###### Abstract  
For the problem of high waste heat in the active area of high-power VCSEL arrays and the difficulty of heat dissipation, we took advantage of laser 3D printing technology and combined it with the relevant principles of fluid-structure coupling, three kinds of microchannel heat sink with different structures of pin-fin, honeycomb, and double-layer reflow were designed. The heat dissipation capacity of three kinds of heat sinks to the heat flux density 200 W/cm\({}^{2}\) VCSEL array and the influence of the key characteristics of the microchannel on the heat dissipation capacity was studied. The results show that the double-layer reflow microchannel heat sink has the strongest heat dissipation capability, with the minimum thermal resistance value of 0.258 \({}^{\circ}\)C/W when the microchannel diameter and the cooling mass flow rate were 0.5 mm and 24 L/h, respectively. The inner wall roughness of the pure copper microchannel prepared by 3D printing technology was 7.08 \(\upmu\)m, and the heat sink thermal resistance was reduced by 0.7% compared with the smooth channel wall. The deviation of the microchannel diameter from the design size (500 \(\upmu\)m) was \(-\)10 \(\upmu\)m, and the heat sink thermal resistance was reduced by 0.8% compared to the theoretical value, which shows that the surface roughness and size deviation of the 3D printed microchannel had beneficial effect on enhancing heat dissipation. The actual thermal conductivity of the 3D printed pure copper after heat treatment was 310.4 W/m-K, at which point the thermal resistance was 0.306 \({}^{\circ}\)C/W, and the maximum temperature was 35.3 \({}^{\circ}\)C, which satisfied the operating temperature range of the chip. This study provides a theoretical basis and implementation method for the fabrication of heat sinks for high-energy VCSEL arrays using laser 3D printing technology. VCSEL array; 3D printing; microchannel; thermal management +
Footnote †: journal: Applied Sciences
[PERSON] and [PERSON] [4] first proposed the concept of liquid-cooled microchannel heat sink in 1981, and achieved an excellent heat transfer coefficient of up to 10 W/cm\({}^{2}\) - K, but the disadvantage of single-layer microchannels was the uneven heat distribution along the channel. [PERSON] [5] designed a double-layer microchannel structure, which had a certain effect on improving heat dissipation uniformity. [PERSON] et al. [6] studied the effect of dual inlets at different positions and spacing on the heat transfer performance of microchannel heat sink, the result shows that splitting a single inlet into two could effectively alleviates the phenomenon of uneven flow distribution on the heat sink and improves the heat dissipation capacity. [PERSON] et al. [7,8] prepared a diamond microchannel heat sink with excellent heat dissipation capability using porous copper as a substrate. Inspired by biomimicry, some scholars refer to some excellent structures in nature. [PERSON] [9] designed a diamond-shaped microchannel, [PERSON] [10] introduced microneedle fins of different shapes into microchannels, [PERSON] et al. [11] designed a double-layer microchannel heat sink with pyramid-shaped disturbance structure. Compared with the ordinary double-layer trapezoidal microchannel heat sink, the double-layer trapezoidal microchannel heat sink with pyramid-shaped disturbance structure had a stronger heat transfer capacity. The study found that the microchannel heat sink has the advantages of high specific surface area, large convective heat transfer coefficient, and requires just a small amount of coolant. However, it is also shown that the poor channel structure causes uneven temperature distribution, which, in turn, leads to significant temperature gradients at the heat source surface, optimizing the structural design to increase the contact area between the coolant and the heat sink can solve this problem and help to further improve the heat dissipation capability of the microchannel heat sink.