Glass substrates are emerging as key platforms for next generation advanced packaging owing to their favorable dielectric properties, surface flatness, dimensional stability, and thermal expansion compatibility with silicon. However, laser fabrication of micro-holes and micro-grooves becomes increasingly challenging as feature dimensions decrease, aspect ratios and array densities increase, and low damage, high dimensional consistency, and subsurface integrity must be maintained simultaneously. This review examines laser micromachining of glass substrates from the perspective of advanced packaging requirements. The interaction mechanisms of ultrafast and long pulse lasers with glass are first discussed, including nonlinear ionization, plasma evolution, energy deposition, thermomechanical response, melting, vaporization, and stress and shock wave induced damage. Feature formation is then related to heat accumulation, residual stress, cracking, and subsurface damage, together with their characterization and implications for subsequent integration. Laser induced chemical etching, filament machining, and direct laser machining are quantitatively compared in terms of achievable dimensions, aspect ratio, taper, roughness, processing rate, and parameter dependent quality evolution. Their applications in advanced packaging and high frequency electronics, microfluidics and biodetection, and photonic integration and precision sensing are further discussed by linking machining quality to device function and reliability. Finally, challenges in controlled energy deposition, thermomechanical damage, atomistic modeling, process monitoring, data driven prediction, and packaging oriented process windows are examined, together with future directions involving optical field control, multi laser processing, and auxiliary field assistance. This review connects laser–glass interaction mechanisms, processing capabilities, and device requirements to guide the scalable manufacturing of glass microstructures.
Ultrashort-pulse laser peening, an emerging surface-engineering technique, has been hindered from widespread industrial adoption by its tendency to roughen or damage surfaces. Here, we shift the processing paradigm from the traditional high-energy, single-pulse strategy to a low-energy, high-repetition regime, which successfully tailors a subsurface nanogradient in copper while maintaining relatively high surface integrity. Systematic investigation reveals how pulse duration, wavelength, and fluence govern microstructural evolution. Pulses ranging from 500 fs to 1 ps prove particularly effective, as the shock intensity could trigger substantial nanocrystallization, while still maintaining a relatively longer shockwave duration. Moreover, the 513-nm green laser exhibits a comparative advantage in fabricating highly homogeneous gradient nanocrystalline structures, while 1026‑nm near‑infrared laser sources are relatively more proficient at engineering a wider repertoire of controllable micro‑ to nanoscale subsurface features. The ultrashort-pulse laser-induced typical nano gradient architecture, spanning from an amorphous layer to dislocation-rich coarse grains, is consistent with a nanotwinning-assisted dynamic recrystallization mechanism under extreme strain rates, different from conventional dislocation-dominant processes, highlighting the unique nanoscale tailoring capability of ultrashort-pulse laser peening. This work establishes a new paradigm for modifying copper surface with engineered nanoscale gradients, offering transformative potential for electronics and aerospace.
Joining ultra-high-strength press-hardened steel (PHS) to high-pressure die-cast aluminum (HPDC Al) is critical for lightweight hybrid bodies, yet remains challenging: fusion welding generates brittle Fe–Al intermetallic compounds (IMC), while self-piercing riveting (SPR) struggles to pierce PHS and often cracks HPDC Al. Here, we propose an active expulsion-assisted resistance spot welding (AERSW) process with a purpose-designed cold-stamped rivet. Unlike conventional resistance rivet welding that relies on progressive mechanical extrusion of softened aluminum, AERSW actively induces transient melting and eruptive expulsion of the aluminum alloy, drastically reducing material resistance and freeing the weld spot. This enables the rivet to fully penetrate the HPDC Al and directly contact the PHS, while the deep-ring rivet cap captures the expelled aluminum in real time, forming a fully martensitic nugget through the direct fusion of the dissimilar ferritic rivet and the 2.2 GPa PHS. This nugget, with a stable diameter of 5.29 ± 0.10 mm, ensures robust joint formation. The AERSW joint achieves a peak load of 12309.7 N and an energy absorption of 17.6 J, significantly outperforming SPR Al/steel and SPR Al/Al joints. The fatigue life is slightly lower than that of SPR Al/Al joints due to solidification defects in the annular aluminum melted zone, yet the 10⁷-cycle fatigue limit remains comparable, and the performance is competitive among reported Al/steel joining methods.
Diamond tools are among the most promising cutting tools for precision machining of difficult-to-machine materials. However, their widespread application is severely restricted by rapid mechanochemical wear induced by graphitization and amorphization transformations under high-load cutting conditions, particularly during machining of ferrous materials. In this study, an in situ covalently integrated diamond–nano-graphite–graphene architecture is implemented on commercial diamond tools through a combination of laser-induced graphitization and flywheel-assisted mechanical cleavage. This tool-level implementation enables direct integration of the CDGG architecture while remaining compatible with the subsequent conventional tool-manufacturing route. Cutting experiments demonstrate that the obtained tool effectively suppresses mechanochemical wear and improves the tribological conditions at the tool–workpiece interface. Compared with the pristine diamond tool, the modified tool reduces the main cutting force, crater wear depth, and surface roughness by up to 44%, 75%, and 32%, respectively, during dry machining of hardened AISI 52100 steel. Molecular dynamics simulations combined with experimental characterization were further employed to examine the underlying interfacial processes. The results suggest that the graphene/nano-graphite architecture contributes to friction reduction and mechanochemical-wear suppression through interfacial lubrication and physical shielding of the diamond substrate. The graphene-rich structures undergo progressive deformation and consumption near the cutting edge while retaining partial structural integrity away from the edge. These findings demonstrate the feasibility of integrating the CDGG architecture into practical diamond cutting tools and provide mechanistic insight into its role in improving diamond-tool performance during ferrous-material machining.
Ultrasonic vibration-assisted milling (UVAM) is an effective hybrid machining technology for difficult-to-machine materials and complex components. However, to address the machining challenges of SiCp/Al thin-walled parts (TWPs) with complex structures such as webs, ribs, and corners in engineering applications, the mechanisms by which UVAM characteristics affect machining deformation and surface integrity remain an open problem. To address this challenge, this study develops a hybrid machining platform for UVAM of SiCp/Al TWPs, establishes the kinematic equations of the cutting edge under ultrasonic vibration, proposes a physical model of periodic tool-workpiece interaction, and extends an analytical method for machining deformation prediction. Results indicate that UVAM reduces the maximum macroscopic residual stresses in the X and Y directions to −98.4 MPa and −123.2 MPa, respectively, which is closely associated with suppressed subsurface plastic deformation, reduced lattice distortion, and inhibited dislocation accumulation. The bending deformation of TWPs is governed by the bending moments and aspect ratio, while UVAM combined with optimized machining strategies effectively reduces the overall deformation. Moreover, by altering the material removal mechanism, UVAM decreases the surface roughness Sa of the six-frame and long-beam parts by 19.05% and 24.53%, respectively, while suppressing subsurface particle agglomeration and alleviating tool wear, thereby achieving the synergistic improvement of machining deformation and surface integrity. This study clarifies the intrinsic links of "UVAM process – residual stress evolution – machining deformation" and "UVAM process – material removal mechanism – surface integrity", providing new insights into the high-precision, low-damage machining of complex-structured metal matrix composite components.
