###### Abstract
Although the microchannel water-cooled heat sink obtains obvious advantages, limited by the high difficulty of precision machining of microchannels, the application of microchannel water-cooling technology in the field of VCSEL chip cooling is not mature yet. At present, the microchannel heat sink is usually produced by using plasma etching technology to etch different hollow structures on multi-layer high thermal conductivity rectangular sheets, respectively, then, through hot press welding technology for precision welding. However, the multi-layer welding will also introduce additional thermal resistance, which will reduce the mechanical strength and service life of the heat sink manufactured by hot-press welding. For this situation, it is urgent to introduce a new technology to break through the current technological bottleneck. Laser 3D printing technology is an additive manufacturing technology based on the idea of near-net forming [12, 13, 14], which uses laser as the energy source to scan the metal powder bed layer by layer according to the planned path in the 3D CAD slice model, and the scanned metal powder is melted and solidified to achieve metallurgical bonding and finally obtain the metal parts of the model design. 3D printing technology has the characteristics of flexible design and high degree of freedom for complex structures. Compared with the traditional laminated soldering technology, 3D printing one-piece formed channel structure avoids the additional thermal resistance introduced by multi-layer pressed soldering and the risk of solder diffusion into the microchannel blocking the channel. Therefore, the use of 3D printing technology to prepare microchannel heat sinks is expected to drive a significant development in chip thermal management. In 2011, the Fraunhofer Institute in Germany fabricated a steel, titanium, and aluminum alloy heat exchanger for automobiles by 3D printing technology. The experimental results show that 3D printing technology increases the possibility of complex and precise design fabrication [15]. In 2019, the University of Nottingham proposed a method to fabricate pure copper under a low-power small laser spot diameter 3D printing device and obtained parts with a high density of 85.8% and high electrical conductivity [16], providing a research idea to fabricate pure copper parts under a low-power device. In 2021, a topologically bionic pure copper microchannel heat sink was fabricated by 3D printing of fused wire fabrication at Texas State University, providing a new way to manufacture heat sinks [17]. [PERSON] et al. studied the preparation of single-layer diamond-shaped fork-row microchannel heat sink using laser 3D printing technology to dissipate heat for a chip with a heat flux of 60 W/cm\({}^{2}\). The results show that the maximum temperature of the heat source surface is 75.62 \({}^{\circ}\)C, and the experimental results are in good agreement with the simulation results. This work can provide a comparative reference for the development of our research [18]. Based on the design principles of 3D printing technology and the theory of fluid-solid coupling, this paper designs three types of heat sink with microchannel structures: honeycomb type, pin-fin type, and multi-layer reflux type. FEA software ANSYS was used to simulate the influence of heat sink structure, coolant flow and hydraulic diameter of microchannel on-chip thermal resistance and temperature distribution. The influence of key characteristics (dimensional accuracy, surface roughness) and thermal conductivity of 3D printed samples on the heat sink's heat dissipation capability was also studied, providing theoretical support and implementation methods for the preparation of heat sinks for high-power VCSEL arrays using 3D printing technology.