Densely packed polymer/boron nitride composite for superior anisotropic thermal conductivity

Abstract

High heat conduction performance of electrical insulating composite is highly desired in thermal management of electronics. In this study, densely packed boron nitride (BN) composites with resin matrices of epoxy, polymethyl methacrylate, and an acrylic copolymer based binder were prepared through a solvent mediated mixing and compression molding method. The solvent mediated mixing assisted homogeneous dispersion; the compression molding removed excessive resin and led to alignment of BN flakes with high filler content. The resulted composites exhibited superior in‐plane thermal conductivity k// up to 21.3 W/mK and pronounced anisotropic heat conduction properties. The thermal conductivity was positively correlated with density bold-italicρ of a specimen in experimental. A presentation of thermal conductivity bold-italick=bold-italick|bold-italicρ was proposed, and the dependence of thermal conductivity on specimen density bolddbold-italicktrue(bold-italicρtrue)/bolddbold-italicρ > 0 was proven mathematically. The application of BN composite in LED thermal management was demonstrated. An epoxy/BN heat spreader was used to efficiently cool down a 0.3‐W LED. The cooling effect was close to that with Al board heat spreader. POLYM. COMPOS., 39:E1653–E1658, 2018. © 2017 Society of Plastics Engineers

Densification: A Route towards Enhanced Thermal Conductivity of Epoxy Composites

“…In the simplest case, pressure can be applied to the uncured mixture at RT simply to consolidate it, to remove voids, or to induce some orientation of the BN particles, the pressure being removed before heating the sample in order to cure it [ 9 , 10 , 11 ]. On the other hand, there are several reports of samples prepared by curing under controlled pressure-temperature schedules [ 13 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ], though some authors do not specify the magnitude of the pressure applied [ 14 , 15 , 16 , 17 , 18 ].…”

Thermal Conductivity and Cure Kinetics of Epoxy-Boron Nitride Composites—A Review

“…Much higher pressures and filler contents were used by Zhu et al [158], but there seems to be very little effect of the magnitude of the pressure on thermal conductivity. In some way this is consistent with the observation by Zhang et al [153] that a low pressure can induce significant orientation and hence dramatically enhance thermal conductivity.…”

“…First, the usually observed upward curvature in the dependence of the thermal conductivity on BN content is not displayed by the results of Yung and Liem [54], which are shown separately in Figure 8; instead, there appears to be a tendency to reach a limiting value as the BN content increases. Second, the results of Yung et al [151] Open circles refer to data from references [54,151], open squares refer to data from references [89,90,114,116,125,127,132,143,147,153,158]. The dashed trend lines indicate the overall tendency for the dependence of thermal conductivity on BN content (excluding the data represented by the open circles): an upper trend line, below which more than 95% of the values fall; and a lower trend line, below which fewer than 5% of the values fall.…”

“…These are the data which correspond to samples in which orientation of the BN particles has deliberately been introduced. The orientation can be induced by various means: gravity alignment and subsequent resin infiltration [147]; the application of high pressure to partially cured samples before the final cure [90,153,158]; spin-coating of films and hot pressing after pre-cure [116]; magnetic alignment of Fe 3 O 4 -decorated BN particles [114,125,127]; or by resin infiltration of hierarchically ordered 3-dimensional templates [89,132,143]. The orientation induced usually results in a highly anisotropic thermal conductivity.…”

Dual‐direction high thermal conductivity polymer composites with outstanding electrical insulation and electromagnetic shielding performance

“…Generally, high TC polymer composites are formulated by compounding high TC fillers with polymer matrix . During the past decades, ceramic‐based fillers such as aluminum oxide (Al 2 O 3 , 30 Wm −1 K −1 ), aluminum nitride (AlN, 170‐220 Wm −1 K −1 ), silicon carbide (SiC, 120 Wm −1 K −1 ), and boron nitride (BN, 380 Wm −1 K −1 ) have been widely applied to improve the TC performance of polymer composites without deteriorating the electrical insulation performance . However, it is hard to improve the TC performance of polymer composites through simple mixing high TC fillers with polymers.…”