Effects of vapor duct thickness on the thermal performance of ultra-thin vapor chambers under forced-convection cooling

Abstract

Ultra-thin vapor chambers (UTVCs) have drawn considerable attention for the growing need of thermal management for thin portable electronic devices. In fact, our novel UTVC design has the potential for high-power applications. This work presents the performance test results under forced convective cooling for our novel UTVCs with thicknesses t = 0.40, 0.50 or 0.58 mm, having vapor duct thickness h = 0.15, 0.25, or 0.35 mm, respectively. The vapor duct thickness is shown to exert great effect on the maximum heat transfer rate (Qmax) and mild effect on the values of thermal resistance (Rvc) of the UTVC. These novel copper–water UTVCs simply comprise a top plate etched with arrayed pillars as the condenser and a mesh-wicked bottom plate as the evaporator and liquid path. The inner surface of the top plate contains cross parallel vapor ducts configured by aligned pillars for vapor spreading all over the vapor chamber. The pillars provide strong structural support, an enlarged condensation area, and a direct shortcut for liquid return. The condenser, with a footprint of 140 × 80 mm2, is cooled by a cold plate with running water of 50 °C. The UTVCs having h = 0.35 or 0.25 mm display values of Qmax of about 140 W or 90 W, respectively, with similar values of Rvc of 0.036–0.055 K/W. The UTVCs with h = 0.15 mm display greatly degraded values of Qmax of about 55 W with higher values of Rvc of 0.053–0.078 K/W. With a shorter return distance for the condensed water directly through the arrayed pillars, this UTVC design demonstrates a rather high Qmax of 140 W using only a single layer of #200 copper mesh wick at h = 0.35 mm.