For detailed study please go to Heat transfer: Electronic design documentation.
The current analysis is carried out on a high-power IC package that is attached between the heatsink base and the PCB substrate as shown in figure below. The components explicitly represented in the model are the die, TIM1, lid, TIM2 and the heat sink base (where TIM = Thermal Interface Material). To proceed with the simulation, only a portion of the geometry is considered with width and length of all components equal to that of the die.
The simulation ready CAD model is shown below.
A tet-dominated mesh elements with fine local mesh refinements at the contact interfaces between the components are as shown in the figure below.
A transient heat transfer analysis is performed on the IC-package design with the material properties and boundary conditions as mentioned in the  and the results are compared with the SimScale simulations results.
The below figure shows the temperature distribution and the corresponding temperature difference plots.
Temperature change w.r.t ambient temperature versus time plot comparison with [Bruce] and SimScale simulation results for 3 different location of the model, Die-top, Lid-top and heatsink-bottom
A slight deviation in temperature graphs from  with SimScale is due to the approximation error caused during the extraction of temperature values from the digital plots.
 Bruce Guenin, “Calculation Corner: Transient Thermal Modeling of a High-Power IC Package, Part 1” Calculation Corner, Computer, IT Products, Number 4, Software/Modeling, Volume 17, December 22, 2011