How to draw double-layer pcb board _ double-layer pcb board wiring rules (operational skills and case analysis)

Double-layer pcb means to draw wires on the top and bottom of a pcb board. The double panel solves the difficulty of wiring interleaving in a single panel (it can be conducted to the other side through the hole), that is, the wiring is provided on both the front and the back, the components can be soldered on the front side, or the reverse side, the double-layer circuit board There are components and wiring on both sides of the board. It is unquestionable that it is more difficult to design a double-layer PCB board. Let's analyze the wiring rules of the double-layer pcb board and share with you how to draw a double-layer pcb board.

How to draw a double-layer pcb board
For double-layer pcb boards, the wires on both sides must be used. It is necessary to have proper circuit connections between the two sides. The "bridge" between such circuits is called a via. The via hole is a small hole filled or coated with metal on the pcb, which can be connected to the wires on both sides. When using PROTEL to draw a double-sided pcb board, draw a wire connection component on the TopLayer (top layer), which is the top layer drawing board; select BottomLayer (bottom layer), draw the wire connection component on the bottom layer, and draw the board on the bottom layer. The above is the basis for drawing a double layer pcb.

Before drawing a double-layer pcb board, first determine the layout of the components, and firstly distribute the key crystal, crystal oscillator circuit, clock circuit, CPU and other signal lines when wiring. Be sure to follow the principle that the circulation area is as small as possible.

After the two-layer board is determined by the reasonable layout of the components, the power line of the ground-screen copy board is designed first, and then the important lines---sensitive lines, high-frequency lines, and general lines---low-frequency lines. The key leads preferably have separate power supplies, ground loops, and very short leads, so sometimes a ground wire is placed on the critical line next to the signal line to allow it to form a minimum working loop.

When drawing a double-layer PCB board, follow the layout principle of [first big, then small, first difficult and easy", that is, important unit circuits and core components should be prioritized. The layout should refer to the principle block diagram, according to the main board. The main components of the signal flow are regularly arranged.

The total connection is as short as possible, and the key signal line is the shortest; the high voltage and high current signals are completely separated from the low current and low voltage weak signals; the analog signal is separated from the digital signal; the high frequency signal is separated from the low frequency signal; and the high frequency component is separated. Be full.

It should be noted that the two double-layer boards have a ground plane on the lower layer of the board. This is designed so that engineers can quickly see the wiring when troubleshooting, which is often seen on the device manufacturer's demonstration and evaluation board. But a more typical approach is to lay a ground plane on the upper layer of the board to reduce the electromagnetic dry (emi).

Steps to draw a double-layer pcb board:

1, prepare the circuit schematic

2, create a new pcb file and load the component package library

3, planning the circuit board

4, load the network table and components

5, automatic placement of components

6, layout adjustment

7, network density analysis

8, wiring rules set

9, automatic wiring

10, manually adjust the wiring

How to draw double-layer pcb board _ double-layer pcb board wiring rules (operational skills and case analysis)

How to draw a double-layer pcb board case details
Commonly used EDA circuit software can design multi-layer PCB circuit boards. Although the methods are different, the principle is the same.

For PCB design, AD provides a detailed set of 10 different design rules, including wire placement, wire routing methods, component placement, routing rules, component movement, and signal integrity. According to these rules, Protel DXP performs automatic layout and automatic routing. To a large extent, the success of wiring and the quality of the wiring depend on the rationality of the design rules and on the user's design experience.

Different design rules can be used for specific circuits. If you are designing a dual panel, many rules can use the system default value. The system default value is the setting for wiring the dual panel.

Here to share with you a four-layer PCB setup steps, such as 8-layer boards and so on. Other versions of AD are similar to this.

First create a new PCB file, if you have your own project, then you can build it under your own project.

Select File-New-PCB

How to draw double-layer pcb board _ double-layer pcb board wiring rules (operational skills and case analysis)

You can see that the built PCB has only two layers, Top Layer and Bottom Layer. As shown below.

How to draw double-layer pcb board _ double-layer pcb board wiring rules (operational skills and case analysis)

Open cascading management. Design-Layer Stack Manager, enter the cascading management interface.

How to draw double-layer pcb board _ double-layer pcb board wiring rules (operational skills and case analysis)

It can be seen that there are currently only two layers of Top Layer and Bottom Layer. You can see the Add Layer option on the right.

How to draw double-layer pcb board _ double-layer pcb board wiring rules (operational skills and case analysis)

Click Add Layer twice to add two layers as shown below.

How to draw double-layer pcb board _ double-layer pcb board wiring rules (operational skills and case analysis)

Double-click the added layer name to modify the name. The following picture shows the modified content.

How to draw double-layer pcb board _ double-layer pcb board wiring rules (operational skills and case analysis)

After the modification, we can see that the four layers of the PCB board are set up, the GND and VCC layers are added, and the compiled schematic diagram can be used to draw the PCB diagram of the four-layer board.

How to draw double-layer pcb board _ double-layer pcb board wiring rules (operational skills and case analysis)

The operation skill of each layer is the same as that of the single panel, but it needs to be considered as a whole when designing.

Double-layer pcb board wiring rules
(1) Components are best placed on one side. If you need to place components on both sides, placing pin-type components on the Bottom Layer may cause the board to be difficult to place and not suitable for soldering. Therefore, it is best to place only the chip components on the Bottom Layer. Common component placement methods on the PCB of a computer graphics card. When laying on one side, it is only necessary to make a silk screen on one side of the board to reduce the cost.

(2) Reasonably arrange the position and orientation of the interface components. In general, the connector components that are connected to the circuit board and the outside (power, signal lines) are usually placed on the edge of the board, such as the serial port and the parallel port. It is placed in the center of the board, which is not conducive to wiring, and may not be connected due to obstruction of other components. Also pay attention to the direction of the interface so that the cable can be pulled out smoothly away from the board. After the interface is placed, the String (string) of the interface component should be used to clearly indicate the type of interface; for the power supply interface, the voltage level should be marked to prevent the board from burning due to wiring errors. (3) It is better to have a wide electrical isolation strip between the high voltage component and the low voltage component. Do not place components with widely different voltage levels, which is beneficial to electrical insulation and has great benefits for signal isolation and interference immunity. (4) Components with close electrical connections are best placed together. This is the modular layout idea.

(5) For components that are prone to noise, such as clock generators and crystal oscillators, the layout should be placed close to the clock input of the CPU. High-current circuits and switching circuits are also prone to noise. These components or modules should also be away from high-speed signal circuits such as logic control circuits and storage circuits. If possible, use control boards in conjunction with power boards to connect them with interfaces to improve The overall anti-interference ability and working reliability of the circuit board.

(6) Place decoupling capacitors and filter capacitors around the power supply and chip as much as possible. This is an important measure to improve the power quality of the board and improve the anti-interference ability. In practical applications, traces, pin connections, and wiring on printed circuit boards can cause large parasitic inductances, resulting in high-frequency ripple and glitch in power waveforms and signal waveforms, while in power and ground. Place a 0.1μF or larger capacitor to further improve power quality. For power conversion chips, or power supply inputs, it is best to place a 10μF decoupling capacitor to effectively filter out these high frequency ripples and glitches. If a chip capacitor is used on the board, the chip capacitor should be placed close to the component's power supply pin.

(7) The component number should be arranged close to the frame of the component, the size is uniform, the direction is neat, and it does not overlap with the components, vias and pads. The first pin of the component or connector indicates the direction; the positive and negative signs should be clearly marked on the PCB and must not be covered; power conversion components (such as DC/DC converter, linear converter power supply and switching power supply) There should be enough space for heat dissipation and installation space, and there should be enough welding space on the outside.

(8) The two-layer board ground line is designed to form a grid-like frame, that is, a plurality of parallel ground lines are arranged on one side of the printed board, and the other side is a vertical line of the board, and then metalized vias are used where they intersect. Connected (the via resistance is small).

(9) In order to consider that each IC chip should be provided with a ground line, a ground wire is often laid every 1 to 115 cm. Such a dense ground wire makes the signal loop area smaller, which is beneficial to reduce radiation. The design method of the ground network should be before the signal line, otherwise it is difficult to implement.

(10) Factors that need to be considered: electromagnetic compatibility, impedance matching at the beginning end, and clock synchronization.

(11) The high-speed line is best to go inside, and the top layer is easily affected by external temperature, humidity and air, and is not easy to stabilize. If you need to test, you can test the via lead. Don't have the illusion of flying and secant.

How to draw double-layer pcb board _ double-layer pcb board wiring rules (operational skills and case analysis)

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