20A Trace Width Calculator

Understanding 20A Trace Width Requirements

When designing a PCB that needs to carry 20 amperes of current, proper trace width calculation is critical for thermal management and reliability. Based on the IPC-2221 standard, a 2oz copper external layer trace requires approximately 9.41mm (370.6 mil) width to safely handle this current with a 10°C temperature rise. This calculation ensures your printed circuit board maintains optimal performance without excessive heating, which could lead to solder joint failure, delamination, or fire hazards in extreme cases.

Key Parameters for 20A Design

• Current Capacity: 20A (amperes) - the maximum continuous current this trace is designed to carry
• Copper Weight: 2 oz/ft² (70μm) - determines the conductor cross-sectional area
• Layer Type: External ( better heat dissipation to ambient air)
• Temperature Rise: 10°C above ambient (IPC-2221 conservative design guideline)
• Cross-Section Area: 1,015.33 sq mil (0.6550 mm²)

Why Layer Type Matters for 20A Current

External layers can dissipate heat more effectively through convection to the surrounding air, allowing for narrower traces compared to internal layers. For 20A on 2oz copper, this means you can achieve adequate current carrying capacity with a trace width of 9.41mm. External copper layers benefit from both top and bottom surface area exposure for thermal radiation and convection.

IPC-2221 Standard Formula

The IPC-2221B standard provides the industry-accepted formula for PCB trace width calculation: I = k × ΔT^b × A^c, where I is current in amperes, ΔT is temperature rise in °C, A is cross-sectional area in square mils, and k, b, c are empirical constants specific to external layers. This formula has been validated through extensive testing and is used by PCB designers worldwide for 20A and higher current applications.