Research Outputs

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Now showing 1 - 10 of 39
  • Publication
    Effect of the loop forming process on the lifetime of aluminum heavy wire bonds under accelerated mechanical testing
    (2024-03)
    Florens Felke
    ;
    Anne Groth
    ;
    Martin Hempel
    ;
    ;
    Golta Khatibi 
    ;
    Torsten Döhler
    ;
    Ute Geissler 
  • Publication
    A novel approach for evaluation of material interfaces in electronics
    (2016-03-05) ;
    Khatibi, Golta 
    ;
    Lassnig, Alice 
    ;
    Lederer, Martin 
    ;
    Nicolics, Johann 
    ;
    Magnien, Julien 
    ;
    Suhir, Ephraim 
    The rapid technological advancements and market demands in electronic sector requires application of highly accelerated, still practice relevant reliability assessment methods. At present, accelerated power and temperature cycling tests count as the state of the art for qualification of the devices. However due to physical characteristics of the devices, there are limitations to accelerated thermal and power cycling tests. Further acceleration by exceeding a critical temperature or time reduction may result in occurrence of failure mechanisms other than those encountered in real application or suppressing these failures. An alternative approach for further acceleration of the testing procedures is based on the application of isothermal mechanical fatigue testing at high frequencies (AMT). The principle idea of this approach is replacement of thermally induced strains by means of equivalent mechanical strains. Based on a physics of failure approach, the relevant failure modes in the material interfaces are induced enabling detection of weak sites of the devices in a very short duration of time. In addition of time saving factor a further advantage of mechanical fatigue testing is the possibility of decoupling of thermal, mechanical and environmental stress factors for a more effective investigation and diagnosis. This paper presents an overview of our recent reliability studies on different types of electronic components by using the proposed methodology with the aim to give an insights into the advantages and some restrictions of AMT for qualification of electronic devices.
      61Scopus© Citations 3
  • Publication
    Thermomechanical Reliability Investigation of Insulated Gate Bipolar Transistor Module
    (Elsevier, 2018-05-16) ;
    Khatibi, Golta 
    ;
    Liedtke, Magnus 
    ;
    Nicolics, Johann 
    Though, significant efforts have led to high solder joint quality, thermomechanical fatigue and delamination of the solder joints are still considered as one main failure cause in Insulated Gate Bipolar Transistor (IGBT) power modules. Frequently used test procedures such as accelerated power cycling and thermal cycling allow to rate reliability and to predict lifetime under assumed power load conditions. However, these tests are less capable of detecting the root physical failure cause. In this paper a non-destructive thermal method to observe the successive effect of solder layer fatigue is suggested and discussed. Somewhat similar to power cycling, the method is based on an accelerated temperature cycling process where the power component is self-heated. The resulting change of thermal conductivity of the solder joint due to degradation is detected by contactless temperature measurement. First metallurgical analyses confirm the degraded solder structure as cause of the thermal changes due to aging.
      53Scopus© Citations 5
  • Publication
    Cyclic robustness of heavy wire bonds: Al, AlMg, Cu and CucorAl
    (Elsevier, 2018-09) ;
    Khatibi, Golta 
    Development of advanced electronic packages can be drastically affected by implementation of new materials. The ever increasing demands for high performance and reliable power electronics, raise the need for rapid robustness evaluation of interconnects. In this study the lifetime of heavy wire bonded interconnects, fabricated with different wire material types Al, AlMg, Cu and Al coated Cu (CucorAl) bonded onto direct copper bonded ceramic substrates was investigated. The tests were performed using an accelerated mechanical fatigue testing system, which allows to determine the lifetime of the interconnects with regard to wire bond lift-off failure in a short period of time. Thus, the influence of ultrasonic power variation and the impact of aging on the performance of wire bonds with different material combinations was studied. Cu wire bonds showed clearly the best fatigue performance as well as static shear strength followed by AlMg and Al bonds. Increasing the ultrasonic power results in a higher fatigue resistance of CucorAl in comparison to pure Al wires. In certain cases, the results of the fatigue experiments and static shear tests were found to be contradictory. The presented results suggest that accelerated mechanical fatigue testing can be used as an additional fast method for qualification of interconnects and assessment of the influence of wire material, bond parameter and aging.
      60Scopus© Citations 23
  • 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.
      56Scopus© Citations 19
  • Publication
    Loop formation effects on the lifetime of wire bonds for power electronics
    (2020-03-24) ;
    Ribbeck, Hans-Georg von 
    ;
    Doehler, Torsten 
    ;
    Khatibi, Golta 
    ;
    Geissler, Ute 
    In the present work, the influence of loop forming aspects on the reliability of US-bonded aluminium heavy wires was studied, combining three measurement techniques, for the first time: Laser confocal microscopy based wrinkling characterization, accelerated lifetime measurements BAMFIT and destructive pull tests. The focus of this study was the systematic investigation of the heel region of the wire bond depending on process parameters and especially on the loop geometry regarding durability and lifetime. As first results, effects reducing durability were identified which are not apparent in normal testing and a recommendation for the use of reverse movements can be given.
      69