Development of consistent interconversions between linear viscoelastic functions for multiaxial viscoelastic models

Characterizations for the comprehensive viscoelastic behaviors of materials were conducted in this research. For considering the multiaxial viscoelastic behaviors of the polymeric constituents in finite element models for package stress and deformation simulations, it is required to construct the mathematical models of the viscoelastic bulk and shear relaxation moduli. In order to obtain the consistent viscoelastic functions, the interconversion relations were developed and applied as a new fitting procedure. By using the consistently fitted values of viscoelastic bulk and shear relaxation moduli, the constitutive behaviors of organic packaging materials by using time-dependent viscoelastic models for warpage predictions could be more accurate.