Minimum Clearance in PCB: Definition and Practical Guide

Minimum clearance in a PCB is the smallest allowed distance between two conductive elements, such as traces, pads, or vias. It ensures electrical safety and prevents short circuits by keeping components properly spaced.

How It Works

Think of minimum clearance in a PCB like the space between lanes on a highway. Just as cars need enough room to avoid crashing, electrical signals need enough space to avoid unwanted contact. This space is called clearance.

Clearance is measured as the smallest gap between any two conductive parts on the board. If this gap is too small, electricity might jump across, causing shorts or damage. Designers set minimum clearance rules to keep the board safe and working well.

Example

This example shows how to check minimum clearance between two copper traces in a PCB design using a simple rule in a PCB design software script.

javascript

function checkClearance(trace1, trace2) {
  const distance = Math.abs(trace1.position - trace2.position);
  const minimumClearance = 0.2; // in millimeters
  if (distance < minimumClearance) {
    return 'Clearance too small: ' + distance + 'mm';
  } else {
    return 'Clearance OK: ' + distance + 'mm';
  }
}

const traceA = { position: 1.0 };
const traceB = { position: 1.15 };
console.log(checkClearance(traceA, traceB));

Output

Clearance too small: 0.1499999999999999mm

When to Use

Minimum clearance rules are used during PCB layout to ensure the board is safe and reliable. They are critical when designing high-voltage circuits, dense boards, or when following manufacturing limits.

For example, if you design a power supply PCB, you must keep enough clearance to prevent sparks or shorts. Also, manufacturers specify minimum clearance to avoid production defects. Always check and apply these rules before finalizing your design.

Key Points

• Minimum clearance is the smallest gap allowed between conductive parts on a PCB.
• It prevents electrical shorts and ensures safety.
• Clearance values depend on voltage, manufacturing capabilities, and design rules.
• Always verify clearance during PCB layout and before manufacturing.

Key Takeaways

Minimum clearance prevents electrical shorts by keeping conductive parts apart.

Clearance depends on voltage levels and manufacturing limits.

Always apply clearance rules during PCB design to ensure safety and reliability.

Check clearance values with your PCB manufacturer before production.