Ultraviolet picosecond laser fabrication of Cu/diamond composite microchannel heat sinks for enhanced thermal management

Diamond-particle-reinforced copper matrix composites (Cu/diamond composites) are attractive heat-sink materials for high-power electronic packaging. However, their pronounced phase heterogeneity makes it challenging to fabricate microchannels with well-controlled geometry and reliable thermal performance. To address this coupled design–fabrication challenge, this study develops an integrated framework combining thermal-hydraulic evaluation and picosecond-laser machining for Cu/diamond composite microchannel heat sinks. Conjugate heat-transfer simulations were first conducted to parametrically evaluate the effects of channel width, depth, and inter-channel spacing on thermal-hydraulic performance, from which a practical target geometry was selected by considering thermal performance, hydraulic resistance, structural requirements, and fabrication feasibility. To realize the target geometry, a transient localized-ablation model was established to elucidate the phase-dependent response of the Cu/diamond composite under laser irradiation. The simulations revealed preferential ablation of the copper matrix and localized protrusion of diamond particles, explaining the difficulty in achieving uniform channel profiles. Single-factor experiments were subsequently conducted to quantify the effects of laser power, number of scanning passes, scanning speed, repetition frequency, and defocusing distance on groove width and depth. A Particle Swarm Optimization–Backpropagation (PSO-BP) neural network was further developed to describe the nonlinear relationship between processing parameters and groove dimensions, with maximum relative prediction errors of 9.0% for depth and 1.6% for width, thereby providing a quantitative basis for identifying suitable processing windows. Based on the combined thermal-hydraulic and fabrication considerations, a practical microchannel configuration with a width of 0.25 mm, a depth of 1.2 mm, and an inter-channel spacing of 0.25 mm was adopted. A two-stage multi-line scanning strategy combining edge-first scanning and edge trimming was then implemented, producing microchannels with an average width of 255 μm, a depth of 1207 μm, and a sidewall taper below 2°. Convective heat-transfer experiments further demonstrated that the fabricated Cu/diamond heat sink maintained the peak heat-source temperature below 160 °C under an applied heat flux of 600 W/cm 2 at a total coolant flow rate of 2.0 L/min. These results demonstrate an integrated route from thermal-hydraulic geometry evaluation to controllable laser fabrication and experimental performance validation for Cu/diamond composite microchannel heat sinks.