Kristian Bonderup Pedersen

Degradation Assessment in IGBT Modules Using Four-Point Probing Approach

Four-point probing of electrical parameters on various components of IGBT modules is suggested as an approach for the estimation of degradation in stressed devices. By comparison of these parameters for stressed and new components one can evaluate an overall degradation of the module and find out the wear state of individual components. This knowledge can be applied for preventing early failures and for optimization of the device design. The method is presented by regarding a standard type power module subjected to power cycling.

Interface structure and strength of ultrasonically wedge bonded heavy aluminium wires in Si-based power modules

Abstract In this paper the microscopical structure of wedge bonded interfaces is investigated, with a focus on what effect the power in the ultrasonic bonding and the initial microscopical structure of the

Bond wire lift-off in IGBT modules due to thermomechanical induced stress

Al

A Temperature-Dependent Thermal Model of IGBT Modules Suitable for Circuit-Level Simulations

Al wire have on the quality of the bonding. The quality evaluation is based on mapping the microscopical restructuring of the wire grains during bonding and thereby assessing the effective bonding area. Three approaches are utilized in the interface characterization: mechanical shear test, optical microscopy combined with micro-sectioning, and scanning electron microscopy assisted by focused ion beam milling. The shear test is applied to quantify the strength of the bonded interfaces, while the other methods are used to map the grain reconstruction caused by the bonding. From the results it is possible to map a 3D image of the wire deformation, and the grain refinement region which is the dominating parameter with respect to fatigue related cracking of the interfaces. It is found that the bonding power, as well as the initial wire structure directly affects the refinement region and thereby the strength of the interface.

Degradation evolution in high power IGBT modules subjected to sinusoidal current load

A micro-sectioning approach for characterizing the quality or degradation state of interconnect interfaces in electronic components is described. The method is presented as a means of investigating the bonding quality of the Al wedge bonding process in IGBT modules. But in general it is applicable to any type of interface and may be used to assess the present quality of the interface. The micro-sectioning is based on mechanical polishing, chemical polishing, electro-etching, and various types of microscopy.

Test setup for accelerated test of high power IGBT modules with online monitoring of V ce and V f voltage during converter operation

In this paper the bond wire lift-off failure mechanism experienced in insulated gate bipolar transistor modules, under realistic operation conditions, is investigated theoretically. This failure type is generally believed to be due to thermally induced stress arising from a mismatch in the coefficients of thermal expansion of the materials constituting the module. The theoretical evaluation is based on a finite element approach combined with empirical equations. Here the thermomechanical stress around the bond wire/substrate interface is evaluated. Based on the computations a new approach for characterizing degradation of bond wire junctions is proposed. From this function the lifetime as well as module performance may be evaluated for varying parameters: load, geometry etc.

Online chip temperature monitoring using υ ce -load current and IR thermography

A degradation model investigating the electro-thermo-mechanical fatigue, experienced by insulated gate bipolar transistors modules, is presented. To illustrate the concept, a specific case of power modules subjected to active power cycling which induce failure through bond wire lift-off is considered. Bond wire lift-off is believed to be due to thermally induced stress arising from a mismatch in the coefficients of thermal expansion between the wires and the given substrate. Overall, the theoretical evaluation is based on determining the thermo-mechanical stress around the bond wire/substrate interface through multiphysics-based models. The simulation detail and included equations are specified according to the region of interest and their complexity. In common, however, is the use of the finite element method combined with empirical equations. The final result is a numerical approach to evaluate the damage accumulated by a given load which may be used for prediction of lifetime or optimization of work points and module geometry.

Comprehensive physical analysis of bond wire interfaces in power modules

A basic challenge in the insulated gate bipolar transistor (IGBT) transient simulation study is to obtain the realistic junction temperature, which demands not only accurate electrical simulations but also precise thermal impedance. This paper proposed a transient thermal model for IGBT junction temperature simulations during short circuits or overloads. The updated Cauer thermal model with varying thermal parameters is obtained by means of finite-element method (FEM) thermal simulations with temperature-dependent physical parameters. The proposed method is applied to a case study of a 1700 V/1000 A IGBT module. Furthermore, a testing setup is built up to validate the simulation results, which is composed of a IGBT baseplate temperature control unit, an infrared camera with a maximum of 3 kHz sampling frequency, and a black-painted open IGBT module.