Laser Drilling

"Over 1 billion holes drilled annually"

How Laser Drilling Works
Depending on the drilling application, LLTI has a variety of commercial wavelengths from (UV to IR) that could be adapted to achieve best quality fit and finish. There are two common techniques used for laser hole drilling; image projection and direct write. Both these techniques could be used in conjunction with percussion or trepanning to develop the most efficient method. Choosing a method depends on type of the hole (blind hole vs. through or a hole vs. slot), depth requirement, thickness, hole diameter, number of holes, edge quality and production quantity.

Image Projection (Mask Illumination) vs. Direct Write
Mask illumination in short is to use an imaging lens to image a mask at a plane other than that of the focal point of the lens. This process differs from direct write technique in the fundamental premise that in mask illumination, a mask is imaged at its conjugate plane opposed to in direct write, where the laser beam is used at its focal point. Mask size and shape provide control of the hole geometry, size and shape. This enables added capability to produce multiple holes in one mask or make complex features on a large area using coordinated motion between mask and image plane. In direct write, the focal spot is moved around (using galvo scanner) holding the part steady or part is moved in reference to the laser beam (fine-kerf cutting) to achieve the desired feature sizes. In image projection, the extent of demagnification develops the required energy density to machine a particular material in contrast to direct write, the energy deposited at the focal plane complemented by assist gas or multiple passes machine the necessary material.

Percussion Laser Drilling
Percussion laser drilling uses a “rapid-fire burst-of-pulses” micromachining method. Varying the laser pulse duration, spot size, optics and beam characteristics, percussion laser drilling produces a high-quality hole with minimal residue and consistent edge quality from entry to exit point. Percussion laser drilling evaporates the machined substrates layer by layer without noticeable strata or striations. Percussion laser drilling technology is especially suitable for metal, ceramic, polyimide/polyamide, polycarbonate, Pyrex, quartz and composite substrates.

Trepanning Laser Drilling
Trepanned laser drilling is a method used to remove a cylindrical core, or circular disc from a substrate. Unlike percussion laser drilling, the position of the beam or substrate is moved in conjunction with a predetermined laser beam “overlap” to achieve the desired edge quality and production throughput. Less overlap trepanning laser drilling increases throughput but produces a more jagged edge quality. More overlap creates finer hole resolution and edge quality.

Certain types of trepanning laser drilling can completely eradicate first pulse suppression which is a common concern in laser micromachining. Laser drilling in a trepanned, spiral pattern begins in the approximate center of the laser drilled hole and prevents hole inconsistencies related to the start/stop of the laser beam.

Laser drilling utilizing the trepanning method can also produce proportionately larger exit holes by “tilting” the laser beam within an already drilled entrance hole. This method of trepanning laser drilling is achieved through the special use of optics and galvos.

Specifications and Tolerances
In general, the resolution of features produced by laser micro-hole drilling is proportional to the wavelength used and beam quality. Two-micron features have been successfully demonstrated on some specific materials. Our imaging systems provide a depth-of-field sufficient to machine relatively thick materials. Positional accuracy on a single micron level allows us to make unique parts not achievable using conventional methods.