Printed circuit board and preparation method thereof

Abstract

The invention discloses a printed circuit board and a preparation method thereof, the printed circuit board comprises a substrate and transmission lines located on the substrate, the substrate is provided with at least one transmission line, each transmission line comprises an outer shielding layer, an inner transmission layer and a supporting layer, the outer shielding layer is of a hollow structure with an air cavity inside, and the inner transmission layer is of a hollow structure with an air cavity inside. And the inner transmission layer is suspended in the corresponding air cavity through the supporting layer and is insulated from the outer shielding layer. According to the printed circuit board, the signal transmission path is optimized fundamentally, the energy loss in the transmission process is remarkably reduced, and meanwhile, the reflection and crosstalk phenomena are effectively inhibited, so that the signal transmission characteristics of wide bandwidth, low loss and high isolation are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and in particular to a printed circuit board and a preparation method thereof. Background Art

[0002] In the current electronic technology field, printed circuit board (PCB) plays a vital role as the core component that supports and interconnects various functional sub-boards. It builds the main communication channel between functional devices through surface microstrip wiring, built-in perforations, and multi-layer complex laminated circuit design. It is not only responsible for the power distribution of each sub-board, but also ensures the electrical connection and efficient signal transmission between sub-boards. With its high-speed transmission capability and long routing characteristics, printed circuit board design has become the key to realizing complex system functions and improving the overall electrical performance of equipment.

[0003] However, with the rapid development of information technology, the data rate and communication frequency continue to rise, and the bandwidth demand for communication channels is increasing, which poses unprecedented challenges to the design of printed circuit boards. Existing printed circuit board technology is limited by material properties and structural design, and generally faces problems such as high loss, severe reflection, and crosstalk interference. These problems not only limit the further improvement of transmission rate, but also seriously affect the stability and reliability of the system.

[0004] Therefore, developing a new type of printed circuit board that can support higher transmission rates, have lower transmission losses, wider bandwidth and isolation, while maintaining high reliability has become an urgent need for current technological development. Summary of the invention

[0005] In view of the above problems, the present invention is proposed to provide a printed circuit board and a method for manufacturing the same that overcome the above problems or at least partially solve the above problems.

[0006] In a first aspect, a printed circuit board is provided, comprising a substrate and a transmission line located on the substrate, wherein the substrate has at least one transmission line, each of the transmission lines comprises an outer shielding layer, an inner transmission layer and a supporting layer, the outer shielding layer is a hollow structure having an air cavity inside, the inner transmission layer is suspended in the corresponding air cavity through the supporting layer, and is insulated from the outer shielding layer.

[0007] Optionally, when there are a plurality of transmission lines on the substrate, the plurality of transmission lines are stacked on the substrate in a parallel manner, and each layer includes at least one transmission line, and the at least one transmission line is arranged at intervals or adjacently.

[0008] Optionally, when there are a plurality of transmission lines on the substrate, the plurality of transmission lines are stacked on the substrate in a cross-stacked manner, and each layer includes at least one transmission line, and the at least one transmission line is arranged at intervals or adjacently.

[0009] Optionally, the outer shielding layer is provided with at least one release hole communicating with the air cavity.

[0010] Optionally, the printed circuit board includes connection ports corresponding one-to-one to the at least one transmission line, and each of the connection ports is used to be electrically connected to an inner transmission layer of the corresponding transmission line.

[0011] Optionally, the support layer is a photosensitive film layer.

[0012] In a second aspect, a method for preparing a printed circuit board is provided, the method comprising:

[0013] Providing a substrate for a printed circuit board;

[0014] At least one transmission line is formed on the surface of the substrate, and each of the transmission lines includes an outer shielding layer, an inner transmission layer and a support layer. The outer shielding layer is a hollow structure with an air cavity inside, and the inner transmission layer is suspended in the corresponding air cavity through the support layer and is insulated from the outer shielding layer.

[0015] Optionally, when the substrate has a plurality of transmission lines, and the plurality of transmission lines are stacked on the substrate in a parallel stacking or cross stacking manner, forming at least one transmission line on the surface of the substrate includes:

[0016] Using a first preparation method, forming a first layer of transmission lines on the substrate, wherein the first layer of transmission lines includes at least one transmission line;

[0017] A second preparation method is adopted to form a plurality of transmission lines on the first transmission line layer, each transmission line layer includes at least one transmission line, and the at least one transmission line is arranged at intervals or adjacent to each other.

[0018] Optionally, the first preparation method comprises:

[0019] forming at least one outer shielding bottom layer on the substrate;

[0020] forming a layer of the support layer on each of the outer shielding bottom layers;

[0021] Forming a first portion of outer shielding side walls on each of the outer shielding bottom layers, wherein the first portion of the outer shielding side walls has the same height as the supporting layer;

[0022] forming the inner transmission layer on each of the support layers, and forming a second portion of the outer shaft side wall on each of the first portion of the outer shielding side wall;

[0023] forming a third portion of the outer shaft side wall on each of the second portion of the outer shaft side wall, wherein the first portion of the outer shielding side wall, the second portion of the outer shielding side wall and the third portion of the outer shielding side wall constitute the outer shielding side wall layer;

[0024] An outer shielding top layer is formed on each outer axial side wall of the third portion, wherein the outer shielding top layer, the outer shielding side wall layer and the outer shielding bottom layer constitute the outer shielding layer.

[0025] Optionally, the second preparation method comprises:

[0026] Selecting the outer shielding top layer of at least one transmission line as the target bottom layer;

[0027] forming a layer of the support layer on each of the target bottom layers;

[0028] forming a first portion of an outer shielding side wall on each of the target bottom layers;

[0029] forming the inner transmission layer on each of the support layers, and forming the second portion outer shaft side wall on each of the first portion outer shield side wall;

[0030] forming the third portion outer shaft side wall on each of the second portion outer shaft side walls;

[0031] The outer shield top layer is formed on each of the third portion outer shaft side walls, wherein the outer shield top layer, the outer shield side wall layer and the target bottom layer constitute the outer shield layer.

[0032] The technical solution provided in the embodiments of the present invention has at least the following technical effects or advantages:

[0033] A printed circuit board and a preparation method thereof provided by an embodiment of the present invention, wherein the substrate of the printed circuit board has at least one transmission line, and each transmission line is an air core micro-coaxial structure including an outer shielding layer, an inner transmission layer and a support layer. Since the air core micro-coaxial transmission line is filled with air in the middle, its dielectric constant is much lower than that of conventional dielectric materials. In the process of microwave transmission, the lower the dielectric constant, the smaller the signal loss on the transmission line. Therefore, the air core micro-coaxial transmission line can significantly reduce the signal loss during transmission and improve the signal transmission efficiency. And the structural characteristics of the air core micro-coaxial transmission line enable it to support wider frequency band transmission. Compared with traditional coaxial transmission lines, air core micro-coaxial transmission lines have better transmission performance in high frequency bands and can transmit microwave signals more effectively. This has significant advantages for application scenarios requiring high frequency and wide bandwidth transmission. Therefore, the printed circuit board provided by the present invention fundamentally optimizes the signal transmission path, significantly reduces the energy loss during transmission, and effectively suppresses reflection and crosstalk phenomena, thereby achieving wide bandwidth, low loss, and high isolation signal transmission characteristics.

[0034] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0036] Figure 1 is a schematic structural diagram of a printed circuit board provided by an embodiment of the present invention;

[0037] Figure 2 is a schematic structural diagram of another printed circuit board provided by an embodiment of the present invention;

[0038] Figure 3 is a structural schematic diagram of another printed circuit board provided by an embodiment of the present invention;

[0039] Figure 4 is a structural schematic diagram of another printed circuit board provided by an embodiment of the present invention;

[0040] Figure 5 is a schematic diagram of a connection port of a printed circuit board provided by an embodiment of the present invention;

[0041] Figure 6It is a flow chart of a method for preparing a printed circuit board provided by an embodiment of the present invention;

[0042] Figure 7 is a flow chart of a first preparation method provided by an embodiment of the present invention;

[0043] Figures 7a to 7f 1 is a schematic diagram of the preparation structure of a printed circuit board corresponding to steps S710 to S760 respectively. DETAILED DESCRIPTION

[0044] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings.

[0045] Various structural schematic diagrams according to embodiments of the present disclosure are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may further design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0046] In the context of the present disclosure, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be an intervening layer / element therebetween. Additionally, if a layer / element is "on" another layer / element in one orientation, the layer / element may be "below" the other layer / element when the orientation is reversed. In the context of the present disclosure, similar or identical components may be denoted by the same or similar reference numerals.

[0047] In order to better understand the above-mentioned technical scheme, the above-mentioned technical scheme will be described in detail below in combination with specific implementation methods. It should be understood that the embodiments of the present disclosure and the specific features in the embodiments are detailed descriptions of the technical scheme of the present application, rather than limitations on the technical scheme of the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other.

[0048] Figure 1 is a schematic diagram of the structure of a printed circuit board provided by an embodiment of the present invention, such as Figure 1 As shown, the printed circuit board 100 includes a substrate 110 and a transmission line 120 located on the substrate 110. The substrate 110 has at least one transmission line 120, and each transmission line 120 includes an outer shielding layer 120a, an inner transmission layer 120b and a support layer 120c. The outer shielding layer 120a is a hollow structure with an air cavity S inside, and the inner transmission layer 120b is suspended in the corresponding air cavity S through the support layer 120c and is insulated from the outer shielding layer 120a.

[0049] It should be noted that Figure 1 Only one transmission line 120 on the substrate 110 is shown. In the actual preparation process, a plurality of transmission lines 120 are usually provided on the substrate 110, and the plurality of transmission lines 120 can be prepared according to the actual circuit layout, which is not limited in this embodiment.

[0050] In this embodiment, if Figure 1 As shown, at least one release hole P connected to the air cavity S is provided on the outer shielding layer 120a of each transmission line 120, so as to facilitate the release of the photoresist, the seed layer, etc. when the transmission line is subsequently prepared.

[0051] Optionally, the supporting layer 120c is a photosensitive film layer, which can play an insulating and supporting role, ensuring the insulation between the inner conductor 20 and the rectangular outer conductor 10, thereby ensuring the signal transmission quality.

[0052] The support structure 120c may be a strip structure distributed along the axial direction of the outer shielding layer 120a, or may be a structure of multiple support columns distributed along the axial direction of the outer shielding layer 120a. The multiple support columns may be rectangular to ensure that the support structure 120c has a better supporting effect.

[0053] Optionally, the outer shielding layer 120a and the inner transmission layer 120b are both copper layers. Copper has good electrical conductivity and mechanical properties and can meet the requirements of high-frequency transmission. Among them, the inner transmission layer 120b is responsible for transmitting signals. The outer shielding layer 120a and the inner transmission layer 120b together form a conductive path to ensure stable signal transmission. At the same time, the outer shielding layer 120a can also play a shielding role to prevent external electromagnetic interference from affecting signal transmission.

[0054] In one implementation, a plurality of transmission lines are provided on the substrate, and the plurality of transmission lines are stacked on the substrate in a parallel manner, and each layer includes at least one transmission line, and at least one transmission line 120 is arranged at intervals or adjacently.

[0055] Figure 2 is a schematic diagram of the structure of another printed circuit board provided by an embodiment of the present invention, such as Figure 2 As shown, at this time, a first transmission line 221 and a second transmission line 222 are provided on the substrate 210. The first transmission line 221 and the second transmission line 222 are divided into two layers and are stacked on the substrate 210 in a parallel stacking manner, and the axes of the first transmission line 221 and the second transmission line 222 are parallel. Figure 3 is a schematic diagram of the structure of another printed circuit board provided by an embodiment of the present invention, such as Figure 3As shown, at this time, the substrate 310 is provided with a first transmission line 321, a second transmission line 322, a third transmission line 323 and a fourth transmission line 324, and the four transmission lines are stacked in parallel on the substrate 310, and the axes of the four transmission lines are parallel. The first transmission line 321 and the second transmission line 322 are located in the first layer, the third transmission line 323 and the fourth transmission line 324 are located in the second layer, and the transmission line 321 and the transmission line 322 are arranged in parallel.

[0056] In one implementation, a plurality of transmission lines are provided on the substrate, and the plurality of transmission lines are stacked on the substrate in a cross-stacked manner, and each layer includes at least one transmission line, and at least one transmission line is arranged at intervals or adjacently.

[0057] Figure 4 is a schematic diagram of the structure of another printed circuit board provided by an embodiment of the present invention, such as Figure 4 As shown, at this time, the substrate 410 is provided with a first transmission line 421 and a second transmission line 422 ( Figure 2 Only a portion of the second transmission line is shown), the first transmission line 421 includes an outer shielding layer 421a, an inner transmission layer 421b and a support layer 421c, and the second transmission line 422 includes an outer shielding layer 422a, an inner transmission layer 422b and a support layer 422c. The first transmission line 421 and the second transmission line 422 are stacked on the substrate 410 in a cross-stacked manner, that is, the second transmission line 422 is stacked on the first transmission line 421, and the axes of the two transmission lines are perpendicular (or at a set angle).

[0058] It should be noted that in the above implementation, two contacting transmission lines can share part of the outer shielding layer to reduce the number of outer shielding layers, save costs, and reduce the volume occupied by the transmission lines.

[0059] Through the above implementation, multiple transmission lines can be arranged on the substrate in a parallel stacking or cross stacking manner, which is beneficial to reduce the volume occupied by the transmission lines on the substrate, and at the same time can ensure that the transmission lines do not interfere with each other.

[0060] Optionally, the printed circuit board may further include connection ports corresponding to at least one transmission line, each connection port being used to electrically connect to the inner transmission layer of the corresponding transmission line. Each connection port may be arranged according to the arrangement of each transmission line.

[0061] Figure 5 FIG. 1 is a schematic diagram of a transmission line arrangement method provided by an embodiment of the present invention. Figure 5 As shown, the figure shows different arrangements of the outer shielding layer 520a and the inner transmission layer 520b of the transmission line, for example, Figure 5(a), (b), and (d) all show a transmission line, and the inner transmission layer 520b of the transmission line is arranged parallel to the substrate, but the end of the inner transmission layer 520b of the transmission line in (d) is oriented in a direction perpendicular to the substrate and extends from the top of the outer shielding layer 520a. Figure 5 (c) and (e) both show two transmission lines, and the inner transmission layers 520b of the two transmission lines are arranged parallel to the substrate, but the ends of the inner transmission layers 520b of the two transmission lines in (e) are both oriented in a direction perpendicular to the substrate and extend from the top of the outer shielding layer 520a. Figure 5 (f) shows four transmission lines, and the four transmission lines are arranged parallel to the substrate, but the ends of the inner transmission layers 520b of the four transmission lines are all oriented perpendicular to the substrate and extend from the top of the outer shielding layer 520a. In specific implementation, the connection ports can be arranged according to the following example: Figure 5 The end position of the inner transmission layer in each transmission line shown is set so as to achieve electrical connection with the corresponding inner transmission layer through the connection port.

[0062] Based on the same inventive concept, the embodiment of the present invention also provides a method for preparing a printed circuit board, Figures 1 to 4 A printed circuit board as described in any one of the preceding claims. Figure 6 is a flow chart of a method for preparing a printed circuit board provided by an embodiment of the present invention, such as Figure 6 As shown, the preparation method comprises:

[0063] Step S610, providing a printed circuit board substrate;

[0064] Step S620, forming at least one transmission line on the surface of the substrate, each transmission line comprising an outer shielding layer, an inner transmission layer and a support layer, the outer shielding layer is a hollow structure with an air cavity inside, the inner transmission layer is suspended in the corresponding air cavity through the support layer and is insulated from the outer shielding layer.

[0065] In one implementation, when there are multiple transmission lines on the substrate, and the multiple transmission lines are stacked on the substrate in a parallel stacking or cross stacking manner, step S620 includes:

[0066] Using a first preparation method, forming a first layer of transmission lines on a substrate, the first layer of transmission lines including at least one transmission line;

[0067] The second preparation method is used to form multiple layers of transmission lines on the first layer of transmission lines, each layer of transmission lines includes at least one transmission line, and the at least one transmission line is arranged at intervals or adjacently.

[0068] Figure 7 is a flow chart of a first preparation method provided by an embodiment of the present invention, such as Figure 7As shown, in one implementation, the first preparation method includes:

[0069] Step S710: forming at least one outer shielding bottom layer on a substrate.

[0070] In this embodiment, a copper layer may be deposited on the substrate by electroplating, and then the copper layer may be photoetched to remove a portion of the copper layer to form the required outer shielding bottom layer.

[0071] Step S720: forming a support layer on each outer shielding bottom layer.

[0072] In this embodiment, the support layer may be a photosensitive material, and the required support layer may be formed on the outer shielding bottom layer by spraying the photosensitive layer on the outer shielding bottom layer and removing part of the photosensitive polyimide layer by photolithography.

[0073] Step S730: forming a first portion of outer shielding side walls on each outer shielding bottom layer, wherein the first portion of the outer shielding side walls is at the same height as the supporting layer.

[0074] In this embodiment, a first sacrificial layer may be coated on the outer shielding bottom layer, then the first sacrificial layer may be photolithographically processed to form a desired pattern on the first sacrificial layer, and finally a copper layer may be electroplated in the groove of the pattern to form the desired first portion of the outer shielding sidewall.

[0075] Step S740: forming an inner transmission layer on each supporting layer, and forming a second portion outer shaft side wall on each first portion outer shielding side wall.

[0076] In this embodiment, a second sacrificial layer can be first coated on the first sacrificial layer, and then the second sacrificial layer can be photolithographically processed to form a desired pattern on the second sacrificial layer, and finally a copper layer can be electroplated in the groove of the pattern to form the desired inner transmission layer and the second part of the outer shaft side wall.

[0077] Step S750: forming a third portion of the outer shaft side wall on each second portion of the outer shaft side wall, wherein the first portion of the outer shielding side wall, the second portion of the outer shielding side wall and the third portion of the outer shielding side wall constitute an outer shielding side wall layer.

[0078] In this embodiment, a third sacrificial layer may be coated on the second sacrificial layer first, and then the third sacrificial layer may be photolithographically processed to form a desired pattern on the third sacrificial layer, and finally a copper layer may be electroplated in the groove of the pattern to form the desired third portion of the outer shaft sidewall.

[0079] Step S760: forming an outer shielding top layer on the outer shaft side wall of each third portion, wherein the outer shielding top layer, the outer shielding side wall layer and the outer shielding bottom layer constitute an outer shielding layer.

[0080] In this embodiment, a fourth sacrificial layer may be coated on the third sacrificial layer first, then the fourth sacrificial layer may be photolithographically processed to form a desired pattern on the fourth sacrificial layer, and finally a copper layer may be electroplated in the grooves of the pattern to form a desired outer shielding top layer.

[0081] It should be noted that, in the process of preparing the outer shielding side wall layer and the outer shielding top layer in the above steps S730 to S760, a release hole can be formed on the outer shielding side wall layer and the outer shielding top layer by electroplating a discontinuous copper layer, and the discontinuous position is the position of the release hole. After executing step S760, if no more transmission lines are needed, each sacrificial layer can be released through the release hole by wet etching or the like to finally obtain the desired transmission line structure.

[0082] Figures 7a to 7f Schematic diagram of the preparation structure of the printed circuit board corresponding to steps S710 to S760, as shown in FIG. Figure 7a As shown, corresponding to step S710, at this time, two outer shielding bottom layers 721a are formed on the substrate 710; Figure 7b As shown, corresponding to step S720, at this time, a support layer 720c is formed on each outer shielding bottom layer 721a; Figure 7c As shown, corresponding to step S730, at this time, a first portion of outer shielding side walls 721b is formed on each outer shielding bottom layer 721a; Figure 7d As shown, corresponding to step S740, at this time, an inner transmission layer 720b is formed on each supporting layer 720c, and a second portion outer shaft side wall 721c is formed on each first portion outer shielding side wall 721b; Figure 7e As shown, corresponding to step S750, at this time, a third portion of the outer shaft side wall 721d is formed on each second portion of the outer shaft side wall 721c; Figure 7f As shown, corresponding to step S760, an outer shielding top layer 721e is formed on each third-part outer shaft side wall 721d, wherein the outer shielding bottom layer 721a, the first-part outer shaft side wall 721b, the second-part outer shaft side wall 721c, the third-part outer shaft side wall 721d and the outer shielding top layer 721e constitute the outer shielding layer 720a.

[0083] In one implementation, the second preparation method includes:

[0084] Selecting at least one outer shielding top layer of a transmission line as a target bottom layer;

[0085] forming a support layer on each target substrate;

[0086] forming a first portion of an outer shield sidewall on each target substrate;

[0087] forming an inner transmission layer on each support layer and simultaneously forming a second portion outer shaft side wall on each first portion outer shield side wall;

[0088] forming a third portion outer shaft side wall on each second portion outer shaft side wall;

[0089] An outer shielding top layer is formed on the outer shaft side wall of each third portion, wherein the outer shielding top layer, the outer shielding side wall layer and the target bottom layer constitute an outer shielding layer.

[0090] It should be noted that the difference between the first preparation method and the second preparation method is that in the second preparation method, the outer shielding top layer of the transmission line whose bottom layer has been prepared can be used as the outer shielding bottom layer of the transmission line to be prepared in the next layer, so as to simplify the preparation process of the transmission line and save the preparation cost. Therefore, the specific implementation of each step in the second preparation method can refer to the relevant description of the first preparation method, and this embodiment will not be repeated here.

[0091] by Figure 2 Taking the printed circuit board structure shown as an example, a first preparation method can be first used to form a first transmission line 221 on a substrate 210, and then a second preparation method can be used to form a second transmission line 222 on the first transmission line 221 using the outer shielding top layer of the first transmission line 221 as the outer shielding bottom layer of the second transmission line 222.

[0092] by Figure 3 Taking the printed circuit board structure shown in the figure as an example, the first preparation method can be firstly adopted to simultaneously form the first transmission line 321 and the second transmission line 322 on the substrate 310, and then the second preparation method can be adopted to use the outer shielding top layer of the first transmission line 321 as the outer shielding bottom layer of the third transmission line 323, and the outer shielding top layer of the second transmission line 322 as the outer shielding bottom layer of the fourth transmission line 324, so as to form the third transmission line 323 on the first transmission line 321, and form the fourth transmission line 324 on the second transmission line 322.

[0093] by Figure 4 Taking the printed circuit board structure shown as an example, a first preparation method can be first used to form a first transmission line 421 on a substrate 410, and then a second preparation method can be used to form a second transmission line 422 on the first transmission line 421 using the outer shielding top layer of the first transmission line 421 as the outer shielding bottom layer of the second transmission line 422.

[0094] It should be noted that in the formation of Figure 2 The plurality of transmission lines stacked in parallel on the substrate 210 as shown, or Figure 4When multiple transmission lines are stacked and arranged on the substrate 410 in a cross-stacked manner, transmission lines with different stacking methods can be obtained by simply adjusting the patterns required to be formed in each step of the first preparation method and the second preparation method during photolithography. If only one transmission line layer is required to be formed, the first preparation method can be directly used to prepare it. If multiple transmission line layers are to be formed, the second preparation method can be used multiple times on the basis of the first transmission line layer to prepare multiple transmission line layers. This embodiment will not be described in detail here.

[0095] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0096] A printed circuit board and a preparation method thereof provided by an embodiment of the present invention, wherein the substrate of the printed circuit board has at least one transmission line, and each transmission line is an air core micro-coaxial structure including an outer shielding layer, an inner transmission layer and a support layer. Since the air core micro-coaxial transmission line is filled with air in the middle, its dielectric constant is much lower than that of conventional dielectric materials. In the process of microwave transmission, the lower the dielectric constant, the smaller the signal loss on the transmission line. Therefore, the air core micro-coaxial transmission line can significantly reduce the signal loss during transmission and improve the signal transmission efficiency. And the structural characteristics of the air core micro-coaxial transmission line enable it to support wider frequency band transmission. Compared with traditional coaxial transmission lines, air core micro-coaxial transmission lines have better transmission performance in high frequency bands and can transmit microwave signals more effectively. This has significant advantages for application scenarios requiring high frequency and wide bandwidth transmission. Therefore, the printed circuit board provided by the present invention fundamentally optimizes the signal transmission path, significantly reduces the energy loss during transmission, and effectively suppresses reflection and crosstalk phenomena, thereby achieving wide bandwidth, low loss, and high isolation signal transmission characteristics.

[0097] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0098] Similarly, it should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the intention that the claimed invention requires more features than those explicitly recited in each claim. More specifically, as reflected in the claims below, inventive aspects lie in less than all the features of the individual embodiments disclosed above. Therefore, the claims that follow the specific embodiment are hereby expressly incorporated into the specific embodiment, with each claim itself serving as a separate embodiment of the present invention.

[0099] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims.

Claims

1. A printed circuit board comprising a substrate and a transmission line located on the substrate, It is characterized in that The substrate has at least one transmission line, each of which includes an outer shielding layer, an inner transmission layer and a support layer. The outer shielding layer is a hollow structure with an air cavity inside. The inner transmission layer is suspended in the corresponding air cavity through the support layer and is insulated from the outer shielding layer.

2. The printed circuit board according to claim 1, It is characterized in that When there are a plurality of transmission lines on the substrate, the plurality of transmission lines are stacked on the substrate in a parallel manner, and each layer includes at least one transmission line, and the at least one transmission line is arranged at intervals or adjacently.

3. The printed circuit board according to claim 1, It is characterized in that When there are a plurality of transmission lines on the substrate, the plurality of transmission lines are stacked on the substrate in a cross-stacked manner, and each layer includes at least one transmission line, and the at least one transmission line is arranged at intervals or adjacently.

4. The printed circuit board according to claim 1, It is characterized in that The outer shielding layer is provided with at least one release hole communicating with the air cavity.

5. The printed circuit board according to claim 1, It is characterized in that The printed circuit board includes connection ports corresponding to the at least one transmission line, and each of the connection ports is used to be electrically connected to an inner transmission layer of the corresponding transmission line.

6. The printed circuit board according to claim 1, It is characterized in that The supporting layer is a photosensitive film layer.

7. A method for preparing a printed circuit board, It is characterized in that The preparation method comprises: Providing a substrate for a printed circuit board; At least one transmission line is formed on the surface of the substrate, and each of the transmission lines includes an outer shielding layer, an inner transmission layer and a support layer. The outer shielding layer is a hollow structure with an air cavity inside, and the inner transmission layer is suspended in the corresponding air cavity through the support layer and is insulated from the outer shielding layer.

8. The preparation method according to claim 7, It is characterized in that When the substrate has a plurality of transmission lines, and the plurality of transmission lines are stacked on the substrate in a parallel stacking or cross stacking manner, forming at least one transmission line on the surface of the substrate includes: Using a first preparation method, forming a first layer of transmission lines on the substrate, wherein the first layer of transmission lines includes at least one transmission line; A second preparation method is adopted to form a plurality of transmission lines on the first transmission line layer, each transmission line layer includes at least one transmission line, and the at least one transmission line is arranged at intervals or adjacent to each other.

9. The preparation method according to claim 8, It is characterized in that The first preparation method comprises: forming at least one outer shielding bottom layer on the substrate; forming a layer of the support layer on each of the outer shielding bottom layers; Forming a first portion of outer shielding side walls on each of the outer shielding bottom layers, wherein the first portion of the outer shielding side walls has the same height as the supporting layer; forming the inner transmission layer on each of the support layers, and forming a second portion of the outer shaft side wall on each of the first portion of the outer shielding side wall; forming a third portion of the outer shaft side wall on each of the second portion of the outer shaft side wall, wherein the first portion of the outer shielding side wall, the second portion of the outer shielding side wall and the third portion of the outer shielding side wall constitute the outer shielding side wall layer; An outer shielding top layer is formed on each outer axial side wall of the third portion, wherein the outer shielding top layer, the outer shielding side wall layer and the outer shielding bottom layer constitute the outer shielding layer.

10. The preparation method according to claim 9, It is characterized in that The second preparation method comprises: Selecting the outer shielding top layer of at least one transmission line as the target bottom layer; forming a layer of the support layer on each of the target bottom layers; forming a first portion of an outer shielding side wall on each of the target bottom layers; forming the inner transmission layer on each of the support layers, and forming the second portion outer shaft side wall on each of the first portion outer shield side wall; forming the third portion outer shaft side wall on each of the second portion outer shaft side walls; The outer shield top layer is formed on each of the third portion outer shaft side walls, wherein the outer shield top layer, the outer shield side wall layer and the target bottom layer constitute the outer shield layer.

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