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Time and Temperature Dependent Mechanical Characterization of Polymers for Microsystems Applications

: Wittler, O.; Walter, H.; Gollhardt, A.; Vogel, D.; Sprafke, P.; Michel, B.

Materials Week 2000. Proceedings
Frankfurt: Werkstoffwoche-Partnerschaft GbRmbH, 2000
8 S.
Materials Week <2000, München>
Werkstoffwoche <3, 2000, München>
Fraunhofer IZM ()

As microsystems are increasingly set out to thermal and mechanical loads, a simulation of strains and stresses becomes a subject of matter in assessing the reliability of such systems. If polymers are characterised for such simulations, the temperature and loading rate dependence of their mechanical properties has to be considered. In a first approach an isotropic viscoelastic model has been assumed and two different methods of acquiring simulation data have been applied and compared for different crosslinked polymers. On the one hand the relaxation modulus for tension is being measured at different temperatures on a tensile testing machine. On the other hand temperature dependent material data has been determined by DMA (Dynamic-Mechanical-Analysis) in three-point-bending. This dynamic method has the practical advantage of being less time and effort consuming than the static tension testing method. For the description of the material properties in the whole temperature range an approach for the time-temperature-superposition is applied, that leads to a dataset for FE-simulations that can be obtained in a straightforward and objective way. Besides the time dependent Young's modulus also another elastic modulus has to be obtained for the simulation of multiaxial states of stress. For example the Poisson's ratio represents an important parameter relating. Its estimation is based on its temperature dependent measurement with a new digital image correlation system.