Strategy-driven water-jet guided laser machining for high-aspect-ratio curved microchannels on copper

Curved, high-aspect-ratio microchannels on copper are integral to next-generation thermal-management architectures for advanced electronic packaging. However, achieving deterministic fabrication remains a formidable challenge, owing to copper’s inherent high optical reflectivity, rapid heat diffusion, and strong plasticity, which collectively compromise throughput, geometric fidelity, and sidewall integrity. Herein, water-jet guided laser (WJGL) machining emerges as a highly efficient and precision-driven methodology to circumvent these limitations. A three-dimensional photothermal coupling model—functioning under an idealized unrestricted drainage baseline—is established and experimentally validated. This comparative approach definitively elucidates that the ultimate machining depth in single-row scanning is fundamentally constrained by a hydrodynamic-optical bottleneck, wherein restricted drainage disrupts the gas–liquid interface and induces total internal reflection (TIR) breakdown. To transcend these physical constraints, a strategy-driven multi-row scanning paradigm is systematically investigated. The present study demonstrates that the in–out scanning strategy dynamically reconfigures transient spatial boundary conditions by proactively establishing lateral drainage corridors. This inward relief mechanism stabilizes the jet interface and sustains guided TIR transmission. Consequently, this underlying mechanism substantially enhances morphological consistency, yielding near-vertical, symmetric sidewalls with an areal roughness (Sa) below 2 μm. Capitalizing on this optimized strategy, diverse complex geometries—including wavy, zigzag, and stepped curved microchannels—are reproducibly fabricated with a representative width of ≈250 μm, a depth of ≈4.1 mm, and a high aspect ratio of ≈16:1. This work provides a predictive physical framework and a robust scanning-strategy paradigm, positioning WJGL as a compelling platform for the precision manufacturing of copper-based functional microstructures with minimal thermal damage.