25 April 2017

Fraunhofer IAF’s GaN-on-Si monolithic multi-level power converter demonstrated using AT&S’ embedded component technology

The Fraunhofer Institute for Applied Solid State Physics IAF of Freiburg, Germany has developed a fully integrated monolithic multi-level converter in high-voltage AlGaN/GaN-on-Si technology. The integrated inverter circuit is designed for maximum voltages of +/-400V and currents of 5A. The multi-level converter comprises four transistors and six diodes but covers an area of just 2mm x 3mm, suiting compact voltage-converter applications. DC/AC inverter operation has been demonstrated for US mains voltage. The circuit exhibits minimal dynamic losses at very high frequencies. The switching performance of the multi-level converter was demonstrated with a test setup based on the Embedded Component Technology (ECP) of printed-circuit board (PCB) maker AT&S (Austria Technologie & Systemtechnik) AG of Leoben, Austria.

A corresponding test setup is necessary in order to evaluate the chip, since the packaging of the die constitutes a key factor. If lateral components are employed, then the source, drain and gate pads are on one side and the back of the die is used for heat dissipation. Since the conventional approach using wirebonds imposes restrictions, the second step of the evaluation saw AT&S’ ECP technology being used. The power components – like the multi-level converter – are hence embedded into the PCB material and can be connected from both sides. The chips are connected directly via copper-plated microvias. This permits low-impedance connections and significantly lower inductances compared with wirebond technology. The rear of the die is also connected by means of copper-plated microvias, ensuring excellent heat dissipation.

“We see this [AT&S ECP] mounting technology as opening up entirely new possibilities – particularly also for more complex monolithic integrated GaN power circuits, as used on our multi-level converter chip,” says Fraunhofer IAF scientist Richard Reiner. “With a conventional design, we were hardly able to use and/or evaluate the powerful chip,” he adds.

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

AT&S (in Hall 6, Stand 323) and Fraunhofer IAF (in Hall 7, Stand 237) are presenting their power solutions at the PCIM (Power Conversion Intelligent Motion) Europe 2017 exhibition in Nuremberg, Germany (16-18 May).

Tags: IAF GaN-on-Si Power electronics inverters Power management integrated circuits

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