Isothermal DSC Study of the Curing Kinetics of an Epoxy/Silica Composite for Microelectronics
Résumé
Curing kinetics of an industrially important printedcircuit
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.