Study On Preparation And Performance Of Integrated Sintering Copper Plate Evaporator

Advanced intelligent electronic devices in the field of information technology are developing towards integration,miniaturization and high power.Electronic components are facing the contradiction between the improvement of equipment integration and the increase of heat flux density.The operation stability of high power and high heat consumption electronic devices is subject to its heat dissipation efficiency.Heat pipe is based on the principle of phase change to transfer and distribute heat,so as to realize rapid and efficient heat dissipation in limited space.The evaporator composed of capillary wicks and shells are the key component within heat pipe.Copper is often used in heat pipe preparation because of its extremely high thermal conductivity and low cost.In this paper,the powder metallurgy process was used to realize the simultaneous preparation of porous wicks and fully dense shell materials.The effects of copper powder properties,forming and sintering process on the number,size and structural characteristics of pores in sintered billets and the service performance of corresponding materials were studied.The sintering mechanism of pure copper powder was discussed and analyzed.Finally,the integrated preparation of pure copper plate evaporator was realized by constrained sintering technology.The main research results and conclusions are as follows:（1）The sintered capillary wick of reduced copper powder prepared by reduction of cuprous oxide powder has the advantages of small maximum pore size,high porosity and low sintering shrinkage.Compared with the sintered capillary wick of atomized copper powder and electrolytic copper powder,its porous performance and binding force with the tube shell both are better.The increase of powder reduction temperature,powder particle size and green porosity all lead to the increase of maximum pore size and porosity of capillary wicks,while the permeability increases under the synergistic effect of the former two.The green body with 55%porosity was formed by reducing copper powder（600℃,500 mesh）,and sintered at 700℃ for 60 min,the highest capillary efficiency of copper capillary wick can be obtained.The maximum pore size is 2.4μm,the porosity is 51.5%,and the permeability is 1.353×10^-13 m².The maximum pore size is smaller than reported in the literature.（2）The relative density of the sintered body of airflow crushing powder is higher,compared with the electrolytic and reduced copper powder.In the range of 6.0-8.0 g/cm³,the relative density increases first and then decreases with the increase of density.The relative density of copper powder sintered in reducing atmosphere is higher than that in vacuum atmosphere,and the density of sintered body is the highest in reducing atmosphere at 1000℃ and 1040℃.The relative density of the sintered material is proportional to the grain size,and its thermal conductivity and hardness are positively correlated and negatively correlated with the density,respectively.The copper powder was molded into 7.0 g/cm³ green body,and sintered at 1000℃ for 180 min in a reducing atmosphere.A high pyknosis and high thermal conductivity material with extremely high density of 99.66%,high thermal conductivity of 399.0 W·m^-1·K^-1,and the Brignell hardness of 40.8 HBW5/250 was obtained.（3）The constrained mold for pure copper plate evaporator was designed and developed,and the pure copper evaporator was prepared by constrained sintering technology to realize the metallurgical bonding between capillary wick and the shell.The evaporator sintered at 700℃ has the highest efficiency,and its capillary performance is consistent with the independently fabricated wicks and also meets the engineering requirements.