Deterioration of microwave dielectric properties of low-loss thermosetting polyphenylene oxide/hydrocarbon resin induced by short-term thermo-oxidative aging

Deterioration of the low-loss property of substrate materials significantly affects the service life of high-frequency and high-speed circuits. In this work, the effect of short-term thermal aging on the microwave dielectric property of thermosetting polyphenylene oxide/hydrocarbon resin was investigated. Dielectric and dynamic thermo-mechanical spectra were used to evaluate changes in polar structure and crosslinking structure over the aging process. Infrared spectroscopy was applied to monitor the evolution of chemical structure, and the changes in microwave dielectric properties at 10GHz were recorded. An apparent linear relationship was discovered between the polar group accumulation in the superficial layer and the change in microwave dielectric loss factor. Finally, the effect of aging on moisture absorption and the influence of thickness on the aging rate were preliminarily examined to investigate the impact of aging on practical applications.