Synthesis of tetra(epoxy)-terminated open-cage POSS and its particle thermo-crosslinking with diphenols for fabricating high performance low-k composites adopted in electronic packaging

Polyhedral oligomeric silsesquioxanes (POSSs) are ideal particles to reduce the dielectric constant (k) and loss (tan δ) values of resin matrixes for electronic packaging, but greatly limited by its finite addition due to phase-separation. Herein, tetra(epoxy)-terminated open-cage TG-POSS was synthesized and utilized as a unique building block to crosslink with bisphenol A or hexafluoro-bisphenol A, respectively, for the preparation of novel high performance low-k composites (POSS/BPA or POSS/FBPA). Results reveal that such rational design endows these two materials with homogeneous hybridization even at high POSS loading (>72.0 wt%), which is the main reason for superior dielectric, thermal and hydrophobic properties as compared with counterparts reported previously. Especially, fluorinated POSS/FBPA shows the lowest k value of 2.38, lowest tan δ value of 0.008, highest initial decomposition temperature of 396.1 °C and largest water contact angle of 117.0°, under the extra-contribution of trifluoromethyl units. In addition, its well-dispersed, moderate-crosslinked and rigid-flexible polymer network also leads to outstanding mechanical properties (elongation at break of 3.50% and modulus of 2.75 GPa) for practical applications. Summarily, this work highlights a useful strategy to fabricate high performance low-k composites with high POSS content, which is not only potential for advanced microelectronic industry but also instructive for academic fields.