Heat Sink Thermal Resistance Calculator

Use this online calculator to determine the heat sink thermal resistance required to maintain a specified component junction temperature.

The resistance to heat flow from the junction of the heat generating component, through the casing, thermal interface material, heat sink and finally to environment is represented by the thermal resistance circuit shown in the diagram below. The following equation is used to calculate R_hs, the thermal resistance of the heat sink:

R_hs = (T_j - T_amb) / P - R_th-jc - R_interface

Where:

T_j

is the junction temperature

T_amb

is the ambient temperature

is the heat dissipated from the heat source

R_th-jc

is the junction to case thermal resistance

R_interface

is the thermal interface material resistance calculated using the following equation:

t_interface

is the thermal interface material thickness:

k_interface

is the thermal conductivity of interface material

L_s

is the length of heat source:

W_s

is the width of heat source

T_amb: °C

T_j (max): °C

P: Watts

Thermal interface material

t_interface: mm

k_int: Watts/(m⋅K)

W_s: mm

L_s: mm

Junction to case thermal resistance R_th-jc:

C/W

Calculate

Thermal resistance path from junction T_j through R_th-jc, R_interface and R_hs to ambient T_amb, for a heat source of size W_s by L_s on a finned heat sink

Do you need more functionality?

The HeatSinkCalculator offers online heat sink analysis software that allows you to analyze plate fins heat sinks cooled via radiation, and natural or forced convection. Multiple heat sources attached to the heat sink can be evaluated. In addition the calculator automatically determines the optimal dimensions of your heat sink to achieve the lowest heat source temperature. Click below to learn more.