The most comprehensive PCB wiring tutorial summary includes 14 PCB wiring principles and techniques.

1、 Adhere to manual wiring

Generally speaking, PCB design software includes the function of automatic routing, but in reality, no automatic routing can completely replace the skills, experience, and flexibility of PCB layout engineers.

In some cases, you can use automatic routing:

After placing all the components, you can use automatic routing to check your completion rate. If it is below 85%, you need to adjust the placement of your components.

During wiring, bottlenecks and other critical connection points may detach from cracks and can be identified using automatic routing functionality.

When you don’t know how to start wiring or encounter difficulties, you can use automatic wiring as a source of inspiration

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2、 Understand the manufacturer’s specifications

Before you start laying copper traces, take the time to ask your manufacturer if they have requirements for minimum trace width, trace spacing, and the number of PCB layers they can assemble.

By understanding this information in advance, you can set the routing width and spacing values in the design rules to avoid rewiring the entire PCB layout.

3、 Choose the appropriate wiring width

The geometric shape (thickness and width) of the wiring ensures that the circuit operates properly under all environmental and load conditions. The wiring of PCBs is used for transmitting electrical signals, therefore it must have a width compatible with the current passing through them.

PCB layout engineers must determine the minimum width of each wire to avoid the risk of overheating of the circuit board; This parameter directly affects the wiring process as it reduces the available space on the PCB.

If available space is not an issue, it is recommended to use wiring with a width greater than the minimum value to improve the thermal management and reliability of the circuit board. The wiring on the outer layer can achieve better heat exchange, so it may have a smaller width

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4、 Leave enough space between wiring and pads

It is crucial to reserve sufficient space between PCB wiring and solder pads (as shown below) to avoid short circuits during PCB manufacturing or assembly stages.

Generally speaking, it is recommended to leave appropriate gaps between each adjacent wire and pad, and there must always be sufficient space around them without wires or pads to avoid the risk of electric shock.

V PCB component placement

The placement of components determines the success of PCB design. To properly place components, it is necessary to fully understand their characteristics.

For example, thermosensitive electrolytic capacitors must be kept away from heating diodes, resistors, and inductors.

Here are some simple rules of thumb:

It is necessary to pay attention to components with multiple pins, as these components occupy a large amount of space.

Keep components placed in the same direction

Consider the functionality of each component and its relationship with other components before placement.

If the components have already been purchased, it is recommended to print the layout on paper according to the size and check if the components are suitable

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6、 Keep analog and digital wiring separate

The PCB wiring carrying digital signals, especially high-frequency signals, must be separated from the wiring carrying analog signals.

Separating the routing of analog and digital signals can reduce the possibility of mutual interference, thereby improving the stability and reliability of the circuit. When analog signals and digital signals are running on the same line, the following problems may occur:

Bringing crosstalk: The high-frequency components of digital signals can interfere with analog signals, leading to a decrease in the accuracy of analog signals.

Introducing noise: Digital signals themselves contain noise, which can also affect analog signals when they share the same line.

Lag or delay: There may be a certain delay or lag in the transmission process of digital signals, which may cause distortion of analog signals.

7、 Pay attention to the grounding layer

Each PCB requires at least one ground plane as it provides the same reference point for all wiring to measure voltage.

On the contrary, if you choose to wire each individual cable to ground instead of ground level, you will get countless different ground connections, each with its own resistance and voltage drop.

The simplest and most linear solution is to create a sturdy grounding layer, which can be the entire copper area, or even the entire layer in the case of multiple layers of boards.

Placing a ground plane under the routing of the transmission signal can help reduce its impedance and improve its noise resistance. It is recommended to place the power supply and ground plane at the innermost layer of the circuit board to maintain symmetry and center, which can prevent PCB bending.

8、 Leave enough space for wiring and installation hole

In the process of placing components, you should first place all plugins. Do you leave enough space between other components and all the wiring that connects them together?

If this is not done, there may be a risk of electric shock on the PCB, and relying on a solder mask layer as the sole insulator cannot guarantee safety.

When using plugins, remember to leave a circle of space outside the physical size of the installation hole to protect it from the influence of nearby components and wiring.

9、 Alternating wiring direction

If most of the routing of a layer follows a certain direction (such as horizontal), then priority should be given to the vertical direction (such as vertical) of its adjacent routing, which can reduce crosstalk between tracks.

In addition, the alternating wiring direction can also improve the stability of the signal. On the same direction of the wiring, signal reflection, attenuation, and distortion may occur due to the interaction of capacitance and inductance between signal lines.

It should be noted that alternating wiring directions may also increase the complexity and cost of wiring, so trade-offs and considerations need to be made in actual design.

10、 Avoiding capacitive coupling

In order to reduce capacitive coupling caused by wiring placed above and below a large grounding plane, it is necessary to ensure that the wiring assigned to the power supply and analog signals is arranged on a dedicated layer.

Reduce capacitance value: The smaller the capacitance value, the smaller the impact of capacitance coupling. Therefore, when designing circuits, it is possible to use capacitance values as small as possible to reduce the impact of capacitance coupling.

Increasing impedance: Increasing the impedance of relevant signals in the circuit can reduce the impact of capacitive coupling. For example, adding appropriate resistors to the signal input or output can minimize the capacitance coupling effect between the signal source and the load.

Using differential signal lines: Differential signal lines can to some extent reduce the impact of capacitive coupling. Due to the fact that differential signal lines are composed of two lines, signals are transmitted through the difference between the two lines, thus avoiding the capacitance coupling problem caused by a single line.

11、 Place heat dissipation holes and pads

Placing heat dissipation holes can improve the heat dissipation efficiency of PCB boards. Heat dissipation holes can introduce air flow into the interior of the PCB board and increase the surface area of the PCB board, making it easier for heat to dissipate. In addition, heat dissipation holes can also reduce air bubbles on the surface of PCB boards and gas accumulation during welding.

Placing solder pads can improve the reliability of PCB boards. In the design of solder pads, it is necessary to consider the welding process and quality, as well as the mechanical strength and stability between components and PCB boards. By optimizing the design and layout of solder pads, welding quality can be improved, welding defects can be reduced, thereby improving the reliability and performance of PCB boards

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12、 Grounding and power wiring

The wiring related to power and ground signals is thicker than the wiring carrying digital or analog signals, which allows them to carry larger currents. This can be easily identified through simple visual inspection, thereby reducing the possibility of connection errors between the signal and power lines.

A common rule is to use a 0.040 inch width for grounding and power wiring, and a 0.025 inch width for all other wiring.

If you don’t make the power and ground wires wider than the average width, a large amount of heat trying to flow through those narrow spaces may eventually burn the wires and damage the PCB board.

Compared to all signal wiring connected to integrated circuits, you can see that the width of the+5V power supply wiring is larger.

13、 Utilizing silk screen layers

The silk screen layer attached to the PCB board can be used to mark the information you want to mark.

Don’t use too much text to take up space.

There is no need to write down all available information, for example, there is absolutely no need to label resistance values.

If allowed, the text can be larger so that it can be printed more clearly.

Do not label the exposed copper solder pads to be soldered, as ink may hinder the flow of solder, leading to poor joints.

14、 Avoid 90 ° angles

Ordinary engineers should know that sharp angles and right angle curves can cause problems at high frequencies, leading to discontinuity and damaging signal integrity by increasing crosstalk, radiation, and reflection.

The wiring runs through the entire PCB and around the components, and the optimal angle is 45 °.