EPE Association: EPE 2019 - LS3a: Reliability

EPE 2019 - LS3a: Reliability
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2019 ECCE Europe - Conference > EPE 2019 - Topic 01: Devices, Packaging and System Integration > EPE 2019 - LS3a: Reliability

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   Crosstalk in SiC Power MOSFETs for Evaluation of Threshold Voltage Shift Caused by Bias Temperature Instability
By Jose ORTIZ GONZALEZ [View]
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Abstract: Threshold voltage drift from Bias Temperature Instability is known to be a reliability concern for SiC MOSFETs. Negative bias temperature instability (NBTI) results from positive charge trapping at the gate dielectric interface and is more problematic in SiC due to the higher interface trap density. Turning SiC MOSFETs OFF with negative voltages to avoid Miller coupling induced cross-talk can cause VTH shifts in periods with long standby duration and high temperatures. This paper proposes a novel test method for BTI characterization that relies on measuring the shoot-through current and charge during switching transients. The method exploits the Miller coupling between 2 devices in the same phase and uses the shoot-through current from parasitic turn-ON to monitor VTH. Standard techniques require the use of static measurements (typically from a parameter analyzer or a curve tracer) to determine the threshold voltage shift. These conventional methods can underestimate the VTH shift since the recovery from charge de-trapping can mask the true extent of the problem. The proposed methodology uses the actual converter environment to investigate the VTH shift and should therefore be of more interest to applications engineers as opposed to device physicists. Furthermore, it avoids the problem of VTH recovery and is therefore more accurate in VTH shift characterization.

   Model-Based Condition Monitoring of Power Semiconductor Devices in Wind Turbines
By Alexander BRUNKO [View]
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Abstract: A model-based condition monitoring has been established to assess the degradation of IGBT modules in wind turbines due to power cycling (thermo-mechanical degradation) and humidity (electrochemical degradation). For the estimation of the over-all lifetime of the IGBT modules, the model extracts the power losses from the converter currents and voltages and calculates the semiconductors' junction temperature based on a Cauer-model. A similar approach is applied for the calculation of the microclimate at the chip surface based on the outside humidity and operation conditions. To parametrise the degradation models, accelerated power cycling and temperature humidity tests were performed in the laboratory. Fed with operational and environmental data, the overall model can provide the health status of thedevices and this can be done even in real-time, if implemented into the converter controller. To test the system, data from an active wind farm was gathered by several data acquisition systems. The field data covers all seasons and various weather conditions. However, the calculated useful lifetimes were well beyond 100 years even for worst-case scenarios and, thus, the investigated wind turbines should not fail within their projected lifetime. Neither the degradation due to power cycling nor the degradation due to humidity driven effects nor special events like lightning strikes should become lifetime limiting. Either the failure mechanisms investigated are not the predominant ones or the powersemiconductor devices are not the primary failure. In fact, the same power semiconductors survive themuch harsher operating conditions in traction applications and, thus, the wind converters investigatedseem to be significantly overdesigned for their operation conditions. Nevertheless, there are indeedfailures that a suspected to be humidity related and, thus, require more attention.

   Power cycling results of high power IGBT modules close to 50 Hz heating process
By Guang ZENG [View]
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Abstract: The dominating heating time of power semiconductor devices in 50 Hz grid connected converters in applications such as renewable energies (wind or photovoltaic) or high voltage direct current transmission is 10 ms, since the conduction losses created by the 50 Hz AC component are dominating. In the power cycling test, a heating time of several seconds is however usually used, which may trigger different failure mode and deduce a wrong lifetime. For a precise lifetime prediction of power semiconductor devices in such applications, power cycling test with heating time and temperature swing closed to the application condition is necessary. Experimental results for 10 ms heating time at small temperature swing with more than 500 million cycles to failure are presented in this paper for the first time.

   The test method to confirm robustness against condensation
By Keiichi NAKAMURA [View]
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Abstract: This paper describes a test method to confirm the robustness of HVIGBTs (High Voltage Insulated Gate Bipolar Transistor) against dew condensation. The influence on condensation robustness was evaluated in dependency on ambient conditions applied before a condensation event. The influence of ambient conditions on the condensation robustness was first evaluated. A new cycling condensation test was proposed on the basis of the first step's result, and the acceleration factor of the cycling test was also confirmed. The accelerated cycling test is very important to reduce effort for experimental evaluation because condensation might happen some times in the field. This contribution provides us with a basis to consider HVIGBT reliability against condensation. Finally, the proposed cycling condensation test confirmed the robustness of the new generation X-series HVIGBT against condensation.

EPE 2019 - LS3a: Reliability
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2019 ECCE Europe - Conference > EPE 2019 - Topic 01: Devices, Packaging and System Integration > EPE 2019 - LS3a: Reliability
	[return to parent folder]

	Crosstalk in SiC Power MOSFETs for Evaluation of Threshold Voltage Shift Caused by Bias Temperature Instability By Jose ORTIZ GONZALEZ	[View] [Download]
Abstract: Threshold voltage drift from Bias Temperature Instability is known to be a reliability concern for SiC MOSFETs. Negative bias temperature instability (NBTI) results from positive charge trapping at the gate dielectric interface and is more problematic in SiC due to the higher interface trap density. Turning SiC MOSFETs OFF with negative voltages to avoid Miller coupling induced cross-talk can cause VTH shifts in periods with long standby duration and high temperatures. This paper proposes a novel test method for BTI characterization that relies on measuring the shoot-through current and charge during switching transients. The method exploits the Miller coupling between 2 devices in the same phase and uses the shoot-through current from parasitic turn-ON to monitor VTH. Standard techniques require the use of static measurements (typically from a parameter analyzer or a curve tracer) to determine the threshold voltage shift. These conventional methods can underestimate the VTH shift since the recovery from charge de-trapping can mask the true extent of the problem. The proposed methodology uses the actual converter environment to investigate the VTH shift and should therefore be of more interest to applications engineers as opposed to device physicists. Furthermore, it avoids the problem of VTH recovery and is therefore more accurate in VTH shift characterization.

	Model-Based Condition Monitoring of Power Semiconductor Devices in Wind Turbines By Alexander BRUNKO	[View] [Download]
Abstract: A model-based condition monitoring has been established to assess the degradation of IGBT modules in wind turbines due to power cycling (thermo-mechanical degradation) and humidity (electrochemical degradation). For the estimation of the over-all lifetime of the IGBT modules, the model extracts the power losses from the converter currents and voltages and calculates the semiconductors' junction temperature based on a Cauer-model. A similar approach is applied for the calculation of the microclimate at the chip surface based on the outside humidity and operation conditions. To parametrise the degradation models, accelerated power cycling and temperature humidity tests were performed in the laboratory. Fed with operational and environmental data, the overall model can provide the health status of thedevices and this can be done even in real-time, if implemented into the converter controller. To test the system, data from an active wind farm was gathered by several data acquisition systems. The field data covers all seasons and various weather conditions. However, the calculated useful lifetimes were well beyond 100 years even for worst-case scenarios and, thus, the investigated wind turbines should not fail within their projected lifetime. Neither the degradation due to power cycling nor the degradation due to humidity driven effects nor special events like lightning strikes should become lifetime limiting. Either the failure mechanisms investigated are not the predominant ones or the powersemiconductor devices are not the primary failure. In fact, the same power semiconductors survive themuch harsher operating conditions in traction applications and, thus, the wind converters investigatedseem to be significantly overdesigned for their operation conditions. Nevertheless, there are indeedfailures that a suspected to be humidity related and, thus, require more attention.

	Power cycling results of high power IGBT modules close to 50 Hz heating process By Guang ZENG	[View] [Download]
Abstract: The dominating heating time of power semiconductor devices in 50 Hz grid connected converters in applications such as renewable energies (wind or photovoltaic) or high voltage direct current transmission is 10 ms, since the conduction losses created by the 50 Hz AC component are dominating. In the power cycling test, a heating time of several seconds is however usually used, which may trigger different failure mode and deduce a wrong lifetime. For a precise lifetime prediction of power semiconductor devices in such applications, power cycling test with heating time and temperature swing closed to the application condition is necessary. Experimental results for 10 ms heating time at small temperature swing with more than 500 million cycles to failure are presented in this paper for the first time.

	The test method to confirm robustness against condensation By Keiichi NAKAMURA	[View] [Download]
Abstract: This paper describes a test method to confirm the robustness of HVIGBTs (High Voltage Insulated Gate Bipolar Transistor) against dew condensation. The influence on condensation robustness was evaluated in dependency on ambient conditions applied before a condensation event. The influence of ambient conditions on the condensation robustness was first evaluated. A new cycling condensation test was proposed on the basis of the first step's result, and the acceleration factor of the cycling test was also confirmed. The accelerated cycling test is very important to reduce effort for experimental evaluation because condensation might happen some times in the field. This contribution provides us with a basis to consider HVIGBT reliability against condensation. Finally, the proposed cycling condensation test confirmed the robustness of the new generation X-series HVIGBT against condensation.