Study On Preparation And Properties Of Diamond Reinforced Aluminum Matrix Thermal Conductive Composites

In recent years,with the rapid development of miniaturization and high power density of electronic equipment,solving the heat dissipation problem of the chip has become a research central issue in the development of the electronic information industry.In this context,high-performance metal-based composites have been widely studied.Although high thermal conductivity materials have experienced development stages such as Invar/Kovar alloy,W?Mo?-Cu alloy,and ceramic/metal matrix composite,they still cannot meet the high heat dissipation requirements of various new electronic devices.Diamond-reinforced metal matrix composites have higher thermal conductivity,which brings new hope for the effective heat dissipation of high-power electronic devices.Compared with the diamond-reinforced copper matrix composite,the diamond-reinforced aluminum matrix composite has obvious advantages such as easy preparation,low density and low cost,so it is expected to become one of the new heat dissipation materials in the future.In this paper,the vacuum hot pressing method and the high temperature and high pressure technology are used to prepare the diamond/aluminum composite,which aims to improve the thermal conductivity of the composite.The details are as follows:?1?Preparation of diamond/aluminum composite by vacuum hot pressingThe best preparation process of diamond/aluminum composite was explored by vacuum hot pressing method,and the properties of the composites were characterized.When the volume fraction of diamond?200?m?is 50 vol%,the best preparation process of the composite is to keep it at a temperature of 650°C for 120 minutes.At this time,relative density,thermal conductivity and the thermal expansion coefficient of the diamond/aluminum composite is 99%,566 W/m K and 7.2?12.6 diamond content,as the size of diamond particle increases from 20?m to 500?m,thermal conductivity of the composite increases from 286 W/m K to 678 W/m K.Compared with diamond/aluminum composite with untreated diamond,pre-coated with a layer of aluminum metal on the surface of diamond particles can improve relative density and thermal conductivity of diamond/aluminum composite to a certain extent,and shorten its preparation cycle.?2?Preparation of diamond/aluminum composite by high temperature and high pressure methodThe process of preparing diamond/aluminum composite by high temperature and high pressure method was explored.The surface of diamond particles was coated with titanium,tungsten and boron by spark plasma sintering,and the performance of coated-diamond/aluminum composites prepared by high temperature and high pressure method was studied.In a wide range of preparation pressure?1GPa-4GPa?and temperature?500°C-700°C?,when the volume fraction of diamond?200?m?is50 vol%,thermal conductivity of diamond/aluminum composites is in the range of 69W/m K to 151 W/m K.This shows that high pressure in range of 1GPa to 4GPa cannot improve the wettability between diamond and aluminum matrix and thermal conductivity of the composite.By adjusting the sintering temperature and time,using spark plasma sintering technology can coat diamond surface with different thickness of Ti and Ti C,WC and W₂C,or B₄C coating layer,which can improve thermal conductivity of diamond/aluminum composite in varying degrees.Titanium coating can increase thermal conductivity of diamond/aluminum composite to 529 W/m K,and the thermal expansion coefficient to 8.9×10^-6/K.Similarly,Tungsten coating and boron coating can increase thermal conductivity of the composite to 335 W/m K,399 W/m K,respectively.The results show that the diamond/aluminum composite with high thermal conductivity and low thermal expansion coefficient can be prepared in a short time by combining the high temperature and high pressure method with the surface coating treatment of diamond particles.