In the electronic industry, chips are usually joined to substrates by a thin layer of epoxy. Similar situations are encountered in other industries. Modeling the epoxy layer as a separate component requires the use of a very small element size that can result in meshing failure or an unnecessarily large number of elements.
To consider the thermal resistance caused by the epoxy layer, you do not need to model it. Thermal contact resistance is implemented as a surface-to-surface contact condition. You can either specify the total resistivity or the resistivity per unit area.
Modeling Thermal Contact Resistance