Investigation of Packaged Miniature Heat Pipe for Notebook PC Cooling

Miniature heat pipe (MHP) with woven-wired wick was used to cool the CPU of a notebook PC. The pipe with circular cross-section was pressed and bent for packaging the MHP on the very limited space of a notebook PC. A cross-sectional area of the pipe is reduced about 30% when the MHP with 4mm diameter is pressed to 2mm thickness. In this study, a performance test has been performed in order to review the change of operating performance according to the pressed thickness variation and the heat dissipation capacity of MHP cooling module that is packaged on a notebook PC. New wick type was considered for overcoming low heat transfer limit when MHP is pressed to thin-plate. The limitation of the pressed thickness is shown to be within the range of 2mm ~ 2.5mm through the performance test. When the wall thickness of pipe is reduced to 0.25mm from 0.4mm to minimize the conductive thermal resistance through the wall of heat pipe, limiting power and thermal resistance of MHP were improved about 10%. In the meantime, it is shown that the thermal resistance and heat transfer limit for the MHP with central wick type are higher than those of MHP with existing wick types. As a result, the performance test of MHP cooling modules with woven-wired wick to cool a notebook PC shows the good stability as cooling system since Tj (Junction Temperature of Processor) satisfies a requirement condition of 0 ~ 100°C under CPU heat, 11.5W.