Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    Advanced mixed-mode bending test: A rapid, inexpensive and accurate method for fracture-mechanical interface characterisation
    ( 2012)
    Wunderle, B.
    ;
    Schulz, M.
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    Keller, J.
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    May, D.
    ;
    Maus, I.
    ;
    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.
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    Dermitzaki, E.
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    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
    Automated test system for in-situ testing of reliability and aging behaviour of thermal interface materials
    ( 2011)
    AboRas, M.
    ;
    Haug, R.
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    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.
  • Patent
    Verfahren und Vorrichtung zur thermischen Ueberwachung von Ausfallprozessen
    ( 2009)
    Wittler, O.
    ;
    Wunderle, B.
    ;
    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.
  • Publication
    Reliability concepts of microsystem integration
    ( 2009)
    Wunderle, B.
    ;
    Michel, B.
  • Publication
    Reliability modeling & test for flip-chip on flex substrates with Ag-filled anisotropic conductive adhesive
    ( 2008)
    Wunderle, B.
    ;
    Kallmayer, C.
    ;
    Walter, H.
    ;
    Braun, T.
    ;
    Michel, B.
    ;
    Reichl, H.
    This paper addresses the reliability of flip-chip on flex (FCOF) assemblies glued with an Ag-particle filled anisotropic conductive adhesive (ACA). As the description of FCOF failure gives still much scope for speculation, a physics of failure based approach is developed here, taking into account the changing thermo-mechanical properties of the ACA under temperature and moisture. A failure hypothesis is formulated based on the loss of contact pressure. Material analysis, material characterisation, finite element (FE) modeling and lifetime tests have been employed to establish correlations to support this failure hypothesis. It was found, that moisture plays the most important role for interconnect failure. The model is able to predict quantitative changes of force as function of loading parameters and correlate them qualitatively to the experimental mean time to failure. New insights are provided about the stress fields at the ACA bump. The model is discussed with respect to a direct prediction of failure versus time.
  • Publication
    In-situ measurement of various thin bond-line-thickness thermal interface materials with correlation to structural features
    ( 2008)
    Wunderle, B.
    ;
    Kleff, J.
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    Mrossko, R.
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    Abo Ras, M.
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    May, D.
    ;
    Schacht, R.
    ;
    Oppermann, H.
    ;
    Keller, J.
    ;
    Michel, B.
    Thermal characterisation of thermal interfaces becomes even tougher a challenge at low bond line thicknesses and higher thermal conductivities of the interface materials as more accurate measurement techniques are required. As in parallel the quest for high conductivity adhesives and greases is ongoing, a correlation between thermal bulk or interface properties and structure is in high demand. We have developed test-stands for various classes of thermal interface materials. These permit characterisation for materials with thin bond line thickness and high thermal conductivity still using steady state techniques. The methods are benchmarked for greases, adhesives and sintered silver. For the latter, the technology development is described. Then, structural features such as particle density and porosity are examined. It will be the aim to compare and correlate them to thermal resistance. Part of the work has been accomplished within the running EU. Project "Nanopack".
  • Publication
    Mechanical Characterisation of Thin Metal Layers by Modelling of the Nanoindentation Experiment
    ( 2008)
    Wittler, O.
    ;
    Mroßko, R.
    ;
    Kaulfersch, E.
    ;
    Wunderle, B.
    ;
    Michel, B.
    Obtaining material data for thin metal layers is a mayor issue in the reliability assessment of microelectronic products. Therefore a method for obtaining elastic-plastic material data is analyzed and discussed in this paper. It is based on the nanoindentation of a film on a silicon substrate and the modeling of it. Thus it becomes possible to fit specific material models to the indentation experiment. Results are shown for two AlSiCu layers.
  • Publication
    Lifetime Model for Flip-Chip on Flex using Anisotropic Conductive Adhesive under Moisture and Temperature Loading
    ( 2008)
    Wunderle, B.
    ;
    Kallmayer, C.
    ;
    Walter, H.
    ;
    Braun, T.
    ;
    Michel, B.
    ;
    Reichl, H.
    This paper addresses the reliability of .ip-chip on flex (FCOF) assemblies glued with an Ag-particle filled anisotropic conductive adhesive (ACA). As the description of FCOF failure gives still much scope for speculation, a physics of failure based approach is developed here, taking into account the changing thermo-mechanical properties of the ACA under temperature and moisture. A failure hypothesis is formulated based on the loss of contact pressure. Material analysis, material characterisation, Finite Element (FE) modeling and lifetime tests have been employed to establish correlations to support this failure hypothesis. It was found, that moisture plays the most important role for interconnect failure. The model is able to predict quantitative changes of force as function of loading parameters and correlate them qualitatively to the experimental mean time to failure. New insights are provided about the stress .elds at the ACA bump. The model is discussed with respect to a direct prediction of failure versus time.
  • Publication
    Challenges for multi-scale modeling of multiple failure modes in microelectronics
    ( 2008)
    Auersperg, J.
    ;
    Wunderle, B.
    ;
    Dudek, R.
    ;
    Walter, H.
    ;
    Michel, B.
    Design studies of electronics components on the basis of parameterized Finite Element Models and DoE/RSM-approaches (Design of Experiments/Response Surface Methods) are more and more performed for optimizations at early phases of the product development process. That is why electronics components especially in the field of RF (Radio Frequency), optoelectronics, high temperature and power applications are often exposed to extreme thermal environmental conditions, mechanical shock and vibrations. However, a continuous industry drive for miniaturization and function integration forces the development of eature sizes down to the nanometer regime. Simultaneously, the well known thermal expansion mismatch problem of the several materials, residual stresses generated by several steps of the manufacturing process and various kinds of inhomogeneity attribute to interface delamination, chip cracking and fatigue of interconnects, in particular. The applied methodologies typically base on classical stress/strain strength evaluations or/and life time estimations of solder interconnects using modified Coffin-Manson approaches. Recent studies show also how the evaluation of mixed mode interface delamination phenomena, classical strength hypotheses along with fracture mechanics approaches and thermal fatigue estimation of solder joints can simultaneously be taken into account. Over and above that, new materials will be introduced especially in Back-end of line (BEoL) layers of advanced Cu/Low-k 90, 45, ..., 22 nanometer CMOS (Complementary Metal-Oxide Semiconductor) technologies. So, black diamond-I or black diamond-II as new materials are increasingly porous and interconnect materials or new functional layers come up as nano-particle filled high-tech compounds. Thus, it is to be checked whether it can be handled as homogeneous materials anymore. For sure, this will have most important impacts on the thermo-mechanical performance of the total IC (Integrated Circuit) tack. The problems appearing during packaging of CMOS-ICs at least showed that IC and package reliability are strongly interacted. Thus, the challenge for simulations in this field is not only the wide range of structural dimensions but also, the different approaches that have to be combined: Molecular or atomistic level simulations and "conventional" Finite Element Analysis (FEA) with global-local modeling, substructuring as well as fracture and damage mechanics, cohesive zone models, viscoelasticity, plasticity and creep of homogeneous constitutive models. Furthermore, it is known that multiple failure modes competitively act simultaneously wherefore, design optimizations have to incorporate all failure modes that are essential for the overall reliability. Moreover, considering that variables of the simulation models are naturally stochastic parameters leads to the consequence that all results show also scattering. First steps towards robust designs show the potential of the utilized FEA-based RMS/DOE approach to evaluate the thermo-mechanical reliability of various electronics assemblies in a more complex way giving at the same time a more solid basis for design optimizations.