Fabrication And Heat Transfer Performance Of Vapor Chambers With Reentrant Porous Composite Wick

With the rapid development of aerospace,high speed computer,photovoltaic power generation,fuel cell,high power LED,microelectronic equipment and so on,the high heat flux is accumulated in a narrow and limited space.And it has provided an urgent demand for the thin and high efficiency vapor chamber.The thickness reduction,optimization of the packaging process and heat transfer performance improving have become the key problem of the vapor chamber.In this paper,a vapor chamber with reentrant grooved porous composite structure and its manufacturing method were proposed.The mechanism of both manufacturing processing and boiling heat transfer of the reentrant grooved porous composite structure were studied.Besides,The integrated package technology and the heat transfer performance of the vapor chamber were also studied.The main research work is as follows:(1)Using solid phase sintering and micro milling technology,the reentrant grooved porous composite structure was formed.The optimum processing parameters were obtained.Besides,the cause of burr formation and tool wear is analyzed.(2)Since the motion and heat transfer characteristics of the bubble in the nucleate boiling process of the porous composite structure,the wall overheat of the porous composite structure is decreased,and the critical heat flux is greatly delayed.With the increase of liquid subcoolings,the bubble gradually grows from nucleation to detachment,and the size of bubbles gradually decreases.Comparing with the solid copper in the reentrant cavities,the porous composite structure shown a better heat transfer performance under the low heat flux conditions,while worse under the high heat flux conditions.(3)The formed porous composite wick structure was integrated into the vapor chamber.And the integrated packaging technology is optimized as well.A series of vapor chambers with 3mm thick were finally prepared.It is determined that the optimum filling rate is 40%.And the instantaneous starting characteristics of the vapor chambers were studied in such filling rate.The results show that the vapor chamber perform well in temperature uniformity.Besides the minimum heat resistance about 0.052 ?/W of the vapor chamber was obtained.(4)Optimized the design of the high-power LED vapor chamber cooling system integrated packaging process,set up a cooling performance test platform for this cooling system,studied the instantaneous start-up characteristics of the cooling system and different thermal power,tilt angle and wind speed conditions for the entire cooling system impact.