CN113993281B - A PCB differential via design method and PCB design method - Google Patents

Abstract

The present invention provides a PCB differential via design method and a PCB design method, comprising: dividing the same-layer differential via combination into a first pair of holes and a second pair of holes, each of the first pair of holes and the second pair of holes includes two Via hole, set the internal via hole spacing of the first pair of holes and the second pair of holes; the connecting line of the center of the first pair of holes and the axis of the differential signal pin form an angle of 45°; locate the center of the first pair of holes The vertical bisector of the connection line, and according to the set distance between the first pair of holes and the second pair of holes, create the second pair of holes on the vertical bisector so that the center connection line of the second pair of holes is perpendicular to the The bisectors coincide. The invention improves the design method of the differential vias, and by changing the punching mode of the differential vias at the gold fingers, the crosstalk between high-speed signals is optimized, the integrity of the signals is improved, and the transmission quality of the high-speed signals is improved.

Description

A PCB differential via design method and PCB design method

technical field

The invention belongs to the technical field of layout design, and in particular relates to a PCB differential via design method and a PCB design method.

Background technique

With the development of electronic technology and the increase of signal rate, people have put forward higher requirements for the performance of the signal. In the process of research and development, R&D designers need to consider and deal with many problems in the PCB design process more carefully, so as to Pursue the minimization of cost on the basis of performance optimization.

In a high-speed printed circuit board (PCB), vias have long been criticized for degrading signal integrity performance. However, the use of vias is unavoidable. On a standard PCB, components are placed on the top layer, while differential pairs are traced on the inner layers. Inner layers have lower electromagnetic radiation and pair-to-pair crosstalk. Vias must be used to connect components on the plane of the PCB to the inner layers. In the existing PCB design process, when designing differential vias for devices such as gold fingers or connectors with high-speed differential lines, parallel hole punching is usually used. Such a via design method takes up a relatively large space, and signals interfere with each other in the horizontal direction. When the signal rate becomes higher, the transmission quality of high-speed signals will decrease. The horizontal, horizontal and vertical arrangement of the differential holes in the prior art occupies a relatively large space, and in the horizontal direction, there will be a large crosstalk between signals, which is not conducive to the transmission of high-speed signals. And it is usually necessary to dig the antipad in the inner layer. Due to space constraints, the 10-degree trace of the differential signal is very easy to be very close to the edge of the antipad, and it is not even possible to refer to the complete GND plane, resulting in cross-segmentation problems.

Contents of the invention

In view of the above-mentioned shortcomings of the prior art, the present invention provides a PCB differential via design method and a PCB design method to solve the above-mentioned technical problems.

The present invention provides a PCB differential via design method, comprising:

Divide the combination of differential vias on the same layer into the first pair of holes and the second pair of holes. Both the first pair of holes and the second pair of holes include two vias. Set the internal vias of the first pair of holes and the second pair of holes spacing;

The center connection line of the first pair of holes forms an included angle of 45° with the axis of the differential signal pin;

Locate the vertical bisector of the center connection line of the first pair of holes, and create the second pair of holes on the vertical bisector according to the set distance between the first pair of holes and the second pair of holes so that the second pair of holes The center connecting line coincides with the perpendicular bisector.

Further, the method also includes:

According to the set minimum center distance between the ground via and the differential via, multiple ground vias are created based on the principle that two differential vias share one ground via preferentially.

Further, the method also includes:

If there are two layers of differential via combinations, establish a coordinate system with the center point of the leftmost pin of a group of differential signal pins as the origin;

Create the first layer of differential signal via combinations on the coordinate system, wherein the via coordinates of the first layer of differential signal via combinations are respectively Among them, a is the via hole spacing in the pair of holes, b is a set constant, and c is the minimum distance between the center connection line of the first pair of holes and the center of the second pair of holes in the combination of differential vias in the same layer;

Create a second-layer differential signal via combination on the coordinate system, wherein the via coordinates of the second-layer differential signal via combination are respectively Where a is the via hole spacing in the pair of holes, b is a set constant, c is the minimum distance between the center connection line of the first pair of holes and the center of the second pair of holes in the combination of differential vias on the same layer, and d is the ground wire pass The minimum distance between the center of a hole and a differential via.

Further, the connection lines between the differential vias and the differential pins are generated according to the set minimum distance between the traces and the via holes and the set minimum spacing between the traces.

Further, the via hole pitch a in the pair of holes is set to be 30 mils.

Further, set the minimum distance c between the center connection line of the first pair of holes and the center of the second pair of holes in the combination of differential vias on the same layer as

Further, the first-layer differential signal via combination is a TX signal via combination, and the second-layer differential signal via combination is an RX signal via combination.

Further, simulate and analyze the differential via combination to obtain signal contamination, and verify the differential via combination scheme.

The present invention also provides a PCB design method, which uses the above PCB differential via design method to design the differential vias of the PCB.

The beneficial effect of the present invention is that the PCB differential via design method and the PCB design method provided by the present invention divide the same-layer differential vias into the first pair of holes and the second pair of holes, and the first pair of holes and the second pair of holes Each hole includes two via holes, set the internal via hole spacing of the first pair of holes and the second pair of holes; make the center connection line of the first pair of holes and the axis of the differential signal pin form an angle of 45°; locate the first The vertical bisector of the center connection line of the pair of holes, and according to the set distance between the first pair of holes and the second pair of holes, create a second pair of holes on the vertical bisector so that the center connection line of the second pair of holes coincides with the perpendicular bisector. The invention improves the design method of the differential vias, and by changing the punching mode of the differential vias at the gold fingers, the crosstalk between high-speed signals is optimized, the integrity of the signals is improved, and the transmission quality of the high-speed signals is improved. The design method of differential vias to reduce crosstalk saves more space in PCB design. Moreover, due to the short routing distance, the uncoupling length of DP and DN is short, and the wiring space is sufficient, thereby avoiding the problem of cross-segmentation.

In addition, the design principle of the present invention is reliable, the structure is simple, and has very wide application prospects.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, In other words, other drawings can also be obtained from these drawings on the premise of not paying creative work.

FIG. 1 is an exemplary flow chart of a method for designing differential via holes in a PCB according to an embodiment of the present application.

FIG. 2 is an exemplary schematic diagram of a PCB differential via design method according to an embodiment of the present application.

FIG. 3 is an exemplary effect diagram of a PCB differential via design method according to an embodiment of the present application.

Wherein, 1. the first pair of holes; 2. the second pair of holes; 3. the ground via hole; 4. the differential signal pin; 5. the ground signal pin.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described The embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

In the description of the present invention, it should be understood that the terms "first", "second" and so on are only used for descriptive purposes, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features . Thus, a feature defined as "first", "second", etc. may expressly or implicitly include one or more of that feature. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it may be mechanically connected or electrically connected; it may be directly connected or indirectly connected through an intermediary, and it may be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention based on specific situations.

Layout design is a mask design based on the requirements of microelectronics technology circuits and their manufacturing processes. Layout design generally includes two interrelated design steps of layout (placement of circuit components and devices) and wiring (interconnection of circuit components and devices). The main task of layout design is to complete the arrangement of circuit components and devices and the necessary interconnection between components according to the given manufacturing process conditions, so as to ensure that: the chip has a high layout density; the interconnection conforms to the electrical performance of components and devices Requirements (such as load capacity, etc.); the influence of parasitic effects generated by interconnection (such as wiring parasitic capacitance, etc.) is within the allowable range of design requirements and considers design and manufacturing cycle, design correctness verification, and design costs.

PCB (Printed Circuit Board), the Chinese name is printed circuit board, also known as printed circuit board, is an important electronic component, a support for electronic components, and a carrier for electrical interconnection of electronic components. Because it is made using electronic printing, it is called a "printed" circuit board. PCB (printed circuit board) is a printed circuit board, referred to as a printed board, and is one of the important components of the electronics industry. Almost every kind of electronic equipment, ranging from electronic watches and calculators to computers, communication electronic equipment, and military weapon systems, as long as there are electronic components such as integrated circuits, in order to make the electrical interconnection between various components, printed circuit boards must be used. plate. The printed circuit board is composed of an insulating base plate, connecting wires and pads for assembling and welding electronic components, and has the dual functions of a conductive line and an insulating base plate. It can replace complex wiring and realize the electrical connection between components in the circuit, which not only simplifies the assembly and welding of electronic products, reduces the workload of wiring in traditional methods, and greatly reduces the labor intensity of workers; it also reduces the size of the whole machine. Volume, reduce product cost, improve the quality and reliability of electronic equipment. The printed circuit board has good product consistency, and it can adopt a standardized design, which is conducive to the realization of mechanization and automation in the production process. At the same time, the entire printed circuit board that has been assembled and debugged can be used as an independent spare part, which is convenient for the exchange and maintenance of the whole machine. At present, printed circuit boards have been widely used in the production and manufacture of electronic products. The earliest printed circuit boards were paper-based copper-clad printed boards. Since the advent of semiconductor transistors in the 1950s, the demand for printed boards has risen dramatically. Especially with the rapid development and wide application of integrated circuits, the volume of electronic equipment is getting smaller and smaller, and the density and difficulty of circuit wiring are getting higher and higher, which requires continuous updating of printed boards. At present, the variety of printed boards has developed from single-sided boards to double-sided boards, multi-layer boards and flexible boards; the structure and quality have also developed to ultra-high density, miniaturization and high reliability; new design methods, design supplies and Board-making materials and board-making processes continue to emerge. In recent years, various computer-aided design (CAD) printed circuit board application software has been popularized and promoted in the industry. In specialized printed circuit board manufacturers, mechanized and automated production has completely replaced manual operations.

The present invention will be described in detail below with reference to the accompanying drawings and examples.

Example 1

Please refer to FIG. 1 and FIG. 2. This embodiment provides a PCB differential via design method, including the following steps:

S1. Divide the combination of differential vias on the same layer into the first pair of holes 1 and the second pair of holes 2. Both the first pair of holes 1 and the second pair of holes 2 include two vias. Set the first pair of holes 1 and the second pair of holes. Internal via spacing of two pairs of holes 2;

S2. The connecting line of the center of the first pair of holes 1 and the axis of the differential signal pin 4 form an angle of 45°;

S3, locate the perpendicular bisector of the connecting line of the center of the first pair of holes 1, and create the second pair of holes 2 on the perpendicular bisector according to the set distance between the first pair of holes 1 and the second pair of holes 2 to Make the connecting line of the centers of the second pair of holes 2 coincide with the perpendicular bisector.

Example 2

This embodiment provides a PCB differential via design method, please refer to Figure 3, including:

If there is a combination of two layers of differential vias, taking the differential vias of the golden finger as an example, a coordinate system is established with the center point of the leftmost pin of a group of differential signal pins 4 as the origin.

Create the first layer of differential signal via combinations (TX differential vias) on the coordinate system, where the via coordinates of the first layer of differential signal via combinations are respectively Among them, a is the via hole spacing in the pair of holes, b is a set constant, and c is the minimum distance between the center connection line of the first pair of holes 1 and the center of the second pair of holes 2 in the combination of differential vias in the same layer;

Create a second-layer differential signal via combination (RX differential via) on the coordinate system, where the via coordinates of the second-layer differential signal via combination are respectively Where a is the via hole spacing in the pair of holes, b is a set constant, c is the minimum distance between the center connection line of the first pair of holes 1 and the center of the second pair of holes 2 in the same layer differential via combination, and d is the ground The minimum distance between the center of the line via 3 and the differential via.

Among them, the via spacing a in the pair of holes is set to 30 mils; the minimum distance c between the center connection line of the first pair of holes 1 and the center of the second pair of holes 2 in the combination of differential vias in the same layer is set as That is, the minimum distance between the center of the first pair of holes 1 and the center of the second pair of holes 2 is 40 mils.

The connection lines between each differential via hole and the differential pin are generated according to the set minimum distance between the trace and the via hole and the set minimum distance between the traces.

After generating all the differential vias and the connection lines between the differential vias and the differential pins, according to the set minimum center distance between the ground via 3 and the differential via, two differential vias share a ground via according to priority 3 The principle of creating multiple ground vias 3. Under this principle, the number of ground wire via holes 3 and the distribution area of the ground wire via holes 3 can be reduced as much as possible, thereby achieving the effect of saving PCB board space. Finally, a connection line between the ground via hole 3 and the ground signal pin 5 is generated.

As shown in Figure 3, the lower two pairs of differential vias A and B are for TX signals, the upper two pairs of differential vias C and D are for RX signals, and the rest of the vias are GND return holes. The center distance between differential vias DP and DN is 30mils, differential pair via B is on the vertical bisector of differential pair via A, and the center distance from differential pair via B to differential pair via A is 40mils. Similarly, the differential pair via D is on the vertical bisector of the differential pair via C, and the center distance from the differential pair via D to the differential pair via C is 40mils.

Carry out simulation analysis on the ordinary differential via parallel design method at the gold finger and the differential via design method to reduce crosstalk, and check the signal crosstalk. The signal crosstalk of the ordinary differential via parallel design method is about -46dB@ 16GHz, the signal crosstalk of the differential via design method to reduce crosstalk is about -39dB@16GHz. From the perspective of crosstalk, the design method of differential vias to reduce crosstalk is more optimal.

From the perspective of PCB design space, the space occupied by the common differential via parallel design at the gold finger is 5.35mm from the pin of the gold finger to the via at the top, while the differential via design of this embodiment The space occupied by the method is 4.15mm from the pin of the golden finger to the via at the top. The space for PCB layout and wiring is saved.

For the ordinary parallel design method of differential vias at the gold finger, it is easy to cause the 10-degree reference Antipad cross-segmentation problem due to insufficient space; for the design method of this embodiment, due to the short routing distance, DP and DN are not coupled The length is short and the wiring space is sufficient, thereby avoiding the phenomenon of cross-segmentation.

Although the present invention has been described in detail in conjunction with preferred embodiments with reference to the accompanying drawings, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those skilled in the art can make various equivalent modifications or replacements to the embodiments of the present invention, and these modifications or replacements should be within the scope of the present invention/any Those skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present invention, and all should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (8)

1. The PCB differential via design method is characterized by comprising the following steps:

dividing the same-layer differential via hole combination into a first pair of holes and a second pair of holes, wherein the first pair of holes and the second pair of holes comprise two via holes, and setting the inner via hole spacing of the first pair of holes and the second pair of holes;

the center connecting line of the first pair of holes forms an included angle of 45 degrees with the axis of the differential signal pin;

positioning a perpendicular bisector of a circle center connecting line of the first pair of holes, and creating a second pair of holes on the perpendicular bisector according to the set distance between the first pair of holes and the second pair of holes so that the circle center connecting line of the second pair of holes coincides with the perpendicular bisector;

the method further comprises the steps of:

if two layers of differential via combinations exist, a coordinate system is established by taking the center point of the leftmost pin of one group of differential signal pins as an origin;

creating a first layer of differential signal via combinations on the coordinate system, wherein the via coordinates of the first layer of differential signal via combinations are respectively as follows Wherein a is the distance between the holes in the pair of holes, b is a set constant, c is the minimum distance between the center of the circle of the first pair of hole center connecting lines and the center of the circle of the second pair of holes combined by the same-layer differential holes;

creating a second-layer differential signal via combination on the coordinate system, wherein via coordinates of the second-layer differential signal via combination are respectively as follows Wherein a is the distance between the through holes in the pair of holes, b is a set constant, c is the minimum distance between the center of the circle of the first pair of hole center connecting lines and the center of the circle of the second pair of holes combined by the same-layer differential through holes, and d is the minimum center distance between the ground wire through holes and the differential through holes.

2. The method according to claim 1, wherein the method further comprises:

and creating a plurality of ground wire through holes according to the set minimum circle center distance between the ground wire through holes and the differential through holes and the principle that two differential through holes share one ground wire through hole.

3. The method of claim 1, wherein the connection lines of each differential via and differential pin are generated based on a set minimum distance between the traces and the vias and a set minimum spacing between the traces.

4. The method of claim 1 wherein the via pitch a in the pair of holes is set to 30mils.

5. The method of claim 1, wherein the minimum distance c between the center of the first pair of hole connecting lines and the center of the second pair of holes of the same-layer differential via combination is set as

6. The method of claim 1, wherein the first layer of differential signal via combinations are TX signal via combinations and the second layer of differential signal via combinations are RX signal via combinations.

7. The method of claim 1, wherein the differential via combination is subjected to a simulation analysis to obtain a signal infection, and wherein the differential via combination scheme is verified.

8. A method of designing a PCB, characterized in that the method is used to design a differential via of a PCB using the method of any of claims 1-7.