In the layout process, the method is the most refined, and the limitations are the highest. Although PCB engineers with over ten years of experience often think they may not have encountered every possible issue, their broad exposure to various challenges allows them to predict the consequences of certain design choices. They understand the potential problems that might arise from a particular layout, which leads to uncertainty in how to proceed. However, there are still skilled engineers who possess a strong, logical understanding, while also approaching their work with a bit of creativity.
To begin, let’s provide a basic overview. PCBs can be categorized by the number of layers, which include single-layer, double-layer, and multi-layer boards. Single-layer boards are now largely obsolete. Double-layer boards are commonly used in audio systems and are often the simpler, more basic designs found in mobile power amplifiers. Multi-layer boards, on the other hand, refer to those with four or more layers. Typically, these boards have a lower component density, and a four-layer configuration is often sufficient. From the perspective of vias, they can be categorized as through-hole vias, blind vias, and buried vias. A through-hole via connects the outermost layer to the internal layers, while a blind via connects the top or bottom layer to an inner layer without reaching the opposite side. A buried via, in contrast, connects only internal layers, with no connection to the outer layers.
The advantage is that the via’s reputation is not blocked at the end. Other layers can still be routed using this via’s reputation; the buried via, which connects the central layers and is hidden from the surface, remains invisible. The complete setup is illustrated in the figure below.
Before performing manual routing, use interactive routing to pre-manage the high-frequency lines. The input and output edges should not be adjacent or parallel to avoid signal reflections. If necessary, a ground wire can be added to block interference. The routing of two adjacent layers should ideally be perpendicular to each other, as parallel traces are more susceptible to parasitic coupling. The success of manual routing depends on meticulous planning. Routing rules can be set in advance, such as limiting the number of wire bends, vias, or routing steps. Typically, a “walk-through” routing approach is used, where short connections are made quickly, followed by optimization of routing paths using maze-like routing. In some cases, previously routed lines may be disconnected and re-routed to achieve the best overall wiring efficiency.
For organization, a key principle is to isolate signals and components as much as possible. For instance, low-speed traces should not be routed near high-speed traces. The most fundamental rule is to keep digital ground separate from analog ground. Digital ground, due to the high current generated by switching devices, exhibits significant transient currents, and therefore cannot be mixed with analog ground. A recommended layout might look like the diagram below.
1. **Wiring between Power and Ground:** A decoupling capacitor should be placed between the power supply and the ground. The power supply must be connected to the chip pin through these decoupling capacitors. The figure below shows several incorrect connection methods alongside the correct one. Decoupling capacitors serve two primary purposes: one is to supply high current to the chip during switching, and the other is to filter out power supply noise that could affect system stability.
2. **Widen Power and Ground Traces:** Power and ground traces should be as wide as possible. Ideally, the ground trace should be wider than the power trace, and their connection should follow this order: ground, power, and signal. A large copper area can be used as the ground plane, with unused regions connected to the ground. For multilayer boards, power, ground, digital circuits, and analog circuits are integrated efficiently.
Due to the high frequency of digital circuits and the sensitivity of analog circuits, signal lines should be routed as far away from sensitive analog components as possible. However, in all PCB designs, the ground plane is typically on the surface, and there should be only one ground node. Therefore, special care must be taken to handle the common ground between the digital and analog circuits within the PCB. While the digital and analog grounds are isolated within the board, they are connected at a single point where the PCB interfaces with external components (such as connectors). This common ground connection is crucial, and it must be managed to avoid interference between the two types of circuits. Proper isolation and grounding are determined by the system’s layout.
If you have any PCB manufacturing needs, please do not hesitate to contact me.Contact me
To begin, let’s provide a basic overview. PCBs can be categorized by the number of layers, which include single-layer, double-layer, and multi-layer boards. Single-layer boards are now largely obsolete. Double-layer boards are commonly used in audio systems and are often the simpler, more basic designs found in mobile power amplifiers. Multi-layer boards, on the other hand, refer to those with four or more layers. Typically, these boards have a lower component density, and a four-layer configuration is often sufficient. From the perspective of vias, they can be categorized as through-hole vias, blind vias, and buried vias. A through-hole via connects the outermost layer to the internal layers, while a blind via connects the top or bottom layer to an inner layer without reaching the opposite side. A buried via, in contrast, connects only internal layers, with no connection to the outer layers.
The advantage is that the via’s reputation is not blocked at the end. Other layers can still be routed using this via’s reputation; the buried via, which connects the central layers and is hidden from the surface, remains invisible. The complete setup is illustrated in the figure below.
Before performing manual routing, use interactive routing to pre-manage the high-frequency lines. The input and output edges should not be adjacent or parallel to avoid signal reflections. If necessary, a ground wire can be added to block interference. The routing of two adjacent layers should ideally be perpendicular to each other, as parallel traces are more susceptible to parasitic coupling. The success of manual routing depends on meticulous planning. Routing rules can be set in advance, such as limiting the number of wire bends, vias, or routing steps. Typically, a “walk-through” routing approach is used, where short connections are made quickly, followed by optimization of routing paths using maze-like routing. In some cases, previously routed lines may be disconnected and re-routed to achieve the best overall wiring efficiency.
For organization, a key principle is to isolate signals and components as much as possible. For instance, low-speed traces should not be routed near high-speed traces. The most fundamental rule is to keep digital ground separate from analog ground. Digital ground, due to the high current generated by switching devices, exhibits significant transient currents, and therefore cannot be mixed with analog ground. A recommended layout might look like the diagram below.
1. **Wiring between Power and Ground:** A decoupling capacitor should be placed between the power supply and the ground. The power supply must be connected to the chip pin through these decoupling capacitors. The figure below shows several incorrect connection methods alongside the correct one. Decoupling capacitors serve two primary purposes: one is to supply high current to the chip during switching, and the other is to filter out power supply noise that could affect system stability.
2. **Widen Power and Ground Traces:** Power and ground traces should be as wide as possible. Ideally, the ground trace should be wider than the power trace, and their connection should follow this order: ground, power, and signal. A large copper area can be used as the ground plane, with unused regions connected to the ground. For multilayer boards, power, ground, digital circuits, and analog circuits are integrated efficiently.
Due to the high frequency of digital circuits and the sensitivity of analog circuits, signal lines should be routed as far away from sensitive analog components as possible. However, in all PCB designs, the ground plane is typically on the surface, and there should be only one ground node. Therefore, special care must be taken to handle the common ground between the digital and analog circuits within the PCB. While the digital and analog grounds are isolated within the board, they are connected at a single point where the PCB interfaces with external components (such as connectors). This common ground connection is crucial, and it must be managed to avoid interference between the two types of circuits. Proper isolation and grounding are determined by the system’s layout.
If you have any PCB manufacturing needs, please do not hesitate to contact me.Contact me
