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

2018 2018 2017 2017 2016 2016 2015 2015 2014 2014 2013 2013 2012 2012 0.0 0.0 0.2 0.2 0.4 0.4 0.6 0.6 0.8 0.8 1.0 1.0 1.2 1.2 1.4 1.4 1.6 1.6 1.8 1.8 2.0 2.0

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  • No Thumbnail Available
    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
  • No Thumbnail Available
    Publication
    Experimental investigation of transient electrical, thermal and mechanical behavior of IGBT inverter modules during operation
    (Elsevier, 2013-05-26)
    Czerny, Bernhard 
    ;
    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
  • No Thumbnail Available
    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
  • No Thumbnail Available
    Publication
    A novel approach for evaluation of material interfaces in electronics
    (2016-03-05)
    Czerny, Bernhard 
    ;
    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.
      61  1Scopus© Citations 4
  • No Thumbnail Available
    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
  • No Thumbnail Available
    Publication
    Investigation on the Lifetime of Copper Wire Bonds in Electronic Packages under Thermal and Mechanical Cyclic Loading
    (Elsevier, 2018-09-18)
    Czerny, Bernhard 
    ;
    Lederer, Martin 
    ;
    Mazloum-Nejadari, Ali 
    ;
    Khatibi, Golta 
    ;
    Weiss, Laurens 
    ;
    Nicolics, Johann 
    In this study, the results of simulative and experimental investigations regarding thermal cycling (TC) of a LQFP (Low Profile Quad Flat Exposed Pad) with embedded copper wire bonds are discussed. The focus of this study is to analyze cyclic thermal and mechanical loading at high plastic strain in the heat affected zone (HAZ) above the nail-head, which may lead to fatigue failure of wire bonds in the packages. Thereby, a comparison with multiaxial mechanical test results obtained in a previous study will be drawn [1]. Indeed, the lifetime diagrams for these two methods show a clear correlation. Convincing agreement was found on experimental and on theoretical level. The described accelerated test method can be used as a rapid test for the determination of the lifetimes of wire bonds at various positions on the chip. Moreover, our testing method leads to conclusions, which enable improvements of package design.
      63  1Scopus© Citations 3
  • No Thumbnail Available
    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