PCB Thermal Via Calculator

Estimate idealized heat transfer through an array of plated PCB thermal vias using finished hole diameter, barrel plating, board thickness, thermal conductivity, and via count.

The calculator reports per-via conductance, parallel thermal resistance, heat flow, and the temperature difference associated with a specified power load.

Engineering tool

PCB Thermal Via Calculator

Estimate idealized plated-barrel conductance, parallel thermal resistance, and temperature difference for a thermal via array.

Number of thermal vias

Whole number of similar vias acting in parallel.

Finished hole diameter

Finished via diameter after plating.

Via plating thickness

Copper barrel wall thickness.

PCB thickness

Length of the vertical thermal path.

Copper thermal conductivity

Use the selected copper material value; default is 385 W/m·K.

Power dissipation

Heat flow assigned to the via array.

Ambient reference temperature

Reference temperature below the idealized via thermal path.

Result console

Barrel area per via: 0.023562mm²
Conductance per via: 0.00567W/K
Resistance per via: 176.379504°C/W
Equivalent thermal resistance: 11.023719°C/W
Estimated temperature drop: 22.047438°C
Estimated hot-side temperature: 47.047438°C
Heat flow per via: 125mW
Total heat flow: 2W

Thermal via status

Review

The idealized via-array temperature difference is elevated. Consider more vias, thicker plating, a shorter thermal path, filled vias, or larger connected copper planes.

Plated barrels act approximately as parallel thermal conductors between connected copper regions.

Formula reference

PCB Thermal Via Formulas

Each plated barrel is modeled as a thin cylindrical copper conductor. Identical vias are treated as ideal parallel thermal paths.

Copper barrel area: A ≈ π × D × tConductance per via: Gvia = k × A / LResistance per via: Rθ,via = L / (k × A)Parallel resistance: Rθ,total = Rθ,via / NTemperature difference: ΔT = P × Rθ,totalHeat per via: Pvia = P / N

Variable definitions

D: finished via hole diameter
t: copper plating thickness
L: PCB thickness
k: copper thermal conductivity
N: number of thermal vias

Worked Example

For sixteen 0.3 mm vias with 25 µm plating through a 1.6 mm board, each barrel has approximately 0.02356 mm² of copper area.

At 385 W/m·K, each via has about 176.4 °C/W ideal barrel resistance. Sixteen parallel vias reduce this to about 11.0 °C/W, producing approximately 22.1°C temperature difference at 2 W.

Engineering Notes

Thermal vias transfer heat primarily through their plated copper barrels.
More equivalent vias reduce idealized array resistance approximately in parallel.
Via fill, plating thickness, connected planes, and solder mask affect real performance.
Thermal vias work best when connected to large copper pours or planes.
Use thermal simulation or measurement for high-power designs.

Support reference

FAQ

What is a thermal via?

A thermal via is a plated-through hole used to conduct heat between PCB copper layers, often from a component thermal pad to a larger internal or bottom copper plane.

How do thermal vias reduce temperature?

Their plated copper barrels create parallel vertical heat paths through the PCB. Lower equivalent thermal resistance reduces the temperature difference required to move a given amount of heat.

How many thermal vias do I need?

The count depends on power, via geometry, available pad area, connected planes, assembly constraints, and the allowed temperature rise. Add vias until spreading and interface resistance become the dominant limits.

Does via plating thickness affect thermal performance?

Yes. Thicker plating increases copper barrel area, raising conductance and lowering barrel thermal resistance. Use the manufacturer's minimum finished plating for conservative analysis.

Should thermal vias be filled or tented?

Filled or capped vias can improve assembly under exposed pads and may add conductive material, while tenting controls solder flow. The correct process depends on package, pitch, cost, and fabricator capability.

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