Extending the lifetime of power electronic assemblies by increased cooling temperatures

摘要

The lifetime of power electronic modules can be assessed by an active power cycling test. The results are often compared to empirical (e.g. LESIT) and physical lifetime models (e.g. Suhir). During the last years new device technologies, such as silver-sintering instead of soldering and SiC instead of Si semiconductors, found their way into power electronics. For the evaluation of lifetime prediction models for assemblies with these new technologies, power cycling tests were performed. Thereby, the cooling temperature T_(min) and the temperature swing AT were varied on two stages for SiC diodes that were silver-sintered to DBC substrates and wire bonded from the topside. All samples failed due to sinter layer degradation. While a higher AT decreased the number of cycles to failure, an increased Y_(min) did not lead to a lower lifetime of the tested devices. Instead, lifetime increased with a higher cooling temperature. No empirical model can deal with this behaviour. In order to explain these results, only physical approaches are appropriate.