1. What is Trace Current Carrying Capacity?

Trace current carrying capacity refers to the maximum amount of electrical current a PCB trace can safely carry without exceeding temperature rise limits. It depends on trace width, thickness, and material properties.

2. How Does the Calculator Work?

The calculator uses the basic trace current capacity formula:

Where:

• \( Width \) — Trace width in mils (1 mil = 0.001 inch)
• \( Thickness \) — Copper thickness in ounces (oz/ft²)
• \( Factor \) — Current per cross-sectional area (A/mil/oz)

Explanation: The formula calculates the current capacity based on the cross-sectional area of the trace, with a default factor of 0.048 A/mil/oz for external traces at 10°C temperature rise.

3. Importance of Current Capacity Calculation

Details: Proper trace sizing is crucial for PCB reliability. Undersized traces can overheat, leading to thermal damage or fire, while oversized traces waste board space.

4. Using the Calculator

Tips: Enter trace width in mils, copper thickness in ounces, and the appropriate factor. The default factor of 0.048 is conservative for most applications.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between internal and external traces?
A: External traces (on outer layers) can typically carry more current than internal traces due to better heat dissipation.

Q2: How does temperature rise affect capacity?
A: Higher allowed temperature rises permit more current, but excessive temperatures can damage components or the PCB substrate.

Q3: What are typical copper thickness values?
A: Common values are 0.5 oz (18 μm), 1 oz (35 μm), and 2 oz (70 μm) per square foot.

Q4: When should I use more precise calculations?
A: For high-current applications (>5A) or when operating near temperature limits, consult more detailed IPC standards.

Q5: How do I convert mm to mils?
A: 1 mm = 39.37 mils. For trace width, multiply mm by 39.37 to get mils.