Electrothermal Multiscale Modeling and Simulation Concepts for Power Electronics This paper presents a finite element based simulation methodology to improve on multiscale modeling and analysis limitations of power electronics development. The method utilizes homogenization and non-matching grid concepts to offer a high degree of flexibility and reduce computational effort. The applied homogenization method provides effective material properties to realize full chip modeling performance without the need to model geometric details. The concept of non-matching grids allows the inclusion of a sub-region with substantially finer mesh than its surrounding regions. This allows the flexible integration of micrometer scale geometries with a high degree of detail within the full chip model. Both concepts are thoroughly introduced and an application to a state-of-the-art power electronicssemiconductor technology is presented. This work focus on electrothermal interaction and is experimentally verified on a dedicated test structure. The presented results provide electrothermal insights in current power electronic technologies and emphasize their potential to further improve the robustness and reliability of next generation technologies.