Thermal performance of a flat polymer heat pipe heat spreader under high acceleration

Abstract

This paper presents the fabrication and application of a micro-scale hybrid wicking structure in a flat polymer-based heat pipe heat spreader, which improves the heat transfer performance under high adverse acceleration. The hybrid wicking structure which enhances evaporation and condensation heat transfer under adverse acceleration consists of 100 μm high, 200 μm wide square electroplated copper micro-pillars with 31 μm wide grooves for liquid flow and a woven copper mesh with 51 μm diameter wires and 76 μm spacing. The interior vapor chamber of the heat pipe heat spreader was 30 × 30 × 1.0 mm 3 . The casing of the heat spreader is a 100 μm thick liquid crystal polymer which contains a two-dimensional array of copper-filled vias to reduce the overall thermal resistance. The device performance was assessed under 0-10 g acceleration with 20, 30 and 40 W power input on an evaporator area of 8 × 8 mm 2 . The effective thermal conductivity of the device was determined to range from 1653 W (m K) −1 at 0 g to 541 W (m K) −1 at 10 g using finite element analysis in conjunction with a copper reference sample. In all cases, the effective thermal conductivity remained higher than that of the copper reference sample. This work illustrates the possibility of fabricating flexible, polymer-based heat pipe heat spreaders compatible with standardized printed circuit board technologies that are capable of efficiently extracting heat at relatively high dynamic acceleration levels.

Advanced thermal management technologies for defense electronics

“…A selected bibliography of TGP team publications is included in this paper [10][11][12][13][14][15][16][17][18][19][20][21][22].…”

Microfabricated ultra-thin all-polymer thermal ground planes

“…Thermo-pressing occurs at 300°C and 75 psi (1 kPa = 0.145 psi) for 20 s. The final side is epoxy bonded to a copper tube to allow evacuation and charging of 0.15 mL water, as in Ref. [8]. The optimal water charge of 0.15 mL is determined experimentally.…”

“…The test apparatus is shown in schematically in Fig. 4a and is adapted from previous work [8]. Heat is supplied to the evaporator of the FTGP by a small ceramic heater; heat is removed from the condenser by an aluminum block with a known 1 cm 9 1 cm cross section and linear array of thermocouples down the length.…”

“…Various polymer flexible thermal ground planes (FTGPs) have been developed, which use aluminized Mylar as the casing material and woven copper mesh bonded to electroplated copper micropillars as the wicking structure [7,8], as well as silicone rubber as the casing material and multi-layer copper mesh as the wick [9]. Allpolymer FGTPs are of great interests for wearable electronics and mobile computing, with potential enhancements in weight, flexibility, and manufacturability.…”

Towards Embedded Cooling - Gen 3 Thermal Packaging Technology

“…The plot shows the effective conductivity of each TGP in a gravity-neutral, horizontal orientation. Additional details on the characteristics and performance of the TGPs can be found [20][21][22][23][24][25][26][27][28][29][30][31]. …”