Introduction

The Thermal Resistance Calculator evaluates the required thermal resistance of a baseline heat sink design. This tool provides an immediate, analytical indication of how specific boundary conditions and material choices affect the overall thermal requirements of a system. The calculation is structured across three progressive refinement levels.

Minimal amount of boundary information

The baseline calculation determines the total resistance to heat flow from the junction of the heat-generating component, through the case and heat sink, to the surrounding environment. It requires three primary parameters:

Input symbol	Explanation	Units
	This is the ambient temperature	Kelvin
	This is the maximum junction temperature	Kelvin
	This represents the heat dissipated from the heat source	Watts

The resistance to heat flow from the junction of the heat-generating component, through the case and the heat sink to the environment, will be automatically calculated using the following equation:

R_{heat\;sink}=\frac{T_j-T_{amb}}{P}

Thermal interface material refinement

Input symbol	Explanation	Units
	This is the thickness of the thermal interface material	Meters
	This is the thermal conductivity of the thermal interface material
	This is the width of the heat source	Meters
	This is the length of the heat source	Meters

The resistance to heat flow from the junction of the heat-generating component, through the case and the heat sink to the environment, will be automatically calculated using the following equation:

R_{heat\;sink}=\frac{T_j-T_{amb}}{P}-R_{interface}

R_{interface}=\frac{t_{interface}}{L_s \cdot W_s\cdot \kappa_{interface}}

Junction information refinement

Input symbol	Explanation	Units
	This is the thermal resistance between the junction and the case

The resistance to heat flow from the junction of the heat-generating component, through the case and the heat sink to the environment, will be automatically calculated using the following equation:

R_{heat\;sink}=\frac{T_j-T_{amb}}{P}-R_{th-jc}