CN117528914A

CN117528914A - Grounding filter structure used in PCB

Info

Publication number: CN117528914A
Application number: CN202410016440.XA
Authority: CN
Inventors: 刘辉; 冯裕龙; 郭光凯
Original assignee: Wudi Yuantong Electronic Technology Co ltd
Current assignee: Wudi Yuantong Electronic Technology Co ltd
Priority date: 2024-01-05
Filing date: 2024-01-05
Publication date: 2024-02-06

Abstract

The invention belongs to the field of circuit boards, and provides a grounding filter structure for a PCB, wherein the structure is arranged in multiple layers and comprises the following components from top to bottom: a top layer, which is two mutually coupled microstrip lines; the first grounding layer is provided with two first grounding metal plates which are not in direct contact, and a plurality of groups of mushroom nail assemblies are arranged between the two grounding metal plates; the second grounding layer is provided with a second grounding metal plate, the middle part of the second grounding metal plate is provided with a slot, two side edges of the second grounding metal plate are respectively connected with the two first grounding metal plates through a plurality of groups of first through holes, a plurality of groups of grounding plates are arranged in the slot and are respectively connected with a plurality of groups of mushroom nail assemblies through corresponding second through holes, and two ends of each grounding plate are connected to the second grounding metal plate through extension lines; the bottom layer is a plurality of bonding pads which are respectively integrated with the first via holes and the second via holes; the multilayer filtering structure provided by the invention has a simple structure and can solve the electromagnetic interference problem.

Description

Grounding filter structure used in PCB

Technical Field

The invention relates to the field of circuit boards, in particular to a grounding filter structure used in a PCB.

Background

The printed circuit board, namely the PCB, realizes the electrical connection between the electronic components and is an indispensable important component in the electronic product. High density PCB boards are essential hardware for computers, servers, etc. The PCB boards of these high performance devices require compact size and high density, and consideration is given to various problems such as grounding, filtering, signal attenuation, etc. In the prior art, due to the high density and asymmetric routing of the PCB layout, signal noise is easy to occur in the PCB and signal integrity is influenced, electromagnetic interference is caused, and high-speed transmission of signals is seriously influenced.

Disclosure of Invention

In view of the above technical problems, the invention provides a grounding filter structure for a PCB (printed circuit board) to solve the problem that the high-density PCB in the prior art is easy to generate signal noise and cause electromagnetic interference.

Other features and advantages of the present disclosure will be apparent from the following detailed description, or may be learned in part by the practice of the disclosure.

The invention discloses a grounding filter structure used in a PCB board, wherein the structure is arranged in a plurality of layers, and the structure comprises the following components from top to bottom:

a top layer, wherein the top layer is two mutually coupled microstrip lines;

the first grounding layer is provided with two first grounding metal plates which are not in direct contact, a plurality of groups of mushroom nail assemblies are arranged between the two grounding metal plates, and the two first grounding metal plates and the plurality of groups of mushroom nail assemblies form axisymmetry;

the second grounding layer is provided with a second grounding metal plate, a slot is formed in the middle of the second grounding metal plate, two side edges of the second grounding metal plate are respectively connected with the two first grounding metal plates through a plurality of groups of first through holes, a plurality of groups of grounding plates are arranged in the slot, a plurality of groups of grounding plates are respectively connected with a plurality of groups of mushroom nail assemblies through corresponding second through holes, and two ends of each grounding plate are connected to the second grounding metal plate through extension lines;

the bottom layer is a plurality of bonding pads which are integrated with the first via holes and the second via holes respectively.

Further, the two microstrip lines are parallel to each other and equal in size.

Further, the number of the mushroom nail assemblies is 3-6.

Further, the mushroom nail assembly comprises a metal belt and a metal cover protruding from the surface of the metal belt, and the metal belt is connected with the second through hole.

Further, the number of the metal caps and the second vias corresponding to the same metal strip is two.

Further, on the same plane, two microstrip lines are located between two metal covers.

Further, the second grounding metal plate includes a grounding frame and two third grounding metal plates connected in the frame, the slots are formed between the two third grounding metal plates, opposite sides of the two third grounding metal plates are respectively connected with two sides in the frame, other sides of the two third grounding metal plates are not contacted with the frame and form central symmetry, and two extension lines connected with the same grounding plate are respectively connected to the two third grounding metal plates, and the first via hole is connected with the frame.

Further, the number of the first through holes on one first grounding metal plate is 3-5.

Further, in the first via holes of the same first ground metal plate, two first via holes are respectively connected to two corners of the same side of the frame.

Further, on the same plane, the mushroom spike assembly is located between two adjacent first through holes.

The technical scheme of the present disclosure has the following beneficial effects:

the multilayer filtering structure is simple in structure, easy to inlay into the PCB, and capable of effectively reducing signal noise in the high-density PCB, solving the electromagnetic interference problem and meeting the quality control requirement of the high-speed PCB.

Drawings

Fig. 1 is a schematic structural diagram of a grounding filter structure in an embodiment of the present disclosure;

fig. 2 is a schematic top view of a second ground layer according to an embodiment of the present disclosure;

fig. 3 is a schematic top view of a third ground layer according to an embodiment of the present disclosure;

FIG. 4 is a schematic signal flow diagram of a grounding filter structure according to an embodiment of the present disclosure;

fig. 5 is a cross-sectional view of a grounded filter structure in an embodiment of the present disclosure.

Wherein, the reference numerals illustrate:

100. a top layer; 101. a microstrip line; 200. a first ground layer; 201. a first grounded metal plate; 202. a mushroom spike assembly; 2021. a metal belt; 2022. a metal cover; 300. a second ground layer; 301. a second grounded metal plate; 3011. a frame; 3012. a third grounded metal plate; 3013. slotting; 302. a first via; 303. a grounding plate; 304. an extension line; 305. a second via; 400. a bottom layer; 401. and a bonding pad.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings.

The drawings are merely schematic illustrations of the present disclosure. The same reference numerals in the drawings denote the same or similar parts, and thus a repetitive description thereof will be omitted. It will be understood that the scale of the various components in the figures do not constitute limitations of the present disclosure.

As shown in fig. 1-3, an embodiment of the present disclosure provides a grounded filtering structure for use in a PCB board, where the filtering structure includes, from top to bottom: a top layer 100, wherein the top layer 100 is two mutually coupled microstrip lines 101; the first grounding layer 200, the first grounding layer 200 is provided with two first grounding metal plates 201 which are not in direct contact, a plurality of groups of mushroom nail assemblies 202 are arranged between the two grounding metal plates, and the two first grounding metal plates 201 and the plurality of groups of mushroom nail assemblies 202 form axisymmetry; the second grounding layer 300, the second grounding layer 300 is provided with a second grounding metal plate 301, a slot 3013 is formed in the middle of the second grounding metal plate 301, two side edges of the second grounding metal plate 301 are respectively connected with two first grounding metal plates 201 through a plurality of groups of first through holes 302, a plurality of groups of grounding plates 303 are arranged in the slot 3013, the plurality of groups of grounding plates 303 are respectively connected with the plurality of groups of mushroom nail assemblies 202 through corresponding second through holes 305, and two ends of the grounding plates 303 are connected to the second grounding metal plate 301 through extension lines 304; the bottom layer 400, the bottom layer 400 is a plurality of bonding pads 401 which are respectively integrated with the first via 302 and the second via 305.

Among them, since the server PCB layout is very compact, the differential signal often has a path asymmetry problem, thereby generating a lot of common mode noise. The transmission of the common mode signal is returned to the source along the reference ground, so that modifications to its return path can affect the common mode signal to change it. As shown in fig. 4, fig. 4 illustrates a common mode signal return path of the filtering structure of fig. 1-3 in this embodiment, with signal flow direction indicated by dashed arrows. Since the two first ground metal plates 201 of the first ground layer 200 are isolated from each other on the first ground layer 200, the common mode signal on the first ground layer 200 is blocked, and the common mode signal exhibits the flow direction as in fig. 4. Specifically, the common mode signal flows through the first via 302 to the second ground plane 300, and other common mode signals smoothly flow through the mushroom spike assembly 202 to the second ground plane 300, which creates more resonance points such that the transmission on the common mode return signal path is near zero, thereby achieving a wider rejection bandwidth. Meanwhile, since the differential signal transmission adopts the virtual reference ground, the structures of the first ground layer 200 and the second ground layer 300 do not affect the signal integrity thereof, and the integrity of the differential signal can be maintained. The first ground plane 200 is split into two parts to block common mode current that flows through the first via 302 to the second ground plane 300. The common mode current smoothly flows through the three mushroom pin assemblies 202 to the second ground plane 300. These structural variations result in more resonance points and bring the transmission on the common-mode return current path close to zero, thus achieving a wider rejection bandwidth, avoiding electromagnetic interference.

Specifically, with continued reference to fig. 4, fig. 4 includes a lateral cross-sectional view of the filtering structure of fig. 1, with the signal flow direction indicated by the dashed arrow attached, the common mode current enters from the right side of the first ground plane 200, i.e., along the right side of the first ground plate 201 in fig. 2, enters the second ground plane 300 along the right side first via 302, and then reaches the left side first ground plane through the left side second via 305, forming a complete current return path, i.e., through arrow a, b, c, d, e. Meanwhile, the mushroom spike assembly 202 has a common mode signal return path, and the common mode signal of the mushroom spike assembly 202 enters the second via 305 to reach the second ground layer 300, and the paths such as arrows f, h and g, h converge with the return path formed by arrow a, b, c, d, e and finally together reach the left first ground layer 200 through the left first via 302, thus forming a complete current return path. Under the cooperation of the two, more resonance points are generated, so that common mode noise is suppressed, and the electromagnetic interference problem can be better avoided.

In an embodiment, please continue to refer to fig. 1, the two microstrip lines 101 are parallel to each other and have the same size, i.e. the two coupling microstrip lines 101 are parallel to each other and have the same length and width, so that the same differential impedance between the two microstrip lines 101 can be maintained, and the electromagnetic interference problem can be further solved.

In one embodiment, with continued reference to FIG. 1, the number of mushroom spike assemblies 202 is a plurality, such as 3-6, and may be three, which may provide a better narrow stopband. The mushroom spike assembly 202 includes a metal strap 2021 and a metal cap 2022 protruding from a surface thereof, the metal strap 2021 being connected to the second via 305. Wherein the metal cover 2022 is coupled to the metal strip 2021 or connected by an inductor, which can filter out noise in a specified frequency range, i.e., by designing the shape and size of the metal strip 2021 and the metal cover 2022 so that it can select a specific operating frequency so that noise of other frequencies is blocked.

Additionally, the number of metal caps 2022 and second vias 305 corresponding to the same metal strap 2021 is two. The two metal covers 2022 constitute a double-layer mushroom filter structure so as to increase the frequency selectivity and performance of the filter, allowing finer control of the signal passing therethrough, while the constituted double-layer mushroom filter structure can also provide a wider operating frequency range and more complex filtering characteristics. And at the same time, on the same plane, the two microstrip lines 101 are located between the two metal covers 2022, i.e. the microstrip lines 101 pass between the two metal covers 2022 of the mushroom spike assemblies 202 of the plurality of groups, so that a wider bandwidth suppressing effect is generated.

In an embodiment, referring to fig. 1-4, the second ground metal plate 301 includes a ground frame 3011 and two third ground metal plates 3012 connected in the frame 3011, a slot 3013 is formed between the two third ground metal plates 3012, wherein opposite sides of the two third ground metal plates 3012 are respectively connected to two sides in the frame 3011, and other sides of the two third ground metal plates 3012 are not in contact with the frame 3011 and form a central symmetry, and two extension lines 304 connected to the same ground plate 303 are respectively connected to the two third ground metal plates 3012, and the first via 302 is connected to the frame 3011.

The third ground metal plate 3012 has a structure in which only one side is connected to the frame 3011 and the other side is not connected to the frame 3011, and thus forms a signal path as shown in fig. 4. Taking the direction of the second ground layer 300 as shown in fig. 3 as an example, the signal of any mushroom spike assembly 202 enters the ground plate 303 of the second ground layer 300 along the second through holes 305, because the number of the second through holes 305 is two, the signal of the second through hole 305 at the upper end flows to the third ground metal plate 3012 at the upper side and then to the frame 3011 at the right side, the signal of the second through hole 305 at the lower end flows to the third ground metal plate 3012 at the lower side and then to the frame 3011 at the left side, and then the signal can flow back along the first through holes 302 of the frame 3011. The number of first vias 302 on one first ground plate 201 may be 1-5, a larger number will be difficult to layout due to the limited size of the filter structure, and 3-5, such as 4, may be chosen for better suppression. In the case where the number of the first vias 302 is greater than 2 on the same first ground metal plate 201, two first vias 302 are connected to two corners on the same side of the frame 3011, respectively, among the first vias 302 of the same first ground metal plate 201, and the mushroom nail assembly 202 is located between two adjacent first vias 302 on the same plane.

In summary, the description will be given of the equivalent circuit element formed by the filtering structure taking 3 groups of mushroom spike assemblies 202, one group of mushroom spike assemblies 202 having two second through holes 305 and 8 first through holes 302 on both sides of the first grounding metal plate 201 as an example. As shown in fig. 5, fig. 5 includes a transverse cross-sectional view of the filter structure of fig. 1, with the equivalent components being framed for each portion. Specifically, the microstrip line 101 is equivalently coupled into five parts, which are equivalent coupling parts M1, M2, M3, M4, and M5, equivalent inductances L1, L2, L3, and L4 are formed between the equivalent coupling parts M1, M2, M3, M4, and M5, two ends of the equivalent inductances L1, L2, L3, and L4, and the first ground layer 200 and the mushroom nail assembly 202 form equivalent capacitances C1, C2, C3, C4, C5, C6, C7, and C8, the parts of the first via holes 302 on two sides connected to the second ground layer 300 form equivalent inductances L5 and L9, and the parts of the second via holes 305 connected to the second ground layer 300 form equivalent inductances L6, L7, and L8. In operation, the respective equivalent inductances, equivalent capacitances, and coupling portions of the microstrip line 101 exert equivalent characteristics, forming the operation procedure as in the above-described embodiment.

The multi-layer filtering structure is simple, is easy to inlay into the PCB, can effectively reduce signal noise in the high-density PCB, solves the problem of electromagnetic interference, and meets the quality control requirement of the high-speed PCB.

Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any adaptations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains.

Claims

1. A grounded filter structure for use in a PCB board, wherein the structure is multi-layered, the structure comprising from top to bottom:

a top layer, wherein the top layer is two mutually coupled microstrip lines;

2. A grounded filter structure for use in a PCB board according to claim 1, wherein two of said microstrip lines are parallel to each other and of equal size.

3. The ground filter structure for use in a PCB board of claim 1, wherein the number of mushroom spike assemblies is 3-6.

4. The ground filter structure of claim 1, wherein the mushroom spike assembly comprises a metal strap and a metal cap protruding from a surface thereof, the metal strap being connected to the second via.

5. The ground filter structure of claim 4, wherein the number of metal caps and second vias corresponding to the same metal strap is two.

6. A grounded filter structure for use in a PCB board according to claim 5, wherein two of said microstrip lines are located between two of said metal covers on the same plane.

7. A grounding filter structure for use in a PCB board according to claim 1, wherein the second grounding metal plate includes a grounding frame and two third grounding metal plates connected in the frame, the slots are formed between the two third grounding metal plates, wherein opposite sides of the two third grounding metal plates are respectively connected to both sides in the frame, and other sides of the two third grounding metal plates are not in contact with the frame and constitute a center symmetry, and two extension lines connected to the same grounding plate are respectively connected to the two third grounding metal plates, and the first via hole is connected to the frame.

8. The ground filter structure of claim 7, wherein the number of first vias on one of the first ground metal plates is 3-5.

9. A grounding filter structure for use in a PCB panel as in claim 8, wherein two of said first vias of a same said first grounding metal plate are connected to two corners of a same side of said frame, respectively.

10. A grounded filter structure for use in a PCB board as in claim 8, wherein said mushroom spike assembly is located between two adjacent said first vias on the same plane.