Laser Processing High Aspect Ratio Groove Wick for Improving the Thermal Performance of Flat Micro Heat Pipe

Groove wick micro heat pipes are characterized by light weight, fast thermal response and high permeability which are in line with the current trend of lightweight electronic devices. As an efficient heat transfer device, flat micro heat pipes (FMHP) have been widely used for thermal management of electronic devices because of their excellent thermal performance and high reliability. In this paper, FMHP with microgrooves wick was processed on the copper substrate by 1064nm pulsed fiber laser. The influence of various laser processing parameters including pulse duration, scanning speed, scanning interval and the number of scanning cycles on the size and morphology of groove structures have been studied. The grooves with different aspect ratio are obtained by changing the number of scanning cycles, and the effects of aspect ratio on the droplet flow velocity are investigated respectively. Experimental results indicate that grooves with larger aspect ratio exhibits greater capillary pressure which leads to a faster droplet flow velocity. Groove wick with the aspect ratio of 2.5 whose average groove depth of 125 mu m and groove width of 50 mu m is fabricated successfully, and the FMHP with the groove wick of this type have the best heat transfer property.