The Development of Polymer-Based Flat Heat Pipes

Abstract

In this paper, polymer-based flat heat pipes (PFHPs) with a thickness on the order of 1 mm have been successfully developed and tested. Liquid-crystal polymer (LCP) films with copper-filled thermal vias are employed as the case material. A copper micropillar/woven mesh hybrid wicking structure was designed and fabricated to promote evaporation/condensation heat transfer and the liquid supply to the evaporator of the PFHP. Water was selected as the working fluid because of its superior thermophysical properties. An experimental study was conducted to examine the PFHP performance. The test data demonstrated that the PFHP can operate with a heat flux of 11.94 W/cm 2 and results in effective thermal conductivity ranging from 650 to 830 W/m · K, with the value varying with the input heat flux and the tilt angle. With the employment of flexible LCP as casing material, the PFHP could potentially be directly integrated into a printed circuit board or flexible circuits for thermal management of heat-generating components.[ 2010-0280]Index Terms-Cooling, flat heat pipe (FHP), hybrid wick, polymer.

Recent Advances in Vapor Chamber Transport Characterization for High-Heat-Flux Applications

“…Subsequent investigations by Oshman et al [181,182] focused on development of flexible polymer-based heat pipes.…”

“…In order to increase the inherently low polymer thermal conductivity, copper thermal vias were inserted into the LCP at the heat input and condenser locations. A detailed description of thermal via insertion and fabrication of the copper hybrid wick structure for LCP heat pipe walls is provided in [181]. A prototype PFHP (60 × 30 × 1 mm 3 ) was fabricated using these techniques (Figure 29d).…”

“…A prototype PFHP (60 × 30 × 1 mm 3 ) was fabricated using these techniques (Figure 29d). Using the same definition above, the maximum effective thermal conductivity was measured to be 830 W/mK over an input power range of ~3-12 W/cm 2 [181]. Using the same fabrication approaches, a 40 × 40 × 1 mm 3 PFHP was later fabricated with different heat input and condenser configurations [182].…”

Numerical Study on Heat Transfer Characteristics of Heated/Cooled Rods Having a Composite Board in between: Effect of Thermal Vias

“…In addition to the PCB, the thermal via has been also used for polymer heat pipes. Wits and Kok [8] developed a polymer heat pipe using the PCB, while liquid-crystal polymer films were employed by Oshman et al [9] as a casing material. Because the thermal conductivities of these polymer materials were much lower than those of metals, the thermal vias were placed at a heated and a cooled section of their polymer heat pipes.…”

Patterning the condenser-side wick in ultra-thin vapor chamber heat spreaders to improve skin temperature uniformity of mobile devices

“…Ding et al [11] developed a titanium-based vapor chamber with a thickness of 0.6 mm that included a uniform array of microfabricated titanium pillars as the wick structure. Oshman et al [12] fabricated a 1 mm-thick heat pipe with a hybrid copper mesh and micropillared wick encased in a liquid-crystal polymer chamber. Lewis et al [13] fabricated a 0.5 mm-thick flexible heat pipe made of copper-cladded polyimide, with a copper mesh wick.…”