Development of high-efficiency flexible heat pipe device for thermal management in foldable phones

Conventional flexible heat pipes (FHPs) are limited by stress differences between the inner and outer sides, and plastic deformation of their flexible shells can lead to blocked vapor channels and stress damage, making it difficult to realize their full thermal management potential in small, compact, and flexible consumer electronics devices. In this paper, a flexible heat pipe is developed with a multi-directional bending corrugated structure flexible shell and a self-supporting structural wick as the core components and deionized water as the working fluid. It has high efficient heat transfer performance and excellent bending durability. The evolution of the microscopic morphology of the flexible heat pipe and the decay process of the bending durability are revealed using visualization and quantifiable techniques. The experimental results show that the heat pipe possesses 0°–180° spatial heat transfer characteristics with a minimum thermal resistance of 1.77 °C/W and a bending life of 5000 times. The flexible heat pipe is designed to be suitable for foldable phones with cyclic bending, and meets the thermal management requirement of cross-axis heat transfer using “vapor-liquid” two-phase high-efficiency heat transfer. Compared with the copper foil cooling solution, the flexible heat pipe solution can reduce the chip temperature by up to 23.2 °C, which improves the temperature uniformity of the body.