Signal transmission circuit board and preparation method thereof
By setting a neutral transmission line layer in a flexible circuit board and using an RF converter, electromagnetic signals are transferred from the inner layer to the outer layer for transmission, solving the problem of reduced transmission performance of flexible circuit boards when bent and improving the stability and efficiency of signal transmission.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- AVARY HLDG (SHENZHEN) CO LTD
- Filing Date
- 2024-10-24
- Publication Date
- 2026-05-01
AI Technical Summary
During the bending process, the impedance change of the transmission line in existing flexible circuit boards leads to a decrease in transmission performance.
The transmission line layer is placed on the neutral layer and covered with an insulating protective layer. An RF converter is set up to transfer electromagnetic signals from the inner layer to the outermost layer for transmission when the circuit is bent, thus avoiding excessive impedance changes.
It improves the overall transmission performance of the signal transmission circuit board, ensuring the stability and efficiency of signal transmission when bent.
Smart Images
Figure CN121968432A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of circuit board technology, and in particular to a signal transmission circuit board and its manufacturing method. Background Technology
[0002] Existing flexible circuit boards typically have an impedance controlled at around 50 ohms to keep the return loss below -20dB, thus avoiding electromagnetic reflection during transmission. Currently, the transmission lines of flexible circuit boards are generally located in a neutral layer (a transition layer that is neither subjected to tension nor compression) to reduce the impact of stress. However, during bending, the impedance of the transmission lines changes, no longer being 50 ohms, resulting in a decrease in transmission performance. Summary of the Invention
[0003] In view of this, this application proposes a signal transmission circuit board and its manufacturing method to improve the transmission performance of the transmission line.
[0004] One embodiment of this application discloses a signal transmission circuit board, comprising an inner substrate and an outer substrate located on the surface of the inner substrate. The inner substrate includes a transmission line layer, an insulating protective layer, a radio frequency converter (RF converter), and two opposing dielectric layers. The transmission line layer is located between the two dielectric layers and embedded within the insulating protective layer. Along the extension direction of the dielectric layers, the RF converter is located on at least one side of the transmission line layer. The outer substrate includes a first circuit layer, a protective layer, and a second circuit layer. The first circuit layer is located on the surface of the dielectric layer opposite to the transmission line layer, and the protective layer is located between the first circuit layer and the second circuit layer. The second circuit layer is located on the surface of the protective layer opposite to the dielectric layer and is correspondingly disposed to the RF converter.
[0005] In one embodiment, the outer substrate further includes a via. One end of the via is connected to the first circuit layer, and the other end is exposed from the protective layer.
[0006] In one embodiment, the distance between the edge of the via exposed in the protective layer and the edge of the second circuit layer adjacent to the via is λ / 4. Here, λ is the wavelength corresponding to the applied frequency.
[0007] In one embodiment, the distance between the second circuit layer and the RF converter along the thickness direction of the inner substrate is 2λ, where λ is the wavelength corresponding to the applied frequency.
[0008] In one embodiment, the inner substrate further includes an adhesive layer. The adhesive layer is located between two dielectric layers and encapsulates the radio frequency converter.
[0009] In one embodiment, the insulating protective layer comprises polytetrafluoroethylene (PTFE). The protective layer includes an adhesive layer and a substrate layer, the adhesive layer being located between the dielectric layer and the substrate layer.
[0010] One embodiment of this application discloses a method for fabricating a signal transmission circuit board, comprising the following steps: fabricating an inner layer substrate; wherein the inner layer substrate includes a transmission line layer, an insulating protective layer, a radio frequency converter, and two dielectric layers disposed opposite to each other; the transmission line layer is located between the two dielectric layers and embedded in the insulating protective layer; along the extension direction of the dielectric layer, the radio frequency converter is located on at least one side of the transmission line layer; a copper foil layer is laminated onto the surface of the inner layer substrate to form a first circuit layer; a protective layer is laminated onto the surface of the first circuit layer opposite to the dielectric layer; and a copper foil layer is laminated onto the surface of the protective layer opposite to the first circuit layer to form a second circuit layer.
[0011] In one embodiment, prior to the step of "laminating a copper foil layer onto the surface of the protective layer away from the first circuit layer", the preparation method further includes: forming a blind via in the protective layer, with a portion of the surface of the first circuit layer exposed through the blind via; and plating copper in the blind via to form a through hole.
[0012] In one embodiment, the distance between the edge of the via exposed in the protective layer and the edge of the first circuit layer adjacent to the via is λ / 4. Here, λ is the wavelength corresponding to the applied frequency.
[0013] In one embodiment, the method for fabricating the inner layer substrate includes the following steps: providing a copper-clad laminate, the copper-clad laminate including a dielectric layer and a copper foil layer located on the surface of the dielectric layer; forming a transmission line layer from the copper foil layer; covering the surface of the transmission line layer with an insulating protective layer, such that the transmission line layer is embedded in the insulating protective layer; disposing a dielectric layer on each of the two opposite surfaces of the insulating protective layer; disposing an adhesive layer between the two dielectric layers, the adhesive layer being located on at least one side of the transmission line layer; disposing a radio frequency converter in the adhesive layer; and curing the adhesive layer.
[0014] This application places the transmission line layer on the neutral layer to reduce stress, covers the surface of the transmission line layer with an insulating protective layer to protect the transmission line layer, and places an RF converter on at least one side of the transmission line layer. When bent, the RF converter can transfer the electromagnetic signal from the inner transmission line layer to the outermost second line layer for transmission, thereby avoiding the problem of reduced transmission performance caused by excessive impedance change of the transmission line layer and improving the overall transmission performance of the signal transmission circuit board. Attached Figure Description
[0015] Figure 1This is a cross-sectional view of a signal transmission circuit board according to an embodiment of this application.
[0016] Figures 2A to 2E For preparation Figure 1 A cross-sectional view of the inner substrate of the transmission circuit board shown.
[0017] Figures 3A to 3H In order to be in Figure 2E The diagram shows a cross-sectional view of an outer substrate disposed on an inner substrate.
[0018] Explanation of main component symbols
[0019] Signal transmission circuit board 100
[0020] Inner substrate 10
[0021] Outer substrate 20
[0022] Transmission line layer 11
[0023] Insulation protective layer 12
[0024] RF converter 13
[0025] Adhesive layer 131
[0026] Dielectric layer 14
[0027] Copper clad laminates 10a, 20a, 30a
[0028] Copper foil layers 11a, 21a, 23a
[0029] Dielectric layers 15, 25, 35
[0030] First line layer 21
[0031] Protective layer 22
[0032] Second line layer 23
[0033] Through hole 24
[0034] Blind hole 220
[0035] Adhesive layer 221
[0036] Substrate layer 222
[0037] The following detailed description, in conjunction with the accompanying drawings, further illustrates the embodiments of this application. Detailed Implementation
[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this application pertain. The terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the embodiments of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0039] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.
[0040] It will be understood that when a layer is referred to as "on" another layer, it can be directly on that other layer or there may be an intermediate layer in between. Conversely, when a layer is referred to as "directly on" another layer, there is no intermediate layer. When a component is referred to as "attached to," "mounted to," "set on," or "connected to" another component, it can be directly on that other component or there may be an intervening component. The term "and / or" as used herein includes all and any combination of one or more of the associated listed items.
[0041] Embodiments of this application are described herein with reference to cross-sectional views, which are schematic diagrams of idealized embodiments (and intermediate configurations) of this application. Therefore, variations in the shapes illustrated due to manufacturing processes and / or tolerances are foreseeable. Consequently, embodiments of this application should not be construed as limited to the specific shapes of the areas illustrated herein, but should include, for example, deviations in shape due to manufacturing processes. The areas shown in the figures are merely illustrative, and their shapes are not intended to represent the actual shapes of the illustrated devices, nor are they intended to limit the scope of this application.
[0042] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.
[0043] Please see Figure 1 The first aspect of this application provides a signal transmission circuit board 100, which includes an inner substrate 10 and an outer substrate 20 located on the surface of the inner substrate 10. In this embodiment, the outer substrate 20 is located in the thickness direction of the inner substrate 10 (i.e., Figure 1 The signal transmission circuit board 100 has a symmetrical overall structure with its two opposing surfaces (vertical direction) on both sides.
[0044] like Figure 1As shown, the inner substrate 10 includes a transmission line layer 11, an insulating protective layer 12, an RF converter 13, and two opposing dielectric layers 14. The transmission line layer 11, the insulating protective layer 12, and the RF converter 13 are all located between the two opposing dielectric layers 14. The transmission line layer 11 is embedded in the insulating protective layer 12; that is, the surface of the transmission line layer 11 is completely covered by the insulating protective layer 12, and the pattern gaps of the transmission line layer 11 are also filled by the insulating protective layer 12. The insulating protective layer 12 is used to protect the transmission line layer 11, prevent it from being oxidized, and protect it from the effects of temperature and humidity. Along the extension direction of the dielectric layer 14 (i.e., ... Figure 1 The horizontal direction of the transmission line layer 11 (which can be either the length or width of the dielectric layer 14) is defined as follows: the middle transmission line layer 11 can be a ground line (GND), and the two ends of the transmission line layer 11 can be signal lines. The transmission line layer 11 is located in the neutral layer of the signal transmission circuit board 100. When bent, the neutral layer experiences almost zero force, which can reduce or even avoid the impact of bending on the transmission line layer 11.
[0045] like Figure 1 As shown, along the extension direction of the dielectric layer 14, the RF converter 13 is located on at least one side of the transmission line layer 11. In this embodiment, the RF converter 13 is located on both sides of the transmission line layer 11 along the extension direction of the dielectric layer 14; in other embodiments, the RF converter 13 may be located on only one side of the transmission line layer 11. The RF converter 13, also known as an RF converter (switcher), can be used to convert electromagnetic signals from the inner substrate 10 to the outer substrate 20 for transmission, ensuring that the lines are not affected.
[0046] like Figure 1 As shown, the outer substrate 20 includes a first circuit layer 21, a protective layer 22, and a second circuit layer 23. The first circuit layer 21 is located on the surface of the dielectric layer 14 opposite to the transmission line layer 11, and the protective layer 22 is located between the first circuit layer 21 and the second circuit layer 23. The protective layer 22 encloses the first circuit layer 21 and covers the surface of the dielectric layer 14 exposed from the first circuit layer 21. The second circuit layer 23 is located on the surface of the protective layer 22 opposite to the dielectric layer 14 and is correspondingly disposed with respect to the RF converter 13. This corresponding disposal means that the orthographic projection of the circuit pattern of the second circuit layer 23 onto the dielectric layer 14 at least partially overlaps with the orthographic projection of the RF converter 13. This ensures that the RF converter 13 transmits electromagnetic signals from the inner layer to the outer layer without being affected by the circuitry. Furthermore, the second circuit layer 23 is correspondingly disposed with the RF converter 13, that is, misaligned with the transmission line layer 11 (projections do not overlap), which avoids mutual interference. The wiring design between transmission line layer 11, first line layer 21 and second line layer 23 forms a microstrip line and stripline structure, which can ensure the signal transmission speed and effectively prevent electromagnetic radiation.
[0047] When the signal transmission circuit board 100 is bent, if the bending angle is too large (for example, greater than 35 degrees), the impedance change will also be large (exceeding 5%). At this time, the RF converter 13 can transfer the electromagnetic signal from the inner transmission line layer 11 to the outermost second line layer 23 for transmission, thereby avoiding the problem of reduced transmission performance caused by excessive impedance change of the transmission line layer 11.
[0048] In some embodiments, such as Figure 1 As shown, the outer substrate 20 also includes vias 24 penetrating the protective layer 22. The number of vias 24 can be one or more, and can be adjusted according to actual needs; this application does not impose any limitations. Along the thickness direction of the outer substrate 20 (i.e.,...) Figure 1 In the vertical direction, one end of the via 24 is connected to the first circuit layer 21, and the other end protrudes from the protective layer 22. The surface of the via 24 facing away from the first circuit layer 21 may be flush with the surface of the protective layer 22 facing away from the dielectric layer 14. The via 24 is not connected to the second circuit layer 23, and there is a certain distance between them. The via 24 may be a metal via (i.e., the via is filled with metal) to shield against noise interference.
[0049] Furthermore, such as Figure 1 As shown, the distance L between the edge of the via 24 exposed in the protective layer 22 and the edge of the adjacent second circuit layer 23 is λ / 4. Here, λ is the wavelength corresponding to the applied frequency, which can be 10mm to 37.5mm, and the frequency can be 2GHz to 7.5GHz. It can be understood that L is the distance between the edge of the via 24 and the edge of the second circuit layer 23 along the extension direction of the dielectric layer 14 (i.e., the extension direction of the protective layer 22). Figure 1 The shortest straight-line distance in the horizontal direction.
[0050] In some embodiments, such as Figure 1 As shown, along the thickness direction of the inner substrate 10, the distance H between the second circuit layer 23 and the RF converter 13 is 2λ. Here, λ is the wavelength corresponding to the applied frequency, which can be 10mm to 37.5mm, and the frequency can be 2GHz to 7.5GHz. It can be understood that H is the surface of the second circuit layer 23 facing (close to) the protective layer 22 (i.e.,...). Figure 1 The lower surface of the second circuit layer 23) and the surface of the RF converter 13 facing the dielectric layer 14 (i.e. Figure 1 The distance between the upper surface of the RF converter 13 and the upper surface of the RF converter 13.
[0051] In some embodiments, such as Figure 1As shown, the inner substrate 10 also includes an adhesive layer 131. The adhesive layer 131 is located between the two dielectric layers 14 and encapsulates the RF converter 13, thereby fixing the RF converter 13 between the two dielectric layers 14. The adhesive layer 131 may not be in contact with the insulating protective layer 12, and there may be a certain distance between them. The adhesive layer 131 may be formed from conventional or unconventional pure adhesives in the art, and this application is not limited thereto.
[0052] In some embodiments, such as Figure 1 As shown, the protective layer 22 may be a cover film layer (CVL), which may include an adhesive layer 221 and a substrate layer 222, with the adhesive layer 221 located between the dielectric layer 14 and the substrate layer 222. The adhesive layer 221 may be, but is not limited to, acrylic hot melt adhesive (AD), and the substrate layer 222 may be, but is not limited to, polyimide (PI).
[0053] In some embodiments, the insulating protective layer 12 may be made of, but is not limited to, polytetrafluoroethylene (PTFE, also known as Teflon), and the dielectric layer 14 may be made of, but is not limited to, prepreg (PP).
[0054] Please see Figures 2A to 3H This application proposes a method for manufacturing a signal transmission circuit board 100, which includes the following steps.
[0055] Step S10, please refer to Figures 2A to 2E The inner layer substrate 10 is then prepared. In some embodiments, step S10 may further include steps S11 to S17. That is, the inner layer substrate 10 can be formed by steps S11 to S17.
[0056] S11, such as Figure 2A As shown, a copper-clad laminate 10a is provided. The copper-clad laminate 10a includes a dielectric layer 15 and a copper foil layer 11a located on one surface of the dielectric layer 15. The dielectric layer 15 may be made of, but is not limited to, polyimide (PI), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polydimethylsiloxane (PDMS), liquid crystal polymer (LCP), modified polyimide (MPI), etc. In this embodiment, the dielectric layer 15 is made of PI.
[0057] S12, as Figure 2B As shown, the copper foil layer 11a can be fabricated into the transmission line layer 11 through steps such as lamination, exposure, development, etching, and film removal. The steps of lamination, exposure, development, etching, and film removal are common techniques in this field and will not be described in detail here.
[0058] S13, as Figure 2CAs shown, the dielectric layer 15 can be removed by means of, but not limited to, laser. In some embodiments, the dielectric layer 15 may also be retained.
[0059] S14, as Figure 2D As shown, an insulating protective layer 12 is covered on the surface of the transmission line layer 11, so that the transmission line layer 11 is embedded in the insulating protective layer 12. The insulating protective layer 12 may be, but is not limited to, PTFE.
[0060] S15, such as Figure 2E As shown, a dielectric layer 14 is attached to each of the two opposite surfaces of the insulating protective layer 12. The extension length of the dielectric layer 14 exceeds the extension length of the insulating protective layer 12, and the dielectric layer 14 may be, but is not limited to, a prepreg.
[0061] S16, as Figure 2E As shown, an adhesive layer 131 is disposed between the two dielectric layers 14, and the adhesive layer 131 is in contact with both dielectric layers 14. Along the extending direction of the dielectric layer 14 ( Figure 2E In the horizontal direction of the transmission line layer 11, the adhesive layer 131 is located on at least one side. In this embodiment, the adhesive layer 131 is located on both the left and right sides of the transmission line layer 11; in other embodiments, the adhesive layer 131 may be located on only one side of the transmission line layer 11. The adhesive layer 131 may be formed of pure adhesive.
[0062] S17, as shown Figure 2E As shown, an RF converter 13 is disposed in an adhesive layer 131, and the RF converter 13 is encapsulated within the adhesive layer 131. The adhesive layer 131 is then cured to fix the RF converter 13 between the two dielectric layers 14 through the adhesive layer 131, thereby obtaining the inner substrate 10.
[0063] like Figure 2E As shown, the inner substrate 10 includes a transmission line layer 11, an insulating protective layer 12, an RF converter 13, and two opposing dielectric layers 14. The transmission line layer 11, the insulating protective layer 12, and the RF converter 13 are all located between the two opposing dielectric layers 14. The transmission line layer 11 is embedded in the insulating protective layer 12, that is, the surface of the transmission line layer 11 is covered by the insulating protective layer 12, and the pattern gaps of the transmission line layer 11 are also filled by the insulating protective layer 12. Along the extending direction of the dielectric layer 14, the RF converter 13 is located on at least one side of the transmission line layer 11.
[0064] Step S20, please refer to Figures 3A to 3C A copper foil layer 21a is laminated onto the surface of the inner substrate 10 to form the first circuit layer 21. In some embodiments, step S20 may further include S21 to S23.
[0065] like Figure 3AAs shown, in step S21, a copper-clad laminate 20a can be laminated onto both surfaces of the inner substrate 10. The copper-clad laminate 20a may include a dielectric layer 25 and a copper foil layer 21a located on one surface of the dielectric layer 25, with the copper foil layer 21a situated between the dielectric layer 14 and the dielectric layer 25. The dielectric layer 25 may be, but is not limited to, PI, PET, PEN, PDMS, LCP, MPI, etc.
[0066] like Figure 3B As shown, in step S22, the dielectric layer 25 can be removed by means of, but not limited to, laser.
[0067] like Figure 3C As shown in step S23, the copper foil layer 21a can be fabricated to form the first circuit layer 21 through steps such as lamination, exposure, development, etching, and film removal. The steps of lamination, exposure, development, etching, and film removal are common techniques in this field and will not be described in detail here.
[0068] Step S30, please refer to Figure 3D A protective layer 22 is laminated onto the surface of the first circuit layer 21 facing away from the dielectric layer 14. The protective layer 22 may include an adhesive layer 221 and a substrate layer 222. The adhesive layer 221 is located between the dielectric layer 14 and the substrate layer 222, and the adhesive layer 221 encapsulates the first circuit layer 21. The adhesive layer 221 may be, but is not limited to, an adhesive (AD adhesive), and the substrate layer 222 may be, but is not limited to, a polyimide (PI) adhesive.
[0069] For step S40, please refer to... Figure 3E Blind vias 220 can be formed in the protective layer 22 by means of, but not limited to, laser drilling or mechanical drilling, and a portion of the surface of the first circuit layer 21 can be exposed through the blind vias 220. The number of blind vias 220 can be adjusted according to actual needs, and this application does not impose any limitations.
[0070] For step S50, please refer to... Figure 3F Copper is plated in the blind via 220 to form the via 24. Along the thickness direction of the protective layer 22 (i.e.,...) Figure 1 (Vertically, in the middle), one end of the via 24 is connected to the first circuit layer 21, and the other end protrudes from the protective layer 22. The surface of the via 24 facing away from the first circuit layer 21 can be flush with the surface of the protective layer 22 facing away from the dielectric layer 14. The via 24 can shield noise interference.
[0071] For step S60, please refer to... Figure 3G and Figure 3H A copper foil layer 23a is laminated onto the surface of the protective layer 22 opposite to the first circuit layer 21, thereby forming the second circuit layer 23 from the copper foil layer 23a. Step S60 may further include steps S61 to S63.
[0072] like Figure 3GAs shown, in step S62, a copper-clad laminate 30a can be laminated onto the surface of the protective layer 22 opposite to the first circuit layer 21. The copper-clad laminate 30a may include a dielectric layer 35 and a copper foil layer 23a located on one surface of the dielectric layer 35, with the copper foil layer 23a situated between the protective layer 22 (substrate layer 222) and the dielectric layer 35. The dielectric layer 35 may be, but is not limited to, PI, PET, PEN, PDMS, LCP, MPI, etc.
[0073] like Figure 3H As shown, in S62, the dielectric layer 35 can be removed by means of, but not limited to, laser.
[0074] like Figure 1 As shown in step S63, the copper foil layer 23a can be fabricated into a second circuit layer 23 through steps such as lamination, exposure, development, etching, and film removal, thereby obtaining the signal transmission circuit board 100. The second circuit layer 23 can be correspondingly configured with the radio frequency converter 13. The steps of lamination, exposure, development, etching, and film removal are common techniques in this field and will not be described in detail here.
[0075] The signal transmission circuit board 100 and its manufacturing method provided in this application embodiment reduce stress by setting the transmission line layer 11 in the neutral layer, covering the surface of the transmission line layer 11 with an insulating protective layer 12 to protect the transmission line layer 11, and setting an RF converter 13 on at least one side of the transmission line layer 11. When bent, the RF converter 13 can convert the electromagnetic signal from the inner transmission line layer 11 to the outermost second line layer 23 for transmission, thereby avoiding the problem of transmission performance degradation caused by excessive impedance change of the transmission line layer 11, and improving the overall transmission performance of the signal transmission circuit board 100.
[0076] The above description describes some specific embodiments of this application, but in actual applications, the application should not be limited to these embodiments. For those skilled in the art, other modifications and alterations made based on the technical concept of this application should fall within the protection scope of this application.
Claims
1. A signal transmission circuit board, characterized in that, include: The inner substrate includes a transmission line layer, an insulating protective layer, an RF converter, and two opposing dielectric layers; The transmission line layer is located between two dielectric layers and is embedded in the insulating protective layer; along the extension direction of the dielectric layer, the radio frequency converter is located on at least one side of the transmission line layer; and An outer substrate is located on the surface of the inner substrate. The outer substrate includes a first circuit layer, a protective layer, and a second circuit layer. The first circuit layer is located on the surface of the dielectric layer opposite to the transmission circuit layer. The protective layer is located between the first circuit layer and the second circuit layer. The second circuit layer is located on the surface of the protective layer opposite to the dielectric layer and is correspondingly disposed with respect to the radio frequency converter.
2. The signal transmission circuit board as described in claim 1, characterized in that, The outer substrate also includes a via, one end of which is connected to the first circuit layer, and the other end is exposed from the protective layer.
3. The signal transmission circuit board as described in claim 2, characterized in that, The distance between the edge of the via exposed in the protective layer and the edge of the second circuit layer adjacent to the via is λ / 4, where λ is the wavelength corresponding to the applied frequency.
4. The signal transmission circuit board as described in claim 1, characterized in that, Along the thickness direction of the inner substrate, the distance between the second circuit layer and the RF converter is 2λ, where λ is the wavelength corresponding to the applied frequency.
5. The signal transmission circuit board as described in claim 1, characterized in that, The inner substrate further includes an adhesive layer located between two dielectric layers and encapsulating the radio frequency converter.
6. The signal transmission circuit board as described in claim 1, characterized in that, The insulating protective layer comprises polytetrafluoroethylene; the protective layer comprises an adhesive layer and a substrate layer, wherein the adhesive layer is located between the dielectric layer and the substrate layer.
7. A method for manufacturing a signal transmission circuit board, characterized in that, Includes the following steps: An inner layer substrate is fabricated; wherein the inner layer substrate includes a transmission line layer, an insulating protective layer, a radio frequency converter, and two dielectric layers disposed opposite to each other; the transmission line layer is located between the two dielectric layers and is embedded in the insulating protective layer; along the extension direction of the dielectric layer, the radio frequency converter is located on at least one side of the transmission line layer; A copper foil layer is laminated onto the surface of the inner substrate to form a first circuit layer. A protective layer is laminated onto the surface of the first circuit layer that is opposite to the dielectric layer; A copper foil layer is laminated onto the surface of the protective layer opposite to the first circuit layer to form the second circuit layer.
8. The preparation method according to claim 7, characterized in that, Before the step of "laminating a copper foil layer on the surface of the protective layer away from the first circuit layer", the preparation method further includes: forming a blind hole in the protective layer, with a portion of the surface of the first circuit layer exposed from the blind hole; and plating copper in the blind hole to form a via.
9. The preparation method according to claim 8, characterized in that, The distance between the edge of the via exposed in the protective layer and the edge of the first line layer adjacent to the via is λ / 4, where λ is the wavelength corresponding to the applied frequency.
10. The preparation method according to claim 7, characterized in that, The method for preparing the inner layer substrate includes the following steps: A copper-clad laminate is provided, the copper-clad laminate comprising a dielectric layer and a copper foil layer located on the surface of the dielectric layer; The copper foil layer is fabricated to form a transmission line layer; An insulating protective layer is wrapped around the surface of the transmission line layer, so that the transmission line layer is embedded in the insulating protective layer; A dielectric layer is disposed on each of the two opposite surfaces of the insulating protective layer; An adhesive layer is disposed between two dielectric layers, the adhesive layer being located on at least one side of the transmission line layer; An RF converter is disposed in the adhesive layer, and the adhesive layer is then cured.