Thermal Behavior of an Electronics Compartment with Respect to Real Driving Conditions

Reliability of electronic components is of increasing importance for further progress towards automated driving. Thermal ageing processes such as electromigration is one factor that can negatively affect reliability of electronics. Resulting failures are mainly depending on components’ thermal load within vehicle lifetime - called temperature collective, which is described by the temperature frequency distribution of the components. At present, the only possibility to examine the temperature collective is performed by vehicle endurance testing. Knowledge about the temperature frequency distribution in early development stages is one of the key factors to ensure electronics’ reliability in future vehicles. Vehicle Thermal Management (VTM) tools, which provide numerical simulation, allows lifetime thermal prediction in early development stages, but also challenges current VTM processes. Due to changing focus from underhood to numerous electronic compartments in vehicles, the number of simulation models has steadily increased. Since the electronics compartments are mostly located inside the vehicle cabin, common load cases such as the “Slow Uphill Drive” and the “High Speed” cannot be applied to these models. Defining new load cases for maximum component temperatures as well as lifetime temperatures forces comprehensive analysis of specific compartment boundary conditions. At Mercedes Benz Cars Group, this analysis includes parallel testing and a numerical approach using a Mercedes-Benz S-Class V222. The impact of HVAC and environmental conditions on electronics’ temperature are determined by means of wind-tunnel tests for one specific compartment in the vehicles’ trunk. Numerical Design of Experiments (DoE) is used to extend boundary condition range, and main and interaction effects can be estimated. In addition, impact of different package configurations were investigated. That facilitates the application of appropriate measures for future cars. A vehicle endurance test provides an overview of lifetime temperatures as well as corresponding boundary conditions for electronic components in this compartment. Based on the data acquired in these tests, load cases for temperature collectives can be derived and applied to numerical simulation.