Our research in this paper seeks to determine how advanced package substrates thermally interact with high power components (GaN / SiC chips, MOSFETS, capacitors). By using differing copper weights, material stack ups and dielectrics, we have determined that certain defining characteristics of the entire packages can significantly increase / decrease the overall thermal conductivity of the package, thus affecting performance and mean time to failure. We will showcase these interconnections and variables and how they assist in sustaining and increasing overall substrate performance and longevity.