Phthalonitrile/Epoxy Copolymers Endowing Molding Compounds with High T_g, Low CTE, and Intrinsic Flame Retardancy

Abstract

The rapid development of third-generation semiconductor power devices has been driving the requirement for high-temperature stable molding compounds. In this study, three kinds of phthalonitrile-etherified phenolic resins (PNP) with different degrees of etherification were prepared from linear phenolic resin and 4-nitrophthalonitrile by a facile one-pot method. Subsequently, a new electronic packaging molding compound (PEM) was prepared according to the processing method of traditional epoxy molding compounds (EMC), based on the resin blends of the PNP with a 50% etherification and polyfunctional epoxy resin as the resin matrix and triphenylphosphine employed as the curing accelerator. The reaction of the epoxy groups with both the phenol hydroxyl and cyano groups endowed the resin matrix with a high curing activity, thus making the molding process of PEM be compatible with that of EMC. The cured products of PEM showed a much superior thermal performance to that of EMC. For the cured PEM, the glass transition temperature (T g) was up to 300 °C and the coefficients of thermal expansion (CTE) decreased significantly in comparison to EMC, due to the generated rigid structures of oxazoline, isoindoline, triazine, and phthalocyanine, as well as the high cross-linking density. It is worth noting that the cured PEM could achieve a V-0 rating in the UL-94 vertical burning test without the addition of any flame retardants, demonstrating its remarkable intrinsic flame retardancy. Moreover, the cured PEM also exhibited good dielectric properties, thermal conductivity, high temperature aging resistance, and flexural performance at both room temperature and 200 °C. In sum, a promising strategy for the preparation of electronic packaging molding compounds with high T g, low CTE, and intrinsic flame retardancy was provided.