Differential via hole structure, design method and printed circuit board

Abstract

The invention discloses a differential via hole structure, a design method and a printed circuit board, relates to the field of circuit design, and is used for solving the problem that a differential via hole occupies a large space of the printed circuit board. According to the scheme, by designing the structure that the two backflow via holes are tangent and the two backflow via holes are tangent to the two signal via holes respectively, symmetry is kept between the signal via holes and the backflow via holes, the via hole layout of differential signals is optimized, the distance between the differential via holes is shortened, the wiring space on the printed circuit board is effectively saved, and the wiring efficiency of the printed circuit board is improved. The structure is divided into three parts by adding the milling grooves in the printed circuit board, so that differential signals can obtain good isolation and backflow channels among different parts, the isolation and backflow effects of GND signals are enhanced, the integrity of high-speed signals is improved, signal crosstalk in high-density design can be reduced, and the reliability of the circuit board is improved. Therefore, high-density and miniaturized design is supported under the condition that the production difficulty is not increased, and the flexibility and the replicability of the design are improved.

Description

Technical Field

[0001] The present invention relates to the field of circuit design, and in particular to a differential via structure, a design method and a printed circuit board. Background Art

[0002] With the development of electronic information technology and the increase in signal transmission rate, the requirements for signal performance and quality are also increasing, and the margin of link design is gradually shrinking. This requires designers to deal with various optimization issues more carefully in printed circuit board design to achieve performance optimization, minimize costs, shorten design cycles and improve production efficiency.

[0003] In the related printed circuit board and signal integrity design, differential via design is usually adopted, that is, a pair of high-speed signal holes corresponding to a pair of differential signal lines (DP and DN) are accompanied by a pair of return via holes for GND signals (such as Figure 1 However, as the number of high-speed signal pins on chips and connectors increases, the density of signal layer-changing vias in the fan-out area also increases, and the required layout and wiring space increases; and as the signal rate increases, the optimization requirements for high-speed signal layer-changing vias are higher, and the number of return vias for GND signals increases from one pair to two or even three pairs, which occupies more space and is not conducive to the high-density design of printed circuit boards. Summary of the invention

[0004] The purpose of the present invention is to provide a differential via structure, design method and printed circuit board, which effectively saves the wiring space on the printed circuit board, enables the differential signal to obtain good isolation and return channels between different parts, not only enhances the isolation and return effects of the GND signal, improves the integrity of the high-speed signal, but also can reduce the signal crosstalk in the high-density design, thereby supporting high-density and miniaturized design without increasing the difficulty of production, and improving the flexibility and reproducibility of the design.

[0005] In a first aspect, the present application provides a differential via structure, including at least one via unit, wherein the via unit includes:

[0006] a first return via and a second return via, wherein the first return via and the second return via are tangent to each other;

[0007] A first signal via and a second signal via, the first signal via and the first return via being tangent to each other, and the second signal via and the second return via being tangent to each other;

[0008] The first signal via and the second signal via are symmetrical about a first tangent plane, the first tangent plane is a plane where the two return vias are tangent, and a first distance between a central axis of the first signal via and a central axis of the second signal via is not greater than a second distance between a central axis of the first return via and a central axis of the second return via;

[0009] at least two milling grooves, the first milling groove is used to separate the two return vias and the two signal vias, and the second milling groove is used to separate the two signal vias;

[0010] The first signal via is connected to the first signal line of the differential line, the second signal via is connected to the second signal line of the differential line, and the two return vias serve as signal return holes.

[0011] Optionally, a second tangent plane where the first signal via and the first return via are tangent coincides with a third tangent plane where the second signal via and the second return via are tangent, and the second tangent plane or the third tangent plane is perpendicular to the first tangent plane.

[0012] Optionally, the number of the milled grooves is 2;

[0013] The first milling groove is arranged along the second tangent plane or the third tangent plane, passes through the two reflow vias and the two signal vias, and the length of the first milling groove is ≥ 2×the diameter of the reflow via+2×the width of the pad outside the reflow via, and the first milling groove is used to separate the two reflow vias and the two signal vias;

[0014] The second milling groove is arranged along the first cutting plane, passing through the two return vias and the two signal vias, and the diameter of the signal via + the width of the pad outside the signal via + the diameter of the return via / 2≤the length of the second milling groove≤the diameter of the signal via + the width of the pad outside the signal via + the diameter of the return via, and the second milling groove is located between the two signal vias.

[0015] Optionally, there are multiple via units, and in the multiple via units, the central axes of all the return vias are on a first plane, and the central axes of all the signal vias are on a second plane, and the first plane is parallel to the second plane;

[0016] The plurality of first milling grooves are integrally formed.

[0017] Optionally, there are multiple via units, the first tangent planes of all the via units coincide, the central axis of the return via of the ith via unit and the central axis of the return via of the i+2th via unit are on the same plane, the central axis of the signal via of the ith via unit and the central axis of the signal via of the i+2th via unit are on the same plane, i≥1, i is an integer;

[0018] The plurality of first milling grooves are integrally formed.

[0019] Optionally, there are a plurality of via units, and the first milling grooves in each two adjacent via units are staggered so that the distance between the second milling grooves in the two adjacent via units is less than the width of the via unit;

[0020] The width of the via unit=2×the diameter of the reflow via+2×the width of the pad outside the reflow via.

[0021] Optionally, the diameter of the first return via is the same as the diameter of the second return via, the diameter of the first signal via is the same as the diameter of the second signal via, and the diameter of each return via is larger than the diameter of each signal via.

[0022] Optionally, the width of each of the milling grooves is not less than the width of the pad outside the reflow via or the pad outside the signal via.

[0023] In a third aspect, the present application provides a printed circuit board, comprising the differential via structure as described above.

[0024] In a third aspect, the present application provides a design method for a differential via structure, which is applied to the differential via structure as described above, comprising:

[0025] Determine the target size of the differential vias based on target requirements and printed circuit board space;

[0026] Drilling a first return via hole and a second return via hole using a first drill needle, wherein the first return via hole and the second return via hole are tangent to each other;

[0027] A first signal via and a second signal via are drilled using a second drill, wherein the first signal via is tangent to the first return via, and the second signal via is tangent to the second return via; the first signal via and the second signal via are symmetrical about a first tangent plane, the first tangent plane is a plane where the two return vias are tangent, and a first distance between a central axis of the first signal via and a central axis of the second signal via is not greater than a second distance between a central axis of the first return via and a central axis of the second return via;

[0028] Performing electroplating treatment on the two reflow vias and the two signal vias respectively;

[0029] Drilling at least two milling grooves using a third drill, wherein the first milling groove is used to separate the two return vias and the two signal vias, and the second milling groove is used to separate the two signal vias; wherein the first signal via is connected to the first signal line of the differential line, the second signal via is connected to the second signal line of the differential line, and the two return vias serve as signal return holes;

[0030] The milling groove, the reflow via and the signal via are filled with resin.

[0031] The present invention provides a differential via structure, a design method and a printed circuit board, which relate to the field of circuit design and are used to solve the problem that differential vias occupy a large space on a printed circuit board. The solution optimizes the via layout of differential signals by designing a structure in which two return vias are tangent to each other and two return vias are tangent to two signal vias respectively, and the signal vias and the return vias are symmetric, so that the spacing between the differential vias is reduced, and the wiring space on the printed circuit board is effectively saved. By adding a milling groove on the printed circuit board to divide the structure into three parts, the differential signal can obtain good isolation and return channels between different parts, which not only enhances the isolation and return effects of the GND signal, improves the integrity of the high-speed signal, but also reduces the signal crosstalk in the high-density design, thereby supporting high-density and miniaturized design without increasing the difficulty of production, and improving the flexibility and replicability of the design. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 is a schematic diagram of a differential via structure in the related art;

[0034] Figure 2 A schematic diagram of the positions of four vias in a differential via structure provided by the present invention;

[0035] Figure 3 A schematic diagram of the positions of four vias and surrounding pads in a differential via structure provided by the present invention;

[0036] Figure 4 A complete schematic diagram of a differential via structure provided by the present invention;

[0037] Figure 5A schematic diagram of a first embodiment of a differential via structure provided by the present invention;

[0038] Figure 6 A schematic diagram of a second embodiment of a differential via structure provided by the present invention;

[0039] Figure 7 A schematic diagram of a third embodiment of a differential via structure provided by the present invention;

[0040] Figure 8 A schematic flow chart of a design method for a differential via structure provided by the present invention. DETAILED DESCRIPTION

[0041] The core of the present invention is to provide a differential via structure, design method and printed circuit board, which effectively saves the wiring space on the printed circuit board, enables the differential signal to obtain good isolation and return channels between different parts, not only enhances the isolation and return effects of the GND signal, improves the integrity of the high-speed signal, but also can reduce the signal crosstalk in the high-density design, thereby supporting high-density and miniaturized design without increasing the difficulty of production, and improving the flexibility and replicability of the design.

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] First, as Figure 2 , Figure 3 and Figure 4 As shown, the present application provides a differential via structure, including at least one via unit, and the via unit includes:

[0044] A first return via hole 11 and a second return via hole 12, wherein the first return via hole 11 and the second return via hole 12 are tangent to each other;

[0045] A first signal via 21 and a second signal via 22, wherein the first signal via 21 is tangent to the first return via 11, and the second signal via 22 is tangent to the second return via 12;

[0046] The first signal via 21 and the second signal via 22 are symmetrical about a first tangent plane, the first tangent plane being a plane where the two return vias are tangent, and a first distance between the central axis of the first signal via 21 and the central axis of the second signal via 22 is not greater than a second distance between the central axis of the first return via 11 and the central axis of the second return via 12;

[0047] At least two milling grooves, the first milling groove is used to separate the two return vias and the two signal vias, and the second milling groove is used to separate the two signal vias;

[0048] The first signal via is connected to the first signal line of the differential line, the second signal via is connected to the second signal line of the differential line, and the two return vias serve as signal return holes.

[0049] In this embodiment, the differential via structure uses two tangent return vias to achieve more effective signal return and isolation effects. It should be noted that all vias in this application run through the first signal layer and the second signal layer of the PCB. Specifically, the two return vias are tangent to each other. The purpose of this tangent design is to save wiring space to the maximum extent while ensuring the continuity and symmetry of the GND signal. By increasing the density of the return vias, the length of the return path can be effectively reduced in high-speed signal transmission, thereby reducing signal loss and interference caused by path extension and improving the integrity of high-speed signals.

[0050] The tangent design of the first signal via 21 and the second signal via 22 is similar to the return via, and the purpose is to ensure the transmission symmetry of the differential signal. In terms of design, the differential signal line needs to maintain strict symmetry to reduce differential mode interference and common mode noise. By making the first signal via 21 tangent to the first return via 11, and the second signal via 22 tangent to the second return via 12, it is ensured that the differential signal can be tightly coupled with the corresponding return path when the vias are switched, providing a good signal return path and electromagnetic shielding effect.

[0051] The first signal via 21 and the second signal via 22 are symmetrical about the first tangent plane, which is the plane where the two return vias are tangent. The symmetry of the differential via is crucial to the transmission quality of the differential signal, because the asymmetry of the signal line may cause inconsistent signal delays, thereby introducing differential mode interference. By ensuring the symmetry of the signal vias and the return vias, the signal delay difference can be reduced during high-speed signal switching, and reflection and signal integrity issues can be reduced. In addition, it is stipulated that the center axis distance of the first signal via 21 and the second signal via 22 is not greater than the center axis distance of the two return vias to further avoid occupying the PCB board space. This design can reduce the impedance mismatch of the differential signal, thereby reducing reflections and improving signal quality.

[0052] In this embodiment, at least two milling grooves are added, the first milling groove is used to separate the two return vias and the two signal vias, and the second milling groove is used to separate the two signal vias, dividing the entire differential via structure into three parts. This segmentation design helps to further improve signal isolation, because the milling groove can effectively suppress the coupling and crosstalk between adjacent signals. The design of the milling groove can also form a clear physical boundary, constraining the electromagnetic field of each part within a specified area, thereby reducing electromagnetic interference in high-speed signal transmission. In addition, the milling groove can also optimize the current distribution, so that the transmission path of the differential signal in each part remains consistent, effectively improving the signal integrity.

[0053] Among them, as an optional embodiment, the diameter of the first return via 11 is the same as the diameter of the second return via 12, the diameter of the first signal via 21 is the same as the diameter of the second signal via 22, and the diameter of each return via is larger than the diameter of each signal via. This design is intended to ensure that the electrical properties of the two return vias are consistent, thereby providing a uniform current distribution in the signal return path. The same diameter helps to ensure the transmission stability of the return signal and avoid signal asymmetry or reflection problems caused by inconsistent sizes. The main function of the return via is to provide a channel for signal return, so its size design should give priority to meeting the needs of signal return while ensuring the electrical performance of the hole. At the same time, the diameters of the first signal via 21 and the second signal via 22 are also the same. This design principle is to ensure that the transmission characteristics of the two signal vias are consistent and reduce signal delays, distortions or mismatches that may be caused by different apertures. The size of the signal via needs to be precisely controlled to ensure the integrity and reliability of the signal, especially in the case of high-speed signal transmission, where mismatched via sizes may cause signal loss or interference. In addition, the diameter of the return via is larger than the diameter of the signal via. The core of this design idea is to ensure that the impedance and current capacity of the signal return path can carry the return current of the high-speed signal, avoiding excessive current density due to the return via being too small, which in turn causes overheating or electrical instability. A larger return via diameter helps reduce the resistance and inductance of the return path, thereby improving the flow of current and the stability of the signal. This design also helps to achieve better electromagnetic compatibility on the PCB and reduce interference during signal transmission.

[0054] Among them, as an optional embodiment, the width of each milling groove is not less than the width of the pad 3 outside the reflow via or the pad 3 outside the signal via. The design requires that the width of each milling groove is not less than the width of the pad 3 outside the reflow via or the pad 3 outside the signal via. The core of this design idea is to ensure that the size of the milling groove can effectively accommodate and support the size of the corresponding pad 3 outside the reflow via or the signal via, and avoid the milling groove from interfering with or affecting the area of ​​these pads 3 during the processing. The pad 3 is an important part connecting the signal via and the reflow via. Their width is usually determined according to the electrical connection requirements and mechanical strength requirements to ensure that the pad 3 can stably carry the welding point. The width of the milling groove is not less than the width of these pads 3, first of all to ensure the processing accuracy of the milling groove, to avoid too narrow milling grooves limiting the space between the reflow via and the signal via, thereby affecting the welding quality. Too narrow milling grooves may cause the pad 3 to be unable to form a reliable connection with the via during the welding process, affecting the stability and electrical performance of signal transmission. Secondly, milling slots of appropriate width help provide sufficient space for the transition of signal and return paths, reducing signal loss or resistance to return current.

[0055] Through the above structural design, the differential via architecture reduces the differential via spacing without increasing the production complexity, thereby saving PCB layout and wiring space, and is suitable for high-density and miniaturized design requirements. At the same time, the design can also enhance the GND signal isolation and return effect, improve the integrity of high-speed signals, and meet the strict requirements of modern high-speed circuits for signal quality and performance.

[0056] As an optional embodiment, the second tangent plane where the first signal via 21 and the first return via 11 are tangent coincides with the third tangent plane where the second signal via 22 and the second return via 12 are tangent, and the second tangent plane or the third tangent plane is perpendicular to the first tangent plane.

[0057] In this embodiment, the second tangent plane formed by the tangent point of the first signal via 21 and the first return via 11 is overlapped with the third tangent plane formed by the tangent point of the second signal via 22 and the second return via 12, thereby ensuring the symmetry of the differential signal on both sides. The overlapping tangent plane design can accurately align the positions of the two pairs of signal and return vias, so that the differential signal vias maintain strict mirror symmetry in structure, thereby reducing the offset or imbalance of the differential signal in the via area and improving the phase consistency of the signal. This symmetry can significantly reduce the common mode noise in the differential signal, reduce the crosstalk between signals, and improve the signal integrity and anti-interference ability.

[0058] In addition, the design of the second or third cutting plane being perpendicular to the first cutting plane further enhances the three-dimensional symmetry, so that the signal vias and the return vias are evenly arranged on different planes. The vertical plane layout can not only reduce the interference of differential signals when they are transmitted in the multilayer board, but also ensure the integrity and uniformity of the return path, providing a more stable return channel and better electromagnetic compatibility for high-speed signals.

[0059] For example, Figure 2 As shown, the two reflow vias are equal in size and are tangent to each other in the horizontal direction after electroplating. Their original diameter F is 12 mil, and the finished diameter E of the reflow via after electroplating is 10 mil, that is, E=F-2mil. The signal vias are equal in size, and their original diameter H is 8 mil. The finished diameter G of the signal via after electroplating is 6 mil, that is, G=H-2mil. The centers of the first reflow via 11 and the first signal via 21 are on the same center line, and are tangent to each other in the vertical direction after electroplating. The centers of the second reflow via 12 and the second signal via 22 are on the same center line, and are tangent to each other in the vertical direction after electroplating. The first signal via 21 and the second signal via 22 are on the same horizontal line.

[0060] like Figure 3 As shown, the width of pad 3 is 4 mil. The diameter P of pad 3 of two reflow vias is 18 mil, that is, P=E+8 mil. The diameter Q of pad 3 of two signal vias is 14 mil, that is, Q=G+8 mil.

[0061] As an optional embodiment, the number of milled grooves is 2;

[0062] The first milling groove 41 is arranged along the second tangent plane or the third tangent plane, passes through the two reflow vias and the two signal vias, and the length of the first milling groove 41 is ≥ 2×the diameter of the reflow via+2×the width of the pad 3 outside the reflow via. The first milling groove 41 is used to separate the two reflow vias and the two signal vias;

[0063] The second milling groove 42 is arranged along the first cutting plane, passing through two reflow vias and two signal vias, and the diameter of the signal via + the width of the pad 3 outside the signal via + the diameter of the reflow via / 2≤the length of the second milling groove 42≤the diameter of the signal via + the width of the pad 3 outside the signal via + the diameter of the reflow via, and the second milling groove 42 is located between the two signal vias.

[0064] In this optional embodiment, two milling grooves are designed to divide the differential via structure and enhance the isolation and transmission quality of the signal. The first milling groove 41 is arranged along the second tangent plane or the third tangent plane, passing through two return vias and two signal vias, and its length satisfies the condition of being at least equal to 2 times the diameter of the return via plus 2 times the width of the external pad 3 of the return via. This length design is to ensure that the milling groove can cover the area of ​​the two return vias, provide sufficient electromagnetic isolation effect, and effectively block the electromagnetic coupling between the return paths. Through such division, the two sides of the differential signal can be transmitted in independent parts, thereby reducing crosstalk between signals and improving signal integrity and stability.

[0065] The second milling groove 42 is arranged along the first tangent plane, passes through two reflow vias and two signal vias, and is located between the two signal vias. The length of the second milling groove needs to meet a range: that is, the diameter of the signal via plus the width of its outer pad 3 plus half of the length of the reflow via, as the minimum length; and the maximum length is the diameter of the signal via plus the width of the pad 3 plus the diameter of the reflow via. Such a design ensures that the second milling groove can provide appropriate isolation without excessively cutting the reflow path. The limitation of this range helps to achieve effective partitioning of the via structure, while avoiding structural instability caused by the milling groove being too long or too short. The design of the second milling groove is located between the signal vias, which can further reduce the mutual interference between the differential signal pairs and achieve more efficient signal isolation without destroying the signal integrity. This milling groove layout can provide sufficient signal isolation in miniaturized PCB design, so that the signal vias and the reflow vias maintain electrical symmetry and a good reflow path in the via structure, thereby meeting the requirements of electromagnetic compatibility and signal integrity for high-speed signal design.

[0066] like Figure 4 As shown, the length of the first milling groove 41 is L and the width is K. The first milling groove 41 is centered on the symmetric center point of the four circles. The length L needs to ensure that the two reflow vias and the two signal vias are completely disconnected, so the minimum value of L is equal to the diameter of the two reflow vias plus the width of the pad 3, that is, Lmin=E+E+8mil. The width K needs to be larger than the ring width of the pad 3, that is, Kmin=4mil. The length of the second milling groove 42 is M and the width is N. The second milling groove 42 is centered on the symmetry axis of the two reflow vias. The pads 3 of the two reflow vias are not milled off at the top, and the pads 3 of the two signal vias need to be milled off at the bottom, so Mmin=1 / 2E+G+4mil. The width N needs to be larger than the ring width of the pad 3, that is, Nmin=4mil.

[0067] Through the setting of these two milling grooves, the differential via structure is divided into three parts in space. These three parts are used to transmit DP, DN and GND signals respectively, which effectively improves the isolation between signals and ensures high signal integrity in high-frequency and high-speed applications. This design effectively suppresses various interference factors in the process of high-speed signal transmission without increasing the PCB area, and provides more reliable return path support for differential signals, which helps to improve the stability and reliability of the overall circuit performance.

[0068] like Figure 5 As shown, Figure 5 Schematic diagram of the distribution of two via units.

[0069] like Figure 6 As shown, as an optional embodiment, there are multiple via units, and in the multiple via units, the central axes of all return vias are on the first plane, and the central axes of all signal vias are on the second plane, and the first plane and the second plane are parallel;

[0070] The plurality of first milling grooves 41 are integrally formed.

[0071] In this embodiment, the via unit includes two return vias, two signal vias and two milling grooves. Through this combination, a more complete high-speed signal differential via unit is realized, which has better isolation and symmetry. The design of multiple via units ensures that the central axis of the return via and the signal via of each via unit are respectively on the first plane and the second plane. The two planes are parallel to each other, which ensures the overall symmetry of each unit when arranged longitudinally and reduces the phase difference and reflection problems during signal transmission. The parallel plane setting helps to ensure the consistency of the signal path in the multilayer board design and improve the integrity of the high-speed signal.

[0072] In multiple via units, the first milling groove 41 can be made into a through groove by an integrated molding method, thereby forming a continuous physical isolation channel in the entire row of via structures. This through groove design simplifies the processing process, reduces manufacturing complexity, and helps to arrange multiple high-speed signal differential via units in a row, such as 4, 8 or 16, to facilitate the layer change operation of a group of high-speed signals. The structure of the through groove also improves the isolation effect between signals, further exerts the shielding effect of the GND signal, reduces electromagnetic interference between signals, and ensures the quality of signal transmission. When multiple groups of layer change vias need to be distributed side by side, the through groove provides a unified isolation channel, so that multiple differential signals can be stably transmitted on the same plane, while effectively reducing noise coupling and interference across layers. This design also meets the requirements of high-density and high-speed PCB design, so that high-speed signal transmission has better electromagnetic compatibility while maintaining signal integrity.

[0073] As an optional embodiment, there are multiple via units, the first tangent planes of all via units coincide, the central axis of the return via of the i-th via unit and the central axis of the return via of the i+2-th via unit are on the same plane, the central axis of the signal via of the i-th via unit and the central axis of the signal via of the i+2-th via unit are on the same plane, i≥1, i is an integer;

[0074] The plurality of first milling grooves 41 are integrally formed.

[0075] In this embodiment, the via unit is composed of two return vias, two signal vias and two milling slots, forming a structured differential via design for improving the density and signal transmission quality of the PCB design. The design of multiple via units ensures that the same first tangent plane coincides, that is, the tangent planes of all these structures are on the same horizontal plane, thereby providing higher symmetry and consistency, ensuring that the layout of the signal vias and the return vias is uniform on different parts of the PCB.

[0076] Specifically, the central axis of the return vias of the i-th via unit and the i+2-th via unit in the design are located on the same plane. This design ensures the consistency and stability of the return path between multiple structures and reduces signal reflection or return path interference caused by misaligned vias. Similarly, the central axis of the signal vias of the i-th and i+2-th via units are also on the same plane, ensuring good symmetry of the signal path, thereby enhancing the transmission stability of the differential signal and reducing the risk of crosstalk.

[0077] The implementation of this design simplifies the manufacturing and layout process by keeping multiple via units on a common cutting plane. Multiple via units further optimize production efficiency through a unified milling groove design (i.e., multiple first milling grooves 41 are integrally formed). By integrally forming the milling groove, the precise position of each via unit can be ensured, and the electrical signals between the vias can be effectively isolated, reducing cross-interference, while reducing the difficulty and time cost in the manufacturing process. This design not only improves electromagnetic compatibility, but also enables a higher-density wiring design on the PCB to meet the transmission requirements of high-performance and high-speed signals.

[0078] like Figure 7 As shown, as an optional embodiment, there are multiple via units, and the first milling grooves 41 in each two adjacent via units are staggered so that the distance between the second milling grooves 42 in the two adjacent via units is less than the width of the via unit;

[0079] The width of the via unit=2×the diameter of the reflow via+2×the width of the pad 3 outside the reflow via.

[0080] In this embodiment, the via unit includes two reflow vias, two signal vias and two milling slots, the purpose of which is to optimize the space utilization and design density of the PCB board while ensuring the quality of signal transmission. The first milling slots 41 in the plurality of via units are arranged by staggering, the purpose of which is to reduce the close arrangement between the via units, thereby maintaining a small spacing (less than the overall width of the via unit) between two adjacent milling slots. Through the staggered arrangement, the distance between the second milling slots 42 in the via unit is optimized, avoiding excessive crowding between the via units, providing more isolation space for signal transmission, and also helping to reduce interference and reflection between signals.

[0081] The width of the via unit is defined as twice the diameter of the reflow via plus twice the width of the reflow via outer pad 3, in order to ensure sufficient layout space and avoid the situation where the space is too tight when densely wiring signals. This design allows the via unit to have a wider spacing during wiring, while improving the manufacturing accuracy and processability of the PCB.

[0082] For the side-by-side design of multiple via units, the design is not limited to arranging them on the same horizontal line. In order to further optimize the integrity of the signal, a staggered placement can be adopted, such as a high and low arrangement or staggered with equal spacing in sequence. Such a design helps to reduce unnecessary crosstalk and electromagnetic interference at the electrical level, especially in differential signal transmission, the side-by-side arrangement of DP (positive differential signal) and DN (negative differential signal) signal holes may cause greater crosstalk.

[0083] In order to further reduce crosstalk and improve signal integrity, the design also proposes a rotational layout method: the direction of the DP and DN signal holes is rotated 180 degrees for every other via unit. This layout ensures that the distance between two adjacent pairs of differential signals is increased, and at the same time, the signals are effectively isolated through the spaced GND signal holes. Since the adjacent differential signal pairs are shielded by the GND signal, the mutual interference (crosstalk) between the signals is significantly reduced, thereby improving the integrity and stability of high-speed signals. This optimized design ensures that the differential signal pairs can effectively reduce unnecessary interference and loss during high-frequency signal transmission, and improves the signal transmission performance of the overall PCB design.

[0084] In a third aspect, the present application provides a printed circuit board, comprising the differential via structure as described above.

[0085] Thirdly, Figure 8 As shown, the present application provides a design method for a differential via structure, including:

[0086] S11: Determine a target size of the differential via according to target requirements and board space of the printed circuit board;

[0087] In this step, the size of the differential vias is determined based on the functional requirements and available space of the board before the design begins. Designers need to consider multiple factors, including the frequency of the signal, the space limitations of the board, the electrical performance requirements, and the manufacturing process. The determination of the target size ensures that the differential signal can be effectively transmitted within the specified space without compromising the integrity of the signal and the overall performance of the board. At this stage, designers need to conduct a comprehensive analysis of the length of the signal line, the transmission speed, the signal strength, and the number of layers of the PCB to determine the size of the via to meet the design requirements.

[0088] S12: Drilling a first return via hole and a second return via hole using a first drill needle;

[0089] The first return via is tangent to the second return via;

[0090] In this step, the processing of the return vias is completed by drilling with the first drill needle. These return vias are used to provide a signal return path to ensure the integrity of the differential signal between the two layers. The two return vias pass through the two layers of the printed circuit board (the first signal layer and the second signal layer), and the two are tangent. The tangent design of the return vias helps to improve the stability of the signal return path, reduce electrical noise, and avoid signal interference. This design can ensure that the signal return path is closely matched with the signal transmission path, further improving the electrical performance of the PCB.

[0091] S13: Drilling a first signal via hole and a second signal via hole using a second drill needle;

[0092] The first signal via is tangent to the first return via, and the second signal via is tangent to the second return via; the first signal via and the second signal via are symmetrical about a first tangent plane, the first tangent plane is a plane where the two return vias are tangent, and a first distance between a central axis of the first signal via and a central axis of the second signal via is not greater than a second distance between a central axis of the first return via and a central axis of the second return via;

[0093] In this step, the second drill is used to drill the signal vias and ensure that the signal vias are tangent to the return vias to ensure that the signal transmission path and the return path are coordinated. The design of the signal vias is the key to changing the layers of the differential signal lines, and the symmetric design is achieved by the layout of the signal vias to reduce signal crosstalk and optimize signal integrity. The key design idea here is to ensure that the distance difference between the signal vias and the return vias is within an acceptable range (i.e. not greater than the preset value) by precisely controlling the relative position between them. By precisely controlling these dimensions, the design can ensure that signal loss and interference are minimized during high-speed signal transmission.

[0094] S14: performing electroplating processing on the two reflow vias and the two signal vias respectively;

[0095] In this step, electroplating is performed to enhance the conductivity of the vias. During the electroplating process, metal materials (such as copper) are deposited on the inner wall of the via to form a conductive layer to ensure reliable signal transmission and electrical connection. Both reflow vias and signal vias require electroplating because these vias need to connect different layers of the printed circuit board and maintain signal integrity and transmission stability. The thickness and uniformity of the electroplating layer directly affect the quality of signal transmission, so this step is crucial to ensure the stability and reliability of the signal transmission path.

[0096] S15: Drilling at least two milling grooves using a third drill bit;

[0097] The first milling groove is used to separate the two return vias and the two signal vias, and the second milling groove is used to separate the two signal vias; wherein the first signal via is connected to the first signal line of the differential line, the second signal via is connected to the second signal line of the differential line, and the two return vias serve as signal return holes;

[0098] In this step, the PCB board is divided into three main parts by milling grooves using the third drill bit, ensuring that each part is connected to different signal channels and return paths. The design of the milling grooves ensures that the return vias and signal vias are located in different parts, ensuring effective isolation of the signal and return paths and improving signal integrity. By reasonably dividing the structure of the PCB, the milling groove design can effectively optimize the layout of the signal transmission path and the return path, thereby improving the overall performance.

[0099] S16: Fill milling slots, reflow vias, and signal vias with resin.

[0100] In this step, after the milling and via processing is completed, the filling resin is used to fix and seal the via area, enhance the structural stability, and prevent the signal path from being disturbed. Resin filling can also provide additional mechanical support to ensure that the milling and via areas will not be damaged by vibration or external force during use. In addition, the use of resin can also reduce signal crosstalk and effectively isolate different signal channels to ensure that the electrical performance of the PCB is effectively guaranteed. This step is necessary to ensure the long-term stability and high reliability of the entire differential via structure.

[0101] In this embodiment, four vias are short-circuited and connected together by electroplating copper on the inner wall of the via. Then, through the process of milling grooves, the high-speed signal layer-changing via unit is separated into three parts, which transmit DP, DN and GND signals respectively. Finally, the drilled holes and milled grooves are filled completely with resin to reduce the loss and crosstalk of high-speed signals at the vias, optimize the electrical performance of the PCB, and improve the signal transmission quality. In summary, the differential via structure obtained by the design method of the differential via structure provided by the present application effectively saves the wiring space on the printed circuit board, and can make the differential signal obtain good isolation and reflux channels between different parts, which not only enhances the isolation and reflux effects of the GND signal, improves the integrity of the high-speed signal, but also can reduce the signal crosstalk in high-density design, thereby supporting high-density and miniaturization design without increasing the difficulty of production, and improving the flexibility and reproducibility of the design.

[0102] As an optional embodiment, the method further includes: testing the differential via structure to determine whether the differential via structure meets a preset test result;

[0103] If the preset test result is met, the differential via structure is determined to be the final differential via structure. Specifically, the differential via structure is tested to determine whether the differential via structure meets the preset test result, including: determining whether the electroplated copper of the first signal via used to transmit the first signal line and the second signal via used to transmit the second signal line is damaged; performing an open circuit test on the first signal line of the first signal layer and the first signal line of the second signal layer, and performing an open circuit test on the second signal line of the first signal layer and the second signal line of the second signal layer, respectively, to determine whether there is an electrical connection between the signal line of the first signal layer and the corresponding signal line of the second signal layer; performing a short circuit test on the first signal line and the second signal line of the first signal layer and the first signal line and the second signal line of the second signal layer, respectively, to determine whether there is an electrical connection between the two signal lines of the first signal layer and the two signal lines of the second signal layer; if the electroplated copper of the first signal via used to transmit the first signal line and the second signal via used to transmit the second signal line is not damaged, there is an electrical connection between the signal line of the first signal layer and the corresponding signal line of the second signal layer, and there is no electrical connection between the two signal lines of the first signal layer and the two signal lines of the second signal layer, then it is determined that the differential via structure meets the preset test result.

[0104] Check for electroplated copper damage: The purpose is to ensure that the copper layer of the electroplated through-hole is not mechanically or chemically damaged during the production process and maintains its good conductive properties. If the electroplated copper layer is damaged, it may cause unstable signal transmission or poor electrical connection.

[0105] Perform open circuit test on signal lines: test the first signal line of the first signal layer and the first signal line of the second signal layer, and the second signal line of the first signal layer and the second signal line of the second signal layer respectively. The purpose of these tests is to verify whether there is a correct electrical connection between the signal lines between the vias, that is, to ensure that the signal between the first signal layer and the second signal layer can be transmitted normally through the first signal via without being cut off. In other words, the open circuit test is to confirm whether the signal line is connected normally. If there is an electrical connection between the signal lines, it means that the first via has correctly completed the signal transmission path.

[0106] Perform a short circuit test on the signal lines: Test the first signal line and the second signal line of the first signal layer, and the first signal line and the second signal line of the second signal layer respectively. The purpose of this step is to ensure that there is no unnecessary electrical short circuit in the first via design, that is, to confirm that there is no unexpected electrical connection between the signal lines. In other words, the short circuit test is used to verify whether there is an unexpected electrical connection between the signal lines. If the test results show that there is a short circuit connection between the signal lines, it may mean that the design is defective and needs to be adjusted.

[0107] By checking whether the electroplated copper is damaged and performing an open circuit test, it can be ensured that the electroplated through-hole will not have signal transmission problems in actual use; the short circuit test can confirm whether the design of the two signal vias effectively avoids unwanted signal interference, thereby ensuring the purity and electrical performance of the signal; the design conditions that meet all preset test results indicate that the design architecture of the differential via can operate stably in actual applications, thereby meeting the design requirements and ensuring the performance and reliability of the circuit board.

[0108] Overall, this design method not only ensures signal integrity and electrical performance through fine control of each step, but also effectively improves the space utilization efficiency of PCB design, reduces production complexity and cost, and provides a solid foundation for the realization of high-density, high-performance electronic devices. For other introductions to the design method of the differential via structure, please refer to the above embodiment, and this application will not repeat them here.

[0109] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0110] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A differential via structure, characterized in that: The method comprises at least one via unit, wherein the via unit comprises: a first return via and a second return via, wherein the first return via and the second return via are tangent to each other; A first signal via and a second signal via, the first signal via and the first return via being tangent to each other, and the second signal via and the second return via being tangent to each other; The first signal via and the second signal via are symmetrical about a first tangent plane, the first tangent plane is a plane where the two return vias are tangent, and a first distance between a central axis of the first signal via and a central axis of the second signal via is not greater than a second distance between a central axis of the first return via and a central axis of the second return via; at least two milling grooves, the first milling groove is used to separate the two return vias and the two signal vias, and the second milling groove is used to separate the two signal vias; The first signal via is connected to the first signal line of the differential line, the second signal via is connected to the second signal line of the differential line, and the two return vias serve as signal return holes.

2. The differential via structure according to claim 1, characterized in that: A second tangent plane where the first signal via and the first return via are tangent coincides with a third tangent plane where the second signal via and the second return via are tangent, and the second tangent plane or the third tangent plane is perpendicular to the first tangent plane.

3. The differential via structure according to claim 2, characterized in that: The number of the milling grooves is 2; The first milling groove is arranged along the second tangent plane or the third tangent plane, passes through the two reflow vias and the two signal vias, and the length of the first milling groove is ≥ 2×the diameter of the reflow via+2×the width of the pad outside the reflow via, and the first milling groove is used to separate the two reflow vias and the two signal vias; The second milling groove is arranged along the first cutting plane, passing through the two return vias and the two signal vias, and the diameter of the signal via + the width of the pad outside the signal via + the diameter of the return via / 2≤the length of the second milling groove≤the diameter of the signal via + the width of the pad outside the signal via + the diameter of the return via, and the second milling groove is located between the two signal vias.

4. The differential via structure according to claim 3, characterized in that: There are a plurality of via units, and in the plurality of via units, the central axes of all the return vias are on a first plane, and the central axes of all the signal vias are on a second plane, and the first plane is parallel to the second plane; The plurality of first milling grooves are integrally formed.

5. The differential via structure according to claim 3, characterized in that: There are multiple via units, the first tangent planes of all the via units coincide, the central axis of the return via of the ith via unit and the central axis of the return via of the i+2th via unit are on the same plane, the central axis of the signal via of the ith via unit and the central axis of the signal via of the i+2th via unit are on the same plane, i≥1, i is an integer; The plurality of first milling grooves are integrally formed.

6. The differential via structure according to claim 3, characterized in that: There are a plurality of via units, and the first milling grooves in each two adjacent via units are staggered so that the distance between the second milling grooves in the two adjacent via units is less than the width of the via unit; The width of the via unit=2×the diameter of the reflow via+2×the width of the pad outside the reflow via.

7. The differential via structure according to any one of claims 1 to 6, characterized in that: The diameter of the first return via is the same as the diameter of the second return via, the diameter of the first signal via is the same as the diameter of the second signal via, and the diameter of each return via is larger than the diameter of each signal via.

8. The differential via structure according to any one of claims 1 to 6, characterized in that: The width of each of the milling grooves is not less than the width of the pad outside the reflow via or the pad outside the signal via.

9. A printed circuit board, characterized in that: It comprises the differential via structure as described in any one of claims 1 to 8.

10. A method for designing a differential via structure, characterized in that: The differential via structure as claimed in any one of claims 1 to 8 comprises: Determine the target size of the differential vias based on target requirements and printed circuit board space; Drilling a first return via hole and a second return via hole using a first drill needle, wherein the first return via hole and the second return via hole are tangent to each other; A first signal via and a second signal via are drilled using a second drill, wherein the first signal via is tangent to the first return via, and the second signal via is tangent to the second return via; the first signal via and the second signal via are symmetrical about a first tangent plane, the first tangent plane is a plane where the two return vias are tangent, and a first distance between a central axis of the first signal via and a central axis of the second signal via is not greater than a second distance between a central axis of the first return via and a central axis of the second return via; Performing electroplating treatment on the two reflow vias and the two signal vias respectively; Drilling at least two milling grooves using a third drill, wherein the first milling groove is used to separate the two return vias and the two signal vias, and the second milling groove is used to separate the two signal vias; wherein the first signal via is connected to the first signal line of the differential line, the second signal via is connected to the second signal line of the differential line, and the two return vias serve as signal return holes; The milling groove, the reflow via and the signal via are filled with resin.

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