Papers by Author: Peter Türkes

Abstract: In this paper we compare the thermal behavior of identical SiC Schottky diodes mounted in i) a standard TO220 package (TO220) with non-isolated backside applying standard soft solder and diffusion solder die attach with ii) a so called FULLPAK TO220 package (TO220FP, only diffusion soldering). Depending on the solder technique the heat transport from the junction area of the SiC Schottky diode to the heat sink or to the package backside is improved for the diodes mounted via diffusion solder. For small chips this holds even for TO220FP in comparison to TO220 with standard solder. Simulations of the vertical temperature distribution after electrically heating with a half sine wave for 10ms up to 190W show a decrease of the maximal junction temperature of the SiC Schottky diode from TJ=260 °C to TJ=180 °C if the diffusion solder is used independent from the package type.

Abstract: After the successful introduction of silicon carbide Schottky-Barrier diodes in 2001, next commercial devices will be switching components. The development focus is targeted to MOSFETs and VJFETs. Regarding VJFETs, a promising device was presented several years ago and tested successfully in several applications. Since the unconventional device structure does not allow the use of classical JFET models, a new electro-thermal model was developed, taking into account the features of the design as well as the targeted enlarged range of operating temperatures.

Abstract: 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.

Abstract: Other than open micropipes (MP), overgrown micropipes do not necessarily lead to a^significantly reduced blocking capability of the affected SiC device. However they can lead to a degradation of the device during operation. In this paper the physical structure of overgrown micropipes will be revealed and their contribution to the leakage current will be shown. The possible impact of the high local power dissipation in the surrounding of the overgrown micropipe will be discussed and long term degradation mechanisms will be described. Failure simulation under laboratory conditions shows a clear correlation between the position of overgrown micropipes and the location of destructive burnt spots.