PCB Trace Guide: From Basics to In-Depth

When we observe various stages of human history, we can easily recognize that networks have always played a crucial role. Whether it’s the modern Internet of Things, the past internet, or ancient water networks, these systems connect various parts, creating a vast and intricate whole. Just as when we examine the surface of a printed circuit board, we can also discover the presence of these networks. The complexity of these carefully designed network patterns in the PCB field varies with the circuit density. These patterns have a specific name in the PCB domain: PCB Trace.

pcb trace

What is a PCB Trace and Its Function

A printed circuit board plays a crucial role in supporting electronic components and providing electrical connections. When a circuit is powered, current flows through the connection points of each component, driving their operation. This necessitates the existence of a reliable current path, which is the key function of PCB traces. Trace design is closely related to circuit performance, and factors such as trace width, thickness, and resistance need careful consideration.

During the PCB design and layout phase, designers select and arrange components based on the circuit’s functional requirements and then use traces to connect them. In the manufacturing stage of PCB production, manufacturers apply specific materials to the PCB surface, and then the trace design pattern is exposed on the copper layer through a photolithography process. Subsequently, the chemical etching process removes unwanted copper material, leaving precise traces. These highly conductive traces are supported by an insulating substrate, typically including elements such as wiring, copper conductors, and fuses.

PCB Trace Width

Trace width refers to the width of the conductive copper traces on the surface of a PCB. Setting these parameters is crucial for ensuring the reliable operation of electronic devices, based on an analysis of project requirements, including current-carrying capacity, signal integrity, thermal considerations, and manufacturing constraints, while strictly adhering to standards.

  • Current Analysis: Conducting current analysis is essential to determine the appropriate trace width required to accommodate the maximum current without exceeding temperature rise limits and voltage drop thresholds. This ensures that the PCB can operate safely and reliably under various load conditions.
  • Signal Integrity: Considering the frequency and impedance requirements of signals helps determine the optimal trace width for high-speed digital and analog circuits, minimizing signal attenuation, reflection, and electromagnetic interference. This ensures effective transmission of high-speed signals.
  • Thermal Management: By incorporating heat dissipation holes, heat sinks, and copper layers, excess heat generated by current flow can be effectively dissipated, preventing overheating and maintaining the optimal operating temperature of the PCB and its components. This enhances the overall reliability and lifespan of electronic devices.
  • Partner Selection: Choosing to collaborate with companies like FS Technology, which includes a design team, in the early stages of design, helps ensure that trace width design aligns with manufacturing capabilities and limitations. This ensures manufacturability and cost-effectiveness, minimizing the risks of manufacturing defects and flaws.

PCB Trace Resistance

Resistance is a physical property that opposes the movement of electric current and is inherently present in all materials. Excessive resistance in traces on a PCB can lead to signal attenuation, increased power consumption, and heat generation. Therefore, designers need to assess this property rationally.

To reduce the resistance of PCB traces, copper is commonly used as the material. Additionally, trace resistance is intimately related to trace thickness, width, and length. According to Ohm’s law, resistance (R) is associated with current (I), voltage (V), and the physical characteristics of the resistance material and can be expressed as follows:

                                                                                                          R = (ρ * L) / A

Where:

  • R represents resistance (measured in ohms).
  • ρ (rho) signifies resistivity and reflects the material’s electrical resistance.
  • L corresponds to the length of the trace (measured in meters).
  • A indicates the cross-sectional area of the trace, which is typically connected to its width (W) and thickness (T), as A = W * T.
 

From the formula above, it becomes evident that trace resistance is directly proportional to its length and inversely proportional to the cross-sectional area. Therefore, to adjust the trace resistance, changes in length, width, and thickness are made. These parameters are typically optimized during the PCB design phase to meet the circuit’s performance requirements. It’s important to note that resistivity (ρ) is an inherent property of the material and is typically a fixed value that is not easily modified.

How to Repair PCB Copper Traces

  1. First, you need to identify the damaged or broken traces. This can be done through visual inspection or using specialized equipment like thermal imaging or multimeters.
  2. Before proceeding with the repair, clean the damaged area with anhydrous isopropyl alcohol to remove any dust, oxidation, or impurities.
  3. Use a small knife to remove the damaged traces, then reconnect the traces using a micro soldering iron and the appropriate solder.
  4. If the damage to the traces is severe, you can consider using wires or specialized PCB repair adhesive. Wires can connect two endpoints, while PCB repair adhesive can fill in cracks.
  5. After completing the repair, be sure to test the PCB to ensure its functionality.
  6. Upon successful confirmation, immediately coat and cover the repaired area with an insulating adhesive, tape, or transparent sealant for protection.

Conclusion

The PCB trace guide helps in designing and developing reliable and high-performance printed circuit boards. By carefully considering key factors that influence trace design, engineers can determine the optimal trace width and layout configuration for a given application. This ensures seamless transmission of electrical signals within the PCB, mitigating signal integrity and thermal issues. As a leading PCBA manufacturer, FS Technology is well-versed in various aspects of circuit board knowledge. If you have any questions about PCB traces, please feel free to contact us, and our experts will be happy to assist you.

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