In the frame of this work, a purely thermal model based on the resolution of the heat equation in an electronic component was developed. The objective is to be able to access the value of the junction temperature from external temperature measurements. From a two-dimensional geometry, the semi-analytical models in steady-state and transient regimes provide access to the temperature profile on the upper face using the heat dissipation of the chip and the temperature profile at the lower face. The results of this semi-analytical model were compared to the numerical results obtained using the finite element method under COMSOL Multiphysics. The comparison of the temperature profiles on the upper face illustrates a good agreement between analytical and numerical models, with a maximum error of less than 0.1 K, which can be derived from various numerical errors such as truncations of the spectrum conversion and approximations of numerical Laplace inversion.