Classification of PCB Traces
Printed Circuit Board (PCB) traces can be categorized based on functionality, structure, material, manufacturing process, and other characteristics. Below are common classification methods:

I. By Function

1. Power Lines

• Transmit high current or voltage, typically wider to reduce resistance and heat.

• Examples: CPU power lines on motherboards, output lines of power modules.

2. Signal Lines

• Transmit low-current signals (e.g., digital, analog), narrower in width.

• Divided into high-speed signal lines (e.g., USB, HDMI) and low-speed signal lines (e.g., button control signals).

3. Ground Lines

• Provide reference potential for circuits, often using large-area copper pours to reduce impedance and electromagnetic interference (EMI).

• Common types: single-point grounding, multi-point grounding, hybrid grounding.

4. Differential Pairs

• Paired traces with equal length and width for transmitting differential signals, offering strong noise immunity.

• Applications: USB, Ethernet, PCIe, and other high-speed interfaces.

II. By Layer Structure

1. Single-Layer PCB

• One conductive layer, simple design, low cost; used in low-complexity circuits (e.g., toys, basic appliances).

2. Double-Layer PCB

• Conductive layers on both sides, connected by vias; suitable for medium-complexity circuits (e.g., home appliance control boards).

3. Multi-Layer PCB

• Four or more layers with internal power and ground planes; used for high-density, high-speed designs (e.g., smartphones, computer motherboards).

III. By Material and Process

1. Rigid PCB

• FR-4 (glass-reinforced epoxy) substrate; widely used in consumer electronics and industrial equipment.

2. Flexible PCB (Flex PCB)

• Polyimide (PI) substrate; bendable for wearables, camera modules, etc.

3. High-Frequency PCB

• Special materials (e.g., Rogers RO4000, PTFE); used in 5G communications, radar systems, and high-frequency applications.

4. Metal Core PCB (MCPCB)

• Aluminum or copper substrate for superior heat dissipation; common in LED lighting and power modules.

5. High-Density Interconnect PCB (HDI PCB)

• Uses microvias and buried vias for dense routing; found in smartphones, drones, etc.

IV. By Special Design Requirements

1. Impedance-Controlled Traces

• Precisely calculated trace width, spacing, and dielectric thickness to match specific impedance (e.g., 50Ω, 100Ω); critical for RF and high-speed signals.

2. Shielded Traces

• Surrounded by ground planes or guard rings to minimize crosstalk; used in analog circuits and sensitive signals.

3. Antenna Traces

• Designed for wireless communication, optimizing radiation efficiency and frequency matching (e.g., Wi-Fi, Bluetooth antennas).

4. Power Planes

• Full-layer copper in multi-layer PCBs for uniform power distribution and reduced voltage fluctuations.

V. By Application Scenarios

Industry

Typical Trace Types

Summary

PCB trace classification depends on design requirements:

• High-speed signals require impedance matching and length matching.

• High-power circuits demand wider traces and thermal management.

• High-frequency applications need low-loss materials.
  Selecting appropriate trace types and processes is key to ensuring circuit performance and reliability!