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

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Now showing 1 - 10 of 30

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
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
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
Cyclic robustness of heavy wire bonds: Al, AlMg, Cu and CucorAl
(Elsevier, 2018-09)
Czerny, Bernhard
;
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.
60 1Scopus© Citations 25
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
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
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
Versatile ultrasonic fatigue testing method with variable load ratio for small scaled samples
(2019-05-16)
Czerny, Bernhard
;
Gasser, Christoph
;
Khatibi, Golta
57 1

Czerny, Bernhard

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