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.
    ;
    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
    Local stress measurement on metal lines and dielectrics of BEoL pattern by stress relief technique
    ( 2011)
    Vogel, D.
    ;
    Rzepka, S.
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    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.
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    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.
  • 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.
    ;
    Koyuncu, M.
    ;
    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.
    ;
    Doering, R.
    ;
    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.
  • Publication
    Reliability concepts of microsystem integration
    ( 2009)
    Wunderle, B.
    ;
    Michel, B.
  • Publication
    Challenges for multi-scale modeling of multiple failure modes in microelectronics packaging
    ( 2008)
    Auersperg, J.
    ;
    Dudek, R.
    ;
    Vogel, D.
    ;
    Michel, B.
    Design for thermo-mechanical reliability 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. This is especially the case for electronic components in the fields of RF (Radio Frequency), optoelectronics, high temperature, and power applications, which are often exposed to extreme thermal environmental conditions, mechanical shock and vibrations. Additionally, a continuous industry drive for miniaturization and function integration forces the development of feature sizes down to the nanometer range and the introduction of new high-tech, nano-particle filled or nano-porous materials. These developments cause new challenges for reliability analysis and prediction, i.e. the development of multiple failure criteria for combined loadings including residual stresses, interface delamination, cracking and fatigue of interconnects simultaneously. That's why, the authors face up to multiscale modeling approaches, damage and fracture mechanics approaches on the basis of continuum mechanics, and measurement techniques of material properties in the miniaturized range addressed. Evaluations of residual stresses, especially of thin films, resulting from several manufacturing steps are an important precondition for high-quality FEA-based RSM/DOE-simulations towards robust designs, too.
  • Publication
    Lifetime Model for Flip-Chip on Flex using Anisotropic Conductive Adhesive under Moisture and Temperature Loading
    ( 2008)
    Wunderle, B.
    ;
    Kallmayer, C.
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    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.