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 circuit board body and a surface-mounted bonding pad, the circuit board body is provided with a hollow area, the surface-mounted bonding pad is located on the surface layer of one side of the circuit board body, the hollow area is located on the side, away from the surface layer, of the surface-mounted bonding pad, and the hollow area is located on the surface layer of the surface-mounted bonding pad. And the bottom surface of the surface-mounted bonding pad is exposed from the hollow area. According to the printed circuit board provided by the invention, the hollow region is arranged on the circuit board body, the bottom surface of the surface-mounted bonding pad is exposed from the hollow region, and the arrangement of the hollow region effectively reduces the area of a corresponding circuit board medium below the surface-mounted bonding pad, so that the impedance of the surface-mounted bonding pad can be effectively improved; the impedance matching degree of the surface-mounted bonding pad and the high-speed connector is higher, reflection, attenuation and crosstalk in signal transmission are reduced, and the transmission integrity and reliability of high-frequency and high-speed signals are further enhanced.

Description

Technical Field

[0001] This invention relates to the field of circuit board technology, and in particular to a printed circuit board and a method for preparing the same. Background Technology

[0002] In modern electronic devices, the impedance of PCB surface mount pads has a significant impact on the impedance matching of high-speed connectors. When transmitting high-speed signals, high-speed connectors require the impedance of the signal path to remain continuous and matched in order to reduce signal reflection, attenuation, and crosstalk, and ensure signal integrity and transmission quality.

[0003] In modern electronic devices, PCB surface-mount pads often have low impedance due to their large size, which significantly impacts the impedance matching of high-speed connectors. Low surface-mount pad impedance disrupts impedance balance, leading to signal reflection and distortion, signal attenuation affecting receiver recognition, and crosstalk causing noise and reducing reliability. While back-drilling is commonly used to remove some dielectric material and adjust impedance, the depth control of back-drilling is difficult to precisely meet requirements. Therefore, there is an urgent need for more effective methods to optimize surface-mount pad impedance, achieve good matching with high-speed connectors, improve the performance and reliability of electronic devices, and meet the demands of high-speed signal transmission. Summary of the Invention

[0004] To address the problem that the pad impedance on printed circuit boards in the prior art is too low to match the impedance of high-speed connectors, a printed circuit board and its fabrication method are provided.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: On one hand, the present invention provides a printed circuit board, including a circuit board body and surface mount pads. A hollow area is provided on the circuit board body, the surface mount pads are located on one side of the surface layer of the circuit board body, the hollow area is located on the side of the surface mount pads away from the surface layer, and the bottom surface of the surface mount pads is exposed through the hollow area.

[0006] Optionally, the circuit board body is further provided with a through hole, which extends from the other side of the printed circuit board body to the location of the hollow area.

[0007] Optionally, along a direction parallel to the circuit board body, the cross-sectional area of ​​the hollow region is smaller than the cross-sectional area of ​​the surface mount pad.

[0008] Optionally, a first circuit layer is formed on one side of the surface layer of the circuit board body at a location other than the surface mount pads. The first circuit layer is electrically connected to the surface mount pads. A second circuit layer is provided on the other side of the surface layer of the circuit board body. Both the first circuit layer and the second circuit layer are copper circuit layers.

[0009] Optionally, it further includes a solder mask layer, which includes a first solder mask layer and a second solder mask layer, wherein the first solder mask layer covers the first circuit layer and the second solder mask layer covers the second circuit layer.

[0010] Optionally, the circuit board body includes multiple layers of core boards stacked on top of each other, an insulating adhesive layer is provided between two adjacent core boards, and a third circuit layer is provided on the surface of the core board; The circuit board body also includes a through hole that passes through at least one core board. The inner wall of the through hole is provided with a metal layer that electrically connects to two or more of the first circuit layer, the second circuit layer, and the multiple third circuit layers.

[0011] Optionally, the multilayer core board includes at least one first core board and at least one second core board, the hollow area penetrates at least one first core board, and the through hole penetrates the second core board.

[0012] Optionally, the method for manufacturing the printed circuit board includes the following operations: A hollow area is formed on the circuit board body, and a filling material is placed in the hollow area; A surface mount pad is provided on one side of the circuit board body at a position corresponding to the hollow area, and the surface mount pad is partially attached to the filler material; Remove the filler material to expose the bottom surface of the surface mount pads at the location of the hollow area.

[0013] Optionally, "forming a hollow area on the circuit board body and setting a filling material in the hollow area" includes the following operations: The first core board and the position of the surface mount pad corresponding to the insulating adhesive layer are cut out to form a hollow area, and filling material is placed in the hollow area; The first copper foil, the first core board, and the insulating adhesive layer are laminated to obtain the circuit board body, with the first copper foil located on one side of the surface of the circuit board body. "Setting surface mount pads on one side of the circuit board body at the location corresponding to the hollow area" includes the following operations: The first copper foil is etched to form surface mount pads at the corresponding positions in the hollow area and a first circuit layer at the corresponding positions in the non-hollow area.

[0014] Optionally, the filling material is a washable material; A through hole is formed by drilling a hole in the circuit board body away from the surface layer, and the through hole penetrates the circuit board body to the hollow area. Clean the removable material in the hollow area to expose the hollow area and improve the impedance of the surface mount pads.

[0015] Optionally, during the lamination and lamination process, a second core board and a second copper foil are also included. The first copper foil, the first core board, the insulating adhesive layer, the second core board, and the second copper foil are laminated and laminated to obtain a circuit board body. The first copper foil is located on one side of the surface of the circuit board body, and the second copper foil is located on the other side of the surface of the circuit board body. The second copper foil is etched to form a second circuit layer.

[0016] Optionally, after "Setting filling material in the hollow area", the following operations are also included: Holes are drilled into the circuit board body to form vias for signal transmission. The vias are then electroplated to form a metal layer on the inner wall of the vias.

[0017] The beneficial effects of this application are: The printed circuit board provided in this application includes a circuit board body and surface mount pads. A hollow area is provided on the circuit board body, and the surface mount pads are disposed on one side of the surface layer of the circuit board body. The hollow area is located on the side of the surface mount pads away from the surface layer, and the bottom surface of the surface mount pads is exposed through the hollow area. The above-mentioned hollow area effectively reduces the area of ​​the circuit board dielectric corresponding to the surface mount pads, which can effectively improve the impedance of the surface mount pads, making them closer to the impedance of the surface mount devices. This solves the problem of low impedance caused by the large size of the surface mount pads, improves the impedance matching effect with high-speed connectors, and reduces signal reflection, attenuation and crosstalk, thereby ensuring the integrity and quality of high-speed signal transmission and improving the reliability of electronic devices. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the printed circuit board provided by the present invention; Figure 2 This is a schematic diagram of the hollow area set in the circuit board body of the present invention; Figure 3 This is a schematic diagram of the lamination of the multilayer structure of the circuit board body of the present invention; Figure 4 This is a schematic diagram of the through holes on the circuit board body of the present invention; Figure 5 This is a schematic diagram of the circuit layer on the circuit board body of the present invention; Figure 6 This is a schematic diagram of the through holes on the circuit board body of the present invention.

[0019] The reference numerals in the accompanying drawings are as follows: 1. Circuit board body; 11. Hollow area; 12. Through hole; 2. Surface mount pad; 3. First circuit layer; 4. Second circuit layer; 5. First solder mask layer; 6. Second solder mask layer; 7. Insulating adhesive layer; 8. Through hole; 81. Metal layer; 9. First core board; 10. Second core board; 13. Filler material; 14. First copper foil; 15. Second copper foil. Detailed Implementation

[0020] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0021] In the description of this invention, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention 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, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] Reference Figure 1 The present invention provides a printed circuit board, including a circuit board body 1 and surface mount pads 2. A hollow area 11 is provided on the circuit board body 1. The surface mount pads 2 are located on one side of the surface layer of the circuit board body 1. The hollow area 11 is located on the side of the surface mount pads 2 away from the surface layer, and the bottom surface of the surface mount pads 2 is exposed through the hollow area 11.

[0024] Specifically, the printed circuit board provided in this application includes a circuit board body 1 and surface mount pads 2. A hollow area 11 is provided on the circuit board body 1, and the surface mount pads 2 are disposed on one side of the surface layer of the circuit board body 1. The hollow area 11 is located on the side of the surface mount pads 2 away from the surface layer, and the bottom surface of the surface mount pads 2 is exposed through the hollow area 11. The above-mentioned hollow area 11 effectively reduces the area of ​​the circuit board dielectric corresponding to the surface mount pads 2, which can effectively improve the impedance of the surface mount pads 2, making it closer to the impedance of the surface mount devices. This solves the problem of low impedance caused by the large size of the surface mount pads 2, improves the impedance matching effect with high-speed connectors, and reduces signal reflection, attenuation and crosstalk, ensuring the integrity and quality of high-speed signal transmission, thereby improving the reliability of electronic devices.

[0025] In some embodiments, the circuit board body 1 is further provided with a through hole 12, which extends from the other side of the printed circuit board body 1 to the position of the hollow area 11.

[0026] Specifically, a through hole 12 is provided on the circuit board body 1, extending from the other side to the hollow area 11. The through hole 12 further removes the dielectric at the location of the hollow area 11, ensuring that the bottom surface of the surface mount pad 2 forms a preset spatial structure, avoiding interference from the residual part of the hollow area 11 on the impedance of the surface mount pad 2, thereby more accurately improving the impedance of the surface mount pad 2, making the impedance matching degree between the surface mount pad 2 and the high-speed connector higher, reducing reflection, attenuation and crosstalk in signal transmission, and further enhancing the transmission integrity and reliability of high-frequency and high-speed signals.

[0027] In some embodiments, along a direction parallel to the circuit board body 1, the cross-sectional area of ​​the hollow region 11 is smaller than the cross-sectional area of ​​the surface mount pad 2.

[0028] Specifically, along the direction parallel to the circuit board body 1, the cross-sectional area of ​​the hollow region 11 is set to be smaller than the cross-sectional area of ​​the surface mount pad 2. This setting reduces the dielectric of the circuit board body 1 below the surface mount pad 2 through the hollow region 11, effectively improving the pad impedance to match the high-speed connector. At the same time, it is conducive to the stable connection between the edge area of ​​the surface mount pad 2 and the circuit board body 1, avoiding the decrease in the structural strength of the surface mount pad 2 or the inability to reliably connect with the surrounding circuits due to the hollow region 11 being too large. Setting the cross-sectional area of ​​the hollow region 11 to be smaller than the cross-sectional area of ​​the surface mount pad 2, the smaller cross-section of the hollow region 11 is conducive to the precise control of the impedance of the surface mount pad 2, preventing excessive impedance increase. That is, this setting ensures that while improving the impedance, the mechanical stability of the surface mount pad 2 and the continuity of signal transmission are taken into account, better meeting the performance requirements of printed circuit boards used in high-frequency and high-speed products.

[0029] Reference Figure 5In some embodiments, a first circuit layer 3 is formed on one side of the surface layer of the circuit board body 1 at a position other than the surface mount pad 2. The first circuit layer 3 is electrically connected to the surface mount pad 2. A second circuit layer 4 is provided on the other side of the surface layer of the circuit board body 1. Both the first circuit layer 3 and the second circuit layer 4 are copper circuit layers.

[0030] Specifically, a first copper circuit layer and a second copper circuit layer electrically connected to the surface pad 2 are respectively provided on the surface layers of both sides of the circuit board body 1. The electrical connection between the first circuit layer 3 and the surface pad 2 serves as the main transmission path for the signal to extend from the surface pad 2 to the inside of the circuit board, ensuring the continuity of high-speed signal transmission. The electrical connection between the first circuit layer 3 and the surface pad 2 can reduce the impedance change of the signal at the transition between the surface pad 2 and the circuit. The second line layer 4 can serve as a ground reference plane or a signal return path, forming a symmetrical transmission environment with the first line layer 3, reducing electromagnetic interference and crosstalk during signal transmission. Setting line layers on both sides of the circuit board body 1 can also increase wiring space, avoid cross-interference between different signal lines, and, together with the hollow area 11 below the surface mount pad 2, further improve the impedance matching of the entire signal path, improve the reflection and attenuation of high-speed signals during transmission, and enhance the impedance matching effect between the printed circuit board and the high-speed connector.

[0031] In some embodiments, a solder mask layer is further included, the solder mask layer including a first solder mask layer 5 and a second solder mask layer 6, the first solder mask layer 5 covering the first circuit layer 3, and the second solder mask layer 6 covering the second circuit layer 4.

[0032] Specifically, by covering the first circuit layer 3 with the first solder mask layer 5 and the second circuit layer 4 with the second solder mask layer 6, physical protection can be formed on the circuit layers on both sides of the circuit board body 1 to prevent damage to the circuits during subsequent processing or use, and to ensure the integrity of the circuit layer structure and the stability of its conductivity.

[0033] In some embodiments, the circuit board body 1 includes multiple core boards stacked on top of each other, an insulating adhesive layer 7 is disposed between two adjacent core boards, and a third circuit layer is disposed on the surface of the core board; Reference Figure 4 The circuit board body 1 also includes a through hole 8, which passes through at least one core board. The inner wall of the through hole 8 is provided with a metal layer 81, which electrically connects to two or more of the first circuit layer 3, the second circuit layer 4, and multiple third circuit layers.

[0034] Specifically, the circuit board body 1 adopts a multi-layer core board stacked on top of each other. The multi-layer core board setting can increase the wiring density on the circuit board and meet the circuit layout requirements of high-frequency and high-speed products. A third circuit layer is set on the surface of the core board, which is conducive to the signal transmission and connection between the layers of the circuit board body 1. The insulating adhesive layer 7 not only ensures the solid bonding of adjacent core boards, but also provides good electrical insulation, avoids inter-layer signal interference, and ensures the independence of signal transmission. The multi-layer structure of the circuit board body 1, together with the surface mount pads 2 and the hollow area 11, further optimizes the overall impedance distribution, reduces signal loss and reflection during inter-layer transmission, enhances the stability of impedance matching, and improves the mechanical strength and structural stability of the printed circuit board.

[0035] The via 8 and the metal layer 81 on the inner wall of the via 8 can effectively realize the electrical connection between different circuit layers. The metal layer 81 on the inner wall of the via 8 serves as a conductive medium, which can electrically conduct two or more of the first circuit layer 3, the second circuit layer 4, and the multi-layer third circuit layer, breaking the spatial barrier between each circuit layer and allowing the signal to be transmitted smoothly in the multi-layer structure, avoiding signal interruption or attenuation caused by poor inter-layer connection. In conjunction with other structures, the impedance continuity of the overall circuit is further optimized, so that the surface mount pad 2 and the high-speed connector can achieve better impedance matching, ensuring the stability and integrity of high-frequency and high-speed signal transmission.

[0036] In some embodiments, the multilayer core board includes at least one first core board 9 and at least one second core board 10, the hollow region 11 penetrates at least one first core board 9, and the through hole 12 penetrates the second core board 10.

[0037] Specifically, the hollow area 11 penetrates at least one first core board 9, forming a space below the surface mount pad 2 within the first core board 9. This allows it to target a local area below the surface mount pad 2, reducing the distribution of dielectric material and copper layer in that area, adjusting the impedance characteristics of the surface mount pad 2, and improving the impedance matching between the surface mount pad 2 and the high-speed connector. The through hole 12 extends through the second core plate 10, which can confine the through hole 12 to the second core plate 10 and avoid causing structural impact on the first core plate 9 with the hollow area 11. At the same time, the through hole 12 on the second core plate 10 is beneficial for the subsequent removal of the filling material 13 in the hollow area 11.

[0038] In some embodiments, the method for manufacturing a printed circuit board includes the following operations: A hollow region 11 is formed on the circuit board body 1, and a filling material 13 is disposed in the hollow region 11; A surface mount pad 2 is provided on one side of the surface layer of the circuit board body 1 at a position corresponding to the hollow area 11, and the surface mount pad 2 is partially attached to the filler material 13; Remove the filler material 13 to expose the bottom surface of the surface mount pad 2 at the location of the hollow area 11.

[0039] Specifically, in this operation, firstly, filler material 13 is set in the hollow area 11, then the surface mount pad 2 is partially attached to the filler material 13, and finally the filler material 13 is removed to expose the bottom surface of the surface mount pad 2. The filler material 13 provides stable support during the surface mount pad 2 setup process, ensuring the bonding accuracy and structural stability of the surface mount pad 2 and the circuit board body 1. After removing the filler material 13, the exposed bottom surface of the surface mount pad 2, through the hollow area 11, reduces dielectric interference under the pad, effectively improving the impedance of the surface mount pad 2, and enabling the surface mount pad 2 to achieve impedance matching with the high-speed connector. Figure 2 ).

[0040] Reference Figure 6 In some embodiments, "forming a hollow region 11 on the circuit board body 1 and providing a filling material 13 in the hollow region 11" includes the following operations: The first core board 9 and the insulating adhesive layer 7 are cut out at the positions corresponding to the surface mount pads 2 to form a hollow area 11, and a filling material 13 is placed in the hollow area 11. The first copper foil 14, the first core board 9 and the insulating adhesive layer 7 are laminated and pressed together to obtain the circuit board body 1, with the first copper foil 14 located on one side of the surface of the circuit board body 1. "Setting surface mount pads 2 on one side of the surface layer of the circuit board body 1 at the position corresponding to the hollow area 11" includes the following operations: The first copper foil 14 is etched to form a surface mount pad 2 at the corresponding position in the hollow area 11, and a first circuit layer 3 is formed at the corresponding position in the non-hollow area 11.

[0041] Specifically, in the above operation, a hollow area 11 is formed by hollowing out the positions of the first core board 9 and the insulating adhesive layer 7 corresponding to the surface mount pad 2, and a filling material 13 is set. Then, the first copper foil 14, the first core board 9 and the insulating adhesive layer 7 are pressed together. During the pressing process, the filling material 13 is used to maintain the structural stability of the hollow area 11 during pressing, avoiding the deformation of the hollow area 11 during interlayer pressing or the problem of not being able to fit tightly, and ensuring the bonding strength between the layers of the circuit board body 1. Then, the first copper foil 14 is etched to form the surface mount pad 2 at the corresponding position of the hollow area 11 and the first circuit layer 3 in the non-hollow area 11, ensuring the electrical connection between the surface mount pad 2 and the first circuit layer 3. At the same time, the operation of removing the filling material 13 to expose the bottom surface of the surface mount pad 2 can make the impedance of the surface mount pad 2 and the high-speed connector more matched.

[0042] In some embodiments, the filler material 13 is a washable material; A through hole 12 is formed by drilling a hole at a position away from the surface layer of the circuit board body 1. The through hole 12 penetrates the circuit board body 1 to the position of the hollow area 11. Clean the removable material in the hollow area 11 to expose the location of the hollow area 11, thereby increasing the impedance of the surface mount pad 2.

[0043] Specifically, the washable material provides stable support for the hollow area 11 during the initial lamination and pressing of the first copper foil 14, the first core board 9, and the insulating adhesive layer 7, preventing structural deformation and ensuring the positioning accuracy and bonding stability of the surface mount pad 2. The through holes 12 formed by drilling can be used to clean the washable material, ensuring that the washable material is removed and exposing the bottom surface of the surface mount pad 2. The hollow area 11 effectively reduces the influence of the dielectric under the pad on its impedance, thereby better matching the impedance of the high-speed connector.

[0044] For washable materials, an alkaline solution can be used for cleaning.

[0045] Reference Figure 3 In some embodiments, during the lamination and pressing process, a second core board 10 and a second copper foil 15 are also included. The first copper foil 14, the first core board 9, the insulating adhesive layer 7, the second core board 10 and the second copper foil 15 are laminated and pressed to obtain the circuit board body 1. The first copper foil 14 is located on one side of the surface of the circuit board body 1, and the second copper foil 15 is located on the other side of the surface of the circuit board body 1. The second copper foil 15 is etched to form the second circuit layer 4.

[0046] Specifically, by stacking and pressing the first copper foil 14, the first core board 9, the insulating adhesive layer 7, the second core board 10, and the second copper foil 15 together, a stable multilayer circuit board body 1 structure is formed. The insulating adhesive layer 7 enables stable adhesion between the layers while achieving electrical insulation between the layers, thus avoiding interference between interlayer signals. The first copper foil 14 and the second copper foil 15 are located on the two sides of the surface of the circuit board body 1, respectively. The first circuit layer 3 and the second circuit layer 4 are formed after etching. The first circuit layer 3 and the second circuit layer 4 cooperate to form a complete signal transmission and return path, and work together with the hollow area 11 to optimize the impedance characteristics.

[0047] In some embodiments, after “filling the hollow region 11 with filling material 13”, the following operations are also included: Drill holes in the circuit board body 1 to form through holes 8 for signal transmission, and electroplate the through holes 8 to form a metal layer 81 on the inner wall of the through holes 8.

[0048] Specifically, after filling material 13 is placed in the hollow area 11, holes are drilled and electroplated to form conductive holes 8, which can effectively realize the electrical connection between multiple circuits in the circuit board body 1. The electroplated metal layer 81 realizes the conduction between the first circuit layer 3, the second circuit layer 4 and the third circuit layer, thus optimizing the signal transmission path.

[0049] 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 within the protection scope of the present invention.

Claims

1. A printed circuit board, characterized in that, The circuit board includes a circuit board body and surface mount pads. The circuit board body has a hollow area. The surface mount pads are located on one side of the surface layer of the circuit board body. The hollow area is located on the side of the surface mount pads away from the surface layer, and the bottom surface of the surface mount pads is exposed through the hollow area.

2. The printed circuit board according to claim 1, characterized in that, The circuit board body is also provided with a through hole, which extends from the other side of the printed circuit board body to the location of the hollow area.

3. The printed circuit board according to claim 1, characterized in that, Along a direction parallel to the circuit board body, the cross-sectional area of ​​the hollow region is smaller than the cross-sectional area of ​​the surface mount pad.

4. The printed circuit board according to claim 3, characterized in that, A first circuit layer is formed on one side of the surface of the circuit board body at a position other than the surface mount pads. The first circuit layer is electrically connected to the surface mount pads. A second circuit layer is provided on the other side of the surface of the circuit board body. Both the first circuit layer and the second circuit layer are copper circuit layers. It also includes a solder mask layer, which includes a first solder mask layer and a second solder mask layer, wherein the first solder mask layer covers the first circuit layer and the second solder mask layer covers the second circuit layer.

5. The printed circuit board according to claim 4, characterized in that, The circuit board body includes multiple layers of core boards stacked on top of each other, with an insulating adhesive layer between two adjacent core boards, and a third circuit layer on the surface of each core board; The circuit board body also includes a through hole, which passes through at least one core board. The inner wall of the through hole is provided with a metal layer, which electrically connects to two or more of the first circuit layer, the second circuit layer, and multiple third circuit layers. The multilayer core board includes at least one first core board and at least one second core board, the hollow area penetrates at least one first core board, and the through hole penetrates the second core board.

6. The method for manufacturing a printed circuit board according to any one of claims 1-5, characterized in that, Includes the following operations: A hollow area is formed on the circuit board body, and a filling material is placed in the hollow area; A surface mount pad is provided on one side of the circuit board body at a position corresponding to the hollow area, and the surface mount pad is partially attached to the filler material; Remove the filler material to expose the bottom surface of the surface mount pads at the location of the hollow area.

7. The method for preparing a printed circuit board according to claim 6, characterized in that, "Forming a hollow area on the circuit board body and setting a filling material in the hollow area" includes the following operations: The first core board and the position of the surface mount pad corresponding to the insulating adhesive layer are cut out to form a hollow area, and filling material is placed in the hollow area; The first copper foil, the first core board, and the insulating adhesive layer are laminated to obtain the circuit board body, with the first copper foil located on one side of the surface of the circuit board body. "Setting surface mount pads on one side of the circuit board body at the position corresponding to the hollow area" includes the following operations: The first copper foil is etched to form surface mount pads at the corresponding positions in the hollow area and a first circuit layer at the corresponding positions in the non-hollow area.

8. The method for preparing a printed circuit board according to claim 6, characterized in that, The filling material is a washable material; A through hole is formed by drilling a hole in the circuit board body away from the surface layer, and the through hole penetrates the circuit board body to the hollow area. Clean the removable material in the hollow area to expose the hollow area and improve the impedance of the surface mount pads.

9. The method for manufacturing a printed circuit board according to claim 7, characterized in that, During the lamination and lamination process, a second core board and a second copper foil are also included. The first copper foil, the first core board, the insulating adhesive layer, the second core board and the second copper foil are laminated and laminated to obtain the circuit board body. The first copper foil is located on one side of the surface of the circuit board body and the second copper foil is located on the other side of the surface of the circuit board body. The second copper foil is etched to form a second circuit layer.

10. The method for preparing a printed circuit board according to claim 7, characterized in that, After "setting filling material in the hollow area", also Includes the following operations: Holes are drilled into the circuit board body to form vias for signal transmission. The vias are then electroplated to form a metal layer on the inner wall of the vias.

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