摘要
It is important to determine the dielectric characteristics of semiconductor encapsulation materials based on epoxy resins.We employed the dielectric spectroscopy technique to investigate the dielectric relaxation in the presence of water and how it changes the relaxation.It was observed that the dielectric relaxation of the material was significantly influenced by absorbed water,the local segmental motion(also known as Johari-Goldstein(β)relaxation)was influenced most by the presence of the water,it was modified by the wet sample compared to dry one,and required high activation energy.The relaxation related to the glass transition was contributed by the cooperative motion(the a-relaxation)of the epoxy resin system.The a-relaxation was shifted to a low temperature in the wet sample compared to dry one.The relaxation was modeled with a clear Vogel-Fulcher-Tammann-Hesse(VFTH)behavior;the Vogel temperature of the wet sample was 8 K lower than the dry sample.The presence of water acts as a plasticizer for the molecular relaxation,and speed-up the cooperative process.The measured data were also used to estimate the electrical properties of the resin system by employing an effective-medium model together with a porous media continuum model by taking into account the physical properties of the system.It is already known that the influence of water in semiconductor packaging is important in sensitive applications.The presented measurements and the analysis method would be appreciated within the semiconductor packaging community to improve material selection and performance evaluation efforts.
