] Figure 6 This is a schematic diagram of the laser cutting process of the present invention, showing the process of the laser beam precisely cutting the entire exposed PI composite film (including the PI film layer and the AD epoxy adhesive layer) along the boundary of the pad, and presenting the correspondence between the cutting path and the pad area.

[0032] Figure 7 This is a schematic diagram of the PI membrane separation process of the present invention. It shows the final state after laser cutting, in which the entire PI composite membrane (including the PI membrane layer and the AD epoxy adhesive layer) has been removed. It also shows the cleanliness of the pad surface and the forming effect of the cavity structure after the cover is opened. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0035] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of the embodiments of this application, it should be understood that the terms "upper," "lower," "left," "right," "vertical," "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship commonly used when the product of this application is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0037] The technical solutions in this application will now be described with reference to the accompanying drawings. Example 1

[0038] This embodiment provides a method for opening and processing a printed circuit board with embedded devices, including the following steps: providing a printed circuit board with inner layer pads; disposing a PI composite film on the surface of the inner layer pads, wherein the PI composite film includes at least one non-adhesive PI film layer; laminating the PI composite film on the printed circuit board with the PI composite film; removing part of the dielectric layer covering the PI composite film using controlled depth milling to expose the PI composite film; laser cutting the exposed PI composite film, the cutting path being determined according to the boundary of the inner layer pads, and penetrating the PI film layer and the AD epoxy adhesive layer; removing the cut PI composite film to separate it from the inner layer pads.

[0039] This open-cap processing method achieves high-precision and non-destructive processing of the embedded device area through a systematic sequence of steps. Starting with a printed circuit board with inner pads, it ensures the clarity and fundamental stability of the processing object, providing an accurate starting point for subsequent operations. A PI composite film is applied to the surface of the inner pads, with the composite film containing at least one non-adhesive PI film layer. This design significantly improves process reliability. The non-adhesive nature allows for smooth separation of the PI film layer during the removal step, fundamentally eliminating the risk of residual adhesive and ensuring the surface cleanliness and electrical performance of the inner pads, avoiding contamination problems caused by adhering materials in traditional methods. The lamination step integrates the PI composite film into the board body, forming a stable multi-layer structure through thermo-pressing. This creates a sealed space for device embedding while enhancing overall mechanical strength, ensuring no displacement or deformation occurs during subsequent processing. The method employs controlled-depth milling to remove the overlay dielectric layer. This highly controllable machining technique allows for precise control of the removal depth, exposing only the PI composite film while preserving the underlying dielectric layer. This prevents physical damage to the inner layer pads, ensuring the flatness and dimensional consistency of the uncovered area, and improving processing accuracy and repeatability. Laser cutting of the exposed PI composite film utilizes the focused energy of a laser beam to achieve micron-level cutting, resulting in clean, burr-free cuts suitable for complex-shaped overlays. This enhances design flexibility and adaptability, meeting the stringent requirements of high-density interconnects. Removing the cut PI film layer to separate it from the inner layer pads is achieved without additional chemical or mechanical intervention due to the non-adhesive nature of the PI film. This simplifies the process, reduces production time and labor costs, and minimizes quality defects caused by improper cleaning. The overall method features seamless integration of steps and a high degree of automation. This not only improves production efficiency and product yield but also ensures processing consistency through physical means. It is suitable for large-scale manufacturing environments, providing reliable technical support for the miniaturization and high performance of electronic products. Furthermore, it avoids the use of chemical etchants, enhancing environmental friendliness and operational safety.

[0040] In this embodiment, the PI composite film further includes an AD epoxy adhesive layer, which is located between the PI film layer and the printed circuit board, and bonds the PI film layer to the surface of the printed circuit board; the laser cutting step includes cutting the PI film layer and the AD epoxy adhesive layer.

[0041] By introducing an AD epoxy adhesive layer, the bonding strength and sealing effect between the PI composite film and the printed circuit board are enhanced. The AD epoxy adhesive layer, located between the PI film and the printed circuit board, plays a crucial bonding role, ensuring that the PI film maintains a fixed position during processing and avoiding processing deviations caused by displacement. The properties of the epoxy adhesive material provide excellent adhesion and heat resistance, maintaining adhesion at high pressing temperatures and preventing delamination. At the same time, the adhesive layer fills microscopic unevenness, forming a continuous seal that effectively blocks the intrusion of external media, protects the surface of the inner pads, and creates ideal conditions for subsequent laser cutting and removal steps. This design simplifies the film application process, improves the overall process stability and finished product quality, and reduces the risk of failure caused by weak adhesion.

[0042] In this embodiment, the projected area of ​​the PI film layer on the inner layer pad is smaller than the projected area of ​​the AD epoxy adhesive layer on the inner layer pad.

[0043] This dimensional relationship ensures that the PI film layer is completely surrounded by the AD epoxy adhesive layer, thus providing more uniform sealing and protection during lamination and processing. The smaller projected area of ​​the PI film layer avoids its edges being directly exposed to external stress, reducing the risk of tearing during cutting and removal. Meanwhile, the larger coverage area of ​​the AD epoxy adhesive layer enhances the bonding area and improves the overall structural stability. This design allows the PI composite film to better adapt to uneven board surfaces during lamination, preventing media leakage or displacement. At the same time, it provides a clear boundary reference for laser cutting, improving processing accuracy and consistency, reducing quality problems caused by dimensional mismatch, and is suitable for high-precision electronic manufacturing needs.

[0044] In this embodiment, the orthographic projection area of ​​the PI film layer on the inner layer pad is located inside the orthographic projection area of ​​the AD epoxy adhesive layer on the inner layer pad.

[0045] This spatial layout further optimizes the sealing and bonding effect. The PI film layer is completely embedded inside the AD epoxy adhesive layer, forming a double protective structure that effectively isolates the inner pads from the external environment, preventing resin or impurities from intruding during the lamination process and ensuring the original state of the pad surface. This design also enhances the overall mechanical strength of the PI composite film, reduces the risk of deformation during controlled-depth milling and laser cutting, and provides a smoother separation interface for the removal step. Since the PI film layer is non-adhesive and surrounded by the adhesive layer, no external force intervention is required during separation, avoiding residue or damage, improving the reliability and efficiency of the process, and making it suitable for complex device embedding applications.

[0046] In this embodiment, the depth control method is either depth-controlled groove or depth-controlled laser ablation.

[0047] It offers a variety of controllable processing options to adapt to different production needs and material properties. Depth-controlled groove cutting, as a mechanical milling method, can achieve high-precision depth control and is suitable for large-area cap opening operations, ensuring uniform removal of the medium layer without damaging the underlying structure. Depth-controlled laser ablation uses laser energy for non-contact processing and is suitable for cap openings with fine or complex shapes, reducing the risk of deformation caused by mechanical stress. Both methods can accurately expose the PI composite film, laying the foundation for subsequent laser cutting and improving processing flexibility and adaptability. At the same time, by selecting the appropriate method, production efficiency and cost can be optimized to meet diverse manufacturing requirements.

[0048] In this embodiment, after removing the dielectric layer using a depth-controlled method, the thickness of the remaining dielectric layer above the PI composite film is not less than 0.1 mm.

[0049] By controlling the thickness of the remaining dielectric layer, the protective and stable properties of the PI composite film during exposure are ensured. A certain thickness buffers processing stress, prevents accidental damage to the inner layer pads, and provides sufficient working space for laser cutting, reducing the risk of cutting through. This design also enhances the mechanical strength of the overall structure, providing support in subsequent stacking or device embedding, avoiding fragility issues caused by excessive removal, and improving product durability and reliability, making it suitable for high-reliability electronic applications.

[0050] In this embodiment, the increased lamination thickness due to lamination is adapted to the height of the device to be embedded.

[0051] This adaptive design ensures precise matching of the device embedding space, avoiding installation difficulties or performance degradation caused by height mismatch. By adjusting the lamination thickness, it can flexibly accommodate different device sizes, improving the versatility and scalability of the method. At the same time, the optimized lamination structure enhances the overall mechanical stability and thermal management performance of the board, reducing the risk of stress concentration or deformation during use. This design also simplifies production planning, reduces the need for customized adjustments, improves production efficiency and product consistency, and is suitable for a variety of electronic packaging scenarios.

[0052] In this embodiment, during the removal step, the PI composite film is separated from the inner pads based on the non-adhesive nature of the PI film layer and the laser cutting of the AD epoxy adhesive layer.

[0053] By utilizing the non-stick properties of the PI film layer, a highly efficient and clean separation process is achieved without the need for additional chemical or mechanical assistance, reducing operational complexity and costs. This design completely eliminates the problem of residual adhesive, ensuring the surface quality and electrical performance of the inner layer pads. At the same time, the separation process is smooth and fast, improving the overall production rhythm and yield, making it suitable for high-speed manufacturing environments. In addition, non-stick separation reduces the risk of human error and enhances the automation and reliability of the process.

[0054] In this embodiment, the laser cutting path is determined based on the boundary of the inner layer pads.

[0055] By setting the cutting path based on the pad boundaries, precise alignment and size control of the uncovered area are ensured, avoiding problems such as insufficient or excessive pad exposure caused by cutting deviations. This design improves processing accuracy and consistency, and is suitable for high-density interconnect requirements. At the same time, the optimization of the laser path reduces material waste and processing time, improving production efficiency and economic benefits. In addition, the clear path reference simplifies the operation process, reduces the risk of setup errors, and enhances the repeatability and applicability of the method. Example 2

[0056] This embodiment details the specific design implementation method and processing flow of the open-cover stacked structure in the embedded device area. Through in-depth explanation of each step, it demonstrates the implementation details and process characteristics of this technical solution.

[0057] I. Open-cover stacked structure design for embedded device area In the open-cap stack design of printed circuit boards with embedded components, the rationality of the structural configuration directly affects the final open-cap effect and the quality of component embedding. This embodiment adopts a layered design concept, and the specific implementation is as follows: like Figure 1 As shown, a PI composite film is pre-laminated in the uncovered area of ​​the L5 layer pad on the FR4 substrate. This design choice is based on a comprehensive consideration of interlayer insulation performance and mechanical strength. Subsequently, the L2 layer is laminated, requiring precise control of the combined thickness of the L2 and L5 layers to ensure it matches the height of the device to be embedded. This thickness-matching design helps create a properly sized accommodating space during the subsequent uncovering process, providing a structural basis for device embedding. Optimized lamination parameters ensure a stable bonding interface between the layers during lamination, reducing the risk of interlayer delamination.

[0058] II. Precision Design of PI Composite Membranes As a core material component of this solution, the structural design of the PI composite film directly affects the smoothness of the opening process and the final result. like Figure 2 As shown, the PI composite film employs a precise multi-layer structure design. The PI film is precisely cut to a size 0.1mm smaller on each side according to the pad opening dimensions, while the AD epoxy adhesive is configured to a size 0.5mm larger on each side according to the PI film dimensions. This differentiated dimensional design is the optimal parameter combination determined after numerous process trials, achieving a good balance between protective effect and adhesion reliability.

[0059] Through a specialized die-cutting and lamination process, PI film and AD epoxy adhesive are combined into a single, structurally complete composite film. After this composite film is attached to the pads of the printed circuit board, the AD epoxy adhesive effectively bonds and seals the pad area containing the PI film. Notably, the PI film itself lacks adhesive properties, a characteristic that facilitates subsequent separation. The extended design of the AD epoxy adhesive forms an effective sealing ring, preventing resin leakage into the pad area during lamination, while simultaneously providing a stable supporting foundation for the PI film.

[0060] III. Systematic Processing Flow for Embedded Component Cover Area The opening process in this embodiment includes five main stages, each stage being interconnected to form a complete process chain: like Figure 3 As shown, the PI composite film is first precisely pre-attached to the open area of ​​the solder pads, i.e., the area indicated by the arrow in the diagram. This step requires ensuring positioning accuracy to guarantee that the PI composite film and the open area of ​​the solder pads are accurately aligned. During the attachment process, the cleanliness of the environment must be controlled to avoid introducing impurities that could affect the bonding quality. After pre-attachment, a preliminary inspection is necessary to confirm the tightness of the adhesion between the composite film and the solder pad surface, laying the foundation for subsequent processes.

[0061] like Figure 4 As shown, after pre-applying the PI composite film, PP and copper foil are laminated according to design requirements, followed by lamination. At this stage, the opening depth needs to be precisely calculated based on the device height design, and the number of layers adjusted accordingly. The temperature, pressure, and time parameters during lamination need to be optimized based on material properties to ensure a stable bond between the layers while maintaining the structural integrity of the PI composite film. The quality of this step directly affects the accuracy and reliability of subsequent opening.

[0062] like Figure 5 As shown, depth-controlled groove technology is used for precision machining of the cover area. A professional depth control device ensures that a dielectric layer thickness of no less than 0.1mm is maintained above the L5 layer pads. Maintaining this thickness has multiple benefits: it provides a safe buffer space for subsequent laser cutting and avoids the risk of directly damaging the pad surface. During depth-controlled machining, the machining depth needs to be monitored in real time, and a feedback adjustment mechanism ensures machining consistency.

[0063] like Figure 6As shown, the laser beam precisely cuts the entire exposed PI composite film (including the PI film layer and the AD epoxy adhesive layer) along the pad boundary, separating it from the surrounding composite film. The laser parameters, including power, frequency, and scanning speed, need to be specifically optimized based on the material properties and thickness of the PI film. The cutting path should be planned strictly according to the pad boundary to ensure the accuracy of the cutting contour. The non-contact nature of laser cutting avoids mechanical stress interference with surrounding materials while ensuring cut quality.

[0064] like Figure 7 As shown, automatic separation is achieved by utilizing the non-adhesive properties of the PI film. After laser cutting, the entire PI composite film in the cut area can be easily removed from the inner pad surface due to the non-adhesive nature of the PI film layer and the fact that the AD epoxy adhesive layer has been cut, thus exposing a clean, residue-free pad surface to form a cavity for device embedding. Because there is no adhesive connection between the PI film and the pad surface, the cut PI film portion can be smoothly separated from the printed circuit board. This separation process requires no additional chemical or mechanical assistance, significantly simplifying the operation. After separation, the uncovered area reveals a clean pad surface, creating ideal conditions for subsequent device embedding.

[0065] Summary and explanation: This embodiment presents a complete solution for opening capping of printed circuit boards (PCBs) for embedded devices through a systematic stack-up design and meticulous process flow. From the precise design of the PI composite film to the step-by-step processing flow, every step reflects in-depth consideration of process details. This solution ensures no residual adhesive on the inner layer pads while balancing processing efficiency and quality stability, providing reliable technical support for the manufacturing of PCBs for embedded devices. Particularly noteworthy is the synergistic coordination between various process parameters and the full utilization of material properties, which makes the entire capping process highly controllable and repeatable, adaptable to the embedding requirements of devices of different specifications. Example 3

[0066] This embodiment focuses on illustrating the specific structural features of the printed circuit board manufactured using the aforementioned open-cover processing method and its technical advantages in practical applications.

[0067] The printed circuit board, processed using the opening and closing method described in the foregoing embodiments, forms a precision cavity structure specifically designed to accommodate embedded devices. This cavity is manufactured through a systematic controlled-depth milling and laser cutting process, resulting in precise dimensional control and clear boundary definitions. The dimensional matching between the cavity and the embedded devices is carefully designed to ensure a perfect fit during device insertion, effectively reducing mechanical stress or signal transmission loss caused by improper installation gaps.

[0068] The application of a non-adhesive PI film layer is one of the key technical features during cavity formation. This material choice avoids the residual adhesive problem common in traditional capping methods, allowing the inner layer pads to maintain their original cleanliness after capping. The cleanliness of the pad surface plays an important role in ensuring the stability of electrical connections and maintaining low impedance characteristics, especially in high-frequency or high-current applications, where this advantage is even more pronounced.

[0069] From a structural integrity perspective, this printed circuit board exhibits excellent mechanical stability after device embedding. The supporting structure around the cavity is specially reinforced to withstand various stresses generated during device installation and use. This structural design makes this printed circuit board particularly suitable for high-density integration applications, such as high-end communication equipment and high-performance computing modules, where space utilization and reliability are critical.

[0070] In terms of electrical performance, this printed circuit board provides a stable signal transmission path and a reliable power distribution network by maximizing the protection of the inner pads during the opening process. The undamaged state of the pad surfaces ensures a high-quality electrical connection with the embedded devices, reducing signal reflection and insertion loss, thereby improving the overall electrical performance of the system.

[0071] Consistent manufacturing processes ensure stable quality in mass production. This method features a good process window and parameter tolerance, enabling printed circuit boards from different batches to maintain a high level of consistent quality. This consistency has significant economic and technical value for large-scale electronic product manufacturing.

[0072] In practical applications, the design of this printed circuit board fully considers the development needs of modern electronic products. Its structural features enable it to meet the stringent requirements of PCB integration, reliability, and performance in emerging technology fields such as 5G communication, artificial intelligence hardware, and IoT devices. Through optimized thermal management design and signal integrity planning, this printed circuit board can maintain stable performance even in complex operating environments.

[0073] In summary, the printed circuit board described in this embodiment not only demonstrates the technical advantages of the open-cover processing method, but also showcases its practical value in modern electronic manufacturing through its specific structural implementation. From its precise cavity structure to its stable electrical performance, from its reliable mechanical characteristics to its excellent process adaptability, this printed circuit board provides strong technical support for the miniaturization and high-performance development of electronic devices.

[0074] 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 method for opening and processing a printed circuit board with embedded devices, characterized in that, Includes the following steps: Provide printed circuit boards with inner pads; A PI composite film is disposed on the surface of the inner layer pad, wherein the PI composite film comprises at least one non-adhesive PI film layer; The PI composite film is laminated on a printed circuit board. A portion of the dielectric layer covering the PI composite film is removed using a depth-controlled method to expose the PI composite film; The exposed PI composite film is laser-cut and removed to separate it from the inner layer pads.

2. The opening and processing method according to claim 1, characterized in that, The PI composite film further includes an AD epoxy adhesive layer, which is located between the PI film layer and the printed circuit board, and bonds the PI film layer to the surface of the printed circuit board; the laser cutting step includes cutting the PI film layer and the AD epoxy adhesive layer.

3. The opening and processing method according to claim 2, characterized in that, The projected area of ​​the PI film layer on the inner layer pad is smaller than the projected area of ​​the AD epoxy adhesive layer on the inner layer pad.

4. The opening and processing method according to claim 3, characterized in that, The orthographic projection area of ​​the PI film layer on the inner layer pad is located inside the orthographic projection area of ​​the AD epoxy adhesive layer on the inner layer pad.

5. The opening and processing method according to claim 1, characterized in that, The depth control method is either depth-controlled groove or depth-controlled laser ablation.

6. The opening and processing method according to claim 1, characterized in that, After removing the dielectric layer using a depth-controlled method, the remaining dielectric layer thickness above the PI composite film is not less than 0.1 mm.

7. The opening and processing method according to claim 1, characterized in that, The increased lamination thickness resulting from the lamination process is adapted to the height of the device to be embedded.

8. The opening and processing method according to claim 1, characterized in that, In the removal step, the PI composite film is separated from the inner layer pads based on the non-adhesive nature of the PI film layer and the laser cutting of the AD epoxy adhesive layer.

9. The opening and processing method according to claim 1, characterized in that, The laser cutting path is determined based on the boundary of the inner layer pad.

10. A printed circuit board, characterized in that, The printed circuit board has an embedded device cavity formed by the method described in any one of claims 1 to 9.

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