Preparation And Research On Thermal Properties Of Filled Functional Thermal Interface Materials

Rapid heat dissipation is the pain point of modern miniaturized electronic equipment and components.High-power and high-efficiency operation puts forward higher requirements on the heat transfer capability of thermal interface materials(TIMs).This paper focuses on the preparation and research on thermal performance of filled functional TIMs to develop TIMs-solutions to improve the heat dissipation efficiency of electronic components.Firstly,taking advantage of synergistic effect between graphene(G)and spherical Al₂O₃thermally conductive fillers on thermal conductivity to reduceR_TIMs(thermal resistance of TIMs),G/Al₂O₃ silicone grease TIMs was prepared.The effect of temperature and pressure on the total thermal interface resistance and thermal stability of thermally conductive silicone grease was tested.As shown in the test results,when the mass fraction of dimethicone is 7 wt%,the thermal performance of G/Al₂O₃ silicone grease reaches the best effect,whose thermal resistance is 0.255 K cm²/W with thermal conductivity being as high as 4.38 W/(m K).In addition,low thermal resistance is maintained in case that the temperature and pressure strain capability within a certain range(40?80?,10?60 psi)is subsequently considerable.Furthermore,the oil leakage is fractional when the silicone grease was placed at 80°C for 600hours,showing good thermal stability.Turning the sight to the heat transfer process of the thermal interface material,as we know,thermal contact resistance(TCR)between TIMs and the upper and lower contact surfaces plays an important role in the heat dissipation process of electronic devices.When the critical operating temperature of the electronic device is reached,if solid-solid contact between two contact surfaces is changed into solid-liquid contact,TCR will be greatly reduced.Based on this idea,a novel form-stable phase change thermal interface materials(Ph-TIMs)Al₂O₃/OBC/PA is proposed.The thermal conductivity of phase change material paraffin(PA)is improved by filling Al₂O₃ particles.The addition of olefin block copolymer(OBC)improves the stability and solves the leakage problem of PA.In addition,the effects of temperature and pressure on the TCR,especially near the phase transition point,are systematically studied.These results confirm that TCR of Al₂O₃/OBC/PA is very sensitive to temperature.When the temperature rises from 37?to 41?,TCR of all samples decreases sharply from 10?20K·cm²/W to 1?2 K·cm²/W.TCR of all samples decreases slowly with the increase of pressure(10?50 psi,45?).Finally,when the mass fraction of Al₂O₃ is higher than 60 wt%,the thermal conductivity of the Al₂O₃/OBC/PA increases sharply with the increase of Al₂O₃.Based on the previous two chapters,we know that G can effectively enhance the thermal conductivity of composite systems and Ph-TIMs transformation from solid state to molten state by heat inducing to improve wettability is an efficient way to reduce the TCR.Therefore,a novel G/OBC/PA Ph-TIMs filled with G(?4.0 wt%)was prepared.Furthermore,the influence of temperature and pressure on thermal contact resistance was studied,and the change rule of TCR and R_TIMs was analyzed systematically.The result exhibit that when the temperature increases from 37?to 45?(50 psi),the TCR of G/OBC/PA decrease sharply from 8?20K·cm²/W to 0.1?0.2 K·cm²/W.This is because the contact state changes from solid-solid contact to solid-liquid contact,which greatly improves the wettability between two contact surfaces.In addition,the thermal contact resistance decreases slightly with the increase of pressure(10?50 psi,48?).A small amount of G can significantly enhance the thermal conductivity of G/OBC/PA,but the effect on the TCR is relatively weak.Moreover,critical thickness T_c is proposed to quantitatively evaluate the dominant position of TCR and R_TIMs in total thermal resistance.It facilitates the quantitative analysis and optimization of thermal resistance in practical application.