San Francisco Circuits specializes in PCB manufacturing and assembly, catering to both prototype and large-scale production needs for various unmanned system applications.
A 4-layer PCB showcasing diverse trace widths and styles.
In PCB design, trace width, along with length and configuration, plays a crucial role and is tailored to meet specific submission demands.
A PCB trace serves to transmit electrical signals—whether analog, digital, or power—between connection points like component pins or test pads. Trace widths are generally expressed in mils (thousandths of an inch).
Understanding Trace Widths & Design Considerations
Typical trace widths for standard signals fall between 7 to 12 mils. However, design specifics—such as operational speed, noise mitigation, or current/voltage requirements—can necessitate different trace dimensions. These choices must be weighed against factors like manufacturing costs, board dimensions, and overall performance.
Certain trace specifications can elevate PCB manufacturing expenses due to stricter tolerances and the requirement for specialized equipment. This includes trace widths and spacing below 5 mils, via holes smaller than 8 mils, non-standard copper thicknesses, differential pairs, and controlled impedance traces.
For high-density designs, traces may need to be as narrow as 2.5 mils, with micro-vias measuring just 6 mils. Conversely, high-power applications might require wider traces or copper pours that span entire layers, while compact designs could utilize thinner boards with half-ounce copper pours.
Key Performance Factors for High-Speed & Noise-Resistant Designs
A 6-layer PCB featuring a 256-pin BGA component with 5-mil trace widths.
The width of a trace is steadfast by the current it needs to carry. As an example, a power trace carrying 2 Amps over a length of 0.8 inches, utilizing 1-ounce copper at room temperature, requires a minimum width of approximately 30 mils.
This calculation adheres to IPC standards and established formulas to ascertain trace area and width. The resulting voltage drop for this configuration is around 26mV, which is acceptable for applications like a DC motor.
For high-speed digital signals, trace spacing and length are vital. For example, USB 2.0, which operates at 480 Mbit/s, necessitates differential pair routing with matched lengths and a 90-Ohm impedance.
A discrepancy in trace length exceeding 50 mils can result in signal reflections. Maintaining signal integrity requires careful attention to trace width, spacing, and precise length matching. DDR3 memory interfaces impose even stricter constraints and often require software-based adjustments for trace length.
Components sensitive to noise,such as wireless chips or antennas,benefit from ground-filled traces and planes with embedded vias. These strategies help minimize coupling and shield against external noise. Examples include ground-shielded antenna traces and perimeter ground planes on noise-sensitive PCBs.
San Francisco Circuits recommends adhering to routing best practices to achieve an optimal balance between manufacturing costs,circuit density,and electrical performance.The company is equipped to handle designs that demand intricate routing and fabrication beyond conventional manufacturing capabilities.
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