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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
Now showing 1 - 10 of 37
- PublicationTowards adequate qualification testing of electronic products: Review and extension(Elsevier, 2014-12-03)
; 41 1 - PublicationAccelerated mechanical fatigue interconnect testing method for heavy wire bonds in power modules(2017-05-11)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.
55 1 - PublicationInterface characterization of Cu-Cu ball bonds by a fast shear fatigue methodA highly accelerated shear fatigue testing method is presented to test the long-term reliability and reveal the bonded interface of thermosonic Cusingle bondCu ball bonds. The method is an adaptation to a new industrial fatigue tester (BAMFIT) and can be conducted without an intricate specimen preparation. This method induces mechanical cyclic shear stresses to the Cu nailhead in order to initiate fatigue fracture until lift-off, revealing the actual bonded interface. This study compares the fatigue resistance of Cu wire bonded to coarse and fine grained Cu and Al metallization. The fatigue experiments are accompanied by nano indentation tests, shear tests and finite element analysis. The fatigue results showed the best performance for Cu bonds on coarse grained Cu pads (metallization), followed by those bonded on fine grained Cu while the Cusingle bondAl nailheads failed at least a decade earlier than Cusingle bondCu bonds. Annealing the specimens prior to testing resulted in slight increases in the number of loading cycles to failure (Nf) for Cu bonds as well as for Cusingle bondAl bonds, while the scattering in Nf for Cu bonds increased. Nevertheless the calculated endurance limit of the fatigue data decreases with increasing annealing stages, due to a change in the fracture probability curve. With the ability to compare the fatigue behaviour of the bonded interface within minutes, this method is most suitable for rapid qualification at an early stage of development.
80 2Scopus© Citations 4 - PublicationHighly Accelerated Mechanical Lifetime Testing for Wire Bonds in Power ElectronicsThis 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 - PublicationInterface reliability and lifetime prediction of heavy aluminum wire bondsIn 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 - PublicationBAMFIT - Accelerated Mechanical Fatigue Interconnect Test(2018-01-01)
; Seidl, Siegfried80 1 - PublicationApplication of in-situ non-invasive failure detection methods for wire bonds(2020-09-15)
; 68 1Scopus© Citations 1 - PublicationSimulation of stress concentrations in wire-bonds using a novel strain gradient theory(Elsevier, 2013-04-14)
; 38 1Scopus© Citations 1 - PublicationThermo-mechanical analysis of bonding wires in IGBT modules under operating conditions(Elsevier, 2012-09)
; 43 2Scopus© Citations 76