Abstract
For the thermal management of high watt density circuit layers, it is common to use a filled epoxy system to provide an electrically insulating but thermally conducting bond to a metal substrate. An epoxy-thiol system filled with boron nitride (BN), in the form of 2, 30 and 180 µm platelets, has been investigated with a view to achieving enhanced thermal conductivity. The effect of BN content on the cure reaction kinetics has been studied by differential scanning calorimetry and the thermal conductivity of the cured samples has been measured by the Transient Hot Bridge method. The heat of reaction and the glass transition temperature of the fully cured samples are both independent of the BN content, but the cure reaction kinetics is systematically affected by both BN content and particle size. These results can be correlated with the thermal conductivity of the cured systems, which is found to increase with both BN content and particle size. For a given BN content, the thermal conductivity found here is significantly higher than most others reported in the literature; this effect is attributed to a Lewis acid-base interaction between filler and matrix.
Highlights
Composite systems consisting of epoxy resin filled with boron nitride (BN), or other suitable fillers such as aluminium nitride or silicon carbide, are widely used for the thermal management of electronic devices on account of their high thermal conductivity and electrical insulating properties, combined with ease of manufacture
Given the very high thermal conductivity of the boron nitride, up to 600 W/mK parallel to the basal plane and 30 W/mK perpendicular to the basal plane for hexagonal BN [3,4], one might expect that values considerably higher than 3.0 W/mK could be achieved with relatively simple preparation procedures
The thermal conductivity of epoxy-thiol composites filled with boron nitride, BN, particles in the form of platelets has been shown to increase with BN content in the usual way
Summary
Composite systems consisting of epoxy resin filled with boron nitride (BN), or other suitable fillers such as aluminium nitride or silicon carbide, are widely used for the thermal management of electronic devices on account of their high thermal conductivity and electrical insulating properties, combined with ease of manufacture. Given the very high thermal conductivity of the boron nitride, up to 600 W/mK parallel to the basal plane and 30 W/mK perpendicular to the basal plane for hexagonal BN [3,4], one might expect that values considerably higher than 3.0 W/mK could be achieved with relatively simple preparation procedures Such an outcome, though, is generally not observed, and there have been numerous studies aimed at understanding how the thermal conductivity depends on the epoxy-BN composite fabrication process, and what are the important parameters involved; these aspects are discussed in some recent reviews of thermal conductivity in polymer-based composites [5,6]. There is a practical limit to the BN content, as the viscosity of the simple epoxy-BN mixture increases rapidly and the mixture becomes essentially
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