Propagation
The governing equation of the physics of the problem to be analyzed is the heat diffusion equation. It relates the flux of heat in space, its variation in time and the generation of power.
Where is the thermal conductivity, is the density of the medium, is the specific heat
the thermal diffusivity and is the rate of heat generation per unit volume. Heat diffuses from the source following equation and solution in an homogeneous medium of has a Gaussian distribution.
Read more about this topic: Heat Generation In Integrated Circuits