Thermal Conductivity Enhancement of Epoxy Composites by Interfacial Covalent Bonding for Underfill and Thermal Interfacial Materials in Cu/Low-K Application

Nowadays with enhanced performance and reduced profile, electronics and photonics devices demand efficient heat dissipation and low operation temperature. Thereby, instead of traditional fillers (e.g., fused silica), thermally conductive silicon carbide (SiC) particles and multiwall carbon nanotubes (MWNTs) are applied here as fillers in composites for underfill and thermal interfacial materials (TIMs), respectively. SiC particles are coated with an ultrathin layer of silicon oxide by thermal oxidation at 800°C in air and consequently functionalized by γ-glycidoxypropyl-trimethoxysilane in order to graft epoxides on their surface. Moreover, MWNTs were chemically functionalized with carboxyls and hydroxyls in a concentrated acid mixture. Transmission electron microscopy, Fourier-transform infrared spectrascopy, and thermogravimetric analysis characterization indicates that both of the fillers are successfully functionalized, which makes their surface reactive with epoxy resin, resulting in interfacial covalent chemical bonding between the thermally conductive fillers and epoxy resin. It is found that interfacial chemical bonding across the interface between these functionalized fillers and polymer matrix can promote significant thermal conductivity enhancement of epoxy composites, which is promising for underfill and TIMs in Cu/low-K application.