Increasing demands emerging from the automotive, medical, electronics and precision instrument industry require high quality holes with diameters in the range of 25 µm to 500 µm (0.001 to 0.020”). In comparison to wire EDM, chemical etching, mechanical machining, electroforming, laser hole drilling is non-contact and flexible. Laser drilling provides high aspect ratios and the capability to drill all types of material, including ceramics, silicon, diamond, and polymers. EDM is a highly precise tool, however it lacks the speed demanded that is important for high volume production.
Laser drilling requires lasers with close to diffraction-limited high beam quality in order to extremely tightly focus the beam over a long depth-of-focus. There are two ways of generating holes: percussion and trepanning drilling. Laser percussion drilling is typically used for hole diameters similar or slightly larger than the beam spot diameter, while trepanning drilling can be applied for generating holes having diameter significantly larger than the beam spot diameter.
Percussion drilling is carried out by firing a single pulse or a defined number of pulses, while the workpiece is held stationary. The most popular drilling lasers are pulsed Nd:YAG lasers. Their high pulse peak powers remove material mostly through vaporization. The vapor also builds up pressure that also pushes molten material out of the hole.
It is advantageous to use short pulsed lasers that heat up and remove a small volume very quickly with each pulse. In general, shorter pulsed lasers work better than longer pulsed lasers. Higher power density is better as long as plasma shielding effects are not significant. Due to enhanced absorptivity, visible and ultraviolet Q-switched lasers work better than infrared lasers, but the production throughput is low due to the limited average output power of these lasers.
Excimer lasers, second and third harmonic of Nd:YAG or Nd:YVO4 lasers with pulse duration in range of 10 to 100 ns have found wide applications in micro hole drilling, while microsecond pulsed CO2 lasers are used for micro drilling of ceramics. Lamp pumped Nd:YAG lasers, providing 0.1 to 20 ms pulse duration at 1.064 µm and up to several kW in average power are typically used to drill holes of 0.2 to 0.8 mm diameter through most metals up to several millimeters thick.
Hole diameter and hole taper can be modified by increasing or decreasing pulse energy or pulse duration. The hole taper can also be minimized by proper beam focusing. The roundness of the percussion-drilled holes is determined by the spatial intensity distribution. Round apertures or spatial filters are used to improve hole roundness. Repeatability of percussion-drilled holes is as good as the pulse-to-pulse stability.
Trepanning drilling is to cut a hole around its periphery by moving the workpiece with an xy-table or the beam with a trepanning head. The speed of drilling is dictated by the material removal rate and the relative laser/workpiece moving speed. It is possible to trepan holes with one or more circles to improve the hole quality or to produce holes in thick materials. For high throughput drilling or drilling of conical holes, trepanning heads using galvanometer scanners, off-axis rotating lenses or rotating wedge prisms are used. In this case, the focused laser beam is rotated at very high rates (up to 40,000 rpm) around a center point and exactly describes the hole geometry.
Holes drilled by trepanning are cleaner on their edges. Both hole roundness and hole diameter’s repeatability are high. However, a small fluctuation of pulse energy (pulse to pulse stability) still can cause a change in hole diameter. Quarter wave plates are introduced into the beam path to obtain circular from linear polarization as similar to fine cutting, trepanning drilling is beam polarization dependent.
- Using diffractive, refractive or reflective optical elements to produce arrays of micro holes
- Drill-on-the-fly by synchronization of motion system with pulse repetition rate
Area of expertise
KJ Laser Micro Machining provides quick turn-around laser micro drilling services. Our expertise covers a wide range of laser drilling technology, including beam shaping, steering and polarization as well as water soluble coating, suction and assist gas blowing for debris free laser micromachining. We are able to apply different laser wavelengths, pulse regimes and post-processing to produce clean and debris-free holes at diameter tolerances up to 0.0005″ (12.5 µm). Typical hole diameters are between 20 – 500 µm and hole depths up to 2 mm.
Almost any type of material can be micro-drilled such as stainless steels, super hard materials (e.g. polycrystalline diamond, carbides and nitrides), transparent materials (e.g. glass, sapphire), plastics and semiconductor materials.
Sub-contract micromachining and R&D
Our laser drilling services provide world-class micro machining technology for the mass production of thousands of parts per month. We can also play a vital role during your product design and development period by conducting scientific and innovative R&D investigations in laser micro drilling.
Our variety of far-infrared, infrared, green and UV lasers allows the selection of an appropriate laser wavelength for your particular laser processing application, whether the material is metals, plastics, ceramics or semiconductors.
System development and process automation
KJ Laser Micromachining has the capability to design and develop customized laser micro drilling systems for the high-volume and automated parts manufacture.