Preparation And Thermal Properties Of Diamond/Cu Composites By Vacuum Hot Pressing

The high power density,miniaturization and high reliability of microelectronic devices are urgently demanding packaging materials with superior thermal performance.Diamond/Cu composite have attracted much attention because of its high thermal conductivity and adjustable thermal expansion coefficient.In this paper,Diamond/Cu composites were prepared by vacuum hot pressing technology,and the influence of different factors on the microstructure and thermal conductivity of the composites was investigated.The main research work in this paper focuses on the following aspects:The influence of minor Ti addition on interfacial microstructure and thermal conductivity of Diamond/Cu composites was studied.The thermal conductivity of composites first increases and then decreases with increasing Ti contents,the highest thermal conductivity of 511 W m-1·K-1 was achieved for the composite with 1.1 wt%Ti contents in matrix.When Ti contents are less than 1.1 wt%,the number and area of carbides generated during the sintering process increase with the increase of Ti content,optimize the interface bonding,increase the number of interface heat transfer channels and improve the thermal conductivity of composites.With Ti content increasing from 1.1 wt%to 1.4wt%,the thickness of interfacial transition layer increases from 211μm to 3.04μm,indicating that the excession of Ti element increases the thickness of the carbide layer.The carbide layer with low thermal conductivity becomes a new thermal resistance layer,which decreases the interfacial thermal conductivity and the thermal conductivity of the composites.On the basis of Diamond/Cu-1.1 wt%Ti composites,the material composition and sintering pressure were kept constant,and the influence of the sintering time on the microstructure and thermal conductivity of the composites was studied.The thermal conductivity of composites decreases slightly and then increases with the sintering time prolonging.The lowest thermal conductivity of Diamond/Cu-1.1 wt%Ti composites was 339W ·m-1 ·K-1.When sintering time is 30min,60min and 90min,the thickness of interfacial transition layer is 1.23,1.34 and2.11μm,respectively,which indicates that the thickness of interfacial transition layer increases gradually with the sintering time prolonging.The optimum effect of carbide on the overall thermal conductivity of composites requires that the carbide layer reach a certain thickness.Based on the Diamond/Cu-1.lwt%Ti composite,the total volume fraction of the reinforcement particles was kept constant.The increase of the content of small particle size(D2,60μm)affects the bonding state of the original large particle size(D1,300μm)with the matrix and the thermal conductivity of the composites decreases continuously with the increase of D2 content.Under the same volume fraction,the number of small particle size particles is more and the surface area is larger,which increases the obstruction to the interface heat transfer.As the D2 content increases from 10 vol%to 40 vol%,the thickness of the carbide layer between D1 and the matrix decreases from 2.35μm to 0.81μm.Due to the increase of diamond quantity and surface area,the distance between the particles decreases,so that the Ti source in the matrix is insufficient and the thickness of the carbide layer formed on the D1 surface is reduced.The thinner carbide layer makes it impossible to form an effective chemical bond between D1 and the matrix,thus reducing the thermal properties of the composites.