PCB Trace Width Calculator
External Layer Trace
Calculate trace width for external (outer) PCB layers using IPC-2221
Internal Layer Trace
Calculate trace width for internal PCB layers using IPC-2221
Formula
Area (mils²) = (I / (k × ΔT^0.44))^(1/0.725) | Width = Area / Thickness | External: k=0.048, Internal: k=0.024
Frequently Asked Questions
What is IPC-2221?
IPC-2221 is a generic standard for printed circuit board design published by IPC (Association Connecting Electronics Industries). It defines formulas for calculating minimum trace widths based on current, temperature rise, and copper thickness.
Why do internal layers need wider traces?
Internal layers are surrounded by insulating material (FR-4) which reduces heat dissipation compared to external layers that can radiate heat to the air. The IPC-2221 constant for internal layers (k=0.024) is half that of external layers (k=0.048).
What temperature rise should I use?
A common design guideline is 10°C temperature rise above ambient. For high-reliability applications, use lower values (5°C). For less critical designs, 20-30°C may be acceptable. Always consider the maximum ambient temperature in your application.
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