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
    Towards adequate qualification testing of electronic products: Review and extension
    (Elsevier, 2014-12-03)
    Czerny, Bernhard 
    ;
    Khatibi, Golta 
    ;
    Lederer, Martin 
    ;
    Magnien, Julien 
    ;
    Suhir, Ephraim 
    ;
    Nicolics, Johann 
    Electronic product manufacturers are constantly seeking efficient, cost-effective and trustworthy accelerated test (AT) methods to keep up with the today's market demands. At present, accelerated temperature cycling testing is viewed as the state of the art for reliability assessment of electronic products. Accelerated mechanical fatigue testing has been proposed recently as a novel concept and an attractive cost-effective and time-saving qualification alternative for electronic devices. The principle idea of this approach is replacement of thermally induced loading with equivalent and adequate mechanical loading. Using mechanical fatigue testing set-ups, the devices under test can be subjected to single or multi-axial cyclic loading conditions at high frequencies. As a result, physically meaningful lifetime curves can be obtained. The suggested methodologies and procedures enable one to detect the vulnerable sites of the devices in a very short time. Exemplary results for power semiconductor products demonstrate the applicability of the proposed method for qualification of first and second level interconnects. The advantages and limitations of the proposed concept are addressed and discussed in detail.
      41  1
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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
    Wire bond degradation under thermo- and pure mechanical loading
    (Elsevier, 2017-09)
    Czerny, Bernhard 
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    Pedersen, Kristian Bonderup 
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    Nielsen, Dennis A. 
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    Khatibi, Golta 
    ;
    Iannuzzo, Francesco 
    ;
    Popok, Vladimir N. 
    ;
    Pedersen, Kjeld 
    This paper presents a fundamental study on degradation of heavy Al bond wires typically used in high power modules. Customized samples are designed to only consist of Al bond wires on standard Si diodes. These samples are subjected to pure mechanical and passive thermal cycling to investigate the bond degradation behavior on a simple system as well as compare these two test methods. Although an appreciable difference in fracture behavior is observed between these two methods, both provide correlation between the number of cycles and degree of degradation, especially in the case of the passive thermal test. To enable investigation of degradation rate a large number of bond interfaces is analyzed and they are found to follow conventional accepted fracture laws like Paris-Erdogan. With additional work this could enable the possibility of obtaining empirical parameters to be used in actual physics based lifetime laws.
      48  1Scopus© Citations 16
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    Publication
    Bond Wire Fatigue of Au, Cu, and PCC in Power LED Packages
    (MDPI, 2023)
    Czerny, Bernhard 
    ;
    Schuh, Sebastian 
    Bond wire failure, primarily wire neck breakage, in power LED devices due to thermomechanical fatigue is one of the main reliability issues in power LED devices. Currently, the standard testing methods to evaluate the device’s lifetime involve time-consuming thermal cycling or thermal shock tests. While numerical or simulation methods are used as convenient and quick alternatives, obtaining data from material lifetime models with accurate reliability and without experimental fatigue has proven challenging. To address this issue, a mechanical fatigue testing system was developed with the purpose of inducing mechanical stresses in the critical region of the bond wire connection above the ball bond. The aim was to accelerate fatigue cracks at this bottleneck, inducing a similar failure mode as observed during thermal tests. Experimental investigations were conducted on Au, Cu, and Pd-coated Cu bonding wires, each with a diameter of 25 µm, using both low- and high-frequency excitation. The lifetime of the wire bond obtained from these tests ranged from 100 to 1,000,000 cycles. This proposed testing method offers material lifetime data in a significantly shorter timeframe and requires minimal sample preparation. Additionally, finite element simulations were performed to quantify the stresses at the wire neck, facilitating comparisons to conventional testing methods, fatigue test results under various operating conditions, material models, and design evaluations of the fine wire bond reliability in LED and microelectronic packages.
      19  226
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    Publication
    In situ vibration measurements on power modules under operating conditions
    (Elsevier, 2012-04-16)
    Czerny, Bernhard 
    ;
    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
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    Publication
    Accelerated mechanical fatigue interconnect testing method for heavy wire bonds in power modules
    (2017-05-11)
    Czerny, Bernhard 
    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.
      54  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 
    ;
    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
    Thermomechanical Reliability Investigation of Insulated Gate Bipolar Transistor Module
    (Elsevier, 2018-05-16)
    Czerny, Bernhard 
    ;
    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.
      53  1Scopus© Citations 5
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    Publication
    Reliability analysis of Cu wire bonds in microelectronic packages
    (Elsevier, 2016-04-18)
    Czerny, Bernhard 
    ;
    Mazloum-Nejadari, Ali 
    ;
    Khatibi, Golta 
    ;
    Lederer, Martin 
    ;
    Nicolics, Johann 
    ;
    Weiss, Laurens 
    In this study the thermo-mechanical response of 25 μm Cu wire bonds in an LQFP-EPad package was investigated by numerical and experimental means. The aim was to develop a methodology for fast evaluation of the packages, with focus on wire bond fatigue, by combining FEA and mechanical fatigue testing. The investigations included the following steps: (i) simulation of the warpage induced displacements in the encapsulated LQFP-176-Epad package due to temperature changes, (ii) reproducing the thermally induced stresses in the wire bond loops in an unmolded (non-encapsulated) LQFP package using an accelerated multiaxial mechanical fatigue testing set-up under the displacement amplitudes determined in case (i) and determination of the loading cycles to failure (Nf), (iii) FEA of the experiments performed in (ii) based on the boundary conditions determined in (i) to calculate the states of stress and strain in the wire bonds subjected to multiaxial mechanical cyclic loading. Our investigations confirm that thermal and mechanical cyclic loading results in occurrence of high plastic strains at the heat affected zone (HAZ) above the nail-head, which may lead to fatigue failure of the wire bonds in the packages. The lifetime of wire bonds show a proportional relation between the location and angle of the wire bond to the direction of loading. The calculated accumulated plastic strain in the HAZ was correlated to the experimentally determined Nf values based on the volume weighted averaging (VWA) approach and presented in a lifetime diagram (Δd - Nf) for reliability assessment of Cu wire bonds. The described accelerated test method could be used as a rapid qualification test for the determination of the lifetimes of wire bonds at different positions on the chip as well as for related improvements of package design.
      62  1Scopus© Citations 3