Implementation of non-linear viscoelasticity for epoxy based thermoset polymers

Epoxy based polymers are widely used as thermal or / and electrical interfaces and as encapsulation material in the semiconductor industry. In order to shorten the product development process, simulation plays a more and more important role, especially in a very early design stage. Accurate description of the thermo-mechanical behavior of the individual materials is crucial for quantitative finite element analysis of the designed product. This paper focus on non-linear characterization of epoxy based thermoset polymers and presents the comparison of the material behavior based on the linear viscoelastic (LVE) method and non-linear viscoelastic (NLVE) method. Both methods can consider the effect of time and temperature. However, the LVE method is not capable to reproduce the behavior at large strain, where highly non-linear mechanical behavior of the tested thermosets is present. Here an advanced hyperviscoelastic Bergstrom-Boyce (BB) model is used to describe the highly non-linear effects quantitatively. Utilizing the NLVE method, significant improvement in the time and temperature domain as well as for the strain dependent relaxation is achieved.