The thermal resistance calculator is a free tool on ColdStream to calculate the thermal resistance of a default heat sink design. This tool finds its use in giving the user a clear indication of how some of the boundary conditions affect the thermal resistance of this standard heat sink.
The thermal resistance calculator tool has 3 refinement levels. The following chapters delve deeper into each of these refinement levels.
Default heat sink
Minimal amount of boundary information
Input symbol
Explanation
Units
\(T_{amb}\)
This is the ambient temperature
Kelvin [K]
\(T_{j}\)
This is the maximum juntion temperature
Kelvin [K]
\(P\)
This represents the heat dissipated from the heat source
Watts [W]
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:
\[R_{heat\space sink}=\frac{T_j - T_{amb}}{P}\]
Thermal interface material refinement
Input symbol
Explanation
Units
\(t_{interface}\)
This is the thickness of the thermal interface material
Meters [m]
\(\kappa_{interface}\)
This is the thermal conductivity of the thermal interface material
[\(\frac{W}{m*K}\)]
\(W_s\)
This is the width of the heat source
Meters [m]
\(L_s\)
This is the length of the heat source
Meters [m]
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:
\[R_{heat\space sink}=\frac{T_j - T_{amb}}{P}-R_{interface}\]\[R_{interface}=\frac{t_{interface}}{L_s*W_s*\kappa_{interface}}\]
Junction information refinement
Input symbol
Explanation
Units
\(R_{th-jc}\)
This is the thermal resistance between the junction and the case
[\(\frac{K}{W}\)]
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:
\[R_{heat\space sink}=\frac{T_j - T_{amb}}{P}-R_{th-jc}\]
