CN208241977U - A kind of pcb board - Google Patents

Abstract

The application discloses a PCB board, including a substrate and signal traces distributed on the substrate; the first signal trace in the signal trace has a signal trace branch segment, and the branch current of the signal trace branch segment The transmission direction is opposite to the main current transmission direction of the first signal wiring, so as to reduce the coupling interference of the first signal wiring to the second signal wiring in the signal wiring. The PCB wiring structure provided by this application is simple, convenient and easy to implement, and is conducive to miniaturization. By adding signal wiring branch segments to the first signal wiring, the influence of the first signal wiring on the second signal wiring can be effectively weakened. Coupling interference effectively enhances the ability to suppress crosstalk interference, thereby effectively ensuring the integrity of the transmitted signal.

Description

A PCB board

technical field

The present application relates to the technical field of integrated circuit design, in particular to a PCB board.

Background technique

With the rapid development of modern electronic technology, high component density and volume miniaturization have become the unified development trend of PCB (Printed circuit board, printed circuit board) of modern electronic equipment. At the same time, the transmission speed (frequency) of circuit signals is also improving.

For high-speed circuit systems, due to the high electromagnetic frequency of the transmission signal, the problem of crosstalk interference between lines, that is, coupling noise, is particularly significant, and in severe cases, it will greatly affect the integrity of the transmission signal.

Some methods for suppressing crosstalk interference are provided in the prior art, such as adopting serpentine lines for signal lines on the PCB board, adding protective lines for signal isolation, and increasing the distance between signal lines. However, on the one hand, these methods need to sacrifice additional wiring space, which is not conducive to the miniaturization of the PCB board; on the other hand, they cannot solve the problem of near-end crosstalk and far-end crosstalk at the same time, that is, the suppression of crosstalk interference limited ability.

It can be seen that it is a technical problem to be solved urgently by those skilled in the art to adopt a PCB board with a simple routing structure and easy miniaturization, and at the same time effectively enhance the ability to suppress crosstalk interference to improve signal transmission quality.

Utility model content

The purpose of the present application is to provide a PCB board with a simple routing structure and easy miniaturization, and at the same time effectively enhance the ability to suppress crosstalk interference to improve signal transmission quality.

In order to solve the above technical problems, the application provides a PCB board, including a substrate and signal traces distributed on the substrate; the first signal trace in the signal traces has a signal trace branch segment, so The branch current transmission direction of the branch segment of the signal wiring is opposite to the main current transmission direction of the first signal wiring, so as to reduce the distance between the first signal wiring and the second signal wiring in the signal wiring. coupling interference.

Optionally, the signal routing branch segment is located at a transmission end of the first signal routing.

Optionally, the signal routing branch segment is "L" shaped.

Optionally, the signal routing branch segment is "F" shaped.

Optionally, there are multiple signal routing branch segments.

Optionally, the signal routing branch segment and the second signal routing are located on the same side of the first signal routing.

The PCB board provided by the application includes a substrate and signal traces distributed on the substrate; the first signal trace in the signal traces has a signal trace branch segment, and the signal trace branch The branch current transmission direction of the segment is opposite to the main current transmission direction of the first signal wiring, so as to reduce the coupling interference of the first signal wiring to the second signal wiring in the signal wiring.

It can be seen that compared with the prior art, the PCB wiring structure provided by this application is simple, convenient and easy to implement, and is conducive to miniaturization. By adding a signal wiring branch segment for the first signal wiring, and making the signal wiring branch The branch current transmission direction of the circuit segment is roughly opposite to the main current transmission direction, which can effectively reduce the coupling interference of the main current to the second signal line, effectively enhance the ability to suppress crosstalk interference, and effectively ensure the integrity of the transmitted signal sex.

Description of drawings

In order to illustrate the prior art and the technical solutions in the embodiments of the present application more clearly, the following briefly introduces the drawings that need to be used in the description of the prior art and the embodiments of the present application. Of course, the following drawings related to the embodiments of the application describe only a part of the embodiments of the application, and those of ordinary skill in the art can obtain other The accompanying drawings, and other obtained drawings also belong to the protection scope of the present application.

FIG. 1 is a layout diagram of some signal traces on a PCB provided by the present application.

Detailed ways

The core of the present application is to provide a PCB board with a simple wiring structure and easy miniaturization, and at the same time effectively enhance the ability to suppress crosstalk interference to improve signal transmission quality.

In order to describe the technical solutions in the embodiments of the present application more clearly and completely, the technical solutions in the embodiments of the present application will be introduced below in conjunction with the drawings in the embodiments of the present application. Apparently, the described embodiments are only some of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of this application.

Generally, when the frequency of a digital logic circuit reaches or exceeds 45MHZ to 50MHZ, and the circuit operating above this frequency has already accounted for a certain amount (for example, 1/3) of the entire electronic system, it can be called a high-speed circuit. In essence, the reason why high-speed circuits need to adopt high-speed wiring technology different from ordinary circuits is that the frequency increase of high-speed signals leads to the rise time (rise time) Tr of the signal and the signal transmission time (line time) of the signal trace on the PCB. Delay) The size relationship of Tpd has changed.

Specifically, the transmission of the signal on the signal routing also takes a certain time, that is, the signal transmission time, which will be detrimental to the real-time performance of the signal processing. The signal arrives at the receiving end after a period of time from the driving end. If the signal transmission time Tpd is greater than 1/2 of the signal rise time Tr, then the reflected signal from the receiving end will reach the driving end after the signal changes state. If the reflected signal is very strong, superposition The waveform of the signal has the potential to change the current logic state of the signal. Therefore, it is generally required that the signal transmission time Tpd be as short as possible.

Generally, it can be considered that: if Tpd≤Tr/4, the signal falls in the safe area; if Tr/4≤Tpd≤Tr/2, the signal falls in the uncertain area; if Tpd≥Tr/2, the signal falls in the problem area. For high-speed signals, the signal rise time Tr is relatively small. If ordinary wiring technology is still used, the signal will fall into an uncertain area or a problem area. Therefore, a high-speed wiring method is required to reduce the signal transmission time Tpd.

However, crosstalk interference is still an important problem to be solved in high-speed circuits. Due to the high change frequency of high-frequency signals, the electromagnetic coupling problem between different signals, that is, the crosstalk interference problem is more significant, which affects the integrity of the transmitted signal. Crosstalk is further divided into far-end crosstalk and near-end crosstalk: far-end crosstalk is the signal transmitted by the sender of other signal traces in the same direction to the signal trace for the receiving end of this signal trace. crosstalk interference; near-end crosstalk occurs at the same end, which is the crosstalk of the signal transmitted by this signal trace from the sending end of other signal traces transmitted in the opposite direction to the receiving end of this signal trace interference. Near-end crosstalk is not smoothly attenuated by loop transmission, so its impact is much greater than far-end crosstalk.

In order to effectively suppress the problem of crosstalk interference, the application provides a PCB board, including a substrate and signal traces distributed on the substrate; the first signal trace in the signal trace has a signal trace branch segment, and the signal trace The branch current transmission direction of the line branch segment is opposite to the main current transmission direction of the first signal trace, so as to reduce the coupling interference of the first signal trace to the second signal trace in the signal trace.

Specifically, in this application, the first signal trace can be any signal trace on the PCB that needs to suppress crosstalk interference, that is, electromagnetic coupling, and the second signal trace can be any one that is compatible with The first signal trace is a signal trace in which crosstalk interference occurs. Of course, crosstalk interference generally occurs between two signal traces that are relatively close to each other.

The present application specifically reduces the crosstalk interference of the first signal routing to the second signal routing by setting signal routing branch segments for the first signal routing. The so-called signal routing branch segment is the same as the first signal routing body, which is the copper foil wiring in the PCB board, except that the branch current transmission direction on the signal routing branch segment is different from that of the first signal routing body. The transmission direction of the main body current is opposite, so the electromagnetic coupling of the main body current to the second signal line can be appropriately weakened, and the crosstalk interference caused by the first signal line to the second signal line can be effectively suppressed.

It is easy to understand that the direction and magnitude of the branch current in the signal routing branch segment depends on the routing shape and size of the signal routing branch segment, so it can be specifically designed by designing a reasonable The shape and size are used to control the branch current. In addition, the "opposite" of the branch current transmission direction and the main current transmission direction does not only include the absolute opposite of flipping 180°, but the general opposite, that is, as long as the reverse current component is included.

Therefore, this application only needs to simply add some small signal routing branch segments in the process of designing and manufacturing the PCB to solve the problem of crosstalk interference, which is not only convenient and simple, conducive to miniaturization, but also effective. Moreover, since the present application specifically targets the source of crosstalk interference, that is, the first signal routing for interference suppression, no matter whether the crosstalk occurs on the same side of the two ends of the signal transmission, that is, whether it is for near-end crosstalk Also for the far-end crosstalk, the present application has a good suppression effect, that is, the present application has a strong suppression ability for crosstalk interference.

Specifically, when setting the signal routing branch segment, the setting scheme of the signal routing branch segment can be verified and adjusted by calculating specific related formulas:

Among them, V _NEXT is the near-end crosstalk; V _FEXT is the far-end crosstalk; V _i is the input signal; L _m is the mutual inductance of the first signal trace; C _m is the mutual capacitance of the first signal trace; The inductance of a signal line; C is the capacitance of the first signal line; T _d is the signal transmission time of the first signal line; T _r is the rise time of the transmission signal.

For the first signal trace with added signal trace branch segments of a certain shape, size, quantity, etc., its self-inductance, self-capacitance, mutual inductance and mutual capacitance are determined, and then the above formula can be used to calculate the suppressed The size of near-end crosstalk and far-end crosstalk, and compare with the near-end crosstalk and far-end crosstalk when no signal routing branch segment is added, so as to verify or adjust the shape of the signal routing branch segment, parameters such as size.

In addition, the setup scheme of signal trace branch segments can be verified and adjusted with the help of eye diagrams. The eye diagram is a graph displayed by a series of digital signals accumulated on the oscilloscope. Connect the oscilloscope to the output terminal of the signal, and then adjust the scanning period of the oscilloscope so that the horizontal scanning period of the oscilloscope is synchronized with the period of the received symbol. At this time, the oscilloscope screen The pattern you see is called an eye diagram. The eye diagram is named for its shape like an eye. It contains a wealth of information. It can observe the influence of noise on the transmission signal, reflects the overall characteristics of the digital signal, and can most intuitively describe the quality and performance of high-speed digital signals.

The size of the "eye" opening of the eye diagram reflects the strength of crosstalk. The bigger the "eye" is, and the more correct the eye diagram is, the smaller the crosstalk is; otherwise, the bigger the crosstalk is. Among them, the eye height, the parameter of the eye diagram, is the size of the eye diagram on the vertical axis, and the eye width is the size of the eye diagram on the horizontal axis. The larger the eye height and eye width, the transmission of the signal The higher the quality.

It can be seen that the PCB board wiring structure provided by this application is simple, convenient and easy to implement, and is conducive to miniaturization. By adding signal wiring branch segments to the first signal wiring, and making the branch current transmission The direction is roughly opposite to the transmission direction of the main current, which can effectively weaken the electromagnetic coupling of the main current to the second signal line, effectively enhance the ability to suppress crosstalk interference, and then effectively ensure the integrity of the transmitted signal.

The PCB board provided by this application, on the basis of the above-mentioned embodiments:

As a preferred embodiment, the signal routing branch segment is located at the transmission end of the first signal routing.

Specifically, since the signal may continue to reflect during transmission and affect the quality of the signal finally output to the receiving end, this application recommends but is not limited to setting the signal routing branch segment at a position closer to the receiving end of the first signal routing, That is, the so-called transmission end.

As a preferred embodiment, the branch segment of the signal routing is in an "L" shape.

Specifically, the present application may specifically adopt an "L"-shaped signal routing branch segment. For details, reference may be made to FIG. 1 , which is a layout diagram of some signal traces on a PCB provided by the present application. Among them, 1 is the first signal trace; 2 is the second signal trace; 3 is the substrate of the PCB board; 1_a is the main body of the first signal trace 1; 1_b is the signal trace branch of the first signal trace 1 Segment; the arrow indicates the direction of the current flow in the first signal trace 1. The signal routing branch segment 1_b shown in FIG. 1 is specifically "L" shaped, and the extending direction of the branch extending from it is opposite to the main body current transmission direction on the main body 1_a.

When the first signal trace shown in Figure 1 is used, the eye diagram of the signal transmitted on the second signal trace can be obtained through testing. The corresponding eye height and eye width are 140mV and 316ps respectively, which are higher than those without The eye height (114mV) and eye width (294ps) of the signal routing branch segment.

As a preferred embodiment, the branch segment of the signal routing is in the shape of an "F".

Specifically, an "F"-shaped signal trace branch segment can also be used to increase the sum of branch currents, thereby increasing the suppression effect on the electromagnetic coupling between the main body current and the second signal trace. Of course, those skilled in the art can also choose signal routing branch segments of other shapes according to actual application conditions, which is not limited in this application.

As a preferred embodiment, there are multiple signal routing branch segments.

It is easy to understand that the suppression effect on electromagnetic coupling can also be increased by increasing the number of signal routing branch segments, which can be designed and implemented by those skilled in the art.

As a preferred embodiment, the signal routing branch segment and the second signal routing are located on the same side of the first signal routing.

It is easy to understand that when the signal routing branch segment is arranged on the same side of the second signal routing relative to the first signal routing, the suppression effect obtained is greater than that of the signal routing branch segment and the second signal routing. The suppression effect when the wires are arranged on both sides of the first signal trace respectively. Therefore, the present application recommends but is not limited to arranging the signal trace branch segment and the second signal trace on the same side of the first signal trace.

Each embodiment in the present application is described in a progressive manner, each embodiment focuses on the differences from other embodiments, and the same and similar parts of the various embodiments can be referred to each other. As for the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and for the related information, please refer to the description of the method part.

It should also be noted that in this application, relative terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between such entities or operations. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or device. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

The technical solution provided by the present application has been introduced in detail above. In this paper, specific examples are used to illustrate the principles and implementation methods of the present application, and the descriptions of the above embodiments are only used to help understand the methods and core ideas of the present application. It should be pointed out that those skilled in the art can make some improvements and modifications to the application without departing from the principles of the application, and these improvements and modifications also fall within the protection scope of the claims of the application.

Claims (6)

1. A PCB board, comprising a substrate and signal traces distributed on the substrate; it is characterized in that, the first signal trace in the signal trace has a signal trace branch segment, and the signal trace The branch current transmission direction of the line branch segment is opposite to the main current transmission direction of the first signal trace, so as to reduce the coupling interference of the first signal trace to the second signal trace in the signal trace . 2 . The PCB board according to claim 1 , wherein the signal routing branch segment is located at the transmission end of the first signal routing. 3 . 3. The PCB board according to claim 2, characterized in that, the signal routing branch segment is "L" shaped. 4. The PCB board according to claim 2, characterized in that, the signal routing branch segment is "F" shaped. 5. The PCB board according to claim 2, characterized in that, the number of the signal routing branch segments is multiple. 6. The PCB board according to any one of claims 1 to 5, wherein the branch segment of the signal trace and the second signal trace are located on the same side of the first signal trace.