Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> 1) Bond wire lift-off or rupture. <s> This paper develops a real-time condition-monitoring algorithm for pulsewidth modulation (PWM) inverter induction-motor drives. It is designed to detect the intermittent loss of firing pulses of an individual switching device within the inverter. The mathematical model of the induction machine is linearized in the field-torque coordinates, and the misfiring of the inverter is represented by pulse functions, which have effects in both the field and torque directions. Since the fault considered is of an intermittent nature, the time-domain response of the magnetizing and the torque-producing components of the motor stator current is used to form the condition-monitoring signal. The method is adaptive to changes in the operating point during variable-speed operation. Digital simulation and laboratory experiment are utilized to illustrate the method and to evaluate the computational effort required. <s> BIB001 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> 1) Bond wire lift-off or rupture. <s> Abstract This paper reviews the main failure mechanisms occurring in modern power modules paying special attention to insulated gate bipolar transistor devices for high-power applications. This compendium provides the main failure modes, the physical or chemical processes that lead to the failure, and reports some major technological countermeasures, which are used for realizing the very stringent reliability requirements imposed in particular by the electrical traction applications. <s> BIB002 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> 1) Bond wire lift-off or rupture. <s> In this paper, thermal cycling reliability along with ANSYS analysis of the residual stress generated in heavy-gauge Al bond wires at different bonding temperatures is reported. 99.999% pure Al wires of 375 mum in diameter, were ultrasonically bonded to silicon dies coated with a 5mum thick Al metallisation at 25degC (room temperature), 100degC and 200degC, respectively (with the same bonding parameters). The wire bonded samples were then subjected to thermal cycling in air from -60degC to +150degC. The degradation rate of the wire bonds was assessed by means of bond shear test and via microstructural characterisation. Prior to thermal cycling, the shear strength of all of the wire bonds was approximately equal to the shear strength of pure aluminum and independent of bonding temperature. During thermal cycling, however, the shear strength of room temperature bonded samples was observed to decrease more rapidly (as compared to bonds formed at 100degC and 200degC) as a result of a high crack propagation rate across the bonding area. In addition, modification of the grain structure at the bonding interface was also observed with bonding temperature, leading to changes in the mechanical properties of the wire. The heat and pressure induced by the high temperature bonding is believed to promote grain recovery and recrystallisation, softening the wires through removal of the dislocations and plastic strain energy. Coarse grains formed at the bonding interface after bonding at elevated temperatures may also contribute to greater resistance for crack propagation, thus lowering the wire bond degradation rate. <s> BIB003 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> 1) Bond wire lift-off or rupture. <s> This paper proposes a useful smart gate drive with self-diagnosis for power MOSFETs and IGBTs. This new method is based on monitoring of the gate charge and discharge currents. Two gate current monitoring circuits are proposed and validated with experimental results. The implemented smart functions include self-acknowledgement, gate drive connection verification, power device status diagnosis, gate dielectric wearout detection and prediction. The proposed method can detect abnormal conditions that occur either within the gate drive circuit itself or in the driven power device. It also features simple and low cost implementation and can be easily integrated into gate drive circuits or gate drive chips. <s> BIB004 </s> Catastrophic failure and fault-tolerant design of IGBT power electronic converters - an overview <s> 1) Bond wire lift-off or rupture. <s> The compliance to the fault tolerant operation requirement for power electronics is commonly assessed with reference to fault models applicable at component level. For switching MOSFET, the fault models include the short-circuit and open-circuit failures, implicitly assuming that the Gate open failure is equivalent to a switch open or short failure. MOSFET Gate open failure, also called floating Gate failure, may however entail a Drain to Source channel conduction with non-zero impedance and the subsequent power dissipation in the failed device may prove critical because of the thermal failure propagation risk. The present paper is dedicated to that question. It is shown that a power MOSFET with floating Gate is driven by leakage current from whatever initial conduction status either into a steady-state dissipative status or into run-away due to thermal instability. The analysis is confirmed by practical tests. As a conclusion, provisions to mitigate the MOSFET Gate open failure are proposed to be implemented at MOSFET level and/or at converter design level. <s> BIB005
Bond wire lift-off failure can happen after short-circuit failure. It is generally due to mechanical reasons. The main mechanisms are related to mismatch of coefficients of thermal expansion (CTEs) between Silicon and Aluminum, together with high temperature gradients. Crack initiates at the periphery of the bonding interface, and the bond wire finally lifts-off when crack propagates to the weaker central bond area BIB003 . Central emitter bond wires normally fail first, and then the survivor bond wires follow. Another failure mechanism is bond wire rupture, which is slower than lift-off and usually observed after long power cycling tests BIB002 . 2) Gate driver failure. There are various causes of gate driver failure, such as power stage devices (e.g. BJTs or MOSFETs) damaged; wires between drive board and IGBT disconnected BIB001 . The driver failure may result in IGBT intermittent misfiring, degraded output voltage, and overstress of other IGBTs and capacitors. Abnormal work conditions in power terminals of IGBT can also lead to driver failure. Continued narrow overvoltage spikes between collector and emitter may open the gate-emitter resistance, while over-current of IGBT's collector may lead to gate-emitter resistance degradation BIB004 . Gate open-circuit failure can result in thermal runaway or high power dissipation BIB005 ; however detailed research on the physical failure mechanism is still lacking. Moreover, modern IGBTs can work at 175°C junction temperature, which means the case temperature could reach 100°C or more, while most components in the driver cannot work normally at such high temperature. Thus this is a challenge for gate driver working at high temperature.