Bare-Die Embedding Technique for Highly Integrated Power Electronics for Small Mobility

Abstract

Small mobility vehicles such as electric scooters are becoming an integral part of the transition toward electrified transportation. However, the limited driving range and the lack of onboard charging capability are the major challenges for widespread adaptation, which arises due to the limited space for power electronics units and batteries on the chassis of small mobility vehicles. This research introduces a new bare-die embedding printed circuit board (PCB) packaging technology, ensuring a very compact, high power density, and integrated design for the power electronics unit. The design incorporates the bare die of the switching devices into the PCB layers and uses multilayers for routing and cooling purposes. A silicon (Si) MOSFET bare die is embedded into the FR4 layers using the stomach cell approach, electrically connected, and cooled through laser-drilled micro vias and copper fills. The electrothermal design reduces the parasitic loop inductance by 74%, increases the power density by 113%, and enhances the driving range of the small mobility vehicle by 16.6% compared with the traditional TO-247 packaging approach. Moreover, a new thermal model is also presented and validated for the bare-die embedded board. A high power density power electronics unit integrating the motor drive and the onboard charger was developed using the proposed bare-die embedding technology, and a benchmark comparison was made to evaluate the effectiveness of the proposed bare-die embedding technique.