In-Situ Cure Monitoring of EMC by Fiber Bragg Grating and Dielectric Sensors with Molecular Dynamics Validation for Accurate Warpage Prediction

초록

The present work introduces a comprehensive multiscale framework to characterize the thermo-mechanical evolution of liquid epoxy molding compound (EMC) under industrial compression molding conditions. Central to this approach is the rigorous characterization of the EMC’s transition from a viscous, zero-modulus state to a load-bearing viscoelastic solid. To establish a robust stress-free reference, the gelation point—the critical onset of modulus evolution and residual stress accumulation—was identified via in-situ dielectrometry. Post-gel effective cure shrinkage was quantified through real-time strain monitoring using Fiber Bragg Grating (FBG) sensors. The hallmark of this framework is the high-fidelity reconstruction of cure-dependent Young’s modulus, achieved by seamlessly embedding the dynamic evolution of Poisson’s ratio— derived from Molecular Dynamics (MD) simulations—into both the inverse calculation and the subsequent FEM-based property validation. Furthermore, frequency-dependent viscoelasticity obtained from Dynamic Mechanical Analysis (DMA) was incorporated to account for stress relaxation during the post-mold cooling phase. The proposed framework was validated using an Al/EMC bi-material strip model, where the FEM simulation—integrated with the extracted multiscale properties—demonstrated a high correlation with experimental measurements, achieving an accuracy of 97.96%. Sensitivity analyses definitively show that superior warpage modeling requires simultaneous consideration of all cure-dependent thermo-mechanical properties. The integration of atomistic-to-macroscopic properties establishes a new standard for high-accuracy warpage prediction, essential for ensuring the structural integrity of next-generation semiconductor packages.

키워드