Development of thin loop heat pipe for compact electronics

Abstract

This study experimentally evaluates the thermal performance of a thin diffusion-bonded loop heat pipe (LHP) designed for electronics cooling applications. The device represents the third generation of an LHP with the same top-view dimensions of 76 x 60 mm² and an identical wick structure. However, the thickness has been progressively reduced from 1.6 mm to 1.1 mm, and now to 0.8 mm. Despite this reduction, the LHP demonstrates good thermal performance. An advanced testing workbench, simulating actual electronic operating conditions, enables performance evaluation in horizontal, gravity-assisted, and against-gravity orientations. The evaporator and part of the condenser incorporate a sintered copper powder wick structure. While the lowest thermal resistance of 2.16 °C/W is observed in the gravity-assisted orientation, the LHP operates nearly independent of gravitational effects, exhibiting comparable thermal resistances in all orientations. The reduction in internal channel thickness led to an average decrease of 50 % in thermal performance compared to previous generations with thicker channels (1 mm and 0.5 mm). Nonetheless, the current LHP remains highly suitable for electronic applications due to its thin profile, efficiency, and ability to dissipate up to 8 W/cm² without exceeding the maximum operating temperature of 100 °C.