Laser Hole Drilling for Via Holes & Micro-Holes

A design calls for hundreds of small holes in a thin ceramic substrate, a glass wafer, or a stainless steel component. Mechanical drilling can produce them, but brittle materials crack under drill pressure, small bits wear and break, and hole size and edge quality change as tools dull. Electrical discharge machining (EDM) avoids some of these problems but requires a conductive workpiece and adds cycle time for fine features.

Laser hole drilling removes material with focused energy instead of a cutting tool. For via holes, through-holes, and micro-holes in delicate or hard materials, that difference expands what a designer can specify.

Key Takeaways

• No tool contact means no tool wear. Laser drilling removes material without touching the part, so hole quality stays consistent from the first part in a run to the last.
• Brittle and thin materials stay intact. With no drill pressure, ceramics, glass, and semiconductor wafers avoid the cracking and stress fractures that mechanical drilling can cause.
• Hole geometry depends on material and thickness. Entrance and exit diameters differ in laser-drilled holes, so drawings should state where the diameter tolerance applies.
• Slag needs a plan. Laser drilling leaves slag at hole entrances and exits, and post-drill lapping or polishing removes it before metallization or assembly.

Why Mechanical Drilling Struggles With Via Holes and Small Holes

As hole diameters shrink, the drill bit becomes the weak point in the process.

Tool Wear and Drill Breakage

Small bits flex, wander on entry, and break under load. They also dull with every hole, so diameter and edge quality at the end of a run differ from the start. Tool changes add downtime and introduce new variation.

Mechanical Stress on Brittle Materials

Downward force and vibration cause microcracks, exit chipping, and stress fractures in ceramics, glass, and semiconductor wafers. These defects reduce lot yields.

Friction Heat and Fixturing

Drilling friction can melt edges or thermally cycle glass and semiconductor materials, which may change their electrical and physical properties. Parts also need rigid clamping to resist drill torque, which is difficult for thin sheets, foils, and curved surfaces.

How Laser Hole Drilling Works

Non-Contact Material Removal

A focused laser beam delivers pulses of energy that heat the material past its vaporization point, removing it until the beam breaks through. An inert assist gas clears vaporized material from the hole. Nothing touches the part, so the process applies no mechanical force, needs minimal fixturing, and has no tool to wear out.

Small Heat-Affected Zone

Because the energy is concentrated in a small spot, the heat-affected zone (HAZ) around each hole stays small. This limits cracking, melting, and thermal stress in heat-sensitive materials. Different laser types, including CO2, YAG, and fiber lasers, suit different materials based on how well each material absorbs the laser’s wavelength.

Multiple Hole Diameters Without Retooling

Hole diameter is a programming parameter rather than a tool size. A single job can include a range of hole diameters without stopping to change tools.

Aspect Ratio and Hole Taper in Laser-Drilled Holes

High Aspect Ratio Holes

Aspect ratio compares a hole’s depth to its diameter. Mechanical drilling at high aspect ratios requires long, slender bits that deflect and break. Laser drilling has no physical tool, so it can produce deep, narrow holes with consistent results. It also handles angled, curved, and uneven surfaces, since there is no drill tip to walk off the entry point.

Entrance and Exit Diameter Differences

Laser-drilled holes have a natural taper. The beam enters from one side, so the entrance diameter tends to be larger than the exit diameter, and the difference grows as material thickness increases. When writing specs:

• State whether the diameter tolerance applies at the entrance or the exit.
• Expect entrance tolerances to widen on thicker material.
• Flag the critical side of the hole if the via will be filled, plated, or used for alignment.

For material-specific tolerances on metal parts, see the Design Guideline: Tolerances for Laser Cutting and Drilling Metals.

Materials and Applications for Laser Hole Drilling

PCB and Ceramic Substrate Vias

Laser drilling produces through-holes and vias in PCBs and in thick-film, thin-film, and as-fired ceramic substrates for RF, microwave, and microelectronic circuits.

Glass and Semiconductor Wafers

Thin, delicate sheets and wafers, including silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), and silicon carbide (SiC), can be drilled without the pressure that causes cracking.

Metals, Foils, Screens, and Filters

Stainless steel and other metals take small, repeatable holes, and thin foils can carry fine features for shields, masks, and stencils. Fine meshes and screen filters, such as those used in medical nebulizers, benefit from thousands of consistent holes.

Medical and Reactive Materials

Laser drilling uses inert gases with no chemicals, cutting fluids, or tool contact, which reduces debris and cleaning steps on sensitive components.

Managing Slag and Surface Quality After Laser Drilling

Where Slag Forms in Laser-Drilled Holes

Laser drilling is a non-contact process, but it still produces a byproduct. Material that melts instead of vaporizing can re-solidify as slag at the hole entrance, the exit, and along the interior wall. On substrates headed for metallization, slag at hole edges can interfere with film adhesion and lower circuit yields.

Post-Drill Lapping and Polishing

Lapping or polishing after drilling removes surface slag and entrance and exit slag, and it reduces loose slag inside the hole. Protective coatings applied before drilling can also shield the surface from spatter. When comparing suppliers, ask whether slag removal is part of the process or a separate step you need to arrange.

Precision Laser Hole Drilling Services at Accumet

Accumet provides micro laser hole drilling for ceramic substrates, metals, plastics, glass, and semiconductors from its facility in Devens, Massachusetts.

Laser Drilling Tolerances for Ceramic Substrates

On ceramic substrates, Accumet drills holes as small as 0.005″ with diametric tolerances as close as ±0.001″, and hole-to-hole tolerances of ±0.001″ that are non-cumulative. Tighter tolerances are available on request.

Substrate Drilling and Slag Removal From One Source

Accumet drills thick-film, thin-film, and as-fired substrates, so you don’t need to buy substrates from one source and send them to another for laser processing. After drilling, Accumet laps or polishes substrates to remove surface slag and hole entrance and exit slag, supporting better adhesion and higher circuit yields. A water-soluble protective coating is also available.

Laser Drilling Metals and Foils

For metal parts, laser-drilled hole diameters can be held to ±0.003″ measured on the exit side. Thin metal foils can be drilled with holes as small as 0.003″, depending on thickness.

Certified Quality Systems

All work is performed under AS9100 and ISO 9001 certified quality systems.

Learn more about Accumet’s industrial laser hole drilling capabilities, or request a quote to discuss your hole sizes, materials, and tolerances with the Accumet team.

Related reading:

everythingRF Spotlights Accumet’s Precision Laser Capabilities
5 Takeaways From everythingRF’s Interview With Accumet on Laser Machining, Ceramic Processing, and RF Substrates
5 Keys to Laser Processing of Ceramic Substrates