Isothermal DSC Study of the Curing Kinetics of an Epoxy/Silica Composite for Microelectronics

Abstract

Abstract Curing kinetics of an industrially important printed-circuit board (PCB) base material (epoxy–phenol/glass fillers) were studied by isothermal differential scanning calorimetry (DSC) measurements between 150 and 190°C, as relevant curing temperatures for the PCB industry. The extent of cure was calculated by integration of the exothermic peak and normalization by the total heat of reaction (obtained by nonisothermal DSC). Although the cross-linking was completed above 180°C, the kinetic profiles show two regimes: one fast and one slow. The kinetic parameters have been elucidated using an isoconversional model-free kinetic method, with the exact method of Friedman, to give to the PCB manufacturers a road map to predict curing behavior of base material. The linearity of Arrhenius plots was satisfactory. The apparent activation energy of curing reaction has been found to increase with the degree of conversion. The elucidation of the kinetic parameters allows us to propose an accurate and predictive description of the curing kinetics within the fast regimen of reaction (i.e., without vitrification). Finally, we discuss how these kinetic measurements and models can be completed and optimized.