Study On The Liquid Metal Aging As Thermal Interface Materials

With the rapid development of the shipping industry,the automation and electrification of ships have been enhanced,which has made the effective thermal management in electronic components cooling a great challenge.While the existence of the interface thermal resistance is the main bottleneck of heat dissipation of electronic components.Therefore,enhancing the ability of the interface heat transfer is crucial way to improve the reliability,stability and work efficiency of many ship systems.The research work of this paper focused on the heat transfer characteristics through interfaces,used the liquid metal(LMA)as a thermal interface material(TIM).The thermal conductivity and thermal interface resistance of the liquid metal weremeasured at its initial state and after aging The influence of the contact surface roughness on the sample thermal interface resistance was researched;The mathematic model to predict the thermal interface resistance at its initial state and after aging between liquid metal and solid surface was built.In the experimental on the relationship between thermal contact resistance and liquid metal aging,the LMA Ga62.5In21.5Sni6 and the copper-doped liquid metal were used as TIMs in the experiments.Results show that the thermal conductivity of the liquid metal at its initial state is 37.707 W/(m K),and the thermal conductivity of liquid metal doped with 7.5%copper powder is 38.774 W/(m-K).The final stable thermal conductivity of the liquid metal after aging is 22 W/(m K).And the final stable thermal conductivity of liquid metal doped with 7.5%copper powder is 9 W/(m·K).In the experiment on the influence of surface roughness on the aging of LMA,four samples with Cu-LMA-Cu three-layer structure were fabricated for the experiments.The roughness of the copper plates used in the samples are 0.0951?m 0.1748?m,0.2252?m and 0.3267?m,respectively.In the experiments,the samples were aged in a furnace with the temperature of 130?.The longest aging time was 800 hours.During this time span,the samples were taken out to measure its thermal conductivity every 100 hours.Then the contact thermal resistance can be calculated based on the test results.The results show that the initial contact thermal resistance of the four samples with copper roughness of 0.0951?m,0.1748?m,0.2252?m and 0.3267?m are 2.29 mm2K/W,2.44 mm2K/W 2.73 mm2K/W and 2.97 mm2K/W.After aging 400 hours,the contact thermal resistance of the four samples are 4.54 mm2K/W,6.11 mm2K/W,6.46 mm'K/W,and 8.60 mm2K/W.After aging 800 hours,the contact thermal resistance of the four samples are 5.88 mm2K/W 6.42 mm2K/W,6.87 mm2K/W,and 8.76 mm2K/W,respectively.Based on the experimental data above,a maematical model for predicting the total thermal resistance of the LMA sample was established.The mathematical model expresses the total thermal resistance as a function of the external pressure,contact surface morphology,aging time and other factors.The calculated results of the model agreed well with the experimental results.From the above experimental data and theoretical model,this thesis draws the following conclusions:(1)The thermal conductivity of the liquid metal doped with 7.5%copper powder at the initial state is slightly higher than the pure liquid metal,but the thermal conductivity of the liquid metal doped with 7.5%copper powder after aging is much lower than the pure liquid metal(2)The thermal interface resistance of the liquid metal sample at the initial state is comparable to the thermal interface resistance of the liquid metal sample doped with the copper powder.However,The liquid metal sample is much lower than the copper-doped liquid metal sample after aging.(3)With the same contact surface roughness,the contact thermal resistance increases as the aging time increased,but its increased rate slowed down.Also with the same aging time,the contact thermal resistance increases as the contact surface roughness increased.And the contact surface roughness has a greater effect on the contact thermal resistance of the aged sample compared to the initial state.