Showing papers on "Junction temperature published in 2017"

Evaluation of Vce at Inflection Point for Monitoring Bond Wire Degradation in Discrete Packaged IGBTs

Abstract: A novel scheme is proposed for online condition monitoring of bond wires present in insulated gate bipolar transistor (IGBT) package. The proposed method detects bond wire degradation using on-state collector emitter voltage at the inflection point. Previously reported condition monitoring methods based on on-state collector-emitter voltage as a precursor of aging require an accurate knowledge of junction temperature which is difficult to measure online during an inverter operation. The key advantage of the proposed scheme is that it monitors the bond wire degradation irrespective of the junction temperature. Therefore, this technique is not affected by increase in junction temperature due to die attach degradation or change in ambient temperature. The proposed scheme is verified experimentally under realistic operating conditions.

An Investigation of Temperature-Sensitive Electrical Parameters for SiC Power MOSFETs

Abstract: This paper examines dynamic temperature-sensitive electrical parameters (TSEPs) for SiC MOSFETs. It is shown that the switching rate of the output current ( dI DS /dt ) coupled with the gate current plateau (I GP) during turn-ON could be an effective TSEP under specific operating conditions. Both parameters increase with the junction temperature of the device as a result of the negative temperature coefficient of the threshold voltage. The temperature dependency of dI DS /dt has been shown to increase with the device current rating (due to larger input capacitance) and external gate resistance ( $R_{G}^{\rm EXT}$ ). However, as dI DS /dt is increased by using a small $R_{G}^{\rm EXT}$ , parasitic inductance suppresses the temperature sensitivity of the drain and gate current transients by reducing the “effective gate voltage” on the device. Since the temperature sensitivity of dI DS /dt is at the highest with maximum $R_{G}^{\rm EXT}$ , there is a penalty from higher switching losses when this method is used in real time for junction temperature sensing. This paper investigates and models the temperature dependency of the gate and drain current transients as potential TSEPs for SiC power MOSFETs.

Single-Pulse Avalanche Mode Robustness of Commercial 1200 V/80 mΩ SiC MOSFETs

Abstract: Commercialization of 1200-V silicon carbide (SiC) MOSFET has enabled power electronic design with improved efficiency as well as increased power density. High-voltage spikes induced in applications such as solenoid control, solid-state transformer, boost converter, and flyback converter can drive the MOSFET into avalanche mode operation due to high di / dt coupled with parasitic inductance. Avalanche mode operation is characterized by high-power dissipation within the device due to the high voltage and current crossover. This study focuses on the evaluation of two commercially available SiC MOSFETs from different manufacturers, each rated for 1200 V with an ON-state resistance of 80 mΩ, during unclamped inductive switching (UIS) mode operation. To determine device reliability, a decoupled UIS testbed was developed to evaluate the avalanche energy robustness at 22 $ \,^{\circ}$ C and 125 $ \,^{\circ}$ C during two specific conditions: high current and low energy, and low current and high energy. The SiC MOSFETs were evaluated using a load inductance of 1.42, 5.1, 10.5, and 15.8 mH to understand the effect of current and avalanche energy on device failure. To correlate the experimental results with the failure mechanism, estimated junction temperature and static device characteristics are presented; additionally, MOSFETs were decapsulated to examine the failure sites on the semiconductor die.

IR Camera Validation of IGBT Junction Temperature Measurement via Peak Gate Current

Abstract: Infrared measurements are used to assess the measurement accuracy of the peak gate current (I GPeak ) method for Insulated-gate bipolar transistor (IGBT)junction temperature measurement. Single IGBT chips with the gate pad in both the center and the edge are investigated, along with paralleled chips, as well as chips suffering partial bondwire lift-off. Results are also compared with a traditional electrical temperature measurement method: the voltage drop under low current (V CE (low ) ). In all cases, the IG Peak method is found to provide a temperature slightly overestimating the temperature of the gate pad. Consequently, both the gate pad position and chip temperature distribution influence whether the measurement is representative of the mean junction temperature. These results remain consistent after chips are degraded through bondwire lift-off. In a paralleled IGBT configuration with nonnegligible temperature disequilibrium between chips, the I GPeak method delivers a measurement based on the average temperature of the gate pads.

Condition Monitoring IGBT Module Bond Wires Fatigue Using Short-Circuit Current Identification

Abstract: Finding and replacing the defective insulated-gate bipolar transistor (IGBT) module timely by monitoring the ageing state of IGBT can improve the reliability of a power converter and reduce the loss caused by IGBT failure. A method for detecting the condition of bond wires in IGBT module by identifying the short-circuit current of IGBT module is presented in this paper. It is based on the fact that parasitic parameters of IGBT module are affected by the local damage induced by ageing over time, and these changes can be easily detected by monitoring the difference of short-circuit current. The study results indicate that short-circuit current of IGBT module decreases with module ageing over time, and the difference of short-circuit current caused by junction temperature is much smaller than that caused by bond wires fatigue on a specific gate driving voltage. Therefore, the IGBT module in the power converter can be diagnosed by detecting the difference of short-circuit current without considering the effects of junction temperature. Finally, a confirmatory experiment is carried out, and the correctness of the method proposed in this paper is verified.

Power cycling methods for SiC MOSFETs

Abstract: The evaluation of power cycling results needs correct measurement of the course of thermal resistance. Hence an accurate online measurement of the junction temperature is necessary. Different measurement and power cycling methods were evaluated. The method of measuring the voltage drop of the SiC MOSFET body diode pn-junction at low measurement current with sufficient negative gate-voltage was found most suitable one. In addition power losses during power cycling test should be generated in forward MOSFET-mode at high positive gate-voltage. Otherwise test results will not be application conform.

Study on Effect of Junction Temperature Swing Duration on Lifetime of Transfer Molded Power IGBT Modules

Abstract: In this paper, the effect of junction temperature swing duration on lifetime of transfer molded power insulated gate bipolar transistor (IGBT) modules is studied and a relevant lifetime factor is modeled. This study is based on 39 accelerated power cycling test results under six different conditions by an advanced power cycling test setup, which allows tested modules to be operated under more realistic electrical conditions during the power cycling test. The analysis of the test results and the temperature swing duration dependent lifetime factor under different definitions and confidence levels are presented. This study enables to include the t △ Tj effect on lifetime model of IGBT modules for its lifetime estimation and it may result in improved lifetime prediction of IGBT modules under given mission profiles of converters. A postfailure analysis of the tested IGBT modules is also performed.

Short-Circuit Degradation of 10-kV 10-A SiC MOSFET

Abstract: The short-circuit behavior of power devices is highly relevant for converter design and fault protection. In this paper, the degradation during short circuit of a 10-kV 10-A 4H-SiC MOSFET is investigated at 6 kV dc-link voltage. The study aims to present the behavior of the device during short-circuit transients as it sustains increasing short-circuit pulses during its lifetime. As the short-circuit pulse length increases, degradation of the device can be observed in periodically performed characterizations. The initial degradation seems to be associated with the channel region, and continuous stressing leads to an overall increase in device on-state resistance at the end of the degradation study. Thermal simulation shows that the surface aluminum metalization reached its melting temperature and the top part of the device reaches temperatures above the rated junction temperature. Scanning electron microscope investigation shows aluminum reconstruction and cavities at the contact interface between the aluminum surface metalization and source contacts.

Evaluating Different Implementations of Online Junction Temperature Sensing for Switching Power Semiconductors

Abstract: Switching power semiconductor online junction temperature $T_{j}$ sensing is essential for device switching performance evaluation, device switching control, and device lifetime optimization. The contribution of this paper is a detailed evaluation of the implementation issues (including circuit invasiveness, hardware integration, signal processing, and so forth) of different online $T_{j}$ sensing methods. This paper includes $T_{j}$ sensing methods based on device power dissipation, $T_{j}$ sensing methods based on the “sensor-on-die technology,” $T_{j}$ sensing methods based on device on-state analysis, and $T_{j}$ sensing methods based on device switching transients. Advantages and limits of these methods are also provided.

Analytical and Experimental Investigation on A Dynamic Thermo-Sensitive Electrical Parameter With Maximum $dI_{C}/dt$ During Turn-off for High Power Trench Gate/Field-Stop IGBT Modules

Abstract: In this paper, a dynamic thermo-sensitive electrical parameter (DTSEP) for extracting the junction temperature of the trench gate/field-stop insulated gate bipolar transistor (IGBT) modules by using the maximum collector current falling rate is proposed. First, a theoretical model of the transient collector current during turn- off process is developed in terms of the behavior characteristics of the inside storage carriers. Then, the inherent linear relationship between the maximum collector current falling rate $dI_{C}/dt$ and junction temperature $T_{j}$ is demonstrated and investigated. Fortunately, benefitting from the presence of the intrinsic parasitic inductance $L_{\rm eE}$ between the Kelvin and power emitters of IGBT modules, the maximum $dI_{C}/dt$ can be easily measured to validate the theoretical analysis. Consequently, the maximum $dI_{C}/dt$ during turn- off process is a promising DTSEP for IGBT module junction temperature estimation. Moreover, the physical device parameters that affect the temperature sensitivity of the maximum $dI_{C}/dt$ are also discussed with the derived transient collector current falling model.

Comparison of IGBT junction temperature measurement and estimation methods-a review

Abstract: Recent growth of power semiconductor device market has been driven largely by the growing demand for an efficient way to convert and distribute energy in the field of renewable energy, electrical vehicles, aerospace, marine and applications. For safety, critical applications, temperature management and control are the most important functions. Therefore, estimating or measuring the junction temperature of the power semiconductor device is useful to perform thermal management and converter control. Several methods have been published to measure the junction temperature of the insulated gate bipolar transistor (IGBT). This paper attempts to summarize the past developments and recent advances in measuring junction temperature of power semiconductor device is presented. Finally, the promising methods are recommended for future work.

Short circuit capability and high temperature channel mobility of SiC MOSFETs

Abstract: Short circuit capability of a 1200V SiC MOSFET and a 1200V Si IGBT is compared and analyzed in this work, and the channel mobility in the SiC MOSFET over a broad temperature range from room temperature up to 2000 °C has been extracted for the first time. Experimental results show that SiC MOSFET exhibits shorter short circuit withstand time (SCWT) compared to Si IGBT. 1-D transient finite element thermal models of SiC MOSFETs and Si IGBTs have been implemented to simulate the dynamic temperature profiles in devices during short circuit tests. The junction temperature of SiC MOSFET rises much faster than that of Si IGBT and the heat spreading thickness of SiC MOSFET is much narrower, leading to shorter SCWT of the SiC MOSFET. Combining the experimental and thermal simulation results, the temperature-dependent saturation drain current in SiC MOSFETs is extracted. Based on this, the channel mobility over a wide temperature range is obtained.

Thermal Coupling Analysis in a Multichip Paralleled IGBT Module for a DFIG Wind Turbine Power Converter

Abstract: Thermal coupling between adjacent insulated gate bipolar transistor (IGBT) or diode chips is the result of nonuniform temperature distribution in a multichip IGBT module. This affects the junction temperatures and hence the total power loss predicted for the module. The study first investigates the impact of thermal coupling effect on the junction temperatures through a finite element method, and then develops a thermal coupling impedance model to represent such effects. The effect is shown to reduce with the distance exponentially. The model result agrees well with the test. The validated model is then used to predict the junction temperature swings during operational power cycling in a doubly fed induction generator wind turbine, showing the difference between the rotor and grid side converters. The model presented and the results obtained may be important for reliability evaluation and condition monitoring in the wind turbine power converters as well as in other multichip-paralleled power electronic systems.

Control of Junction Temperature and Its Rate of Change at Thermal Boundaries via Precise Loss Manipulation

Abstract: To optimize the lifetime of switching power semiconductors, this paper presents a methodology to control power device junction temperature T j and its change during power cycles ΔT j at thermal boundaries This paper proposes a supervisory state machine to interrupt nominal system-level control only when temperature bounds are exceeded, and coordinates smooth transitions as T j (k) and ΔT j (k) approach their respective boundaries To ensure that thermal states are regulated via precise and independent modulation of conduction and switching loss elements, decoupling methods are proposed Also proposed is a ΔT j control law that closes a control loop on the rate of change state Ṫ j , and introduces active thermal capacitance and conductance into the closed-loop thermal system dynamics Experimental evaluation of the proposed system illustrates well damped T j (k) and ΔT j (k) responses, and gradual adjustment of the manipulated inputs switching frequency and duty ratio Finally, comparison with a current limit-based T j regulation method illustrates how the proposed system allows power converters to push harder against their thermal limits

Applications of Wide Bandgap (WBG) devices in AC electric drives: A technology status review

Abstract: This paper is an effort to put together all the potential applications of Wide Bandgap (WBG) devices in AC electric drives. Low inductance motors, high speed motors, and electric drives operating in a high temperature environment are the main application areas of WBG devices. Low voltage permanent magnet motors and slotless motors have a low inductance and require a stringent high-bandwidth current regulation strategy to obtain an acceptable current ripple. Silicon (Si) devices cannot be used in this case due to their limited switching frequency. MW-level high speed motors have devices operating at high voltage and current levels and a high fundamental frequency (600–1200 Hz) that cause very high switching losses in Si IGBT devices. SiC devices have enabled the use of power electronic converters for MW-level high speed motors. Integrated motor drives (IMDs) are also benefitted by WBG devices as they reduce the size of the power converter and allow operation at a high junction temperature. Therefore, the inverter can be mounted on the motor itself which can be a significant heat source due to motor losses. Cooling requirements in high temperature environment applications such as hybrid Electric Vehicle (EV), ground vehicles in combat zones, and power converters used in space technology like land rovers etc., are greatly reduced due to low losses and high junction temperatures. Operation at high frequencies and high temperatures reduces the size of electric drive significantly.

A Fast Electro-Thermal Model of Traction Inverters for Electrified Vehicles

Abstract: In this paper, a fast electro-thermal model of traction inverters for electrified vehicles is proposed. First, a thermal model considering the thermal coupling is presented and experimentally verified. The impact of the thermal spreading effect, heat convection, and temperature-dependent material thermal properties on the accuracy of the linear assumption is investigated by ANSYS-Fluent simulation. In order to reduce the influence of the temperature-dependent thermal conductivity on the accuracy of the thermal model, the average temperature is applied to determine the thermal conductivity of the power module package. Second, an accurate temperature-dependent switching power loss model is represented as the lookup table through experimental measurements. In order to simplify the lookup table, the switching power loss is considered proportional to the dc-link voltage and, therefore, the inputs of the lookup table are current and temperature. Finally, a scheme to speed up the online junction temperature estimation is proposed by considering both the thermal network properties and the required accuracy. With the proposed calculation rate determination method, the total computational time for the junction temperature estimation is reduced significantly.

Potential thermally conductive alumina filled epoxy composite for thermal management of high power LEDs

Abstract: Thermal properties of thermally conductive epoxy based composites are mainly influenced by their formulation and thermal processing. The present study is intended to develop an effective thermally conductive filler filled epoxy composite as thermal interface material (TIM) for light emitting diode (LED) application. Two different average particle sizes of aluminium oxide (Al2O3) powder (44 and 10 µm) were studied for its feasibility as filler material at its maximum loading. For given filler loading of 75 wt%, larger; 44 µm Al2O3 particle filled composite resulted in enhanced thermal conductivity of 2.06 W/mK. 10 µm Al2O3 composites achieved maximum thermal conductivity of 1.19 W/mK. Computational fluid dynamics software was utilized in order to investigate the thermal performance of the LED with the fabricated TIMs. The analyses were carried out using FloEFD 15 to predict the junction temperature (TJ) at the active region of the LED under test. The simulation predictions were validated with experimental results employing thermal transient measurement. The least TJ was achieved for 10 µm Al2O3 filled TIM followed by 44 µm and then neat epoxy with the average values of 66.30, 86.16 and 92.03 °C respectively.

Aging precursors and degradation effects of SiC-MOSFET modules under highly accelerated power cycling conditions

Abstract: A highly accelerated power cycling test platform using current source converter for SiC-MOSFET power modules is proposed. The control principles of delta and average junction temperatures are introduced. By using isolated thermal fibers, the junction temperature (T j ) variations can be monitored during the test process without removal of silicone gel. The power module is tested in the conditions of ΔT j =60 °C, mean temperature T jm =145 °C and the maximum T j =175 °C. By means of device analyzer, the degraded conditions of electrical parameters after power cycling test are fully investigated and compared. As a result, the effects of degradation on the static and dynamic characteristics during conventional operation are discussed. Finally, the research results can help examine the failure precursors and then estimate the remaining useful lifetime of SiC MOSFET modules.

Microchannel cooling strategies for high heat flux (1 kW/cm 2 ) power electronic applications

Abstract: The wide band-gap (WBG) semiconductor electronics such as silicon carbide (SiC) and gallium nitride (GaN) are becoming more popular in power electronics applications due to their excellent functionality at higher operating temperatures, powers, frequencies and in high radiation environments compared to Si devices. However, the continued drive for higher device and packaging densities has led to extreme heat fluxes on the order of 1 kW/cm2 that requires aggressive microchannel cooling strategies in order to maintain the device junction temperature below acceptable limits. A reduced order single/two phase thermal-fluidic model is developed to investigate the effect of micro-channel geometry parameters, packaging materials and fluid flow conditions on the cooling performance of various cooling strategies. Water and R245fa refrigerant are used as single- and two-phase working fluids, respectively. We consider three cooling strategies: • Design A: copper cold-plate micro-channel module bonded to the device substrate • Design B: embedded micro-channels directly etched into the device substrate and • Design C: embedded micro-channels with a 3D manifold with inlet and outlet module. The proposed embedded micro-channels with 3D-manifold with R245fa working fluid has the potential to achieve the lowest thermal resistance ∼0.07 K/W and pressure drop ∼10 kPa for flow rate Q ∼ 0.21 l/min (T in = 90 °C) and exit quality x = 0.44.

Monolithic optical link in silicon-on-insulator CMOS technology.

Abstract: This work presents a monolithic laterally-coupled wide-spectrum (350 nm < λ < 1270 nm) optical link in a silicon-on-insulator CMOS technology. The link consists of a silicon (Si) light-emitting diode (LED) as the optical source and a Si photodiode (PD) as the detector; both realized by vertical abrupt n+p junctions, separated by a shallow trench isolation composed of silicon dioxide. Medium trench isolation around the devices along with the buried oxide layer provides galvanic isolation. Optical coupling in both avalanche-mode and forward-mode operation of the LED are analyzed for various designs and bias conditions. From both DC and pulsed transient measurements, it is further shown that heating in the avalanche-mode LED leads to a slow thermal coupling to the PD with time constants in the ms range. An integrated heat sink in the same technology leads to a ∼ 6 times reduction in the change in PD junction temperature per unit electrical power dissipated in the avalanche-mode LED. The analysis paves way for wide-spectrum optical links integrated in smart power technologies.

Enhanced Optical and Thermal Performance of Eutectic Flip-Chip Ultraviolet Light-Emitting Diodes via AlN-Doped-Silicone Encapsulant

Abstract: This paper investigated the optical and thermal performance of the nitride-based ultraviolet light-emitting diodes fabricated by the eutectic flip-chip method. A new packaging structure was proposed by introducing a thin encapsulation layer doped with 0.4 wt% AlN nanoparticles (NPs) and uniform quartz lens simultaneously. Experimental results showed that the packaging structure proposed in this paper could significantly enhance the light output power, reduce the junction temperature, and increase the emission angle compared with the encapsulation layer consisting silicone only. When the NPs concentration increased from 0.1 to 0.4 wt%, the light output power increased from 7.6% to 17.4% at the forward current of 800 mA. Meanwhile, the junction temperature decreased by 5.7 °C, while the emission angle increased by 11.3°. What is more, it was found that the enhancement of light output power depended on the NPs concentration and showed the maximum at the concentration of 0.4 wt%. The enhanced light output power was attributed to the additional light scattering and the increased average refractive index resulted from the NPs introduced in the proposed package structure.

Assessment of thermal network models for estimating IGBT junction temperature of a buck converter

Abstract: Accurate estimation of semiconductors' junction temperature is particularly important that the impact of the temperature on their reliability and performance is evident. The analysis in this paper reveals that the using of RC thermal network models with reduced number of layers can be tremendously useful. Additionally, a simple technique for transforming n-layer Foster model to a one-cell Cauer ladder model is proposed. The one-cell Cauer model implemented by state-space equations can accelerate calculations. This study also presents a finite element method (FEM) validation based on the real IGBT module geometry for the analyses. A buck converter is considered as the case study. The obtained results show that the one-layer Cauer model can provide the exact outcomes. The difference between the thermal impedance curves is considerable; however, both curves have almost the same peak value.