CeramTec in Germany has developed a ceramic cooling solution for a power module in inverters in the drive trains of electric cars.
High-performance ceramics are particularly suitable for cooling silicon carbide (SiC) MOSFETs as they offer high thermal conductivity, electrical insulation and resistance to corrosion and wear. Particularly high power densities are achieved with liquid coolers that use water or glycol mixtures to achieve a significantly higher cooling capacity.
To ensure efficient heat dissipation, the new generation of ceramic cooling systems uses chip-on-heatsink technology to attach the chip directly to the metallised ceramic heat sink. In this way, it is particularly close to the cooling liquid. To achieve this, the structured copper sheets are applied directly to the front and back of the ceramic cooler. This makes it possible to use both sides as circuit carriers and to cool them simultaneously.
The inner cooling structure of the ceramic is designed as a pin-fin structure. This significantly increases the heat transfer surface of the heat sink and enables ideal circulation around the pin-fin surface. In this way, heat is optimally dissipated and at the same time the structure increases the mechanical strength, which can thus absorb pressure, torsion and bending forces well.
Compared to conventionally constructed systems, the thermal resistance of chip-on-heatsink heat sinks is reduced by half.
The heat sink measures only 48 x 36 mm and is 3.6 mm thick (including metallisation) and weighs ten grams. Based on the thermal characterisation, the thermal resistance of the power module with Pin-Fin ceramic cooler is 0.15 K*cm²/W at the design point from the chip to the cooling water.
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