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SiC power devices have reached a high market penetration, especially for high-voltage applications like switch mode power supplies. In the past, however, the superior material properties like, e.g., good thermal conductivity, have often not been put to full use due to the limitations of current packaging techniques. Especially the inferior thermal conductivity of current die attach materials have been an obstacle to realise the full potential of SiC technologies. In this paper, we describe in detail the use of diffusion solder for the die attach of SiC chips. Replacing the conventional solder layer by a thin metal stack for diffusion soldering, the thermal conductivity of the device is significantly improved. In addition, we show the positive impact of diffusion soldering on the assembly process and on the device reliability. These results are interesting for, both, SiC diodes and switches.

This paper describes the calibration of a high precision AC current measurement device which is required in a system to measure AC voltages up to 800 kV in the frequency range of 10 Hz to 400 Hz. The AC current measurement unit of such a system requires the calibration of the input current in the milliampere range at a frequency of approximately 50 Hz, and all measurements have been made at a suitable frequency of 62.5 Hz. An AC Quantum Voltmeter is used to achieve a traceability chain from DC resistance calibration, when it works as DC quantum standard, and as AC quantum standard for the AC current measurement. All DC and AC measurements needed for one calibration point (one current level) can be done in a rapid sequence within 30 minutes using the same AC Quantum Voltmeter, such that the combined uncertainty is at a level of 1 µA A-1 (k = 1).

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