2019 Volume 55 Issue 12 Pages 421-426
In situ analysis of the residual stress in a glass-fiber-reinforced phenolic resin and copper foil compositematerial during curing and thermal-cycle testing was performed via time-resolved X-ray diffractionmeasurements. The semi-cured resin–copper composite exhibited a large compressive stress in copper beforecuring. This indicates the stress-free adhesive interface between resin and copper was first formed when theresin melted in the molding process and the magnitude of the thermal contraction of the resin was largerthan that of copper in the subsequent cooling to room temperature, which was caused by the difference inthe coefficients of thermal expansion between resin and copper. This compressive stress decreased as thetemperature was increased to curing temperature. As the curing proceeded at 180℃ , the compressive stressin the copper again increased because of cure shrinkage of the resin. When the cured sample was reheated tothe curing temperature, the compressive stress in the copper at 180℃ was relaxed. This thermal-annealinginducedstress relaxation suggests that cross-linking reactions during the curing process caused structuralstrains and the relaxation of the cross-link strain induced the stress relaxation.
