Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    On the crack and delamination risk optimization of a Si-interposer for LED packaging
    ( 2014)
    Auersperg, J.
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    Dudek, R.
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    Jordan, R.
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    Bochow-Neß, O.
    ;
    Rzepka, S.
    ;
    Michel, B.
    3D-integration becomes more and more an important issue for advanced LED packaging solutions as it is a great challenge for the thermo-mechanical reliability to remove heat from LEDs to the environment by heat spreading or specialized cooling technologies. Thermal copper-TSVs provide an elegant solution to effectively transfer heat from LED to the heat spreading structures on the backside of a substrate. But, the use of copper-TSVs generates also novel challenges for reliability as well as also for reliability analysis and prediction, i.e. to manage multiple failure modes acting combined - interface delamination, cracking and fatigue, in particular. In this case, the thermal expansion mismatch between copper and silicon yields to risky stress situations. To overcome cracking and delamination risks in the vicinity of thermal copper-TSVs the authors performed extensive simulative work by means of fracture mechanics approaches - an interaction integral approach within a simulative DoE and the X-FEM methodology to help clarifying crack propagation paths in silicon. The results provided a good insight into the role of model parameters for further optimizations of the intended thermal TSV-approaches in LED packaging applications.
  • Publication
    Advanced mixed-mode bending test: A rapid, inexpensive and accurate method for fracture-mechanical interface characterisation
    ( 2012)
    Wunderle, B.
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    Schulz, M.
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    Keller, J.
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    May, D.
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    Maus, I.
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    Pape, H.
    ;
    Michel, B.
    This paper presents a comprehensive method for obtaining urgently required critical interface delamination data of material pairings used in electronic packaging. The objective is to thereby enable rapid, inexpensive and accurate lifetime prediction for that failure mode. A new testing method is presented which allows maximum mode-angle range and enhanced throughput testing under multiple loading conditions, the coverage of which is usually a rather lengthy and resource-demanding procedure. The approach is specimen-centred in the sense that the accent is put on test-specimens which are easily manufacturable industrially, rather than having to adapt them to a special testing machine. The concept is also scalable, i.e. it has potential to work also for smaller samples cut from real devices. We show the first version of a newly developed test-stand and discuss the obtained results for copper-molding compound interfaces in the light of the current state of the art used for delamination testing in electronic packaging.
  • Publication
    Basic thermo-mechanical property estimation of a 3D-crosslinked epoxy/SiO2 interface using molecular modelling
    ( 2011)
    Hölck, O.
    ;
    Dermitzaki, E.
    ;
    Wunderle, B.
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    Bauer, J.
    ;
    Michel, B.
    In this work we present a procedure for the construction of 3D networked epoxy moulding compounds and an estimation of basic thermodynamic properties by molecular dynamics simulations. Our investigations present part of general trend to extend failure analysis, reliability assessment and the development of packaging materials from the conventional discrete usage of simulation techniques to a more holistic approach of an interconnected multimethods- procedure, enabling bottom-up simulation of complex microsystems. Within that framework, the task at hand for detailed atomistic molecular modelling is to develop practical methods in order to take materials development as well as materials failure analysis to the nanoscale level. This paper reports a cross linking scheme for the construction of three dimensionally cross linked simulation packages and presents a first property analysis of an industry-oriented moulding compound material. First models and results are presented of model packages of ideal epoxy/silicon-dioxide interfaces.
  • Publication
    Local stress measurement on metal lines and dielectrics of BEoL pattern by stress relief technique
    ( 2011)
    Vogel, D.
    ;
    Rzepka, S.
    ;
    Michel, B.
    ;
    Gollhardt, A.
    The paper presents a new measurement method for residual stresses introduced by manufacturing in BEoL structures. Material removal by FIB ion milling is used to release elastically frozen stresses. Normal stress components are calculated from local stress relaxation nearby milled trenches. A validation of the new technique is accomplished by additional bow measurements on defined layers on substrate. Spatially resolved determination of stress values in metal lines and the dielectrics in between demonstrates the capability of the tool for future applications.
  • Publication
    Automated test system for in-situ testing of reliability and aging behaviour of thermal interface materials
    ( 2011)
    AboRas, M.
    ;
    Haug, R.
    ;
    Schacht, R.
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    Monory-Plantier, C.
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    May, D.
    ;
    Wunderle, B.
    ;
    Winkler, T.
    ;
    Michel, B.
    Thermal interface materials (TIMs) are widely needed to improve thermal contacts for facilitation heat transfer in electronic packaging, such as that associated with the flow of heat from microprocessor to a heat spreader or a heat sink in a computer. Due to thermal mismatch between these components mechanical strain occur which cause pump-out, cracks or delamination of TIM. In order to qualify the reliability and aging of TIMs, traditional power cycle test is commonly used to detect potential thermal failures. This traditional power cycle test is a time consuming process due to its long heating and cooling time. Therefore a new automated test system for in-situ reliability testing of TIMs is developed and will be presented in this paper. The new test system is designed to be able to analyze the aging and reliability behavior of most common TIMs. The TIMs can be measured in-situ and under real conditions as they are used in real applications.
  • Publication
    Localized high-resolution stress measurements on MEMS structures
    ( 2010)
    Vogel, D.
    ;
    Gollhardt, A.
    ;
    Michel, B.
    Three different methods of stress measurement with strong spatial resolution are presented. They base on stress relief techniques caused by focused ion beam milling, on altered electron backscattering by deformed lattices and on Stokes line shift measurements by Raman spectroscopy. The capability of these methods is demonstrated by their application to typical MEMS structures. A comparison between the methods is performed in order to outline potentials and limitations.
  • Publication
    Advanced virtual qualification methods to reduce the time-to-market of microelectronic assemblies
    ( 2010)
    Shirangi, M.H.
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    Koyuncu, M.
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    Keller, J.
    ;
    Michel, B.
    This work presents some recent progresses in reliability assessment of electronic assemblies in automotive industry and shows how coupled numerical-experimental techniques can help save time and reduce the cost of IC package qualification. In order to fulfill the continuous trends in miniaturization of the electronic devices together with the demand to shorten the time to market, it is essential to use virtual qualification methods with the simulation tools. One of the main concerns in electronic packages is the structural integrity during their fabrication, surface mount process, and service life. A prominent example of failure in electronic assemblies is the interface delamination between two dissimilar materials. This failure mode is accelerated when the polymeric materials absorb moisture from humid environments. Moisture results in degradation of the physical properties of polymers, induces additional deformation due to hygroscopic swelling, and more importantly, d egrades the adhesion strength of the polymer to metal joints.
  • Publication
    Comparative study of residual stress measurement techniques with high spatial resolution
    ( 2010)
    Vogel, D.
    ;
    Maus, I.
    ;
    Schindler-Saefkow, F.
    ;
    Michel, B.
    Three different methods of stress measurement with strong spatial resolution are presented. They base on stress relief techniques caused by focused ion beam milling, on altered electron backscattering by deformed lattices and on Stokes line shift measurements by Raman spectroscopy. The capability of these methods is demonstrated by their application to typical MEMS structures. A comparison between the methods is performed in order to outline potentials and limitations.
  • Publication
    Simulation based analysis of secondary effects on solder fatigue
    ( 2009)
    Dudek, R.
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    Doering, R.
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    Bombach, C.
    ;
    Michel, B.
    Secondary effects on thermal fatigue of solderjoints, which frequently have been neglected, were studied by means of the finite element method (FEM). Based on a semi-empirical approach to predict fatigue life by evaluating the cyclic accumulated equivalent creep strain or energy density, effects of organic boards intrinsic properties on solder joint fatigue were investigated. Aspects of more realistic FR-4 board modelling were studied, in particular concerning its in-plane anisotropy and intrinsic warpage behaviour. Intrinsic board warpage was measured on test board level as well as for boards from series production. High intrinsic warpage was in particular found for several test boards. The effects for the worst case scenario observed so far were analysed for both first level and second level interconnects. The change in predicted fatigue life varied between 30% and 500%, the latter most critical effects were found at large QFN components. Another secondary effect studied was to include the frequently neglected interfacial intermetallics into FEM. It turned out that for components with relatively large standoff like LFBGAs the effects were actually negligible, but for the highly miniaturized components like chip resistors CR0201 they are the decisive factor.
  • Patent
    Verfahren und Vorrichtung zur thermischen Ueberwachung von Ausfallprozessen
    ( 2009)
    Wittler, O.
    ;
    Wunderle, B.
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    Mazloum Nejadari, S.
    ;
    Schacht, R.
    ;
    Michel, B.
    (A1) Die Erfindung betrifft ein Verfahren und eine Vorrichtung zur thermischen Ueberwachung eines Gegenstandes 3, bei welchem eine durch die fortschreitende Beschaedigung des zu untersuchenden Gegenstandes 3 hervorgerufene Veraenderung des Antwortverhaltens einer oder mehrerer temperaturabhaengiger Messgroessen auf die Einpraegung eines definierten Heizimpulses 10 auf den Gegenstand untersucht wird. Hierbei wird der definierte Heizimpuls 10 durch elektrische Ansteuerung von Mitteln zur Waermeerzeugung 1, die an oder in dem Gegenstand 3 angeordnet sind, erzeugt und das Antwortverhalten auf das Aufbringen des definierten Heizimpulses an Mitteln zur Temperaturerfassung 2, die an oder in dem Gegenstand 3 angeordnet sind, ueber mindestens eine durch die Mittel zur Temperaturerfassung 2 erzeugte elektrische Messgroesse gemessen.