Study On Pore Control Of Powder Metallurgy Pure Copper Thermal Conductive Material

With the development of electronic components towards high integration and high power density,thermal management has become one of the key factors affecting their performance and life.Powder metallurgy(P/M)pure copper material has the advantages of high thermal conductivity,controllable porosity,near net forming and uniform structure,and is one of the widely used heat pipe materials.Porosity is an inherent property of P/M materials.Different types of P/M pure copper materials have great differences in heat transfer mode,performance and pore structure.At present,the research on pore control and properties of P/M pure copper is not comprehensive enough.Pure copper powder as raw materials,this paper uses the apparent sintering and pressure sintering process of preparation of porous pure copper and thermal conductive materials and thermal conductive density pure copper material,studied the powder properties and material preparation process influence on powder sinter porosity,the porosity and pore morphology variation and its effect on the properties of materials,this paper discusses the mechanism of pure copper powder sintering,High thermal conductivity powder sintered pure copper flat heat pipe has been developed.The main research results are as follows:(1)The morphology of the powder has a great influence on the porosity and the maximum pore size of the sintered body.The developed branch shaped electrolytic copper powder is advantageous to the preparation of high porosity pure copper materials,with the porosity up to 66.6%,and the corresponding maximum pore size of 48.7 μm.(2)Oxidation treatment is beneficial to sintering of P/M pure copper under certain conditions.When the green density is less than or equal to 5.00 g/cm3,the sintering activity of the powder can be improved by oxidation at 400℃ for 30～90 min,which is about 0.17 g/cm3 higher than that of the unoxidized powder;When the green density is more than 5.00 g/cm3,the density is about 0.26 g/cm3 lower than that of the non-oxidized sinter.(3)With the increase of pressing density,the density of sintered bulk increases first and then decreases,and the maximum values of different atmospheres are different.In the process of reducing atmosphere sintering,the density of sintered bulk obtained from electrolytic copper powder is the highest,8.66 g/cm3,and the density is 96.7%,when the green density is 6.66 g/cm3.In the vacuum sintering process,the density of sintered bulk obtained from electrolytic copper powder is 8.88 g/cm3 when the green density is 7.46 g/cm3,and the density is 99.1%,the thermal conductivity is 332.3 W/(m·K).(4)The pore structure has a significant effect on the mechanical properties of powder metallurgy pure copper materials.When the porosity of low-density green sintered body increases from 14.3%to 56.6%,the strength decreases from 272.0 MPa to 17.6 MPa,and when the porosity of high-density green sintered body increases from 13.5%to 29.7%,the strength increases from 156.6 MPa to 221.2 MPa.When the porosity is less than 22%,the strength of the sintered sample of high-density green billet is lower than that of low-density green billet;when the porosity is more than 22%,the opposite is true.(5)A pure copper plate heat pipe evaporator with high thermal conductivity and powder sintering was prepared.The optimum technological conditions of powder sintered pure copper flat plate heat pipe are as follows:holding at 800℃ for 6 h,raw material size of 70%(-150～+325 mesh)+30%(-325 mesh).The porosity of the wick is more than 50%,and the maximum pore size is less than 50μm.The structure of the core is complete,forming metallurgical bonding with the bottom plate,and the processed heat pipe has excellent thermal response performance.