Present Problems of Reliability of Power Semiconductor Devices

The paper presents an overview of the main causes of failures of modern switching devices as power MOSFETs, IGBTs, GTOs. The attention is paid to problems of both homogeneity of semiconductor structures and operating conditions, especially at high power devices, which are usually realised as an integration of a high number in parallel connected individual devices. One of the most frequent cause of the device failure is electro-thermally induced stress (especially in the case of power module encapsulations) which can result in thermal fatigue faults in applications with sequential operation mode. A comparison of empirical formulas with experimental results has been done and considerations concerning conditioning reliability of power semiconductor devices have been formulated. In the paper are also discussed some modern trends in controlling devices and the optimum operating conditions of power GTO and IGBT are discussed