High modulus and high Tg epoxy resin system regulation: Based on rigid frameworks of bisphenol fluorene and adamantane

For decades, high-performance epoxy resins have been pivotal in advancing high-temperature electronic materials. Conventional epoxy resins tend to soften and deform under high-temperature conditions, which compromises their structural stability and fails to meet the stringent thermal reliability requirements of high-temperature processes and equipment. Regarding this, this study presented two new kinds of fluorene-based epoxy monomers bisphenol fluorene epoxy resin (BFEP), isopropyl bisphenol fluorene epoxy resin (IBFEP) and a novel curing agent (1,3-bis(4-aminophenyl) adamantane, AMA) derived from adamantane. The two monomers were cured with two hardeners, 4,4-diaminodiphenyl sulfone (DDS) and AMA, respectively. The DDS cured resins showed high glass transition temperature (BFEP/DDS, 236 °C; IBFEP/DDS, 209 °C), excellent storage modulus, good thermal stability ( T d5% >395 °C) and dimensional stability, low water absorption and good adhesion. However, the dielectric constant (κ) of those two resins were relatively high, e.g. 4.6 was for BFEP/DDS, 4.23 was for IBFEP/DDS at 10 MHz. Compared with DDS system, both resins exhibited a lower glass transition temperature ( T g ) after cured by AMA. However, the latters also possessed a notably high storage modulus at room temperature (RT) (BFEP/AMA, 4420 MPa; IBFEP/AMA, 4630 MPa), lower dielectric constant (BFEP/AMA, 4.05; IBFEP/AMA, 3.74 at 10 MHz), better adhesion and thermal conductivity. In summary, the two kinds of fluorene-based epoxy resins cured with different curing agents exhibited different performance characteristics. The performance of AMA cured epoxy resin exhibited more balanced behaviors due to its excellent rigid and hollow structure, which could be suitable for high- T g PCB substrate materials.