Research On Interficial Heat Transfer Of Vertically Aligned Copper Nanowires Arrays

With the rapid development of microelectronics technology,electronic chips are becoming more and more integrated.While the computing power of chips has been improved,the heat dissipation of chips has also become a key problem in the industry.Currently,the main method to improve heat dissipation efficiency of chips is to build a low thermal resistance channel between the chip and the heat sink with the help of thermal interface materials,so as to achieve efficient heat transport.High-performance thermal interface materials usually exhibit high thermal conductivity and good mechanical flexibility.On the one hand,it is necessary to minimize the thermal resistance between the chip and the heat sink as much as possible,and on the other hand,it is necessary to minimize the thermal stress generated by thermal expansion to suppress fatigue damage at the thermal interface.In the last dozen years,thermal interface materials with large-scale nanofiber array structures have emerged.High aspect ratio nanofiber array structural materials can be manufactured with high thermal conductivity bulk materials.These materials balance high thermal conductivity and mechanical compliance,meeting the heat dissipation needs while also reducing the magnitude of thermal stress.Among them,vertically arranged copper nanowire array is a typical representative of the nanofiber array structure.Early research mainly focused on the characterization of thermal conductivity and mechanical properties of copper nanowire arrays.Research has shown that the contact thermal resistance between the end of the copper nanowires and the target surface is the main source of thermal resistance in copper nanowire array packaging,and the contact interface between the two is also the most vulnerable part in the entire packaging.However,research on the interfacial heat transfer performance of copper nanowire arrays is still very limited,and exploring the interfacial heat transfer characteristics between copper nanowire arrays and target surfaces reserves certain research value.Thermal stress is the main factor of the generation and expansion of thermal interface defects,which has a significant impact on interface heat transfer.Therefore,research on the interfacial heat transfer performance of copper nanowire arrays under thermal stress coupling condition is of great significance.This work revolves around copper nanowire arrays,examines the interfacial heat transfer performance of copper nanowire arrays,proposes and verifies a method for optimizing interfacial heat transfer of copper nanowire arrays,studies the interfacial heat transfer characteristics of copper nano wire arrays under thermal stress coupling conditions,and conducts a preliminary exploration of the thermal fatigue characteristics of copper nanowire arrays.In this work,the preparation process and method of four layer(quartz glassindium film-copper nanowire array-copper substrate)thermal interface material samples based on copper nanowire arrays were explored through experiments,forming a complete set of thermal interface sample preparation methods.Then,the phase sensitive transient thermal reflection system for data measurement was built,and the calibration and verification of the thermal reflection system were completed.Subsequently,the heat conduction model of the sample was established and the theoretical analysis of the model was solved.The best fitting between experimental data and theoretical analysis was achieved through MATLAB algorithm to obtain the thermal property parameters of the sample.The interfacial heat transfer performance of the copper nanowire array was tested and optimized.Finally,a preliminary exploration was conducted on the interface heat transfer characteristics under thermal stress coupling conditions and the thermal fatigue characteristics of copper nanowire arrays.The experimental results show that the contact thermal conductivity between the copper nanowire array and indium falls around 0.4 MW/m2·K,and the equivalent thermal conductivity of the copper nanowire array prepared in the experiment is about 45 W/m·K.By coating Cr/Au layers on the surface of copper nanowires,the contact thermal conductivity between the copper nanowire array and indium can be significantly improved.The influence of thermal stress on the copper nanowire array is minimal,and the copper nanowire array-indium thermal interface maintains a stable contact thermal conductivity value within the testing temperature range of 30℃ to 70℃.The investigation of thermal fatigue experiments on copper nanowire arrays verified the ability to withstand periodic thermal stress conditions.In addition,this work used the nano-indenter to study the mechanical properties of copper nanowires,and calculated the equivalent Young’s modulus of the copper nanowire array based on the obtained force-displacement curve.The equivalent Young’s modulus of the copper nanowire array is about 36 MPa.The COMSOL numerical simulation results further demonstrate that the copper nanowire array,as a flexible material,avoids the generation of excessive thermal stress and produces a low stress effect.This work indicates that copper nanowire arrays are thermal interface materials with certain application potential.