General Principles of Component Routing

PCB component routing is a crucial stage in circuit design, significantly influencing the performance, stability, and cost of production. A well-planned layout not only minimizes trace length and signal delay but also reduces electromagnetic interference and enhances the board's resistance to noise. Moreover, it contributes to better thermal management, helping to prevent overheating issues on the board. During the routing process, both electrical and mechanical considerations must be taken into account, along with manufacturing constraints.

1. Spacing between different network lines depends on factors like electrical insulation, manufacturing capabilities, and component size. It’s important to ensure that spacing settings align with what the manufacturer can handle. Electrical insulation becomes particularly critical when there are large voltage differences between components or circuits, especially in mixed-voltage designs where safety clearance must be strictly maintained.
2. The routing corners should be chosen carefully to improve manufacturability and aesthetics. Common options include 45°, 90°, and arc-shaped turns, with sharp angles generally avoided. The connection between the wire and the pad should be smooth to avoid sharp points. When a wire runs between two pads without connecting to them, it should maintain an equal and maximum distance from both. Similarly, the spacing between wires should be uniform and as wide as possible.
3. Determining the trace width is essential for handling current flow and minimizing interference. Wider traces are typically used for power lines compared to signal lines. To stabilize the ground potential and reduce the impact of ground current fluctuations, the ground line should also be wider. Within acceptable board density limits, using the widest possible traces helps reduce impedance and improves overall performance. For power and ground lines, increasing their width is recommended if space allows, with a minimum width of 50 mils commonly required.
4. Interference and electromagnetic shielding are key concerns in PCB design. Trace interference can come from adjacent signals, power lines, and crosstalk. Proper layout and grounding techniques help minimize these issues and enhance the board’s electromagnetic compatibility (EMC). For high-frequency or critical signals, such as clock lines, wider traces are preferred. Shielding can also be applied by surrounding the signal line with a ground trace, acting as a protective layer that isolates the signal from other nearby lines.
5. High-frequency or critical signal lines, such as clock lines, benefit from wider traces to reduce signal degradation. In addition, enclosing the signal with a ground trace forms a shield, effectively isolating it from other signals and improving signal integrity.
6. A single via introduces approximately 10pF of parasitic capacitance, which can be problematic in high-speed circuits. Too many vias can also weaken the board’s mechanical strength. Therefore, it’s best to use as few vias as possible during routing. When using through-hole vias, it’s common to replace them with pads, as pads are guaranteed to be fully drilled during manufacturing, ensuring reliability.

These are general guidelines for PCB routing, but in practice, the process remains highly flexible. Each project may require unique adjustments based on specific design needs. As a result, while these principles serve as valuable references, real-world application and testing remain the ultimate measures of success.