22. Comprehensive Viscoelastic Properties Characterization of EMC Using FBG Sensor

An advanced system based on a fiber Bragg grating (FBG) sensor is proposed to characterize the comprehensive viscoelastic properties of epoxy molding compound (EMC). The FBG sensor is embedded in the center of a cylindrical EMC specimen, and the strain of the EMC is measured as a function of time under a constant loading condition. The constant loading condition is achieved by utilizing an automated gas pressure system. Two loading conditions are considered: compressive pressure for the Young’s modulus and hydrostatic pressure for the Bulk modulus. The constant loadings are repeated at different temperatures. The time dependent properties at different temperatures are shifted and overlapped to create the master curves of the Young’s modulus and bulk modulus. A piece-wise shift function is developed to fit the shift factors with extreme non-linearity. The results confirm the TRS assumption about the EMC; i.e., a single set of the shift factors can be used for both Young’s modulus and bulk modulus. The comprehensive properties are used to predict the behavior of an EMC/chip bi-material joint subjected to the thermo-mechanical loadings. The results clearly show enhanced modeling predictability.