Tiny Power Box – Mechanical Investigations for Automotive Very High Power Density Onboard Chargers

The use of wide bandgap semiconductors, increased switching frequencies and Surface Mount Technology (SMT) power semiconductor packages lead to higher loss densities in the power components of any power electronic system, hence the cooling of semiconductor components gets critical. As a preventative measure for such setbacks, the designer needs to plan for an optimal heat transfer from the semiconductor die to the cooling media via the package and Thermal Interface Material (TIM) in between. In particular, the top-side cooled packages make it possible to achieve high power densities. In order to address the above-mentioned design gap, this paper formalizes the design process for cooling aspects of a selected 7kW single phase automotive on-board charger (OBC) and executes the mechanical optimization of the setup to illustrate how beyond state-of-the-art power density for OBC applications (>3.1kW/dm(exp 3) including housing) can be achieved. The investigation shows mechanical integration of top-side cooling devices with minimal cooling system volume and low mechanical stress in order to prevent Printed Circuit Board (PCB) warpage and ensure optimal heat transfer.