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Bayesian Optimization of PCB-Integrated Field Grading for a High-Density 10 kV SiC Power Module Interface
Year: 2022 | Author: Mark Cairnie | Paper: H-S1.1
Fig.1. SiC 10 kV power module cross-section
To reduce the electric field strength in the air surrounding the interface, copper traces inside the PCB are used as field-grading plates that shift the peak electric field from the air to the FR4 dielectric, which has a higher breakdown field strength than air. The geometry and location of the field-grading plates is critical to their effectiveness. To design the geometry, a numerical optimi-zation technique is used in conjunction with finite element analysis. The system is first decom-posed into critical 2D design regions, which are then parameterized, and the locations of field crowding are identified. A weighted cost function is formulated using the breakdown strength of the materials and is optimized using an interior-point algorithm with finite difference derivatives.
One of these optimized cross-sections is shown in Fig. 2. The optimization results in copper conductors shaped such that the high strength electric field is contained inside the FR4 dielec-tric, where the field can be supported without partial discharge. Meanwhile, the electric field in air is kept below the breakdown strength of air, resulting in safe, reliable, partial-discharge-free op-eration. The optimized laminate bus bar and optimized module housing were built and experimen-tally demonstrated a partial discharge inception voltage of 11.6 kV rms under 60 Hz sinusoidal excitation.
