Preparation And Properties Of High Thermal Conductivity Diamond/Copper Composites

With the rapid development of microelectronic technology,electronic components are gradually developing towards high integration and high power density.Increasing amount of heat is generated during the operation of electronic components.These heat is accumulated in devices,which leads to the gradual increase of the working temperature of and thereby the thermal failure risk of the devices.Therefore,modern electronic industry urgently needs a new generation of electronic packaging material of high thermal conductivity and suitable thermal expansion coefficient.Diamond/copper composite has attracted extensive attention of researchers and industry because of its high thermal conductivity and low thermal expansion coefficient.In this thesis,to improve the poor bonding between diamond/copper phase in their composite,a coating of double-layer structure was constructed at the diamond surface via surface thermal diffusion tungsten plating and electroless plating,and the composite were prepared by Spark plasma sintering(SPS)technology and hot oscillating pressing(HOP)technology respectively.The microstructure,thermal conductivity and thermal expansion coefficient of the composites were characterized and analyzed;The effects of different sintering processes on the properties of diamond/copper composites were studied;Meanwhile,by comparing the performance differences between tungsten plated diamond/copper composite and double-layer coated diamond/copper composite,the effect of double-layer structure on the whole heat dissipation performance of the composite was investigated.Main research results are as follows:(1)The best properties of diamond/copper composites prepared via SPS process are obtained in this work when the sintering temperature reaches 950℃,the sintering pressure reaches 50 MPa and the condition holding time is 20 min.Meanwhile,the properties of the composites decrease with the increase of diamond volume fraction.Thermal conductivity and relative density of 50 vol.%diamond/copper composite obtained at 950℃ and 50 MPa for 20 min are 370 W/m·K and 98.9%respectively.And the coefficient of thermal expansion is 4.9 × 10-6/K.(2)The double-layer diamond/copper composite was prepared via spark plasma sintering technology.Comparing with tungsten coated diamond/copper composites,the double-layer structure at the surface of diamond is beneficial to the improvement of the density and thermal conductivity of the composites.Taking 50 vol.%diamond/copper composites as an example,the relative density of diamond/copper composites with double-layer coated diamond is 99%,and the thermal conductivity is 407.4 W/m·K.(3)Tungsten-coated diamond/copper composites were prepared by hot oscillating pressing.The results show that the 50 vol.%diamond/copper composites obtained at 850℃,30±5 MPa for 60 min have the best properties.With the increase of diamond volume fraction,the properties decrease gradually.When the diamond volume fraction reaches 50%,the relative density and thermal conductivity of the sample reach 98.9%and 604.8 W/m·K.(4)Diamond/copper composites with double layer was prepared by hot oscillating pressing.When the volume fraction of diamond is 50%,the relative density and thermal conductivity of composite are 99.8%and 629.2 W/m·K respectively.