Investigations on laser micromilling of circular micro pin fins for heat sink cooling systems

Micro pin fin heat sink has been widely utilized to cool high-heat-flux devices in a variety of industrial fields, such as microelectronic, nuclear, and aerospace devices. The fabrication of micro pin fins is critical for the development of pin fin heat sink cooling systems. In this study, a laser micromilling method is proposed to process circular micro pin fins (CMPFs) in pure copper plates. A pulsed fiber laser is used, and multiple-pass reciprocating scanning is conducted. The effects of processing parameters, i.e., laser output power, scanning speed, and scanning times, on the geometric dimensions of CMPFs are systematically assessed together with the metal removing mechanisms. The results show that the height of micro pin fins increased greatly with increasing laser output power and scanning times, while it decreased with the increase in scanning speeds. Nevertheless, a reversed trend was noted for the bottom width between two pin fins. The top width was notably dependent on the laser output power. These results are believed to be closely related to the energy density and remelting process during the laser micromilling process. Furthermore, the effects of pin fins diameter on the geometric dimensions of CMPFs were also explored. This study sheds some lights on the fabrication of circular micro pin fins for their promising applications in heat sink cooling systems and is believed to be of practical importance.