Enhancing heat dissipation performance of paraffin/silicone rubber phase change thermal pad by introducing carbon nanotubes

doi:10.11949/0438-1157.20220297

Abstract

Abstract:

The rapid development of electronic technology has put forward higher requirements for heat dissipation technology. As one of the key materials of heat dissipation technology, thermal interface materials are facing the challenge of improving thermal conductivity and reducing heat transfer resistance. In this paper, a novel VACNTs/PA/SR phase change gasket was developed by combining vertically aligned carbon nanotubes (VACNTs) and a solid-liquid phase change material, paraffin (PA), with silicone rubber (SR). It is shown that the magnetic field calibration method could make the surface modified nickel coated multi-wall CNTs vertically oriented in SR, and the obtained VACNTs/SR gaskets had higher thermal conductivity than the gaskets with CNTs randomly arranged. The appropriate content of CNTs in the VACNTs/SR gasket was determined to be 6% (mass), and the corresponding gasket reached a thermal conductivity of 0.71 W /(m·K). As for a series of VACNTs/PA/SR phase change gaskets at different loadings of PA, it is found that, the leakage problem of the liquid PA was overcome at the addition of PA of less than 12.5% (mass). After the solid-liquid phase transition of PA, the gasket shows a significant decrease in hardness, and even the thermal resistance can be reduced by up to 55.14%, and has excellent thermal reliability. By comparing the heat dissipation performance between the optimal VACNTs/SR gasket and the optimal VACNTs/PA/SR phase change gasket it is revealed that, when employing the phase change gasket, the simulation chip not only showed a lower rising rate in temperature but also had a lower equilibrium temperature with a decline of 3.5℃, suggesting the better heat dissipation performance of the VACNTs/PA/SR phase change gasket than the VACNTs/SR gasket. The VACNTs/PA/SR phase change gasket shows promise in the fields of electronic equipment heat dissipation.

Key words: carbon nanotubes, phase change, thermal resistance, thermal interface materials, heat transfer, electronic materials

摘要：

电子技术的高速发展对散热技术提出了更高的要求，热界面材料作为散热技术的关键材料之一，面临着提高热导率以及减小传热热阻的挑战。将垂直碳纳米管阵列(VACNTs)和固-液相变材料石蜡(PA)与硅橡胶(SR)复合，研制了一种新型VACNTs/PA/SR复合相变垫片。研究表明，通过磁场校准方法可以使表面改性的镀镍多壁CNTs在SR中实现垂直定向排列，所得VACNTs/SR垫片较CNTs随机排列的垫片具有更高的热导率，并确定VACNTs/SR垫片中CNTs的适宜含量为6%(质量)，对应垫片的热导率可达0.71 W/(m·K)。对于固定CNTs含量为6%(质量)但PA含量不同的一系列VACNTs/PA/SR相变垫片，PA的添加量不大于12.5%(质量)时，相变垫片克服了液态PA的泄漏问题；相变垫片在PA发生固-液相变后表现出硬度显著下降，热阻减少可达55.14%，并具备优异的热可靠性。将最佳VACNTs/SR垫片样品及最佳VACNTs/PA/SR相变垫片样品进行散热性能对比发现，与使用VACNTs/SR垫片的情况相比，使用VACNTs/PA/SR相变垫片时的模拟芯片不仅在温度上升阶段的升温速率更小，而且当芯片温度达到平衡后对应的平衡温度也更低，降低了3.5℃，显示出更好的散热性能。VACNTs/PA/SR相变垫片优良的特性和散热性能使其在电子设备散热领域具有良好的应用前景。

关键词: 碳纳米管, 相变, 热阻, 热界面材料, 传热, 电子材料

CLC Number:

TB 34

Chuyue CAI, Xiaoming FANG, Zhengguo ZHANG, Ziye LING. Enhancing heat dissipation performance of paraffin/silicone rubber phase change thermal pad by introducing carbon nanotubes[J]. CIESC Journal, 2022, 73(7): 2874-2884.

蔡楚玥, 方晓明, 张正国, 凌子夜. CNTs阵列增强石蜡/硅橡胶复合相变垫片的散热性能研究[J]. 化工学报, 2022, 73(7): 2874-2884.

Figures/Tables 15

Fig.1 Schematic diagram for preparing VACNTs/PA/SR phase change thermal pads

Fig.2 Experimental set-up for evaluating heat dissipation performance of thermal pads

Fig.3 FT-IR spectra of CNTs（a）, acid treated CNTs（b） and surface modified CNTs（c）

Fig.4 Photographs of different CNTs dispersions at different storing durationsA—CNTs; B—acid treated CNTs; C—surface modified CNTs

Fig.5 Cross-section SEM images of thermal pads

Fig.6 Thermal conductivity of the CNTs/SR和VACNTs/SR thermal pads containing different mass fractions of CNTs

Fig.7 FT-IR spectra of silicone elastomer, surface modified CNTs and TIM-6

Fig.8 DSC curves of the VACNTs/PA/SR phase change thermal pads containing different mass fractions of PA

Table 1 Phase change characteristics of phase change thermal pads containing different mass fractions of PA

样品	w/%	T_m/℃	H_m/(J/g)	T_f/℃	H_f/(J/g)	η/%
PA	100	49.0	199.1	52.4	198.7	100
PCTIM-1	5.0	51.8	8.5	53.0	7.8	4.1
PCTIM-2	7.5	51.0	12.9	52.2	12.1	6.3
PCTIM-3	10.0	51.0	17.7	52.6	17.1	8.8
PCTIM-4	12.5	50.5	23.7	53.2	23.2	11.8
PCTIM-5	15.0	50.1	26.6	52.8	25.8	13.2

Fig.9 Mass loss percentages of the phase change thermal pads containing different mass fractions of PA during the heating

Fig.10 Thermal conductivity, hardness, and resistance of the thermal pads containing different mass fractions of PA under different temperature

Fig.11 FT-IR spectra of PCTIM-4 and its components, DSC curves of PCTIM-4 before and after 100 cycles

Fig.12 Temperature rise curves of the simulative chip when employing no thermal pads and the different thermal pads at different heating power

Table 2 Equilibrium temperatures of the simulative chip when employing no TIM and different TIMs at different heating power

功率/W	T_空载/℃	T_TIM/℃	T_PCTIM/℃	ΔT/℃
100	141.0	130.6	129.5	1.1
30	109.1	98.2	96.5	1.7
20	81.4	71.9	69.8	2.1
10	57.0	48.7	45.2	3.5

Table 3 Characteristics of TIM-6 and PCTIM-4

性能参数	TIM-6	PCTIM-4
热导率/(W/(m·K))	0.71	0.71
厚度/mm	0.98	0.98
硬度/HA	47.5	34.7
热阻/(K·cm²/W)	19.1483	15.2650

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