Czerny, Bernhard

Official Name

Czerny, Bernhard

Main Affiliation

Energie-Umweltmanagement

Akademische Titel

Mag. Dr.

bernhard.czerny@fh-burgenland.at

ORCID

0000-0001-8147-3122

Scopus Author ID

36238795900

Status

staff

Research Outputs

Visualization by Date

Now showing 1 - 10 of 15

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
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
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.
19 252
A new approach for evaluation of fatigue life of al wire bonds in power electronics
(Elsevier, 2014-02-16)
Czerny, Bernhard
;
Khatibi, Golta
;
Lederer, Martin
;
Kotas, Agnieszka Betzwar
;
Weiss, Brigitte
Ultrasonically bonded A1 wire bonds on A1 metallization pads are widely used in power semiconductors. The required long time reliability of the devices is highly dependent on the interfacial quality of A1 wire and the bond pad. Reliability of wire bonds is commonly assessed by thermal and power cycling tests. Accelerated mechanical fatigue testing can be used as an alternative to these time consuming procedures. In the present study, lifetime of thick A1 wedge bonds on Si substrates was investigated using a novel mechanical fatigue testing technique operating at high frequencies and elevated temperatures. The influence of microstructure, testing temperature and frequency on lifetime of A1 wire bonds was investigated. Finite element analysis was applied to calculate the stress distribution at the interfacial region and to establish life time prediction curves. The results of mechanical isothermal fatigue curves were compared and correlated with thermal cycling data of Al wire bonds. Copyright © 2014 by The Minerals, Metals & Materials Society.
72 1Scopus© Citations 2
Wire bond degradation under thermo- and pure mechanical loading
(Elsevier, 2017-09)
Czerny, Bernhard
;
Pedersen, Kristian Bonderup
;
Nielsen, Dennis A.
;
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
Fatigue testing method for fine bond wires in an LQFP package
(Elsevier, 2016-09)
Czerny, Bernhard
;
Mazloum-Nejadari, Ali
;
Khatibi, Golta
;
Weiss, Laurens
;
Zehetbauer, M.
A mechanical testing setup was developed to study the fatigue response of fine thermo-sonic wire bond connection in low profile quad flat packages (LQFP). The testing set-up was designed to induce pre-defined multi-axial stresses in the wire bond loops of non-encapsulated packages in order to mimic their deformation behavior during the thermo-mechanical loading. Lifetime curves were obtained up to 1.0E7 loading cycles with fatigue failure occurring in the heat affected zone of the ball bond. The experimental fatigue data in combination with extended FEA provided the basis for a Coffin Manson lifetime model. The proposed fatigue testing procedure can be applied as a highly efficient method for evaluation of various wire bonded packages by using a limited number of test samples and simultaneous testing of several wire bonds.
69 2Scopus© Citations 12
Reliability of Cu wire bonds in microelectronic packages
(Elsevier, 2017)
Czerny, Bernhard
;
Mazloum-Nejadari, Ali
;
Khatibi, Golta
;
Lederer, Martin
;
Nicolis, Johann
;
Weiss, Laurens
In this study the thermo-mechanical response of 25 μm Cu wire bonds in an LQFP-EPad (Low Profile Quad Flat Exposed Pad) package was investigated by numerical and experimental means. The aim was to develop a meth odology for fast evaluation of the packages, with focus on wire bond fatigue, by combining finite element analysis (FEA) and mechanical fatigue testing. The investigations included the following steps: (i) simulation of the warp age induced displacements in the encapsulated LQFP-176-Epad package due to temperature changes, (ii) repro ducing 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 deter mined 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 propor tional relation between the location and angle of the wire bond to the direction of loading. The calculated accu mulated plastic strain in the HAZ was correlated to the experimentally determined Nf values based on the volume weighted averaging (VWA) approached 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 deter mination of the lifetimes of wire bonds at different positions on the chip as well as for related improvements of package design.
61 1Scopus© Citations 20
Highly Accelerated Mechanical Lifetime Testing for Wire Bonds in Power Electronics
(IMAPS, 2022-06)
Czerny, Bernhard
;
Khatibi, Golta
This article presents various experimental studies on fatigue evaluation of wire bond interconnects and interfaces in electronic devices using an accelerated mechanical fatigue testing system. This dedicated experimental setup is designed to induce fatigue failure in the weak sites of the wire bond by reproducing the thermomechanical failure modes occurring during operation. An exceptional highly test acceleration is achieved by increasing the mechanical testing frequency into the kHz regimen enabling the determination of lifetime curves in a very short time. A com parison of this method to conventional testing methods such as power cycling, a shear testing exploits the potential of customized accelerated mechanical testing. Exemplary studies on the degra dation and fatigue failure of heavy Al wire bonds typically used in power electronics and novel Cu wire bonds are presented and advantages and some restrictions of the proposed method are discussed.
106 1
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
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

Czerny, Bernhard

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