Development and Validation of E-Modulus Kinetics Testing Method via DMA for Thermo-Mechanical Analysis of Epoxy Resin

Printed circuit boards (PCBs) are indispensable key components in modern electronic devices, and epoxy resins are widely used in the manufacture of PCBs due to their excellent electrical insulation and mechanical properties. However, temperature variations during the lamination process can induce complex curing behaviors, leading to residual stresses and warpage that compromise product reliability. In order to perform more accurate finite element simulations of the thermo-mechanical behavior of the curing process, it is crucial to accurately characterize elastic modulus (E-Modulus) kinetics during the curing process. Although the cure hardening instantaneous linear elastic (CHILE) model has been shown to be effective in predicting the E-Modulus of composites, its application still has many limitations. For example, the CHILE model does not accurately describe the correlation between temperature, degree of cure, and E-Modulus of pure epoxy resins at different heating rates. Furthermore, the model is only applicable to lower degree of cure conditions and does not consistently reflect the changes in material properties during the dynamic heating process. More importantly, discrepancies between DSC-derived cure data and DMA measurements can introduce systematic errors. Therefore, the main objective of this study is to develop a reproducible and reliable DMA test method for uncured and partially cured epoxy resin samples, which will provide high-quality experimental data for improving the CHILE model. At the same time, these experimental data can also be used to validate other theoretical models, such as the model free kinetics model based on the isoconversional state diagram (ISD) theory. Secondly, the CHILE model is systematically modified and improved by combining the DMA data, and its engineering applicability is verified under the actual production line conditions. The experimental results show that the obtained DMA data have good repeatability and are highly consistent with the predictions of the ISD theory. The improved CHILE model based on DMA data, shows enhanced accuracy across the full curing range compared with the original model. The methods and models established in this study provide a solid foundation for high-precision modeling of the thermodynamic behavior of epoxy resin during the curing process.