Visco-elastic properties of micron-thick SU-8 polymers measured by two different types of uniaxial tensile tests

This paper describes the effects of specimen size and temperature on viscoelastic properties of microscale SU-8 polymers at intermediate temperatures. Two different types of uniaxial tensile testers examine glassy/rubbery moduli, fracture strain and relaxation modulus of SU-8 polymer specimens. The average glassy modulus at R.T. is 3.5 GPa, which decreases with temperature elevations up to 573 K irrespective of specimen size. Yield stress and fracture strain, however, exhibit the size and temperature dependencies. Besides, we have constructed the master curves of relaxation modulus for micro/milliscale SU-8 polymer specimens. The master curve of microscale SU-8 polymers is in good agreement with that of milliscale polymers, which indicates that the apparent activation energy is independent of the size. The master curves approximated using a Prony series would be widely used to conduct viscoelastic finite element analysis, leading to reliable design of SU-8 micro-components.