Thermally conductive glass fiber reinforced epoxy composites with intrinsic self-healing capability

To tackle the challenges of insufficient heat conduction capacity and thermally/mechanically induced internal damages of glass fiber reinforced epoxy composite (that traditionally serves as circuit board substrate), hexagonal boron nitride (h-BN) was functionalized using natural flavonoid dihydromyricetin (DMY) and then compounded with reversible Diels–Alder (DA) bonds crosslinked epoxy and glass fiber cloth (GFC) reinforcement to fabricate self-healing thermally conductive glass fiber cloth reinforced epoxy (GFREP) composite by a facile two-step coating method. Particularly, the GFC was coated with the solution containing high concentration modified h-BN, and then impregnated with dip coating solution containing lower concentration h-BN. The gradient variation of modified h-BN concentration not only effectively reduced the interfacial heat resistance, but also avoided excessive deterioration of mechanical strength. The produced GFREP composite exhibited excellent in-plane (6.22 W m−1 K−1) and through-plane (1.53 W m−1 K−1) thermal conductivities at 35.0 wt% h-BN content. The reversible DA reaction helped to realize interlaminar crack healing of the composite as characterized by high degrees of recovery of mechanical strength (70 ~ 85%) and thermal conductivities (62 ~ 89%). Besides, the attenuated thermal conductivity caused by interfacial debonding between copper clad and the composite in the model copper clad laminates can also be restored via the same mechanism. Lastly, the composite laminates proved to be coupled with controlled degradability in good solvent so that they can be recycled. This study offered an efficient way to prolong the service life of thermally conductive GFREP composite for integrated circuit packaging applications. The reversible DA reaction at the crack interface proves to be able to recover the structural integrity, which pushes the physical reconnection of the separated h-BN micron sheets residing on the fractured surfaces at the same time and re-establishes the continuous phonon transfer pathways.