High Thermal Conductivity Design,Preparation And Thermophysical Properties Of Diamond/Magnesium Composites

With the rapid development of electronic information technology in the direction of high power,miniaturization,and integration,the iterative update speed of electronic packaging materials has been accelerating,and more stringent requirements have been placed on its thermophysical properties.Diamond/Mg(Diamond/Mg)composite materials have outstanding lightweight advantages and are important candidates for thermal management.In order to explore the application prospects of Diamond/Mg composites in the field of electronic packaging,this paper designs the Diamond/Mg composites with high thermal conductivity based on the theoretical model of composite thermal conductivity,and introduces carbonization between the magnesium matrix and the diamond through the method of diamond surface metallization.Material layer,and the use of extrusion infiltration method to prepare Diamond/Mg composite material.Use SEM,EDS,XRD,FIB and EPMA to conduct microscopic characterization and phase analysis of the coating on the diamond surface and the interface structure of the composite material,and determine the thermal conductivity and thermal expansion coefficient of the composite material,and study the effect of the salt bath plating process on the coating The influence of structural evolution and the interface bonding of composite materials reveals the relationship between the interface bonding state of composite materials and their thermophysical properties.The specific research contents and results are as follows:The differential effective medium model(DEM)is used to predict the influence of different carbides on the thermal conductivity and thermal conductivity of the composite material interface.The results show that under the same coating thickness,the promotion effect of the carbide layer on the thermal conductivity of the composite material is in the following order:WC>Al₄C₃>Cr₃C₂>Cr₇C₃>Mo₂C>ZrC>TiC.Considering the graphitization transformation of diamond at high temperature And Al₄C₃ is easy to deliquesce and other factors,Cr is selected as the interface modification element.At the same time,the DEM model is used to study the effect of diamond particle size and volume fraction on the thermal conductivity of Diamond/Mg composites.The calculation results show that the thermal conductivity of the composite material increases with the increase of diamond particle size and volume fraction.Combined with the feasibility of the experimental program,the diamond particle size used in the selected experimental study is 230?m and the volume fraction is 70%.The salt bath method is used to plate Cr on the diamond surface.The effect of the plating process on the evolution of the coating structure and phase composition is studied.The thickness of the coating is measured by FIB+SEM,and the relationship between the Cr coating process and the thickness of the coating on the diamond surface is explored.The results show that at the plating temperature of 950?and holding for 30 minutes,the diamond surface undergoes a complete metallization transition.With the increase of the plating temperature and holding time,the thickness of the coating increases,and the phase composition of the coating also changes from Cr₂₃C₆ to Cr₇C₃,Cr₃C₂ conversion,the coating thickness can be adjusted between 1.09?2.95?m at the coating temperature of950?1050?and the holding time of 30?90min,and the main structure of the coating from the inside to the outside is diamond-Cr₇C₃-Cr₃C₂.The interface structure and thermophysical properties of Diamond(Cr)/Mg composites prepared by squeeze casting method are studied.The results show that the introduction of Cr₇C₃ and Cr₃C₂ between the interface of the composite material improves the mutual wettability of the magnesium matrix and the diamond,and the two are connected in an infiltration bonding manner,which can significantly improve the interface bonding strength of the composite material.When the plating process is held at 950?for 60 minutes,the interface bonding of the composite material is the most ideal.At this time,the density of the composite material reaches 97.24%,and the thermal conductivity reaches the highest202.42 W/(m·K),Which is 81.1%higher than that of the composite material without interface modification.As the plating temperature increases,the interface layer continues to thicken.In addition to the defects of the plating layer and the existence of extrusion stress,pores and graphite phases appear between the interfaces,which leads to an increase in the interface thermal resistance and a decrease in the thermal conductivity of the material.The thermal expansion coefficient of Diamond(Cr)/Mg composite material decreases and then increases as the coating thickness increases.The thermal expansion coefficient of Diamond(Cr)/Mg composite material with a coating thickness of 2.50?m at room temperature is 5.82×10^-6/K,and the coefficient of thermal expansion of the unplated Diamond/Mg composite is 9.29×10^-6/K,which is a 40%reduction in comparison.In summary,this article introduces Cr₇C₃ and Cr₃C₂ between the Diamond/Mg composite interface through the interface design to improve the interface bonding and increase the density of the composite material.The experimental results confirm that the composite material has a density of 2.84?2.94 g/cm³,The thermal conductivity is up to202.42 W/(m·K),and the thermal expansion coefficient is only 6.22×10^-6/K in the temperature range of 353?363K(the CPU's severe working temperature),which not only successfully matches the thermal expansion coefficient of semiconductor materials,It is also hoped to help the integrated circuit system to achieve lighter weight,and it can also provide a reference for subsequent research on the improvement of the thermal conductivity of Diamond/Mg composite materials.