Microvia drilling is where laser throughput meets substrate reality

Every via must stop cleanly on a copper pad a few micrometres away. Throughput is set by how reliably the process finds that stop, not by how fast it drills.

By LasersNews Desk·24 Jul 2026·2 min read

A series of microscopes on a lab table, ideal for scientific research and education. — Photo by Vladimir Srajber on Pexels

High-density interconnect substrates need vias between layers, and at current densities those vias are laser-drilled. A modern substrate may need hundreds of thousands of them, so throughput matters enormously. What limits throughput is rarely the drilling rate.

The stopping problem

A blind microvia passes through dielectric and must stop on the copper pad beneath. Drill too little and the dielectric is not cleared, leaving residue that prevents plating adhesion. Drill too much and the pad is damaged or perforated.

The window is narrow because the dielectric thickness varies across a panel, and because copper and dielectric absorb very differently. The process must be self-limiting enough to tolerate that variation.

How wavelength choice interacts

CO2 lasers ablate dielectric efficiently and are largely reflected by copper, which provides natural stopping. But the wavelength cannot produce the smallest via diameters, and it does not remove copper when a copper-clad layer must be opened.

UV solid-state lasers produce far smaller features and remove copper, but that also removes the natural stop, so the process depends on controlled pulse counting and monitoring.

Many production lines use both: UV to open the copper layer, CO2 to clear dielectric down to the stop pad.

Where the time actually goes

The drilling itself is fast — microseconds per via. Time goes into positioning between vias, into panel alignment and distortion compensation, and into inspection.

Panels distort during processing, so the drill positions computed from the design file do not match the physical panel. Systems measure fiducials and compute a distortion map, and that measurement and correction is a substantial share of cycle time.

The inspection burden

A defective via is invisible until plating fails, so inline inspection is standard. That inspection is often the throughput constraint, and it is why via drilling systems are sold as measurement systems with a laser attached rather than the other way round.

Where it is heading

Advanced packaging is driving via counts and densities upward faster than substrate technology is simplifying. The pressure is on positioning accuracy and inspection speed, not on the ablation physics, which has been adequate for some time.

This article was produced by the LasersNews AI desk and reviewed by our editors.