Experimental and simulation study of UV laser micromachining high-aspect-ratio microchannels of diamond heat sink

Diamond emerges as the ultimate heat sink material for ultra-high-heat-flux devices, but its extreme hardness obstructs fabrication of deep microchannels (<200 μm width, >1 mm depth) with sub-1° tapers using conventional methods. While laser ablation offers precision, existing approaches face inherent trade-offs: spatial beam shaping enables high aspect ratios but requires complex optics and struggles with direct ablation of diamond; multi-axis scanners facilitate angular control but incur high costs and lack scalable strategies for complex diamond heat sinks. To overcome these limitations, we demonstrate an efficient Symmetric Profile-Interior (SPI) strategy enabling precision diamond micromachining via commercial UV nanosecond lasers and 2D galvanometers. Combined experimental and numerical analysis reveals that V-shaped degradation and asymmetric sidewalls originate from cumulative thermal imbalance during ablation. The SPI strategy counteracts this by implementing bidirectional scanning to eliminate thermal gradients and decoupling profile/interior ablation to delay geometric degradation, thereby achieving microchannels with depths exceeding 1236 μm (over three times the Rayleigh length) and taper angles of less 0.5°. This approach delivers ±20 μm depth control accuracy across 400–1200 μm targets and enables fabrication of cm-scale polycrystalline/single-crystal diamond heat sinks. The SPI strategy establishes a hardware-agnostic paradigm for diamond structuring, with direct applicability to shorter-pulse lasers and other refractory materials.