Hierarchical curing regulation and interpenetrating network construction of BT resin via multi-component additives: Synergistic enhancement of dielectric properties and dimensional stability for high-frequency packaging

The rapid advancement of 5G/6G communication and high-frequency packaging imposes stringent demands on integrated circuit substrate materials, particularly regarding thermal resistance, dimensional stability, and low dielectric loss. Bismaleimide–triazine (BT) resins are promising high performance thermoset whose properties are governed by curing mechanism and network architecture. However, conventional BT resins suffer from high curing temperatures, high dielectric loss (D f ), and elevated coefficients of thermal expansion (CTE). This study investigates curing pathway regulation in BT resins using a cyanate ester curing agent (nonylphenol zincoctoate), a radical initiator (bis(t-butylperoxyisopropyl)benzene), and an allyl-based crosslinker (diallyl bisphenol A), establishing structure-property relationships. Multi-scale characterization reveals that these additives induce a transition from copolymerization to hierarchical curing, forming IPNs. This transition suppresses the formation of polar heterocycles such as pyrimidine/pyridine, while increasing s-triazine rings, maleimide homopolymer segments, and MI allyl addition units. The designed system lowers curing temperature and enables synergistic optimization of dielectric properties and dimensional stability. Notably, the introduction of BIPB into BT resins reduces the D f by 0.0006–0.0013 and decreases CTE by 14.5% along the Z-axis, and 37.8% along the X/Y-axis. The resulting BT50 BIPB composites exhibit high glass transition temperature (T g = 295 °C), low water absorption (0.6 N/mm), and satisfactory mechanical properties, meeting high frequency packaging requirements. By precisely selecting curing agents, this work realizes controllable construction of BT resin crosslinked networks, deepens the understanding of multi stage curing mechanism, and provides theoretical and practical guidance for developing advanced BT based materials for next generation communication and electronic packaging.