Development of a 0.3 mm ultra-thin loop heat pipe for 10 W heat dissipation in thin mobile devices

Abstract

An ultra-thin (0.3 mm thickness) and high heat flux (10 W/cm2) loop heat pipe (UTLHP) was developed for heat dissipation in thin mobile devices. A steady-state numerical model was developed, and the UTLHP was designed based on the model. The UTLHP was fabricated by etching two copper plates to form flow channels and welding them together. Wicks were formed by sintering copper powder, and secondary wicks were provided to support the fluid supply. Water was used as the working fluid, and two types of liquid fill ratio were prepared: 51 % and 65 %. A series of tests were performed to evaluate the heat transport performance of the UTLHP. The same tests were conducted in five different orientations, and the orientations dependence of the UTLHP were discussed. The maximum heat transport of the UTLHP in horizontal orientation was 10 W (10 W/cm2), regardless of the fill ratio. In horizontal orientation and at 65 % liquid fill, the maximum temperatures of the heat source and evaporator were 139 °C and 115 °C, respectively, and the minimum thermal resistance of the system was 0.48 °C/W. In the orientation evaluation test, the heat transport performance was up to 10 W (10 W/cm2) at all/ orientations tested when the liquid fill was 65 %, indicating that the UTLHP is anticipated to be integrated into mobile devices. Furthermore, the developed model aligned with the operating test results within an error of 10 °C.