70 research outputs found

    Dependence of overcurrent failure modes of IGBT modules on interconnect technologies

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    Insulated gate bipolar transistor (IGBT) modules which can fail to short circuit mode have great of applications in electricity network related fields. Single IGBT samples have been constructed with the standard Al wire bonding, flexible printed circuit board (PCB) interconnect and sandwich structure technologies. The overcurrent failure modes of the constructed IGBT samples have been tested under a range of energy levels, and the structures of the tested samples have been characterized with scanning electronic microscopy and three-dimensional X-ray computed tomography imaging. The results obtained indicate that the IGBT samples constructed with the three interconnect technologies can fail to both open circuit mode and short circuit mode. The sandwich structure IGBT sample can fail to short circuit mode under an energy level of 750 J which can meet realistic industrial applications. The networked conductive phases within the solidification structure and the Sn-3.5Ag filled in the cracks within the residual Si IGBT are responsible for forming the conducting paths in the tested samples. Both liquid phase and gas phase can be formed and the highest temperature can reach the boiling point of Si even if the sandwich structure IGBT sample is tested with short circuit failure mode

    Interconnect materials enabling IGBT modules to achieve stable short circuit failure behavior

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    Insulated gate bipolar transistor (IGBT) modules, which can fail to stable short-circuit mode, have major applications in electricity network-related fields. Sn-3.5Ag solder joints and sintered Ag joints for the die attachment and Mo, Cu, Sn-3.5Ag, Al, and Ag foils for the top side insert (TSI) material in press pack like single IGBT samples have been investigated using overcurrent and current passage tests. The results reveal that Sn-3.5Ag solder joints in combination with Sn-3.5Ag, Al, or Ag foils can be employed to achieve stable short-circuit failure mode, where the best results are achieved with Ag foils. This can be attributed to the formation of conductive networks/channels through the failed IGBT and good alignment between the residual TSI material and the failed IGBT

    Comparison of power cycling reliability of flexible PCB interconnect smaller/thinner and larger/thicker power devices with topside Sn-3.5Ag solder joints

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    The power cycling reliability of flexible printed circuit board (PCB) interconnect smaller/thinner (ST) 9.5 mm × 5.5 mm × 0.07 mm and larger/thicker (LT) 13.5 mm × 13.5 mm × 0.5 mm single Si diode samples have been studied. With the assumption of creep strain accumulation-induced fatigue cracking as the failure mechanism of the Sn-3.5Ag solder joints, finite element (FE) simulations predicted a higher power cycling reliability of soldering the flexible PCB on a ST Si diode than on a LT Si diode under similar power cycling conditions. Then the power cycling test results of 10 samples for each type are reported and discussed. The samples were constructed with commercially available ST Si diodes with 3.2/0.5/0.3 μm thick AlSiCu/NiP/Pd topside metallization and LT Si diodes with 5/0.1/1/1 μm thick Al/Ti/Ni/Ag topside metallization. In contradiction with the FE prediction, most ST Si diode samples were less reliable than those LT Si diode samples. This can be attributed to the fact that the failure of the ST diode samples was associated with the weak bonding and hence the shear-induced local delamination of the topside solder joints from the AlSiCu metallization, while the failure of the LT diode samples was mainly caused by the creep strain accumulation-induced fatigue cracking within the solder joints. Such results can be used to not only provide better understanding of the different failure mechanisms, but also demonstrate the importance of employing an appropriate topside metallization on the power devices

    Investigation into stable failure to short circuit in IGBT power modules

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    This doctoral thesis investigates modes of failure of the IGBT power module and how these modes can be coerced from an open circuit failure mode (OCFM) to a stable short circuit failure mode (SCFM) by using different interconnect technologies and material systems. SCFM is of great importance for a number of applications where IGBT power modules are connected in series string e.g. high voltage modular multi-level converters (M2LC) where one module failing to an OCFM can shut down the whole converter. The failure modes of IGBT samples based on wirebond, flexible PCB, sandwich and press pack structured interconnect technologies have been investigated. Destructive Type-II failure test were performed which concluded that the SCFM is dependent on the energy level dissipating in the power module and the interconnect technology. The higher thermal mass and stronger mechanical constraint of the interconnect enables module to withstand higher energy dissipation. The cross-sections of the tested samples have been characterised with the scanning electron microscope and three dimensional X-ray computed tomography imaging. It was observed that the networked conductive phases within the solidification structure and the Sn-3.5Ag filled in cracks of the residual Si IGBT are responsible for low resistance conduction paths. The best networked conductive phase with lowest electrical resistance and high stability was offered by Ag if used as an intermediate interconnect material on emitter side of an IGBT. To offer a stable SCFM, a module has to be custom designed for a particular application. Hence for the applications which demand a stable SCFM, the IGBT module design becomes an integrated part of the complete power electronics system design

    10-kV SiC MOSFET Power Module With Reduced Common-Mode Noise and Electric Field

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    The advancement of silicon carbide (SiC) power devices with voltage ratings exceeding 10 kV is expected to revolutionize medium- and high-voltage systems. However, present power module packages are limiting the performance of these unique switches. The objective of this research is to push the boundaries of high-density, high-speed, 10-kV power module packaging. The proposed package addresses the well-known electromagnetic and thermal challenges, as well as the prominent electrostatic and electromagnetic interference (EMI) issues associated with high-speed, 10-kV devices. The high-speed switching and high voltage rating of these devices causes significant EMI and high electric fields. Existing power module packages are unable to address these challenges, resulting in detrimental EMI and partial discharge that limit the converter operation. This article presents the design and testing of a 10-kV SiC mosfet power module that switches at a record 250 V/ns without compromising the signal and ground integrity due to an integrated screen reduces the common-mode current by ten times. This screen connection simultaneously increases the partial discharge inception voltage by more than 50%. With the integrated cooling system, the power module prototype achieves a power density of 4 W/mm 3

    Investigation into stable failure to short circuit in IGBT power modules

    Get PDF
    This doctoral thesis investigates modes of failure of the IGBT power module and how these modes can be coerced from an open circuit failure mode (OCFM) to a stable short circuit failure mode (SCFM) by using different interconnect technologies and material systems. SCFM is of great importance for a number of applications where IGBT power modules are connected in series string e.g. high voltage modular multi-level converters (M2LC) where one module failing to an OCFM can shut down the whole converter. The failure modes of IGBT samples based on wirebond, flexible PCB, sandwich and press pack structured interconnect technologies have been investigated. Destructive Type-II failure test were performed which concluded that the SCFM is dependent on the energy level dissipating in the power module and the interconnect technology. The higher thermal mass and stronger mechanical constraint of the interconnect enables module to withstand higher energy dissipation. The cross-sections of the tested samples have been characterised with the scanning electron microscope and three dimensional X-ray computed tomography imaging. It was observed that the networked conductive phases within the solidification structure and the Sn-3.5Ag filled in cracks of the residual Si IGBT are responsible for low resistance conduction paths. The best networked conductive phase with lowest electrical resistance and high stability was offered by Ag if used as an intermediate interconnect material on emitter side of an IGBT. To offer a stable SCFM, a module has to be custom designed for a particular application. Hence for the applications which demand a stable SCFM, the IGBT module design becomes an integrated part of the complete power electronics system design

    DC Microgrid Protection: A Comprehensive Review

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    Fault analysis and protection for wind power generation systems

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    Wind power is growing rapidly around the world as a means of dealing with the world energy shortage and associated environmental problems. Ambitious plans concerning renewable energy applications around European countries require a reliable yet economic system to generate, collect and transmit electrical power from renewable resources. In populous Europe, collective offshore large-scale wind farms are efficient and have the potential to reach this sustainable goal. This means that an even more reliable collection and transmission system is sought. However, this relatively new area of offshore wind power generation lacks systematic fault transient analysis and operational experience to enhance further development. At the same time, appropriate fault protection schemes are required. This thesis focuses on the analysis of fault conditions and investigates effective fault ride-through and protection schemes in the electrical systems of wind farms, for both small-scale land and large-scale offshore systems. Two variable-speed generation systems are considered: doubly-fed induction generators (DFIGs) and permanent magnet synchronous generators (PMSGs) because of their popularity nowadays for wind turbines scaling to several-MW systems. The main content of the thesis is as follows. The protection issues of DFIGs are discussed, with a novel protection scheme proposed. Then the analysis of protection scheme options for the fully rated converter, direct-driven PMSGs are examined and performed with simulation comparisons. Further, the protection schemes for wind farm collection and transmission systems are studied in terms of voltage level, collection level wind farm collection grids and high-voltage transmission systems for multi-terminal DC connected transmission systems, the so-called “Supergrid”. Throughout the thesis, theoretical analyses of fault transient performances are detailed with PSCAD/EMTDC simulation results for verification. Finally, the economic aspect for possible redundant design of wind farm electrical systems is investigated based on operational and economic statistics from an example wind farm project

    Electro-thermal Modeling of Modern Power Devices for Studying Abnormal Operating Conditions

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