Different approaches are available for coupling an electrical and a thermal simulation. The decisive factor is essentially the type of electrical analysis. For example, the power loss for an individual component can already be determined with a 1D simulation and transferred to a corresponding volume in the thermal 3D analysis.
A challenge that arises in the multidisciplinary simulation of these two disciplines has nothing to do with the combination itself. Electrical components, including printed circuit boards, have very small structures that are relevant for the electrical aspects. In a temperature field simulation, however, this level of detail would quickly exceed any limit to the model size. At this point, compromises and simplifications are usually necessary.
The coupling is normally unilateral. As a result of the electrical analysis, the power losses of the components and circuit paths are transferred, often also as RMS values (root mean square). In the case of a bidirectional multiphysics simulation, it is the local temperatures that are returned to the electrical analysis.