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The trace width of a flex PCB refers to the width of the conductive paths (usually made of copper) that carry electrical signals across the board. Trace width is an important parameter in flex PCB design because it affects the board’s electrical performance, mechanical flexibility, and heat dissipation.
How to Determine the Trace Width?
1 Current-Carrying Capacity: Wider traces are needed to carry higher currents without overheating. Trace width is calculated based on the required current using industry standards such as IPC-2221, which provides formulas and guidelines for calculating trace width.
2 Flexibility: Flex PCBs are designed to bend and flex, so trace widths are often minimized to enhance flexibility. Narrower traces allow for more bending, but they must still meet electrical requirements.
3 Spacing and Density: In high-density circuits, particularly in HDI (High-Density Interconnect) designs, the trace width may need to be narrower to accommodate more components and connections in a small area.
Manufacturing Limitations: The capabilities of the PCB manufacturer play a significant role in determining the minimum trace width. For many manufacturers, the typical minimum trace width for flex PCBs is between 50 to 75 micrometers (µm), though it can go smaller with advanced technology.
- Standard Trace Width: A common range for trace width in flex PCBs is between 4 to 10 mils (0.1 to 0.25 mm), depending on current and design requirements.
- Fine-Pitch Designs: In high-density designs, trace widths as small as 2-3 mils (0.05 to 0.08 mm) are achievable.
What Key Considerations for Trace Width in Flex PCBs?
- Current Handling: Wider traces are required for power delivery circuits to handle larger currents without causing excessive heating. Narrower traces can carry signals or low-power data lines.
- Bending and Flexing: Flex PCBs are often designed to bend, so trace widths need to balance flexibility and reliability. Excessively wide traces can reduce the board’s flexibility, while traces that are too narrow might break under repeated bending.
- Thermal Management: Wider traces help dissipate heat more effectively, which is particularly important in high-current applications.
What the Manufacturing Tolerances of Trace Width?
The minimum achievable trace width depends on the capabilities of the manufacturer. For M2PCB, the min. trace width we can do is 0.075mm.
In conclusion, the trace width of a flex PCB is typically between 4 and 10 mils, though it can vary based on current requirements, flexibility needs, and manufacturing constraints. Designers must carefully balance these factors to ensure both mechanical flexibility and reliable electrical performance
