Lin Chiao-Xian, Tang Wei-Renn, Tseng Li-Ting, Valinton Joey Andrew A, Tsai Cheng-Han, Kurniawan Alfin, Chiou Kevin, Chen Chun-Hu
Department of Chemistry, National Sun Yat-sen University, No. 70, Lien-hai Road, Kaohsiung 80424, Taiwan.
Ample Electronic Co. No. 32, Dayou 3rd St., Daliao Dist., Kaohsiung City 831, Taiwan.
Langmuir. 2022 Jan 18;38(2):727-734. doi: 10.1021/acs.langmuir.1c02631. Epub 2022 Jan 3.
Modern electronics continue to shrink down the sizes while becoming more and more powerful. To improve heat dissipation of electronics, fillers used in the semiconductor packaging process need to possess both high electrical and thermal conductivity. Graphene is known to improve thermal conductivity but suffers from van der Waals interactions and thus poor processibility. In this study, we wrapped silver microflakes with graphene sheets, which can enable intercoupling of phonon- and electron-based thermal transport, to improve the thermal conductivity. Using just 1.55 wt % graphene for wrapping can achieve a 2.64-times greater thermal diffusivity (equivalent to 254.196 ± 10.123 W/m·K) over pristine silver flakes. Graphene-wrapped silver flakes minimize the increase of electrical resistivity, which is one-order higher (1.4 × 10 Ω·cm) than the pristine flakes (5.7 × 10 Ω·cm). Trace contents of wrapped graphene (<1.55 wt %) were found to be enough to bridge the void between Ag flakes, and this enhances the thermal conductivity. Graphene loading at 3.76 wt % (beyond the threshold of 1.55 wt %) results in the significant graphene aggregation that decreases thermal diffusivity to as low as 16% of the pristine Ag filler. This work recognizes that suitable amounts of graphene wrapping can enhance heat dissipation, but too much graphene results in unwanted aggregation that hinders thermal conducting performance.
现代电子产品在不断缩小尺寸的同时，功能也越来越强大。为了提高电子产品的散热性能，半导体封装过程中使用的填料需要同时具备高电导率和高导热率。众所周知，石墨烯能提高热导率，但由于存在范德华相互作用，其加工性能较差。在本研究中，我们用石墨烯片包裹银微片，这可以实现基于声子和电子的热传输的相互耦合，从而提高热导率。仅使用1.55 wt%的石墨烯进行包裹，就能使热扩散率比原始银片提高2.64倍（相当于254.196±10.123 W/m·K）。石墨烯包裹的银片使电阻率的增加最小化，其电阻率比原始银片（5.7×10 Ω·cm）高一个数量级（1.4×10 Ω·cm）。研究发现，痕量的包裹石墨烯（<1.55 wt%）就足以弥合银片之间的空隙，从而提高热导率。当石墨烯负载量为3.76 wt%（超过1.55 wt%的阈值）时，会导致明显的石墨烯聚集，使热扩散率降至原始银填料的16%。这项工作表明，适量的石墨烯包裹可以增强散热，但过多的石墨烯会导致不必要的聚集，从而阻碍热传导性能。
