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Design and Analysis of a PCB Embedded SiC Half-bridge Module

SiC MOSFET half-bridge module
Fig. 1. PCB-embedded SiC MOSFET half-bridge module.
  This work presents a printed circuit board (PCB) embedded 1.2 kV silicon carbide (SiC) MOSFET half-bridge module that shows marked improvement over a conventional wire-bonded power semiconductor package in terms of electrical and thermal performance, and manufacturability. The 1.2 kV SiC MOSFET die are embedded in FR4 using embedding technology developed by AT&S. The die electrical connections and thermal paths are created using copper-filled microvias. Embedding the die allows for short conduction paths and small gate and power loops. Steady-state thermal simulations verify that large copper planes in the embedded module allow for increased heat spreading and lower junction temperature compared to a conventional TO-247 package under similar conditions.
  The design of this module (Fig. 1) is based on maximizing the benefits and understanding the trade-offs of the die PCB-embedding technique. The two die are kept far enough apart to minimize thermal coupling, while also maintaining a small power loop. The gate drive circuitry is included in the module to ensure a small gate loop. Copper-filled microvias are used to thermally connect the inner and outer copper layers between the die and the solder mask openings. Copper planes that are electrically connected to the die are designed to maximize power density, while allowing for sufficient heat spreading.
  Thermal and electrical FEA simulations were performed on the module. The power and gate loop inductances are 1.8 nH and 2.0 nH, respectively. The double-sided thermal resistance of the embedded half-bridge module is 0.27° C/W. As seen in Fig. 2, the PCB-embedded module has a lower junction temperature than a conventional TO-247 wire-bonded package under similar conditions.
  The PCB-embedded, half-bridge module presented here is expected to outperform industry-standard packages both thermally and electrically. Future experimental work includes thermal impedance measurement and analysis, power cycling tests, failure analysis, and converter testing to further explore the benefits and trade-offs of the PCB-embedded 1.2 kV SiC power module.
Junction temperature vs. convection coefficient
Fig. 2. Simulated junction temperature vs. convection coefficient for the PCB-embedded module with single (red) and double (blue) sided cooling, and a TO-247 package (green).

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