CN113709962B - Differential signal transmission multilayer PCB structure - Google Patents
Differential signal transmission multilayer PCB structure Download PDFInfo
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- CN113709962B CN113709962B CN202110794284.6A CN202110794284A CN113709962B CN 113709962 B CN113709962 B CN 113709962B CN 202110794284 A CN202110794284 A CN 202110794284A CN 113709962 B CN113709962 B CN 113709962B
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- differential
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- differential via
- via hole
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- 230000008054 signal transmission Effects 0.000 title claims abstract description 16
- 230000005540 biological transmission Effects 0.000 claims abstract description 24
- 239000004020 conductor Substances 0.000 claims abstract description 16
- 230000011664 signaling Effects 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 3
- 229910052751 metal Inorganic materials 0.000 claims description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000005553 drilling Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- LAXBNTIAOJWAOP-UHFFFAOYSA-N 2-chlorobiphenyl Chemical compound ClC1=CC=CC=C1C1=CC=CC=C1 LAXBNTIAOJWAOP-UHFFFAOYSA-N 0.000 description 1
- 101710149812 Pyruvate carboxylase 1 Proteins 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/0296—Conductive pattern lay-out details not covered by sub groups H05K1/02 - H05K1/0295
- H05K1/0298—Multilayer circuits
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/11—Printed elements for providing electric connections to or between printed circuits
- H05K1/111—Pads for surface mounting, e.g. lay-out
- H05K1/112—Pads for surface mounting, e.g. lay-out directly combined with via connections
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/11—Printed elements for providing electric connections to or between printed circuits
- H05K1/115—Via connections; Lands around holes or via connections
- H05K1/116—Lands, clearance holes or other lay-out details concerning the surrounding of a via
Abstract
The invention discloses a differential signal transmission multi-layer PCB structure, which comprises a plurality of layers of PCB boards which are arranged in a laminated way, wherein each layer of PCB board is relatively attached and fixed, anti-bonding pads with the same size are arranged at the corresponding positions of each layer of PCB board, the anti-bonding pads are circular areas, and wiring is forbidden in the anti-bonding pad areas; a pair of differential via holes are formed in the anti-bonding pad area, the differential via holes of each layer of PCB board are aligned with each other, signal conductors for transmitting signals are uniformly arranged on the inner walls of the differential via holes along the circumferential direction, the signal conductors are led out from signal layers for inputting and outputting signals through differential transmission lines, signals output from one signal layer are transmitted to the other signal layer through the differential transmission lines and the signal conductors, and conductive structures on the PCB board are insulated and isolated from the differential via holes through the arrangement of the anti-bonding pads; the invention adopts the round anti-bonding pad to prevent the differential via hole from being short-circuited with the reference plane, avoids the phenomenon of discontinuous impedance at the differential via hole, and effectively improves the signal integrity of the differential via hole.
Description
Technical Field
The invention relates to the technical field of integrated circuits, in particular to a differential signal transmission multi-layer PCB structure.
Background
The development of printed circuit boards, PCB (Printed Circuit Board), electronic technology and integrated circuit technology has led to an increasing trend in higher speed, integration and refinement of circuitry, which is also increasingly demanding in terms of signal integrity.
Compared with single-ended signals, differential signals have the advantages of being strong in anti-interference capability, capable of effectively inhibiting electromagnetic interference, accurate in time sequence positioning and the like in signal integrity, and the differential signals are increasingly applied to current circuit system designs.
Along with the great improvement of signal rate and circuit system density, the routing density of the PCB board level design is also improved, and meanwhile, the routing inevitably has the phenomenon of layer replacement, so that the signal integrity problem of the via hole for layer replacement by routing is not ignored, and especially the signal integrity problem of the differential via hole with more complex structure and higher rate is more prominent.
Anti-pad refers to the distance between the copper deposit in the negative and the pad, preventing the negative layer copper deposit from shorting to the hole. At present, in practical engineering design, the anti-pad shape design of the differential via hole mostly adopts an elliptic or rectangular design, namely, two circular anti-pads of the via holes are connected together to form an elliptic or rectangular anti-pad, and fig. 1A and fig. 1B are schematic structural diagrams of the elliptic anti-pad and the rectangular anti-pad adopted in the prior art respectively; the oval or rectangular anti-pad design can meet the design requirements of most practical design projects, but with the great improvement of signal rate, the engineering design has higher and higher requirements on the signal integrity characteristics of the differential via hole, and the traditional differential via hole anti-pad structure cannot meet the requirements.
It is a technical problem that needs to be solved at present for those skilled in the art how to ensure the signal integrity characteristics of differential vias during high-speed signal transmission.
Disclosure of Invention
The invention provides a differential signal transmission multi-layer PCB structure, which adopts a round anti-bonding pad to prevent a differential via hole from being short-circuited with a reference plane, avoids the phenomenon of discontinuous impedance at the differential via hole, and effectively improves the signal integrity of the differential via hole, and has the following specific scheme:
the differential signal transmission multi-layer PCB structure comprises a plurality of layers of PCB boards which are arranged in a stacked manner, wherein anti-bonding pads with the same size are arranged at the corresponding positions of each layer of the PCB boards, and the anti-bonding pads are circular areas for prohibiting wiring;
a pair of differential via holes are formed in the anti-pad area, signal conductors for transmitting signals are uniformly arranged on the inner walls of the differential via holes along the circumferential direction, and the signal conductors are led out from the signal layers of input and output signals through differential transmission lines.
Optionally, at least two layers of the PCB board are disposed between the two signal layers, and at least one reference plane layer is disposed between the two signal layers.
Optionally, the upper surface of the reference plane layer is provided with a metal layer without gaps, cracks and clearances.
Optionally, the differential via is an equal diameter hole, the distance between the edge of the anti-bonding pad and the center of the differential via is greater than or equal to R+9mil, and R is the outer diameter of the differential via.
Optionally, the differential via is a back drilled hole, the distance between the edge of the anti-bonding pad and the center of the differential via is greater than or equal to R+12mil, and R is the outer diameter of the largest part of the differential via.
Optionally, the two differential vias and the two differential transmission lines are respectively symmetrical about the same diameter of the anti-pad;
each of the differential vias is itself symmetrical about the same diameter of the anti-pad.
Optionally, the corner angle of the differential transmission line is equal to or greater than 135 °.
The invention provides a differential signal transmission multi-layer PCB structure, which comprises a plurality of layers of PCB boards which are arranged in a laminated way, wherein each layer of PCB board is relatively attached and fixed, anti-bonding pads with the same size are arranged at the corresponding positions of each layer of PCB board, the anti-bonding pads are circular areas, and wiring is forbidden in the anti-bonding pad areas; a pair of differential via holes are formed in the anti-bonding pad area, the differential via holes of each layer of PCB board are aligned with each other, signal conductors for transmitting signals are uniformly arranged on the inner walls of the differential via holes along the circumferential direction, the signal conductors are led out from signal layers for inputting and outputting signals through differential transmission lines, signals output from one signal layer are transmitted to the other signal layer through the differential transmission lines and the signal conductors, and conductive structures on the PCB board are insulated and isolated from the differential via holes through the arrangement of the anti-bonding pads; the invention adopts the round anti-bonding pad to prevent the differential via hole from being short-circuited with the reference plane, avoids the phenomenon of discontinuous impedance at the differential via hole, and effectively improves the signal integrity of the differential via hole.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIGS. 1A and 1B are schematic views of structures of an elliptical anti-pad and a rectangular anti-pad, respectively, according to the prior art;
fig. 2 is a schematic cross-sectional view of a differential signal transmission multi-layer PCB structure provided by the present invention;
FIG. 3 is a schematic top view of anti-pad 2;
FIG. 4 is a schematic view of a reference planar layer;
FIG. 5 is a graph of differential impedance in the time domain for three models;
fig. 6 is a graph comparing transmission coefficients of S parameters of three models.
The drawings include:
the PCB board 1, the anti-bonding pad 2, the differential via hole 3, the signal conductor 4 and the differential transmission line 5.
Detailed Description
The invention aims at providing a differential signal transmission multi-layer PCB structure, which adopts a round anti-bonding pad to prevent a differential via hole from being short-circuited with a reference plane, avoids the phenomenon of discontinuous impedance at the differential via hole, and effectively improves the signal integrity of the differential via hole.
In order to enable those skilled in the art to better understand the technical scheme of the present invention, the following describes the differential signaling multilayer PCB structure of the present invention in detail with reference to the accompanying drawings and specific embodiments.
Fig. 2 is a schematic cross-sectional view of a differential signal transmission multi-layer PCB structure according to the present invention; the differential signal transmission multi-layer PCB structure comprises a plurality of layers of PCB boards 1 which are arranged in a stacked manner, eight layers of PCB boards are arranged in the mode in fig. 2, and all the layers of PCB boards are mutually contacted, adhered and fixed into a whole to form a PCB board group.
The corresponding positions of the layers of PCB 1 are provided with anti-bonding pads 2 with equal sizes, and the anti-bonding pads 2 are circular areas for prohibiting wiring; as shown in fig. 3, which is a schematic top view of the anti-pad 2, a printed circuit is disposed on the upper surface of the PCB board 1, no wiring is disposed on the upper surface of the PCB board 1 in the anti-pad 2 region, and the body of the PCB board 1 is an insulating structure.
A pair of differential through holes 3 are formed in the anti-bonding pad 2 area, each differential through hole 3 is used for transmitting one path of signal, and the two differential through holes 3 are matched with each other to transmit differential signals; signal conductors 4 for transmitting signals are uniformly arranged on the inner wall of the differential via hole 3 along the circumferential direction, the signal conductors 4 are plated in the differential via hole 3, and signals are transmitted between the PCB boards 1 in different layers through the signal conductors 4; the signal conductor 4 is led out from the signal layer of the input and output signals through the differential transmission line 5, and the signal layer of the output signal passes through the differential transmission line 5 of the layer, the signal conductor 4 and the differential transmission line 5 on the signal layer of the input signal in sequence, and transmits the signals to the signal layer of the output signal.
The invention adopts the round anti-bonding pad 2, prevents the differential via hole 3 from being short-circuited with the reference plane through the anti-bonding pad 2, avoids the phenomenon of discontinuous impedance at the differential via hole, and effectively improves the signal integrity of the differential via hole. The anti-bonding pad is used as an important part of the differential via structure, is not only used for controlling the distance between the differential via and the reference plane in the PCB board group and preventing the short circuit between the hole and the reference plane, but also has profound influence on the signal integrity of the differential via, and the phenomenon of discontinuous impedance at the position of the differential via can be avoided by arranging the circular anti-bonding pad, so that the signal integrity characteristic of the differential via is effectively improved.
On the basis of the scheme, at least two layers of PCB boards 1 are arranged between two signal layers, and at least one layer of reference plane layer is arranged between the two signal layers, namely, the reference plane is positioned on the PCB board between the two signal layers.
As shown in fig. 4, a schematic view of a reference planar layer; the upper surface of the reference plane layer is provided with a metal layer without gaps, cracks and gaps.
The invention herein provides two specific dimensional requirements:
first, as shown in fig. 2, the differential via hole 3 of the present invention is an equal diameter hole, the diameters of the differential via hole 3 are equal, the distance between the edge of the anti-pad 2 and the center of the differential via hole 3 is equal to or greater than r+9mil, and R is the outer diameter of the differential via hole 3.
Second, the differential via hole 3 is a back drilling hole, the back drilling hole is a hole with different diameters, the distance between the edge of the anti-bonding pad 2 and the center of the differential via hole 3 is more than or equal to R+12mil, and R is the outer diameter of the largest part of the differential via hole 3.
On the basis of any one of the above technical solutions and the combination thereof, in the present invention, the two differential vias 3 and the two differential transmission lines 5 are respectively symmetrical about the same diameter of the anti-pad 2, as shown in fig. 3, the two differential vias 3 are symmetrical about the straight line a, and the two differential transmission lines 5 are symmetrical about the straight line a.
Each differential via 3 is itself symmetrical about the same diameter of the anti-pad 2, as shown in fig. 3, the differential via 3 itself being symmetrical about a straight line B.
The corner angle of the differential transmission line 5 is more than or equal to 135 degrees, namely the angle of the included angle alpha in fig. 3 is not less than 135 degrees, the included angle of the bending part of the differential transmission line 5 is larger, and the generated interference loss is smaller.
The invention is verified by constructing a differential via model of a circular anti-pad proposed by the invention in HFSS (high frequency structural simulation High Frequency Structure Simulator) and comparing three anti-pads. The PCB is laminated into four layers, the differential transmission line is positioned on the top layer and the bottom layer, the middle is a reference plane layer, two differential via hole models of elliptical and rectangular anti-bonding pads with the same area are constructed on the premise of ensuring the consistency of other parameters, the change of differential impedance in the time domain of the three models and the transmission coefficient of S parameters are extracted and compared, FIG. 5 is a comparison chart of differential impedance in the time domain of the three models, and FIG. 6 is a comparison chart of the transmission coefficient of S parameters of the three models.
As can be seen from fig. 5, under the models of oval, rectangular and circular three different anti-pad shapes, the differential impedance variation amplitude in the time domain is smaller and smaller, and at the moment, the impedance continuity and stability of the differential via hole are better and better. Meanwhile, as can be seen from fig. 6, in the three cases, the transmission coefficients are sequentially improved, the transmission loss is sequentially reduced, and the more obvious the loss gap is along with the increase of the frequency. Therefore, the differential via anti-pad design method provided by the invention can effectively improve the impedance continuity of the differential via, so that the signal integrity characteristic of the differential via is effectively improved, the signal integrity problem caused by imperfect differential via anti-pad design in actual engineering is avoided, and a reference is provided for the design of the differential via anti-pad in actual engineering.
The previous description of the disclosed embodiments is provided to enable any person 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 applied to 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 (7)
1. The differential signal transmission multi-layer PCB structure is characterized by comprising a plurality of layers of PCB (1) which are arranged in a stacked manner, wherein anti-bonding pads (2) with equal size are arranged at corresponding positions of each layer of the PCB (1), and the anti-bonding pads (2) are circular areas for prohibiting wiring;
a pair of differential via holes (3) are formed in the anti-bonding pad (2) area, signal conductors (4) used for transmitting signals are uniformly arranged on the inner walls of the differential via holes (3) along the circumferential direction, and the signal conductors (4) are led out from the signal layers of input and output signals through differential transmission lines (5).
2. The differential signaling multilayer PCB structure of claim 1, wherein at least two layers of the PCB (1) are disposed between two signal layers, and at least one reference plane layer is disposed between two signal layers.
3. The differential signaling multilayer PCB structure of claim 2, wherein the upper surface of the reference planar layer is provided with a metal layer without gaps, cracks, voids.
4. The differential signal transmission multi-layer PCB structure according to claim 1, wherein the differential via hole (3) is an equal diameter hole, the distance between the edge of the anti-bonding pad (2) and the center of the differential via hole (3) is equal to or greater than R+9mil, and R is the outer diameter of the differential via hole (3).
5. The differential signal transmission multi-layer PCB structure according to claim 1, wherein the differential via hole (3) is a back drilled hole, the distance between the edge of the anti-bonding pad (2) and the center of the differential via hole (3) is equal to or more than R+12mil, and R is the outer diameter of the largest part of the differential via hole (3).
6. The differential signal transmission multilayer PCB structure according to any of the claims 1 to 5, characterized in that two of said differential vias (3) and two of said differential transmission lines (5) are respectively symmetrical with respect to the same diameter of said anti-pad (2);
each differential via (3) is itself symmetrical about the same diameter of the anti-pad (2).
7. The differential signaling multilayer PCB board structure of claim 6, wherein the corner angle of the differential transmission line (5) is not less than 135 °.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110794284.6A CN113709962B (en) | 2021-07-14 | 2021-07-14 | Differential signal transmission multilayer PCB structure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110794284.6A CN113709962B (en) | 2021-07-14 | 2021-07-14 | Differential signal transmission multilayer PCB structure |
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| Publication Number | Publication Date |
|---|---|
| CN113709962A CN113709962A (en) | 2021-11-26 |
| CN113709962B true CN113709962B (en) | 2023-05-02 |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6420778B1 (en) * | 2001-06-01 | 2002-07-16 | Aralight, Inc. | Differential electrical transmission line structures employing crosstalk compensation and related methods |
| CN109842990A (en) * | 2019-03-22 | 2019-06-04 | 重庆邮电大学 | A kind of optimization method of high-speed differential via |
| CN111343801A (en) * | 2020-03-31 | 2020-06-26 | 苏州浪潮智能科技有限公司 | Impedance optimization method for circuit board via hole and circuit board |
| CN111741593A (en) * | 2020-07-17 | 2020-10-02 | 浪潮商用机器有限公司 | PCB and differential wiring impedance matching optimization structure thereof |
-
2021
- 2021-07-14 CN CN202110794284.6A patent/CN113709962B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6420778B1 (en) * | 2001-06-01 | 2002-07-16 | Aralight, Inc. | Differential electrical transmission line structures employing crosstalk compensation and related methods |
| CN109842990A (en) * | 2019-03-22 | 2019-06-04 | 重庆邮电大学 | A kind of optimization method of high-speed differential via |
| CN111343801A (en) * | 2020-03-31 | 2020-06-26 | 苏州浪潮智能科技有限公司 | Impedance optimization method for circuit board via hole and circuit board |
| CN111741593A (en) * | 2020-07-17 | 2020-10-02 | 浪潮商用机器有限公司 | PCB and differential wiring impedance matching optimization structure thereof |
Non-Patent Citations (2)
| Title |
|---|
| High-speed Flip Chip Package Co-Design with Optimization of Anti-Pad size Variations on Metal Plane Layout;Hojeong Lim et al;IEEE;第1-4页 * |
| 高速PCB中差分过孔分析与优化;严冬;电子测量与仪器学报;第34卷(第1期);第1-7页 * |
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| CN113709962A (en) | 2021-11-26 |
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