Study On Thermal Interface Materials Based On Phase-Sensitive Transient Thermal Reflection System

With the continuous improvement of the integration of electronic chips,the heat dissipation has become a bottleneck restricting the further development of electronic devices.Therefore,the problem of thermal management inside the chip is becoming increasingly important.Currently,the main way to enhance the heat dissipation is to use the thermal interface material(TIMs)to fill the package interface between the chip and the heat sink,which reduces air thermal resistance and increases heat dissipation.Excellent thermal interface materials should meet the performance characteristics in two aspects:the high thermal conductivity in the longitudinal direction to ensure efficient heat transfer,and a certain degree of mechanical compliance in the lateral direction to ensure structural stability so as to reduce the interference of the external environment,such as thermal stress and vibration on the sample packaging part.As a newly-emerging nanomaterial,copper nanowire arrays(CuNWs)have the potential to become a promising thermal interface material due to the high thermal conductivity of the copper and the structural advantages of nanowire arrays.Therefore,this paper focuses on thermal interface materials,and launches research work in two aspects:thermal measurement system and copper nanowire array performance testing.The phase-sensitive transient thermal reflection(PSTTR)system is a non-contact thermal measurement system.It tests the thermal parameters,for example the interface thermal conductivity of micron-scale thermal interface materials,to evaluate the performance advantages of thermal interface materials.The study found that the higher the test frequency of multilayer samples,the shorter the depth of thermal penetration.Therefore,this paper innovatively proposes a fitting method for multi-layer samples in different frequency intervals,which solves the problem of fitting samples with complex structures.A four-layer sample(Cr/Au-plated glass-In-Cr/Au-plated Si02-Si)was designed and prepared for experimental testing,and the relative error of the fitting method was within ±8%.We compared and analyzed the sensitivity of the thermal parameter signals at different thermal penetration depths,and found that the choice of frequency directly affected the sensitivity of the fitting parameters.We evaluate the performance of the copper nanowire array by mechanical test and thermal test.In the mechanics test,the nano-indentation instrument is mainly used to perform the compression test.The experiment found that during the compression process,the nanowire array underwent elastic deformation and plastic deformation,with a yield platform in the middle.We prepared four-layer samples(Cr/Au plated glass layer-In solder layer-copper nanowire array layer-substrate)for thermal tests.The phase-sensitive transient thermal reflection system is used to test the thermal parameters to study the influence of package contact pressure and thermal environment on the interface thermal conductivity.The experimental results first show that a certain package contact pressure can improve the interface contact between the copper nanowire array and the solder layer,and improve the interface thermal conductivity.During the compression process,combined with the change of the thermal conductivity and the morphology of the nano wire array,the optimal package contact pressure can be determined as 0.5MPa.Then,the experiment found that the copper nanowire array is not sensitive to the thermal environment.In the test temperature range of 20?70?,the thermal conductivity of interfacial contact can be kept stable without any significant drop.The thermal stress has little effect on the properties of the material.