Study On Interfacial Regulation And Thermal Conductivity Of Diamond/Copper Composites

Diamond/copper composite is a new generation of thermal conductive material prepared with copper as the matrix and diamond as the particle reinforced phase.The introduction of diamond into the copper matrix can greatly improve the thermal conductivity of diamond/copper composites,which have broad application prospects especially in the field of electronic packaging that urgently requires high thermal conductivity materials.As the latest generation of thermal conductive materials,diamond/copper composite materials have attracted the attention of many scholars,and the interface between diamond and copper has become a difficult point for scholars to overcome.The industry hopes that copper and diamond can obtain a good interface bond,but due to the special nature of diamond,it is not wetted with copper even in a high temperature environment,and the physical gap caused by it hinders heat transfer,which greatly affects the thermal conductivity of the composite.Therefore,the effective improvement of the interface structure between diamond and copper is of great significance to improve the thermal conductivity of the composite.In this paper,the formation mechanism of the plating layer was explored by salt bath plating method on the surface of diamond,the diamond/copper interface was regulated by adjusting the sintering process and the interface reaction products were confirmed,and the effects of different interfaces on thermal conductivity were explored by vacuum hot pressing sintering to prepare diamond/copper composites,and the experimental results showed that:（1）Salt bath plating TiC between 800-1000℃ can obtain dense plating.The surface coating of diamond gradually thickens with the increase of temperature and the extension of coating time,and the thickness of TiC plating obtained under different coating process conditions is 50-1050 nm,TiC first nucleates and then grows,island TiC is connected to form a film,and TiC after film formation grows to cause macroscopic thickening.The TiC-Tidouble-layer structure can be obtained by secondary salt bath of TiC-coated diamond,and the influence of holding time,titanium concentration and temperature on titanium deposition is explored,and at750℃,although the thickness of the titanium layer can be adjusted by extending the holding time,but for diamond particles with thinner TiC layer,it is easy to cause the continued thickening of TiC layer.In contrast,under the condition of 715℃,the concentration of titanium in the molten salt environment can be better controlled.The total thickness of TiC-Tiwas measured under different coating process conditions:250 nm,570 nm,890 nm,1.29μm,1.49μm and 1.51μm.（2）Design the diamond/copper interface,and regulate the inter-interface reaction under vacuum sintering conditions,the diffusion and reaction of copper titanium at800℃ sintering temperature is not obvious,when the sintering temperature is increased to 850℃ and 900℃,obvious inter-interface copper-titanium diffusion is found through EDS,and by analyzing its phase,the interface product is Cu Tiphase,and Cu₃Ti₂may exist.When the sintering time is adjusted,by analyzing the phase of the sintered powder at 950℃,the Cu₃Ti₂phase appears obvious,which is formed because the Cu Tiphase is precipitated in the second phase of Cu₃Ti₂,and finally retained in the form of Cu₃Ti₂phase at room temperature.The reaction of copper and titanium at 800-900℃ is slow,the diffusion thickness of copper and titanium does not exceed 400 nm,and the diffusion thickness of 60 min to 300 min at 950℃ is 600nm-1μm.（3）The influence of diamond particle size on the thermal conductivity of composites was explored.Diamond with large particle size has a smaller specific surface area under the same volume fraction,which can reduce the loss of heat at the interface and is more conducive to the improvement of the thermal conductivity of the overall composite.The density of the prepared diamond/copper composites was above97.5%.The copper-titanium reaction affects the density of the composite,which can reach up to 99.2%.Comparing the theoretical thermal conductivity with the actual thermal conductivity,the thermal conductivity of TiC can reach more than 75%of the theoretical thermal conductivity when the thickness of the TiC coating is 380-740 nm,and the thermal conductivity is most conducive to thermal conductivity when the coating thickness is 690 nm,and the thermal conductivity is about 540 W/（m·K）.The structure of diamond-TiC-Ti-Cu is not conducive to the improvement of thermal conductivity,and the introduction of titanium at the interface strengthens the interface bonding to a certain extent,but the multi-interface structure causes the loss of heat between the interface transfers,which is easy to cause the decline of the overall thermal conductivity of the composite.In summary,the results of this paper enrich the relevant basic research on the interface regulation of titanium-plated diamond/copper composites,and have certain guiding significance for the optimization of the interface of high thermal conductivity diamond/copper composites.