Embedded-cHow-ToBeginner · 4 min read

How to Add Thermal Vias on PCB: Step-by-Step Guide

To add thermal vias on a PCB, place multiple small vias around heat-generating components connecting the top copper layer to inner or bottom layers to spread heat. Use your PCB design software's via tool, set via size and drill, and arrange them evenly in a thermal pad or area for effective heat transfer.

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Syntax

In PCB design software, adding thermal vias involves these steps:

Select Via Tool: Choose the via creation tool in your PCB editor.
Set Via Parameters: Define the via drill size and pad size suitable for thermal conduction.
Place Vias: Position multiple vias evenly within or around the thermal pad area.
Connect Layers: Ensure vias connect the top copper layer to internal or bottom copper layers for heat spreading.

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Via {
  drill_diameter: 0.3mm;
  pad_diameter: 0.6mm;
  layers: Top, Inner1, Bottom;
  position: array of coordinates within thermal pad;
}

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Example

This example shows how to add a grid of thermal vias inside a thermal pad area in a PCB design tool script or configuration.

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thermal_pad {
  size: 5mm x 5mm;
  via {
    drill_diameter: 0.3mm;
    pad_diameter: 0.6mm;
    layers: Top, Inner1, Bottom;
    grid_spacing: 1mm;
    count_x: 4;
    count_y: 4;
  }
}

Output

A 5mm by 5mm thermal pad with 16 thermal vias arranged in a 4x4 grid spaced 1mm apart, connecting top, inner, and bottom layers.

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Common Pitfalls

Common mistakes when adding thermal vias include:

Using vias that are too large or too few, reducing heat transfer efficiency.
Placing vias too close to component pads, causing soldering issues.
Not connecting vias to inner or bottom copper layers, limiting heat spreading.
Ignoring via fill or plating options that improve thermal conductivity.

Always check your PCB manufacturer's via capabilities and design rules.

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Wrong way:
Via {
  drill_diameter: 1.0mm;
  pad_diameter: 1.2mm;
  layers: Top;
  position: single via in pad center;
}

Right way:
Via {
  drill_diameter: 0.3mm;
  pad_diameter: 0.6mm;
  layers: Top, Inner1, Bottom;
  position: multiple vias evenly spaced in thermal pad;
}

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Quick Reference

Parameter	Recommended Value	Notes
Via Drill Diameter	0.3 mm	Small size improves thermal conduction and manufacturability
Via Pad Diameter	0.6 mm	Slightly larger than drill for plating and solder mask clearance
Via Count	Multiple (4+)	More vias spread heat better
Via Spacing	1 mm or more	Avoid soldering issues and maintain mechanical strength
Layer Connection	Top to Inner/Bottom	Ensures heat spreads through PCB layers

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Key Takeaways

Place multiple small vias evenly in thermal pads to improve heat dissipation.

Connect thermal vias through top, inner, and bottom copper layers for effective heat spreading.

Use via sizes and spacing that comply with your PCB manufacturer's capabilities.

Avoid placing vias too close to component pads to prevent soldering problems.

Consider via plating or filling options to enhance thermal conductivity.