Research Outputs

2024 2024 2023 2023 2022 2022 2021 2021 2020 2020 2019 2019 2018 2018 2017 2017 2016 2016 2015 2015 0.0 0.0 1.0 1.0 2.0 2.0 3.0 3.0 4.0 4.0 5.0 5.0 6.0 6.0
Now showing 1 - 10 of 39
  • Publication
    Accelerated mechanical fatigue interconnect testing method for heavy wire bonds in power modules
    (2017-05-11)
    Every new development in device performance and packaging design, due to new materials and design changes can influence the device reliability drastically. High performance and high reliability demands in power electronics over several decades and a short time to market development, raise the need for very fast reliability testing methods. In this study a mechanical fatigue testing method is presented for evaluating the interfacial fatigue resistance of heavy Al wire bonded interconnects in high power modules. By separating the concurrent thermal, mechanical and environmental failure mechanisms a selective investigation of the desired failure mode is possible. The setup is designed to reproduce the thermo-mechanical shear stresses by mechanical means, while provoking the same lift-off failure mode as in power cycling tests. With a frequency variable test setup of a few Hz up to several kHz, measurements from 1E3 up to 1E8 and determining the influence of the testing frequency on the fatigue life were possible.
      55  1
  • Publication
    Electro-thermal analysis of in situ vibration measurements on IGBT modules under operation conditions
    (Elsevier, 2012-09-17) ;
    Nagl, Bernhard 
    ;
    Lederer, Martin 
    ;
    Khatibi, Golta 
    ;
    Thoben, Markus 
    ;
    Nicolics, Johann 
    This paper discusses different application relevant electrical loading cases of an IGBT module of a power inverter. Thereby, different operation conditions such as pulse frequencies, inverter output currents and output frequencies, as well as two different operation modes are discussed. Each load case investigation is conducted by electrical, thermal, and in situ vibration measurements. Moreover, on the base of finite element analyses a deeper insight is gained into reliability relevant thermo-mechanical behavior. For this purpose an IGBT module is operated at a load of 30% to 80% of its nominal value in order to cause representative thermo-mechanical displacements of dies and bond wires. By applying an inverter output frequency in a range of 1 to 280 Hz a temperature ripple of up to 40 K on the dies and a vertical displacement of up to 9 μm on a bond wire is observed. These results are important to improve life-time-predictions.
      44  1Scopus© Citations 3
  • Publication
    Step-by-Step Building of a Four Dimensional Fatigue Compatible Regression Model including Frequencies
    (2021-12) ;
    Castillo, Enrique 
    ;
    Fernández Lavín, Alfonso Antonio 
    ;
    Blasón, Sergio 
    ;
    Khatibi, Golta 
    ;
    Zareghomsheh, Mohammad 
    The purpose of this research is to develop a model, with emphasis on compatibility conditions and model building, valid for high cycle fatigue design components such as wind turbines, automobiles, high speed railways and aeronautical material. In this work, we have added the frequency as one more variable to an existing fatigue model that already includes maximum stress, stress ratio and lifetime. As a result, a model and estimation method has been proposed and a random variable V has been identified, which, allows the accumulated damage and the probability of failure to be assessed for any load history in terms of stress levels, stress ranges and frequencies. Finally, the model is validated using a large set of real experimental data.
      198  1
  • Publication
    Experimental and analytical study of geometry effects on the fatigue life of Al bond wire interconnects
    (Elsevier, 2013-09) ;
    Khatibi, Golta 
    ;
    Paul, Indrajit 
    ;
    Thoben, Markus 
    The reliability of power electronic devices is mainly limited due to thermo-mechanical fatigue of the internal bond wire interconnections. The bond wire shape is already defined at the design stage of the device. Thus preliminary lifetime assessments become more and more important in order to satisfy the high quality demands and the short time to market of the devices. In this study a fast experimental test setup is used in order to determine the lifetime of a large number of wire bond shapes. Furthermore an analytical model is applied to calculate optimized wire bond shapes for a given set of parameters. The results of this investigation should help to optimize the shape parameters at an early stage of development using the presented analytical model in combination with the fatigue tests. © 2013 Elsevier Ltd. All rights reserved.
      56  2Scopus© Citations 21
  • Publication
    Experimental investigation of transient electrical, thermal and mechanical behavior of IGBT inverter modules during operation
    (Elsevier, 2013-05-26) ;
    Thoben, Markus 
    ;
    Khatibi, Golta 
    ;
    Lederer, Martin 
    ;
    Nagl, Bernhard 
    ;
    Nicolics, Johann 
    This study comprises the electrical analysis of an experimental investigation on thermo-mechanical vibration measurements on an IGBT inverter structure under operating conditions and shows a new way how to experience reliability relevant phenomena. In order to perform transient temperature measurements with IR thermography and optical vibration measurements one sub-system of the inverter module was extracted and operated at equivalent conditions. Necessary circuit modifications including parasitic impedances and their most important influences are discussed. The investigation revealed a strong dependence of the thermo-mechanical bonding wire vibrations on the inverter output frequency. At 1 Hz an amplitude of more than 4 μm was measured at the loop peak of a short bonding wire.
      49  1Scopus© Citations 1
  • Publication
    In situ vibration measurements on power modules under operating conditions
    (Elsevier, 2012-04-16) ;
    Nagl, Bernhard 
    ;
    Lederer, Martin 
    ;
    Trnka, A. 
    ;
    Khatibi, Golta 
    ;
    Thoben, Markus 
    The subject of this investigation was determination of thermo-mechanically induced displacement of the components inside a power module under operation conditions. It is well known that lifetime of insulated gate bipolar transistor (IGBT) modules is limited by thermo-mechanical fatigue. Wire bonded interconnects inside the IGBTs count as critical sites where crack initiation and failure is observed. In this study the temperature dependent periodic deformation of wire-bonds under operating conditions was determined by using a laser Doppler vibrometer (LDV) and thermal imaging camera. Furthermore finite element analyses (FEA) were conducted to obtain the strain values needed for lifetime assessments.
      43  1Scopus© Citations 6