Zoubir Khatir

Ageing and Failure Modes of IGBT Modules in High-Temperature Power Cycling

This paper presents an experimental study on the ageing of insulated-gate bipolar transistor (IGBT) power modules. The aim is to identify the effects of power cycling on these devices with high baseplate temperatures (60 °C to 90 °C) and wide temperature swings (60 °C to 100 °C). These values for thermal stresses have been defined according to automotive applications. The test conditions are provided by two types of test benches that will be described in this paper. The changes in electrical and thermal indicators are observed regularly by a monitoring system. At the end of the test (reaching damage criterion or failure), different analyses are performed (acoustic scanning and SEM imaging), and the damage is listed systematically. Nineteen samples of 600-V 200-A IGBT modules were thus aged using five different power-cycling protocols. The final summary of results shows that ageing mechanisms mainly concern wire bonds and emitter metallization, with gradual impact depending on protocol severity.

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.

Effects of metallization thickness of ceramic substrates on the reliability of power assemblies under high temperature cycling

This study focuses on the influence of metallization thickness of ceramic substrates on reliability and lifetime of electronic power assemblies under high temperature cycling. The paper presents experimental and numerical results on different test vehicles with a number of DCB substrates with AlN ceramic and different copper thicknesses. It will be shown the influence of the DCB metallization on failure modes such as ceramic fracture and solder delamination under high temperature cycles. Finally, these samples will be compared with DCB substrates equipped with dimples and DAB substrates. Furthermore, the main factors that could increase the lifetime expectancy of power modules in such harsh environments will be identified.

Experimental behavior of single-chip IGBT and COOLMOS devices under repetitive short-circuit conditions

This work presents the behavior of single-chip insulated gate bipolar transistors (IGBT) devices under repetitive short-circuit operations. The 600 and 1200 V nonpunch through IGBTs as well as 600 V COOLMOS (trademark of Infineon Technologies) have been tested. The repetition of these severe working conditions is responsible for devices ageing, and results unavoidably in the components failure. A series of experimental tests were made in order to determine the number of short-circuit operations the devices can support before failure for different dissipated energies. The temperature influence has been also investigated. Results show two distinct failure modes depending on the dissipated energy during the tests. A critical value of short-circuit energy has been pointed out which separates these failure modes. Experimental and numerical investigations have been carried out in order to analyze these failure modes. A detailed analysis of the physical mechanisms occurring during the short-circuit failures for dissipated energies equal or lightly higher than the critical value is presented.

Degradation behavior of 600 V-200 A IGBT modules under power cycling and high temperature environment conditions

One challenge for automotive hybrid traction application is the use of high power IGBT modules that can withstand high ambient temperatures, from 90 °C to 120 °C, for reliability purpose. The paper presents ageing tests of 600 V-200 A IGBT modules subjected to power cycling with 60 °C junction temperature swings at 90 °C ambient temperature. Failure modes are described and obtained results on the module characteristics are detailed. Especially, physical degradations are described not only at the package level, like solder attach delaminations, but also at the chip level, with a shift on electrical characteristics such as threshold voltage. Finally, numerical investigations are performed in order to assess the thermal and thermo-mechanical constraints on silicon dies during power cycling and also to estimate the effect of ambient temperature on the mechanical stresses.

Robustness of SiC JFET in Short-Circuit Modes

This letter presents first destructive results showing the robustness of SiC JFET transistors from SiCED in current limitation regime or short-circuit operation. Crystal temperature during failure was estimated after different electrical characterizations and using appropriate models of saturation current. This letter shows the exceptional robustness of SiC JFET transistors in current limitation mode compared to Si devices (MOSFETS and IGBTs).

Comparison study on performances and robustness between SiC MOSFET & JFET devices – Abilities for aeronautics application

Abstract This paper deals with performances and reliability aspects of MOSFET and JFET power transistors devices based on silicon carbide technology. The purpose of this article is to evaluate the abilities and effects of each technology on the conception of power converter for avionic applications. Experimental measurements of steady-on-state resistance dependence and transient performances with temperature are presented and discussed. The second section focuses mainly on robustness aspects of the two types of power transistors in order to analyze their capability to withstand with aeronautic harsh environmental constrains.

Boundary element analysis of thermal fatigue effects on high power IGBT modules

Abstract The technology of high power IGBT modules has been significantly improved these last years against thermal fatigue. The most frequently observed failure modes, due to thermal fatigue, are the solder cracks between the copper base plate and the direct copper bonding (DCB) substrate and bond wire lift-off. Specific simulation tools are needed to carry out reliability researches and to develop device lifetime models. In other respects, accurate temperature and flux distributions are essential when computing thermo-mechanical stresses in order to assess the lifetime of high power modules in real operating conditions. This study presents an analysis method based on the boundary element method (BEM) to investigate thermal behavior of high power semiconductor packages subjected to power cycling loads. The paper describes the boundary integral equation which has been solved using the BEM and applied to the case of a high power IGBT module package (3.3 kV–1.2 kA). A validation of the numerical tool is presented by comparison with experimental measurements. Finally, the paper points out the effect on the thermal stress of the IGBT chips position on the DCB substrate. In particular, a light shifting of the silicon chips may be sufficient to delay significantly the initiation and the propagation of the cracks, allowing a higher device lifetime of the studied module.

Robustness of 1.2 kV SiC MOSFET devices

This paper provides an evaluation of robustness and performances of two types of 1.2 kV SiC MOSFETs in order to investigate these power devices for aircraft applications in medium power range. The paper focuses on robustness results showing the weakness of the gate under short-circuit tests. Observed failures appear at the gate level with effects on the mode of failure depending of the short-circuit duration.

Investigations on junction temperature estimation based on junction voltage measurements

Reliability and ageing tests on power semiconductor devices require estimation of junction temperatures in order to control thermal stresses and monitor failure criteria. For this purpose, thermo-electrical parameters, such as voltage forward drop dependence with temperature are usually carried out in low injection level. Nevertheless, it is still difficult to evaluate the limits of such exploitation. An analytical model has been developed and validated by experimental measurements in order to evaluate self-heating effects and to understand high temperature effects. This model should also allow to highlight the role of some physical parameters in the voltage-temperature dependence and to clarify such thermal calibration.