A Novel Flat Micro Heat Pipe With a Patterned Glass Cover

Abstract

The light-emitting diode (LED) is a promising lighting source because of its energy-saving and environment friendly features. High-power LEDs have specific wide applications, such as car headlights and street lamps. However, heat transfer is still a critical issue that limits the usage of LEDs. The flat microheat pipe (FMHP) is a suitable passive heat transfer device for LEDs. Silicon substrate was selected to fabricate LED electrodes and the wick structure of the FMHP, and thus, LEDs' mount base and the FMHP were integrated together and the contact thermal resistance could be reduced. Meanwhile, Pyrex 7740, which could be anodic bonded to the silicon substrate and sustained relatively high temperature and pressure, was used to fabricate its cover plate. In this paper, a new type of FMHP is proposed. The cover plate had circles patterned on it, and the etched structure was shell shaped. The contact angle of it was 81.46°, whereas that of the normal cover was 67.97°, which meant that the new cover was more hydrophobic. Theoretically, the new cover could make working fluid drops fall down to the grooves in a relatively shorter time and speed up heat transfer. The evaporator temperatures of the novel FMHP and that of the normal one were 71.6°C and 79.4°C, respectively. In addition, the new designed FMHP also had better temperature uniformity. The experimental results proved that the patterns on the cover plate of the FMHP could promote the heat transfer capability of the LED module.Index Terms-Flat microheat pipe (FMHP), glass cover plate, light-emitting diode (LED) thermal management.

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