Cure dependent characterisation of moulding compounds

Curing effects and difference in thermal contraction of components cause residual stresses and warpage during encapsulation of electronic packages. Residual stresses combined with thermal and mechanical loads influence package reliability and performance and may eventually lead to product failure. Comprehensive material characterisation is needed in order to perform numerical simulations which take into account the effect of shrinkage and stress development during the curing reaction of the moulding compound. With that, more reliable predictions can be made. The paper deals with detailed characterisation of moulding compounds. These materials show a clear viscoelastic behaviour, which is both temperature and cure dependent. The performed analyses cover cure kinetics, determination of elongation modulus and the studies on viscoelastic behaviour during cure. Furthermore, dilatometric tests were performed to obtain chemical shrinkage, bulk modulus and to check its time dependency. The obtained parameters including cure shrinkage will be implemented in the finite element software (ANSYS) using user programmable subroutines and APDL code.