Thermal and dielectric multiple percolation in α‐Si₃N₄ whiskers/silicone rubber

Abstract

Currently, thermal interfacial materials (TIMs) play a great role to electronic and semiconductor devices working at high voltage, power and frequency. The urgent need for electrical insulating TIMs and relevant theory are not addressed yet. This study adopted an electrical insulating α‐Si3N4 whisker as a filler to prepare Si3N4w/silicone rubber. The results show that the elongation at break and thermal conductivity of silicone rubber are promoted from 91.6% and 0.343 to 402.9% and 1.011 W m−1 K−1, respectively, at a filler fraction of 8.0 vol%. It reveals a multiple percolation phenomenon which has not been previously observed in an electrical insulating TIMs. The thermal percolation threshold is decreased to 4.0 vol% with increasing aspect ratio of the whisker. The behavior of the dielectric strength is explained by a double percolation model. A phonon quasi‐ballistic transportation mechanism based on Coulomb interactions is proposed for the TIMs.