Printed circuit board and preparation method thereof

Abstract

The invention provides a printed circuit board and a preparation method thereof, the printed circuit board comprises a core board, a first bonding insulating layer and a high-speed line layer, the first bonding insulating layer is located on the surface of the core board, the first bonding insulating layer is provided with a high-speed wiring area, and the high-speed wiring area is located on the surface of the core board. A line groove is formed in the face, away from the core plate, of the first bonding insulation layer in the high-speed wiring area, and the high-speed line layer is embedded in the line groove. According to the printed circuit board provided by the invention, after the high-speed line layer is embedded into the line groove, the relative position of the high-speed line layer and the surrounding medium is fixed and uniform, further, due to the existence of the line groove, the distance between the high-speed line layer and the first bonding insulating layer is kept stable, and the medium distribution is uniform; impedance fluctuation caused by factors such as electroplating in operation is reduced, consistency of wiring characteristic impedance can be better maintained, and high-speed signal transmission quality is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit boards, and in particular to a printed circuit board and a method for preparing the printed circuit board. Background Art

[0002] As the Ethernet protocol continues to evolve from 112G bps to a higher bandwidth of 224Gbps, the overall link loss control requirements in high-speed transmission scenarios are extremely strict. From the perspective of printed circuit boards, insertion loss anomalies are mainly due to poor impedance matching consistency. For high-speed traces on the surface of the PCB, impedance control consistency is generally more difficult than for traces on the inner layers. This is because the copper on the surface needs to be thickened, and the uniformity of the plating is sometimes difficult to control during the thickening electroplating process. This is also one of the difficulties restricting the development of high-bandwidth transmission links. Summary of the Invention

[0003] Aiming at the problem in the prior art that the uniformity of the plating layer is difficult to control when the copper thickening electroplating on the surface of a printed circuit board is carried out, resulting in poor impedance control consistency and affecting the overall performance of a high-speed transmission link, a printed circuit board and a method for preparing the printed circuit board are provided.

[0004] The technical solutions adopted by the present invention to solve the above technical problems are as follows: On the one hand, the present invention provides a printed circuit board, including a core board, a first adhesive insulating layer and a high-speed circuit layer, wherein the first adhesive insulating layer is located on the surface of the core board, a high-speed routing area is provided on the first adhesive insulating layer, and a circuit groove is opened on the side of the first adhesive insulating layer away from the core board at the position of the high-speed routing area, and the high-speed circuit layer is embedded in the circuit groove.

[0005] Optionally, a surface circuit layer is formed on a side of the first adhesive insulating layer facing away from the core board at a position in a non-high-speed routing area.

[0006] Optionally, the high-speed circuit layer and the surface circuit layer are both copper circuit layers.

[0007] Optionally, a solder resist layer is further included, and the solder resist layer at least partially covers the first adhesive insulating layer and the side of the high-speed circuit layer facing away from the core board.

[0008] Optionally, the first adhesive insulating layer is a prepreg.

[0009] Optionally, the core board includes at least an inner circuit layer and at least one second adhesive insulating layer alternately stacked.

[0010] Optionally, the method for preparing the printed circuit board includes the following operations: Taking a prefabricated substrate, the prefabricated substrate comprises a substrate and a metal conductive layer attached to the surface of the substrate; A prefabricated substrate, a first adhesive insulating layer, and a core board are stacked in sequence, with the side of the prefabricated substrate with the metal conductive layer facing the first adhesive insulating layer. The area of ​​the first adhesive insulating layer corresponding to the metal conductive layer is the high-speed routing area. The prefabricated substrate is pressed together, and the metal conductive layer is embedded in the first adhesive insulating layer to form a substrate. Stripping the substrate from which the metal conductive layer is attached; The metal conductive layer is patterned to form a high-speed circuit layer in the high-speed routing area.

[0011] Optionally, before “stripping the substrate adhered to the surface of the metal conductive layer”, perform the following operations: Performing a pore treatment on the substrate to form conductive holes; An electroplating process is performed on the substrate to form electrical connections in the conductive holes and simultaneously form an electroplating layer on the surface of the substrate.

[0012] Optionally, after the substrate is electroplated, the method further comprises: The substrate is copper foil, and the surface circuit layer of the substrate and the electroplating layer is etched at a position in a non-high-speed routing area.

[0013] Optionally, the substrate and the metal conductive layer are connected via an adhesive sheet, and the glass transition temperature of the adhesive sheet is 200° C.-250° C.

[0014] Optionally, the operation of stripping the substrate includes: The bonding sheet softens under high temperature treatment, and the substrate is peeled off from the metal conductive layer.

[0015] Optionally, the temperature of the high temperature treatment is 200°C-250°C.

[0016] The beneficial effects of this application are: The printed circuit board provided in the present application includes a first adhesive insulating layer and a high-speed circuit layer. A high-speed routing area is provided on the first adhesive insulating layer. A circuit groove is provided on the side of the first adhesive insulating layer facing away from the core board at the location of the high-speed routing area. The high-speed circuit layer is embedded in the circuit groove. After the high-speed circuit layer is embedded in the circuit groove, the relative position of the high-speed circuit layer and the surrounding medium is fixed and uniform. Furthermore, due to the presence of the circuit groove, the distance between the high-speed circuit layer and the first adhesive insulating layer remains stable, and the medium is evenly distributed, which is conducive to reducing impedance fluctuations caused by factors such as electroplating during operation. Compared with traditional surface routing methods, the printed circuit board provided in the present application can better maintain the consistency of the routing characteristic impedance and ensure the quality of high-speed signal transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1This is a schematic diagram of laminating a substrate and a metal conductive layer provided by one embodiment of the present invention; Figure 2 This is a schematic diagram of a substrate preparation process provided by one embodiment of the present invention; Figure 3 1 is a schematic diagram of substrate electroplating provided by one embodiment of the present invention; Figure 4 This is a schematic diagram of a non-high-speed routing area on a substrate provided by an embodiment of the present invention; Figure 5 This is a schematic diagram of a substrate with a metal conductive layer removed from its surface according to one embodiment of the present invention; Figure 6 This is a schematic diagram of a high-speed circuit layer and a surface circuit layer on a substrate provided by one embodiment of the present invention; Figure 7 It is a schematic diagram of the structure of a printed circuit board provided in one embodiment of the present invention.

[0018] The reference numerals in the drawings of the specification are as follows: 1. Core board; 2. First bonding insulation layer; 3. High-speed circuit layer; 4. High-speed routing area; 5. Circuit trough; 6. Surface circuit layer; 7. Solder mask layer; 8. Second bonding insulation layer; 9. Prefabricated substrate; 91. Substrate; 92. Metal conductive layer; 10. Adhesive sheet; 11. Baseboard; 12. Electroplating layer; 13. Non-high-speed routing area; 14. Internal circuit layer. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] In the description of the present invention, it should be understood that the terms "longitudinal", "radial", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0021] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0022] Reference Figure 7 The present invention provides a printed circuit board, comprising a core board 1, a first adhesive insulating layer 2 and a high-speed circuit layer 3, wherein the first adhesive insulating layer 2 is located on the surface of the core board 1, a high-speed routing area 4 is provided on the first adhesive insulating layer 2, and a circuit groove 5 is opened on the side of the first adhesive insulating layer 2 facing away from the core board 1 at the position of the high-speed routing area 4, and the high-speed circuit layer 3 is embedded in the circuit groove 5.

[0023] Specifically, the printed circuit board provided in the present application includes a first adhesive insulating layer 2 and a high-speed circuit layer 3. A high-speed routing area 4 is arranged on the first adhesive insulating layer 2. The first adhesive insulating layer 2 opens a circuit groove 5 on the side of the high-speed routing area 4 facing away from the core board 1. The high-speed circuit layer 3 is embedded in the circuit groove 5. After the high-speed circuit layer 3 is embedded in the circuit groove 5, the relative position of the high-speed circuit layer 3 and the surrounding medium is fixed and uniform. Furthermore, due to the presence of the circuit groove 5, the distance between the high-speed circuit layer 3 and the first adhesive insulating layer 2 remains stable, and the medium is evenly distributed, which is conducive to reducing impedance fluctuations caused by factors such as electroplating during operation. Compared with the traditional surface routing method, the printed circuit board provided in the present application can better maintain the consistency of the routing characteristic impedance and ensure the quality of high-speed signal transmission.

[0024] The first adhesive insulating layer 2 serves as the dielectric for the high-speed circuit layer 3. The presence of the circuit groove 5 ensures closer and more uniform contact between the high-speed circuit layer 3 and the first adhesive insulating layer 2, thereby helping to reduce uneven areas in the dielectric. In traditional printed circuit board designs, if the circuit is laid directly on the surface of the insulating layer, there may be a loose fit between the insulating layer and the circuit, resulting in an uneven dielectric and, in turn, impedance fluctuations. In this technical solution, the high-speed circuit layer 3 is embedded in the circuit groove 5, allowing the insulating layer to evenly wrap the circuit, ensuring that the dielectric constant of the dielectric remains stable throughout the entire length of the circuit, thereby reducing impedance fluctuations and improving impedance consistency.

[0025] In addition, the printed circuit board will be affected by external electromagnetic interference during operation, and this interference may change the impedance characteristics of the circuit, resulting in inconsistent impedance. The circuit groove 5 and the first adhesive insulating layer 2 together constitute a relatively closed environment, which plays a certain shielding and protective role for the high-speed circuit layer 3. The structure of the circuit groove 5 can block some external electromagnetic interference, further avoiding impedance changes caused by external interference, and ensuring reliable signal transmission.

[0026] Reference Figure 6-7 In some embodiments, a surface circuit layer 6 is formed on a side of the first adhesive insulating layer 2 facing away from the core board 1 at a location in the non-high-speed routing area 13 .

[0027] Specifically, the surface circuit layer 6 of the non-high-speed routing area 13 can be used to transmit low-frequency signals. The high-speed circuit layer 3 cooperates with the surface circuit layer 6 of the non-high-speed routing area 13, thereby enabling signal transmission lines with different functions to be reasonably divided, thereby realizing diversified integration of printed circuit board signal transmission.

[0028] In some embodiments, the high-speed circuit layer 3 and the surface circuit layer 6 are both copper circuit layers.

[0029] Copper has excellent conductivity, and its low resistivity can effectively reduce resistance loss during signal transmission. For high-speed line layer 3, high-speed signals have high requirements for signal integrity during transmission, and slight resistance changes may cause signal attenuation and distortion.

[0030] Specifically, setting the high-speed circuit layer 3 and the surface circuit layer 6 as copper circuit layers can ensure that high-speed signals are transmitted with lower loss, maintain signal strength and stability, and ensure accurate transmission of high-speed data.

[0031] Reference Figure 7 In some embodiments, a solder resist layer 7 is further included, and the solder resist layer 7 at least partially covers the first adhesive insulating layer 2 and the high-speed circuit layer 3 on the side away from the core board 1.

[0032] Specifically, the solder resist layer 7 at least partially covers the first adhesive insulating layer 2 and the high-speed circuit layer 3 on a side away from the core board 1 , and the solder resist layer 7 also covers the surface circuit layer 6 formed on the first adhesive insulating layer 2 ; The solder resist layer 7 has good insulation properties. After covering the circuits, it can increase the insulation distance between the circuits and reduce the risk of signal crosstalk. For the high-speed circuit layer 3, the high-speed signal it transmits is susceptible to interference. The solder resist layer 7 can effectively isolate different circuits, reduce the mutual influence between signals, and ensure signal integrity. Although the surface circuit layer 6 transmits low-frequency signals, it may also be interfered with. The operation of the solder resist layer 7 covering the surface circuit layer 6 formed on the first adhesive insulating layer 2 can also provide insulation protection for the surface circuit layer 6.

[0033] In some embodiments, the first adhesive insulating layer 2 is a prepreg.

[0034] The semi-cured sheet is mainly composed of resin and reinforcing material. Specifically, the semi-cured sheet has good bonding properties. Under corresponding temperature and pressure conditions, it is firmly bonded to the core board 1, the high-speed circuit layer 3 and the surface circuit layer 6. During the printed circuit board manufacturing process, the semi-cured sheet will gradually solidify through the hot pressing process, tightly combining the layers.

[0035] As the first adhesive insulating layer 2, the prepreg exhibits excellent insulation properties, effectively isolating the electrical connections between the high-speed circuit layer 3 and the surface circuit layer 6 and the core substrate 1, while also preventing signal interference between different circuit layers. During high-speed signal transmission, the prepreg's insulating properties reduce signal leakage and attenuation, ensuring accurate and stable signal transmission. For high-frequency signals, the prepreg's low dielectric constant and low dielectric loss properties further optimize the signal transmission environment, improving both the quality and speed of signal transmission.

[0036] Reference Figure 2 In some embodiments, the core board 1 includes at least an inner circuit layer 14 and at least one second adhesive insulating layer 8 alternately stacked.

[0037] Specifically, the second adhesive insulating layer 8 plays a key insulating role between the internal circuit layers 14, and can effectively isolate the electrical signals between different circuit layers; the stacked structure of the core board 1 can provide more internal wiring space, and by setting multiple internal circuit layers 14, the connection between multiple electronic components can be achieved within a limited space; in addition, the internal circuit layer 14 and the second adhesive insulating layer 8 support each other, thereby enhancing the overall strength of the core board 1.

[0038] Reference Figure 1-7 In some embodiments, the method for preparing a printed circuit board includes the following operations: Take a prefabricated substrate 9, which includes a substrate 91 and a metal conductive layer 92 attached to the surface of the substrate 91; A prefabricated substrate 9, a first adhesive insulating layer 2, and a core board 1 are stacked in sequence. The side of the prefabricated substrate 9 on which the metal conductive layer 92 is attached faces the first adhesive insulating layer 2. The area of ​​the first adhesive insulating layer 2 corresponding to the metal conductive layer 92 is the high-speed wiring area 4. Pressing is performed so that the metal conductive layer 92 is embedded in the first adhesive insulating layer 2 to form a substrate 11. The substrate 91 adhered to the surface of the metal conductive layer 92 is peeled off; The metal conductive layer 92 is patterned to form a high-speed circuit layer 3 in the high-speed wiring area 4 .

[0039] Specifically, in the preparation method of the printed circuit board provided in the present application, by first pressing and then peeling off the substrate 91, the metal conductive layer 92 can better combine with the surrounding medium after being embedded in the first adhesive insulating layer 2, thereby ensuring close contact and fixed relative position between the high-speed circuit layer 3 and the first adhesive insulating layer 2, thereby helping to maintain the characteristic impedance consistency of the high-speed circuit layer 3 and improve the stability and reliability of high-speed signal transmission.

[0040] During the lamination process, the metal conductive layer 92 is pre-positioned and shaped by the prefabricated substrate 9, so that when pressed with the first adhesive insulating layer 2, it can be more accurately embedded in the high-speed routing area 4 of the first adhesive insulating layer 2; in addition, the metal conductive layer 92 is embedded in the first adhesive insulating layer 2 through lamination, and the two form an integral structure, which enhances the mechanical strength and deformation resistance of the high-speed circuit layer 3. In the subsequent processing, installation and use, the high-speed circuit layer 3 can better resist external forces, which helps to extend the service life of the printed circuit board.

[0041] Reference Figure 3-4 In some embodiments, before “stripping the substrate 91 attached to the surface of the metal conductive layer 92”, the following operations are performed: Performing a hole treatment on the substrate 11 to form conductive holes; An electroplating process is performed on the substrate 11 to form electrical connections in the conductive holes and simultaneously form an electroplating layer 12 on the surface of the base material 91 .

[0042] Specifically, the substrate 11 is perforated to form conductive holes, and then electrical connections are formed in the conductive holes through electroplating, so that different layers of the printed circuit board (such as the internal circuit layer 14 and the high-speed circuit layer 3) can be stably electrically connected to form a complete circuit network, ensuring that current can be smoothly transmitted between the circuits of each layer.

[0043] The metal coating formed within the conductive vias during electroplating effectively reduces the contact resistance between different circuit layers. Low contact resistance reduces energy loss and signal attenuation during signal transmission, improving the quality and efficiency of signal transmission. For high-speed signal transmission lines (such as high-speed differential lines), lowering contact resistance can significantly reduce signal reflections, ensuring signal integrity and improving the communication performance of electronic devices.

[0044] In addition, the formed electroplating layer 12 not only fills the conductive holes, but also forms an electroplating covering layer on the surface of the substrate 91. The electroplating covering layer helps to enhance the overall mechanical strength of the printed circuit board and ensure the long-term stability of the printed circuit board.

[0045] In some embodiments, after the substrate 11 is electroplated, the method further includes: The substrate 91 is a copper foil, and the surface circuit layer of the substrate 91 and the electroplating layer 12 is etched at a position of the non-high-speed wiring area 13 .

[0046] Specifically, etching the surface wiring layer in the non-high-speed routing area 13 reduces parasitic capacitance and inductance between the wiring, thereby reducing crosstalk and interference between signals. Separating the layout and etching from the high-speed wiring layer 3 also prevents high-speed signals from interfering with non-high-speed signals, ensuring independent and stable transmission of different types of signals.

[0047] Through the etching operation, the required surface circuit layer can be accurately formed in the non-high-speed routing area 13, which is used to transmit low-frequency signals, realize power distribution or connect some components that do not require high signal transmission speed. The printed circuit board can simultaneously meet the transmission requirements of different types of signals and realize diversified circuit function layout.

[0048] The etched circuit is tightly bonded to the electroplating layer 12 and the copper foil substrate 91 , and can better resist the influence of the external environment (such as vibration, temperature, and humidity), thereby improving the reliability of the circuit board under different working conditions.

[0049] Reference Figure 1 In some embodiments, the substrate 91 and the metal conductive layer 92 are connected via an adhesive sheet 10 , and the glass transition temperature of the adhesive sheet 10 is 200° C.-250° C.

[0050] Specifically, the bonding sheet 10 can effectively bond the substrate 91 and the metal conductive layer 92 to prevent the metal conductive layer 92 from falling off the substrate 91 , thereby ensuring that the metal conductive layer 92 is always firmly attached to the substrate 91 and maintaining the normal operation of the circuit.

[0051] The bonding sheet 10 has a good insulating effect, avoiding electrical short circuits between the metal conductive layer 92 and the substrate 91 and reducing signal interference. Furthermore, in high-frequency circuits, the insulating properties of the bonding sheet 10 can effectively isolate the crosstalk signals generated between the substrate 91 and the metal conductive layer 92, ensuring the accuracy and stability of signal transmission. The bonding sheet 10 can also fill the gap between the metal conductive layer 92 and the substrate 91, reducing signal reflections caused by air gaps and further optimizing electrical performance.

[0052] During the printed circuit board manufacturing process, multiple high-temperature, high-pressure processes are performed. The bonding sheet 10 exhibits excellent heat and chemical resistance, maintaining stable performance under these complex process conditions. During the high-temperature lamination process, the bonding sheet 10 softens under certain temperatures and pressures, effectively filling the gap between the metal conductive layer 92 and the substrate 91 and achieving a tight fit. Upon cooling, the bonding sheet 10 returns to a stable solid state, maintaining a good bond. Furthermore, the bonding sheet 10 is protected from chemical corrosion during subsequent chemical treatments such as etching and electroplating, ensuring a reliable connection.

[0053] In order to ensure that the adhesive sheet 10 plays a bonding role in the bonding between the substrate 91 and the metal conductive layer 92, and to realize the subsequent operation of peeling the substrate 91 from the metal conductive layer 92, the glass transition temperature of the adhesive provided in this application is 200°C-250°C.

[0054] In some embodiments, the operation of peeling off the substrate 91 includes: The adhesive sheet 10 softens under high temperature treatment, and the substrate 91 is peeled off from the metal conductive layer 92 .

[0055] Specifically, the bonding sheet 10 has good bonding properties in low-temperature and normal-temperature environments, and can firmly bond the substrate 91 and the metal conductive layer 92. When the bonding sheet 10 is subjected to high-temperature treatment so that the temperature is higher than the glass transition temperature of the bonding sheet 10, the bonding sheet 10 will change from a glassy state to a highly elastic state, the movement of molecular segments will intensify, and the fluidity of the material will increase, thereby causing the bonding performance to decrease, and the substrate 91 can be peeled off from the metal conductive layer 92.

[0056] In some embodiments, the high temperature treatment temperature is 200°C-250°C.

[0057] The bonding sheet 10 has good bonding properties in low and normal temperature environments, and can thus firmly bond the substrate 91 and the metal conductive layer 92. However, in the high temperature range of 200°C-250°C, the state of the bonding sheet 10 changes from a glassy state to a highly elastic state. At this time, the mobility of its molecular segments is enhanced, the viscosity and fluidity of the material increase, and the bonding properties decrease, so that the substrate 91 can be peeled off from the metal conductive layer 92. If the temperature is lower than 200°C, the bonding sheet 10 may not be fully softened, making it difficult to peel off the substrate 91, and may even require a large external force, increasing the risk of damage to the metal conductive layer 92. If the temperature is higher than 250°C, the bonding sheet 10 may be over-softened or even carbonized, which will also affect the performance of the metal conductive layer 92 and the entire printed circuit board.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A printed circuit board, characterized in that: It includes a core board, a first adhesive insulating layer and a high-speed circuit layer. The first adhesive insulating layer is located on the surface of the core board. A high-speed routing area is provided on the first adhesive insulating layer. A circuit groove is opened on the side of the first adhesive insulating layer away from the core board at the position of the high-speed routing area. The high-speed circuit layer is embedded in the circuit groove.

2. The printed circuit board according to claim 1, wherein: A surface circuit layer is formed on a side of the first adhesive insulating layer facing away from the core board at a position in a non-high-speed wiring area; The high-speed circuit layer and the surface circuit layer are both copper circuit layers.

3. The printed circuit board according to claim 1, wherein: A solder resist layer is also included, and the solder resist layer at least partially covers the first adhesive insulating layer and the side of the high-speed circuit layer facing away from the core board.

4. The printed circuit board according to claim 1, wherein: The first adhesive insulating layer is a prepreg.

5. The printed circuit board according to claim 1, wherein: The core board includes at least one inner circuit layer and at least one second adhesive insulating layer which are alternately stacked.

6. The method for preparing a printed circuit board according to any one of claims 1 to 5, wherein: The following operations are included: Taking a prefabricated substrate, the prefabricated substrate comprises a substrate and a metal conductive layer attached to the surface of the substrate; A prefabricated substrate, a first adhesive insulating layer, and a core board are stacked in sequence, with the side of the prefabricated substrate with the metal conductive layer facing the first adhesive insulating layer. The area of ​​the first adhesive insulating layer corresponding to the metal conductive layer is the high-speed routing area. The prefabricated substrate is pressed together, and the metal conductive layer is embedded in the first adhesive insulating layer to form a substrate. Stripping the substrate from which the metal conductive layer is attached; The metal conductive layer is patterned to form a high-speed circuit layer in the high-speed routing area.

7. The method for preparing a printed circuit board according to claim 1, wherein: Before "peeling off the substrate attached to the metal conductive layer surface", perform the following operations: Performing a pore treatment on the substrate to form conductive holes; An electroplating process is performed on the substrate to form electrical connections in the conductive holes and simultaneously form an electroplating layer on the surface of the substrate.

8. The method for preparing a printed circuit board according to claim 7, wherein: After the substrate is electroplated, the method further comprises: The substrate is copper foil, and the surface circuit layer of the substrate and the electroplating layer is etched at a position in a non-high-speed routing area.

9. The method for preparing a printed circuit board according to claim 6, wherein: The substrate and the metal conductive layer are connected via an adhesive sheet, and the glass transition temperature of the adhesive sheet is 200° C.-250° C.

10. The method for preparing a printed circuit board according to claim 9, wherein: The operations for stripping the substrate include: The bonding sheet softens under high temperature treatment, and the substrate is peeled off from the metal conductive layer.

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