Ultra-thin aluminum vapor chambers with nano Cu capillary pump loops for LED heat dissipation

• Main Authors: Yi-LingLi, 李依玲
• Other Authors: Hong-Paul Wang
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/29014335643631956961

碩士 === 國立成功大學 === 環境工程學系碩博士班 === 101 === Recently, the high efficiency, high brightness, environmental friendly, and long lifetime light-emitting diodes (LED) have been widely applied in lighting. However, LEDs which have relatively high energy (15%) used in lighting have suffered problems of heat dissipation, which also lead to decrease their lifetime and stability. Compared with the traditional forced heat convection, the liquid/vapor phase change for vapor chambers is more effective to enhance the heat dissipation. The core-shell (Cu@C) nanoparticles can be prepared by a simple method which was developed in our laboratory. The size (Dp) of the Cu@C nanoparticles in the range of 7-40 nm can be selected by simply changing the Cu/C ratio during preparation. A ultra-thin vapor chamber containing nano capillary pump loops (CPLs) can be prepared by removing the carbon-shell of the coated Cu@C with steam reforming (Cu@C + H2O → Cu + CO + H2). Methanol (MeOH) and ethanol (EtOH) were used as the working fluid in the Al vapor chambers. Experimentally, the LED heat dissipation associated with the partial pressures of the working fluid in vapor chambers, structures of the nano Cu CPLs, MeOH/EtOH ratios, Dp of the Cu@C nanoparticles, material of vapor chambers, and the amount of the ionic liquid added were investigated. By XRD and TEM, it is clear that the nanostructured Cu encapsulated in carbon-shell has a Dp range of 8.9-35 nm. Note that the thickness of the carbon-shell in the Cu@C was reduced from 3-5 nm to 1.0-2.2 nm during steam reforming, and without a perturbation of the core Cu. The wettability of the vapor chambers is increased in the presence of the nano Cu CPLs coated on the internal surface of the Al vapor chambers, which can accelerate the circulation of working fluid. The novel ultra-thin Al vapor chambers with nano Cu CPLs have been applied in the enhanced LED heat dissipation. For instance, for the vapor chamber containing nano Cu CPLs, in the presence of 80 torr of MeOH vapor, have a high thermal diffusivity (3.65 cm2/sec) and thermal spreading conductivity (668.1 W/m-K). The best thermal diffusivity (11.68 cm2/sec) and thermal spreading conductivity (2230 W/m-K) for the Al vapor chamber can be obtained, which greater than the bulky Al by at least nine times. The ionic liquids can play the role of preventing the thermal shock for the ultra-thin Al vapor chambers.