CN113747656B - PCB and differential wiring structure thereof - Google Patents

Abstract

The invention discloses a differential wiring structure, which includes a first via hole group and a second via hole group provided on the surface of a substrate, a first differential line group passing through the first via hole group, and a first differential line group passing through the second via hole group. a via group and a second differential line group parallel to the first differential line group, a first return hole provided outside the first differential line group, and a second return hole provided outside the second differential line group. Return hole, a common return hole provided between the first differential line group and the second differential line group, the common return hole includes mutually isolated channels for returning signals of the first differential line group The first half hole and the second half hole are used for signal return of the second differential line group. The differential wiring structure disclosed in the present invention can realize signal recirculation of differential signal lines under limited space, while avoiding crosstalk effects on the differential signal lines. The invention also discloses a PCB, the beneficial effects of which are as mentioned above.

Description

A kind of PCB and its differential wiring structure

Technical field

The present invention relates to the field of PCB technology, and in particular to a differential wiring structure. The invention also relates to a differential wiring structure.

Background technique

As the signal rate accelerates, the requirements for high-speed signals are getting higher and higher, and PCBs are also developing towards high-speed and high-density. When the single board space is limited, the problem of insufficient signal line routing space is usually made up by increasing the number of PCB layers. At the same time, it is also necessary to use vias to complete the layer change of signals. In this way, the signal at the vias is complete Sexual issues require special attention.

In order to optimize the signal problem at the layer-changing via hole, a reflow hole is generally added within a certain distance of the high-speed signal layer-changing via hole. The properties of the reflow hole are the same as those of the high-speed line reference plane. For differential signal wiring, a return hole is generally provided outside both sides of a group of differential signal lines to connect to two paired signal lines in the group of differential signal lines. When the PCB surface space is limited, the arrangement positions of each group of differential signal lines become very close, and the distance between two adjacent groups of differential signal lines is very small. At this time, it is easy for the two groups of differential signal lines to share the same return hole. Condition.

At present, as the signal rate becomes higher and higher, the situation of sharing return holes will introduce a certain amount of crosstalk between the two sets of differential signal lines, resulting in a reduction in the quality of differential signal transmission. Therefore, some PCBs are required to avoid sharing return holes during design. situation, but when space is limited, it is difficult to achieve a structure in which two return holes are drilled between two adjacent groups of differential signal lines at the same time.

In the existing technology, some PCBs try to reduce crosstalk by adding a return hole at both ends of the common return hole along the extension direction of the differential signal line. Although this can have a certain optimization effect, it does not It occupies the horizontal space between two adjacent vias, but still needs to occupy the vertical space between two adjacent sets of differential signal lines. In the case of dense wiring and extremely high space utilization, even two adjacent sets of differential signal lines The vertical space between the signal lines may not leave enough space to add two additional return holes, which makes the crosstalk problem difficult to solve.

Therefore, how to realize signal recirculation of differential signal lines under limited space while avoiding crosstalk effects on the differential signal lines is a technical problem faced by those skilled in the art.

Contents of the invention

The purpose of the present invention is to provide a differential wiring structure that can realize signal reflow of differential signal lines under limited space while avoiding crosstalk effects on the differential signal lines. Another object of the present invention is to provide a PCB.

In order to solve the above technical problems, the present invention provides a differential wiring structure, including a first via group and a second via group provided on the surface of a substrate, a first differential line group passing through the first via group, A second differential line group that passes through the second via group and is parallel to the first differential line group, a first return hole provided outside the first differential line group, and a first return hole provided outside the first differential line group, A second return hole on the outside of the line group and a common return hole provided between the first differential line group and the second differential line group. The common return hole includes mutually isolated channels for supplying the first differential line group. A first half hole for the differential line group signal to return and a second half hole for the second differential line group signal to return.

Preferably, the common return hole further includes a partition hole opened between the opposite end surfaces of the first half hole and the second half hole.

Preferably, the partition hole is a rectangular hole.

Preferably, the first half hole and the second half hole are symmetrically distributed on both sides of the partition hole.

Preferably, both the first half hole and the second half hole are arcuate.

Preferably, the cross-sectional areas of the first half hole and the second half hole are equal.

Preferably, the cross-sectional area of the first half hole and the second half hole is 30% to 70% of the cross-sectional area of the first return hole or the second return hole respectively.

The present invention also provides a PCB, including a substrate and a differential wiring structure provided on the substrate, wherein the differential wiring structure is specifically the differential wiring structure described in any one of the above.

The differential wiring structure provided by the present invention mainly includes a first via group, a second via group, a first differential line group, a second differential line group, a first return hole, a second return hole and a common return hole. Wherein, the first via hole group and the second via hole group are both opened on the surface of the substrate, and are respectively used to realize layer switching wiring of the first differential line group and the second differential line group. The first differential line group is distributed on the surface of the substrate and passes through the first via group for layer switching wiring. The second differential line group is distributed on the surface of the substrate and passes through the second via group for layer change wiring. The first differential line group and the second differential line group are parallel and adjacent to each other. The first return hole is provided outside the first differential line group and is mainly used for signal return of the first differential line group. The second return hole is provided outside the second differential line group and is mainly used for signal return of the second differential line group. The common return hole is provided between the first differential line group and the second differential line group, and is mainly used to provide signal return for both at the same time. The common return hole has a split structure and includes a first half hole and a second half hole. The first half hole and the second half hole are isolated from each other, and the interfaces are kept insulated. The first half hole is close to the first differential line group and is used for signal return flow by the first differential line group, while the second half hole is close to the second differential line group and is used for signal return flow by the second differential line group. In this way, the first return hole and the first half hole jointly realize the signal return of the first differential line group, and at the same time, the second return hole and the second half hole jointly realize the signal return of the second differential line group. Since the first The half hole and the second half hole are isolated from each other and are equivalent to two independent signal flows, so crosstalk can be avoided, and the area occupied by both is smaller than the conventional return holes in the prior art, so they can be used in space-limited spaces. In this case, the signal reflow of the differential signal line is realized.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only These are embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the provided drawings without exerting creative efforts.

Figure 1 is a schematic diagram of the overall structure of a specific embodiment provided by the present invention.

Figure 2 is a cross-sectional view of Figure 1.

Figure 3 is a schematic diagram of the overall structure of another specific embodiment provided by the present invention.

Figure 4 is a cross-sectional view of Figure 3.

Figure 5 is a comparison of differential signal insertion loss parameters between the present invention and the prior art.

Figure 6 is a comparison of differential signal return loss parameters between the present invention and the prior art.

Figure 7 is a comparison of far-end crosstalk parameters of differential signals of the present invention and the prior art.

Figure 8 is a comparison of near-end crosstalk parameters of differential signals of the present invention and the prior art.

Among them, in Figures 1 to 4:

Substrate - 1, first via group - 2, second via group - 3, first differential line group - 4, second differential line group - 5, first return hole - 6, second return hole - 7, Common return hole—8;

The first half hole - 81, the second half hole - 82, the partition hole - 83.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Please refer to Figures 1 and 2. Figure 1 is a schematic diagram of the overall structure of a specific embodiment provided by the present invention, and Figure 2 is a cross-sectional view of Figure 1.

In a specific implementation provided by the present invention, the differential wiring structure mainly includes a first via group 2, a second via group 3, a first differential line group 4, a second differential line group 5, a first reflow Hole 6, second return hole 7 and common return hole 8.

Among them, the first via hole group 2 and the second via hole group 3 are both opened on the surface of the substrate 1, and are respectively used to realize the layer switching wiring of the first differential line group 4 and the second differential line group 5. Of course, due to differential signal characteristics, the first via group 2 and the second via group 3 each include two paired vias, and the first differential line group 4 and the second differential line group 5 each include two paired vias. signal line.

The first differential line group 4 is distributed on the surface of the substrate 1 and passes through the first via hole group 2 for layer switching wiring. The second group of 5 differential lines is distributed on the surface of the substrate 1 and passes through the second group of via holes 3 for layer change wiring. The first differential line group 4 and the second differential line group 5 are parallel to and adjacent to each other. Of course, the first differential line group 4 and the second differential line group 5 can not only be distributed on the surface of the substrate 1, but can also be routed inside the substrate 1. For example, when the substrate 1 includes a six-layer board, the first differential line group 4 and the second differential line group 5 can be routed from the first layer to the sixth layer of the substrate 1, or from the first layer to the third layer, etc., or can be multi-layer routed.

The first return hole 6 is provided outside the first differential line group 4 and is mainly used for the first differential line group 4 to carry out signal return. The second return hole 7 is provided outside the second differential line group 5 and is mainly used for the second differential line group 5 to carry out signal return. Generally, the areas of the first return hole 6 and the second return hole 7 are comparable to conventional return holes.

The common return hole 8 is provided between the first differential line group 4 and the second differential line group 5, both are located inside the two groups, and is mainly used to provide signal return for both groups at the same time. The common return hole 8 has a split structure and specifically includes a first half hole 81 and a second half hole 82. The first half hole 81 and the second half hole 82 are isolated from each other, and the interfaces are kept insulated. The first half hole 81 is close to the first differential line group 4 and is used for the first differential line group 4 to carry out signal return, while the second half hole 82 is close to the second differential line group 5 and is used for the second differential line group 5 Perform signal reflow.

In this way, the first return hole 6 and the first half hole 81 jointly realize the signal return of the first differential line group 4, and at the same time, the second return hole 7 and the second half hole 82 jointly realize the signal return of the second differential line group 5. For signal return, since the first half hole 81 and the second half hole 82 are isolated from each other and are equivalent to two independent signal flows, crosstalk can be avoided, and the area occupied by both is smaller than conventional return holes in the prior art. , so the signal reflow of differential signal lines can be realized under limited space.

As shown in Figures 5 to 8, Figure 5 is a comparison of differential signal insertion loss parameters between the present invention and the prior art. Figure 6 is a comparison of differential signal return loss parameters between the present invention and the prior art. Figure 7 is a comparison between the present invention and the prior art. Comparison of far-end crosstalk parameters of differential signals in the prior art. Figure 8 shows a comparison of near-end crosstalk parameters of differential signals between the present invention and the prior art (the solid line in the figure represents the present invention, and the dotted line in the figure represents the prior art).

The simulation experiment results illustrate that: Compared with the differential wiring structure in the prior art, the differential wiring structure provided by this embodiment has better performance in various parameters of differential signal integrity, such as insertion loss, return loss, far-end crosstalk, near-end Crosstalk, etc., have been improved and optimized to a certain extent.

In a preferred embodiment of the common return hole 8 , in order to facilitate keeping the first half hole 81 and the second half hole 82 isolated and insulated from each other, a partition hole 83 is added to the common return hole 8 in this embodiment. Specifically, the partition hole 83 is opened between the opposite end surfaces of the first half hole 81 and the second half hole 82, so that the hole walls of the first half hole 81 and the hole walls of the second half hole 82 that are opposite to each other are connected to each other. spaced, and insulated by air or inert gas filled in the partition holes 83 . Of course, the hole walls of the first half hole 81 and the second half hole 82 will be subjected to conductive plating treatment in the later manufacturing stage.

Generally, the partition hole 83 is a rectangular hole and is located in the middle of the common return hole 8 . With this arrangement, the common return hole 8 can be divided into two parts by using the partition holes 83. Preferably, the partition holes 83 are distributed along the extension direction of the first differential line 4 or the second differential line 5, thereby dividing the first half hole. 81 and the second half hole 82 are arranged on both sides in the lateral direction, so that the first half hole 81 is close to the first differential line 4, and the second half hole 82 is close to the second differential line 5, which facilitates connection and wiring.

Furthermore, in order to facilitate processing planning, in this embodiment, the first half hole 81 and the second half hole 82 are axially symmetrically distributed in the entire common return hole 8, and the partition hole 83 serves as the axis of symmetry.

In addition, in order to minimize the occupation of lateral space between the first differential line group 4 and the second differential line group 5, the area occupied by the entire common return hole 8 can be equivalent to the area of a conventional return hole, that is, in the shape of a round hole , and the partition hole 83 occupies a small area of the middle part, and the first half hole 81 and the second half hole 82 are both arcuate, the corresponding chord lengths of both are smaller than the diameter of the conventional return hole, and the areas of both are smaller than Half the size of a regular return hole.

Generally, the cross-sectional areas of the first half hole 81 and the second half hole 82 are equal, for example, they are both arcuate shapes smaller than half of the area of the conventional return holes. In this case, the first half hole 81 , the second half hole 82 and the partition hole 83 The sum of the areas is exactly equal to the area of the conventional return hole.

As shown in Figures 3 and 4, Figure 3 is a schematic diagram of the overall structure of another specific embodiment provided by the present invention, and Figure 4 is a cross-sectional view of Figure 3.

However, if the lateral space between the first differential line group 4 and the second differential line group 5 allows, the cross-sectional area of the first half hole 81 and the second half hole 82 can also be appropriately increased, such as the first half hole 81 and the second half hole 82 . The cross-sectional area of the hole 81 and the second half hole 82 can both be 60% of the area of the conventional return hole. In this case, the sum of the areas of the first half hole 81, the second half hole 82 and the partition hole 83 is equal to the conventional return hole. 1.5 times the area, which is equivalent to fusing two complete conventional return holes. Generally, the cross-sectional area of the first half hole 81 and the second half hole 82 is 30% to 70% of the cross-sectional area of a conventional return hole.

In addition, if necessary, the cross-sectional area of the first half hole 81 and the second half hole 82 may not be equal. For example, the cross-sectional area of the first half hole 81 is 60% of the cross-sectional area of the conventional return hole, while the cross-sectional area of the first half hole 81 is 60% of the cross-sectional area of the conventional return hole. It is also feasible that the cross-sectional area of the two half holes 82 is 40% of the cross-sectional area of the conventional return hole.

This embodiment also provides a PCB, which mainly includes a substrate 1 and a differential wiring structure provided on the substrate 1. The specific content of the differential wiring structure is the same as the above-mentioned relevant content and will not be described again here.

The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be practiced in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (8)

1. The utility model provides a differential wiring structure, its characterized in that, including set up in first via group (2) and second via group (3) on base plate (1) surface, pass first via group (2) first differential line group (4), pass second via group (3) and with first differential line group (4) parallel second differential line group (5), and set up in first return current hole (6) in first differential line group (4) outside, set up in second return current hole (7) in second differential line group (5) outside, set up in public return current hole (8) between first differential line group (4) and second differential line group (5), public return current hole (8) are including the first half hole (81) that separate each other, be used for supplying first differential line group (4) signal back flow and be used for supplying second differential line group (5) signal back flow, first half hole (81) and second half hole (82) keep each other insulating interface.

2. The differential routing structure according to claim 1, wherein the common return hole (8) further comprises a partition hole (83) open between the opposite end faces of the first half hole (81) and the second half hole (82).

3. The differential routing structure according to claim 2, wherein the partition holes (83) are rectangular holes.

4. The differential routing structure according to claim 2, wherein the first half hole (81) and the second half hole (82) are symmetrically distributed on both sides of the partition hole (83).

5. The differential routing structure of claim 1, wherein the first half-hole (81) and the second half-hole (82) are each arcuate.

6. The differential routing structure of claim 5, wherein the first half-hole (81) and the second half-hole (82) have an equal cross-sectional area.

7. The differential routing structure according to claim 5, wherein the cross-sectional areas of the first half-hole (81) and the second half-hole (82) are 30% -70% of the cross-sectional area of the first reflow hole (6) or the second reflow hole (7), respectively.

8. A PCB comprising a substrate (1) and a differential routing structure arranged on the substrate (1), characterized in that the differential routing structure is in particular a differential routing structure according to any of claims 1-7.