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.
    ;
    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.
    ;
    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.
    ;
    Monory-Plantier, C.
    ;
    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
    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
    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
    Reliability concepts of microsystem integration
    ( 2009)
    Wunderle, B.
    ;
    Michel, B.
  • 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
    Thermo-mechanical pre-optimisation of radar sensor design by means of FEA and microDAC measurements
    ( 2008)
    Sommer, J.-P.
    ;
    Michel, B.
    ;
    Noack, E.
    ;
    Seiler, B.
    More and more dense packaging is one of the most important challenges in advanced electronics and micro technology, driven by requirements like low cost and high reliability. One way to meet these demands is to follow the so-called ldquochip in duromerrdquo approach, which allows an extremely dense integration and very short interconnects. Already in the very first design phase of advanced products, numerical studies by means of finite element analyses (FEA) are very efficient to check the desired properties regarding functionality as well as reliability aspects. This has been carried out with a new generation of active distance control (ADC) devices for automobiles, based on a radar principle. In order to obtain sufficiently flat modules for subsequent manufacturing steps, thermally induced deformations were measured at suitable specimens by means of the microDAC technique, developed by CWM GmbH Chemnitz and Fraunhofer IZM. Combining FE analyses and measured deformations, a methodology was developed which can be generalised and applied to many design procedures before any real parts are available. It is helpful to reduce cost and time-to-market for future products by minimising real tests and an expensive redesign.
  • Publication
    FEA Based Reliability Prediction for Different Sn-Based Solders Subjected to Fast Shear and Fatigue Loadings
    ( 2008)
    Dudek, R.
    ;
    Kaulfersch, E.
    ;
    Rzepka, S.
    ;
    Röllig, M.
    ;
    Michel, B.
    Recent studies revealed that there is no simple ldquodrop inrdquo solution for the lead-free replacement of SnPb joints, instead different Sn-based solders are advantageous for different use conditions, which can be dominated either by drop loading or by thermal cyclic loading in harsh use conditions. By way of high-speed shear testing reliability assessments of components during drop and shock events can be studied in a simplified manner. Dynamic 3-D finite element simulations have been performed applying explicit FEA to replicate the shear tests virtually. It was shown in this way that SAC 1305 solder outperformed SAC 387 solder. The low cycle fatigue behavior of different SAC alloys is additionally of interest. Fatigue life predictions require both the constitutive description of the lead-free solders and a fatigue hypothesis linked to the material selected. Based on recently measured creep properties the solder joint creep strain and creep dissipation responses were analyzed for several components and thermal cycling conditions. The results based upon non-linear finite element calculations indicate different trends for creep strain and energy dissipation: while the first is clearly increasing with lowered alloying Ag-content, the latter is almost stable and does only slightly vary. Furthermore, these trends are different for different test- and field cycling conditions as well as the different components studied.