This paper presents design requirements and solution strategies for power semiconductor modules targeting traction converters for electric trucks (eTRUCK). It is shown that, due to the needed high load, long distance mission profiles, robustness against cycling load, i.e., device lifetime, is the main differentiator to consider. For optimized efficiency and reduced module package size, a low inductive, direct liquid cooled power module design with SiC MOSFETs is mandatory. To achieve competing design targets, the fundamental elements are total drain source resistance, joining technology, and heat spreading. Especially, joining technology and heat spreading are the key parameters for a power module with optimized cost performance ratio.
Based on these considerations and findings, we introduce a new 1400 V SiC MOSFET chip technology and a low inductive package design. In this design, eTRUCK specific application conditions such as high output currents above 800 ARMS, low inductive commutation paths, and enhanced power cycling capability are considered and implemented. In addition to the well established power module designs such as HybridPACK TM Drive with sixpack topology, the new HybridPACK TM HD provides a half bridge topology per module. This approach offers more flexibility for designing the main inverter and cooling system; especially if different electrification strategies such as single electric axle operation or multiple electric axle operation are under consideration.
Focusing on the chip technology, a new 1400 V SiC MOSFET technology is proposed. Main drivers for this new technology are high load currents of, typically, over 800 ARMS occur during operation and, especially in combination with high speed electric motors, high pulse frequencies during inverter operation. As, in eTRUCKs, typically, 800 V battery technology is used, DC link voltages of up to 900 V or even higher are in focus and, thus, a required blocking voltage of above 1200 V is required.
For the new HybridPACK TM HD package, increased lifetime, high power density, and suitability for fast switching devices such as SiC MOSFETs are main design criteria. The new HybridPACK TM HD combines a low inductive busbar concept that allows for a laser welding connection of module’s power terminals and DC link capacitor, and a thermally optimized substrate layout with minimum on substrate routing. By implementing a high performance joining technology with a robust package design, this cost effective performance optimized package has been developed for eTRUCK application.
In this paper, we show that high performance joining technology combined with parallelized SiC MOSFET chips in a smart module design can enable high reliability and long term operation. Heat spreading is a key factor for minimizing the number of chips per system, optimize the total cost of ownership, and also maximize the performance. Comprehensive performance evaluations based on the new low inductive HybridPACK TM HD package and a new 1400 V SiC MOSFET technology were are presented in this paper. It is worked out that eTRUCK specific mission profiles and corresponding climate conditions are crucial and must be considered while designing power modules. It is shown that using a heat spreading optimized layout, a high performance joining technology, a low inductive design, and a SiC MOSFET technology are the key enablers and mandatory future requirements for demanding electrified vehicle applications like eTRUCK.