1. What is a PCB Trace Ampacity Calculator?

Definition: This calculator estimates the current carrying capacity (ampacity) of a PCB trace based on its cross-sectional area, allowable temperature rise, and material properties.

Purpose: It helps electronics designers ensure their PCB traces can handle the required current without excessive heating.

2. How Does the Calculator Work?

The calculator uses the IPC-2221 formula:

Where:

• \( I \) — Current capacity (Amperes)
• \( \Delta T \) — Temperature rise above ambient (°C)
• \( A \) — Cross-sectional area (mm²)
• \( k \) — Material constant (0.024 for inner layers, 0.048 for outer layers)

Explanation: The formula accounts for heat dissipation through the PCB material and relates trace dimensions to safe current levels.

3. Importance of PCB Trace Ampacity Calculation

Details: Proper trace sizing prevents overheating, ensures reliability, and maintains signal integrity in electronic circuits.

4. Using the Calculator

Tips: Enter the desired temperature rise (typically 10-20°C), trace cross-sectional area (width × thickness), and material constant. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between inner and outer layer constants?
A: Outer layers (k=0.048) can dissipate heat better than inner layers (k=0.024), allowing higher current for the same trace size.

Q2: How do I calculate cross-sectional area?
A: Multiply trace width by thickness (e.g., 0.5mm × 0.035mm = 0.0175mm²).

Q3: What's a typical temperature rise limit?
A: 10°C is conservative, 20°C is common, and higher values may be used depending on application requirements.

Q4: Does this account for high-frequency effects?
A: No, this is for DC/low-frequency current. Skin effect at high frequencies reduces effective ampacity.

Q5: How should I derate for multiple traces?
A: For closely spaced parallel traces, reduce current by 15-20% to account for reduced heat dissipation.