Electronic device radiator - QuickField simulation example
The semiconductor device attached to a sapphire substrate installed on a copper header. The thermal resistance of interest is the resistance from the semiconductor device to the ambient.
How to find transient thermal resistance of electronic heat sinks?
Answer Typical applications Geometry
Given
Solution
Results
Electronic device radiator temperature after 2 seconds:
Engineering question
Set up a plane-parallel QuickField Transient Heat Transfer problem for an electronic heat sink and evaluate transient thermal resistance from computed field results.
electronic heat sinks, semiconductor cooling radiators, power electronics cooling devices
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Simulation problem
Problem Type
Plane-parallel problem of transient heat transfer.
The Rca block represents the known thermal resistance from the header to the ambient.
Model z-length is 4 mm.
Thermal load of semiconductor device 60 W/mm².
Heat conductivity of blocks: sapphire 28 J/K-m, copper 394 J/K-m, Rca 1 J/K-m.
Mass density of blocks: sapphire 3985 kg/m³, copper 8950 kg/m³.
Specific heat of blocks: sapphire 3985 J/Kg·K, copper 8950 J/Kg·K.
The transient thermal resistance is calculated as the instantaneous temperature increase divided by the heat flux. A normalized curve can be obtained by dividing the instantaneous temperature by the final temperature.
The shape of the graph can be qualitatively explained by the presence of two very different thermal time constants in the system. The first time constant corresponds to sapphire substrate (it works up to 0.005 sec.). The second time constant corresponds to copper header. The second time constant will be better visible if the simulation time is extended above 2 sec., so two simulations are necessary to visualize the system behavior.
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