Cost Effective Synthesis of Boron Nitride Agglomerates and Formulation of Resin by Recycling Strategy for Thermal Interface Materials Application

Abstract

In electronics sector, the trend of miniaturization will undoubtedly continue to drive forward with several technological advancements, however, there are some crucial issues especially in the thermal management of electronic devices that limits to what is pragmatically and economically feasible. For ensuring efficient thermal dissipation and preventing temperature overloads at local sites, in this work, an advanced thermal filler material (BN aggregate) synthesized via a cost effective and scalable route from h-BN (Hexagonal Boron Nitride) is proposed. To assess the suitability of the BN aggregate as a conventional ceramic filler material and its effectiveness for thermal management, a thermally conductive thin composite sheet is (200 μm) fabricated with the synthesized BN aggregates and spherical Al2O3. The thermal sheet made out of an optimized ratio between the Al2O3 and BN aggregate delivers an excellent through-plane (k⊥) and in-plane (k∥) thermal conductivity of 8.142 W/m.K and 5.601 W/m.K respectively. Even at higher filler concentration, this thin sheet which mimics a papery film, practically endured no deterioration in the mechanical integrity. This thermal sheet given its reasonable thermal and mechanical properties can be employed in electrical devices that demands high power cycles. With wearable technology gaining greater attention in the recent days, the proposed filler system when dispersed in polyethylene fibers, may find potential applications in thermoelectric devices, smart textiles, wearable displays and health monitoring systems. In addition to this work, a low-cost resin is developed by using Aramid fibers retrieved from waste materials. Aramid, chemically called as para phenylene terephthalamide or PPD-T, has been widely used in the reinforcement of telecommunication cables, rubber materials (transmission belts, pneumatic belts), ballistic clothing and frictional materials primarily due to their high tensile resistance, high elastic modulus, excellent thermal stability (-80 oC – 200 oC) with good dielectric properties. Here, in this work inspired by these properties a heat spreader as Thermal Interface Material (TIM) is developed by synthesizing a resin from scrap Aramid fibres. When hexagonal boron nitride (h-BN) as filler is introduced into the as-synthesized Aramid resin to form a thin film of thermal sheet (50 μm), a thermal conductivity as high as 32.973 W/mK is achieved in the in-plane direction. Moreover, the influence of h-BN platelet size is studied by using fabricating thermal sheets with three different sizes of h-BN (6 - 7.5 μm, 15 – 21 μm, 30 – 35 μm) in the Aramid resin. The results of the study show that as the platelet size is increased thermal conductivity increases significantly. Since the resin reported herein is developed out of scrap Aramid fibres, the cost involved in the manufacture of thermal sheet will be greatly lower. As the thermal sheet is designed with the h-BN rather than graphene or carbonaceous materials, this high heat spreading sheet can be employed for 5G antennae module where properties like low dielectric constant and high electrical insulation are mandated.