Power Electronics

CIPS 2008 Explored Reliability and Many Other Issues

The recent 5th International Conference on Integrated Power Electronics Systems (CIPS 2008) in Nuremberg, Germany brought together 232 attendees from industry, research institutes and universities to discuss a variety of advanced power technology topics. The conference, which ran March 11 to 13, addressed areas such as the robustness and reliability of power modules, advanced packaging technology and EMC and thermal management.

Other subjects addressed included gate drives and control, passive components, SiC devices and silicon integrated smart power, and power electronics and system integration. The conference was organized by ETG, the Power Engineering Society within VDE, and co-organized by ECPE, the European Center for Power Electronics.

In the opening session, Helmut Keller (ZVEI) explained a new concept of robustness validation for automotive and aerospace electronic components and systems. The concept means a paradigm shift from “fit for test” to “fit for application” and is based on a knowledge of mission profiles (it describes all the stresses applied during operation), physics-of failure and the end-of-life tests. The robustness validation initiative is a joint effort of ZVEI, Society of Automotive Engineers (SAE) and the Japanese SAE (JSAE).

Chris Bailey (University of Greenwich, UK) presented his approach on “predictive reliability, prognostics and risk assessment for power modules”. Accurate lifetime prediction based on realistic mission profiles represents a challenge for the design of complex devices and systems. Mauro Ciappa (ETH Zurich) gave some examples where this problem has been solved by proper analysis, by dedicated physical modeling, and by efficient calculation tools.

It is a common understanding that reliability has to be built-in from the beginning in a design process. This is true as well for building-in EMI. Jean-Luc Schanen (G2ELab, CNRS, France) and Eckart Hoene (Fraunhofer IZM, Berlin) described in detail the effects that may occur and methods for avoiding electromagnetic disturbances. Examples were given for power modules and power electronic systems.

A review of highly integrated solutions for power electronics devices was given by Jürgen Schulz-Harder (Electrovac Curamic, Germany). He described several concepts of how to extract heat from IGBT and diode chips. Of great interest are double-sided liquid cooling concepts like those from Alstom, Toyota, Fraunhofer and Curamik.

Uwe Scheuermann (Semikron) introduced the new solderless SKIM module and showed promising reliability data. Here, solderless refers to the application of silver sintering technology instead of soft solder. One of the big advantages is the high melting temperature of silver (962°C) which results in more stable thermomechanical properties for the joint. Guo-Quan Lu (CPES, USA) described pros and cons of nano-silver joining: For getting good and reliable joints, a small amount of pressure in comparison to “classic” silver sintering is needed.

Peter Friedrichs (SiCED, Germany) reported on system solutions where SiC Schottky diodes and JFETs are yielding compact systems that have good potential for cost reduction. Dominique Bergogne (Ampere, INSA-Lyon, France) discussed circuit topologies for normally-on SiC JFETs. He showed that inverters using normally-on power switches do not differ from inverters based on normally-off devices when the gate driver is taken into account. He proposed building blocks of a gate driver solely using SiC normally-on JFETs.

Three invited papers were presented in the system-integration session. Gerald Deboy (Infineon, Austria) took the power supply for server applications to discuss specific challenges for power factor correction, isolating PWM stage and synchronous rectification. A deep understanding of the behavior of the CoolMOS devices, however, is necessary to optimize the overall system.

Dushan Boroyevich (CPES, USA) gave an overview of the results achieved during ten years of operation of the Center for Power Electronics Systems (CPES) at Virginia Tech. Many of the demonstrators built and tested by CPES—like non-wirebond packages—were accepted by industry. The activities at Virginia Tech will continue even as CPES’s role as an NSF center of excellence will end.

Hiromichi Ohashi (AIST/PERC, Japan) reported on SiC activities and achievements. These include micropipe-free wafers, MOSFETs, high-voltage devices, and power electronics systems. It was noted that Japan is aiming for a fully electrified society in 2050 to be independent from fossil materials. Power electronics will be a dominant technology.

ECPE organized a panel discussion on ´Intelligent Power Electronics for Energy Efficiency - Research Needs and Opportunities´ focusing on the future role of power electronics research topics in the ICT Programme of EC FP7. Manuel Sanchez (EC, ICT for Sustainable Growth) presented actions at the EU level in the field of Information & Communication Technologies for Energy Efficiency. Experts from CPES, AIST/PERC and ECPE highlighted the key role of power electronics for energy saving and improved energy efficiency.

In the last session ECPE proposed Research and Technology Roadmaps in the fields of automotive, high frequency power conversion. To support the seven power electronics roadmaps a bottom-up roadmap, containing roadmaps for all parts and components used in the power electronics system was introduced as well.

The next CIPS Conference will take place in Nuremberg in the spring of 2010. For more information, contact Juergen Bublitz of the ECPE European Center for Power Electronic at +49 (0)911 / 810 288 12 or [email protected]

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