Fabrication of large aspect ratio single crystal diamond microchannel by femtosecond laser

Abstract

As heat dispersing materials, Diamond has high thermal conductivity, extremely low coefficient of thermal expansion, low coefficient of friction, and good chemical stability, which have broad application prospects in the field of highpower device heat dissipation. This study aims to address the inability of traditional laser processing methods to meet the processing requirements of high aspect ratio diamond heat dissipation microchannels. Based on a femtosecond laser fiveaxis machining system, a five-axis attitude alternating machining method is used to study the forming size, surface roughness, and aspect ratio of femtosecond laser surface microchannels, and to compare it with the direct machining method using a galvanometer. The experimental results show that using a super depth of field optical microscope for detection, the cross-sectional shape of diamond microchannels processed using a galvanometer direct machining method is triangular, with an edge unilateral taper of 62 °. The cross-sectional shape of diamond microchannels processed using a five axis attitude alternating machining method is ladder shaped, with a maximum edge unilateral taper of 88 °, approaching a vertical state of 90 °. As the width of microchannels increases, the unilateral taper value increases. By using a confocal microscope, the roughness of diamond microchannels processed using a galvanometer direct machining method is Ra0.88, and the optimal roughness of diamond microchannels processed using a five axis attitude alternating machining method is Ra0.29. The use of five-axis attitude alternating machining method is superior to the use of galvanometer direct machining in terms of unilateral taper and roughness. Finally, diamond rectangular microchannels were prepared using a five axis attitude alternating machining method, with a maximum aspect ratio of 10.7:1 and a maximum depth of 1.072mm.