Embedded substrate allows fully integrated GaN-on-Si multilevel power converter

Embedded substrate allows fully integrated GaN-on-Si multilevel power converter

Technology News |
By Nick Flaherty

The integrated inverter circuit is designed for a maximum voltage of ±400 V and current of 5 A. The multilevel converter measures just 2 × 3 mm and is built from four transistors and six diodes for compact voltage converter applications. It was possible to demonstrate DC/AC inverter operation for American mains voltage and the circuit exhibits minimal dynamic losses at very high frequencies.

Packaging the die was a key consideration for the evaluation board. If lateral components are employed, the source, drain and gate pads are on one side and the back of the die is used for heat dissipation. As the conventional approach with wirebonds imposed restrictions, ECP embedded substrate technology from AT&S was used. This allowed the power components such as the multilevel converter to be embedded into the PCB material and connected from both sides. The chips are connected directly via copper-plated microvias for low impedance connections that significantly lower the inductance compared with wirebond technology. The rear of the die is also connected by means of copper-plated microvias. This ensures excellent heat dissipation.

“We see this mounting technology as opening up entirely new possibilities – particularly also for more complex monolithic integrated GaN power circuits, as used on our multilevel converter chip,” said Richard Reiner, researcher at Fraunhofer IAF. “With a conventional design, we were hardly able to use and/or evaluate the powerful chip.”

“Power electronics constitutes a major field of application and focus for the embedding technology from AT&S,” said Dietmar Drofenik, CEO of the Business Unit Advanced Packaging at AT&S. “Particularly for the use of ‘wide bandgap semiconductor’ materials, such as GaN, the embedding technology makes innovative miniaturised power packages possible for higher efficiencies, enhanced thermal performance and higher power densities. In collaboration with partners, AT&S has for example already implemented various GaN power circuits, which are characterised by excellent switching performance and high efficiency.”

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