Preparation And Properties Of Diamond/W/Copper Composites

With the continuous and rapid development of modern scientific information technology in the world,the power density of various electronic devices is gradually increasing,and the heat generated per unit volume is also increasing.There are also certain requirements for the thermal expansion coefficient of the heat dissipation material.If it does not match the thermal expansion coefficient of the chip,it may cause the chip burning and cause the serious consequences of the failure of electronic components.Therefore,for modern commonly used industrial electronic packaging materials,high conductivity and low coefficient of thermal expansion become the most basic requirements.At present,the third-generation thermal management materials represented by diamond-copper-based composite materials are favored by many scholars because of its good thermophysical properties.However,the affinity between diamond and copper is poor.If the decoration is not directly compounded,the surface connection state is not good.There will be a large number of holes at the interface to reduce the thermal conductivity of the interface and deteriorate the thermal performance of the composite.At the same time,the traditional single-particle-scale diamond-based composite material thermal guidance is also limited by diamond volume scores,resulting in the heat guide that can no longer be significantly improved.Therefore,this paper is based on the urgent needs of high heat-conducting and low-thermal expansion coefficient composite materials.Taking diamond and copper as a research object,based on the effective theoretical model of micro-division medium,and introduced double-particle-size diamonds.The transition layer of the metal W,and the confidentiality of the composite material through the thermal pressure sintering technology,and finally prepared a high-heat guidance and low thermal expansion coefficient of diamond-copper-based composite thermal guide materials.The specific research content is as follows:（1）Research on theoretical heat guidance calculationThis article uses the DEM model,and at the same time introduces the method of Gaussian distribution and multi-particle size iteration to calculate thermal guidance method.The theoretical heat guidance value of diamond-copper-based composite materials.The research results show that:（1）The increase of the thickness of the surface metal layer and the carbide layer will reduce the thermal performance of the composite.The modified element can select W>Mo>Cr>Zr>Ti according to the following order.（2）For the single-size diamond-copper matrix composites and double-size diamond-copper matrix composites,with the increase of diamond particle size,the theoretical thermal conductivity of the composite increases first and then tends to decrease.（3）The theoretical heat guidance of diamond-copper-based composite materials gradually increased with the increase in volume scores of diamonds,showing a similar index increase.（4）Among the double particle size diamond copper-based composite materials,when the volume score of large granules is 74.2%,the composite has a minimum porosity of 14.5%.（5）As the volume fraction of diamond increases,the thermal expansion coefficient of the composite decreases gradually.（2）Metalization on the surface of diamondIn this paper,molten salt method is used for diamond surface metallization,which mainly discusses the effects of different reaction temperature,thermal insulation time,and the ratio of raw materials between diamond and nano-tungsten powder,the thickness of the transition layer,and the crystallization of its objects.This article focuses on metal on the surface of metal W.Experimental results show that（1）The best melting salt reaction temperature is 1050^oC,and the best response time at this temperature is 120 minutes.The reaction temperature and reaction time of too low will incomplete the response,too high reaction temperature and reaction time will crack the surface of the diamond surface,and even cause graphitization on the surface of diamond.（2）The best quality ratio of raw material diamond and nano-tungsten powder is 1:1.When the raw material tungsten powder is too much,the surface plating layer of diamond is thicker,and the extra nano-tungsten powder is difficult to remove.When the content of tungsten powder is too low,the surface of diamond could not be completely covered.Under the above optimal reaction conditions,the metallic plating obtained by diamonds obtained shows a good surface appearance and crystalline.The thickness of the transition layer is about 200 nm,which is conducive to the combination of diamond and copper interface.（3）Preparation and performance research of metallic diamond-copper-based composite thermal guidance materialsThis article uses the above W metallic diamond to prepare the diamond-copper-based composite material through the hot pressure sintering method.In turn,the thickness of transition layer on the diamond surface,particle size,volume fraction,and the effect of introducing double particle size on the thermal properties of diamond-copper matrix composites.At the same time,the corresponding actual scene application test is designed.The experimental results show that:（1）The optimum coating thickness on the diamond surface is 200 nm.The too thin interface is more fragile.Too thick will also increase the interface thermal resistance and reduce the thermal performance of the composite material.（2）The best particle size of diamonds is 200μm,If the particle size is too small,there are too many thermal interfaces,and if the particle size is too large,the copper powder cannot completely fill the gaps between the diamonds.（3）In the single particle size composite material,the volume score threshold of diamond volume is 60%,the thermal conductivity reaches the peak of 619 W/（m·K）,the CTE drops to 7.8×10^-6/K,and the relative density is 95.2%.Among the double-particle size composite material,the volume score threshold of the diamond volume increases to 70%,the peak of the heat guidance rate is 698 W/（m·K）,and the CTE is reduced to 5.8×10^-6/K,and the relative density is 93.2%.When the volume score is too low,due to the small content of diamonds,the thermal performance of the composite material is poor;when the volume score is too high,the phenomenon of the enhancement of the phase particles increases,and a large amount of pores appear in the composite materials.（4）Through the COMSOL simulation and LED light heat dissipation experiments,the thermal density of the double-particle size diamond copper-based composite material is more uniform than the single particle size composite material.At the same time,the minimum work temperature.After repeating the experiment three times,the temperature change curve of the LED light has not changed much.It further proves that the double particle size oriented diamond composite material has better thermal performance superiority and stability compared to single particle size composite materials.