With motor control units being located close to the hot motor and navigation systems being located in the air-conditioned passenger cabin, the thermal challenges vary with the product and application. This paper will address how heat can be dissipated most efficiently in various environments and under various conditions, to ensure reliability and product quality. Using thermal and fluid flow analysis for electronics cooling applications, critical component junction temperatures that can be improved can be identified through the visualization of the patented bottleneck and shortcut numbers. The high current and voltage drops running through the PCB traces were simulated with HyperLynx PI and the Expedition PCB interface was used to get detailed PCB traces and both then used for the thermal simulation. By applying these methods, an efficient cooling system can be found for various automotive electronic systems from navigation system and dashboard instruments to engine control units and inverters for EVs and HEVs. Increased shielding from EMI is increasing the complexity of efficiently and easily cooled electronic systems. With the bottleneck and shortcut number, new unseen ways to improve the heat flow path can be detected and used to achieve an efficient cooling system even in complex assemblies. This paper gives an overview of interoperability between ECAD and CFD software with help of interfaces to transfer the PCB layout and power density on the PCB traces to use in detailed Joule heating effects in CFD. It not only considers electronic components as heat sources but also the heating effects in high power traces on the PCB. In addition, new post processing methods will be shown to visualize heat flow path shortcuts and bottlenecks to improve the thermal design in ways never visible to engineers before. By using ECAD interfaces and unique post-processing technologies, it is possible to analyse the systems in high detail and evaluate the results by showing directly locations that, when improved, can improve the thermal management. With this type of assistance it is possible to enhance the thermal design to safely cool power electronics and reduce the energy consumption which is especially important to EVs and HEVs where reduced energy consumption increases the traveling range. Weight and size reduction also can be optimized to increase the range of the vehicle.