How to Calculate Heat Sink Thermal Resistance

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 Rhs, the thermal resistance of the heat sink:

                                                                         

Where:

Tj is the junction temperature
Tamb is the ambient temperature
P is the heat dissipated from the heat source
Rth-jc is the junction to case thermal resistance
Rinterface is the thermal interface material resistance calculated using the following equation:

                                                                                     

Tinterface is the thermal interface material thickness:
kinterface is the thermal conductivity of interface material
Ls is the length of heat source:
Ws is the width of heat source
                                                        

Tags :

• Custom Heatsink