Abstract
Epoxy composites with ZnO powders characterized by different structures as inclusion are prepared and their thermal properties are studied. The experimental results demonstrate that the epoxy resins filled by tetrapod-shaped ZnO (T-ZnO) whiskers have the superior thermal transport property in comparison to ZnO micron particles (ZnO MPs). The thermal conductivity of ZnO/epoxy and T-ZnO/epoxy composites in different mass fraction (10, 20, 30, 40, 50 wt%) are respectively investigated and the suitable models are compared to explain the enhancement effect of thermal conductivity. The thermal conductivity of T-ZnO/epoxy composites with 50 wt% filler reaches 4.38 W m−1 K−1, approximately 1816% enhancement as compared to neat epoxy. In contrast, the same mass fraction of ZnO MPs are incorporated into epoxy matrix showed less improvement on thermal conduction properties. This is because T-ZnO whiskers act as a thermal conductance bridge in the epoxy matrix. In addition, the other thermal properties of T-ZnO/epoxy composites are also improved. Furthermore, the T-ZnO/epoxy composite also presents a much reduced coefficient of thermal expansion (∼28.1 ppm K−1) and increased glass transition temperature (215.7 °C). This strategy meets the requirement for the rapid development of advanced electronic packaging.
Highlights
With the development of integrated circuit chips toward higher density and high frequency, more and more waste heat must be removed to make the device work stable
We propose a facile method for the preparation of epoxy composites containing tetrapod-shaped zinc oxide (ZnO) (T-ZnO) llers by solution
The aspect ratio of ZnO micron particles (ZnO MPs) is difficult to determine, but it can be estimated that the aspect ratio of ZnO MPs is approximately from 1.5 to 1.7
Summary
Tetrapod-shaped ZnO whisker (T-ZnO) is a new type of ZnO whisker with superior performances, such as thermally conductive and other uses.[12,13,14] Yuan et al.[15] prepare a phenolic formaldehyde composite with an in-plane thermal conductivity of 1.96 W mÀ1 KÀ1 by compounding with 30 wt% T-ZnO. A relatively high thermal conductivity of 3.96 W mÀ1 KÀ1 is achieved for the epoxy composite with 55 wt%, while the fabrication process is quite fussy and time consuming.[17] Based on the previous study, the inclusion of T-ZnO into polymer matrix is still one of the hardest challenges in polymer composites with high thermal conductivity. A high thermal conductivity of 4.38 W mÀ1 KÀ1 is achieved for the epoxy composite with 50 wt% T-ZnO ller, which is higher than previous references at the same content. The interconnected network of T-ZnO llers in epoxy matrix results in enhancing thermal transportation properties and retaining low coefficient of thermal expansion (CTE) performance. The characteristics of high thermal conductivity and low CTE of T-ZnO/epoxy composites make it more applicable in thermal management of power devices and other electrical devices
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