CN109561571B - System and method for shielding strip line and connecting pipe in printed board and printed board - Google Patents
System and method for shielding strip line and connecting pipe in printed board and printed board Download PDFInfo
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- CN109561571B CN109561571B CN201811443817.0A CN201811443817A CN109561571B CN 109561571 B CN109561571 B CN 109561571B CN 201811443817 A CN201811443817 A CN 201811443817A CN 109561571 B CN109561571 B CN 109561571B
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- 238000000034 method Methods 0.000 title claims abstract description 69
- 239000002344 surface layer Substances 0.000 claims abstract description 45
- 238000001465 metallisation Methods 0.000 claims abstract description 8
- 238000012545 processing Methods 0.000 claims description 18
- 239000010410 layer Substances 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 239000011347 resin Substances 0.000 claims description 4
- 229920005989 resin Polymers 0.000 claims description 4
- 230000003071 parasitic effect Effects 0.000 claims description 3
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- 230000005540 biological transmission Effects 0.000 description 3
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000009713 electroplating Methods 0.000 description 2
- 230000010354 integration Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005476 soldering Methods 0.000 description 2
- 238000013459 approach Methods 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
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- 229910052802 copper Inorganic materials 0.000 description 1
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- 239000011889 copper foil Substances 0.000 description 1
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- 230000005670 electromagnetic radiation Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
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- 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
- H05K1/0213—Electrical arrangements not otherwise provided for
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- H05K1/0218—Reduction of cross-talk, noise or electromagnetic interference by printed shielding conductors, ground planes or power plane
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Abstract
The invention relates to a system and a method for shielding strip lines and connecting pipes in a printed board and the printed board. A system for shielding strip lines in a printed board and connecting pipes connected to the surface layer of the printed board, comprising: a first ground groove and a second ground groove symmetrically arranged on both sides of the strip line; and a third ground groove provided around the connection pipe; the first grounding groove, the second grounding groove and the third grounding groove are all metallization grooves and penetrate through the printed board from top to bottom so as to be connected to an upper ground plane and a lower ground plane of the printed board, the first grounding groove and the second grounding groove are respectively long strips with a first width and a second width when the printed board is seen from the surface layer, the third grounding groove is an arc with a third width and taking the center of the connecting pipe as a circle center, and the arc is arranged on one side, far away from the strip line, of the connecting pipe and is symmetrical about an extension line of the strip line.
Description
Technical Field
The invention relates to the technical field of printed board processing, in particular to a system and a method for shielding a strip line in a printed board and a connecting pipe connected with the surface layer of the printed board and the printed board comprising the system.
Background
With the improvement of the technology and the improvement of the chip manufacturing process, electronic products gradually go on the development path of high frequency, high speed, high integration and high reliability. In the development of circuit boards, high-speed digital-analog hybrid circuits are becoming a new development trend, and are widely applied to different fields and industries. However, when the transmission lines with different frequencies and rates are designed in a common board, the problems of crosstalk and electromagnetic compatibility are inevitable. For example, critical signal lines such as antenna input and output signals, high frequency clock signals, etc. in a digital-to-analog hybrid board are often not desired to interfere with or be interfered by other signal lines. At present, many methods for designing shielding of such critical signal lines have been used, and the common methods include soldering shielded cables on a printed board, processing a special signal line in a wiring manner, and designing a closed strip line. All three methods have been used in industrial production, but the three methods still have limitations and disadvantages in use.
The disadvantage of soldering the shielded cable on the printed board is that: the assembly difficulty of the printed board is increased, and the attractiveness of the printed board is influenced; when the transmission frequency is required to be higher, the welding process requirement of the shielding line and the printed board connecting pipe is higher. The disadvantage of the special signal line ground processing is that: the printed board adopts a laminating process, and prepregs are used between layers and cannot shield electromagnetic signals, so that electromagnetic radiation is influenced. The design method of the closed strip line has the following disadvantages: the implementation means of the closed strip line and the connection mode of the closed strip line and the printed board surface device are not clear.
Therefore, there is a need in the prior art for a solution that can effectively avoid the crosstalk and electromagnetic compatibility problems of the key signal line during the signal transmission process without increasing the printed board processing technology.
Disclosure of Invention
In view of the disadvantages of the prior art, the present invention provides a system and a method for shielding a strip line in a printed board and a connection pipe connected to a surface layer of the printed board, and a printed board including the system.
According to an aspect of the present invention, there is provided a system for shielding a strip line in a printed board and a connection pipe connected to a surface layer of the printed board, the system comprising:
a first ground groove and a second ground groove symmetrically arranged on both sides of the strip line; and
a third ground groove provided around the connection pipe,
wherein the first grounding groove, the second grounding groove and the third grounding groove are all metallization grooves and all penetrate through the printed board up and down to be connected to an upper ground plane and a lower ground plane of the printed board,
the first grounding groove and the second grounding groove are respectively long strips with a first width and a second width when being observed from the surface layer of the printed board, the third grounding groove is an arc with a third width and taking the center of the connecting pipe as a circle center, and the arc is arranged on one side of the connecting pipe, which is far away from the strip line, and is symmetrical about an extension line of the strip line.
Preferably, if the first ground groove and the second ground groove intersect with the third ground groove, the first ground groove, the second ground groove, and the third ground groove are filled with resin or metal.
Preferably, the first width, the second width, and the third width are the same and are determined by a thickness-to-diameter ratio at the time of processing the printed board.
Preferably, the line width of the strip line is determined by the control requirement of the characteristic impedance of the strip line; the diameter of the connecting pipe and the radius of the third grounding groove are determined by the control requirement of the characteristic impedance of the connecting pipe; the arc length of the third grounding slot is determined by the wiring space of the printed board.
According to another aspect of the present invention, there is provided a method for shielding a strip line in a printed board and a connection pipe connected to a surface layer of the printed board, the method including:
symmetrically arranging a first grounding groove and a second grounding groove on two sides of the strip line; and
a third ground groove is provided around the connection pipe,
wherein the first grounding groove, the second grounding groove and the third grounding groove are all metallization grooves and all penetrate through the printed board up and down to be connected to an upper ground plane and a lower ground plane of the printed board,
the first grounding groove and the second grounding groove are respectively long strips with a first width and a second width when being observed from the surface layer of the printed board, the third grounding groove is an arc with a third width and taking the center of the connecting pipe as a circle center, and the arc is arranged on one side of the connecting pipe, which is far away from the strip line, and is symmetrical about an extension line of the strip line.
Preferably, the first width, the second width and the third width are determined by a thickness-to-diameter ratio at the time of processing the printed board; determining a line width of the strip line from a control requirement of a characteristic impedance of the strip line; determining a diameter of the connection pipe and a radius of the third ground groove by a control requirement of a characteristic impedance of the connection pipe; and determining the arc length of the third grounding slot by the wiring space of the printed board.
Preferably, the method further comprises:
adjusting the line width of the strip line according to the control requirement of the characteristic impedance of the strip line; and
and adjusting the diameter of the connecting pipe and the radius of the third grounding groove according to the control requirement of the characteristic impedance of the connecting pipe.
Preferably, adjusting the line width of the strip line according to the control requirement of the characteristic impedance of the strip line is performed according to the following formula:
wherein Z is0Is the characteristic impedance of the stripline; w is the line width of the strip line; epsilonrThe relative dielectric constant of a prepreg in the printed board is obtained; t is the thickness of the strip line; h1The thickness of a prepreg between the strip line and the lower ground plane of the printed board; h2The thickness of the prepreg between the strip line and the upper ground plane of the printed board.
Preferably, the adjusting of the diameter of the connection pipe and the radius of the third ground groove according to the control requirement of the characteristic impedance of the connection pipe is performed according to the following formula:
wherein Z is0"is a characteristic impedance of the connection tube; r is the resistance of the connecting pipe and has the unit of omega/m; g is the conductance of the connecting pipe, and the unit is s/m; l is the inductance of the connecting pipe, and the unit is H/m; c is the parasitic capacitance of the connecting pipe, and the unit is F/m;
wherein,
l is the length of the connecting pipe, f is the working frequency of the connecting pipe, mu is the magnetic conductivity of the connecting pipe, ρ is the electrical conductivity of the connecting pipe, d is the diameter of the connecting pipe,
wherein,
is the dielectric loss angle of the connection tube,
wherein L is 5.08L [ ln (4L/d) +1],
wherein,
R0is the radius of the third grounding groove, A is the arc length of the third grounding groove, epsilonrK is the relative dielectric constant of the prepreg in the printed board, k is the electrostatic force constant, and k is 9.0 × 109N·m2/C2，ε0Is a function of the dielectric constant of the free space,
by the above formula, R satisfying the control requirement of the characteristic impedance of the connection pipe is obtained0-d/2。
According to another aspect of the invention, a printed board is provided comprising a system for shielding strip lines in the printed board and connecting pipes connecting to the skin of the printed board.
Compared with the prior art, one or more embodiments in the above scheme can have the following advantages or beneficial effects:
the invention arranges a plurality of grounding grooves in a certain range around the strip line and the connecting pipe of the strip line and the printed board surface layer which need to adopt electromagnetic shielding, and combines the upper and lower ground planes of the printed board to form a complete circle of grounding shell for the strip line and the connecting pipe of the strip line and the printed board surface layer, thereby providing a complete shielding channel for the signal transmission of the strip line from the inside of the printed board to the printed board surface layer, and effectively avoiding the crosstalk and electromagnetic compatibility problems of the strip line in the signal transmission process. In addition, the characteristic impedance of the strip line, the strip line and the connecting pipe on the surface layer of the printed board is controlled, so that the loss and reflection of signals in a circuit are reduced, and the signal integrity and the electromagnetic shielding requirements of the strip line are ensured. The invention can effectively control the impedance of the strip line, the strip line and the connecting pipe on the surface layer of the printed board, can ensure the electromagnetic shielding requirement of the strip line, and only needs to be produced according to the conventional printed board processing technology without increasing the processing cost.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 shows a top view of a system for shielding strip lines in a printed board and their connecting tubes to be connected to the skin of the printed board according to an embodiment of the invention;
fig. 2 shows a cross-sectional view of a system for shielding strip lines in a printed board and connecting pipes connected to the skin of the printed board according to an embodiment of the invention;
fig. 3 shows a three-dimensional side view of a system for shielding strip lines in a printed board and connecting tubes to be connected to the skin of the printed board according to an embodiment of the invention;
fig. 4 shows a three-dimensional top view of a system for shielding strip lines in a printed board and their connecting tubes connected to the skin of the printed board according to an embodiment of the invention;
fig. 5 is a flow chart of a method for shielding strip lines in a printed board and connecting pipes connected to a skin layer of the printed board according to an embodiment of the present invention;
FIG. 6 illustrates additional optional steps of the method illustrated in FIG. 5;
fig. 7 shows a schematic view of a strip line without a shielding method;
FIG. 8 shows a schematic diagram of a stripline employing a stripline ground shielding approach;
fig. 9a to 9c show impedance control curves of strip lines, in which fig. 9a is an impedance control curve of a strip line not using a shielding method, fig. 9b is an impedance control curve of a strip line using a strip line ground shielding method, and fig. 9c is an impedance control curve of a strip line using a method for shielding a strip line in a printed board and a connection pipe connected to a surface layer of the printed board according to an embodiment of the present invention;
fig. 10a to 10c show near-end crosstalk curves of strip lines, where fig. 10a is a near-end crosstalk curve of a strip line without a shielding method, fig. 10b is a near-end crosstalk curve of a strip line with a ground shielding method of a strip line, and fig. 10c is a near-end crosstalk curve of a strip line with a method for shielding a strip line in a printed board and a connection pipe connected to a surface layer of the printed board according to an embodiment of the present invention;
fig. 11a to 11c show far-end crosstalk curves of strip lines, where fig. 11a is a far-end crosstalk curve of a strip line without using a shielding method, fig. 11b is a far-end crosstalk curve of a strip line using a strip line ground shielding method, and fig. 11c is a far-end crosstalk curve of a strip line using a method for shielding a strip line in a printed board and a connection pipe connected to a surface layer of the printed board according to an embodiment of the present invention.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.
In order to solve the problems that in the prior art, when shielding treatment is performed on a strip line on a printed board, the processing difficulty is high, the processing technology is complex, and crosstalk and electromagnetic compatibility of the strip line in the signal transmission process cannot be avoided, the embodiment of the invention firstly provides a system for shielding the strip line in the printed board and a connecting pipe connected with the surface layer of the printed board.
Fig. 1 shows a top view of a system for shielding strip lines in a printed board and their connecting tubes to be connected to the skin of the printed board according to an embodiment of the invention. Fig. 2 shows a cross-sectional view of a system for shielding strip lines in a printed board and their connecting tubes connected to the skin of the printed board according to an embodiment of the invention. Fig. 3 shows a three-dimensional side view of a system for shielding strip lines in a printed board and their connecting tubes to be connected to the skin of the printed board according to an embodiment of the invention. Fig. 4 shows a three-dimensional top view of a system for shielding strip lines in a printed board and their connecting tubes connected to the skin of the printed board according to an embodiment of the invention. A system for shielding a strip line in a printed board and a connection pipe connected to a surface layer of the printed board according to an embodiment of the present invention will be described in detail with reference to fig. 1 to 4.
As shown in fig. 1 to 4, a system for shielding strip lines in a printed board and connecting pipes connected to the surface layer of the printed board comprises:
a first ground groove and a second ground groove symmetrically arranged on both sides of the strip line; and
a third ground groove provided around the connection pipe,
wherein the first grounding groove, the second grounding groove and the third grounding groove are all metallization grooves and penetrate through the printed board up and down to be connected to the upper ground plane and the lower ground plane of the printed board,
the first grounding groove and the second grounding groove are respectively long strips with a first width and a second width when viewed from the surface layer of the printed board, the third grounding groove is an arc with a third width and taking the center of the connecting pipe as a circle center, and the arc is arranged on one side of the connecting pipe far away from the strip line and is symmetrical about the extension line of the strip line.
As shown in fig. 1 to 4, the strip lines 101 and 201 are high-frequency transmission lines disposed between prepregs disposed between an upper ground plane 206 and a lower ground plane 207 of the printed board, and are connected to the surface layer of the printed board through connection pipes 102 and 202.
As shown in fig. 1, the system for shielding a strip line in a printed board and a connection pipe connected to a surface layer of the printed board includes first ground grooves 103, 203, 403 and second ground grooves 104, 204, 404 symmetrically disposed at both sides of the strip line. Specifically, the central axis of the strip line 101, 201 having the width w and the thickness T is set as a central line, and the first ground grooves 103, 203, 403 having the first width and the second ground grooves 104, 204, 404 having the second width are symmetrically provided on both sides of the central line. The first ground grooves 103, 203, 403 and the second ground grooves 104, 204, 404 are long strips having a first width and a second width, respectively, as viewed from the surface of the printed board. The distance between the inner side wall of any one of the first grounding grooves 103, 203, 403 and the second grounding grooves 104, 204, 404 and the strip line 101, 201 is K.
The system further comprises a third grounding slot 105, 405 arranged around the connecting tube. In particular, a plated-through hole of length l and diameter d is preferably formed in the printed board by means of a blind hole or back-drilling process as a connection line 102, 202 between the strip line 101, 201 and the surface layer of the printed board. The connection tubes 102, 202 may be formed by other processes, but the invention is not limited thereto. The center of the connecting pipe 102, 202 (hole center) is set at a radius R0Has a third width of the third ground slot 105, 405. The third ground slot 105, 405 may shield the connection tube 102, 202. The third ground groove 105, 405 is an arc having a third width centered on the center of the connection pipe 102, 202 when viewed from the surface of the printed board, and is provided on the side of the connection pipe 102, 202 away from the strip line 101, 201 and is symmetrical with respect to the extension line of the strip line 101, 201. Wherein the radius R0Refers to the middle of the connecting pipe 102, 202The distance from the center to the inner side wall of the third grounding groove 105, 405, and the length l of the connection pipe 102, 202 is the distance between the strip line 101, 201 and the surface layer of the printed board.
In an embodiment of the invention, the first grounding groove, the second grounding groove and the third grounding groove are all metallization grooves. As shown in fig. 2 and 3, the first grounding slot, the second grounding slot and the third grounding slot penetrate through the printed board from top to bottom to be connected to the upper ground plane and the lower ground plane of the printed board, and form a complete grounding shell for the strip line and the connecting pipe between the strip line and the printed board surface layer by combining the upper ground plane and the lower ground plane of the strip line, so that a complete shielding channel is provided for the signal transmission of the strip line from the inside of the printed board to the printed board surface layer.
In an embodiment of the present invention, the first ground groove and the second ground groove do not intersect with the third ground groove, and the first ground groove, the second ground groove, and the third ground groove are hollow or filled with resin or metal.
In another embodiment of the invention, the first grounding groove, the second grounding groove and the third grounding groove intersect, in order to ensure the rigidity of the printed board, resin or metal is filled in the grounding groove, preferably copper strip, and after electroplating, the grounding groove and the printed board form a whole to improve the rigidity of the printed board.
In an embodiment of the present invention, the first width, the second width, and the third width are the same and are determined by a thickness-to-diameter ratio at the time of processing the printed board. Specifically, as shown in fig. 1, the first width, the second width, and the third width are the same and are all the width D. The widths D of the first grounding groove, the second grounding groove and the third grounding groove are determined according to the thickness-diameter ratio processing capacity of a printed board manufacturer. Preferably, the first width, the second width and the third width are determined at a minimum value of the thickness to diameter ratio. For example, if the ratio of the thickness to the diameter of the batch production capacity of the printed circuit board processing manufacturer is 10:1 and the printed circuit board design thickness is 2mm, the width of the grounding slot is 0.2 mm. The thickness-diameter ratio of a manufacturer is determined according to the capacity of an electroplating process, and if the thickness-diameter ratio is too high, the aperture is too small, which may cause the condition that the plating layer in the middle of the via hole is incomplete and the via hole is broken.
In one embodiment of the present invention, the line width of the strip line is determined by the control requirement of the characteristic impedance of the strip line. The diameter of the connection pipe and the radius of the third ground groove are determined by the control requirement of the characteristic impedance of the connection pipe. The distance K between the strip line and the first grounding groove and the distance K between the strip line and the second grounding groove are determined according to the processing capability of a printed board manufacturer. The strip line thickness T is determined by the printed board material. The arc length A of the third grounding groove is determined by the wiring space of the printed board.
According to an embodiment of the present invention, as shown in fig. 2 to 3, the printed board further includes: a first prepreg 301 located between the stripline and the lower ground plane of the printed board and a second prepreg 302 located between the stripline and the upper ground plane of the printed board. The relative dielectric constants of the first prepreg 301 and the second prepreg 302 are both epsilonr. The purpose of the first prepreg 301 and the second prepreg 302 in the printed board is to bond and support the copper foil.
Correspondingly, the embodiment of the invention also provides a method for shielding the strip line in the printed board and the connecting pipe connected with the surface layer of the printed board. Fig. 5 is a flowchart of a method for shielding a strip line in a printed board and a connection pipe connected to a surface layer of the printed board according to an embodiment of the present invention. As shown in fig. 5, the method includes:
step S501: symmetrically arranging a first grounding groove and a second grounding groove on two sides of the strip line; and
step S502: a third ground groove is provided around the connection pipe,
wherein the first grounding groove, the second grounding groove and the third grounding groove are all metallization grooves and all penetrate through the printed board up and down to be connected to an upper ground plane and a lower ground plane of the printed board,
the first grounding groove and the second grounding groove are respectively long strips with a first width and a second width when being observed from the surface layer of the printed board, the third grounding groove is an arc with a third width and taking the center of the connecting pipe as a circle center, and the arc is arranged on one side of the connecting pipe, which is far away from the strip line, and is symmetrical about an extension line of the strip line.
In an embodiment of the present invention, step S501 and step S502 may be executed simultaneously, or step S502 may be executed first and then step S501 is executed, which is not limited in this disclosure.
In one embodiment of the invention, the first width, the second width and the third width are determined by the thickness-diameter ratio of the printed board during processing; determining the line width of the strip line according to the control requirement of the characteristic impedance of the strip line; determining the diameter of the connecting pipe and the radius of the third grounding groove according to the control requirement of the characteristic impedance of the connecting pipe; the arc length of the third grounding slot is determined by the wiring space of the printed board.
Fig. 6 shows additional optional steps of the method shown in fig. 5. As shown in fig. 6, in an embodiment of the present invention, the method may further include:
step S601: adjusting the line width of the strip line according to the control requirement of the characteristic impedance of the strip line; and
step S602: and adjusting the diameter of the connecting pipe and the radius of the third grounding groove according to the control requirement of the characteristic impedance of the connecting pipe.
With the improvement and application of the integrated circuit integration level, the operating speed of the circuit is faster and faster, and for a strip line with higher signal transmission frequency and speed, the characteristic impedance value of the strip line must be controlled within a certain tolerance range, otherwise, once the characteristic impedance value of the strip line exceeds the tolerance, the transmitted signal energy will have reflection, scattering, attenuation or delay phenomena, and the signal integrity can be seriously affected. Therefore, an embodiment of the present invention further provides a shielded strip line and a characteristic impedance control method of a shielded connection tube.
In step S601, adjusting the line width of the strip line according to the control requirement of the characteristic impedance of the strip line is performed according to the following formula:
wherein Z is0Is the characteristic impedance of the stripline; w is the line width of the strip line; epsilonrFor relative of prepregs in printed boardsA dielectric constant; t is the thickness of the strip line; h1Is the thickness of the prepreg between the stripline and the lower ground plane of the printed board; h2Is the thickness of the prepreg between the stripline and the upper ground plane of the printed board.
Therefore, in one embodiment of the present invention, the characteristic impedance Z of the strip line can be adjusted by adjusting the line width W of the strip line0And controlling within a tolerance range.
More specifically, an embodiment of the present invention depends on the characteristic impedance Z of the stripline0The control requirement of (2) calculating the line width W of the strip line by using simulation specifically comprises:
step S1: determining the desired characteristic impedance Z of the strip line0；
Step S2: selecting a printed board material to determine the relative dielectric constant ε of the first and second prepregsrAnd determining a stripline thickness T;
step S3: designing the laminated structure and thickness of the printed board, and determining the thickness H of the first semi-cured sheet1And thickness H of the second prepreg2；
Step S4: and calculating the line width W of the strip line meeting the requirement.
At step S4, preferably, an embodiment of the present invention calculates the width W of the stripline satisfying the requirement using Si9000 software. However, other similar software may be used to perform step S4, and the invention is not limited thereto.
In step S602, the diameter of the connection pipe and the radius of the third ground groove are adjusted in accordance with the control request of the characteristic impedance of the connection pipe. The method specifically comprises the following steps:
adjusting the diameter of the connection pipe and the radius of the third ground groove according to the control requirement of the characteristic impedance of the connection pipe is performed according to the following formula:
wherein Z is0"is the characteristic impedance of the connecting tube; r is the resistance of the connecting pipe and has the unit of omega/m; g is the conductance of the connecting pipe and has the unit of s/m; l is a connecting pipeInductance, unit H/m; c is the parasitic capacitance of the connecting pipe, and the unit is F/m;
wherein,
l is the length of the connecting pipe, f is the working frequency of the connecting pipe, mu is the magnetic conductivity of the connecting pipe, rho is the electrical conductivity of the connecting pipe, d is the diameter of the connecting pipe,
wherein,
is the dielectric loss angle of the connection tube,
wherein L is 5.08L [ ln (4L/d) +1],
wherein,
R0is the radius of the third grounding slot, A is the arc length of the third grounding slot, epsilonrThe relative dielectric constant of the prepreg in the printed board, k is the electrostatic force constant, k is 9.0 × 109N·m2/C2，ε0Is a function of the dielectric constant of the free space,
by the above formula, R satisfying the control requirement of the characteristic impedance of the connection pipe is obtained0-d/2。
Therefore, in one embodiment of the present invention, the diameter d of the connecting pipe and the radius R of the third grounding groove are adjusted0The requirement Z for controlling the characteristic impedance of the connection pipe can be satisfied0Within tolerances.
More specifically, an embodiment of the present invention is based on the control requirement Z of the characteristic impedance of the connection tube0' calculating the diameter d of the connection tube and the radius R of the third ground groove by means of simulation0The method specifically comprises the following steps:
step S10: determining the working frequency f of the connecting pipe;
step S20: the diameter d of the connecting pipe and the radius R of the third grounding groove are determined0；
Step S30: modeling a connecting pipe, a strip line, a first grounding groove, a second grounding groove, a third grounding groove, a ground plane and a laminated structure of a printed circuit board, and solving the characteristic impedance Z' of the connecting pipe under the working frequency;
step S40: the obtained characteristic impedances Z' and Z0Comparison, if Z' is not at Z0Returning to step S20 if Z' is within the allowable error range0"within the allowable error range, the routine proceeds to step S50;
step S50: the diameter d of the connecting pipe and the radius R of the third grounding groove which meet the requirements are obtained0。
In step S30, the characteristic impedance Z' of the connection tube at the operating frequency is preferably determined by modeling the connection tube, the strip line, the first ground slot, the second ground slot, the third ground slot, the ground plane and the pcb stack using HFSS software. However, other similar software may be used to perform step S30, and the invention is not limited thereto.
In an embodiment of the present invention, step S601 and step S602 may be executed simultaneously, or step S602 may be executed first and then step S601 is executed, which is not limited in the present invention.
In order to further embody the technical effects of the embodiment of the present invention, the impedance and near-far end crosstalk curves of the strip line in the three methods of not using the shielding method, using the strip line ground shielding method, and using the method for shielding the strip line in the printed board and the connection pipe connected to the surface layer of the printed board according to the embodiment of the present invention are compared below. The following description will be made with reference to fig. 7 to 11.
Fig. 7 shows a schematic view of a strip line not employing a shielding method, and fig. 8 shows a schematic view of a strip line employing a strip line ground shielding method. Fig. 9a to 9c show impedance control curves of strip lines, in which fig. 9a is an impedance control curve of a strip line not using a shielding method, fig. 9b is an impedance control curve of a strip line using a strip line ground shielding method, and fig. 9c is an impedance control curve of a strip line using a method for shielding a strip line in a printed board and a connection pipe connected to a surface layer of the printed board according to an embodiment of the present invention.
In fig. 9a to 9c, the horizontal axis represents time in units of ps; the vertical axis represents the resistance value in Ω. Wherein the characteristic impedance requirement of the strip line under these three methods is set to 50 Ω in the simulation. As shown in fig. 9a to 9c, at 180ps, fig. 9a is 46.7 Ω, fig. 9b is 44.9 Ω, and fig. 9c is 47 Ω. Therefore, the impedance of the strip line adopting the method for shielding the strip line in the printed board and the connecting pipe connected with the surface layer of the printed board according to the embodiment of the invention is closer to the control requirement of the impedance of the strip line by 50 Ω compared with the method without shielding and the method adopting the strip line ground shielding, so that the signal integrity of the strip line is ensured.
Fig. 10a to 10c show near-end crosstalk curves of strip lines, where fig. 10a shows a near-end crosstalk curve of a strip line without using a shielding method, fig. 10b shows a near-end crosstalk curve of a strip line using a strip line ground shielding method, and fig. 10c shows a near-end crosstalk curve of a strip line using a method for shielding a strip line in a printed board and a connection pipe connected to a surface layer of the printed board according to an embodiment of the present invention.
Fig. 11a to 11c show far-end crosstalk curves of strip lines, where fig. 11a is a far-end crosstalk curve of a strip line without using a shielding method, fig. 11b is a far-end crosstalk curve of a strip line using a strip line ground shielding method, and fig. 11c is a far-end crosstalk curve of a strip line using a method for shielding a strip line in a printed board and a connection pipe connected to a surface layer of the printed board according to an embodiment of the present invention.
In fig. 10a to 10c and 11a to 11c, the horizontal axis represents frequency in GHz; the vertical axis represents the signal-to-noise ratio in dB. As can be seen from fig. 10a to 10c and fig. 11a to 11c, the strip line processed in the conventional covering manner has better near-end crosstalk and far-end crosstalk effects than the strip line without any shielding measures, and the near-end crosstalk and far-end crosstalk of the strip line using the method for shielding the strip line in the printed board and the connection pipe connected to the surface layer of the printed board according to an embodiment of the present invention are still lower than-68 dB in a bandwidth of 3GHz, and are lower than the near-end crosstalk and far-end crosstalk of the strip line without any shielding measures and processed in the conventional covering manner, so that the shielding effects on the strip line are more significant.
Correspondingly, the embodiment of the invention also provides a printed board, which comprises a system for shielding the strip line in the printed board and the connecting pipe connected with the surface layer of the printed board.
In summary, an embodiment of the present invention provides a system and a method for shielding a strip line in a printed circuit board and a connecting pipe connected to a surface layer of the printed circuit board, and a printed circuit board, in which a plurality of grounding slots are disposed in a certain range around the strip line and the connecting pipe of the strip line and the surface layer of the printed circuit board, which need to be electromagnetically shielded, and a complete grounding shell is formed for the strip line and the connecting pipe of the strip line and the surface layer of the printed circuit board by combining upper and lower ground planes of the printed circuit board, so that a complete shielding channel is provided for signal transmission of the strip line from the inside of the printed circuit board to the surface layer of the printed circuit board, and thus, the problems of crosstalk and electromagnetic compatibility of the strip line in the signal transmission process can be effectively avoided. In addition, the characteristic impedance of the strip line, the strip line and the connecting pipe on the surface layer of the printed board is controlled, so that the loss and reflection of signals in a circuit are reduced, and the signal integrity and the electromagnetic shielding requirements of the strip line are ensured. The invention can effectively control the impedance of the strip line, the strip line and the connecting pipe on the surface layer of the printed board, can ensure the electromagnetic shielding requirement of the strip line, and only needs to be produced according to the conventional printed board processing technology without increasing the processing cost.
Those skilled in the art will appreciate that the modules or steps of the invention described above can be implemented in a general purpose computing device, centralized on a single computing device or distributed across a network of computing devices, and optionally implemented in program code that is executable by a computing device, such that the modules or steps are stored in a memory device and executed by a computing device, fabricated separately into integrated circuit modules, or fabricated as a single integrated circuit module. Thus, the present invention is not limited to any specific combination of hardware and software.
Although the embodiments of the present invention have been described above, the above description is only for the convenience of understanding the present invention, and is not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A system for shielding strip lines in a printed board and connecting pipes connected to a skin layer of the printed board, the system comprising:
a first ground groove and a second ground groove symmetrically arranged on both sides of the strip line; and
a third ground groove provided around the connection pipe,
wherein the first grounding groove, the second grounding groove and the third grounding groove are all metallization grooves and all penetrate through the printed board up and down to be connected to an upper ground plane and a lower ground plane of the printed board,
the first grounding groove and the second grounding groove are respectively long strips with a first width and a second width when being observed from the surface layer of the printed board, the third grounding groove is an arc with a third width and taking the center of the connecting pipe as a circle center, and the arc is arranged on one side of the connecting pipe, which is far away from the strip line, and is symmetrical about an extension line of the strip line.
2. The system of claim 1, wherein if the first and second grounding slots each intersect the third grounding slot, the first, second, and third grounding slots are all filled with resin or metal.
3. The system of claim 1, wherein the first width, the second width, and the third width are the same and are determined by a thickness to diameter ratio at which the printed board is processed.
4. The system of claim 1, wherein the linewidth of the stripline is determined by control requirements of a characteristic impedance of the stripline; the diameter of the connecting pipe and the radius of the third grounding groove are determined by the control requirement of the characteristic impedance of the connecting pipe; the arc length of the third grounding slot is determined by the wiring space of the printed board.
5. A method for shielding a strip line in a printed board and a connection pipe connected to a surface layer of the printed board, the method comprising:
symmetrically arranging a first grounding groove and a second grounding groove on two sides of the strip line; and
a third ground groove is provided around the connection pipe,
wherein the first grounding groove, the second grounding groove and the third grounding groove are all metallization grooves and all penetrate through the printed board up and down to be connected to an upper ground plane and a lower ground plane of the printed board,
the first grounding groove and the second grounding groove are respectively long strips with a first width and a second width when being observed from the surface layer of the printed board, the third grounding groove is an arc with a third width and taking the center of the connecting pipe as a circle center, and the arc is arranged on one side of the connecting pipe, which is far away from the strip line, and is symmetrical about an extension line of the strip line.
6. The method of claim 5, wherein the first width, the second width, and the third width are determined by a thickness to diameter ratio at the time of processing the printed board; determining a line width of the strip line from a control requirement of a characteristic impedance of the strip line; determining a diameter of the connection pipe and a radius of the third ground groove by a control requirement of a characteristic impedance of the connection pipe; and determining the arc length of the third grounding slot by the wiring space of the printed board.
7. The method of claim 5, further comprising:
adjusting the line width of the strip line according to the control requirement of the characteristic impedance of the strip line; and
and adjusting the diameter of the connecting pipe and the radius of the third grounding groove according to the control requirement of the characteristic impedance of the connecting pipe.
8. The method of claim 7, wherein adjusting the line width of the strip line according to the control requirement of the characteristic impedance of the strip line is according to:
wherein Z is0Is the characteristic impedance of the stripline; w is the line width of the strip line; epsilonrThe relative dielectric constant of a prepreg in the printed board is obtained; t is the thickness of the strip line; h1The thickness of a prepreg between the strip line and the lower ground plane of the printed board; h2The thickness of the prepreg between the strip line and the upper ground plane of the printed board.
9. The method of claim 7, wherein adjusting the diameter of the connection pipe and the radius of the third ground slot according to the control requirement of the characteristic impedance of the connection pipe is according to the following equation:
wherein Z is0"is a characteristic impedance of the connection tube; r is the resistance of the connecting pipe and has the unit of omega/m; g is the conductance of the connecting tube in s-m; l is the inductance of the connecting pipe, and the unit is H/m; c is the parasitic capacitance of the connecting pipe, and the unit is F/m;
wherein,
l is the length of the connecting pipe, f is the working frequency of the connecting pipe, mu is the magnetic conductivity of the connecting pipe, ρ is the electrical conductivity of the connecting pipe, d is the diameter of the connecting pipe,
wherein,
is the dielectric loss angle of the connection tube,
wherein L is 5.08L [ ln (4L/d) +1],
wherein,
R0is the radius of the third grounding groove, A is the arc length of the third grounding groove, epsilonrK is the relative dielectric constant of the prepreg in the printed board, k is the electrostatic force constant, and k is 9.0 × 109N·m2/C2，ε0Is a function of the dielectric constant of the free space,
by the above formula, R satisfying the control requirement of the characteristic impedance of the connection pipe is obtained0-d/2。
10. A printed board comprising a system for shielding strip lines in a printed board and connecting pipes connected to the skin of the printed board according to any of claims 1-4.
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| CN207820316U (en) * | 2018-02-02 | 2018-09-04 | 中山奥士森电子有限公司 | Multilayer impedance wiring board with hole mesoporous shield effectiveness |
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| US6624729B2 (en) * | 2000-12-29 | 2003-09-23 | Hewlett-Packard Development Company, L.P. | Slotted ground plane for controlling the impedance of high speed signals on a printed circuit board |
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|---|---|---|---|---|
| CN1812697A (en) * | 2005-01-25 | 2006-08-02 | 财团法人工业技术研究院 | High-wide-band impedance matching transmitting hole |
| CN103179782A (en) * | 2013-02-21 | 2013-06-26 | 广州兴森快捷电路科技有限公司 | Impedance-controlled low-loss single-ended via hole structure |
| CN107969065A (en) * | 2017-11-02 | 2018-04-27 | 四川九洲电器集团有限责任公司 | A kind of printed circuit board (PCB) |
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