Printed circuit board and method for manufacturing the same

Abstract

The present application discloses a printed circuit board and a preparation method thereof, wherein the printed circuit board comprises a first sub-circuit board, a supporting structure, an inner conductor, a first positioning structure and a second sub-circuit board; the supporting structure is arranged on one side of the first sub-circuit board; the inner conductor is arranged on the side of the supporting structure away from the first sub-circuit board; the first positioning structure is arranged on the side of the first sub-circuit board close to the supporting structure, the first positioning structure at least partially surrounds the supporting structure, and is spaced from the supporting structure; the second sub-circuit board is arranged opposite to the first sub-circuit board, a groove is arranged on the side of the second sub-circuit board close to the first sub-circuit board, the depth of the groove along the direction perpendicular to the first sub-circuit board is less than the thickness of the second sub-circuit board, the supporting structure, the inner conductor and the first positioning structure are located in the accommodating space enclosed by the groove and the first sub-circuit board, forming a coaxial transmission structure, thereby improving the signal transmission frequency and bandwidth of the printed circuit board.

Description

Technical Field

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

[0002] PCB (Printed Circuit Board) is the core basic component used to carry signal transmission, signal reception and power supply of electronic equipment.

[0003] The transmission lines of conventional PCB boards have good signal transmission characteristics in lower frequency bands. As 5G+ millimeter wave communication technology develops towards high frequency and high speed of signals, the data transmission bandwidth and capacity increase exponentially, and the requirements for signal transmission rate and transmission loss are significantly improved. The transmission lines of traditional PCB boards cannot meet the transmission requirements of high-speed signals due to their large losses and small bandwidth. Summary of the invention

[0004] The present application provides a printed circuit board and a method for preparing the same, so as to solve the technical problem of low operating frequency of the existing printed circuit boards.

[0005] In view of the above problems, the present application is proposed to provide a printed circuit board and a method for preparing the same that overcomes the above problems or at least partially solves the above problems.

[0006] In a first aspect, a printed circuit board is provided, comprising: a first sub-circuit board, a support structure, an inner conductor, a first positioning structure, and a second sub-circuit board;

[0007] The supporting structure is arranged on one side of the first sub-circuit board;

[0008] The inner conductor is arranged on a side of the support structure away from the first sub-circuit board;

[0009] The first positioning structure is disposed on a side of the first sub-circuit board close to the supporting structure, the first positioning structure at least partially surrounds the supporting structure, and is spaced apart from the supporting structure;

[0010] The second sub-circuit board is arranged opposite to the first sub-circuit board. A groove is arranged on a side of the second sub-circuit board close to the first sub-circuit board. Along the direction perpendicular to the first sub-circuit board, the depth of the groove is less than the thickness of the second sub-circuit board. The support structure, the inner conductor and the first positioning structure are located in the accommodating space enclosed by the groove and the first sub-circuit board.

[0011] Optionally, the printed circuit board also includes a first semi-cured sheet; the first semi-cured sheet is located between the first sub-circuit board and the second sub-circuit board, and is arranged around the first positioning structure. Along the direction perpendicular to the first sub-circuit board, the thickness of the first semi-cured sheet is less than or equal to the thickness of the first positioning structure.

[0012] Optionally, the first sub-circuit board includes a first core board, and the second sub-circuit board includes a second core board and a third core board;

[0013] The first core plate is arranged opposite to the second core plate;

[0014] The second core plate is provided with a through hole, and the through hole penetrates the second core plate in a direction perpendicular to the second core plate;

[0015] The third core plate is disposed on a side of the second core plate away from the first core plate, and at least covers an opening of the through hole on a surface of the second core plate away from the first core plate. The groove is formed by the third core plate and the through hole.

[0016] Optionally, the printed circuit board further includes a second positioning structure;

[0017] The second positioning structure is disposed on a side of the third core plate close to the second core plate. The second positioning structure is located in the groove and is spaced apart from the inner conductor.

[0018] Optionally, the printed circuit board also includes a second semi-cured sheet, which is arranged between the second core board and the third core board. The second semi-cured sheet at least partially surrounds the second positioning structure, and the thickness of the second semi-cured sheet along the direction perpendicular to the third core board is less than or equal to the thickness of the second positioning structure.

[0019] Optionally, the orthographic projection of the first semi-cured sheet on the first sub-circuit board is a first projection area, the orthographic projection of the supporting structure on the first sub-circuit board is a second projection area, and the orthographic projection of the first positioning structure on the first sub-circuit board is a third projection area. The third projection area includes a first boundary line and a second boundary line that are relatively set. The first boundary line is located outside the third projection area, the second boundary line is located between the first boundary line and the second projection area, and the first projection area is located on the side of the first boundary line away from the second projection area.

[0020] Optionally, the printed circuit board also includes a shielding layer, which covers at least the side and bottom surfaces of the groove and a first area of ​​the first surface of the first sub-circuit board, the first surface being the surface of the first sub-circuit board close to the side of the groove, and the first area being the area of ​​the first surface opposite to the opening of the groove. There is a gap between the shielding layer and the inner conductor, and they are insulated from each other, and the shielding layer is electrically contacted with the ground terminal of the printed circuit board.

[0021] Optionally, the orthographic projection of the first positioning structure on the first sub-circuit board is an annular area, and the orthographic projections of the support structure and the inner conductor on the first sub-circuit board are located within the annular area and have a gap with an inner boundary of the annular area.

[0022] Optionally, the printed circuit board further includes a signal transmitting end and a signal receiving end, one end of the inner conductor is electrically connected to the signal transmitting end, and the other end is electrically connected to the signal receiving end. The inner conductor is used to transmit the signal output by the signal transmitting end to the signal receiving end.

[0023] In a second aspect, a method for preparing a printed circuit board is provided, comprising:

[0024] providing a first sub-circuit board and a second sub-circuit board;

[0025] A support structure and a first positioning structure at least partially surrounding the support structure and spaced apart from the support structure are formed on one side of the first sub-circuit board;

[0026] forming an inner conductor on a side of the support structure away from the first sub-circuit board;

[0027] The side of the second sub-circuit board provided with the groove is fixed to the side of the first sub-circuit board close to the first positioning structure, so that the groove and the first sub-circuit board enclose a space for accommodating the inner conductor, the support structure and the first positioning structure to obtain a printed circuit board.

[0028] Optionally, the second sub-circuit board includes a second core board and a third core board, the second core board is provided with a through hole, and the through hole penetrates the second core board in a direction perpendicular to the second core board;

[0029] The side of the second sub-circuit board provided with the groove is fixed to the side of the first sub-circuit board close to the first positioning structure, so that the groove and the first sub-circuit board enclose a space for accommodating the inner conductor, the support structure and the first positioning structure, including:

[0030] The two sides of the second core board are respectively arranged and fixed opposite to the third core board and the side of the first sub-circuit board close to the first positioning structure, so that the third core board at least covers the opening of the through hole on the surface of the second core board away from the first sub-circuit board, and the third core board, the through hole and the first sub-circuit board form a space to accommodate the inner conductor, the support structure and the first positioning structure.

[0031] The technical solution provided by this application has at least the following technical effects or advantages:

[0032] The printed circuit board and its preparation method provided by the present application, in the first aspect, a receiving space for accommodating a support structure, an inner conductor and a first positioning structure is formed by the grooves of the first sub-circuit board and the second sub-circuit board, and the receiving space and the inner conductor form a coaxial transmission structure of the printed circuit board. When the signal is transmitted through the inner conductor, the dielectric constant of the air around the inner conductor is approximately equal to 1 and the loss factor is very small (about 1e-6), so that the energy loss and signal attenuation in the coaxial transmission structure are greatly reduced. Therefore, the use of air to fill the cavity helps to broaden the bandwidth of the coaxial transmission structure, increase the frequency range of the transmittable signal, and improve the working bandwidth of the printed circuit board, thereby improving the capacity and speed of the printed circuit board during data transmission, and meeting the transmission requirements of high-speed chips. In the second aspect, the accommodating space provides physical protection for the inner conductor and prolongs the service life of the inner conductor. In the third aspect, by setting the first positioning structure, it is convenient to position the first sub-circuit board and the second sub-circuit board during lamination, reduce quality problems caused by position deviation, improve the consistency and stability of mass production of printed circuit boards, and avoid relative dislocation of the first sub-circuit board and the second sub-circuit board during the production process, causing abnormal friction, collision and wear between the inner conductor and the inner wall of the groove, further prolonging the life of the printed circuit board.

[0033] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] 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 application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0035] Figure 1 A schematic diagram of a cross-sectional structure of a printed circuit board provided in an embodiment of the present application;

[0036] Figure 2 A schematic diagram of an orthographic projection of a first positioning structure of a printed circuit board on a first sub-circuit board provided in an embodiment of the present application;

[0037] Figure 3 A schematic diagram of a cross-sectional structure of another printed circuit board provided in an embodiment of the present application;

[0038] Figure 4 A schematic diagram of the cross-sectional structure of another printed circuit board provided in an embodiment of the present application;

[0039] Figure 5 A schematic diagram of a cross-sectional structure of another printed circuit board provided in an embodiment of the present application;

[0040] Figure 6 A schematic diagram of a cross-sectional structure of another printed circuit board provided in an embodiment of the present application;

[0041] Figure 7 A schematic diagram of a cross-sectional structure of another printed circuit board provided in an embodiment of the present application;

[0042] Figure 8 A schematic diagram of a cross-sectional structure of another printed circuit board provided in an embodiment of the present application;

[0043] Fig. 9 A schematic diagram of a cross-sectional structure of another printed circuit board provided in an embodiment of the present application;

[0044] Fig.10 A flow chart of a method for preparing a printed circuit board provided in an embodiment of the present application;

[0045] Fig.11 A flow chart for preparing a first core board of a printed circuit board provided in an embodiment of the present application;

[0046] Fig.12 A flow chart for preparing a second core board of a printed circuit board provided in an embodiment of the present application;

[0047] Fig.13 A flow chart of the preparation of a prepreg for a printed circuit board provided in an embodiment of the present application;

[0048] Fig.14 A flow chart of preparing the third core board of the printed circuit board provided in the embodiment of the present application;

[0049] Fig.15 A lamination flow chart of a printed circuit board provided in an embodiment of the present application;

[0050] Fig.16 A lamination flow chart of another printed circuit board provided in an embodiment of the present application. DETAILED DESCRIPTION

[0051] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings.

[0052] Various structural schematic diagrams according to embodiments of the present application 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 additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0053] In order to facilitate the clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, words such as "first" and "second" are used to distinguish between identical or similar items with substantially the same functions and effects. For example, the first value and the second value are only used to distinguish different values, and their order is not limited. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit them to be different.

[0054] It should be noted that, in this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0055] In the context of the present disclosure, when a layer / element is referred to as being disposed "on" another layer / element, the layer / element may be disposed directly on the other layer / element, or there may be an intervening layer / element therebetween. Additionally, if a layer / element is disposed "on" another layer / element in one orientation, the layer / element may be disposed "under" 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.

[0056] 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.

[0057] At present, the signal transmission lines set on PCB mainly include conventional transmission lines such as microstrip lines, coplanar waveguides or coplanar striplines. Microstrip lines, coplanar waveguides or coplanar striplines have good transmission characteristics in lower frequency bands. As 5G+ millimeter wave communication technology develops towards high frequency and high speed of signals, the data transmission bandwidth and capacity increase exponentially, and the requirements for signal transmission rate and transmission loss of various electronic products are significantly improved. With the increase of frequency, dielectric loss and radiation loss will increase exponentially. Therefore, traditional transmission lines cannot meet the transmission requirements of high-speed signals due to their large loss and small bandwidth.

[0058] The conventional technical solution now is to use insulating dielectric materials with smaller dielectric constants and dielectric loss factors to reduce dielectric loss, such as Rogers high-frequency boards and Teflon high-frequency boards. At a frequency of 10GHz, their relative dielectric constants are between 2 and 3, and their loss tangents are around 0.003. At the same time, it is necessary to use transmission lines with shielding functions to reduce radiation losses, such as putting shielding columns on both sides of the strip line to further reduce radiation losses. Although wafer-based coaxial transmission lines can meet the requirements of use, they have the practical difficulties of complex processes, high costs, and difficulty in large-scale application.

[0059] The signal transmission lines currently set on PCB boards have good transmission characteristics in the lower frequency band. As the operating frequency increases, the loss will increase exponentially. Conventional solutions use high-frequency boards, but the increased operating frequency band is very limited and cannot fundamentally solve the problem of increased loss.

[0060] In view of this, please refer to Figure 1 , Figure 1 A schematic diagram of a cross-sectional structure of a printed circuit board provided in an embodiment of the present application; the printed circuit board comprises: a first sub-circuit board 101, a support structure 102, an inner conductor 103, a first positioning structure 104 and a second sub-circuit board 105; the support structure 102 is arranged on one side of the first sub-circuit board 101; the inner conductor 103 is arranged on the side of the support structure 102 away from the first sub-circuit board 101; the first positioning structure 104 is arranged on the side of the first sub-circuit board 101 close to the support structure 102, the first positioning structure 104 at least partially surrounds the support structure 102, and is spaced from the support structure 102; the second sub-circuit board 105 is arranged opposite to the first sub-circuit board 101, a groove is arranged on one side of the second sub-circuit board 105 close to the first sub-circuit board 101, the depth of the groove along the direction perpendicular to the first sub-circuit board 101 is less than the thickness of the second sub-circuit board 105, the support structure 102, the inner conductor 103 and the first positioning structure 104 are located in the accommodating space surrounded by the groove and the first sub-circuit board 101.

[0061] The printed circuit board provided in the embodiment of the present application, on the first aspect, forms an accommodation space for accommodating a support structure, an inner conductor and a first positioning structure through grooves of the first sub-circuit board and the second sub-circuit board. The accommodation space and the inner conductor form a coaxial transmission structure of the printed circuit board. When signals are transmitted through the inner conductor, since the dielectric constant of the air around the inner conductor is approximately equal to 1 and the loss factor is very small (approximately 1e-6), the energy loss and signal attenuation in the coaxial transmission structure are greatly reduced. Therefore, using air to fill the cavity helps to broaden the bandwidth of the coaxial transmission structure, increase the frequency range of transmittable signals, and improve the working bandwidth of the printed circuit board, thereby improving the capacity and speed of the printed circuit board during data transmission, and meeting the transmission requirements of high-speed chips.

[0062] Secondly, the accommodation space provides physical protection for the inner conductor, extending the service life of the inner conductor. Thirdly, by setting the first positioning structure, it is convenient to position the first sub-circuit board and the second sub-circuit board during lamination, reducing quality problems caused by position deviation, improving the consistency and stability of mass production of printed circuit boards, and avoiding relative misalignment of the first sub-circuit board and the second sub-circuit board during the production process, causing abnormal friction, collision and wear between the inner conductor and the inner wall of the groove, further extending the service life of the printed circuit board.

[0063] The relative dielectric constant of air is 1, and the loss factor is very small (10e-6). Air is the most ideal filling medium and is filled in the containing space to form an air-core coaxial cable structure. Theoretically, the main mode operating frequency of the air-core coaxial cable based on micron precision technology can reach 450GHz and the bandwidth is extremely large (from 0 to the main mode operating frequency), which can meet the transmission of high-speed signals and can be applied to high-speed printed circuit boards (PCBs) with a rate of 112Gbps, 224Gbps and higher.

[0064] In some optional implementations, the inner conductor is arranged centrally in the accommodation space. The inner conductor is centered in the accommodation space, which can achieve good signal transmission function and avoid deterioration of the performance of the printed circuit board.

[0065] In the printed circuit board provided in the embodiment of the present application, the first sub-circuit board 101 includes a core board, and the second sub-circuit board 105 includes a core board provided with a groove, such as Figure 1 shown.

[0066] The material of the core board can be organic polymer materials such as paper-based phenolic resin, glass fiber cloth-based epoxy resin, polyimide, etc., composite materials such as ceramic-epoxy composite materials, metal-based composite materials, etc., and inorganic materials such as ceramics and glass.

[0067] The surface of the core board can be plated with a conductive material, and the conductive material can be a metal element and its alloy, and the metal element includes copper, silver, gold, aluminum, zinc, iron, tin or platinum, and the alloy includes copper alloy, silver alloy, gold alloy, aluminum alloy, zinc alloy, iron alloy, tin alloy, platinum alloy, etc. For example, the core board is plated with copper on both sides, and copper mainly has the functions of electrical connection, providing mechanical support, facilitating welding and preventing corrosion, and also plays the role of electromagnetic shielding for the inner conductor 103, ensuring the stability and reliability of signal transmission, reducing the dissipation and radiation loss of the inner conductor 103 when transmitting high-frequency signals, thereby improving the transmission bandwidth of the transmission line structure.

[0068] The present application does not limit the specific materials of the first sub-circuit board 101 and the second sub-circuit board 105. It is understandable that when the core board of the second sub-circuit board 105 is a double-sided copper-clad board, after processing the groove, a conductive metal material can be plated on the inner wall of the groove to enhance the electromagnetic shielding effect, forming a metallized inner wall, and the metallized inner wall is in contact with and conductive to the copper layers coated on the upper and lower surfaces of the core board of the second sub-circuit board 105, so as to describe a shielding layer that completely surrounds the inner conductor.

[0069] The printed circuit board provided in the embodiment of the present application has the first positioning structure 104 at least partially surrounding the support structure 102, and is used to keep the relative positions of the first sub-circuit board 101 and the second sub-circuit board 105 consistent, so as to avoid the relative misalignment of the first sub-circuit board 101 and the second sub-circuit board 105 during the production process, thereby preventing abnormal friction, collision and wear between the inner conductor 103 and the inner wall of the groove. Figure 2 As shown, in an example provided in the present application, the orthographic projection of the first positioning structure 104 on the first sub-circuit board 101 is an annular area, and the orthographic projections of the support structure 102 and the inner conductor 103 on the first sub-circuit board 101 are located within the annular area and have a gap with the inner boundary of the annular area.

[0070] like Figure 2 As shown in the figure, the orthographic projection of the first positioning structure 104 on the first sub-circuit board 101 is an annular area 201, and the orthographic projection 202 of the support structure 102 and the inner conductor 103 on the first sub-circuit board 101 is located in the annular area 201 and has a gap with the inner boundary of the annular area 201.

[0071] It can be understood that the shape of the area of ​​the orthographic projection of the first positioning structure 104 on the first sub-circuit board 101 is related to the overall shape of the first positioning structure 104. When the first positioning structure 104 completely surrounds the supporting structure 102, the orthographic projection of the first positioning structure 104 on the first sub-circuit board 101 is an annular area. When the first positioning structure 104 partially surrounds the supporting structure 102, the orthographic projection of the first positioning structure 104 on the first sub-circuit board 101 has a gap. For example, the orthographic projection of the first positioning structure 104 on the first sub-circuit board 101 can also be an annular area with a gap, or two parallel strip areas, etc., which are not described here.

[0072] In some optional embodiments, such as Figure 3 As shown, the printed circuit board also includes a first prepreg 301; the first prepreg 301 is located between the first sub-circuit board 101 and the second sub-circuit board 105, and is arranged around the first positioning structure 104. In a direction perpendicular to the first sub-circuit board 101, the thickness of the first prepreg 301 is less than or equal to the thickness of the first positioning structure 104. Figure 3 As shown, in one example, the thickness h1 of the first prepreg 301 is equal to the thickness h2 of the first positioning structure 104. Figure 5 As shown, in another example, the thickness h1 of the first prepreg 301 is smaller than the thickness h2 of the first positioning structure 104 .

[0073] Exemplarily, along the direction perpendicular to the first sub-circuit board 101, the thickness of the first prepreg 301 is 5 to 30 microns, and the thickness of the first positioning structure 104 is 7 to 50 microns. For example, the thickness h1 of the first prepreg 301 is 5 microns, the thickness h2 of the first positioning structure 104 is 7 microns, and the thickness h1 of the first prepreg 301 is 8 microns. The thickness h2 of the first positioning structure 104 is 10 microns, the thickness h1 of the first prepreg 301 is 10 microns, and the thickness h2 of the first positioning structure 104 is 10 microns. The thickness h2 of the first positioning structure 104 is 15 microns, the thickness h1 of the first semi-cured sheet 301 is 15 microns, the thickness h2 of the first positioning structure 104 is 17 microns, the thickness h1 of the first semi-cured sheet 301 is 20 microns, the thickness h2 of the first positioning structure 104 is 30 microns, the thickness h1 of the first semi-cured sheet 301 is 30 microns, the thickness h2 of the first positioning structure 104 is 50 microns, and the thickness of the first semi-cured sheet 301 and the thickness of the first positioning structure 104 are not limited here.

[0074] The first semi-cured sheet 301 serves to bond and fix the first sub-circuit board 101 and the second sub-circuit board 105. The first semi-cured sheet 301 can be made of a composite material consisting of a resin material and a reinforcing material. The resin material can be at least one of epoxy resin, bismaleimide triazine resin, thermosetting cyanate resin, thermosetting polyphenylene ether resin, and polyimide resin. The reinforcing material can be glass fiber cloth, paper base, a mixed material of aramid fiber and glass fiber, etc. The present application does not limit the specific material of the first semi-cured sheet 301.

[0075] The first prepreg 301 is used to bond and fix the first sub-circuit board 101 and the second sub-circuit board 105. According to the curing process requirements of the first prepreg 301, appropriate temperature, pressure and time parameters are set for curing. Generally speaking, the curing temperature may be around 100°C-200°C, and the curing time may vary from tens of minutes to several hours, depending on the type and material of the first prepreg 301. During the curing process, the resin in the first prepreg 301 will undergo a cross-linking reaction, changing from a semi-solid state to a solid state, thereby firmly bonding the first sub-circuit board 101 and the second sub-circuit board 105 together.

[0076] The first positioning structure 104 also has a function, which is to prevent the first semi-cured sheet 301 from overflowing into the accommodating space surrounded by the groove and the first sub-circuit board 101 due to fluidity after being heated during the curing process, so as to avoid the semi-cured sheet and the inner conductor 103 from sticking to each other and reducing the electrical and mechanical properties of the inner conductor 103, thereby ensuring the yield and qualified rate of the printed circuit board. In the direction perpendicular to the first sub-circuit board 101, the thickness of the first semi-cured sheet 301 is less than or equal to the thickness of the first positioning structure 104, thereby ensuring that the first positioning structure 104 completely blocks the first semi-cured sheet 301.

[0077] In the printed circuit board provided in the embodiment of the present application, the support structure 102 may use more than one support column 1021 , and the more than one support column 1021 is arranged at intervals along the length extension direction of the inner conductor 103 and / or arranged at intervals along the width extension direction of the inner conductor 103 .

[0078] In one example, if Figure 3 As shown, three support pillars 1021 are disposed between the inner conductor 103 and the first sub-circuit board 101 and are arranged at intervals along the length extension direction of the inner conductor 103 to stably support the inner conductor 103 in the accommodation space.

[0079] The second sub-circuit board 105 may also adopt a composite structure composed of at least two layers of core boards. In some optional embodiments, the first sub-circuit board 101 includes a first core board, such as Figure 4As shown, the second sub-circuit board 105 includes a second core board 401 and a third core board 402; the first core board and the second core board 401 are arranged opposite to each other; the support structure 102 is arranged on one side of the first core board; the inner conductor 103 is arranged on the side of the support structure 102 away from the first core board; the first positioning structure 104 is arranged on the side of the first core board close to the support structure 102, the first positioning structure 104 at least partially surrounds the support structure 102, and is spaced from the support structure 102. The second core board 401 is provided with a through hole 4011, and the through hole 4011 penetrates the second core board 401 in a direction perpendicular to the second core board 401; the third core board 402 is arranged on the side of the second core board 401 away from the first core board, and at least covers the opening of the through hole 4011 on the surface of the second core board 401 away from the first core board, and the groove is formed by the third core board 402 and the through hole 4011.

[0080] Along the direction perpendicular to the third core plate 402, the thickness of the second core plate 401 is 50 to 500 microns, along the direction perpendicular to the third core plate 402, the thickness of the third core plate 402 is 100 to 1000 microns, and along the direction perpendicular to the first core plate, the thickness of the first core plate is 100 to 1000 microns.

[0081] The thickness of the second core plate 401 determines the height of the through hole 4011 , and further determines the height of the accommodation space. The thickness of the third core plate 402 and the first core plate has little effect on the height of the accommodation space.

[0082] Exemplarily, the second core board 401 uses a core board with a thickness of 240 microns, and the third core board 402 and the first core board use a core board with a thickness of 100 microns. After the first core board, the second core board 401 and the third core board 402 are stacked and laminated in sequence, a accommodating space with a height between 240 and 300 microns can be enclosed.

[0083] In specific applications, reducing the thickness of the second core board 401 is helpful to reduce the size of the accommodating space and increase the frequency of the transmission signal.

[0084] In some optional embodiments, the printed circuit board further includes a signal transmitting end and a signal receiving end, one end of the inner conductor 103 is electrically connected to the signal transmitting end, and the other end is electrically connected to the signal receiving end. The inner conductor is used to transmit the signal output by the signal transmitting end to the signal receiving end.

[0085] Electronic components such as resistors, capacitors, inductors, diodes, triodes, integrated circuits, sockets, connectors, crystal oscillators, sensors, etc. are arranged on the printed circuit board. When the signal sending end is connected to the first electronic component and the signal receiving end is connected to the second electronic component, the accommodating space and the inner conductor constitute a coaxial transmission line, which can realize signal transmission between the first electronic component and the second electronic component.

[0086] The signal transmitting end or the signal receiving end can also be connected to a third electronic component outside the printed circuit board, and the accommodating space and the inner conductor form a coaxial transmission line, which can realize signal transmission between the printed circuit board and the third electronic component. This application does not limit the specific type of electronic components on the printed circuit board.

[0087] In some optional embodiments, Figure 4 As shown, the printed circuit board further includes a second positioning structure 403 ; the second positioning structure 403 is disposed on a side of the third core board 402 close to the second core board 401 , and the second positioning structure 403 is located in the groove and spaced apart from the inner conductor 103 .

[0088] In some optional embodiments, such as Figure 6 As shown, the printed circuit board further includes a second prepreg 601, which is disposed between the second core board 401 and the third core board 402. The second prepreg 601 at least partially surrounds the second positioning structure 403, and the thickness of the second prepreg 601 is less than or equal to the thickness of the second positioning structure 403 along a direction perpendicular to the third core board 402. Figure 6 As shown, in one example, along a direction perpendicular to the third core board 402 , a thickness h3 of the second prepreg 601 is smaller than a thickness h4 of the second positioning structure 403 .

[0089] Exemplarily, along the direction perpendicular to the third core plate 402, the thickness of the second semi-cured sheet 601 is 5 to 30 microns, and the thickness of the second positioning structure 403 is 7 to 50 microns. For example, along the direction perpendicular to the third core plate 402, the thickness h3 of the second semi-cured sheet 601 is 5 microns, the thickness h4 of the second positioning structure 403 is 7 microns, and the thickness h3 of the second semi-cured sheet 601 is 8 microns. The thickness h4 of the second positioning structure 403 is 10 microns, and the thickness h3 of the second semi-cured sheet 601 is 10 microns. meters, the thickness h4 of the second positioning structure 403 is 15 microns, and the thickness h3 of the second semi-cured sheet 601 is 15 microns, the thickness h4 of the second positioning structure 403 is 17 microns, and the thickness h3 of the second semi-cured sheet 601 is 20 microns, the thickness h4 of the second positioning structure 403 is 30 microns, and the thickness h3 of the second semi-cured sheet 601 is 30 microns, the thickness h4 of the second positioning structure 403 is 50 microns, and the thickness of the second semi-cured sheet 601 and the thickness of the second positioning structure 403 are not limited here.

[0090] The second semi-cured sheet 601 is used to bond and fix the second core plate 401 and the third core plate 402. The second semi-cured sheet 601 can be made of the same material as the first semi-cured sheet 301, and the first core plate, the second core plate 401 and the third core plate 402 are firmly bonded together through a one-time curing process.

[0091] The second positioning structure 403 also has a function, which is to prevent the second semi-cured sheet 601 from overflowing into the accommodation space surrounded by the groove and the first sub-circuit board 101 due to fluidity after being heated during the curing process, thereby avoiding the semi-cured sheet and the inner conductor 103 from sticking together and reducing the electrical and mechanical properties of the inner conductor 103, thereby ensuring the yield and qualified rate of the printed circuit board. In the direction perpendicular to the second sub-circuit board 105, the thickness of the second semi-cured sheet 601 is less than or equal to the thickness of the second positioning structure 403, thereby ensuring that the second positioning structure 403 completely blocks the second semi-cured sheet 601.

[0092] In some optional embodiments, the orthographic projection of the first semi-cured sheet 301 on the first sub-circuit board 101 is a first projection area, the orthographic projection of the supporting structure 102 on the first sub-circuit board 101 is a second projection area, and the orthographic projection of the first positioning structure 104 on the first sub-circuit board 101 is a third projection area. The third projection area includes a first boundary line and a second boundary line that are relatively set. The first boundary line is located outside the third projection area, the second boundary line is located between the first boundary line and the second projection area, and the first projection area is located on the side of the first boundary line away from the second projection area.

[0093] In this way, the first positioning structure 104 completely isolates the first prepreg 301 from the support structure 102 , thereby preventing the first prepreg 301 from adhering to the inner conductor 103 on the support structure 102 .

[0094] In some optional embodiments, such as Figure 7 As shown, the printed circuit board also includes a shielding layer 701, which covers at least the side and bottom surfaces of the groove and the first area of ​​the first surface of the first sub-circuit board 101. The first surface is the surface of the first sub-circuit board 101 close to the side of the groove, and the first area is the area of ​​the first surface opposite to the opening of the groove. There is a gap between the shielding layer 701 and the inner conductor 103, and they are insulated from each other. The shielding layer 701 is electrically in contact with the ground terminal of the printed circuit board.

[0095] The thickness of the shielding layer 701 is 0.5 to 10 micrometers. For example, the thickness of the shielding layer 701 is 0.5 micrometers, 1 micrometer, 2 micrometers, 4 micrometers, 6 micrometers, 8 micrometers or 10 micrometers, etc., which is not limited here.

[0096] The second core board 401, the third core board 402 and the first sub-circuit board 101 may be core boards plated with conductive materials. After the through hole 4011 is processed on the second core board 401, the conductive material is plated on the inner wall of the through hole 4011. Figure 8As shown, the printed circuit board also includes a first conductive column 801 and a second conductive column 802. The first conductive column 801 is arranged in a through hole 4011 that sequentially penetrates the first sub-circuit board 101 and the first semi-cured sheet 301 and is electrically contacted with the conductive material on the surface of the second core board 401 close to the first sub-circuit board 101. The second conductive column 802 is arranged in a through hole 4011 that sequentially penetrates the third core board 402 and the second semi-cured sheet 601 and is electrically contacted with the conductive material on the surface of the second core board 401 close to the third core board 402.

[0097] In this way, the first conductive column 801 and the second conductive column 802 electrically connect the conductive material on the surface of the first sub-circuit board 101, the surface of the second core board 401 and the conductive material on the inner wall of the through hole 4011, and the conductive material on the surface of the second core board 401 to form a synthetic shielding layer 701. The shielding layer 701 is arranged around the inner conductor 103 and is insulated from the inner conductor 103, thereby protecting the inner conductor 103 from interference from external electromagnetic fields and preventing the magnetic field generated by the inner conductor 103 when transmitting signals from leaking out and affecting other components.

[0098] The first conductive pillar 801 and the second conductive pillar 802 connect the conductive materials on each core board to obtain a shielding layer 701 that completely covers the accommodation space, and can also be used to electrically contact the shielding layer 701 with the ground terminal of the printed circuit board.

[0099] In an optional embodiment, the material of the second core board 401 may be a conductive material, thus eliminating the need to plate the conductive material on the surface of the second core board 401 .

[0100] In one example, the materials of the second core board 401, the third core board 402 and the first sub-circuit board 101 can be conductive materials. In this way, the third core board 402, the second core board 401 and the first sub-circuit board 101 are bonded and fixed, and the third core board 402, the second core board 401 and the first sub-circuit board 101 form a hollow space surrounding the inner conductor 103, the support structure 102 and the first positioning structure 104, and form a shielding layer 701 surrounding the inner conductor 103. In this way, the operation of plating the second core board 401, the third core board 402 and the first sub-circuit board 101 with conductive materials is omitted, and the operation of processing the conductive column is also omitted. As long as the surface of any one of the second core board 401, the third core board 402 and the first sub-circuit board 101 is electrically contacted with the ground terminal of the printed circuit board, the shielding layer 701 can be electrically contacted with the ground terminal of the printed circuit board.

[0101] In one example, the first semi-cured sheet 301 and the second semi-cured sheet 601 can also be made of conductive materials. In this way, the conductive columns do not need to penetrate the first semi-cured sheet 301 or the second semi-cured sheet 601 to electrically connect the conductive materials on each layer of the core board to form a complete shielding layer 701.

[0102] The shielding layer 701 is in electrical contact with the grounding terminal of the printed circuit board in order to ground the shielding layer 701. When the printed circuit board is working, on the one hand, the inner conductor 103 transmits electrical signals, which will generate an electromagnetic field. On the other hand, the inner conductor 103 will also be disturbed by the external electromagnetic field. After the shielding layer 701 is grounded, the charge generated by electromagnetic induction can be introduced into the earth, so that the potential of the shielding layer 701 is zero, which plays the role of electric field shielding, reduces the interference of the external electric field on the internal circuit, and prevents the leakage of the electric field generated by the internal circuit, reduces the interference to other surrounding electronic devices, and meets the requirements of electromagnetic compatibility (EMC). For high-speed signal transmission, the grounding of the shielding layer 701 can provide a stable signal reference potential, reduce signal reflection and crosstalk, ensure the accuracy and stability of signal transmission, and avoid signal distortion, bit error and other problems. The grounding of the shielding layer 701 can also prevent static electricity from accumulating on the shielding layer 701, and avoid the accumulated static electricity from generating electrostatic discharge, damaging circuit components or causing other safety problems. At the same time, it can also prevent the entire printed circuit board from being damaged due to accidental contact with high voltage by the shielding layer 701.

[0103] Based on the same inventive concept, the present application also provides a method for preparing a printed circuit board, such as Fig.10 As shown, the method includes:

[0104] S1001, providing a first sub-circuit board 101 and a second sub-circuit board 105;

[0105] S1002, forming a support structure 102 and a first positioning structure 104 at least partially surrounding the support structure 102 and spaced apart from the support structure 102 on one side of the first sub-circuit board 101;

[0106] S1003, forming an inner conductor 103 on a side of the support structure 102 away from the first sub-circuit board 101;

[0107] S1004, fix the side of the second sub-circuit board 105 provided with the groove to the side of the first sub-circuit board 101 close to the first positioning structure 104, so that the groove and the first sub-circuit board 101 form a space for accommodating the inner conductor 103, the support structure 102 and the first positioning structure 104, and obtain a printed circuit board.

[0108] The method provided in the embodiments of the present application can be used to prepare the above embodiments and the attached Figures 1 to 8 Supplied printed circuit board.

[0109] In the method provided by the embodiment of the present application, in the first aspect, a receiving space for receiving a support structure, an inner conductor and a first positioning structure is formed by the grooves of the first sub-circuit board and the second sub-circuit board, and the receiving space and the inner conductor form a coaxial transmission structure of the printed circuit board. When the signal is transmitted through the inner conductor, the dielectric constant of the air around the inner conductor is approximately equal to 1 and the loss factor is very small (approximately 1e-6), so that the energy loss and signal attenuation in the coaxial transmission structure are greatly reduced. Therefore, the use of air to fill the cavity helps to broaden the bandwidth of the coaxial transmission structure, increase the frequency range of the transmittable signal, and improve the working bandwidth of the printed circuit board, thereby improving the capacity and speed of the printed circuit board during data transmission, and meeting the transmission requirements of high-speed chips. . In the second aspect, the receiving space provides physical protection for the inner conductor and prolongs the service life of the inner conductor. In the third aspect, by setting the first positioning structure, it is convenient to position the first sub-circuit board and the second sub-circuit board during lamination, reduce quality problems caused by position deviation, improve the consistency and stability of mass production of printed circuit boards, and avoid relative dislocation of the first sub-circuit board and the second sub-circuit board during the production process, causing abnormal friction, collision and wear between the inner conductor and the inner wall of the groove, further prolonging the life of the printed circuit board.

[0110] The method provided in the embodiment of the present application solves the technical problem that the conventional PCB transmission line has large high-frequency loss and low bandwidth by manufacturing an air core coaxial transmission structure, and will cause signal integrity problems during high-speed signal transmission, resulting in signal distortion and high bit error rate, and therefore cannot be used for high-speed signal transmission.

[0111] In some optional embodiments, the second sub-circuit board 105 includes a second core board 401 and a third core board 402, the second core board 401 is provided with a through hole 4011, and the through hole 4011 penetrates the second core board 401 in a direction perpendicular to the second core board 401;

[0112] The side of the second sub-circuit board 105 provided with the groove is fixed to the side of the first sub-circuit board 101 close to the first positioning structure 104, so that the groove and the first sub-circuit board 101 enclose a space for accommodating the inner conductor 103, the support structure 102 and the first positioning structure 104, including:

[0113] The two sides of the second core board 401 are respectively arranged and fixed relative to the third core board 402 and the side of the first sub-circuit board 101 close to the first positioning structure 104, so that the third core board 402 at least covers the opening of the through hole 4011 on the surface of the second core board 401 away from the first sub-circuit board 101, and the third core board 402, the through hole 4011 and the first sub-circuit board 101 form a space to accommodate the inner conductor 103, the supporting structure 102 and the first positioning structure 104.

[0114] The method provided in the above embodiment can be used to prepare the above embodiment and the accompanying Figures 4 to 8 Supplied printed circuit board.

[0115] The following specific embodiments are used to describe in detail the technical solution of the present application and how the technical solution of the present application solves the above technical problems. The following specific embodiments can be implemented independently or in combination with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0116] The first step is to select a suitable first core board 1101, a second core board 1102 and a third core board 1103, wherein the first core board 1101, the second core board 1102 and the third core board 1103 are double-sided copper-clad core boards.

[0117] The second step is, Fig.11 As shown, the insulating support column 1104 and the first positioning ring 1105 shown in FIG. b are manufactured on the first core board 1101 shown in FIG. a, and the micro-coaxial inner conductor 1106 shown in FIG. c is manufactured on the insulating support column 1104.

[0118] like Fig.11 As shown, the width of the insulating support column 1104 along the x-direction shall not exceed the width of the inner conductor 103; the length along the y-direction is between 50um and 200um, and the spacing between adjacent insulating support columns 1104 is between 500um and 1000um.

[0119] The third step is Fig.12 As shown, a groove 1201 shown in FIG. b is made on the second core board 1102 shown in FIG. a, and the groove 1201 penetrates the second core board 1102 in a direction perpendicular to the surface of the second core board 1102. The method of making can be plasma, laser, wet etching, dry etching, etc.; the position of the groove 1201 corresponds to the first positioning ring 1105 of the first core board 1101. On the side wall of the groove 1201, the groove side wall metallization is formed, and the metallized side wall is completely electrically connected with the copper cladding on the upper and lower surfaces of the second core board 1102.

[0120] The fourth step is Fig.13 As shown, a groove 1303 as shown in FIG. b is made on the first prepreg 1301 as shown in FIG. a, and a groove 1304 as shown in FIG. b is made on the second prepreg 1302 as shown in FIG. a.

[0121] Step 5: Fig.14 As shown, the second positioning ring 1401 shown in FIG. b is made on the third core plate 1103 shown in FIG. a, and the position of the second positioning ring 1401 corresponds to the position of the first positioning ring 1105.

[0122] Step 6: Fig.15As shown, the first core board 1101, the first semi-cured sheet 1301, the second core board 1102, the second semi-cured sheet 1302 and the third core board 1103 shown in Figure a are laminated together through a lamination process, and holes are formed on the upper and lower surfaces of the laminated structure through drilling, laser punching and other processes, the hole groups are metallized, and the first conductive column group 1501 and the second conductive column group 1502 are formed by electroplating to obtain the printed circuit board 1503 shown in Figure b.

[0123] As shown in Figure c, the first conductive column group 1501 penetrates the first core board 1101 and the first semi-cured sheet 1301, and is electrically connected to the copper clad layer of the second core board 1102; the second conductive column group 1502 penetrates the second core board 1102 and the second semi-cured sheet 1302, and is electrically connected to the copper clad layer of the second core board 1102.

[0124] In another example, if Fig.16 As shown in Figure a, the first positioning ring 1105, the first semi-cured sheet 1301, the second positioning ring 1401 and the second semi-cured sheet 1302 can be made into a ring structure, the first positioning ring 1105 completely surrounds the insulating support column 1104 and the micro-coaxial inner conductor 1106, the first semi-cured sheet 1301 completely surrounds the first positioning ring 1105, and the second semi-cured sheet 1302 completely surrounds the second positioning ring 1401, and the printed circuit board 1601 shown in Figure b is obtained by lamination.

[0125] During the lamination process, the first semi-cured sheet 1301 and the second semi-cured sheet 1302 tightly bond the first core board 1101, the second core board 1102 and the third core board 1103, and the first positioning ring 1105 and the second positioning ring 1401 prevent the second semi-cured sheet 1302 from misaligning the first core board 1101, the second core board 1102 and the third core board 1103, thereby forming a coaxial transmission line structure.

[0126] By adopting the solution of the present application, it is possible to manufacture high-frequency signal coaxial transmission lines on printed circuit boards. Based on the characteristics of low dielectric loss, low radiation loss and wide operating frequency band of coaxial transmission lines, it can meet the signal transmission requirements of 112Gbps or 224Gbps high-speed chips.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0128] In the description provided herein, a large number of specific details are described. However, it is understood that the embodiments of the present application 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.

Claims

1. A printed circuit board, characterized in that: include: A first sub-circuit board, a support structure, an inner conductor, a first positioning structure, and a second sub-circuit board; The supporting structure is arranged on one side of the first sub-circuit board; The inner conductor is arranged on a side of the support structure away from the first sub-circuit board; The first positioning structure is disposed on a side of the first sub-circuit board close to the supporting structure, the first positioning structure at least partially surrounds the supporting structure, and is spaced apart from the supporting structure; The second sub-circuit board is arranged opposite to the first sub-circuit board, and a groove is provided on a side of the second sub-circuit board close to the first sub-circuit board. Along the direction perpendicular to the first sub-circuit board, the depth of the groove is less than the thickness of the second sub-circuit board, and the supporting structure, the inner conductor and the first positioning structure are located in an accommodating space enclosed by the groove and the first sub-circuit board.

2. The printed circuit board according to claim 1, wherein: It also includes a first semi-cured sheet; the first semi-cured sheet is located between the first sub-circuit board and the second sub-circuit board, and is arranged around the first positioning structure. Along the direction perpendicular to the first sub-circuit board, the thickness of the first semi-cured sheet is less than or equal to the thickness of the first positioning structure.

3. The printed circuit board according to claim 1 or 2, characterized in that: The first sub-circuit board includes a first core board, and the second sub-circuit board includes a second core board and a third core board; The first core plate is arranged opposite to the second core plate; The second core plate is provided with a through hole, and the through hole penetrates the second core plate in a direction perpendicular to the second core plate; The third core plate is disposed on a side of the second core plate away from the first core plate, and at least covers an opening of the through hole on a surface of the second core plate away from the first core plate. The groove is formed by the third core plate and the through hole.

4. The printed circuit board according to claim 3, wherein: Also included is a second positioning structure; The second positioning structure is disposed on a side of the third core plate close to the second core plate, and the second positioning structure is located in the groove and is spaced apart from the inner conductor.

5. The printed circuit board according to claim 4, wherein: It also includes a second semi-cured sheet, which is arranged between the second core plate and the third core plate. The second semi-cured sheet at least partially surrounds the second positioning structure. Along the direction perpendicular to the third core plate, the thickness of the second semi-cured sheet is less than or equal to the thickness of the second positioning structure.

6. The printed circuit board according to claim 2, wherein: The orthographic projection of the first semi-cured sheet on the first sub-circuit board is a first projection area, the orthographic projection of the supporting structure on the first sub-circuit board is a second projection area, and the orthographic projection of the first positioning structure on the first sub-circuit board is a third projection area. The third projection area includes a first boundary line and a second boundary line that are relatively set, the first boundary line is located outside the third projection area, the second boundary line is located between the first boundary line and the second projection area, and the first projection area is located on the side of the first boundary line away from the second projection area.

7. The printed circuit board according to claim 1, wherein: It also includes a shielding layer, which covers at least the side and bottom surfaces of the groove and the first area of ​​the first surface of the first sub-circuit board, the first surface is the surface of the first sub-circuit board close to the side of the groove, and the first area is the area of ​​the first surface opposite to the opening of the groove. There is a gap between the shielding layer and the inner conductor, and they are insulated from each other, and the shielding layer is in electrical contact with the ground terminal of the printed circuit board.

8. The printed circuit board according to claim 1, wherein: The orthographic projection of the first positioning structure on the first sub-circuit board is an annular area. The orthographic projections of the support structure and the inner conductor on the first sub-circuit board are located within the annular area and have a gap with the inner boundary of the annular area.

9. The printed circuit board according to claim 1, wherein: It also includes a signal sending end and a signal receiving end, one end of the inner conductor is electrically connected to the signal sending end, and the other end is electrically connected to the signal receiving end.

10. A method for preparing a printed circuit board, characterized in that: include: providing a first sub-circuit board and a second sub-circuit board; A support structure and a first positioning structure at least partially surrounding the support structure and spaced apart from the support structure are formed on one side of the first sub-circuit board; forming an inner conductor on a side of the support structure away from the first sub-circuit board; The side of the second sub-circuit board provided with the groove is fixed to the side of the first sub-circuit board close to the first positioning structure, so that the groove and the first sub-circuit board form a space for accommodating the inner conductor, the supporting structure and the first positioning structure, thereby obtaining a printed circuit board.

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