A Study On Preparation And Properties Of Diamond/Copper Composites

Compared with traditional electronic packaging materials, diamond/copper composites have higher thermal conductivity, lower relative density, thermal expansion coefficient matching with semiconductor materials, etc., which has gained extensive attention as a new generation of electronic packaging materials. Therefore, the research of diamond/copper electronic packaging materials has important theoretical and practical value.The current preparation methods of diamond-reinforced metal matrix composites with high volume fraction have powder metallurgy,pressure infiltration and other methods. As the powder metallurgy method has low cost, simple process, high relative density of prepared composite materials, this paper adopted repressing and re-sintering and vacuum hot -pressing technology of powder metallurgy to prepare diamond/copper composite materials.The relative density, thermal conductivity and thermal expansion coefficient of composites were mainly investigated as main performance indicators. Under different process conditions diamond/copper composites with different diamond particle sizes of 20μm,40μm,60μm,90μm and different volume fraction of 40%,50%,60%,70% were prerared.In this paper, Diamond/copper composite with diamond size of 90μm, volume fraction of 50%,60%,70% were prepared firstly by repressing and re-sintering technology,which is repressing and re-sintering after pressing and sintering with sintering temperature of 890℃, sintering time of 8h. The results showed that:its relative density is not high, only about 80%; the highest thermal conductivity is only 93.01W/(m·K).According to exsisting problems and expierences from repressing and re-sintering technology, the vacuum second hot-pressing technology were used to prerare diamond/ copper composites for process improvement under hot pressure of 25MPa, the sintering temperature of 900℃and holding time of 1.5h. The results showed that:the relative density and thermal conductivity of composites by vacuum second hot-pressing technology are higher than repressing and resintering technology,the relative density is about 90%;the second pressing obviously improves the relative density of composites,where the relative density of composite with diamond volume fraction of 40%, particle size of 90μm is up to 98.45%.This paper also investigated the effects of diamond particle size, volume fraction and other parameters on relative density, thermal expansion coefficient and thermal conductivity. The results showed that:the relative density of diamond/copper composite increases with the increase of diamond particle size and decreases with the increase of diamond volume fraction;when the volume fraction of diamond is certain thermal expansion coefficient gradually increases with the increase of temperature and diamond particle size, and when diamond particle size is constant thermal expansion coefficient decreases with increase of diamond volume fraction; the thermal conductivity of diamond /copper composite increases with the increase of relative density and diamond particle size, and decreases with the increase of volume fraction of diamond.The relative density and thermal conductivity of composites prepared by vacuum second hot -pressing are greatly improved in compare with repressing and re-sintering technology, the thermal conductivity of composites with diamond volume fraction of 40%, particle size of 90μm is up to 207.571 W/(m·K). But the interfacial bonding of diamond/cu matrix composites is more complex and interfacial thermal resistance have very large effect on thermal conductivity of composites,which needs further attention and study.