Czerny, Bernhard

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Official Name
Czerny, Bernhard
Main Affiliation
Akademische Titel
Mag. Dr.
Email
bernhard.czerny@fh-burgenland.at
ORCID
Scopus Author ID
36238795900
Status
staff

Research Outputs

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Now showing 1 - 10 of 39
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    Publication
    Thermo-mechanical analysis of bonding wires in IGBT modules under operating conditions
    (Elsevier, 2012-09)
    Czerny, Bernhard 
    ;
    Lederer, Martin 
    ;
    Nagl, Bernhard 
    ;
    Trnka, A. 
    ;
    Khatibi, Golta 
    ;
    Thoben, Markus 
    The lifetime of IGBT (Insulated Gate Bipolar Transistor) modules is limited by thermo-mechanical fatigue. Thereby bonding wires represent the critical links where damage initiation is observed. For the first time Laser Doppler Vibrometer measurements and thermal imaging were employed to determine the temperature-dependent deformations of bond wires at different frequencies under operation conditions. This should be considered as an important step to facilitate more precise life-time predictions of power modules in long term usage.
      43  2Scopus© Citations 76
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    Publication
    Comparative study of wire bond degradation under power and mechanical accelerated tests
    (Elsevier, 2019-09-01)
    Czerny, Bernhard 
    ;
    Buhrkal-Donau, Steffen 
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    Popok, Vladimir 
    ;
    Khatibi, Golta 
    ;
    Luo, Haoze 
    ;
    Iannuzzo, Francesco 
    ;
    Pedersen, Kristian Bonderup 
    Degradation of wire bonds under accelerated power cycling tests is compared to that caused by mechanical high-frequency cycling for commercial power devices. Using micro-sectioning approach and optical microscopy it is found that the bond fracture under the mechanical cycling follows the same tendencies as that found under power cycling. Results of shear tests of the mechanically cycled bonds also agree well with the bond cracking tendencies observed by optical microscopy investigations. It is found that reduction of contact area of the wire at the bond/metallization interface due to the crack development follows the Paris-Erdogan law, which defines the degradation rate leading to wire lift-off. The results obtained on mechanical cycling in the current work also show good agreement with literature data on wire bond fracture under power cycling proving that main mechanism for wire lift-off failure is related to the mechanical stress development at the interface with metallization layer. The carried out study also creates a potential to further develop a high-frequency mechanical cycling into an alternative for reliability analysis of wire bonds. However, more studies have to be performed to compare degradation mechanisms occuring under power and mechanical accelerated tests. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
      57  1Scopus© Citations 10
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    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
    ;
    Bernhard Czerny 
    ;
    Golta Khatibi 
    ;
    Torsten Döhler
    ;
    Ute Geissler 
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    Publication
    Accelerated mechanical fatigue interconnect testing method for electrical wire bonds
    (2018-04-25)
    Czerny, Bernhard 
    ;
    Khatibi, Golta 
    Every new development in device performance and packaging design, can drastically affect the reliability of devices due to implementation of new materials and design changes. 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 103 up to 108 loading cycles and determining the influence of the testing frequency on the fatigue life are possible. A semi-automated bond wire fatigue tester operating at 60 kHz is presented which is suitable for rapid screening and qualification of a variety of wire bonds at the stages of development and during the production. © 2018 Walter de Gruyter GmbH, Berlin/Boston.
      60  1Scopus© Citations 19
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    Publication
    A rapid test for reliability of heavy wire bonds
    (Konradin-Verl. Kohlhammer, 2019-04-17)
    Czerny, Bernhard 
    ;
    Seidl, Siegfried 
    Bond-Drahtverbindungen müssen über mehrere Dekaden und unter hohen thermomechanischen Belastungen zuverlässig halten. Dafür sorgt ein Bondtester mit einem extrem schnellen automatischen Qualitätstest zur Lebensdauerbestimmung der Bond-Drahtverbindungen.
      60  1
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    Publication
    Electro-thermal analysis of in situ vibration measurements on IGBT modules under operation conditions
    (Elsevier, 2012-09-17)
    Czerny, Bernhard 
    ;
    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
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    Publication
    Step-by-Step Building of a Four Dimensional Fatigue Compatible Regression Model including Frequencies
    (2021-12)
    Czerny, Bernhard 
    ;
    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.
      197  1
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    Publication
    Application of in-situ non-invasive failure detection methods for wire bonds
    (2020-09-15)
    Czerny, Bernhard 
    ;
    Chavan, Vinayak 
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    Gasser, Christoph 
    ;
    Rosc, Jördis 
    ;
    Khatibi, Golta 
    Two in-situ failure detection methods by measuring acoustic emissions and transducer responses are presented to investigate the wire bond degradation failure during a highly accelerated mechanical fatigue test. This BAMFIT fatigue test is used to induce cyclic shear stresses in the bond interface until wire bond lift-off, operating at 60 kHz. The task was to incorporate non-invasive failure detection to identify the degree of degradation prior to end of life as an extension to the BAMFIT method and a possible quality control method. The acoustic emission investigations uses a Fabry Perot interferometer to detect high frequency emissions in the vicinity of the wire bond and detecting changes in the first three harmonics to identify a bond degradation. The transducer response approach observes systematic changes in the vibration and the damping behavior of the coupled resonance system by using the transducer as a piezo sensor. The results have shown that defective bond interconnect can be identified as early as ~50% of end of life, using high power but very short vibration pulses, and at ~80% for low power and completely non-invasive pulses. The obtained responses from the presented methods were correlated to the degree of degradation of the bond wire interface, by completing BAMFIT tests until end of life, cross section analysis as well as non-destructive X-ray computer tomography.
      68  1Scopus© Citations 1
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    Publication
    Interface reliability and lifetime prediction of heavy aluminum wire bonds
    (Elsevier, 2016-03-01)
    Czerny, Bernhard 
    ;
    Khatibi, Golta 
    In this study a high frequency mechanical fatigue testing procedure for evaluation of interfacial reliability of heavy wire bonds in power semiconductors is presented. A displacement controlled mechanical shear testing set-up working at a variable frequency of a few Hertz up to 10 kHz is used to assess the interfacial fatigue resistance of heavy Al wire bond in IGBT devices. In addition, power cyclic tests were conducted on IGBT modules for in-situ measurement of the temperature distribution in the devices and determination of the thermally induced displacements in the wire bond loops. Finite Element Analysis was conducted to calculate the correlation between the thermally and mechanically induced interfacial stresses in the wire bonds. These stress values were converted into equivalent junction temperature swings (ΔTj) in the devices based on which lifetime curves at different testing frequencies were obtained. Comparison of the fatigue life curves obtained at mechanical testing frequencies of up to 200 Hz with the power cycling data related to the wire bond lift-off failure revealed a very good conformity in the ranges of 50 to 160 K. A lifetime prediction model for Al wire bonds in IGBT modules is suggested by which the loading cycles to failure can be obtained as a function of ΔTj and the mechanical testing frequency. The proposed accelerated shear fatigue testing procedure can be applied for rapid assessment of a variety of interconnects with different geometries and material combinations. Decoupling of the concurrent failure mechanisms and separation of the thermal, mechanical and environmental stress factors allows a more focused and efficient investigation of the interfaces in the devices.
      59  2Scopus© Citations 35