Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    Non-destructive failure analysis and modeling of encapsulated miniature SMD ceramic chip capacitors under thermal and mechanical loading
    ( 2007)
    Wunderle, B.
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    Braun, T.
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    May, D.
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    Mazloum, A.
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    Bouazza, M.
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    Walter, H.
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    Wittier, O.
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    Schacht, R.
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    Becker, K.-F.
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    Schneider-Ramelow, M.
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    Michel, B.
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    Reichl, H.
    The use of multi-layer ceramic chip capacitors as integrated passive in e. g. system in package applications needs methods to examine and predict their reliability. Therefore, a nondestructive failure analytical technique is described to detect cracks in the ceramic and the metallic layers within encapsulated 0402 SMD capacitors. After choosing from techniques to reproducibly generate cracks, it is shown that an in-situ capacitance measurement is a convenient method to detect these failures unambiguously. Finite Element simulations support the experimental results. A reliability estimate for capacitor integrity under given loading conditions is given.
  • Publication
    Performance and thermo-mechanical reliability of micro-channel coolers - a parametric study
    ( 2004)
    Wunderle, B.
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    Schacht, R.
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    Wittler, O.
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    Michel, B.
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    Reichl, H.
    In the paper we present an approach based on this principle to design reliable thermal management solutions for high power applications. Thermal and thermo-mechanical reliability are measured and calculated for a flip-chip mounted die with a hot-spot using reverse-side micro-channel water cooling as cooling concept. Hereby the methodology starts by material characterisation and consistent numerical implementation. Then a numerical parametric study as to geometrical features and interface materials is carried out by coupled fluidic-thermal analysis in order to evaluate the most promising variant for optimum thermal performance within the employed technology. For experimental verification a computer-controlled closed-loop thermal-fluidic testing set-up was constructed. Good correlation was found between measured, simulated and analytical results.
  • Publication
    Reliability assessment of flip-chip assemblies with lead-free solder joints
    ( 2002)
    Schubert, A.
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    Dudek, R.
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    Walter, H.
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    Jung, E.
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    Gollhardt, A.
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    Michel, B.
    ;
    Reichl, H.
    Due to environmental awareness, and the health hazards involved in using lead in solders, large efforts to develop lead-free soldering have been made in recent years. Sn-Ag alloys are expected to be one of the best candidate lead-free solders. Furthermore, from a reliability viewpoint, there has been interest in improved thermal fatigue resistance of solder interconnects. In this study, two lead-free solder alloys (Sn96.5Ag3.5, Sn95.5Ag3.8Cu0.7) were investigated in comparison to lead-containing solder alloys (Sn63Pb37, Sn59Pb40Ag1). These investigations were focused on mechanical and physical properties (coefficient of thermal expansion, stress-strain curves at different strain-rates) as well as on the microstructural appearance of the solders. The mechanical and thermomechanical behavior of the solders were examined by TMA, DTMA, tensile tests, and creep tests. Constant-load creep tests were performed on the specimens at temperatures from 20 degrees C to 150 degrees C. Steady-state strain rates spanned seven orders of magnitude ranging from 10/sup -11/ s/sup -1/ to 10/sup -4/ s/sup -1/. The second step is a reliability study of flip-chip assemblies on FR-4 (high T/sub g/ material) with three different underfill materials and with Sn63Pb37, Sn96.5Ag3.5, and Sn95.5Ag4.0Cu0.5 bumps, undergoing thermal cycles from - 55 degrees C to 125 degrees C and -55 degrees C to 150 degrees C. The deterioration (characterized by electrical resistance and SEM) are described. Furthermore, it is shown that the material parameters obtained from the tests will increase the precision of finite-element analysis for reliability studies of microelectronic packages with lead- free solder interconnects.
  • Publication
    Materials mechanics and mechanical reliability of flip chip assemblies on organics substrates
    ( 1997)
    Schubert, A.
    ;
    Dudek, R.
    ;
    Michel, B.
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    Reichl, H.
    ;
    Jiang, H.
    This paper demonstrates a combined approach of numerical analysis and experimental investigations to study the mechanical reliability of flip chip solder joints. The effect of various design parameters like bump geometry, "soft" and "hard" underfill, and used solder mask on the thermal fatigue life of solder joints is discussed. Since special attention has been directed towards Flip Chip on Board (FCOB) assemblies, constitutive properties of polymeric and solder materials are discussed in detail. The solder is modeled using a nonlinear constitutive law with time dependent (creep) and time independent plastic strains. Furthermore, material testing shows that the underfill and solder mask materials might be considered as linear viscoelastic with temperature time shift properties. Thermal mismatch between the materials assembled is often the main reason for thermally induced stresses. Thermal cycling (125 degrees C...-55 degrees C...125 degrees C) is therefore the load generally used in t he 3D non-linear finite element analysis. Calculation results of the solder bump deformation due to temperature changes are accompanied by experimental deformation analysis. The used MicroDAC method is based on algorithms of local object tracking in images obtained from electron scanning microscopy. The measured deformation fields were utilized for proper materials selection and processing, as well as for verification of finite element analysis.
  • Publication
    Materials mechanics and mechanical reliability of flip chip assemblies on organics substrates
    ( 1997)
    Schubert, A.
    ;
    Dudek, R.
    ;
    Vogel, D.
    ;
    Michel, B.
    ;
    Reichl, H.