Tailoring Dielectric Properties and Dimensional Stability of Poly(Phenylene Ether) Using Bismaleimide Crosslinkers for High-Frequency PCB Applications

With the increasing demand for high-performance printed circuit boards (PCBs) in the 6G communication era, dielectric substrate materials must exhibit a low dielectric constant (D_k), low dielectric loss (D_f), and high dimensional stability. In this study, a series of bismaleimide-incorporated poly(phenylene ether) resins (PPE-BMI) with varying bismaleimide (BMI) crosslinker contents is developed, exhibiting significantly enhanced dielectric properties and dimensional stability, owing to the restricted polymer chain mobility and increased crosslinking density. Dielectric property measurements reveal that the PPE-BMI resins exhibit low D_k and D_f values at frequencies above 100 GHz, while maintaining an excellent dielectric performance even after an 85 °C/85% relative humidity reliability test. A significant reduction in the coefficient of thermal expansion is observed with an increase in the BMI content. Molecular dynamics simulations are employed to clarify the role of BMI crosslinkers in reducing the free volume, enhancing the crosslinking in the PPE (poly(phenylene ether)) matrix, and influencing the thermophysical properties of PPE-BMI. The infiltration of PPE-BMI into glass fabrics and liquid crystal fabrics highlights their potential for practical use in advanced PCB applications operating at high frequencies.