The first batch of high-voltage switching cells implemented with SiC MOSFETs embedded into PCB boards from Schweizer was successfully characterized from both a functional and electrical perspective. These tests confirmed the correct operation of the switching cells, enabling the implementation of multilevel converters with improved efficiency, compactness, and modularity. The evaluation of their thermal performance has also been recently completed.

Under normal operation, all power devices dissipate heat, which must be removed to keep the semiconductor temperature below critical limits and prevent degradation or malfunctions. The SCAPE high-voltage chip-embedded switching-cells were designed by IMB-CNM (CSIC) researchers to ensure optimal heat dissipation from the SiC MOSFETs to the board’s backside. This capability is quantified by the so-called “junction-to-case thermal resistance,” and the value achieved in SCAPE—lower than 0.5 ºC/W—is fully in line with expectations for power modules and even better than its counterpart using discrete devices.

Additionally, Deep Concept developed an efficient heat exchange solution to transfer the dissipated power to the liquid cooling system. This approach uses an aluminum heatsink attached to the board’s backside and a 3D-printed enclosure that directs the liquid flow through the dissipator. The thermal resistance achieved between the SiC MOSFET semiconductor and the liquid coolant was 1 ºC/W under typical operating conditions in an electric vehicle.

In conclusion, the SCAPE project is demonstrating the suitability of the chip-embedding approach for implementing high-voltage (750 V) modular and scalable switching cells—not only from an electrical standpoint but also in terms of thermal management.

a) Cross-sectional view of a high-voltage chip-embedding switching-cell showing the SiC power MOSFETs inside the PCB structure. b) Experimental thermal impedance curve showing a junction-to-case thermal impedance of 0.47 ºC/W. c) Experimental set-up used for the thermal characterization of the switching-cells under liquid cooling conditions that revealed a junction-to-coolant thermal resistance of 1 ºC/W at 7.5 l/min liquid flow rate.