Key technologies for laser microvia machining in detail

In the field of micro- and nano-manufacturing, the precision of apertures directly determines product performance. 

From the micron-sized flow channels of aerospace fuel nozzles to the nanopore arrays on the surface of medical scaffolds, laser microvia machining technology is driving precision manufacturing to the submicron level. 

This paper analyzes the principle, technical difficulties, mass production applications and cutting-edge direction.

Processing principle:

heat conduction and nonlinear absorption mechanism 

Traditional laser hole processing relies on the thermal effect of nanosecond pulsed laser, through the material melting or vaporization to achieve hole formation. 

This type of process is suitable for millimeter to hundred micron level hole diameters, but the problems of carbonization and microcracks caused by heat-affected zone (HAZ) limit its application in sensitive scenarios such as semiconductor wafers and biological materials.

Ultrafast lasers (femtosecond/picosecond class) change the processing mode through a nonlinear absorption mechanism: 

Multiphoton ionization dominates material removal when the pulse width is shorter than the material electron-lattice thermal relaxation time (<10 ps).

For example, femtosecond laser processing of fused silica, the focal region generates plasma, realizing sub-micron precision, near-zero thermal damage cold processing, and the hole wall roughness can be controlled at Ra<0.1 μm.

Technical difficulties:

Currently, the main technical bottlenecks are concentrated in two aspects:

1.Depth-to-diameter ratio limitations

When the processing depth of Gaussian beam exceeds 500 μm, the Rayleigh length limitation leads to insufficient energy at the bottom of the hole. 

The use of Bessel beam (no diffraction characteristics) can increase the effective processing depth by 3-5 times, such as MEMS pressure sensor deep hole processing has been realized in 50:1 depth-to-diameter ratio.

2.Complex structure molding

Microfluidic chips need to be tapered holes, spiral holes and other shaped structures. 

Through the spatial light modulator (SLM) dynamic modulation of the wavefront phase, programmable control of the laser focus three-dimensional trajectory. 

A German research institute in the PDMS material processed cone angle precision ± 0.5 ° micro-flow channel, fluid efficiency increased by 40%.

Mass production applications:

Mass production process needs to consider the accuracy and economy:

1.Automobile fuel injector processing

Using green nanosecond laser (pulse width 20 ns), single hole processing time <50 ms, average daily capacity of 100,000 holes, the cost of 0.02 yuan / hole;

2.Heart stent microporous processing

Femtosecond laser (pulse width 300 fs) with gas-assisted system, in 316L stainless steel surface processing diameter 30 ± 2 μm microporous, heat-affected zone <2 μm, but the cost of equipment exceeds 5 million yuan, the cost of a single hole 1.2 yuan.

3.Composite processing technology has become a new trend

For example, Japan’s Fanuc laser – electrolytic composite process, the first nanosecond laser pre-processing, and then through electrochemical polishing will be the hole wall roughness from Ra 3.2 μm down to 0.4 μm, the efficiency of 6 times.

Frontier direction:

Ultra-fast laser in transparent materials within the three-dimensional modification capabilities are expanding application scenarios:

1, the U.S. Lawrence Laboratory in the sapphire internal processing of 5 μm diameter, depth of 1.2 mm three-dimensional micro-channels for high-power laser heat dissipation;

2, the Chinese Academy of Sciences, Xi’an Institute of Optical Machinery developed laser-induced reverse deposition (LIRD) technology, can be generated in the inner wall of the micro-hole silicon nitride insulating layer, applied to terahertz waveguide devices.

When the aperture enters the submicron scale, the process is no longer just the physical removal of material, but also the precise manipulation of quantum effects such as electronic states and photonic-phonon coupling. 

With the emergence of new tools such as attosecond lasers and topological beams, micro and nanohole processing technology is breaking through the classical optical limit, laying the manufacturing cornerstone for future industries such as quantum chips and bionic organs.

In this game of precision and cost, whether Chinese manufacturers can realize breakthroughs in core components such as ultra-fast lasers and high-precision motion platforms will determine the final pattern of the new landscape of global micro-nano manufacturing.

Conclusion

Laser microvia machining is at the forefront of precision manufacturing, continuously pushing the boundaries of micro- and nano-scale fabrication. 

The transition from traditional nanosecond pulsed lasers to ultrafast femtosecond lasers has enabled near-zero thermal damage processing, achieving submicron precision essential for advanced applications in aerospace, medical devices, and semiconductor manufacturing.

Despite significant advancements, key technical challenges remain, particularly in achieving high aspect ratios and complex 3D structures. 

Innovations such as Bessel beams, spatial light modulators, and hybrid processing techniques are addressing these limitations, enabling mass production with improved efficiency and cost-effectiveness.

Looking ahead, the integration of ultrafast laser processing with emerging quantum and photonic technologies is set to redefine the possibilities of micro- and nanofabrication. 

The ability to manipulate electronic states and photonic interactions at the submicron level will open doors to next-generation applications, from quantum chips to bionic materials.

For Chinese manufacturers, the ability to develop core technologies—such as high-performance ultrafast lasers and precision motion platforms—will be a decisive factor in shaping the global landscape of micro-nano manufacturing. 

As the competition intensifies, breakthroughs in these areas will not only enhance industrial capabilities but also establish leadership in the future of precision engineering.