Yvan Avenas

Temperature Measurement of Power Semiconductor Devices by Thermo-Sensitive Electrical Parameters—A Review

This paper proposes a synthesis of different electrical methods used to estimate the temperature of power semiconductor devices. The following measurement methods are introduced: the voltage under low current levels, the threshold voltage, the voltage under high current levels, the gate-emitter voltage, the saturation current, and the switching times. All these methods are then compared in terms of sensitivity, linearity, accuracy, genericity, calibration needs, and possibility of characterizing the thermal impedance or the temperature during the operation of the converter. The measurement of thermo-sensitive parameters of wide bandgap semiconductors is also discussed.

Comparison of Junction Temperature Evaluations in a Power IGBT Module Using an IR Camera and Three Thermosensitive Electrical Parameters

The measurement of the junction temperature with thermosensitive electrical parameters (TSEPs) is largely used by electrical engineers or researchers, but the obtained temperature value is generally not verified by any referential information of the actual chip temperature distribution. In this paper, we propose to use infrared (IR) measurements in order to evaluate the relevance of three commonly used TSEPs with insulated gate bipolar transistor chips: the saturation voltage under a low current, the gate-emitter voltage, and the saturation current. TheIR measurements are presented in detail with an estimation of the emissivity of the black paint deposited on the power module. The temperatures obtained with IR measurements and with the different TSEPs are then compared in two cases: the use of only one chip and the use of two paralleled chips.

Improved Reliability of Power Modules: A Review of Online Junction Temperature Measurement Methods

Power electronic systems play an increasingly important role in providing high-efficiency power conversion for adjustable-speed drives, power-quality correction, renewable-energy systems, energy-storage systems, and electric vehicles. However, they are often presented with demanding operating environments that challenge the reliability aspects of power electronic techniques. For example, increasingly thermally stressful environments are seen in applications such as electric vehicles, where ambient temperatures under the hood exceed 150 °C, while some wind turbine applications can place large temperature cycling conditions on the system. On the other hand, safety requirements in the aerospace and automotive industries place rigorous demands on reliability.

Junction temperature measurements via thermo-sensitive electrical parameters and their application to condition monitoring and active thermal control of power converters

The temperature of a power semiconductor device is important for both its optimal operation and reliability. If the temperature is known during the operation of a converter, it can be used to monitor the health of power modules: a measurement of aging, scheduling of maintenance, or even implementation of active thermal control to reduce losses and increase lifetime can be performed given an accurate knowledge of temperature. Temperature measurements via thermo-sensitive electrical parameters (TSEP) are one way to carry out immediate temperature readings on fully packaged devices. However, successful implementation of these techniques during the actual operation of a device has not yet been achieved. This paper provides an overview of literature where the usage of TSEPs has been hypothesised or realised in realistic power electronic converter setups. Barriers and limitations preventing wider scale implementation of these methods are discussed. Their potential use in the aforementioned goals in condition monitoring and active thermal control is also described.

Comparison of junction temperature evaluations in a power IGBT module using an IR camera and three thermo-sensitive electrical parameters

The measurement of the junction temperature with thermo-sensitive electrical parameters (TSEPs) is largely used by electrical engineers or researchers but the obtained temperature value is generally not verified by any referential information of the actual chip temperature distribution. In this paper, we propose to use infrared (IR) measurements in order to evaluate the relevance of three commonly used TSEP with IGBT chips: the saturation voltage under a low current, the gate-emitter voltage and the saturation current. The IR measurements are presented in details with an estimation of the emissivity of the black paint deposited on the power module. The temperatures obtained with IR measurement and with the different TSEPs are then compared in two cases: the use of only one chip and the use of two paralleled chips.

A Bus-Bar-Like Power Module Based on Three-Dimensional Power-Chip-on-Chip Hybrid Integration

This paper focuses on a new generation of power modules, trying to optimize the tradeoff between thermal and electromagnetic interference (EMI) managements. At the same time, the packaging technique is considered in order to simplify the implementation of the power dies while improving the reliability of the structure. The approach considers the hybrid integration of the power dies, one on top of the other, into a 3-D power-chip-on-chip configuration. Due to this structure, the power dies can directly be inserted within electrical plates, with the whole structure emulating a bus-bar-like power module. This paper presents the characteristics and the benefits of this approach. Then, it focuses on the practical characterizations of two prototypes having their active components packaged with the presented technique: a buck converter structure and a full-bridge single-phase diode rectifier. Both of them are based on double-sided thermal cooling, and electrothermal contacts are obtained by pressure. The prototypes exhibit great performances while offering really reduced parasitic and EMI coupling.

Evaluation of IGBT thermo-sensitive electrical parameters under different dissipation conditions - Comparison with infrared measurements

Junction temperature evaluation is a key parameter used to control a power module assembly. But measuring the junction temperature by thermo-sensitive electrical parameters (TSEPs) does not reveal the actual temperature of the semiconductor device. In this paper, a specific electronic board used to compare four common TSEPs of IGBT chips is presented. For this comparison, two dissipation modes are used: dissipation in active and saturation regions. In order to have referential measurements we carried out surface temperature measurements of IGBT chips with an infrared (IR) camera. A dedicated numerical tool is presented to estimate the mean surface temperature of active region. In the case of a single IGBT chip, the comparison between IR and TSEP measurements show that the best studied parameter (in terms of robustness and usability) is the gate emitter voltage.

Study and realization of a low force 3D press-pack power module

The purpose of this study concerns the packaging of the vertical power chips used for medium power level modules, from hundreds of W up to several kW. We present a new vision of electrical components packaging that permits to improve the standard switching cell characteristics commonly used in power electronics. We define a generic element that could be the basic element used for the power modules assembly as it is presented in the PEBB approach. The concept developed consists in a 3 Dimension geometrical switching cell packaging. The implementation strategy is based on a low force pressed contact. Then, the feasibility evaluation requires an electrical and a thermal characterization of metal-metal interface in the case of contact under reduced force. A measure bench dedicated to the characterization of joints like the ones in press-pack modules has been realized. We characterized first an Al-Cu pressed contact. Results were compatible with targeted applications. (i.e. thermal contact resistance Rth = 0.15degC.cm2/W and the electrical contact resistance Relec = 0.2 mOmega.cm2). After that we modified the first measure bench to be consistent with the characterization of electro-thermal contacts on both sides of a power diode. The resulting values of thermal and electric contact resistance were still consistent with our application (i.e. Rth = 0.12degC.cm2/W and 0.2 mOmega.cm2 < Relec < 0.9 mOmega.cm2). To validate our concept and substantiate this research, a power module prototype operating under low force clamping, and implemented to emulate a buck chopper function, has been designed and realized. First experimental tests validate the operation and feasibility.

Analytical investigation of flat silicon micro heat spreaders

Conventional methods of cooling are not an ideal way to overcome the heat problem in power electronics today. A simple solution would be using micro heat spreader as an integrated part in the silicon substrate. This investigation presents a detailed analysis on maximum heat transfer capabilities of silicon-water cooling devices, flat plate micro heat spreaders. The predictive hydraulic and thermal models were developed to define the heat spreader thermal performances and capillary limitations. Theoretical results of the maximal heat flux that could be transferred agreed reasonably well with the experimental data and the developed model provides a better understanding of the heat transfer capability of micro heat spreaders.

Preliminary Evaluation of Thermo-Sensitive Electrical Parameters Based on the Forward Voltage for Online Chip Temperature Measurements of IGBT Devices

The temperature of power semiconductor devices is one of the main issues affecting the performance, availability, and reliability of power converters. The chip temperature is generally measured using thermosensitive electrical parameters (TSEPs). These parameters are well controlled for laboratory temperature measurements, where the power devices are not used under functional conditions. However, the use of TSEPs for chip temperature measurements in online conditions has yet to be demonstrated. This paper presents an experimental evaluation of two new TSEPs based on measuring the forward voltage, which could be used during operation of the converter. It examines the accuracy of the chip temperature measurement and also discusses the results in terms of robustness to the aging of power devices.