I. Design Preparation

Schematic Design

Carefully plan the circuit connection relationships to ensure that the signal paths meet the functional requirements.

Component Placement

Prioritize Key Components: Place key components such as microprocessors and FPGAs close to relevant connectors and interfaces to shorten signal transmission paths and reduce latency. For example, in a computer motherboard design, the CPU chip should be close to the memory slots and bus interfaces.

Reduce Crosstalk: Avoid placing sensitive components (such as high - gain amplifiers) near high - speed signals or high - power circuits. For instance, the pre - amplifier in an audio circuit should be kept away from high - speed USB interface lines.

Netlist Generation

Generate a netlist from the schematic diagram, accurately recording all electrical connection information, which serves as the basis for subsequent routing.

Layer Stack - up Design

Determine the Number of Layers: Decide the number of layers according to the design complexity and performance requirements. For example, a graphics card PCB for high - speed data transmission may require 8 - 10 layers, while a simple consumer electronics device PCB may only need 4 - 6 layers.

Define Layer Functions: Clearly identify signal layers, power planes, and ground planes. The power plane provides a stable power supply for components, and the ground plane provides a reference potential for signals, reducing electromagnetic interference.

II. Signal Layer Routing

Principles of Signal Routing

Shortest Path Principle: Route signals along the shortest path to reduce signal transmission delay and attenuation. For example, clock signal routing should be as short as possible to ensure timing accuracy.

Impedance Control: Maintain consistent trace width and spacing to achieve controlled impedance. Common characteristic impedances are 50Ω (for high - speed digital signals) and 75Ω (for video signals).

Avoid Acute Angles: Replace 90 - degree corners with 45 - degree angles to reduce signal reflection. Because 90 - degree corners can cause a sudden change in the characteristic impedance of the signal transmission line, resulting in reflection.

III. Power and Ground Plane Routing

Dedicated Planes

Allocate an entire layer to power and ground, providing a stable reference voltage and return path for components. For example, in a multi - layer PCB, there are usually dedicated VCC power planes and GND ground planes.

Decoupling Capacitors Placement

Place decoupling capacitors near the power pins to filter out power noise and stabilize the voltage. Generally, high - frequency decoupling capacitors are placed close to the chip power pins, and low - frequency decoupling capacitors are placed a bit farther away.

IV. Differential Pair Routing

This is often used for high - speed signals to reduce noise and crosstalk.

Equal Length Traces

Ensure that the two traces in a differential pair have the same length to maintain signal timing. For example, for the differential signal pairs of an Ethernet interface, the length difference needs to be controlled within a very small range.

Consistent Spacing

Keep the spacing between the traces constant to control impedance.

V. Via Placement

Vias are used to connect traces on different layers.

Minimize Via Usage

Minimize the number of vias as much as possible to reduce interference with the signal path. Since vias introduce parasitic capacitance and inductance.

Strategic Placement

Arrange via positions reasonably to optimize signal flow and manufacturability. For example, avoid placing a large number of vias densely in areas with dense signals.