Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

Filters
3
Reset filters

Settings
Now showing 1 - 3 of 3
  • Publication
    On the crack and delamination risk optimization of a Si-interposer for LED packaging
    ( 2014)
    Auersperg, J.
    ;
    Dudek, R.
    ;
    Jordan, R.
    ;
    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
    Micro- and nanoreliability research in the micro materials center Chemnitz of Fraunhofer ENAS
    ( 2009)
    Michel, B.
    ;
    Dudek, R.
    ;
    Auersperg, J.
    ;
    Winkler, T.
  • 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.