Interface Microstructure And Thermal Properties Of Titanium Coated Diamond/Copper Composites

With the rapid development of information technology,the degree of integration of electronic devices has increased significantly,and their power density has continuously increased.The problem of heat dissipation has become the key to restricting the reliability and efficiency of electronic devices.Therefore,there is an urgent need to develop a new generation of high thermal conductivity heat-dissipating materials.The heat dissipation material needs high thermal conductivity and thermal expansion coefficient is matched with the electronic components.Diamond has excellent thermal physics（1200²000 W/m?K）and low expansion(2.3×10^-6/K).Because of this,we use diamond particles to reinforce the copper matrix to produce a new generation of heat-dissipating materials with high thermal conductivity and a suitable thermal expansion coefficient.Due to the chemical inertness and non-wetting between the diamond and the copper matrix,the interface of the composite material is weakly bonded,and the excellent thermal physical properties of the diamond itself cannot be exerted.In this paper,the surface of diamond was plated with Ti by magnetron sputtering.The interface thermal resistance and theoretical thermal conductivity of composites were calculated by phonon mismatch（AMM）model.A reasonable coating thickness was designed and diamonds/ Copper composites were prepared by pressure infiltration method.Using scanning electron microscope（SEM）,transmission electron microscopy（TEM）and laser thermal conductivity tester（LFA）,to study the microstructure,thermophysical properties and mechanical properties of the composites.The results show that the Ti coating on the diamond surface greatly improves the properties of the composites.The coating thickness increases from 50 nm to 200 nm.The thermal conductivity of Ti-coated diamond/copper composites increases first and then decreases.The Ti_{100 nm} diamond/copper composite has the highest overall performance and its thermal conductivity is 654 W/m?K,which is 263% higher than uncoated diamond/copper composites;its bending strength is 267 MPa,compared to uncoated diamond/copper composites.The material is increased by 507%;the thermal expansion coefficient of the project is 5.2×10^-6/K,while the engineering thermal expansion coefficient of the uncoated diamond/copper composite is 13×10^-6/K.The diamond particles in the composite material were extracted by chemical method and characterized by XRD.It was found that the Ti coating was transformed into Ti C by reacting with diamond during the preparation of the composite material.The Ti_{100 nm} diamond/copper composite plated interface is a layer of Ti C particles with different thickness of 100 nm.There is no obvious phase relationship between different Ti C particles.The Ti C layer and the diamond particles are chemically bonded.Therefore,the bonding force is strong,and there is only a small amount of pores at the interface.There is only a wetting effect between the Ti C layer and the copper matrix,the bonding force is weak,and there are more pores in the interface.The chromium element was introduced into the Ti-plated diamond/copper composite through the chromium bronze matrix.The results showed that the Cr element in the matrix was enriched at the interface and reacted with the C element that diffused from the diamond particle surface to the interface to form Cr₃C₂ due to the Cr₃C₂ particles.Larger,it will produce a pinning effect on the copper matrix,and enhance the binding force between the interface layer and the copper matrix.Therefore,the Cr₃C₂-plated Ti-plated diamond/copper composite interface is tightly bonded and has no pores.However,Cr element catalyzes the graphitization of diamond.The diamond surface of the Ti100nm/chromium bronze composite has a 5μm thick graphite layer,while the Ti100nm/Cu composite diamond surface has only a 5nm thick graphite layer.Graphite is amorphous,which increases the probability of phonon scattering and adversely affects the thermal conductivity of composites.At the same time,the intrinsic thermal conductivity of the Cr₃C₂ layer is low,so the thermal conductivity of the composite decreases when the thickness of the Cr₃C₂ layer is greater than a certain value.For Ti-plated diamond/chromium bronze composites,the thermal conductivity of the composite is up to 611 W/m?K when the coating thickness is 200 nm,and the bending strength of the composite is up to 361 MPa when the coating thickness is 150 nm.Taking into account the thermal and mechanical properties of diamond/copper composites,the Ti_{100 nm} diamond/copper composite has high thermal conductivity,a suitable thermal expansion coefficient and a certain degree of bending strength.Can be used as a heat sink material in microelectronics chips,semiconductor lighting,lasers and other high-power devices to show a good application prospects.