PCB structure and PCB assembly

Abstract

The application discloses a PCB structure and a PCB assembly, wherein the PCB structure comprises a PCB plate body and an air waveguide arranged in the PCB plate body and comprising at least a first waveguide section, the length direction of the first waveguide section is parallel to the plate surface of the PCB plate body, so that the air waveguide can transmit the introduced high-frequency signal along the extension direction of the plate surface of the PCB plate body. The technical scheme of the application can reduce the transmission loss of the high-frequency signal (for example, a millimeter wave signal) in the PCB.

Description

Technical Field

[0001] This invention relates to the field of circuit board technology, and in particular to a PCB structure and PCB assembly. Background Technology

[0002] Printed circuit boards (PCBs) are the core carriers of radio frequency and millimeter-wave communication equipment. Traditional PCBs rely on solid insulating substrates such as FR-4, high-frequency PTFE (Teflon), and hydrocarbon resins as the interlayer signal transmission medium. However, all solid insulating substrates have a fixed loss tangent Df. The Df of conventional FR-4 substrates is approximately 0.02, and it is difficult to further reduce the Df of high-end ultra-low loss high-frequency substrates. When the frequency of high-frequency signals increases to the millimeter-wave band of 112 GHz and above, the dielectric molecules are repeatedly polarized by the high-frequency electric field, and the polarization loss increases exponentially with the frequency, which leads to a significant attenuation of the signal amplitude.

[0003] The relevant improvement plans are divided into two categories: The first type involves replacing the substrate with a high-end, low-loss substrate, which can only slightly reduce the loss and cannot eliminate the polarization loss caused by the solid-state dielectric itself. Furthermore, the procurement cost of high-end millimeter-wave substrates is extremely high, the processing technology is stringent, and the performance of the substrates has an iterative ceiling.

[0004] The second type uses substrate integrated waveguide (SIW) to achieve waveguide transmission within the PCB. However, the SIW cavity is still filled with PCB dielectric, and dielectric polarization loss cannot be eliminated. The attenuation in the 112GHz and above millimeter wave bands is severe, which cannot meet the requirements for ultra-low loss interconnection. Summary of the Invention

[0005] The main objective of this invention is to propose a PCB structure designed to reduce transmission loss of high-frequency signals (e.g., millimeter-wave signals) within the PCB.

[0006] To achieve the above objectives, the PCB structure proposed in this invention includes: PCB board; and An air waveguide is disposed within the PCB board, and the air waveguide includes at least a first waveguide segment. The length direction of the first waveguide segment is parallel to the surface of the PCB board, so that the air waveguide can transmit the introduced high-frequency signal along the extension direction of the PCB board surface.

[0007] Optionally, the cross-section of the air waveguide is rectangular, with the length of the long side being a and the length of the short side being b; a is equivalent to twice the length of b.

[0008] Optionally, multiple air waveguides are provided at intervals, and the multiple air waveguides are arranged in one or more layers.

[0009] Optionally, the cross-section of the air waveguide is rectangular, the length of the long side of the rectangle is a, the frequency of the high-frequency signal is f, and a satisfies: 0.5c / f < a < c / f; where c is the speed of light in vacuum.

[0010] Optionally, the air waveguide further includes a second waveguide segment that is bent and connected to the first waveguide segment, the length direction of the second waveguide segment intersecting the surface of the PCB board.

[0011] Optionally, the wavelength of the high-frequency signal is λ, and the PCB structure further includes a coaxial probe for transmitting or receiving the high-frequency signal; the long side is parallel to the surface of the PCB board, the coaxial probe extends into the middle position of one end of the air waveguide, and the extension length L1=λ / 4, and / or, the distance between the coaxial probe and the end wall of the extended air waveguide end is L2=λ / 4; and / or, the coaxial probe for transmitting the high-frequency signal and the coaxial probe for receiving the high-frequency signal are located on the same surface or different surfaces of the PCB board.

[0012] Optionally, the air waveguide is configured as a metal waveguide embedded in the PCB board.

[0013] Optionally, the PCB board body includes multiple stacked layers, and the PCB structure further includes one or more metal plates. The metal plates are stacked in the multiple stacked layers of the PCB board body. When the metal plates are multi-layered, the multi-layered metal plates are staggered with the multiple stacked layers of the PCB board body. At least one of the two opposite surfaces of the metal plates is provided with one or more grooves, and among the multiple stacked layers of the PCB board body, the stacked layer that is stacked with the surface of the metal plate that is provided with the groove is a metal layer. The air waveguide is formed between the metal layer and the groove, or the air waveguide is formed in the metal plate.

[0014] Optionally, the air waveguide is configured as an air cavity formed within the PCB board, and the cavity wall of the air cavity is provided with a metal layer.

[0015] Optionally, the metal layer includes at least one of a metal plating layer, a metal coating layer, a metal deposition layer, and a metal cladding layer.

[0016] Optionally, the air waveguide includes a bend, the cross-section of the air waveguide is rectangular, and it has a long side and a short side, the dimension of the long side being a; when the bend is bent toward the side where the short side is located, the radius of curvature R of the bend satisfies: R≥2a; when the bend is bent toward the side where the long side is located, the radius of curvature R of the bend satisfies: R≥1.5a.

[0017] Optionally, the air waveguide includes a bend, and the inner side of the bend with a larger arc length is provided with a sawtooth compensation profile.

[0018] The present invention also proposes a PCB assembly comprising at least two of the aforementioned PCB structures, wherein the air waveguide of one PCB structure is connected to the air waveguide of the other PCB structure via a connecting tube or via a dual-headed coaxial probe.

[0019] Optionally, the two ends of the connecting pipe are flared.

[0020] The PCB structure of this invention transmits high-frequency signals by setting up air waveguides, thereby eliminating polarization losses caused by the solid insulating medium of traditional PCB solid transmission lines, SIW waveguides, etc., and reducing the transmission loss of high-frequency signals (such as millimeter-wave signals) within the PCB. Simultaneously, the air waveguide is integrated into the PCB board, meaning it is integrated with the PCB board itself. Compared to directly using mature waveguides, the PCB structure of this invention does not require a complex fixed structure to connect the air waveguide to the PCB board, and its height is smaller (mature waveguides are usually placed on the surface of a conventional PCB, and their height is at least the sum of the height of the conventional PCB and the mature waveguide, requiring more space). This results in less space required for communication equipment and reduces signal loss caused by the length and complexity of traditional waveguide interfaces, making it more suitable for multi-GPU, high-density board-level interconnect scenarios in AI servers. Furthermore, the air waveguide in the PCB structure of this invention includes at least a first waveguide segment parallel to the PCB board surface in the length direction, enabling lateral transmission of high-frequency signals within the PCB board through the first waveguide segment. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the first embodiment of the PCB structure of the present invention; Figure 2 for Figure 1 Exploded view of the PCB structure; Figure 3 for Figure 1 A partial cross-sectional structural diagram of the PCB structure; Figure 4 for Figure 3Enlarged view of point A in the middle; Figure 5 This is a cross-sectional structural diagram of the second embodiment of the PCB structure of the present invention; Figure 6 for Figure 5 Enlarged view of point G in the middle; Figure 7 This is a schematic diagram of the third embodiment of the PCB structure of the present invention; Figure 8 This is a schematic diagram of the fourth embodiment of the PCB structure of the present invention; Figure 9 A schematic diagram of the structure of a bend in an air waveguide of a PCB structure; Figure 10 for Figure 9 Top view of the middle bend; Figure 11 for Figure 9 Schematic diagram of the cross-sectional structure of the mid-turn section; Figure 12 This is a schematic diagram of the fifth embodiment of the PCB structure of the present invention; Figure 13 for Figure 12 Enlarged view of point D in the middle; Figure 14 for Figure 12 Exploded view of the PCB structure; Figure 15 This is a schematic diagram of the sixth embodiment of the PCB structure of the present invention; Figure 16 for Figure 15 Enlarged view at point F; Figure 17 for Figure 15 Exploded view of the PCB structure; Figure 18 This is a schematic diagram of the structure of the first embodiment of the PCB assembly of the present invention; Figure 19 for Figure 18 A schematic diagram of the cross-sectional structure of the PCB assembly; Figure 20 for Figure 19 Enlarged view of point B in the middle; Figure 21 for Figure 19 Exploded view of the PCB assembly; Figure 22 for Figure 21 Enlarged view of point C in the middle; Figure 23 This is a schematic diagram of the structure of the second embodiment of the PCB assembly of the present invention; Figure 24 This is a structural schematic diagram of the third embodiment of the PCB assembly of the present invention; Figure 25 for Figure 24 Enlarged view of point E in the middle.

[0023] Explanation of icon numbers: 1. PCB structure; 11. PCB board body; 111. Core board; 112. Insulating layer; 113. Metal cladding; 12. Air waveguide; 121. First waveguide section; 122. Second waveguide section; 123. Turning point; 124. Sawtooth compensation profile; 12a. Metal waveguide; 12b. Air cavity; 12c. Metal layer; 12d. Metal plate; 12d1. Trench; 13. Coaxial probe; 13a. Dual-head coaxial probe; 14. Connecting tube; 141. Horn mouth; 15. Waveguide conversion module; 151. Connector; 16. Chip device.

[0024] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0027] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0028] This invention proposes a PCB structure.

[0029] Reference Figures 1 to 3 , Figure 21 In one embodiment of the present invention, the PCB structure 1 includes: PCB board 11; and An air waveguide 12 is disposed within the PCB board 11, and the air waveguide 12 includes at least a first waveguide segment 121. The length direction of the first waveguide segment 121 is parallel to the surface of the PCB board 11, so that the air waveguide 12 can transmit the introduced high-frequency signal along the extension direction of the PCB board 11.

[0030] In this embodiment, the PCB board 11 can also typically have the structure of a conventional PCB. For example, it can be formed by laminating core board 111, metal cladding 113 (e.g., copper foil layer), insulating layer 112, etc., with pads on its surface and power supply lines, conventional signal transmission lines (usually etched by metal cladding 113) etc. embedded inside.

[0031] The PCB structure 1 of the present invention transmits high-frequency signals by setting an air waveguide 12, thereby eliminating the polarization loss caused by the solid insulating medium of traditional PCB solid transmission lines, SIW waveguides, etc., and reducing the transmission loss of high-frequency signals (such as millimeter-wave signals) in the PCB. At the same time, the air waveguide 12 is set in the PCB board body 11, that is, the air waveguide 12 is integrated with the PCB board body 11. Compared with the technical solution of directly using mature waveguides, the PCB structure 1 of the present invention does not need to set up a complex fixed structure to connect the air waveguide 12 to the PCB board body 11, and the height dimension is smaller (mature waveguides are usually set on the surface of conventional PCBs, and their height is at least the sum of the conventional PCB and the mature waveguide, requiring more space). The required communication equipment space is smaller, and the signal loss caused by the length and complexity of traditional waveguide interface leads can be reduced. It is more conducive to adapting to the multi-GPU, high-density board-level interconnection scenarios of AI servers.

[0032] Furthermore, in the technical solution of the present invention, the air waveguide 12 of the PCB structure 1 includes at least a first waveguide segment 121 parallel to the surface of the PCB board 11 in the length direction. This allows high-frequency signals to be transmitted laterally from one position on the PCB board 11 to another position on the PCB board 11 via the first waveguide segment 121. It is understood that different chip devices 16 on the PCB board 11 are typically located at different positions in the lateral direction, rather than simply on opposite sides of the PCB board 11. For high-frequency signal transmission between chip devices 16 at different lateral positions, the first waveguide segment 121 is required for transmission. Alternatively, when two different chip devices 16 requiring high-frequency signal transmission are located on two PCB structures 1, the high-frequency signal of the chip device 16 on one PCB structure 1, after being introduced into the air waveguide 12, can be transmitted via the first waveguide segment 121 to the edge of the PCB board 11 of that PCB structure 1, and then transmitted via the edge of the PCB board 11 of the other PCB structure 1 to the first waveguide segment 121 thereon, and subsequently to the chip device 16 on the other PCB structure 1.

[0033] Optionally, the air waveguide 12 further includes a second waveguide segment 122 that is bent and connected to the first waveguide segment 121. The length direction of the second waveguide segment 122 intersects the surface of the PCB board 11. For example, the second waveguide segment 122 can be perpendicular to the surface of the PCB board 11. It is understood that the arrangement of the second waveguide segment 122 allows one end of the air waveguide 12 to extend towards the surface of the PCB board 11, or even extend to the surface of the PCB board 11, facilitating the connection of the air waveguide 12 of another PCB structure 1 to it (see...). Figure 22 ).

[0034] Reference Figure 8 Optionally, multiple air waveguides 12 are provided at intervals, and the multiple air waveguides 12 are arranged in one or more layers to improve the utilization rate of the PCB board 11, thereby meeting the needs of dense transmission of high-frequency signals in scenarios such as AI servers.

[0035] Reference Figure 9 Optionally, the air waveguide 12 has a rectangular cross-section. The rectangular air waveguide 12 satisfies the principle of electromagnetic field superposition, allowing multiple high-frequency signals to be transmitted synchronously and in parallel through independent waveguide channels. Typically, the longer side of the rectangle is parallel to the surface of the PCB board 11. Furthermore, Figure 9 Although the air waveguide 12 in this embodiment is a rectangular waveguide, in other embodiments, the air waveguide 12 may also be, but is not limited to, a circular waveguide, a ridge waveguide, a double ridge waveguide, etc., in order to meet the single-ended or differential signal transmission under different requirements.

[0036] In some embodiments, refer to Figure 3 and Figure 4 The PCB structure 1 further includes a coaxial probe 13 for transmitting or receiving the high-frequency signal. The coaxial probe 13 can be disposed between the chip device 16 and the PCB board 11. Typically, multiple coaxial probes 13 need to be simultaneously disposed between a chip device 16 and the PCB board 11 to meet the transmission requirements of multiple high-frequency signals from the chip device 16. It is understood that during multi-channel parallel transmission, the coaxial metal probe can effectively isolate electromagnetic signals and suppress electromagnetic crosstalk between channels. Optionally, multiple coaxial probes 13 can be fixed on the same connector 151 to form a waveguide conversion module 15. A plurality of air waveguides 12 are correspondingly disposed within the PCB board 11, and a coaxial probe 13 is correspondingly disposed at one end of an air waveguide 12. It is understood that within the coaxial probe 13, the high-frequency signal is a TEM mode signal, and the portion of the coaxial probe 13 inserted into the air waveguide 12 forms a radio frequency antenna to transmit the TEM mode signal as a TEM signal. 10 Analog signal, the TE 10 The analog signal is transmitted within the air waveguide 12 to another chip device 16 located laterally on the PCB board 11. It is understood that another set of coaxial probes 13 is provided between this other chip device 16 and the PCB board 11; this set of coaxial probes 13 is used to receive multiple TE signals. 10 The high-frequency signal is converted back to a TEM signal for transmission to the other chip device 16. The wavelength of the high-frequency signal is λ. Optionally, the coaxial probe 13 extends into the middle of one end of the air waveguide 12, with an insertion length L1 = λ / 4, and / or, optionally, the distance between the coaxial probe 13 and the endwall of the extended air waveguide end is L2 = λ / 4, to effectively excite a TEM signal. 10 Mode signal. Optionally, a multi-level widened metal stepped impedance matching structure is provided at the root of the coaxial probe 13 to achieve a smooth impedance transition between the microstrip TEM line and the air waveguide 12, thereby widening the matching bandwidth and reducing port reflection loss.

[0037] In other embodiments, reference is made to Figure 5 and Figure 6 The structure is similar to Figure 3 and Figure 4 The difference lies in that the air waveguide 12 extends from inside the PCB board 11 to its surface in advance, achieving a three-dimensional waveguide arrangement, making full use of space, and facilitating the direct insertion of multiple coaxial probes 13. Its effect is similar to... Figure 3 and Figure 4 Similar. Optionally, the coaxial probe 13 extends from the center of the waveguide end face on the surface of the PCB board 11, and the extension length is λ / 4.

[0038] Optionally, the coaxial probe 13 for transmitting the high-frequency signal and the coaxial probe 13 for receiving the high-frequency signal are disposed on the same surface of the PCB board 11 (refer to...). Figure 1 ) or different panels (refer to) Figure 7 To adapt to the different requirements of different communication devices for PCB structure 1.

[0039] Reference Figure 9 The rectangle has a long side dimension of 'a' and a short side dimension of 'b'. Optionally, 'a' and 'b' are roughly twice each other. Twice the length of 'b' represents the optimal ratio of the long side to the short side for single-mode transmission in a rectangular waveguide. At this ratio, all signal frequencies transmitted synchronously fall within the TE range. 10 In the single-mode bandwidth range, each high-frequency signal is transmitted only in the main mode, and the mode crosstalk is extremely low; "equivalent" here means a=2b, or a≈2b.

[0040] Optionally, the frequency of the high-frequency signal is f, and a satisfies: 0.5c / f < a < c / f; where c is the speed of light in a vacuum, and a is in millimeters. Based on the above formula, the size of the air waveguide 12 can be customized according to the frequency of the high-frequency signal to be transmitted; for example, when f is 112 GHz, 1.34 mm < a < 2.68 mm, so a can be 2 mm, and correspondingly, b can be 1 mm. Below this size, the air waveguide 12 is suitable for embedding in the PCB board 11. Alternatively, one or more high-frequency signals that can be transmitted in single-mode within the air waveguide 12 can be selected based on the size of the air waveguide 12 determined in the PCB structure 1, since 0.5c / a < f < c / a.

[0041] For TE mn The signal is a modal signal, where m is the number of half-cycles of the electromagnetic wave distributed along the longer side a, and n is the number of half-cycles of the electromagnetic wave distributed along the shorter side b. m and n are natural numbers that are not both zero. TE mn The general cutoff frequency formula for analog signals is:

[0042] The lowest-order transmitted dominant mode of the rectangular waveguide is TE. 10 The modulus has m=1 and n=0, therefore TE 10 The cutoff frequency of the modulus simplifies to: f c =0.5c / a, meaning that the high-frequency signal's operating frequency f > f c At that time, TE 10 The mode can be stably transmitted within the air waveguide 12.

[0043] The second-highest order interference mode is TE. 20 The modulus has m=2 and n=0, and the corresponding cutoff frequency is c / a=2f. c That is, the upper limit frequency of single-mode transmission is 2f.c Therefore, TE 10 The single-mode bandwidth range is f c up to 2f c .

[0044] Since practical engineering applications often cannot be used close to the boundaries, TE may be used alternatively. 10 The effective single-mode bandwidth range is 1.25f. c up to 1.9f c Thus, 0.625c / f < a < 0.95c / f, or 0.625c / a < f < 0.95c / a, is used to keep the air waveguide 12 away from the high-loss region. This helps to ensure impedance flatness across the entire frequency band, low insertion loss, low VSWR, and avoid excitation of higher-order noise modes, resonance, and signal crosstalk.

[0045] Optionally, refer to Figure 9 and Figure 21 The air waveguide 12 is configured as a metal waveguide 12a embedded in the PCB board 11. Its fabrication process can be as follows: a pre-embedded receiving groove, slightly larger than the outer contour of the metal waveguide 12a, is fabricated from the middle core board of the PCB board 11 using machining technology; the pre-fabricated complete rectangular metal waveguide 12a is then embedded entirely into the pre-embedded receiving groove; and finally, the upper and lower substrates of the PCB board 11 are pressed together.

[0046] It is understood that the prefabricated metal waveguide 12a is an embedded air waveguide 12. However, this design is not limited to this. In other embodiments, the air waveguide 12 may not be embedded but formed. In this case, the air waveguide 12 is configured as an air cavity 12b formed within the PCB board 11, and the cavity wall of the air cavity 12b is provided with a metal layer 12c. Further optionally, the metal layer 12c includes at least one of a metal plating layer, a metal coating layer, a metal deposition layer, and a metal cladding layer. For the formed air waveguide 12, its fabrication process may be as follows: 1. Substrate construction - A conventional solid dielectric core board is selected, and a continuous copper foil overlay is laminated on the entire upper surface of the core board as the bottom conductive wall of the rectangular waveguide. The copper foil overlay also serves as the global grounding layer of PCB structure 1, achieving full waveguide grounding shielding. 2. Processing of the intermediate cavity layer and pressing the intermediate cavity layer onto the lower substrate: Select a dielectric substrate with a thickness equal to the short side dimension of the rectangular waveguide, use machining technology to completely cut through the substrate along the high-frequency signal transmission trajectory to form a continuous waveguide main cavity, and press it onto the lower substrate.

[0047] 3. All-metal interconnection of cavity sidewalls - Chemical copper plating and thickening electroplating are performed on all inner surfaces of the waveguide main cavity to form continuous and dense copper conductive sidewalls on the inner wall of the cavity, and the bottom of the copper conductive sidewalls is electrically connected to the copper foil coating of the lower substrate.

[0048] 4. Upper substrate construction – Prepare an upper substrate with copper cladding on the lower surface. The copper foil on the bottom surface serves as the upper conductive wall of the rectangular waveguide. Then, perform the PCB lamination process to electrically connect the copper foil on the bottom surface of the upper substrate with the copper conductive sidewall of the main cavity of the waveguide.

[0049] In addition to the two manufacturing methods mentioned above, the air waveguide 12 can also be directly formed through a lamination and pressing process. Without loss of generality, such as Figures 12 to 17 The PCB board 11 includes multiple stacked layers, some of which may be a core board 111, a metal layer 113 (e.g., a copper foil layer), or an insulating layer 112 (e.g., a PP dielectric layer). In this embodiment, the PCB structure 1 further includes a metal plate 12d, which is stacked among the multiple stacked layers of the PCB board 11. When the metal plate 12d has multiple layers, the multiple metal plates 12d are staggered with the multiple stacked layers of the PCB board 11. At least one of the two opposite surfaces of the metal plate 12d is provided with one or more grooves 12d1, and among the multiple stacked layers of the PCB board 11, the grooves are provided on the metal plate 12d. The stacked layer on the 12d1 board surface is a metal cladding 113, which forms the air waveguide 12 between the metal cladding 113 and the trench 12d1. Furthermore, the metal plate 12d is distinct from the metal stacked layer on the board surface where the trench 12d1 is located. The metal plate 12d serves as the main transmission carrier of the air waveguide 12, while the metal stack serves as the copper foil layer on the PCB dielectric surface. Typically, the thickness of the metal plate 12d is significantly greater than the thickness of the metal stack. Its fabrication process can be selected as follows: 1. Fabrication of 12d metal plate – Using machining processes, grooves 12d1 are formed on the surface of the 12d metal plate along the high-frequency signal transmission trajectory. The direction of the grooves 12d1 can be straight or partially curved, and the grooves 12d1 can be formed on only one surface of the 12d metal plate (e.g., Figure 14 Grooves 12d1 can also be machined on both surfaces (e.g.) Figure 17 ).

[0050] 2. Lamination and lamination with multiple layers of the PCB board 11 – such as Figures 12 to 14For a metal plate 12d with grooves 12d1 formed on only a single surface, a dielectric layer with a metal cladding layer 113 (e.g., a copper foil layer) is laminated on the side where the groove is located (e.g., a double-sided copper foil core board; in this case, either side of the double-sided copper foil core board can be laminated with the side where the groove is located on the metal plate 12d; or it can be a single-sided copper foil core board; in this case, the side where the copper foil is located on the single-sided copper foil core board must be laminated with the side where the groove is located on the metal plate 12d). On the other side of the metal plate 12d, any layer of the PCB board 11 can be laminated, that is, it can be an insulating layer 112 (e.g., a PP dielectric layer) or any core board 111 (a core board without copper foil, or a core board with single-sided or double-sided copper foil). Figures 15 to 17 For a metal plate 12d with grooves 12d1 formed on both sides, a dielectric layer with a metal cladding 113 (e.g., a copper foil layer) is laminated on both sides (e.g., a double-sided copper foil core board, in which case either side of the double-sided copper foil core board can be laminated with the metal plate 12d; or it can be a single-sided copper foil core board, in which case the single-sided copper foil core board must be laminated with the side where the copper foil is located to the metal plate 12d).

[0051] Thus, the metal plate 12d can be stacked with the PCB boards 11 on both sides to form a closed air waveguide 12.

[0052] However, this design is not limited to this. In other embodiments, the air waveguide 12 may not be formed between the metal plate 12d and the adjacent metal cladding 113, but may be formed directly within the metal plate 12d. For example, the air waveguide 12 may be integrally formed within the metal plate 12d. Alternatively, the metal plate 12d may include two stacked metal sub-plates. Each metal sub-plate has a half-groove on its surface facing the other metal sub-plate. When the two metal sub-plates are stacked, the two half-grooves are joined together to form the air waveguide 12.

[0053] Reference Figure 2 The air waveguide 12 within the PCB board 11 includes both straight and partially bent waveguides. For partially bent waveguides, there is a bend 123. When this bend 123 bends towards the side containing the shorter side (e.g....), Figure 9 and Figure 10 The radius of curvature R of the turning portion 123 satisfies R ≥ 2a, to reduce the probability of higher-order miscellaneous modes being excited due to magnetic field distortion; and when the turning portion 123 bends towards the side with the longer side (not shown), the radius of curvature R of the turning portion 123 satisfies R ≥ 1.5a, to reduce the probability of higher-order miscellaneous modes being excited due to electric field distortion. It can be understood that, generally, the electric field is less affected by curvature disturbances than the magnetic field.

[0054] However, this design is not limited to this. In other embodiments, when the space cannot meet the above requirements for the radius of curvature R, optionally, a sawtooth-shaped compensation profile 124 is provided on the inner side of the curved surface with a larger arc length of the turning part 123 (such as...). Figure 11 The compact turn features a concentrated electric field on the inner side, naturally introducing an equivalent concentrated capacitance. The serrated contours on the inner side periodically fine-tune the effective width of the waveguide cavity along the electromagnetic wave propagation direction, forming a gradually changing capacitive compensation structure to offset the inherent equivalent capacitance of the turn. Combined with the stepped structure at the entrance / exit of the turn (123), this compensates for the equivalent inductance, achieving LC-coordinated dispersion compensation. Simultaneously, the serrated structure on the inner side of the turn can disturb the distribution of higher-order mode electromagnetic fields excited in the turning area, disrupting the continuous propagation conditions of higher-order modes, suppressing higher-order mode resonance and energy leakage, reducing in-band reflection loss, and extending the effective operating bandwidth of the compact turn. It is worth noting that the serrated structure is only locally located at the turn (123), and the waveguide straight-line transmission section still maintains a standard rectangular cross-section, ensuring TE... 10 Stable transmission of the main module.

[0055] The present invention also proposes a PCB assembly for achieving high-speed interconnection between boards. The PCB assembly includes at least two PCB structures 1, the specific structure of which is as described in the above embodiments. Since the PCB assembly adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0056] In one embodiment, reference is made to Figures 18 to 22 An air waveguide 12 of one PCB structure 1 is connected to an air waveguide 12 of another PCB structure 1 via a connecting pipe 14, thereby enabling the transmission of high-frequency signals from one PCB structure 1 to another, i.e., enabling high-frequency signal transmission between boards. It is understood that the cross-section of the connecting pipe 14 is typically rectangular and is a metal tube. During assembly, the ends of the air waveguide 12 of one PCB structure 1 and the ends of the air waveguide 12 of the other PCB structure 1 are inserted into the two openings of the connecting pipe 14, respectively, so that the two air waveguides 12 are coupled and connected inside the cavity of the connecting pipe 14. Air is used as the transmission medium throughout, achieving low-loss inter-board interconnection. Optionally, for the two PCB structures 1 connected by the air waveguide 12 through the connecting tube 14, each PCB structure 1 has a portion of the air waveguide 12 that extends beyond the PCB board 11 (it can extend from the surface of the PCB board 11 or from the end face of the PCB board 11). The length of the portion extending beyond the PCB board 11 is usually greater than or equal to 1 / 2 of the height of the connecting tube 14. This avoids the phenomenon of discontinuous electromagnetic wave transmission caused by a large gap between the two air waveguides 12 after the connecting tube 14 is inserted due to insufficient length extending beyond the PCB board 11.

[0057] Optionally, refer to Figure 23 A PCB structure 1 (let's define it as the first PCB structure) can also be connected to multiple PCB structures 1 (let's define it as the second PCB structure) at the same time with air waveguides 12. The first PCB structure has multiple layers of air waveguides 12. For example, the first PCB structure has one layer of air waveguide 12 for each second PCB structure, so that the air waveguides 12 of different second PCB structures are connected to different layers of air waveguides 12 of the first PCB structure. Of course, different layers of air waveguides 12 are led out at different positions on the PCB board 11 of the first PCB structure to achieve a space-dense board layout and meet the high-speed transmission requirements of multiple interconnections in the AI ​​server rack.

[0058] Optionally, both ends of the connecting pipe 14 are flared out at the ends 141 (see...). Figure 22 It can be understood that the flared opening 141 serves as an assembly guide, improving the tolerance of structural alignment.

[0059] In another embodiment, reference is made to Figure 24 and Figure 25 The air waveguide 12 of one PCB structure 1 is connected to the air waveguide 12 of another PCB structure 1 via a dual-headed coaxial probe 13a. In this embodiment, the transmission process of the high-frequency signal from one PCB structure 1 to the other PCB structure 1 is respectively TE 10 From TEM to TE 10 In this way, high-frequency signal transmission between boards can also be achieved.

[0060] The above description is only a preferred embodiment of the present invention and does not limit the scope of protection of the present invention. All equivalent structural transformations made under the inventive concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A PCB structure, characterized in that, include: PCB board; as well as An air waveguide is disposed within the PCB board, and the air waveguide includes at least a first waveguide segment. The length direction of the first waveguide segment is parallel to the surface of the PCB board, so that the air waveguide can transmit the introduced high-frequency signal along the extension direction of the PCB board surface.

2. The PCB structure as described in claim 1, characterized in that, The air waveguide has a rectangular cross-section, with the length of the long side being a and the length of the short side being b. The a is equivalent to twice the b.

3. The PCB structure as described in claim 1, characterized in that, Multiple air waveguides are provided at intervals, and the multiple air waveguides are arranged in one or more layers; and / or The air waveguide has a rectangular cross-section, the length of the longer side of the rectangle is 'a', the frequency of the high-frequency signal is 'f', and 'a' satisfies: 0.5c / f < a < c / f; where c is the speed of light in vacuum; and / or The air waveguide further includes a second waveguide segment that is bent and connected to the first waveguide segment, the length direction of the second waveguide segment intersecting the surface of the PCB board; and / or The wavelength of the high-frequency signal is λ, and the PCB structure further includes a coaxial probe for transmitting or receiving the high-frequency signal; the long side is parallel to the surface of the PCB board, the coaxial probe extends into the middle position of one end of the air waveguide, and the extension length L1=λ / 4, and / or, the distance between the coaxial probe and the end wall of the extended air waveguide end is L2=λ / 4; and / or, the coaxial probe for transmitting the high-frequency signal and the coaxial probe for receiving the high-frequency signal are located on the same surface or different surfaces of the PCB board.

4. The PCB structure as described in claim 1, characterized in that, The air waveguide is configured as a metal waveguide embedded in the PCB board; or The PCB board body includes multiple stacked layers, and the PCB structure also includes one or more metal plates. The metal plates are stacked in the multiple stacked layers of the PCB board body. When the metal plates are multi-layered, the multi-layered metal plates are staggered with the multiple stacked layers of the PCB board body. At least one of the two opposite surfaces of the metal plates is provided with one or more grooves. Among the multiple stacked layers of the PCB board body, the stacked layer that is stacked with the surface of the metal plate that is provided with the groove is a metal layer. The air waveguide is formed between the metal layer and the groove, or the air waveguide is formed in the metal plate.

5. The PCB structure as described in claim 1, characterized in that, The air waveguide is configured as an air cavity formed within the PCB board, and the cavity wall of the air cavity is provided with a metal layer.

6. The PCB structure as described in claim 5, characterized in that, The metal layer includes at least one of metal plating, metal coating, metal deposition layer, and metal cladding.

7. The PCB structure as described in claim 1, characterized in that, The air waveguide includes a bend, and the cross-section of the air waveguide is rectangular, having a long side and a short side, the dimension of which is a; When the turning part bends toward the side containing the short side, the radius of curvature R of the turning part satisfies: R≥2a; When the turning part bends toward the side containing the long side, the radius of curvature R of the turning part satisfies: R≥1.5a.

8. The PCB structure as described in claim 1, characterized in that, The air waveguide includes a bend, and the inner side of the bend with a large arc length is provided with a sawtooth compensation profile.

9. A PCB assembly, characterized in that, It includes at least two PCB structures as described in any one of claims 1 to 8, wherein the air waveguide of one PCB structure is connected to the air waveguide of the other PCB structure via a connecting tube or via a dual-headed coaxial probe.

10. The PCB assembly as claimed in claim 9, characterized in that, The two ends of the connecting pipe are flared.

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