A study on thermophysical properties of printed wick structures and their applications in ultrathin devices

Abstract

The printed wick shows great potential in ultrathin heat pipe and vapor chamber fabrications. The recipe of printing paste is crucial to the thermophysical properties of the printed wick structures and the resulting heat transfer performance of the terminal devices. In this study, the dynamics of wettability, water absorption, and evaporation of two typical sintered wick structures with printing pastes A and B were investigated. Their typicality lies in that the wick structure A has uniform small pores, while the wick structure B has a bimodal porous structure. In our intended applications, the liquid line is 35–50 mm long. Therefore, the water absorption behavior in this range is of our interest. Wick A absorbs water faster in this range due to its higher capillary force, promising more suitable for liquid line construction. Wick B has higher evaporation cycling rate due to its bimodal design, which makes it more suitable for evaporator construction. As a comparison, the performance of copper mesh slumps during this range, greatly increasing the failure risk, and is thus unusable. In the end, we applied the printing pastes to the ultrathin loop heat pipe and distributed loop vapor chamber, revealing their potential in constructing increasingly complicated patterns for ultrathin heat dissipation devices.

Keywords

• Printed wick structure
• Wettability
• Water absorption
• Evaporation
• Ultrathin loop heat pipe
• Distributed loop vapor chamber