Preparation And Properties Of Polymer/SiO₂@BN Thermal Conductive Composites

With the development of technology,electronic components are rapidly developing in the direction of high-integration and miniaturization,leading to rapid rise of heat and power density in per unit volume.If the accumulated heat can't be dissipated in time,the reliability and lifetime of electronic products will be in danger.So how to quickly dissipate heat becomes a hot issue in the field of microelectronic packaging.Polymer is widely used because of good processability and low cost.However,the thermal conductivity of common polymers is very low,which can't meet the thermal dissipation requirements of electronic devices.Generally,the following two methods are used to improve the thermal conductivity of polymer-based composites:increasing intrinsic thermal conductivity of polymer and adding thermal conductive fillers in polymer matrix.Compared with the difficulty of increasing polymer intrinsic thermal conductivity,adding high thermal conductivity fillers can effectively improve thermal conductivity of polymer.The thermal conductivity of polymer-based composites is determined by the thermal conductivity of polymer matrix,the thermal conductivity of filler,the interaction between matrix and filler and the distribution of filler.Two commonly-used methods to improve the thermal conductivity are as follows:surface modification of the filler and construction of thermal conduction pathway.Surface modification can improve the interaction between matrix and filler and reduce the interfacial thermal resistance,resulting to higher thermal conductivity.By adjusting the preparation method,the thermal conductivity can be effectively improved through forming thermal conduction pathway and conducting heat more effectively.Hexagonal boron nitride(h-BN)is considered as a promising thermal conductive filler and widely utilized owing to its high thermal conductivity,electrical insulation and excellent mechanical properties.However,the surface modification of h-BN is extremely difficult due to its chemical inertness,which became a huge drawback in practical application.In this paper,two surface modification methods are used.Compared with KH550 surface modification,the modification effect of PVP coating-TEOS hydrolysis modification is better.SiO2 with a diameter of about 15nm and a thickness of 20-30nm tend to aggregate together and distributed all over the surface of BN.SiO2@BN/epoxy resin composites were prepared via precuring and hot-pressing.Compared with pristine BN,SiO2@BN filler can effectively improve the thermal conductivity of the composite because of improved interaction between SiO2@BN and epoxy resin.At 30wt%filler content,the thermal conductivity of SiO2/epoxy resin composites is 0.7763 W/m·K,which is 283%higher than pure epoxy.Two different methods are used to prepare BN/PMMA composites.Compared with randomly distributed BN in melting mixing samples,for solution mixing samples,BN is selectively distributed in PMMA matrix and formed thermal conductive pathway,leading to higher thermal conductivity.Thus SiO2@BN/PMMA composites are prepared through solution mixing method.Due to the improved interaction and reduced interfacial thermal resistance,the thermal conductivity and mechanical properties of SiO2@BN/PMMA composites are better than BN/PMMA composites.The maximum thermal conductivity is 5.583 W/m·K,which is 3292%higher than pure PMMA.At the same time,compared with pure PMMA,SiO2@BN/PMMA has lower coefficient of thermal expansion,higher thermal stability,and relatively low dielectric constant and dielectric loss.