Simulation of moisture-induced plasticization in transfer-molded optical sensor packages using a time - temperature - moisture concentration superposition

Moisture sorption of microelectronics packages may lead to plasticization of materials such as epoxide-based transfer-molding compounds. This does not only result in a reduction of the modulus but also to a change in the frequency response of the materials. In this work, moisture-induced plasticization effects of unfilled transparent molding compounds are modeled using finite-element reliability simulations of an optical sensor package. Storage modulus data from humidity-controlled dynamic mechanical analysis is used to extend the temperature-dependent linear viscoelastic constitutive model, usually applied using a Prony series and time - temperature superposition, to apply a previously presented time - temperature - moisture concentration superposition of viscoelastic relaxation time-constants. Eventually, stress fields at the die-to-mold compound interface resulting from thermal and hygroscopic strains are compared, applying different complexity of the constitutive model of the compound.