Comparison of methods for the mechanical characterization of polymers for MEMS applications

This paper gives an overview of a series of experiments conducted in order to characterize the mechanical behavior of two photodefinable epoxies. In particular, it focuses on the stiffness of the materials. The (complex) modulus is measured using five different methods: conventional nanoindentation, continuous stiffness measurement nanoindentation, nanoindentation on MEM structures, dynamic tensile tests and static tensile tests. The measured moduli range from 0.9 to 7.4 GPa for SU-8 and from 1 to 4.1 GPa for Epoclad, depending on the type of experiment and the loading speeds used in the experiments. Results reveal that conventional nanoindentation is not well optimized for polymer characterization and that there is a need for stiffness measurements using more fundamental approaches like a (dynamic) tensile test.