During multilayer printed circuit board production, cyclic pressure-temperature (P-T) treatments can give rise to mechanical and thermal stresses with subsequent inner delamination phenomena. These are mainly related to the thermomechanical properties of epoxy resins used in the manufacturing process. In this study, the physical and chemical changes of commercial epoxy-based prepregs were investigated as a function of P-T treatments by means of thermogravimetric analysis, differential scanning calorimeter, and Fourier transform infrared-photoacoustic spectroscopy. It was verified that the thermal properties start to decrease after the first P-T treatment. In connection, absorbance spectra indicated that the peaks at 2273 cm À1 and 2235 cm À1 (cyanate group) disappeared after this treatment. Heat transfer as a function of laminate thickness (consequently, as a function of P-T treatment) is one variable that probably contributes to the findings in the work. The results of this study indicated that the analytical methods were satisfactory to determine the beginning of the deterioration of the printed circuit as a function of the P-T treatments. They can be used as a reference for quality controls and to prevent mechanical problems such as interlaminar fractures in the relevant printed circuits.